WO3添加量對TiO2介孔結構及光學性質之研究

Effect of WO3 additive on the mesostructure and optical properties of mesoporous TiO2

鄭浩余(Hao Yu Cheng)

指導教授 ： 張莉毓

國立屏東科技大學/工學院/機械工程系所/碩士(2008年)

https://doi.org/10.6346/NPUST.2008.00276

摘要

介孔材料由於具有高比表面積及均勻孔洞分佈之特性，其應用相當廣泛，是近年來在奈米材料科學領域中引人注目的研究領域。本實驗以溶膠-凝膠法製備介孔TiO2，使用三嵌段兩性共聚物作為天然模板，並藉由添加不同比例WO3，探討其添加量對TiO2 介孔結構及光學性質之影響。以熱重分析、X-ray繞射分析、穿透式電子顯微鏡、N2吸脫附曲線分析及紫外-可見光光譜儀分析試樣之微結構、比表面積及光吸收特性。
實驗結果顯示，本實驗所合成之介孔TiO2，經250~400 ℃煆燒後，可獲得anatase之結構。使用1.5 g三嵌段兩性共聚物經煆燒溫度 300 ℃，可合成出最大比表面積約為288.20 m2/g 和平均孔洞直徑約為6.7 nm。三嵌段兩性共聚物添加量對試樣介孔結構影響甚大。
WO3 加入TiO2 後，添加量從0增至3 mol %時，經煆燒溫度300 ℃，其比表面積從288.20 m2/g減少至201.86 m2/g，而平均孔徑從6.7 nm 增加到 8.6 nm。但當添加量增至5 mol %時，比表面積反而上升至 252.85 m2/g，平均孔徑則縮小至6.7 nm。隨著WO3添加量的增加，TiO2在紫外光區的吸收逐漸增加，(αhυ)1/2與hυ存在線性關係，光學能隙由純TiO2的3.64 eV減小為x=5 mol %時的3.14 eV，光學能隙與x滿足Eg(x) = Eg(0) + [Eg(1) - Eg(0) - b]x + bx2關係式。

關鍵字

二氧化鈦 ； 氧化鎢 ； 溶膠-凝膠法 ； 三嵌段兩性共聚物

並列摘要

Due to their large surface area, tunable pore size and suitable morphology in comparison with powder materials, mesostructured materials of transition metal oxides, especially of TiO2, are promising candidates for many applications. In this study, the mesoporous TiO2 has been prepared by using sol-gel process with TiCl4 as the inorganic precursor and block copolymer as the structure-directing agent. We adjusted the additive of WO3 to investigate its effect on structure and the properties of mesoporous TiO2.Various techniques were used for characterization of the samples, including TGA, XRD, TEM, N2 adsorption-desorption isotherms and UV-vis spectroscopy.
Mesoporous TiO2 obtained are characterized with anatase structure after calcined at 250~400°C. For the sample using 1.5 g block copolymer as the structure-directing agent, the high specific surface area is 288.20 m2/g and the relatively narrow pore size distribution centered at 6.7 nm after it is calcined at 300 °C. The results show that the mesostructure of TiO2 can be controlled by the block copolymer.
When the additive of WO3 increased from 0 to 3 mol %, the specific surface areas decreased from 288.20 to 201.86 m2/g, but the average pore sizes increased from 6.7 to 8.6 nm after being calcined at 300°C. However, the surface area of TiO2 substantially increase to 252.85 m2/g, and the pore size is drastically decrease to 6.7 nm as the WO3 content is increased to 5 mol %.
Optical absorption in the UV region enhanced gradually with the increase of WO3 content, and (αhυ)1/2 varied linearly with hυ. The optical bandgap decreased in the region from 3.64 eV for pure TiO2 to 3.14 eV with 5 mol % WO3 and the relationship between optical bandgap and WO3 content (x) fitted to the equation: Eg(x) = Eg(0) + [Eg(1) - Eg(0) - b]x + bx2.

並列關鍵字

TiO2 ； WO3 ； sol-gel method ； block copolymer

參考文獻

2. M. Grätzel, 2001, “Ultrafast colour displays,” Nature 409, 575-576.

3. H. Verweij, 1998 “Nanocrystalline and nanoporous ceramics,” Advanced Materials, 10, 17, 1483-1486.

4. M. Itoh, H. Hattori and K. Tanabe, 1976, “Catalytic sites on SnO2 and TiO2-SnO2 for the isomerization of 1-Butene,” J. Catal., 43, 192.

6. S. S. Park and J. D. Mackenzie, 1996, “Thickness and microstructure effects on alcohol sensing of tin oxide thin films,” Thin Solid Films, 274, 154-159.

7. K. Langer, E. Mutschler, G. Lambrecht, D. Mayer, G. Troschau, F. Stieneker and J. Kreuter, 1997, “Methylmethacrylate sulfopropylmethacrylate copolymer nanoparticles for drug delivery, part Ⅲ: evaluation as drug delivery system for ophthalmic application,” International Journal of Pharmaceutics, 158, 219-231.