检索结果-南通市图书馆

Fabrication of AION transparent ceramics with Si_(3)N_(4) sintering additive

在线全文

学校读者我要写书评

暂无评论

Journal of Advanced Ceramics 2023年第7期12卷 1361-1370页

作者： Liqiong An Rongwei Shi Xiaojian Mao buhao zhang Jianmin Li Jian zhang Shiwei Wang College of Ocean Science and Engineering Shanghai Maritime UniversityShanghai 201306China State Key Laboratory of High Performance Ceramics and Superfine Microstructures Shanghai Institute of CeramicsChinese Academy of SciencesShanghai 200050China Faculty of Engineering University of NottinghamNottingham NG72RDUK

In this paper,Si_(3)N_(4) was used as a novel solid-state sintering additive to prepare AION transparent ceramics with high transparency and flexural strength via the pressureless pre-sintering and hot isostatic pressing(HIP)method at a relatively low HIP temperature(1800℃).The effect of Si_(3)N_(4) content on the phase,microstructure,optical property,and flexural strength was *** experimental results showed that a Si element was homogenously distributed in both pre-sintered and HIPed AION *** densification enhanced,the grain grew with the increasing Si_(3)N_(4) content in the pre-sintered AION ceramics,and all the samples became pore-free after HIP,which favor *** AION ceramics doped with 0.10 wt%Si_(3)N_(4) had the highest transmittance of 83.8%at 600 nm and 85.6%at 2000 nm(4 mm in thickness),with flexural strength of 404 MPa,which were higher than those of the previous reports.

关键词： transparent ceramics alumina oxynitride(AION) sintering additive Si_(3)N_(4) hot isostatic pressing(HIP)

Cross-scale microstructure design of precursor-derived SiC-AlN nanoceramic composites hybrid with ex-situ ZrB_(2)

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Advanced Powder Materials

Advanced Powder Materials 2023年第1期2卷 35-42页

作者： Aidong Xia buhao zhang Jie Yin Xiao Chen Sea-Hoon Lee Xuejian Liu Zhengren Huang State Key Laboratory of High Performance Ceramics and Superfine Microstructures Shanghai Institute of CeramicsChinese Academy of SciencesShanghai 200050China Ningbo Institute of Materials Technology and Engineering Chinese Academy of SciencesNingbo 315201China College of Materials Science and Opto-Electronic Technology University of Chinese Academy of SciencesBeijing 100049China Ceramic Materials Division Korea Institute of Materials ScienceChangwon 51508Republic of Korea

ZrB_(2)/SiC–AlN nanoceramic composites were densified at 1950℃ by hot pressing using an organic-precursorderived SiC and commercially available AlN and ZrB_(2).A cross-scale microstructure was constructed by distributing the ZrB_(2) secondary phase(~421 nm)within the SiC–AlN solid solution *** substructure of the SiC–AlN matrix was agglomerated by nanograins with an average size of only 62 ***_(2) connected around the majority of pores within the SiC–AlN matrix and contributed to the formation of numerous weak interfacial bonding,resulting in improved strength and *** highest flexural strength and fracture toughness of 579±52 MPa and 6.7±0.1 MPa m^(1/2) were obtained from a 10 wt%-ZrB2/SiC–AlN sample,*** high concentration of grain boundaries of the ZrB2/SiC–AlN nanoceramic composites resulted in heat insulation *** thermal diffusivity and conductivity were 3.6 mm^(2)·s^(-1) and 14.3 W⋅(m·K)^(-1) at 1400℃,respectively,while the electrical resistivity was 3.9×10^(3)Ω·cm for the 10 wt%-ZrB_(2)/SiC–AlN sample.

关键词： Nanoceramic composites Precursor-derived ceramics SiC-AlN solid Solution Mechanical properties Thermal and electrical properties

Low temperature densification mechanism and properties of Ta_(1-x)Hf_(x)C solid solutions with decarbonization and phase transition of Cr_(3)C_(2)

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Materiomics 2021年第4期7卷 672-682页

作者： buhao zhang Jie Yin Yichen Wang Duo Yu Huan Liu Xuejian Liu Michael JReece Zhengren Huang State Key Laboratory of High-Performance Ceramics and Superfine Microstructure Shanghai Institute of CeramicsChinese Academy of SciencesShanghai200050China School of Engineering and Materials Science Queen Mary University of LondonMile End RoadLondonE14NSUK University of Chinese Academy of Sciences Beijing100049China

