微波CVD金刚石热沉片的制备研究

采用化学气相沉积法（CVD）制备的金刚石薄膜具有接近于天然金刚石的导热性能,是目前最为理想的热沉材料。利用微波等离子体化学气相沉积法（MPCVD）制备了金刚石热沉片,并在此基础上研究了不同沉积工艺对金刚石热沉片散热性能的影响。采用扫描电子显微镜（SEM）和激光拉曼光谱（Raman）检测了薄膜的表面形貌及纯度,金刚石热沉片的导热性能则通过测量封装LED后薄膜的散热效果来进行表征。结果表明,在其他条件不变的情况下,提高生长过程中的微波输出功率、降低反应气压以及增加基片温度有利于制备出散热性能更佳的金刚石热沉片。     

Effect of heat treatment on mechanical properties and microstructure of CrN/AlN multilayer coatings

Polycrystalline CrN/AlN multilayer coatings were deposited by RF magnetron sputtering on silicon (001) substrates. The bilayer periods of CrN/AlN were controlled from 4 nm to 20 nm by the use of shutters, which were adjusted by a programmable logic control (PLC). To evaluate the thermal stability, the films were annealed at 500 °C, 600 °C, 700 °C, 800 °C, and 850 °C, for 1 h in both vacuum and air environments. The phase transformation during thermal evolution was studied by X-ray diffraction (XRD). The microstructure of CrN/AlN multilayer coatings as-deposited and after annealing was observed by transmission electron microscopy (TEM). The hardness of as-deposited CrN/AlN coating with a period of 4 nm was 28.2 GPa, which was 60% higher than that predicted by the rule of mixtures. The hardness of CrN/AlN multilayer coatings annealed at 850 °C in vacuum remained similar to the as-deposited state, and the nano-layered structure still persisted. The thermal stability of CrN/AlN coatings was better than that of CrN coating. The hardness degradation ratio of CrN/AlN coating with modulation period of 4 nm was only 8.1% at 700 °C, which was superior to that of a simple CrN coating.     

Formation of Cu Nanodots on Diamond Surface to Improve Heat Transfer in Cu/D Composites

Diamond‐dispersed copper matrix (Cu/D) composite materials with different interfacial configurations are fabricated through powder metallurgy and their thermal performances are evaluated. An innovative solution to chemically bond copper (Cu) to diamond (D) has been investigated and compared to the traditional Cu/D bonding process involving carbide‐forming additives such as boron (B) or chromium (Cr). The proposed solution consists of coating diamond reinforcements with Cu particles through a gas–solid nucleation and growth process. The Cu particle‐coating acts as a chemical bonding agent at the Cu–D interface during hot pressing, leading to cohesive and thermally conductive Cu/D composites with no carbide‐forming additives. Investigation of the microstructure of the Cu/D materials through scanning electron microscopy, transmission electron microscopy, and atomic force microscopy analyses is coupled with thermal performance evaluations through thermal diffusivity, dilatometry, and thermal cycling. Cu/D composites fabricated with 40 vol% of Cu‐coated diamonds exhibit a thermal conductivity of 475 W m^?1 K^?1 and a thermal expansion coefficient of 12 × 10^?6 °C^?1. These promising thermal performances are superior to that of B‐carbide‐bonded Cu/D composites and similar to that of Cr‐carbide‐bonded Cu/D composites fabricated in this study. Moreover, the Cu/D composites fabricated with Cu‐coated diamonds exhibit higher thermal cycling resistance than carbide‐bonded materials, which are affected by the brittleness of the carbide interphase upon repeated heating and cooling cycles. The as‐developed materials can be applicable as heat spreaders for thermal management of power electronic packages. The copper‐carbon chemical bonding solution proposed in this article may also be found interesting to other areas of electronic packaging, such as brazing solders, direct bonded copper substrates, and polymer coatings.

