Synthesis of Al₂O₃–SiC from kyanite precursor

Abstract

Carbothermal reduction of kyanite, a natural aluminosilicate with high alumina content (Al 2 O 3 и SiO 2 ), was used as a way to synthesize SiC-Al 2 O 3 powder. Carbon black was mixed with the mineral precursor in a molar ratio of (C/SiO 2 ) ‫ס‬ 5.5. The Carbothermal reaction sequence was studied in the temperature range 1260-1550°C. Completion of the reaction at 1550°C gave ␤-SiC-whiskers and ␣-Al 2 O 3 particles as final products. From observations, the impurities contained in the mineral precursor behave as catalysts for the vapor-liquid-solid whisker growth mechanism. When the specific surface area of the starting carbon was increased from 330 to 996 m 2 /g, the carbothermal reaction rate increased but the morphology of the SiC-whiskers became very irregular. This study aimed to identify the main reaction conditions for obtaining a favorable morphology of the synthesized powder for elaborating Al 2 O 3 -SiC-whisker composite materials by using low cost starting materials and a relatively simple in situ synthesis route in comparison to the conventional way of separately preparing the phases SiC (whiskers) and Al 2 O 3 before elaborating composites.

Enhancement of In situ Self-crack-healing Efficient Temperature Region by SiC Nanosizing

“…In the present study, for preparing alumina/SiC nanocomposite, the authors investigated the effect of size reduction in SiC particles on crack-healing behavior. Reaction syntheses (Chaklader et al, 1992;Borsa et al, 1999;Amroune and Fantozzi, 2001;Pathank et al, 2001;Zhang et al, 2004) were proposed for directly fabricating alumina/SiC nanocomposites which are difficult to obtain by the normal sintering of nanosized starting powder compacts of the formed alumina/SiC nanocomposite. Zhang et al (2004) also proposed the following self-propagating high temperature synthesis (SHS):…”

Reactive Hot Pressing of Alumina‐Silicon Carbide Nanocomposites

“…Ultimately, a dense Al 2 O 3 -SiC composite with nanometer-sized SiC particles homogeneously distributed in an Al 2 O 3 matrix was obtained by hot pressing the synthesized composite powders. Borsa et al 16 and Amroune et al 17,18 recently studied the reaction conditions for obtaining SiC whiskers in an Al 2 O 3 matrix from kaolin, andalusite, or kyanite (Al 2 O 3 ⅐SiO 2 ) and carbon in an argon atmosphere.…”