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Chinese Journal of Aeronautics 2020年第5期33卷 1541-1548页

作者： Xue-Song LIU Qian-Gang FU Hui WANG Qiang SONG State Key Laboratory of Solidification Processing Shannxi Province Key Laboratory of Fiber Reinforced Light Composite MaterialsNorthwestern Polytechnical UniversityXi'an 710072PR China

Uni-directional carbon/carbon composites with high thermal conductivity are suitable to supply continuous thermal protection for future reentry vehicles since they could reduce surface temperature and ablation rates simultaneously in harsh *** this work,the high thermal conductivity carbon/carbon composites were prepared by chemical vapor *** heat-treatment,both their open porosity and internal friction increase due to the fiber/matrix thermal expansion mismatch;while their thermal conductive performance become better due to more complete carbon *** raising heat-treatment temperature from 1800℃to 2450℃,the mass and linear ablation rates of C/C composites with fibers vertical to the oxyacetylene torch for 60 s decrease from 0.66 mg/s and 2.95μm/s to 0.51 mg/s and 2.05μm/s *** improved ablation resistance is resulted from the increased thermal conductivity from 282 to 508 W/(m·K)and more carbon fibers exposed to the flame during ablation,which have better oxidation resistance than those of carbon *** such ablation rates become larger for composites with fibers parallel to the flame,from 1.02 mg/s and 3.73μm/s to 1.28 mg/s and 5.0μm/s respectively since the ablation occurred more easily through gaps at the fiber/matrix interfaces,which become larger and are always exposed to the flame for this case.

关键词： Ablation Carbon/carbon composites Fiber orientation Heat treatment Thermal conductivity

Pattern recognition of messily grown nanowire morphologies applying multi-layer connected self-organized feature maps

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Journal of Materials Science & Technology 2019年第5期35卷 946-956页

作者： Qing Liu Hejun Li Yulei Zhang Zhigang Zhao State Key Laboratory of Solidification Processing Carbon/Carbon Composites Technology Research Center Northwestern Polytechnical University

Multi-layer connected self-organizing feature maps(SOFMs) and the associated learning procedure were proposed to achieve efficient recognition and clustering of messily grown nanowire morphologies. The network is made up by several paratactic 2-D SOFMs with inter-layer connections. By means of Monte Carlo simulations, virtual morphologies were generated to be the training samples. With the unsupervised inner-layer and inter-layer learning, the neural network can cluster different morphologies of messily grown nanowires and build connections between the morphological microstructure and geometrical features of nanowires within. Then, the as-proposed networks were applied on recognitions and quantitative estimations of the experimental morphologies. Results show that the as-trained SOFMs are able to cluster the morphologies and recognize the average length and quantity of the messily grown nanowires within. The inter-layer connections between winning neurons on each competitive layer have significant influence on the relations between the microstructure of the morphology and physical parameters of the nanowires within.

关键词： Artificial neural networks Self-organizing feature maps Monte Carlo simulation Pattern recognition Messily grown nanowire morphologies

Two birds with one stone: Simultaneous fabrication of HfC nanowires and CNTs through efficient utilization of polymer-derived ceramics

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Journal of Materials Science & Technology 2022年第34期129卷 163-172页

作者： Yanqin Fu Yulei Zhang Xuemin Yin Liyuan Han Qiangang Fu Hejun Li Ralf Riedel Shaanxi Province Key Laboratory of Fiber Reinforced Light Composite Materials Northwestern Polytechnical UniversityXi’an 710072China Technische Universität Darmstadt Institut für MaterialwissenschaftOtto-Berndt-Straβe 3Darmstadt D-64287Germany

