Silica bricks only used the combined mineralizer of calcium hydroxide and iron scale in the early domestic production. It is feasible and necessary to explore novel mineralizers to improve the performance of silica bricks. In this paper, novel silica bricks were prepared with ferrosilicon nitride and calcium carbonate as mineralizers instead of calcium hydroxide and iron scale. The prepared silica bricks have good properties, and the content of tridymite with 2% ferrosilicon nitride and calcium carbonate added reaches 62% and 65%, respectively. The effects of ferrosilicon nitride and calcium carbonate on the formation of tridymite in silica bricks were investigated by X-ray diffraction and scanning electron microscopy. The results show that in the silica brick with ferrosilicon nitride as mineralizer, Si₃N₄ network formed by the intertwined columnar Si₃N₄ in the sea urchin-like structure ferrosilicon nitride protects Fe and Fe₃Si through its oxidation reaction, thereby achieving a higher FeO/Fe₂O₃ ratio and a lower liquid formation temperature in the FeO-Fe₂O₃-SiO₂ ternary phase. The FeO/Fe₂O₃ ratio in the liquid phase fluctuates at a high temperature, and then the constant change of the solubility of tridymite in the saturated liquid phase promotes the crystallization of tridymite due to the reducibility of Fe, Fe₃Si and Si₃N₄. When calcium carbonate is used as a mineralizer of silicon brick, the formation temperature of the liquid phase in the brick is increased to 1 436 ℃. Before that, the reactions in the bricks are mainly the decomposition of calcium carbonate and the transformation from β-quartz to α-quartz and to metastable α-cristobalite. The increase of the formation temperature of the liquid phase does not reduce the content of tridymite in the brick, and the content of glass phase in the brick is less than that in the brick with iron mineralizer.

Crucible refractories are very important for the quality of titanium alloy smelting. In order to develop novel crucible material with high performance, in this work, Y₂O₃-Al₂O₃-MgO-CaO composite refractories were prepared with commercial yttrium oxide and Al₂O₃-MgO-CaO powders (AMC) as raw materials, and the effects of sintering temperature (i.e., 1 500 ℃, 1 600 ℃) and AMC contents (i.e., 0, 25%, 50%, 75% and 100%, in mass fraction) on the phase compositions, sintering properties (i.e., linear shrinkage, volumetric shrinkage, apparent porosity, and bulk density), compressive strength at room temperature, thermal shock resistance and microstructures of as-prepared refractories were investigated. The results show that the most properties of the composites are improved, compared with Y₂O₃ and AMC. The performance becomes better as the sintering temperature increases. Moreover, the linear shrinkage, volumetric shrinkage, bulk density and compressive strength at room temperature of the composites increase with the increase of AMC contents. At the AMC content of 75%, the composite sintered at 1 500 ℃ for 3 h has the optimum comprehensive performance (i.e., the apparent porosity of 4.37%, the compressive strength at room temperature of 274.99 MPa, the residual strength after three water-cooling and thermal shocks of 161.60 MPa, and the residual strength ratio of 58.78%).

Sintering process directly affects the microstructure and properties of ceramics. BaTiO₃ piezoelectric ceramic was sintered by an ultrafast-high temperature sintering method. The result was compared with that of BaTiO₃ sintered by a conventional furnace sintering method. The effect of sintering current on the phase composition, microstructure and property of BaTiO₃ sintered in ultrafast-high temperature sintering method was investigated. Ultrafast-high temperature sintering suppresses the grain growth. After ultrafast sintering at 180 A for 5 min, the superior property with the dielectric constant of 3 450, dielectric loss of 1.89% and piezoelectric constant 283 pC·N^-1 is obtained. The whole sintering time is reduced by 196 times, indicating that ultrafast-high temperature sintering is a promising densification method for functional materials.

ZrB₂-based composite ceramics have great potential for applications at ultra-high temperatures, but the low toughness and poor oxidation resistance of them limit their practical applications. In this work, the Zr, B₄C, Al, C and Si raw powders were used to prepare ZrB₂-SiC-Zr₂Al₄C₅ composite ceramics by reactive spark plasma sintering. The reaction processes and mechanism were studied. The effects of Zr₂Al₄C₅ content and oxidation temperature on high-temperature oxidation behavior of multiphase ceramics were investigated for revealing the anti-oxidation mechanism. The results indicated that the B₄C reacted with Zr to form ZrB₂ at 900 ℃, and then the SiC formed at 1 100 ℃. At 1 400 ℃, the Zr₂Al₄C₅ formed from the reaction of Zr₃Al₃C₅, ZrC and Al₄C₃ which formed at the early initial reaction stage. And the Zr₂Al₄C₅ transformed into Zr₃Al₄C₆ with further increasing temperature. The main phases of the composite ceramics after oxidation are ZrO₂, ZrSiO₄, aluminosilicate and SiO₂ glass. With increasing Zr₂Al₄C₅ content, the surface of the oxide layer of the composite ceramics became uneven, loose and porous, while obvious long strip grains and inhomogeneous distribution of glassy phases were also observed. This study not only provides a new experimental reference for in-depth understanding of the high-temperature oxidation behavior of ZrB₂-SiC based multiphase ceramics, but also provides new experimental and theoretical support for developing high-performance ZrB₂-SiC based high-temperature composite ceramics.