     

Effect of thermal cycling on the adhesion strength of Ti/Ni/Ag films on AlN substrate

The adhesion strength of Ti/Ni/Ag multi-layers on AlN substrates before and after thermal cycling treatment was studied. The Ti/Ni/Ag layers with thicknesses of 0.6, 1.0, and 0.2 μm, respectively, were deposited sequentially on bulk AlN substrates using direct current (DC) sputtering. Thermal cycling test (TCT) was conducted for 0, 15, 100, and 300 cycles to measure the adhesion strength of Ti/Ni/Ag on AlN. The adhesion strength of the deposited specimen increased slightly over 15 thermal cycles and increased abruptly after 100 thermal cycles. After 100 thermal cycles, Ti reacted with AlN substrate to form TiN and TiO. The formation of TiN and TiO at the Ti/AlN interface may be responsible for the increase of the adhesion strength after a large number of thermal cycles.     

Mechanical and tribological properties of Ti/TiAlN duplex coatings on high and low alloy tool steels

In this research work, different steels were hardened using plasma nitriding process in an Arc-PVD device. Afterwards, on both non-nitrided and plasma nitrided substrates, different Ti/TiAlN multilayer coatings were deposited by a magnetron sputtering device. Scratch tests were performed on the duplex systems in order to characterize their adhesive properties. The failure modes of individual coating systems under various normal loads were described using light optical microscope. Furthermore, to study the effect of plasma nitriding on the friction coefficient and wear rate of the systems, ball-on-disc tests were carried out. It was shown that high and low alloy tool steels obtained different levels of hardness after plasma nitriding process. The results of scratch tests showed that both Ti/TiAlN multilayer coatings have a higher adhesion to plasma nitrided steels compared to non-nitrided steels. In addition, plasma nitriding of the substrates resulted in an increase in the wear rates of multilayer coatings. It was also revealed that the adhesion and the tribology of multilayers depend strongly on the amount of titanium interlayers. An increase of the thickness of titanium interlayers enhanced the adhesion of multilayers. However, increasing the thickness of titanium interlayers decreased the hardness and wear resistance of multilayers.     

Preparation and characterization of carbon and titanium carbide coatings

Carbon and titanium carbide coatings were deposited onto 304 and 316 stainless steel, Monel 400, molybdenum and copper substrates by the d.c. diode sputtering method. The former were prepared using a graphite target in an argon atmosphere whereas the latter were deposited using a titanium target in an argon-methane gas mixture. The coatings were characterized using Auger electron spectroscopy, X-ray photoelectron spectroscopy, Rutherford backscattering spectrometry, scanning electron microscopy and X-ray diffraction techniques. The adhesion of the coatings to the substrates and the effect of annealing on their crystallinity were studied.     

Studies of calcium-precipitating oral bacterial adhesion on TiN,TiO2 single layer,and TiN/TiO2 multilayer-coated 316L SS

Titanium nitride (TiN), titanium oxide (TiO₂) single layer, and TiN/TiO₂ multilayer coatings were deposited on a 316L stainless steel substrate using reactive magnetron sputtering process with the aim of preventing bacterial adhesion. The crystal structures of as-prepared coatings were evaluated using X-ray diffraction analysis. The cubic structure of TiN, anatase, and rutile structure of TiO₂ was noticed. Atomic force microscopy images exhibited a relatively smooth surface for all coatings. The surface wettability studies confirmed that the coatings were hydrophilic in nature. The rate of bacterial adhesion was evaluated using scanning electron microscopy and epifluorescence microscopy. These results demonstrated that the coated substrates could help to effectively reduce the bacterial adhesion and biofilm formations.     

