To investigate the strengthening and toughening effect of fiber on seawater coral aggregate concrete (SCAC) under an impact load, the dynamic mechanical response of SCAC with mono PVA fiber or hybrid PVA-steel fiber at different strain rates was tested by using a 75 mm Split Hopkinson Pressure Bar. The impact properties and failure characteristics were simulated using a software named ANSYS/LS-DYNA. The results indicate that the addition of fibers may improve the embrittlement degree and dynamic mechanical properties of SCAC. The enhancement effect of hybrid fiber on the strain rate sensitivity and dynamic increase factor of SCAC is better than that of mono PVA fiber. The damage degree of SCAC gradually decreases with the increase of PVA fiber content, while the integrity of the hybrid fiber SCAC is better at each strain rate. The number of final deleted elements in the simulated sample is significantly reduced after adding fibers, and the simulated results show the dynamic mechanical properties and failure degree of SCAC with various fiber contents.

The theoretical models for the application of low-field nuclear magnetic resonance (LF NMR) to the cementitious materials are reviewed, in response to the three common questions, namely the data reliability, result stability and model validity problems. The major applications, including the characterization of pores, the quantification of hydration products and the diffusion dynamics, are linked to four theoretical models, namely the two-fraction fast-exchange model, the Korb model, the amplitude model and the cryoporometry related Gibbs-Thomson model. In addition, the limitations in models as well as in instruments are pointed out. In particular, for the mentioned applications, most commonly used pulse sequences together with recommended parameters are provided. Based on the latest progress in the field, challenges and outlooks are discussed.

High-magnesium Portland cement clinker with MgO content of 6% was synthesized with chemical reagent. The effect of cooling method (i.e., furnace cooling, air cooling and liquid-nitrogen quenching) on the mineral composition, C3S crystal type, solid solubility of MgO, and formation of periclase of high-magnesium Portland clinkers with different alumina modulus (IM) (i.e., 0.64, 1.10 and 3.00) was investigated. The samples were characterized by X-ray powder diffraction with Rietveld method, petrographic method and scanning electron microscopy. The results show that a rapid cooling can stabilize C3S crystal into M3 type, and prevent the transformation of C3S crystal from M3 to T3 type. And this has a little effect on the change of IM. The content of C3S is relatively high in the clinker with a low IM and by furnace cooling, and the clinker with a high IM and by liquid-nitrogen quenching. Rapid cooling rate inhibits the crystallization of periclase, and the inhibition effect is more dominant in a low IM clinker. Clinker quenching can keep the morphology of C3S intact, and promote periclase to turn into a fine round granule.

In order to obtain stable and dispersed calcium silicate hydrate (C-S-H) crystal nucleus, improve its crystal nucleus-inducing effect on cement hydration, and realize the efficient utilization of cement clinker. Polycarboxylate superplasticizers (PCE) with different proportions of acrylic acid (AA) and silane group (KH570) were prepared via free radical polymerization to disperse calcium silicate hydrate (C-S-H) seeds. The corresponding C-S-H/PCE seeds were synthesized by a solution precipitation method. The grain size/size distribution, the stability of C-S-H/PCE seeds and the bonding mode of PCE on C-S-H interface were investigated. The results show that the PCE with an appropriate proportion of KH570 can effectively control the grain size of C-S-H/PCE seeds. The adsorption mode of PCE on C-S-H surface changes from Ca2+ complexation to a more stable Si-O-Si chemical bond, and the grain size of C-S-H/PCE seeds firstly decreases and then increases with the increase of KH570 ratio. At a KH570 to AA ratio of 1, the adsorption layer thickness of PCE on the surface of C-S-H is 2.5 nm, the grain size of C-S-H/PCE seeds is 60 nm and the stability is optimum. The PCE undergoes an intramolecular dehydration condensation process under alkaline condition with further increasing the proportion of KH570, forming a reticulated silicone resin structure, which is unfavorable for the regulation of grain size of C-S-H/PCE seeds.

