Latest ArticlesLaminated SiC/BN ceramics with different structures were prepared via tape casting and hot pressing sintering to develop high-performance ceramic armor with structural and functional designs. The sinter ability, microstructure, mechanical properties and impact resistance of the prepared ceramics were investigated. The results show that the laminated structure of the ceramics can achieve the strengthening and toughening effects, and the failure mode is non-brittle fracture, and its ability to maintain the structural integrity is improved. The flexural strength of 410 MPa and the fracture toughness of 7.6 MPa·m1/2 can be obtained. The bullet shooting results show that the laminated ceramic has a good energy absorption effect and an ability to maintain the structural integrity, which can resist the impact of multiple projectiles. The impact depth is 7.5 mm, the diameter of crushing cone is 40 mm, and the dynamic damage is mainly circumferential damage. The comprehensive protection ability is improved.
Yb:YCa4O(BO3)3 (Yb:YCOB) self-frequency doubling (SFD) crystals with different doping concentrations (5%-30%, mole fraction, the same below) were grown by the Czochralski method, and the relationship between the structure and doping concentration of the as-grown crystals was analyzed. The crystals were cut along the direction with a maximum effective nonlinear coefficient, and the microchip structure design was realized. The yellow laser output with a maximum power of 1.71 W can be obtained in Yb:YCOB crystal with a doping concentration of 30% and a crystal length of 4 mm with respect to the electric-phonon coupling effect. The conversion efficiency is 11.97% and the output wavelength is stabilized at 570 nm based on the proper coating parameter design. The results show that Yb:YCOB SFD crystals can realize the practical yellow laser.
Developing room-temperature superconductors is the ultimate goal of superconducting research field. Recent work focus onthe development of high-temperature superconductors in hydrogen-rich materials under high pressure. Sulfur hydride (H3S) and lanthanide hydride (LaH10) with superconducting transition temperatures (Tc) of >200 K are theoretically predicted and then experimentally confirmed. Hydrogen-rich materials are considered as one of optimum candidates for room-temperature superconductors, thus becoming a hot research aspect in physics and materials. Some contributions in this aspect were achieved involve a variety of new cage-like superhydridesPrH9 and NdH9 are synthesized under high pressure, and their Tc is determined, The magnetic properties of NdH9 are discovered and its magnetic properties suppress a superconductivity; Novel cage-like superhydrides of CaH9 are designed under high pressure, and its Tc is predicted to be 266 K; superconducting zirconium hydrogen compounds ZrH3 and Zr4H15 are synthesized under mild pressure conditions by experimental and theoretical studie; The binary hydrides are extended to ternary hydrides, and MgXH6 (X=Si, Ge) with Tc of 60 K are designed.
Sodium-ion batteries (SIBs) are regarded as one of the most promising electrochemical devices for large-scale energy storage due to the abundant sodium resource and the physical and chemical properties similar to lithium. This short review mainly represented recent studies on the development of some typical cathode and anode materials for SIBs, and provided the related information on the key electrode materials for the commercialization and practical application of SIBs.
Thermoelectric materials as novel clean energy materials have application prospects in waste-heat recovery and solid-state refrigeration. The thermoelectric compounds evolve from simple unitary- or binary-component crystalline systems to multinary complex systems. Among them, the multinary diamond-like compounds, the compounds with distinct sublattice and chemical bond hierarchy characteristics and their derivatives exhibit a complex crystalline-amorphous hybrid behavior in an atomic scale and present some transport effects, providing a prospect for the exploration of effects of electrical-thermal transport and systems of thermoelectric materials. This review summarized recent research progress on thermoelectric materials in sublattice engineering, including the structural design of novel "quasi-crystalline" thermoelectric compounds, the optimization of thermoelectric property and the characterization of microstructures in a sublattice scale. In addition, the relationship between the crystalline-semi-crystalline sublattice structure and the thermoelectric property of the compound was also discussed.
Metal-organic frameworks (MOFs) are a novel type of inorganic-organic hybrid material, which is composed of metal ions or metal clusters and organic bridging ligands through coordination. The combination of inorganic and organic components in the MOFs can possess the characteristics and performances of inorganic and organic elements simultaneously, and realize the cooperative optimization. Furthermore, the ordered micro-pores can be used to encapsulate the guest molecules within the MOFs to generate novel photonic functions. Therefore, the design and construction of MOFs for photonics applications become popular. This paper summarized the latest results obtained from a research project 'Investigation of photonic functions based on ordered microporous materials' supported by the National Natural Science Foundation of China, i.e., the design and controllable preparation methods of metal-organic frameworks, and the encapsulation of organic dyes and perovskite quantum dots in ordered microporous of the MOFs. In addition, future development and application prospects of the MOFs were also discussed.
The effects of water-to-binder ratio and basalt coarse aggregate on the compressive behavior of ultra-high-performance concrete (UHPC) were investigated. The results show that the compressive strength of UHPC firstly increases and then decreases, while the elastic modulus decreases with the increase of water-to-binder ratio, and the optimum compressive strength is obtained at a water-binder ratio of 0.16. The compressive strength firstly increases and then decreases, while the elastic modulus increases with the increase of coarse aggregate. In addition, a semi-empirical equation considering the parameters of coarse aggregate was also proposed for the prediction of elastic modulus of UHPC, which was validated using the existing literature data.
The effects of strength grade, steel fiber content on the compressive strength and its scale effect of ultra-high performance concrete (UHPC) were investigated via cubic compressive strength tests on the UHPC cubic specimens with different sizes, strength grades and fiber contents. The results show that the scale effect of the cubic compressive strength becomes more obvious with the increase of strength grade. The scale effect of the cubic compressive strength of the plain UHPC specimen with a strength grade R160 is 1.72 times greater than that of the specimen with a strength grade of R120. The content of steel fiber has an effect on the scale effect of the cubic compressive strength. The greater the content of steel fiber is, the more pronounced the scale effect will be. The scale effect on the cubic compressive strength of specimens with a fiber content of 3% is 46% greater than that of the specimens without steel fiber reinforcement. The size conversion factors for cubic compressive strength of the UHPC with different strength grade sand the calculation formulas for the scale effect law of the cubic compressive strength of the UHPC are proposed. The proposed formulas can be used to analyze the cubic compressive strength of the UHPC.
The non-uniform deformations of C50 concrete under drying at different relative humidities (i.e., 73%, 55% and 40%) from 1 d to 60 d were determined by a digital image correlation (DIC) technique. The equivalent tensile strains ɛ̃ in concrete were calculated based on the meso-scale damage model of concrete, which were used to identify the damage distribution in concrete. The results show that the mortar phase surrounding the coarse aggregates has great tensile strains, thus readily occurring damage and micro-cracks. The damage index (Dɛ̃) calculated from the value and distribution of ɛ̃ was used to quantify the drying-induced damage in concrete. The Dɛ̃ of the concretes under drying at 55% and 40% relative humidities increases to 101 μm/m and 135 μm/m, respectively, indicating that the drying conditions with ≤55% relative humidity could cause damage and micro-cracks.
Influence of plug flow on the nonlinearity and continuity of angular velocity-torque curve obtained in a Couette rhometer during the measurement of Bingham fluid was analyzed. The feasibility of linear regression on angular velocity-torque curve to obtain the Bingham parameters was discussed, showing the error caused by ignoring the influence of plug flow in the annulus of Couette rheometer. A method to obtain the Bingham fluid parameters based on linear regression of shear stress-shear rate curve with respect to the effect of plug flow was proposed. The denoise method of the angular velocity-torque data was recommended for guaranteeing the precision of the angular velocity-torque curve.
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