Dispersion of Ultrafine Oxide Particles Utilizing Micromulsion

获得氧化物细颗粒在水或非水介质中的稳定分散具有重要意义。本研究采用O/W乳剂和O/W微乳剂在水介质中稳定赤铁矿细颗粒（中位直径为0.47 um， BET比表面积为5.6 m^2/g）。实验包括两个步骤；1)赤铁矿颗粒在正癸烷中的稳定，2)制备油滴中含有赤铁矿细颗粒的稳定油水乳状液。采用两种不同的方法获得稳定的赤铁矿癸烷悬浮液。一种方法是通过在水介质中单层油酸钠（Na-Ol）涂层，然后水洗和干燥，使赤铁矿颗粒表面疏水。在质量比为1%的赤铁矿悬浮液中，用1 × 10^<-3> M Na-Ol在PH为6的条件下对赤铁矿颗粒进行处理，得到了相对稳定的赤铁矿癸烷悬浮液。另一种方法是使用气溶胶OT将赤铁矿颗粒直接分散到正癸烷中，浓度范围为5 × 10^<-2> m ~ 1 × 10^<-1> M.这种悬浮液的稳定性比Na-Ol方法要好得多。以十烷赤铁矿悬浮液与水为原料，体积比为1:10，两种方法均以1 × 10^<-3> M十二烷基硫酸钠（SDS）为乳化剂，采用超声法制备油水乳状液。Na-Ol法得到的含赤铁矿的O/W乳剂即使在放置7天或更长时间后也表现出稳定的分散性，而气溶胶OT法得到的乳剂的稳定性较差，尽管后者在正癸烷中表现出比前者更稳定的分散性。将正丁醇（5-7 ml/20 ml）加入到含有0.5 M SDS的普通O/W乳液中，制备O/W微乳液。采用与制备含赤铁矿油水乳状液相同的工艺制备含赤铁矿油水乳状液。而将普通油水乳状液改为连续添加sds的微乳状液后，乳滴中含有的赤铁矿颗粒在短时间内被挤出并沉淀。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