C.M.Cheng
,
C.P.Chou
,
I.K.Lee
,
H.Y.Lin
材料科学技术（英文）
In this study we conducted single V-groove butt welding (GTAW) on three types of heat treatable aluminum alloys 2024-T351, 6061-T6 and 7075-T6 and compared the angular distortion levels of the three aluminum alloys at different Vee preparation angles with or without restraint. Experimental results demonstrated that when the Vee preparation angle was 0℃ (I-shaped groove), the angular distortion level of the restrained weldment can exceed that of the unrestrained weldments. Moreover, when the Vee preparation angle was 45℃, 60℃ or 90℃, the restrained weldment had lower angular distortion than the unrestrained weldments. The single Vee preparation angle (amount of filler metal) in butt welding affected the angular distortion of the weldment. Without restraint, the angular distortion tended to increase with the single Vee preparation angle. Meanwhile, the angular distortion tended to decrease when the single Vee preparation angle was 60℃. Additionally, a restrained weldment had high angular distortion when the single Vee preparation angle was 0℃. Notably, the angular distortion tended to reduce with increasing single Vee preparation angle. The angular distortion of the weldment was minimized at an angle of 60℃. However, the angular distortion increased when the Vee preparation angle exceeded 60℃. The high-temperature yield strength of a material also affected its angular distortion. Angular distortion increased with high-temperature yield strength. Experimental results also showed that, from the strongest to the weakest, the high-temperature yield strength of the three types of aluminum alloys followed the order 6061-T6 and 2024-T351>7075-T6.
关键词:
Angular distortion
,
null
,
null
Journal of Physics and Chemistry of Solids
By using the defect structure data (characterized by the coordinates of impurity center) obtained from the shell model and the density functional theory in the generalized gradient approximation (GGA) corresponding to two supercell sizes, the zero-field splitting D of the tetragonal Fe-K(3+)-O-I center in KTaO3 crystal is calculated from the high-order perturbation formula based on the dominant spin-orbit coupling mechanism. The calculated results suggest that the sign of zero-field splitting D is negative and the defect structure data obtained from GGA method are more reasonable. Compared with that corresponding to the smaller supercell size, the calculated D value based on the GGA coordinates corresponding to the larger supercell size is closer to the observed value, suggesting that the GGA coordinates obtained from the larger supercell size are more accurate. (c) 2006 Elsevier Ltd. All rights reserved.
关键词:
inorganic compounds;oxides;crystal fields;defects;electron;paramagnetic resonance (EPR);fe centers;ions;scattering;spectra;sites;model;epr
王德强
,
陈玮
,
程继健
硅酸盐通报
doi:10.3969/j.issn.1001-1625.2006.06.012
以油酸钾为熔盐,GeS2-Ga2S3-AgX(X=Cl,Br,I)玻璃为基玻璃,在270℃的环境温度下,以氮气作为保护气氛,成功地进行了K+-Ag+离子交换.在50GeS2-25Ga2S3-25AgI玻璃中,K+离子的交换深度可达256μm,并对交换深度、离子扩散系数以及离子浓度之间的规律进行了初步研究.通过离子交换研究,为制备硫卤玻璃光波导奠定了基础,并可以进一步拓宽硫卤玻璃的应用前景.
关键词:
硫卤玻璃
,
离子交换
,
光波导
,
浓度分布
蔡振钦
,
徐春明
,
赵锁奇
,
许志明
,
孙学文
,
张民
催化学报
采用同位素示踪技术,系统地研究了K2CO3/CH3I促进的CO2插入甲醇直接合成碳酸二甲酯(DMC)的反应机理.结果表明,固体碱碳酸钾催化剂直接参与了DMC的合成过程, DMC分子中的羰基由CO2插入甲醇后形成,两个甲基分别来源于甲醇和碘甲烷.本文将以往文献中提出的DMC生成机理和二甲醚生成机理结合起来,并对其进行适当补充后,可以很好地解释实验结果.
关键词:
碳酸二甲酯
,
合成
,
碳酸钾
,
碘甲烷
,
同位素示踪
,
反应机理
肖胜
,
徐克西
,
刘石香
,
付华明
低温物理学报
doi:10.3969/j.issn.1000-3258.2002.04.009
从磁通运动图象出发,推导了YBa2Cu3O7-δ(YBCO)颗粒膜的I-V特性关系式,并从实验上加以验证,结果表明:在TI-V表现出很强的非线性,样品主要是非欧姆损耗;在T>TKT时,I-V呈线性关系,样品以欧姆损耗为主;而在T=TKT时,I-V将出现突变,这跟K-T相变模型所描述的一致.
