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Journal of Materials Science & Technology 2014年第7期30卷 631-638页

作者： Yanchun Zhou Huimin Xiang zhihai feng Science and Technology of Advanced Functional Composite Laboratory Aerospace Research Institute of Materials and Processing Technology

An investigation on the mechanical and thermal properties of Yb3Al5O12 is conducted by a combination of first- principles calculations and chemical bond theory calculation. Density functional theory （DFT） computations were performed for the structural, mechanical, and thermal properties, and the results are confirmed by chemical bond theory. Based on the calculated equilibrium crystal structure, heterogeneous bonding nature is revealed. The full set of elastic constants and mechanical properties of Yb3Al5O12 are presented for the first time. The thermal expansion coefficient of Yb3Al5O12 is calculated to be 7.5 × 10^-6 K-1 by chemical bond theory. In addition, the minimum thermal conductivity of Yb3Al5O12 is estimated to be 1.22 W m-t K-1, and the origin of such low thermal conductivity is discussed. Our theoretical results highlight the potential of Yb3Al5O12 as a prospective thermal barrier coating material.

关键词： Thermal barrier coating Ytterbium aluminum garnet First principles calculations Chemical bond theory

General Trends in Electronic Structure, Stability, Chemical Bonding and Mechanical Properties of Ultrahigh Temperature Ceramics TMB_2(TM=transition metal)

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Journal of Materials Science & Technology 2015年第3期31卷 285-294页

作者： Yanchun Zhou Huimin Xiang zhihai feng Zhongping Li Science and Technology on Advance Functional Composite Laboratory Aerospace Research Institute of Materials & Processing Technology

The electronic structure, stability, chemical bonding and mechanical properties of 3d, 4d and 5d transition metal diboride TMB2 were investigated using first-principles calculations based on density functional theory. All the primary chemical bonds, i.e., metallic, ionic and covalent have contributions to the bonding of TMB2. The number of valence electrons of transition metals or the valence electron concentration(VEC) of TMB2 has strong effects on the lattice parameters, stability and mechanical properties of TMB2. Both lattice constants a and c decrease with VEC, but c decreases faster than a, which is attributed to the enhanced TM de B p(sp2) bonding. Bulk modulus B of TMB2 increases continuously with VEC due to the enhanced TM de B p(sp2) and TM dd bonding. Shear modulus G increases with VEC,reaching a maximum at VEC=3.33, and then decreases with further increase of VEC. YB2 and Mn B2 have low Young’s modulus and are predicted to have good thermal shock resistance. According to Pugh’s criterion(G/B < 0.571), Mn B2, Mo B2 and WB2are predicted as ductile or damage tolerant ultrahigh temperature ceramics(UHTCs).

关键词： Ultrahigh temperature ceramics Transition metal di

Cr5Si3B and Hf5Si3B:New MAB phases with anisotropic electrical,mechanical properties and damage tolerance

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Journal of Materials Science & Technology 2018年第8期34卷 1441-1448页

作者： Yanchun Zhou Huimin Xiang Fu-Zhi Dai zhihai feng Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Materials&Processing TechnologyNo.1 South Dahongmen RoadBeijing 100076China

Through a combination of electronic structure, chemical bonding and mechanical property investigations, anisotropic electrical and mechanical properties, and damage tolerant ability of MAB phases CrsSi3 B and HfsSi3B are predicted. The anisotropic electrical conductivity is due to the anisotropic distribution of Cr in CrsSiaB and Hf in HfsSi3B, which mainly contribute to the electrical conductivity. The anisotropic mechanical properties are underpinned by the anisotropic chemical bonding within the crystal structures of CrsSi3B and HfsSi3B. The high stiffness is determined by the strong covalent-ionic Crl--B--Crl and Crl--Si bonds in CrsSi3B and the ionic-covalent Hfl--B--Hfl and Si--B bonds in HfsSi3B; while the low shear deformation resistance is attributed to the presence of metallic Cr--Cr, Hf--Hf and Si--Si bond. Based on the low Pugh＇s ratio, CrsSi3B and Hfs Si3B are predicted tolerant to damage. The possible cleavage plane is （0001） and the possible slip systems are 〈1 100〉1{11 20} and 〈11 20〉1{0001} for both CrsSi3B and HfsSi3B.

