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Improvement of oxidation behaviour of dense silicon nitride by surface modification

Oberflächenmodifikation zur Verbesserung der Oxidationsbeständigkeit von dichtem Siliziumnitrid


Journal of the European Ceramic Society 13 (1994), pp.239-246
ISSN: 0955-2219
Journal Article
Fraunhofer IKTS ()
Oberflächenmodifizierung; oxidation resistance; Oxidationsbeständigkeit; platinum layer; Pt-Schicht; silicon nitride; Silizium-Nitrid; surface modification

The effect or surface modifications by ion assisted deposition of platinum layers on the oxidation behaviour of dense silicon nitride was examined. Gas-pressure sintered silicon nitride containing neodymia or yttria and alumina as sintering aids was coated with up to 1.5 mym Pt by magnetron sputtering. The morphology, residual stresses, chemical composition and crystal parameters of the coatings were characterized by SEM, XRD and electron beam microanalysis. The oxidation behaviour was investigated at 1 100 degree, 1300 degree and 1450 degree in flowing air. In comparison with uncoated surfaces the Pt-coated surfaces were after oxidation less damaged by cracking, bubbles formation and spalling. The oxidation reaction was masked by the decomposition of platinum oxide and crystallization processes. Experimental results indicate that the observed Improvement of oxidation resistance of the investigated materials is caused by the change of the composition and properties of the growing oxide layers, by the change of diffusion - and oxidation - processes and by promotion of the selective crystallization of silicates in the oxide