Fabrication And Structure Characteristics Of Silica Hollow Microsphere

Due to the inner hollow structure, the hollow microspheres have many special physical and chemical properties and have extensive potential applications in various fields of medicine, bio-chemistry and chemical engineering. In this work, SiO₂ hollow spheres are prepared with two different templates: calcium carbonate (CaCO₃) and octylamine(OA). The SEM, TEM, XRD, FTIR and nitrogen adsorption methods have been employed to study the properties of as-synthesized SiO₂ hollow spheres (SHS), and the factors which have effects on the fabrication of the samples were also investigated.By using CaCO₃ (including the original one, the one after grinding and the one synthesized via experimental fabrication.) template and CTAB as the mesoporous–directing agents, mesoporous SHS were synthesized via sol-gel method.The SHS fabricated with the original CaCO₃ template had a good roundness, but there were aggregation between spheres because of their small size. The SHS fabricated with CaCO₃ templates after a treatment of grinding exhibited a much larger particle size and higher surface area (864m²/g). Combine the particle size analysis results with the TEM images,it was found that the SiO₂ was coated on the aggregation of CaCO₃ templates. The template with a mean particle size of 10μm resulted in well-dispersed SHS but also resulted in inadequate coating.With the results of XRD and FTIR tests for samples gained respectively after coating reaction, calcinations and acid dipping,we got to know the process of fabricating SHS: Under basic condition, CTAB was adsorbed onto CaCO₃ template, and made up of the organic-inorganic template together. TEOS hydrolyzed and polymerized on the compound template, which resulted in the SiO₂ coating shell/core structure. Under calcination and acid dipping, the organic and inorganic templates were removed respectively,and then the final SHS were gained.By using OA as template, SHS with a good quality were fabricated with or even without the adding of hydrochloric acid. As-synthesized SHS was between 10μm and 40μm , with a high surface area of 1244 m²/g, a mean pore diameter of 2.39nm,and a mean pore volume of 77.02cc/g.With the cooperation of the optical microscope, XRD, SEM and FTIR, it was found that a higher stirring speed would improve the degree of homogeneity. The particle size increased with the reaction temperature, but the samples intended to aggregate when the temperature was above 50℃. With the elongation of the reaction time,the particle size would decreased first and then slightly increased with a low stirring speed, while with a higher stirring speed the particle size exhibit a tendency of gradual increase. These experimental results, especially the very simple way to fabricate SHS without any analysts could be valuable for the investigation of SHS.By comparision,We found that SHS can be fabricated quickly and simply by using OA as the template. While inorganic CaCO₃ template can reduce the cost of the fabrication process, and it is more environment-friendly and more suitable for industry production.