Oxyacetylene Torch Environment Research Articles

Effects of TaC amount on the properties of 2D C/SiC–TaC composites prepared via precursor infiltration and pyrolysis

Variously contented tantalum carbide (TaC) were introduced into C/SiC composites by slurry infiltration, and then 2D C/SiC–TaC composites were prepared via precursor infiltration and pyrolysis (PIP). With increasing TaC content in the C/SiC–TaC composites, the density increased, the flexural strength and modulus decreased, and the ablation properties increased at first and then fell. The flexural strength and modulus of the composites with 19.0vol% of TaC at ambient temperature were 246MPa and 65GPa, respectively. The flexural strengths of the composites reached to 98MPa at 1800°C, 122MPa at 2000°C, and 174MPa (74% of the original value) after 20min of oxidation at 1200°C in air. After 60s of ablation in an oxyacetylene torch environment, the mass loss and linear recession rates of the sample with 30.5vol% of TaC were 0.017g/s and 0.013m/s, respectively.

Structural evolution and ablation mechanism of a hafnium carbide coating on a C/C composite in an oxyacetylene torch environment

HfC coating was deposited on carbon/carbon composites by chemical vapor deposition. The evolution of morphology and microstructure of the coating during ablation is investigated and the ablation mechanism is proposed. Results show that the coating shows an outstanding ablation resistance. After ablation, three distinct regions (central, transitional and outer ablation region) can be detected on the coating surface. In the former two regions, four layers can be divided from the cross-section of the ablated coating. Both molten HfO2 and HfCxOy could act as oxygen diffusion barrier during ablation. Oxidation and mechanical erosion are main ablation behavior of the HfC coating.

Ablation behavior and mechanism of 3D C/ZrC composite in oxyacetylene torch environment

Ablation property of three dimensional carbon fiber reinforced zirconium carbide composite (3D C/ZrC composite) was determined using oxyacetylene torch test with a heat flux of 4187 kW/m 2 and flame temperature of over 3000 °C. C/ZrC composite exhibited an excellent configurational stability with a surface temperature of over 2000 °C during 60–300 s period, while 3D C/SiC composite was perforated at 55 s. After ablation for 300 s, the composite showed a mass loss rate of 0.006 g/s and a linear recession rate of 0.004 mm/s. The formation of zirconia melt on the surface of the C/ZrC composite contributed mainly the ablation property improvement. The C/ZrC composite after ablation showed four different layers due to the temperature and pressure gradients: the melting layer, the loose tree-coral-like ZrO 2 layer, the undersurface oxidation layer, and the composite layer.

Preparation and characterization of C/SiC–ZrB 2 composites by precursor infiltration and pyrolysis process

Ultra-high temperature ceramic matrix composites (C/SiC–ZrB 2) are prepared by slurry and precursor infiltrations and pyrolysis method. C/SiC–ZrB 2 composites with ZrB 2 volume content from 10% to 24.6%, have balanced performance of fracture toughness (17.7–8.1 MPa m 1/2), flexural strength at room temperature (367–163 MPa) and at high temperature (strength retention 74% at 1800 °C and over 32% at 2000 °C), better oxidation and ablation resistance under oxyacetylene torch environment (recession rate 0.01 mm/s).

Preparation of 3D C/SiC-Cu Composites via Precursor Pyrolysis and Property Investigation

A novel composite, 3D C/SiC-Cu, which contained copper as transpiration agent, was designed and prepared. The influence of copper contents (2.18, 4.86, 6.53vol %) upon the mechanical and anti-ablative properties was investigated. The flexural strengths of three composites were over 450MPa, and fracture toughness over 15.0MPa•m1/2. After being ablated for 35 seconds in flowing oxyacetylene torch environment, the composites remained integral, and the flexural strength and strength retention ratio of the composite increased with the copper content increase. The maximum recession rate of the samples in oxyacetylene torch test was as low as 0.0490mm/s.