Introduction The famous “10 ℃ law” indicates that the reliability of electronic devices is closely related to the temperature, i.e., the reliability can be reduced by 50% for every 10 ℃ increase in temperature when the temperature of electronic devices exceeds 80 ℃. It is thus extremely important to discharge the waste heat of electronic devices in time to achieve an efficient device cooling. Heat transfer methods include heat conduction, heat convection and heat radiation. Conventional air-cooled and liquid-cooled achieve cooling via heat convection and heat conduction. In addition, the cooling technologies also include magnetic cooling (i.e., magneto-thermal effect), phase change cooling (i.e., phase change heat storage) and thermoelectric cooling (i.e., the Peltier effect). With the high integration and miniaturization of electronic devices, especially flexible electronic devices limited by size and deformation, conventional cooling technologies are no longer applicable. The newly flexible radiative cooling films with zero power consumption become potential candidates for cooling electronic devices and are expected to promote the development of the national dual-carbon cause, which can emit heat to outer space through thermal radiation and reject solar irradiance. However, it is extremely difficult to combine outstanding radiative cooling performance with excellent thermostability limited by materials and preparation process. In this paper, Al2O3-doped colorless polyimide hybrid films were prepared by a sol-gel method. The infrared radiation enhanced by Al2O3 phonon-enhanced resonance and the higher thermostability because of the interaction of Al2O3 nanoparticles with the molecular chains were analyzed. Methods TFMB (0.365 7 g) was mixed with DMAc (6 mL) under electromagnetic stirring at 0 ℃. Al(OH)3 sol at different contents (i.e., 0%, 5%,10%, 15%, and 20%, in mass fraction) was added to the solution above. An accurately weighed 6FDA (0.503 6 g) was sequentially added to a trident flask in batches for 1h, and then stirred continuously for 30 min. Subsequently, the mixture was stirred at room temperature for 4 h. The obtained precursor poly(amido acid) (PAA) solution was rested for 12 h. The PAA solution was coated onto a dry clean glass substrate by a spin-coating method and dried in a vacuum tube furnace at 80 ℃ for 1 h and then at 50 ℃ for 12 h to ensure that the solvent was removed completely. The sample was heated in a vacuum tube furnace in respective heating steps (i.e., at 110 ℃ for 30 min; at 140 ℃ for 30 min; at 170 ℃ for 30 min; at 200 ℃ for 30 min; at 220 ℃ for 30 min; and at 280 ℃ for 60 min). The obtained Al2O3-doped colorless polyimide (CPI) films were ultrasonically cleaned with absolute alcohol and deionized water for 30 min. The films were blown dry and put into a vacuum chamber. A 300 nm thick silver (Ag) film was deposited on the backside of the Al2O3-doped CPI film via direct current sputtering at 6×10-4 Pa. The argon flow rate, sputtering pressure and Ag target power were 50 cm3/min, 0.5 Pa and 100W, respectively. Results and discussion The mid-infrared emissivities (5-20 μm) of Al2O3-doped CPI/Ag hybrid films increase with increasing Al2O3 content. The mid-infrared emissivities are measured as e(0%)=87.54%, e(5%)=92.15%, e(10%)=92.23%, e(15%)=93.25%, and e(20%)=94.51%, respectively. The solar reflectivities (0.4-2.5 μm) decrease with increasing Al2O3 content. The solar reflectivities (R) are measured as R(0%)=94.81%, R(5%)=91.12%, R(10%)=89.31%, R(15%)=88.36%, and R(20%)=83.87%, respectively. This is because the scattering effect of the hybrid films increases with increasing Al2O3 content. The visible reflectivities (0.40-0.75 μm) firstly increase and then decrease with increasing Al2O3 content. The 5% Al2O3-doped CPI/Ag hybrid film has the maximum reflectance in the visible band, which can effectively improve the net cooling power of the hybrid film. Meanwhile, the intense interaction of Al2O3 nanoparticles with the molecular chains can effectively enhance the thermostability of the hybrid films. Compared with 0%Al2O3-doped CPI film, the glass-transition temperature (Tg) of 5% Al2O3-doped CPI film is 328 ℃, which is increased by 22 ℃. Conclusions The Al2O3-doped CPI hybrid film was prepared by a sol-gel method. The infrared radiation increased due to the phonon-enhanced resonance, and the thermostability improved due to the interaction between Al2O3 nanoparticles and molecular chains. The 5% Al2O3-doped CPI/Ag hybrid film had a high solar (0.4-2.5 mm) reflectivity (i.e., 91.12%) and a mid-infrared (5-20 mm) emissivity (i.e., 92.15%). The maximum cooling capability of 7.7 ℃ and 11.1 ℃ that were lower than that of bare aluminum device was achieved under sunlight. The Al2O3-doped CPI hybrid film exhibited superior thermostability (i.e., Tg～328 ℃), and thermal decomposition temperature (i.e., T5%～554 ℃). The results indicated an effective strategy to realize efficient radiative cooling for electronic devices and appendages in spacecraft.

Introduction Lithium metal batteries (LMBs) are regarded as candidates for next-generation batteries due to their low electrochemical potential (i.e., -3.040 V vs. standard hydrogen electrode) and high theoretical specific capacity (i.e., 3 860 mA?h·g?1). Lithium (Li) metal anode is susceptible to side reactions with organic electrolytes, leading to the uneven formation of the solid electrolyte interphase (SEI). The non-uniformity and fragility of the SEI can aggravate the growth of Li dendrites and excessive electrolyte consumption, ultimately resulting in a rapid attenuation of capacity and safety risks. These issues severely hinder the commercialization of LMBs. The development of an artificial SEI is crucial for protecting Li metal anode, suppressing Li dendrite growth, and accommodating volume changes during cycling. This advancement is essential for improving the stability and cycling life of LMBs.In this paper, we synthesized an artificial elastic polymer SEI (EP-SEI) constructed on the surface of Li metal anode by an in-situ UV-curing method. The main composition of EP-SEI was poly (ethyleneglycol) diacrylate-co-vinylene carbonate (PEGDA-CO-VC) cross-linking polymer.Methods For the synthesis of an artificial elastic polymer SEI (EP-SEI) constructed on the surface of Li metal anode by an in-situ UV-curing method, polyethylene glycol diacrylate (PEGDA) and vinylene carbonate (VC) were mixed in a mass ratio of 4:1 (i.e., 80 mg and 20 mg) under stirring. Afterwards, 2 mL of dimethoxyethane (DME) was added for dissolution. Subsequently, the mixture was dripped onto Li metal foils, followed by polymerization under a mercury lamp after the addition of 2-hydroxy-2-methylpropiophenone (HMPP). This method utilized UV light to rapidly excite the unsaturated bonds of polymer monomers, thereby shortening the polymerization reaction time and enhancing the preparation efficiency of the artificial SEI. This method was simple to operate, conducive to batch production, and aids in advancing the commercialization of LMB. The LMBs were assembled with LiFePO4 (LFP) or LiNi0.8Co0.1Mn0.1O2 (NCM811) as a cathode material, Li metal foil as an anode, polypropylene (PP) as a separator, and 1 M LiPF6 EC/DEC as an electrolyte. The batteries were assembled in a glove box filled with argon to ensure a moisture-free and oxygen-free environment during the process.Results and discussion An artificial EP-SEI with PEGDA?co?VC was prepared on the surface of Li metal by an in-situ UV-curing polymerization method. The thickness of EP?SEI is 1.6 μm. The EP-SEI exhibits an uniform and dense morphology and tightly covers the surface of Li metal. In the results of electrochemical test, Li symmetric (Li || Li) cells assembled with EP?SEI protected Li exhibit highly reversible electrochemical behavior and faster charge transfer rates. The Li || Li cells with EP?SEI Li maintain stable cycling at a current density of 1 mA?cm?2 and a capacity density of 1 mA?h?cm?2 for over 300 h. And the impedance values of Li || Li cells with EP?SEI Li continuously decrease during the cycle, and eventually stabilize at 15 Ω. This indicates that EP?SEI exhibits a high stability during prolonged electrochemical reactions and a high lithium ion conductivity. In the results of Li || Cu cells test, the low nucleation overpotential (μnuc) and plateau potential (μpla) indicate a reduction in the nucleation energy barrier for Li deposition. It is confirmed that EP-SEI can promote the uniform deposition of Li+ on the surface of Li metal. After cycling of Li || Cu cell with EP?SEI Cu, the thickness of Li+ deposition approaches the theoretical thickness. The surface of EP?SEI Cu remains smooth and flat without the growth of Li dendrites. In the results of full cell test, the LFP || Li batteries with EP?SEI Li exhibit a discharge specific capacity of 164.1 mA?h·g?1 and a capacity retention rate of 72% after 500 cycles with a coulombic efficiency of 98.5% at 0.5 C rate. The NCM811 || Li batteries with EP?SEI Li maintain a discharge specific capacity of 100 mA?h·g?1 after 500 cycles. This demonstrates that EP?SEI effectively reduces electrolyte consumption and improves coulomb efficiency, cycle stability and safety of LMBs.Conclusions In this study, an elastic polymer artificial solid electrolyte interphase membrane (EP?SEI) was constructed on the Li metal anode by an in-situ UV-curing polymerization method. This EP?SEI exhibited excellent uniformity, stability and elasticity, promoting the uniform deposition of Li+ during cycling. These properties indicated that EP-SEI could inhibit Li dendrite formation, buffer the volume changes of the Li metal anode, and reduce electrolyte consumption. The LFP || Li and NCM811 || Li batteries assembled with EP?SEI-protected Li metal anodes achieved discharge specific capacities of 164.1 mA·h·g?1 and 187.1 mA·h·g?1 at 0.5 C rate, respectively. The LMBs maintained stable cycling for 500 cycles. The EP-SEI could effectively protect the Li metal anode, improve the coulombic efficiency and extend the cycling life of LMB. The EP-SEI protected Li metal anode provided the possibilities for the commercialization of LMBs.

Introduction Polymer based dielectric capacitors are used in pulse power systems due to their ultrafast charge-discharge speed, mechanical flexibility, good reliability, light weight, and low cost. Although the breakdown strength of the commercial biaxially oriented polypropylene film (BOPP) capacitor is greater than 700 MV/m and the dielectric loss is less than 0.02%, its energy density is only 2-3 J/cm3, and its long-term service temperature does not exceed 105 ℃. Poly(ether imide) (PEI) as a linear polymer with excellent thermal and chemical stability has a high breakdown strength (Eb) and an extremely low loss, thus is widely used at high temperatures. Nevertheless, the discharged energy density of pristine PEI as low as 2.90 J/cm3 inhibits the enhanced energy storage performance. Composites composed of dielectric ceramic particle and polymer matrix have the combined advantages of a large dielectric constant of ceramic and a high breakdown strength of polymer. In this paper, titanium dioxide (TiO2) particles were introduced into the PEI matrix to prepare a TiO2/PEI composite, and the dielectric properties were analyzed. Methods TiO2 particles were prepared by a sol-gel method, and TiO2/PEI composites were prepared by a tape casting method. TiO2 particles with a target content were firstly dispersed in NMP solvent under ultrasound for 60 min to form a stable suspension, and then the PEI particles were added into the suspension in a small amount repeatedly and stirred for several hours until a uniform and stable solution was formed. Subsequently, the suspension was cast on a smooth glass plate, and the thickness of the composite was controlled by a scraper. The composites were further dried in a vacuum oven at 120 ℃ for several hours to thoroughly remove the solvent. Finally, the electrode with the diameter of 2 mm was coated onto the film via ion sputtering before testing.Results and discussion The relative dielectric constant of the composite is improved as TiO2 content is increased. When the volume fraction of TiO2 content is 9%, the relative dielectric constant of composite increases to 4.9, which is 1.75 times greater than that of pristine PEI. Moreover, at 25-150 ℃, the dielectric constant of 5% TiO2/PEI composite increases from 4.3 to 4.5, showing that its dielectric properties are stable and independent of temperature. The conductivity polarization caused by diffusion current in the Cole-Cole curve shows a straight line with a certain slope, indicating that there are a few conductive paths in the composite. Thus, the characteristic breakdown strength Eb of composite is significantly enhanced in comparison with pristine PEI. The Eb of 5% TiO2/PEI composite reaches 615 MV/m. The improvement of Eb is since TiO2 particles hinder the expansion path of the electrical branches inside the composite, reducing the possibility of electrical breakdown, and the uniform distribution of TiO2 particles in the PEI matrix weakens the distortion of the local electric field of the composite, and the uniform distribution of electric field can effectively improve the Eb of the composite. Also, the addition of TiO2 improves the elastic modulus of the composite, which is conducive to the improvement of Eb. Its energy storage density Udis of composite is 7.10 J/cm3, which is 2.3 times higher than that of pristine PEI and the discharged efficiency η is 94.9% due to the synchronous improvement of dielectric constant and breakdown strength. However, excessive TiO2 ceramic particles form some inevitable defects such as holes and agglomerations that increase the electrical breakdown paths, thus weakening the breakdown strength and energy storage performance. While the breakdown strength and energy storage performance of the composite film at 150 ℃ are tested. Although Eb is lower than that at 25 ℃, its value is still as high as 487 MV/m. Compared with the case at 25 ℃, Udis and η at 150 ℃ also decrease. At 150 ℃, the maximum Udis of 5% TiO2/PEI composite is 5.05 J/cm3, and η is 88.5%. The stability comparison of Udis and η of 5% TiO2/PEI composite film under 300 MV/m is further conducted at different temperatures. As the temperature increases to 150 ℃, the Udis stability of 5% TiO2/PEI composite remains 98.5% with a η stability of 97.4% in comparison with an Udis stability of 99.5% and a η stability of 99.2% for pristine PEI. The faint decrease of Udis and η at high temperature is due to the unavoidable massive dielectric loss and joule heat during the frequent charge-discharge processes. All these results prove that benefiting from an inherent low dielectric loss, TiO2/PEI composite basically possesses a satisfactory fatigue resistance at room temperature and even at high temperatures.Conclusions TiO2 particles were prepared by a sol-gel method, and TiO2/PEI composites were prepared by a tape casting method. The addition of TiO2 particles increased the dielectric constant and breakdown strength of the composite, improving its energy storage performance. At room temperature, the breakdown strength of TiO2/PEI composite reached 615 MV/m, and the energy storage density was 7.10 J/cm3, which was 2.3 times greater than that of pristine PEI. And the charge-discharge efficiency could reach 94.9%. Moreover, when the temperature increased to 150 ℃, the maximum energy storage density of 5% TiO2/PEI composite film was 5.05 J/cm3, while the charge-discharge density stability remained 98.5% with an efficiency stability of 97.4%. TiO2/PEI composite prepared could have a great potential in high temperature capacitors due to the excellent energy storage performance and stability.

