Premium
Investigation of Phase Stability in the System Sic‐AlN
Author(s) -
RAFANIELLO WILLIAM,
PLICHTA MARK R.,
VIRKAR ANIL V.
Publication year - 1983
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1983.tb15713.x
Subject(s) - materials science , hot pressing , carbothermic reaction , precipitation , phase (matter) , solid solution , scanning electron microscope , wurtzite crystal structure , alloy , powder mixture , homogeneity (statistics) , analytical chemistry (journal) , chemical engineering , composite material , metallurgy , sintering , carbide , chemistry , zinc , physics , statistics , mathematics , organic chemistry , chromatography , meteorology , engineering
Dense samples of several compositions in the system SiC‐AIN were fabricated by hot‐pressing. The SiC‐AIN powder was prepared by carbothermal reduction of an intimate mixture of alumina, silica, and carbon in a nitrogen atmosphere. X‐ray diffraction and electron and optical microscopy were used to determine the chemical and microstructural characteristics of the hot‐pressed specimens. Materials with bulk compositions between 15 and 75 wt% AIN were found to be nonhomo‐geneous when hot‐pressed below 2100°C. These materials were determined to be a mixture of SiC‐AIN solid solutions with different compositions. The observed compositional variations were distinctly bimodal. The source of the in‐homogeneity was the starting SiC‐AIN powder. The powders, as well as the hot‐pressed samples, consisted of a mixture of small crystals rich in SiC and large AIN‐rich crystals. Compositions outside the 15 to 75 wt% AIN region were found to be single phase and to have the wurtzite structure. Hot‐pressing SiC‐AIN in the intermediate composition range at 2300°C produced an optically and chemically homogeneous material. The precipitation of an SiC‐rich phase from a 75 wt% AIN solid solution and the precipitation of an AIN‐rich phase from a 47 wt% AIN alloy when annealed at 1700°C are strong indications that a miscibility gas exists in the system SiC‐AIN.