工艺温度下树脂与纤维的接触角及其粘附作用研究

针对复合材料成型工艺条件下环氧树脂与碳纤维表面的物理化学作用,研究了不同温度下E51树脂以及E51/DDS、E51/咪唑树脂体系的表面张力,E51树脂与T700纤维单丝的接触角;并考察了E51树脂在T700纤维束表面的初始表观接触角。进而对比分析了升温过程中T700纤维与E51/DDS树脂体系的浸润特性,计算出纤维与树脂体系的热力学粘附功,考察了工艺温度条件下纤维与树脂体系的粘附特性。结果表明,升高温度、降低树脂黏度可有效改善纤维与树脂的浸润特性,树脂的黏度作用尤其显著。在树脂体系发生化学反应之前,升温对纤维/树脂粘附特性的促进作用较不明显。     

降低固-液界面粘附作用的微观结构调整方向研究

固-液界面粘附作用是影响液相在固体表面动态性能的关键因素,降低固-液界面粘附力是疏液表面迈向实际应用的关键突破点。为探讨固相表面微观结构对固-液界面粘附作用的影响,采用高粘低表面张力液相端羟基聚丁二烯(HTPB)为主要指示液相,通过反应溶液和条件控制来调控固相表面的微观结构和形貌,制备疏液表面,并利用接触角仪、高精度天平和高速摄像等手段研究HTPB在疏液表面的静态接触角和动态粘附-脱附过程行为,揭示降低固-液界面粘附作用的微观结构调整方向。结果表明,固相微观结构在一定程度的变化对静态接触角影响较小,但对HTPB在脱附过程中液滴的形变产生较大影响,同时对比研究了低粘高表面张力液相水和甘油在疏液表面的动态粘附-脱附行为和粘附力值,通过力学物理模型简化,表明固-液界面的粘附力除了与液滴形状的变形量和本质特性紧密关联,还取决于固相表面微观结构。通过固相表面微观结构对界面粘附力的影响特性,认为构筑的微观结构更均匀致密,三维(X\Y\Z)方向上尺寸均实现纳米、亚微米到微米的连续性跨越时,可使固-液界面粘附力显著下降。     

环状SMA微夹钳工作原理的研究

利用ＳＭＡ的形状记忆特性，制作微小的功能夹持器，用于微机械零部件的装配中，并从马氏体热弹性变形出发，对这种ＳＭＡ微夹钳的设计原理，动力学特性，变位量的可控性及其与温度的关系进行研究，分析了ＳＭＡ微夹钳工作过程中的能量关系，并对具有共性的微夹钳尺寸的效应问题，即夹持粘附力问题，进行了研究和讨论。     

微注塑成型充模流动中的表面张力

微尺度通道中的高聚物熔体流动行为与宏观熔体流动有许多不同。基于对微注塑成型中的熔体充模流动特性的理论分析,建立了微小通道中熔体流动的表面张力模型,并以不同的表面张力系数和不同接触角,对矩形微通道中的熔体流动速度分布进行了数值模拟。结果表明,接触角小于90°时,熔体在通道壁面附近具有最大速度;接触角大于90°时,熔体在壁面处具有最大速度。无表面张力时,熔体填充流动所需时间明显长于有表面张力时的填充时间,即表面张力对微小通道中的熔体流动具有促进作用。     

超细粉碎对煤颗粒润湿性及表面张力的影响

采用EasyDrop DSA20型接触角测量仪,研究3种不同变质煤样经湿法超细粉碎后润湿性的变化,计算得到超细粉碎后煤颗粒表面张力、煤-水界面表面张力和煤-水体系粘附功的变化。结果表明:神木不粘煤与淮南气煤2种低阶煤经湿法超细粉碎后疏水性增强,太西无烟煤在长时间超细粉碎后疏水性减弱;超细粉碎后,煤颗粒表面张力、煤-水体系粘附功与接触角呈负相关。     

表面张力对共轴微通道气液两相流的影响

本文以共轴流微通道芯片为研究对象,采用分散相为氩气、连续相为十二烷基硫代硫酸钠(SDS)的水溶液,在400μm×600μm矩形通道内形成气液两相流。改变表面活性剂的浓度,观察表面张力改变下流型的变化趋势,绘制出以连续相毛细数为横坐标、分散相韦伯数为纵坐标的流型分布图。实验得到滴流、滴状射流、弹状流、环状流的四种流型。随着表面张力减小,弹状流与环状流之间的边界向右移,滴流与射流之间的向边界右移。弹状流与滴流、射流之间的边界向右移不明显。     

