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Chinese Journal of Aeronautics 2020年第3期33卷 1064-1073页

作者： Chunxia HU He SHEN shouyang zhang Hejun LI State Key Laboratory of Solidification Processing C/C Composites Research CenterNorthwestern Polytechnical UniversityXi’an 710072China Department of Mechanical Engineering California State UniversityLos AngelesCA 90032USA

The density functional theory has been successfully applied in analyzing pyrolytic carbon deposition by methane pyrolysis from the view of thermodynamics and kinetics based on a total number of 39 elementary reactions.M06-2X/def2-TZVP level was employed to optimize species structures and locate the transition *** enthalpy changes and Gibbs free energy changes of all the reactions in the temperature range of 298.15–1800K were derived with optimized *** show that the reacting temperature should be above 1200 K based on the equilibrium constant analysis,which is consistent with the typical reaction temperature adopted in *** energy surface profiles report that radical attacking reactions have lower energy barriers than those direct decomposition reactions,especially hydrogen radical attacking *** energy barriers of the first steps,dehydrogenations of methane and ethylene,are 272.4 kJ·mol^(-1)and 288.9 kJ·mol^(-1)at 1200 K,which are very close to the experimental activation energy for methane *** most favorable decomposition reaction path is the path of hydrogen radical attacking *** highest energy barrier of the path at 1200K is 185.7kJ·mol^(-1)presented by the C–H bond breaking in ethynyl attacked by hydrogen radical.

关键词： Density functional theory Kinetics Methane pyrolysis Pyrolytic carbon Thermodynamics

Thermophysical properties of a novel high entropy hafnate ceramic

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Journal of Materials Science & Technology 2021年第26期85卷 152-157页

作者： Longkang Cong shouyang zhang Shengyue Gu Wei Li State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi'an710072China Author links open overlay panel Department of Materials Physics School of ScienceXi’an University of Posts and TelecommunicationsXi’an710121China State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi'an710072China

High-entropy oxides(HEOs)are considered promising thermal barrier coating(TBC)materials due to their unique thermophysical performances induced by the entropy *** this work,(La_(0.2)Ce_(0.2)Pr_(0.2)Sm_(0.2)Eu_(0.2))_(2)Hf_(2)O_(7)high entropy hafnate,as a thermal barrier coating(TBC)material,was successfully synthesized by solution combustion method for the first *** the X-ray diffraction,scanning electron microscopy,and transmission electron microscopy results,it is confirmed that(La_(0.2)Ce_(0.2)Pr_(0.2)Sm_(0.2)Eu_(0.2))_(2)Hf_(2)O_(7)has pure single-phase ordered pyrochlore structure with highly homogeneous composition at both micrometer and nanometer *** synthesized(La_(0.2)Ce_(0.2)Pr_(0.2)Sm_(0.2)Eu_(0.2))2 Hf2O7 possesses excellent phase stability at 1600℃and demonstrates a low thermal conductivity(1.0-1.24 W·m^(-1)·K^(-1))which is lower than those of rare earth hafnates(RE2Hf2O7,RE=La,Ce,Pr,Sm,Eu).Therefore,it provides a new perspective and potential to prompt the next generation TBC materials with better performance.

关键词： High-entropy ceramic Rare-earth hafnate Thermal barrier coating Thermal conductivity

High-entropy(Y_(0.2)Gd_(0.2)Dy_(0.2)Er_(0.2)Yb_(0.2))2Hf_(2)O_(7) ceramic: A promising thermal barrier coating material

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Journal of Materials Science & Technology 2022年第6期101卷 199-204页

作者： Longkang Cong Wei Li Jiancheng Wang Shengyue Gu shouyang zhang State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an 710072China Department of Materials Physics School of ScienceXi’an University of Posts and TelecommunicationsXi’an 710121China

