无机类富勒烯过渡金属硫化物纳米材料的合成及其摩擦学应用研究进展

评述了无机类富勒烯（IF）与过渡金属硫化物（WS2和MoS2等）纳米材料的合成技术及其摩擦学应用研究的最新进展，外型为球形或近似于球形并具有嵌套中空结构的IF－WS2和IF－MoS2纳米果粒具有潜在的摩擦学应用前景；对含有IF－WS2纳米颗粒的复合材料和Ni-P复合镀层的研究表明，其比含有石墨和层状2H－WS2粉末的固体润滑剂具有更优异的摩擦学性能。     

偏压及测试环境对新型MoS2-Ti复合膜摩擦学性能的影响

采用新型高功率脉冲复合磁控溅射技术制备MoS2-Ti复合膜,并研究基体偏压和测试环境对复合膜摩擦学性能的影响.结果表明:制备的MoS2-Ti复合膜表面呈现颗粒状结构,Ti在薄膜表层与O反应形成氧化物有效抑制MoS2的氧化.随着基体负偏压从OV增大到-400 V,复合膜的S/Mo原子比逐渐减小.在-300 V偏压下,颗粒堆积最为紧密,薄膜硬度和弹性模量达到最大值,分别为9.7和137.1GPa,并具有最低的平均摩擦系数值(0.04)和磨损率[(10-7mm3/(N·m)].多种测试环境下的摩擦研究显示:在室温大气环境下复合膜的摩擦学性能与其结构的致密性紧密相关,而在N2以及不同湿度环境下薄膜表现出的优异摩擦学性能则归因于在摩擦过程中有效形成的转移膜贡献.     

钢表面钼沉积及渗硫复合改性层的摩擦学性能

采用多弧离子镀及低温离子渗硫复合镀渗工艺在45^#钢表面制备了含MoS2的钼基复合表面改性薄膜，在QP-100型球-盘式摩擦磨损试验机上考查了复合薄膜在油润滑条件下的摩擦学性能．用原子力显微镜及扫描电子显微镜观察分析了薄膜表面、截面和其磨损表面形貌及成分，用X射线衍射仪及俄歇电子能谱仪分析了薄膜的相结构及组成元素沿深度分布．结果表明，含MoS2的复合镀渗薄膜由Mo、MoS2及少量FeS组成，其在油润滑条件下同轴承钢对摩时表现出优良的摩擦学性能．     

南海海洋大气环境二硫化钼纳米多层薄膜摩擦学行为研究

MoS_2薄膜在湿热大气环境长期存储后,由于严重的氧化导致其摩擦学性能大幅劣化,通常表现出较高的摩擦系数和较短的使用寿命.为了改善MoS_2薄膜在湿热大气环境下的抗氧化和摩擦学性能,通过非平衡闭合场磁控溅射技术制备了MoS_2/Pb-Ti纳米多层薄膜,首次研究了MoS2纳米多层复合薄膜与纯MoS_2薄膜在恶劣的南海海洋大气环境暴露储存6个月后的薄膜成分、摩擦学性能的衍化行为.结果表明:与纯MoS_2薄膜相比,MoS_2/Pb-Ti纳米多层薄膜具有更好的抗湿热氧化性能,其摩擦学性能几乎未受到南海储存环境的影响,依然表现出较低的摩擦系数和磨损率.借助XRD、XPS、TEM和纳米压痕硬度等分析手段发现其摩擦学性能的大幅改善是由于薄膜中大量的异质界面对其晶面结构、薄膜致密性和机械性能的改善,以及Pb/Ti金属复合相对MoS_2氧化的抑制作用.     

