Oxidation Kinetics of Silicon Carbide Crystals and Ceramics: I, In Dry Oxygen

Abstract

The oxidation kinetics of several single-crystal and polycrystalline silicon carbide materials and single-crystal silicon in dry oxygen over the temperature range 1200" to 1500°C were fitted to the linear-parabolic model of Deal and Grove. The lower oxidation rates of silicon carbide compared to silicon can be rationalized by additional consumption of oxidant in oxidizing carbon to carbon dioxide. The (0001) Si face of the silicon carbide platelets exhibited lower parabolic oxidation rates than the (000%) C face, by a factor of 10 at 1200°C. Apparent activation energies increased from a value of 2120 kJ/mol below 1400°C to a value of =300 kJ/mol above this temperature. The (0001) Si face exhibited this high activation energy over the entire temperature range. The controlled nucleation thermally deposited material exhibited the highest oxidation rates of the polycrystalline materials followed by the hot-pressed and sintered a-silicon carbides. In general, the oxidation rates of the polycrystalline materials were bracketed by the oxidation rates of the basal planes of the single-crystal materials. Higher impurity concentrations and higher density of nucleation sites led to a greater susceptibility to crystallization of the scale which significantly complicated the oxidation behaviors observed. When crystallization of the oxide scale occurred in the form of a layer of spherulitic cristobalite crystals, a retardation of the oxidation rates was observed. An accelerated oxidation behavior was found when this coherent layer was superseded by the formation of fine mullite crystals.

Improvement of Oxidation Resistance and Oxidation-Induced Embrittlement by Controlling Grain Boundary Microstructure in Silicon Carbides with Different Dopants

“…reference of the literature data, 14,17,22,23) these obtained values are 1-2 order magnitude lower than those for hot-pressed SiC samples but similar to those for CVD SiC in dry oxygen atmosphere. Figures 7(a) and (b) show the effects of oxygen partial pressure and temperature on the specific mass gain of Mgdoped SiC, respectively.…”

“…Since non-oxide silicon carbide has been expected as a structural material under severe environments such as nuclear fusion reactor and aerospace systems, oxidation behaviour of silicon carbides at high temperatures has been extensively studied so far. [13][14][15][16][17][18][19][20][21][22][23] At higher oxygen partial pressure, such as the level of air, silicon carbide possesses good oxidation resistance at high temperatures because of protective SiO 2 thin film formed on the surface. The ''passive oxidation'' occurs by the reaction:…”

Oxidation behaviour of SiC/SiC ceramic matrix composites in air

“…Castello and Tressler [6] studied the oxidation behaviour of sintered SiC and chemical vapour deposition (CVD) SiC at * Corresponding author.…”

Tailoring Oxide/Silicon Carbide Interfaces: NO Annealing and Beyond

“…For details on SiC oxidation kinetics and parameters corresponding to various orientations, pressures, and temperatures, see Refs. [43,68,98,113,122,127,135,136]. But unlike Si oxidation, Eq.…”