利用原子力显微镜研究了氯化镁介质中氧化铝表面的相互作用力随盐浓度、ｐＨ的变化规律．在中性条件下；当ＭｇＣｌ２盐浓度由１０－５ｍｏｌ／Ｌ增加到１０－2ｍｏｌ／Ｌ时，长程排斥作用由于双电层压缩，作用范围从一百多纳米减弱到十几纳米，实验测得的双电层厚度的实际值与理论值较好的吻合．保持ＭｇＣｌ２介质浓度不变；ｐＨ由３．６４变化到９．０９；氧化铝表面的相互作用始终表现为排斥力，与测得的Ｚｅｔａ电位值始终为正值相一致．当ｐＨ＝９．５时，由于镁离子的水合氢氧化物在氧化铝表面的特性吸附，产生了短程非静电徘斥力，首次用原子力显微镜证实了Ｍｇ２＋特性吸附层的存在，厚度约为５ｎｍ。
The surface forces between alumina colloidal sphere and alumina flat surface in magnesium chloride
solutions were measured by an atomic force microscope. The forces between alumina surfaces were measured as a function of surface separation, salt
concentration, and pH. Experimental decay lengths for the repulsive electric double layer interaction were in good agreement with the theoretical Debye
lengths in the range of 0.0001mol/L to 0.01mol/L. The Debye length decreased with the increasing of the salt concentrations due to the compression of the
electric double layer. No attractive force could be detected in the pH range between 3.64 and 9.09, and the zeta potential was always positive, which
strongly verified the existence of the specific adsorption. The short-ranged non-DLVO forces were observed in the magnesium chloride solutions at pH 9.52.
Magnesium ions took the form of Mg(OH)+ and Mg2(OH)3+ to form the adsorption layer, which changed into precipitation layer with the rise of pH,
the thickness was estimated as 5nm.
参考文献
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