Maxwell Selase Akple
,
刘敬祥
,
秦志扬
,
S. Wageh
,
Ahmed. A. Al-Ghamdi
,
余家国
,
刘升卫
催化学报
doi:10.1016/S1872-2067(15)60989-5
化石能源的使用可产生大量CO2,带来严重的温室效应。光催化CO2还原生产太阳燃料技术既有望缓解温室效应,又可以将低能量密度的太阳能转化为高能量密度的化学能储存起来方便使用。高效光催化材料的开发是发展光催化技术的关键。迄今,在已开发的所有半导体光催化材料中, TiO2仍是广泛研究的明星材料。在实际使用中, TiO2的光催化效率仍受限于其极弱的可见光利用率和较高的电子-空穴复合几率。近年来,越来越多的研究表明TiO2的结构与形貌特征极大地影响其光催化效率。尤其, TiO2的外露晶面设计与晶面效应研究引起了广泛关注。由于具有较高表面能和较多表面不饱和键,起初大多数理论和实验研究认为锐钛矿TiO2(001)晶面是光催化活性晶面。后来,越来越多研究表明并非锐钛矿TiO2(001)晶面的暴露比例越高其光催化活性就越高。最近,我们发现锐钛矿TiO2(001)晶面与(101)晶面在调控光催化CO2还原性能上具有良好的协同效应。密度泛函理论计算表明,锐钛矿TiO2的(001)晶面与(101)晶面的能带结构有差异,(001)晶面的导带位置相对于(101)晶面而言较高,而(101)晶面的价带位置相对于(001)晶面而言较低。基于此我们提出,具有合适比例的锐钛矿TiO2的(001)晶面与(101)晶面的交界处可以形成最佳的表面异质结或晶面异质结。表面异质结的形成导致光生电子倾向于向(101)扩散,光生空穴倾向于向(001)扩散,从而促进光生电子-空穴分离,降低光生电子-空穴复合几率。在此工作基础上,我们直接以氮化钛为原料,氢氟酸为添加剂,通过简单的水热反应一步合成了氮自掺杂的TiO2微米片。利用X射线粉末衍射、扫描电镜、X射线光电子能谱、紫外-可见漫反射光谱、氮气吸附-脱附以及电化学阻抗谱等方法手段对所制备的光催化剂进行了基本结构与理化性质表征分析,并研究了其可见光光催化CO2还原性能。电镜照片结果表明,我们所制备的氮自掺杂锐钛矿TiO2微米片的(001)晶面与(101)晶面比例分别为65%和35%。基于我们前期研究结果, TiO2微米片的(001)晶面与(101)晶面可以形成表面异质结,具有良好的电荷分离效率,这也得到了电化学阻抗谱研究结果的证明。同时,由于N的原位掺杂,所制备的TiO2微米片具有优异的可见光捕获能力。由于可见光利用效率增强与光生电子-空穴分离效率提高这两方面的综合作用,所制备的氮自掺杂TiO2微米片具有非常好的可见光光催化CO2还原制甲醇性能,比商用P25及氮掺杂TiO2纳米粒子等参考样品的可见光光催化性能更优异。研究表明,通过原位自掺杂方法与晶面设计方法相结合,可以同时改善TiO2的可见光利用效率和光生电子-空穴分离效率,优化TiO2的可见光光催化性能,这也为后续开发新型高效光催化材料提供了新思路。
关键词:
氮自掺杂
,
二氧化钛
,
(001)晶面
,
二氧化碳还原
,
表面异质结
Acta Chimica Sinica
Passive film formed on 304 stainless steel in 2.5 mol/L H2SO4 solution by using alternating voltage (A. V.) passivation have been investigated by measuring capacitance and photoelectrochemical parameters. The investigation of the effect of measure frequency on the slope of Mott-Schottky curve has been carried out. The photoelectrochemical measurements were consistent with the capacitance measurement. Analysis of the experimental results showed that the passive film formed 304 stainless steel by using A. V. passivation exhibits semiconducting properties. Using the simple model of semiconductor rather than the multi-donor level model can explain satisfactorily the semiconducting behavior of the film formed on 304 stainless steel by using A.V. passivation.