关键词： MAB phases CrsSi3B and HfsSi3 BFirst-principles calculations Mechanical properties Chemical bonding

Preparation,mechanical,and thermal properties of a promising thermal barrier material:Y_(4)Al_(2)O_(9)

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Journal of Advanced Ceramics 2015年第2期4卷 94-102页

作者： Yanchun ZHOU Xinpo LU Huimin XIANG zhihai feng Science and Technology of Advanced Functional Composite Laboratory Aerospace Research Institute of Materials and Processing TechnologyNo.1 South Dahongmen RoadBeijing 100076China

In our previous work,anisotropic chemical bonding,low shear deformation resistance,damage tolerance ability,low thermal conductivity,and moderate thermal expansion coefficient of Y_(4)Al_(2)O_(9)(YAM)were *** this work,phase-pure YAM powders were synthesized by solid-state reaction between Y2O3 and Al_(2)O_(3)and bulk YAM ceramics were prepared by hot-pressing *** parameters and a new set of X-ray powder diffraction data were obtained by Rietveld *** mechanical and thermal properties of dense YAM ceramics were *** measured elastic moduli are close to the theoretical predicted values and the stiffness can be maintained up to 1400℃.The flexural strength and fracture toughness are 252.1±7.3 MPa and 3.36±0.20 MPa·m^(1/2),*** tolerance of YAM was also experimentally *** measured average linear thermal expansion coefficient(TEC)of YAM is 7.37×10^(-6)K^(-1),which is very close to the theoretical predicted *** high-temperature X-ray diffraction(XRD)analysis,volumetric TEC is determined(23.37±1.61)×10^(-6)K^(-1)and the anisotropic TEC areaa=7.34×10^(-6)K^(-1),ab=7.54×10^(-6)K^(-1),andac=7.61×10^(-6)K^(-1).

关键词： Y4Al2O9 X-ray diffraction(XRD)pattern mechanical properties thermal expansion damage tolerance

Shear anisotropy： Tuning high temperature metal hexaborides from soft to extremely hard

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Journal of Materials Science & Technology 2017年第11期33卷 1371-1377页

作者： Yanchun Zhou Fuzhi Dai Huimin Xiang Bin Liu zhihai feng Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Material & Processing Technology Beijing 100076China School of Materials Science and Engineering Shanghai University Shanghai 200444 China

Easy machining into sharp lending edge, nose tip and complex shape components plays a pivotal role in the application of ultrahigh temperature ceramics in hypersonic vehicles, wherein low and controllable hardness is a necessary parameter to ensure the easy machinability. However, the mechanism that driving the hardness of metal hexaborides is not clear. Here, using a combination of the empirical hardness model for polycrystalline materials and density functional theory investigation, the hardness dependence on shear anisotropic factors of high temperature metal hexaborides has been established. It has come to light that through controlling the shear anisotropic factors the hardness of polycrystalline metal hexaborides can be tailored from soft and ductile to extremely hard and brittle, which is underpinned by the degree of chemical bonding anisotropy, i.e., the difference of B-B bond within the B;octahedron and that connecting the B;octahedra.

关键词： Microhardness Electronic structure Elastic constant Borides Structural ceramics

Heat-induced Internal Strain Relaxation and its Effect on the Microstructure of Polyacrylonitrile-based Carbon Fiber

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Journal of Materials Science & Technology 2014年第10期30卷 1051-1058页

作者： Denghua Li Chunxiang Lu Gangping Wu Yu Yang zhihai feng Xiutao Li feng An Baoping Zhang National Engineering Laboratory for Carbon Fiber Technology Institute of Coal ChemistryChinese Academy of Sciences University of Chinese Academy of Sciences National Key Laboratory of Advanced Functional Composite Materials Aerospace Research Institute of Materials & Processing Technology

The transformation of the internal strain and its effect on the microstructure of polyacrylonitrile-based carbon fiber during the high-temperature graphitization were investigated. The internal compressive strain within the carbon turbostratic structure was confirmed through a careful analysis by wide-angle X-ray diffraction and Raman spectroscopy. Heat-induced strain/stress relaxation along the fiber axis was observed and was found to have a profound effect on the structure of both the crystallites and microvoids. The results indicated that, the relaxation of residual strain changed the graphite layers from a wrinkled and distorted morphology to a straight and smooth one, and consequently led the crystallites to stack closely and orderly with increasing stack height. The strain relaxation also changed the morphology of crystallites and microvoids, resulting in an anisotropic growth for the latters.

