Oxidation of Boron Carbide-Silicon Carbide Composite at 1073 to 1773 K

Abstract

The oxidation behavior of B 4 C-(25-60 mol%)SiC composites prepared by arc-melting was investigated in the temperature range of 1073 to 1773 K using a thermogravimetric technique. Liquid borosilicate, solid SiO 2 and carbon were identified as oxidation products by X-ray diffraction and Raman spectroscopy. Mass gain was observed during oxidation at 1073 K, while mass loss due to the vaporization of boron oxide in liquid borosilicate was observed at temperatures of 1273 K and higher. In situ Raman spectra of the surface of B 4 C-SiC composites indicated that the silica concentration in the liquid borosilicate increased with increasing SiC content in the composite. Micro-Raman spectroscopy showed that carbon was enriched in the borosilicate layer close to the oxide/composite interface. The parabolic rate constants for B 4 C-50 mol%SiC composites at 1073 K were proportional to ambient oxygen partial pressures ranging between 30 and 100 kPa. The diffusion of oxygen molecules through the liquid borosilicate layer could be the rate-controlling process. The increase of SiC content in the B 4 C-SiC composites improved the oxidation resistance in both the mass gain and mass loss regions.

Silicon carbide fiber oxidation behavior in the presence of boron nitride

“…In contrast with previous Raman results of thermally grown borosilicate glasses formed from oxidation at 600°C and 800°C, peaks assigned to the B 2 O 3 boroxol ring at ~800, 808 cm −1 (Figure , dotted line) in their studies are absent in this study. According to Narushima et al, this B 2 O 3 peak is a function of the boria concentration in the borosilicate glass. The thermally grown borosilicate glasses in the study by Quemard et al were either pure boria or boria enriched, based on their vibrational spectroscopic results, and further supported by quantitative surface analyses that determined molar ratios of B 2 O 3 : SiO 2 ranging from ~1.3:1 to 4.8:1.…”

“…Although formation of the low viscosity glass sealed the matrix cracks, considerable SiC fiber recession adjacent to regions of a thick borosilicate glass was also observed . Other studies found the oxidation rates of Si‐based materials to accelerate in the presence of boron (B) . Parabolic rate constants (k p ) from a few of these studies conducted at 800°C are extrapolated here to 1 atm of dry oxygen (O 2 ) using derived SI units.…”

“…16,17 Other studies found the oxidation rates of Si-based materials to accelerate in the presence of boron (B). [19][20][21][22][23] Parabolic rate constants (k p ) from a few of these studies conducted at 800°C are extrapolated here to 1 atm of dry oxygen (O 2 ) 19,22,23 using derived SI units. The k p values were~0.3 mg 2 cm À4 h À1 for B 4 C-50 mol% SiC composites, 19 2 9 10 À3 mg 2 cm À4 h À1 for Hi-Nicalon TM fibers embedded in B 2 O 3 powder, 22 and up to 60 mg 2 cm À4 h À1 for Si coupons coated with sol-gel-derived borosilicate glass layers having nominal B 2 O 3 concentrations ranging from 1 to 30 mol%.…”

Boria Effects on the High Temperature Oxidation of Silicon Carbide

“…Using the 1200˚C kp for CVD-SiC reported by Ogbuji and Opila 17 , it would take 9.9 h to grow an equivalent SiO2 oxide thickness. This order of magnitude increase in SiC oxidation kinetics is in line with others 23,39,41 who also observed orders of magnitude increases in the oxidation kinetics of Si-based materials due to the presence of B2O3.…”

Characterization of a powder metallurgy SiC/Cu–Al composite

“…Si, Mg, Nb, Ti, Cu, and some rare earth elements cannot only enhance the bonding between SiC and Al but also increase the matrix strength (Gu et al, 1999;Starink et al, 1999;Lee et al, 2001;Lima et al, 1999). The oxidation layer of SiO 2 on the surface of SiC particles was reported to facilitate the wetting between SiC and Al at the interface (Narushima et al, 2003;Tang et al, 2001). * Corresponding author.…”