关键词:
A. V. passivation;passive film;semiconducting properties;stainless;steel;model;electrodes
Fatigue & Fracture of Engineering Materials & Structures
Fatigue data for welded joints subjected to an explosion treatment (ET) were obtained using rotary bending fatigue specimens. The fatigue fracture surfaces were observed by SEM and the dislocation morphologies by TEM. Mechanical properties have been quantitively studied by considering elastic and plastic shock wave characteristics. The test results indicate that the fatigue strength of welded joints subjected to ET is apparently improved due to the action of elastic or plastic stress waves while the ductility of the welded joints, i.e., reduction in area, is greatly increased.
关键词:
W.H. Tian and M. Nemoto2(Department of Materials Physics
,
University of Science and Technology Beijing
,
Beijing 100083
,
China)(Department of Materials Science and Engineering
,
Faculty of Engineering
,
Kyushu University
,
812
,
Fukuoka
,
Japan)
金属学报(英文版)
Precipitation of Ni2Al in supersaturated NiAl containing Ta and corresponding hardening have been investigated by hardness measurements and by transmission electron microscope observations. Selected area electron diffraction, high resolution electron microscopy and energy dispersive X-ray spectrometer analysis have shown that the Ni2Al with a hexagonal structure precipitates coherently in the B2-NiAl matrix. Ni2Al is an ordered phase with a. unit cell parameter, aNi2All=aNiAl and CNi2Al= aNiAl. The orientation relationship between the Ni2Al precipitate and the B2-NiAl matrix is (0001)Ni2Al (111)NiAl and [1120]Ni2Al[110]NiAl. NiAlhardens appreciably by the precipitation of Ni2Al phase.
关键词:
intermetallic compound
,
null
,
null
,
null
,
null
徐瑞
,
崔玉友
,
李东
,
胡壮麒
,
徐达鸣
,
李庆春
材料研究学报
研究了气体雾化Ti-25Al-10Nb-3V-1Mo(a.%)合金的粉末颗粒特征及快速凝固组织.雾化气体压力大于8MPa时,Ti_3Al基合粉末颗粒圆整,颗粒质量分数与其直径间存在对数正态关系,颗粒表面具有明显的合金结晶特征,其凝固组织具有清晰的二次枝晶,观照冷却速度与二次技晶间距的关系,得到合金的冷却速度为103-105K/s.
关键词:
Ti_3Al基合金
,
rapid solidification
,
microstructure
,
distribution of particle-size
罗宗强
,
张卫文
,
辛保亮
,
李元元
中国有色金属学报
采用中性盐雾加速试验、扫描电镜、X射线衍射仪、光电子能谱仪等研究了Cu-17Ni-3Al-X合金在中性盐雾中的腐蚀行为.结果表明:在中性盐雾腐蚀过程中,该合金具有良好的耐盐雾腐蚀性能,合金的腐蚀速率随腐蚀时间的延长而迅速降低,腐蚀480 h后平均腐蚀速率仅为0.010 mm/a.这是因为腐蚀后合金表面生成一层致密的Cu2O膜,随着腐蚀的进行,Cu2O膜增厚,同时外层的Cu2O膜被进一步氧化生成疏松的Cu2(OH)3Cl颗粒.合金在中性盐雾中腐蚀后,主要是α(Cu)固溶体被腐蚀,合金中的第二相仍残留在晶界处.
