表面修饰氟化镧纳米粒子的制备及摩擦学性能研究

采用化学沉淀法以氟化物(NaF)和稀土氯化盐(LaCl3)为原料制备LaF3纳米粒子;采用透射显微镜(TEM)和X射线衍射仪(XRD)对纳米粒子的结构和形貌进行表征及分析;用硅烷偶联剂KH550对其表面改性,在高速高温摩擦磨损试验机上研究改性后的LaF3纳米粒子添加到纯基础油中的摩擦学性能,分析其抗磨减摩机制。结果表明,LaF3纳米粒子添加到润滑油中能提高其摩擦学性能,起到减摩耐磨效果;摩擦过程中LaF3纳米粒子渗透到试件中,起到修复作用。     

油溶性钙掺杂氟化镧纳米粒子的制备及其摩擦性能研究

在乙醇-水体系中,以二辛基二硫代磷酸双(β-)羟乙基十八胺盐为表面修饰剂,以氯化钙和氯化镧为原料,制备了油溶性钙掺杂氟化镧纳米粒子和氟化镧与氟化钙混合体纳米粒子.通过X射线衍射仪(XRD)、透射电镜(TEM)、热重仪(TG)及傅立叶红外(FTIR)表征了表面修饰纳米粒子的结构及形貌,利用离心沉降法和升温法结合研究了添加剂中纳米粒子在500SN基础油中的分散稳定性和高温稳定性,利用四球机考察了纳米粒子的摩擦学性能,并通过SEM分析了钢球磨斑表面.结果表明:La、Ca摩尔比为1∶1时,纳米粒子为氟化镧晶体和氟化钙晶体的混合物;La、Ca摩尔比为1∶2时,其结构为掺杂体;2种纳米粒子形貌和粒径一样,平均粒径在10 nm左右;在500SN基础油中具有良好的分散稳定性;掺杂体纳米粒子的摩擦学性能高于混合体纳米粒子,含掺杂体纳米粒子油样的最大无卡咬负荷值比基础油提高了1.15倍,磨斑直径比基础油降低了42.6%.     

纳米二氧化铈润滑油添加剂的摩擦学特性

用适当的表面活性剂对纳米二氧化铈粒子进行表面改性处理,采用透射电镜(TEM)和X-射线衍射法(XRD)观察与测量纳米二氧化铈粒子的形貌、结构和平均直径。将改性后的纳米二氧化铈粒子作为润滑油添加剂,采用四球摩擦磨损试验机测定添加纳米二氧化铈粒子的润滑油的摩擦学性能。利用扫描电镜(SEM)观察磨斑表面形貌以及纳米二氧化铈粒子在摩擦表面的形态等,并探讨了纳米二氧化铈粒子具有优良摩擦学性能的机制。结果表明,经表面改性的纳米二氧化铈在润滑油中具有良好的分散、稳定性;纳米二氧化铈粒子的添加量为0.6%(质量分数)左右时,润滑油在室温与较高温度下均具有优良的减摩、抗磨作用。     

纳米二硫化钼作为润滑油添加剂的摩擦学性能研究

研究纳米二硫化钼作为润滑油添加剂的摩擦学性能。以不同的表面活性剂和不同的超声波分散时间制备纳米二硫化钼润滑油,考察表面活性剂和超声波分散时间对纳米二硫化钼分散稳定性的影响。采用四球机和描电镜考察纳米二硫化钼在润滑油中的摩擦学性能。结果表明,2%油酸表面活性剂和超声波分散30 min可有效提高纳米二硫化钼在润滑油中的分散稳定性,纳米二硫化钼在润滑油中具有良好的抗磨性能、减摩性能,特别是0.01%二硫化钼在润滑油中的抗磨性能和高负荷下的减磨性能更为突出。     

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。     

表面修饰剂的亲油链长度对纳米氟化镧摩擦学性能的影响

以亲油基链长度不同的十二酸二乙醇胺、十四酸二乙醇胺、十六酸二乙醇胺及十八酸二乙醇胺为表面修饰剂,在醇-水体系中制备了4种纳米氟化镧粒子,通过透射电镜（TEM）、红外光谱（FTIR）、热重仪（TG）研究了纳米氟化镧粒子的形貌及表面修饰情况,利用四球机研究了亲油链长度对纳米氟化镧粒子的摩擦学性能及对基础油感受性的影响。结果表明：随着表面修饰剂烷基链长度的增长,纳米LaF3粒子在基础油中摩擦学性能呈现出逐渐增强的趋势;亲油链越长,纳米粒子在液体石蜡中的摩擦学感受性比500SN基础油中更好。这主要是因为亲油基链的长度影响了纳米粒子的界面活性,而且同系有机酸皂类物质,亲油基碳链越长,其减摩作用也越好;基础油的性质影响了纳米粒子的界面活性。     

