温度对PbS纳米微粒摩擦学性能的影响

研究了粒径为７ｎｍ的二烷基二硫代磷酸（ＤＤＰ）修饰ＰｂＳ纳米微粒以及未修饰ＰｂＳ纳米微粒从室温到７７３Ｋ的摩擦学行为。结果表明,修饰ＰｂＳ纳米微粒从室温到７７３Ｋ均具有良好的摩擦学性能,未修饰ＰｂＳ纳米微粒在７７３Ｋ时具有和修饰钠米微粒相近的摩擦学性能,而低于此温度时,未修饰ＰｂＳ的摩擦学性能较差。     

表面修饰PbS纳微粒的合成及其抗磨性

合成了二烷基二硫代磷酸修饰的ＰｂＳ纳米微粒，用透射电子显微镜和电子衍射对其形貌和晶体结构作了观察分析，通过四球试验考察了它有润滑油中的摩擦学行为。结果表明，这种微粒的粒径大都在３－５ｎｍ之间，具有方铅矿的晶体结构，其在液体石蜡中的抗磨性良好。     

表面修饰 PbS 纳米微粒的合成及其抗磨性

合成了二烷基二硫代磷酸修饰的ＰｂＳ纳米微粒，用透射电子显微镜和电子衍射对其形貌和晶体结构作了观察分析，通过四球试验考察了它在润滑油中的摩擦学行为．结果表明，这种微粒的粒径大都在３～５ｎｍ之间，具有方铅矿的晶体结构，其在液体石蜡中的抗磨性良好．     

油酸表面修饰PbO纳米微粒作为润滑油添加剂的摩擦学性能研究

利用四球摩擦磨损试验机考察了油酸修饰PbO纳米微粒作为润滑油添加剂的摩擦学行为,并用X射线光电子能谱仪（XPS）、扫描电子显微镜（SEM）和能量散射谱仪（EDS）等现代分析工具对钢球磨损表面进行了分析,摩擦磨损试验结果表明,油酸修饰PbO纳米微粒作为润滑油添加剂能够明显提高基础油的减摩抗磨能力,当添加质量分数为0.30%时,与基础油相比可以使摩擦系数和钢球磨厂主 直径降低30%左右。XPS、SEM及EDS分析结果表明,钢球表面在摩擦过程中形成了一层富含PbO的边界润滑膜,这使得油酸修饰PbO纳米微粒作为润滑油添加剂表现出良好的摩擦学性能。     

十六烷基三甲基溴化铵(CTAB)修饰的蜡烛灰作为润滑油添加剂的摩擦学性能研究

通过简单方法收集的蜡烛灰表面呈负电性,可以用阳离子表面活性剂十六烷基三甲基溴化铵(CTAB)进行修饰,利用透射电镜观察修饰后蜡烛灰的形貌,发现蜡烛灰是由20 nm左右的洋葱状碳纳米颗粒组成,分散性更好,粒径更加均匀,修饰后明显改善其在液体石蜡(LP)中的分散稳定性.利用Optimol SRV-IV往复振动摩擦磨损试验机评价了修饰前后蜡烛灰在LP中的摩擦学性能.结果表明:蜡烛灰作为LP的添加剂不能明显改善其润滑性能,但是表面修饰的蜡烛灰在LP中能够显著降低摩擦和减小磨损,因而具有良好的润滑性能.通过扫描电子显微镜、拉曼光谱以及X-射线能谱进一步推测两种蜡烛灰在LP中的润滑机理.     

油酸修饰纳米氟化钙的萃取法制备及其摩擦学性能

采用萃取法制备了油酸修饰的纳米CaF2,用X射线衍射(XRD)对纳米CaF2粉体样品进行物相分析,同时用透射电子显微镜(TEM)及傅立叶变换红外光谱仪(FT-IR)进行表面形貌和成分分析,并在四球摩擦磨损试验机上评价了CaF2在润滑脂中的摩擦学性能.结果表明,制备的纳米CaF2粒径在23 nm左右,油酸以化学吸附的方式吸附在CaF2纳米核表面;作为添加剂油酸修饰纳米CaF2在润滑脂中具有良好的抗磨性能和极压性能,在高载荷时具有良好的减摩性能.SEM,EDS和XPS分析表明在摩擦过程中形成了由CaF2、CaO、氧化铁和有机添加剂所组成的边界润滑膜,从而使OA-CaF2具有良好的摩擦学性能.     

