Effects of laser surface texturing on friction behavior of silicon nitride under lubrication with water

Water lubrication is one of the candidates of the tribo-system with low negative environmental impact. It is well known that some kinds of ceramics show excellent tribological properties under lubrication with water. The characteristic improvement was attempted by giving texturing to Si₃N₄ so that the water lubrication might spread as a representative of the ecotribology system. The surface laser texturing showed the friction reducing effect under the sliding condition of the low bearing characteristic number. The mechanism of the triblogical property improvement by the laser surface texturing was discussed based on the experiment results and the surface analytical results.     

Microscopic changes in surface topography and elemental concentration on the track formed by the intermittent motion of friction

A preliminary investigation of the molecular weight of polytetrafluoroethylene (PTFE) wear debris was undertaken. It was found that the molecular weight of PTFE wear debris generated from thrust washers was drastically reduced compared with that of the thrust washer. A consistent difference in the molecular weight of the wear debris was observed in samples obtained at high and at low pressure velocities. A fluorocarbon composite material yielded wear debris of molecular weight even lower than that of unfilled PTFE wearing below its limiting pressure-velocity.     

Studies on friction and transfer layer: role of surface texture

Friction influences the nature of transfer layer formed at the interface between tool and metal during sliding. In the present investigation, experiments were conducted using “Inclined Scratch Tester” to understand the effect of surface texture of hard surfaces on coefficient of friction and transfer layer formation. EN8 steel flats were ground to attain surfaces of different textures with different roughness. Then super purity aluminium pins were scratched against the prepared steel flats. Scanning electron micrographs of the contact surfaces of pins and flats were used to reveal the morphology of transfer layer. It was observed that the coefficient of friction and the formation of transfer layer depend primarily on the texture of hard surfaces, but independent of surface roughness of hard surfaces. It was observed that on surfaces that promote plane strain conditions near the surface, the transfer of material takes place due to the plowing action of the asperities. But, on a surface that promotes plane stress conditions the transfer layer was more due to the adhesion component of friction. It was observed that the adhesion component increases for surfaces that have random texture but was constant for the other surfaces.     

Characterization and local modification of atomically flat gold surfaces by STM

In order to characterize the surface of epitaxial gold on mica in air we have used a scanning tunnelling microscope (STM) to image and to modify this surface. It was possible to create controlled features by applying voltage pulses on the tip while scanning. The voltage threshold for writing (about 3 V, 100 ns pulses) was dependent of the tip condition. The lowest pulses were associated with sub-50 Å feature size. We observed that at ambient temperature the written features disappeared in a time scale of half an hour for the smallest (<30 Å) to a few hours for the bigger features (～500 Å). We have used the same surface as a substrate for organic imaging. We also present images of a polymer deposited on gold.     

Role of nanometer roughness on the adhesion and friction of a rough polymer surface and a molecularly smooth mica surface

Friction and adhesion measurements between surfaces of cross-linked, stiff polymers of varying roughness against smooth, bare mica surfaces were carried out in dry air as well as in the presence of lubricating oil. The nominal (macroscopic) contact area varies with the applied load according to the Johnson, Kendall and Roberts (JKR) theory, yet shows significant hysteresis due to the irreversibility arising from the loading/unloading curves of multiple asperities. Upon introducing the oil between the surfaces, the critical shear stress is reduced to zero due to the elimination of the adhesion force. However, the effect is less noticeable on the friction coefficient. Lastly, the effect of increasing the (RMS) roughness was greatest over the first few nanometers due to the diminution of the adhesion-controlled contribution to the friction, after which a further increase in roughness had less dramatic effects. A model is presented to account for the observed adhesion hysteresis during repeated loading/unloading cycles of purely elastically deforming rough surfaces. Bruno Zappone and Kenneth J. Rosenberg made equal contributions.     

Determination of gold-labelled surface receptors on single cells by X-ray microanalysis

A standardless X-ray microanalytical procedure has been developed to determine the number of gold-labelled surface receptors on whole single cells. The effect of the injection of K₂PtCl₄ into mice on gold-labelled concanavalin A (Con A) receptors on peritoneal macrophages was examined with an energy dispersive X-ray detector in an SEM. The numbers of gold particles seen in electron micrographs and estimated by fluorescence photometric measurements of fluorescein isothiocyanate-labelled Con A receptors were correlated with the X-ray microanalytical results.     

