First‐principles study of metal/nitride polar interfaces: Ti/TiN

We have examined the optimal interface structure, ideal work of adhesion and bonding character of polar Ti(110)/TiN(111) interfaces by first‐principles density‐functional plane‐wave pseudopotential calculations. Both Ti‐ and N‐terminated interfaces, including six different interface structures, were calculated. The interface structure for each termination, continuing the TiN crystal structure across the interface, has the largest work of adhesion. Although both terminations yield substantial adhesion energies in the range 3–7 J m^?2, the N‐terminated interface is ～4 J m^?2 stronger than the Ti‐terminated interface. Analysis of the interfacial electronic structure shows that the Ti‐terminated interface is a mixed strong, metallic and weak covalent character, whereas the N‐terminated interface is a polar covalent bond similar to the Ti/TiC interface. Further study of the separation of the optimal interface shows that the cleavages will never fracture at the interface due to the strong bonding, which is consistent with the experimental results. Copyright © 2003 John Wiley & Sons, Ltd.     

First‐principles study of the TiN(111)/ZrN(111) interface

The TiN(111)/ZrN(111) interface was studied by first‐principles method to provide the theoretical basis for developing the TiN/ZrN coatings. Twelve geometry structures of TiN(111)/ZrN(111) interfaces were established. The calculated interfacial work of adhesion reveals that the N‐terminated TiN/N‐terminated ZrN interface with TL site shows the strongest stability. For this TiN(111)/ZrN(111) interface, the results of the partial density of state indicate that the chemical bonding at the interface appeals both ionic and covalent characteristic, which is same as that in the bulk materials. The partial density of states for Zr, Ti, and N atoms at the interface are very similar with those in the bulk, which reveals that the electronic structure transition at the interface is smooth. The results of charge density and charge density difference demonstrate that the lost charge of Ti atom is larger than that of Zr atom, indicating that TiN is more ionic than ZrN. Calculations of the work of fracture indicate that the mechanical failure of the ZrN(111)/TiN(111) interface will take place at the interface. Besides that, the calculation result of the TiN(111)/ZrN(111) interface implies that the TiZrN₂ phase might be formed at the interface because the contacting of the N―N bond is the most stable.     

N-K electron energy-loss near-edge structures for TiN/VN layers: an ab initio and experimental study

We study N-K-edge electron energy-loss near-edge structures for well-defined TiN/VN bilayers grown on a MgO(100) substrate by both calculations and experiments. The structural relaxations and the electronic structure of TiN/VN multilayers are calculated using the Vienna Ab Initio Simulation Package computer code, which uses density functional theory to describe the electronic interaction. The effects of the core hole created in the excitation process are included in the calculations. For VN, off-stoichiometric effects due to nitrogen vacancies are modelled. The partial density of states (PDOS) for the N-K edge of atoms in the vicinity of the TiN/MgO interface revealed that two new peaks appear between 7 and 9 eV instead of a broad shoulder typical for the bulk. For the VN/TiN interface, the PDOS is modified only slightly, owing to similar bonding on both sides of the interface, and is thus very similar to the respective bulk spectra. An experimental spectrum taken at the VN/TiN interface is, however, well described by an average of the simulated spectra for VN and TiN bulk (interface). Such a finding is characteristic of an intermixed interface.      

Atomic configuration,electronic structure,and work of adhesion of TiN(111)//B2-NiTi(110) and TiN(111)//B19′-NiTi(010) interfaces: Insights from first-principles simulations

In this paper, the atomic configuration, electronic structure, and work of adhesion for TiN(111)//B2-NiTi(110) and TiN(111)//B19′-NiTi(010) interfaces were investigated by first-principles calculations based on density functional theory (DFT), which aim to provide a theoretical guidance for analyzing the service reliability of TiN films modified NiTi alloy devices. The results of this paper indicated that a hollow-site stacking structure was formed on the interface when Ti and N were the terminal atoms on two sides. Such interfaces demonstrated a stronger bonding performance and a more stable structure than that with Ni and Ti as the terminal atoms. The work of adhesion of the TiN(111)//B19′-NiTi(010) interface was 17.47 J/m², which is greater than the work of fracture of TiN(111) (6.73 J/m²), whereas the work of adhesion of the TiN(111)//B2-NiTi(110) interface was found to reach 5.49 J/m², which is lower than the work of fracture of TiN(111). The models of the work of adhesion between the two interfaces indicate that there are significant bond strength changes in the TiN/NiTi interface, when the NiTi substrate undergoes martensitic transformation. The results of this paper contribute significantly to the service reliability analysis of TiN films coated on NiTi alloy devices.     

