Preparation and Properties of High-Purity Porous Calcium Hexaluminate Material

Abstract

In this paper, high-purity porous calcium hexaluminate materials were prepared with α-alumina, nano-meter calcium carbonate and ρ-alumina as raw materials. The properties of the prepared porous materials, such as bulk density, true density, thermal conductivity, and cold crushing strength, were investigated. The increase in sintering temperature led to the increase of true density. Bulk density and cold crushing strength of the specimen fired at 1500°C had the lowest values. As ρ-alumina content increased, bulk density, true density, and cold crushing strength had no obvious changes, but the thermal conductivity decreased at first and then increased. The calcium hexaluminate formation was intense from 1450°C to 1500°C and finished at 1500°C. Above 1500°C, the main phase of specimens was calcium hexaluminate (CA6). And CA6 grains were regular hexagonal plates morphology and widely spread after firing at 1550°C.

Calcium aluminate cement in castable alumina: From hydrate bonding to the in situ formation of calcium hexaluminate

“…As a consequence of the high levels of total porosity (36-50 vol.%), compositions containing 20 and 34 vol% of CAC showed smaller gains of strength and rigidity. Nevertheless, such properties' values are similar to those reported in [1,6,13,14,19,30], which tested porous CA 6 structures of comparable porosity levels.…”

“…As heating continues, these low melting point phases melt and help to dissolve the neighboring particles, and since such liquids are progressively enriched in alumina, the Al 2 O-richer compounds (CaAl 4 O 7 or CA 2 and CA 6 ) crystallize. Several studies have evaluated the effects of different raw materials [12][13][14] and processing techniques [15][16][17][18][19] on the physical properties of the resulting CA 6 porous structures [20][21][22][23][24][25]. For instance, compared to the sintering of pre-reacted particles [1,26], the in situ formation of CA 6 from aqueous suspensions of individual oxides or their precursors is a straightforward process of substantial energy-saving potential.…”