薄膜润滑研究的进展与问题

论述了薄膜润滑与润滑状态划分,薄膜润滑的特性,固/液转变与有序分子膜,薄膜润滑的失效,微流体的等效粘度与流动特性,高分子薄膜润滑的机理,纳米级固-液二相流,超滑等方面的研究进展和目前存在的尚未解决的问题.     

薄膜润滑与纳米流变学研究的进展

综述了薄膜润滑和纳米流变学最新研究成果及其对宏观摩擦学的贡献。当润滑膜厚度接近分子尺度时，润滑剂的流变性质和物理状态将经历很大的变化，包括有序结构形成，等效粘度增加，松驰过程减缓，固化或玻璃态转化以及由此产生的粘滑运动。说明在弹流和边界润滑之间可能存在一种特殊的薄膜润滑状态，即润滑剂的流动及流体动力效应依然存在，但其行为已大大不同于经典理论所预测的规律。目前有关薄膜润滑的理论尚在发展之中，它将为高技术微系统的开发，实现摩擦控制和界面设计提供理论基础。     

液体超滑技术发展现状及展望

随着我国现代工业的飞速发展,人类发展所必需的能量消耗与日渐匮乏且不可再生资源之间的矛盾日趋严重,其中不必要的摩擦造成的能量损耗约占我国国民生产总值的4.5%。超滑作为摩擦学的一个重要领域,自提出以来吸引着众多研究人员的密切关注与研究。这是因为超滑技术不仅可以提高润滑效率,还能够降低能量损耗并显著提高能源利用率,从而达到节约能源和资源的目的。因此,对超滑现象的产生规律和机理的深入研究,对进一步丰富和完善摩擦学体系有重要的理论意义,同时对超滑系统在工程中的应用有重要的实用价值。该文回顾近年来新型液体材料的超滑特性,并归纳各类液体润滑材料实现超滑的机理。最后,对当前超滑研究中的优劣势做出总结并提出展望。     

宇航空间超流氦低温技术的现状与发展

重点论述空间探测器超流氦冷却技术，低温冷却系统中的关键技术，如多孔塞相分离，微重力环境下杜瓦力ＨｅⅡ的管理，界面热阻等，宇航空间飞行中ＨｅⅡ的在轨补充，以及空间超流氦低温实验技术的最新进展。     

速度对凹陷表面微弹流润滑特征的影响

研究了在稳态速度以及不同的滚滑率等工况下,表面凹坑通过润滑接触区时的微弹流润滑特征。根据对油膜压力、油膜形式以及中心位置膜厚的分析发现,在非稳态速度条件下,凹坑通过弹流接触区引起的微弹流特征与稳态速度工况的区别明显,这一区别来源于凹坑的干扰与速度非稳态干扰的组成与叠加,另外发现,不论何种滚滑率、何种速度,其微弹流基本特征均保持一致,但速度的大小影响干扰凹陷以及几何凹坑在接触区中的深度。     

轴向柱塞泵回程装置对滑靴动态特性的影响研究

考虑了滑靴的倾斜以及滑靴底面的弹流润滑效应,同时引入了滑靴与不同回程装置间的相互作用,对轴向柱塞泵滑靴副润滑油膜的动态规律进行了数学建模,研究不同回程装置对滑靴动态油膜特性的影响。实现滑靴动力学特性与摩擦特性的耦合求解,获得了缸体转动周期内滑靴润滑油膜的变化规律,探讨了中心弹簧回程机构以及固定间隙回程机构对滑靴动态油膜特性的影响。分析结果表明:高速运转下,滑靴在低压区会发生严重倾斜。采用中心弹簧回复装置在减缓滑靴倾斜程度时会减小滑靴在高低压区的工作膜厚。使用固定间隙回程机构不仅不影响滑靴在高压工作区的膜厚状态,还可以提高滑靴低压工作区的最小膜厚,因而显著改善滑靴倾斜程度。      

克尔非线性黑体中光超流态的研究

研究了克尔非线性黑体中一种新的光超流态.研究表明:非线性黑体中具有相反波矢和旋量的裸光子结合成对,未成对的裸光子则转换成一种新的准粒子--非极化激元;光子对系统是一个超流态,而非极化激元系统是一个正常流态.正常流态的光谱能量密度和辐射压强都比普通黑体大并且随温度单调增加.在理论上证明了克尔非线性黑体中光超流态的存在并给出了测量这种光超流态的方法.     

