超分散稳定纳米硫化锌油样的摩擦学综合评价及作用机制研究

应用非水原位构筑方法获得了超分散稳定的纳米ZnS油样,利用四球摩擦试验机、环块试验机对其抗磨减摩性能、极压性能进行了评价,用扫描电子显微镜(SEM)及X射线光电子能谱(XPS)表征了磨斑表面.依据表面分析结果,对膜的形成过程进行了解释.结果表明:超分散稳定纳米ZnS的存在,能改善油品的抗磨减摩性能和极压性能.但就抗磨减摩性能而言,环块试验评价结果好于四球试验评价结果.磨损表面分析表明,摩擦磨损过程中发生了摩擦化学反应,生成了富含硫化物、氧化物和硫酸盐的沉积膜或化学转化膜,从而在一定程度上改善了摩擦学性能.     

表面修饰硼酸镁纳米微粒的制备及其在水中的润滑性能

用化学沉淀法制备了油酸三乙醇胺修饰的硼酸镁纳米微粒,并用透射电子显微镜、X射线衍射仪和红外光谱仪等对微粒进行了表征;采用四球摩擦磨损试验机研究了其在水溶液中的润滑,用扫描电子显微镜观察了磨斑表面形貌,用x射线光电子能谱分析了磨斑表面的化学成分。结果表明：所制备的硼酸镁纳米微粒粒径为40-60nm,并且表面修饰剂与纳米微粒发生了化学反应;纳米微粒在摩擦副表面形成了一层润滑膜;在摩擦副表面检测出镁、硼、铁等的氧化物,这些氧化物保护膜起到良好的润滑作用。     

表面修饰硼酸镁纳米微粒的制备及其在水中的润滑性能

用化学沉淀法制备了油酸三乙醇胺修饰的硼酸镁纳米微粒,并用透射电子显微镜、X射线衍射仪和红外光谱仪等对微粒进行了表征;采用四球摩擦磨损试验机研究了其在水溶液中的润滑,用扫描电子显微镜观察了磨斑表面形貌,用X射线光电子能谱分析了磨斑表面的化学成分。结果表明:所制备的硼酸镁纳米微粒粒径为40~60 nm,并且表面修饰剂与纳米微粒发生了化学反应;纳米微粒在摩擦副表面形成了一层润滑膜;在摩擦副表面检测出镁、硼、铁等的氧化物,这些氧化物保护膜起到良好的润滑作用。     

硅镁型复合纳米添加剂的摩擦学及自修复性能研究

用化学方法制得粒径约为40 nm的硅镁型复合纳米添加剂,分别采用四球摩擦磨损试验机、环-块摩擦磨损试验机和齿轮试验机考察了其作为矿物油添加剂的抗磨减摩性能及对磨损表面的修复作用.用扫描电子显微镜、粗糙度测定仪以及X射线光电子能谱仪等对摩擦副磨损表面进行了分析,并探讨其修复作用机制.结果表明:制备的硅镁型复合纳米添加剂具有优良自修复性能,可以很好覆盖磨损表面,能显著降低磨损表面的粗糙度.其自修复作用机制是由于硅镁型复合纳米粒子在摩擦表面形成沉积并在接触区的高温高压下熔融铺展形成低剪切强度的表面膜, 由于这层膜的剪切强度比较低,可以减少摩擦界面的粘着磨损,故表现出良好的减摩抗磨和自修复性能.     

