基于LFM的类金刚石膜纳米摩擦现象研究

使用原子力显微镜(AFM)中的侧向力(LFM)模式对类金刚石膜纳米尺度的摩擦现象进行了研究,主要考察了载荷、微观形貌、粘附对类金刚石膜纳米摩擦性能的影响.首先结合粘附的影响提出了适用于外加载荷在100 nN以下类金刚石膜纳米摩擦力表征的修正Amonton公式.其次,试验发现摩擦过程中表面接触峰的斜率对薄膜的微观摩擦力的影响较大,微观摩擦系数与倾角θ成正比例关系,最后结合两者给出了综合考虑载荷、表面形貌、粘附且可用于类金刚石膜纳米尺度摩擦力表征的数学方法.     

工况参数对类金刚石膜摩擦学性能的影响

采用非平衡磁控溅射技术在高速钢基体上以C2H2为反应气源制备了含氢类金刚石(DLC)膜.使用激光拉曼光谱仪、X射线光电子能谱仪和原子力显微镜分析和观察了DLC膜的微观结构及表面形貌,结果表明:DLC膜表面由纳米级别的圆形颗粒堆积而成,其结构呈现出DLC的典型Raman光谱特征,薄膜中的碳元素主要以sp2C键、sp3C键和C-O键的形式存在.以G Cr15钢球为摩擦配副,在球盘式摩擦磨损试验机上考察了DLC膜在大气干摩擦条件下的摩擦学性能.实验结果发现:在摩擦初始阶段,DLC膜的摩擦系数从实验开始到达峰值的时间随着载荷和速度的增大都是减少的;而在摩擦稳定阶段,DLC膜的平均摩擦系数随着载荷和速度的增大先减小后增大;速度对DLC膜摩擦系数的影响比载荷更加显著.用扫描电子显微镜观察了磨痕形貌并分析了磨损机理:DLC膜的磨损特征主要为以犁沟现象为主的粘着磨损.随着速度的增加,磨痕表面犁沟现象变弱;而随着载荷的增加,磨损表面的犁沟现象变明显.     

DLC膜在磨损、表面改性及力电耦合作用下损伤特性

为评价超薄类金刚石（DLC）膜在使用过程中的安全状况，利用原子力显微镜（AFM）的多模式功能，从磨损、表面改性、力电失效3个方面对DLC膜进行了试验研究．研究结果表明：相同法向力作用在不同厚度薄膜的磨损深度不同；对DLC膜的形貌和电学特性进行比较发现，磨损区域导电性比未磨损区域强；在厚度为64．09nm薄膜施加正向25V电场作用下，当针尖作用在表面的压力超过一定临界压力（375nN）之后，薄膜发生击穿，形成凹坑。     

Si_3N_4球表面DLC膜在干摩擦条件下的摩擦学性能分析

采用非平衡磁控溅射技术在Si3N4球及高速钢基体上制备了类金刚石(DLC)膜。采用UMT-II型球盘式摩擦磨损试验机分别考察了Si3N4球、镀DLC膜Si3N4球及GCr15球的摩擦学性能,并分析了不同滑动速度和载荷下Si3N4球表面DLC膜的摩擦学性能。研究结果表明:Si3N4球的摩擦系数及磨损率约为GCr15球的一半,但因Si3N4球脆性较大,在摩擦过程中摩擦接触表面容易剥落;Si3N4球表面镀DLC膜能有效地改善Si3N4球脆性大的弱点,并具有良好的减摩作用;Si3N4球表面DLC膜所组成摩擦副的平均摩擦系数随着载荷的增加而增大;随着速度的增加摩擦副的摩擦系数先增大而后减小,滑动速度对摩擦副摩擦系数的影响比载荷明显。实验结果表明Si3N4球表面镀DLC膜适合于高速轻载的工况。     

基于RFPECVD方法不锈钢上沉积类金刚石薄膜的机械与摩擦特性

讨论用射频等离子体增强化学气相沉积(RFPECVD)工艺,在室温下实现在1Cr18Ni9Ti不锈钢基底上镀类金刚石(DLC)膜.为提高DLC膜的结合力,首先在不锈钢基底上沉积Ti/TiN/TiC功能梯度膜.借助所设计的界面过渡层,成功地在不锈钢基底上沉积了一定厚度的DLC膜.通过优化沉积参数,所沉积的DLC膜在与100Cr6钢球对磨时摩擦系数低于0.020.在摩擦过程中DLC膜的磨损机制借助SEM、Raman分析进行了研究.     

厚度对DLC薄膜内应力的影响研究

采用ECR微波等离子体增强化学气相沉积的方法于C1H2/H2/Ar2等离子环境中在单晶Si(111)晶面上制备了不同厚度的DLC膜样品,研究了薄膜的厚度随沉积时间的变化及薄膜的硬度、内应力随厚度的变化关系.结果表明,在沉积时间变化范围内,厚度与沉积时间基本呈线性关系,沉积速率可达80nm/min;制备态样品存在的内应力...     

