Fine-Grained Transparent Spinel Windows by the Processing of Different Nanopowders

Authors


  • J. Halloran—contributing editor

†Author to whom correspondence should be addressed. e-mail: andreas.krell@ikts.fraunhofer.de

Abstract

The study investigated the deagglomeration of spinel nanopowders (MgO·nAl2O3, n≈1) from different syntheses in correlation with their resulting performance on green processing and sintering. Transmission results are addressed as a means of evaluating the degree of last pore elimination. As a result, clear transparent components with a thickness of up to 20 mm and lateral dimensions up to about 240 mm were manufactured equally successfully from spinel powders with lower specific surface areas (13–15 m2/g↔120 nm particle size) or from nanopowders (25–35 m2/g↔55 nm particle size) if the different performance of these powders was balanced by differently accommodated processing and sintering. However, without additives only the 55 nm starting powders enabled the preparation of microstructures with a grain size of 270 nm and a maximum transmittance at sintering temperatures <1300°C. On the other hand, a better optical homogeneity was achieved for materials fabricated from the 120 nm powder.

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