Introduction As a semiconductor material with superior optical properties, amorphous TiO2 with the valence band, conduction band, and bandgap structure of crystalline TiO2 is prone to forming a loose porous structure with more surface defects. During the photocatalytic reaction process, it can generate a large number of electron and hole capture traps, which is conducive to improving a photocatalytic efficiency. However, its photocatalytic activity still needs to be improved. Widening its absorption range, narrowing its band gap and promoting the migration of the internal electron-hole to the surface to react with the target product are all still the current important research aspects.Doping or loading is a normal modification method of TiO2. The doping with rare-earth element La is simple and effective, narrowing the band gap of TiO2 and reducing the energy consumption of photocatalytic reaction. To further improve the photocatalytic activity, loading La-TiO2 on SBA-15 can be an effective option. The high specific surface area and the mesopores of SBA-15 can be beneficial to the dispersion of the active component and the diffusion of reactants, thereby improving the photocatalytic performance. In this paper, TiO2 was firstly doped with La, and La-TiO2 was then supported on mesoporous molecular sieves SBA-15. The obtained catalyst La-TiO2/SBA-15 was characterized and applied in the photocatalytic oxidation desulfurization for the model and real diesel oil. In addition, the photocatalytic reaction mechanism was also proposed.Methods 4 mmol tetrabutyl titanate was dropped slowly into a solution of 0.9 mL of deionized water with 10 mL of absolute ethanol under magnetically stirring until a white gel was generated. After stirring for 0.5 h, the white gel was aged at 25 ℃ for 14 h, and then stirred at 40 ℃ until the absolute ethanol was completely evaporated. This white powder becomes an amorphous TiO2 after drying at 100 ℃ and grinding. The synthesis process of La-TiO2 was similar to that of amorphous TiO2. However, deionized water was replaced with a solution of lanthanum nitrate (Its concentration was calculated according to the doping amount of La). To support La-TiO2 on SBA-15, lanthanum nitrate and tetrabutyl titanate were put into 10 mL absolute ethanol. The ratio of the feed stocks in this mixture is same as that of the synthesis of La-TiO2. SBA-15 mesoporous molecular sieve was also put into this mixture, and the loading of La-TiO2 on the supported catalyst was 10% (in mass content). 1 mL deionized water was dropped slowly into the mixture under stirring.The X-ray diffraction (XRD) patterns of the samples were determined on a model D/max-RB X-ray diffractometer with Cu-Kα radiation operating at 40 kV and 150 mA. The composition of the catalyst was identified by a model D/max-R X-ray fluorescence spectrometer (XRF) with a tungsten target at 40 kV and 50 mA. The elemental quantitative or semi-quantitative analysis was carried out based on the characteristic peak intensity of each element. The pore structure was characterized by a model ASAP 2010 physical adsorption instrument (BET). After 16-h pretreatment in vacuum at 110 ℃, N2 adsorption-desorption was operated at -196 ℃. The transmission electron microscope (TEM) images were determined on a model JEM-2010CX electron microscope at 200 kV. The Fourier-transform infrared spectra (FT-IR) in the range of 4 000-400 cm-1 were recorded on a model WQF 510 spectrometer at a resolution of 4 cm-1. The UV-Vis diffuse reflection spectra (UV-Vis) were recorded on a model Cary 2450 UV-Vis spectrometer with BaSO4 as a reference sample in the wavelength range of 200-800 nm. The photoluminescence (PL) spectra were recorded on a model FluoroMax-4 spectrofluorometer, which was excited at 240 nm in the scanning range of 260-460 nm. The valence-band X-ray photoemission spectroscopic data (VB-XPS) were obtained on a model ESCALAB 250 X-ray photoelectron spectrometer equipped with an Al Kα X-ray source and the spot size of 500 μm. At ambient temperature, PODS reaction was operated in a beaker under magnetically stirring. 10 mL model or real fuel was added firstly into a beaker, and then some amount of CH3OH as an extractant (calculated in volume ratio of the extractant to the fuel), a catalyst (calculated in the mass percent in the model fuel) and H2O2 (calculated in n(O)/n(S)) were added. The beaker was placed in the dark under magnetically stirring for 0.5 h to establish adsorption-desorption equilibrium of DBT on catalysts. PODS proceed under the visible light irradiation and the samples were withdrawn periodically every 0.5 h from the upper phase, and the sulfur content of the clear liquid sample was detected on a model TSN-5000 sulfur nitrogen detector after high-speed centrifuge.Catalyst was separated from the reaction mixture via filtration and washing with deionized ethanol, dried at 80 ℃ and then directly used for the next run.Four PODS processes were repeated, and in each process 1.0 mmol/L a kind of active intermediate capture agent was added. Isopropanol (IPA), p-benzoquinone (p-BQ) and disodium ethylenediaminetetraacetate (EDTA-2Na) were used for detecting hydroxyl radicals, superoxide radicals and holes, respectively.Results and discussion The XRD patterns show that La-TiO2/SBA-15 retains a two-dimensional hexagonal highly ordered mesoporous structure of SBA-15. TiO2, La-TiO2 and La-TiO2/SBA-15 do not show any characteristic diffraction peaks, indicating that they all are amorphous. Compared with the sample SBA-15, the specific surface area, pore volume and pore size of sample La-TiO2/SBA-15 decrease due to the loading of La-TiO2. However, its specific surface area is still higher than that of amorphous TiO2. The TEM images present an ordered mesoporous structure of La-TiO2/SBA-15, and La-TiO2 is also evenly dispersive in the pore channels. The UV-Vis analysis shows that the absorption edge of La-TiO2 is higher than that of TiO2. A reason is that lanthanum doping reduces a band gap energy of TiO2 and improves a light absorption ability of the catalyst. Although a band gap width is almost unchanged for loading. The PL spectra indicate that the intensity of fluorescence emission peak decreases after doping and loading, proving that the doping and loading both can reduce an electron-hole recombination rate, thereby prolonging the photogenerated carrier lifetime of amorphous titania material.The effect of reaction condition on the results of PODS was investigated and optimized. The results are obtained under optimum conditions (i.e., catalyst dosage of 1% (in mass fraction), n(O):n(S) of 15:1, and the of agent:oil ratio of 1:1). Under such conditions, the desulfurization rate is 95.12%, and it can still reach more than 85% after four runs of reusing. For La-TiO2/SBA-15 as a catalyst, the active intermediate species in PODS were ?O2- and h+ based on active intermediate species capture experiments.Conclusions La-TiO2/SBA-15 prepared had a two-dimensional hexagonal pore structure, a high specific surface area, and well-dispersion. Lanthanum doping broadened a light response range, increased the absorbance of the light, and reduced the photogenerated electron-hole recombination rate of TiO2. La-TiO2/SBA-15 had a higher catalytic activity rather than TiO2 and La-TiO2, and a good reusability. The main active intermediate species were ?O2- and h+.

Introduction Supercapacitors are widely used due to their fast charging and discharging processes, high power density (i.e., 10 kW·kg-1), fast charging and discharging (i.e., minutes or even seconds), and long cycle term (i.e., up to 100 000 cycles theoretically). The electrode materials determine the electrochemical energy storage performance of the supercapacitor. It is thus important for the development of high-performance electrode materials to improve the performances of the supercapacitor. Many electrode materials are explored for supercapacitors, such as transition metal oxides, transition metal hydroxides and transition metal sulfide. The electrode materials show the promising practical applications. To further optimize the electrochemical performances of the electrode materials, the supercapacitors with the composites are developed as electrode materials. Among the composites, transition metal sulfide-based electrode materials have attracted much attention because of their outstanding performances for energy performances of supercapacitors. In this paper, Ni3Se2/Ni3S2 nanocomposites were synthesized on nickel foam by a solvothermal and selenization method, and their structures and electrochemical energy storage performances were systematically investigated.Methods 4.4 g Na2S·9H2O was dissolved in 40 mL methanol under stirring vigorously for 30 min. The solution was moved to 2 Teflon-lined stainless steel autoclaves, equally, and two cleaned Ni foams were immersed in the solution, respectively, then the autoclaves were kept in an oven 140 ℃ for 16 h. After the reaction, Ni3S2 nanorods on Ni foam (Ni3S2/Ni ) were obtained.0.01 g Se powder was dissolved in 6 mL hydrazine?hydrate (resolution A). 9 mL DI-water and 15 mL ethanol were added into resolution A, obtaining resolution B. Resolution B was transfered to 2 autoclaves. Two Ni3S2/Ni samples were put into two autoclaves with resolution B. The autoclaves were kept in an oven at 140 ℃ for 10 h. The samples were prepared at different growth temperatures and time.The crystal structure and morphology of the samples were determined by X-ray diffraction (XRD, Bruker-D8, λ=0.154 05 nm), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The chemical elements and valence bond states were analyzed by X-ray photoelectron spectroscopy (XPS, Al Kα) and X-ray energy spectrometry (EDS). The electrochemical properties were examined on an electrochemcial system with Ni3Se2/Ni3S2 nanocomposites as working electrodes at room temperature.Results and discussion The SEM images of Ni3Se2/Ni3S2 nanocomposites show that Ni3Se2 nanoparticles cover Ni3S2 nanorods. Besides, some Ni3Se2 clusters are on the top of Ni3S2 nanorods. Moreover, the HRTEM images of Ni3Se2/Ni3S2 nanocomposites reveal the interfaces between Ni3Se2 and Ni3S2.Under the optimized growth conditions, the specific capacitance of Ni3Se2/Ni3S2 nanocomposites can reach 2 482.00 mF·cm-2 (@1 mA·cm-2), and the specific capacitance retention rate is still 68.45% after 2 000 charge-discharge cycles at 10 mA·cm-2, and the coulombic efficiency is 97.20%-99.28%. The assembled liquid (6 mol/L KOH) Ni3Se2/Ni3S2//AC asymmetric supercapacitor demonstrates a specific capacitance of up to 768.75 mF·cm-2 (@2.5 mA·cm-2). The assembled Ni3Se2/Ni3S2//AC all solid-state supercapacitor (ASS) has a specific capacitance of 983.57 mF·cm-2 (@7.5 mA·cm-2). The outstanding electrochemical performances of Ni3Se2/Ni3S2 nanocomposites can be since: 1) Ni3Se2/Ni3S2 nanocomposites are fabricated on Ni foam, directly, reducing the contact resistance due to the good conductivity of Ni foam; 2) Ni3Se2/Ni3S2 nanocomposites on Ni foam have a three-dimensional structure, exhibiting the large specific surface area for the electrochemical reactions; and 3) the synergies of Ni3Se2 and Ni3S2 can improve the electrochemical performances. In addition, the integrated circuits with Ni3Se2/Ni3S2//AC solid-state capacitor are also analyzed. The series Ni3Se2/Ni3S2//AC ASSs demonstrate a typical increase in the operating voltage window, and the parallel ones show the improvement of the specific capacitance, indicating the promising practical applications for energy storage of Ni3Se2/Ni3S2 nanocomposites.Conclusions Ni3Se2/Ni3S2 nanocomposites were prepared as electrode materials for supercapacitors and their the electrochemical performances were investigated. As the electrode material, Ni3Se2/Ni3S2 nanocomposites showed the outstanding properties for energy storage. At 1 mA·cm-2, the constructed supercapacitor in 6 mol/L KOH solution exhibited the specific capacitance of 2 482 mF·cm-2. the ASS devices were also constructed with Ni3Se2/Ni3S2 nanocomposites, showing good electrochemical performances for energy storage. Furthermore, the ASS devices with Ni3Se2/Ni3S2 nanocomposites as electrode material showed the typical integrated features in series and parallel circuits. Singe ASS device demonstrated 0-1.4 V working voltage window, and two series devices could work well in 0-2.8 V, while the specific capacitance presented the obvious improvement for two parallel ASS devices. Therefore, the study could demonstrate a potential application of Ni3Se2/Ni3S2 nanocomposites, and provide an approach to design the new materials for energy storage.

