2011 Volume 52 Issue 11 Pages 2083-2090
In a preceding work, we reported attempts of synthesizing nitride of d-group transition metals including Ti, V, Nb and Ta using a solar furnace at PROMES-CNRS. In standard solar furnace experimental setup, graphite crucible is used as the sample holder on account of its resistance against high temperature and thermal shock. Plume of C2 radical with high chemical activity a(C) of C was reported to yield from graphite crucible under irradiation of concentrated solar beam. Thus, synthesis of pure metal nitride MN was not successful in the preceding work done in N2 gas environment heated by solar beam irradiation under standard experimental setup. To overcome this problem of undesired carburization in solar furnace, insertion of colour filter in the path of solar beam was tried and it was found that the C2 radical yield from the graphite crucible was effectively suppressed by insertion of Sky blue filter and carbo-nitride M(C,N) with comparatively low C-content was synthesized for Ti, V, Nb and Ta at 2000°C in N2 gas environment while, without the Sky blue filter, M(C,N) with high C-content and low N-content was synthesized under the otherwise comparable conditions of temperature and nitrogen partial pressure. These evidences appeared to suggest that nitride synthesis might be realized in standard solar furnace experimental setup using standard sample holder made of graphite by insertion of Sky blue filter. In the present work, reaction products from Mo and W in N2 gas environment under solar heating to 2000°C were characterized and effectiveness of the Sky blue filter for suppression of C2 radical yield from the graphite crucible was ascertained.
