Reequilibrium kinetics of NiO-Cr2O3 solid solutions

Electrical conductivity has been measured to monitor the reequilibration kinetics for single crystals of NiO-Cr2O3 solid solutions. It has been found that the rate for the reduction process is higher than that for the oxidation runs, thus indicating that the obtained kinetic data are not purely bulk controlled. The following expressions for the apparent chemical diffusion coefficient have been obtained within the temperature range 900–1200°C and oxygen partial pressure range 1–10−5 atm: % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpu0de9vqpee9Lq% pepeea0xd9q8as0-LqLs-lirpepeea0-as0Fb9pgea0lrP0xe9Fve9% Fve9qapdbaqaaeGaciGaaiaabeqaamaabaabaaGceaqabeaaieaace% WFebGbaGaadaWgaaWcbaacbiGaa4xmaiaa+bcacaWGYbGaamyzaiaa% dsgaaeqaaOGaeyypa0tefeKCPfgBaGqbciaa9fdacaqFUaGaa0Nmai% aa9jdacaqFxdGaa0xmaiaa9bdadaahaaWcbeqaaiaa91cacaqFYaaa% aOGaa4hiaiaa+vgacaGF4bGaa4hCaiaa+bcadaqadaqaamaalaaaba% Gaa0Nmaiaa9rdacaqFSaGaa0hnaiaa9jdacaqFWaGaa0xSaiaa9fda% caqFYaGaa0xmaiaa9bdacaGFGaGaam4yaiaadggacaWGSbGaai4lai% aad2gacaWGVbGaamiBaiaadwgacqGHflY1cqGHWcaScaWGlbaabaGa% a8Nuaiaa-rfaaaaacaGLOaGaayzkaaaabaGab8hrayaaiaWaa0baaS% qaaiaa+fdacaGFGaGaam4BaiaadIhacaWGPbGaamizaaqaaiaacQca% aaGccqGH9aqpcaqFXaGaa0Nlaiaa9rdacaqF0aGaa031aiaa9fdaca% qFWaWaaWbaaSqabeaacaqFTaGaa0Nmaaaakiaa+bcacaGFLbGaa4hE% aiaa+bhacaGFGaWaaeWaaeaadaWcaaqaaiaa9jdacaqF3aGaa0hlai% aa9ndacaqF0aGaa0hmaGqbaiaa8flacaqF3aGaa0hmaiaa9bdacaGF% GaGaam4yaiaadggacaWGSbGaai4laiaad2gacaWGVbGaamiBaiaadw% gacqGHflY1cqGHWcaScaWGlbaabaGaa8Nuaiaa-rfaaaaacaGLOaGa% ayzkaaaabaGab8hrayaaiaWaaSbaaSqaaiaa+jdacaGFGaGaa4NCai% aa+vgacaGFKbaabeaakiabg2da9iaaikdacaqFUaGaa0Nmaiaa9Lda% caqFxdGaa0xmaiaa9bdadaahaaWcbeqaaiaa91cacaqFYaaaaOGaa4% hiaiaa+vgacaGF4bGaa4hCaiaa+bcadaqadaqaamaalaaabaGaa0Nm% aiaa9vdacaqFSaGaa03maiaa9rdacaqFWaGaaWxSaiaa9jdacaqFYa% Gaa03maiaa9bdacaGFGaGaam4yaiaadggacaWGSbGaamyBaiaad+ga% caWGSbGaamyzaiabgwSixlabgclaWkaadUeaaeaacaWFsbGaa8hvaa% aaaiaawIcacaGLPaaaaeaaceWFebGbaGaadaqhaaWcbaGaa4Nmaiaa% +bcacaWGVbGaamiEaiaadMgacaWGKbaabaGaaiOkaaaakiabg2da9i% aa9bdacaqFUaGaa0xmaiaa9bdacaqF5aGaa4hiaiaa+vgacaGF4bGa% a4hCaiaa+bcadaqadaqaamaalaaabaGaa0Nmaiaa9LdacaqFSaGaa0% Nnaiaa9fdacaqFWaGaaWxSaiaa9ndacaqFYaGaa0hmaiaa9bdacaGF% GaGaam4yaiaadggacaWGSbGaai4laiaad2gacaWGVbGaamiBaiaadw% gacqGHflY1cqGHWcaScaWGlbaabaGaa8Nuaiaa-rfaaaaacaGLOaGa% ayzkaaaabaGab8hrayaaiaWaaSbaaSqaaiaa+ndacaGFGaGaa4NCai% aa+vgacaGFKbaabeaakiabg2da9iaa9ndacaqFUaGaa0xmaiaa9zda% caqFxdGaa0xmaiaa9bdadaahaaWcbeqaaiaa91cacaqFYaaaaOGaa4% hiaiaa+vgacaGF4bGaa4hCaiaa+bcadaqadaqaamaalaaabaGaa0Nm% aiaa9zdacaqFSaGaa0hmaiaa9jdacaqFWaGaaWxSaiaa9jdacaqF0a% Gaa03maiaa9bdacaGFGaGaam4yaiaadggacaWGSbGaai4laiaad2ga% caWGVbGaamiBaiaadwgacqGHflY1cqGHWcaScaWGlbaabaGaa8Nuai% aa-rfaaaaacaGLOaGaayzkaaaabaGab8hrayaaiaWaa0baaSqaaiaa% +ndacaGFGaGaam4BaiaadIhacaWGPbGaamizaaqaaiaacQcaaaGccq% GH9aqpcaqFWaGaa0Nlaiaa9jdacaqFWaGaa0Nmaiaa9bcacaGFLbGa% a4hEaiaa+bhacaGFGaWaaeWaaeaadaWcaaqaaiaa9ndacaqFXaGaa0% hlaiaa9vdacaqFWaGaa0hmaiaa8flacaqFYaGaa0Nnaiaa9rdacaqF% WaGaa0hiaiaadogacaWGHbGaamiBaiaac+cacaWGTbGaam4BaiaadY% gacaWGLbGaeyyXICTaeyiSaaRaam4saaqaaiaa-jfacaWFubaaaaGa% ayjkaiaawMcaaaaaaa!2EB3! $$\begin{gathered} \tilde D_{1 red} = 1.22 \times 10^{ - 2} exp \left( {\frac{{24,420 \pm 1210 cal/mole \cdot ^\circ K}}{{RT}}} \right) \hfill \\ \tilde D_{1 oxid}^* = 1.44 \times 10^{ - 2} exp \left( {\frac{{27,340 \pm 700 cal/mole \cdot ^\circ K}}{{RT}}} \right) \hfill \\ \tilde D_{2 red} = 2.29 \times 10^{ - 2} exp \left( {\frac{{25,340 \pm 2230 calmole \cdot ^\circ K}}{{RT}}} \right) \hfill \\ \tilde D_{2 oxid}^* = 0.109 exp \left( {\frac{{29,610 \pm 3200 cal/mole \cdot ^\circ K}}{{RT}}} \right) \hfill \\ \tilde D_{3 red} = 3.16 \times 10^{ - 2} exp \left( {\frac{{26,020 \pm 2430 cal/mole \cdot ^\circ K}}{{RT}}} \right) \hfill \\ \tilde D_{3 oxid}^* = 0.202 exp \left( {\frac{{31,500 \pm 2640 cal/mole \cdot ^\circ K}}{{RT}}} \right) \hfill \\ \end{gathered} $$ .