The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Hejun Li - One of the best experts on this subject based on the ideXlab platform.
-
effect of tantalum carbide on the ablation behaviors of hafnium carbide coating for c c composites under single and cyclic Oxyacetylene Torch environments
Surface & Coatings Technology, 2020Co-Authors: Guanghui Feng, Dou Hu, Hejun Li, Bo Li, Li Yang, Jinhua LuAbstract:Abstract A HfC-TaC/SiC multilayer coating was synthesized on carbon/carbon (C/C) composites by supersonic atmospheric plasma spray (SAPS) and pack cementation (PC) methods. Ablation performance of the coating was characterized under single and cyclic Oxyacetylene Torch with a heat flux of 4.18 MW/m2, and the phase composition and morphology of the oxide layer were surveyed systematically. During single ablation, a continuous Hf-Ta-O compound scale was formed on the surface, which is responsible for the better ablation performance of HfC-TaC coating compared with monophasic HfC coating. As for cyclic ablation, ablation crater appears on both HfC and HfC-TaC coating surfaces due to the multiple thermal shocks, but the size of the latter is reduced significantly.
-
microstructure mechanical and anti ablation properties of sicnw pyc core shell networks reinforced c c zrc sic composites fabricated by a multistep method of chemical liquid vapor deposition
Ceramics International, 2019Co-Authors: Qinchuan He, Hejun Li, Changcong Wang, Jinhua LuAbstract:Abstract C/C–ZrC–SiC composites reinforced by SiC nanowire (SiCnw)/pyrocarbon (PyC) core-shell networks were prepared by a multistep method of chemical liquid-vapor deposition (CLVD). The microstructure, mechanical property and ablation resistance were researched. The investigations presented that the PyC was deposited on the SiC nanowires, and the micro-scale core-shell structures were produced. Moreover, these micro-scale structures not only connected with the fibers and matrices, but also filled the pores in the composites. In contrast with C/C–ZrC–SiC composites, the flexural modulus and strength of SiCnw/PyC-C/C–ZrC–SiC composites increased by 36.91% and 44.53%, and the fracture mode was changed from the brittle to pseudo-plastic fracture. After the Oxyacetylene Torch ablation at two temperatures for 90s, the composites strengthened by SiCnw/PyC core-shell possessed a better resistant ablation. At ablation temperature of 2300 °C, the mass loss rate and linear reduction rate of the composites with core-shell networks decreased by 66.18% and 57.55% in contrast with the non-reinforced composites, and declined by 56.46% and 57.48% at ablation temperature of 3000 °C. The obvious decrease of ablation rates was ascribed to the dense microstructure, the small coefficient of thermal expansion (CTE), the good thermal conductivity, and the resistant ablation roles of SiCnw/PyC core-shell systems.
-
ablation mechanism of wc sic double layer coating under Oxyacetylene Torch test
Ceramics International, 2016Co-Authors: Jian Peng, Hejun Li, Kezhi LiAbstract:Abstract A WC-SiC double-layer coating was prepared on C/C composites to improve their anti-ablation property. The WC outer layer was designed to withstand high heat flux by its high mechanical strength, the SiC inner layer could transform into SiO 2 to block oxygen by its good anti-oxygen permeability. During ablation process, amounts of SiO 2 filled into the pores and cracks of WC outer layer, forming a steadily self-filling and cooling structure. As a result, the mass and linear ablation rates of WC-SiC coated C/C composites were 0.013 mg s −1 cm 2 and −1.61 µm/s, respectively. Compared with single SiC coated and single WC coated C/C composites, the linear ablation rates decreased by 46.3% and 27.3%, respectively, indicating that WC-SiC coating has a remarkable effect to resist chemical and mechanical ablation.
