Early stages of the pyrolytic crystallization in amorphous nanopowders of silicon carbonitrides SixCy,Nzby combined wide-angle X-ray and neutron diffractometries
| Autor: | N. Herlin, J. Dixmier, R. Bellissent, F. Ténégal, M. Cauchetier, B. Bouchet |
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| Rok vydání: | 1998 |
| Předmět: |
Materials science
Physics and Astronomy (miscellaneous) Silicon Crystal chemistry Annealing (metallurgy) Neutron diffraction Metals and Alloys chemistry.chemical_element Condensed Matter Physics Radial distribution function Electronic Optical and Magnetic Materials Amorphous solid law.invention Crystallography chemistry law General Materials Science Pyrolytic carbon Crystallization |
| Zdroj: | Philosophical Magazine A. 78:803-817 |
| ISSN: | 1460-6992 0141-8610 |
| Popis: | The transition from the amorphous to the crystalline state has been followed by coupled X-ray and neutron wide-angle diffraction in silicon carbonitrides powders prepared by laser pyrolysis of hexamethyldisilazane. The short-range order (SRO) and the medium-range order (MRO) modifications under heating have been observed using the drastic contrast effect of the scattering factors (or lengths) of N and Si for X-ray and neutrons respectively. In the amorphous state, the fit by models of the first neighbours peak (SRO) of the radial distribution function reveals the existence of C-N bonds in addition to the Si-C and Si-N bonds existing in mixed tetrahedra Si[C1−x N x ]4 with 0>x>1. Extended annealing for 24h at 1400°C modifies the MRO through a solid-state diffusion process increasing the chemical composition fluctuations in Si x C y N z puckered layers, by changing their stacking mode from the α to the β sequences encountered in the Si3N4 polytypes. The destruction of the mixed tetrahedra yields na... |
| Databáze: | OpenAIRE |
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