Analysis of the interface between a pulsed laser deposited calcium phosphate coating and a titanium alloy substrate

Calcium phosphate coatings deposited on titanium alloy are intended to add a bioactive surface to medical implants. This work presents the characterisation of the interface between Ti-6Al-4V and a crystalline calcium phosphate coating obtained by pulsed laser deposition, with a KrF excimer laser, at 575 °C and under a 45 Pa water-vapour atmosphere. The coating–substrate system was studied by secondary-ion mass spectrometry, scanning electron microscopy, X-ray diffractometry, Raman spectroscopy and X-ray photoelectron spectroscopy. The results show that the deposition process promotes the interdiffusion of substrate elements into the coating and coating elements into the substrate oxide layer. Thus, a graded layer of mixed calcium phosphate and amorphous titanium oxide is formed. For the substrate, a hydroxyapatite coating acts more as a barrier for oxygen incoming from a gas than as an oxygen source during deposition. Moreover, oxygen diffusion into the substrate occurs. Thus, the content of oxygen of this oxide layer diminishes with depth. When the oxygen concentration is low enough it is incorporated in solid solution in the titanium alloy . PACS 81.15.Fg; 68.55.-a; 87.68.+z     

Microstructure and Mechanical Properties of Multilayer α-AlN/α-BCN Coating as Functions of the Current Density during Sputtering of a B<Subscript>4</Subscript>C Target

Multilayer AlN/BCN coating of nanometer scale have been prepared by magnetron sputtering of Al and B₄C targets in an argon–nitrogen atmosphere during deposition on a Si substrate. These coating have an X-ray amorphous structure and the maximum Knoop hardness of 27 GPa (at the current density 100 mA). The first-principle molecular dynamics calculations show that the B4–BN layer is dynamically unstable; thus, it will not be epitaxial and will be amorphous or have a structure different from the B4–BN structure. The thermal vacuum annealing from 600 to 800°C of samples with multilayer nanosized coating leads to the decrease in the Knoop hardness to 18 GPa; however, the coating structure is retained X-ray amorphous.     

氮化铬过渡层对四面体非晶碳薄膜在高速钢基底上附着特性影响的研究

利用磁过滤阴极电弧与磁控溅射相结合的薄膜沉积技术在高速钢基底上 制备了氮化铬/四面体非晶碳(CrN/ta-C)复合涂层, 通过改变过渡层氮化铬(CrN)的制备工艺, 研究了四面体非晶碳(ta-C)薄膜在钢基底材料上的附着特性的变化. 结果表明, 随着氮气流量的增大, CrN/ta-C复合涂层中的氮化铬经过了Cr-Cr₂N-CrN的相变过程. 同时涂层的附着力也随着氮气流量的增大而增加, 但是当氮气流量超过30 sccm时, 涂层附着力会有所下降; 通过改变基片偏压, 复合涂层中氮化铬的择优取向与晶粒结构发生改变, 随着偏压的增大, 涂层附着力也会大大改善, 但是当偏压超过200 V, 涂层附着特性会略微降低. 通过涂层耐磨性的测试也表明, 在高速钢基底上, CrN涂层能显著提高ta-C薄膜在高速钢基底上的附着力, 同时显著提高耐磨特性. 关键词： 附着力 四面体非晶碳薄膜 X射线衍射 拉曼光谱     

Fabrication and characteristics of ta-C biomaterial coatings on Ti–6Al–4V using metal plasma immersion ion implantation and deposition

We have formed amorphous diamond (ta-C) coatings on Ti–6Al–4V substrates using a metal plasma immersion ion implantation and deposition (MEPIIID) technique, and characterized the mechanical properties and biological compatibility of the coating material. The hemocompatibility of the coating compared favorably with that of low temperature isotropic (LTI) carbon, with kinetic clotting time and hemolysis rate approximately the same as for LTI carbon, and platelet consumption about twice that of the latter. The mechanical properties were good, with a microhardness greater than that of the uncoated metal substrates, and high adhesion of >0.75 GPa (interface shear stress) as estimated from a thermal quench method. Glancing-angle X-ray diffraction measurements indicated the presence of a TiC transition layer, suggesting the formation of a Ti/TiC/ta-C multilayer structure, leading in turn to good film–substrate adhesion. We conclude that this kind of amorphous diamond coating could provide benefit as a biocompatible hard coating for Ti–6Al–4V substrate material.     