等离子体辅助球磨制备表面修饰纳米TiO2的摩擦学性能分析

以季铵盐和月桂酸钠为过程处理剂,利用等离子体辅助球磨制备表面修饰纳米TiO_2粉体,并测试其摩擦学性能.结果表明:在等离子体的热爆效应及脉冲电子轰击效应的协同作用下,辅助球磨11 h制备的表面修饰纳米TiO_2粉体粒径在20 nm左右,晶型发生由锐钛矿型向金红石型的转变.等离子体辅助球磨使得纳米TiO_2获得了良好的亲油疏水表面特性,在40CA船用润滑油中表现出稳定的分散性.由于纳米TiO_2粉体的"微轴承"作用,复合润滑油的摩擦系数降低,摩擦副的磨损失重量减少.纳米TiO_2粉体在摩擦过程中容易吸附沉积在摩擦副表面并修补磨痕,使得复合润滑油具备良好的减摩及自修复性能.     

表面修饰SiO2纳米微粒对锂基脂抗磨性能影响的研究

合成了表面修饰SiO2纳米微粒,利用四球摩擦磨损试验机考察了SiO2纳米微粒作为锂基脂添加剂的摩擦磨损行为,用扫描电子显微镜、能量色散谱仪和X射线光电子能谱仪对钢球磨损表面进行了分析.结果表明:SiO2纳米微粒作为锂基脂添加剂具有良好的抗磨损性能,能够显著提高锂基脂的失效载荷.这是由于在摩擦过程中,SiO2纳米微粒富集在磨损表面并形成边界润滑膜,对磨损表面起到修复作用,从而使得锂基脂的抗磨和承载能力明显提高.     

油酸修饰TiO2纳米微粒水溶液润滑下GCr15钢摩擦磨损性能研究

用四球摩擦磨损试验机考察了脂肪酸修饰TiO2纳米微粒水溶液润滑下GCr15钢的摩擦磨损性能,并用电子探针和X射线光电子能谱研究了钢球磨损表面边界润滑膜的化学组成和元素分布.摩擦磨损试验结果表明:脂肪酸修饰TiO2纳米微粒在水中具有较好的润滑性能、良好的极压性能及较高的承载能力.添加质量分数为0.1%～1.0%的油酸TiO2纳米微粒可使水的承载能力提高6～12倍,烧结负荷提高51～100%,抗磨减摩性能也有较大提高,卡咬负荷由150N提高至1000～1800N.磨损表面分析表明:油酸TiO2纳米微粒在较高负荷(>300N)下发生了摩擦化学反应,生成含TiO2及油酸复合物的边界润滑膜,从而起减摩抗磨作用     

表面能对纳米颗粒的晶格收缩和固有频率的影响

由于纳米颗粒具有很大的比表面积，因此，表面能对它的力学性能有着不可忽略的影响．本文给出了由表面能所导致的纳米颗粒晶格收缩效应的解析结果，与试验观察定量上相当一致；计算了表面能对纳米颗粒固有频率的影响，预测了由于表面能的影响，纳米颗粒出现的“振动软化”现象．     

New 1:1:1 periodic solutions in 3-dimensional galactic-type Hamiltonian systems

Applying the averaging theory, we prove the existence of new families of periodic orbits for \(3\) -dimensional type-galactic Hamiltonian systems.     

