ANISOTROPIC SINTRRING SHRINKAGE AND GRAIN GROWTH FOR SPHERICAL ALUMINA POWDER COMPACTS ALIGNED IN HIGH MAGNETIC FIELD

摘要

Spherical alumina powder compacts were prepared by drying alumina slurry in a high magnetic field and cold isostatic pressing. Shrinkage and grain growth during sintering were examined for the alumina compacts in detail. The compacts prepared in 10 T showed significant anisotropies of sintering shrinkage and grain growth. The sintering shrinkage was larger in the direction parallel to the magnetic field direction (i.e., the c-axis direction of alumina crystal) than in its perpendicular direction at any sintering times (2-24 h). and the grain growth rate was faster in the plane normal to the magnetic field direction (i.e., the c-plane of alumina crystal) than in its perpendicular plane (i.e.. the a-b plane of the alumina crystal). On the other hand, the compacts prepared in 0 T did not undergo these anisotropies. The experimental results indicate that sintering shrinkage of alumina powder compact depends on alumina crystal axis direction, and grain growth depends on alumina crystal plane. Origin of these anisotropies for the spherical alumina powder compacts can be attributed to particle orientation caused by the high magnetic field.