Zr(0001)表面氢吸附机理的第一性原理研究

利用基于密度泛函理论的第一性原理,采用平面波赝势方法,研究了H₂分子在Zr(0001)晶面的表面吸附。通过研究Zr(0001)/H₂体系的吸附能、稳定吸附构型和电子结构,阐明了Zr(0001)表面吸氢反应的微观机制。结果表明：H₂分子在Zr(0001)表面的最稳定吸附位为面心立方(fcc)位,其吸附能为0.899eV,解离的H原子最终稳定吸附在Zr(0001)表面的穴(hollow)位和面心立方(fcc)位。被吸附H原子与Zr(0001)表面间出现了大量的电荷转移,同时,H原子的1s轨道和Zr原子的5s、4d轨道出现杂化,表明H₂分子解离吸附后H原子与表层Zr原子间同时存在离子键和共价键。此外,研究了覆盖度对吸附能的影响,吸附能随覆盖度的增大而增大,当覆盖度达到4/5ML时,氢分子解离后有一半的氢原子吸附到Zr(0001)的亚表面。     

铂铱合金与316L不锈钢微激光点焊气孔形成机理

采用第一性原理方法研究了H2分子在Li2NH (110) 晶面的表面吸附。通过研究Li2NH (110)/H2体系的吸附位置、吸附能和电子结构,发现H2分子吸附在Li长桥位时会发生解离,并在Li2NH (110) 面形成NH2基,其吸附能为1.178 eV,属于强化学吸附,吸附最稳定。此时,NH2基中的H原子与Li2NH表面的相互作用主要源于H 1s轨道与Li2NH表层N原子的2s,2p轨道重叠杂化的贡献,且N–H键为共价键;另一个H原子与Li2NH表面的相互作用主要是与Li之间的离子键作用;H2分子的解离能垒为1.31 eV,表明在一定热激活条件下H2分子在Li2NH (110)表面发生解离吸附。N顶位吸附时,优化结束后形成NH3,但该吸附方式不稳定,可见Li2NH (110)面与H2反应不易直接生成NH3。     

Effect of NbN and ZrN films formed by magnetron sputtering on Ti and porcelain bonding

Niobium nitride (NbN) and zirconium nitride (ZrN) were deposited on Ti substrates by direct-current (DC) reactive magnetron sputtering; the deposited NbN and ZrN films served as intermediate layers of a Ti and porcelain interface. X-ray diffraction (XRD) results proved that the deposited NbN and ZrN films were polycrystalline with a cubic microstructure. The Ti and porcelain bonding strength of the samples in Group Control (27.2 ± 0.75 MPa), Group NbN (43.1 ± 0.59 MPa), and Group ZrN (52.4 ± 0.80 MPa) were measured. The surface roughness in the case of Group Control (1.863 ± 0.10 μm), Group NbN (2.343 ± 0.07 μm), and Group ZrN (2.346 ± 0.10 μm) was also investigated. Statistical analysis showed that both films helped improve the Ti and porcelain bonding strength and increase the surface roughness. Scanning electron microscopy (SEM) results showed that no apparent oxide layer was formed at the Ti and porcelain interface in both Group NbN and Group ZrN. Energy-dispersive X-ray spectroscopy (EDS) results showed that ZrN was more effective in preventing Ti oxidation than was NbN. Overall, the experimental results showed that the deposition of both NbN and ZrN films helps improve the Ti and porcelain bonding strength and that ZrN films are more effective.     

离子渗金属中表层合金元素的贫化及其消除

离子渗金属中，工件表层合金贫化主要是由于离子轰击在工件表层造成一个严重的畸变层，畸变层原子具有高的扩散系数面非畸变层原子具有低的扩散系数，结果使区出现原子富集；同时在变层存在畸变梯度，这一梯度的存在支持这样的富集。     

氢分子在Mg(0001)表面的吸附与解离性能研究

采用基于密度泛函理论的第一原理计算方法,研究了氢分子(H2)在清洁、空位缺陷及Pd原子吸附的Mg(0001)表面的吸附与解离性能.结果显示:H2在清洁Mg(0001)表面呈较弱的物理吸附,H2解离需克服较高的能垒(1.3774 eV);空位缺陷的存在增强了Mg表面对H2的物理吸附能力,且使H2的解离能垒(1.2221 eV)有所降低;而清洁表面吸附的Pd原子则会与H2产生强烈的化学吸附作用,极大地降低了H2的解离能垒(0.2860 eV).电子结构分析发现:3种表面对H2吸附与解离的催化活性与Mg(0001)表面最上层与H2直接产生吸附作用的金属原子在费米能级(EF)附近s轨道的成键电子数密切相关.     