-
ablation behavior of zrc la2o3 coating for sic coated carbon carbon composites under an Oxyacetylene Torch
Ceramics International, 2016Co-Authors: Hejun Li, Qiangang Fu, Lu LiAbstract:Abstract To improve the ablation resistance of carbon/carbon (C/C) composites, ZrC-La 2 O 3 coating was prepared on SiC-coated C/C composites by supersonic atmosphere plasma spraying. Ablation resistance of the coating was evaluated under an Oxyacetylene Torch with a heat flux of 4.2 MW/m 2 . The coating shows a significant improvement on the ablation resistance compared with monophase ZrC coating and ZrC coating with LaB 6 . The good ablation resistance of the coating is mainly attributed to the formation of dense and high-viscosity scale surface which is beneficial to reducing the infiltration of oxygen and resisting the scouring from the flame during ablation. The positive effect of La 2 O 3 is to improve the compactness of the scale surface during ablation.
-
ablation behavior of rare earth la modified zrc coating for sic coated carbon carbon composites under an Oxyacetylene Torch
Corrosion Science, 2016Co-Authors: Hejun Li, Kezhi Li, Lei Feng, Qiangang FuAbstract:Abstract To improve the ablation resistance of carbon/carbon (C/C) composites at ultra-high temperature, La-modified ZrC coating was prepared on SiC-coated C/C composites by supersonic atmosphere plasma spraying. The coating shows a significant improvement on the ablation resistance compared with ZrC coating and could protect C/C composites for more than 120 s under heat flux of 2.4 MW/m 2 . La acted as a role in promoting the liquid phase sintering of ZrO 2 and forming a compact scale with high thermal stability, improving the ablation resistance of C/C composites.
Kezhi Li - One of the best experts on this subject based on the ideXlab platform.
-
ablation behavior of c c zrc sic composites prepared by reactive melt infiltration under Oxyacetylene Torch at two heat fluxes
Ceramics International, 2018Co-Authors: Zhigang Zhao, Kezhi Li, Wei Li, Yulei ZhangAbstract:Abstract C/C-ZrC-SiC composites were prepared by reactive melt infiltration and tested using an Oxyacetylene Torch with the heat fluxes of 4.18 and 2.38 MW/m 2 . The results showed that compared to C/C and C/C-SiC at the heat flux of 4.18 MW/m 2 , the mass ablation rates of C/C-ZrC-SiC were decreased by 60.8% and 44.8%, respectively. Its linear ablation rate was 7.3% higher than that of C/C, but was 13.5% lower than that of C/C-SiC. The C-SiC matrix and fibers of C/C-SiC in the center region were severely depleted by the high ablation temperature. C/C-ZrC-SiC composites experienced the temperature exceeding 2400 °C associated with intense mechanical scouring of gas flow. The severe depletion of SiC and carbon fibers on the surface led to the formation of the porous ZrO 2 layer. The spallation of ZrO 2 occurred in the center of the ablated surface as a result of mechanical denudation of high temperature gas flow. At the heat flux of 2.38 MW/m 2 , the mass and linear ablation rates of C/C-ZrC-SiC were decreased by 76.8% and 88.4% (C/C), 66.9% and 58.3% (C/C-SiC), respectively. The oxide was slightly peeled off in the center region of C/C-SiC. The surface temperatures of C/C-SiC and C/C-ZrC-SiC were lower than that of C/C composites. The island-like ZrO 2 and SiO 2 layer were formed on the ablated surface of C/C-ZrC-SiC and acted as effective barriers to shield the ablation heat and slow inward transport of oxygen to the underlying material.
-
ablation mechanism of hfc hfo2 protective coating for sic coated c c composites in an Oxyacetylene Torch environment
Journal of Materials Science & Technology, 2017Co-Authors: Yang Yang, Kezhi Li, Zhigang ZhaoAbstract:To prevent the C/C composites from ablation, HfC-HfO2 protective coating was prepared by supersonic atmospheric plasma spraying. The morphology and microstructure of HfC-HfO2 coating were characterized by X-ray diffraction and scanning electron microscopy. The ablation resistance test was carried out by an Oxyacetylene Torch. The results show that the as-prepared coating is dense with little pinholes and crack free. The elements Hf, C and O were uniformly distributed in the cross-section. After ablation for different time, the mass ablation rate fluctuated along with the change of ablation time. The ablation process of the surface coating could be divided into rapid oxidation and solid state sintering stages. During ablation, an HfCxOy-HfO2 transitional layer was generated in the coating, which resulted from the active oxidation of HfC. After cooling, some microcracks were observed on the surface of coating, and the structure of cross-section was broken, which were due to the phase transition of HfO2.
