Porous silicon carbide ceramics were prepared by using SiC powders and SiC_f as raw materials treated at 1600–2200 ℃ for 1 h in Ar atmosphere. The effects of SiC fiber on phase composition, microstructure, mechanical properties and pore size distribution of recrystallized silicon carbide were studied. It is demonstrated that the mass transfer rate of evaporation-condensation was increased at high temperatures owing to the decomposition of the silicon carbide fibers.Moreover, the growth of silicon carbide sintered necks and the mechanical properties of recrystallized silicon carbide cerami cs were effectively promoted. When the content of SiC fiber was 20 wt.%, the apparent porosity, bulk density and flexural strength at room temperature were (36.4 ± 0.1)%, (2.02 ± 0.01) g·cm^-3 and (76.40 ± 8.16) MPa, respectively.

SiC honeycomb ceramics were prepared using α-SiC powders, carbon black and flake graphite as raw materials by extrusion molding, combined with the reaction sintering process. The effects of sintering temperature on phase composition, microstructure, pore size distribution, and main physical properties of the materials were studied. The main phases of the honeycomb ceramic materials were α-SiC, β-SiC, and Si after firing at high temperatures. With increasing sintering temperature, the SiC grains developed well, and the mass content of residual silicon increased, resulting in a more extensive and concentrated pore size distribution. At the same time, the apparent porosity and specific pore volume decreased while the bulk density and cold crush strength were increased. When the sintering temperature was 1500 ℃, the material was more suitable for honeycomb ceramics for diesel vehicle exhaust purification. In addition, the apparent porosity, cold crush strength and median pore diameter were (45.2±0.3)%, (14.11±0.14) MPa and 15.24 μm, respectively.

The production and preparation of clean steel have become one of the current research hotspots in the metallurgical casting industry. In order to achieve deep purification of liquid steel, ceramic foam are often used in the industry to filter liquid steel to remove non-metallic inclusions and greatly improve the qualified rate of special steel. Based on the most widely used organic polymer sponge replica technique in the preparation of ceramic foam, the research status of the polyurethane foam pretreatment, high-performance ceramic slurry process, secondary centrifugal slurry preparation, vacuum infiltration and high-temperature sintering for the ceramic foam filter for steel casting are systematically elucidated. The main methods to improve the mechanical properties and filtration efficiency of ceramic foam materials are summarized, while the future research directions of ceramic foam filters for cast steel are also discussed.

Fly ash cenospheres, feldspar powder and alumina powder with various specifications were utilized as the raw materials and mullite fibers were introduced as a reinforcing phase to fabricate porous ceramics. The effect of mullite fiber on properties of the porous ceramics and the mechanism were studied. It is indicated that the incorporation of low-melting phases from feldspar powder at high temperatures was employed to reduce the eutectic point of materials, transforming the physical interface between the matrix phases into a chemical bond. An increase in mullite fiber content led to rise in closed porosity of the porous ceramics after sintering at 1100 ℃. Simultaneously, room-temperature compressive strength and bulk density initially increased and then decreased with rising content of mullite fiber. Optimal comprehensive performance was achieved when the mullite fiber content was 10 wt.%, resulting in a volume density of (0.74±0.01) g·cm^-3, a true porosity of (72.70±0.58)%, and a room-temperature compressive strength of (7.30±0.64) MPa. In addition, average thermal conductivities of the specimens at 300 ℃, 600 ℃ and 900 ℃ were 0.202 W·m^-1·K^-1, 0.214 W·m^-1·K^-1 and 0.244 W·m^-1·K^-1, respectively.