Dispersion of Ultrafine Oxide Particles Utilizing Micromulsion

实现氧化物微粒在水或非水介质中的稳定分散具有重要意义。采用O/W型乳状液和O/W型微乳液对水介质中的赤铁矿微粉(中值直径0.47um，BET比表面积5.6m^2/g)进行了稳定化试验。实验包括两个步骤：1)赤铁矿粒子在正庚烷中的稳定；2)制备稳定的O/W乳状液，其中的油滴含有赤铁矿微粒。采用两种不同的方法获得稳定的赤铁矿正庚烷悬浮液。一种方法是通过在水介质中单层包覆油酸钠(Na-Ol)使赤铁矿颗粒表面疏水，然后用水洗涤和干燥。在pH值为6的赤铁矿悬浮液中，经1×10~(-3)~(-3)Na-Ol处理的赤铁矿粒子可得到相对稳定的赤铁矿正庚烷悬浮液。另一种方法inv…在5×10；-2~1×10；-1~1×10；-1~1×10；~(-1)M的浓度范围内，更多的人使用气溶胶OT将赤铁矿粒子直接分散到正庚烷中，该悬浮液的稳定性比Na-Ol法好得多。含赤铁矿的O/W乳状液在放置7d或更长时间后仍表现出稳定的分散性，而气溶胶OT法的稳定性较差，尽管后者在正庚烷中的分散性比前者更稳定。采用与制备含赤铁矿O/W乳状液相同的工艺制备含赤铁矿O/W型微乳液。而在连续加入十二烷基硫酸钠的条件下，将普通O/W乳状液转变为微乳液后，乳滴中的赤铁矿颗粒在短时间内被挤出并沉淀下来。较少

It is of great significance to get stable dispersions of oxide fine particles in aqueous or non-aqueous media. In this study a trial was in which hematite fine particles (median diameter and BET specific surface area being 0.47 um and 5.6 m^2/g, respectively) are stabilized in aqueous media by utilizing O/W emulsions and O/W micro-emulsions. Experiments consist of two steps; 1) stabilization of hematite particles in n-decane and 2) preparation of stable O/W emulsions in which oil droplets contain hematite fine particles. Two different methods were employed to get stable decane suspensions of hematite. One method involves making hematite particles whose surfaces are made hydrophobic by monolayer coating of sodium oleate (Na-Ol) in aqueous media, followed by water washing and drying. The relatively stable hematite decane suspension was obtained with hematite particles which had been treated with 1x10^<-3> M Na-Ol at PH 6 in aqueous hematite suspensions of 1% by weight. Another method inv … More olves dispersing hematite particles directly into n-decane using Aerosol OT in a concentration range of 5x10^<-2> to 1x10^<-1> M. This suspension revealed much better stability than that obtained by Na-Ol method.O/W emulsion was prepared by ultrasonic method using the hematite decane suspension and water, volume ratio being 1:10, where 1x10^<-3> M sodium dodecyl sulfate (SDS) was used as an emulsifier in both methods. Hematite-included O/W emulsions obtained by the Na-Ol methed revealed stable dispersion even after standing for 7 days or more, while less stability was indicated with those by the Aerosol OT method, in spite of the fact that the latter showed more stable dispersion in n-decane than the former.O/W micro-emulsions were prepared by adding n-butanol (5-7 ml/20 ml eater) into ordinary O/W emulsion containing 0.5 M SDS. The same procedure was applied as used in preparing the hematite-included O/W emulsion in order to make hematite-included O/W micro emulsion. However, hematite particles included in emulsion droplets were squeezed out of the emulsion droplets and settled down within a short period of time after ordinary O/W emulsion had been changed to micro-emulsion with successive addition of sds. Less