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Synthesis of nearly spherical AlN particles by an in-situ nitriding combustion route

Journal of Advanced Ceramics 2021年第2期10卷 291-300页

作者： Zhilei Wei Kang Li Bangzhi Ge Chaowei guo Hongyan Xia yajie guo Zhongqi Shi State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an710049China Engineering Research Center of Transportation Materials of Ministry of Education School of Materials Science and EngineeringChang’an UniversityXi’an710064China

Spherical AlN powders with micrometer size have attracted great attention owing to their good fluidity and dispersity. However, the industrial preparation methods usually require high temperature and long soaking time, which lead to the high cost and limit the wide application of the products. Herein, nearly spherical AlN particles with the average size of 2.5 μm were successfully synthesized via an in-situ combustion synthesis method. The effect of N_(2) pressure, NH_(4)Cl content, and Al particle size on the combustion reaction procedure, phase composition, and microstructure of the products was systematically investigated. The results showed that the decreased N_(2) pressure, increased NH_(4)Cl content, and Al particle size led to the decreasing of combustion temperature and speed, which further affected the morphology of the products. As a result, low N_(2) pressure(0.2 MPa), a small amount of NH4Cl(0.5 wt%), and fine Al particles(~2.5 μm) contributed to a moderate combustion temperature and facilitated the formation of nearly spherical AlN particles. In addition, based on the gas-releasing assisted quenching experiments and thermo-kinetic analysis, a two-step growth mechanism for the nearly spherical AlN particles was rationally proposed. The present method shows the advantages of low cost and high efficiency for preparing nearly spherical AlN particles, which can be used as raw materials for electronic substrates and fillers for packaging materials.

关键词： combustion synthesis AlN microstructure growth mechanism

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Brazing of WC–8Co cemented carbide to steel using Cu–Ni–Al alloys as filler metal: Microstructures and joint mechanical behavior

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Journal of Materials Science & Technology 2018年第7期34卷 1180-1188页

作者： Xiangzhao Zhang Guiwu Liu Junnan Tao yajie guo Jingjing Wang Guanjun Qiao School of Materials Science and Engineering Jiangsu University Engineering Research Center of Transportation Materials of Ministry of Education School of Materials Science and Engineering Chang'an University School of Materials Science and Engineering Shanghai University State Key Laboratory for Mechanical Behavior of Materials Xi'an Jiaotong University

Three novel Cu-Ni-A1 brazing filler alloys with Cu/Ni weight ratio of 4：1 and 2.5-10 wt% Al were developed and characterized, and the wetting of three Cu-Ni-Al alloys on WC-8Co cemented carbide were investigated at 1190-1210 ℃ by the sessile drop technique. Vacuum brazing of the WC-8Co cemented carbide to SAE1045 steel using the three Cu-Ni-Al alloys as filler metal was further carried out based on the wetting test results. The interfacial interactions and joint mechanical behaviors involving microhardness, shear strength and fracture were analyzed and discussed. The experimental results show that all the three wetting systems present excellent wettability with final contact angles of less than 5 °and fast spreading. An obvious degeneration layer with continuous thin strip forms in the cemented carbide adjacent to the Cu-Ni-A1/WC-8Co interface. The variation of microhardness in the joint cross-section is closely related to the interactions （such as diffusion and solid solution） of WC-8Co/Cu-Ni-Al/steel sys- tem. Compared with the other two brazed joints, the WC-8Co/Cu-19Ni-SAl/steel brazed joint presents more reliable interlayer microstructure and mechanical property while brazing at the corresponding wetting temperatures for 5 rain, and its average shear strength is over 200 MPa after further optimizing the brazing temperature and holding time. The joint shear fracture path passes along the degeneration layer, Cu-Ni-A1/WC-8Co interface and brazing interlayer, showing a mixed ductile-brittle fracture.2018 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science ＆ Technology.