类金刚石薄膜在干摩擦、油和脂润滑条件下的摩擦学性能分析

通过钢/类金刚石(DLC)薄膜摩擦副在干摩擦4、122油和L252脂润滑条件下的球-盘摩擦学试验,对比分析润滑条件、载荷、速度对DLC膜摩擦系数的影响,利用原子力显微镜分析膜层磨损性能,研究润滑条件对膜层磨损寿命的影响。结果表明:油、脂润滑下DLC膜最大静摩擦系数分别减小了17%和38%;从0～2000 r/min转速范围内,DLC膜摩擦系数随转速增加而减小,油润滑下相比干摩擦DLC膜摩擦系数小15%～48%,脂润滑下相比干摩擦DLC膜摩擦系数在0～500 r/min转速范围小,超过500 r/min后干摩擦DLC膜摩擦系数小;油和脂润滑条件下,DLC膜层的磨损程度明显降低,磨损率相比干摩擦条件下分别减小了7.4倍和15.5倍。     

FCVA法沉积的超薄类金刚石薄膜的结构与热稳定性

采用FCVA方法沉积了厚度分别为2nm、5nm、10nm和30nm的类金刚石薄膜.在氩气保护下对类金刚石薄膜进行了180、300、400和600℃,保温6h的退火处理.用Raman光谱和宽光谱变角度椭偏仪研究了DLC薄膜的结构和热稳定性.实验结果表明,随着薄膜厚度增大,FCVA法沉积的DLC薄膜中的sp3键含量增加,薄膜热稳定性逐渐改善.当DLC薄膜的厚度为30nm时,薄膜中的sp3键含量达到最高值,薄膜具有最好的热稳定性.当退火温度为600℃时,厚度为2nm和5nm的DLC薄膜结构由非晶态转变为微晶态;厚度为10nm和30nm的DLC薄膜结构发生转变但仍保持非晶态.随着退火温度的升高,各个厚度的DLC薄膜的光学带隙Eg均先增大后减小.     

DLC膜厚度对镁基表面DLC/MAO复合膜层性能的影响

采用线性离子束沉积技术于AZ80镁合金微弧氧化(MAO)陶瓷层表面沉积不同厚度的类金刚石碳(DLC)膜,形成DLC/MAO复合膜层。对比研究4种膜基系统的表面结构特征、力学性能以及摩擦学性能差异。结果表明:随DLC膜厚度增加,复合膜层表面微孔数量减少,孔径减小,但凹凸不平趋势增加,且DLC膜表面颗粒特征更加明显,表现为DLC-80min/MAO/AZ80膜基系统具有最小的表面粗糙度,最大的硬度H、弹性模量E及H/E值;不同厚度DLC/MAO/AZ80膜基系统平均摩擦因数较MAO/AZ80显著降低;DLC膜厚度增加导致3种复合膜基系统的表面微观结构改变,使得摩擦因数与磨痕形貌存在差异;各膜基系统表面磨痕处均形成了Fe的转移层,由于表层DLC膜"裸露"的大量C对磨损界面具有很好的润滑作用,而使得镁合金基体获得有效保护。     

打桩机用GCr15钢表面磁控溅射DLC膜的组织和摩擦学性能

为了提高打桩机用GCr15钢的摩擦学性能,采用磁控溅射在其表面制备了一层掺Cr的DLC膜,对比了该膜层处于不同工况下的微观组织和摩擦学特性.结果 表明:DLC膜的表面区域出现了许多球形颗粒,DLC膜的组织形态较为均匀,表面粗糙度接近9 nm.DLC膜形成了单一衍射峰,表明DLC膜属于一种非晶态组织.对DLC膜进行纳米压痕测试形成了光滑过渡的载荷变化曲线,推断制备得到的DLC膜由均匀组织构成.以NaCl溶液作为润滑介质时测试得到的摩擦系数为0.079,得到了较为稳定的曲线.NaCl溶液可以对摩擦配副的接触面产生良好的减摩作用.与不合DLC膜的GCr15/GCr15配副相比,DLC/GCr15配副有更小的摩擦系数,表明DLC膜能够对GCr15钢起到良好的减摩效果.接触压力由1.00 MPa提高到3.60 MPa时,摩擦系数下降;随着接触压力的进一步提高,摩擦升温会加速DLC膜的石墨化进程,使得摩擦系数发生一定程度的增加.     