Thermal barrier coating(TBC)materials perform an increasingly important role in the thermal or chemical protection of hot components in a gas *** this study,a novel high entropy hafnate(Y_(0.2)Gd_(0.2)Dy_(0.2)Er_(0.2)Yb_(0.2))_(2)Hf_(2)O_(7) was synthesized by solution combustion method and investigated as a potential TBC *** as-synthesized(Y_(0.2)Gd_(0.2)Dy_(0.2)Er_(0.2)Yb_(0.2))_(2)Hf_(2)O_(7) possesses a pure single disordered fluorite phase with a highly homogeneous distribution of rare earth(RE)cations,exhibiting prominent phase stability and excellent chemical compatibility with Al_(2)O_(3) even at 1300°***,(Y_(0.2)Gd_(0.2)Dy_(0.2)Er_(0.2)Yb_(0.2))_(2)Hf_(2)O_(7) demonstrates a more sluggish grain growth rate than Y_(2)Hf_(2)O_(7).The thermal conductivity of(Y_(0.2)Gd_(0.2)Dy_(0.2)Er_(0.2)Yb_(0.2))_(2)Hf_(2)O_(7)(0.73-0.93 W m^(-1)K^(-1))is smaller than those of components RE_(2)Hf_(2)O_(7) and many high entropy TBC ***,the calculated thermal expansion coefficient(TEC)of(Y_(0.2)Gd_(0.2)Dy_(0.2)Er_(0.2)Yb_(0.2))_(2)Hf_(2)O_(7)(10.68×10^(-6)/K,1100°C)is smaller than that of yttriastabilized zirconia(YSZ).Based on the results of this work,(Y_(0.2)Gd_(0.2)Dy_(0.2)Er_(0.2)Yb_(0.2))_(2)Hf_(2)O_(7) is suitable for the next generation TBC materials with outstanding properties.

关键词： High entropy ceramic Thermal barrier coating material Disordered fluorite structure Thermophysical properties

Microstructure and Mechanical Properties of Multilayertextured 2D Carbon/Carbon Composites

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Journal of Materials Science & Technology 2014年第12期30卷 1202-1207页

作者： Yan Jia Kezhi Li shouyang zhang Lei Li Junjie Ren State Key Laboratory of Solidification Processing Northwestern Polytechnical University

Two-dimensional（2D） carbon/carbon（C/C） composites with multilayered texture, especially with different thickness of high-textured（HT） pyrocarbon layer, were prepared by isothermal, isobaric chemical vapor infiltration（CVI） technique. The influence of matrix microstructure on mechanical properties of C/C composites was investigated by polarized light microscopy, scanning electron microscopy and three-point bending test. The results show that the samples with multilayer-textured pyrocarbon matrix own a higher flexural strength than the one with pure medium-textured structure, which is attributed to multiple crack deflection and interfacial sliding between different textured pyrocarbon layers and between sub-layers within HT layer. The increase in thickness of HT pyrocarbon layer improves the plasticity of the samples and renders the fracture in pseudo-plastic behavior.

关键词： Carbon/carbon composites Mechanical properties Fracture Texture

Ultrahigh thermal conductive graphite film via the in-situ construction of aligned nanographene skeleton using chemical vapor deposition

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Journal of Materials Science & Technology 2023年第17期148卷 1-9页

作者： Qingliang Shen Qiang Song Caixiang Xiao Qiangang Fu Wei Li shouyang zhang Hejun Li Shaanxi Key Laboratory of Fiber Reinforced Light Composite Materials State Key Laboratory of Solidification ProcessingNorthwestern Polytechnical UniversityXi’an 710072China

Both high thermal conductivity(K)and large cross-sectional area are essential for thermal dissipation materials to maximize their heat transfer ***,the drastic decrease of K values with the increased thickness makes the existing graphite/graphene films less favored for practical *** this work,graphite film with both large thickness and high K value is produced based on an in-situ com-position strategy between nanographene(G)and pyrocarbon(PyC)via chemical vapor deposition(CVD)using CH_(3) OH/C_(2)H_(5)OH mixed ***’s found that an optimized O/C ratio of precursors facilitates the construction of ordered G skeletons within the deposited G/PyC *** G/PyC compos-ites can be completely graphitized at a lower temperature than the existing *** 2400℃ an-nealing,dense,thick,and highly aligned graphite films were *** K values reach 1350 and 1010 W m^(-1) K^(-1) at the thickness of 40 and 120μm,respectively,surpassing the existing records with similar *** importantly,the proposed method is insensitive to the deposition substrates,and the G/PyC can be infiltrated into large-size fiber preforms as a matrix for preparing centimeter-thick high K ***,the G/PyC also exhibits better mechanical and electromagnetic shielding per-formances than the existing products,indicating a promising multifunctional application prospect.

