Structural Design, Fabrication And Properties Of Anorthite-based Porous Ceramics

In this thesis, porous anorthite ceramics with total porosity within the range53.71～91.40%, volume density of0.24～1.27g/cm3, compressive strength from0.27MPa to13.39MPa and thermal conductivity in vacuums of0.02—0.29W/(m·K) were fabricated by foam-gelcasting method and tert-butyl alcohol (TBA)-based gel-casting process. Effects of sintering temperature, solid content and foaming agent concentration on microstructure and properties of porous ceramics were studied. Thermal insulation mechanisms and matching law between thermal and mechanical properties of porous anorthite ceramics were also investigated. Using foam gelcasting method, mullite whiskers reinforced anorthite porous ceramics were fabricated, and effects of mullite whiskers content on microstructure and properties were investigate. As sintering temperature increased, connections between grains became tight, the total porosity declined, the volume density, compressive strength and thermal conductivity increased simultaneously. As solid content increased, the walls of pores got thickened and the total porosity decreased, while the volume density, thermal conductivity and compressive strength increased. The thermal conductivity and compressive strength declined while the total porosity increased with the increasing of foaming agent concentration. With the adding of mullite whisker, the compressive strength increased obviously, while thermal conductivity changed very small. And with the mullite whiskers content increased, compressive strength increased too.The matching equations between thermal and mechanical properties with various processing parameters were obtains from the analysis among the data of the thermal conductivity, compressive strength and the total porosity according to the theoretical models, from which it was available to predict and design the thermal conductivity and compressive strength of porous anorthite ceramics. Porous anorthite ceramics with high porosity and small spherical pore size structure would have excellent properties from these two methods.