油溶性纳米铜的制备、表征及其对SF15W/40汽油机油摩擦性能的影响

采用界面生长法,以醋酸铜为母体,抗坏血酸(Vc)为还原剂,吐温-85为修饰剂,正丁醇为生长剂,合成了粒径约15.5 nm的油溶性球形纳米铜粉;通过X-射线衍射(XRD)和透射电子显微镜(TEM)对纳米铜粉进行了表征;将其作为润滑油添加剂分散于SF15W/40汽油机油中制得纳米润滑油;通过高浓度激光粒度仪考察了纳米润滑油的分散稳定性;通过UMT-Ⅱ摩擦磨损实验机考察了纳米润滑油的摩擦学性能;采用扫描电子显微镜(SEM)分析了磨损表面形貌.结果表明:纳米铜粉在润滑油中具有优异的分散稳定性;纳米铜粉显著改善了SF15W/40汽油机油的润滑性能,其最佳添加量为0.8%.分析认为纳米铜在摩擦表面的划痕和犁沟处沉积并铺展成膜,从而改善了摩擦磨损性能.     

中等粒度纳米金刚石抛光陶瓷表面研究

研究了用各种不同粒度分布的纳米金刚石抛光CaTiO3陶瓷表面。讨论了纳米金刚石颗粒大小及其悬浮液的分散稳定性对磁头表面形貌的影响,评价了由该种材料抛光所形成的缺陷和表面质量。试验分析表明,用粒径越小、粒度分布越窄的纳米金刚石抛光时试样表面粗糙度越小,而粒径越大,即使分布窄,所得的试样表面粗糙度也越大。同时,即使纳米金刚石粒径较小,如果分散稳定性不好,也会在试样表面产生若干很深的划痕和凹坑,从而影响表面粗糙度。     

硼酸锌超微粒子在水溶液中的摩擦学性能研究

采用沉淀法原位合成了油酸钠修饰硼酸锌纳米颗粒,用透射电子显微镜(TEM)和红外光谱(IR)对其形貌和表面结构进行了表征,用四球机考察了其在水中的摩擦学性能,用扫描电子显微镜(SEM)观察了磨斑表面形貌,用X射线光电子能谱(XPS)分析了试球磨斑表面的化学成分.结果表明:制备的油酸钠修饰硼酸锌纳米粒子粒径在80～100 nm,能在水中均匀分散,可使水的承载能力显著提高,抗磨减摩性能也有较大提高.XPS分析表明,硼酸锌纳米粒子作为水基润滑剂,在摩擦过程中在摩擦副表面生成了Zn、B、Fe等的氧化物保护膜, 起到良好的抗磨减摩作用.     

纳米二氧化硅对锂基润滑脂摩擦学性能的影响

利用溶胶-凝胶法,以正硅酸乙酯为原料制备了纳米二氧化硅微粒,通过透射电子显微镜对其结构进行了表征,利用四球摩擦磨损试验机测定了添加不同含量纳米二氧化硅锂基润滑脂摩擦学性能,采用扫描电子显微镜观察磨损表面形貌。结果表明:制备的纳米二氧化硅是粒径为60 nm左右的球形微粒,具有很高的表面能和表面活性;纳米二氧化硅作为锂基润滑脂添加剂能够提高最大无卡咬负荷和烧结负荷,降低摩擦因数,添加量为2.0%(质量分数)时的润滑剂性能最好,相对应的钢球磨斑直径最小,摩擦因数最低。     

纳米二硫化钼的水热法可控制备及极压性能研究

为获得产率高、重复性好的纳米二硫化钼制备工艺,提出纳米级二硫化钼的水热法可控制备方法。以钼酸钠、硫代乙酰胺为前驱体,分别以聚乙二醇(PEG-20 000)、十六烷基三甲基氯化铵(CTAC)、无水乙醇为表面活性剂,利用水热法制备出球状和花状纳米二硫化钼粒子。通过X射线衍射仪、扫描电子显微镜对产物特性进行表征,通过四球摩擦磨损试验机考察2%纳米二硫化钼在N46润滑油中的极压性能测试。结果表明:酸性环境下,添加表面活性剂PEG-20 000和CTAC可得到球状结构的纳米二硫化钼颗粒,粒径均匀,粒径约为100 nm;而添加无水乙醇时可得到花状结构的纳米二硫化钼颗粒,在硫酸和盐酸环境下粒径分别为190和70 nm;在硫酸环境下,以聚乙二醇为表面活性剂时二硫化钼产率最高,可达78.82%;制备的纳米球状二硫化钼作为润滑油添加剂显著提高了润滑油的极压性能,与工业二硫化钼相比,最大无卡咬负荷最大可提高42%左右。     

