| Tantalum carbide (TaC) is characterized by high hardness, high melting point (approximately 3880℃), high chemical stability, good resistance to chemical attack and thermal shock, and excellent oxidation resistance and corrosion resistance, which makes it very attractive for anti-ablation application as one of the most promising throat materials among transition metal carbides. The use of liquid precursor route has been attracting significant attention in recent years as an alternative method for preparing ceramic materials. One of the most important reasons for this is the potential for reductions in manufacturing costs due to shorter processing time, energy savings and relatively simple equipment requirement. Moreover, preparing tantalum carbide by liquid polymer precursor conversion can be ingredient-designable and achieve the high-purity products in comparison to other conventional synthesis methods.C/C-TaC composite materials were prepared by liquid route and the influence of vacuum-pumping infiltration time, pressurized infiltration time and the high temperatures on the density, porosity, phase compositions, the crystalline state and the microstructures of final products have been investigated and characterized by various facilities. The best processing parameters have been determined and the formation mechanism of TaC has been revealed. On this basis, the ablation evaluation tests of C/C-TaC composite materials under the oxygen-acetylene flame test condition have been explored. The main conclusions are as follows:(1) The tantalum carbide polymer precursors were prepared by liquid route and the best mass rate of defferent components was determined as following: tantalum chloride : hydrofluoric acid : ethanol : furan resin=6:l:9:2~6:1:9:4, and tantalum fluoride : furan resin : ethanol =4:1:2~4:1:4.(2) The effects of vacuum-pumping infiltration time and pressurized infiltration time on the liquid infiltration rate were determined and the best parameters of liquid infiltration is vacuum-pumping infiltration for 2-3 hours and then pressurized infiltration for 1-2 hours.(3) Carbonization treatment at 900℃ transformed the solidified precursors intosamples consisting of tantalum pentoxide micro crystallites which disperse homogeneously in a pyrolytic carbon matrix and reveal promoted reaction kinetics. After 1600~2000°C high temperature treatment under inert atmosphere, samples can be almost transformed into cubic TaC without any other impurity compounds. The TaC particles disperse relatively uniformly throughout the samples, but the grain size distribution is inhomogeneous and diverse. Elevating the final anneal temperatures of material systems can increase the degree of graphitization of matrix, augment the quantity of graphitic carbon, reduce porosity, increase density, raise the quantity of tantalum carbide grains and ascend the crystallite sizes, all of which will contribute greatly to improving the anti-ablation properties of materials.(4) Under the test condition of oxygen-acetylene flame with a heat flux of 4186KW/m2 and of plasma arc heat with that of 25120 KW/m2, the mass ablation rates are 2.1 xlO"3 g-s"1, 1.8xlO"3 g-s"1 and 1.1 *10"3 g-s'1, while the linear ablation rates are 1.8xlO'2mm-s"', 2.0x10"2mm-s"' and 1.5xlO'2mm-s"] for three C/C-TaC composites respectively. The ablation properties of C/C-TaC composites are subject to the porosity and TaC material. At the same time, the anti-ablation properties of C/C-TaC composites are better than C/SiC with similar porosity under the same test conditions.(5) For C/C-TaC composite materials, the ablation mechanisms are sublimation, thermal-oxidation and michenical erosion.
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