高承载高耐磨Cr3C2-NiCr/DLC复合涂层制备及摩擦学行为

采用超音速火焰喷涂(HVOF)和等离子体辅助化学气相沉积(PACVD)技术制备Cr₃C₂-NiCr/DLC复合涂层,对比研究其与单层DLC薄膜的微观结构、机械性能和不同载荷下的摩擦磨损行为. 结果表明:Cr₃C₂-NiCr/DLC复合涂层的结合力、承载力和摩擦学性能比单层DLC薄膜显著提高;HVOF制备的Cr₃C₂-NiCr中间承载层对表层DLC薄膜的微观结构和纳米硬度影响不大;Cr₃C₂-NiCr/DLC复合涂层在高载下的优异摩擦学性能归因于避免了高接触应力下发生塑性变形而导致DLC薄膜在摩擦磨损过程中的脆性断裂和剥落失效行为. 此外,在不同载荷下的摩擦过程中DLC薄膜和Cr₃C₂-NiCr/DLC复合涂层均未发生石墨化,其摩擦学行为主要取决于不同接触应力下的磨损机制变化和对偶球表面摩擦转移膜演化.      

Y—TZP／MoS2自润滑材料的摩擦学性能研究

利用醇-水溶液加热方法制备了具有特殊显微结构、优良力学性能的Y-TZP/MoS2复合材料,考察了室温下复合材料与GCr15钢球及ZrO2陶瓷球配副时的摩擦学性能.结果表明当复合材料与GCr15钢配副时,GCr15钢在复合材料表面形成转移膜并发生粘着磨损,相应的摩擦系数较高;当复合材料与ZrO2配副时,随着复合材料中MoS2润滑相含量的增加,摩擦系数和复合材料磨损率逐渐减小,当复合材料中MoS2的体积分数为50.0%,其摩擦系数小于0.25,磨损率小于1.02×10-6 mm2/m*N.     

PTFE及UHMWPE改性PA6复合材料的摩擦学性能研究

采用熔融共混法制备了聚四氟乙烯(PTFE)和超高分子量聚乙烯(UHMWPE)改性的两种聚酰胺6(PA6)复合材料,研究了改性PA6复合材料的摩擦学性能,通过扫描电子显微镜观察复合材料的磨损表面,并对其磨损机理进行了分析.结果表明:使用单一润滑剂改性,添加量相同时,PTFE比UHMWPE改性的PA6复合材料具有更优的摩擦学性能;使用复合润滑剂改性时,PA6复合材料获得了比使用单一润滑剂改性时更好的摩擦学性能;添加不同种类的固体润滑剂,PA6复合材料的磨损表面呈现不同的形态特征,表现出不同的磨损机理.     

聚丙烯和二硫化钼对超高分子量聚乙烯复合材料摩擦磨损性能的影响

采用模压法制备了聚丙烯(PP)和MoS2填充超高分子量聚乙烯(UHMWPE)复合材料;在MM-200型摩擦磨损试验机上考察了UHMWPE/PP/MoS2复合材料的摩擦磨损性能;采用扫描电子显微镜观察分析复合材料磨损表面形貌.结果表明:单独添加MoS2可以提高UHMWPE的抗磨性能,但摩擦系数增大、力学性能降低;而采用PP和MoS2对UHMWPE进行改性可以显著改善加工性能;72.7%UHMWPE/18.2%PP/9.1%MoS2三元复合材料的加工性能、承载能力和长时抗磨性能明显优于UHMWPE;UHMWPE主要发生粘着磨损和疲劳磨损;而72.7%UHMW-PE/18.2%PP/9.1%MoS2三元复合材料在相同试验条件下同钢对摩时仅发生轻微塑性变形.     

聚酰亚胺/二硫化钼插层复合材料的制备及其摩擦磨损性能研究

用插层法制备了聚酰亚胺/二硫化钼插层复合材料(PI/MoS2),采用X射线衍射仪、红外光谱仪以及扫描电子显微镜等对材料的结构进行表征,采用四球长磨摩擦磨损试验机考察了聚酰亚胺/二硫化钼插层复合材料作为润滑脂添加剂的摩擦磨损行为.结果表明,所合成的PI/MoS2插层复合材料作为锂基脂添加剂对钢-钢摩擦副表现出良好的减摩抗磨作用.这主要是由于在摩擦过程中钢球表面形成了由FeSO4、MoO3及Fe的氧化物等组成的边界润滑及防护薄膜所致.     

