沈曾民
,
田艳红
,
常维璞
,
J B Doneet
,
T K Wang
复合材料学报
doi:10.3321/j.issn:1000-3851.2004.01.002
研究了PAN基碳纤维浸渍不同硼化物溶液进行高温热处理后(2500℃)对力学性能的影响.采用扫描隧道显微镜观察了渗硼处理对碳纤维表面微观形态结构的影响,同时还采用X-ray衍射技术分析了渗硼处理对纤维结构参数的影响.结果表明渗硼处理可提高CF的力学性能,采用硼化物A浸渍热处理后CF的模量和强度分别提高了10.3 %和15.3 %.通过STM观察可以很清楚看到渗硼处理可提高CF的择优取向和晶体尺寸,减少表面缺陷.X-ray衍射分析结果与STM一致,渗硼热处理提高了CF的晶体尺寸.
关键词:
碳(石墨)纤维
,
渗硼
,
表面微观结构
,
STM
,
XRD
Physics Letters A
Except for a Peierls transition at T(p) = 180 K, a new transition around T = 270 K in K0.3MoO3 single crystals has been found as evidenced by the anomalies in electrical, magnetic and thermodynamic properties. This transition may be caused by the variation of carrier characteristics or of the charge transfer between cations and anions.
关键词:
Journal of Physics and Chemistry of Solids
Two different potential models to the molecular dynamics (MD) simulations have been applied to investigate the thermoelastic parameter alpha K-T of sodium chloride (NaCl) under high pressure and high temperature. The first one is the shell model (SM) potential that due to the short-range interaction when pairs of ions are moved together as is the case in that polarization of a crystal due to the motion of the positive and negative ions, and the second one is the two-body rigid-ion Born-Mayer-Huggins-Fumi-Tosi (BMHFT) potential with full treatment of long-range Coulomb forces. Particular attention is paid to the comparison of the SM- and BMHFT-MD simulations with the Debye model for the first time, and this model combines with ab initio calculations within local density approximation (LDA) and generalized gradient approximation (GGA) using ultrasoft pseudopotentials and a plane-wave basis in the framework of density functional theory (DFT), and it takes into account the phononic effects within the quasi-harmonic approximation. Note that the MD calculated volumes using SM model is somewhat larger than both the DFT and experimental volumes despite not considering the temperature effect. Compared with SM potential, the MD simulated 300 K isotherm of NaCl with BMHFT potential is very successful in reproducing accurately the measured volumes and the GGA calculated volumes. Generally, it is found that there exist minor differences between the LDA and GGA computed the thermoelastic parameter alpha K-T of NaCI, with both average results giving good agreement with SM-MD simulations. At an extended pressure and temperature ranges, the variation of thermoelastic parameter alpha K-T which play a central role in the formulation of approximate equations of state has also been predicted. The properties of NaCl are summarized in the pressure range of 0-300 kbar and the temperature up to 2000 K. (C) 2012 Elsevier Ltd. All rights reserved.
关键词:
Inorganic compounds;ab initio calculations;High pressure;Thermodynamic properties;molecular-dynamics simulation;density-functional theory;equation-of-state;alkali-halides;thermodynamic properties;elevated-temperatures;thermal expansivity;bulk modulus;ionic solids;nacl
B.H. Kim N.H. Kang W.T. Oh C.H. Kim J.H. Kim Y.S. Kim Y.H. Park
材料科学技术（英文）
For Al 6k21-T4 overlap weld joint, the shear-tensile strength by using the weaving laser was improved as compared to the case of linear laser. For the specimen of low strength, the porosity was distributed continuously along the intersection between the plates and fusion line. However, for the optimized welding condition, large oval-shaped porosities were located only in the advancing track of the concave part. Therefore, the continuity of cracks and porosities played a key role to determine the strength. And, the weaving width was also the important parameter to control the strength. Furthermore, the concave part had more significant hot and cold cracking in the weld and heat-affected zone (HAZ), respectively, than the convex part.