Adhesion and friction studies of a nano-textured surface produced by spin coating of colloidal silica nanoparticle solution

This paper presents the results of adhesion and friction studies on a nano-textured surface. The nano-textures were produced by spin coating colloidal silica nanoparticle solution on a flat silicon substrate. Surface morphology was characterized by environmental scanning electron microscopy (ESEM) and scanning probe microscopy (SPM). Adhesion and friction studies were conducted using a TriboIndenter employing diamond tips with 5 μm and 100 μm nominal radii of curvature. The results show that the adhesion forces and coefficients of friction of the nano-textured surface measured by the 100 μm tip were reduced up to 98 and 88%, respectively, compared to those of a baseline silicon oxide film surface.     

Vit1块体金属玻璃微铣削表面粗糙度试验研究

为研究金属玻璃的微铣削表面粗糙度,采用直径为0.5 mm的双刃硬质合金微铣刀,在Vit1块体金属玻璃表面加工微尺度沟槽结构;以试件表面粗糙度Ra值为衡量指标,利用三因素五水平正交试验方法分析主轴转速、进给速度和铣削深度对微铣削表面质量的影响。试验结果表明:主轴转速对表面质量影响最为显著,而进给速度影响较小。对影响表面质量及形貌的原因进行了深入分析,其结果对研究Vit1块体金属玻璃的微铣削加工机理具有一定的借鉴意义。     

X PS － EDS 联用技术分析金电极表面焊接不良的原因

金电极焊接不良,影响产品质量,焊接不良产生的原因通常与表面存在污染物有关。本实验采用能谱仪（EDS）结合X－射线光电子能谱仪（XPS）对样品表面成分进行分析。分析结果表明,样品由Au、C、O、N等元素组成,而表面污染物中含有F元素,F1s的结合能为688.5ev ,而C1s的结合能在291.7ev处有拟合峰,表明表面存在C F2污染,C F2污染是金电极焊接不牢的原因。     

Influence of surface roughness on friction and scuffing behaviour of cast iron under sparse lubrication

Friction and scuffing behaviour of grey cast iron as influenced by the surface roughness under sparse lubrication conditions is studied. The studies are carried out on a three-shoe-on-disc machine under the conditions of parallel sliding. The experiments were conducted at three oil supply rates of 0.10, 0.22 and 0.36 μg/cm² per contact obtained through a mist oiling system and with specimens of cast iron shoes of different roughness values, Ra, between 0.04 and 2.0 μm against a 0.55% C steel disc. In a step load procedure, the friction torque at the end of each load step and the scuffing load are the major parameters measured. Results of friction and scuffing behaviour as a function of roughness and oil supply rates have been discussed.     

The influence of contact conditions on surface reaction layers formed between steel surfaces lubricated by an aviation oil

This study focuses on the influence of load and temperature on the formation and stability of tribo-films for bearing steel on bearing steel contacts lubricated with an aviation oil, EXXON Turbo 2380 (TCP based - tricresyl phosphate) at ambient temperatures. Experiments were carried out on a pin-on-disc (POD) tribometer (with a ball-on-flat geometry) under an average loading rate of 0.17 N s⁻¹ and sliding speed of 3 m s⁻¹. The X-ray photoelectron spectroscopy (XPS) analysis on the worn surfaces of ball and disc shows that a tribo-film forms on both surfaces at room temperature. The formation and removal of the tribo-film are faster on the ball due to the nature of contact between the ball and disc. It was found that the tribo-films formed at room temperature are vulnerable to initial disc temperature. The higher the initial temperature the higher the load carrying capacity. The tribo-film growth and contact deterioration have been monitored by acoustic emission (AE) and electrostatic charge (ESP) sensing systems in real time. The results show that both AE and ESP can detect the tribo-film and contact breakdown and have great potential for on-line condition monitoring of lubricated tribo-contacts.     

Adsorption of ZDDP on iron surfaces and its relation with surface tension

This paper reports work on the relationship of surface tension of ZDDP solutions to adsorption isotherms. The surface tension of the solutions varies with their composition, and information about adsorption, decomposition or other chemical changes of ZDDP in solution can be obtained from the correlation of solution concentration and surface tension. From this work, the authors conclude that adsorption of ZDDP on iron can occur at even low concentrations, increasing with temperature, and that decomposition, association and interaction between components may occur in solution at high temperatures.     