关键词： Cu-Ni-Al alloy Cemented carbide Brazing Microstructures Mechanical properties

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Mullite whiskers prepared by molten salt method using Si powders

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Journal of Advanced Ceramics 2012年第4期1卷 283-289页

作者： Wei WANG Hongwei LI yajie guo Qiang SUN Chen CHEN Department of Chemical Engineering College of Environment Science and EngineeringChang’an UniversityXi’an 710054China College of Materials Science and Engineering Chang’an UniversityXi’an 710061China

Mullite whiskers were prepared from Si powders in molten Al2(SO4)3-Na2SO4 mixture salts with different Al/Si molar ratio(R)of raw *** resulting mullite whiskers,had been investigated using X-ray diffraction(XRD),scanning electron microscopy(SEM),energy dispersive spectrometer(EDS)and infrared spectroscopy analysis(FT-IR).Mullite phase was obtained in molten salts when the temperature reached at 850℃.SEM and EDS results revealed that two kinds of microstructures were formed in the final product,Al-rich mullite pellets and clusters of tiny mullite crystals,and the content of Al-rich mullite pellets increased with the higher Al/Si molar ratio(R)adopted in raw materials.A new oxidation-dissolution mechanism was proposed to explain mullite whiskers *** to thermodynamic analysis,mullite phase might be spontaneously formed as the temperature reached the decomposition temperature of aluminum sulfate(1023 K).

关键词： chemical preparation whiskers mullite infrared spectroscopy

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The size distribution of airborne bacteria and human pathogenic bacteria in a commercial composting plant

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Frontiers of Environmental Science & Engineering 2021年第3期15卷 87-96页

作者： Min Gao Ziye Yang yajie guo Mo Chen Tianlei Qiu Xingbin Sun Xuming Wang Beijing Key Laboratory of Agricultural Genetic Resources and Biotechnology Beijing Agro-Biotechnology Research CenterBeijing Academy of Agriculture and Forestry SciencesBeijing 100097China College of Forestry Northeast Forestry UniversityHarbin 150040China

Composting plants are regarded as one of the important sources of environmental ***,limitations in the size distribution of airborne bacteria have prevented our comprehensive understanding of their risk to human health and their dispersal *** this study,different sizes of airborne bacteria were collected using an eight-stage impactor from a full-scale composting ***-related abundance and communities of airborne bacteria as well as human pathogenic bacteria(HPB)were investigated using 16S rRNA gene sequencing coupled with droplet digital *** results indicate that the bacterial concentrations from the eight stages were approximately 10^(4)-105copies/m^(3).Although no statistical correlation was detected between the particle size and the Shannon index,the influence of size on bacterial lineages was observed in both composting and packaging *** airborne bacteria from different stages,the dominant phyla were Firmicutes,Proteobacteria,and Actinobacteria,and the dominant genera was *** out of eight HPB with a small geometric mean aerodynamic diameter had a high concentration in composting *** on diameters of 2.42 to 5.09μm,most HPB in the composting areas were expected to be deposited on the bronchus and secondary ***,in the packaging areas,the deposition of HPB(diameters 3.70 to 8.96μm)occurred in the upper part of the respiratory *** results on the size distribution,abundance,and diversity of these bacteria offer important information for the systematic evaluation of bacterial pathogenicity and the potential health impacts on workers in composting plants and the surrounding residents.

关键词： Size distribution Airborne bacteria Biological diversity Human pathogenic bacteria Composting plants

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Effects of acid,acid-ZVI/PMS,Fe(Ⅱ)/PMS and ZVI/PMS conditioning on the wastewater activated sludge(WAS)dewaterability and extracellular polymeric substances(EPS)

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Journal of Environmental Sciences 2020年第5期32卷 73-84页

作者： Xiaoyang Fan Yili Wang Daxin Zhang yajie guo Shihui Gao Enrui Li Huaili Zheng College of Environmental Science and Engineering Beijing Key Lab for Source Control Technology of Water PollutionBeijing Forestry UniversityBeijing 100083China Jinyun Forest Ecosystem Research Station Beijing Forestry UniversityBeijing 100083China Key Laboratory of the Three Gorges Reservoir Regions Eco-Environment State Ministry of EducationChongqing UniversityChongqing 400045China