Magnesium oxychloride cement (MOC) has some advantages like light weight, early strength, low thermal conductivity, and fire resistance, but poor water resistance restricts the application of MOC in civil, construction and other fields. This paper was to improve the water resistance of MOC by using soluble sulfates containing different metal cations as additives. The effect of soluble metal cations on the setting time and compressive strength of MOC was investigated. The phase composition, microstructure and pore structure of modified MOC were characterized by X-ray diffraction, scanning electron microscopy, and mercury intrusion porosimetry. The results show that Al3+, Fe2+, Cu2+ ions and free OH- ions in the MOC slurry can preferentially form a precipitate, inhibiting the formation of Mg(OH)2, delaying the hydration of MgO, prolonging the setting time, reducing the total porosity of the MOC matrix, and improving the water resistance of MOC. In addition, SO42- ions can also improve the stability of 5Mg(OH)2·MgCl2·8H2O after soaking in water through the adsorption and coordination with Mg2+ ions in 5Mg(OH)2·MgCl2·8H2O.

The influence of cold CaCl2 solution on the setting behavior, strength development, mineralogical composition, microstructure, and chloride content of calcium sulphoaluminate (CSA) cement at –10 ℃ was investigated. The results show that there is a significant and persistent temperature peak in CSA cement pastes mixed with 16% and 28% cold CaCl2 solution, so CSA cement can hydrate continuously. The temperature peak retards from 90 min to 150 min as the solution concentration increases from 16% to 28%. The pastes with 16% CaCl2 solution set quickly and the compressive strength is high (initial setting time 15 min and final setting time 24 min, compressive strength 41.0 MPa at 1 day and 85.2 MPa at 28 days); while the pastes with 28% CaCl2 solution set slowly and the compressive strength is low (initial setting time 85 min and final setting time 155 min, compressive strength 24.3 MPa at 1 day and 57.7 MPa at 28 days). Ettringite is the primary hydration product and its morphology is needle in hydrated pastes with 16% CaCl2 solution. The Friedel?s salt turns to be dominant and the morphology is hexagonal plate in hydrated pastes with 28% CaCl2 solution. There is little binding chloride for 16% CaCl2 solution and 0.95% binding chloride for 28% CaCl2 solution. In the presence of CaCl2 solution, the CSA cement can hydrate continuously at –10 ℃. Furthermore, a shorter setting time and a higher strength can be obtained in CSA cement pastes mixed with 16%?20% CaCl2 solution.

In order to improve the rheology and stability of ultra-high performance concrete containing coarse aggregate (CA-UHPC), the effects of silica fume, coarse aggregate, and steel fiber contents on the rheological properties of CA-UHPC were investigated, and the relationship among the rheological parameters, fiber, and coarse aggregate distribution was established. The results show that CA-UHPC usually exhibits a shear-thinning behavior. The modified Bingham model has more accurate fitting results of rheological parameters, and the fluidity required for the rheological properties test can be controlled at 450-690 mm. Increasing the silica fume content increases the yield stress, decreases the viscosity, and weakens the shear-thinning behavior. Increasing the coarse aggregate content firstly decreases and then increases the yield stress and viscosity, and intensifies the shear-thinning behavior. And increasing the steel fiber content increases the yield stress and viscosity, and intensifies the shear-thinning behavior. The number of steel fiber decreases from the top to the bottom of samples, while the proportion of coarse aggregate increases. The uniform dispersion degree of coarse aggregate increases with the increase of coarse aggregate content, but steel fibers deteriorate the uniform dispersion degree of coarse aggregate. The uniform distribution degree of steel fiber and coarse aggregate firstly increases and then decreases with the increase of steel fibers content.