Controlled preparation of well-ordered transition metal oxide layers on a metallic surface

A method to create various well-ordered two dimensional transition metal oxide films on a metallic substrate has been exploited. The formation of an intermediate amorphous layer with controllable metal-oxygen stoichiometry serves as an important precursor condition for the final transformation into a mono-phase, crystalline oxide layer via mild annealing. As a key ingredient serves a Cu₃Au(1 0 0) substrate covered by oxygen. The flat Cu-O topmost layer stops completely intermixing of the substrate material with the subsequently evaporated transition metal film. Likewise the wetting of the surface is considerably enhanced and a homogeneous oxidation of the film is strongly promoted. The proposed technique appears to be widely efficient for preparation of various two dimensional oxide films covering the entire Cu₃Au(1 0 0) substrate. Its usefulness is demonstrated successfully for vanadium, niobium and molybdenum to produce a set of single-phase transition metal oxides of different stoichiometry and geometrical structure. All created oxides are found to be thermally stable at least up to a substrate temperature of 800 K.     

Study and simulation of the growth of solid lubricant MoSe<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> coatings during pulsed laser deposition

The chemical composition and tribological properties of the thin-film diselenide molybdenum coatings deposited by pulsed laser deposition in vacuum and a rarefied inert gas (argon) atmosphere are studied. Upon deposition in a gas at a pressure of ∼2 Pa, stoichiometric coatings with improved antifriction properties as compared vacuum-deposited coatings form. However, a too strong increase in the argon pressure (to ∼10 Pa) degrades the tribological properties of the coating. Structure formation in the MoSe _x coatings grown by pulsed laser deposition on an unheated substrate is investigated. Deposition in vacuum or argon at a pressure of 2 Pa leads to formation of rather smooth coatings with a dense amorphous structure containing molybdenum nanoinclusions. Deposition at a high argon pressure results in a developed surface relief and a loose coating structure. A mathematical model is developed using the kinetic Monte Carlo method in order to describe structure formation in the coatings that grow during physical deposition of an atomic flux. A comparative analysis demonstrates satisfactory agreement between the simulated and experimentally studied structures in the coatings created by pulsed laser deposition at various gas pressures.     

用低压反应离子镀的方法制备Ge_(1-x)C_x单层非均匀增透膜的研究

用低压反应离子镀(RLVIP)的方法在Ge基底上制备了Ge1-xCx单层非均匀增透薄膜。随着沉积速率在0.05~0.4nm/s之间的变化,其折射率在2.31~3.42之间可变。实验结果表明,镀制的Ge1-xCx单层非均匀增透保护薄膜均为无定形结构,并实现了从2000~8000nm的宽波段增透。当沉积速率为0.1nm/s时,单面平均透过率从68.6%提高到了80.9%,比单面未镀膜时提高了17.9%。通过对薄膜的稳定性和牢固度进行测试表明,制备的Ge1-xCx单层非均匀增透薄膜具有良好的性能。     

Amorphous Structures in Laser Cladding of ZL111 Aluminum Alloy:Semi-quantitative Study by Differential Thermal Analysis (DTA)

This paper deals with amorphous structures in the laser cladding. ZL111 alloy is the substrate and Ni-Cr-Al alloy is sprayed on the substrate as the coating material. The coating is clad by a 5 kW transverse flow CO2 laser. The observation of SEM and TEM reveal that in the laser cladding there are amorphous structures of two different morphologies: one is space curved flake-like, and exists in the white web-like structures; the other is fir leaf-like, and exists in the grain-like structures. Differential thermal analysis (DTA) is used to semi-quantitatively determine the content of the amorphous structures. A relation is obtained between the content of amorphous structures and the dimensionless laser cladding parameter C. We also show the changes of the amorphous structures after annealing.     

AlN/Al dual protective coatings on NdFeB by DC magnetron sputtering

AlN/Al dual protective coatings were prepared on NdFeB by DC magnetron sputtering in a home-made industrial apparatus. Comparing with Al coating, AlN/Al coatings have a denser structure of an outmost AlN amorphous layer following an inner Al columnar crystal layer. The coatings and NdFeB substrate combine well, and moreover, there is occurrence of metallurgy bonding in the interface layer. Both Al and AlN/Al coatings have a good protective ability to NdFeB. Especially, the corrosion resistance of AlN/Al coated NdFeB is improved largely. AlN/Al and Al protective coatings not only do not deteriorate the magnetic properties of NdFeB, but contribute to their slight increase.     

