Reactions of Ti, V, Nb and Ta with N<SUB>2</SUB> Gas at 2000&deg;C under Concentrated Solar Beam in a Solar Furnace at PROMES-CNRS

Abstract

Reactions of d-group transition metals including Ti, V, Nb and Ta with N 2 gas were investigated at target temperature of 2000 C under heating with concentrated solar beam at PROMES-CNRS in Odeillo (France). In the typical experimental setup using graphite crucible as the sample holder, synthesis of pure nitride with fcc (face centred cubic) structure was proved to be difficult on account of inevitable C 2 radical plume with high carbon activity a(C) from the graphite components and the majority of reaction products were carbo-nitride. By insertion of Sky blue filter in the solar beam path before entering into the parabolic concentrator, C 2 radical formation appeared to be efficiently suppressed and phases with high N content were synthesized. However, under conditions in which C 2 radical plume yield was considerable, nitrogen content in the reaction products became suppressed and tetragonal Nb 4 N 3 yielded in place of fcc NbN from Nb or N-deficit sub-nitride Ta 2 N in place of mono-nitride TaN formed.

Influence of Colour Filter on Reaction Products from Mo and W Heated to 2000&deg;C by Concentrated Solar Beam in N<SUB>2</SUB> Gas Environment in a Solar Furnace at PROMES-CNRS

“…As reported in the preceding publication, 1) filtering experimental results revealed intriguing features such as (i) temperature drop by inserting the colour filter in the light path was negligible under otherwise comparable optical setting under absence of colour filter suggesting that the heating effect by the concentrated solar beam must arise mainly from the IR (infra-red) range of waves, (ii) significant retardation of carburizing reaction was realized with the Sky blue filter implying that C 2 radical emission from the graphite crucible was suppressed efficiently by the Sky blue filter.…”

“…The effective power of the solar furnace was 2 kW with a peak density at the focal spot 16 MW/m 2 . As the details of the experimental setup and procedure are referred to elsewhere, 1) only the essential features of the experimental setup and the procedure are described below.…”

“…In a preceding publication, 1) we reported nitriding performances of d-group transition metals including Ti, V, Nb and Ta at a target temperature of 2000 C in a solar furnace at PROMES-CNRS in Odeillo, France. The PROMES-CNRS is located in southern Pyrenees at height about 1500 m from the sea level.…”

“…1) Two colour filters, Sky blue filter (Ref.# 068) and Medium yellow filter (Ref.# 010), supplied from Lee Filters (http:// www.leefilters.com/) that were readily available at PROMES-CNRS were tested for this purpose. The Sky blue filter cuts more than 60% of the light of wavelength between 500 nm and 700 nm while the Medium yellow filter cuts more than 80% of the light of wavelength below 475 nm (Fig.…”

Effects of Colour-filtering Solar Beam on Reaction Product Fromd-group Transition Metals in N<SUB>2</SUB>Gas Environment under Heating with Concentrated Solar Beam

“…During the course of recent attempts of nitride synthesis using a solar furnace at PROM ES-CNRS (Laboratoire Procédés Materiaux et Energie Solaire) in Odeillo (France) undertaken in July 2010, the authors [3][4][5] detected also some intriguing effects of colour filtering of solar beam on reaction products.…”