J.D.Hunt
,
Q.Hant and X.Wan(Dept. of Materials
,
University of Oxford
,
Parks Road
,
Oxford OX1 3PH
,
U.K.)
材料科学技术（英文）
This paper describes a time dependent numerical model for the steady and non-steady growthof a cellular/dendritic array in a moving linear temperature field. The model gives fully selfconsistent solutions for axisymmetric interface shapes, predicts cellular and dendritic spacings,undercoolings and the transition between structures. An important feature of the model is thatthe spacing selection mechanism has been treated. The model predicts two different dendriticgrowth regions. One occurs at low dimensionless velocities where the dendrite array is uniform:a small stable range of spacings is predicted and the prediction agrees very well with existing experiments. The other occurs at high dimensionless velocities where the dendrite array is irregular, its minimum spacing is inversely proportional to velocity Experiment was carried out to verify the prediction. The irregular dendrite array was observed and the measured minimum spacing fitted extremely well with the prediction. By fitting the numerical results. Relatively simple analytic expressions are obtained which provide an insight into the cellular and dendritic growth processes and are useful for comparing theory with experiment.
关键词:
杨金瑞
,
余尚先
,
顾江楠
高分子材料科学与工程
通过对resol(羟甲基酚化合物和低分子量羟甲基酚树脂)DEPT135图谱的分析讨论,得到一系列计算resol微细结构参数的经验公式.根据DEPT135图谱可判断是否发生缩聚反应,根据经验公式可计算酚单体各个活性点参与反应百分率或酚羟基导入率、不同类型缩聚所占百分率及低分子量羟甲基酚树脂的平均核体数.
关键词:
羟甲基酚化合物
,
羟甲基酚树脂
,
DEPT135
,
结构参数
原子核物理评论
研究了高电荷态离子~(40)Ar~(q+)(q＝7-14)轰击金属Au表面产生的特征X射线谱.实验结果表明,在弱束流(nA量级)的情况下,对于动能相同的入射离子,当电荷态比较高(q＝11)时,便能有效地激发靶原子的特征X射线,单离子的X射线产额高达10~(-8)量级.分析结果显示,入射离子的势能、动能和这种相互作用特有的镜像相互作用势能沉积在靶表面,使靶原子内壳层电子激发和电离,形成空穴和产生外壳层电子填充空穴辐射特征X射线,特征X射线的产额随入射离子的势能(电荷态)的增加而增加.
关键词:
高电荷态离子
,
X射线
,
产额
杜翠薇
,
王胜荣
,
刘智勇
,
李晓刚
,
朱敏
,
李琼
,
黄一中
,
刘明
腐蚀学报（英文）
doi:10.11903.1002.6495.2014.210
通过土壤理化性质分析、现场埋样的腐蚀形貌观察、腐蚀产物的扫描电镜观察和X射线衍射分析以及腐蚀失重实验等分析手段,研究了国产X70钢和Q235钢在新加坡土壤中现场埋样1a后的短期腐蚀行为特征.结果表明,新加坡土壤属于酸性土壤;埋样1a后Q235钢平均腐蚀速率略大于X70钢,两种钢以局部腐蚀为主,Q235钢的局部腐蚀较严重;两种钢的腐蚀产物组成相似,均为Fe2O3,Fe3O4,FeOOH和FeOCl,腐蚀产物表面粗糙,存在裂纹与空隙,从而加速局部腐蚀的进行.
关键词:
X70钢
,
Q235钢
,
酸性土壤
,
土壤腐蚀
王燕
,
闫永贵
,
董超芳
,
钱建华
,
李晓刚
腐蚀学报（英文）
通过腐蚀速率测定、腐蚀形貌观察、腐蚀坑深度测量及分形维数计算等方法,研究了杂散电流作用下涂层破损率对Q235、16Mn和X70钢腐蚀的影响.结果表明,杂散电流作用下,Q235钢腐蚀程度最严重,16Mn次之,X70最小;随杂散电流增大和涂层破损率减小,腐蚀速率和腐蚀坑深度均相应增大,腐蚀程度加剧;根据"盒子"维法测定杂散电流腐蚀形貌的分形维数,反映的腐蚀规律与实测腐蚀速率吻合,分形维数可定量表征杂散电流腐蚀形貌.
