Oscillation of interfacial tension at a liquid/liquid interface composed of di(2-ethylhexyl) phosphoric acid and calcium chloride
Oscillation of interfacial tension at a liquid/liquid interface composed of di(2-ethylhexyl) phosphoric acid and calcium chloride
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DOI：
10.1021/la000431v
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发表时间：
2000-10-31
期刊：
影响因子：
3.9
通讯作者：
Nagaoka, R
中科院分区：
文献类型：
--
作者：
Shioi, A;Sugiura, Y;Nagaoka, R
研究了二(2-乙基己基)磷酸/正庚烷/氯化钙/水组成的液/液界面张力的非线性振荡。振荡的范围超过每米几毫秒，最长的一次持续了几个小时。观察到了各种各样的振荡模式，但它们被分为两类。其中一组表明功率谱与f(-2)成正比，f是频率，幅度的分布函数遵循高斯分布函数。这种A型振荡随着温度的降低而变弱，看起来像是一个随机过程，可能与热能有关。另一种类型，类型B，与类型A完全不同。功率谱近似遵循标度定律。标度指数基本一致，但标度律与A型相比并不完美，幅值分布函数不是正态分布。温度的升高使平均振幅变小。这类振荡对界面张力的要求比A类高，而且有时会观察到准周期的界面张力变化。这些变化表明，B型振荡是由表面活性剂分子之间的吸引相互作用引起的。它在界面压力-界面面积等温线中引入了一个不稳定区域，从而导致了B型振荡。提出了一个简单的模型来解释B型振荡，该模型可以捕捉到一些实验趋势。
Nonlinear oscillation of interfacial tension was found for a liquid/liquid interface composed of di(2-ethylhexyl) phosphoric acid/n-heptane/calcium chloride/water. The range of the oscillations was over several millineutons per meter, with the longest one continuing over a few hours. A wide variety of oscillation patterns was observed, but they were classified into two groups. One group showed that the power spectrum was proportional to f(-2), with f being the frequency, and the distribution function of the amplitudes followed a Gaussian distribution function. This type of oscillation, type A, became slightly weaker with decreasing temperature and looked like a random process which may be associated with thermal energy. Another type, type B, was entirely different from type A. The power spectrum approximately followed a scaling law. The scaling index was almost unity; however, the scaling law was not perfect compared to that of type A. The distribution function of the amplitudes was not a Gaussian distribution. An increase in temperature made the average amplitude smaller. This type of oscillation required a higher interfacial tension than that for type A. Further, a quasi-periodic change of interfacial tension was sometimes observed. Those changes suggested that type B oscillation was caused by an attractive interaction between surfactant molecules. It introduced an unstable region in the interfacial pressure-interfacial area isotherm which caused type B oscillation. A simple model was proposed to explain type B oscillations, which could capture some experimental trends.