Coarse pore evolution in dry-pressed alumina ceramics during sintering

Coarse pores in a sintered ceramic often degrade its mechanical properties and reliability. In this paper, the evolution of coarse pores in a dry-pressed alumina ceramic during sintering is characterized by direct observation. Alumina compacts prepared by dry-pressing alumina powder granules were characterized using optical microscopy, electron microscopy, and micro-focus X-ray computed tomography (micro-CT) after forming and after sintering at temperatures 1300-1500 degrees C. Coarse pores characteristic of particle packing voids are present at granule triple points after pressing and sintering, along with remnants of the alumina granules. The coarse pores present in the powder compact grow in size and number during sintering. Coarse pore growth during sintering is attributed to the coalescence of the smaller, neighboring pores in the microstructure. (C) 2016 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.