Quantitative study on structural evolutions and associated energetics in polysilazane-derived amorphous silicon carbonitride ceramics

    Authors

    Y. H. Chen; X. P. Yang; Y. J. Cao; Z. H. Gan;L. A. An

    Comments

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    Abbreviated Journal Title

    Acta Mater.

    Keywords

    Polymer-derived ceramics; Structure evolution; Thermodynamics; Energetics; Nanodomain; SICN CERAMICS; HIGH-TEMPERATURE; SIALCN CERAMICS; SILICOALUMINUM; CARBONITRIDE; ELECTRONIC-PROPERTIES; WATER-VAPOR; THIN-FILMS; X-RAY; C-N; SPECTROSCOPY; Materials Science, Multidisciplinary; Metallurgy & Metallurgical; Engineering

    Abstract

    Several important structural changes and their energetics during high-temperature annealing of polysilazane-derived amorphous silicon carbonitride ceramics were quantitatively studied. A Si-29 solid-state NMR study indicated that the structural transition in the Si-containing area can be described by an equilibrium reaction, 4SiCN(3) = SiC4 + 3SiN(4). The enthalpy and entropy for the reaction were calculated to be positive. Raman and electron paramagnetic resonance (EPR) studies revealed that the structural evolution within the free carbon area includes the graphitization of amorphous carbon and the lateral growth of nanographite, accompanied by a decrease in the point defect concentration. EPR results also suggested that the materials contain two kinds of point defects: carbon-dangling bonds at the edge and in the interior of the nanographite. It was found that the lateral growth of the nanographite followed a 2-D grain growth process, and that the decrease in the defect concentration was mainly due to the growth of the nanographite. The energetics of the structural changes was rationalized according to a simple structural model, and the effects of these changes on the stability of the materials were discussed. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

    Journal Title

    Acta Materialia

    Volume

    72

    Publication Date

    1-1-2014

    Document Type

    Article

    Language

    English

    First Page

    22

    Last Page

    31

    WOS Identifier

    WOS:000336696900003

    ISSN

    1359-6454

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