β-phase high thermal conductivity silicon nitride ceramics were prepared by sintering at 1 900 ℃ for 2 h using silicon nitride (α-phase≥95%, particle size 0.5 μm) as a raw material, and MgO-Y₂O₃ as a composite sintering aid. The effects of sintering aid content and ratio on the densification process, thermal conductivity, mechanical properties and microstructure of silicon nitride ceramics were discussed. The results show that when the addition amount of sintering aid is 5% MgO+4% Y₂O₃, the thermal conductivity, bending strength, fracture toughness of the sample sintered in air at 1 890 ℃ for 2 h can reach 85.96 W·m^-1·K^-1, 873 MPa and 8.39 MPa·m^1/2, respectively. In the sintering process, Y₂O₃ reacts with Si₃N₄ to form a compound fixed at the grain boundary, which plays a role in purifying the silicon nitride lattice and improves the thermal conductivity of the sintered sample. Excessive MgO and Y₂O₃ will form compounds during the sintering process and remain at the grain boundary, which will reduce the mechanical properties and thermal conductivity of the material.

Flash sintering is a new type of electric field/current assisted sintering technology developed in recent years, which can densify ceramic materials in very short time at low temperatures. Although flash sintering has been demonstrated in many ceramic materials, there is no consensus on the sintering mechanism. In this paper, several main sintering mechanisms have been reviewed, including Joule heating, defect generation, electrochemical reaction, etc. In addition, the advantages and disadvantages of various mechanisms are discussed based on the reported works. Finally, the research direction of the flash sintering mechanism is proposed.

A preparation method of ceramic direct ink writing based on solvent evaporation was proposed, and the process parameters to change the solvent evaporation rate of ceramic slurry in the printing process were adjusted. For zirconia ceramic, a zirconia ceramic slurry with a high solid loading was prepared, and the rheological properties and printability of zirconia ceramic slurries with different solid loadings were analyzed. The results show that zirconia ceramic slurries with 54%-58% (volume fraction) solid loadings can be used to form a ceramic body without deformation or collapse by changing the solvent evaporation rate. Based on the preparation and characterization of ceramic tooth and cuboid samples, it is verified that this method can prepare some complex-shaped ceramic parts with a high strength.

In view of the support problem of slurry based ceramic additive preparation, a novel method of selective laser curing of frozen slurry was proposed. Water glass was used as a binder to prepare ceramic slurry, the whole slurry layer was frozen by cryoplate in order to establish a solid support, the dehydration effect of water glass heated was used to fix ceramic particles, and the frozen support materials were melted in water. The effects of solid content, laser power, scanning speed and scanning distance on the size and morphology of curing line, surface and body were investigated. A green body with a compressive strength of 29.4 MPa, a bending strength of 2.53 MPa, and a thin-wall structure with the thickness of 130 µm and span of 60 mm was prepared. This proposed method has the characteristics of high efficiency of solid support establishment and removal, and the processed thin-wall and cantilever structure is not easy to deform, thus having a promising application potential in the field of rapid casting.

CT models come from the three-dimensional data of industrial CT test which contain the internal defects, and can draw the more accurate conclusion rather than some ideal models. A CT finite element geometry model of three different ceramic components, containing internal details such as inner defects, was proposed based on the CT non-destructive test. The stress distributions of ceramic components were analyzed by both an ideal finite element model and a CT finite element model. It is indicated that the STL files obtained from the industrial CT test data can be processed to obtain the geometric model to realize the finite element analysis. The results of stress distribution obtained by the fault-free CT model are similar to those obtained by the ideal model. However, the simulation data obtained by the CT model are closer to the results under the actual working conditions when there are defects or special structures.

Silicon carbide (SiC) microfiltration membranes were fabricated via dip-coating on tubular SiC supports with an average pore size of 1.4 μm with SiC powder (the average particle size of 0.8 μm) as a raw material and PMAA-NH₄ as a dispersant. The effects of pH value and dispersant amount on the stability of SiC suspensions, as well as the effects of sintering temperature and atmosphere (i.e., Air, Ar and N₂) on the properties of SiC microfiltration membranes were investigated. The results show that the stable slurry can be obtained when pH value is 10 and PMAA-NH₄ amount is 0.6% (in mass fraction). The SiC microfiltration membrane sintered in N₂ at 1 200 ℃ shows the optimized performance (i.e., the average pore size of 78 nm, the membrane thickness of 10 μm and the pure water permeability of 860 L·m^-2·h^-1·bar^-1).