Properties of GaAs solar cells coated with diamondlike carbon films

Thin films of amorphous diamondlike carbon (a:DLC) were deposited on GaAs solar cells, with and without antireflecting coating. The films were deposited by decomposition of CH₄ plasma using a r.f. generator (13.56 MHz). The reflected light from these cells, in the visible light, decreased after deposition of a:DLC film thickness (from 33% for t=0 nm to 14% for t=60 nm) which indicates antireflecting properties. The I–V measurements show an increase of the short circuit current (I_sc) with films thickness up to t40–60 nm, where it reaches a maximum and then decreases for higher thickness (t>60 nm). The efficiency (η) of the cells, as a function of the a:DLC thickness, shows a maximum value of 15% for t=50 nm. It was also shown, that the a:DLC films is a useful material as a protecting material for cells for operation in an abrasive environment. In abrasive environment, the efficiency of the coated cell maintains the level of about 12% whereas the efficiency of uncoated cells drop sharply from 15.5% to 6%.     

Adhesion studies of diamond-like carbon films deposited on Ti6Al4V substrate with a silicon interlayer

Diamond-like carbon (DLC) films have proven quite advantageous in many tribological applications due to their low friction coefficient, their extreme hardness, and more recently their high adherence on different substrate materials. However, for many applications, DLC films as thick as 2 μm are required, which cause high residual stress. In order to overcome this problem, this study observed the behavior of different thicknesses of silicon interlayer between DLC films and Ti6Al4V substrates. The study also analyzed the relation of growth parameters to the mechanical properties of DLC films. Silicon and DLC films were grown by using a rf-PECVD at 13.56 MHz with silane and methane atmospheres, respectively. The contribution of an interlayer thickness to the adhesion between the DLC films and Ti6Al4V substrate was evaluated by using a micro-scratch technique. The hardness and friction coefficient were evaluated by using microindentation and lateral force microscopy (LFM), respectively. Raman scattering spectroscopy was used to characterize the film quality. A correlation was found between the intrinsic stress and adhesion of DLC film and the parameters of the silicon interlayer growth. The addition of a silicon interlayer successfully reduced intrinsic stress of the films, even as measured by using a perfilometry technique.     

FCVA法制备的超薄类金刚石薄膜的结构分析

用真空阴极过滤电弧(Filtered Cathode Vacuum Arc,FCVA)法制备厚度分别为50 nm,30 nm,10 nm,5 nm,2 nm的类金刚石(DLC)薄膜,利用拉曼光谱和电子能量损失谱研究了薄膜的结构,分析了硬度和内应力的变化趋势。结果表明,随着薄膜厚度的减小,可见光拉曼光谱高斯分解的G峰位置向低波数方向移动,D峰和G峰强度之比Id/Ig不断增大,G峰面积与D峰面积之比Ag/Ad减小;说明随着薄膜厚度的减小,DLC薄膜中的sp3键含量减少,有序化的sp2团簇增加。电子能量损失谱的结果也表明薄膜厚度的减小会引起薄膜中sp3键含量的减少。当薄膜的厚度由50 nm变为30 nm时,薄膜硬度由53.85 GPa减小为39.64 GPa,内应力由4.63 GPa降低为3.47 GPa,随着厚度降低,薄膜的硬度和内应力呈下降趋势。     

Tribological properties of multilayer DLC/W-DLC films on Si

Multilayer films of diamond-like carbon (DLC) and tungsten-containing diamond-like carbon (W-DLC) films were deposited onto silicon wafers using radio frequency chemical vapor deposition (RFCVD) and a magnetron sputtering method. The W-DLC layer was deposited on the silicon wafer with less than 60 W magnetron output. The DLC layer was then deposited on the W-DLC layer.Surface morphology was investigated by atomic force microscopy and the film structure by transmission electron microscopy. Friction tests for multilayered films were performed in a nitrogen atmosphere at room temperature using a ball-on-disk tribometer. A conventional stainless steel ball was used for the test.The surface profiles seen by atomic force microscopy showed that round-shaped clusters of around 100 nm were observed in just the single W-DLC layer. These clusters were considered to be tungsten or tungsten-carbon composites. In the case of the DLC/W-DLC multilayered structure, the top DLC layer covered the W-DLC single layer and smoothed the surface of the W-DLC film.Friction tests demonstrated that the friction coefficient of the W-DLC single layer was above 0.6 and increased gradually as the number of cycle increased. The W-DLC films partially broke down during our measurements. However the DLC/W-DLC multilayer films showed stable friction properties and were observed for up to 100,000 cycles. Their friction coefficient was typically less than 0.1 at 10 cm/s rotating speed. The DLC/W-DLC multilayer films exhibited stable low friction properties in a long term test under a nitrogen atmosphere.     