金刚石/碳化硅复合梯度膜制备研究

采用微波等离子化学气相沉积(MW-PCVD)制备金刚石/碳化硅复合梯度膜.工作气体为H₂,CH₄和Si[CH₃]₄(四甲基硅烷,TMS),其中H₂∶CH₄=100∶0.6,Si[CH₃]₄为0％-O.05％,沉积压力为3300Pa,基体温度为700℃,微波功率为700W.基体为单晶硅,在沉积前用纳米金刚石颗粒处理.沉积后的样品经扫描电子显微镜(SEM),电子探针显微分析(EPMA),X射线能量损失分析(EDX)表明:沉积膜中的碳化硅含量是随Si[CH₃]₄流量的变化而改变.通过改变Si[CH₃]₄的流量可以制备金刚石/碳化硅复合梯度膜,且梯度膜中金刚石与复合膜过渡自然平滑.     

Effect of Plasma Power on the Deposition of Diamond Coatings on Pure Titanium

Diamond coatings appear to be a promising solution for the improvement of tribological behavior of titanium alloys. By means of microwave plasma assisted chemical vapor deposition (MW-PACVD), diamond coating was deposited on pure titanium using CH₄/H₂ gas mixtures under different plasma powers. Surface and interface characterization of the deposited coating under different plasma powers was carried out using SEM, grazing incidence x-ray diffraction (GIXD) and Raman spectroscopy. Adhesion of diamond coating with substrate was evaluated using an indentation tester. Results showed that adhesion of diamond coatings was not good under high plasma power, whereas the crystallinity of diamond coating was not good under low plasma power. The higher the plasma power, the larger the diamond crystal size, the less content of non-diamond carbon and the poorer the adhesion strength. During the diamond deposition, growth of TiC competed with diamond formation for the available carbon content. Relatively low plasma power inhibited TiC formation more than diamond formation. Under a high plasma power, the formation of a thick and porous TiC layer appeared to promote interfacial debonding and spallation of the diamond coating.     

Adhesion Enhancement of Diamond Films on Various Substrates by Carbide Interlayer

Diamond films were prepared on various substrates by a combustion flame technique using an oxyacetylene torch. During the deposition, a carbide interlayer was formed between the surface of the substrate and deposited diamond. The hard interlayers were seen on the molybdenum, tungsten as well as silicon substrates. The adhesion of diamond on the molybdenum substrate was improved with increase in the hardness of the carbide layer. This result strongly supports the premise that the carbide interlayer and/or carbon diffused layer enhances the adhesion of diamond to substrates.     

Improved adhesion between a sputtered alumina coating and a copper substrate

The influence of various metallic intermediate layers on the adhesion between a copper substrate and an alumina coating was studied. The alumina coatings and the intermediate layers were prepared by r.f. sputtering. Titanium and combined Ni/Ti intermediate layers were used. The adhesion properties of alumina with different combinations of coatings were compared by an interrupted tensile testing method and by thermal cycling from room temperature to 600°C.The adhesion of a sputtered alumina coating to a copper substrate without any intermediate layer appeared to be rather poor. The use of titanium as an intermediate layer enhanced the adhesion significantly. The adhesion was further increased when the deposition temperature of the titanium was increased from 200 to 350°C. The combined Ni/Ti intermediate layer led to better adhesion than the titanium layer alone did.     

SOI built-in heat spreader with temperature and pressure integrated sensors for cooling optimization and in situ monitoring

This contribution presents an original solution for sensor integration into a heat spreader which is directly micromachined into the silicon substrate of the device to be cooled. Having both a high thermal conductivity coefficient and a high level of miniaturization, the vapor chamber heat spreader provides a high robustness due to the absence of any moving pumping parts. Simulation results as well as experimental results obtained with a prototype of the heat spreader with integrated temperature and pressure microsensors are presented. The results concerning device cooling optimization using the integrated sensors are highlighting the interest of this approach for accurate in situ monitoring and cooling optimization of silicon-integrated heat spreaders.     