固体-油脂复合润滑Ⅰ:二硫化钼膜在干摩擦及空间用油脂润滑下的摩擦学性能

本文采用射频溅射技术制备了MoS2薄膜,用UMT-2MT摩擦试验机考察了MoS2膜/钢球摩擦副分别在干摩擦、氟丙基氯苯基硅油(115#油)和KK-5脂(由115#润滑油经聚四氟乙烯粉稠化制成)润滑条件下的摩擦学性能,并分析了其润滑和失效机制.结果表明:脂润滑状态下,MoS2+KK-5复合膜处于不连续的边界润滑,其摩擦学性能得到改善但不明显;115#油润滑条件下,由于连续、有效的边界润滑,使得MoS2+115#固体-油复合体系的摩擦系数低而平稳,其耐磨损寿命与单独MoS2薄膜相比提高了至少8倍;相对于上述2种情况,干摩擦条件下的MoS2膜磨损明显.     

不同配副下ZrB2-SiC复相陶瓷的摩擦学性能

以微米级ZrB_2和SiC粉末为原料,采用热压烧结制备ZrB_2-SiC复相陶瓷,考察了SiC含量,摩擦对偶,速度和载荷对ZrB_2-SiC复相陶瓷摩擦磨损特性的影响.结果表明:ZrB_2-SiC复相陶瓷的摩擦系数和磨损率对SiC含量和摩擦对偶的变化较为敏感,速度和载荷变化,摩擦系数和磨损率的波动较大;以WC为对偶,速度0.1 m/s,载荷5 N时的ZrB_2-SiC复相陶瓷的平均摩擦系数和磨损率分别仅为0.4和2.41×10–4 mm3/(N·m).ZrB_2-SiC复相陶瓷的磨损机制以机械磨损为主,伴有轻微摩擦氧化,摩擦层的形成有利于摩擦系数的减小.     

Fe_3Al/WS_2复合材料的真空摩擦学性能研究

采用热压烧结的方法制备了添加WS2质量百分数为10%、20%和30%的Fe-28Al-5Cr基复合材料,通过XRD和SEM等手段分析了样品的相组成和组织结构.利用自制的真空摩擦试验机测试了样品在4×10-4Pa真空下的摩擦学性能.研究结果显示:通过与WS2的复合能够显著降低Fe3Al基金属间化合物在真空条件下的摩擦系数,但三种不同WS2含量复合材料的摩擦系数差别不大.随着WS2含量增加,复合材料的磨损率逐渐降低,特别是30%复合材料的磨损率较纯Fe-28Al-5Cr的磨损率低约1个数量级.滑动速度和载荷对三种材料的摩擦系数和磨损率均有一定的影响.纯Fe3Al的磨损表面较为粗糙,出现严重的剥落坑和剥落痕迹,磨损机理为严重的疲劳磨损.添加质量百分数为10%WS2的复合材料的磨损机理为磨粒磨损和疲劳磨损;添加WS2质量百分数为20%和30%的复合材料,其磨损表面相对较为光滑平整,磨损机理为轻微剥落.因此,在复合材料制备中添加WS2能够显著提高Fe3Al金属间化合物的真空摩擦学性能.     

Ti_3SiC_2的加入对Ag-MoS_2-graphite复合材料力学及摩擦磨损性能的影响

采用热压烧结技术制备了Ag-Mo S2-graphite和Ag-Mo S2-graphite-Ti3Si C2两种银基自润滑复合材料,考察了两种材料的致密度、硬度、弯曲强度及其在不同环境(大气和低真空)中的摩擦磨损性能.结果表明:低润湿性使得Ti3Si C2与基体界面处的孔隙增多,降低了致密度和弯曲强度,但对硬度影响不明显;摩擦过程中Ti3Si C2颗粒易于从基体材料表面剥落,阻碍了润滑膜的形成,造成Ag-Mo S2-graphite-Ti3Si C2复合材料的摩擦系数高于Ag-Mo S2-graphite复合材料;但Ti3Si C2的添加能够明显提高复合材料在大气中的耐磨性能,这主要与摩擦过程中的材料转移和摩擦化学反应有关.     