-
ablation mechanism of carbon carbon composites modified by hfc sic in two conditions under Oxyacetylene Torch
Journal of Materials Science & Technology, 2017Co-Authors: Kezhi Li, Tao Duan, Jiaping Zhang, Maoyan ZhangAbstract: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 HfO2 was not melted completely in the heat flux of 2.38 MW/m2 (HF-L). So, both HfO2 and SiO2 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.
-
hfc zrc sic multiphase protective coating for sic coated c c composites prepared by supersonic atmospheric plasma spraying
Ceramics International, 2017Co-Authors: Yang Yang, Kezhi Li, Zhigang ZhaoAbstract:HfC-ZrC-SiC (HZS) multiphase coating was deposited on the surface of SiC-coated carbon/carbon composites by supersonic atmospheric plasma spraying. The morphology and microstructure of HZS coating were characterized by XRD and SEM. The as-prepared coating was composed of different carbides and oxides. The structure was dense and crack free. Each element distributed uniformly in the coating. Ablation resistance test was carried out by Oxyacetylene Torch. During ablation, the outer coating underwent a process of solid state sintering and formed a dense Hf-Zr-Si-O layer on the surface of coating gradually, which could prevent the oxygen diffusing inward. The inner coating was oxidized gradually with the oxygen permeation and the structure was loose. In addition, the newly formed HfSiO4 and ZrSiO4 were generated after cooling, which could play a pinning effect and prevent crack extension.
-
ablation mechanism of wc sic double layer coating under Oxyacetylene Torch test
Ceramics International, 2016Co-Authors: Jian Peng, Hejun Li, Kezhi LiAbstract:Abstract A WC-SiC double-layer coating was prepared on C/C composites to improve their anti-ablation property. The WC outer layer was designed to withstand high heat flux by its high mechanical strength, the SiC inner layer could transform into SiO 2 to block oxygen by its good anti-oxygen permeability. During ablation process, amounts of SiO 2 filled into the pores and cracks of WC outer layer, forming a steadily self-filling and cooling structure. As a result, the mass and linear ablation rates of WC-SiC coated C/C composites were 0.013 mg s −1 cm 2 and −1.61 µm/s, respectively. Compared with single SiC coated and single WC coated C/C composites, the linear ablation rates decreased by 46.3% and 27.3%, respectively, indicating that WC-SiC coating has a remarkable effect to resist chemical and mechanical ablation.
Qiangang Fu - One of the best experts on this subject based on the ideXlab platform.
-
ablation behavior of nose shaped hfb2 sic modified carbon carbon composites exposed to Oxyacetylene Torch
Corrosion Science, 2019Co-Authors: Junling Qu, Jiaping Zhang, Qiangang FuAbstract:Abstract Nose-shaped C/C-H fB2-SiC with good mechanical property were fabricated by PIP. During ablation in 2.38 MW/m2 using Oxyacetylene Torch, the composites showed good ablation performance and structural stability. Because of the nose-shaped feature, protective ablation products including borosilicate glass, HfO2-glass and HfO2 scale covered on the surface according to their distances to the nose tip, which were beneficial for enduring the heating conditions. As heat flux increased to 4.18 MW/m2, more serious ablation occurred, and the protective performance degradation of the ablation products accelerated, especially at the nose tip, the partly ruptured HfO2 layer was difficult to withstand the enhanced denudation.
-
interface design and hfc additive to enhance the cyclic ablation performance of sic coating for carbon carbon composites from 1750 c to room temperature under vertical Oxyacetylene Torch
Corrosion Science, 2017Co-Authors: Jiaping Zhang, Qiangang Fu, Yongjie WangAbstract:Abstract To enhance the cyclic ablation performance of SiC coating from1750 °C to room temperature under vertical Oxyacetylene Torch, interface design and HfC additive were combined. A porous surface of C/C composites was firstly constructed by Oxyacetylene flame so as to form an inlaid interface after the pack cementation preparation of HfC-SiC coating. After 8 ablation thermal cycles, the mass loss per unit area of the HfC-SiC coating was only 36.47 mg cm −2 . Based on thermogravimetric analysis, adhesive strength and thermal expansion test, effect of the inlaid interface on oxidation as well as ablation performance of the HfC-SiC coating was discussed.