Introduction With the continuous growth in energy storage demands for portable electronic devices, electric vehicles, and grid energy storage, rechargeable metal-ion batteries have found extensive applications in energy supply and storage due to their advantages of low self-discharge, high energy density, and environmental friendliness. One of the essential components of metal-ion batteries is the negative electrode material, and its physical and chemical properties are crucial for battery performance. However, in practical applications, there is still a shortage of high-performance negative electrode materials for metal-ion batteries. Traditional three-dimensional electrode materials suffer from limited storage capacity and less than ideal charge-discharge rates, primarily because of the limited number of lattice vacancies in their structure. This limitation hinders their ability to meet market demands, particularly in scenarios where faster charge-discharge rates are required, such as electric vehicles and grid energy storage. In contrast, two-dimensional materials offer advantages such as a larger specific surface area and enhanced metal ion diffusion, making them suitable for energy storage in batteries. Among two-dimensional materials, the emerging class of two-dimensional transition metal borides (MBenes) exhibits excellent electrical conductivity, structural stability, and high specific capacity. As a result, an increasing amount of research work is considering them as electrode materials for energy storage systems. Compared to traditional experimental research methods, first-principles computational techniques can better assist in designing novel high-performance electrode materials at the atomic and electronic scale. In this paper, we aim to explore the potential of h-Mo2B2 MBene as a negative electrode material for metal-ion batteries using first-principles calculation methods. We systematically investigate its structural stability, electronic structure, and electrochemical properties. The studies suggest that h-Mo2B2 holds promise as a prospective negative electrode material for application in metal-ion batteries.Methods In this paper the calculations are based on Density Functional Theory (DFT) first-principles methods, implemented using the Vienna Ab initio Simulation Package (VASP). The Projector Augmented Wave (PAW) pseudopotential approach is utilized, with a plane wave cutoff energy of 500 eV. The Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation (GGA) is employed for the exchange-correlation functional. To account for the interaction between metal cations and 2D materials, van der Waals interactions are considered in the calculations. During the geometric structure optimization, energy and force convergence criteria are set to 10-5 eV/atom and 0.01 eV/?, respectively. The K-point grids used for h-Mo2B2 unit cell and 2×2×1 supercell calculations are 20×20×1 and 5×5×1, respectively. A vacuum layer with a thickness of 20 ? is included to eliminate the spurious interaction. Phonon spectra calculations are performed using density functional perturbation theory. Differential charge calculations are employed to study charge redistribution and transfer between adsorbed metal atoms and 2D materials. Bader charge analysis is utilized to assess the amount of charge transfer between the metal ions and the 2D material. The Climbing Image Nudged Elastic Band (CI-NEB) method is used to calculate the migration energy barriers and migration pathways of metal ions on h-Mo2B2.Results and discussion The 2D h-Mo2B2 studied in this paper belongs to the P6/mmm space group within the hexagonal crystal system. It comprises three atomic layers stacked in a Mo-B-Mo sequence, with hexagonal B atomic layers situated between the upper and lower Mo atomic planes. To evaluate the dynamical stability of h-Mo2B2, phonon spectrum calculations were conducted, and no imaginary frequencies were observed throughout the entire Brillouin zone. This indicates that h-Mo2B2 exhibits dynamical stability. The band structure of h-Mo2B2 reveals numerous bands crossing the Fermi level, confirming its metallic nature. This exceptional electrical conductivity of h-Mo2B2 can significantly enhance the rate performance of electrodes. Adsorption energy is a fundamental criterion for assessing whether a material can be utilized as a negative electrode. The adsorption energies of Li, Na, Mg, and K on the h-Mo2B2 surface were calculated, and all exhibited negative values, indicating effective adsorption of all metal atoms on a monolayer of h-Mo2B2. Rapid charge-discharge rates are crucial for secondary batteries, and the migration energy barrier of metal ions is a key factor determining the charge-discharge rate. The migration energy barriers for the four metal atoms on the h-Mo2B2 surface are ranked as K (7 meV)<Na (10 meV)<Mg (37 meV)<Li (39 meV). The extremely low migration energy barriers suggest that Li, Na, Mg, and K can easily diffuse on h-Mo2B2, making it a promising high-rate electrode material. As a negative electrode material for lithium-ion batteries, h-Mo2B2 exhibits a theoretical specific capacity of 735 mA·h·g-1, significantly surpassing graphite’s 372 mA·h·g-1. For sodium ion, h-Mo2B2 boasts a theoretical specific capacity of 314 mA·h·g-1, while for magnesium ion, due to multilayer adsorption and divalent ions carrying more charge, it reaches 1 506 mA·h·g-1, far exceeding the capacity for Li and Na. Theoretical calculations also indicate that h-Mo2B2 possesses low average open-circuit voltages of 0.36 V (Li), 0.47 V (Na), and 0.63 V (Mg), all within the 0-1 V range. This lowers the likelihood of dendrite formation in the negative electrode, thereby enhancing the safety and stability of metal-ion batteries. This paper, from a theoretical standpoint, elucidates and confirms the potential of h-Mo2B2 as a negative electrode material for rechargeable metal-ion batteries. It paves the way and provides valuable insights for the design of high-performance electrode materials.Conclusions Based on first-principles calculations, we systematically investigated the physical properties and electrochemical performance of 2D h-Mo2B2 MBene. It was found that h-Mo2B2 is dynamically stable and exhibits metallic conductivity. The diffusion barriers for metal atoms (M=Li, Na, Mg, K) on h-Mo2B2 are remarkably low, all being less than 0.04 eV, indicating that h-Mo2B2 can facilitate rapid charge and discharge when employed as a negative electrode material in metal-ion batteries. The theoretical specific capacities of h-Mo2B2 for Li, Na, and Mg are 753, 314, and 1 506 mA·h·g-1, respectively. Furthermore, the average open-circuit voltages (OCV) for h-Mo2B2 with Li, Na, and Mg are calculated to be 0.36, 0.47, and 0.63 V, respectively. All these findings collectively support that 2D h-Mo2B2 MBene can serve as a high-performance negative electrode material for lithium, sodium, and magnesium ion batteries.

Introduction Solid oxide fuel cell (SOFC), as an efficient and environmentally friendly energy conversion device, has attracted much attention due to its numerous advantages, i.e., high electrical efficiency, low emissions, and high fuel flexibility, compared to other power generation technologies. To address the degradation issues faced by SOFCs operating at high temperatures, developing proton-conducting electrolytes as an alternative to oxygen-conducting electrodes is recognized as an effective strategy to lower the operating temperature of SOFCs. BZCY721 (BaZr0.7Ce0.2Y0.1O3-δ), a proton-conducting electrolyte material used in protonic ceramic fuel cells (PCFCs), exhibits both high proton conductivity and excellent chemical stability at lower temperatures. However, sintering the BZCY material typically requires high temperatures exceeding 1 700 ℃ for over 4-5 h, resulting in significant energy consumption and residual stress induced failures of components. It is thus imperative to explore advanced sintering technology to fabricate the BZCY electrolyte materials. Microwave sintering is a field-assisted sintering technique that utilizes the heat generated by the interaction between the specific microwave band and the microstructure of the material to heat the entire material, thereby achieving the desired density. This method effectively reduces the sintering temperature and significantly shortens the sintering time.Methods Commercial BZCY721 powder and NiO powder were mixed at a mass ratio of 20:1, and ground in a ball mill for 24 h to obtain a homogeneous mixed powder. Subsequently, the mixed NiO-BZCY721 powder was blended with a 10% PVA solution at a mass ratio of 10:1 for wet granulation. The granulated powder of 0.8 g was weighted and pressed into a die with a diameter of 15 mm at 350 MPa for 30 s. This process yielded circular specimens with the diameter of 15 mm and the thickness of approximately 1 mm. The experiment was repeated to produce several sets of green samples.The samples were categorized into two groups for traditional sintering and microwave sintering experiments, respectively. The samples from the traditional sintering group were placed directly into a box furnace for debinding and sintering. The debinding process was carried out at a rate of 1 ℃/min to 400 ℃, for 2 h, then heating at 5 ℃/min to 1 600 ℃ for 6 h, and finally cooling at 5 ℃/min to 500 ℃ before naturally cooling to room temperature. In contrast, the samples from the microwave sintering group underwent the same debinding process in the box furnace but were then transferred to a microwave sintering furnace for sintering at different temperatures and holding time. The mechanical properties and electrochemical properties of the samples prepared using two sintering methods were investigated.Results and discussion Based on the results by the Archimedes method, the density of samples prepared by both traditional sintering and microwave sintering exceeds 96%. The scanning electron microscopy images reveal that the samples both exhibit a high degree of density. The grain size distribution is relatively uniform. The statistical analysis of the grain size distribution demonstrates that as the microwave sintering temperature increases, the overall grain size of the resulting sample decreases, becoming more uniform. The average grain size of the sample sintered by microwave method at 1 500 ℃ is 0.49 μm, whereas the average grain size of the sample sintered by traditional method is 0.53 μm.The impedance analysis reveals that there is a minimal variance in the impedance of the BZCY electrolyte produced by both sintering techniques when the operating temperature remains below 500 ℃. However, once the temperature surpasses 500 ℃, the impedance of the sample sintered by microwave method exceeds that of the sample sintered traditional method. This indicates that the microwave sintered sample exhibits a greater sensitivity at different operating temperatures, resulting in higher impedance values at elevated temperatures. Among the samples, the conductivity peaked in the sample sintered by traditional method at 1 600 ℃ for 6 h reaches a maximum value of 1.01×10-3 S·cm-1 at 650 ℃. Meanwhile, the sample sintered at 1 500 ℃ for 40 min exhibits a conductivity of 6.41×10-4 S·cm-1 at 650 ℃. Note that the activation energy associated with microwave sintering conductivity is only 1.071 eV.The sample sintered by microwave method at 1 500 ℃ for 40 min exhibits the maximum hardness (i.e., an average value of 12.379 GPa). The sample sintered by traditional method at 1 600 ℃ for 6 h demonstrates a slightly lower hardness (i.e., 11.521 GPa), which is still higher than the sample sintered at 1 450 ℃. In terms of elastic modulus, the sample sintered by traditional method at 1 600 ℃ for 6 h displays the maximum elastic modulus (i.e., 194.68 GPa), slightly surpassing that of the sample sintered by microwave method at 1 500 ℃. According to the Evans and Niihara empirical formulas, the sample sintered by traditional method at 1 600 ℃ exhibits a fracture toughness of 0.280 MPa·m1/2 and 0.305 MPa·m1/2, respectively. Also, the sample sintered by microwave method at 1 500 ℃ has a fracture toughness of 0.359 MPa·m1/2 and 0.347 MPa·m1/2, respectively.Conclusions The density of the BZCY electrolyte with 5% (in mass) NiO sintering aids sintered by microwave method at 1 500 ℃ for 40 min was comparable to that of the sample sintered by traditional method at 1 600 ℃ for 6 h, achieving a density of over 96%. The grain size obtained by microwave sintering was smaller.The impedance and conductivity of the sample produced by microwave sintering exhibited minimal differences, compared to those obtained by traditional sintering. The grain impedance at 650 ℃ measured was 34.81 Ω·cm2, and the conductivity was 6.41× 10-4 S·cm-1. The grain boundary impedance of microwave-sintered sample decreased as the operating temperature increased. This decrease could be attributed to the smaller grain size achieved by microwave sintering since a smaller grain size resulted in a greater number of grain boundaries, thereby increasing the impact on the grain boundary impedance. Furthermore, the activation energy for conductivity in microwave-sintered samples was only 1.071 eV.The average hardness of the samples sintered by microwave sintering at 1 500 ℃ for 40 min reached 12.379 GPa, which was higher than that obtained by conventional sintering at 1 600 ℃ for 6 h. The average elastic modulus of the microwave-sintered sample reached 190.8 GPa, which was similar to that of traditional sintered samples. According to the statistics of indentation and crack length in SEM images, the crack type was radial crack. Based on the Evans and Niihara formulas, the results of microwave-sintered samples were 0.359 MPa·m1/2 and 0.347 MPa·m1/2 respectively, which were higher than those of conventionally-sintered samples.

Introduction Aqueous zinc-ion battery is considered as one of the most promising candidates for large-scale energy storage device due to its low cost, high safety and recyclability. Compared with other alkali-based batteries, zinc-based batteries can realize energy storage through 2-electron charge transfer delivering a high specific capacity (820 mA?h/g) and low price. However, the existing development of zinc-ion battery is far from commercialization. Main challenges exhibit in three aspects, i.e., a serious dendrite effect caused by the uneven deposition of zinc ions in the battery; uncontrollable water-induced parasitic reactions such as hydrogen evolution reaction (HER) in acidic electrolyte; and metal corrosion and irreversible side reactions on surface of anode. These challenges result in a low coulombic efficiency, a shorten cycle life of battery and even serious security risks. In order to solve the shortcomings of zinc anode, some methods (i.e., zinc anode structure modification, electrolyte optimization and artificial interface layer (SEI) construction) are developed. Among them, a tunning electrolyte is a directive method to avoid negative side reactions and inhibit the dendrite growth. Electrolyte modification can realize a long-cycle-life zinc anode and a high efficient battery. In this paper, tetraethylene glycol dimethyl ether (TEGDME) was added into ZnSO4 based electrolyte as s co-solvent to investigate the plating/stripping behavior of Zn metal. The reaction mechanism of co-solvation effect from multi-scale was analyzed. Methods All reagents with analytical purity were used without any treatment. For the preparation of bare electrolyte, 2.87 g of ZnSO4·7H2O was dissolved into 10 mL distilled water to prepare 1 mol/L ZnSO4 electrolyte. For the preparation of co-solvent electrolyte, 2.87 g of dried lithium bistrifluoromethyl sulfonate (LITFSI) was dissolved into 10 mL dehydrated tetraethylene glycol dimethyl ether (TEGDME) in an argon glove box under stirring for overnight. The final concentration was controlled to 1 mol/L LITFSI/TEGDME. A mixed electrolyte was prepared via dissolving 5 mL aqueous ZnSO4 electrolyte, 3 mL of LITFSI/TEGDME electrolyte, and 2 mL of distilled water. The mixture was stirred at room temperature for 2 h, and then aged for 12 h to obtain the final electrolyte.The monitoring during charge/discharge process was carried out on a model EQCM-D instrument (AWS, A-20, Spain). In this experiment, a 12 mm diameter titanium-gold quartz wafer was used as a cathode, and a high purity zinc foil was used as an anode. The amount of electrolyte was 2 mL. Before the measurement, the cell was active at a low current density. Afterwards, the frequency and dissipation were recorded during the electrochemical process.The surface roughness was determined by ex-situ atomic force microscopy (AFM) (EIS) method, The impedance detection during electrochemical process was carried out by in-situ electrochemical impedance. The distribution of relaxation times (DRT) analysis was carried out based on the in-situ EIS results. The electrochemical performance was measured on 1470E electrochemical workstation. The surface conditions of the two electrodes were analyzed by X-ray diffraction.Result and discussion An electrolyte (Co-Solv) for aqueous zinc battery was designed via mixing aqueous electrolyte with TEGDME/LITFSI. The electrochemical measurement reveals that the Coulomb efficiencies (CE) of Co-Solv is 97.2%, which is higher than that of bare electrolyte based battery (i.e., 94.4%). The main reason is due to the co-solvent effect from water and TEGDME in Co-Solv electrolyte. This further confirmed by in-situ E-QCM results. Compared to the frequency and dissipation evolution during charge/discharge process, the surface electro-deposition process can be revealed. A rigid film with TEGDME/LITFSI can form on the top of anode, which further inhibits the occurrence of side reaction such as HER.Based on the results by AFM, the roughness in the bare electrolyte increases after electrochemical process. The roughness surface is closely related to the side reactions. The formation of irreversible basic zinc sulfate affects the anode performance. In the Co-Solv based battery, the roughness decreases and a rigid film appears on the top of anode to avoid the side reactions. This protected film is dense and firm to inhibit the formation of dendrite. According to the results from DRT analysis, the co-solvation effect can affect the double electric layer structure of the metal surface, and induce the uniform deposition of metal zinc via maintaining the stability of the local electric field on the electrode surface. Combined with the results by E-QCM and AFM, the addition of TEGDME/LITFSI can improve the electrochemical performance via inhibiting dendrite growth, reducing side reactions and blocking the HER. Conclusions TEGDME/LITFSI was a mixture adding into ZnSO4 based electrolyte to optimize the plating/stripping behavior of Zn metal. TEGDME could partly replace water to combine with Zn2+ and form the co-solvent structure of Zn2+-TEGDME/H2O. It was indicated that the electrochemical reaction could related to the electric double layer structure near anode. Co-solvents could regulate the deposition of metallic zinc via affecting and stabilizing the local electric field. This work could provide a perspective potential for further development and mechanism analysis of co-solvent systems.