As a novel member of the ultra-high temperature ceramic family,which have extremely high melting points and remarkable hardness,Ta1-xHfxC solid solution ceramics are promising for applications in thermal protection ***_(1-x)Hf_(x)C(x=0,0.2,0.5,0.8,and 1.0)with 2 vol%Cr_(3)C_(2),were densified up to 98.8%at 2000℃ using a two-step spark plasma sintering *** of Cr_(3)C_(2) on the linear shrinkage of Ta1-xHfxC was ***‘eutectic’reaction within TaCeCr_(3)C_(2) ceramic was inferred to contribute to the shrinkage at 1462 ***-angle annular dark-field scanning transmission electron microscopy combined with energy-dispersive spectroscopy was employed to further confirm the mutual diffusion between rock-salt structured‘CrCx’and *** strength,fracture toughness and Vicker’s hardness of Ta1-xHfxC ceramics were in the range of 439e492 MPa,4.0e5.8 MPa∙m^(1/2) and 14.9e19.9 GPa *** coefficient of thermal expansion(in the temperature range of 25e1000℃)and thermal conductivity(at 1000℃)of Ta_(1-x)Hf_(x)C varied from 7.17 to 7.51×10^(-6) K^(-1) and 31.9e42.9 W/m·K,*** high-temperature strength of Ta_(0.5)Hf_(0.5)C decreased to 165 MPa up to 1600℃,approximately 34%of room-temperature strength,and a‘zig-zag’load-displacement curve was observed.

关键词： Solid solution Ultra-high temperature composites Spark plasma sintering Low-temperature densification Mechanical/thermal properties

Carbon deficiency introduced plasticity of rock-salt-structured transition metal carbides

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2023年第33期164卷 205-214页

作者： buhao zhang Youwei Wang Jie Yin Yichen Wang Hangfeng zhang Tamás Csanádi Ján Dusza Michael J.Reece Nan Lin Xiao Yang Xuejian Liu Zhengren Huang Dongliang Jiang State Key Laboratory of High-Performance Ceramics and Superfine Microstructure Shanghai Institute of CeramicsChinese Academy of SciencesShanghai200050China Faculty of Engineering University of NottinghamNottinghamNG7 2RDUnited Kingdom School of Engineering and Materials Science Queen Mary University of LondonMile End RoadLondon E1 4NSUK Institute of Materials Research Slovak Academy of SciencesWatsonova 4704353KošiceSlovak Republic College of Materials Science and Engineering Hunan UniversityChangsha410082China

High-hardness rock-salt structured transitional metal carbides(TMC)are attracting substantial interest as potential next-generation thermal protection ***,the intrinsic brittleness of TMC ceramics impedes their performance in aerodynamically harsh *** this work,a promising strategy is proposed to introduce plasticity in TaC–HfC solid solutions by manipulating carbon *** approach combines density-functional theory(DFT)with experiments and takes Pugh's ratio(k)as the *** of carbon atoms in TaC–HfC solid solutions results in the de-localizing of valence electrons,deviation of spatial modulus along different crystal plane directions,and leading to significant elastic *** carbon deficient Ta_(0.8)Hf_(0.2)C_(0.8) is predicted to be a‘softer phase’with reduced modulus and Pugh's ratio(k=0.58).A series of Ta1–xHfxCy(x=0.2 and 0.8,y=0.8,0.9,and 1.0)bulk ceramics are experimentally fabricated by an excessive metal alloying *** and hexagonal close-packed structured carbides are derived when the carbon deficiency y decreased to *** indentation modulus drops from 641.8±14.8 GPa for Ta_(0.8)Hf_(0.2)C_(1.0) to 555.8±9.9 GPa for *** specific stoichiometric composition of Ta_(0.8)Hf_(0.2)C_(0.8) is experimentally verified to possess both plasticity(k=0.41)and ultra-high nanohardness(41.3±1.3 GPa).

