3.20 Oxidation of thin magnesium films at high temperatures

Murgulescu, I. G.; Cismaru, D.; Costeanu, E

doi:10.1016/0042-207x(67)92243-9

Cited by 2 publications

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“…The mass flux of CrO3(g) across the boundary layer is given by kmMcros (Pcros,s --Pcros,8) ~hD -- [5] Pt where T~D is in g-cm-2-sec-1; km is the mass transfer coefficient which can be calculated from boundary layer theory (mole-cm-2-sec-1); Pcros,s and Pcros,8 are the steady-state values of the partial pressures of CrO3(g) at the surface of the chromium ribbon and at the outer edge of the boundary layer, respectively; and Pt is the total pressure or the stagnation pressure in a flowing system~ Generally, Pcros,8 ----0 and Eq. [5] reduces to I~%D : kmMcro3Pcros,s/Pt [6] The rate of formation of CrO3 (g) by chemical reaction is given by ?ha : Mcro3 (kfPo2,s 3/4 --kbPcroa,s) [7] where kf and kb are the forward and backward rate constants of the reaction, respectively. Po2,s is the partial pressure of oxygen at the surface of the chromium ribbon.…”

Section: Resultsmentioning

confidence: 99%

“…We have tacitly assumed in Eq. [7] that the condensation coefficient of CrO3(g) on the chromium is one.…”

Section: Resultsmentioning

confidence: 99%

“…However, it can be eliminated from Eq. [6] and [7]. In addition, from consideration of the mass balance, 7~ D = T~R; and by definition, Ke = kf/kb.…”

Section: Resultsmentioning

confidence: 99%

“…Numerous investigators have studied the kinetics of chromium(III) oxide (Cr2Os) scale formation on chromium and chromium-containing alloys heated in oxidizing environments (1)(2)(3)(4)(5)(6)(7)(8). Gravimetric measurements above 1000~ yield a net weight loss which has been shown to be due to the loss of the gaseous species chromium(VI) oxide (CrOs) formed from the reaction of the Cr20~ protective scale with oxygen (3).…”

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confidence: 99%

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Oxidative Vaporization Kinetics of Cr[sub 2]O[sub 3] in Oxygen from 1000° to 1300°C

Stearns

Kohl

Fryburg

1974

J. Electrochem. Soc.

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Rates of oxidative vaporization of Cr208 on preoxidized resistively heated chromium were determined in flowing oxygen at a pressure of 0.115 Torr for temperatures from 1000 ~ to 1300~ Reaction controlled rates were obtained from experimental rates by a gold calibration technique, and these rates were shown to agree with those predicted by thermochemical analysis. The activation energy obtained for the oxidative vaporization reaction corresponded numerically with the thermochemical enthalpy of the reaction. A theoretical equation is given for calculating the rate from thermodynamic data using boundary-layer theory. Grimley et al. (11) subsequently identified this mole-) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 134.129.120.3 Downloaded on 2015-05-30 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 134.129.120.3 Downloaded on 2015-05-30 to IP I T h e r m o d y n a m i c data for Cr(g), CrO(g), and e r o s ( g ) w e r e taken from Schlck (24). Data for Cr2Oa(s) w e r e calculated f r o m h G ' f values given by Wicks and ]]lock (31). T h e r m o d y n a m i c data for CrO~(g) and the " n e w " chromium-oxygen molecules are given in the following paper (16).) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 134.129.120.3 Downloaded on 2015-05-30 to IP

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Section: Resultsmentioning

confidence: 99%

“…We have tacitly assumed in Eq. [7] that the condensation coefficient of CrO3(g) on the chromium is one.…”

Section: Resultsmentioning

confidence: 99%

“…However, it can be eliminated from Eq. [6] and [7]. In addition, from consideration of the mass balance, 7~ D = T~R; and by definition, Ke = kf/kb.…”

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

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Oxidative Vaporization Kinetics of Cr[sub 2]O[sub 3] in Oxygen from 1000° to 1300°C

Stearns

Kohl

Fryburg

1974

J. Electrochem. Soc.

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“…(2,3) ]. A few studies on kinetics under widely varying conditions have been reported: these include linear, parabolic, and logarithmic laws of nitridation and 5-50 kcal/mole activation energy for this process (4)(5)(6)(7)(8)(9)(10)(11).…”

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confidence: 99%

Thermal Nitridation of Magnesium at Lower Temperatures and Pressures of the Nitrogen Atmosphere

Kodymova-Turkova¹,

Láska²,

Krejčí³

1974

J. Electrochem. Soc.

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The dependence of the thermal nitridation of polycrystalline magnesium specimens, located in pure nitrogen, on time, temperature, and pressure has been investigated. Parameters of the experiments were chosen with regard to the conditions of nitridation in a d‐c and rf discharge plasma. The temperature dependence was measured up to 500°C and was not detectable below 300°C. The long term kinetic plot at intermediate temperature 450°C, following the initial period, can be approximated by a logarithmic dependence, and the best explanation of the nitridation mechanism seems to be Fehlner and Mott's conception based on boundary diffusion. The value of the activation energy of the process calculated from the linear parts of the nitridation curves at different temperatures was 19.2 kcal/mole. The pressure dependence of the nitridation was measured in the range of 0.2–400 Torr and could best be described by a p¼ dependence.

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3.20 Oxidation of thin magnesium films at high temperatures

Cited by 2 publications

References 0 publications

Oxidative Vaporization Kinetics of Cr[sub 2]O[sub 3] in Oxygen from 1000° to 1300°C

Oxidative Vaporization Kinetics of Cr[sub 2]O[sub 3] in Oxygen from 1000° to 1300°C

Thermal Nitridation of Magnesium at Lower Temperatures and Pressures of the Nitrogen Atmosphere

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