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Oxidation kinetics of an amorphous silicon carbonitride ceramic

Raj, Rishi and An, L. and Shah, S. and Riedel, R. and Fasel, C. and Kleebe, Hans-Joachim (2001):
Oxidation kinetics of an amorphous silicon carbonitride ceramic.
84, In: Journal of the American Ceramic Society, (8), pp. S. 1803-1810, [Article]

Abstract

The oxidation kinetics of amorphous silicon carbonitride (SiCN) was measured at 1350°C in ambient air. Two types of specimens were studied: one in the form of thin disks, the other as a powder. Both specimens contained open nanoscale porosity. The disk specimens exhibited weight gain that saturated exponentially with time, analogous to the oxidation behavior of reaction-bonded Si3N4. The saturation value of the weight gain increased linearly with specimen volume, suggesting the nanoscale pore surfaces oxidized uniformly throughout the specimen. This interpretation was confirmed by highresolution electron microscopy and secondary ion mass spectroscopy. Experiments with the powders (having a particle size much larger than the scale of the nanopores) were also consistent with measurements of the disks. However, the powder specimens, having a high surface-to-volume ratio, continued to show measurable weight gain due to oxidation of the exterior surface. The wide range of values for the surfaceto-volume ratio, which included all specimens, permitted a separation of the rate of oxidation of the free surface and the oxidation of the internal surfaces of the nanopores. Surface oxidation data were used to obtain the rate constant for parabolic growth of the oxidation scale. The values for the rate constant obtained for SiCN lay at the lower end of the spectrum of oxidation rates reported in the literature for several Si3N4 and SiC materials. Convergence in the behavior of SiCN and CVD-SiC is ascribed to the purity of both materials. Conversely, it is proposed that the high rates of oxidation of sintered polycrystalline silicon carbides and nitrides, as well as the high degree of variability of these rates, might be related to the impurities introduced by the sintering aids.

Item Type: Article
Erschienen: 2001
Creators: Raj, Rishi and An, L. and Shah, S. and Riedel, R. and Fasel, C. and Kleebe, Hans-Joachim
Title: Oxidation kinetics of an amorphous silicon carbonitride ceramic
Language: English
Abstract:

The oxidation kinetics of amorphous silicon carbonitride (SiCN) was measured at 1350°C in ambient air. Two types of specimens were studied: one in the form of thin disks, the other as a powder. Both specimens contained open nanoscale porosity. The disk specimens exhibited weight gain that saturated exponentially with time, analogous to the oxidation behavior of reaction-bonded Si3N4. The saturation value of the weight gain increased linearly with specimen volume, suggesting the nanoscale pore surfaces oxidized uniformly throughout the specimen. This interpretation was confirmed by highresolution electron microscopy and secondary ion mass spectroscopy. Experiments with the powders (having a particle size much larger than the scale of the nanopores) were also consistent with measurements of the disks. However, the powder specimens, having a high surface-to-volume ratio, continued to show measurable weight gain due to oxidation of the exterior surface. The wide range of values for the surfaceto-volume ratio, which included all specimens, permitted a separation of the rate of oxidation of the free surface and the oxidation of the internal surfaces of the nanopores. Surface oxidation data were used to obtain the rate constant for parabolic growth of the oxidation scale. The values for the rate constant obtained for SiCN lay at the lower end of the spectrum of oxidation rates reported in the literature for several Si3N4 and SiC materials. Convergence in the behavior of SiCN and CVD-SiC is ascribed to the purity of both materials. Conversely, it is proposed that the high rates of oxidation of sintered polycrystalline silicon carbides and nitrides, as well as the high degree of variability of these rates, might be related to the impurities introduced by the sintering aids.

Journal or Publication Title: Journal of the American Ceramic Society
Volume: 84
Number: 8
Divisions: 11 Department of Materials and Earth Sciences > Earth Science > Geo-Material-Science
11 Department of Materials and Earth Sciences > Material Science > Dispersive Solids
11 Department of Materials and Earth Sciences > Earth Science
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences
Date Deposited: 19 Nov 2008 16:27
Funders: Supported, in part, by a joint grant between the U.S. and Germany supported through the North Atlantic Treaty Organization. Work in the U.S. was supported by the Air Force Office of Scientific Research under Grant No. F49620-00-1-0109. Work in Germany was, supported by KSB Stiftung and Fonds der Chemischen Industrie, Frankfurt.
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