To investigate the occurrence of periclase in clinker aluminate and reveal the hydration mechanism, aluminates were synthesized via MgO doping at various contents. Their structure and hydrates were characterized by scanning electron microscopy, X-ray diffraction and Fourier transform infrared spectroscopy. The results indicate that higher sintering temperature and MgO content improve the formation and stability of C4AF and C12F7. A phase separation occurs in molten aluminum phase. The black phase includes the main minerals like C3A and periclase, while glass and yellow phases both have a low MgO content. The hydration heat of aluminate phase in the first day decreases with the increase of MgO content, indicating that MgO doping decreases the hydration rate of aluminate phase. In addition, the layered double hydroxides with a Mg:Al ratio of 2 or 3 appear in the hydration products of aluminate incorporated with MgO.

The effect of cracking ages (i.e., 3, 7, 14 d and 28 d) on the self-healing of pure fly ash-based engineered geopolymer composite (FA-EGC) was evaluated by crack characteristics, tensile properties and water absorption. The components and microstructure of self-healing products of FA-EGC were investigated by Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy with energy dispersive spectroscopy. The results show that there is an optimum self-healing effect of FA-EGC samples when cracking age is 7 d, a better recovery of ultimate tensile strength and a reduction in average water absorption rate can be obtained at the maximum decrease in crack width. The self-healing products of FA-EGC are the geopolymer gel generated by ongoing geopolymerization reaction and CaCO3.

The bonding strength of epoxy grout-concrete composite was investigated by axial tensile test to reveal the bonding damage evolution mechanism between epoxy grout and concrete under dry and wet interface condition. The ringing count, b value and the spatial position of acoustic emission (AE) source during the tensile process of composite were obtained by AE technique, and the spatial evolution process of bonding damage of composite was analyzed. The evolution characteristics of strain and displacement damage on the fracture surface of the composite under wet and dry interface condition were obtained by a digital image correlation method. The results show that the bonding strength under dry interface condition is 60% higher than that under wet interface condition. Under wet interface condition, the AE source of epoxy grout-concrete is concentrated at the interface, and a regular strain concentration zone is formed at the interface, showing the characteristics of interface failure. Under dry interface condition, however, there are a lot of AE sources in the concrete, and there are several irregular strain concentration zones on the fracture surface, indicating the failure mode of the concrete matrix as a whole.

Aiming at the problem that the backfill grouting of the shield project must have a short setting time and maintain good fluidity, Rapid hardening sulfoaluminate cement (R·SAC) and triethanolamine (TEA) are used as external accelerated setting materials, Analysis of the influence law and microscopic mechanism of the two on grout properties. The results show that with the increase of R·SAC, the setting time of the grout decreases from 9.5 h to 2.0 h, but the fluidity loss at 150 min is about 50%; With 0.6% dosage of TEA as the inflection point, the setting time and fluidity of the grout both increased first and then decreased; In compound blending, The two have a synergistic effect on grout hydration, rapid hydration in the initial stage, shortened setting time, and TEA deflocculation improves grout fluidity and slows down the loss of fluidity over time; By adding 15% R·SAC and 0.05% TEA, a fast-setting and high-fluidity backfill with a setting time of 6 h and a fluidity of 250 mm in 150 min can be prepared.

Tin-based oxides and their alloys with high specific capacities are considered as promising anode materials for Na-ion batteries. However, the tin-based oxides and their alloys suffer from a large volume variation and particle agglomeration during the charge-discharge process, resulting in electrode pulverization, capacity fading, and poor rate performance. In this paper, Bi/SnOx particles anchored on an ultrathin carbon layer (Bi/SnOx@C) were synthesized by a sodium chloride template method, and a uniform Bi/SnOx@C heterostructure is constructed. The ultrathin carbon layer can effectively inhibit the agglomeration of Bi/SnOx particles and increase the specific surface area of the electrode material, providing more active sites. Bi/SnOx can also contribute the more specific capacity. The synergistic effect of ultrathin carbon layer and Bi/SnOx composite can effectively improve the cycling stability, which is of great significance for the construction of high-performance electrode materials.