关键词:
杂散电流腐蚀
,
涂层破损率
,
腐蚀速率
,
分形维数
,
腐蚀坑深
田为中
,
钱蓉
,
喻筱静
,
齐鸣
功能材料与器件学报
doi:10.3969/j.issn.1007-4252.2007.06.019
在介电常数为2.20±0.02,厚度为254μm的Rogers5880衬底上用混合集成技术制作了9.5～10.5GHz平衡,I-Q矢量调制器.测试结果表明:各状态插入损耗为(7.5±1)dB,回波损耗大于16dB,均方根(RMS)相位误差小于5.,各状态之间的幅度不平衡小于0.5dB,可实现对9.5～10.5GHz载波信号的直接QPSK调制.文中还提出电路性能优化的一些方法.
关键词:
Rogers5880
,
I-Q矢量调制器
,
BPSK调制器
E.Bayraktar
,
F.Montembault
,
C.Bathias
材料科学技术（英文）
The study of microstructural network and damage mechanism of polymer and rubber, although deceptively simple, involves a complex interplay between material properties and service conditions. So, the study of the texture, deformation and the failure of rubber specimens are of considerable practical interest. In fact, the occurrence of defects such as the initiation and the growth of cavitations in rubber specimens in working conditions is an important problem. These deal with the improvement of microstructure (for delaying instability) in order to obtain a higher service capacity. The scope of the present paper is, therefore, to evaluate principal mechanisms, in-situ observation of damage at mesoscopic, microscopic and macroscopic levels by using X-ray computed tomography (CT) installed in the ITMA research centre for confirming the behaviour of natural rubber (NR) and styrene butyl rubber (SBR) specimens used in automotive and aeronautical fields.
关键词:
X-ray computed tomography
,
null
,
null
,
null
H. N. Chen
,
D. Li and H. Y. Du Institute of Metal Research
,
The Chinese Academy of Sciences
,
Shenyang 110015
,
China
金属学报(英文版)
The weldability is an important property to metal materials. Materials weldability becomes worse with the yield strength increasing. The experimental results indicate that the specific shock waves treatment could improve the weldability of steels such as 16MnR, SM 58Q, e.g. increase the notch toughness of coarse grains zone in HAZ and decrease cold cracking sensibility. The work would explore initially the mechanisms of improvement of weldability by shock waves. The further study on the low alloy high strength steel WEL TEN80 indicates that the shock waves may increase the material weldability on this grade of trength.
关键词:
shock waves
,
null
,
null
Masahiko MORINAGA
,
Yoshinori MURATA
,
Hiroshi YUKAWA
材料科学技术（英文）
A molecular orbital approach to materials design has recently made great progress. This approach is based on the electronic structure calculations by the DV-Xα cluster method. In this paper recent progress in this approach is reviewed. In particular, it is stressed that New PHACOMP approach is useful for predicting the formation of topologically close-packed (TCP) phases (e.g., σ phase and μphase ) in nickel based superalloys. Compared to the current PHACOMP, New PHACOMP provides a better tool for designing those alloys which are free from such TCP precipitates at service temperatures. In addition, the d-electrons concept is shown for alloy design and development.
关键词:
High temperature materials
,
null
,
null
,
null
Advanced Materials
Popularization of portable electronics and electric vehicles worldwide stimulates the development of energy storage devices, such as batteries and supercapacitors, toward higher power density and energy density, which significantly depends upon the advancement of new materials used in these devices. Moreover, energy storage materials play a key role in efficient, clean, and versatile use of energy, and are crucial for the exploitation of renewable energy. Therefore, energy storage materials cover a wide range of materials and have been receiving intensive attention from research and development to industrialization. In this Review, firstly a general introduction is given to several typical energy storage systems, including thermal, mechanical, electromagnetic, hydrogen, and electrochemical energy storage. Then the current status of high-performance hydrogen storage materials for on-board applications and electrochemical energy storage materials for lithium-ion batteries and supercapacitors is introduced in detail. The strategies for developing these advanced energy storage materials, including nanostructuring nano-/microcombination, hybridization, pore-structure control, configuration design, surface modification, and composition optimization, are discussed. Finally, the future trends and prospects in the development of advanced energy storage materials are highlighted.
关键词:
lithium-ion batteries;carbon nanotube electrodes;enhanced hydrogen;storage;metal-organic frameworks;double-layer capacitors;n-h system;carbide-derived carbons;ammonia borane dehydrogenation;ordered;mesoporous carbons;high-rate performance
