非对称布置液滴在波纹状基底上的聚并过程

基于润滑理论建立在波纹基底上两个含表面活性剂液滴聚并的演化模型，模拟液滴位于波纹基底波峰和波谷处的聚并过程，分析液滴初始间距和基底高度对聚并的影响，并与对称布置液滴进行比较.结果表明：液滴高度随时间呈现五个阶段变化；活性剂浓度在短时间内完成三个阶段变化；初始间距的增大将延长液滴及活性剂聚并时间；增大基底高度将缩短液滴及活性剂聚并时间；非对称液滴相较于对称液滴聚并时间短，聚并速度快.     

非平整基底上受热液膜流动稳定性研究

本文研究了二维黏性流体薄膜沿非平整不均匀加热基底流动时非线性表面波的演化及其流动稳定性.利用长波摄动法推导出非平整线性加热基底上非线性表面波的零阶和一阶演化方程,基于所得演化方程,绘制出正弦波纹基底上液膜的表面波形图,并研究液膜流动的线性稳定性,分析了各无量纲参数对液膜线性稳定性的影响.分析结果表明:在正弦波纹基底上,液膜自由表面随同壁面作相同频率的正弦型波动,且液膜厚度沿流动方向逐渐变小;Marangoni数为稳定影响因素,随Marangoni数的增大,液膜稳定区域增大;Peclet数和倾角θ均为不稳定影响因素,随Peclet数和倾角θ的增大,液膜稳定区域减小;在非平整基底的波峰和波谷处,Peclet数、Marangoni数和倾角θ对稳定性的影响趋势一致,但基底波谷处的液膜稳定区域小于波峰处区域,流动更易失稳.     

关于波的类型的思考

波动按其振动方向和传播方向的关系，可分为横波和纵波．横波的传播方向垂直于振动方向，而纵波的传播方向与振动方向在同一直线上．横波传播时，介质中出现波峰和波谷；纵波传播时，介质中则出现密部和疏部．     

石墨烯/柔性基底复合结构双向界面切应力传递问题的理论研究

界面力学性能是影响石墨烯/柔性基底复合结构整体力学性能的关键因素,因此对该结构界面切应力传递机理的研究十分必要.考虑了石墨烯和基底泊松效应的影响,本文提出了二维非线性剪滞模型.对于基底泊松比相比石墨烯较大的情况,利用该模型理论研究了受单轴拉伸石墨烯/柔性基底结构的双向界面切应力传递问题.在弹性粘结阶段,导出了石墨烯双向正应变和双向界面切应力的半解析表达式,分析了不同位置处石墨烯正应变和界面切应力的分布规律.导出了石墨烯/柔性基底结构发生界面滑移的临界应变,结果表明该临界应变低于利用经典一维非线性剪滞模型得到的滑移临界应变,并且明显受到石墨烯宽度尺寸以及基底泊松比大小的影响.基于二维非线性剪滞模型建立有限元模型(FEM),研究了界面滑移阶段石墨烯双向正应变和双向界面切应力的分布规律.与一维非线性剪滞模型的结果对比表明,当石墨烯宽度较大时,二维模型和一维模型对石墨烯正应变、界面切应力以及滑移临界应变的计算结果均存在较大差别,但石墨烯宽度很小时,二维模型可近似被一维模型代替.最后,通过与拉曼实验结果的对比,验证了二维非线性剪滞模型的可靠性,并得到了石墨烯/聚对苯二甲酸乙二醇酯(PET)基底结构的界面刚度(100 TPa/m)和界面剪切强度(0.295 MPa).     

光学薄膜残余应力分配预测模型计算方法研究

残余应力是光学薄膜研究的一个重要组成部分，它对光学元器件有很大的影响。根据弹性力学原理，基于应变不匹配，提出了一种可以预测薄膜残余应力分配的理论模型计算方法，并将计算结果与干涉仪测量值进行了对比。利用所建立的模型分析了薄膜参数变化时基底残余应力的变化情况。结果表明：所建模型合理；随着镀膜温度的增加，基底总残余应力随镀膜温度升高而呈增大的趋势;本征应力变化不太大；随着基底厚度的减小，基底上下表面应力呈增大的趋势，而薄膜应力则呈减小趋势，但变化趋势很小。基底的中心轴约位于基底上表面以下2／3处。     

