化学气相沉积金刚石薄膜的摩擦学性能研究进展

介绍了化学气相沉积金刚石薄膜的主要方法 ,着重讨论了金刚石薄膜的摩擦学性能研究 ,简要分析了化学气相沉积金刚石薄膜中存在的问题。     

化学气相沉积金刚石薄膜的摩擦学性能研究进展

介绍了化学气相沉积金刚石薄膜的的主要方法，着重讨论了金刚石的摩擦学性能研究，简要分析了化学气相沉积金刚石薄膜中存在的问题。     

类金刚石薄膜的摩擦学特性及磨损机制研究进展

类金刚石薄膜已显示了重要的摩擦学应用价值,其中化学气相沉积的类金刚石薄膜(DLC)具有膜层致密、厚度均匀、摩擦学性能优良等特点成为广泛采用的一种沉积方法.本文介绍了气源成分、基体材料、摩擦环境、摩擦对偶、载荷及速度对化学气相沉积制备类金刚石薄膜的摩擦学特性的影响,概述了其摩擦磨损机理,同时探讨了进一步研究工作的方向.     

CVD金刚石薄膜摩擦学性能的研究现状

化学气相沉积(Chemical vapor deposition,CVD)金刚石薄膜通常是一种表面粗糙的多晶薄膜,其摩擦系数相对于光滑金刚石明显偏高,这制约着其在摩擦学领域的应用。在综合分析近年来该领域研究的基础上,总结了CVD金刚石薄膜摩擦学性能的主要影响因素,并从降低其摩擦系数的角度出发,着重讨论了几种提高CVD金刚石薄膜摩擦性能的途径。     

CVD金刚石薄膜抛光技术的研究进展

采用化学气相沉积方法在非金刚石衬底上沉积的金刚石薄膜,本质上为多晶,而且表面粗糙。本文论述了目前国际上出现的抛光ＣＶＤ金刚石薄膜的主要方法,包括机械抛光法、热－化学抛光法、化学－＝机械抛光法、等离子体／离子束抛光法以及激光抛光法等。     

PECVD法制备类金刚石薄膜的结构和摩擦学性能研究

采用射频一直流等离子体增强化学气相沉积技术在单晶硅衬底上沉积了类金刚石薄膜。用激光拉曼光谱仪和原子力显微镜对薄膜的结构和表面形貌进行了表征，并用纳米压痕仪测定了薄膜的硬度。用UMT微摩擦磨损试验机考察了薄膜在不同的滑行速度下薄膜的摩擦学性能。结果表明：所沉积的薄膜具有典型类金刚石薄膜的结构特征，薄膜表面光滑致密，硬度较高；薄膜与氧化铝陶瓷球对磨显示出良好的摩擦学性能，随着滑行速度的增加，薄膜的摩擦系数单调降低，但磨损寿命先增加后降低。     

金刚石晶粒和薄膜的侧向沉积

将传统的灯丝热解化学气相沉积系统改装成侧向沉积系统，并在其中进行了金刚石薄膜的正、侧向沉积。研究表明，侧向沉积的成核密度和生长度与正向沉积的情况基本相同，崦侧向沉积系统中金刚石颗粒和薄膜的沉积速率要比传统的沉积系统的高，但结构更趋复杂。讨论服基底对金刚石成核和生长过程的影响，深化了厂金刚石沉积机理的理解。     

CVD金刚石薄膜的成核机制

已有许多有效的方法来提高ＣＶＤ金刚石薄膜的成核密度，但成核机理仍有很多问题，本文简要介绍作者在这方面的一些工作。     

等离子体化学气相法沉积金刚石薄膜

本文介绍和评述了化学气相沉积法制备人造金刚石薄膜及其进展，重点评述了反应机理，发展历史，沉积方法，补底材料，检测手段，论述了有利于形成立方晶系金刚石材料的沉积条件。     

Latest progress on tribological properties of industrial materials

Wear is closely related to friction and lubrication; the study of these three subjects is known as tribology. In science and technology it is concerned with interacting surfaces in relative motion. Soft or hard film coating, alloying and composite structuring have all been developed to control wear and friction. This is achieved by improving materials and surfaces with some characteristics that improve resistance to friction and wear. In recent years, several new solid lubricant and modern lubrication concepts have been developed to achieve better lubricity and longer wear life in demanding tribological applications. Most of the traditional solid lubricants were prepared in the form of metal, ceramic and polymer–matrix composites. They have been used successfully in various engineering applications. Recent progress in thin-film deposition technologies has led to the synthesis of new generations of self-lubricating coatings with composite or multilayered architectures, by using multiplex surface treatments. In this study, typical wear behaviors of representative materials of metallic alloys, ceramics, polymeric materials, and composites are reviewed in relation to their friction behaviors. Additionally, modeling for the wear prediction is outlined.     

