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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

Initial precursor reaction mechanism of CVD-HfC coating based on density functional theory

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Chinese Journal of Aeronautics 2024年第7期37卷 511-521页

作者： Yunzhou LIN Yulei ZHANG yanqin fu Jian ZHANG Jing’an KONG Ruicong CHEN State Key Laboratory of Solidification Processing Carbon/Carbon Composites Research CenterNorthwestern Polytechnical UniversityXi’an 710072China Henan Key Laboratory of High Performance Carbon Fiber Reinforced Composites Carbon Matrix Composites Research InstituteHenan Academy of SciencesZhengzhou 450046China

Recently,the preparation of ultra-high temperature HfC ceramic coating has gained significant attention,particularly through the application of the HfCl_(4)-CH_(4)-H_(2)-Ar system via Chemical Vapor Deposition(CVD),which has been found widely applied to C/C ***,an analysis of the reactions that occur in the initial stage of the CVD-HfC coating process is presented using Density functional Theory(DFT)and Transition State Theory(TST)at the B3LYP/Lanl2DZ *** results reveal that HfCl4 can only cleave to produce hypochlorite,which will further react with methyl to synthesize intermediates to form *** to the analysis of the energy barrier and reaction constant,HfCl preferentially reacts with methyl groups to form complex adsorptive intermediates at 1573 *** a C—Hf bond production energy of 212.8 kcal/mol(1 kcal=4.18 kJ),the reaction rate constant of HfCl+CH is calculated to be 2.15×10^(-18) cm^(3)/s at 1573 ***,both the simulation and experimental results exhibit that the upward trend of reaction rate constants with temperature is also consistent with the deposition rate,indicating that the growth curve of the reaction rate constants tends to flatten *** proposed reaction model of the precursor’s decomposition and reconstruction during deposition process has significant implication for the process guidance.

关键词： Carbon composite HfC coating Chemical vapor deposition Density functional theory Precursor reaction mechanism

Novel Hf_(x)Ta_(1−x)C solid solution nanowire toughened HfC coating:An effective strategy for synchronous enhanced mechanical and anti-ablation performance

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Journal of Advanced Ceramics 2024年第5期13卷 590-601页

作者： Hui Chen Yulei Zhang yanqin fu Wenhan Gai Junhao Zhao Haohui Zhang Shaanxi Key Laboratory of Fiber Reinforced Light Composite Materials Northwestern Polytechnical UniversityXi’an 710072China Henan Key Laboratory of High Performance Carbon Fiber Reinforced Composites Institute of Carbon Matrix CompositesHenan Academy of SciencesZhengzhou 450046China

Ultra-high-temperature ceramic nanowires have shown increasing potential for use as thermal structural ***,novel single-crystal Hf_(0.5)Ta_(0.5)C solid solution nanowires were synthesized and incorporated with a HfC coating to construct a robust structure with Hf_(0.5)Ta_(0.5)C solid solution nanowires uniformly distributed and interconnected within the *** novel Hf_(0.5)Ta_(0.5)C solid solution nanowires could effectively hinder crack propagation through crack tip pinning and crack *** mechanism substantially enhanced the elastic modulus and fracture toughness of the HfC coating by 53.29%and 59.67%,*** toughened HfC coating displayed superior fracture toughness and good interfacial binding strength with the substrate to resist severe oxidation and ***,the high thermal conductivity of the toughened HfC coating promoted heat ***,in comparison to the pure HfC coating,the toughened HfC coating displayed smaller mass and linear ablation rates of−0.35 mg·s^(−1)and−0.46μm·s^(−1),which decreased by 39.66%and 36.98%,*** work not only simultaneously enhances the mechanical properties and ablation resistance of HfC-coated carbon/carbon(C/C)composites but also provides novel prospects for advanced ultrahigh-temperature ceramic nanowires under extreme conditions.

