 NDTnetWCNDT '96 - New Delhi Table of Contents |  |
  | X-Ray and Gamma Ray Techniques |  |
| NDTnet WCNDT '96 - New Delhi Table of Contents | |
| | X-Ray and Gamma Ray Techniques | |
- SiC. The common polytypes of - SiC are 2H, 4H, 6H, 15R out of which 6H is the most widely grown and frequently reported in literature due to its stabilityat higher temperature. Compared to neutron diffraction and electron diffraction, X-ray diffraction (XRD) is a simpler technique to identify polytype in SiC. The present paper reports the identification of an unusual polytype, that is 21R, in SiC employing XRD technique. Although rhombohedral -SiC is quite rare to grow, for the first time we notice that the growth of such a phase is possible at atmospheric pressure in thermal plasma. SiC was prepared from rice husk by carrying out synthesis between SiO2 and carbon (3: 1) in a thermal arc plasma reactor. The synthesis was carried out in 200-250 g scale at a power level of 15-18 kW h/kg. The product was obtained in the form of powder and characterized by laser analyser for particle size distribution. About 90% (by volume) of the product were found to lie below 160 µm size. XRD analysis was carried out to determine the d values and intensities accurately. By use of a computer aided Search- Match program polytype of the polycrystalline SiC sample (in the form of powder) was determined. Best fit was obtained for - SiC-21R which does not grow in conventional methods of preparation. Details of the polytype identification shall be discussed in the full text of the paper.
| | X-Ray and Gamma Ray Techniques | |