-
The ablation behavior and mechanical property of C/C-SiC-ZrB2 composites fabricated by reactive melt infiltration
Ceramics International, 2017Co-Authors: Yue Liu, Qiangang Fu, Beibei Wang, Tianyu Liu, Jia SunAbstract:In order to improve the ablation resistance of carbon/carbon (C/C) composites, SiC-ZrB2 di-phase ceramic were introduced by reactive melt infiltration. The ablation properties of these composites were evaluated by Oxyacetylene Torch with a heat flux of 2.38 MW/m2 for 60 s. Compared with the pure C/C composites, the C/C-SiC-ZrB2 composites show a significant improvement in the ablation resistance, and the linear and mass ablation rates decreased from 10.28×10−3 mm/s to 6.72×10−3 mm/s and from 3.08×10−3 g/s to 0.61×10−3 g/s, respectively. After ablation test, the flexural strength retentions of the C/C and C/C-SiC-ZrB2 composites near the ablated center region are 39.7% and 81.6%, respectively. The higher strength retention rate of C/C-SiC-ZrB2 composites was attributed to the introduction of SiC-ZrB2 ceramic phases, which have excellent ablation resistant property. During ablation test, an ‘embedding structure’ of Zr-O-Si glass layer was formed, which could act as an effective barrier for oxygen and heat. The oxide ceramic coating could protect the C/C-SiC-ZrB2 composites from further ablation, and thus contribute to retaining the mechanical property of C/C-SiC-ZrB2 composites after ablation.
-
erosion resistance of c c sic zrb2 composites exposed to Oxyacetylene Torch
Journal of The European Ceramic Society, 2016Co-Authors: Qiangang Fu, Lu Li, Jiaping Zhang, Lei ZhuangAbstract:Abstract Carbon/carbon (C/C) composites were modified with SiC-ZrB 2 by reactive melt infiltration (RMI). The erosion resistance of the modified C/C composites, which machined into leading edge to simulate the real working condition, was investigated by exposure to the Oxyacetylene Torch. The erosion morphology and phase composition were examined by SEM and XRD. After exposure to Oxyacetylene Torch with a heat flux of 2.38 MW/m 2 for 60 s, the modified leading edge was slight damaged with linear ablation rate of 0.013 mm/s and mass ablation of 0.0014 g/s, decreased by 70% and 48% compared to pure C/C composites. During ablation, a homogeneous and dense oxide layer was formed on the front of the leading edge, contributing to enhance the ablation resistance of the modified C/C composites. The ablation mechanism of the C/C-SiC-ZrB 2 composites is related to the combined effects of thermochemical ablation by oxidative species and the thermomechanical damage by the shear action of high speed Oxyacetylene Torch.
-
ablation resistance of wedge shaped c c zrb2 zrc sic composites exposed to an Oxyacetylene Torch
Corrosion Science, 2016Co-Authors: Lei Zhuang, Qiangang FuAbstract:Abstract The ablation resistance of wedge-shaped C/C-ZrB2-ZrC-SiC composites was studied under an Oxyacetylene Torch. Ablation morphologies and phase compositions were examined by SEM and XRD. As exposed to low heat flux of 2.38 MW/m2, a porous and homogeneous ZrC-ZrO2 skeleton generated. With the increasing of heat flux, ceramic oxides at the tip became loose and fragmented instead of sintering together. Besides that, owing to the wedge-shape of the specimen, high gas pressure mainly concentrated at this region. The high gas pressure and strong shear scouring of flame resulted in the limited accumulation of ceramic oxides. This led to an inferior ablation of wedge-shaped C/C-ZrB2-ZrC-SiC composites in high heat flux of 4.18 MW/m2.
Yulei Zhang - One of the best experts on this subject based on the ideXlab platform.