Physical and tribological properties of diamond films grown in argoncarbon plasmas

Nanocrystalline diamond films have been deposited using a microwave plasma consisting of argon, 2–10% hydrogen and a carbon precursor such as C₆₀ or CH₄. It was found that it is possible to grow the diamond phase with both carbon precursors, although the hydrogen concentration in the plasma was 1–2 orders of magnitude lower than normally required in the absence of the argon. Auger electron spectroscopy, X-ray diffraction measurements and transmission electron microscopy indicate the films are predominantly composed of diamond. Surface roughness, as determined by atomic force microscopy and scanning electron microscopy indicate the nanocrystalline films grown in low hydrogen content plasmas are exceptionally smooth (30–50 nm rms) to thicknesses of 10 m. The smooth nanocrystalline films result in low friction coefficients (μ = 0.04–0.06) and low average wear rates as determined by ball-on-disk measurements.     

Mechanical properties of diamond thin films

Abstract

The mechanical properties of diamond films deposited via hot filament chemical vapour deposition have been determined using a range of techniques, and related to the composition and morphology of the diamond films as determined by laser Raman spectroscopy. As the quality of the film increases, its hardness (as determined by the volume law of mixtures hardness model) also increases until it is larger than values often reported for polycrystalline bulk material, a consequence of the very small grain size in the films. Coating adhesion, as determined from indentation adhesion tests, also appears to improve with coating quality. Variations in the behaviour of the friction coefficient between diamond films and diamond and steel counterfaces are less well defined, but it appears that the surface morphology of the film is important in dictating the behaviour rather than the quality of the diamond. These results are discussed in the context of the potential use of diamond coatings in tribological applications.

MST/1695     

Polarization properties of thin films of diamond

Thin films transparent to optical radiation offer polarization properties that are enhanced when the thickness of the film is an odd multiple of the quarter-wavelength. The transmission and reflection properties of a 1.16-μm-thick film of diamond realized by plasma-assisted chemical vapor deposition have been studied at 10.6 μm. A compact polarizer built with four films at a Brewster angle revealed an extinction ratio of better than 1:1000 of the S polarization. The interest in optics in which parasitic-reflected or transmitted beams do not exist is pointed out. The high damage threshold of diamonds opens the possibility of controlling the polarization characteristics of high-power lasers used, for example, for soldering and cutting applications.     

Structure and tribological properties of reactively sputtered Zr-Si-N films

Zr-Si-N films were deposited on silicon and steel substrates by magnetron sputtering of a Zr-Si composite target in Ar-N₂ reactive mixtures. The silicon concentration in the films was adjusted in the 0-7.6 at.% range by varying the surface of Si chips located on the erosion zone of the target. The films were characterised by X-ray diffraction, electron probe microanalysis, atomic force microscopy and wear tests. The structure and the tribological properties of Zr-Si-N films were compared to those of ZrN coatings. Depending on the silicon concentration, the films were either nanocomposites (nc-ZrN/a-SiN_x) or amorphous. Introduction of silicon into the zirconium nitride coatings induced a change in the preferential orientation of the ZrN grains: [111] for ZrN films and [100] for Zr-Si-N ones. This texture modification was also observed for a ZrN film deposited on an amorphous SiN_x layer. Thus, within our deposition conditions, the occurrence of a-SiN_x enhanced the [100] preferred orientation. Friction and wear behaviour of the films were carried out against spheres of alumina or 100 Cr6 steel by using a ball-on-disc tribometer. The results showed that addition of silicon into ZrN-based coating induced a strong decrease in the friction coefficient and in the wear rate compared to those of ZrN films. These results were discussed as a function of the films structure and composition.     