Introduction Aqueous zinc-ion batteries (AZIBs) as one of the highly anticipated areas in the new generation of battery technologies have broad application prospects and potential. Compared to conventional lithium-ion batteries, AZIBs have higher safety, cost-effectiveness, environmental friendliness, and higher energy density, making them highly sought after in energy storage and renewable energy. Nevertheless, a high concentration of water molecules in the AZIBs can result in the decomposition of water into H+ and OH- during the charging/discharging process, which triggers significant hydrogen evolution reactions and corrosion problems, ultimately compromising the stability of the metal zinc electrode. Meanwhile, zinc dendrites are easily formed due to the uneven zinc deposition. To address these issues, this paper innovatively proposed an electrolyte additive of ethylene glycol methyl ether (MECS) to enhance the stability of the zinc electrode. The impact of MECS electrolyte additives on the AZIBs performance was systematically investigated via the experiments and theoretical calculations.Methods An electrolyte was prepared via adding different concentrations of MECS into 2 mol/L ZnSO4 solution. The concentrations of MECS additives used were 2%, 4%, and 9% (in volume fraction, referred to as ‘2% MECS’, ‘4% MECS’, and ‘9% MECS’).V6O13·H2O was prepared. Firstly, 2.73 g of V2O5 and 4.52 g of H2C2O4 were added to 40 mL of deionized water (referred to as “solution A”) and stirred at 90 ℃ for 1 h. Subsequently, 10 mL of H2O2 and 30 mL of ethanol were added to solution A, which was then transferred to a high-pressure vessel lined with PTFE. The vessel was heated at 180 ℃ for 3 h. Finally, the product was filtered, washed with ethanol and deionized water for at least 3 times, and then the washed material was dried in vacuum at 60 ℃ for 24 h. The preparation steps for the cathode plate were as follows: V6O13·H2O, conductive agent (acetylene black), and PVDF were mixed at a weight ratio of 7:2:1, with NMP used as a solvent, and stirred evenly. The obtained slurry was coated on Ti foil, and dried in vacuum at 80 ℃ for 24 h. The samples were characterized by nuclear magnetic resonance (NMR), Fouier transform infrared spectroscopy (FTIR) and Raman spectroscopy (RS). Also, the binding energy was calculated based on the density functional theory (DFT).Results and discussion Based on the results by BMR, FTIR and RS, the shift of 1H peaks and the stretching vibrations of O—H both indicate a change in the solvation structure of Zn2+ in the solution with the MECS additives. The analysis of the DFT calculation results reveals that the binding energy between MECS and Zn2+ is significantly higher than that between Zn2+ and H2O, indicating the preference of MECS to coordinate with Zn2+ and replace the positions of water molecules in the solvation structure of Zn2+. The restructured solvation structure of Zn2+ reduces the number of active water molecules in the electrolyte, thereby lowering the activity of parasitic reactions and enhancing the stability of the metal zinc anode.The effect of MECS additives on the electrochemical performance of batteries was thoroughly investigated via assembling Zn//Zn symmetrical cells, Zn//Ti cells, and full cells. Under relatively mild testing conditions (i.e., 0.5 mA/cm2 and 0.5 mA?h/cm2), Zn//Zn symmetrical cells with MECS additives can cycle stably for 1 250 h, while those without MECS additives only cycle for about 250 h before short-circuiting occurs. The batteries with MECS additives demonstrate an excellent performance even under different testing conditions due to the regulation effect of MECS at the zinc anode/electrolyte interface.Conclusions A novel electrolyte additive (MECS) was developed to stabilize zinc metal anode. Based on experimental and theoretical calculations, MECS molecules could participate in altering the solvation structure of Zn2+, reduce the quantity of active water molecules at the zinc anode interface through strong coordination with Zn2+, resulting in a smooth zinc deposition and a decreased by-product formation. Consequently, Zn//Zn symmetrical cells assembled with the improved electrolyte demonstrated stable cycling for over 1 250 h. In addition, the assembled Zn//V6O13?H2O full cell also showed an excellent performance, maintaining a high capacity even after 800 cycles at a current density of 1 A/g. This study could present a simple, effective, and economic electrolyte modification approach to achieve effective utilization of zinc in aqueous zinc-ion batteries, providing innovative pathways for the development of next-generation secondary batteries.

Introduction Silicalite-1 zeolite membrane has a high separation performance due to its hydrophobic properties, which can preferentially permeate organic molecules and effectively block water molecules in aqueous-organic phase mixtures. However, the hydrophilic Si—OH on the surface of Silicalite-1 zeolite membrane is one of the most important reasons for the low hydrophobicity and selectivity of membrane, which preferentially adsorbs water molecules, and easily reacts with ethanol in the solution and generates Si—OC2H5 to block the zeolite pores. To solve the problems above, the n-octyltriethoxysilane (OTES) was grafted onto the surface of Silicalite-1 zeolite membrane to eliminate Si—OH, further improving hydrophobicity and separation ability of the membrane. The effects of mass fraction of OTES, reaction temperature and modification time on the membrane modification were investigated. The modification mechanism was analyzed, and the pervaporation stability of Silicalite-1 zeolite membrane before and after modification was compared.Methods A molar ratio of precursor solution was n(TEOS):n(TPAOH):n(H2O):n(NaOH) of 1.00:0.05:75.00:0.03. Silicalite-1 zeolite with a particle size of 400 nm was used as seeds to prepare Silicalite-1 zeolite membranes by a secondary growth method. The membranes were hydrothermally crystallized at 175 ℃ for 8 h. After washing, the membranes were calcined at 550 ℃ for 4 h to remove the template, obtaining silicalite-1 zeolite membranes.Silicalite-1 zeolite membranes were placed in a solution with OTES as a solute and toluene as a solvent at different mass fractions of 1%-5%, and modified at 20-100 ℃ for 5-20 h. The membranes were washed with anhydrous ethanol to remove the residual solvent, and finally dried at 80 ℃ for 12 h to obtain the OTES@Silicalite-1 zeolite membranes.The separation performance of OTES@Silicalite-1 zeolite membranes was tested by a laboratory homemade pervaporation device. The membrane flux was calculated via a weighing method, the separation factor was analyzed with the solution composition data on the feed-side and permeate-side. The physical phase composition of the membranes was determined by X-ray diffractometry. The chemical bonds and functional groups of the membranes were analyzed by Fourier transform infrared spectroscopy. The microscopic morphology and elemental distribution of the membranes were determined by scanning electron microscopy. The hydrophobicity of the membranes was analyzed via water contact angle measurement.Results and discussions The separation factor of OTES@Silicalite-1 zeolite membranes shows an upward trend with the increase of the mass fraction of OTES. A part of the Si—OH on the membrane surface are replaced by OTES, and the membrane surface becomes more hydrophobic, which favors the adsorption and diffusion of ethanol molecules. At the OTES mass fraction of 3%, the OTES@Silicalite-1 zeolite membrane has the maximum separation factor. However, the separation factor decreases as the mass fraction of OTES further increases. This is possibly due to the excess OTES covering the pores on the membrane surface and affecting the transportation of ethanol. As Si—OH eliminates, the amount of Si—OC2H5 decreases, so the membrane flux trenda upward initially. However, the hydrophobicity of OTES hinders the water molecule transportation, thus reducing the membrane flux.As the temperature increases, the grafting reaction is easier to accomplish, and the hydrophobicity of the OTES@Silicalite-1 zeolite membrane enhances. At 60 ℃, the membrane shows the maximum separation factor and membrane flux. However, the separation performance of the membrane decreases slightly as the temperature further increases, which is attributed to the excessive and promiscuous organic groups that block ethanol permeation, while reducing water flux.The hydrophobicity and selectivity of the membrane improve at 5-10 h as the modification time increases. At 10 h, the membrane has the maximum separation factor. However, the separation performance of the membrane decreases sharply as the modification time further increases possibly due to the OTES cross-link with each other to form polymers, which severely block the pores of the zeolite, resulting in a significant decrease in membrane flux. Also, the transport of ethanol is impeded, thus decreasing the separation factor.Conclusions The surface modification of OTES could not damage the framework and crystal structure of Silicalite-1 zeolite membrane. It could effectively eliminate the Si—OH on the membrane surface, improve the hydrophobicity and separation performance of the membrane. The Silicalite-1 zeolite membrane showed the membrane flux of 0.92 kg·m-2·h-1 and the separation factor of 30.4 at 70 ℃ for 3.5%±0.1% ethanol aqueous solution, which was modified at a mass fraction of OTES of 3% and 60 ℃ for 10 h. Meanwhile, this membrane could also maintain a great stability during the pervaporation test for 120 h. This study indicated that alkylsilane grafting could be an effective measure to substantially improve the hydrophobicity and separation performance of Silicalite-1 zeolite membrane, having promising application prospects in the field of organic component recovery by pervaporation.

Introduction As a bulk solid waste in iron and steel industry, steel slag occupies a large amount of land, and causes environmental pollution, having a great burden to iron and steel industry and society. It is thus of great theoretical and practical significance to explore effective ways of steel slag recycling and utilization. Formaldehyde (HCHO) as a colorless, irritating smell of toxic gas is one of common volatile organic compounds (VOCs) in indoor air, which can cause chronic respiratory diseases, leukemia, and bronchial asthma and damage to the nervous system. Activated carbon (AC) is extensively used as an adsorbent for removal of HCHO. AC is an extraordinary adsorbent, but its adsorption efficiency for HCHO is low. The modification of AC using metal oxides (such as V2O5, MnO2, CuO, Fe2O3, etc.) can improve the service life of AC and its formaldehyde adsorption performance. However, the preparation cost will increase due to the high price of metal oxides. Steel slag is rich in oxides of calcium, silicon, magnesium, iron, manganese, phosphorus and other elements. Therefore, the composite preparation of ecological AC by steel slag and biomass waste materials solves the problems of high modification cost, short service life and poor absorptivity, and expands a way of high value-added utilization of steel slag.Methods Steel slag/peanut shell activated carbon (SPAC) was firstly prepared via microwave heating and phosphoric acid activation. According to the national standard of “Formaldehyde emission limit in wood-based panels and their Products of Interior Decoration Materials” (GB18580-2017), a formaldehyde absorptivity experiment by SPAC was systematically made. The porosity of samples was determined by a model ASAP 2020M surface area & porosity analyzer based on the N2 adsorption-desorption isotherm. The microscopic morphology of SPAC was analyzed by a model NANO SEM430 scanning electron microscope with energy disperse spectroscope (SEM-EDS). The elements content of SPAC in ultra-high vacuum with Al Kα laser radiation (hυ=1 486.6 eV) was characterized by a model ESCALAB250 X-ray photoelectron spectrometer (XPS).Results and discussion The result show that the sample has an excellent removal efficiency (i.e., 93.2%) under the preparation condition of 550 W microwave power, 1.25 impregnation ratio and 15% steel slag content. The correlation coefficients of the experimental results and the fitted values for the pseudo-second-order kinetic model and the Freundlich model are 0.998 0 and 0.953 7, respectively. It is indicated that the removal process of formaldehyde on SPAC is more dominant due to chemisorption. The N2 adsorption-desorption isotherm is a type IV adsorption isotherm with H3 and H4 hysteresis loops, indicating that the sample is a mesoporous material. Based on the results of SEM-EDS and XPS, steel slag is loaded into the SPAC sample and elements Fe and Mn have a crucial role for the absorptivity of formaldehyde. This study provided a reference for the exploration of steel slag based functional materials, and a theoretical support for the efficient formaldehyde removal at room temperature.Conclusions Steel slag powder could be loaded into the composite activated carbon. The prepared composite activated carbon still retained the porous structure characteristics suitable for removal of formaldehyde. The synergistic action of the elements Fe and Mn from steel slag powder was beneficial to improving the formaldehyde removal.