Amorphous Structures in Laser Cladding of ZL111 Aluminum Alloy:Semi-quantitative Study by Differential Thermal Analysis (DTA)

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Wafer-level manufacturing technology of glass microlenses

In high-tech products, there is an increasing demand to integrate glass lenses into complex micro systems. Especially in the lighting industry LEDs and laser diodes used for automotive applications require encapsulated micro lenses. To enable low-cost production, manufacturing of micro lenses on wafer level base using a replication technology is a key technology. This requires accurate forming of thousands of lenses with a diameter of 1–2 mm on a 200 mm wafer compliant with mass production. The article will discuss the technical aspects of a lens manufacturing replication process and the challenges, which need to be solved: choice of an appropriate master for replication, thermally robust interlayer coating, choice of replica glass, bonding and separation procedure. A promising approach for the master substrate material is based on a lens structured high-quality glass wafer with high melting point covered by a coating layer of amorphous silicon or germanium. This layer serves as an interlayer for the glass bonding process. Low pressure chemical vapor deposition and plasma enhanced chemical vapor deposition processes allow a deposition of layer coatings with different hydrogen and doping content influencing their chemical and physical behavior. A time reduced molding process using a float glass enables the formation of high quality lenses while preserving the recyclability of the mother substrate. The challenge is the separation of the replica from the master mold. An overview of chemical methods based on optimized etching of coating layer through small channels will be given and the impact of glass etching on surface roughness is discussed.     

The structure of Mo/Si multilayers prepared in the conditions of ionic assistance

The influence of a negative substrate-applied bias potential on the structure of periodic Mo/Si multilayer compositions has been investigated by means of cross-sectional electron microscopy, small-angle X-ray reflectivity, X-ray diffraction and by modeling the small-angle spectra. It is known that the crystalline structure of molybdenum layers is the main source of interface roughness. In the absence of a bias potential application, the interface roughness tends to develop from the substrate towards the surface of a Mo/Si multilayer composition. A negative bias potential (up to -200 V) applied to a substrate during silicon layer deposition leads to smoother interfaces and improves the layer morphology. After increasing the bias potential over -200 V a considerable growth of an amorphous interlayer transition zone can be observed at Si-on-Mo interfaces. By raising the bias potential during the deposition of Mo layers a development of roughness at Mo-on-Si interfaces as well as growing interlayer thicknesses were found. PACS 61.10.Kw; 68.37.-d; 68.65.Ac     

Composition design and laser cladding of Ni-Zr-Al alloy coating on the magnesium surface

The cluster line criterion was used for optimized design of a Ni-Zr-Al alloy used as coating on the AZ91HP magnesium alloy by laser cladding. Results show that the coating mainly consists of an amorphous, two ternary intermetallic phases with Ni₁₀Zr₇ and Ni₂₁Zr₈ type structures resulting in high hardness, good wear resistance and corrosion resistance. The interface between the clad layer and the substrate has good metallurgical bond.     

High-quality hydroxyapatite coating on biocompatible materials by laser-assisted laser ablation method

A new method for high-quality hydroxyapatite (HAp) coating is developed, the laser-assisted laser ablation method. In this method, two lasers are used. One is used for ablation of a HAp target. The other, the assist laser, is used to irradiate a Ti substrate surface. The effects of the assist laser irradiation are to anneal the HAp coating and to improve its adhesive strength to the Ti substrate. The quality of the HAp coating depends on the delay time of the assist-laser irradiation. HAp coatings obtained at a delay time of 10 microseconds or more are more amorphous. It was confirmed that the amorphous part of a coating dissolves in simulated body fluid, while the crystalline part does not. The value of the Ca/P ratio in a coating obtained at a delay time of a few microseconds is close to the stoichiometric value. PACS 81.16.Mk     

Structural analysis of electron beam irradiated steel/molybdenum systems

Layered systems, obtained by e-beam irradiation of molybdenum sheets mechanically clamped to ARMCO iron, plain carbon steel and high alloy austenitic steel substrates, have been analysed by means of conversion X-ray Mössbauer scattering and X-ray diffraction. When the substrate is iron or carbon steel, the structure of the surface layer is completely ferritic with a certain amount of iron-atoms coordinated with molybdenum atoms. If the substrate is fully austenitic, the e-beam treated surface structure presents a broad ferritic-martensitic component. The influence of the cooling rate of the e-beam molten layer is also discussed in relation to the observed surface structures.     

