自修复添加剂的热处理及其分散性研究

采用差热-热重分析仪(DTA-TG)研究了自修复添加剂-蛇纹石粉体的热处理过程;采用X射线衍射仪(XRD)和红外光谱分析仪研究了其相变情况;采用不同的分散剂对蛇纹石粉体和热处理后粉体进行表面修饰,使用红外光谱仪分析了它们的分散特性;采用MM-200摩擦磨损试验机研究了表面修饰后粉体的自修复特性。结果显示:蛇纹石粉体在795℃发生相变生成非晶态的顽火辉石和镁橄榄石并且在890℃发生晶化反应;油酸与蛇纹石粉体表面的羟基发生酯化反应;钛酸酯偶联剂NXT-105与热处理前后粉体不但发生了物理吸附,并且与粉体表面的羟基发生了化学反应,因此,添加剂在润滑油中具有更好的分散性;钛酸酯偶联剂修饰后的粉体,不管是热处理前还是热处理后都能在摩擦磨损过程中在磨损金属表面生成自修复膜。     

润滑油中纳米铜粉聚甘油酯分散剂的合成与性能

为提高铜纳米颗粒在润滑油中的分散性能,以聚甘油和硬脂酸为原料合成了一系列聚甘油硬脂酸酯（PGFE）。通过沉降试验和流变性能的测试,考察了聚甘油的聚合度大小、硬脂酸含量等对分散性能的影响,通过热分析和红外光谱分析对分散剂吸附在铜粉表面的形态和性质做进一步考察。结果表明：当聚合度n=6、硬脂酸含量为65％时分散剂的分散性能良好,分散剂质量分数为1．5％时对流体流变性的影响最小,此时分散剂不仅有物理吸附还有化学吸附,并且极性酯基和羟基是影响吸附性能的主要官能团。     

用正交实验法优化纳米铋粉制备工艺参数

采用高能球磨的方法，直接分散铋粒制备纳米铋粉。实验选用无水乙醇为液相介质、聚乙烯吡咯烷酮（PVP）和硬脂酸作为复合修饰剂，通过正交实验研究铋粒的加入量、复合修饰剂的相对用量、转速和时间等工艺参数对纳米铋粉的产量、产率和粉体的特征数据D50的影响。研究表明：本方法能够制备出纯净的纳米铋粉；适当增加铋粒的加入量，减少修饰剂的相对用量，降低转速，适当缩短时间，有利于降低颗粒的平均粒径，提高纳米铋粉的产量和产率。在本试验条件下，制备纳米铋粉的优化参数为铋粒加入量取0．06mol，复合修饰剂与铋粒的质量比为1：3，转速取250r／min，时间为4h。     

C18—脂肪酸类的摩擦特性

作者应用摆式摩擦试验机研究了C_(18)-脂肪酸类(硬脂酸、油酸和异硬脂酸)的摩擦特性。尽管这些脂肪酸具有相同的极性基团(羟基)和C_(18)-烃基链,但是由于它们的分子结构不同,因而具有不同的抗摩特性。这些脂肪酸的抗摩特性次序是:硬脂酸>油酸>异硬脂酸。这表示作为滑膜而在摩擦表面生成的膜的状态是有差别的。用这些脂肪酸在空气/水界面上的单分子层测得的表面压力-面积等温线检验了这些吸附膜的状态。     

油酸修饰纳米氟化镧的摩擦学性能

以油酸为修饰剂制备表面改性的氟化镧纳米粒子,在环块式摩擦磨损试验机上考察氟化镧纳米粒子在150N基础油中的摩擦学性能,借助透射电镜(TEM)、金相显微镜及X射线衍射仪(XRD),分别对磨损试样的表面形貌和元素成分进行观察和分析,探讨表面修饰氟化镧纳米添加剂的抗磨减摩机制.结果表明:油酸修饰的氟化镧纳米粒子在150N基础油中减摩抗磨效果明显,与纯基础油润滑相比,在250 N压力和450 r/min转速条件下,质量分数2％的氟化镧纳米粒子在稳定磨损阶段可使45#钢试样摩擦因数降低40％,总失重降低43.75％.EDX分析表明,氟化镧纳米粒子在摩擦过程中在磨损表面生成了自修复膜.     