关键词:
Weaving laser
,
Weld microstructure
,
Void
,
Al alloy
B.H. Kim N.H. Kang W.T. Oh C.H. Kim J.H. Kim Y.S. Kim Y.H. Park
材料科学技术（英文）
For Al 6k21-T4 overlap weld joint, the shear-tensile strength by using the weaving laser was improved as compared to the case of linear laser. For the specimen of low strength, the porosity was distributed continuously along the intersection between the plates and fusion line. However, for the optimized welding condition, large oval-shaped porosities were located only in the advancing track of the concave part. Therefore, the continuity of cracks and porosities played a key role to determine the strength. And, the weaving width was also the important parameter to control the strength. Furthermore, the concave part had more significant hot and cold cracking in the weld and heat-affected zone (HAZ), respectively, than the convex part.
关键词:
Weaving laser
,
Weld microstructure
,
Void
,
Al alloy
Physica C-Superconductivity and Its Applications
Superconducting cuprate fluorides Nd0.7Sr1.3Cu(O,F)(4-delta) with T-c = 44 K were obtained by solid phase fluorination of the T-structure Nd0.7Sr1.3CuO4-gamma at low temperature (200-300 degrees C) using CuF2 as fluorinating reagent. The oxyfluoride has K2NiF4 structure with S.G. I4/mmm as its precursors, but the evident lattice expansions were observed. The a-axis expands from 3.7257(2) Angstrom to 3.9288(5) Angstrom and c-axis from 12.8240(3) Angstrom to 12.9630(2) Angstrom. No trace of SrF2 was detected in these fluorinated products. XRD and magnetic measurement revealed that the superconductivity in the fluorinated products originated from the oxyfluorides with reduced CuO2 plane and in the presence of the apical anion.
关键词:
hole concentration;copper;route;a=ca;tc
张健
,
张罡
,
毕鉴智
,
李玉海
,
姚俊
腐蚀学报（英文）
TIA－450自绝缘二极管碳离子加速器对T5K10刀具进行了强流脉冲离子束辐照表面处理，加速器的加速电压为250 keV,束流密度为60 A/cm2～150 A/cm2, 脉冲时间为80纳秒，脉冲次数为2次.XRD、SEM、EDS以及显微硬度分析研究结果表明：当束流密度达到100 A/cm2，材料表面为完全熔化凝固组织；当束流密度达到150 A/cm2时，表面层下也出现熔化凝固组织；熔化凝固组织没有明显相变.在100 A/cm2～150 A/cm2内，同未辐照表面相比，显微硬度提高1.25倍.硬度增加的主要原因是表面快速凝固组织产生硬化相和基体相中化学成分的重新分布、碳元素的烧损以及晶界的强化.
关键词:
离子束
,
null
,
null
张健
,
张罡
,
毕鉴智
,
李玉海
,
姚俊
腐蚀学报（英文）
doi:10.3969/j.issn.1002-6495.2005.03.008
采用TIA-450自绝缘二极管碳离子加速器对T5K10刀具进行了强流脉冲离子束辐照表面处理,加速器的加速电压为250 keV,束流密度为60 A/cm2～150 A/cm2,脉冲时间为80纳秒,脉冲次数为2次.XRD、SEM、EDS以及显微硬度分析研究结果表明:当束流密度达到100 A/cm2,材料表面为完全熔化凝固组织;当束流密度达到150 A/cm2时,表面层下也出现熔化凝固组织;熔化凝固组织没有明显相变.在100 A/cm2～150 A/cm2内,同未辐照表面相比,显微硬度提高1.25倍.硬度增加的主要原因是表面快速凝固组织产生硬化相和基体相中化学成分的重新分布、碳元素的烧损以及晶界的强化.
关键词:
强流脉冲离子束
,
碳离子加速器
,
表面改性
牟淑坤
,
栗卓新
,
张飞虎
,
陈延清
,
章军
,
刘宏
机械工程材料
采用不同的热输入(12.98,15.88,18.47,20.37,22.59 kJ·cm-1)、用E81T1-K2药芯焊丝对FH36船用钢板进行焊接,研究了热输入对熔敷金属显微组织和-60℃低温冲击韧性的影响.结果表明:熔敷金属的-60℃低温冲击韧性随着热输入的增加而呈现先升高后降低的变化趋势,当热输入为18.47kJ·cm-1时达到最大值79 J;随热输入的增加,晶界铁素体和侧板条铁素体的面积分数均先减小后增加,针状铁素体的面积分数先增加后减小,并在热输入为18.47kJ·cm-1时达到最大,为85.2％.
关键词:
热输入
,
药芯焊丝
,
冲击韧性