关键词:
Cu-Ni合金
,
中性盐雾试验
,
腐蚀速率
,
腐蚀产物膜
,
选择性腐蚀
朱家俊
,
黎三华
,
申镭诺
,
杨武霖
,
李周
中国有色金属学报(英文版)
doi:10.1016/S1003-6326(17)60128-6
设计并制备了一种新型超高强Cu?6.5Ni?1Al?1Si?0.15Mg?0.15Ce合金,采用扫描电镜观察、透射电镜观察、光电子能谱分析等手段研究该合金在3.5%NaCl溶液中的腐蚀行为.合金经固溶、冷轧80%并在450℃时效1 h后具有最佳的综合性能,其硬度为HV 314,导电率为19.4%IACS,抗拉强度为1017 MPa,年平均腐蚀速率为0.028 mm/a.腐蚀初期合金表面形成了氧化腐蚀产物和氯化腐蚀产物,随着腐蚀时间延长形成了氢氧化物腐蚀产物.合金具有超高的强度、优良的导电率和耐腐蚀性能是由于Ni2Si能够抑制晶界处粗大NiAl相的析出,并能抑制合金的脱Ni腐蚀.
关键词:
Cu?Ni?Al?Si合金
,
Ni2Si析出相
,
腐蚀行为
,
年平均腐蚀速率
,
腐蚀产物
Journal of Applied Physics
The structure, magnetic properties, and magnetostriction of arc-melted polycrystalline Sm0.88Dy0.12(Fe1-xMx)(2) (M = Mn, Al, 0 less than or equal to x less than or equal to 0.2) alloys were investigated by microscopy, x-ray diffraction, A. C. initial susceptibility, vibrating sample magnetometry, and standard strain gauge techniques. It was found that the matrix consists almost entirely of the MgCu2-type cubic Laves phase, with a small amount of rare-earth rich phase. The lattice parameter increases approximately linearly with increasing x from 0.740 to 0.750 nm for M = Al. For M = Mn the lattice parameter increases by 0.002 8 nm over the same increase in x. The Curie temperature decreases with increasing x from 670 to 410 and 550 K for M = Al and Mn, respectively. The spontaneous magnetostriction, lambda(111), and polycrystalline magnetostriction, lambda(s), both decrease with increasing Al or Mn substitution for Fe from their initial values of -1452 and -1010 ppm, respectively. Premature disappearance of the splitting of the (440) line and changes in the shape of the magnetostriction curves suggest the substitution of Mn for Fe may produce a change in the anisotropy. No such effects were observed for M = Al. The saturation magnetization, M-S, decreases approximately linearly with increasing substitution of Al or Mn. The changes in the magnetization and magnetostriction can be understood on the basis of a decreasing 3d sublattice moment. (C) 1999 American Institute of Physics. [S0021-8979(99)02409-3].
关键词:
substitution
Acta Materialia
In this paper, the five-layer modulated (5M) martensitic structures of Ni(2)Mn(Al(x)Ga(1-x)), with x = 0, 0.1 and 0.2, are investigated by the use of the exact muffin-tin orbital method in combination with the coherent potential approximation. The 5M martensite is modeled by varying c/a (shear) and wave-like displacements of the atoms on (1 1 0) plane (shuffle) scaled by eta according to Martynov and Kokorin (J. Phys. III 2, 739 (1992)). For Ni(2)MnGa, we obtain 5M martensite with equilibrium c/a of 0.92 and eta of 0.08, in reasonable agreement with the experiment results (0.94 and 0.06, respectively). c/a and eta are linearly coupled to each other. Al-doping increases c/a and decreases eta, but the linear c/a similar to eta coupling remains. Comparing the total energies of the 5M martensite and L2(1) austenite, we find that the martensite is more stable than the austenite. Al-doping increases the relative stability of the austenite and finally becomes energetically degenerated with the 5M martensite at an Al atomic fraction (x) of about 0.26. The relative phase stability is analyzed based on the calculated density of states. The calculated total magnetic moments mu(0) as a function of c/a exhibit a maximum around the equilibrium c/a. Al-doping reduces mu(0) (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
关键词:
Heusler alloy;First-principles calculations;Modulated structure;Martensitic transformation;Shape memory alloys (SMA);ni-mn-ga;magnetic shape-memory;field-induced strain;crystal-structures;heusler alloys;phase-transformation;potential;model;ni2mnga;approximation;transition
