Molecular Physics
The ab initio method based on density functional theory at the B3PW91 level has been applied to study the geometric, electronic, and magnetic properties of neutral and anionic Au(n)Pd (n = 1-9) clusters. The results show that the most stable geometric structures adopt a three-dimensional structure for neutral Au(7)Pd and Au(8)Pd clusters, but for anionic clusters, no three-dimensional lowest-energy structures were obtained. The relative stabilities of neutral and anionic Au(n)Pd clusters were analysed by means of the dependent relationships between the binding energies per atom, the dissociation energies, the second-order difference of energies, the HOMO-LUMO energy gaps and the cluster size n, and a local odd-even alternation phenomenon was found. Natural population analysis indicates the sequential transfer from the Pd atom to the Au(n) frame in Au(1,2,3,5)Pd and Au(2,3)Pd(-) clusters, and from the Au(n) frame to the Pd atom in other clusters. Much to our surprise, irrespective of whether it is the total magnetic moment or the local magnetic moment, the magnetic moment presents an odd-even alternation phenomenon as a function of the cluster size n. The magnetic effects are mainly localized on the various atoms (Au or Pd) for different cluster size n.
关键词:
neutral and anionic Au(n)Pd clusters;geometrical configuration;density;function method;generalized gradient approximation;photoelectron-spectroscopy;palladium clusters;gold nanoclusters;metal-clusters;exchange;nanoparticles;molecules;chemistry;au-n(-)
Surface & Coatings Technology
Ti-B-N coatings were deposited on W18Cr4V high speed steels by using EB-ion plating with different boron contents. The chemical compositions of the coating are Ti, B and N. It was found that Ti, B and N in the coating are homogeneous, but there exists a diffusion zone at the coating/substrate interface on the basis of the results of ion probe microanalysis and Auger electron spectrometry. The boron content of the coating is 3-16 at.% given by nuclear reaction analysis. The ratio of nitrogen to titanium of the coating is about 1 given by electron probe microanalysis. The microhardness (HV) of the coating is 35-45 GPa (load of 0.25 N). The critical load of the coating using the scratch test is 12-14 N. The sliding friction coefficient of the coating on diamond stylus is 0.086-0.097 (load of 8.8 N). X-ray diffraction measurement shows that the coating consists of f.c.c. TiN, simple orthorhombic TiB, cubic BN and simple hexagonal Ti-B-N phases. As expected, the higher the boron content, the higher the content of cubic BN and TiB phases; and the higher the microhardness, the lower the adhesion.
关键词:
composition;property;EB-ion plating;Ti-B-N coating;tribological properties;hard coatings;behavior;film;gas
贾素秋
,
于淑敏
,
李军
,
雷军
电镀与涂饰
doi:10.3969/j.issn.1004-227X.2007.06.001
将Si3N4纳米粒子加入电镀镍的基础镀液中,在碳钢上制备了Ni-Si3N4复合镀层.扫描电镜观察表明,复合镀层的表面晶粒细小致密.能谱分析结果表明,镀层表面以Ni元素为主,且含有少量的Si和N.随着镀液中纳米Si3N4粒子含量的增加,镀层的显微硬度升高.热震法和划痕法实验表明,镀层与基体结合良好.
关键词:
Ni-Si3N4复合镀层
,
电沉积
,
形貌
,
显微硬度
Journal of Physical Chemistry C
The Li-Mg-N-H system was prepared by reacting magnesium amide [Mg(NH(2))(2)] with lithium nitride (Li(3)N) and investigated with regard to the hydrogen storage properties. Our study shows that the present method is superior to the conventional route in enhancing the reversible dehydrogenation properties. Through optimizing the Li(3)N:Mg(NH(2))(2) ratio in the starting materials, the reversible capacity of U-Mg-N-H system increases to 4.9 wt %, 18% higher than that typically obtained from the Mg(NH(2))(2) + 2LiH mixture at 200 degrees C. Furthermore, increasing the Li(3)N:Mg(NH(2))(2) ratio is effective for mitigating the ammonia release from thus-prepared samples. Combined property/structure investigations indicate that the obtained enhancements should be ascribed to the effects of LiNH(2) and LiH that were in situ generated from the excess Li(3)N. LiNH(2) may promote the dehydrogenation reaction via seeding the reaction intermediate. The concurrently generated LiH acts as an effective ammonia trapping agent. These findings highlight the potential of "intermediate seeding" as a strategy to enhance the reversible hydrogen storage properties of metal-N-H systems.