Surface acoustic wave properties of freestanding diamond films

"Ideal" diamond has the highest acoustic velocity of any material known, and is of great interest as a substrate material for high frequency surface acoustic wave (SAW) device structures. However, little is known of the acoustic wave propagation properties of polycrystalline diamond grown by chemical vapour deposition (CVD) techniques, the commercially accessible form of this material. We report on propagation of laser-generated SAW on three forms of freestanding CVD diamond samples, "white" polycrystalline, "black" polycrystalline, and "highly oriented" diamond. Despite differing sample nature, SAW waves propagating along the smooth (nucleation) side of the diamond showed similar velocities in the range 10600-11900 ms(-1). These results are discussed in terms of the potential of each form of CVD diamond for SAW device fabrication.     

Temperature enhanced gas sensing properties of diamond films

Nanocrystalline diamond (NCD) film was used as a functional part of gas sensor. The gas sensing properties of H-terminated nanocrystalline diamond films were examined to oxidizing gases (i.e., COCl₂ and humid air). Pronounced increase in the surface conductivity (3 orders of magnitude) was found after sensor exposure to phosgene gas and was explained by the surface transfer doping effect. We also present a possible way how to achieve sensor selectivity, i.e. how to distinguish between phosgene and humid air (the mostly present background gas in a common environment).     

Structure and tribological properties of Ag films deposited at low temperature

The effects of substrate temperature on the structure and tribological properties of Ag films deposited at low temperatures (LT, 130-217 K) by arc ion plating (AIP) have been studied. The structure and morphology of the Ag films were analyzed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and field emission scanning electron microscope (FESEM). The results showed that there exist (1 1 1) and (2 0 0) preferred orientation transitions for decreasing temperature at different bias voltages. The tribological properties were evaluated by a ball-on-disk tribometer and wear tracks were analyzed by means of scanning electron microscopy (SEM). The results show that substrate deposition temperature significantly affected the wear of LT Ag films. For each bias voltage studied, the film showing the highest wear rate was deposited at the lowest temperature and the film with the lowest wear rate, (significantly lower than room temperature (RT) deposited Ag films), was deposited at a temperature between the highest and the lowest temperatures examined. The wear mechanism was discussed in terms of lubrication effect of film material transferred to the counterpart and its dependence on the microstructure of the original deposited film.     

Electrical properties of diamond films grown at low temperature

The unique electronic properties of diamond, associated with the emergence of chemical vapour deposition (CVD) methods for the growth of thin films on non-diamond substrates, have led to considerable interest in electronic devices fabricated from this material. In our previous work, we found that polycrystalline diamond films can be deposited at 250 °C using CH₄---CO₂ gas mixtures. Studying the electrical properties and the upcoming problems of applications of low-temperature diamond films are relevant concerns.

In this work, the electrical properties of diamond films grown at low temperatures were studied and compared with those of conventional diamond films. Platinum was used as the upper electrode. The resistivity of low-temperature diamond was around three orders of magnititude lower than that of conventional diamond. However, both the low temperature and conventional growth diamond exihibited rectifying behavior when platinum was used as the upper electrode.     

Preparation and tribological properties of novel carbon nanotube self-assembled composite films

Carbon nanotube (CNT) composite thin films were prepared on a single-crystal silicon substrate by a self-assembling process from a specially formulated solution. Rare earth solution (RES) surface modification and appropriate acid-treatment methods were used to functionalise carbon nanotubes (CNTs). Silane coupling regent (3-mercaptopropyl trimethoxysilane (MPTS)) was prepared first. The terminal thiol groups (–SH) in the film was oxidised to sulphonic acid groups (–SO₃H) in situ to enhance the film with good chemisorption ability. Treated Caron nanotubes were deposited on the oxidised MPTS–SAM by means of chemisorption with the SO₃H group. The surface energy, chemical composition, phase transformation and surface morphology of the films were analysed using contact angle measurements, X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) and atomic force microscopy. As a result, a conclusion could be made that some lanthanum elements react with –SO₃H groups on the surface of the substrate by a chemical bond, which will improve the bonding strength between the films and the CNTs. Since the CNT thin films were well adhered to the silicon substrate, it might find promising application in the surface-modification of single-crystal Si and SiC in microelectromechanical systems (MEMS).