The Frictional Response of VC(100) Surfaces: Influence of 1-Octanol and 2,2,2-Trifluoroethanol Adsorption

In this report, we present ultrahigh vacuum (UHV) atomic-scale measurements of the frictional response of the VC(100) surface and the influence on friction through the adsorption of 1-octanol (CH₃(CH₂)₇OH) and 2,2,2-trifluoroethanol (CF₃CH₂OH). Atomic force microscopy (AFM) has been used to determine the changes in interfacial friction and adhesion, while scanning tunneling microscopy (STM) has revealed changes in surface morphology upon adsorption. X-ray photoelectron spectroscopy (XPS) has been utilized to determine the composition of the surface formed through the reaction of these adsorbates with VC. Adsorption of 1-octanol on the VC(100) surface at room temperature causes a 15% reduction in the friction measured between a clean VC surface and a silicon nitride AFM tip. STM images, combined with XPS results, reveal that 1-octanol does not completely cover the surface and that saturation occurs approximately at a 500L exposure. Adsorption of 2,2,2-trifluoroethanol on the VC(100) surface at room temperature produces a significant increase in friction while at the same time producing a decrease in adhesion. These contrasting results are interpreted in terms of differences in interfacial shear strength, chemical composition, and the molecular details of the adsorbed layer.     

砂带磨削1Cr13叶片表面粗糙度的试验研究

为改善叶片材料的表面磨削效果,本文进行了砂带磨削1Cr13叶片表面粗糙度的试验研究,系统分析了磨削用量对表面粗糙度的影响规律。该研究对生产实践具有理论指导意义。     

The ultra-low friction of the articular surface is pH-dependent and is built on a hydrophobic underlay including a hypothesis on joint lubrication mechanism

In this study, the influence of pH on interfacial energy distributed over the phospholipids-bilayer surface model and the effect of hydrophobicity on coefficient of friction (f) were investigated by using microelectrophoresis. An important clinical implication of deficiency in hydrophobicity is the loss of phospholipids that is readily observed in osteoarthritis joints. This paper establishes the influence of pH on interfacial energy upon an increase f, which might be associated with a decrease of hydrophobicity of the articular surface.     

Influence of the surface layer structure on the interaction character of friction pairs formed by X155CrMo12-1, 41Gr4, and 35GrMnSi4 steels with CuAl9Fe4 bronze

A comparative analysis of tribotechnical characteristics of friction pairs of X155CrMo12-1, 41Gr4, and 35GrMnSi4 steels with a counterbody of CuAl9Fe4 bronze, which were tested under conditions corresponding to operation of friction units of axial-piston pumps, is carried out. Practical recommendations on the substitution of 35GrMnSi4 structural steel with the diffusion surface hardening for X155CrMo12-1 high-alloy steel when making the supporting and distributor disks of hydraulic pumps are formulated.     

表面活性剂及复配在云母片上吸附的AFM研究

借助原子力显微镜对十二烷基硫酸钠(SDS)/十六烷基三甲基溴化铵(CTAB)及其复配溶液在云母表面的吸附以及吸附后不同的表面形貌和微摩擦特性进行了研究,探讨了摩擦力与表面形貌的关系。结果表明,SDS与CTAB表面活性剂分子都以纳米级颗粒吸附于云母表面;摩擦力受表面形貌的影响,但不成一一对应关系;在0.8和2倍临界胶束浓度(CMC)下,SDS/CTAB=1∶1复配溶液在云母表面吸附后的润滑效应较其它配比好。     

Effects of microwave irradiation and chemical fixation on the localization of perisinusoidal cells in rat liver by gold impregnation

Modified gold impregnation is one of the methods that are used in light microscopical demonstration of hepatic perisinusoidal cells. This method has some disadvantages, such as restriction of fixation time to 16 h, which allows limited time for processing the tissues, especially when dealing with a large amount of material, and a long impregnation time (16–24 h). We investigated the effect of prolonged fixation on the staining of sections, to shorten the time needed for gold impregnation by using microwave irradiation. Liver specimens were fixed in Baker's calcium–formalin for different periods of time. After fixation, frozen sections were impregnated in gold chloride solution either at room temperature or in a microwave oven. The staining quality of the sections which had been impregnated in the microwave oven for a much shorter time were equal to or even superior to the ones impregnated at room temperature. Prolonging the fixation time up to 7 days did not affect the staining results by microwave irradiation, whereas satisfactory results were not obtained from sections stained at room temperature and fixed for more than 3 days. We conclude that microwave irradiation can be used to shorten the impregnation time in gold chloride solution and the duration of fixation can be prolonged up to 3 days in the original method and up to 7 days when microwave irradiation is used during impregnation.