High thermal conductivity silicon nitride ceramics were prepared via aqueous gel-casting with a slurry of a low viscosity. The effect of MgO sintering aid on the rheological properties of slurry and the thermal conductivity of silicon ceramics was investigated. The results show that MgO sintering aid causes the particles aggregation and increases the slurry viscosity. The slurry viscosity becomes sensitive to the pH value change when the addition amount of MgO increases. A ceramic slurry with a low viscosity is achieved by adjusting pH value and dispersant concentration. The thermal conductivity, bending strength, and fracture toughness of the sample prepared by aqueous gel-casting can reach 83.7 W·m-1·K-1, 945 MPa, and 8.4 MPa·m1/2, respectively. The feasibility of high thermal conductivity silicon nitride ceramics prepared by aqueous gel-casting was verified.

The 99.7K0.5Na0.5(Nb(1-x)Tax)O3-0.3BaBiO3 lead-free piezoelectric single crystals of tantalum pentoxide and manganese dioxide doped were prepared by a seed-free solid-state crystal growth method, and the effects of mono-doping and co-doping of Ta and Mn on the growth, structure and electrical properties of the crystals were investigated. The result shows that a proper amount of Ta and Mn co-doping is beneficial to the growth of the single crystal. The single crystal surface becomes more regular and compact, and the maximum size of the obtained crystal can reach 30.0 mm×9.2 mm×2.6 mm when 0.9% (mole fraction) Ta and 0.1% Mn are co-doped. When 0.1% Mn doping is fixed and the amount of Ta is changed, the single crystals with a greater amount of tantalum pentoxide doping have higher piezoelectric properties. When the co-doping amounts of Ta and Mn are 0.9% and 0.1%, the crystals have greater remanent polarization (i.e., Pr = 26.96 μC/cm2) and piezoelectric constant (i.e., d33 = 227 pC/N), respectively.

ZnO-Bi2O3-MnO2-Cr2O3 varistor ceramics doped with different amounts of silicon dioxide (SiO2) were prepared by a conventional solid-phase sintering method. The phase composition and microstructure of the samples were investigated by X-ray diffraction and scanning electron microscopy. The electrical properties were measured by sourcemetry and inductance capacitance resistance, and the double Schottky barrier parameters were measured by a capacitance-voltage characteristic method. The results show that when the frequency is near 105 Hz, the relative dielectric constant (εr) decreases rapidly since the polarization cannot change with the frequency of electric field, resulting in the corresponding loss peak. The loss peak (tanδ) firstly decreases and then increases with the increase of the doping amount, and its maximum tanδ is obtained witrhout SiO2 and the minimum tanδ is achieved at 1.0% SiO2. The value of tanδ at a frequency of 105 Hz is reduced by doping SiO2. The nonlinear coefficient firstly increases and then decreases with the increase of SiO2 doping amount. The value of α reaches 43.36, the value of φb is 1.98 eV at 10 kHz, the donor concentration is 2.97×1024 m-3, and the leakage current IL is 0.31 μA/cm2 at SiO2 doping amount of 1.0%.

The perovskite solid solution ceramics, (1-x)BaTiO3-xDyFeO3, were synthesized by a solid-state reaction method. The magnetic properties of different compositions at various temperatures were investigated. The effect of phase content on the magnetic behavior was analyzed. The results show that the magnetization and susceptibility in an applied field increase with increasing x value due to the increasing concentration of magnetic elements. The temperature-dependent static and dynamic susceptibilities follow the Curie-Weiss law, but the fitting parameters are different.

n(Ca2+)/n(Co2+)(n is mole) co-doped LaAlO3 ceramics were synthesized by a solid-phase reaction technique. The effect of n(Ca2+)/nCo2+ doping ratio on the infrared radiation performance of LaAlO3 ceramics (La1-xCaxAl0.8Co0.2O3, 0.25≤n(Ca2+)/n(Co2+)≤2.00) was investigated, and the mechanism for improving infrared radiation property was analyzed. The result reveals that n(Ca2+)/n(Co2+) co-doped LaAlO3 ceramics have a perovskite crystal structure. Increasing the doping ratio (0.25≤n(Ca2+)/n(Co2+)≤1.00) improves the emissivity in the wavelength range of 0.76-2.50 μm. The ceramic specimen with n(Ca2+)/n(Co2+) of 1.00 (La0.8Ca0.2Al0.8Co0.2O3) has the maximum average emissivity (0.87). In the 2.50-14.0 μm band, the average emissivity of all n(Ca2+)/n(Co2+) co-doped LaAlO3 ceramics is generally greater than 0.94. The improvement of emissivity can be attributed to the enhancement of free carrier absorption, impurity absorption and lattice vibration absorption. This novel infrared ceramic with a high emissivity has promising prospects for energy-saving applications of thermal equipment.

