An indirect model for sintering thermodynamics

Authors : Yüksel SARIKAYA, Müşerref ÖNAL

Pages : 841-845

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Publication Date : 0000-00-00

Article Type : Research Paper

Abstract :A model was proposed and used to calculated the changes in enthalpy $insert ignore into journalissuearticles values(\Delta H^{o});$, entropy $insert ignore into journalissuearticles values(\Delta S^{o});,$ and Gibbs energy $insert ignore into journalissuearticles values(\Delta G^{o});$, as well as equilibrium constant $insert ignore into journalissuearticles values(K);$ relating to the sintering of alumina compacts. Specific nanopore volume $insert ignore into journalissuearticles values(V);$ of the compacts was assumed as a thermodynamic variable. A hypothetical equilibrium constant $insert ignore into journalissuearticles values(K_{h});$ and corresponding Gibbs energy $insert ignore into journalissuearticles values(\Delta G_{h}^{o});$ were calculated depending on the $V$ value measured after each sintering. The thermodynamic relationships with the SI units were respectively evaluated for the initial-stage $insert ignore into journalissuearticles values(i);$ sintering between 1000 and 1200 $^{\circ}$C and final-stage $insert ignore into journalissuearticles values(f);$ sintering between 1200 and 1600 $^{\circ}$C in the following form: $\, \Delta G_{i}^{o}=-RT\ln K_{i}=\Delta H_{i}^{o}-T\Delta S_{i}^{o}=$161,042$-$110.5$T$ and $\Delta G_{f}^{o}=-RT\ln K_{f}=\Delta H_{f}^{o}-T\Delta S_{f}^{o}=$39,000$-$47.5$T$.
Keywords : Alumina, nanoporosity, sintering, thermodynamics