鸟苷发酵不同阶段发酵液紫外特征光谱的研究

研究了发酵不同阶段鸟苷发酵液的紫外吸收光谱,结果表明,鸟苷发酵不同阶段发酵液紫外吸收光谱会呈现相应的特征光谱。发酵前期除了275nm处的波峰外,在249nm又出现了一个新峰,并且随着发酵时间增加新峰逐渐升高成为主峰;发酵中期275nm处的波峰逐渐减弱并最后消失;发酵后期249nm处的波峰成为发酵液的特征波峰,并随时间的增加逐渐上升;发酵末期的显著特征为发酵液λmax的吸光值基本不变。鸟苷发酵不同阶段发酵液特征光谱研究为人们认识鸟苷发酵的动态过程提供了一种新的技术和途径,对于鸟苷发酵生产具有一定的指导意义。     

轴向冲击载荷作用下双壁碳纳米管的动力屈曲

应用改进的有限元方法,建立考虑层间范德华力作用的壳-弹簧非线性有限元模型,基于B-R运动准则,系统地研究了双壁碳纳米管的动力屈曲问题,得到了轴向冲击载荷作用下双壁碳纳米管的临界动力屈曲载荷和临界动力失效载荷. 研究结果表明,在动力屈曲过程中,双壁碳纳米管层间距的变化非常小,各管的变形相互协调;碳纳米管中应力波的传播导致碳纳米管出现非对称屈曲模态,可明显观测到四个环向波瓣,沿着碳纳米管的轴线方向,四个波瓣的波峰和波谷交替变化. 对碳纳米管动力屈曲问题的研究表明,冲击载荷的大小和持续时间对碳纳米管的动力屈曲有 关键词： 碳纳米管 动力屈曲 冲击载荷     

硅油基底表面铁薄膜的生长机理及表面有序结构

利用直流溅射方法在液体基底(硅油)表面成功制备出金属铁薄膜系统，研究了其生长机理及特征的表面有序结构.实验发现铁薄膜的生长过程与液相基底表面非磁性金属薄膜的情况类似，基本服从二阶段生长模型.连续铁薄膜中可观测到尺寸巨大的圆盘形有序结构，其生长演化与溅射功率、沉积时间和真空环境中的生长时间等实验条件密切相关.实验证明，此类有序结构是在薄膜内应力作用下，铁原子及原子团簇在液体表面自由扩散迁移，并最终在硅油基底表面某些区域成核凝聚所致.在较大溅射功率和沉积时间条件下，圆盘外部区域的铁薄膜中形成周期分布的波纹褶皱，其波长约为10 μm，波峰基本与圆盘的边界平行.进一步研究表明：在沉积过程中，由于沉积铁原子的局域能量作用，导致硅油的表面层结构发生改变而形成一聚合物层；在随后的冷却过程中，聚合物层的强烈收缩使铁薄膜处于很大的压应力场中，促使薄膜起皱形成波纹结构. 关键词： 液体基底 铁薄膜 生长机理 有序结构     

连续凹槽基底对含非溶性活性剂薄液膜流动特性的影响

针对连续凹槽基底上含非溶性活性剂液膜的流动过程, 采用润滑理论建立了液膜厚度和活性剂浓度演化模型, 利用PDECOL程序数值模拟得到了液膜流动的动力学特征及基底结构参数的影响. 研究表明: 活性剂液膜流经连续凹槽时, 负向台阶处形成凹陷, 正向台阶处形成隆起, 且随时间逐渐增大; 与平整基底相比, 连续凹槽下的活性剂液膜铺展速度加快; 基底凹槽的高度增加或斜度减小可加速液膜破断的可能性; 增大凹槽宽度可促进液膜流动; 减小斜度会使液膜进入第一凹槽前形成隆起特征; 重力在液膜的爬坡和下坡过程中具有相反的作用, 但均使得流动稳定性变差; 分子间作用力形成的结合压可加速液膜流动, 进而引发去湿润现象, 分离压则与之相反. 关键词： 活性剂液膜 非平整基底 铺展 分子间作用力     

薄膜光学 光学薄膜参数测试

O484.52006010535光纤测厚中光谱“双峰”现象的分析=“Double peak”phe-nomenonin detection of thin fil mthickness[刊,中]/孙艳(西安交通大学机械工程学院.陕西,西安(710049)),赵宏…∥半导体光电.—2005,26(4).—356-358在用反射干涉频谱法(Rifs)测量薄膜厚度的过程中,薄膜的反射光谱经常见到“双峰”现象,即相邻的波峰(或波谷)连在一起,区别于通常按吸收曲线有规律分布的光谱。对该现象进行了深入研究,结果表明,该现象和被测试处薄膜厚度不均匀有关,当厚度差异较大时,入射光在薄膜的不同厚度点发生反射,各点的反射干涉光谱叠加就会…     

