Ablation Performance of a Novel Super-hybrid Composite

A novel super-hybrid composite (NSHC) was boron-modified phenolic resin (BPR) with three-dimensional reticulated SiC ceramic (3DRC) and high silica fibers. Ablation performance of the NSHC was studied. The results show that the linear ablation rate of NSHC was lower than that of pure BPR and the high silica/BPR composite. Its linear ablation rate is 1/17 of the high silica/BPR. Mass ablation rate of the NSHC is very close to that of the pure BPR and the high silica/BPR composite. Scanning electron microscope (SEM) analysis indicates that 3DRC has scarcely changed its shape at the ablation temperature. Its special reticulated structure can restrict the materials deformation and prevent high velocity heat flow from eroding the surface of the materials largely and thus increase ablation resistance of the NSHC.

Ablation Property of Ceramics/Carbon Fibers/Resin Novel Super-hybrid Composite

A novel super-hybrid composite (NSHC) is prepared with three-dimension reticulated SiC ceramic (3DRC), high performance carbon fibers and modified phenolic resin (BPR) in this paper. Ablation performance of super-hybrid composite is studied. The results show that the NSHC has less linear ablation rate compared with pure BPR and CF/BPR composite, for example, its linear ablation rate is 50% of CF/BPR at the same fiber content. Mass ablation rate of the NSHC is slightly lower than that of pure BPR and CF/BPR composite because of their difference in the density. Scanning electron microscopic analysis indicates that 3DRC can increase anti-erosion capacity of materials because its special reticulated structure can control the deformation of materials and strengthen the stability of integral structure.

Microstructural evolution of carbon fiber reinforced SiC-based matrix composites during laser ablation process

In this work, four different carbon fiber reinforced SiC-based matrix composites(C/SiC) were prepared,and microstructure evolution during laser ablation process was characterized. Laser irradiation provided a special high-temperature environment up to 3500℃. For all four composites, different morphologies can be obtained in the transition region due to the oxidation of different matrices. While only needle-shaped carbon fiber and nanolayered carbon without any matrix remained in the central region, indicating that graphitization process occurred in the center, resulting from the high-temperature and low-oxygen environment in the laser process. Therefore, the laser ablation of C/SiC composites is controlled by chemical and physical erosion, and mainly by the physical erosion in the center.

Effect of Monolithic LaB_6 on the Ablation Resistance of ZrC/SiC Coating Prepared by Supersonic Plasma Spraying for C/C Composites

Ablation resistance of monolithic LaB-doped ZrC coating for SiC-coated carbon/carbon composites by supersonic atmospheric plasma spray was investigated under an oxyacetylene torch with a heat flux of 4.18 MW/m~2. Result shows that ZrC coating with 10 vol.% LaBhas a good ablation resistance compared with pure ZrC, ZrC with 20 vol.% LaBand SiC-doped ZrC coating. After ablation for 15 s, the weight is increased by 1.12 mg/s. The good ablation resistance is ascribed to the formation of a stabilized scale which consists of protective LaZrO-containing molten phase and ZrOparticles keeping the integrity of the coating.

Ablation Mechanism of Carbon/Carbon Composites Modified by HfC–SiC in Two Conditions Under Oxyacetylene Torch

C/C-HfC-SiC composites prepared by precursor infiltration and pyrolysis process were ablated by oxyacetylene torch under two different flame conditions. The ablation performance of the composites was investigated in the heat flux of 2.38 MW/m2 （HF-L） and 4.18 MW/m2 （HF-H） for 60 s. The mechanical denudation in 4.18 MW/m2 （HF-H） was higher than that in 2.38 MW/m2 （HF-L）, while the results indicated that the composites had a similar and good ablation property under two different flame conditions. C/C- HfC-SiC composites can adapt the heat flux from 2.38 MW/m2 to 4.18 MW/m2. The Hf02 was not melted completely in the heat flux of 2.38 MW/m2 （HF-L）. So, both Hf02 and Si02 layers acted as an effective barrier to the transfer of heat and oxidative gases into the underlying carbon substrate. SiO2 was severely consumed in 4.18 MW/m2 （HF-H）, where the HfO2 molten layer played a more important role in protecting the inner composite.

Nano-TiO_(2) coate d nee dle carbon fib er reinforced phenolic aerogel composite with low density, excellent heat-insulating and infrared radiation shielding performance

High-performance thermal protection materials(TPMs)for spacecraft are becoming current research hotspots.Lightweight polymer-based ablators are considered to be the most promising candidates for TPMs due to their excellent designability and versatility.In this study,a unique nano-TiO_(2) coated needled carbon fiber felt/phenolic resin aerogel composite(TiCF/PR)is reported.Wherein the anatase nano-TiO_(2) was in-situ coated on the surface of carbon fibers uniformly through the sol-gel and calcination method,then,the phenolic resin aerogel was in-situ synthesized in the nano-TiO_(2) coated needled carbon fiber felt(TiCF)preform through vacuum impregnation and solvothermal method.The as-prepared aerogel com-posite possesses a low density(0.30–0.32 g/cm^(3)),low thermal conductivity(0.034 and 0.312 W/(m K)in the z and xy directions),and excellent thermal stability with 13.86%residual weight at 1300℃ in air.It is worthwhile to note that the TiCF/PR composite exhibits excellent antioxidant ablation and infrared(IR)radiation shielding properties in a high-temperature heating environment.With an oxygen-acetylene blaze heating of 1.5 MW/m^(2) for 150 s,the linear ablation rates decreased by 13.4%,and the backside temperature reduced from 322.3 to 179.1℃ compared to that of the sample without nano-TiO_(2) coating.The experimental and theoretical analysis showed that the present TiCF/PR nanocomposite has competitive and potential application prospects in the field of future TPMs.

SiC Nanowires Toughed HfC Ablative Coating for C/C Composites

In order to improve ablation resistance of carbon/carbon(C/C) composites,SiC nanowires were prepared on C/C composites surface in prior through chemical vapor reaction before HfC coating.SiC nanowires grew randomly and had good combination with HfC coating.SiC nanowires toughed HfC coating had lower linear and mass ablation rates than original HfC coating.The surface was much flatter and exhibited smaller cracks in center region.The ablation mechanism of HfC coating has been changed by SiC nanowires.Thicker HfO2 fused layer was formed on the surface of the toughed HfC coating,which could provide efficient protection for C/C composites.Therefore,SiC nanowires toughed HfC coating behaved in better ablation resistance.

Ablative Property of C/C–SiC–HfC Composites Prepared via Precursor Infiltration and Pyrolysis under 3,000 °C Oxyacetylene Torch

C/C–SiC–HfC composites were fabricated via precursor infiltration and pyrolysis using a mixture solution of organic hafnium-containing polymer and polycarbosilane as precursor. The microstructures and the phases of the composites were analyzed by scanning electron microscopy and X-ray diffraction. The ablation resistance of the composites was evaluated under 3,000 °C oxyacetylene torch. After ablation for 120 s, the composites exhibit good ablation properties with the linear and mass ablation rates of 9.1 9 10-4mm/s and 1.30 9 10-3g/s, which are far lower than those of the C/C–SiC composites. The excellent ablative property of the C/C–SiC–HfC composites is resulted from the formation of HfO2 molten layer on the surface of the composites, which could play a positive role in reducing heat transfer and preventing oxygen transport to the underlying carbon substrate.