Characterization and tribological application of diamond-like carbon (DLC) films prepared by radio-frequency plasma-enhanced chemical vapor deposition (RF-PECVD) technique

Diamond-like carbon (DLC) films were successfully prepared on glass substrates and surfaces of selenium drums via radio frequency plasma enhanced chemical vapor deposition method. The microstructure, surface morphology, hardness, film adhesion, and tribological properties of the films were characterized and evaluated by X-ray photoelectron spectroscopy, atomic force microscopy, and micro-sclerometer and friction-wear spectrometer. The results showed that DLC films have smooth surfaces, homogeneous particle sizes, and excellent tribological properties, which can be used to improve the surface quality of the selenium drums and prolong their service life.     

类金刚石薄膜的表面纳米划擦性能评价

用射频等离子体增强化学气相沉积在钛合金表面制备了类金刚石薄膜,利用纳米压入仪及其附件研究了薄膜与纳米划擦有关的力学性能．结果表明：随薄膜厚度的增加,其硬度略有增加,但增幅较小,弹性模量没有明显的相应规律;薄膜在划擦过程中,随载荷增加,先后经历薄膜变形、薄膜与基体共同变形及薄膜剥离三个阶段;在薄膜变形阶段,划擦对薄膜的损害较小;当压头进入薄膜一定深度后,划擦后薄膜与基体的变形不同步,造成薄膜沿划痕向两边形成整齐排列的小裂纹,呈鱼骨状;达到临界载荷值时,薄膜在界面处发生脆性剥落;随膜厚增加,薄膜的临界载荷增大,因其残余应力的相应增大而发生大面积脆性剥落．     

Characteristics and mechanical properties of titanium-containing diamond like carbon films deposited by cathodic arc evaporation

Depositions of titanium-containing diamond-like carbon (Ti-DLC) films were conducted by mixing C+ and Ti+ plasma streams originated from cathodic arc plasma sources in argon (Ar). The deposition was processed at Ti target current ranging from 20 Amp to 70 Amp. Film characteristics were investigated using Raman spectroscopy, X-ray photoelectron spectroscopy (XPS). Film microstructures were evaluated using field emission scanning electron microscopy (FEGSEM), an atomic force microscope (AFM), X-ray diffractometry (XRD) and high-resolution transmission electron microscopy (HRTEM). Mechanical properties were investigated by using a nanoindentation tester and ball on disc wear test. Results shows that surface roughness (Ra) of the films ranged between 2.4 and 7.2 nm and roughness increased relative to the increase in Ti target current. The FESEM studies showed that the surface micrographs of Ti-DLC films revealed a cauliflower-like microstructure and the cross-sectional micrograph revealed a snake-skin like structure. HRTEM studies showed that the Ti-DLC films consisted of nano scale TiC particles which were comparable with low angle XRD and XPS results. XPS analysis established that the Ti2p spectrum is present when the Ti target current reaches 30 Amp or higher. Ti concentration increased as the Ti target current was increased. An extremely thin TiO2 layer exists on the top of the Ti-DLC films which was comparable with the AES results. The film thickness which could be deposited for Ti-DLC is much higher than that of conventional DLC films. Nanoindentation tests show that the nanohardness of the films ranging 15-22 GPa, with Er values ranging from 145 to 175 GPa. The wear test demonstrates the friction coefficient of the 420SS substrate, DLC and Ti-DLC films were about 0.8, 0.3 and 0.2, respectively. Obviously, the friction coefficients of the Ti-DLC films were lower than that of the DLC films.     

The use of the scratch test to measure the fracture strength of brittle thin films

The feasibility of the use of the scratch test to measure the fracture strength of brittle thin films has been proved. In particular, amorphous diamond-like carbon (DLC), SiC and TiO₂ films deposited on a soda-lime glass substrate, in which damage initiated on the film surface in the form of partial cone cracks, have been considered. Optical inspection of the scratch tracks allowed the normal and lateral force at the point of fracture to be determined. The critical values were subsequently used to calculate the fracture strength. The great advantage of this method is that it allows the contribution of surface defects to strength to be obtained. Weibull analysis of the strength data was carried out, showing that the SiC film possess higher strength and reliability compared to DLC and TiO₂ films.     

Characterization and tribological application of diamond-like carbon (DLC) films prepared by radio-frequency plasma-enhanced chemical vapor deposition (RF-PECVD) technique

Diamond-like carbon (DLC) films were successfully prepared on glass substrates and surfaces of selenium drums via radio frequency plasma enhanced chemical vapor deposition method. The microstructure, surface morphology, hardness, film adhesion, and tribological properties of the films were characterized and evaluated by X-ray photoelectron spectroscopy, atomic force microscopy, and micro-sclerometer and friction-wear spectrometer. The results showed that DLC films have smooth surfaces, homogeneous particle sizes, and excellent tribological properties, which can be used to improve the surface quality of the selenium drums and prolong their service life.