涂学炎
,
王登武
,
陈秀敏
贵金属
doi:10.3969/j.issn.1004-0676.2004.03.004
采用密度泛函理论的广义梯度近似(DFT/GGA),对Run簇(n=2～7)与氧相互作用的几何结构与电子结构及吸附能之间的关系进行讨论.对氧原子及氧分子在Run金属簇上的吸附研究表明:电荷主要是从Ru的5s、4d轨道向O的2p轨道迁移,并使得金属-金属之间的键减弱.比较特殊的是当氧分子在桥位吸附时,Ru与吸附的O2会发生化学反应,并且由于Ru金属轨道的电子向O2的反键πg轨道转移,导致Ru-O之间的键的生成以及O-O之间的键发生断裂.同时,作者也观察到Ru-Ru之间的化学键发生断裂,形成具有原子活性的自由Ru原子,这可以部分解释一旦氧化物种形成,经过一诱导期后,氧化反应会加速进行的实验事实.
关键词:
无机化学
,
氧
,
钌金属簇
,
密度泛函理论
,
布居分析
,
吸附能
WANG Xiao-dong
,
LI Fei
,
JIANG Zheng-yi
钢铁研究学报(英文版)
Non-uniformity of temperature distribution across strip width direction is the ultimate reason why the flatness defect occurs on the strip after cooling process although the strip is flat at the exit of finishing mill. One thermal, microstructural and mechanical coupling analysis model for predicting flatness change of steel strip during the run-out table cooling process was established using ABAQUS finite element software. K Esaka phase transformation kinetics model was employed to calculate the phase transformation, and coupled with temperature calculation using the user subroutine program HETVAL. Elasto-plasticity constitutive equations of steel material, in which conventional elastic and plastic strains, thermal strain, phase transformation strain and transformation induced plastic strain were considered, were derived and programmed in the user subroutine program UMAT. The conclusion that flatness of steel strip will develop to edge wave defect under the functions of the differential thermal and microstructural behaviors across strip width during the run-out table cooling procedure was acquired through the analysis results of this model. Calculation results of this analysis model agree well with the actual measurements and observation.
关键词:
hot rolled strip
,
internal stress
,
phase transformation
,
run-out table cooling
,
flatness
王芳
贵金属
doi:10.3969/j.issn.1004-0676.2007.03.012
采用密度泛函理论中的广义梯度近似(DFT/GGA)方法,对Run团簇(n = 9～26)的几何结构与稳定性、团簇表面的Ru与内部Ru间相互作用进行了研究.结果表明:将金属团簇体系放大后,基态稳定结构的原子平均束缚能Eb随着团簇尺寸的增大而增大,当原子数n = 26时,Eb = -6.69eV,与大块金属的Eb(-6.74eV)接近,表明其已接近大块金属的性质;Ru26的平均间距(R)=2.65(A),与理论值2.70(A)和实验值2.704(A)相近;平均配位数CN随着n值的增大而增大,呈现收敛于块体值的趋势.另外,由于大块金属表面的原子不能与足够的原子配位形成饱和的配位结构,所以其上的电子向内层原子转移,使得内层Ru原子呈负电荷,而外层原子呈正电荷,最终导致内层原子之间的相互作用增强而导致键的收缩,外层原子之间键的减弱,从而出现所谓的"驰豫效应".
关键词:
物理化学
,
密度泛函
,
Ru
,
团簇
,
结构稳定性
,
电子结构
王玮
,
罗明
,
张启富
,
赵吉庆
材料保护
为了给核燃料后处理硝酸体系的设备腐蚀控制提供理论参考,对000Cr25Ni20超低碳奥氏体不锈钢在40%硝酸中,沸腾和非沸腾(接近沸腾温度)条件下进行腐蚀试验.结果表明,Cr6+和Run+都能显著促进超低碳Cr-Ni奥氏体不锈钢发生过钝化腐蚀和晶间腐蚀;在沸腾条件下,腐蚀更加严重,Run+加速腐蚀作用更大,在非沸腾务件下,2种离子加速腐蚀作用相差不大.
关键词:
沸腾
,
非沸腾
,
Cr-Ni奥氏体不锈钢
,
过钝化腐蚀
,
晶间腐蚀
,
硝酸
,
Cr6+
,
Run+
F.T.Cheng
材料科学技术（英）
The present communication addresses an interesting problem related to the indeterminacy in hardness of superelastic NiTi reported by Xu et al. The origin of the indeterminacy is attributed to the inadequacy of the conventional Vickers hardness testing measurement which does not record elastic deformation, and thus the indeterminacy may be removed with suitable techniques. Concepts of hardness in relation to deformation are clarified. Recommendations for measuring the hardness of NiTi and other elastic-plastic materials are suggested, together with comments on the advantages and disadvantages of each of these methods.
关键词:
Hardness
,
null
,
null
,
null
,
null
,
null
中国腐蚀与防护学报
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