具有自旋轨道耦合的冷原子费米气中的拓扑超流和FFLO超流

研究了具有自旋轨道耦合的冷原子费米气在外磁场作用下的物理性质.通过自洽求解Bogoliubove-de Gennes方程,发现了在不同磁场强度和粒子填充数下,体系分别存在拓扑超流态和Fulde-Ferrell-LarkinOvchinnikov超流态.当体系处于拓扑超流态时,存在零能Majorana费米子.     

薄膜润滑研究的回顾与展望

薄膜润滑是20世纪90年代以来广泛研究的新型润滑状态。它是界于弹流润滑和边界润滑之间的一种过渡润滑状态，有着自己独特的润滑规律。文章回顾了薄膜润滑的研究历史，包括薄膜润滑概念的提出、测试技术的发展、薄膜润滑的膜厚特性、润滑机理探索以及计算理论等方面的研究成果与主要进展。     

凹坑深度对表面动态弹流润滑的影响

把一种快速求解非稳态弹流润滑方程的数值方法应用于微弹流润滑分析，研究了几种深度的表面凹坑在三种滚滑接触运动条件下的压力波动和油膜变化特征，指出不仅运动条件变化带来不同的润滑特征，而且不同深度的凹坑在不同运动条件下对润滑扰动的程度也不同．研究结果适用于零件表面点蚀后的润滑状态分析．     

Developments and unsolved problems in nano-lubrication

The main achievements in the area of nano liquid film, e.g. the distinction between different lubrication regimes, properties of thin film lubrication, the transition between liquid and solid state, ordered and disordered state, the failure of thin lubricant film, the equivalent viscosity and flowing characteristics of micro-fluid, the influence of solid surfaces on nano-lubrication, thin film lubrication of polymer, superlubricity, have been reviewed and some unsolved problems are discussed.     

空间超流氦中低温界面热阻最佳热耦合研究

针对红外探测器与制冷元器件的接触中低界温面热阻最佳热耦合问题，分析了两固体接触面的情况，认为接触热阻是一个受材料性质、表面粗糙度、负载、温度、介质、表面氧化物膜和环境等众多因素影响的非线性问题，在此基础上制作了Al-Cu超导热开关，电子显微镜观测结果表明，接触界面不是一个简单的几何面，而是一个具有纳米级厚度的三维“界面层”。     

Analysis on mechanism of thin film lubrication

It is an important concern to explore the properties and principles of lubrication at nano or molecular scale. For a long time, measurement apparatus for film thickness of thin film lubrication （TFL） at nano scale have been devised on the basis of superthin interferometry technique. Many experiments were carried out to study the lubrication principles of TFL by taking advantages of aforementioned techniques, in an attempt to unveil the mechanism of TFL. Comprehensive experiments were conducted to explore the distinctive characteristics of TFL. Results show that TFL is a distinctive lubrication state other than any known lubrication ones, and serves as a bridge between elastohydrodynamic lubrication （EHL） and boundary lubrication （BL）. Two main influence factors of TFL are the solid surface effects and the molecular properties of the lubricant, whose combination effects result in alignment of liquid molecules near the solid surfaces and subsequently lubrication with ordered film emerged. Results of theoretical analysis considering microstructure are consistent with experimental outcomes, thus validating the proposed mechanism.     

Probable heat capacity signature of the supersolid transition

Liquid 4He enters the superfluid state and flows without friction below 2.176 K. Thin liquid films adsorbed on solid substrates undergo the same transformation, although at a lower temperature. When the substrate is subjected to oscillatory motion a portion of the film, known as the superfluid fraction, decouples from the oscillation. A similar phenomenon has been observed in solid 4He, in which a fraction of the solid seems to decouple from the motion of the surrounding lattice. Although this observation has been replicated in various laboratories, no thermodynamic signature of the possible supersolid transition has been seen. Here we report the finding of a heat capacity peak that coincides with the onset of mass decoupling. This complementary experimental evidence supports the existence of a genuine transition between the normal solid and supersolid phases of 4He.     

Electrode/electrolyte interface and interface reactions of solid oxide cells:Recent development and advances

High temperature solid oxide cells(SOCs) consisted of solid oxide fuel cells(SOFCs) and solid oxide electrolysis cells(SOECs) are considered one of the most environmentally friendly and efficient energy conversion technology to store renewal energy from sun and wind in hydrogen and generate electricity from the fuels such as hydrogen and natural gas with high efficiency and very low greenhouse gas emission. Over the last few decades, the development of SOC technologies in particularly SOFCs has experienced significant progress and much of the recent research have paid great efforts in understanding the processes occurring at the electrode/electrolyte interfaces. As electrochemical reactions mainly proceed at the gas, electrode and electrolyte three phase boundaries(TPBs), the microstructure and properties of the electrode/electrolyte interfaces thus play a crucial role in determining the overall cell performance and durability. Herein, we review the progress and achievements in the fundamental researches of the electrode/electrolyte(mainly oxygen-conducting) interface evolution behavior under open circuit and polarization conditions. Studies involving interfacial phenomena such as interface formation and reactions, element segregation and diffusion, micropore formation and delamination are summarized and discussed in detail. Besides, the state of the art characterization techniques that have been employed to examine the interface behavior are reviewed. Finally, the challenges and prospects of the interface research in the improvement of the performance and durability of a SOC device are discussed.     