快冷熔覆法原位合成大厚度铁基非晶复合涂层的研究

通过水冷提高凝固速率及降低基体金属对熔覆层的稀释,采用改进的钨极惰性气体氩弧熔覆的方法,原位制备了大厚度(1—5 mm)Fe基非晶/纳米晶复合涂层.利用X射线衍射,光学显微镜和透射电子显微镜对涂层成分和组织进行分析,并测试了涂层的显微硬度.结果表明,采用快冷熔覆的方法可以制备出含有50%以上非晶含量的非晶/纳米晶复合涂层,涂层内纳米晶颗粒表面被非晶过渡层包覆.较厚涂层的显微硬度达到1600HV_0.3,与基体为冶金连接,有良好的结合强度及耐磨性.非晶/纳米晶复合结构使得涂层与基体之间的过渡区具备较强的弹塑性,提高了涂层的抗冲击性. 最后重点讨论了微观结构和性能之间的内在联系,涂层内非晶相与纳米晶相的协同作用是造成涂层高硬度的主要原因. 关键词： 非晶 涂层 熔覆 显微硬度     

Multi-layered electroless Ni–P coatings on powder-sintered Nd–Fe–B permanent magnet

This paper has shown a successful protective coating scheme for powder-sintered Nd–Fe–B permanent magnet using multi-layered electroless nickel (EN) deposition. A low-phosphorus nickel layer is plated with an alkaline EN solution first, followed by a high-phosphorus nickel layer plated with an acidic solution. An additional topcoat by medium-phosphorus nickel on the high-phosphorus coating is also explored. It is shown that the high-phosphorus nickel layer coated in acidic solution provides the best corrosion protection because of its dense amorphous structure. The medium phosphorus topcoat is also dense and is able to provide reasonable corrosion resistance. The low-phosphorus layer itself does not have enough corrosion resistance; its main role is to provide an intermediate coating on the powder-sintered magnet. X-ray diffraction measurement shows that the low-phosphorus coating consists of nano-crystallines, and the high- and the medium-phosphorus coatings are dominated by amorphous structure. Microscopic observation and scratch test on these composite coatings demonstrate good adhesion between the magnet and the coatings. Remanence and coercivity of the plated magnet decrease with the applied coatings, but measured values are still very attractive for practical applications among known hard magnets.     

耐高温CrAlON基太阳能光谱选择性吸收涂层的制备与热稳定性

光谱选择性吸收涂层是太阳能光-热利用技术的核心部件,直接决定着整个系统的转换效率,为了提高涂层的选择吸收性和热稳定性,本文提出以金属氮化物替代金属纳米颗粒,构建纳米晶-非晶异质结构的思路,并采用多弧离子镀制备了Cr/CrAlN/CrAlON/CrAlN/CrAlON/CrAlO多吸收层光谱选择性吸收涂层,其吸收率达0....     

Study of hafnium-oxide coatings by means of nuclear backscattering spectrometry

Single-layer coatings made of hafnium oxide and double-layer structures with an intermediate nickel layer, the total thickness of which is 70 μm, are obtained via plasma spraying with a supersonic jet in a rarefied atmosphere. A nozzle extension capable of implementing a Prandtl–Meyer expansion fan is used to generate nanostructured coatings. The coatings are investigated via the nuclear backscattering of spectrometry 7.6 MeV protons, scanning electron microscopy, X-ray microanalysis, and X-ray diffraction. The studies of the surface and transverse microsection of the coatings indicate that they comprise not only deformed particles of the sprayed powder with sizes of greater than 20 μm but also layers and conglomerates of nanoparticles with sizes of 30–60 nm. Depth profiling of the elemental composition performed by means of the nuclear backscattering spectrometry of protons demonstrates that transition layers exist at the interface between the substrate and coating layers characterizing the average size of the coating microparticles. A comparison of thicknesses defined by two methods allows estimation of the overall porosity of the hafnium-oxide layer. In accordance with X-ray diffraction data, the cubic and monoclinic phases of hafnium oxide with a high fraction of the amorphous component are formed in the coating.     

立方氮化硼薄膜生长过程中的界面控制

在立方氮化硼薄膜气相生长过程中生成的无定形初期层和乱层结构氮化硼中间层，一直是阻碍立方氮化硼薄膜外延生长的主要原因.系统地分析了硅衬底预处理对立方氮化硼薄膜中无定形初期层成分的影响，发现在等离子体化学气相生长法制备薄膜时，硅衬底上形成无定形初期层的可能原因有氧的存在、离子轰击以及高温下硅的氮化物的形成.在H₂气氛中1200K热处理硅衬底可以有效地减少真空室中残留氧浓度，除去硅表面的自然氧化层，保持硅衬底表面晶体结构.控制衬底温度不超过900 K，就能防止硅的氮化物的形成，成功地除去无 关键词： 立方氮化硼薄膜 等离子体化学气相生长 界面 电子显微镜