以溶膠-凝膠法搭配膠體模板粒子製備矽質氧化物中空微球

Abstract

摘要

本研究利用微米尺寸塑膠微球作為犧牲模版並結合化學溶凝膠製程，製備矽質氧化物的中空微球。藉由改變溶膠-凝膠實驗參數，使前驅物披覆於有機膠體微粒表面成為核殼結構，再將中間有機核移除，製備矽質氧化物中空膠體粒子，並透過電子顯微鏡對對合成膠體粒子之表面型態結構、中空結構等進行觀察。 首先利用鹽酸將去離子水調整為pH=2，再將適量的水、乙醇、TEOS混合攪拌一小時，反應物水解後，加入塑膠微球(Spacer)攪拌30分鐘，使微球均勻分散在溶液中，置入恆溫水槽繼續加熱至40-70oC的反應溫度並持溫2小時，使水解產生的中間產物吸附於塑膠微球表面，藉由熱處理使塑膠微球裂解，形成中空的矽質氧化物微球。本研究嘗試改變不同的配方與製程參數，分別探討矽質前驅物TEOS、水、乙醇的濃度與反應溫度對形成矽質氧化物中空微球的影響關係，將獲得的粉末利用傅立葉轉換紅外線光譜儀(FTIR)、比表面積分析儀(BET)、場發射掃描式電子顯微鏡(FE-SEM)、穿透式電子顯微鏡微結構分析(TEM)、X光繞射實驗(XRD)、熱重與熱差分析(TG/DTA)、動態光散射粒徑分析(Dynamic Light-Scattering Particle Size Analyser)分析觀察，並分別敘述空心微球的合成型態觀察與性質。 研究發現此一系列合成出來的空心微球為非晶質結構，膠體粒子表面與塑膠微球表面所帶電荷相反，使得膠體粒子可以吸附於塑膠微球表面上，經過煅燒而形成中空結構。SEM觀察空心微球尺寸為1µm，合成的反應溫度愈低，空心微球愈不容易形成，當合成反應溫度50 oC與60oC，水含量小於4 mole，都有空心微球形成。TG/DTA中溫度上升至約300 oC時，重量開始明顯失重，隨著合成反應溫度上升，最終殘留量由1~3% 提高為約5~7%，動態光散射粒徑分析發現隨著乙醇含量增加，煅燒前與煅燒後的粒徑尺寸均有下降趨勢，隨著水含量的增加，比表面積值隨著下降，煅燒後的殼層孔隙尺寸約為3~5nm，煅燒前的殼層孔隙尺寸為2.7~4 nm，煅燒後的孔隙度會略為上升。

關鍵字：溶凝膠法、中空微球

Abstract

This research synthesized hollow silica microspheres by using a sol-gel technique together with using organic particles to act as a sacrificial template. Precursor materials were first adsorbed on the template surface to form a core-shell composite structure before being subjected to thermal pyrolysis to remove the organic core. Both the surface morphology and the hollow structure of the synthesized silica microspheres were examined by electron microscopy under various sol-gel process parameters. The experimental preparation involved addition of hydrochloric acid (HCl) in de-ionized water to form pH=2 solution, the acidic solution was then mixed with ethanol and tetraethyl orthosilicate (TEOS) in proportions. The organic spacer microspheres were added into the hydrolyzed solution. The mixtures were stirred fully for dispersion, and were then heated to 40 - 70oC with 2 h duration in a water bath to allow the reaction product to adsorb preferentially on the organic template surface. Finally, the organic microspheres were removed by calcination in air and hollow silica spheres were formed. Both the precursor formulation (including the relative concentration of TEOS, water and ethanol) and process parameter were varied, and their effects to the morphology and structural configuration of the hollow spheres were examined by FTIR, BET, FE-SEM, TEM, XRD, TG/DTA and dynamic light-scattering particle size analyser. The synthesized hollow spheres are amorphous in structure. The hydrolyzed silica colloids bear surface charge of different sign when compare to the organic template, facilitating the preferential adsorption of the silica colloids onto the template surface. Particle size of the synthesized hollow spheres is about 1 µm from SEM observations. As the reaction temperature is reduced, hollow spheres appear less likely to form. Hollow silica spheres tend to form when the synthesized reaction temperature are at 50 - 60 oC and the water concentration less than 4 mole. From thermal analysis, weight loss occurs pronouncedly at temperatures above 300 oC in air and the residual weight increases with the reaction temperature. The particle size decreases with the increasing ethanol concentration., while the BET surface area decreases when the concentration of water is increased. Pore size measured from the as-synthesized particles is about 2.7 - 4 nm and this becomes slightly smaller after calcination which is about 3 - 5 nm.

Key word：sol-gel、hollow sphere