DLC基纳米多层膜摩擦学性能的研究进展与展望

类金刚石（DLC）薄膜是一种良好的固体润滑剂,能够有效延长机械零件、工具的使用寿命。DLC基纳米多层薄膜的设计是耐磨薄膜领域的一项研究热点,薄膜中不同组分层具备不同的物理化学性能组合,能从多个角度（如高温、硬度、润滑）进行设计来提升薄膜力学性能、摩擦学性能以及耐腐蚀性能等。综述了DLC多层薄膜的设计目的与研究进展,以金属/DLC基纳米多层膜、金属氮化物/DLC基纳米多层膜、金属硫化物/DLC基纳米多层膜以及其他DLC基纳米多层膜为主,对早期研究成果及现在的研究方向进行了概述。介绍了以上几种DLC基纳米多层膜的现有设计思路（形成纳米晶/非晶复合结构、软/硬交替沉积,诱导转移膜形成,实现非公度接触）。随后对摩擦机理进行了分析总结：1）层与层间形成特殊过渡层,提高了结合力;2）软/硬的多层交替设计,可以抵抗应力松弛和裂纹偏转;3）高接触应力和催化作用下诱导DLC中的sp3向sp2转化,形成高度有序的转移膜,从而实现非公度接触。最后对DLC基纳米多层膜的未来发展进行了展望。     

Use of diamond-like carbon with tungsten (W-DLC) films as biocompatible material

Diamond-like carbon (DLC), also known as amorphous hydrogenated carbon (a-C:H), are a class of materials with excellent mechanical, tribological and biological properties. When the DLC films are enhanced with other elements, all of these properties can be changed within a certain range.In this work, reactive magnetron sputtering was used to deposit W-DLC (hydrogenated tungsten carbide) films on Ti6Al4V (implant material). Many films were made using pure tungsten (99.99%) target and different plasmas processes, with different ratio among argon and methane. It was possible to change the films composition (from pure amorphous carbon to carbon enhanced with tungsten) according to ratio of argon and methane plasma. Between all films processed, the carbon films enhanced with tungsten showed good results in the “in vitro” cytotoxicity testing. Raman spectroscopy was used to analyze the chemical bonds kinds and the chemical bonds quantities. The Rutherford Back Scattering (RBS) was used to analyze the films compositions. The chemical inertness was analyzed by scanning voltametry. W-DLC thin films obtained in these processes have low roughness, high chemical resistance, good adhesion and show a high biocompatibility, when compared with common DLC thin films. Hence we have concluded that the tungsten concentrations in the DLC films make an important role to improve the properties of the DLC layers.     

Determination of residual stress in spherical balls by resonant ultrasound spectroscopy

In this study, resonant ultrasound spectroscopy (RUS) for determining residual stress in small size spherical balls was examined. Natural frequencies of spherical balls with residual stress were analysed by finite element method. Resonant frequencies of spherical balls were experimentally measured by a RUS system. Both natural frequencies in the analysis and the resonant frequencies measured in the experiment decreased as the compressive circumferential stress at the ball surface increased. It was concluded, on the basis of both analytical and experimental results, that the measurement of the resonant frequency by the RUS system along with the analysis of natural frequency are effective for determining the values and distributions of unknown residual stress in spheres.     

梯度掺杂和纳米多层调制类金刚石薄膜的摩擦学性能

采用阴极电弧结合离子源辅助磁控溅射复合技术,充分利用薄膜组成多元化、晶体纳米化、组成和结构多层化、梯度化的优势,分别制备了多元素复合过渡层缓冲的钨元素梯度掺杂的和Cr元素纳米多层调制的类金刚石(DLC)薄膜,研究掺杂元素含量和调制层厚度对薄膜组成与结构、力学性能和摩擦磨损性能的影响。梯度掺杂、多元、多层结构降低了DLC膜和钢基体之间因组成和结构不同产生的应力,改善了膜基结合力,材料综合耐磨损性能大幅度提高。     

不同过渡层对DLC薄膜力学性能和摩擦学性能的影响

薄膜与基体间的界面结合性能是决定薄膜性能发挥的关键要素。针对类金刚石薄膜(DLC)在硬质合金上结合力差的问题,采用线性阳极离子束复合磁控溅射技术在硬质合金YG8基体上设计制备了单层W过渡层、WC过渡层、双层W过渡层和三层W过渡层4种不同W过渡层的DLC薄膜,探讨了不同过渡层对DLC薄膜力学和摩擦学性能的影响。结果表明:不同过渡层结构的DLC薄膜结构致密,界面柱状生长随着层数增加及过渡层厚度的降低而打断,有利于改善薄膜的韧性。当为三层W过渡层时,DLC薄膜的断裂韧性达到最大值6.44 MPa·m1/2;与单层W过渡层相比,薄膜硬度有小幅下降,但薄膜内应力降低了55%,且膜/基匹配性更佳,结合强度高达85N,此时薄膜具有较低的摩擦因数和磨损率,表现出比较优异的抗磨减摩性能。     