纳米ZnS粒子作为润滑油添加剂摩擦学性能研究

采用均匀沉淀法制备了硬脂酸修饰的纳米ZnS粒子,用四球摩擦磨损试验机考察了其作为润滑油添加剂的摩擦学性能,并用扫描电子显微镜和X射线光电子能谱仪对磨斑进行了表面分析.结果表明:在一定添加量范围内,硬脂酸修饰的纳米ZnS粒子可明显改善基础油的摩擦学性能;在摩擦过程中,纳米ZnS粒子在摩擦表面的沉积和通过摩擦化学反应生成的化学反应膜,显著提高了基础油的抗磨减摩性能.     

含纳米铋粉锂基润滑脂抗磨减摩性能研究

采用四球式摩擦磨损试验机,研究了铋粉的平均粒径、加入方式和加入量对锂基润滑脂的摩擦系数和磨斑直径的影响规律,并研究了含纳米铋粉锂基润滑脂在不同载荷下的摩擦学性能.结果表明,铋粉粒径越小,润滑脂的摩擦学性能越好,合适的铋粉平均粒径为45 nm;采用直接加入2%的纳米铋粉时,润滑脂具有良好的抗磨减摩性能;含纳米铋粉锂基润滑脂在较高载荷下具有更好的抗磨减摩性能.     

正十六烷基础油中减摩剂和分散剂相互作用的分子动力学模拟

采用分子动力学模拟加入减摩剂单油酸甘油酯(GMO)和分散剂聚异丁烯琥珀酰亚胺-多胺(PIBSA-PAM)的正十六烷基础油在不同压力条件下剪切时的摩擦学特性.构建光滑铁壁面的纳米间隙润滑剂模型,对GMO分子、PIBSA-PAM分子和壁面之间的吸附和团聚行为进行阐释,得出润滑油膜中每种分子的密度分布及剪切过程中的速度分布,...     

硬脂酸修饰Sn纳米微粒的制备及摩擦学性能

为研究固体润滑剂软金属Sn作为润滑添加剂的摩擦学性能,采用原位表面修饰液相化学还原的方法制备了硬脂酸修饰Sn纳米微粒。通过XRD,TEM,FT-IR等分析手段对其形貌和结构进行了表征,在四球摩擦磨损试验机上考察了硬脂酸修饰Sn纳米微粒作为液体石蜡添加剂在不同添加量和不同施加载荷下的摩擦学性能。结果表明,所制备的纳米微粒具有四方晶型Sn的晶体结构,粒径细小,平均粒径5~10 nm,有机修饰层的存在能防止Sn纳米微粒被氧化。硬脂酸修饰Sn纳米微粒在中低负荷下作为润滑油添加剂具有良好的减摩抗磨性能,并且能够提高基础油液体石蜡的承载力。     

表面修饰氧化锌纳米颗粒的制备及其抗磨性能研究

为改善纳米颗粒在润滑油中的分散稳定性,以硬脂酸锌为单源前驱体,成功制备出硬脂酸修饰的氧化锌纳米颗粒,用透射电子显微镜、X-射线粉末衍射仪、红外光谱仪等仪器对其进行结构表征,并在四球摩擦试验机上测试其抗磨性能。结果表明:所制备的硬脂酸修饰的ZnO纳米颗粒大小均匀,表面修饰层与纳米颗粒表面之间发生化学键合作用;硬脂酸修饰的ZnO纳米颗粒在非极性有机溶剂和润滑油中均具有良好的分散性,其作为润滑油添加剂具有良好的抗磨能力。     

Molecular orientation and bonding of monolayer stearicacid on a copper surface prepared in air

The molecular orientation of a monolayer stearic acid, adsorbedon a copper surface in air, was studied by means of X-rayabsorption spectroscopy above the carbon and oxygen K edges.Carbon-K-edge X-ray absorption measurements were used to quantifythe molecular tilt of the alkyl chain from the surface normal,which was found to be 49° and 39° respectively before andafter rubbing.Tribochemical bonding chemistry was observed using oxygen-K-edgeX-ray absorption measurements. Chemisorbed stearic acid was foundto adsorb initially in both monodentate and bidentate sites. Themonodentate chemisorbed stearic acid was thentransformed to a bidentate surface configuration aftertribochemical reaction. Furthermore, spectra from thechemisorbed stearic acid monolayer were similar to the spectrumfrom a bulk stearic acid powder standard, and the data from thetribochemically modified stearic acid monolayer surface appearedto be identical to that from a bulk cupric stearate.     