-
ablation behavior of c c zrc sic composites prepared by reactive melt infiltration under Oxyacetylene Torch at two heat fluxes
Ceramics International, 2018Co-Authors: Zhigang Zhao, Kezhi Li, Wei Li, Yulei ZhangAbstract:Abstract C/C-ZrC-SiC composites were prepared by reactive melt infiltration and tested using an Oxyacetylene Torch with the heat fluxes of 4.18 and 2.38 MW/m 2 . The results showed that compared to C/C and C/C-SiC at the heat flux of 4.18 MW/m 2 , the mass ablation rates of C/C-ZrC-SiC were decreased by 60.8% and 44.8%, respectively. Its linear ablation rate was 7.3% higher than that of C/C, but was 13.5% lower than that of C/C-SiC. The C-SiC matrix and fibers of C/C-SiC in the center region were severely depleted by the high ablation temperature. C/C-ZrC-SiC composites experienced the temperature exceeding 2400 °C associated with intense mechanical scouring of gas flow. The severe depletion of SiC and carbon fibers on the surface led to the formation of the porous ZrO 2 layer. The spallation of ZrO 2 occurred in the center of the ablated surface as a result of mechanical denudation of high temperature gas flow. At the heat flux of 2.38 MW/m 2 , the mass and linear ablation rates of C/C-ZrC-SiC were decreased by 76.8% and 88.4% (C/C), 66.9% and 58.3% (C/C-SiC), respectively. The oxide was slightly peeled off in the center region of C/C-SiC. The surface temperatures of C/C-SiC and C/C-ZrC-SiC were lower than that of C/C composites. The island-like ZrO 2 and SiO 2 layer were formed on the ablated surface of C/C-ZrC-SiC and acted as effective barriers to shield the ablation heat and slow inward transport of oxygen to the underlying material.
-
synthesis of carbon nanofibers from carbon foam composites via Oxyacetylene Torch ablation
Materials and Manufacturing Processes, 2015Co-Authors: Hejun Li, Manhong Hu, Yunyu Li, Yulei Zhang, Bin Wang, Jingxian XuAbstract:Carbon nanofibers were in-situ synthesized on porous carbon composites via a simple and economic technique of Oxyacetylene Torch ablation without catalyst assistance. The resultant nanofibers with good crystallinity in the (002) plane were polycrystalline graphite, which grew in the ablation center region. They were generally tens of nanometers in diameter, several microns in length, and grew at different orientations, exhibiting flower-like nanofiber clusters covered with amorphous carbon film. The formation mechanism may be governed by exfoliation of graphite layers, or attachment of graphitic carbon atoms to silicon monoxide for growth during the cooling process.
-
ablation behavior of cvd zrc coating under Oxyacetylene Torch environment with different heat fluxes
International Journal of Refractory Metals & Hard Materials, 2015Co-Authors: Shaolong Wang, Kezhi Li, Hejun Li, Yulei Zhang, Weiyang ZhangAbstract:Abstract An ablation resistance ZrC coating composed of micrometer particles was prepared on carbon/carbon composites by chemical vapor deposition. The structure evolution, ablation property and behavior of the coating were investigated under an Oxyacetylene Torch environment with different heat fluxes. Results show that the ablation performance decreases with the increase of heat fluxes from 2380 to 4180 kW/m 2 . Oxidation erosion is proposed as the major ablation mechanism. The ablated coating consists of three layers (outer ZrO 2 layer, transitional ZrC x O y layer and residual ZrC layer). An oxidation progress that the ZrC is oxidized into ZrC x O y firstly and then into ZrO 2 is inferred and accelerated by the continuous diffusion of oxygen resulted from the increase of heat fluxes. During different heat flux environments, the coating exhibits efficacious mechanical denudation resistance and the formed transitional ZrC x O y and outer ZrO 2 layers act as a good oxygen diffusion barrier, which could be the reason for its high ablation resistance at the temperature of 2000–3000 °C.
