测控技术与仪器类外文文献翻译、中英文翻译、外文翻译

使用测角法很难分析纤维，而用测力法就很容易。 缺点

这种技术的应用有两个方面的缺陷，首先，试验者需要有足够的可以利用的测试液，以便可以浸没固体试样的任何一部分。其次，被测固体下次还可以再利用，要求固体试样制作成形或者是有规则的几何外形。这样就有占其长度一定部分的周长了。我们知道的杆状物、平板、纤维的周长都是理想的。

与液体接触的固体试样所有面都必须有相同的表面，试样的量也必须足够的小，以便在Singma70上悬挂时达到平衡。

这种技术更难在高温的测量系统中使用，温度低于或者等于100度时，很容易处理。而超过了这个范围的测量另外讨论。 Washburn法

若待测固体试样是多孔结构时，产生了润湿液的吸收，可以选择这种方法。固体与测试液体接触后，随着时间的改变，测试固体吸收了大量的液体。吸收量是粘滞度、密度、液体的表面张力作用、固体材料的系数和接触角相互影响的结果。如果粘滞度、密度和表面张力已知，那么材料系数和接触角就能够求出来。KSV仪器借助于Washburn法提供了两种寻找接触角的手段，Sigma70和LPR902。从参考文献104中可以得到详细的介绍。 接触角的应用

接触角研究的主要焦点是固液界面相互作用的润湿特性。接触角通常用于润湿性的直接测量，而其他的实验参数可以从接触角和表面张力中推导出来。举例如下：

黏附功:定义黏附功时，要求区分液体和固体的相面或者负面自由能与固体和液体相面的黏附功，它们也要联系在一起。用来表示两种相面的相互作用力，由下面的Young-Dupre等式： Wa=σ(1+cosθ)

内聚功：定义内聚功时，要求把液体分为两部分，测量液体内部的相互作用

为下面的等式：

Wc=2σ

铺展功：负自由能与液体在固体表面的铺展联系起来，由下式给出： Ws=σ(cosθ-1) 润湿张力：如下是定义，张力大小：

τ=Fw/P=σLVcosθ

这个值是润湿张力对长度的标准化，也表示接触角的余弦值和表面张力的乘积。在没有表面张力的独立测量中，考虑到润湿作用力的特性，在某些情况下还是有意义的，而在多组合系统中，界面的表面张力可能不等于平衡时的表面张力，因此这里也指黏附功或者润湿功.

表面张力的测量数据直接反映测试溶液的热力学特性。接触角的测量数据反映液固相互作用的热力特性。只需要知道特殊液固的接触角，就可以表征其润湿行为。也可能用一种更普遍的方式表征固液间的润湿性。可用的方法很多，但每一中方法的基本原理是相同的。一种固体与多种液体相接触，可以测得多个接触角。依据这些测量，计算就可以得到参数（临界表面张力、表面能），而这些参数量化了固体润湿的特性。这里有两种基本的方法：临界表面张力：对于一系列不同表面张力的均匀液体用σ与cosθ做一张曲线图，会发现在一给定的σ下，cosθ的值接近于，这就对应着表面张力的最大值，也就是完全润湿，把这个值称为临界表面张力，通常用来表征固体的特性。表面自由能：另一种表征表面张力的方法是通过计算自由表面能，也称为固体的表面张力。这种方法涉及到测试液对固体有较好的润湿性，使用的液体润湿性要好那样他们的表面张力的极性和色散量已知，由Owens和Wendt给出的相关公式:

σl (1+ cosθ)/(σld)1/2 =(σsp)1/2 [(σlp)1/2/(σld)1/2]+(σsd)1/2

式中的θ是接触角，σl是液体的表面张力，σs固体的表面张力或自由能,另外，d和p分别是色散量和每一部分的极性。等式的组成如下式的形式: y = mx + b.能够作出(σlp)1/2 /(σld)1/2和σ l (1+ cosθ)/(σld)1/2图像，斜率为(σ

sp

)1/2(σsd)1/2.是ym的截距，真个自由表面能基本上就是由他们这两种组成了。

This application note provides a brief introduction to the use and measurement of contact angles. The techniques used for measurement are discussed and compared. What is contact angle?

Contact angle, θ, is a quantitative measure of the wetting of a solid by a liquid. It is defined geometrically as the angle formed by a liquid at the three phase boundary where a liquid, gas and solid intersect as shown below:

It can be seen from this figure that low values of ? indicate that the liquid spreads, or wets well , while high values indicate poor wetting. If the angle θ? is less than 90 the liquid is said to wet the solid. If it is greater than 90 it is said to be non-wetting. A zero contact angle represents complete wetting.

The measurement of a single static contact angle to characterize the interaction is no longer thought to be adequate. For any given solid/ liquid interaction there exists a range of contact angles which may be found. The value of static contact angles are found to depend on the recent history of the interaction. When the drop has recently expanded the angle is said to represent the ‘advanced’ contact angle. When the drop has recently contracted the angle is said to represent the ‘receded’ contact angle. These angles fall within a range with advanced angles approaching a maximum value and receded angles approaching a minimum value.

If the three phase(liquid/solid/vapor) boundary is in actual motion the angles produced are called Dynamic Contact Angles and are referred to as ‘advancing’ and

‘receding’ angles. The difference between ‘advanced’ and ‘advancing’, ‘receded’ and ‘receding’ is that in the static case motion is incipient in the dynamic case motion is actual. Dynamic contact angles may be assayed at various rates of speed. Dynamic contact angles measured at low velocities should be equal to properly measured static angles. Hysteresis

The difference between the maximum(advanced/advancing) and minimum (receded/receding) contact angle values is called the contact angle hysteresis. A great deal of research has gone into analysis of the significance of hysteresis. It has been used to help characterize surface heterogeneity, roughness and mobility. Briefly, for surfaces which are not homogeneous there will exist domains on the surface which present barriers to the motion of the contact line. For the case of chemical heterogeneity these domains represent areas with different contact angles than the surrounding surface. For example when wetting with water, hydrophobic domains will pin the motion of the contact line as the liquid advances thus increasing the contact angles. When the water recedes the hydrophilic domains will hold back the draining motion of the contact line thus decreasing the contact angle. From this analysis it can be seen that, when testing with water, advancing angles will be sensitive to the hydrophobic domains and receding angles will characterize the hydrophilic domains on the surface.

For situations in which surface roughness generates hysteresis the actual microscopic variations of slope in the surface create the barriers which pin the motion of the contact line and alter the macroscopic contact angles. There has been a great deal of research investigating the significance of hysteresis and you are recommended t

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papers cited at the end of this note for further details.