微注塑成型充模流动中的表面张力EI北大核心

微尺度通道中的高聚物熔体流动行为与宏观熔体流动有许多不同。基于对微注塑成型中的熔体充模流动特性的理论分析,建立了微小通道中熔体流动的表面张力模型,并以不同的表面张力系数和不同接触角,对矩形微通道中的熔体流动速度分布进行了数值模拟。结果表明,接触角小于90°时,熔体在通道壁面附近具有最大速度;接触角大于90°时,熔体在壁面处具有最大速度。无表面张力时,熔体填充流动所需时间明显长于有表面张力时的填充时间,即表面张力对微小通道中的熔体流动具有促进作用。     

微齿轮注塑成型正交优化及数值模拟

介绍了采用高聚物成型微齿轮的主要成型方法--微注射成型.比较了不同种类的注射原料ABS、聚丙烯(PP)、聚碳酸酯(PC)的成型工艺,并就影响微注射成型中影响微制件质量的主要工艺过程:充模压力、熔体温度、模具温度和充填时间等进行数值模拟研究,采用正交优化方法对成型方案进行优化,获得优化的成型参数.为微齿轮成型模具的结构设计、成型工艺参数的合理化等等提供理论依据.通过对微齿轮成型过程的数值模拟优化,得到微注射成型的模具温度升高、注射压力增大、注射温度升高都会缩短充模时间;结果显示,聚合物材料对微注塑齿轮的适用性依次为:ABS＞PP＞PC.     

细晶T2紫铜微小齿轮体积微成形研究

目的提高体积微成形件的成形质量。方法利用等径角挤压工艺,沿BC路径对T2紫铜试样进行了8个道次的挤压,获得了延伸率高达56.7%的细晶材料。选择DEFORM软件对微小齿轮的成形过程进行了有限元分析,得到了合适的成形工艺参数。结果利用不同组织的材料,成形出了最小模数为0.1 mm,分度圆直径为1 mm的微小齿轮件。结论实验结果表明,与常规多晶材料相比,细晶材料成形的微小齿轮的尺寸精度有了较大提高。     

液态锂锡合金表面张力的初步研究

液态锂锡合金是很有前景的能源堆液态包层氚增殖剂材料.为了对液态锂锡合金的设计、制备、纯化与输运技术提供理论支持,从表面张力基于波动性理论的方程出发,采用Gibbs方法初步建立了液态锂锡合金的表面张力方程,并开展了影响表面张力因素的计算.结果表明,液态锂锡的表面张力随合金温度的升高而降低;在稀溶液中添加表面张力较高的溶质Sn对合金的表面张力影响有限;可采用最大气泡压力方法测量液态锂锡的表面张力.     

Break-up of a set of liquid threads under influence of surface tension

In this paper it is shown how the long-standing problem of the break-up of a cylindrical interface due to surface tension can be generalized to an arbitrary number of interacting interfaces in an arbitrary configuration. A system of immersed threads starting with two types of configurations is studied, i.e., a system of threads on a row and a system of threads at triangular vertices. From these cases, which are worked out in detail, it becomes clear how the stability of an arbitrary configuration can be determined. The (in)stability of the configuration is discussed in terms of the so-called disturbance growth rate. It turns out that the threads break up in specific phase patterns in which neighbouring threads are either in-phase or out-of-phase. For L threads, in principle 2^L phase patterns are possible. However, it is shown that the stability of the system directly follows from L so-called basic phase patterns. Special attention is paid to the special case of threads and fluid having equal viscosity. Then, the growth rate can be calculated analytically using Hankel transformations. An estimate for the growth rate in this case, which turns out to be quite sharp, is derived.     

The surface tension meniscus of liquid helium

A technique is described for calculating the shape of the surface tension meniscus at a vertical wall, in the presence of Van der Waals forces. The method of analytic continuation is used to compute a solution of the relevant differential equation. Results (believed accurate to better than 0.5%) are presented for He³ and for He⁴ at a variety of film flow rates. It is found that the shape of the classical meniscus remains unaltered over most of its length, but it is displaced horizontally relative to the wall by a flow dependent amount. The results are contrasted with those from a previous calculation.     

The influence of variable surface tension on capillary-gravity waves

Periodic gravity-capillary waves propagating at a constant velocity at the surface of a fluid of infinite depth are considered. The surface tension is assumed to vary along the free surface. A numerical procedure is presented to solve the problem with an arbitrary distribution of surface tension on the free surface. It is found that there are many different families of solutions. These solutions generalize the classical theory of gravity-capillary waves with constant surface tension. An asymptotic solution is presented for a particular distribution of variable surface tension.     