Ag-Cu-MoS2复合材料的真空载流磨损性能

采用粉末冶金方法制备了含有不同Cu质量分数(2%~4%)的Ag-Cu-MoS_2复合材料,并对其力学性能、电学性能和真空载流磨损性能进行了研究.结果表明:较高Cu质量分数的Ag-Cu-MoS_2复合材料表现出较高的硬度和抗弯强度;中等Cu质量分数(2.5%和3%)的Ag-Cu-MoS_2复合材料电刷表现出较低的电压降和电噪声;滑动速度的增加会降低材料间的接触稳定性,进而导致较高的电压降和较大的电噪声.在真空载流条件下与Ag合金盘滑动摩擦过程,不同Cu质量分数的Ag-Cu-MoS_2复合材料电刷均表现出较低的磨损,其磨损率在1×10~(–14)m~3/(N·m)~2.5×10~(–14)m~3/(N·m)范围,其磨损机理主要为疲劳磨损以及黏着磨损.     

Behavior of Pin-loaded Laminated Composites

In this study, an investigation was carried out to determine the effects of joint geometry and fiber orientation on the failure strength and failure mode in a pinned joint laminated composite plate. Behavior of pin-loaded laminated composites with different stacking sequence and different dimensions has been observed experimentally. E/glass–epoxy composites were manufactured to fabricate the specimens. Mechanical properties of the composites were characterized under tension, compression and in-plane shear in static loading conditions. Laminated composites were loaded through pins. Single-hole pin-loaded specimens were tested for their tensile response and width-to-hole diameter (W/D) and edge distance-to-hole diameter (E/D) ratios evaluated. A series of experiments was performed with six different material configurations ([0/±45]_s–[90/±45]_s, [0/90/0]_s–[90/0/90]_s and [90/0]_2s–[±45]_2s), in all, over 120 specimens. E/D ratios and W/D ratios of plates were changed from 1 to 5 and 2 to 5, respectively. Failure propagation and failure type were observed on the specimens. The influence of the joint geometry on the strength of the pin-loaded composites was assessed. When laminated composite plates were loaded to final failure, three basic failure modes consisting of net-tension, shear out and bearing failure were observed for the different geometric dimensions. All the connections tested showed that the fiber orientations have a definite influence on the position around hole circumference at which failure initiated. Net-tension failure occurred for specimens that had small width and large end distance. When the width was increased, the specimens which had small end distances failed in the shear-out modes. When the end distance was increased, bearing failure developed in addition to shear-out failure. The experimental results showed that the ultimate load capacities of E/glass–epoxy laminate plates with pin connection were increased by increasing W and E. However, increasing the E/D and W/D ratios beyond a critical value has an insignificant effect on the ultimate load capacity of the connection.     

电流对Mo2C改性C/C-Cu复合材料载流摩擦磨损性能的影响

通过对炭/炭坯体Mo_2C涂层改性并熔渗Cu制备了Mo_2C改性C/C-Cu复合材料,测试复合材料的载流摩擦磨损性能,研究电流强度对复合材料载流摩擦磨损性能的影响.结果表明电流由0增大至15A时,摩擦系数先减小后增大,5A时达最小值;复合材料体积磨损率逐渐增大;对偶磨损量在0~7.5A范围内较低,然后随电流增大而逐渐增大.电流较低时,磨损机制以磨粒磨损为主,随电流增大氧化磨损及黏着磨损程度提高,电流高至15A时,表现出了较明显的电弧侵蚀作用.     

