The role of carbon in the nitridic high performance ceramics in the system Si-B-N-C |
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Authors: | van Wüllen Leo Roth Angelika Jansen Martin |
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Institution: | Max-Planck Institut für Festk?rperforschung, Heisenbergstr. 1, D-70569 Stuttgart, Germany. |
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Abstract: | Using a multitude of modern solid-state NMR techniques including 11B-MQMAS-NMR, 11B-13C-REDOR NMR, 13C-11B-REAPDOR NMR, 15N-11B-REAPDOR NMR and 13C-2D-RFDR NMR experiments, the network organization in the quaternary high performance ceramic SiBN3C has been studied. Carbon is found to agglomerate into domains with predominant carbon-carbon bonding. The NMR results are compatible with carbon atoms involved in a graphite-like bonding scheme. The network adopted is quite similar to the corresponding one in the related ternary ceramic Si3B3N7, consisting of domains characterized by predominant Si-N bonding and domains of predominant B-N bonding with the carbon agglomerates located within the B-N domains of the network. The homogeneity with respect to the elemental distribution down to the nm regime, observed using electron spectroscopic imaging techniques puts an upper limit of ca. 1 nm to these agglomerates. |
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