Synthesis and characterization of TiBCN coatings deposited by ion beam assisted, co-evaporation electron beam-physical vapor deposition (EB-PVD)

TiC, TiB₂, and super hard TiBCN coatings were successfully deposited by ion beam assisted, electron beam-physical vapor deposition. Titanium, titanium diboride, and carbon (through tungsten) were co-evaporated by energetic electron beams while simultaneously bombarding the substrates with varying ionized gas ratios of nitrogen and argon to obtain super hard TiBCN coatings. The hardness of the TiBCN coating was reported to be equivalent to a soft diamond like carbon film. The adhesion was determined to be greater than 50 N. The hardness, grain size, structure, morphology, crystallographic texture and degree of stress within the coatings were determined using a variety of characterization methods including Vicker's hardness measurements, electron probe microanalysis (EPMA), optical microscopy (OM), scanning electron microscopy (SEM), and X-ray diffraction. The author is not aware of previous TiBCN coatings being deposited by this method.     

CN<em>x/TiN多层复合涂层抗水蚀性能的研究

采用多弧-磁控溅射镀膜机在不锈钢2Cr13衬底上沉积CN_<em>x/TiN多层复合涂层。利用光电子能谱仪(XPS)和透射电子衍射(TED)对涂层的组成和结构进行分析。利用自行研制的高压水蚀试验装置对不锈钢、高铬铸铁、司太立合金以及CN_<em>x/TiN多层复合涂层的抗水蚀性能进行对比试验,最后对涂层的水蚀失效机理进行了探讨。试验结果表明:CN_<em>x/TiN多层复合涂层具有较高的硬度、附着力、抗热冲击性能以及优异的抗水蚀性能,是一种优良的汽轮机末级叶片抗水蚀用涂层。     

Depth distributions of elements in monoatomic and compound coatings deposited onto copper and silicon by IBAD

One-component and multicomponent compound coatings were deposited on substrates of copper and silicon by the method of ion-beam assisted deposition. Atomic species sputtered from the inner surface of hollow truncated cones of different compositions were deposited on these substrates. AES and RBS were used to determine depth distributions of deposited elements. The depth of equal atomic concentrations of deposited and matrix has been considered as a depth marker of produced coatings. It was shown that the layer thickness does not depend on the substrate (copper and silicon in our study) and for a given coating composition is a linear function of the fluence. A few possible mechanisms of radiation-enhanced diffusion are discussed to explain observed phenomena.     

A study on the penetration of platinum into silicon in Ti/Pt/Au beam lead metallization systems

The penetration of platinum into silicon in the Ti/Pt/Au beam lead metallization system was investigated using scanning electron microscopy, electron probe microanalysis and X-ray diffraction. Specimens with different thicknesses of titanium and platinum deposited onto polycrystalline silicon (polysilicon) substrates by vacuum evaporation or r.f. sputtering were heat treated at 360 °C in 1 atm N₂ for up to 2000 h. The platinum penetration was examined by counting the black spot defects under a metallurgical microscope. An increase in the thickness of the titanium layer was shown to be more effective in reducing the formation of defects than an increase in the thickness of the platinum layer. This indicates the role of titanium as a diffusion barrier. The most striking fact is the necessity of the presence of gold for defect formation. The defects were revealed by etching the silicon substrate to be spherical lumps and they consisted of platinum and silicon. X-ray diffraction spectra taken for specimens having a Pt/Ti/polysilicon structure with or without a gold layer on the platinum indicated the effect of gold in promoting the breakdown of the titanium layer as a diffusion barrier and on the formation of platinum silicide. A model for the mechanism is proposed in which the localized formation of platinum silicide is enhanced by gold at a defect in the titanium layer.     