Desorption to delamination: dynamics of detachment in a colloidal thin film

Colloidal thin films of varying rigidity detaching from a substrate under an electric field induced stress are studied by video microscopy. For soft films, the process of detachment shows single-particle dynamics, analogous to desorption. For rigid films, a collective delamination spanning hundreds of particles occurs. A competition among the rigidity of the film, the interaction with the substrate, and the external stress leads to a correlation length over which the film delaminates at a critical stress. The phenomenon is described as a dynamical transition in a disordered elastic medium.     

Controlling the surface buckling wrinkles by patterning the material system of hard-nano-film/soft-matter-substrate

Wrinkling and buckling of nano-films on the compliant substrate are always induced due to thermal deformation mismatch.This paper proposes effective means to control the surface wrinkling of thin film on the compliant substrate,which exploits the curvatures of the curve cracks designed on the stiff film.The procedures of the method are summarized as:1)curve patterns are fabricated on the surface of PDMS(Polydimethylsiloxane)substrate and then the aluminum film with the thickness of several hundred nano-meters is deposited on the substrate;2)the curve patterns are transferred onto the aluminum film and lead to cracking of the film along the curves.The cracking redistributes the stress in the compressed film on the substrate;3)on the concave side of the curve,the wrinkling of the film surface is suppressed to be identified as shielding effect and on the convex side the wrinkling of the film surface is induced to be identified as inductive effect.The shielding and inductive effects make the dis-ordered wrinkling and buckling controllable.This phenomenon provides a potential application in the fabrication of flexible electronic devices.     

Wrinkling of a bilayer resting on a soft substrate under in-plane compression

The wrinkling problem of a bilayer film resting on a soft substrate under in-plane compression is investigated via theoretical analysis and numerical simulations. Such a system may undergo two different wrinkling modes, namely surface wrinkling of the top single layer on a composite substrate or bilayer wrinkling on a homogeneous substrate, depending on the geometric and material parameters. In the present paper, a theoretical solution is first derived for the former case, while a solution available in the literature is applied for the latter. The solution derived here can degenerate both to the classical solution for a stiff layer resting on a semi-infinite soft substrate and that for a stiff layer lying on a compliant substrate of finite thickness. A series of finite element simulations are performed to demonstrate the accuracy of the theoretical solution. In addition, it is found that, at a given compressive strain, a certain change in the elastic modulus of the intermediate layer may lead to a dramatic surface pattern transformation between the two wrinkling modes, indicating a novel approach to realise surface pattern switching.     

热氧化铜箔中的起皱和CuO纳米线的生长机

在500 oC大气条件下热氧化0.5 mm厚的铜箔0.5～10 h有起皱现象,且皱的大小随氧化时间的增加而增大,在皱的侧面和顶部均有生长CuO纳米线,皱侧面生长纳米线的长度比皱顶部的纳米线的长,密度也高;CuO纳米线的生长方向垂直于纳米线的生长表面. 通过计算波动阶段中皱内部的局部电场,发现皱的侧面和顶部的电场强度的数值相差很小,表明在CuO纳米线生长过程中驱动铜离子扩散的主要驱动力不是局部的电场力而是内应力.     

PDMS梯度光栅结构制备技术研究

由于传统方法制作的梯度光栅,工艺条件苛刻,制作过程复杂,难以控制,制作成本高,周期较长,提出了一种成本低、工艺简单、可大量制备梯度光栅的工艺方法,采用基于刚性薄膜/柔性衬底的自组装工艺和氧等离子体(Plasma)的方法制备了微米尺度的梯度光栅,利用Plasma时间的可控性和聚二甲基硅氧烷(PDMS)优异的弹性制得所需要尺寸的光栅。首先在聚乙烯对苯二酸脂(PET)薄膜上旋涂一层PDMS薄膜,待PDMS薄膜固化后将双层薄膜弯曲并用Plasma处理,在其表面生成一层刚性氧化层,借助柔性的PET对刚性层施加均匀应力,当应力超过临界值时,在PDMS基底上自组装形成光栅褶皱结构。由于弯曲时预应力的变化,所以在PDMS薄膜上会形成周期和高度呈阶梯状的的光栅褶皱,也就是梯度光栅。采用可见光作为梯度光栅的性能测试光源,选用一级衍射光作为检测对象,从图谱中可以看出以PDMS为基底制备的光栅具有很好的衍射效应,并可实现很好的分光效果。实验表明：梯度光栅具有明显的衍射现象,并且衍射角变化显著,可广泛用于应力测量。这种方法制备的柔性梯度光栅也可以作为微型应变装置来检测应力的变化,未来有望用于微型光谱仪、扫描仪、光通讯等领域中。     

