The effect of coarse particles on the microstructural evolution of porous alumina sintered at 1375 °C

The objective of this study was to provide quantitative information concerning the microstructural evolution of porous alumina derived from mixtures of a fine, active powder and a coarse powder with a wide size distribution. The coarse powder increased the green density and reduced the densification rate as expected. The addition of the coarse powder also increased the average grain and pore intercepts at any particular density. However, it was concluded that coarsening of the fine powder was not affected by 30% coarse powder when sintering time was considered rather than density. Coarsening did affect the average grain size when a higher fraction of the fine powder particles were in contact with the larger particles. This is expected to be particularly important for cases where coarse particles are bonded by a relatively small fraction of fine particles of the same phase.