The effects of four conditioning approaches:Acid,Acid-zero-valent iron(ZVI)/peroxydisulfate(PMS),Fe(Ⅱ)/PMS and ZVI/PMS,on wastewater activated sludge(WAS)dewatering and organics distribution in supernatant and extracellular polymeric substances(EPS)layers were *** highest reduction in bound water and the most WAS destruction was achieved by Acid-ZVI/PMS,and the optimum conditions were pH 3,ZVI dosage 0.15 g/g dry solid(DS),oxone dosage 0.07 g/g DS and reaction time 10.6 min with the reductions in capillary suction time(CST)and water content(Wc)as 19.67%and 8.49%,*** conditioning approaches could result in TOC increase in EPS layers and supernatant,and protein(PN)content in tightly bound EPS(TB-EPS).After conditioning,organics in EPS layers could migrate to ***(PS)was easier to migrate to supernatant than *** addition,Acid,Acid-ZVI/PMS or Fe(Ⅱ)/PMS conditioning promoted the release of some polysaccharides containing ring vibrations v P=O,v C-O-C,v C-O-P functional groups from *** spectra proved that both radicals of SO4-·and·OH contributed to dewatering and organics transformation and *** value of WAS positively correlated with the ratios of PN/PS in LB-EPS and total EPS,while it negatively correlated with TOC,PN content and PS content in TB-EPS,as well as PS content in supernatant and *** negatively correlated to zeta potential and TOC value,PN content,and HA content in supernatant.

关键词： Conditioning approaches Acid-ZVI/PMS Wastewater activated sludge dewaterability EPS Radicals Correlation

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Preparation and anisotropic thermophysical properties of SiC honeycomb/Al-Mg-Si composite via spontaneous infiltration

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Progress in Natural Science:Materials International 2019年第2期29卷 177-183页

作者： Zhejian Zhang Zhongqi Shi Biguo Yang Bangzhi Ge Xiaoyu Zhang yajie guo State Key Laboratory for Mechanical Behavior of Materials Xi'an Jiaotong University Engineering Research Center of Transportation Materials of Ministry of Education School of Materials Science and Engineering Chang'an University

The SiC honeycomb/Al-Mg-Si composite with interpenetrated microstructure was prepared by spontaneous infiltration of Al-8 wt%Mg-7 wt%Si alloy into directional porous SiC honeycomb served as reinforcement. The microstructure and anisotropic thermophysical properties of this composite were also examined. The results showed that the initial microstructure of the SiC honeycomb can be retained and the as-prepared SiC honeycomb/Al-Mg-Si composite exhibited significantly anisotropic characteristics. Meanwhile, the alloying treatment on the Al matrix can avoid the generation of Al;C;and promote the wettability between Al and ***,the directional porous SiC honeycomb with such a low ceramic content（19 vol.%） made it possible for the composite to have a higher thermal conductivity(138.3 W/（m?K）) in the axial direction and a lower coefficient of thermal expansion(11.40 × 10;/K) in the radial *** influences of the SiC honeycomb reinforcement on the anisotropic thermophysical properties were also studied by the theoretical models in comparing with the experimental results.

关键词： SiC honeycomb Al-Mg-Si alloy Spontaneous infiltration Anisotropy Thermophysical properties

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A Strategy to Find Novel Candidate DKAs Inhibitors Using Modified QSAR Model with Favorable Druggability Properties

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Chemical Research in Chinese Universities 2019年第6期35卷 1111-1118页

作者： ZHANG Xiaoyi NIU Wenling TANG Tang HOU Chengfei guo yajie KONG Ren College of Life Science and Bioengineering Beijing University of TechnologyBeijing 100124P.R.China Institute of Bioinfotmatics and Medical Engineering School of Electrical and Information EngineeringJiangsu University of TechnologyChangzhou 213016P.R.China