Analysis of the substrate effects of strain-hardening thin films on silicon under nanoindentation

Mechanical properties of thin films on substrates can be evaluated directly through nanoindentation. For a comprehensive study, thin films should be characterized via Young’s modulus, yield stress and strain-hardening exponent at constant temperature. In this paper, we evaluate these effects of thin films on silicon substrate through finite element analysis. Thin films, from soft to hard relative to the silicon substrate, are investigated in three categories: soft films on hard substrates, soft to hard films on no elastic mismatch substrates, and hard films on soft substrates. In addition to examining the load-displacement curve, the normalized hardness versus normalized indentation depth is checked as well to characterize its substrate effect. We found that the intrinsic film hardness can be acquired with indentation depths of less than 12% and 20% of their film thickness for soft films on hard substrates and for soft to hard films on no elastic mismatch substrates, respectively. Nevertheless, nanoindentation of hard films on soft substrates cannot determine the intrinsic film hardness due to the fact that a soft substrate cannot support a hard film. By examining the von Mises stresses, we discovered a significant bending phenomenon in the hard film on the soft substrate. PACS 61.43.Bn; 62.20.-x; 68.03.Hj; 68.05.Cf; 68.08.De     

基于XRD的镀锌钝化膜残余应力试验研究

利用XRD技术测试了镀锌钝化膜结合界面的残余应力，同时通过电解抛光法检测了其厚度方向残余应力的分布规律，分析了残余应力对镀锌钝化膜结合强度的影响. 试验结果表明，镀锌钝化膜的残余应力均表现为压应力，并随着基体表面残余应力的增大而减小；钝化膜在2—10μm厚度方向的残应力为-274.5—-428.3MPa，其应力为梯度分布；镀锌钝化膜与基体的界面结合强度与其残余应力成反比，减小薄膜残余应力，有利于提高镀锌钝化膜与基体的结合强度. 关键词： X射线衍射法(XRD) 镀锌钝化膜 结合强度 残余应力     

Spontaneous wrinkling pattern of a constrained thin film membrane

The wrinkling morphology of an inhomogeneously constrained thin film membrane is explored using finite element simulations, where a small circular area in a thin sheet undergoes expansion, and buckles emerge due to differential in-plane deformation. The local wrinkling patterns are characterized by the normalized circular (inner) area size, the modulus mismatch between the inner and outer regions, and the normalized stress in the inner area. As the stress increases, the morphology transits from ripple-like to petal-like and finally to a branched pattern. Through parametric studies, the effect of the governing variables on the pattern evolution, wave number, and maximum deflection is discussed. The model is used to qualitatively explain the delamination/blister morphology observed in thin film/substrate systems. The study has the potential of inspiring new fabrication techniques based on mechanical self-assembly.     

Stability of the viscous fluid film flow on a uniformly heated substrate

The linear stability is investigated of a viscous fluid film on a uniformly heated substrate under an arbitrary angle of inclination against the horizon. At the substrate, the heat flux is set; at the film surface, the fluid-gas heat transfer coefficient is specified. The waves are considered in the film propagating in an arbitrary direction. Within the frame of the integral model, the dispersion ratios are obtained for the wave increment and phase velocity. The analysis is performed of the dispersion ratios, and the flow instability range is determined. At the Marangoni numbers above a certain threshold, standing wave or traveling wave type disturbances take place; the waves increase in the horizontal direction. For the traveling waves, the Marangoni number threshold value is significantly lower than the same for the standing waves.     

Synthesis surface effects on the stress and deformation of film/substrate system

The closed-form solutions of bending curvature and stress distribution in film/substrate system with the synthesis surface effect are proposed by minimizing the total potential energy. Effects of the roughness and the residual surface stress on stress in film are addressed. Results reveal that, at a given thickness of the substrate, effects of roughness and residual surface stress on the bending curvature become significant with decreasing the film thickness. The roughing surface will enlarge the magnitudes of bending curvature and film stress. The direction change of residual surface stresses can lead to a reversed bending of film/substrate system.