Composition and structure of Ti-C/DLC graded composite films

The Ti-C→DLC gradient composite films were characterized systematically.The elemental depth profile and elemental chemical state evolution were determined by X-ray photoelectron spectroscopy (XPS).The transmission electron microscope (TEM) and high-resolution transmission electron microscopy (HRTEM) were used to study the structure of interfacial zone between DLC film and Ti-C layers.Results show that there are composition transition zone between DLC film and either Ti-C layer or steel substrate on condition that pre-deposited Ti layers on the steel substrate then plasma based bias deposited DLC films.In Ti-C graded layer,the chemical state of titanium and carbon are changed gradually.The structures of zone in Ti-C layer near the DLC film is consisted of random oriented nanocrystallines TiC dispersed in amorphous DLC matrix.The structure of the zone between DLC film and Ti-C graded layer is gradually changed too.     

Effect of metallic interfacial layers on the properties of diamond-like carbon thin films

Diamond like carbon (DLC) thin films with metallic interfacial layers of aluminum and nickel-chromium (Al and Ni-Cr) were grown using a low cost hybrid technique involving a resistive heating thermal evaporator and radio frequency plasma enhanced chemical vapor deposition techniques. Stress, hardness, elastic modulus, bonding, phase, and electrical conductivity of these films were investigated. Introduction of interfacial Al and Ni-Cr layers in DLC led to drastic improvement of its conductivity along with a significant reduction in residual stress but with some reduction of hardness and the elastic modulus. The structural and surface properties of thin films were studied using X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy techniques.     

Influence of nitrogen gas on structure and properties of DLC films prepared by XeCl pulsed laser deposition

Diamond-like carbon （DLC） films were prepared by PLD process using 308 nm（XeCl） laser beam with high power （500 W） and high fi＇equency（300 Hz）. The effects of nitrogen pressure on the structure and properties of the DLC films under such extremely high power and repetition rate were studied. The results indicate that the microstructures of the films are varied fi＇om amorphous carbon to graphitized carbon in long-order with the increase of N2 pressure, and the optical properties of the films are deteriorated as compared to that of DLC films without nitrogen.     

Application of Plasma Enhanced Chemical Vapor Deposition for Fingerprint Resistance

SiOx and diamond-like carbon(DLC)coatings as the fingerprint resistance and corrosion resistance layers were deposited by capacitively coupled plasma(CCP)-enhanced chemical vapor deposition powered by radio frequency(RF-PECVD).In here hexamethyldisiloxane(HMDSO)as monomer for SiOx coating,C2H2 as the carbon source for DLC growth precursor,and Ar as the dilution gas were utilized.The important factors affected fingerprint resistance was explored in detail.Besides,the corrosion resistant test on coatings and substrates were then examined by the potentiodynamic polarization measurement and salt-spray corrosion test,respectively.The chemical structure and composition of SiOx and DLC films were analyzed by FTIR,and the relationship between them and anti-corrosion property was discussed.The results show that the DLC coating demonstrates a better anti-fingerprint behavior than that of coated SiOx,especially in acidic solution environment.     

类金刚石薄膜的紫外可见区光学特性研究

在类金刚石薄膜（DLC）光学特性的研究方面,主要工作集中在红外区光学特性,在可见区和紫外区光学特性研究方面存在空白;鉴于此详细研究了采用脉冲电弧沉积DLC薄膜在可见区和紫外区的光学特性。利用脉冲电弧离子镀技术,在石英基片上和不同工艺条件下制备了类金刚石薄膜,研究了类金刚石薄膜在紫外和可见区的光学常数、光学透过率和光学能隙。结果表明,主回路电压是薄膜的光学常数变化的主要影响因素,低主回路电压下制备的类金刚石薄膜具有较低消光系数和折射率;不同的工艺条件下制备的类金刚石折射率从2．56变化到1．89（波长400nm）;沉积速率对薄膜的折射率和消光系数没有明显的影响;DLC薄膜的光学能隙在3．95eV左右;紫外区和可见区的透过率谱和椭偏仪测得的光学常数相互一致。     