A complex-shaped titanium carbonitride (Ti(C, N))-based cermet tool was prepared by microwave sintering. The effects of molding pressure on density distribution and residual stress of green compact, relative density, mechanical properties, and microstructure of the sintered compact tool were studied. The results indicated that a high-performance complex-shaped ceramic tool can be prepared using the combined technology of molding and microwave sintering. The density of the cutting edge was lower than that of the body of the tool. The difference increased first and then decreased with the increase in molding pressure. When the molding pressure was lower than 200 MPa, minimal differences between rake and flank faces with respect to relative density and mechanical properties were noted, while the relative density and mechanical properties of rake face were higher than that of flank face when the molding pressure was higher than 300 MPa. However, excessive molding pressure resulted in cracks within the tool. The optimal molding pressure for preparation of a Ti(C, N)-based cermet tool with three-dimensional breaker was 400 MPa.

A simple and feasible precracking method based on the strain government of ceramics to crack propagation was proposed. Three-point bending loading was carried out to prefabricate cracks in Al₂O₃, SiC and Si₃N₄ ceramic specimens by bonding the specimens with a triangular notch (crack initiation) on a metal beam to form a ductile-brittle composite beam. The specimens with different crack lengths can be controlled by adjusting the tensile zone height of ceramics. The fracture toughness of these three ceramics was measured by a single edge precracked beam method. The crack propagation process in the ceramic specimens was monitored by acoustic emission technology. The result show that this technology is easy to operate and the success rate of pre-cracking is >80%. The fracture toughness of Al₂O₃, SiC and Si₃N₄ measured is 4.45±0.41, 3.45±0.34 MPa·m^1/2 and 5.23±0.49 MPa·m^1/2, respectively.

Amorphous Si₃N₄ powders were synthesized via the pyrolysis of silicon diimide powders that were prepared by a liquid-liquid phase method. α-Si₃N₄ with a high purity was obtained by crystallizing amorphous Si₃N₄ powders at 1550 ℃. The crystallization process of amorphous Si₃N₄ with a short dendritic structure was investigated, and the influence of α-Si₃N₄ crystal seeds on the crystallization process was discussed. Si₃N₄ nuclei form on amorphous Si₃N₄ powders, and grow further into α-Si₃N₄ crystal particles. α-Si₃N₄ crystal seeds were added in amorphous Si₃N₄, which could increase the number of nuclei, and reduce the short branch structure of amorphous Si₃N₄ to accelerate the crystalline transformation from amorphous to α phase. The quality of crystal particles was improved effectively.

A black pigment of C/ZrSiO₄ was prepared by a non-hydrolytic sol gel method with zirconium tetrachloride, tetraethyl orthosilicate and phenolic resin spheres prepared by the Stöber method as zirconium, silicon and carbon sources, respectively. The morphology, structure and residual carbon rate of the phenolic resin spheres were characterized by scanning electron microscopy, energy disperse spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy and differential thermal analysis-thermogravimetry. The effects of phenolic resin spheres amount and calcination temperature on the synthesis and color properties of C/ZrSiO₄ pigments were also investigated. The results show that the obtained phenolic resin spheres are well-dispersive and the average diameter is 550 nm, and they possess oxygen-containing functional groups on their surfaces and achieve a high residual carbon rate of 48.63%. The L* value of prepared C/ZrSiO₄ pigment firstly decreases and then increases with increasing the amount of phenolic resin spheres. When the amount of the phenolic resin spheres is 2% (in mass fraction) and the calcining temperature is 900 ℃, C/ZrSiO₄ pigment with a good color performance (L*=39.76, a*=0.53, b*=2.21) can be obtained. Moreover, the colored glaze samples present a good color rendering performance when applying C/ZrSiO₄ pigment in ceramic glaze calcined at 1 200 ℃. It is indicated that C/ZrSiO₄ pigment could have a promising application in coating, ceramic and glass decoration.

The chemical composition, phase, microstructure and chemical state of iron element of the celadon glazes from the Five dynasty Yaozhou kiln, Northern Song dynasty Ru kiln and Southern Song dynasty Guan kiln, ancient China, were compared and analyzed, and the essential reasons for the color difference and the formation of regional characteristic were summarized. The results indicate that the celadon glaze of the Five dynasty Yaozhou kiln contains relatively high contents of K₂O and CaO, which is beneficial to the formation of green-blue color and the growth and discharge of bubbles in the glaze layer. As a result, the glaze is green-blue with high transparency and glossiness. The celadon glaze of the Northern Song dynasty Ru kiln contains relatively high contents of Fe₂O₃ and P₂O₅. This is precisely because of the anti-polarization effect of P⁵⁺ on Fe³⁺ that the blue tone of glaze is enhanced. Also, the dense bubbles, crystals and phase separation structures in the glaze increase the opacity and form the opal effect of the Ru glaze. The base glaze composition of Southern Song dynasty Guan kiln celadon is similar to that of the Ru kiln, and their microstructures are also similar. However, a higher SiO₂ content promotes the formation of bubble aggregations in the heterogeneous nucleation stage of glaze, which further improves the opacity and is conducive to the formation of the texture properties of jade. In addition, the differences of firing temperature, pH value of buried soil and existence form of iron in the raw material also affect the appearance of celadon glazes and form the regional features.