Interfacial structure, residual stress and adhesion of diamond coatings deposited on titanium

The interfacial structures of diamond coatings deposited on pure titanium substrate were analyzed using scanning electron microscopy and grazing incidence X-ray diffraction. Results showed that beneath the diamond coating, there was one titanium carbide and hydride interlayer, followed by a heat-affected and carbon/hydrogen diffused Ti layer. Residual stress in the diamond coating and TiC interlayer under different process parameters were measured using Raman and X-ray diffraction (XRD) methods. Diamond coatings showed large compressive stress on the order of a few giga Pascal. XRD analysis also showed the presence of compressive stress in the TiC interlayer and tensile stress in the Ti substrate. With increasing deposition duration, or decreasing plasma power and concentration of CH₄ in gas mixture, the compressive residual stress in the diamond coating decreased. The large residual stress in the diamond coating resulted in poor adhesion of the coatings to substrate, but adhesion was also related to other factors, such as the thickness and nature of the TiC interlayer, etc. A graded interlayer design was proposed to lower the thermal stress, modify the interfacial structure and improve the adhesion strength.     

Ultrasonic cavitation test applied to thin metallic films for assessing their adhesion with mercaptosilanes and surface roughness

Evaluating the adhesion of micrometer or nanometer thick coatings is a challenging question which concerns many application fields. This is especially true for thin films deposited on a substrate of elastic modulus higher than that of the film, or for granular coatings, that do not allow the use of common adhesion tests. Usually, applied to characterize the wear resistance of bulk materials or thick coatings, the ultrasonic cavitation test is applied here to evaluate the adhesion strength of gold and copper thin films (~200 nm) that are evaporated on a silicon substrate. The test is shown to be sensitive enough to discriminate the influence of the surface chemistry on the adhesion strength of gold and copper films. Particularly, the role of (3-mercaptopropyl)triethoxysilane as an effective adhesion promotor is demonstrated. Furthermore, the role of surface roughness of the substrate is characterized and discussed in order to get further insights on the way this parameter interferes with the ultrasonic test and determines the adhesive strength of the coating. An estimate of the adhesive strength is given on the basis of the coating delamination kinetics.     

Influence of boron doping on mechanical and tribological properties in multilayer CVD-diamond coating systems

Titanium alloy (Ti6Al4V) substrates were deposited with smooth multilayer coatings, by hot filament chemical vapour deposition technique. The effect of boron doping on lattice parameter, residual stresses, hardness and coefficient of friction in multilayer-diamond coating system was studied. The frictional behaviour of the coatings was studied using a ball-on-disc micro-tribometer by sliding the coated samples of titanium alloy (Ti6Al4V) substrates against alumina (Al₂O₃) balls, and increasing normal load from 1 to 10 N. The average friction coefficient decreased from 0.36 to 0.29 for undoped multilayer-diamond coating system and from 0.33 to 0.18 for boron- doped (BD) multilayer-diamond coating system. The average indentation depths for undoped and BD multilayer- diamond coating systems were found to be equal to ～>58 and ～65 nm, respectively, and their hardness values were 60 and 55 GPa, respectively.     

Laser engineered multilayer coating of biphasic calcium phosphate/titanium nanocomposite on metal substrates

In this work, laser coating of biphasic calcium phosphate/titanium (BCP/Ti) nanocomposite on Ti-6Al-4 V substrates was developed. A continuous wave neodymium-doped yttrium aluminium garnet (Nd:YAG) laser was used to form a robust multilayer of BCP/Ti nanocomposite starting from hydroxyapatite and titanium nanoparticles. In this process, low power coating is realized because of the strong laser-nanoparticle interaction and good sinterability of nanosized titanium. To guide the optimization of laser processing conditions for the coating process, a multiphysics model coupling electromagnetic module with heat transfer module was developed. This model was validated by laser coating experiments. Important features of the coated samples, including microstructures, chemical compositions, and interfacial bonding strength, were characterized. We found that a multilayer of BCP, consisting of 72% hydroxyapatite (HA) and 28% beta-tricalcium phosphate (β-TCP), and titanium nanocomposite was formed on Ti-6Al-4 V substrates. Significantly, the coating/substrate interfacial bonding strength was found to be two times higher than that of the commercial plasma sprayed coatings. Preliminary cell culture studies showed that the resultant BCP/Ti nanocomposite coating supported the adhesion and proliferation of osteoblast-like UMR-106 cells.