表面修饰纳米铜粒子的制备及其摩擦学性能

以微乳化化学还原法制备出表面修饰纳米铜粒子,它们在基础油中显示出良好的油溶性,在苯、甲苯等有机溶剂中有良好的分散性和分散稳定性。用四球摩擦磨损试验机考察了其在26#白油中的摩擦学性能,并对其摩擦化学作用机制进行了研究。结果表明,表面修饰纳米铜添加剂具有良好的抗磨和承载能力。磨斑的表面分析表明,纳米铜添加剂在边界润滑下形成了一层厚度约为13nm含单质铜的沉积膜是其具有良好摩擦学性能的主要原因。     

Effect of Sintering Temperature and Atmosphere on Nonlubricated Sliding Wear of Nano-Yttria-Dispersed and Yttria-Free Duplex and Ferritic Stainless Steel Fabricated by Powder Metallurgy

The nonlubricated sliding wear behavior of nano-yttria-dispersed and yttria-free duplex and ferritic stainless steel against a diamond tip was studied. The stainless steel samples were fabricated by a conventional powder metallurgy route in which nano-yttria-dispersed and yttria-free duplex and ferritic stainless steel powders were cold compacted and then conventionally sintered at either 1000, 1200, or 1400°C in an argon atmosphere. For comparison, another set of samples was sintered at 1000°C in a nitrogen atmosphere. The wear behavior of sintered stainless steel samples against a diamond indenter was investigated using a pin-on-disc apparatus at 10 and 20 N loads and at a constant speed of 0.0041 m/s. It is proposed that yttria-dispersed stainless steels showed higher wear resistance compared to yttria-free stainless steel due to their improved hardness and density. Stainless steel sintered in a nitrogen atmosphere exhibited better wear resistance than those sintered in an argon atmosphere due to the formation of hard and brittle Cr₂N. The wear mechanisms of stainless steels against diamond were found to be mainly abrasive and oxidative. Semiquantitative analysis of the worn surfaces and wear debris confirmed the occurrence of oxidation processes during wear.     

Strength characteristics,structure and wear resistance of ptfe-commercial carbon composites

The present work is devoted to investigations of the structure, mechanical properties, and wear resistance of composites based on polytetrafluoroethylene filled by 0.3–20.0% of commercial carbon. The methods used were mechanical testing, X-ray phase analysis, scanning calorimetry, scanning electron microscopy, and triboengineering tests. The wear resistance of low-filled PTFE-based composites containing 1–5% of ultradispersed commercial carbon was found to increase sharply, by up to 500–600 times, whereas the main strength characteristics of these composites, including relative elongation at rupture and tensile strength, remained at levels close to that of pure polytetrafluoroethylene (PTFE). This effect is attributed to the active cross-linking role of ultradispersed carbon particles, which promote the formation of a transient supermolecular structure in the low-filled composites; this structure is a combination of the unfilled PTFE structure and a spherulite-like supermolecular structure.     

Wear characteristics of circular diamond saws in the cutting of different hard abrasive rocks

Circular diamond saw of wear is affected by a range of factors. However, the principal factors that require consideration in predicting wear rates are the type of diamond saw, the saw operating parameters and the characteristics of the cut rock. A single rock property index is not a sufficient basis for predicting wear performance. A variety of ten types of rocks were cut in the laboratory with two types of circular diamond saw using a fully instrumented cutting rig at different feed rates, depths of cut and at constant peripheral speed. Quantitative determinations of a wide range of textural, mechanical and intact properties of the rocks were also made. Wear (weight loss and height loss) of saw were measured after a series of test in each rock type. The wear of saws can take many forms, however, the most common wear mechanism operating on saws during the rock cutting is abrasion. Impact loading and impact fatigue also accelerates the wear of saws. The analysis indicated that the statistical model for the rock saws have potential for practical application. The application of multiple regression analysis to diamond saw performance is novel and the technique shows promise for the prediction of saw wear in specific rock types. The ability of the technique to provide a mathematical characterization of the performance of new cutting saws in the specific rocks may prove to value to saw manufacturers and users.     