The prediction of surface tension in mixtures of cryogenic liquids

Recently we showed how a fluid model for predicting thermodynamic properties could be used to correlate surface tension of organic liquids. We apply the model here to predict the surface tension of the cryogenic binary mixtures of methane, carbon monoxide, argon and nitrogen.⁵     

表面张力和凝胶时间对膜结构的影响

研究了表面张力和凝胶时间对膜结构的影响。结果表明，表面张力对膜皮层结构有影响，凝胶时间则对整个膜结构都有影响。组分透过膜的阻力是由膜材料与组分间的诸如氢键、静电、极性、非极性等各种作用力形成势能场及形状阻力，动力则是待透组分的热运动，因此，膜的单孔分离系数随孔径的增大存在一极大值，单孔通量则随孔径的增大而增大。     

液体表面张力系数与浓度的关系实验研究

为探究液体表面张力与液体浓度的关系,利用压阻式力敏传感器,采用拉脱法,测试室温下水及不同浓度的蔗糖水、盐水、酒精、肥皂水的表面张力系数。实验结果表明:蔗糖水和盐水的表面张力系数随浓度的增大而增加,而酒精、肥皂水的表面张力系数随浓度的增大而减小。     

A generalized equation for surface tension from the triple point to the critical point

A three-parameter generalized equation is proposed for surface tension from the triple point to the critical point. This equation not only fits the data well but also is good for interpolation between the normal boiling point and the critical point. This equation is also good for extrapolation to the triple point. This equation has been tested using the surface tension of water from the triple point to the critical point. The constants of this equation obtained using orthobaric surface tensions are given for a number of compounds. The isobaric surface tensions determined at a pressure of 1 atm do not differ significantly from the orthobaric surface tensions. Such data also have been used in obtaining equations from the triple to the critical point.Nomenclature T _c Critical temperature, K - T _t Triple point, K - T _m Melting point, K - T _r Reduced temperature, K - X (T _c-T)/T _c - Surface tension, dyne · cm^–1;10^–3N · m^–1 - _m Surface tension at the melting point - _f Surface tension at T _r=0.9 - _t Surface tension at the triple point - Relative deviation 100[ _obsd– _calcd]/ _obsd - Standard deviation [( _obsd– _calcd)²/(No. points—No. parameters)]^0.5     

Simultaneous measurement of surface tension and kinematic viscosity using thermal fluctuations

We have developed a surface laser-light scattering apparatus to measure simultaneously surface tension and kinematic viscosity. In this method, we can obtain the surface properties by the laser heterodyne detection of light scattered from thermally excited capillary waves (called ripplon), which are typically of low amplitude (1 nm) and a characteristic wavelength (100m). Two gratings (d=100 and 200m) were employed to select the wave number of the capillary waves and to produce a reference beam for heterodyne detection. It was found through an experimental study on water that this contact-free method has considerable potential for application to measurements under extreme conditions such as high temperatures and high pressures.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A.     

未变性胶原生物表面活性剂的表面张力及其表面吸附

研究了一种未变性胶原生物表面活性剂(CBS)水溶液的表面张力和表面吸附性质。结果表明,CBS水溶液的表面张力随CBS浓度的增大而降低,最终趋于平缓,达到55.92 mN/m。在等电点附近,CBS表面静电荷降低,使其表面张力显著降低。在低温下,CBS溶液的表面活性较好,当温度继续升高(35℃),由于变性作用,CBS溶液的表面张力急剧增大。CBS水溶液的吸附属于Langmiur型吸附,根据γ-lgC、Γ-C以及C/Γ-C拟合曲线计算得到饱和吸附量相似,分别为1.86×10-10,1.97×10-10和2.03×10-10 mol/cm2。吸附自由能为-3.53kJ/mol,表明其在标准状态下可以自发进行。     

Equation of state for compressed liquids from surface tension

A method for predicting an analytical equation of state for liquids from the surface tension and the liquid density at the freezing temperature ( ₁, ₁) as scaling constants is presented. The reference temperature. T_ref. is introduced and the product (T _ref T ₁ ^{1 2} ) is shown to be an advantageous corresponding temperature for the second virial coeflicienls. B₂(T). of spherical and molecular fluids. Thus, B₂(T) follows a promising corresponding states principle and then calculations for(T) andb(T), the two other temperature-dependent constants of the equation of state, are made possible by scaling. As a result, ( ₁, ₁) are sufficient for the determination of thermophysical properties of fluids from the freezing line up to the critical temperature. The present procedure has the advantage that it can also be used in cases whereT _c andP _c are not known or the vapor pressure is too small to allow accurate measurements. We applied the procedure to predict the density of Lennard-Jones liquids over an extensive range of temperatures and pressures. The results for liquids with a wide range of acentric factor values are within 5%.