Toshio Shimoo

Oxidation kinetics of low-oxygen silicon carbide fiber

The effect of partial pressure and temperature on the oxidation rate of low-oxygen silicon carbide fiber (Hi-Nicalon) has been investigated. The initial oxidation rate was described by a two-dimensional disc contracting formula for reaction control, and the activation energy was 155 kJ/mol. The rate at the later stage of oxidation obeyed the equation for diffusion control, and the activation energy was 109 kJ/mol. Both the rate constants were proportional to oxygen partial pressure. The diffusion species through the SiO2 film are considered to be oxygen molecules.

Active-to-passive oxidation transition for polycarbosilane-derived silicon carbide fibers heated in Ar-O2 gas mixtures

AbstractThe active-to-passive oxidation transition for three types of polycarbosilane-derived SiC fibers (Nicalon, Hi-Nicalon and Hi-Nicalon S) was examined at 1773 K through TG, XRD analysis, SEM observation and tensile tests. The oxygen partial pressure for the active-to-passive oxidation transition decreased in the following order: pO2 = 100–250 Pa for Nicalon, pO2 = 10–25 Pa for Hi-Nicalon and pO2 = 1–2.5 Pa for Hi-Nicalon S. Considerable strength was retained in the passive-oxidation region. The active-oxidation produced a marked decrease in strength of Nicalon and Hi-Nicalon (σ

High-temperature stability of low-oxygen silicon carbide fiber heat-treated under different atmosphere

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Thermal stability of low-oxygen silicon carbide fibers (Hi-Nicalon) in carbon monoxide

0 GPa). On the other hand, the strength of Hi-Nicalon S after active-oxidation was nearly identical to that after passive-oxidation (σ

Reaction between Si3N4 and Fe-Ni alloy

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Oxidation behavior of Si-C-O fibers (Nicalon) in alumina

1 GPa).