Effect of Alumina Micropowders on Properties of Calcium Hexaluminate
摘要
Calcium hexaluminate(CA6) was synthesized by mixing light-weight calcium carbonate and Al2O3micropowder( calcined α-Al2O3, activated α-Al2O3orρ-Al2O3) according to the stoichimetric ratio of CA6,and reaction sintering at 1 200,1 300,1 400 and 1 500 ℃ for 3 h,respectively. Effects of the three alumina micropowders on the phase composition,microstructure and properties of CA6 were investigated. The results show that:(1) for the three Al2O3 micropowders,the reaction to generate CA6 in specimens basically completes at about 1 500 ℃; CA6generated in all specimens is planar,but the array modes are slightly different;(2) the specimens prepared from calcinedα-Al2O3 or ρ-Al2O3 shrink almost,while the specimens prepared from activated α-Al2O3 expand;( 3) the cold crushing strength of the specimen prepared from activated α-Al2O3 is the highest,reaching 42. 5 MPa when only CA6 exists(after firing at 1 500 ℃);(4) the specimen prepared from ρ-Al2O3 has the lowest generation temperature of CA6and the highest apparent porosity,reaching 70. 1% when only CA6 exists( after firing at 1 500 ℃);(5)the specimen prepared from calcined α-Al2O3 has the biggest bulk density.