Carbon nanotubes(CNTs) are fabricated in carbon cloth by ultilizing the waste gasses when fabricating hafnium carbide nanowires(HfC_(NWS)) through thermal pyrolysis of Hf-containing polymer *** formed HfC_(NWS) are distributed uniformly on the surface of the carbon fibers in carbon/carbon(C/C) composites and display perfect single crystal *** pyrolysis of the Hf-containing organic precursor provides hafnium and carbon source for the growth of HfC_(NWS).The released waste gasses containing CO,CH4and CO_(2)are the main carbon source for the growth of ***,the flexural strength of HfC_(NWS) reinforced carbon/carbon(HfC_(NWS)-C/C) composites is enhanced by ~105% compared with pure C/C,and the CNTs/carbon cloth also displays improved electrochemical performance with respect to capacitor *** present study introduces a novel sustainable and eco-friendly process related to polymer-derived ceramics to form advanced ceramic nanocomposites and proposes a deep understanding of the growth mechanism of CNTs.

关键词： HfC nanowires Carbon nanotubes Waste gasses Effective utilization Polymer-derived ceramics

(Hf_(0.5)Ta_(0.5))C ultra-high temperature ceramic solid solution nanowires

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Journal of Materials Science & Technology 2023年第16期147卷 91-101页

作者： Hui Chen Yulei Zhang Yanqin Fu Jiachen Meng Qing Miao Jianhua Zhang Hejun Li State Key Laboratory of Solidification Processing Carbon/Carbon Composites Research CenterNorthwestern Polytechnical UniversityXi’an 710072China Carbon Matrix Composites Research Institute Henan Academy of SciencesZhengzhou 450046China

Ultra-high temperature ceramic(UHTC)nanowires are potential reinforcement materials due to it combines the perfect properties of bulk materials and unique geometric properties of one-dimensional(1D)***,developing 1D nanomaterials that have excellent morphology and structure retention in ultra-high temperature environments is of prime importance to bring their outstanding performance into full ***,we report the novel solid solution((Hf_(0.5)Ta_(0.5))C)ceramic nanowires,which could not only maintain morphological and structural stability at 1900°C but also exhibit 1D nanostructures under oxyacetylene scouring and ablation at 2300°*** morphology evolution of nanowires obeys the Rayleigh instability mechanism,and the internal structure and element distribution of nanowires remain unchanged even if the surface atoms are *** fascinating nanowires are demonstrated to have great potential as ideal reinforcement materials of composite materials and toughening phases of ceramics that are applied in ultra-high temperature environments,as well as excellent performance enhancement phases of functional *** work may provide new insights into the development of ceramic nanowires and widen their applications.

关键词： (Hf_(0.5)Ta_(0.5))C solid solution nanowires Vapor-liquid-solid mechanism Catalyst/nanowire interface High-temperature stability Ablation resistance

Enhancing anti-oxidation and thermal-radiation performance of the repaired borosilicate glass coating on C/C composites by Sm-doping

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Journal of Materiomics 2022年第2期8卷 417-426页

作者： Han-Hui Wang Liu Teng Jing-An Kong Xue-Song Liu Xiao-Hong Shi He-Jun Li State Key Laboratory of Solidification Processing Carbon/Carbon Composites Research CenterNorthwestern Polytechnical UniversityXi'anShaanxi710072China

To repair the damaged SiC coated C/C composites,a double-layer system including a Sm-doped boro-silicate glass external layer and a SieSiC inner layer was prepared by a slurry-based laser cladding *** oxidation experiment and indirect/direct thermal-radiation measurements were *** results showed that the absorbance of borosilicate glass to the laser at 900e1200 nm was improved significantly by ***,the repaired coating with a more compact structure and better oxidation resistance was *** oxidation at 1773 K for 10 h,the mass loss of the damaged sample could be reduced by 74.98%with *** increasing laser-absorption and reducing viscosity,the thermal-radiation property of the repaired coating was enhanced to decrease the surface temperature greatly.A repair system with excellent thermal protection performance was achieved.