The development of cathode materials with excellent electrochemical properties is crucial for the application of hybrid supercapacitors. NiC2O4?2H2O cathode material was synthesized by a precipitation method, and its microstructure, morphology and electrochemical performance were investigated. The results show that NiC2O4?2H2O exhibits a unique polyhedral particle structure, the particle sizes are 0.5?2.0 μm, and each particle is composed of polycrystals, thus achieving a high specific capacity of 1 096.2 F/g at a current density of 1 A/g. The assembled nickel oxalate//activated carbon hybrid supercapacitor still maintains an energy density of 10.2 Wh/kg at a high power density of 3.7 kW/kg. Connecting two hybrid devices in series can light up green and yellow LEDs. This demonstrates that NiC2O4?2H2O has potential application prospects in electrochemical energy storage as a novel, low-cost and environmentally friendly cathode material.

High activity and durable structural catalysts are increasingly needed for carbon monoxide (CO) catalytic removal of industrial flue gas. A series of structural catalysts were prepared by coating polymetallic oxide catalyst on cordierite honeycomb supports. The results showed that silica sol and hot air drying could promote the powder catalyst to evenly and compactly spread on the surface of the support, and improve the anti-shedding performance and catalytic performance of the structural catalyst. The coating shedding rate of the optimized catalyst after 60 min of ultrasonic vibration was 0.97%. The catalytic efficiency of 99% CO can be achieved at 7 500 h-1 space speed, 1% CO, 8% water vapour content and 110 ℃, and remains stable within 72 h. The CO catalytic efficiency can be stabilized above 86% after 720 h in actual sintering flue gas condition.

Scintillator is a core device in X-ray imaging technology. It can convert absorbed X-ray or other high-energy charged particles into visible light, and it is widely used in medical diagnosis, radiation dose measurement and safety inspection. At present, most commercial scintillators are single crystal or thin film materials, which have complex preparation process, long growth cycle, high cost, as well as poor irradiation stability and imaging effect. In this paper, ZnS quantum dots glass-ceramics (GC) as a low cost and weather resistance scintillator for X-ray indirect imaging was prepared through in-situ precipitation of ZnS quantum dots (QDs) into transparent glass matrix. The experimental results show that the emission peak of ZnS GC is located at 518 nm under X-ray irradiation, and the fish bone and chip are imaged by X-ray imaging system. The image contour is clear, the internal structure of the object is clear, and the imaging resolution reaches 18.0 lp/mm due to the uniform distribution of ZnS quantum dots in the glass matrix. Also, the damaged ZnS GC scintillator can completely recover its imaging performance by simple heat treatment at a umulative dose of 288 J/kg. It is indicated that ZnS GC as a scintillator has a broad application prospect in the field of high resolution X-ray imaging.

The phase-change energy storage materials are used in the field of building insulation to achieve a purpose of transferring peak temperature loads and reducing building energy consumption. Well-dispersed two-dimensional montmorillonite nanosheets were prepared, and the energy storage material-paraffin was encapsulated via the adsorption on the surface of its pores (cavities) to form a thin shell structure. The effects of paraffin concentration and cetyltrimethylammonium bromide concentration on the montmorillonite nanosheets and their encapsulation were investigated. The thermal storage properties of the phase-change energy storage composites were analyzed. The phase-change energy storage composite material was applied to the building insulation board, and the mechanical properties and heat storage and temperature regulation performance of the phase-change energy storage insulation board were examined. This composite material can effectively improve its thermal resistance, delay the appearance of peak temperature, and improve the comfort of the indoor living environment, while maintaining the mechanical properties of the insulation board. This work could provide a guidance for the development and application of novel building energy-saving materials.