Gout is a term given to the disorder of uric acid metabolism, which results from the deposition of crystals of monosodium urate monohydrate in various connective tissues. Recent domestic researches on the treatment of gout still focus on the development and application of medicine, mainly through drug treatment and acupuncture to relieve the pain of patients. However, less attention is paid to the mechanism of monosodium urate monohydrate crystallization. In principle, gout is the crystallization of monosodium urate solute when it reaches supersaturation in the body fluid circulation. This review, from the perspective of materials, represented recent research work on the structure, morphology, in vitro preparation method and inhibition method of monosodium urate monohydrate crystals, and put forward the direction of further research in the future.

A zinc aluminate spinel powder was prepared by a molten salt method using Al₂(SO₄)₃·18H₂O, ZnO as raw material and Na₂SO₄ as a flux of molten salt. The influences of molten salt amount, synthesis temperature and soaking time on the synthesis performance of zinc aluminate spinel powder were investigated. The growth mechanism, phase composition and microstructure of synthesized product were analyzed. The reaction processes of two systems without and with 10% (in mass fraction) molten salt Na₂SO₄ were investigated by thermogravimetry and differential scanning analysis. The results indicate that a pure zinc aluminate spinel powder can be obtained at 1 000 ℃ for 3 h when Na₂SO₄ is used as a molten salt at the amount of 10%. Most of the synthesized zinc aluminate spinel crystals are a hexagonal prism shape, a small part is octahedral shape and the crystalline sizes are 100-200 nm. Zinc aluminate spinel can be synthesized at a lower temperature in the presence of Na₂SO₄ as a molten salt. In liquid phase environment, the formation of zinc aluminate spinel is principally controlled via template synthesis reactions, and secondarily controlled via dissolution-precipitation reactions.

Mesoporosity was introduced into the ZSM-5 zeolites by alkaline treatment and the external acid sites were passivated selectively via adsorption of phosphate anions on the surfactant modified surface. The results showed that the mesoporosity was successfully obtained after alkaline treatment, meanwhile, the external acid sites increased and the selectivity decreased. A monolayer or bilayer structutre of surfactant on the surface of zeolites could be formed in the different concentrations of surfactant solutions. The monolayer structure did not absorb the phosphate anions. While the bilayer structure selectively absorbed the phosphate anions on the external surface, which could passivate the external acid sites after calcining. The modified zeolites had high activity, stability and selectivity in the isomerization of styrene oxide with yield of phenylacetaldehyde more than 95% and no significant deactivation after 100 h time on stream.

A NaP zeolite doped with titanium (Ti-NaP) was prepared by a hydrothermal method and a complexation method using sodium silicate and sodium meta-aluminate from coal fly ash by grading extraction as raw materials based on a scientific concept of "sewage purification by solid waste". The crystal phase, morphology, and existed state of elements in NaP zeolites before and after doping titanium were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and solid magic angle spinning nuclear magnetic resonance of silicon and aluminum. The adsorption performance of Ti-NaP was also evaluated. The experimental results show that when n(Al₂O₃)∶n(TBOT)=6∶1, the crystallinity of Ti-NaP reaches 98.2%, and the existed state of titanium in NaP zeolite mainly includes the isomorphous substitution with silicon atom in the skeleton and the balance of skeletal negative charge. The specific surface area of Ti-NaP is 123 m²/g, which is approximately 3.6 times greater than that of NaP zeolite un-doped with titanium (27 m²/g). The test results of Zn(II) adsorption show that the removal rate of Zn(II) of Ti-NaP is 97.71%. Moreover, Ti-NaP still remains a good adsorption stability after 5 cycles of adsorption-regeneration.

Three mordenites with different morphologies (i.e., fiber bundle, regular fiber and flaky) were synthesized via the introduction of cyclohexylamine and hexamethyleneimmonium, respectively. The crystal form, morphology, pore structure and acidity of the samples were characterized by X-ray diffraction and N₂ physical adsorption, scanning electron microscopy and NH₃ temperature-programmed desorption, and the alkylation performance evaluation and regeneration experiments were carried out. The experimental results show that all three mordenites have a great catalytic activity, and the catalyst life of the flaky mordenite can reach 26 h, which is better than that of the fiber bundle mordenite for 5 h and the regular fibrous mordenite for 3 h. The fiber bundle and regular fibrous mordenites can have a selectivity to 2-substituted linear alkylbenzene of more than 75%, and the product selectivity of flaky mordenite can reach more than 50%, which is superior to the existing technology for linear alkylbenzene production. The catalyst regeneration rate is opposite to the catalyst deactivation rate. The three mordenites with fiber bundle regular fiber and flaky morphologies have the maximum catalytic activities of fresh catalysts after regeneration of 8, 11 h, and 5 h, respectively.

