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Thermodynamically Stable SiwCxNyOz Polymer-Like, Amorphous Ceramics Made from Organic Precursors

Authors


  • R. French—contributing editor

  • This work was supported by grants from the Ceramics Program of the Division of Materials Research of the National Science Foundation (DMR-0502781 at the University of Colorado, and DMR-0502446 at the University of California, Davis). These grants are funded under the Materials World Network (MWN) Program between the National Science Foundation and the Deutsche Forschung Gemeinschaft (DFG). The research at Stuttgart is supported by the DFG under grant Mu 1166/12-1.

†Author to whom correspondence should be addressed. e-mail: rishi.raj@colorado.edu

Abstract

This communication reports new results on the enthalpy of formation of pseudo-amorphous ceramic compounds constituted from silicon, carbon, oxygen, and nitrogen (SiCNO), made from the polymer route. Again, like the SiCO materials, although with one exception, the enthalpy of formation from crystalline components (SiO2 cristobalite, β-Si3N4, SiC, and excess C) is negative. Some of the alloyed oxygen–nitrogen compositions yield enthalpies that are much more negative (∼100 kJ/g·atom) in comparison with compositions that contain mainly oxygen or nitrogen (∼20 kJ/g·atom). The exception, having a N/O ratio near 2, has a positive value for the enthalpy. This may reflect the presence of nanoclusters of stoichiometric Si2N2O instead of the pseudo-amorphous nanodomain structure seen for the other samples.

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