Effects of raw material ratio and technical parameters on microstructure of TaC whiskers prepared by molten salt method
TaC whiskers were prepared using the molten salt method with Ta 2 O 5 , activated carbon, NaCl/NaF, and nano Ni powders as raw materials. The study examined the effects of the ratios of these raw materials, reaction temperature, and reaction time on the phase composition and microstructure of the TaC whiskers, as well as their growth mechanisms. The results indicated that production and length-diameter ratio of the TaC whiskers initially increased with higher carbon content until a certain point, after which they began to decrease. The prepared TaC whiskers using NaCl as molten salt were acicular and had a low length-diameter ratio. The TaC whiskers prepared by NaF were quadrangular prism-shaped and had a high ratio of length to diameter. Insufficient molten salt resulted in poor diffusion and uneven distribution of the reactants, while an excessive amount led to increased whisker diameters and agglomeration of the TaC whiskers. When the content of Ni was low, there were not enough nucleation points for whisker growth, resulting in only a small quantity of TaC whiskers. Conversely, a high Ni concentration caused a decrease in the length-to-diameter ratio of the whiskers. As reaction temperature rose, both the production and length-diameter ratio of the TaC whiskers first rose and then fell. Prolonging reaction time could increase production and length-diameter ratio of the TaC whiskers. When the molar ratio of Ta:C:F:Ni was 1:4:1:25:0.10, with a reaction temperature of 1300 °C and a reaction time of 2 h, the TaC whiskers exhibited the highest production, purity and length-to-diameter ratio. These whiskers had with an average diameter of 0.8 μm and lengths spanning several microns. The TaC whiskers had a single crystal structure, with their growth direction aligned along the [001] crystal direction. The growth mechanisms of the TaC whiskers were controlled by both the vapor-liquid-solid and solid-liquid-solid mechanisms.
危险品化学品经营许可证（带存储）