Triode plasma nitriding and PVD coating: A successful pre-treatment combination to improve the wear resistance of DLC coatings on Ti6Al4V alloy

Diamond-like carbon (DLC) coatings have found great applicability in the automotive industry because of their low friction coefficient and high wear resistance. Nevertheless, their tribological performance can be greatly reduced on soft substrates such as titanium alloys. The hard DLC coating cannot usually follow elastic and plastic deformation of the substrate without failing. In order to overcome this property mismatch between hard coating and soft substrate, triode plasma nitriding was applied as a pre-treatment to improve the mechanical properties of the Ti6Al4V alloy and further enhance the load support for the DLC coating. DLC and multilayered TiN/DLC, CrN/DLC CrAlN/DLC coatings were deposited onto “standard” and plasma nitrided Ti6Al4V substrates. Triode plasma nitriding increased the load-bearing capacity of the coating/substrate system, as higher critical adhesion loads were recorded for DLC coatings on plasma nitrided Ti6Al4V substrates. This treatment also reduced the wear rate of the DLC coating/substrate. Further load support and lower wear rates were achieved by using TiN, CrN and CrAlN as intermediate layers on plasma nitrided Ti6Al4V substrates.     

Ultrasound as a probe of dislocation density in aluminum

Dislocations are at the heart of the plastic behavior of crystalline materials yet it is notoriously difficult to perform quantitative, non-intrusive measurements of their single or collective properties. Dislocation density is a critical variable that determines dislocation mobility, strength and ductility. On the one hand, individual dislocations can be probed in detail with transmission electron microscopy. On the other hand, their collective properties must be simulated numerically. Here we show that ultrasound technology can be used to measure dislocation density. This development rests on theory—a generalization of the Granato–Lücke theory for the interaction of elastic waves with dislocations—and resonant ultrasound spectroscopy (RUS) measurements. The chosen material is aluminum, to which different dislocation contents were induced through annealing and cold-rolling processes. The dislocation densities obtained with RUS compare favorably with those inferred from X-ray diffraction, using the modified Williamson–Hall method.     

Preparation of H-terminated and aminated diamond like carbon surfaces

H-terminated DLC layers were synthesized on SiO2 substrate by radio frequency (RF) magnetron plasma-enhanced chemical vapor deposition (PECVD) in a conventional reactor using C4H10 as carbon source. As-deposited DLC films were characterized by Raman spectroscopy, scanning electron microscopy (SEM) as well as atomic force microscopy (AFM). The chemical reactivity of the obtained DLC surface was further investigated by exposing the photochemically oxidized DLC surface to a silane reagent. The course of the reaction was followed using water contact angle and X-ray photoelectron spectroscopy.     

类金刚石薄膜的摩擦学特性研究进展

类金刚石薄膜(DLC)具有优良的摩擦磨损性能,但是DLC薄膜的摩擦学特性强烈依赖于制备技术、摩擦接触点的表面化学状态和物理状态,因此进一步提高类金刚石薄膜的摩擦学特性是目前的热门研究方向之一.在综合分析了近年来该领域研究的基础上,总结了影响DLC薄膜摩擦学性能的因素,并分析了各个因素的影响机理,以期找出一些规律为适应类...     

射频输入功率对类金刚石薄膜性能的影响

为了得到类金刚石薄膜的性质和制备参数之间的对应关系,利用射频等离子体增强化学气相淀积在单晶硅的(100)面上制备了类金刚石薄膜,反应气体是甲烷和氢气的混合气.研究了射频源的输入功率对类金刚石薄膜性能的影响.采用Raman光谱、X射线光电子能谱、原子力显微镜和纳米压痕仪对薄膜的微观结构、表面形貌、硬度和弹性模量进行了研究,结果表明:制备的薄膜具有典型的不定型碳的结构特征、薄膜致密均匀,随着入射功率的提高,薄膜的sp3含量、硬度以及弹性模量先增加后减小,并且在100W时达到最大值,在400W时薄膜出现碳化.     

A critical review of diamond like carbon coating for wear resistance applications

In recent years innovation in carbon based materials have encouraged both researchers as well as industrialists to develop materials/composites with improved tribological properties. Researchers have been fascinated to develop diamond like carbon (DLC) or carbon nanotubes (CNTs) reinforced coatings to their good corrosion resistance, excellent wear resistance, good adhesion strength, and self -lubricious nature. The present review article is mainly focused on various techniques employed in order to process DLC/CNTs coatings as well as provide a summary of DLC/CNTs deposition on different substrates. The present study includes major types, properties and tribological behavior of carbon based materials and mechanisms involved in coating deposition. The study also discusses that deposition of DLC/CNTs coatings on the substrate materials enhances the wear, corrosion and mechanical properties of the substrate.     