关键词： Hf_(x)Ta_(1−x)C solid solution nanowires HfC coating carbon/carbon(C/C)composites mechanical performance ablationresistance

Microstructure and evolution of hafnium carbide whiskers via polymer-derived ceramics:A novel formation mechanism

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Journal of Advanced Ceramics 2023年第3期12卷 578-586页

作者： yanqin fu Yulei Zhang Hao Yan Jinhua Li Xuemin Yin Jia Sun Qiangang fu Ralf Riedel Shaanxi Key Laboratory of Fiber Reinforced Light Composite Materials Northwestern Polytechnical UniversityXi’an 710072China School of Materials and Chemical Engineering Xi’an Technological UniversityXi’an 710021China Institut für Materialwissenschaft Technische Universität DarmstadtDarmstadt D-64287Germany

Polymer-derived ultra-high-temperature ceramic(UHTC)nanocomposites have attracted growing attention due to the increasing demands for advanced thermal structure components in ***,hafnium carbide(HfC)whiskers are successfully fabricated in carbon fiber preforms via the polymer-derived ceramic(PDC)method.A novel carbon nanotube(CNT)template growth mechanism combined with the PDC method is proposed in this work,which is different from the conventional vapor–liquid–solid(VLS)mechanism that is commonly used for polymer-derived nanostructured *** CNTs are synthesized and proved to be the templates for fabricating the HfC whiskers,which are generated by the released low-molecular-weight gas such as CO,CO_(2),and CH4 during the pyrolysis of a Hf-containing *** formed products are composed of inner single crystal HfC whiskers that are measured to be several tens of micrometers in length and 100–200 nm in diameter and outer HfC/HfO_(2)*** work not only proposes a new strategy to prepare the HfC whiskers,but also puts forward a new thinking of the efficient utilization of a UHTC polymer precursor.

关键词： HfC whiskers carbon nanotubes(CNTs) CNT template Hf-containing precursor thermal pyrolysis

(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

Superior synergistic oxidation resistance of medium-entropy carbide ceramic powders rather than multi-phase carbide ceramic powders

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Journal of Advanced Ceramics 2024年第8期13卷 1223-1233页

作者： Jiachen Li Fanyu Lu Tao Li yanqin fu Junhao Zhao Junshuai Lv Yulei Zhang Shaanxi Key Laboratory of Fiber Reinforced Light Composite Materials State Key Laboratory of Solidification ProcessingNorthwestern Polytechnical UniversityXi'an 710072China

To date,some questions about medium-entropy carbide ceramics and the corresponding multi-phase carbide ceramics with the same cations and proportions remain *** oxidation behavior,do both have synergistic oxidation abilities and what role does entropy stabilization play in medium-entropy carbides?In this work,the oxidation behaviors of HfC-ZrC-TiC multi-phase carbide(HZT-MPC)and(Hf_(1/3)Zr_(1/3)Ti_(1/3))C medium-entropy carbide(HZT-MEC)powders were *** thermogravimetry(TG)oxidation,the TG curve of HZT-MPC had a bimodal ***"preferential oxidation"of HfC/ZrC occurred within HZT-MPC,followed by the formation of multi-phase oxides(HfO_(2),ZrO_(2),and TiO_(2)).The uneven compositional distribution slowed their solid solution reactions to form Ti-doped(Hf,Zr)O_(2) and(Hf,Zr)TiO_(4).The TG curve of HZT-MEC had a single peak.A uniform compositional distribution at the atomic scale promoted the rapid interdiffusion of oxides,forming Ti-doped(Hf,Zr)O_(2) and(Hf,Zr)TiO_(4) without ZrO_(2),HfO_(2),and TiO_(2) after TG ***,HZT-MEC had a higher onset oxidation temperature(To;470℃)than did HZT-MPC(430℃),and the TG single peak of HZT-MEC was between the TG bimodal peaks of ***,HZT-MEC showed superior oxidation resistance compared to HZT-MPC,which was attributed to the entropy stabilization effect of HZT-MEC suppressing the"preferential oxidation"of HfC/ZrC and the"delayed oxidation"of TiC,promoting the synergistic oxidation ability of multiple principal elements.

关键词： medium-entropy carbide multi-phase carbide synergistic oxidation ability oxidation resistance

Single-source precursor derived high-entropy metal–carbide nanowires:Microstructure and growth evolution

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Journal of Advanced Ceramics 2023年第11期12卷 2041-2052页

作者： Junhao Zhao Yulei Zhang Hui Chen yanqin fu Qing Miao Jiachen Meng Jiachen Li Shaanxi Key Laboratory of Fiber Reinforced Light Composite Materials Northwestern Polytechnical UniversityXi’an 710072China Henan Key Laboratory of High Performance Carbon Fiber Reinforced Composites Institute of Carbon Matrix CompositesHenan Academy of SciencesZhengzhou 450046China