Introduction Ethanol is one of volatile organic compounds. Long-term exposuring ethanol vapors can cause serious human-being health problems, such as headaches, throat irritation, and liver damage dirty. In addition, the human body will have nerve paralysis, slow brain response, and uncontrolled limbs when ethanol in the human blood reaches a certain concentration, resulting in frequent traffic accidents. It is thus necessary to develop gas sensors that can monitor ethanol in the human body. Metal oxide gas sensors have attracted much attention because of their cheap price, convenient portability and stable performance. Zn2SnO4 and CaFe2O4 are novel ternary metal oxide semiconductors with the advantages of high electron migration rate, strong gas adsorption and good thermal stability, which are widely used in gas sensors. However, single Zn2SnO4 or CaFe2O4 generally has the disadvantages of poor selectivity, high operating temperature and long response-recovery time. Some studies indicate that combining two different metal oxides to construct heterojunctions could greatly improve the gas sensing properties. It is prospected that the construction of CaFe2O4/Zn2SnO4 heterojunction is an effective method to enhance the gas sensing performance. However, little work on CaFe2O4/Zn2SnO4 composite for ethanol detection has been reported yet. In this paper, a p-n heterojunction between CaFe2O4 and Zn2SnO4 was constructed by a hydrothermal method to realize the superior gas sensing properties of CaFe2O4/Zn2SnO4 composite to detect ethanol.Methods To prepare Zn2SnO4 octahedral, 2 mmol Zn(CH3COO)2?2H2O and 1 mmol SnCl4?5H2O were dissolved in 70 mL deionized water. Meanwhile, 0.1 g CTAB (cetyltrimethyl ammonium bromide) and 15 mmol NaOH were dissolved in the solution above. Afterwards, the solution was stirred for 40 min, transferred into a 100 mL Teflon-lined autoclave and heated at 180 ℃ for 24 h. After reaction, the powder was washed and calcined at 550 ℃ for 2 h to obtain Zn2SnO4 octahedral.To prepare CaFe2O4 nanorods, 1 mmol CaCl2 and 2 mmol FeCl3 were dissolved into a mixed solution of ethanol (30 mL) and deionized water (10 mL) under stirring at room temperature for 30 min. The mixed solution was transferred into a 50 mL autoclave, heated at 180 ℃ for 12 h. After reaction, the powder was washed and dried at 80 ℃ for 8 h to obtain CaFe2O4 nanorods.To prepare CaFe2O4/Zn2SnO4 composites, 2 mmol Zn(CH3COO)2?2H2O and 2 mmol Zn(CH3COO)2?2H2O were dissolved in 70 mL deionized water. Meanwhile, 0.1 g CTAB (cetyl trimethyl ammonium bromide) and 15 mmol NaOH were dissolved in the solution. The as-prepared CaFe2O4 samples were added into the Zn2SnO4 reaction mixture, and the mixture was stirred for 40 min, transferred into a 100 mL Teflon-lined autoclave and heated at 180 ℃ for 24 h. After reaction, the powder was washed and calcined at 550 ℃ for 2 h to obtain CaFe2O4/Zn2SnO4 composites. At different addition amounts of CaFe2O4 (i.e., 0.006 3, 0.012 5 g and 0.018 8 g), the CaFe2O4/Zn2SnO4 composites with different mole fractions of 2%, 4% and 6% were obtained, and marked as 2%CaFe2O4/Zn2SnO4, 4%CaFe2O4/Zn2SnO4 and 6%CaFe2O4/Zn2SnO4, respectively.Results and discussion The X-ray diffraction patterns show that Zn2SnO4 is a perovskite structure and CaFe2O4 is a clinopyrite structure. The XRD pattern of CaFe2O4/Zn2SnO4 composites is close to that of Zn2SnO4, and no CaFe2O4 diffraction peaks appear, probably due to the small amount of CaFe2O4. For the Fourier transform infrared spectra of CaFe2O4/Zn2SnO4 composites, Ca-O, Fe-O and Sn-O bonds appear at 565, 478 cm-1 and 574 cm-1 in these composites, demonstrating that CaFe2O4/Zn2SnO4 composites are synthesized. In addition, compared with CaFe2O4 and Zn2SnO4, the characteristic absorption peaks of CaFe2O4/Zn2SnO4 composites all shift slightly to the right region, confirming the existence of interfacial contact between CaFe2O4 and Zn2SnO4. For the scanning electron microscopy and transmission electron microscopy images, Zn2SnO4 is an octahedral structure with a uniform size of approximately 350 nm, while CaFe2O4 has a nanorod structure with a length of approximately180 nm. For the X-ray photoelectron spectra, elements Zn, Sn, Fe, Ca and O coexist in CaFe2O4/Zn2SnO4 composites, and Zn2SnO4 incorporated with CaFe2O4 increases the oxygen vacancy defects by the Gauss peak division method. Compared with pure CaFe2O4, Zn2SnO4 and other CaFe2O4/Zn2SnO4 sensors, 4%CaFe2O4/Zn2SnO4 sensor exhibits a prominent gas sensing performance to ethanol (i.e., a favorable selectivity to ethanol, a low detection limit of 0.07 μmol/L, fast response/recovery time of 21 s/63 s, long-term stability, and high gas response (96) toward 40 μmol/L ethanol). The superior ethanol gas sensing performance of 4%CaFe2O4/Zn2SnO4 is attributed to the formation of CaFe2O4-Zn2SnO4 p-n heterojunctions, the high content of oxygen vacancy defects, and the increased surface electron density. Therefore, CaFe2O4-Zn2SnO4 p-n heterojunction composite has a great potential application for detecting ethanol gas. Conclusions Zn2SnO4 octahedral, CaFe2O4 nanorods and CaFe2O4/Zn2SnO4 composites were prepared by a hydrothermal method. 4% CaFe2O4/Zn2SnO4 based sensor exhibited the maximum gas response of 96 μmol/L to 40 μmol/L ethanol at 400 ℃, which was 2.6 times higher than that of Zn2SnO4 and 34 times higher than that of CaFe2O4. Moreover, 4%CaFe2O4/Zn2SnO4 based sensor also achieved a long-term stability, an excellent humidity resistance, fast response-recovery time (21 s/63 s) and a low theoretical detection limit of 0.07 μmol/L for ethanol. The enhanced gas sensing properties of 4%CaFe2O4/ Zn2SnO4 could be attributed to the following factors, i.e., CaFe2O4 coupled with Zn2SnO4 decreased the electron-hole recombination efficiency, and increased the surface electron density; and the formation of p-n heterojunctions between CaFe2O4 and Zn2SnO4 increased thickness of Debye electron layer, resulting in a drastic resistance change. The appropriate amount of CaFe2O4 coupled with Zn2SnO4 could be a promising strategy to enhance the sensing performance of ethanol, having great potentials in manufacturing high response and low detection limit of ethanol sensors.

Introduction As an important part of perovskite solar cells, the electron transport layer plays a role in transporting electrons and blocking holes, having an impact on the performance of perovskite cells. ZnO is a promising electron transport layer (ETL) material because of its high electron mobility, easy synthesis, low-temperature preparation and low cost. However, the chemical properties of ZnO are unstable, and the surface defects are easy to form recombination centers, leading to the decline of electron extraction and transfer efficiency, and surface residual groups destroy the perovskite structure and reduce the stability of perovskite materials, resulting in the deterioration of device performance. Therefore, selecting a suitable modification layer to improve the stability of ZnO plays an important role in improving the performance of ZnO and perovskite batteries.Methods ZnO/Zn2SnO4 NAs was prepared on ZnO NAs surface by a spin-coating method to passivate ZnO surface defects and residual groups. ZnO/Zn2SnO4/SnO2 NAs was formed via in-situ growth of a layer of SnO2 by a hydrothermal method to improve the stability of ZnO. The phase and morphology of the heterojunction were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The photoelectric performance was measured in electrochemical workstation, in which the photoelectric response ability of the nanoarray was characterized by linear sweep voltammetry. The separation performance of photogenerated electrons and holes in nanoarrays was analyzed via the change of photocurrent. The charge transfer resistance was determined by electrochemical impedance spectroscopy. The conductive type of the semiconductor was determined via the Mott-Schottky test, and the passivation effect of Zn2SnO4 and SnO2 on the ZnO surface defects was reflected by the carrier concentration.Results and discussion The results by XRD, SEM and TEM show that Zn2SnO4 and SnO2 are coated on ZnO nanoarrays. Zn2SnO4 as a protective layer has a superior chemical stability in alkaline environment to prevent direct contact between ZnO and OH- produced by urea hydrolysis, avoiding the corrosion of ZnO. This is beneficial to improving the stability and photoelectric properties of ZnO. The linear scanning voltammetry curves of ZnO, ZnO/SnO2, ZnO/Zn2SnO4 and ZnO/Zn2SnO4/SnO2 NAs at 0-0.6 V vs. RHE under light conditions indicate that ZnO/Zn2SnO4/SnO2 NAs have the maximum photocurrent density. These results demonstrate that the photoelectric response of nanoarrays can be improved via the modification of Zn2SnO4. ZnO/Zn2SnO4 and ZnO/Zn2SnO4/SnO2 NAs modified with Zn2SnO4 exhibit a higher photocurrent. The ZnO/Zn2SnO4/SnO2 NAs photocurrent (i.e., 140 μA·cm-2) is 1.75 times greater than that of ZnO NAs photocurrent (i.e., 80 μA·cm-2). This indicates that the addition of Zn2SnO4 and the construction of double heterojunction have a positive effect on reducing the electron-hole pair recombination phenomenon and improving the photoelectric performance of nanoarray. The charge transfer resistances of ZnO, ZnO/SnO2, ZnO/Zn2SnO4, ZnO/Zn2SnO4/SnO2 NAs measured by electrochemical impedance spectroscopy are 22 403 Ω, 16 854 Ω, 7 018 Ω and 3 131 Ω, respectively. The Zn2SnO4 modified layer reduces a charge transfer resistance via passivating the ZnO surface defects and reducing the scattering effect of the defects on the carriers. The ZnO/Zn2SnO4/SnO2 co-constructed heterojunction structure promotes the separation of electron-hole pairs and electron transport at the interface, further reducing the resistance of photogenerated electrons to transfer at the interface. In the Mott-Schottky test, the carrier concentrations of ZnO, ZnO/Zn2SnO4, ZnO/SnO2, ZnO/Zn2SnO4/SnO2 NAs are 1.22×1019, 2.34×1018, 2.41×1018 and 1.18×1018 cm-3, respectively. ZnO defects are passivated by Zn2SnO4 modification, and the carrier recombination center is reduced. The carrier concentration of ZnO/Zn2SnO4/SnO2 NAs is lower than that of ZnO NAs. ZnO, Zn2SnO4 and SnO2 form a double type II heterojunction with interlaced arrangement of energy level, which drives a transfer of photogenerated electrons from high energy level to low energy level, so that the photogenerated electron-hole pair can be effectively separated at the interface, thus effectively reducing the electron and hole recombination. It also reduces a charge transfer resistance and promotes a photogenerated electron transfer from SnO2 to ZnO. The photoelectric properties of ZnO/Zn2SnO4/SnO2 (i.e., current density, photocurrent and carrier concentration) are improved.Conclusion ZnO NAs surface was coated with Zn2SnO4 nanocrystals by a spin-coating method. Zn2SnO4 reduced the recombination of photo-generated charge carriers at the interface via passivating the defects and residual groups on ZnO NAs surface. Based on ZnO surface defects passivated by Zn2SnO4, a more stable and high-density SnO2 nanoparticle coating layer was in-situ grown on ZnO/Zn2SnO4 NAs by a hydrothermal method, and the double heterojunction was formed with ZnO and Zn2SnO4. The alternating energy level arrangement could improve the separation efficiency of photogenerated charge carriers. The constructed ZnO/Zn2SnO4/SnO2 NAs had higher current density, photocurrent, lower charge transfer resistance and carrier concentration, which could be used as an electron transport layer in perovskite solar cells.

Introduction Ge/Si avalanche photodiode (APD) has attracted much attention in optical communication, optical imaging, and security detection due to its high-speed operation, low noise, high sensitivity, and optical gain characteristics. However, a mismatch between the lattice constants of Si and Ge (i.e., a difference of 4.2%) has a challenge. This mismatch leads to a high density of threading dislocations at the Ge/Si heterojunction interface, ultimately deteriorating the performance of the device. Therefore, addressing the issue of lattice mismatch and reducing the dislocation density in Si-based Ge thin films is crucial for achieving high-performance Ge/Si APDs. To decrease the dislocation density of APDs, Si-based epitaxial Ge thin films are used as a fabrication method. However, the dislocation density continues to be relatively high. In this paper, the lattice mismatch between Ge and Si was alleviated. In addition, the theoretical underpinnings were also proposed.Methods In this research, a polycrystalline silicon (poly-Si) bonding layer was incorporated at the Ge/Si interface to mitigate the lattice mismatch effects. This poly-Si layer acted as a buffer, diminishing the stress and strain induced by the lattice mismatch. To assess the influence of the poly-Si bonding layer on the performance of Ge/Si APDs, a series of experiments at different doping concentrations of the poly-Si layer were carried out. The doping concentration was pivotal as it modulated the electrical and optical properties of the bonding layer, subsequently affecting the overall performance of the APD.The charge distribution, electric field distribution, and carrier transport within the Ge/Si APD device were delineated by the Poisson equation, carrier transport equation, carrier continuity equation, and a parallel electric field dependent model. This facilitated the computation of the device's electrical characteristics. The Ge/Si APD involved electron and hole recombination, the concentration-dependent SRH model was used to characterize the spontaneous emission and Auger recombination processes of carriers. The optical radiation recombination model elucidated the photon Auger recombination process, while the trap recombination model (TRAP.AUGER) described the transition between trap states and non-trap states of carriers, along with their corresponding recombination processes. Ge/Si APD necessitated high voltage operation and substantial doping, and the band-band tunneling standard model was used to explain the carrier transport and ionization process instigated by band-band tunneling under high electric field conditions. In addition, the energy band narrowing model was used to illustrate how changes in band structure impact device performance under high doping conditions. This paper provided a theoretical analysis of Ge/Si APD device performance based on these models, and other related theories.Results and discussion The results indicate that the photocurrent of APD with a bonding layer thickness of 2 nm initially increases and subsequently decreases as the doping concentration of the bonding layer escalates at 95% of the avalanche voltage. In contrast, the photocurrent of an APD with a bonding layer thickness of 5 nm diminishes as the doping concentration increases. Furthermore, the dark current of a Ge/Si APD can reach as low as 10-10 A prior to avalanche due to the lattice mismatch buffering effect of poly-Si between Ge and Si, which is markedly lower than that of an APD based on InP. The maximum gain-bandwidth product of 63.8 GHz for the 2 nm bonding layer thickness significantly surpasses that for the 5 nm bonding layer thickness, and the bandwidth of the 2 nm bonding layer thickness also exceeds the bandwidth of the 5 nm bonding layer thickness when the bias voltage exceeds the avalanche voltage. It is recommended to select a poly-Si bonding layer with a thickness of 2 nm and a low doping concentration to achieve the optimal performance in a Ge/Si APD.Conclusions The efficacy of integrating a poly-Si bonding layer at the Ge/Si interface was under scored, thereby mitigating a threading dislocation density and augmenting the performance of Ge/Si APDs. Theoretical modeling and simulation analyses revealed that a diminished doping concentration in the poly-Si layer yielded superior outcomes. Such insights paved a way for the advancement of more dependable and efficient Ge/Si APDs, having a potential to transform domains such as optical communication, optical imaging, and security detection. The methodology delineated in this study presented a promising avenue for subsequent research within the realm of semiconductor photodiodes. For materials science and device engineering, it is anticipated that Ge/Si APDs could experience a further evolution, potentially yielding enhanced performance and expanding application potential. The incorporation of the poly-Si bonding layer signified a substantial advancement in addressing lattice mismatch challenges, which could be poised to be instrumental in the progression of next-generation photodetection technologies.