偏压对DLC薄膜结构及摩擦学性能的影响

目的通过调节偏压,改善无氢DLC薄膜的微观结构,提高其力学性能和减摩抗磨性能。方法采用离子束辅助增强磁控溅射系统,沉积不同偏压工艺的DLC薄膜。采用原子力显微镜(AFM)观察薄膜表面形貌,采用拉曼光谱仪对薄膜的微观结构进行分析,采用纳米压痕仪测试薄膜硬度及弹性模量,采用表面轮廓仪测定薄膜沉积前/后基体曲率变化,并计算薄膜的残余应力,采用大载荷划痕仪分析薄膜与不锈钢基体的结合力,采用TRB球-盘摩擦磨损试验机评价薄膜的摩擦学性能,采用白光共聚焦显微镜测量薄膜磨痕轮廓,并计算薄膜的磨损率。结果偏压对DLC薄膜表面形貌、微观结构、力学性能、摩擦学性能都有不同程度的影响。偏压升高导致碳离子能量升高,表面粗糙度呈现先减小后增加的趋势,-400V的薄膜表面具有最小的表面粗糙度且C─C sp^3键含量最多,这也导致了此偏压下薄膜的硬度最大。薄膜的结合性能与碳离子能量大小呈正相关,-800 V时具有3.98 N的最优结合性能。不同偏压工艺制备的薄膜摩擦系数随湿度的增加,均呈现减小的趋势,偏压为-400V时,薄膜在不同湿度环境中均显示出最优的摩擦学性能。结论偏压为-400 V时,DLC薄膜综合性能最优,其表面粗糙度、硬度、结合力和摩擦系数分别为2.5 nm、17.1 GPa、2.81 N和0.11。     

Effects of N-doping on the microstructure, mechanical and tribological behavior of Cr-DLC films

We report on the effects of nitrogen doping on Cr-containing diamond-like carbon (Cr-DLC) films. DLC, Cr-DLC and N-doped Cr-DLC films were deposited on (100) Si substrates using a hybrid plasma-assisted CVD/PVD process. Film microstructure, composition and chemical state of elements were studied using transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Mechanical and tribological properties were investigated using microhardness testing and pin-on-disc experiments. Analysis by TEM and XPS shows that the Cr-DLC films contain a dispersion of amorphous, Cr-rich nanoparticles. In the N-doped films, N combines with C and partly transforms the Cr-rich nanoparticles into chromium carbon nitrides, CrC(N), dispersed in the amorphous DLC matrix. Also, a significant portion of N is incorporated into the C network. The N-doped Cr-DLC films were found to possess higher hardness, lower intrinsic stresses and somewhat higher coefficient of friction and wear rate than Cr-DLC and DLC films. Such influence of the N-doping on the properties is attributed to the formation of CrC(N) nanoparticles and C-N bonds in the DLC matrix.     

全方位离子注入与沉积类金刚石碳膜的结构与性能

用等离子体浸没离子注入与沉积(PIIID)复合强化新技术在AISI440C不锈钢表面制备了类金刚石(DLC)碳膜。膜层表面的原子力显微镜(AFM)形貌显示出DLC膜结构致密均匀。Raman光谱分析结果表明,制备的DLC主要是由金刚石键(sp3)和石墨键(sp2)组成的混合无定形碳膜,且sp3键含量大于10%。以纯石墨棒做阴极,C2H2为工作气体条件下合成的DLC薄膜中,sp3键含量总体上较单纯用石墨作阴极而无工作气体条件下合成的DLC薄膜中sp3键含量高。与基体相比,薄膜试样的显微硬度和摩擦磨损性能均得到了较大改善,最大硬度提高88.7%,磨损寿命延长超过4倍。     

Determination of elastic moduli for a spherical specimen by resonant ultrasound spectroscopy

Resonant ultrasound spectroscopy (RUS) is based on the principle that mechanical resonant response of solids depends on its elastic moduli, shape and density. Elastic moduli or the other properties can be identified from resonant frequencies as inverse problem. In this study, the method to determine elastic moduli of a spherical specimen without information of resonant mode was described. We confirmed that resonant frequencies have to be measured under condition of free surface, and adequate number of resonant frequencies used in calculation needs enough number to include the sensitive mode to Poisson's ratio. By this method, we determined elastic moduli of BK-7 glass. The calculated frequencies from the elastic moduli determined by this technique had good agreement with the measured, the absolute accuracies for the Δf was less than 0.4%.