关键词:
Zhaojun LIN
,
Zhanguo WANG
,
Wei CHEN and Lanying LIN(Lab. of Sendconductor Materials Science
,
Institute of Semiconductors
,
Chinese Academy of Sciences
,
Beijing 100083
,
China)
材料科学技术（英文）
Samples have been prepared at different temperatures by loading I2 molecules into the cages of zeolite 5A, and the measurements of the absorption spectra have been carried out for the prepared samples. It is shown that I2 molecular clusters are formed in the cages of zeolite 5A,and it is also found that moIecuIar clusters which are bonded with intermoIecuIar forces have an important feature, namely, the intermolecular distance in molecular clusters can be changed on different preparing conditions and the blue shift of absorption edges can not be as the criterion of forming molecular clusters.
关键词:
Materials Research Innovations
Polycrystalline copper (I) oxide films were deposited on stainless steel substrate by galvanostatic electrodeposition method and were characterized by Xray diffraction and scanning electron microscopy. The effect of bath temperature, bath pH and current density on the compositon, grain size, surface texture and surface morphology of the electrodeposited films were investigated. The films deposited at low bath pH (less than or equal to 7) consisted of copper (I) oxide and metallic copper; while the films deposited at bath pH between 8 and 12 and bath temperature of 60 degrees C were pure copper (I) oxide. The preferred orientation of the copper (I) oxide films depended on the relative growth rate of (111) and (200) faces and could be controlled by adjusting the bath pH and/or the cathodic current density. (100)-oriented copper (1) oxide films could be deposited at pH=9 and current densities in the range of 0.25-1 mA/cm(2) while (111)-oriented films could be prepared at pH=12 or at pH=9 using the current densities between 1.5-2.5 mA/cm(2). Computer simulated crystallite shapes showed that the crystal shape changed from octahedral for (100)-oriented film to trucated pyramids and cubs for (111)-oriented film. And they were approved by scanning electron microscopy.
关键词:
copper(I) oxide;electrochemical deposition;thin films;microstructure;electrochemical synthesis;thin-films
Fatigue & Fracture of Engineering Materials & Structures
Nominal mode I and mixed mode I/II fatigue tests were carried out using the intermetallic compound Ni3Al(CrB) in the form of single crystal specimens. The effects of crystal orientation and load mode on fatigue crack initiation and growth were studied. The fracture surfaces of the single crystals were characterized by a cleavage-like appearance and cracking occurred either on a single {111} plane or on multiple {111} planes irrespective of whether mode I or mixed mode I/II loadings were applied. It was found that the crack initiation and growth behaviour are dependent on both crystal orientation and applied loading mode. The cracking behaviour predicted by three mixed mode fracture criteria (MTS, SED and G criteria) in polycrystalline materials under mixed mode loading can be understood from the present results on single crystals.
关键词:
fatigue cracking;mixed mode loading;crystallographic orientation;resolved shear stress;Ni3Al(CrB) single crystals;growth;alloy
张启伟
,
王桂仙
贵金属
doi:10.3969/j.issn.1004-0676.2009.02.005
研究了改性竹炭对银(I)的吸附性能与机理.研究表明:竹炭对银(I)有良好的吸附性能,平衡吸附量为45.2 mg/g;竹炭对银的吸附动力学可用准一级动力学描述,表观吸附速率常数k298=3.29×10-4 s-1,表观吸附活化能为:Ea=36.1 kJ·mol-1;银在竹炭上的吸附符合Langmiur吸附等温线,吸附系数KL(298 K)为24.427 L·mg-1,饱和吸附量Q∞为62.7 mg/g;温度升高,吸附量减小,表明吸附为放热过程;测得吸附热力学参数为:ΔH= -40.9 kJ·mol-1,ΔG=-36.6 kJ·mol-1,ΔS=-14.46 J·K-1·mol-1.机理研究表明:竹炭对银(I)的吸附主要为还原吸附.
关键词:
物理化学
,
改性竹炭
,
银(I)
,
吸附性能参数
,
机理
刘勤
,
夏锄
,
刘晓东
金属学报
在170,190,210,230,250℃的温度下,采用3.7×10~2,7.4×10~2和1.1×10~(-1)min(-1)的应变速率(平均)对Zn-5%Al共晶合金的m-C-δ(或m-k-δ)关系曲线(简称m-δ关系曲线)进行了测定.所有的曲线均随应变的δ增加而快速上升.俟达到某一定的应变量(极限应变量δ1)后。开始缓慢下降并保持平稳直至断裂.Zn-5%A1共晶合金的m-δ关系曲线不存在k_(?)=k_I(k_(I 1),k_(I 2),k_(I 3),……)=k_F(或C_0=C_I(C_(I 1),C_(I 2),C_(I 3),……)=C_F=1)的简单情况.可应用m-δ方程式[4,5]对曲线上各点C值(包括所有的C_I和C_F值)进行计算.C值随δ值的增加成近似的直线上升.直线的斜率在极限应变(δ1)处突然减小.
关键词:
