Densification of nanocrystalline ceramics by combustion reaction and quick pressing

摘要

The technique of combustion reaction and quick pressing was adopted to prepare dense nanocrystalline ceramics. The densification process of magnesia compact with a particle size of 100 nm was investigated, under the applied pressure of up to 170 MPa, and the temperature of 1740-2080 K with ultra-high heating rate of above 1700 K/min. As a result, pure magnesia ceramics with a relative density of 98.8% and an average grain size of 120 nm was obtained at 1740 K and 170 MPa, while the ones with decreased relative density and increased grain size were produced under the increasing temperature and the identical pressure conditions. The results indicated that grain growth of the nanocrystalline magnesia was effectively restrained by the combined effect of the ultra-high heating rate and the high pressure. Moreover, under the particular sintering conditions, there existed an appropriate temperature range for the preparation of dense nanocrystalline magnesia, and the excessive temperature would not only exaggerate grain growth but also impede densification.