关键词： Brittle Plasticity Transitional metal carbides Pugh's ratio Carbon deficiency

建成环境对共享单车使用特征的非线性影响研究

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

交通运输系统工程与信息 2024年第2期24卷 217-224页

作者：陈奕璠张步镐党振郭唐仪顾子渊张玉梁南京理工大学自动化学院南京210094 银江技术股份有限公司浙江省智能交通工程技术研究中心杭州310040 东南大学交通学院南京211189 浙江大学智能交通研究所杭州310058

为研究共享单车使用特征与建成环境的依赖关系,本文以2020年厦门市共享单车订单数据和电子围栏信息为基础,从集计(栅格区域)和非集计(个体出行)两个层面,利用极端梯度提升模型(XGboost),探究建成环境对共享单车使用特征的非线性解释能... 详细信息

为研究共享单车使用特征与建成环境的依赖关系,本文以2020年厦门市共享单车订单数据和电子围栏信息为基础,从集计(栅格区域)和非集计(个体出行)两个层面,利用极端梯度提升模型(XGboost),探究建成环境对共享单车使用特征的非线性解释能力。首先,识别密度、设计、目的地可达性、土地利用多样性、公共交通可达性和需求管理六个维度的建成环境变量对单车出行生成、吸引以及用户出发时间选择的相对重要性。之后,根据部分依赖图,揭示建成环境变量对单车使用特征指标的影响趋势。结果表明,在集计层面,电子围栏密度是最重要的建成环境因素,对出行生成和吸引的影响程度分别为26.88%和51.90%,且在150个·km^(-2)附近产生阈值效应。在非集计层面,单车用户早高峰借车概率与出行起讫点的建成环境均有关联。其中,目的地栅格中工作场所比例影响最显著(18.17%),出发地栅格CBD邻近度(7.34%)和出发地栅格公交站点密度(5.91%)次之。

关键词：城市交通出行特征极端梯度提升模型共享出行建成环境非线性分析

莫来石助剂对氧氮化铝透明陶瓷显微结构及光学性能的影响

在线全文

学校读者我要写书评

暂无评论

硅酸盐学报 2024年第3期52卷 845-852页

作者：史镕玮安丽琼毛小建张步豪李建民章健王士维上海海事大学海洋科学与工程学院上海201306 中国科学院上海硅酸盐研究所国家重点实验室上海200050 英国诺丁汉大学工程学院英国诺丁汉NG72RD

以自制AlON粉体为原料、莫来石为烧结助剂,结合无压烧结与热等静压烧结在相对较低的温度下(分别为1 880℃和1 800℃)制备了AlON透明陶瓷,研究了莫来石含量对无压烧结和热等静压烧结AlON陶瓷的显微结构以及光学性能的影响。结果表明,莫... 详细信息

以自制AlON粉体为原料、莫来石为烧结助剂,结合无压烧结与热等静压烧结在相对较低的温度下(分别为1 880℃和1 800℃)制备了AlON透明陶瓷,研究了莫来石含量对无压烧结和热等静压烧结AlON陶瓷的显微结构以及光学性能的影响。结果表明,莫来石含量在0.02%~0.20%(质量分数)时,无压烧结AlON陶瓷为纯AlON相,其Raman光谱相似。随着莫来石含量增加,AlON陶瓷无压预烧体的致密度先增加后减小,而其晶粒尺寸逐渐变大。热等静压烧结后,所有样品的致密度均高于理论密度的99.2%且晶粒长大;其致密度、晶粒和透过率随莫来石含量增加呈现出先增大后减小的趋势。最终,0.05%莫来石AlON透明陶瓷致密度为3.67 g/cm^(3),平均晶粒尺寸为80.4μm,其透过率最高,4 mm厚样品在2 000 nm处达到81.9%。

关键词：氧氮化铝透明陶瓷烧结助剂莫来石热等静压

在线全文

学校读者我要写书评

暂无评论

碳化物超高温陶瓷材料研究进展

航空制造技术 2019年第19期62卷 53-64页

作者：于多殷杰张步豪刘学建黄政仁中国科学院上海硅酸盐研究所高性能陶瓷和超微结构国家重点实验室上海200050 中国科学院大学北京100049 中国科学院宁波材料技术与工程研究所宁波315201

航天技术的进步对应用于极端环境的材料提出了更高要求,分为5个部分对超高温碳化物陶瓷近些年来的研究进行调研,分别描述了单组元、二元、多元高熵碳化物材料及其复合材料在理论模拟预测、微观结构调控和宏观性能提升等方面的进展,可以... 详细信息