Characterization of the interfacial structure and perpendicular magnetic anisotropy in CoFeB‐MgO structures with different buffer layers

In this study, we describe the deposition of Hf and Mo metal layers individually on Ta to compose new buffer layers, ie, Ta/Hf and Ta/Mo, where CoFeB/MgO stacks are deposited using magnetron sputtering. The synthesised Ta/Hf buffer has higher surface roughness, while the Ta/Mo buffer has lower surface roughness as compared with the Ta buffer. The surface roughness of the buffer appears to influence the interface of the subsequently deposited layers, resulting in rougher or smoother CoFeB/MgO interfaces. Additionally, we present a report on the magnetic properties of Ta, Ta/Hf, and Ta/Mo buffer samples. As the annealing temperature is below 200 °C, the saturation magnetisation (Ms) values for all buffer layers increase at similar rates, whereas the effective magnetic anisotropy energy (K_eff) values increase at varying rates. After annealing at 350 °C, K_eff reaches its maximum value for Ta/Hf and Ta/Mo buffer layers, whereas the CoFeB/MgO interface width decreases to a minimum value. The width increases as the annealing temperature is increased over 350 °C, and K_eff gradually decreases with increase in the annealing temperature. The CoFeB/MgO interface width is primarily dependent on the buffer/CoFeB interface width, which is a critical parameter to obtain high perpendicular magnetic anisotropy (PMA) and high‐quality films. This work provides perspectives for understanding and controlling PMA from the viewpoint of interfacial structure.     

Sacrificial adhesion promotion layers for copper metallization of device structures

The adhesion of copper films to adjacent device layers including TiN, Ta, and TaN diffusion barriers is a crucial reliability issue for integrated circuits. We report that ultrathin layers of poly(acrylic acid) (PAA) prepared on barrier surfaces or on the native oxide of Si wafers dramatically increase the interfacial adhesion of Cu films deposited by the H2 assisted reduction of bis(2,2,7-trimethyloctane-3,5-dionato)copper in supercritical carbon dioxide. Similar improvements were achieved on Si wafers using a simple vapor phase exposure of the substrate to acrylic acid prior to metallization. The deposited films and the substrate/Cu interfaces were analyzed by X-ray photoelectron spectroscopy (XPS), electron microscopy, atomic force microscopy, and variable-angle spectroscopic ellipsometry. No trace of the adhesion layer was detected at the interface, indicating it was sacrificial at the deposition conditions used. Moreover, the presence and subsequent decomposition of the PAA layer during deposition substantially reduced or eliminated metal oxides at the substrate interface. For depositions on PAA-treated Si wafers, copper was present primarily as Cu0 at the interface and Si was present only as Si0. On PAA-treated Ta substrates, XPS analysis indicated Ta was present primarily as Ta0 at the metallized interface whereas Ta2O5 dominated the interface of samples prepared without the adhesion layers. The technique can be extended to patterned substrates using adsorption of acrylic acid or thermal/UV polymerization of acrylic acid.     

The band structures of some transition metals and their NaCl-type compounds

The band structures of Group IVB (Ti,Zr,Hf),VB (V,Nb,Ta) and VIB (Cr,Mo,W) transition metals and some of their carbides and nitrides (TiN,ZrN,HfN,VC,NbC,TaC,VN,NbN,TaN) with NaCl-type (Bl-type) structure have been calculated by using the tight-binding method within the Extended Hiickel approximation (EHT).The energy bands,densities of states and crystal orbital overlap populations are given.The relationship between the bonding properties and the superconducting transition temperatures (Tc) of them is discussed.The influences of various kinds of metallic atoms and changes of bond lengths on Tc are also discussed.     