The melting of refractory in slag and the penetration of slag into refractory are the main reasons for the damage of refractory. These two aspects are related to the wettability between slag and refractory at a high temperature, and the wettability can be evaluated by the surface tension, adhesion work and spreading coefficient of slag on the refractory surface. The wettability of slag and refractory can be inhibited by changing the composition and roughness of the refractory, thus resulting in the improved service life of the refractory. This review represented the factors affecting the high-temperature wettability between refractories and slag based on the aspects of slag composition, refractory composition and surface microstructure effect. In addition, the future research direction in this field was also prospected.

Cement rotary kilns using refractories require excellent refractoriness, thermal shock stability and corrosion resistance due to the cyclic rotation and feeding-discharging of cement clinker. In this paper, a kind of magnesia-alumina spinel refractory containing coating structured aggregates were prepared by wrapping spinel fines on the surface of magnesia aggregates. The fracture behavior and corrosion resistance of prepared refractories were characterized by three-point bending test combined with digital image correlation, acoustic emission technique, and static slag resistance method. The results indicate that by changing the distribution of spinel to make coating structure aggregates, the alumina content is effectively reduced while a more uniform and extensive distribution of spinel phase is achieved. Compared with the merchant magnesia-alumina spinel refractory (10% Al₂O₃) with pre-synthetic spinel aggregates, the magnesia-alumina spinel refractory (5% Al₂O₃) with spinel coating aggregates has the improved mechanical strength and corrosion resistance, and maintains the thermal shock resistance.

The research of high-efficiency trichromatic phosphors based on vltraviolet/near-ultraviolet (UV/n-UV) excitation is of great significance for the development of white light-emitting diode (LED) applications. A series of Ce³⁺, Tb³⁺ or Eu³⁺ single-doped Ca_xMg_yAl_mSi_nO_z (i.e., Ca₂Mg_0.25Al_1.5Si_1.25O₇, Ca₂Mg_0.5AlSi_1.5O₇, Ca₂Mg_0.75Al_0.5Si_1.75O₇, and Ca₂₀Al₂₆Mg₃Si₃O₆₈) trichromatic phosphors were synthesized by a high-temperature solid-phase method. The crystal structure and band gap of samples were investigated by Rietveld refinement, crystal structure simulation and density functional theory calculation, and the effect of stoichiometry-regulating crystal field on the luminescent performance was analyzed. High-quality blue, green and red trichromatic phosphors with quantum efficiencies of 28.13, 26.42 and 26.75, fluorescence lifetime of 42.23 ns, 2.88 ms and 2.21 ms, as well as a good thermal stability were selected to compare their luminescent performance. Finally, the prototypes of white LED were fabricated with the trichromatic phosphors for UV chip, and their performance parameters (i.e., luminous efficiency, correlated color temperature and color rendering index) were tested. The results show that these phosphors have a promising potential in the application of UV-excited white LEDs.

Two types of porous lead zirconate titanate (PZT) with different pore morphologies and porosities were fabricated by freeze-casting and burnt-out polymer sphere techniques, respectively. The effects of porosity and pore morphology on the sensing application of porous PZT ceramics were investigated. The result shows that the decreasing rate for piezoelectric charge coefficient d₃₃ is slower than that of relative permittivity ε_r for porous PZT ceramics, leading to a better piezoelectric performance for the porous PZT rather than that of the dense ceramic. Moreover, d₃₃ of porous ceramics with random spherical pores decreases, compared to that of the porous ceramics with aligned pores. Therefore, the porous PZT ceramic with aligned pores has a higher output voltage. The maximum output voltage reaches up to 84 V, which is generated by the 55.9% porous PZT with aligned lamellar pores under 8 N external force. This work is beneficial for understanding the effect of the pore characteristic on the sensing properties of piezoelectric ceramics and provides a new idea for the preparation of sensors with high piezoelectric coefficient.

The prestressing reinforcement has been proved to be effective for ceramics, but how this surface prestressing affects other mechanical properties is still unclear. The influence of surface residual compressive stress on the mechanical properties of composite members, including bending strength, elastic modulus, fracture toughness, hardness and damage tolerance are investigated in this work. In order to achieve suitable surface compressive stress and the appropriate interface shear stress, mullite and aluminum oxide are mixed and ground into a slurry with a mass fraction ratio of 1∶1 and coated on the pre-sintered alumina substrate. The coated samples were prepared by pressureless sintering. With the temperature drop, different shrinkage rates and interface constraints of the two materials form the residual compressive stress in the surface layer. Mechanical properties of the coated alumina were tested. The experimental results show that the prestressed design can effectively improve the bending strength of alumina by 38.9%; The fracture toughness is increased by 36.5%, and the elastic modulus and hardness are slightly decreased. The damage tolerance of the prestressed ceramic is increased from 0.389 4 m^1/2 to 0.452 7 m^1/2, which is 16.26% higher.

The flexoelectric effect is a mechanical-electric coupling effect between strain gradient and electric polarization (i.e., positive flexoelectric effect) or electric field strength gradient and mechanical strain (i.e., converse flexoelectric effect). Unlike the piezoelectric effect, the flexoelectric effect, which is not limited by material symmetry and the Curie temperature, increases with decreasing the material size, thus attracting much attention and having a promising application. This review introduced the history of flexoelectric effect, measurement of flexoelectric coefficient, and mechanism to enhance flexoelectric effect. Recent studies on its application in the realm of sensors, actuators, mechanical memories, flexoelectric piezoelectric composites, energy harvesters, and electronic devices were highlighted. In addition, the further development of flexoelectric effect was also prospected.