Diatomite porous ceramics prepared by a foam-gelcasting route were used as a matrix, and SiO2 microspheres in-situ formed by a solvothermal method were used to modify the surface roughness of diatomite porous ceramics. Capstone FS-50 (CS-50) was used as a modifier to prepare SiO2 microspheres and CS-50 co-modified superhydrophilic-superoleophobic diatomite porous ceramics (SSMDPC) for the use of continuous separation of oil/water emulsions. The effects of TEOS/NH3·H2O addition and CS-50 concentration on the microstructure and wettability of the obtained samples as well as the oil/water separation continuous performance and extreme environmental stability were investigated. The results show that the maximum oil contact angles in air and water of the prepared SSMDPC are 153° and 158° respectively at TEOS/NH3·H2O addition of 5%/2% and CS-50 addition of 5% respectively. The continuous separation flux and separation efficiency of SSMDPC for edible oil/water mixture and edible oil-in-water emulsion with a surfactant (5/95, mass ratio) are 162.3 kg·min-1·m-2 and 98.3%, 93.7 kg·min-1·m-2 and 91.3%, respectively. Moreover，SMDPC can still maintain stable hydrophilic and hydrophobic properties under corrosion conditions (i.e., pH value of 1, pH value of 14 and 1 M NaCl), even at -196 ℃ and 200 ℃, which has broad application prospects in oil-in-water emulsion.

The membrane materials of Ba0.95Ce0.8Y0.2O3-δF0.10(BCYF0.10) and Ce0.8Y0.2O2-δ(YDC) ceramic powders were prepared by a sol-gel method. BCYF0.10-YDC/BCYF0.10-Ni double-layered asymmetric dense hollow fiber ceramic membrane was synthesized via co-spinning and co-sintering. The effects of spinning mixture composition and sintering temperature on the structure of hollow fiber membrane were investigated. The thickness of the dense layer, the interface between the two layers and the bending strength of the resultant hollow fiber membranes can be tuned by adjusting the ceramic powder loading in the inner and outer spinning solution. The thickness of the dense outer layer of the membrane is only 14.5 μm when the contents of ceramic powder in the inner and outer spinning solution are 65.7% and 44.4%, respectively. The two layers can be integrated well with the measured bending strength of 168.5 MPa. The prepared hollow fiber membranes were tested for hydrogen separation. At 900 ℃, when the feed gas (50% H2+50% He) and the sweep gas (N2) are controlled at 100 and 100 mL·min-1, respectively, the hydrogen permeation flux of hollow fiber membrane is 0.54 mL·min-1·cm-2.

The ceramic green bodies with different structures can be formed via binder micro-jetting and bonding additive manufacturing technology. However, the density, strength and surface quality of the sintered ceramic bodies are low. The nanozirconia suspension was used as a jet solution to substitute a conventional organic binder, and the effect of nanozirconia suspension jet amount on the properties of additive manufactured zirconia ceramics after sintering was investigated. When the nanozirconia suspension jet amount increases from 0 to 175%, the line shrinkage and surface roughness of sintered zirconia ceramics decrease significantly, and the reduction rates are 6%-8% and 57%, respectively, while the relative density, flexural strength and hardness increase considerably, and the increase rates are 18.1%, 124.0%, and 187.0%. The nano-sized zirconia particles can fill in the pores of the zirconia powder layer after introducing the nanozirconia suspension, thus improving the green density and the sintering quality of the zirconia ceramic. This provides an effective method for rapid manufacturing complex and compact ceramic parts.