-
structure evolution and ablation behavior of zrc coating on c c composites under single and cyclic Oxyacetylene Torch environment
Ceramics International, 2014Co-Authors: Shaolong Wang, Kezhi Li, Hejun Li, Yulei Zhang, Tao FengAbstract:Abstract ZrC ablation resistance coating was prepared on carbon/carbon composites by low pressure chemical vapor deposition using the ZrCl4–C3H6–H2–Ar system. The structure evolution and ablation behavior of the coating under single and cyclic ablation were investigated in an Oxyacetylene Torch environment. Single ablation results show that the ablated coating consists of three layers (outer ZrO2 layer, transitional ZrCxOy layer and residual ZrC layer). An oxidation progress is inferred that ZrC is oxidized into ZrCxOy firstly and then into ZrO2 in the case of the continuous diffusion of oxygen. Cyclic ablation results show that the effect of crack growth inhibition and the oxygen diffusion limitation of ZrO2 and ZrCxOy layers dominate the ablation of the coating and result in two different ablation behaviors. Based on the role of the ZrO2 and ZrCxOy layers in the single and cyclic ablation, two different ablation modes of the coating are proposed.
-
ablation resistance of zrb2 sic coating prepared by supersonic atmosphere plasma spraying for sic coated carbon carbon composites
Ceramics International, 2014Co-Authors: Yulei Zhang, Zhixiong Hu, Hejun LiAbstract:Abstract To improve the ablation resistance of carbon / carbon (C / C) composites, ZrB 2 –SiC coating was prepared on the surface of SiC-coated C / C composites by supersonic atmosphere plasma spraying. Ablation resistance of the coating was investigated by Oxyacetylene Torch under different heat flux. Results show that the multilayer coating is dense and its thickness is about 60 μm. The mass and linear ablation rates of the coated C / C composites are 0.4×10 −3 g/s and 0.6 μm/s after ablation for 60 s under the heat flux of 2400 kW/m 2 . However, the coating is failure after ablation for 60 s under the heat flux of 4200 kW/m 2 . The good ablation resistance of the coating under the heat flux of 2400 kW/m 2 is mainly attributed to the formation of a dense ZrO 2 –SiO 2 scale, which could act as thermal barrier and reduce inward diffusion of oxygen.
Zhigang Zhao - One of the best experts on this subject based on the ideXlab platform.
-
cyclic ablation behavior of c c zrc sic zrb2 composites under Oxyacetylene Torch with two heat fluxes at the temperatures above 2000 oc
Corrosion Science, 2021Co-Authors: Zhigang Zhao, Leilei ZhangAbstract:Abstract The cyclic ablation behavior of C/C-ZrC-SiC-ZrB2 composites was investigated following 30s×4 and 60s×2 cycles at the heat fluxes of 2.38 and 4.18 MW/m2, respectively. At the two heat fluxes, the surface temperature of cyclic ablation of 30s×4 was lower than that of 60s×2. Microstructure characterization indicated that the center and transition region consisted of a layered structure of the outer ZrO2 layer with the subsurface ZrO2-SiO2 layer. The depletion of SiO2 was decreased in the sub layer and the grain size of ZrO2 in the sub layer was smaller than that of ZrO2 in the outer layer.
-
ablation behavior of c c zrc sic composites prepared by reactive melt infiltration under Oxyacetylene Torch at two heat fluxes
Ceramics International, 2018Co-Authors: Zhigang Zhao, Kezhi Li, Wei Li, Yulei ZhangAbstract:Abstract C/C-ZrC-SiC composites were prepared by reactive melt infiltration and tested using an Oxyacetylene Torch with the heat fluxes of 4.18 and 2.38 MW/m 2 . The results showed that compared to C/C and C/C-SiC at the heat flux of 4.18 MW/m 2 , the mass ablation rates of C/C-ZrC-SiC were decreased by 60.8% and 44.8%, respectively. Its linear ablation rate was 7.3% higher than that of C/C, but was 13.5% lower than that of C/C-SiC. The C-SiC matrix and fibers of C/C-SiC in the center region were severely depleted by the high ablation temperature. C/C-ZrC-SiC composites experienced the temperature exceeding 2400 °C associated with intense mechanical scouring of gas flow. The severe depletion of SiC and carbon fibers on the surface led to the formation of the porous ZrO 2 layer. The spallation of ZrO 2 occurred in the center of the ablated surface as a result of mechanical denudation of high temperature gas flow. At the heat flux of 2.38 MW/m 2 , the mass and linear ablation rates of C/C-ZrC-SiC were decreased by 76.8% and 88.4% (C/C), 66.9% and 58.3% (C/C-SiC), respectively. The oxide was slightly peeled off in the center region of C/C-SiC. The surface temperatures of C/C-SiC and C/C-ZrC-SiC were lower than that of C/C composites. The island-like ZrO 2 and SiO 2 layer were formed on the ablated surface of C/C-ZrC-SiC and acted as effective barriers to shield the ablation heat and slow inward transport of oxygen to the underlying material.