Introduction Thermal barrier coatings can be used for the stable operation of aircraft engines under high-temperature environments due to their excellent oxidation resistance, corrosion resistance and heat insulation properties. However, the high-temperature phase transition of conventional 8.0% (in mass fraction) Y2O3 stabilized ZrO2 ceramic (8YSZ) materials exists when the service temperature exceeds 1 200 ℃. Developing thermal barrier coatings, such as rare-earth zirconates and rare-earth silicate, becomes popular. (Gd0.9Yb0.1)2Zr2O7 (GYbZ)/8YSZ coatings with a low thermal conductivity and a high temperature phase stabilization are regarded as potential thermal protective materials. At present, some work focus on the preparation properties optimization of air plasma spraying, electron beam physical vapor deposition and plasma spray physical vapor deposition techniques, respectively. It is important to in-situ investigate the mechanical properties and failure mechanisms of GYbZ/8YSZ coatings at > 1 200 ℃.Methods GYbZ/8YSZ thermal barrier coatings were prepared with NiCrAlY, 8YSZ and GYbZ powders on an Inconel 600 nickel-based superalloy with the thickness of 2 mm via air plasma spraying. GYbZ/8YSZ thermal barrier coatings were subjected to thermal cycle treatments in a Muffle furnace at 1 100 ℃ for 1 h, and then cooled to room temperature for 1 thermal cycle. The times of thermal cycles were 10, 50 and 100, respectively. The phase and microstructure of the coatings were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM) before and after heat-treatments. The elastic modulus, hardness, fracture toughness and residual stress were measured by an indentation method at different temperatures.Results and discussion The XRD patterns show that GYbZ powder and the as-sprayed coating are a defective fluorite structure, and the doping of Yb3+ with small ionic radius makes the material change from a pyrochrite structure to a defective fluorite structure. In addition, the samples treated for different thermal cycles all maintain a defective fluorite structure, indicating that GYbZ has an excellent high-temperature phase stability. The SEM images show that the surface of the as-sprayed GYbZ coating has a good melting state，and massive micro-cracks are distributed on the surface, which is caused due to the quenching stress generated by the molten spray particles during the preparation process and the thermal stress generated by the mismatch between the thermal expansion coefficients between the layers. The bonding between the layers of GYbZ/8YSZ coatings is good, and the bonding interface is clear without any cracks. There are tiny pores in the interior. The distribution of elements in each layer is consistent with the design. After thermal cycling, the crack width of the coating surface gradually widens and the porosity gradually decreases. The thermal growth oxide (TGO) produced between the bond layer and the 8YSZ layer gradually increases, and the TGO grows to 20 μm after 100 thermal cycles. The generation of TGO leads to a large amount of stress concentration, leading to the initiation and rapid expansion of transverse cracks in the bonding layer and 8YSZ, and damages the structural stability of the GYbZ/8YSZ coatings. Also, some vertical cracks occur in GYbZ layer and 8YSZ layer. The results of element distribution test show that the oxygen content in the bond layer increases gradually with the increase of the number of thermal cycles. The creation of vertical cracks in the coating promotes the diffusion of oxygen, thus accelerating the growth of heat-grown oxides.The results of mechanical properties test show that the elastic modulus and hardness of GYbZ/8YSZ coatings surface firstly increase and then decrease with the increase of thermal cycle, and have the maximum values at 50 thermal cycles. After thermal cycling, the coating is sintered and its densification is improved, resulting in an increase in the elastic modulus and hardness. After 100 thermal cycles, the coating oxidation is serious, the binding force between coatings is weakened, massive vertical cracks occur in the coating, the coating structure is damaged, the deformation resistance is weakened, and the elastic modulus and hardness are reduced. The hardness of the coating decreases from 5.09 GPa to 2.20 GPa from room temperature to 700 ℃. At 700-1 100 ℃, the hardness of the coating is 2.00 GPa. The residual stress of the as-sprayed coating is -41.02 MPa. The residual stress accumulates due to thermal expansion mismatch of coating system during thermal cycling. After 10 thermal cycles, the residual stress accumulates to -147.30 MPa. After 50 thermal cycles, the stress relaxation caused by cracks gradually reduces the residual stress. After 100 thermal cycles, the residual stress decreases to -105.92 MPa. The results show that the residual stress of the coating before and after thermal cycling is a compressive stress. The fracture toughness of the as-sprayed GYbZ coating is 0.93 MPa·m1/2. The fracture toughness of the coating firstly increases and then decreases with the increase of the number of thermal cycles, and has a maximum value of 2.02 MPa·m1/2 after 50 thermal cycles. After heat-treatment, the pores of the coating reduce, and the dense area and the compressive stress can prevent the crack propagation. Some microcracks can increase the strain tolerance of the coating to a certain extent, and enhance the fracture toughness of the coating. After 100 thermal cycles, oxidation and massive destructive cracks lead to the instability of the coating structure, the increase of defects and the decline of performance.Conclusions The pore distribution in the as-sprayed GYbZ/8YSZ coatings was uniform, and the bonding interface of each layer was clear. Before and after thermal cycling, GYbZ coating was a defective fluorite structure and had an excellent high-temperature stability. The density of the coating increased with the increase of the number of thermal cycle, occurring some transverse and vertical cracks, and the TGO thickness grew to 20 μm. After 50 thermal cycles, the elastic modulus and hardness reached the maximum values, which were 182.01 GPa and 9.13 GPa, respectively. From room temperature to 700 ℃, the coating hardness reduced to 2.20 GPa. At 700-1 100 ℃, the coating hardness was 2.00 GPa. During the thermal cycle, the residual stress of the coating varied from -41.02 MPa to -123.67 MPa, and the fracture toughness varied from 0.93 MPa·m1/2 to 2.02 MPa·m1/2.

Introduction SiC-based ceramic matrix composites (SiC-CMCs) can meet both of these conditions for excellent high-temperature strength and oxidation resistance simultaneously, making them highly promising lightweight structural materials for future aerospace engine applications. Si dioxide generates volatile Si(OH)4 compounds when reacting with water molecules in the high-temperature environment of an engine in which there exists water and oxygen corrosion. With the progress of the reaction, the SiC substrate is continuously lost, resulting in a sharp decline in the physical and chemical properties of CMCs. Therefore, environmental barrier coatings (EBCs) are needed to be coated on the CMCs surface to prevent the materials from being damaged by corrosive media such as water vapor and improve the service life of SiC-CMCs.Si/Yb2Si2O7 EBCs is formed by a relatively mature controllable preparation method, and its resistance to water vapor corrosion is a key to the related research. Jian et al. found thatYb2Si2O7 coating had an excellent phase stability under the water vapor corrosion at 1 300 ℃. The growth of thermally grown oxides (TGO) was effectively controlled. The oxidation weight gain rate of the coated sample was lower than that of the uncoated sample, thus indicating that Yb2Si2O7 topcoat could have an excellent corrosion resistance. Zhang et al. observed a “self-healing” reaction of Yb2Si2O7 topcoat in the water vapor corrosion at 1 350 ℃, and the growth of the TGO layer showed a positive linear relationship with time, and the overall structure of the coating was basically intact. Ridley et al. reported that after Yb2Si2O7 topcoat was subjected to water vapor corrosion at 1 400 ℃, a porous Yb2SiO5 layer was formed, the thickness and pore size increased with time, and a distinct layered structure appeared in the reaction layers in the high-speed area, i.e., a porous Yb2SiO5 layer, a dense Yb2SiO5 layer, and a highly porous Yb2O3 layer. The existence of the dense layer hindered the inward diffusion of water vapor and oxygen, reducing the total thickness of the reaction layer and effectively protecting SiC substrate. In this paper, a gradient structure yttrium silicate-based environmental barrier coating was prepared for the improvement of high-performance aero-engine thermal protection coating material. In addition, the continuous water vapor damage behavior and corrosion mechanism at 1 350-1 500 ℃ were also investigated.Methods SiC composite samples were cut to a cube of 10 mm × 10 mm × 10 mm. Si bond coat (~50 μm) and Yb2Si2O7 topcoat (~200 μm) both were deposited by an air plasma spray technique in an air plasma spray system. These samples were annealed in vacuum at 1 300 ℃ for 2 h before the corrosion test. The equipment used for continuous water vapor exposure was a self-designed experimental platform. And the coating samples were placed in a flowing 90% (in volume) H2O-10% O2 under an atmospheric pressure. For the experiments, the furnace temperature was set at different temperatures (i.e., 1 350, 1 400, 1 450 ℃ and 1 450 ℃), respectively. The ten samples were prepared in a zirconia crucible. Finally, the sample was removed from the furnace tube at each temperature for different durations (i.e., 50, 100, 150 h and 200 h).The composition phases on the surface of the samples were analyzed by a model XD-3 X-ray diffractomter (XRD, Aeris Co., the Netherlands). The microstructure of the sample cross section and the thickness of the TGO layer in secondary electron (SE) and backscattered electron (BSE) images were determined by a model MIRA 3 emission-scanning electron microscopy (SEM, Tescan Co., Czech Republic). The element distribution and proportion were characterized by an energy dispersive X-ray spectroscope (EDS).Results and discussion After 200 h water vapor corrosion, the coatings at different temperatures show different results. At 1 350 ℃, the coating shows a transformation from Yb2Si2O7 phase to Yb2SiO5 phase, as well as some holes appear due to the volatilization of Si(OH)4. The coefficient of thermal expansion (CTE) mismatch results in a “fragmented” layer on the top of the coating. At 1 400 ℃, a “self-healing” reaction occurs in the coatings. The proportion of Yb2Si2O7 phase increases slightly, and some transverse cracks heal. The “self-healing” reaction is related to Si(OH)4 concentration. Also, Yb2O3 phase appears, and some cracks occur due to the CTE mismatch. At 1 450 ℃, a black phase (i.e., Yb3Al5O12) appears on the top of the coatings. Gaseous Al(OH)3 diffuses into the coating, and a dark mullite phase forms. The “self-healing” reaction still exists at 1 450 ℃. At 1 500 ℃, many transverse cracks appear on the top of the coatings, the “self-healing” reaction is inhibited, Yb2O3 phase appears at the coating interface, and many cracks and holes occur inside the coating. The coating mass gain and TGO growth are linearly related to the corrosion time at <1 500 ℃, but they are not related to the corrosion time at 1 500 ℃.Conclusions After 200 h continuous water vapor corrosion at 1 350-1 500 ℃, Yb2Si2O7 topcoat exhibited an excellent phase stability, and TGO layer grew at a slow rate. This indicated that Si/Yb2Si2O7 bi-layer EBCs could have a good corrosion resistance, and the preparation process of the fully covered sample could reflect the protective effect of the coating on the SiC substrate. The corrosion mechanisms were different at different starting temperatures. At 1 350 ℃, the reaction volume of Yb2Si2O7 and water vapor decreased to generate cracks, and the CTE mismatch of the product Yb2SiO5 led to crack expansion. At 1 400 ℃ and 1 450 ℃, the “self-healing” reaction gradually played a dominant role, and the new phase generated by the penetration of Al(OH)3 led to some holes in the coating. At 1 500 ℃, water vapor diffused to Si/Yb2Si2O7 coat interface in the later stage of corrosion and reacted to produce Yb2O3 phase, resulting in channel cracks at the TGO layer interface.

Introduction Clay mineral crystals are mostly formed by stacking layers of silicon-oxygen tetrahedral sheets and aluminum-oxygen octahedral sheets. They basically have water absorption and expansion because of their unique layered crystal structure. Clay minerals after hydration and expansion usually cause serious engineering problems, which have a negative impact on engineering construction. They have received extensive research attention. It is generally believed that the hydration expansion of clay minerals is mainly divided into two stages, i.e., crystal expansion and osmotic expansion. Crystal expansion is caused by the expansion of water molecules into the interlayer of clay minerals. Permeation expansion is due to the lattice substitution of clay minerals, which leads to the imbalance of valence and electricity of the crystal. Massive exchangeable ions are gathered on the surface of the crystal. After these ions are dissociated in water, they will repel each other with negative charge under the action of the diffusion double layer, resulting in expansion. Compared with osmotic expansion, the degree of crystal expansion is small, kaolinite, illite, pennine and other interlayer cation-free clay minerals do not have an expansibility. However, the problem of expansion disaster occurs under the working condition rich in pennine, indicating the research value of pennine hydration expansion. However, the water absorption characteristics, expansion characteristics and hydration mechanism of pennine in nano-scale are not yet clear, and related research needs to be carried out. In this paper, a molecular dynamics study on water absorption of mesophyll pennine was carried out to explain the hydration characteristics of mesophyll pennine nanocrystal structure. The changes of energy, structure and chemical bond of mesophyll pennine in the process of hydration expansion were discussed.Materials and method The ring cutter samples with different pennine contents (i.e., 0%, 20% and 100%) were prepared with pennine mixed with quartz. The no-load expansion rate was measured. The particle size of the soil sample was controlled to be 200 mesh (0.075 μm), the density of the soil sample was 1.8 g/cm3, and the initial water content was 10%. The hydration degree of pennine with different water contents was analyzed by thermogravimetric analyzer, and the water content controlled was 0%, 5% and 10%. The microstructure and crystal parameters of pennine samples were analyzed by X-ray diffractometer and scanning electron microscope. The crystal model was established based on the results of the microscopic test. The sorption module was used to carry out the adsorption test. A hydration model containing different amounts of water molecules was established through the adsorption test. The geometry optimization task under the Forcite module was used to optimize the structure of the model. The molecular dynamics simulation of the model was carried out using the Dynamics task under the Forcite module, and the expansion deformation of pennine was simulated via dynamic calculation under the NPT ensemble. The Clayff force field suitable for clay minerals was used in the simulation process. The simulated temperature is 298 K and the simulated pressure is 0.001 GPa. The time step is 1 fs, the number of iteration steps is 100 000, and the truncation radius is 12.5 ?. The charge calculation method is the Forcefield Assigned. The non-bond energy Coulomb interaction was calculated by the Ewald sum method. The van der Waals interaction energy was calculated by an atom-based method.Results and discussion The experimental results of the no-load expansion rate show that the no-load expansion rate of the ring knife sample increases with the increase of the content of pennine, indicating that the pennine has an expansibility. The thermogravimetric analysis shows that the higher the initial water content is, the higher the degree of hydration of the pennine will be. In addition to the free water adsorbed between the particles, some water molecules are bonded between the crystal layers via hydrogen bonding. The results of molecular dynamics simulation show that pennine is electrically neutral due to the simultaneous substitution of high-valence cations and low-valence cations, so the crystal expansion occurs. After the water molecules enter the interlayer, they are embedded in the hexagonal holes of the silicon-oxygen backbone layer. The oxygen atoms in the water molecules form a hydrogen bond connection with the hydroxide ions in the talc layer, which controls the hydration limit of the pennine crystal. In the process of hydration and expansion of pennine, it is dominated by electrostatic interaction energy, and followed by van der Waals force, and the bond stretching energy is the smallest. Compared with montmorillonite, pennine hydration is more difficult. The peak of the radial distribution function of water molecules shifts to the right as the degree of hydration increases, indicating that the spacing of water molecules and the diffusivity of water molecules increase. After massive water molecules enter the crystal, the total number of hydrogen bonds increases, the average coordination number of oxygen atoms and hydrogen atoms increases. However, the hydrogen bond length increases, the bond angle decreases, and the crystal expands.Conclusions The experimental and simulation results showed that when water molecules entered the interlayer of the crystal, pennine expanded slightly, which was consistent with kaolinite and illite without cations in the interlayer. The hydration expansion of pennine conformed to the linear growth law as a whole. Pennine crystals continued to expand until the limit as the hydration degree increased. The lattice constants in the limit state were a of 21.52 ?, b of 18.61 ?, and c of 14.54 ?. The limit adsorption amount of the crystal was controlled by the crystal structure. After water molecules entered the interlayer of the crystal, the adsorption site was in the hexagonal holes of the silica backbone layer, and each hexagonal hole could only adsorb one water molecule. When the water-absorbed pennine expanded under dynamic conditions, the electrostatic interaction energy was the largest, the van der Waals force was the second, and the bond stretching energy was the smallest. When water molecules entered the interlayer of pennine, hydrogen bonds could be formed or strengthened. The coordination number of hydrogen and oxygen and the length of hydrogen bond formed increased, but the bond angle decreased with the increase of the number of water molecules.

