利用多重射流氢氧焰燃烧反应器, 通过控制进料方式, 以TiCl4和SiCl4为原料合成了具有典型核壳结构的纳米TiO2/SiO2复合颗粒, 并分析了氢氧焰燃烧合成过程中核壳结构的形成机理. 在纳米TiO2/SiO2复合颗粒中, 无定形的SiO2均匀地包覆在晶态TiO2颗粒表面形成核壳结构, 引入SiO2不但有效抑制TiO2晶粒的生长, 而且抑制了锐钛相向金红石相的转变. 在TiCl4和SiCl4次序进料时, TiCl4优先反应并通过成核生长生成TiO2纳米颗粒, SiCl4反应生成的SiO2通过在TiO2颗粒表面非均相成核生长, 形成核壳结构的纳米复合颗粒.
Core-shell TiO2/SiO2 nanoparticles were synthesized successfully by H2/Air flame combustions, and the formation mechanism of core-shell nanoparticles was analyzed. The structures and properties of these TiO2/SiO2 particles were investigated by using TEM, HRTEM, XRD and FTIR. The transformation from anatase to rutile and the grain growth are hindered due to the addition of silica into matrix. Both the chemical reaction rate and the nucleation rate of TiO2 particles are much faster than those of SiO2. The formation of primary TiO2 particles is faster than that of SiO2 in the third jet due to the low temperature and nuclear rate. Heterogeneous nucleaton of SiO2 on the surface of TiO2 is the main reason of core-shell nanocomposites formation.
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