Ultra-low-density calcium hexaaluminate foams prepared by sintering of thermo-foamed alumina-calcium carbonate powder dispersions in molten sucrose

摘要

Porous calcium hexaaluminate (CA(6)) ceramics have many desirable properties, such as good chemical stability, high refractoriness, low density, low thermal conductivity and high surface area, which make them suitable for various applications. However, the porous CA(6) ceramics prepared thus far have had relatively low porosities. In order to increase porosity, ultra-low-density CA(6) foams were prepared by thermo-foaming followed by sintering of calcined alumina-calcium carbonate powder dispersions in molten sucrose. The percentage of height raise, sintering shrinkage, porosity, compressive strength, cell size, cell window size and cell size distribution are studied as a function of various ceramic powders to sucrose weight ratios and foaming temperatures. Calcium completely transforms to CA(6) when CA(6) is prepared by sintering at 1500 degrees C. To the best of our knowledge, the porosity of 91.7-96.4% achieved in our study is the highest reported for CA(6) foams thus far.