GC法测定东亚飞蝗体内脂肪酸的含量

本论文采用毛细管气相色谱法检测东亚飞蝗体内的5种主要脂肪酸(棕榈酸、硬脂酸、油酸、亚油酸、亚麻酸)的含量,并对比其它常见种类食物脂肪酸的含量。结果表明,东亚飞蝗是富含以上肪脂酸,具有高营养价值的昆虫食品资源。     

The influence of the structure of isomeric octadecanols on their adsorption from solution on iron and their lubricating properties

The influence of the structure of isomeric octadecanols on their adsorption from heptane solutions on iron powder without removal of any oxide film potentially present on the iron surface was studied. The structure of the alcohols was altered by shifting the polar hydroxyl group within the chain and by branching the chain. For comparison stearic acid was included in the investigation. The adsorption isotherms were determined and could be fitted by a Langmuir equation, with the exception of 1-octadecanol. From the adsorption experiments the areas occupied per molecule and the coefficients of adsorption were obtained. These data are related to the lubricating properties of cetane solutions of the compounds.

Lubrication with 1-octadecanol results in a low coefficient of friction and a high durability of the built-up monolayer. The area occupied per molecule is low. Chain branching and/or shifting the hydroxyl group to the middle of the chain results in much higher areas per molecule, higher coefficients of friction and poor durabilities of the monolayers. The coefficients of adsorption of the octadecanols are of the same order of magnitude. The difference in lubricating properties may be explained by the difference in molecular areas occupied. The durability of a monolayer of stearic acid is higher than that of 1-octadecanol although their molecular areas are equal owing to the much higher coefficient of adsorption of stearic acid owing to stronger bonding to the surface.     

尼龙66粉末与纳米Fe3O4粒子作润滑油添加剂的摩擦学匹配性研究

利用化学共沉淀法制备了油酸修饰的粒径大小为8nm左右的Fe3O4纳米粒子，并将其与尼龙66粉末混合作润滑油添加剂进行摩擦学试验。试验结果表明在添加纳米Fe3O4粒子的润滑油中再添加适量的尼龙66粉未，润滑油的摩擦学性能得到改善，在保持润滑油润滑性能不变的情况下，磨损量明显降低。可见，纳米Fe3O4粒子与尼龙66粉末表现出了良好的摩擦学协同性能。     

纳米SiO2包覆硅灰石填充改性尼龙1010的摩擦学性能

以硅灰石和水玻璃为主要原料,用无机化学沉积法制备纳米SiO2包覆硅灰石复合颗粒;利用扫描电镜和X射线衍射分析对包覆效果进行表征。将复合颗粒填充到尼龙1010中,对此复合材料进行拉伸、硬度和摩擦磨损实验,并与分别用硬脂酸改性硅灰石、未处理硅灰石填充的尼龙复合材料进行对比。结果表明,将纳米颗粒包覆硅灰石填充到尼龙1010中,可获得较好的结合界面,提高了尼龙复合材料的拉伸强度和硬度,比硬脂酸改性和未经处理的硅灰石更有效地改善了尼龙的摩擦学性能。     

Mixed Lubrication with C18 Fatty Acids: Effect of Unsaturation

In this paper, the lubrication mechanism of fatty acids is revisited with a new approach combining experimental and computational chemistry studies. The lubricating properties of single and mixtures of stearic, oleic and linoleic acids in a synthetic Poly-Alpha-Olefin base oil (PAO4) on iron oxide surface are investigated under mixed boundary regime with temperatures from 50 °C up to 150 °C. Low friction coefficient (about 0.055) with no visible wear is reported in the presence of single stearic acid at high temperature. This lubricating behavior is inhibited in the presence of unsaturated fatty acids highlighting an anti-synergic effect of a saturated/unsaturated mixture, especially at 150 °C. To understand the anti-synergic effect and the adsorption mechanism of these molecules, molecular dynamic (MD) and quantum chemistry simulations are performed to evaluate their diffusion coefficient in PAO4 and their adsorption mechanism on iron oxide at different temperatures. MD simulation results show a faster diffusion toward the surface for unsaturated fatty acids than for saturated fatty acid at all the studied temperatures. This means that unsaturated molecules arrive and mainly adsorb before stearic acid on the surface leading to a tribological behavior of the mixture characteristic of the unsaturated molecule. Computational chemistry suggests that all fatty acids (saturated and unsaturated) adsorption mechanism is due to the chemisorption of the carboxylic group on iron oxide surface with no desorption up to 150 °C.     

