Surface and interfaces energies of pure and tin-doped magnesium aluminate spinel

Reference	Presenter	Authors (Institution)	Abstract
12-047	Gilberto José Pereira	Pereira, G.J.(Centro Universitário da FEI); Muche, D.N.(University of California - Davis); Castro, R.H.(University of California - Davis); Gouvêa, D.(Universidade de São Paulo);	In this work, pure and tin-doped nanoparticles of magnesium aluminate spinel (MAS) were sinthesized using coprecipitation, and calcined at different temperatures. These Nanoparticles were characterized by X-ray diffraction (XRD), surface specific area (BET) and real density. After nanoparticles caracterization, they were compacted and heated inside a Differential Scanning Calorimeter (DSC), and inside a Thermo Mechanical Analizer (TMA), also known as dilatometer. Both shrinkage (TMA data) and the heat of sintering (DSC data) was acquired. DSC data was used to quantify both surface and grain boundary energies in pure and tin doped MAS. When densification and grain growth were observed, the evolved heat signal was quantitatively attributed to the respective microstructural evolution in terms of interfacial area change, allowing determination of average surface and grain boundary energies for pure MAS as 1.49 J.$m^{-2}$ and 0.57 J.$m^{-2}$. For doped samples, preliminary data of samples containing different amounts of $S{n}^{4+}$, a significant mass loss indicates a temporary stabilization effect probaly due an evaporation of tin segregated during densification. Temperature and significant shrinkage observed on TMA was consistent with DSC data, and was tipically above 20%, with onset temperature of retraction close to calcination temperature. Sintering is an interface elimination/formation process, and reliable data concerning the ratio of interfacial energies may be helpful on understanding and controlling microstructural evolution.
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