Oxidation Behavior of Silicon Carbide

Abstract

September 1958Oxidation Behavior and the angle 8. Consequently, there is a lack of coordination around the periphery of the drop on recrystallized alumina, making the effect much less spectacular.The magnitude of the contact angle characteristic of recrystallized alumina represents an average of the many local values of 0. The mean value of 60 degrees compared with 78 degrees on a flat sapphire surface dictates a decrease in the extent to which spreading can occur before a contraction on recrystallized alumina. Such spreading and contracting must then be of a magnitude that is too small to give rise to gross fluctuations in 9.of Silicon Carbide 347In conclusion, it may be pointed out that, in general, when a liquid is observed to spread on a solid surface at a constant temperature, such spreading may be due not only to a decrease in yl,, and/or yrr but also may be due, in part, to an alteration in the geometry of the surface associated with dissolution or chemical reactions.The oxidation of purified green silicon carbide in controlled atmospheres was studied by weightgain measurement and by observation of the surface reaction products, including optical measurement of the thickness of the oxide surface film. The rate of oxidation was much greater for silicon carbide in contact with fluid silicate glasses than for silicon carbide alone. In a vacuum of 0.1 mm., oxidation proceeded with loss of weight, because of the formation of volatile SiO, and at a greater rate than at atmospheric pressure. It is postulated that the rate-controlling process in the normal oxidation of silicon carbide is the formation of solid Si02 on the surface.

Surface Heterogeneity of Passively Oxidized Silicon Carbide Particles: Hydrophobic–Hydrophilic Partition

“…[3] are reported in Table 3. The value of γ 0 S (the total surface tension of SiC) is comparable to those obtained for quartz and silica which are usually considered as being solids of high surface energy (26,27,33).…”

“…They are used to calculate from (Eq. [3]) the energetic components of solid surface tension. The dispersion term can be considered, in a first approximation, as a hydrophobic term, and the polar term as a hydrophilic term.…”

“…[3], the factor k is linked to the entropy variation during the immersion process. Its value is measured using both immersion calorimetry data and vapor adsorption isotherms (27).…”

“…were strong incentives for many investigations. Most articles published on this material concern surface oxidation properties (3)(4)(5)(6)(7)(8), surface charges using electrokinetic mobility, titration, and XPS (9-11), but there is no paper dealing with chemical evaluations of surface energy and heterogeneity.…”

Oxidation behaviour of SiC/SiC ceramic matrix composites in air

“…This parabolic behaviour illustrates that oxidation of SiC/SiC composites is controlled by diffusional mechanisms. It is suggested that the growth of oxide layers on the composites is due to inward diffusion of either oxygen ions or molecules and it depends strongly on temperature and exposed time [16]. Pultz and Hertl [17] suggested that oxidation of SiC is controlled by the CO desorption from the SiC/SiO 2 interface at 1270-1430 • C as upon desorption more sites become available for further oxidation.…”