Study of the phase composition of fine-grained tungsten carbide based ceramic materials by x-ray phase analysis

Abstract

The results of X-ray diffraction analysis of qualitative and quantitative phase composition of powder and solid polycrysral samples of the system a-WC/W 2 C are presented. Powder (nanopowder) samples were obtained by plasmochemical synthesis from tungsten oxide and hydrocarbon. High-density fine-grained structure of ceramics was formed by electropulse plasma sintering (spark plasma sintering) of initial industrial a-WC powders (AlfaAesar). Experimental data were obtained on a Shimadzu XRD-7000 X-ray diffractometer (CuKa, λ = 1.54 A). The optimal modes of X-ray shooting of the ceramic samples based on tungsten carbide are presented. In the absence of reference standards for initial crystalline phases (WC and W2C), quantitative phase analysis was carried out using the reference intensity ratio (RIR) or corundum number (instead of the method of calibration curve). The required quantitative ratios were calculated using the structural parameters of corundum a-Al 2 O 3 and phases a-WC, W 2 C. The results of determining the repeatability of the intensity values were used to select the optimal exposure time and width of the receiving slit of the detector of diffracted X-rays. Study of the effect of the quality of sample preparation on the sensitivity of qualitative X-ray phase analysis showed the feasibility of grinding of the surface of solid ceramic samples and their pre-polishing with a diamond paste (grain size not less than 5/3 pm). The accuracy of quantitative phase analysis of powder and sintered ceramic samples was evaluated. The layer-by-layer phase analysis of the ceramic preform revealed a preferential crystallite orientation (texture) in the surface layer and the absence of the impurity phase W 2 C. The sensitivity of X-ray phase analysis to the content of a-W 2 C phase in nanopowders of tungsten monocarbide has been estimated.