A Quantum-Chemical Study of the Adsorption of Pb Atoms on Au(111)

The interaction of lead atoms with a gold surface based on the cluster model of a metal surface has been investigated by the density-functional-theory (DFT) method. Geometrical and energy characteristics of these interactions have been evaluated. The adsorbed lead atom formed a strong chemical bond with gold-surface atoms. During the adsorption, there occurred a significant electron-density transfer from lead to gold. At the adsorption of a few lead atoms, flat lead nuclei tending to form a hexagonal structure were formed. The energy of adsorption of each subsequent lead atom depended insignificantly on the number of adsorbed atoms. The average effective lead atomic charge decreased with the increase of the lead quantity on the surface. The contribution of lead–lead interaction increased along with the increase in the number of lead atoms on the surface. Starting with intermediate occupancies, the contribution of lead–lead interaction to the submonolayer formation energy becomes significant. The emergence of adsorbed lead atoms on the gold surface increased the highest-occupied-molecular-orbital (HOMO) energy. This entails a decrease of the electronic work function upon the modification of a gold surface by lead.     

AlN陶瓷表面状态对Ti/Ni金属化薄膜粘结性能的影响

采用电子束蒸发技术在AlN衬底上蒸镀Ti/Ni双层金属化薄膜,通过SEM、EDS和AES等方法分析抛光AlN表面状态及与金属化薄膜间的相互作用.结果表明:离子束清洗可去除AlN衬底表面疏松层,改变AlN衬底表面状态,提高衬底表面能.结合热蒸发原子的作用,膜基界面处Al、N和Ti元素之间产生相互扩散现象,AlN陶瓷和Ti膜的附着机制由未清洗前的简单附着改变为扩散附着,极大提高了金属化薄膜粘结性能,其拉脱强度达300 MPa以上,且无需后续退火处理.     

离子轰击对Be上Al膜的影响

以Be为基体 ,采用磁控溅射离子镀在其上镀制Al膜 ,研究了离子轰击对膜基界面和Al膜微结构的影响。研究表明 ,在薄膜沉积初期 ,施加高能量离子轰击和采取循环轰击镀能增加界面形成的Be、Al共混区宽度。不同能量的离子轰击对Al膜微结构有较大影响 ,不施加离子轰击 ,Al膜在 (111)面择优生长 ;随着轰击能量升高Al膜在(111)面择优生长趋势减弱 ,Al膜在 (2 0 0 )面生长趋势加强 ;当轰击能量超过一定值后 ,Al膜在 (111)面择优生长的趋势又得到加强。晶粒在低能量离子轰击时随轰击能量增加而细化 ,当较高能量离子轰击引起基体温度升高时 ,此时晶粒又变大了。     

The structure and properties of chromium nitride coatings deposited using dc, pulsed dc and modulated pulse power magnetron sputtering

The time averaged ion energy distributions and ion fluxes of continuous dc magnetron sputtering (dcMS), middle frequency pulsed dc magnetron sputtering (PMS), and modulated pulse power (MPP) magnetron sputtering plasmas were compared during sputtering of a Cr target in an Ar/N₂ atmosphere in a closed field unbalanced magnetron sputtering system. The results showed that the dcMS plasma exhibited a low ion energy and ion flux; the PMS plasma generated a moderate ion flux of multiple high ion energy regions; while the MPP plasma exhibited a significantly increased number of target Cr⁺ and gas ions with a low ion energy as compared to the dcMS and PMS plasmas. Cubic CrN coatings were deposited using these three techniques with a floating substrate bias. The structure and properties of the coatings were characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, nanoindentation, microscratch and ball-on-disk wear tests. It was found that the deposition rate of the MPP CrN depositions was slightly lower than those of the dcMS depositions, but higher than in the PMS depositions at similar average target powers. The coatings deposited in the dcMS and PMS conditions without the aid of the substrate bias exhibited large columnar grains with clear grain boundaries. On the other hand, the interruption of the large columnar grain growth accompanied with the renucleation and growth of the grains was revealed in the MPP CrN coatings. The MPP CrN coatings exhibited a dense microstructure, fine grain size and smooth surface with high hardness (24.5 and 26 GPa), improved wear resistance (COF = 0.33 and 0.36) and adhesion, which are the results of the low ion energy and high ion flux bombardment from the MPP plasma.     