To improve the mechanical properties of B4C ceramics, TiB2 was generated in-situ in B4C ceramics by a reaction sintering method with TiO2 as a sintering aid to prepare dense B4C ceramics, and the enhancement mechanism of its mechanical properties was analyzed. The results show that the density and flexural strength of B4C firstly increase and then decrease and the fracture toughness increases with the increase of TiO2 addition. The density of B4C ceramics reaches 99.6% when the TiO2 addition is 5% (in mass fraction) and the sintering temperature is 1 700 ℃. The optimum overall performance of B4C ceramics (i.e., the Vickers hardness of 36.0 GPa, the fracture toughness of 4.38 MPa·m1/2, the bending strength of 405 MPa) can be obtained when the amount of TiO2 added is 15%. The in-situ TiB2 inhibits the growth of B4C grains, eliminates the stress at the crack tip, deflects and bifurcates the crack, and plays a role in grain refinement strengthening and toughening of B4C ceramics.

Investigation on 3D printing of silica ceramic cores is crucial to the development of aviation level in China, but the related problems are high-temperature softening and structural anisotropy. Silica ceramic cores were fabricated by DLP light curing 3D printing technology using fused silica powder as a raw material and mullite powder as a modifier. The results show that the ceramic cores have a layer-packed anisotropic structure. The addition of a small amount of mullite powder promotes the sintering densification of ceramic powder and diffusion binding between printing layers. As a result, the structural anisotropy of ceramic cores is relieved, and the flexural strength is enhanced and tended to isotropy. For ceramic cores with 3% mullite powder, the high-temperature flexural strengths in horizontal and vertical printing are up to 18.5 MPa and 16.3 MPa, respectively, which can satisfy the demands for hollow blade casting.

Piezoelectric ceramics are used in the manufacture of ultrasonic motor because of its inverse piezoelectric effect. However, some problems of poor joint conductivity, easy aging and low connection accuracy caused by organic bonding in the manufacture of ultrasonic motor need to be solved. In this paper, the surface of PZT piezoelectric ceramics was metallized via magnetron sputtering to improve the weldability between PZT piezoelectric ceramic and TC4 titanium alloy. The results show that the bonding force between Ag and base metal is poor, and the unwelded position appears at the junction of Ag layer and base metal. The welding is easy to occur at the junction of Ti and Ag when Ti/Ag is a metallized layer due to the poor bonding force between Ag and Ti. Ni and solder can form Ni-Sn layer to improve the joint reliability when the metallized layer is Ni/Ag.A composite metal layer, that is, the base metal/Ti/Ni/Ag structure, was selected as a metallized layer on the base metal surface, and the typical microstructure of the joint was analyzed. The results show that the composite metal layer can improve the bonding strength between the metallized layer and the base metal and realize the effective bonding between the BASE metal of PZT ceramics and TC4 alloy. The microstructure of the interface is β-Sn/Ag3Sn/β-Sn+Ni3Sn4/Ni3Sn+Ni/Ti2Ni/Ti2Ni+α-Ti/PZT.

Hydroxy aluminum polycation was firstly prepared with AlCl3瘙
簚6H2O and NaOH as raw materials, and then Al-pillared montmorillonite was prepared with hydroxy aluminum polycation as alumina source. A montmorillonite-based ceramic was fabricated via ball milling and hot pressing with Al2O3 and Al(OH)3 as alumina sources. The effect of hot-pressing temperature on the mullitization and mechanical properties of montmorillonite-based ceramic was investigated. The results show that the mechanical properties of montmorillonite-based ceramics are improved by adding three kinds of alumina sources at the hot-pressing temperature of 1 100 ℃. The optimum flexural strength and fracture toughness of Al-pillared montmorillonite-based ceramics at 1 300 ℃ (i.e., 118.07 MPa and 2.30 MPa·m1/2) can be obtained, which are increased by 41.0% and 74.2%, compared with original montmorillonite ceramics.

