Microstructural evolution during sintering in MgO powders precipitated from sea water under induced agglomeration conditions

Green compacts pressed by means of uniaxial compaction with Magnesia (MgO) powders precipitated from sea water and calcined at different temperatures were sintered under H2 atmosphere at 1700 °C. The calcination, carried out between 900 and 1200 °C had a great influence in the final density and the microstructure. The densification of MgO agglomerated powders seems to be predictably related to grain growth and thus coarsening kinetics. At calcination temperatures higher than 900 °C, the volume of large pores was increased notably suggesting that the inhibited grain growth adversely affected the thermodynamics of pore sintering. Relative densities between 74 and 98% of theoretical density were reached in compacts obtained at different compaction pressures. The microstructural differences were examined by Scanning Electron Microscopy (SEM).

Graphical abstractGreen compacts obtained by uniaxial compaction with Magnesia (MgO) powders precipitated from sea water and calcined at different temperatures were sintered at 1700 °C in H2. The calcination had a great influence in the final density and the microstructure. At low calcination temperatures (< 1050 °C), the grain growth during sintering helps to reduce the coordination number of some voids, and thus to achieve a sintered density approaching theoretical.Figure optionsDownload full-size imageDownload as PowerPoint slide