关键词： Graphitizafion Internal strain Microstructures Nanocrystalline Carbon fiber

Theoretical prediction on mechanical and thermal properties of a promising thermal barrier material:Y_(4)Al_(2)O_(9)

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Journal of Advanced Ceramics 2015年第2期4卷 83-93页

作者： Yanchun ZHOU Huimin XIANG Xinpo LU zhihai feng Zhongping LI Science and Technology of Advanced Functional Composite Laboratory Aerospace Research Institute of Materials and Processing TechnologyNo.1 South Dahongmen RoadBeijing 100076China

The mechanical and thermal properties of Y_(4)Al_(2)O_(9)were predicted using a combination of first-principles and chemical bond theory(CBT)*** functional theory(DFT)computations were performed for the structural,mechanical,and thermal properties,and the results were confirmed by chemical bond *** on the calculated equilibrium crystal structure,heterogeneous bonding nature has been revealed,i.e.,Al-O bonds are stronger than Y-O *** second-order elastic constants c44,c55,and c66 demonstrate the low shear deformation *** G/B ratio suggests that Y_(4)Al_(2)O_(9)is a damage tolerant ceramic.Y_(4)Al_(2)O_(9)shows anisotropy in elastic behavior based on the discussion of direction dependence of Young’s *** hardness is predicted to be 10.2 GPa from calculated elastic *** thermal expansion coefficient(TEC)calculated by chemical bond theory is 7.51×10^(-6)K^(-1).In addition,the minimum thermal conductivity of Y_(4)Al_(2)O_(9)is estimated to be 1.13 W·m^(-1)·K^(-1),and the thermal conductivity decreases with temperature as 1305.6/T.

关键词： Y4Al2O9 chemical bonding elastic constants thermal conductivity thermal expansion coefficient(TEC)

Electronic structure and mechanical properties of layered compound YB_2C_2:A promising precursor for making two dimensional(2D) B_2C_2 nets

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Journal of Materials Science & Technology 2017年第9期33卷 1044-1054页

作者： Yanchun Zhou Huimin Xiang Xiaohui Wang Wei Sun Fu-Zhi Dai zhihai feng Science and Technology of Advanced Functional Composite Laboratory Aerospace Research Institute of Materials & Processing Technology Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of Sciences

Layered compounds play pivotal roles as precursors for producing 2D materials through mechanical exfoliation(micro-mechanical cleavage) or chemical approaches. Therefore, searching for layered compounds with sharp anisotropic chemical bonding and properties becomes emergent. In this work, the stability, electronic structure, elastic properties, and lattice dynamics of YBCwere investigated. Strong anisotropy in elastic properties is revealed, i.e., high Young’s modulus in a-b plane but low Young’s modulus in c direction. The maximum to minimum Young’s modulus ratio is 2.41 and 2.45 for YBCwith P42/mmc and P4/mbm symmetry, respectively. The most likely systems for shear sliding or microdelaminating are(001)[100] and(001)[010]. The anisotropic elastic properties are underpinned by the anisotropic chemical bonding, i.e., strong bonding within the BCnets and weak bonding between Y atom layers and BCnets. YBCis electrically conductive and the contributions to the electrical conductivity are from delocalized Y 4deas well as Bpandpzelectrons. The layered crystal structure, sharp anisotropic mechanical properties, and metallic conductivity endorse YBCpromising as a precursor for new 2D BCnets.