The coloration mechanism of different glazes in Na2O-MgO-CaO-Al2O3-SiO2-P2O5 multi-element glaze system was revealed via investigation of the microstructure and crystallization behavior of glaze melts with different iron oxide contents. The results show that the phase separation in glaze is improved by calcium phosphate, which plays an important role in glaze color. Fe3+ ions exist at a lower iron oxide content. The chemical color of Fe3+ ions results in a dark-green glaze. The phase separation effect of glaze layer increases and the phase interface becomes larger with the increase of iron oxide content. Due to multiple scattering and consumption by massive phase interfaces, the incident light is absorbed and a black glaze appears at an excessive iron oxide content. α-Fe2O3 nanocrystals can be precipitated from silicate glaze, and glaze surface appears red color. A needle-like array structure can be formed in the growth of α-Fe2O3 nanocrystals, interfering with an incident light and resulting in silver-gray glaze. It is indicated that the interaction of chemical color and structural color induces different color rendering effects of glaze with the change of iron oxide content.

γ-Ce2S3 is a kind of non-toxic environmental protection red inorganic pigment due to its bright color, intense hiding power and superior ultraviolet resistance. However, its antioxidant temperature is 350 ℃. To improve the oxidation resistance temperature of γ-Ce2S3, a mullite coated Na+ ion-doped γ-Ce2S3 (i.e., γ-［Na］-Ce2S3@mullite) was synthesized by a sol-gel method and a subsequent sulfuration-heating process. The synthetic conditions of mullite as well as the effect of pre-firing temperature on the morphology of precursor and chromaticity value of the coated pigments were investigated, and the thermal stability of the coated pigments was also analyzed. The results show that short rod-like and spheroidal mullite crystals can be synthesized at 1 300 ℃ for 3 h as nAl:nSi=3.2:2.0, and the optimum chromaticity value (i.e., L*=36.24, a*=41.86, b*=36.26) of the coated pigment can be obtained when the pre-firing temperature is 400 ℃. The pigment has a good chromaticity value (i.e., L*=29.84, a*=20.83, b*=18.17) when being in air at 800 ℃ for 10 min. This study indicates that γ-［Na］-Ce2S3@mullite can increase the antioxidant temperature of γ-Ce2S3 from 350 ℃ to 800 ℃.

A trampoline phononic crystal model was proposed based on the trampoline effect. The band structure and eigenmodes of trampoline phononic crystals were calculated by the finite element method. Compared with the conventional phononic crystals, the height of trampoline phononic crystal cylinder was selected to investigate the rainbow trapping effect. For the trampoline phononic crystals with different column heights, 16 trampoline phononic crystal cells were classified in the form of single number as well as ordered and random completely disordered arrays, respectively. The corresponding transmission loss curve was determined, and the influence of array combination form on the rainbow trapping effect was analyzed. Furthermore, three slightly disordered trampoline phononic crystal arrays were designed to analyze the influence of disorder on the rainbow trapping effect. The results show that the band gap width of the new trampoline phononic crystal is 2.1 times greater than that of the conventional phononic crystals. The ordered arrangement of trampoline phononic crystals has an obvious rainbow trapping, while the completely disordered arrangement has a strong ‘inverse rainbow trapping’. The attenuation ability of the three slightly disordered trampoline phononic crystal arrays to the excitation signal is basically the same as that of the orderly arrangement, indicating that the designed trampoline phononic crystal is robust to the slightly disordered arrangement of the array. This paper provides a reference for the directional design of rainbow trapping phononic crystal arrays with attenuation frequency domain and maximum attenuation amplitude.

AlN crystal is a typical brittle and difficult-to-process material. To prepare AlN crystal substrates with a high efficiency and a high quality, slurries with different chemical compositions were designed to lap AlN crystals, and the mechanism of chemical action-assisted material removal was investigated by laser confocal microscopy and X-ray photoelectron spectroscopy. The results show that the alkaline slurry is beneficial to obtaining the optimum lapping results, the material removal rate is 23 μm/h, and the surface roughness (Ra) is 122 nm. The diamond abrasive particles in the slurry have a good dispersibility in alkaline environment. The alkaline solution can corrode the crystal surface, form a metamorphic layer containing basic aluminum salts, and cause some changes in the surface morphology. In the lapping interface, the metamorphic layer produced by chemical etching on the surface of AlN crystal is more conducive to the mechanical removal of abrasive particles, which can lay a foundation for improving the lapping efficiency and quality. The result obtained can provide a reference for optimizing the ultra-precision processing technology of AlN crystals.

