Microstructure and Mechanical Properties of Mullite–Silicon Carbide Composites

Abstract

Mullite‐SiC‐whisker composites were prepared by powder processing using two commercial SiC whiskers. These composites were prepared by sintering rather than hot‐pressing. A mulliteSlC‐powder composite and a base line mallite material were also prepared for comparison with the two whisker composite materials. Fracture toughness measurements showed significant enhancement in only one of the whisker composite materials. The microstructure of the four materials was examined by scanning electron microscopy and transmission electron microscopy to assist in the explanation of the mechanical behavior of these composites. The examinations suggested that most of the toughening results from second‐phase particles, with only limited toughening from effects associated with whiskers per se. In one case, higher toughness was partially associated with the formation of sialon phase by reaction with the whiskers and the furnace environment.

Oxygen diffusivities in mullite/zirconia composites measured by 18O/16O isotope exchange and secondary ion mass spectrometry

“…Previous studies have reported that partially stabilized zirconia (PSZ) and silicon carbide (SiC) effectively improved the mechanical properties of mullite-matrix composites. [1][2][3][4] However, the oxidation of the SiC constituent would deteriorate the mechanical properties of such composites under high-temperature oxidizing environments. Moreover, the oxidation resistance of SiC-reinforced ceramic-matrix composites could be seriously degraded because of the incorporation of PSZ into the matrix.…”

Volume Fraction and Whisker Orientation Dependence of the Electrical Properties of SiC‐Whisker‐Reinforced Mullite Composites

“…S TRUCTURAL type materials such as SiC-whisker-reinforced mullite composites have been studied for many years for their potential use in high-temperature applications. [1][2][3][4][5][6] Hence their mechanical properties 2,5 as well as their thermal properties [7][8][9] have been well characterized. This is not the case with their electrical properties.…”

Phase Evolution in Silicon Carbide–Whisker‐Reinforced Mullite/Zirconia Composite during Long‐Term Oxidation at 1000° to 1350°C

“…C ERAMIC-MATRIX composites toughened by SiC whiskers are possible candidates for use in high-temperature environments. [1][2][3][4][5][6][7] Thus, the oxidation behavior of these composites at high temperatures is of great concern. 8 -17 Previous studies 6 -9,14,15 have indicated that the oxidation behavior and mechanical properties of SiC-whisker or particulate-reinforced ceramic-matrix composites are strongly affected by the reaction between the oxidation product (i.e., SiO 2 ) and the matrix.…”