〈111〉生长铜膜中孪晶形成与出现几率的分子动力学模拟

运用分子动力学和静力学方法对〈111〉生长铜膜中孪晶形成的原子过程与能量进行了模拟研究.所用的原子间相互作用势为Finnis-Sinclair型镶嵌原子法(EAM)势.模拟和计算分析结果表明,〈111〉生长铜膜表面沉积原子在不同局部可形成正常排列的fcc畴或错排的hcp畴;沉积原子处于hcp位置时体系的能量比fcc位置时要高,其增量决定了孪晶面出现几率沉积原子错排能还受相邻{111}孪晶面的影响,其间距小于3个原子层厚时,沉积原子错排能与不形成孪晶的Al晶体表面沉积原子错排能相当,此时形成孪晶面的几率极低;随间距的增加,表面沉积原子错排能迅速降低,在间距达到约12个原子层厚以后,降到略低于完整Cu晶体{111}表面的沉积原子错排能,这表明此时出现孪晶面的几率比在完整晶体表面形成一个新的孪晶面的几率要大.     

Oxidation resistance of decorative (Ti,Mg)N coatings deposited by hybrid cathodic arc evaporation-magnetron sputtering process

Titanium-magnesium nitride coatings (Ti,Mg)N were deposited on steels and silicon substrates by hybrid reactive arc evaporation-magnetron sputtering process from cathodic Ti and sputter Mg targets in an argon/nitrogen gas mixture. X-ray diffraction analyses (XRD) of as-deposited coatings with various Mg/Ti atomic ratios gave evidence of a fcc TiN-like structure strongly oriented in the [111] direction. The TiN lattice parameter increases with the addition of Mg resulting from the substitution of Ti atoms by Mg ones. Optical investigations by spectrophotometry revealed that Mg addition to TiN leads to a change in colour from golden through coppery and violet to grey. Nanoindentation measurements showed that increasing Mg content does not alter the hardness of coatings. As-deposited films were annealed in air from 450 to 750 °C with a 100 °C step. XRD and Raman analyses revealed the formation of rutile TiO₂ and MgTiO₃ phases. Secondary neutral mass spectrometry measurements were performed to study the elemental depth profiles after air annealing. A diffusion of Mg atoms towards the film surface was evidenced above 650 °C, leading to the formation of the MgTiO₃ phase. However, thermogravimetric measurements showed that this oxide phase did not protect the films against high temperature oxidation. On the contrary, below 650 °C Mg affords to TiN a beneficial protective effect, able to reduce the oxidation kinetics by half.     

The adsorption and corrosion inhibition of some cationic gemini surfactants on carbon steel surface in hydrochloric acid

The adsorption and corrosion inhibition of the gemini surfactants 1,2-ethane bis(dimethyl alkyl (C_nH_2n+1) ammonium bromide) (designated as n−2−n, n=10, 12 and 16) on the steel surface in 1 M hydrochloride acid were studied using the weight loss method. It was found that the adsorption of the gemini surfactants on the steel surface is the main reason to cause the steel corrosion inhibition in hydrochloride acid, and the inhibition efficiency increases with the increase of surfactant concentration and reaches the maximum value near the CMC. A possible adsorption model of gemini surfactant onto the metal surface was also discussed.     

Cr基过渡层对钛合金表面类金刚石薄膜摩擦学性能的影响

采用磁控溅射技术在钛合金(Ti6Al4V)表面制备Cr、Cr/Cr N和Cr/Cr N/Cr NC过渡层结构的类金刚石(DLC)薄膜。采用扫描电子显微镜、拉曼光谱仪与原子力显微镜分析薄膜的结构和表面形貌,利用纳米压痕仪、薄膜内应力测试仪、划痕测试仪、摩擦试验机和二维轮廓仪研究薄膜的硬度、内应力、结合力和摩擦磨损性能。结果表明:随着Cr基梯度过渡层的引入,DLC薄膜的内应力逐渐下降,结合力逐渐上升。Cr/Cr N/Cr NC/DLC薄膜具有优异减摩抗磨性能,摩擦因数和磨损率低至0.09±0.02和(1.89±0.15)×10-7 mm3/N·m。试验结果对钛合金表面高性能DLC薄膜制备及应用具有一定的参考价值和指导意义。     

