采用二步法合成核-壳型二氧化硅/二氧化铈复合微粒

以正硅酸已酯为硅源,以氨水为催化剂,无水乙醇为溶剂,采用溶胶-凝胶法并经500℃煅烧1 h后制备了SiO2微粒,运用激光粒度分析方法研究了各原料配比对SiO2粒子大小和粒径分布的影响;再以硝酸铈为铈源,碳酸铵为沉淀剂,十二烷基苯磺酸钠为分散剂,加入SiO2微粒,用化学沉淀法,通过控制反应和焙烧条件,经300℃煅烧1 h后成功合成了核-壳型单分散球状SiO2/CeO2复合微粒.并用差示扫描量热仪/热重分析仪、X射线衍射仪、红外光谱仪、扫描电子显微镜、透射电子显微镜和X射线能谱仪等手段以及zeta电位测定对SiO2/CeO2复合微粒的结构、组成和性能进行了表征.结果表明:SiO2/CeO2复合微粒呈规则球状,粒子分布非常均匀,粒径约300～350 nm;CeO2基本上为膜包覆,伴有少量的CeO2沉积,CeO2包覆层厚度约为30nm;SiO2包覆CeO2后所得复合微粒的表面电性质发生变化,其等电点对应的pH值从2.2增大至5.5.

SYNTHESIS OF SILICON DIOXIDE/CERIUM OXIDE CORE-SHELL COMPOSITE ULTRAFINE PARTICLES BY TWO-STEP METHOD

In absolute ethanolas solvent, SiO2 ultrafine particles were prepared by sol-gel method using tetraethylorthosilicate as silicon resource, ammonia as catalyst and calcining at 500 ℃ for 1 h. The effect of the ratio of the materials on the particle size and distribution of SiO2 particles were researched by the laser particle size analysis. SiO2/CeO2 core-shell composite ultrafine particles were successfully synthesized by the controlling reaction factors and using the chemical precipitation method with sodium dodecyl benzene sulfonate as dispersant, cerium nitrate as cerium resource, ammonium carbonate as precipitating agent and SiO2 ultrafme particles as cores, and calcinating at 300℃ for 1 h. The structures, composition and properties of the samples were analyzed by differential scanning calorimetry-thermal gravimetric analysis, X-ray diffraction, infrared spectrometry, scanning electron microscopy, transmission electron microscopy, energy dispersive analysis and zeta potential testing. The results indicate that the SiO2/CeO2 core-shell composite ultrafine particles have an excellent spherical morphology and uniform particle size. Their diameter is about 300-350 nm. A CeO2 can be primarily coated onto the surface of SiO2 ultrafine particle to form a shell, with a little CeO2 deposition on the SiO2 core. The thickness of the CeO2 shell is about 30 nm. After the coating has been deposited, the surface electric characteristics of the SiO2/CeO2 core-shell particles changes. The pH value at isoelectric point of the core-shell SiO2/CeO2 composite ultrafine particles increases from 2.2 for SiO2 paticles to 5.5, it is almost the same as that of CeO2 particles (pH=6.7).