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Effect of Al antioxidant on the rate of oxidation of carbon in MgO-C refractory

Sadrnezhaad, S.K ; Sharif University of Technology | 2007

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  1. Type of Document: Article
  2. DOI: 10.1111/j.1551-2916.2006.01391.x
  3. Publisher: 2007
  4. Abstract:
  5. Kinetics of air oxidation of MgO-C-Al refractory at 600°-1300°C were investigated using the software based on the modifled shrinking core model (KDA). Commercial bricks containing 88.5% MgO, 10% residual carbon, and 1.5% aluminum anti-oxidant were oxidized isothermally with air. Combination of experimental data with model calculations indicated gas diffusion through solid material and pores as a major controlling step. Previously observed chemisorption process was eliminated from the rate-controlling mechanism with addition of aluminum antioxidant. Comprehensive rate equations were devised for MgO-C-Al and MgO-C oxidation reactions. Overall activation energies of Q id (internal diffusion) = 139.15 kJ/mol at T≤800°C and Q pd (pore diffusion) = 25.48 kJ/mol at T>800°C were obtained for MgO-C-Al oxidation reactions. Corresponding values were determined to be Qid = 134.85 kJ/ mol and Qca (chemical adsorption) = 66.69 kJ/mol at T≤800°C and Qpd = 18.95 kJ/mol and Qca = 66.69 kJ/mol at T>800°C for MgO-C oxidation reactions. Addition of aluminum anti-oxidant indicated a reducing effect on oxidation of MgO-C bricks at 800°C ≤ T ≤ 1250°C. Reverse behavior was observed at T≤700°C. © 2006 The American Ceramic Society
  6. Keywords:
  7. Activation energy ; Antioxidants ; Ceramic materials ; Magnesia ; Oxidation ; Comprehensive rate equations ; Gas diffusion ; Shrinking core model ; Refractory materials
  8. Source: Journal of the American Ceramic Society ; Volume 90, Issue 2 , 2007 , Pages 509-515 ; 00027820 (ISSN)
  9. URL: https://ceramics.onlinelibrary.wiley.com/doi/10.1111/j.1551-2916.2006.01391.x