生长铜膜中孪晶形成与出现几率的分子动力学模拟

运用分子动力学和静力学方法对(111)生长铜膜中孪晶形成的原子过程与能量进行了模拟研究.所用的原子间相互作用势为Finnis-Sinclair型镶嵌原子法(EAM)势.模拟和计算分析结果表明,(111)生长铜膜表面沉积原子在不同局部可形成正常排列的fcc畴或错排的hcp畴;沉积原子处于hcp位置时体系的能量比fcc位置时要高,其增量决定了孪晶面出现几率.沉积原子错排能还受相邻{111}孪晶面的影响,其间距小于3个原子层厚时,沉积原子错排能与不形成孪晶的Al晶体表面沉积原子错排能相当,此时形成孪晶面的几率极低;随间距的增加,表面沉积原子错排能迅速降低,在间距达到约12个原子层厚以后,降到略低于完整Cu晶体{111}表面的沉积原子错排能,这表明此时出现孪晶面的几率比在完整晶体表面形成一个新的孪晶面的几率要大.     

Ag表面性质的第一原理计算

采用第一原理赝势平面波方法,计算了Fcc-Ag晶体及其Ag(111)、Ag(110)与Ag(100)自由表面的能量、几何与电子结构.根据表面能的计算,预测了Ag表面的结构稳定性,结果表明密排Ag(111)面结构稳定性最好,低指数奇异面Ag(100)面次之,Ag(110)面的结构稳定性最差.通过对不同表面几何与电子结构的比较,初步分析了其结构稳定性差异的产生原因.表面原子驰豫不仅引起表面几何结构的变化,而且使表面层的电子结构与键合特性发生改变.驰豫后表面层原子的部分价电子跑到了表面层以上的真空区,使表面层原子的电子态密度峰形发生变化,还新形成了表面态,这是表面能产生的主要原因,而Ag(110)表面相对于Ag(111)与Ag(110)表面具有高表面活性的主要原因则源于其表面层原子显著的结构驰豫.     

New generation hopeite coating on Ti6Al4V (TC4) by radio frequency magnetron sputtering for prosthetic-orthopaedic implant applications: synthesis and characterisation

ABSTRACT

Bioceramic coatings with multifunctionality have emerged as an effective alternative to conventional coatings, owing to their combination of various properties that are essential for bio-implants, such as osseointegration and antibacterial character. In the present study, thin hopeite coatings were synthesised by radio frequency magnetron sputtering on TC4 substrates. The obtained hopeite coatings were thermally treated at 500°C in ambient air and characterised in terms of surface morphology, phase composition, surface roughness, adhesion strength, antibacterial efficacy, apatite forming ability, surface wettability and corrosion resistance by Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), Atomic Force Microscopy(AFM), Tensometer, Fluorescence-Activated Cell Sorting (FACS), Simulated Body Fluid (SBF) immersion, Contact Angle Goniometer and potentiostatic polarisation respectively. It was observed that the post-deposition annealing increases the crystallinity of the synthesised hopeite coatings. SEM analysis showed deposited particles are spherical in shape and small in dimensions (<1?μm in diameter). XRD results confirm the deposited coating is crystalline in nature. AFM analysis reveals deposited hopeite coating has an average surface roughness value of 8.66?nm. Tensile pullout experiments indicated that the adhesive strength of the hopeite coating is 21.75?±?2.1?MPa. FACS study confirms the deposited hopeite coating possesses antibacterial character. SBF immersion experiments clearly demonstrate apatite growth on the surface of the deposited hopeite coating. The surface wettability test showed that the deposited coatings are hydrophobic in character having an average contact angle value of 136.65°. Potentiodynamic polarisation experiments in SBF showed a significant improvement in corrosion resistance (R_p?=?7945.87?Ω?cm²) of hopeite coated samples. In summary, it can be concluded that the new generation multifunctional hopeite coating synthesised by an alternative new process route of radio frequency magnetron sputtering on TC4 substrates is an effective alternative to conventional coatings. This is largely attributed to the strong osseointegration and antibacterial character of deposited hopeite coating ensuring the overall stability of metallic orthopaedic implants.     