关键词： YB2C2 Layered compounds Electronic structure Mechanical properties 2D graphite like materials

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甲状腺未分化癌的CT表现与病理对照分析

临床放射学杂志 2016年第11期35卷 1655-1660页

作者：洪之海陈峰浙江大学医学院附属第一医院放射科杭州在读研究生310003

目的分析甲状腺未分化癌（ATC）的CT表现,并与病理对照,以提高对该少见疾病的认识。方法回顾性分析经病理证实的20例ATC患者的CT资料。男7例,女13例,年龄22-81岁,平均65.5岁。对肿瘤的部位、大小、形态、边缘、CT密度及强化形式进行分... 详细信息

目的分析甲状腺未分化癌（ATC）的CT表现,并与病理对照,以提高对该少见疾病的认识。方法回顾性分析经病理证实的20例ATC患者的CT资料。男7例,女13例,年龄22-81岁,平均65.5岁。对肿瘤的部位、大小、形态、边缘、CT密度及强化形式进行分析,并与病理结果相对照。结果 20例患者中,单侧18例,双侧2例,2例峡部同时受累,共22个病灶。合并结节性甲状腺肿7例,腺瘤性增生1例;肿瘤最大径1.2-8.6 cm,平均（5.2±0.7）cm;病灶呈圆形或类圆形8个,不规则形14个;边缘光整者5个,边缘不光整者17个;6个病灶甲状腺轮廓连线完整,16个病灶出现甲状腺轮廓连线中断,肿瘤呈横向生长,纵横比〈1,其中6个侵犯食管,4个侵犯气管,4个侵犯颈前肌群,2个包绕同侧颈总动脉。CT平扫病灶呈低密度17个,等密度5个;密度均匀6个,不均匀16个;5个病灶内见钙化,以细颗粒状钙化多见（3个病灶）;增强后病灶呈明显强化15个,中度强化5个,轻度强化2个。14例伴颈部淋巴结肿大,增强扫描呈环形强化。结论侵袭性生长、纵横比〈1、钙化少见、易坏死囊变、明显强化的甲状腺区肿块及伴有多区分布、环形强化的颈部肿大淋巴结可以提示ATC的诊断,其影像学表现与肿瘤的病理特征相关,CT检查可以准确显示病灶的范围和淋巴结转移情况,为临床制订治疗方案提供重要依据。

关键词：甲状腺肿瘤未分化癌体层摄影术,X 线计算机

中药活性成分调控mTOR信号通路干预糖尿病肾病的研究进展

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中国药房 2023年第13期34卷 1656-1660页

作者：贾慧雨冯志海河南中医药大学第一临床医学院郑州450046 河南中医药大学第一附属医院内分泌科郑州450003

糖尿病肾病(DN)是引起终末期肾病的主要病因之一,发病机制尚不完全清楚,目前认为与高糖条件下自噬紊乱、氧化应激、炎症反应等多种因素介导的肾脏损伤关系密切。哺乳动物雷帕霉素靶蛋白(mTOR)信号通路是参与蛋白质合成及调节自噬过程的... 详细信息

糖尿病肾病(DN)是引起终末期肾病的主要病因之一,发病机制尚不完全清楚,目前认为与高糖条件下自噬紊乱、氧化应激、炎症反应等多种因素介导的肾脏损伤关系密切。哺乳动物雷帕霉素靶蛋白(mTOR)信号通路是参与蛋白质合成及调节自噬过程的核心通路,在DN的发生发展中起着重要作用。近年来,中医药防治DN的研究取得了关键性进展。大量证据表明,中药活性成分可通过调节mTOR信号通路提高自噬水平,改善氧化应激和炎症反应,抑制细胞的凋亡及异常增殖,从而缓解足细胞损伤、肾小球基底膜增厚、系膜组织异常及肾小管功能障碍等肾脏病理改变,减少蛋白尿并改善肾功能,对延缓DN进展具有重要意义。本文系统总结了中药皂苷类、黄酮类、多酚类、生物碱类、萜类等活性成分通过mTOR信号通路干预DN的研究进展,可为进一步的基础研究和临床新药开发提供一定参考。

关键词：糖尿病肾病中药活性成分哺乳动物雷帕霉素靶蛋白信号通路