Active to passive transition in the oxidation of SiC

Antill, J.E.; Warburton, J.B.

doi:10.1016/s0010-938x(71)80116-6

Cited by 59 publications

(17 citation statements)

References 5 publications

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“…1. 1),12)- 14) This active oxidation has also been reported in some kinds of nitrides. 15) This study examines the replacement of silicon carbide foaming agent with the commonly used nitrides BN, AlN and Si3N4.…”

Section: Introductionsupporting

confidence: 54%

Applicability of nitride powders as foaming agents in superplastically foamed ceramics

Yokota

Hayashi

Kishimoto

2009

J. Ceram. Soc. Japan

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The applicability of several nitride powders for use as foaming agents in superplastically foaming ceramics was investigated. Ceramic mono-foams were fabricated successfully using AlN and Si3N4 foaming agents. By using BN as a foam agent, on the other hand, we cannot fabricated well developed ceramic foams due to cracking and fracture. When the quantity of foaming agent was increased, the porosity increased to a certain amount, then saturated. With equal amounts of Si3N4, the porosity from the dispersed foaming agent was higher than that obtained from a monolithic compact without mixing, which was similar to the case of SiC foam agent.

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Section: Introductionsupporting

confidence: 54%

Applicability of nitride powders as foaming agents in superplastically foamed ceramics

Yokota

Hayashi

Kishimoto

2009

J. Ceram. Soc. Japan

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“…Rosner and Allendorf [7] and Antill and Warburton [8] see no clear dependence of reaction rates on oxidant pressure in a reduced pressure situation. However, Hinze and Graham [11] see a linear dependence of reaction rates on oxidant pressure in O 2 /Ar.…”

Section: Active/passive Transitions In Oxygen/argonmentioning

confidence: 96%

“…Some studies attain low oxygen potentials using oxygen/inert gas mixtures; other studies attain low oxygen potentials using oxygen at low total pressures. Most studies address situations where gas phase diffusion to the surface is rate limiting [4][5][6][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]; however there is one that addresses a situation where chemical reaction at the surface is rate limiting [7]. Listed here are only studies with O 2 as the oxidant; studies with other oxidants are not included in this review.…”

Section: Introductionmentioning

confidence: 99%

Active Oxidation of SiC

2010

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Silicon carbide (SiC) forms a protective condensed-phase oxide (SiO 2 ) in passive oxidation and a volatile sub-oxide (SiO(g)) in active oxidation. The transition between these two modes of oxidation and the rates of active oxidation are critical issues. A literature review indicates that impurity effects, the difference between active-to-passive and passive-to-active transitions, and the effect of total pressure on these transitions remain unexplored for SiC. Measurements were made in a thermogravimetric apparatus (TGA) by changing oxygen potentials either by blending O 2 /Ar mixtures or changing total pressures in a pure oxygen gas stream to the point where a transition occurs. Specimens were examined with standard optical and electron-optical techniques. Active-to-passive and passive-to-active transitions were measured and found to be similar for SiC, which is in contrast to pure Si. The similarity in SiC is attributed to SiC/SiO 2 interfacial reactions producing the necessary conditions for passive scale formation (active-to-passive) or passive scale breakdown (passive-to-active). Comparable results were obtained in both the O 2 /Ar and reduced total O 2 pressure cases for SiC.

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“…3,35 Although this reaction is thermodynamically feasible, the accompanying decrease in free energy ( G = −411.68 kJ/mol) is less than that for the Reaction (7) ( Table 3), indicating that the latter reaction is more preferable under the present experimental conditions. Moreover, it has been shown through experiments and theoretical calculations that the active oxidation of SiC is marginal at 1200 • C in dry air, 34 and is promoted in reducing atmospheres containing CO-CO 2 or H 2 -H 2 O gas mixtures along with low oxygen partial pressures. 35 …”

Section: Oxidation Reactionsmentioning

confidence: 99%