关键词： Coating repair Laser cladding Rare earth Oxidation resistance Thermal radiation

Response mechanism study of alternate ZrC-10vol.%SiC/ZrC-70vol.%SiC coatings with various sublayer thicknesses for cyclic and long-term thermal exposure

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Journal of Materials Science & Technology 2023年第9期140卷 153-162页

作者： Guanghui Feng Xiyuan Yao Yulan Yu Hejun Li State Key Laboratory of Solidification Processing Shaanxi Key Laboratory of Fiber Reinforced Light Composite MaterialsNorthwestern Polytechnical UniversityXi’an 710072China

To explore the influence of sublayer numbers on the structure evolution and thermal stress level,an alternate coating consisting of ZrC-10 vol.%SiC and ZrC-70 vol.%SiC sublayers was designed in this *** a basically consistent general thickness,three coatings constituted by 2,4 and 6 sublayers were prepared by plasma spraying,which then were assessed using an oxyacetylene torch under cyclic and long-term *** coating with 6 sublayers was supposed to be the one with the best ablation property,finite element analysis also evidenced its least thermal stress among all these *** being ablated for 240 s,the linear and mass ablation rates of the coating with 6 sublayers decreased by 51.27%and 14.41%as compared to that with 4 ***-test analysis proved the existence of Si-based products,which help the outmost surface to develop a dense ***,the yielded alternate dense/porous scale had a preferable toughness,allowing it to maintain a good integrity.

关键词： Alternate coating Sublayer numbers Carbon/carbon composites High-temperature test Plasma spraying

Synthesis and performance characterization of Hafnium-based multilayer coating applied over carbon/carbon composites with sharp leading edge

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Journal of Materials Science & Technology 2023年第22期153卷 254-262页

Carbon/carbon(C/C)composites have been acknowledged as potential candidates in aerospace vehicles,but their oxygen sensitivity still remains an enormous *** this work,a novel multilayer coating consisted of HfC-2.5 mol.%Hf_(6)Ta_(2)O_(17),HfC-40 mol.%SiC,HfC-2.5 mol.%Hf_(6)Ta_(2)O_(17) and HfC-60 mol.%SiC sublayers from surface to inside was designed and fabricated on the surface of C/C composites with sharp leading edge by plasma *** ablation resistance was assessed using oxyacetylene torch with a maximum temperature over 2300℃ and compared with monolayered *** multilayer coating revealed preferable ablation retardation capacity evidenced by its integrated profile and less flaw *** benefits were primarily stemmed from the effective structural design and rational material *** former was able to reduce the thermal stress within the ablated scale,the latter contributed to rising the high-temperature resistance and oxygen barrier ability of the coating.

关键词： Multilayer design Ablation resistance Plasma spraying Sharp leading edge C/C composites

纳米管/线多尺度强韧化C/C复合材料研究现状与展望

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航空材料学报 2021年第3期41卷 11-24页

作者：张雨雷付艳芹付前刚宋强西北工业大学炭/炭复合材料工程技术研究中心西安710072

C/C复合材料因具有密度低、高温力学性能保持率高等一系列优异性能,成为航空航天等领域热端部件极佳的热结构候选材料,但因热解碳基体的脆性特征及单一微米尺度碳纤维不能有效增强尖锐薄壁区域,常规C/C复合材料无法满足尖锐薄壁构件的... 详细信息

C/C复合材料因具有密度低、高温力学性能保持率高等一系列优异性能,成为航空航天等领域热端部件极佳的热结构候选材料,但因热解碳基体的脆性特征及单一微米尺度碳纤维不能有效增强尖锐薄壁区域,常规C/C复合材料无法满足尖锐薄壁构件的使用需求。本文综述了纳米管/线增强C/C复合材料的制备方法及其对材料结构和性能方面的影响,概述了引入碳纳米管(CNTs)和碳化硅纳米线(SiCNWs)、碳化铪纳米线(HfCNWs)等纳米材料对改善C/C复合材料力学、抗烧蚀性能影响以及不同纳米增强体对复合材料的增韧机制和抗烧蚀机理。针对目前引入纳米增强体成分、方法以及测试性能单一等不足,提出在这些研究基础上进一步完善和创新工艺技术,并进行合理的组元和结构设计,深入研究多尺度强韧化C/C复合材料的高温力学性能及其增韧机制。

关键词： C/C复合材料纳米增强多尺度热解碳力学性能