Deposition of dense and smooth Ti films using ECR plasma-assisted magnetron sputtering

We report high quality Ti films grown in a novel electron cyclotron resonance (ECR) plasma-assisted magnetron sputtering (PMS) deposition system. The films are compared with films deposited by conventional direct current (DC) magnetron sputtering. Using ECR-PMS, the argon plasma bombardment energy and Ti film deposition rate can be controlled separately, with the substrate bias voltage under feedback control. Results from SEM, AFM, XRD and PAS (scanning electron microscopy, atomic force microscopy, X-ray diffraction and positron annihilation spectroscopy) show that the properties of Ti films prepared by ECR-PMS are greatly improved compared with conventional sputtering. SEM and AFM confirmed that ECR-PMS Ti films have a dense, smooth, mirror-like surface. Increasing the substrate bias of the ECR plasma from − 23 V to − 120 V while keeping a fixed sputtering bias voltage of − 40 V, the intensity of the (100) reflection of Ti film was a little strengthened, but (002) remained strongly preferred orientation. The XRD peak broadening of ECR-PMS Ti films is more than for conventional magnetron sputtering, due to grain refinement induced by Ar ion bombardment. Doppler broadening of PAS analysis reveals that the Ti films have fewer vacancy defects compared with films prepared by the conventional magnetron.     

Effect of Ti Incorporation on the Microstructure and Properties of the a-C:H Films Deposited by Magnetron Sputtering Technique

Amorphous hydrogenated carbon(a-C:H)and Ti-incorporated a-C:H(Ti/a-C:H)films were deposited by magnetron sputtering with a mixture gas of CH4 and Ar.The effect of the Ti incorporation on the chemical composition,microstructure and properties of the as-deposited and the annealed films were investigated by various techniques.It has been shown that the bonding structure and the internal stress were sensitive to the incorporation of the Ti atoms.The results of the XPS revealed that the concentration of Ti atom on the surface of the film increased when the Ti/a-C:H film annealed at 300oC.The tribologcial properties of the(Ti/)a-C:H films changed greatly after annealed,due to the graphitization,oxidation of carbon,and so forth.It compared and discussed in detail the change of the microstructure and properties of the a-C:H and Ti/a-C:H films before and after annealed     

Effects of boronizing process on the surface roughness and dimensions of AISI 1020, AISI 1040 and AISI 2714

In this study, the effects of boronizing treatment on material's dimensional changes and surface roughness were investigated. The parameters chosen were substrate material composition, surface roughness before boronizing treatment, and boronizing time. The AISI 1020, AISI 1040 and AISI 2714 were chosen as substrate materials whereas Ekabor I was selected as boronizing powder. Materials were boronized at 900 °C by using a solid boronizing method for 2 or 4 h. The gradual growth of boride layer on the surface, dimensional changes and their effects on surface roughness were investigated. Variations in topographical surface roughness were determined by SEM. With the boronizing treatment, dimensional increases of the material's were observed. The dimensional increase was one fifth of boride layer thickness for AISI 1020 or AISI 1040, whereas it was one third of boride layer thickness for AISI 2714. Boronizing treatment had also a significant effect on surface roughness of materials. A “threshold roughness” term was defined in our study. This term is a surface roughness value for smooth surfaces, which received boronizing treatment. For the same material and with the same boronizing conditions, the threshold roughness value was achieved after boronizing, when surface roughness of material was below the threshold roughness value, before boronizing was applied. However, when surface roughness of a material was above that threshold roughness value, surface roughness value decreased with boronizing treatment. The thereshold roughness value depended on substrate material composition and boronizing parameters.     

Structurally laminated CrN films deposited by multi pulse modulated pulsed power magnetron sputtering

The paper presents the results on the deposition of nanoscale structurally laminated CrN films using a novel multi pulse modulated pulsed power (MPP) magnetron sputtering technique. With the multi pulse MPP approach, thin films with a structural modulation in the nanometer range are obtained by alternately switching two (or even more) high power MPP pulses on the same target, which have different pulse lengths, frequencies and powers. Each pulse was turned on for a pulse repeat duration during which this given pulse shape was repeated. In this study, CrN films have been deposited in a closed field unbalanced magnetron sputtering system using the multi pulse MPP technique by varying the pulse repeat duration of two different pulses. The CrN films were also deposited by dc magnetron sputtering (dcMS) and single pulse MPP techniques for comparison. The microstructure and properties of the films were characterized using glancing incident X-ray diffraction, scanning electron microscopy, transmission electron microscopy, nanoindentation, and ball-on-disk wear tests. The structure and properties of the multi pulse MPP CrN films depended on the pulse repeat duration. The highest hardness of 30.5 GPa and an H/E ratio of 0.9 have been achieved in the multi pulse MPP CrN films. The wear rate of the single pulse MPP and multi pulse MPP CrN films decreased by a factor of 5.8–17 as compared to the dcMS CrN films.