Characterisation of solar-synthesised TiCx (x=0.50, 0.625, 0.75, 0.85, 0.90 and 1.0) by X-ray diffraction, density and Vickers microhardness

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

“…In the preceding works, [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] M powders mixed with carbon materials (graphite G or amorphous carbon aC) compacted into form of pellet were used as the starting material. Thence, even with the extremely high rate of heating at the onset of solar radiation to reach a set target temperature from the ambient temperature directly, passive oxide film inevitably present over M powder surface must have instantaneously reacted with the tightly compacted C against the M powder surface to be evaporated in form of CO or CO 2 to expose clean M substrate allowing subsequent carbide forming reaction.…”

“…[1][2][3][4][5][6][7][8][9][10] This line of work was continued after 2005 using a solar furnace at PROMES-CNRS (Laboratoire Procédés, Matériaux et Energie Solaire) in Odeillo. [11][12][13][14][15][16][17][18] During the course of these works, we managed to demonstrate that the solar furnaces are capable of concentrating the solar energy by a factor 10 4 or higher to a spot size of diameter, 5 cm (PSA) or 1 cm (PROMES-CNRS), and therefore can be used as the ecological renewable heat source to trigger high temperature reactions leading to refractory carbide synthesis.…”

“…Although our main target of this series of works done using solar furnace at PSA (Spain) [1][2][3][4][5][6][7][8][9][10] and that at PROMES-CNRS (France) [11][12][13][14][15][16][17][18] were carbide synthesis, brief comparative test runs were undertaken to check influence of N 2 gas environment compared with the standard inert Ar gas atmosphere 1,2) on the carbide formation reaction kinetics for M = Si and W. Our observation of the XRD (X-ray diffraction) evidences in these works showed no sign of nitride or carbo-nitride formation for neither Si nor W but certain extent of retardation for carbide formation reaction was detected for Si and it was interpreted as the competing nitriding reaction to form Si 3 N 4 against carbide forming reaction to yield SiC in N 2 gas environment. On the other hand, no such kinetic effect of N 2 gas environment was detected for W and it was appreciated as representing the incomparably strong tendency of W towards carbide formation than towards nitride formation.…”

Synthesis and nitrogen stability of ultrafine titanium carbonitride particles

“…A small decrease in oxygen content may be due to the reduction effect by nitrogen gas. Also, the small carbon loss may be explained by the higher thermodynamic stability of TiN than that of TiC below 1500 K, 16 that is, the diffused nitrogen atoms can push out a few combined carbon atoms to minimize the total free energy of titanium carbonitride.…”

Carbide Phases Synthesised from C/Mo Powder Compacts at Specified Sub-Stoichiometric Ratios by Solar Radiation Heating to Temperatures between 1600&deg;C and 2500&deg;C

“…In the earlier solar-carbide synthesis experiments done at PSA (Tabernas), it took about a few minutes to heat the specimen from ambient temperature to the target temperature depending on the rate of opening of the louvered shutter. 9,10) In cases of the experiments performed at the target temperatures, 1600…”