The study dealed with quantitative structure-activity relationship(QSAR)to explore the important features of diketo acid(DKA)derivatives for exerting potent HIV-1 integrase inhibitors activity.A three-step screening method was proposed to choose ***,additional descriptors were used in the CoMFA and ***,a modified CoMSIA m7 model,constructed by adding Csp^2_03_F descriptor,showed better predictive *** parameters(Q^2 and R^2)for the models were 0.722 and 0.925,*** addition,external validation for the models using a test group revealed R^2pred=*** maps analysis defined favored and disfavored regions of the compounds,and two new compounds with the descriptor structure were designed with better activities than Raltegravir(RAL),well drug-likeness and low *** research provides a base for further DKA development.

关键词： Diketo acid(DKA) Modified quantitative structure-activity relationship(QSAR) Autodock Drug design Descriptor screening

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CRISPR/CasΦ2-mediated gene editing in wheat and rye

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Journal of Integrative Plant Biology 2024年第4期66卷 638-641页

作者： Sanzeng Zhao Xueying Han Yachen Zhu Yuwei Han Huiyun Liu Zhen Chen Huifang Li Dan Wang Chaofan Tian Yuting Yuan yajie guo Xiaomin Si Daowen Wang Xiang Ji State Key Laboratory of Wheat and Maize Crop Science and Center for Crop Genome EngineeringCollege of AgronomyHenan Agricultural UniversityZhengzhou 450046China Collaborative Innovation Center of Henan Grain Crops College of AgronomyHenan Agricultural UniversityZhengzhou 450046China State Key Laboratory of Crop Stress Adaptation and Improvement College of AgronomyHenan UniversityKaifeng 475004China The Shennong Laboratory Zhengzhou 450002China

The recent advancements in developing the CRISPR/Cas9 system and various derivative tools(e.g.,base editors)have accelerated basic plant science research and crop improvement by creating multiple types of genetic vari... 详细信息

关键词： CRISPR/Cas9 CRISPR/Cas

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论末昂语的体范畴

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民族语文 2023年第6期 98-107页

作者：郭亚杰中央民族大学中国少数民族语言文学学院北京100081

本文依据田野调查的语言材料来讨论末昂语的体范畴。通过田野调查语料分析,认为末昂语的体范畴可分为完整体和非完整体两类。其中,完整体分为经历体、已行体、完成体、结果体;非完整体分为进行体、持续体、延续体、起始体。末昂语体范... 详细信息

本文依据田野调查的语言材料来讨论末昂语的体范畴。通过田野调查语料分析,认为末昂语的体范畴可分为完整体和非完整体两类。其中,完整体分为经历体、已行体、完成体、结果体;非完整体分为进行体、持续体、延续体、起始体。末昂语体范畴以动词虚化而来的体标记为主,居于动词之后。通过跨语言比较,发现末昂语不同体范畴之间可以组合共现。体标记与周围彝语、壮语呈现语言区域共性。

关键词：末昂语体标记完整体非完整体

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张峰水库抗冲磨混凝土的原材料性能及选择

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水力发电 2006年第1期32卷 93-95页

作者：郭亚洁山西省水利水电科学研究院山西太原030002

结合混凝土的试拌和硬化混凝土的力学性能试验,对张峰水库抗冲磨混凝土的水泥、骨料、外加剂、掺合料等原材料进行的选择和检验,从而为张峰水库泄水建筑物抗冲磨混凝土选择了经济合理、性能好的原材料,经检验配制的混凝土完全能满足设... 详细信息

结合混凝土的试拌和硬化混凝土的力学性能试验,对张峰水库抗冲磨混凝土的水泥、骨料、外加剂、掺合料等原材料进行的选择和检验,从而为张峰水库泄水建筑物抗冲磨混凝土选择了经济合理、性能好的原材料,经检验配制的混凝土完全能满足设计和施工要求。

关键词：抗冲磨强度原材料混凝土张峰水库

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