Carbon‐Coated and Interfacial‐Functionalized Mixed‐Phase MoxTi1−xO2‐δ Nanotubes as Highly Active and Durable PtRu Catalyst Support for Methanol Electrooxidation

A synchronous carbon‐coating and interfacial‐functionalizing approach is proposed for the fabrication of Mo‐doped Mo_xTi_1?xO_2‐δ nanotubes (C@IF‐MTNTs) under mild hydrothermal reaction with subsequent annealing as advanced catalyst supports for PtRu nanoparticles (NPs) towards methanol electrooxidation. The carbonation of glucose and Mo‐doping takes place simultaneously at the interface of pristine anatase TiO₂ nanotubes (TNTs), generating a unique concentric multilayered one‐dimensional (1D) structure with crystalline an anatase/rutile mixed‐phase TiO₂ core and Mo‐functionalized interface and subsequently a carbon shell. The obtained PtRu/C@IF‐MTNTs catalyst exhibits an over 2 times higher mass activity with comparable durability than that of the unmodified PtRu/C@TNTs catalyst and over 1.7 times higher mass activity with over 20 % higher stability than that of PtRu/C catalyst. Such superior catalytic performance towards methanol electrooxidation is ascribed to the Mo‐functionalized interface, concentric multilayered 1D architecture, and anatase/rutile mixed‐phase core, which facilitates the charge transport through 1D structural support and electronic interaction between C@IF‐MTNTs and ultrafine PtRu NPs. This work reveals the critical application of a 1D interfacial functionalized architecture for advanced energy storage and conversion.     

多弧离子镀TiN与不同金属基材间的接触界面与表面特性

用多弧离子镀技术在不同金属基材上进行TiN镀膜实验,制备了TiN/Fe、 TiN/Cu和TiN/Cr/Cu复合膜.借助扫描电子显微镜(SEM)、 X射线衍射仪(XRD)和光电子能谱(XPS),研究了TiN与Fe、 Cu和Cr/Cu三种不同衬底接触界面的形貌、结构及其表面特性.SEM观察发现,在一定离子镀膜条件下, TiN涂层可与Fe、 Cu和Cr/Cu金属基材形成均匀平整的接触界面,在铜基上TiN界面清晰,在Fe与Cr/Cu界面有明显的层状晶界微结晶分布.XRD分析显示, Fe、 Cu和Cr/Cu表面生成的薄膜都包含TiN、 Ti2N等多晶相,在Cr/Cu界面还包含Ti-Cr的金属间化合物.XPS结果表明,表面除了TiN膜外,还生成TiO2和TiOxNy等氧化膜.Ar+刻蚀5 min后, TiO2消失, TiOxNy减少, TiN则呈增加趋势.TiN与Cr/Cu界面形成明显的Ti-Cr和Cr-Ni互扩散层,这有助于增强薄膜附着力,形成较牢固的TiN涂层.     

Electronic Structure of TiAl-2M(M=V,Nb,Ta,Cr,Mo,W,Mn) Alloy

1INTRODUCTIONTitaniumaluminidesbasedonY-TiAlarereceivingconsiderableattentionaspo-tentialcandidatesformaterialsinhightemperatureaerospaceapplication.Theirlowdensity,hightemperaturescreepresistance,highoxidationresistanceandstrengthmakesthemexcellentpotentialenginematerials.Howevertheirlowductilityandlowfracturetoughnessatroom'temperaturesaremajorhindrancestotheirpracticaluti-lization.TheTiAlalloymayhaveanelongationabout2%t'},furtherimprovementisnecessarybeforethesematerialscouldbeusedin…     

A first-principles study of ultrathin nanofilms of MgO-supported TiN

As a first step towards a microscopic understanding of supported ultrathin nanofilms of TiN, we present state-of-the-art density-functional theory (DFT) calculations to investigate the interfacial properties of the TiN/MgO system as a function of film thickness. Optimized atomic geometries, energetics, and analysis of the electronic structure of the TiN/MgO systems are reported. In particular, we find that the work function of 1 ML of TiN(100) on MgO(100) exhibits a significant decrease, rationalized by the large surface dipole moment formation due to the changes in charge densities at the interface of this system. This decrease in the work function of TiN/MgO systems (as compared to pristine MgO(100) surface) could well benefit their application in metal-oxide-semiconductor devices as an ideal gate-stack material.     