Dynamic instabilities in {1 1 1} silicon

The phenomena occurring during rapid crack propagation in brittle single crystals was studied by cleaving strip-like silicon specimens along the {1 1 1} low-energy cleavage plane under bending. The experiments reveal phenomena associated with rapid crack propagation in brittle single crystals not previously reported, and new crack path instabilities in particular. In contrast to amorphous materials, the observed instabilities are generated at relatively low velocity, while at high velocity the crack path remains stable. The experiments demonstrate that crack velocity in single crystals can attain the theoretical limit. No evidence for mirror, mist, and hackle instabilities, typical in amorphous materials, was found. The important role played by the atomistic symmetry of the crystals on controlling and generating the surface instabilities is explained; the importance of the velocity and orientation-dependent cleavage energy is discussed. The surface instabilities are generated to satisfy minimum energy dissipation considerations. These findings necessitate a new approach to the fundamentals of dynamic crack propagation in brittle single crystals.     

Buckling behavior of Kelvin open-cell foams under [0 0 1], [0 1 1] and [1 1 1] compressive loads

This paper describes buckling modes and stresses of elastic Kelvin open-cell foams subjected to [0 0 1], [0 1 1] and [1 1 1] uniaxial compressions. Cubic unit cells and cell aggregates in model foams are analyzed using a homogenization theory of the updated Lagrangian type. The analysis is performed on the assumption that the struts in foams have a non-uniform distribution of cross-sectional areas as observed experimentally. The relative density is changed to range from 0.005 to 0.05. It is thus found that long wavelength buckling and macroscopic instability primarily occur under [0 0 1] and [0 1 1] compressions, with only short wavelength buckling under [1 1 1] compression. The primary buckling stresses under the three compressions are fairly close to one another and almost satisfy the Gibson–Ashby relation established to fit experiments. By also performing the analysis based on the uniformity of strut cross-sectional areas, it is shown that the non-uniformity of cross-sectional areas is an important factor for the buckling behavior of open-cell foams.     

On invariance in 1+1-dimensional isentropic relativistic gasdynamics

Invariance of a 1+1-dimensional relativistic isentropic gasdynamic system is established under two multi-parameter classes of transformation. The latter constitute, in turn, extensions of reciprocal and Movsesian-type invariance transformations with origin in classical non-relativistic gasdynamics.     

Computer simulations of nanoindentation on Cu (1 1 1) with a void

This paper employs static atomistic simulations to investigate the effect of a void on the nanoindentation of Cu (1 1 1). The simulations minimize the potential energy of the complete system via finite element formulation to identify the equilibrium configuration of any deformed state. The size and depth of the void are treated as two variable parameters. The numerical results reveal that the void disappears when the indentation depth is sufficiently large. A stress concentration is observed at the internal surface of the void in all simulations cases. The results indicate that the presence of a void has a significant influence on the nanohardness extracted from the nanoindentation tests.     

2:1:1 Resonance in the Quasi-Periodic Mathieu Equation

We present a small $ \ddot x + (\delta + \epsilon \cos t + \epsilon \cos \omega t) x=0 $ \ddot x + (\delta + \epsilon \cos t + \epsilon \cos \omega t) x=0      

Analysis of 1:1 internal resonance of a CFRP cable with an external 1/3 subharmonic resonance

Nonlinear Dynamics - Based on the non-planar vibration equations of a cable made of carbon fiber reinforced polymer (CFRP), the nonlinear behaviors of the cable are studied. The one-to-one internal...     

充液挠性航天器俯仰运动 1:1:1 内共振动力学分析

采用已推导的俯仰运动矩形贮箱受控刚-液-弹耦合系统在外力矩作用下的耦合动力 学模型,在刚体上加入控制项,详细分析了系统固有频率的精确解与近似解. 应用多尺 度法对耦合系统1:1:1内共振进行解析分析,与数值解比较验证解析解的正确性. 通过近 似解析分析得到刚-液-弹之间的耦合作用机理：1) 液深影响整个系统的软硬特性,当液体发 生软硬特性转化时,处于液体原多值频率区域的刚体和弹性体幅频曲线分支峰值会减弱,且 具有相同的特性转化趋势;处于液体新多值频率区域的刚体和弹性体幅频曲线分支峰值会增 强,且具有相反的特性转化趋势. 2) 刚体和弹性体幅频曲线的峰值均在以受控刚体和弹性体 为主的耦合系统固有频率处,以液体为主固有频率激励,刚体和弹性体振幅较小.