Tribochemical Wear of Rail Steels Lubricated with Synthetic Ester-Based Model Lubricants

Headchecks are a common type of damage in heavily loaded curved freight tracks. This paper deals with synthetic ester formulations' ability to prevent damage caused by headchecks through mild tribochemical wear. An experimental study pertaining to wear and friction of two rail steels lubricated by two synthetic ester base fluids, TMP-oleate and TMP-C₈-C₁₀, has been carried out. Six different free fatty acids were used in this study to act as performance additives. Three of the fatty acids were mono-acids with different, straight, carbon chain lengths (stearic acid C₁₈, decanoic acid C₁₀ and octanoic acid C₈), one was a mono-unsaturated straight-chain fatty acid (oleic acid C_18:1) while two were dibasic acids with intermediate carbon chain length (C₉ and C₁₀). Each fatty acid was blended with either ester, one at a time. The tests were carried out by using a high frequency reciprocating friction and wear test machine. In these tests, the gage face/wheel flange contact was simulated, and all tests were conducted in the boundary lubrication regime. An initial contact pressure of 316 MPa and a maximum sliding speed of 0.11 m/s were employed during the tests. The tests showed a wide range of wear rates, as well as different surface features depending on the interactions between synthetic esters, fatty acids and steel. The use of stearic and azaleic acid in lubricating rail steels results in very smooth surfaces with significant differences in their wear rates.     

纳米碳球作为合成酯抗磨剂的摩擦学性能研究

采用表面化学改性的方法得到硬脂酸修饰的纳米碳球,在四球摩擦试验机上考察纳米碳球在合成酯类润滑油中的抗摩擦性能,探讨纳米碳球的抗磨与润滑机制。结果表明,通过表面改性,显著提高纳米碳球在润滑油中的分散稳定性;纳米碳球作为合成酯润滑油抗磨剂表现出优良的抗磨减摩性能;在转速1.200 r/min,载荷150 N的实验条件下,质量分数0.07%的改性纳米碳球可使三羟甲基丙烷混酸酯平均摩擦因数减小幅度达到30%左右,磨损率降低33%,质量分数0.15%的改性纳米碳球可使季戊四醇油酸酯的平均摩擦因数降低幅度达到50%以上,磨损率降低14.6%     

Localization of fatty acids with selective chain length by imaging time-of-flight secondary ion mass spectrometry

Localization of fatty acids in biological tissues was made by using TOF-SIMS (time-of-flight secondary ion mass spectrometry). Two cell-types with a specific fatty acid distribution are shown. In rat cerebellum, different distribution patterns of stearic acid (C18:0), palmitic acid (C16:0), and oleic acid (C18:1) were found. Stearic acid signals were observed accumulated in Purkinje cells with high intensities inside the cell, but not in the nucleus region. The signals colocalized with high intensity signals of the phosphocholine head group, indicating origin from phosphatidylcholine or sphingomyelin. In mouse intestine, high palmitic acid signals were found in the secretory crypt cells together with high levels of phosphorylinositol colocalized in the crypt region. Palmitic acid was also seen in the intestinal lumen that contains high amounts of mucine, which is known to be produced in the crypt cells. Linoleic acid signals (C18:2) were low in the crypt region and high in the villus region. Oleic acid signals were seen in the villi and stearic acid signals were ubiquitous with no specific localization in the intestine. We conclude that the results obtained by using imaging TOF-SIMS are consistent with known brain and intestine biochemistry and that the localization of fatty acids is specific in differentiated cells.     

Tribochemical and Thermochemical Reactions of Stearic Acid on Copper Surfaces Studied by Infrared Microspectroscopy

The tribochemistry of copper with stearic acid was studied using a pin-on-disc wear tester under boundary lubrication conditions. Wear, as measured by surface profilometry, indicated that stearic acid was able to reduce the wear fourfold. Surface analysis by Fourier Transform Infrared (FTIR) microspectroscopy revealed that cupric stearate was formed during the rubbing process by tribochemical reactions. The reaction product was confirmed by model compounds and was also found to be comparable with those from the static thermal experiments of stearic acid on copper surface at 140°C-160°C. The affinity between the chemisorbed stearic acid and bidentate copper stearate complex is believed to be responsible for the formation of a protective film on the copper surfaces to reduce the wear from further propagation.