WO3 electrochromic devices (ECDs) with the short response time and high optical contrast show great application potentials in car rearview mirrors and smart windows. With the rapid development of wearable electronics, the fabrication of flexible WO3 films for bendable ECDs has attracted much attention. However, the fabrication of flexible crystalline WO3 films generally requires a sophisticated vacuum vapor deposition technique, including magnetron sputtering and electron-beam deposition due to the high crystallization temperature of WO3 and the limited endurable temperature of polymer substrates. The dense WO3 layers on polymer substrates affect the facile access of electrolyte and fast intercalation/deintercalation of electrolyte ions. In this paper, well-crystallized WO3·H2O microplate powders were pre-synthesized by a chemical reflux method. Monoethanolamine was utilized to intensively dissociate WO3·H2O microplates into a well-dispersed colloidal solution. The flexible nanocrystalline WOx/ polyethylene terephthalate films were fabricated via spin coating deposition and assembled into the flexible ECDs. The accumulated charge repulsion provided by the intense interfacial interaction between amine group and WO3·H2O microplates results in their fast dissociation. The fabricated flexible crystalline WOx electrochromic devices have short coloring and bleaching time of 5.9 s and 5.4 s, respectively, and a coloring efficiency of 146.7 cm2/C, and still exhibit the superior performance after 200 bending cycles.

The addition of chemical admixtures has been an effective approach to improve the performance of cementitious materials. Working mechanisms of the chemical admixtures in molecular scale still need to be clarified. Calcium silicate hydrate (C-S-H), as the main hydration product of cement, determines most macroscopic properties of cement-based materials. Molecular dynamics simulation has been an effective technique to reveal the interaction between chemical admixture molecules and C-S-H and its effect on the properties of C-S-H at the molecular/atomic scale. In this paper, recent progresses in molecular dynamics studies of the interaction between chemical admixtures (organic and inorganic) and C-S-H were reviewed, and their impacts on properties of C-S-H are briefly summarized. In addition, the future research direction of molecular dynamics simulation of chemical admixture-(C-S-H) system is prospected. The summarized chemical admixtures include organic admixtures such as small organic molecules, resins and fibers, water-soluble polymers, and inorganic admixtures such as (modified) graphene, silene, carbon nano-tubes, and various nanoparticles. Most molecular dynamics simulation research focuses on the interaction between the admixtures and C-S-H interface. Understanding of such interfacial interaction is the key to reveal the working mechanisms of the admixtures in improving the mechanical properties of C-S-H. In addition, for admixtures such as small organic molecules, water-soluble polymers and some nanoparticles, a large number of studies have used molecular dynamics method to describe the microscopic processes such as the adsorption of the admixture molecules on C-S-H surface, intercalation into C-S-H layers aggregation of the admixtures that blocks C-S-H layered structure, so as to clarify the mechanism of these admixtures on the mechanical properties, transport properties and even shrinkage behavior of C-S-H. These understandings provide theoretical inspiration for improving the properties of cement-based materials and for designing the molecular structure of admixtures more effectively.

Degradation of cement-based materials with the infrastructure engineering constructed in 20 th century for the end of service-life is increasingly concerned. Acoustic emission (AE) as an intrinsic physical phenomenon of energy emission happening inside material or structure can effectively support a precise sensation of health of material and structure based on its spatiotemporal information. This review briefly introduced the sensing principle and analysis method of AE and summarized the supports from AE to description of degradation process, influence factors, and cement-based material degradation such as alkali aggregate reaction, corrosion induced cracking, fatigue damage, and freeze-thaw spalling. In addition, the potential aspects to enrich AE research on the degradation of cement-based materials were also discussed via considering the time-dependent and large-scale feature of hydraulic structure.

Concrete performance can be improved via the application of multidisciplinary knowledge such as physical chemistry, electromagnetism, and informatics in concrete. This review represented the development of informatization and intelligence of modern concrete material structure, and the research work on the preparation methods in the electric field, magnetic field, etc. to control the rheological properties of fresh concrete and hardened concrete. In addition, the advanced concrete material-technical support for the intelligent construction of modern concrete engineering structures was also discussed.