关键词:
complex hydrides;ultrafast reaction;amide;improvement;desorption;linh2;destabilization;mechanism;mixtures;imides
吕会敏
,
张钧
材料研究学报
采用多弧离子镀技术和Ti-Al合金靶及Zr单质靶的组合,在高速钢基体上制备了(Ti,Al,Zr)N多元N梯度硬质反应膜.分别用扫描电镜、X射线衍射仪观察测定(Ti,Al,Zr)N梯度膜膜层的表面、断面形貌、成分以及相结构,研究了(Ti,Al,Zr)N多元氮梯度硬质反应膜的组织结构和性能.结果表明,与TiN、(Ti,Al)N、(Ti,Zr)N及(Ti,Al,Zr)N等单层硬质膜相比,采用Ti-Al合金靶及单质Zr靶组合方式制备的(Ti,Al,Zr)N多元氮梯度硬质反应膜具有较高的硬度和膜/基附着力,硬度最高可达HV6000,膜/基附着力大于180 N.同时,膜层还具有良好的抗热震性能.
关键词:
材料表面与界面
,
(Ti,Al,Zr)N膜
,
多弧离子镀
,
显微硬度
,
热震
Surface & Coatings Technology
Cr-N coatings were deposited on 1Cr18Ni9Ti stainless steel in the pure N(2) atmosphere by arc ion plating (AIP). The relationships between deposition parameters and coating properties were investigated. X-ray diffraction showed a phase transformation from CrN+Cr(2)N+Cr-->CrN+Cr-->CrN and the CrN preferred orientation changed from (200) to (220) as N(2) pressure increased. Increasing bias voltage led to CrN preferred orientation changed from (200) to (220) and the formation of Cr(2)N. XPS results indicated that chemical composition of the coatings changed as N(2) pressure increased but it changed little with bias voltage. The lower melting point of chromium nitride formed on target surface induced the increase of macroparticles and deposition rate with increasing N(2) pressure; and bias voltage had an obvious effect on reducing macroparticles of the Cr-N coatings. Residual stresses were measured by substrate curvature technique, and the changing tendency coincided with the microhardness of the coatings. (C) 2009 Elsevier B.V. All rights reserved.
关键词:
Arc ion plating;Cr-N coating;Nitrogen pressure;Pulse bias voltage;chromium nitride films;thin-films;cathodic vacuum;tin;behavior;stress;macroparticles;evaporation;plasma;charge
崔新
,
刘栋
,
邓建平
,
杨万泰
高分子材料科学与工程
通过与手性单体共聚，可调控基于非手性单体所制备的螺旋聚合物的光学活性。文中利用[Rh]金属有机催化剂，进行了手性（M1）和非手性（M2）N．炔丙基酰胺单体的共聚反应，聚合物产率高于97％。利用圆二色光谱技术及旋光仪对共聚物的光学活性进行了表征，发现共聚物组成对其光学活性有显著影响，不仅影响共聚物光学活性的大小，甚至还决定看聚合物主链所形成螺旋结构的手性。
关键词:
光学活性
,
螺旋聚合物
,
共聚物组成
张理元
,
刘钟馨
,
于晓龙
,
吕作凤
,
曹阳
钛工业进展
doi:10.3969/j.issn.1009-9964.2010.04.005
采用阳极氧化法在纯钛表面制备了二氧化钛纳米管,并在热处理的过程中提供氨气氛进行掺N.场发射扫描电镜(FESEM)观察结果表明,制得的纳米管管径为70～80 nm,壁厚为5～10 nm;XRD分析结果表明,400℃热处理的未掺杂二氧化钛为纯锐钛矿相,400℃热处理掺杂后的二氧化钛为锐钛矿和金红石混相.以甲基橙为参考污染物,采用分光光度计研究了未掺杂和N掺杂二氧化钛纳米管对污染物的光催化性能.结果显示N掺杂的二氧化钛纳米管的光催化性能比未掺杂的提高了11.1%,光催化效果差异是N掺杂引起的.
关键词:
阳极氧化
,
二氧化钛纳米管
,
N掺杂
,
光催化