扰动对单相合金定向凝固固液界面生长形态的影响

研究了扰动对单相合金在定向凝固过程中平面晶和胞晶固液界面生长形态的影响规律，给出了单相合金由平面晶向胞晶转变的临界条件及胞晶稳定生长的条件，首次用非线性理论中的线性稳定性理论，证明了单相合金在定向凝固过程中，固液界面由平面晶向胞晶转变和胞晶生长的分太 亚临界分叉；利用有机物模拟合金ＢｒＣ４在固液界面的面前沿有扰动的情况下进行实验，研究了固液界面前沿扰动对固液界面平胞转变和胞晶生长的分叉机制的影响规     

应力释放诱导的酞菁钴转子阵列

利用低温扫描隧道显微镜研究了酞菁钴(CoPc)分子在Cd(0001)表面上形成的自组装单层和转子阵列.在低温生长的酞菁钴分子单层中发现了应力诱导的3种空位结构:单分子空位、两分子空位和三分子空位.研究发现高温退火会导致结构相变:3种空位结构转变为均匀分布的单分子空位阵列.特别有趣的是,在每个单分子空位内部都存在一个酞菁钴转子.在液氮温度下(78 K),酞菁钴转子围绕着空位中心发生偏心转动;在液氦温度下(4.7 K),转子被冻结在空位的边缘上.     

Evidence for superfluidity of ultracold fermions in an optical lattice

The study of superfluid fermion pairs in a periodic potential has important ramifications for understanding superconductivity in crystalline materials. By using cold atomic gases, various models of condensed matter can be studied in a highly controllable environment. Weakly repulsive fermions in an optical lattice could undergo d-wave pairing at low temperatures, a possible mechanism for high temperature superconductivity in the copper oxides. The lattice potential could also strongly increase the critical temperature for s-wave superfluidity. Recent experimental advances in bulk atomic gases include the observation of fermion-pair condensates and high-temperature superfluidity. Experiments with fermions and bosonic bound pairs in optical lattices have been reported but have not yet addressed superfluid behaviour. Here we report the observation of distinct interference peaks when a condensate of fermionic atom pairs is released from an optical lattice, implying long-range order (a property of a superfluid). Conceptually, this means that s-wave pairing and coherence of fermion pairs have now been established in a lattice potential, in which the transport of atoms occurs by quantum mechanical tunnelling and not by simple propagation. These observations were made for interactions on both sides of a Feshbach resonance. For larger lattice depths, the coherence was lost in a reversible manner, possibly as a result of a transition from superfluid to insulator. Such strongly interacting fermions in an optical lattice can be used to study a new class of hamiltonians with interband and atom-molecule couplings.     

Probable observation of a supersolid helium phase

When liquid (4)He is cooled below 2.176 K, it undergoes a phase transition-Bose-Einstein condensation-and becomes a superfluid with zero viscosity. Once in such a state, it can flow without dissipation even through pores of atomic dimensions. Although it is intuitive to associate superflow only with the liquid phase, it has been proposed theoretically that superflow can also occur in the solid phase of (4)He. Owing to quantum mechanical fluctuations, delocalized vacancies and defects are expected to be present in crystalline solid (4)He, even in the limit of zero temperature. These zero-point vacancies can in principle allow the appearance of superfluidity in the solid. However, in spite of many attempts, such a 'supersolid' phase has yet to be observed in bulk solid (4)He. Here we report torsional oscillator measurements on solid helium confined in a porous medium, a configuration that is likely to be more heavily populated with vacancies than bulk helium. We find an abrupt drop in the rotational inertia of the confined solid below a certain critical temperature. The most likely interpretation of the inertia drop is entry into the supersolid phase. If confirmed, our results show that all three states of matter-gas, liquid and solid-can undergo Bose-Einstein condensation.     

混合工质制冷机中凝结传热的计算

分析了混合工质制冷机中水平管外凝结传热的计算问题,对守恒方程进行了处理,得出了分析解.通过对分析解的结果的研究,得出了近似算法,它可使计算过程大为简化,且近似程度又较为令人满意.