氧化铝表面短程、非双电层斥力研究

Short-ranged Non-DLVO Forces between Alumina Surfaces

利用原子力显微镜研究了MgCl2介质中氧化铝表面相互作用力随距离的变化.发现当MgCl2介质浓度为10-4mol/L,pH分别为3.96和7.92时,在两表面距离<10nm处存在一 短程非双电层排斥力.pH进一步提高到9.5,MgCl2介质浓度在10-4～10-2mol/L时,也存在短程排斥作用.它阻止了两表面由于范德华力产生的吸引.在较低和中等pH条件下,短程斥力来源于水合镁离子在氧化铝表面的特性吸附;在较高pH条件下,镁离子以各种氢氧化物形式吸附在氧化铝表面产生短程排斥力.随pH的升高,这种吸附层变得致密而失去弹性.

The surface forces between alumina colloidal sphere and alumina flat surface in sodium chloride and magnesium chloride solutions were measured by atomic force microscope. A short-ranged, non-DLVO force was observed in 10(-4) mol/L MgCl2 solutions keeping the pH as 3.96 and 7.92 respectively. When pH was raised to 9.5, the short-ranged repulsive force was also observed, it hindered the two surfaces close to each other due to the attractive Wan der Walls force. We proved that in the first condition, the short-ranged non DLVO force was originated from the specific adsorption of magnesium ions, which could be verified from Zeta potential measurements. In another case, this short-ranged repulsive force was from the specific adsorption of several kinds of magnesium hydroxides. With the rising of pH, the adsorbed layer became dense and lost its elasticity.