纳米Fe_3O_4颗粒的制备及其在乙醇中的分散工艺

为制备硅油基Fe3O4磁流体,采用化学共沉淀法制备平均粒径为11 nm纳米Fe3O4颗粒,利用透射电子显微镜(TEM)、选区电子衍射花样(SAED)、X线衍射分析(XRD)、振动磁强计(VSM)等手段对试样的微观形貌、晶体结构以及磁性能进行表征。在测得无水乙醇中Fe3O4粉体的pH-Zeta电位图基础之上,研究了表面活性剂的类型、表面活性剂的加入量以及超声分散的时间对纳米Fe3O4颗粒分散性能的影响。结果表明:化学共沉淀法制备出的纳米Fe3O4颗粒为面心立方结构,颗粒表面光洁且呈现规则的圆球形,粉体的粒径分布较窄。随着超声时间的延长和表面活性剂使用量的增加,纳米Fe3O4颗粒在无水乙醇中的分散效果在特定点呈现最佳效果之后逐步变差,5种表面活性剂分散效果由好到差的顺序是:聚乙烯吡咯烷酮(PVP)、司班-80(SPAN-80)、司班-85(SPAN-85)、油酸(OA)、硅烷偶联剂KH-550。推荐纳米Fe3O4颗粒在无水乙醇中的分散工艺为:pH=7,PVP加入的质量分数3%,超声时间35 min,超声功率560 W。

超细h-BN粉在无水乙醇介质中复合分散工艺研究

针对超细h-BN粉体易团聚、与有机基体界面相容性较差的缺点,研究了其在无水乙醇介质中的分散工艺。首先在测定其pH-Zeta电位的基础上,选取阴离子型(SA、OA、SDBS)、非离子型(PVP、KH570、司班85)和高分子型(PEG4000)分散剂进行超声分散研究。然后从以上几种分散剂中选取三种分散剂进行复合分散。实验发现:在最佳配比下,复合分散体系较单分散剂分散效果明显提升,PEG4000与SA的复合分散比最佳单分散剂的效果提升了18%;KH570与SA的复合分散体系比最佳单分散剂的效果提升了11%;推荐h-BN粉在无水乙醇中的分散工艺为:pH值为9时,在560 W的功率下用SA(4wt%)与PEG4000(1wt%)或者SA(1wt%)与KH570(4wt%)复合超声90 min。

Influences of collector DLZ on chalcopyrite and pyrite flotation

The interaction mechanism of collector DLZ in the flotation process of chalcopyrite and pyrite was investigated through flotation experiments,zeta potential measurements and infrared spectrum analysis.Flotation test results indicate that DLZ is the selective collector of chalcopyrite.Especially,the recovery of chalcopyrite is higher than 90% in neutral and weak alkaline systems,while the recovery of pyrite is less than 10%.When using CaO as pH regulator,at pH=7-11,the floatability of pyrite is depressed and the recovery is less than 5%.Zeta potential analysis shows that the zeta potential of chalcopyrite decreases more obviously than that of pyrite after interaction with DLZ,confirming that collector DLZ shows selectivity to chalcopyrite and pyrite.And FTIR results reveal that the flotation selectivity of collector DLZ is due to chemical absorption onto chalcopyrite surface and only physical absorption onto pyrite surface.