油溶性氟化镧纳米棒的制备及其摩擦学性能研究

利用超声波辅助处理,在乙醇-水体系中,以二辛基二硫代磷酸双(β-)羟乙基十八胺盐为表面修饰剂制备了表面修饰氟化镧纳米棒,通过相转移法制得油溶性纳米氟化镧添加剂.通过X射线衍射仪(XRD)、透射电镜(TEM)及热重仪(TG)表征了表面修饰氟化镧纳米棒的结构及形貌,利用离心沉降法和升温法结合研究了添加剂中纳米氟化镧在500SN基础油中的分散稳定性和高温稳定性,利用四球机考察了纳米氟化镧的摩擦学性能,并通过SEM和AES分析了钢球磨斑表面.结果表明:氟化镧纳米棒直径在4～7 nm之间,长度为20～30 nm;氟化镧纳米棒在500SN基础油中具有良好的分散稳定性,并可使基础油的最大无卡咬负荷值增加了109.61%,磨斑直径降低39.13%;AES结果表明,氟化镧沉积在磨斑表面形成一层复合膜,并且渗透入磨斑的亚表面,共同提高基础油的摩擦学性能.     

纳米二氧化铈与蛇纹石混合物作为润滑油添加剂的摩擦学性能研究

采用表面活性剂将蛇纹石、纳米二氧化铈以及他们的混合物稳定分散于PAO4基础油中,利用摩擦磨损试验机分别考察蛇纹石、纳米二氧化铈以及蛇纹石与二氧化铈混合物作为润滑油添加剂的摩擦学性能,借助金相显微镜观察磨损表面形貌并测量磨斑直径,并采用能量色散谱仪(EDS)分析磨损表面的元素组成。结果表明:蛇纹石、纳米CeO_2和蛇纹石/CeO_2复合颗粒都可以显著改善润滑油的减摩抗磨性能,而添加蛇纹石/CeO_2复合添加剂的润滑油的摩擦学性能更佳,其中添加质量分数0.25%纳米二氧化铈与0.25%蛇纹石混合物的润滑油的摩擦学性能最佳。蛇纹石/CeO_2复合颗粒优异的摩擦学性能归因于其在磨损表面形成了吸附膜和Fe_2O_3、SiO_2化学反应膜,其中Ce元素可能起到了催化剂的作用。     

原位制备CaCO3微纳米流体及摩擦学性能研究

选用菜籽油、失水山梨糖醇脂肪酸酯(Span 80)、壬基酚聚氧乙烯醚(TX-7)、正丁醇制备W/O型微乳液，并将其作为微反应器原位合成CaCO₃微纳米粒子。对CaCO₃粒子形貌的表征表明，随含水量增加，CaCO₃粒子由球形转变为梭形薄片状，CaCO₃粒子尺寸也可受含水量控制。通过四球摩擦磨损试验机评价CaCO₃微纳米流体的摩擦学性能，结果表明，该微乳液体系相较于基础油的摩擦因数降低了约55.74%,CaCO₃粒子使微乳液P_B值提高了约10.88%,摩擦面粗糙度降低了约16.01%。在摩擦过程中，胶团在表面活性剂的作用下平行吸附于摩擦面且易于剪切，实现优异的减摩效果；梭形薄片状的CaCO₃微纳米粒子可以抑制表面微凸体之间的直接接触，减少黏着磨损与磨粒磨损，从而发挥极压作用并显著改善表面质量。     

羟基硅酸盐/纳米铜复合添加剂摩擦学性能研究

由羟基硅酸镁和纳米铜粉体按质量比1∶1组成复合添加剂,利用MJ-800型四球摩擦磨损试验机考察复合粉体、硅酸盐粉体和纳米铜分别作为N68基础油添加剂的摩擦学性能,借助JSM3010型扫描电子显微镜及EDS测试分析钢球磨痕的表面形貌和成分组成,研究了添加剂的作用机制.结果表明:添加剂的引入明显改善了基础油的摩擦学性能,添加剂粒子通过吸附、填充、微滚珠以及熔融铺展作用降低钢球磨损,并对磨损表面进行一定的修复;硅酸盐粉体和纳米铜表现出良好的协同抗磨效应,复合添加剂的极压抗磨性能优于硅酸盐粉体或纳米铜单独作为添加剂.     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

Limits of topographic measurement by the scanning tunnelling and atomic force microscopes

Parameters describing the topographic character of a surface (height, surface wavelength, slope and curvature) can be derived from equivalent sinusoidal profiles. The response of a surface-measuring instrument may be modelled in terms of instrument parameters such as stylus radius, and scanning range and resolution. The performance of the instrument may then be mapped as a zone in amplitude-wavelength (AW) space to show the sinusoidal profiles it is capable of measuring. In a first-order analysis the STM and AFM are considered as equivalent to contact-stylus instruments with a notional stylus radius equal to the tip radius plus the gap. Comparisons between different instruments and types of instrument are readily made by mapping in AW space. The error arising from convolution of the sinusoidal profile with that of the finite tip may be quantified and plotted as contours in AW space.