Introduction Radiation resistant optical fiber panel is a kind of optical fiber material device with special functions. As a core component of X-ray radiology, this fiber material is widely used in digital X-ray imaging, pet medical treatment, security inspection, industrial nondestructive testing and food safety testing. The industry entry threshold for radiation resistant fiber optic panels is relatively high. The existing market of high lead glass materials for radiation-resistant optical fiber panel is basically monopolized. To ensure high visible light transmittance, good thermal stability, and chemical stability of glass materials used in radiation resistant fiber optic panels, a higher content of PbO is introduced into the glass composition to further improve its refractive index and X-ray absorption performance In this paper, the main factors (i.e., temperature, atmospheric pressure and raw material) affecting the volatilization of PbO in the melt of high-lead glass for radiation-resistant optical fiber panels were analyzed.Materials and method A yellow lead was selected as a raw material to introduce lead into the glass, and the experiments were carried out at different melting temperatures. The melting temperature was optimized based on the experimental results. The atmosphere pressure of crucible kiln changed to further control the volatilization of radiation-resistant glass in the melting process. Under the optimal process conditions, a more effective way to control volatiles was explored via changing the lead oxide introduction method. Also, the volatiles of the glass melt with different raw material introduction methods were determined by energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS), and the main components and contents of the volatiles were analyzed.Results and discussion In the mixed materials with the same lead oxide content, the glass in the melting process of volatile amount decreases, and the volatility rate decreases from 2.00% at 1 530 ℃ to 1.53% at 1 500 ℃ as the melting temperature decreases. In addition, when the melting temperature decreases < 1 500 ℃, hard-melt substances in the glass sample appear possibly due to the enrichment of CaO, LaO and PbO. At 1 500 ℃, the volatilizing amount of glass decreases with the increase of atmospheric pressure in crucible, and the volatilizing rate decreases from 1.53% at 0 MPa to 0.80% at 0.4 MPa. When the pressure of the gas further increases, it leads to massive stripes on the surface of the glass liquid, affecting the quality of the product. At the same lead oxide content in the mixing material, melting temperature and ventilation pressure, lead oxide is introduced into the glass by two approaches, i.e., lead is introduced into the glass with yellow lead as a raw material, and lead is introduced into the glass with red lead as a raw material. Based on the results of composition test and analysis of the glass material obtained by melting, the glass in the melting process of volatile amount decreases, and the volatility rate decreases from 0.80% to 0.51% when red lead is used to introduce lead into the glass. From the EDS spectra of volatile sample, lead oxide volatilizes in glass material during melting process. As yellow lead is used as a raw material to the glass introduction, the percentage of lead atoms in the volatiles is 35.44%. As red lead is used as a raw material, the percentage of lead atoms in the volatiles is 22.21%. The XPS spectra of volatile samples with two different lead introduction methods show that element lead is the main valence state, the valence state is auxiliary.Conclusions The influences of melting temperature, ventilation pressure and raw material introduction mode on the volatiles in the glass melting process were investigated. At the melting temperature of 1 500 ℃, the ventilation pressure of 0.4 MPa, and red lead as a raw material to introduce lead into the glass, the volatile amount of volatiles in the glass melting process was effectively controlled, and the volatility of lead oxide was reduced from 2.00% to 0.51%. At the melting temperature of 1 500 ℃ and ventilation pressure of 0.4 MPa, red lead or yellow lead as a raw material to introduce lead, the valence state of Pb element in the glass melting volatiles was mainly tetravalent, and the divalent was auxiliary. The content ratio of tetravalent lead and divalent lead was 4.79 and 4.94, respectively.

There are many applications for terahertz (THz) waves at different frequencies from 0.1 THz to 10 THz and different wavelengths between millimeter waves and infrared light. THz waves have attracted recent attention due to their extensive applications in detection, imaging, and communication. In terms of the properties of natural materials to THz waves, THz modulation devices have some limitations due to the natural material properties. THz metamaterials, which use periodic structures to modify the phase, amplitude, polarization, and propagation mode of THz waves, can overcome the limitations of natural materials. Compared to passive metamaterials with fixed optical properties, active metamaterials are more capable of reconfiguring and programmability. An active metamaterial can be achieved via combining metamaterial structural units with tunable functional materials. Vanadium dioxide (VO2), undergoing a metal-insulator phase transition, exhibits modulation depths exceeding 85% in electromagnetic wave transmittance from infrared to THz frequencies. Compared with other phase transition materials (i.e., GeTe), the phase transition temperature is closer to room temperature. VO2 has a promising application in active THz metamaterials due to its characteristics. This review represented the design principles and development of reconfigurable THz metamaterials based on VO2, emphasizing the structural design and performance of devices for tunable THz modulation. The structure and performance of VO2-based THz metamaterials were described.In the first part of this review, the application of VO2 in tunable THz metamaterial absorbers is represented. The phase transition of VO2 alters the equivalent resistance, capacitance and inductance of the periodic pattern via replacing the conventional surface metal patterns of absorbers with patterned VO2, resulting in tunable resonance absorption frequencies and absorption rates. Moreover, combining VO2 with different resonance patterns or other functional materials can further enhance the modulation depth and modulation frequency of THz absorbers.In the second part of this review, we discuss the application of VO2 in THz modulator devices based on the electromagnetically induced transparency (EIT) effect. The EIT effect in metamaterials is achieved via coupling "bright modes" and "dark modes" in an external field to generate a transparent window. Integrating VO2 into such terahertz metamaterials can improve the instability issue of traditional materials in exciting the EIT effect and further enhance the tunability of metamaterials. This approach also provides a feasible solution for information encryption. In addition, compared to conventional metamaterials for wavefront manipulation, the combination of VO2 and metamaterials allows a simultaneous manipulation of the amplitude and phase of THz waves, which significantly improves a holographic imaging quality and offers a design approach for THz imaging, optical encryption, optical communication, and other applications. Note that although the phase transition performance of vanadium dioxide can be adjusted theoretically, the thermal control method is susceptible to the influence of thermal diffusion from neighboring units, resulting in a thermal crosstalk. It is thus essential for future efforts increasing unit density and improving the quality of holographic imaging to integrate low thermal conductivity materials between unit structures.In the final part of this review, we introduce the use of VO2 in THz programmable metamaterials. Programmable metamaterials provide some design concepts and directions for metamaterials development. Combining VO2 with metamaterials and the hysteresis effect of first-order phase transition, VO2 demonstrates as a nonvolatile storage component in programmable metamaterials. In this approach, transition states are stored as "memory", allowing for intelligent THz electromagnetic information processing, and this memory functionality can be also used for adaptive control.Summary and prospects Despite the development of tunable THz metamaterials based on different principles, there are some challenges associated with the difficult etching of VO2 as well as the limited precision of the process. In addition, VO2 is not the most stable phase of vanadium oxide, which is greatly affected by oxygen during etching, affecting the performance of THz metamaterial devices. For future applications, power consumption and response time must be considered. It is therefore possible to achieve lower power consumption and faster thermal response time via doping vanadium dioxide or tuning the stain by the substrate to lower the phase transition temperature, although this may introduce some challenges such as a decrease in the magnitude of the conductivity change after the phase transition and a reduction in modulation depth. By contrast, it is possible to significantly improve the response time of devices by using pulsed intense laser excitation. Furthermore, machine learning and other methods can be integrated to achieve additional structural optimization. Field-programmable gate array (FPGA) controlled programmable metamaterials, which can switch different functions via changing input encoding sequences in real time, and greatly extend the application of metamaterials by dynamically manipulating electromagnetic waves. Metamaterials application and functionality will be enhanced by adding sensors to detect temperature, humidity, illumination, etc., facilitating the development of intelligent electromagnetic metamaterials with tunable properties in the future.

With the rapid development of science and technology and the growth of human demand for green energy, lithium-ion batteries as an efficient and reliable energy storage solution are widely used in batteries, power batteries and energy storage batteries. The effectiveness of these batteries is highly contingent on the quality of their electrode materials, with an emphasis on the anode. To meet the growing demand for batteries with a high energy density and an extended cycle life, some innovative approaches are explored to anode material. Despite the strides made in enhancing anode performance, the existing challenges include the often-expensive manufacturing processes and raw materials involved. This factor hinders widespread adoption and affordability in a large scale. A focus in the field shifts towards the next generation of anode materials for lithium-ion batteries. The pursuit of materials are high-performance and cost-effective.Clay minerals as vital mineral resources have natural unique micro-/nano-structures, substantial specific surface area, and good thermal/chemical stability, which have broad applications in environmental remediation, mechanical manufacturing, and petrochemical industries. A recent focus on clay minerals extends to energy storage, particularly in the field of lithium-ion battery anode materials. Clay minerals can serve as inorganic templates for crafting carbon-based anode materials and act as precursors for silicon-based anode materials in lithium-ion batteries due to their abundant silicon elements and micro-/nano-structures. Despite the existing research, there is still a gap in meeting commercialization needs. Summarizing research progress is thus crucial to unearth a potential of clay minerals in preparing anode materials for lithium-ion batteries and advancing their commercialization.This review was to sort out the coupling between the structural features of clay minerals and the structure/ properties of clay mineral-derived nanomaterials. This review categorized clay minerals by ionic type, providing a detailed description of natural clay minerals, particularly the often-overlooked anionic clay minerals, in a systematic manner. Clay mineral-derived nanomaterials are classified into carbon-based and silicon-based materials, accompanied by detailed preparation methods. This review also outlined the specific applications of clay mineral-derived carbon-based and silicon-based nanomaterials in lithium-ion battery anode materials. In addition, some challenges hindering the commercialization of clay mineral-derived anode nanomaterials in the lithium-ion battery anode field were summarized.Summary and prospects Clay minerals with their distinct morphology, crystal structure and surface physicochemical properties have some advantages in the realm of carbon-based and silicon-based materials, having an application potential in commercialized lithium-ion battery anodes. However, the preparation of clay mineral-derived nanomaterials and their commercialization as anode materials still have several challenges.Clay minerals from different geographic environments or mineral sources, along with differing origins and purification methods have challenges to ensure uniformity in the structure and performance of clay mineral-derived carbon-based and silicon-based materials. To address this, there is a need to strengthen mineralogical and process research of clay minerals from diverse origins, structures, and compositions. This can contribute to a comprehensive understanding of the diversity and complexity of clay minerals, and provide abundant basic data for the subsequent development of low-cost, green and efficient clay mineral purification methods and modification technologies.The preparation of clay mineral-derived silicon nanomaterials through magnesium thermal reduction has some challenges like impurities in the products and inhomogeneous properties. The existing process is in the laboratory stage, and there is a need to improve the magnesium thermal reduction method or develop cost-effective methods for producing high-performance silicon nanomaterials to enhance commercialization possibilities. Improving reaction condition (i.e., slower ramp rates, staged ramping and the use of thermal scavengers) can mitigate some issues related to excessively high temperatures and ensure product quality. The emerging electrochemical reduction method is also in the early stages of development and requires a continuous improvement.The development of low-cost and simple preparation methods for silicon/carbon nanocomposites is crucial for their scale-up applications. The development of more low-cost preparation techniques for silicon/carbon nanocomposites in combination with the easily tunable structure and properties of clay minerals is expected to accelerate the commercialization of silicon/carbon anode materials.Clay mineral-derived nanomaterials are widely used in lithium-ion battery anode materials. The further developments on raw materials, preparation methods, and performance optimization are essential to meet commercialization demands. Collaborative research efforts between academia and industry are crucial to exploring key issues in the preparation process. Accelerating the transition from laboratory-scale research to industrial manufacturing via combining practical production experience with advanced technology through industry cooperation is vital for the in-depth development of clay mineral-derived nanomaterials in lithium-ion battery anode materials.