关键词： Graphene Thermal management Chemical vapor deposition

High-aspect-ratio ZrC whiskers:Synthesis,growth mechanism and electromagnetic wave absorption properties

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Journal of Materiomics 2023年第2期9卷 235-243页

作者： Yao Guo Qiang Song Leilei zhang Xu Yang Wei Li Fei Zhao shouyang zhang Lehua Qi State Key Laboratory of Solidification Processing Shaanxi Key Laboratory of Fiber Reinforced Light Composite MaterialsNorthwestern Polytechnical UniversityXi'an710072China School of Mechanical Engineering Northwestern Polytechnical UniversityXi'an710072China

Stealth materials with high dependability at elevated temperatures and outstanding mechanical properties are urgently needed for practical *** one-dimensional ultrahigh temperature ceramic(UHTC)materials,zirconium carbide whiskers(ZrCw)have attracted a great deal of attention due to their desirable mechanical and ablation resistance performance in high-temperature *** have successfully synthesized ZrCw using a carbothermal reduction technique without the introduction of metal catalytic in this *** shows a typically prismatic structure with the diameter of 1e2 mm and the aspect ratio of up to *** growth of ZrCw is controlled by a solid-liquid-solid(SLS)and vaporsolid(VS)compound mechanism in conjunction with the auxiliary action of mesophase *** ZrCw/paraffin hybrids achieve the minimum reflection loss(RL(min))of25.77 dB at 13.28 GHz under the thickness of 1.25 mm,and reach an effective absorption bandwidth(EAB)of 3.04 GHz(14.96 e18.00 GHz)with a thickness of only 1.0 *** work presents a promising approach for large-scale producing high-purity whiskers,and verifies that ZrCw has extensive application prospects in the field of stealth materials.

关键词： ZrC whiskers Microstructure Carbothermal reduction Growth mechanism Electromagnetic wave absorption

Constructing orthogonally structured graphene nanointerface on SiC nanowires reinforced carbon/carbon composites to boost mechanical strength and strength retention rate

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Journal of Materiomics 2024年第3期10卷 615-623页

作者： Yao Guo shouyang zhang Qiang Song Fei Zhao Longkang Cong Wei Li Ruimei Yuan State Key Laboratory of Solidification Processing Shaanxi Key Laboratory of Fiber Reinforced Light Composite MaterialsNorthwestern Polytechnical UniversityXi'an 710072China Advanced Interdisciplinary Research Center for Flexible Electronics Academy of Advanced Interdisciplinary ResearchXidian UniversityXi'an 710072China

Carbon/carbon composites with higher mechanical strength and better reliability at elevated tempera-tures are urgently needed to satisfy the practical applications *** nanowires(SiCNWs)modified C/C(SC-CC)composites have attracted an abundance of attention for their excellent mechanical *** further boost the mechanical strengths of composites and maximize the reinforcing efficiency of SiCNWs,we introduce orthogonally structured graphene nanosheets(OGNs)into SC-CC composites,in which OGNs are grafted on the SiCNWs via chemical vapor deposition(CVD)method,forming SC-G-CC *** from the nano-interface effects,uniform stress distribution,strong SiCNWs/PyC interfacial bonding and elevated stress propagation efficiency in the PyC matrix are achieved,thus SC-G-CC composites accomplish brilliant mechanical properties before and after 1,600℃ heat *** temperature rises to 2,100℃,SiCNWs lose efficacy,whereas OGNs with excellent thermal stability continue to play the nano-interface role in the PyC ***,SC-G-CC com-posites show better mechanical performance after 2,100℃ heat treatment,and the mechanical strength retention rate(MSR)of interlaminar shear strength,out-of-plane and in-plane compressive strength of SC-G-CC composites reach 61.0%,55.7%and 55.3%,*** work proposes an alternative thought for maximizing the potentiality of nanomaterials and edifies the mechanical modification of composites.

关键词： SiC nanowires Orthogonally structured graphene nanosheets Carbon/carbon composites Mechanical properties Heat treatment

Biomedical applications of the powder-based 3D printed titanium alloys:A review

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Journal of Materials Science & Technology 2022年第30期125卷 252-264页

作者： Amy X.Y.Guo Liangjie Cheng Shuai Zhan shouyang zhang Wei Xiong Zihan Wang Gang Wang Shan Cecilia Cao Materials Genome Institute Shanghai UniversityShanghai 200444China

