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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 components.Herein,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 coating.The novel Hf_(0.5)Ta_(0.5)C solid solution nanowires could effectively hinder crack propagation through crack tip pinning and crack deflection.This mechanism substantially enhanced the elastic modulus and fracture toughness of the HfC coating by 53.29%and 59.67%,respectively.The toughened HfC coating displayed superior fracture toughness and good interfacial binding strength with the substrate to resist severe oxidation and scouring.Additionally,the high thermal conductivity of the toughened HfC coating promoted heat transmission.Thus,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%,respectively.Our 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

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A Transcriptome Analysis of Neural Tissue of Litopenaeus vannamei After Acute Exposure to Alexandrium pacificum

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Journal of Ocean University of China 2024年第2期23卷 529-538页

作者： YANG Huijie HUANG Xianghu MA Yukun HU zhangxi zhang Ning LI Changling zhang yulei Department of Aquaculture College of FisheriesGuangdong Ocean UniversityZhanjiang 524088China Guangdong Laboratory of Marine Ecology Environment Monitoring and Warning Zhanjiang 524088China

Alexandrium pacificum(A.pacificum)is a typical paralytic shellfish poisonous dinoflagellate.Harmful algal blooms(HABs)caused by this species can bring serious environmental problems and economic losses to the aquaculture industry.In this study,transcriptome sequencing and analyses were performed on the neural tissue of Litopenaeus vannamei(L.vannamei)after acute exposure to A.pacificum disrupted solution for 72 h,and differentially expressed genes(DEGs)were identified.The results showed that,compared with the control samples,300 DEGs were identified in the experimental group,of which 194 were up-regulated,and 106 down-regulated.The gene ontology(GO)functional enrichment analysis showed that DEGs were significantly enriched in the cortical cytoskeleton organization,troponin complex,amylo-alpha-1,6-glucosidase and thymidine phosphorylase.Kyoto encyclopedia of genes and genomes(KEGG)enrichment analysis found that DEGs were mainly enriched in the oxidative phosphorylation process,intercellular tight junctions and mitophagy.The results showed that the proteoglycans,signaling pathways,and various metabolic processes that regulate cell proliferation,differentiation,and apoptosis all played an essential role in the response of L.vannamei to A.pacificum toxins.

关键词： Litopenaeus vannamei Alexandrium pacificum paralytic shellfish poisoning transcriptome nerve

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(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)nanostructures.Thus,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 play.Herein,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°C.The 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 rearranged.The 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 materials.Our 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

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Sublayer design and ablation resistance of CVD-TaC alternate coatings with different crystallite morphologies for C/C composites

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Journal of Materials Science & Technology 2023年第10期141卷 1-10页

作者： Jing’an Kong yulei zhang Hanhui Wang Guohui Chen Wenhan Gai Pengfei zhang Hejun Li State Key Laboratory of Solidification Processing Carbon/Carbon Composites Research CenterNorthwestern Polytechnical UniversityXi’anShanxi 710072China

Tantalum carbon(TaC)alternate coatings with sublayers comprised of different crystallite morphologies were prepared on carbon/carbon composites by chemical vapor deposition.Their ablative behaviors and defending mechanisms were both investigated.The specimen with the sublayer composed of columnar crystals exhibited a better ablation resistance due to the toughness enhancement induced by the lami-nated structure.However,the mechanical denudation of the sample only containing acicular crystals and the coating spallation caused by superfluous gaseous products of the sample with the sublayer composed of nanocrystals both indicate their inferior anti-ablation properties.It is believed that the results will be helpful for the structural design and practical application of chemical vapor deposition(CVD)alternate coatings.

关键词： Alternate coating Chemical vapor deposition Crystallite morphology Carbon/carbon composite Ablation behavior

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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 precursor.The formed HfC_(NWS) are distributed uniformly on the surface of the carbon fibers in carbon/carbon(C/C) composites and display perfect single crystal appearance.The 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 CNTs.Specifically,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 applications.The 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

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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 properties.The 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 potential.Herein,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 pyrolysis.Prior 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 growth.Additionally,multi-branched,single-branched,and single-branched bending nanowires were synthesized by adjusting the ratio of PHECs to DVB.The 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]direction.Also,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 mechanism.This 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

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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 aerospace.Herein,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 ceramics.The 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 precursor.The 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)particles.Our 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

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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

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Oxidation and Mechanical Properties of SiC/SiC-MoSi_2-ZrB_2 Coating for Carbon/Carbon Composites

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Journal of Materials Science & Technology 2014年第2期30卷 123-127页

作者： Xiyuan Yao Hejun Li yulei zhang Yongjie Wang State Key Laboratory of Solidification Processing Northwestern Polytechnical University

To improve oxidation resistance of carbon/carbon （C/C） composites, a SiC/SiC-MoSi2-ZrB2 double-layer ceramic coating was prepared on C/C composites by two-step pack cementation. The phase compositions and microstructures of as-prepared multilayer coating were characterized by X-ray diffraction and scanning electron microscopy. The oxidation resistance at 1773 K and the effect of thermal shock between 1773 K and room temperature on mechanical performance of coated specimens were investigated. The results show that the SiC/SiC-MoSi2-ZrB2 coating exhibits dense structure and is composed of SiC, Si, MoSi2 and ZrB2. It can protect C/C composites from oxidation at 1773 K for more than 510 h with weight loss of 0.5%. The excellent anti-oxidation performance of the coating is due to the formation of SiO2-ZrSiO4 complex glassy film. The coating can also endure the thermal shocks between 1773 K and room temperature for 20 times with residual flexural strength of 86.1%.

关键词： Carbon/carbon composites Ceramic coating Oxidation resistance Thermal cycle Mechanical properties

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长三角一体化发展:演变历程、现状分析与对策建议

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行政与法 2024年第6期 15-25页

作者：张玉磊淮阴师范学院公共管理学院

作为推进中国式现代化的重要引擎,长三角一体化主要经历了初步探索、合作深化、持续拓展、高质量发展四个发展阶段,并实现了治理模式从分割式治理到一体化协同式治理的转型,主要体现在区域治理组织、区域治理内容、区域治理形态三个方... 详细信息

作为推进中国式现代化的重要引擎,长三角一体化主要经历了初步探索、合作深化、持续拓展、高质量发展四个发展阶段,并实现了治理模式从分割式治理到一体化协同式治理的转型,主要体现在区域治理组织、区域治理内容、区域治理形态三个方面。近年来,长三角一体化建设不断取得实质性发展,区域协同治理绩效日益显现,但仍存在“行政区行政”产生区域分割和地方主义、一体化的体制机制障碍、一体化的领域发展不够均衡等现实问题。为推进长三角一体化发展,应围绕建构跨域治理模式、优化区域一体化体制机制、有序推进各领域一体化建设等方面综合施策。

关键词：长三角一体化高质量发展中国式现代化跨域治理 “行政区行政”

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