Electroless Formation of Hybrid Lithium Anodes for Fast Interfacial Ion Transport

Rechargeable batteries based on metallic anodes are of interest for fundamental and application‐focused studies of chemical and physical kinetics of liquids at solid interfaces. Approaches that allow facile creation of uniform coatings on these metals to prevent physical contact with liquid electrolytes, while enabling fast ion transport, are essential to address chemical instability of the anodes. Here, we report a simple electroless ion‐exchange chemistry for creating coatings of indium on lithium. By means of joint density functional theory and interfacial characterization experiments, we show that In coatings stabilize Li by multiple processes, including exceptionally fast surface diffusion of lithium ions and high chemical resistance to liquid electrolytes. Indium coatings also undergo reversible alloying reactions with lithium ions, facilitating design of high‐capacity hybrid In‐Li anodes that use both alloying and plating approaches for charge storage. By means of direct visualization, we further show that the coatings enable remarkably compact and uniform electrodeposition. The resultant In‐Li anodes are shown to exhibit minimal capacity fade in extended galvanostatic cycling when paired with commercial‐grade cathodes.     

Nature of adhesion of condensed organic films on platinum by first-principles simulations

Understanding the nature of the adhesion of an organic liquid on a metal surface is of paramount importance for elucidating the stability and chemical reactivity at these complex interfaces. However, to date, the morphology, layering and chemical properties at organic liquid metal interfaces have been rarely known. Using semi-empirical dispersion corrected density functional theory calculations and ab initio molecular dynamics simulations, we show that carbon tetrachloride and ethanol films confined to a platinum surface alter their intrinsic properties and exhibit interfacial reactivity. A few interface carbon tetrachloride (ethanol) molecules adsorb dissociatively (molecularly) on platinum thanks to the surrounding medium. The adsorption strength of the interfacial molecules is consequently increased in the condensed phase as compared to the gas phase. This remarkable effect is rationalized by an interaction energy decomposition model and an electrostatic potential analysis.     

Formation of interfacial microstructures of Mo‐coating modified SiCf/Mo/Ti‐6Al‐4V composites

This paper addresses the role of Mo coating to modify the interface of SiC fiber reinforced Ti‐6Al‐4V composite (SiC_f/Mo/Ti‐6Al‐4V). The formation of microstructure as well as the diffusion of elements in the interface of as‐prepared and heat‐treated SiC_f/Mo/Ti‐6Al‐4V composites was investigated. The results show that the phases formed at the interfacial zone are: Mo coating∣TiC∣Mo + β‐Ti∣β‐Ti∣β‐Ti + α‐Ti_strip, ordering from fiber to matrix. Mo coating can effectively hinder the diffusion of elements between the matrix and fiber to some extent, thus it can inhibit fiber/matrix interfacial reaction and protect the fiber from damage. It is believed that the β‐Ti layer formed around the interface can improve the formability of composites. Furthermore, it indicates that Mo coating exhibits excellent thermal stability bellow 700 °C according to the heat treatment of the composites at 700 °C for up to 200 h. Copyright © 2012 John Wiley & Sons, Ltd.     

Ab initio calculation of the adhesion and ideal shear strength of planar diamond interfaces with different atomic structure and hydrogen coverage

We propose a method to calculate the ideal shear strength τ of two surfaces in contact by ab initio calculations. This quantity and the work of adhesion γ are the interfacial parameters usually derived from tip-based friction force measurements. We consider diamond interfaces and quantitatively evaluate the effects of surface orientation and passivation. We find that in the case of fully passivated interfaces, γ is not affected by the orientation and the alignment of the surfaces in contact. On the contrary, τ does show a dependence on the atomic-scale roughness of the interface. The surface termination has a major impact on the tribological properties of diamond. The presence of dangling bonds, even at concentrations low enough to prevent the formation of interfacial C-C bonds, causes an increase in the resistance to sliding by 2 orders of magnitude with respect to the fully hydrogenated case. We discuss our findings in relation to experimental observations.     