In recent years,high-entropy metal carbides(HECs)have attracted significant attention due to their exceptional physical and chemical *** combination of excellent performance exhibited by bulk HEC ceramics and distinctive geometric characteristics has paved the way for the emergence of one-dimensional(1D)HECs as novel materials with unique development ***,we successfully fabricated novel(Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))C nanowires derived via Fe-assisted single-sourced precursor *** to the synthesis of the nanowires,the composition and microstructure of(Ti,Zr,Hf,Nb,Ta)-containing precursor(PHECs)were analyzed,and divinylbenzene(DVB)was used to accelerate the conversion process of the precursor and contribute to the formation of HECs,which also provided a partial carbon source for the nanowire ***,multi-branched,single-branched,and single-branched bending nanowires were synthesized by adjusting the ratio of PHECs to *** obtained single-branched(Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))C nanowires possessed smooth surfaces with an average diameter of 130–150 nm and a length of several tens of micrometers,which were a single-crystal structure and typically grew along the[11¯1]***,the growth of the(Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))C nanowires was in agreement with top-type vapor–liquid–solid *** work not only successfully achieved the fabrication of HEC nanowires by a catalyst-assisted polymer pyrolysis,but also provided a comprehensive analysis of the factors affecting their yield and morphology,highlighting the potential application of these attractive nano-materials.

关键词： (Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))C nanowires high-entropy metal carbides(HECs) (Ti,Zr,Hf,Nb,Ta)-containing precursors vapor–liquid–solid(VLS)mechanism

Cold sintering process:A green route to fabricate thermoelectrics

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Journal of Advanced Ceramics 2024年第11期13卷 1697-1712页

作者： Jinxue Ding Jing Guo Ruijuan Yan Wei Li Shuailing Ma yanqin fu Wenjie Xie Ralf Riedel Anke Weidenkaffa Department of Materials and Earth Sciences Technical University of DarmstadtDarmstadt 64287Germany State Key Laboratory for Mechanical Behavior of Materials&School of Materials Science and Engineering Xi’an Jiaotong UniversityXi’an 710049China Department of Mechanical and Materials Engineering The University of Alabama at BirminghamBirmingham 35294USA Institute of High Pressure Physics School of Physical Scientific and TechnologyNingbo UniversityNingbo 315211China Henan Key Laboratory of High Performance Carbon Fiber Reinforced Composites Carbon Matrix Composites Research InstituteHenan Academy of SciencesZhengzhou 450046China Fraunhofer Research Institution for Materials Recycling and Resource Strategies IWKS Alzenau 63755Germany

Cold sintering is a newly developed low-temperature sintering technique that has attracted extensive attention in the fabrication of functional materials and *** sintering temperatures allow for a substantial reduction in energy consumption,and simple experimental equipment offers the possibility of large-scale *** cold sintering process(CSP)has been demonstrated to be a green and cost-effective route to fabricate thermoelectric(TE)materials where significant grain growth,secondary phase formation,and element volatilization,which are prone to occur during high-temperature sintering,can be well *** this review,the historical development,understanding,and application of thermoelectric materials produced via cold sintering are *** latest attempts related to the cold sintering process for thermoelectric materials and devices are discussed and *** some current technical challenges,cold sintering provides a promising and sustainable route for the design of advanced high-performance thermoelectrics.

关键词： cold sintering process(CSP) thermoelectrics(TEs) low-temperature sintering transport properties transient liquidphase

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

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农牧业机械化措施与对策分析

广东蚕业 2024年第2期58卷 35-37页

作者：付艳琴乌拉特后旗农牧业机械化服务中心内蒙古巴彦淖尔015543

随着经济的发展和科技的进步,我国农牧业机械化水平逐步提高。然而,在实践中,农牧业机械化的推广和应用仍存在诸多制约因素。文章通过分析制约因素,提出了相应的措施与对策,包括加强科技创新,研发先进的农牧业机械设备,提高农业生产效... 详细信息

随着经济的发展和科技的进步,我国农牧业机械化水平逐步提高。然而,在实践中,农牧业机械化的推广和应用仍存在诸多制约因素。文章通过分析制约因素,提出了相应的措施与对策,包括加强科技创新,研发先进的农牧业机械设备,提高农业生产效率和质量;重视宣传教育,更新生产观念,让农民了解和使用农牧业机械设备;建立健全基层农机服务组织体系,加强农机维修服务网络建设,提高服务质量和水平;加大执法力度,完善法律法规,打击假冒伪劣农机产品的生产和销售,维护市场秩序,保护农民的合法权益。

关键词：农牧业机械化发展