A ceramic slurry with a solid content of 57% (in volume fraction) was firstly prepared with α-Al₂O₃ of 92% (mass fraction) and silica fume of 8% as main raw materials, aluminum dihydrogen phosphate of 2.5% as a binder and sodium hexametaphosphate of 0.2% as a dispersant in the presence of Y₂O₃, and then the formed specimen was sintered at 1 600 ℃ for 3 h. The results show that the addition of Y₂O₃ has little effect on the printing properties of ceramic slurry. At high temperatures, Y₂O₃ reacts with Al₂O₃ to form YAG, and promotes the reaction of Al₂O₃ with SiO₂ in the specimen, thus increasing the specimen strength. A rate of the properties change after sintering decreases, and even the slag resistance decreases when the amount of Y₂O₃ addition exceeds 1.2%. The cold compressive strength is 230.2 MPa at the optimal amount of Y₂O₃ addition of 1.2%. For slag resistance, in addition to the densification of the high melting point YAG phase and the solid phase, a dense protective layer is formed on the inner wall of the crucible, thus enhancing the resistance to the penetration of glass melt. It is indicated that the addition of Y₂O₃ is beneficial to printing the specimens with a high strength and a good slag resistance.

Low carbon alumina zirconia carbon (Al₂O₃-ZrO₂-C) slide gate was designed with graphene nanosheets. The morphology of graphene nanosheets was characterized by atomic force microscopy and transmission electron microscopy. The phase composition and microstructure of the fabricated refractories were examined by X-ray diffraction, scanning electron microscopy and energy disperse spectroscopy. The results show that the GNSs can effectively improve the properties of slide gate refractories by filling the micropores and promoting the formation of silicon carbide whisker between particles. As 1.5% GNSs/Al₂O₃ composite powders are added instead of carbon black, the slide gate shows a better oxidation resistance and ensures the strength and thermal shock stability.

Effect of Al on the spinel evolution within Al₂O₃-MgO refractories in nitrogen at 1 600 ℃ was investigated. The results show that Al can markedly change the composition, morphology and reaction path of spinel phase within Al₂O₃-MgO refractories. Without Al addition, MgO reacts with Al₂O₃ to form spinel, and then spinel reacts with Al₂O₃ encompassed by itself to form once-rich-Al₂O₃ spinel. When the oxygen partial pressure by C-O₂ consumed oxygen reaction decreases, MgO becomes unstable and decomposes into Mg(g) and O₂; Mg(g) diffuses and transfers along pores or gaps in the materials, reacting with rich-Al₂O₃ spinel to generate new rich-Al₂O₃ spinel and Al(g), Al(g) is nitrided as AlN and then AlN dissolves into rich-Al₂O₃ spinel to form MgAlON. Al(g) and Al₂O(g) diffuse and transfer along pores or gaps in the materials after introduction of Al into Al₂O₃-MgO refractory. Al(g) and Al₂O(g) change into AlN and further dissolve into rich-Al₂O₃ spinel, enhancing N content of MgAlON. Also, in the gas-gas reaction system, Al(g)/Al₂O(g), Mg(g), N₂ and O₂ react with each other to form flake MgAlON.

A series of lightweight ladle working lining castables were prepared with tabular alumina, microporous corundum, and calcium hexaaluminate (CA₆) as aggregates, respectively, reactive α-Al₂O₃ ultrafine powder, SiO₂ ultrafine powder, tabular alumina powder, and fused magnesia powder as matrices, calcium aluminate cement as a binder, and MgO ultrafine powder (D₅₀=5.4 μm), Al(OH)₃ ultrafine powder (D₅₀=8.2 μm) as additives. The influence of aggregate and ultrafine powder on the physical properties, pore size distribution, thermal conductivity, thermal shock resistance, and slag resistance of lightweight refractory castables was investigated. The results show that calcium hexaaluminate (CA₆) can make the castable lightweight, but increase the pore size and reduce the strength and slag resistance of castable. Using microporous corundum can reduce the bulk density of castble, and increase the proportion of micropores, which is beneficial to reducing the thermal conductivity, and improving the thermal shock resistance and slag resistance of castble. When MgO ultrafine powder and Al(OH)₃ ultrafine powder are used as additives, the fluidity and strength of castable can be improved, the ratio of micropores in the castble can be increased, and the fracture energy, thermal shock resistance and slag resistance can be improved.