HUANG Ze, DENG Chengji, DONG Bo, YU Chao, DING Jun, ZHU Qingyou, ZHU Hongxi, WANG Yibo
(The State Key Laboratory of Refractories and Metallurgy, Wuhan University of
Science and Technology, Wuhan 430081, Hubei, China)

Abstract: 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.
Key words: fly ash cenosphere; mullite fiber; porous ceramic materials; liquid-phase sintering; high temperature thermal conductivity; mechanical properties