Lithium-ion batteries are considered as one of the most promising energy storage devices in the field of renewable energy due to their high energy density, low weight density, long cycle life, and lack of memory effect. The commonly used powder electrode in commercial lithium-ion batteries has some issues such as a poor rate performance and a significant volume expansion, leading to a poor battery cycle stability. The development of fiber materials with advanced nanostructures is a crucial approach to address these challenges. Nanofibers offer unique advantages including high specific surface area, excellent mechanical strength, and good flexibility. When utilizing a negative electrode material for lithium-ion batteries, nanofiber electrodes can accommodate large volume changes and provide an interconnected conductive path during battery cycles. Various anode materials with a carbon nanofiber structure can be prepared by an electrospinning technology. Carbon nanofibers have attracted much attention due to their special nanostructure, outstanding mechanical properties, large specific surface area at the electrode-electrolyte interface, short ion transport length, and efficient longitudinal electron transport. In addition, a variety of lithium-ion battery anode materials can be encapsulated in carbon nanofibers, and special structures such as porous, hollow, and core-shell can be formed via simply changing the parameters of electrospinning or controlling the shape of the fibers during annealing. This special structure has a large specific surface area and enough gap space, which can withstand the volume change during the lithium ion embedding process, and has a large surface area. It can also provide a more open channel for the rapid migration of ions and electrons, thereby improving electrochemical performance and meeting the growing demand for lithium-ion batteries. The electrospinning technology becomes the main method to prepare various nanofiber structures of lithium ion batteries.In this review, the spinning principle of carbon nanofibers and its influencing factors were introduced. And carbon nanofibers prepared by electrospinning were described as a lithium storage mechanism for lithium-ion batteries. Also, carbon nanofiber anode materials for lithium-ion batteries prepared by electrospinning were recommend. The effects of element, metal oxide, polyoxide and sulfide on the structure and properties of carbon nanofiber composite anode materials were described.Elements such as silicon and tin possess a high theoretical energy density and a low working potential. Unfortunately, their poor conductivity and cycling performance limit their commercialization. Dispersing such elemental nanoparticles into carbon nanofibers can effectively improve cycling performance. Metal oxides can serve as electrode materials, exhibiting outstanding electrochemical properties such as high specific capacity, excellent cycle stability, and cost-effectiveness. In addition, metal oxides also have a variety of oxidation states, which are flexible in terms of material design. However, metal oxides have the disadvantages of a high working voltage and a poor electrical conductivity. The composite of two or more kinds of multi-metal oxides with carbon nanofibers can effectively reduce the working voltage and improve the electrical conductivity. Compared with metal oxides, transition metal sulfides usually have higher electrical conductivity, theoretical specific capacity and cycling stability. Metal sulfides can be incorporated into carbon nanofibers to construct carbon metal sulfide materials, which can effectively improve the electronic conductivity.Summary and prospects Although the application of electrospinning technology address certain issues with lithium-ion batteries and a significant number of controllable negative electrode materials are reported, several factors must be taken into consideration when designing the more optimal structures to meet the market demand for high-performance lithium-ion batteries. Developing nanofibers with a diameter less than 50 nm as smaller nanofiber materials can provide shorter diffusion paths and faster lithium ion intercalation kinetics. The preparation of micro-/nano-structured composite fibers, such as using multi-nozzle electrospinning technology to achieve composite fibers with controllable size and morphology, introducing heteroatoms into nanofibers, the presence of heteroatoms on the carbon surface can improve the reaction activity and conductivity, thereby enhancing the storage capacity of lithium ions. Electrospinning flexible batteries can be also developed. For lithium-ion battery flexible negative materials, flexible negative materials have high porosity and interconnected open-hole structures, which can improve the ionic conductivity and mechanical strength, so they can be more suitable for electrode materials used in lithium-ion batteries. In addition, electrospun nanofiber materials can be applied in energy conversion and storage devices such as fuel cells, solar cells, lithium-ion batteries, and supercapacitors. This review is of great significance for the development of these energy storage devices and also paves a way for advanced battery systems such as lithium sulfur batteries, sodium-ion batteries, and lithium-air batterie. It is indicated that high-performance electrospinning technology could be applied in high-performance advanced battery systems in the near future.

With recent development on various functional crystal materials and large-size crystal preparation technologies, the reliance on experience and technological bottlenecks in traditional crystal growth becomes increasingly prominent. To meet the growing theoretical and technical demands, some methods and technologies for crystal growth are developed. Also, the development of computer science and machine learning technologies provides some opportunities in this field. Machine learning, through the analysis of vast amounts of data, can automatically extract the underlying knowledge and patterns, thereby enabling a prediction of crystal structures and an optimization/control of the crystal growth process.Crystal structure prediction involves determining the microstructure of a crystal under given chemical compositions. Traditionally, the structure of crystals can be just determined through the related experiments. However, the experimental methods are time-consuming and costly processes. In contrast, machine learning methods can learn from the crystal structural data and predict the structure of crystals without the experiments. A series of crystal structure prediction softwares named CRYSPNet, USPEX, and CALYPSO are developed.Conventional methods of optimizing growth conditions usually require extensive experience and experimental trial-and-error. Machine learning, via analyzing the existing data on crystal growth, can predict the optimal parameter combinations, guide the selection of parameters in actual production and accelerate the optimization process. Compared to conventional experiments and CFD simulations, machine learning offers faster and more accurate predictions. For instance, model construction based on neural networks is approximately 107 times faster than the CFD simulation. The application of such novel technologies in crystal growth can promote the research and development in the related fields.The crystal growth process is complex and variable, involving the interaction of multiple factors. Conventional control methods largely rely on experience and actual operations. However, with the application and development of machine learning and automatic control methods, crystal growth control is no longer limited to subjective and empirical judgments, but can leverage the capabilities of computer algorithms and data analysis to achieve more accurate and precise control of crystal growth. Machine learning via utilizing large datasets to train and optimize machine learning models can predict and determine the dynamic changes in crystal growth, and timely adjust and control, thereby achieving an effective control over the crystal growth process.Summary and prospects This review provided a brief summary of the research progress in the application of machine learning to crystal growth, and discussed mainly three aspects, i.e., crystal structure prediction, optimization of crystal growth conditions, and methods of controlling crystal growth. In terms of crystal structure prediction, machine learning achieves significant results, but the accuracy and computational efficiency still need to be improved, especially for large-size, multi-component complex systems. In the future, it is necessary to further improve and develop algorithms to increase the accuracy and computational efficiency of prediction models. Regarding the optimization of crystal growth conditions, machine learning methods can predict the optimum parameter combinations, speeding up the optimization process. However, there are still some issues with data accuracy, process complexity, and model interpretability that need to be addressed. Future work should involve the integration of more machine learning algorithms, combined with theoretical and practical research, to develop reliable and interpretable models. In terms of methods for crystal growth control, machine learning algorithms can precisely control the crystal growth process, improving the stability and quality of crystal growth. However, there are still some challenges such as in-depth studies on the physical mechanisms of crystal growth, the laws of control, and the simulation of complex systems with multiple coupled factors. In the future, it is necessary to combine advanced machine learning algorithms and optimization methods to enhance the simulation of multi-factor coupling and complex systems, further improving the control capability of crystal growth.

Silicon carbide (SiC) as a third-generation semiconductor material with stable chemical properties is currently the most widely used wide-band material. Moreover, SiC has significant advantages such as a high device limit temperature, a high critical breakdown field strength, and a high thermal conductivity. SiC single crystals with high-quality, large-size, low-cost can be used in large-scale SiC applications.The high-temperature solution growth method (HTSG) for growing SiC offers some advantages such as reduced crystal dislocations, ease of operation, feasibility of P-type doping, and low cost. These advantages can compensate for the drawbacks of high energy consumption, poor crystal quality, and high costs associated with the crystal growth process of the physical vapor transport (PVT) method. Nevertheless, the selection of solvents in the HTSG method is a key factor in improving the crystal growth efficiency and growth quality. The existing mainstream systems of the HTSG method are Si-Cr binary system and Si-Cr-Al ternary system.4H-SiC has a hexagonal lattice point and a cubic lattice point, and the diatomic layers are connected in the form of ABCB-ABCB. Therefore, a regular atomic arrangement is needed to avoid the entrapment of other solvent atoms. For a deeper understanding of advances in solvents for the growth of 4H-SiC single crystals by HTSG technique, this review firstly summarized the research history of the solvent, analyzed the influence of the solvent system on the crystal growth from different perspectives of thermodynamics, and gave different methods used for solvent research. Finally, this review represented the crucial points and difficulties in the research of solvents in the growth of 4H-SiC single crystals by high-temperature solution growth method.Summary and prospects Recent research on co solutions for the growth of SiC single crystals by HTSG method through various methods is represented. The research scope of solvents involves thermal physical performance parameters, C dissolution, thermochemical properties, thermodynamic properties, and other aspects. However, the existing research has not yet identified the optimal solubilizing system from a theoretical perspective, as well as the substantial impact of element ratios in various solution systems on crystal growth. There are still several difficulties in the research of solutions as follows: 1) It is difficult to test the mixed solution due to the high experimental temperature of the HTSG method. At present, it is possible to roughly predict the thermal and physical performance parameters of solutions through theoretical calculations, but equipment for the related experiments is unavailable and the cost is also high. Effectively improving the accuracy of simulation and conducing accurate predictions for experiments can be achieved via in-depth research on the changes in thermal and physical performance parameters of solutions. 2) The concentration of C in the solution is a key factor affecting the quality of crystal growth. The concentration of C is investigated both theoretically and experimentally under ideal conditions of thermal equilibrium. The seed crystals can experience melt-through during the remelting process of crystal growth, if the concentration of C in the solution is too low. On the contrary, if the concentration of C in the solution is too high, it is likely that crystallization can occur before the impurities on the surface of the seed crystal are completely melted. The situations above could seriously affect the quality of the crystal growth. It plays an important role in improving crystal quality via in-situ detecting the changes in C concentration inside the crucible.3) The existing HTSG method usually uses graphite crucibles as a C source for crystal growth. As the temperature inside the crucible increases, graphite crucible is continuously corroded by the solution, presenting different shapes. Different shaped crucibles can seriously affect the stability of the flow field inside the crucible, and even change the trajectory of the flow field. In-depth research on the corrosion process of graphite crucibles by auxiliary solutions can effectively avoid negative effects caused by changes in flow field and temperature field in the later stage of growth.Although there are still some difficulties to overcome in the study of solvents for the growth of SiC single crystals by the HTSG method with the continuous efforts of numerous research teams, some key issues are constantly proposed and solved. The research on solvents can also accelerate the pace of HTSG method for growing SiC single crystals, opening a door to low-cost and low-energy SiC single crystal growth.

Proton ceramic cells (PCCs) are widely investigated as devices for power generation, energy storage, and sustainable chemical synthesis because of their moderate operating temperature, high efficiency and great application prospects. Nevertheless, a main challenge for oxygen electrode of PCCs remains the sluggish kinetics of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) at intermediate and lower temperatures as well as the insufficient stability of the oxygen electrode materials in the operating environment. Designing and developing high-performance and durable oxygen electrodes is thus crucial for promoting the industrial application of PCCs technology. This review discussed the relationships among composition, structure and electrochemical performance of oxygen electrode materials and summarized the factors that impact the stability of oxygen electrode. The stability of electrolyte and oxygen electrode interface under high steam condition, CO2 atmosphere and Cr atmosphere was discussed. In addition, a future research in oxygen electrode stability was also proposed.The elementary reactions at the oxygen electrode include oxygen adsorption and dissociation, charge/oxygen/proton transfer, as well as water formation and exhaust. It is considered that protons can play a critical role in the reaction process on the oxygen electrode in addition to electrons and oxygen ions based on the elementary reactions occurring on the oxygen electrode. Triple ion-electronic-protonic conducting (TIEC) materials can extend the triple-phase boundary (TPB) area to the entire surface of the oxygen electrode. Besides the basic requirements of high activity and electrochemical performance, the oxygen electrode also needs to have a sufficient porosity, a good stability, and a matched thermal expansion coefficient with the electrolyte.Developing new materials or optimizing their compositions is a possible way to improve the intrinsic characteristics of materials. Effective design strategies include element doping (A/B/O-site doping) or the construction of A- and B-site defects. The A-site in the perovskite structure ensures a large lattice volume and prevents lattice distortion, and doping elements in the A-site with large radii is beneficial to ion transport. The acceptor doping on the B-site can increase the electron cloud density around the oxygen atoms, thereby facilitating proton absorption. Also, the oxygen-site doping is more complicated. The substitution of oxygen by elements with a lower valence state and a higher electronegativity can promote the migration rate of oxide ions and protons. However, electron conductivity and carrier concentration may decrease after anion doping. The realization of optimal TIEC in single-phase materials is a challenge. Composite electrodes with different functions exhibit synergistic effects and strong interactions at the nanoscale, thus garnering increasing attention. Composite oxygen electrode can improve the mismatched thermal mechanical issue between the oxygen electrode and the electrolyte, and enhance the chemical stability towards CO2 and H2O, thereby increasing the long-term stability of PCCs. Methods for preparing composite oxygen electrodes include mechanical mixing, impregnation, self-assembly, and dissolution. Among these methods, the last three can be used to fabricate nano-sized composite oxygen electrodes with a superior performance.The stability of the oxygen electrode and the interface between the oxygen electrode and the electrolyte has a significant impact on the lifespan of the PCCs. The adhesion between the electrode and the electrolyte is strengthened via depositing an intermediate layer to enhance PCCs stability. Active material with a high coefficient of thermal expansion can be combined with a negative thermal expansion material to form a composite oxygen electrode, exhibiting a well-matched thermal expansion characteristic with the electrolyte, which is beneficial to the thermal cycling stability of the PCCs. In addition to interface stability between the electrode and electrolyte, the stability of the oxygen electrode material is also crucial. Most oxygen electrode materials contain Ba and Sr elements, which tend to enrich and segregate on the electrode surface, especially in atmospheres containing H2O and CO2. Water can promote element segregation, leading to the formation of secondary phases through reactions with impurities in air, which affects the catalytic activity of the electrode material. The stability of oxygen electrode materials can be significantly improved via doping, developing materials without alkali elements, and using composite oxygen electrodes. In addition, other pollutants (such as Cr, Si, B) may be generated in the stack, which also affects the stability. Furthermore, the oxygen electrode of PCCs is exposed to humidified air when operated in the electrolysis cell mode. However, there is a limited research on the poisoning of PCCs oxygen electrodes towards high steam and other elements (Cr, Si).Summary and prospects PCCs is a key technology for renewable energy conversion and storage. The degradation of oxygen electrode greatly increases the polarization resistance of the cell and causes obviously declined performance. It is thus urgent to improve the stability of oxygen electrode materials. A further research can be conducted in the following fields, i.e., the relationship between the composition and electrochemical performance of the oxygen electrode, the influence of microstructure evolution and morphology changes under a high humidity on electrochemical performance, and the corresponding degradation mechanisms; the thermal cycle stability and interface stability of oxygen electrode materials under actual operating conditions; the mechanism of the PCCs oxygen electrode poisoned by Cr and Si in a high humidified atmosphere, as well as corresponding detoxification strategies; and it is necessary for commercial application requirements to investigate the stability of large-area PCCs under typical operating conditions.