用等离子体增强化学气相沉积技术制备类金刚石碳薄膜的摩擦磨损性能研究

利用射频-直流等离子体增强化学气相沉积技术在单晶硅衬底上沉积类金刚石碳薄膜,采用激光拉曼光谱仪和原子力显微镜对薄膜的结构和表面形貌进行表征,采用纳米压痕仪测定薄膜的硬度,并用UMT型微摩擦磨损试验机考察了薄膜在不同试验条件下的摩擦磨损性能.结果表明:所制备的类金刚石碳薄膜表面光滑致密且硬度较高;在干摩擦条件下与GCr15钢球或Al2O3球配副时显示出良好的减摩抗磨性能,摩擦系数较低,耐磨寿命较长,而在水润滑条件下同Al2O3球配副时发生灾难性磨损.     

Influence of Precursor Gas Flow Rate on Fluoropolymer Coating Growth Rate During Hot Wire Chemical Vapor Deposition

The formation of a fluoropolymer coating by chemical deposition has been studied experimentally. It has been found that increasing the flow rate of the precursor gas leads to a decrease in the growth rate of the coating. Deposition conditions were analyzed, and the gas-dynamic parameters of the process were estimated. The estimates are consistent with experimental data.     

On the Passage from Atomic to Continuum Theory for Thin Films

We give a rigorous derivation of a continuum theory from atomic models for thin films. This scheme has been proposed by Friesecke and James in [J. Mech. Phys. Solids 48, 1519–1540 (2000)]. The resulting continuum energy expression is obtained by integrating a stored energy density which not only depends on the deformation gradient, but also on ν-1 director fields when ν is the (fixed) number of atomic film layers.     

磁控溅射和脉冲直流化学气相沉积Ti-Si-N薄膜摩擦磨损性能对比研究

分别利用磁控溅射和脉冲直流化学气相沉积(PCVD)技术制备了Ti-Si-N薄膜，测定了2种Ti-Si-N薄膜的显微硬度，并采用球一盘式高温摩擦磨损试验机对比考察了其高温摩擦磨损性能．结果表明，当薄膜中Si含量(原子分数)约为10％时，2种薄膜的显微硬度达到最大值；2种Ti-Si-N薄膜的耐磨性能同其硬度之间不存在对应关系，其中采用PCVD方法制备的Ti-Si-N薄膜的高温抗磨性能较优；2种薄膜在高温下的摩擦系数均有所降低，这归因子高温下氧化膜的润滑作用。     

A Continuum Theory of Deformable,Semiconducting Ferroelectrics

Ferroelectric solids, especially ferroelectric perovskites, are widely used as sensors, actuators, filters, memory devices, and optical components. While these have traditionally been treated as insulators, they are in reality wide-band-gap semiconductors. This semiconducting behavior affects the microstructures or domain patterns of the ferroelectric material and the interaction of ferroelectrics with electrodes, and is affected significantly by defects and dopants. In this paper, we develop a continuum theory of deformable, semiconducting ferroelectrics. A key idea is to introduce space charges and dopant density as field (state) variables in addition to polarization and deformation. We demonstrate the theory by studying oxygen vacancies in barium titanate. We find the formation of depletion layers, regions of depleted electrons, and a large electric field at the ferroelectric–electrode boundary. We also find the formation of a charge double layer and a large electric field across 90° domain walls but not across 180° domain walls. We show that these internal electric fields can give rise to a redistribution or forced diffusion of oxygen vacancies, which provides a mechanism for aging of ferroelectric materials.     

材料生长与变形的连续介质模型:弹性本构方程

本文着重探讨了生长变形体连续介质理论中的本构模型。首先列出了描述生长变形体能量平衡的微分方程以及熵不等式；以此为基础，通过将密度演化的历史作为独立的本构变量扩展了理性力学的因果性公理与决定性公理，具体而详细地推导了简单材料的生长弹性本构方程，给出了这些本构方程中的相关本构变量之间的约束不等式，得到了“生长变形体的自由能与其密度成反比”的结论，并从热力学上对这一结果进行了定性的解释。最后，文中对几个尚待解决的问题进行了说明，并指出了今后的发展方向。     

