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Fine-grained transparent spinel windows by the processing of different nanopowders

: Krell, A.; Hutzler, T.; Klimke, J.; Potthoff, A.


Journal of the American Ceramic Society 93 (2010), Nr.9, S.2656-2666
ISSN: 0002-7820
Fraunhofer IKTS ()
spinel; transparent ceramic; Armor; optical homogeneity

The study investigated the deagglomeration of spinel nanopowders (MgO center dot nAl(2)O(3), n approximate to 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 degrees C. On the other hand, a better optical homogeneity was achieved for materials fabricated from the 120 nm powder.