3D printing technology is a new type of precision forming technology and the core technology of the third industrial *** powder-based 3D printing technology of titanium and its alloys have received great attention in biomedical applications since its advantages of custom manufacturing,costsaving,time-saving,and resource-saving *** particular,the personalized customization of 3D printing can meet specific needs and achieve precise control of micro-organization and structural *** purpose of this review is to present the most advanced multi-material 3D printing methods for titanium-based *** first reviewed the bone tissue engineering,the application of titanium alloy as bone substitutes and the development of manufacturing technology,which emphasized the advantages of 3D printing technology over traditional manufacturing *** is more,the optimization design of the hierarchical structure was analyzed to achieve the best mechanical properties,and the biocompatibility and osseointegration ability of the porous titanium alloy after implantation in living bodies was ***,we emphasized the development of digital tools such as artificial intelligence,which provides new ideas for the rational selection of processing *** 3D printing titanium-based alloys will meet the huge market demand in the biomedical field,but there are still many challenges,such as the trade-off between high strength and low modulus,optimization of process parameters and structural *** believe that the combination of mechanical models,machine learning,and metallurgical knowledge may shape the future of metal printing.

关键词： The powder-based 3D printing technology Ti-based alloys Biomedical applications Artificial intelligence

Densification and microstructure of carbon/carbon composites prepared by chemical vapor infiltration using ethanol as precursor

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Science China(Technological Sciences) 2010年第8期53卷 2232-2238页

作者： LI Wei,zhang shouyang ,YAN XiaFeng,LI HeJun&LI KeZhi State Key Laboratory of Solidification Processing,Northwestern Polytechnical University,Xi’an 710072,China State Key Laboratory of Solidification Processing Northwestern Polytechnical University Xi’an China

Chemical vapor infiltration of carbon fiber felts with uniform initial bulk density of 0.47 g·cm-3 was investigated at the ethanol partial pressures of 5-20 kPa,as well as the temperatures of 1050,1100,1150 and 1200°***,diluted by nitrogen,was employed as the precursor of pyrolytic *** light microscopy(PLM),scanning electron microscopy and X-ray diffraction were adopted to study the texture of pyrolytic carbon deposited at various temperatures.A change from medium-to high-textured pyrolytic carbon was observed in the sample infiltrated at 1050°***,homogeneous high-textured pyrolytic carbons were deposited at the temperatures of 1100,1150 and 1200°*** angles of 19°-21° were determined for different regions in the samples densified at the temperatures ranging from 1100 to 1200°*** electron microscopy of the fracture surface after bending test indicated that the prepared carbon/carbon composite samples exhibited a pseudo-plastic fracture *** addition,fracture behavior of the carbon/carbon samples was obviously effected by their infiltration *** fracture mode of C/C composites was transformed from shearing failure to tensile breakage with increasing infiltration temperature. Results of this study show that ethanol is a promising carbon source to synthesize carbon/carbon composites with homogeneously high-textured pyrolytic carbon over a wide range of temperatures(from 1100 to 1200°C).

关键词： C/C composites ethanol ICVI high-textured pyrolytic carbon

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航空发动机转子螺栓连接预紧力散差分析

清华大学学报（自然科学版） 2021年第10期61卷 1144-1151页

作者：赵兵张守阳王辉清华大学机械工程系北京100084 青海大学机械工程学院西宁810016 南通大学机械工程学院南通226019

螺栓连接预紧力的一致性对于保障航空发动机转子的安全运行有重要作用。该文针对航空发动机转子零部件的法兰止口典型连接结构的螺栓紧固控制问题,提出了含收口自锁力矩的扭拉关系修正模型,分析了收口自锁力矩衰减引入的偏差项的影响;... 详细信息

螺栓连接预紧力的一致性对于保障航空发动机转子的安全运行有重要作用。该文针对航空发动机转子零部件的法兰止口典型连接结构的螺栓紧固控制问题,提出了含收口自锁力矩的扭拉关系修正模型,分析了收口自锁力矩衰减引入的偏差项的影响;并设计了工艺差异条件,搭建模拟试验环境开展了试验研究。结果表明:收口自锁力矩会因收口螺母的重复使用而发生衰减,从而对预紧力转化造成影响;不同润滑方式对预紧力转化有较大影响;随紧固件重复使用次数的增加,预紧力呈一定趋势变化,不同润滑方式下,预紧力变化趋势存在显著差异;不同批次螺栓也存在差异。该研究揭示了影响航空发动机转子螺栓连接预紧力一致性的关键要素,并对各要素引起的预紧力散度进行了精确评估,为下一步优化工艺方案提供了参考依据。

关键词：航空发动机螺栓连接工艺差异预紧力散差