脉冲直流等离子体增强化学气相沉积Ti—Si—N纳米薄膜的摩擦磨损特性

采用工业型脉冲等离子体增强化学气相沉积设备，通过调节氯化物混合比例控制薄膜成分，在高速钢基材表面于550℃下沉积由纳米晶TiN和纳米非晶Si3N4组成的Ti—Si—N复合薄膜；采用扫描电子显微镜、透射电子显微镜、X射线衍射仪及X射线光电子能谱仪分析了薄膜的结构、组成和化学状态；采用球-盘高温摩擦磨损试验机考察了薄膜同GCrl5钢对摩时的摩擦磨损性能．结果表明：薄膜的Si含量在0％～35％范围内变化，随着Si含量增大，薄膜沉积速率增大，但薄膜由致密形态向大颗粒疏松态过渡；薄膜的晶粒尺寸为7～50nm；Ti—Si—N薄膜的显微硬度高于TiN的硬度，最高可达60GPa；引入少量Si可以显著改善TiN薄膜的抗磨性能，但薄膜的摩擦系数较高(室温下约0．8、400℃下约0．7)；随着Si含量的增加，Ti—Si—N薄膜的耐磨性能有所降低，其原因在于引入导电性较差的Si元素使得薄膜的组织变得疏松．     

考虑温度效应的弹性损伤一般理论

现有的各种损伤理论基本上都是关于等温问题的 ,且在不同程度上依赖于某些经验假设。本文在严格的不可逆热力学理论基础之上 ,建立了考虑温度效应的弹性损伤一般理论。推导出热弹性各向同性与各向异性损伤材料全部本构方程的一般形式 ,其中包括应力 应变关系、熵密度方程、损伤对偶张量表达式、热 固 损伤耦合的热传导方程和损伤演化方程。它们的特殊形式包含了等温各向同性与各向异性弹性损伤的本构方程     

固体薄膜/液体膜/基底层状结构中液体膜/基底界面不平整性对结构稳定性影响

考虑液体层较薄的情况下液体膜/基底间界面不平整对结构的稳定性,特别是固体薄膜稳定时的褶皱变形产生的影响。用一扰动函数模拟液体膜/基底间界面的不平整,计算固体膜受力变形前后结构能量的变化,进而分析其稳定性。取两个扰动函数的特例,具体分析了液体膜/基底间界面不平整对结构能量变化以及对结构平衡态的影响。结果表明,平衡时固体膜褶皱变形与原来假设液体膜/基底间界面为理想平整面所得的结果有很大不同。     

A Discontinuous Elastic Interface Transfer Model of Thin Film Nanoindentation

A new model of thin film indentation that accounted for an apparent discontinuity in elastic strain transfer at the film/substrate interface was developed. Finite element analysis suggested that numerical values of strain were not directly continuous across the interface; the values in the film were higher when a soft film was deposited on a hard substrate. The new model was constructed based on this discontinuity; whereby, separate weighting factors were applied to account for the influence of the substrate in strain developed in the film and vice-versa. By comparing the model to experimental data from thirteen different amorphous thin film materials on a silicon substrate, constants in each weighting factor were found to have physical significance in being numerically similar to the bulk scale Poisson’s ratios of the materials involved. When employing these material properties in the new model it was found to provide an improved match to the experimental data over the existing Doerner and Nix and Gao models. Finally, the model was found to be capable of assessing the Young’s modulus of thin films that do not exhibit a flat region as long as the bulk Poisson’s ratio is known.     

Measurement of Mechanical Properties of Thin Film by Membrane Deflection Test

Micro-tensile properties of Au thin films were measured using a membrane deflection testing system. During the membrane deflection test, the deflection of the film was measured by an out-of-plane electronic speckle pattern interferometric (ESPI) system. From the measurement, the tensile loads and strains exerted on the membrane film during the deflection of the film could be determined. Quantitative analysis of the phase maps of the ESPI speckle patterns corresponding to the respective different deflection levels provided the deflection distribution along the testing section of the film. Test pieces were fabricated by electromachining process using 0.5 and 1. 0 μm thick Au films which were deposited on the silicon wafer by sputtering technique. Tensile properties, including elastic modulus, yield and tensile strength, were evaluated in the tensile stress-strain curve determined from the load-deflection relation. These properties were compared to those obtained from the micro-tensile tests. It was found that the yield and tensile strengths obtained from the deflection tests were lesser than those from the micro-tensile tests. Furthermore, the thickness effect, showing the increasing tendency of yield strength with decreasing thickness, was experimentally examined.     

A Generalized Theory of Stress and Strain Measures in the Classical Continuum Mechanics

A generalized theory of stress and strain tensor measures in the classical continuum mechanics is discussed: the main axioms of the theory are proposed, the general formulas for new tensor measures are derived, arid an energy conjugate theorem is formulated to distinguish the complete Lagrangian class of measures. As a subclass, a simple Lagrangian class of energy conjugate measures of stresses and finite strains is constructed in which the families of holonomic and corotational measures are distinguished. The characteristics of holonomic and corotational measures are studied by comparing the tensor measures of the simple Lagrangian class with one another and with logarithmic measures. For the simple Lagrangian class and its families, their completeness and closure are shown with respect to the choice of a generating pair of energetically conjugate measures. The applications of the new tensor measures in modeling the properties of plasticity, viscoelasticity, and shape memory are mentioned.     