A ratiometric fluorescent probe (CQDs/Eu3+) was constructed with carbon quantum dots (CQDs) and europium ions (Eu3+) as fluorophores for the detection of ciprofloxacin (CIP). At excitation at 395 nm wavelength, CQDs/Eu3+ has an intense blue fluorescent peak at 459 nm, and a weak red fluorescent peak at 616 nm in the presence of CIP. The fluorescence (FL) intensity of CQDS at 459 nm is enhanced based on the antenna effect. The major factors like ratio of CQDs and Eu3+, response time and stability were optimized, The results show that the ratio fluorescent probe has a specific recognition ability for CIP. And there is a linear relationship between the fluorescence intensity ratio (F459/F616) and concentration of CIP (0-7×10-6 mol/L), and the lowest detection limit for CIP is 0.3×10-6 mol/L. This probe can be used for the detection of CIP in milk under the addition of CIP.

3C-SiC nanowires were synthesized in Ar atomosphere via Co nanoparticle catalytic reaction with expanded graphite and silicon powders as raw materials and Co(NO3)2·6H2O as a catalyst precursor. The effects of reaction temperature and catalyst addition on the formation of SiC nanowires were investigated. The phase composition and microstructure of the as-prepared products were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The optoelectronic property of as-prepared 3C-SiC nanowires was analyzed. The results show that Co catalyst promotes the growth of 3C-SiC nanowires and decreases the complete reaction temperature and the formation temperature. 3C-SiC nanowires could be synthesized at 1 573 K for 3 h using 3.0% Co as catalysts at C/Si molar ratio of 1:1. The formed 3C-SiC nanowires are approximately 50-60 nm in diameter and tens micrometers in length. According to the results by the first-principles calculation, the activities of the reactants are increased via dwindling the bonding strength of C=C, Si-O and C-O bonds. The room-temperature PL spectra indicate that the as-synthesized 3C-SiC nanowires have a special emission at 307 nm (4.04 eV), which could be used as a potential material for optoelectronic nanodevices.

M′-type Nd3+:GdTaO4 microcrystals, synthetized by a molten salt synthesis method, were investigated via temperature-/pressure-dependent photoluminescence measurement. In the test temperature range 293-373 K, the spectral positions of emissions from 3F3/2→4I9/2 transition exhibit high thermal stabilities. The temperature coefficient of 3F3/2(R2)→4I9/2(Z5) transition is only 0.003 9 cm-1·K?傆b1. The intensity ratio between transitions of 3F3/2(R2)→4I9/2(Z2) and 3F3/2(R1)→4I9/2(Z2) has a large temperature dependence, and its relative sensitivity in the physiological temperature range is (0.60-0.52)(%·K-1). In the test pressure range 105 Pa-11.39 GPa, all the transitions linearly shift with pressure. The spectral position of 3F3/2(R2)→4I9/2(Z5) transition is very sensitive to pressure, with a sensitivity of 15.18 cm-1·GPa?傆b1. The intensities and spectral widths of the transitions in the heating and compression processes were also analyzed. Compared with the other optical sensors in the near-infrared wavelength range, the good performance of M′-type Nd3+:GdTaO4 in temperature and pressure sensing was revealed.

A series of Sr2GdNbO6:xEu3+ (x=0.04-0.12) red phosphors were prepared by a high-temperature solid-phase method, and the target products were characterized by X-ray diffraction, UV-Vis spectrophotometry and fluorescence spectroscopy. The results show that the synthesized phosphor has a monoclinic crystal structure with the space group P21/c. The structural analysis indicates that doped europium replaces Gd3+ ion in the matrix Sr2GdNbO6 with the chemical state of Eu3+ ion, thus forming a single crystal structure phosphor. Sr2GdNbO6:Eu3+ phosphor exhibits a red-orange emission under dual-wavelength excitation of blue light λex of 468 nm and near-ultraviolet light λex of 395 nm, and the main emission peaks are centered at wavelengths of 622 nm and 593 nm, which belong to the 5D0→7F2 and 5D0→7F1 energy level transitions of Eu3+, respectively. When the doping amount (x) of Eu3+ is 8%, its luminescence quantum efficiency for blue light excitation reaches the maximum value of 16%. Based on the analysis and comparison of the temperature (295-568 K) effect on the emission intensity and quantum efficiency under dual-wavelength excitation, the phosphor has a high luminescence quantum efficiency under the excitation of blue light λex of 468 nm and a higher thermal stability. Under the excitation of blue light, the average fluorescence decay lifetime of the sample Sr2GdNbO6: 0.08Eu3+ is 0.841 ms, the color coordinates are (0.648, 0.368), and the luminescence purity reaches 93%. This phosphor is a kind of red fluorescent material with the dual-wavelength response for a promising potential application.