Direct initiation of detonation in cryogenic gaseous H2-O2 mixtures

Critical conditions for the direct initiation of self-sustained detonation in cryogenic hydrogen-oxygen mixtures are examined experimentally. These initial conditions are expected to depend mainly on four parameters: the equivalence ratio of the mixture, the amount of the initial energy deposition, the initial temperature and pressure of the mixture. These critical conditions are determined by fixing alternatively three of these parameters and varying the fourth one from subcritical to supercritical detonation conditions. Results are presented for initial pressuresP _o and equivalence ratios ranging from 0.3 to 1 bar and from 1 to 2 respectively, for the two initial temperaturesT _o, 123 K and 293 K. These results indicate that for the lowest values of the initial pressure, a decrease of initial temperature may favour the onset of detonation. Whatever the initial conditions, the measured detonation pressures and velocities are in reasonably good agreement with the corresponding Chapman-Jouguet values computed using the ideal-gas equation of state.     

Reducible properties of draw temperature,rate of strain and filler content in tensile yield stress of polymethylmethacrylate filled with ultrafine particles

The yield stress of polymethylmethacrylate (PMMA) composites filled with ultrafine SiO₂ particles was measured as a function of the draw temperature, rate of strain and filler content. The yield stress of the composites increased with increasing filler content and decreasing filler size. The tensile yield stress was found to be reducible with regard to draw temperature, rate of strain and filler content. At a given filler content, a master curve was obtained for the yield stress plotted versus the logarithm of the strain rate. The Arrhenius plot of the shift factors (a _T ) used to produce the strain rate-temperature master curve formed a single curve for all sizes and loadings of the filler. The master curves obtained for different loadings of a filler of given size could be further reduced into a master-master curve by shifting them along the axis of strain rate, with the logarithm of the second shift factors (loga _c ) proportional to the 4/5th power of the filler volume fraction (V _f ). The proportionality constant and the exponent represent the extent of the filler reinforcing effect in the polymer. These values were found to be correlated with the critical surface tension of the polymers.     

Supersonic H2-air combustions behind oblique shock waves

In order to study the mechanisms of initiation and stabilization of H₂-Air combustions (stoechiometric mixture initially atT ₀=293 K andp ₀=0.5 bar) in supersonic flow conditions behind an oblique shock wave (OSW), an original technique is used where OSW is generated in this mixture by the lateral expansion of the burnt gas behind a normal CJ gaseous detonation propagating into a bounding reactive mixture. Four Mach numberM of propagation of OSW are considered in the study, namelyM=7.7-6.1-4.4 and 3. Depending on the Mach numberM and inclinaison angle of OSW different regimes of combustion may occur in the driven mixture. For high values ofM (6.1 and 7.7) delayed steady overdriven oblique detonation waves (SODW) were obtained with a near CJ detonation wave as the critical regime. It was found that SODW obtained correspond quite well to prediction of the polar method. When thermal conditions behind the OSW are lower, either for high Mach number 6.1 and 7.7 for smaller angle than the previous case, or for lower Mach number, 4.4 and 3, the flame initiated at the apex is stabilized as a turbulent oblique flame behind the OSW. With much lower conditions, no combustion appears in the H₂-Air mixture.     

Study of heat transfer in the separation zones formed in front of supersonic jets in a subsonic carrier flow

The heat transfer taking place between the gas and the surface of the plate in the zone of three-dimensional separation of the turbulent boundary layer in front of a set of supersonic jets injected perpendicularly to a subsonic carrier flow is considered. The aim of this investigation is to establish the main physical characteristics of heat transfer in the separation zones in front of jet obstacles and to obtain the distributions of the local heat-transfer coefficients and the temperature of the thermally insulating wall as functions of the parameters of the carrier flow and the injected jets. Analysis of the experimental results yields certain approximating relationships for the distribution of the local heat-transfer coefficients as functions of the Mach number of the carrier flow M, the Mach number of the jet M_j, the relative boundary-layer displacement thickness _s= _s ^* /d, and the degree of jet superheating T_ojT_o relative to the separation zones in front of supersonic jet obstacles.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 68–72, July–August, 1975.