激光诱导应力波测量薄膜界面强度研究进展

薄膜界面强度是影响多层薄膜装置性能的重要参数。激光诱导应力波技术是在可控制和非接触条件下定量测量薄膜界面强度最有效的技术之一。在采用高强度应力波短脉冲加载实现界面层裂的同时，通过光学测量薄膜自由面瞬态位移，并利用应力波理论计算得到临界界面强度。通过精确控制试样几何形状及尺寸，包括拉伸、剪切和复合型在内的各种界面加载模式都可以实现。本文对激光诱导应力波测量薄膜界面强度研究进展进行了综述，并特别强调了不同加载模式的实现方法，高强度超薄薄膜的界面测量技术，以及如何通过辨别薄膜自由面瞬态位移光学干涉信号中的某些特殊性征来实时判断和测量界面的层裂。     

石英岩表面分子沉积膜的微观摩擦性能的试验研究

利用原子力显微镜对石英岩表面单层分子沉积膜的微观摩擦特性进行了研究,发现该分子沉积膜具有一定的减摩性.通过对其表面力-位移曲线、表面形貌像、调制力像和摩擦力像的进一步分析表明,石英岩表面分子沉积膜具有减摩作用的原因在于它能够降低表面的粘着力并对表面具有微观修饰作用.     

Characterization of Moisture Diffusion into Polymeric Thin Film

The moisture within polymeric material typically used in electronic devices causes popcorn failures due to the vapor pressure in addition to the thermal stress. The knowledge of characteristics of moisture diffusion into the material is essential in the optimal material development and reliability assessment. The clarified procedures for measuring moisture sorption properties in a thin film form of semicrystalline polyethylene terephthalate (PET) using thermo-gravimetry and differential permeation are studied. The effective diffusivity of moisture into the material obtained from both the moisture transmission through the material and the solubility of moisture is proposed as a reliable method than the direct half time approximation over various water activities and temperatures. The parameterized isothermal desorption process according to Arrhenius equation investigates the possible effect of moisture on the polymer matrix as a form of bound water with polarity. The activation energy of diffusivity and solubility required for moisture diffusion into the material is discussed together with the required energy for evaporation of water.     

薄膜润滑中的应力偶效应

利用应力偶理论计算了薄膜润滑的膜厚特性.计算结果表明:应力偶的作用相当于增加润滑剂粘度,其可以增加油膜厚度,提高承载能力;同时应力偶作用依赖于油膜尺寸,润滑油膜越低,其影响越明显.     

InSb薄膜的剪切性能研究

InSb薄膜广泛应用于高精度的光电存储、红外探测等技术中.为了提高InSb材料的剪切强度,优化其力学性能,论文对InSb薄膜分别从不同厚度、温度、滑移系取向、孔洞密度等几个方面,对InSb薄膜的剪力响应及其原子构型演变进行分析,以研究其剪切强度和韧性的影响因素.发现厚度较大的薄膜具有更大的弹性模量和极限强度.而温度升高会导致材料的强度极限以及剪切韧性降低.同时还观察到10%孔洞密度下孔洞形状对材料的剪切性能有明显影响而20%孔洞密度下形状不再明显影响材料的剪切性能.此外在不同滑移系取向的研究中发现,滑移系取向对于材料的剪切强度和剪切韧性的影响是不同步的,例如(110)[1-10]滑移系下剪切强度降低而剪切韧性增强.上述结论对于提升InSb材料的剪切性能,合成出具有优异力学性能的InSb光电、磁敏材料具有指导意义.     

二氧化钛薄膜材料的制备及其摩擦学研究

利用溶胶－凝胶法（Ｓｏｌ－ｇｅｌ）制备了单层及双层ＴｉＯ２薄膜材料,分析结果表明所制薄膜主要由非晶ＴｉＯ２纳米颗粒组成,单层及双层ＴｉＯ２与钢球及Ｓｉ３Ｎ４陶瓷球对摩在轻载荷（３Ｎ）下具有良好的减摩与抗磨性能,与钢球对摩时失效循环次数分别为３７６和１８５６,与陶瓷球对摩时失效循环次数分别为２２８０和２３４３,玻璃基片主要发生脆性裂纹及严重的磨粒磨损,ＴｉＯ２薄膜则发生塑性变形及轻微磨粒磨损。