Low-temperature synthesis of calcium-hexaluminate/magnesium-aluminum spinel composite ceramics

摘要

Calcium-hexaluminate/magnesium-aluminum spinel ceramic composites were synthesized at 1450 degrees C for 3 h using a precursor from dolomite and industrial aluminium hydroxide through a 200 degrees C hydrothermal treatment, which was 100 degrees C lower than the traditional process. The main reason for this treatment was to initiate a phase transformation from gibbsite to boehmite. The morphology of calcium hexaluminate was determined by the crystal structure of aluminium hydroxide. Loosely stacked platelets were caused by tabular gibbsite, and cross-distribution flakes were due to cross-sheet boehmite. The porosity and compressive strength of composites synthesized at 1500 degrees C for 3 h increased with increasing hydrothermal temperature. CA(6) of composites from hydrothermal treatment at 200 degrees C had a more regular hexagonal plate-like morphology, total porosity of 72.2%, and compressive strength of 142.7 MPa. However, composites from hydrothermal treatment at 25 degrees C exhibited a weaker diffraction peak of calcium hexaluminate and an uncompleted crystal appearance. (C) 2015 Elsevier Ltd. All rights reserved.