航天技术的进步对应用于极端环境的材料提出了更高要求,分为5个部分对超高温碳化物陶瓷近些年来的研究进行调研,分别描述了单组元、二元、多元高熵碳化物材料及其复合材料在理论模拟预测、微观结构调控和宏观性能提升等方面的进展,可以发现材料的硬度、韧性及高温抗氧化等性能得到了有效提高,但更高效实用的制备方法及结构性能机理等还需要进一步探索,同时,对于较新颖的高熵材料而言,通过揭示其组分-构效关系来有效提高其性能的研究也是重中之重。

关键词：单组元碳化物二元碳化物高熵碳化物微观结构力学性能

在线全文

学校读者我要写书评

暂无评论

丘陵地区深切峡谷风特性现场实测研究

湖南大学学报（自然科学版） 2019年第7期46卷 113-122页

作者：张志田谭卜豪陈添乐湖南大学风工程试验研究中心

根据测风塔和当地气象站数据,对江底河大桥桥址处深切峡谷的风场特性进行研究.基于数据统计分析得到桥址处风场的平均风速、风向、湍流强度、湍流积分尺度和湍流的功率谱密度函数.结果表明:该桥所在的深切峡谷地形对风向有锁定作用、对... 详细信息

根据测风塔和当地气象站数据,对江底河大桥桥址处深切峡谷的风场特性进行研究.基于数据统计分析得到桥址处风场的平均风速、风向、湍流强度、湍流积分尺度和湍流的功率谱密度函数.结果表明:该桥所在的深切峡谷地形对风向有锁定作用、对风速有加速作用、并且对各个风向下的湍流特性有明显的影响;深切峡谷顺风向湍流强度与平均速度的关系用反比例型函数拟合,拟合效果良好且高风速下接近规范值;竖风向湍流强度明显高于规范推算值.顺风向实测风谱与Kaimal谱相差较大而与von Karman谱吻合较好;竖风向实测风谱明显大于Panofsky风谱而与von Karman谱比较接近.横风向实测风谱与Panofsky谱、von Karman谱都比较接近.

关键词：深切峡谷平均风速湍流强度湍流积分尺度湍流的功率谱密度

在线全文

学校读者我要写书评

暂无评论

高地应力软岩隧道预留变形量设计方法

隧道建设（中英文） 2023年第11期43卷 1916-1923页

作者：韩常领徐晨夏才初郑卜豪应轶微中交第一公路勘察设计研究院有限公司陕西西安710075 宁波大学岩石力学研究所浙江宁波315211 宁波市能源地下结构重点实验室浙江宁波315211

在弹塑性岩体中开挖隧道,若围岩无明显的流变性,支护施作太早将承受非常大的荷载,但支护结构并非越晚施作越好。如果支护结构刚度和强度设计不足,即使预留了变形空间,隧道仍可能因支护反力不足而发生大变形破坏。为确定合理的支护刚度... 详细信息

在弹塑性岩体中开挖隧道,若围岩无明显的流变性,支护施作太早将承受非常大的荷载,但支护结构并非越晚施作越好。如果支护结构刚度和强度设计不足,即使预留了变形空间,隧道仍可能因支护反力不足而发生大变形破坏。为确定合理的支护刚度和支护时机,基于GZZ强度准则采用大应变分析理论,考虑隧道扩挖影响,修正高地应力软岩隧道的围岩特征曲线。修正后的特征曲线与原始曲线有共同的起点,但随着变形增大逐渐偏离原始曲线;增大开挖半径会使特征曲线更高,这意味着支护结构需要提供更大的反力。因此,在工程设计时需要根据修正后的围岩特征曲线进行支护结构设计,避免因为支护刚度不足而发生大变形破坏。其次,基于初始地应力、围岩强度等参数对修正围岩特征曲线形态的影响,提出高地应力软岩隧道围岩最佳预留变形量的设计方法。当地应力较低时,特征曲线有明显的“最低点”,该点对应的支护反力最小,为最佳支护时机;在高地应力条件下,即使变形很大,围岩特征曲线也仍然未达到最低点,这是因为形变压力占主导,松散压力远小于形变压力。因此,在高地应力条件下,采用应力释放措施是有必要的,可通过特征曲线的曲率寻找最佳预留变形量。

关键词：高地应力软岩隧道大变形预留变形量修正围岩特征曲线