亚纳米量级光滑表面的超精密抛光

软Ｘ射线光学的发展，对光学元件表面提出超光滑要求，为此我们开展了使用锡磨盘的超精密抛光方法研究。本文介绍锡磨盘磨削的实验装置及主要结果。利用这种方法已加工出表面粗糙度优于０．３ｎｍ的超光滑表面     

Diamond particle shape: Its measurement and influence in abrasive wear

The classification of diamond particles in terms of their abrasive characteristics is addressed in this work. Specifically, diamond particles of different grades have been studied in terms of their shape to identify useful trends and correlations with experimental wear rate. Ten diamond types, typically used by the abrasives industry and exhibiting varied shape, were selected. They included highly geometric single crystals, crushed single crystals, and polycrystalline diamond particles, with nominal diameters of between 65 and 197 μm. Electronic boundary projections were obtained using a digital-camera-equipped optical microscope, which were then processed using proprietary software. The parameters calculated include: diameter (minimum, minor and maximum), aspect ratio, convexity and sharpness. Interesting correlations were found between convexity and sharpness that engendered both these parameters to be considered as useful measures of wear rate. This was reinforced by experimental wear tests, using grinding wheels manufactured from six of the 10 diamond types, which demonstrated excellent correlations of sharpness (0.991 correlation coefficient), and convexity (0.987 correlation coefficient), with the wear rate of a polyurethane workpiece.     

On-machine precision preparation and dressing of ball-headed diamond wheel for the grinding of fused silica

In the grinding of high quality fused silica parts with complex surface or structure using ball-headed metal bonded diamond wheel with small diameter,the existing dressing methods are not suitable to dress the ball-headed diamond wheel precisely due to that they are either on-line in process dressing which may causes collision problem or without consideration for the effects of the tool setting error and electrode wear.An on-machine precision preparation and dressing method is proposed for ball-headed diamond wheel based on electrical discharge machining.By using this method the cylindrical diamond wheel with small diameter is manufactured to hemispherical-headed form.The obtained ball-headed diamond wheel is dressed after several grinding passes to recover geometrical accuracy and sharpness which is lost due to the wheel wear.A tool setting method based on high precision optical system is presented to reduce the wheel center setting error and dimension error.The effect of electrode tool wear is investigated by electrical dressing experiments,and the electrode tool wear compensation model is established based on the experimental results which show that the value of wear ratio coefficient K’ tends to be constant with the increasing of the feed length of electrode and the mean value of K’ is 0.156.Grinding experiments of fused silica are carried out on a test bench to evaluate the performance of the preparation and dressing method.The experimental results show that the surface roughness of the finished workpiece is 0.03 μm.The effect of the grinding parameter and dressing frequency on the surface roughness is investigated based on the measurement results of the surface roughness.This research provides an on-machine preparation and dressing method for ball-headed metal bonded diamond wheel used in the grinding of fused silica,which provides a solution to the tool setting method and the effect of electrode tool wear.     