伊敏褐煤中微量元素的地球化学特征及其无机-有机亲和性分析

采用脱矿物质、提取腐殖酸等方法结合ICP-MS对伊敏15_上、16_下煤中的32种微量元素的含量及其赋存特征进行了分析。与地壳克拉克值及中国侏罗-白垩纪煤和世界褐煤中微量元素含量相比,伊敏褐煤中微量元素没有明显富集。脱矿物质处理后,Ni明显富集,As略比原煤高,其他微量元素都低于原煤。原煤提取腐殖酸和脱矿物煤提取腐殖酸中Ni、Mo、Cd、Sn、W明显富集,这表明Ni、Mo、Cd、Sn、W和腐殖酸形成了稳定的有机态化合物。原煤提取腐殖酸残煤和脱矿物煤提取腐殖酸残煤中V、Ni、As富集,表明V、Ni、As与煤的大分子结构形成了稳定的有机态化合物。根据微量元素和灰分的相关性系数,把微量元素分为以下几类:无机富集元素Cr、U;亲无机元素Cu、Cd、In、Sn、Ga、Y、Zr、Hf、Bi、Th;偏无机元素Be、Sc、Rb、Sr、Nb、Cs、Ta、Pb;偏有机元素V、As、Tl、Ba、Se;亲有机元素Li、Co、W;有机富集元素Ni、Zn、Mo、Sb。     

Electrochemical characteristics and interfacial contact resistance of Ni-P/TiN/PTFE coatings on Ti bipolar plates

The Ni-P/TiN/PTFE (poly tetra fluoroethylene) composite coatings were prepared by electroless plating method on Ti plate, which was used as bipolar plates of proton exchange membrane fuel cells (PEMFCs). The morphology, crystallographic texture, electrochemical corrosion, contact resistance, and hydrophobic property of the Ti bipolar plates with coatings were investigated. The results revealed that Ni-P/TiN/PTFE coating had a dense surface morphology, uniform distribution of composite particles. Ti with coating showed 0.48 μA cm² of corrosion current in the simulated solution of PEMFCs and 6 mΩ cm² of interfacial contact resistance (ICR). The hydrophobicity test showed that the coating interface was flat and the wetting angle was 112.4°. In conclusion, The Ni-P/TiN/PTFE composite coatings exhibit superior improvement in corrosion resistance, interface hydrophobicity, and conductivity to Ni-P, Ni-P/TiN, and Ni-P/PTFE coatings. The Ni-P/TiN/PTFE coating was suited for bipolar plate surface modification of bipolar plates.     

Preparation of nanostructured Co–Mo alloy electrodes and investigation of their electrocatalytic activity for hydrazine oxidation in alkaline medium

Cobalt and cobalt–molybdenum alloy electrodes are prepared by galvanic deposition on copper substrates. In this paper, we report a study on the influence of alloying cobalt with molybdenum for the oxidation of hydrazine in 1 M NaOH aqueous solutions. The electrocatalytic properties of the electrodes are studied by cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS). Scanning electron microscopy (SEM), X‐ray diffraction (XRD), energy‐dispersive X‐ray spectroscopy (EDS,) and inductively coupled plasma (ICP) analysis demonstrate that the structural features and compositions of the as‐prepared Co–Mo coatings vary with the deposition conditions. Electrochemical characterization indicates that the electrochemical properties and the electrocatalytic activity of the investigated alloys were strongly dependent on the microstructural features obtained under different deposition conditions. The overall experimental data indicate that alloying cobalt with molybdenum metal leads to an increase of the electrocatalytic activity in hydrazine electroxidation compared to when using the pure cobalt electrode. High catalytic efficiencies were achieved on Co/25 at.% Mo and Co/33 at.% Mo electrodes, the latter being the best electrocatalyst for hydrazine electroxidation.