Tungsten-Titanium Carbide Composite Prepared Using Ammonium Paratungstate by Wet-Chemical Method

Fusion energy has become the most promising clean energy due to its rich raw materials and environment-friendly. In order to product controllable fusion energy, the research of plasma-facing materials (PFMs) is the key issue. W is considered as PFMs due to its excellent properties, such as high melting point, high thermal conductivity, and low tritium retention.

Titanium carbide (TiC)-doped W-based materials are promising PFMs because they have better ductility at low temperatures and enhance the ability to resist radiation-induced embrittlement. Thus, tungsten-2 vol.% titanium carbide composite samples were fabricated by wet-chemical method using ammonium paratungstate (APT) as tungsten source. After D+ irradiation with different fluences, high temperature annealing was used to investigate the evolution of irradiation damage under steady heat treatment.

Synthesis method of W-2 vol.% TiC composite is as below:

W-TiC composite powders were prepared through wet-chemical method, which is effective in producing a core-shell powder structure and contributes to disperse the secondary phase in the W grain interior after sintering. The first step was performed to produce the precursor powder from raw materials, containing oxalic acid (C2H2O4·2H2O), nanosized TiC particles (size of approximately 50 nm, purity of 99.9%), and ammonium paratungstate (NH4)10H2W12O42·XH2O (APT). The TiC particles were added into the prepared APT solution, and oxalic acid was dissolved as the precipitating agent. The W/TiC precursor was precipitated by stirring and evaporating the mixture solution under ultrasonic vibration in a self-designed reaction kettle heated by an oil bath. The obtained precursor was dried in an oven to eliminate the residual inorganic material with low sublimation point. Then, the reduction process was conducted at 1073 K for 1 h in a tubular furnace under high-purity hydrogen atmosphere, where the complicated W oxides in the precursor were completely reduced into W and the TiC remained. Finally, W-2 vol.%TiC composite powder was obtained.

In conclusion, the tungsten-titanium carbide composite materials were successfully prepared by wet chemical method using ammonium paratungstate, the material has a uniform distribution of titanium carbide and the density of the materials was over 98%. After annealing, the thermal diffusivity of the samples in three directions is higher than that in the original state. It shows that annealing reduces the number of defects in the material. In the sample irradiation with higher fluence (4.60 × 1025 D+/m2 and 1.10 × 1026 D+/m2), annealing at 900℃ has little effect on the surface morphology, but after annealing at 1573 K the surface of the second phase TiC particles is smooth and there are only small voids. In general, annealing at high temperature may be used as a means of repairing irradiation damage in the future.

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