The comprehensive utilization of bulk solid waste is of great significance to the realization of carbon neutrality and standards. This review represented recent work on the utilization of solid wastes for preparing foamed ceramics by in-situ foaming process. Especifically, solid waste raw materials, foaming agents and additives, preparation process as well as the performance and application of foamed ceramics were discussed. In addition, the interaction between foaming behavior and sintering process was also revealed, the in-situ pore forming sintering mechanism of foamed ceramics was described, and the existing problems and future development direction were summarized to provide a reference for promoting the further comprehensive utilization of solid waste forpreparing foamed ceramics.

SiC ceramics are difficult to be directly processed into large and complex components due to their high brittleness, high hardness and high wear resistance. Therefore, joining technology is one of the developed methods to facilitate the engineering application of SiC ceramics. Among various joining methods, the joints obtained by the joining method using SiC as a major phase of the joining layer have some advantages like high joint strength, low joint stress, radiation resistance, chemical corrosion resistance and high temperature resistance, thus becoming the key technologies for SiC ceramic joining, i.e., nano-infiltrated transient eutectoid phase joining (i.e., NITE phase joining), silicon-carbon reaction joining (i.e., Si-C reaction joining) and precursor joining. This review represented three kinds of SiC ceramic joining technologies above using SiC as a major phase of the joining layer from the aspects of joining mechanism, joining process, joint composition, microstructure and joining strength. The advantages and deficiencies of the three kinds of joining technologies were analyzed and compared. In addition, the future development was also prospected.

Dendritic mesoporous silica nanoparticles are one of silicon-based mesoporous materials. This material is widely used in various fields due to the special central radial mesoporous channel structure. This review represented recent development on dendritic mesoporous silica nanoparticles, and described the dendritic mesoporous silica nanoparticles from chemical composition and morphology structure. The existing synthetic methods of dendritic mesoporous silica nanoparticles were introduced. The major factors of influencing the structure of dendritic mesoporous silica nanoparticles were mainly discussed. In addition, the future development on dendritic mesoporous silica nanoparticles was also prospected.

Geopolymers have attracted recent attention due to their wide source of raw materials, environmental protection, low-carbon technology and unique properties. However, the geopolymerization behavior of geopolymers is susceptible to the reaction reactivity of raw materials, leading to large fluctuations in the properties such as mechanical properties and durability. The issues mentioned above are directly related to the geopolymerization mechanism of geopolymers, geopolymerization kinetics, and influencing factors and regulation approach of the properties of geopolymers. Therefore, this review represented recent work and gave some future research aspects in this field to promote the utilization of low-quality aluminosilicate minerals or aluminosilicate industrial waste for the possible purpose of ‘peak carbon dioxide emissions’ and ‘carbon neutrality’.

Crystalline and noncrystalline materials activated with 3d transition metal ions (TMIs) featured by rich spectral characteristics are widely used as phosphors as well as laser gain media. In recent years, the broadband NIR LED is regarded as an ideal miniaturized light source for NIR spectrometers, which can be easily integrated in portable electronic devices in food security and biomedicine. The near-infrared (NIR) phosphors activated by TMIs like Cr3+ ions are considered as a key stage in the development of highly efficient broadband NIR LEDs. Unlike the parity forbidden f-f transitions of trivalent rare-earth ions, the d-d transitions of 3d TMIs exhibit large bandwidth and tunable emission wavelengths due to the intense coupling with the surrounding crystal field. At present, materials doped by TMIs except Cr3+ ions are rarely explored for NIR applications. In this review, the spectral characteristics associated with the d-d transition of 3d TMIs were elaborated, and recent development on TMI activators and phosphor matrix for a broadband NIR photoluminescence was represented. In addition, this review also provided a brief summary for the factors that need to be considered in the design of broadband NIR phosphors. This review is expected to offer useful guidelines for the development of advanced NIR pc-LEDs.