It is essential for the quality of concrete to carry out reasonable and adequate curing during the construction of concrete. The conventional external curing methods such as watering and coating, which are commonly used at present, have some problems of limited curing depth and dependence on the shape and construction part of the member. The internal curing method can solve these problems well and has a good application potential for the parts and structures that are easy to shrink, crack and inconvenient for external curing. This review represented recent development on the internal curing materials, and focused on the types of super absorbent polymer (SAP) as the promising internal curing materials and the mechanism of water absorption/release and the corresponding volume change. The water absorption/release behavior of SAP in cementitious materials and its influencing factors were summarized. The influence of SAP on the hydration process, pore structure and macroscopic properties of cementitious materials was discussed. In addition, the future direction of using SAP as an internal curing material for concrete was also envisaged.

Lithium ion batteries and solid oxide fuel cells have become popular as clean energy devices. However, the commercial application of the batteries as complex electric power systems requires the batteries with long-term, multi-dimensional and high-precision performance. Some battery performance prediction methods are still in the initial stage of exploration. With the popularization and promotion of artificial intelligence, machine learning based on the artificial neural network technology has attracted recent attention. Recent advances in data science, such as machine learning, provide the scientific and engineering communities with flexible and rapid prediction frameworks, indicating great application prospects in materials research and development. This review summarized the latest advances on machine learning for the development of renewable energy technologies (i.e., solid oxide fuel cells, lithium batteries) and carbon reduction technologies, and gave some comments for the future development directions.

With the rapid development of consumer electronics, electric vehicles and energy storage, it is urgent to improve the energy density of secondary energy storage devices represented by lithium-ion batteries. Cathode materials are a key issue to improve the energy density of lithium-ion batteries. Li-rich Mn-based layered oxide cathode materials (LRM) are considered as one of the most promising cathode materials for lithium-ion batteries due to their extremely high theoretical specific capacity (>350 mA·h·g-1) and reversible specific capacity (>250 mA·h·g-1). However, the low initial Coulombic efficiency, poor rate performance, and rapid voltage and capacity fading of LRM cathode materials seriously restrict their industrial application. This review introduced the research progress of the crystal structure and electrochemical mechanism of LRM cathode materials, and analyzed the problems of LRM. The modification strategies of LRM cathode materials were comprehensively introduced from the aspects of morphology design control, doping, coating, defect structure design, gradient composition design, layered/spinel heterostructure construction, and electrolyte additives. We provided some ideas and guidance for the future development of LRM cathodes to ultimately promote the practical application of LRM cathode materials.

Natural nano-clay with kaolinite is widely used in photocatalysis. This review represented research progress on the photocatalysis of nanoclay with kaolinite as traditional support, functional support and photocatalyst. A relationship between the structure and photochemical properties of kaolinite was analyzed. In addition, the challenges and future development were also prospected.

Manganese silicate nanomaterials have attracted attention due to their high specific surface area, large pore volume, adjustable pore size and good biocompatibility. Manganese silicate nanomaterials with various morphologies such as hollow nanospheres, solid nanospheres, and core-shell nanospheres are synthesized. Hollow manganese silicate nanomaterials can be applied in cancer diagnosis, cancer therapy, synergistic cancer therapy, etc.. This review mainly introduced the synthesis and applications of manganese silicate nanomaterials. Moreover, the future prospects for development of manganese silicate nanomaterials were discussed.

Precursor continuous silicon carbide (SiC) fiber has a wide application prospect in the fields of aviation, aerospace and nuclear energy. The oxidation behavior and kinetics data of SiC fiber in a high-temperature oxidation environment are rather important for the research of composites. This review summarized the research work on continuous SiC fiber by a precursor method, oxidation type, performance degradation mechanism, oxidation process and oxidation kinetics of SiC fiber, and put forward the future research directions on oxidation behavior of SiC fiber.