Preparation And Properties Of Bi₂SiO₅Powder By Wet Chemical

Bi₁₂SiO₂₀， Bi₂SiO₅and Bi₄Si₃O₁₂are the three compounds inBi₂O₃-SiO₂systerm, Bi₁₂SiO₂₀and Bi₄Si₃O₁₂are stable phase, Bi₂SiO₅is mis stable phase. In recent years, most studies of Bi2O3-SiO2systemare carried around phase equilibrium, BSO crystal preparation,Bi₁₂SiO₂₀and Bi₄Si₃O₁₂powers preparation, material performancedetermination and application. The relative study of Bi₁₂SiO₂₀andBi₄Si₃O₁₂single crystal preparation and application is earlier, and theprocess is also more mature, so Bi₁₂SiO₂₀and Bi₄Si₃O₁₂can grow largesingle crystals. However, the research and reports of system crystalgrowth, performance and powder preparation of Bi₂SiO₅in Bi2O3-SiO2is unusual.This thesis is on the base of predecessors’ research work. Themetastable phase Bi₂SiO₅powders were prepared by chemical solutiondecomposition method and hydrothermal synthesis of wet chemicalmethod, and Bi₂SiO₅powders were modified with NaF doped. Theexperiment divides it into four steps: Bi₂SiO₅powders were prepared bychemical solution decomposition method. Bi₂SiO₅powders wereprepared by hydrothermal synthesis. F doped modified Bi₂SiO₅powderswere prepared by chemical solution decomposition method. F dopedmodified Bi₂SiO₅powders were prepared by hydrothermal synthesis.First, Bi₂SiO₅powders were prepared by chemical solutiondecomposition method. Using bismuth nitrate pentahydrate and TEOSas raw materials the pure Bi₂SiO₅can be prepared, according to the Bi:Si （molar ratio）1:2ratio, formed sol-gel after ultrasonic mixing, dried,then calcined at650℃. The FESEM images indicated that the Bi₂SiO₅power was scale-like, and particle size was between150nm and200nm.The experimental factors of affecting the reaction process liketemperature, the excess of bismuth nitrate and TEOS and surfactant and formation mechanism were studied. The results showed that it wasconducive to the generation of Bi₂SiO₅powders when the temperaturerose to650⁷00°C （700°C not included） and the increase of siliconcontent, within a certain range bismuth excess is not conducive toformation of Bi₂SiO₅powder. Both the types and dosage of surfactantsplayed an important role in morphology of Bi₂SiO₅. Also the powdersphotocatalytic activity of Bi₂SiO₅were test used rhodamine B, a sharpdecline transformation of the main absorption band of rhodamine B,idicated that Bi₂SiO₅samples had good absorption ability andphotocatalytic activity.Second, Bi₂SiO₅powders were prepared by hydrothermal synthesis.Using sodium and bismuth nitrate as raw materials, dissolved in ethanoland Na （OH） mixed solvent （volume ratio5:3）. The mixed solution wastransferred into a70mL Teflon-lined autoclave and heated at180°C for18hours. The precipitates were then separated from the solution bycentrifugation and washed with absolute ethanol for several times. Theobtained products were collected and dried, then Bi₂SiO₅powders wereobtained. The FESEM images indicated that the Bi₂SiO₅particle wassheet, and grain size is200nm⁵00nm. The proportion of bismuthsilicon, holding time, and surfactant were stduied. The results showedthat: pure Bi₂SiO₅powders were obtained when the growth of bismuthsilicon molar ratio of from2:1to1:2. The flake grain grown with theholding time extended. The types of surfactants play an important rolein morphology of Bi₂SiO₅. Also the powders photocatalytic activity ofBi₂SiO₅were test used rhodamine B, a sharp decline transformation ofthe main absorption band of rhodamine B, which idicated that Bi₂SiO₅samples had good absorption ability and photocatalytic activity.Third, preparation of F doped modified Bi₂SiO₅powders bychemical solution decomposition method. On the basis of thepreparation Bi₂SiO₅powders by CSD, Bi₂SiO₅was modified with NaFdoped. The results showed that the absorption ability and photocatalyticactivity of F doped Bi₂SiO₅enhanced, and the order of photocatalyticactivity of Bi₂SiO₅was F5%>F3%>F1%>F10%>F0%. The product Bi₂SiO₅phase did not change with F doping.Fourth, preparation of F doped modified Bi₂SiO₅powders byhydrothermal synthesis. On the basis of the preparation Bi₂SiO₅powders by hydrothermal synthesis, Bi₂SiO₅was modified with NaFdoped. The results showed that: the absorption ability andphotocatalytic activity of F doped Bi₂SiO₅enhanced, and the order ofphotocatalytic activity of Bi₂SiO₅was F3%>F5%>F10%>F1%>F0%.The product Bi₂SiO₅phase did not change with F doping.