-
ablation mechanism of hfc hfo2 protective coating for sic coated c c composites in an Oxyacetylene Torch environment
Journal of Materials Science & Technology, 2017Co-Authors: Yang Yang, Kezhi Li, Zhigang ZhaoAbstract:To prevent the C/C composites from ablation, HfC-HfO2 protective coating was prepared by supersonic atmospheric plasma spraying. The morphology and microstructure of HfC-HfO2 coating were characterized by X-ray diffraction and scanning electron microscopy. The ablation resistance test was carried out by an Oxyacetylene Torch. The results show that the as-prepared coating is dense with little pinholes and crack free. The elements Hf, C and O were uniformly distributed in the cross-section. After ablation for different time, the mass ablation rate fluctuated along with the change of ablation time. The ablation process of the surface coating could be divided into rapid oxidation and solid state sintering stages. During ablation, an HfCxOy-HfO2 transitional layer was generated in the coating, which resulted from the active oxidation of HfC. After cooling, some microcracks were observed on the surface of coating, and the structure of cross-section was broken, which were due to the phase transition of HfO2.
-
hfc zrc sic multiphase protective coating for sic coated c c composites prepared by supersonic atmospheric plasma spraying
Ceramics International, 2017Co-Authors: Yang Yang, Kezhi Li, Zhigang ZhaoAbstract:HfC-ZrC-SiC (HZS) multiphase coating was deposited on the surface of SiC-coated carbon/carbon composites by supersonic atmospheric plasma spraying. The morphology and microstructure of HZS coating were characterized by XRD and SEM. The as-prepared coating was composed of different carbides and oxides. The structure was dense and crack free. Each element distributed uniformly in the coating. Ablation resistance test was carried out by Oxyacetylene Torch. During ablation, the outer coating underwent a process of solid state sintering and formed a dense Hf-Zr-Si-O layer on the surface of coating gradually, which could prevent the oxygen diffusing inward. The inner coating was oxidized gradually with the oxygen permeation and the structure was loose. In addition, the newly formed HfSiO4 and ZrSiO4 were generated after cooling, which could play a pinning effect and prevent crack extension.
-
ablation resistance of hfc sic coating prepared by supersonic atmospheric plasma spraying for sic coated c c composites
Ceramics International, 2016Co-Authors: Yang Yang, Kezhi Li, Zhigang Zhao, Hejun LiAbstract:Abstract In order to improve the ablation properties of carbon/carbon composites, HfC–SiC coating was deposited on the surface of SiC-coated C/C composites by supersonic atmospheric plasma spraying. The morphology and microstructure of HfC–SiC coating were characterized by SEM and XRD. The ablation resistance test was carried out by Oxyacetylene Torch. The results show that the structure of coating is dense and the as-prepared HfC–SiC coating can protect the C/C composites against ablation. After ablation for 30 s, the linear ablation rate and mass ablation rate of the coating are −0.44 μm/s and 0.18 mg/s, respectively. In the ablation center region, a Hf–Si–O compound oxide layer is generated on the surface of HfC–SiC coating, which is conducive to protecting the C/C composites from ablation. With the ablation time increasing to 60 s, the linear ablation rate and mass ablation rate are changed to −0.38 μm/s and 0.26 mg/s, respectively. Meanwhile, the thickness of the outer Hf–Si–O compound layer also increases.