Tool wear and its effect on surface roughness in diamond cutting of glass soda-lime

For the technology of diamond cutting of optical glass, the high tool wear rate is a main reason for hindering the practical application of this technology. Many researches on diamond tool wear in glass cutting rest on wear phenomenon describing simply without analyzing the genesis of wear phenomenon and interpreting the formation process of tool wear in mechanics. For in depth understanding of the tool wear and its effect on surface roughness in diamond cutting of glass, experiments of diamond turning with cutting distance increasing gradually are carried out on soda-lime glass. The wear morphology of rake face and flank face, the corresponding surface features of workpiece and the surface roughness, and the material compositions of flank wear area are detected. Experimental results indicate that the flank wear is predominant in diamond cutting glass and the flank wear land is characterized by micro-grooves, some smooth crater on the rake face is also seen. The surface roughness begins to increase rapidly, when the cutting mode changes from ductile to brittle for the aggravation of tool wear with the cutting distance over 150 m. The main mechanisms of inducing tool wear in diamond cutting of glass are diffusion, mechanical friction, thermo-chemical action and abrasive wear. The proposed research makes analysis and research from wear mechanism on the tool wear and its effect on surface roughness in diamond cutting of glass, and provides theoretical basis for minimizing the tool wear in diamond cutting brittle materials, such as optical glass.     

Wear behavior of diamond wheel for grinding optical connector ferrule — FEA and wear test —

The grinding characteristics and the wear behavior of diamond wheel for grinding the optical connector ferrule were investigated by finite element analysis (FEA) and wear test. FEA of contact between diamond wheel and ferrule shows that the subsurface damage area of ferrule is 13μm from the interface of abrasive particle and matrix. Fallout of abrasive particle is affected by the stress state at the interface. A 2-D finite element model was established to calculate the distribution of stress at the interface. As the result of FEA, fallout condition of abrasive was concerned with the ratio of the critical protrusion; the ratio of particle size is about 0.6. FE model was established to investigate the effects of the diamond concentration of wheel. The FEA result shows that the lower concentration of it has larger wear volume due to the small stress propagation. To investigate grinding performance, the pin-on-disc wear test was carried out for three types of concentrations 75%, 100% and 125%. Through the wear test, it was confirmed that the 75% wheel concentration has the highest amount of wear volume. This result shows good agreement with that of FEA. And 100% concentration by considering the grinding ratio of the wheel shows the best optimized result for the grinding performance. This paper was recommended for publication in revised form by Associate Editor Maenghyo Cho Chang-Min Suh received his B.S. and M.S. degrees in mechanical engineering from Busan Na-tional University in 1964 and 1968, respectively, and received his Ph.D. degree from the University of Tokyo in 1981. He now is a professor at Kyungpook National University. He has served as the Head of the Department of Mechanical Engineering at Kyungpook National University, a Visiting Professor of Materials Science and Engineering in Univ. of California Berkeley, a Head of the Institute of Engineering Design Technology Kyungpook Nat’l Univ, and a Head of the Technology Innovation Center designated by the Department of Commerce and Industry of Korea.     

Wear coatings for magnetic thin film magnetic recording heads

Many coatings are in use today for the wear protection of thin film heads. With the trend towards smaller head-media distances, the thickness of the coating has to diminish. In this paper some of these coatings: zirconia, chromium nitride, chromium oxide and diamond (+diamond-like carbon) will be discussed. It will be shown that the film hardness is influenced by the microcrystalline structure, the texture and the film stress. The film hardness shows a good correlation with the reciprocal wear coefficient. The wear resistance of the materials discussed increases in the order: zirconia, chromium nitride, chromium oxide, diamond.     

基于SMO-SVM的单点金刚笔钝化监测

针对单点金刚笔在砂轮修整过程中易于钝化且难以检测的问题,使用支持向量机建立智能模型。为了得到建立模型所需的样本库,使用小波包分析等方法在线提取修整时声发射信号中的特征信息,并引入钝化平台直径定义钝化临界值。模型本身选用基于串行优化算法的支持向量分类机,使用交叉验证法搭配遗传算法以达到优化模型参数的目的。实验结果表明,该模型在分类精度和计算时间上均优于一般的智能模型,可以有效地监测金刚笔的钝化。