以四異丙醇鈦為前驅物利用化學氣相沉積法和水解法製備二氧化鈦

Abstract

本論文是以四異丙醇鈦為前驅物，利用化學氣相沉積法和水解法來製備二氧化鈦材料，並利用NaOH處理來改變二氧化鈦之形貌。 1.在CVD的結果中發現： CVD反應之氣體產物主要為異丙醇、丙酮、丙烯。其中丙烯，對氧化鈦薄膜的沉積有直接的關係。不同載流氣體對所成長的薄膜之組成、表面形貌和粗糙度並沒有明顯的影響，但對薄膜的成長速率及結晶性則有較大的影響。而活性較大的載流氣體(H2、O2)使成長溫度下降(300 ℃)。 2.在水解法的結果中發現： 水溶液的pH值對所形成的TiO2顆粒大小有直接的影響，當pH值遠離等電位點時，經400 ℃、N2鍛燒二小時，可製得顆粒較小的TiO2；若pH值接近等電位點時，所製得之TiO2顆粒較大。當添加TMC及NP-204為界面活性劑時，水溶液之pH □ 2，可製得顆粒較小的產物；若pH > 3，則產物之顆粒較大。當添加SDS及NP-204為界面活性劑時，水溶液的pH值對產物之顆粒大小並不會有明顯的影響，顆粒大小約為8 nm。 3.在NaOH處理的結果中發現： 當反應溫度為150 ℃時，鹼的濃度對產物的形貌有直接的影響，低濃度(5 M)時可得到片狀產物，濃度升高則可以得到中空管狀產物，其中，當NaOH濃度為10 M時可得到內徑為5 nm、管壁由層間距為0.7 nm的層狀結構所組成，管長超過600 nm。

The objective of this research is the preparation of titanium oxide materials by chemical vapor deposition and hydrolysis methods using titanium tetrakisisopropoxide as the precursor. In the CVD reaction, the major volatile byproducts were i-propanol, acetone, and propene. Propene, the product of reaction, is directly relatied to the formation of titanium oxide thin films. When H2, N2 and O2 were used as the carrier gases, there were no obvious differences on the composition, morphology and surface roughness of the thin films, but did affect the growth rate and microstructure. In the hydrolysis reactions, nano-sized TiO2 particles were obtained by hydrolysis in an aqueous solution and then calcined at 400 ℃. The particle size of TiO2 is dependent on the pH value of the solutions. For instance, when the pH value is close to the isoelectric point, the particle size is large. On the other hand, when the pH value is far from the isoelectric point, the particle size is small. When adding surfactants TMC and NP-204 in the hydrolysis reactions, smaller sized particles were obtained at pH □ 2, whereas the larger particles were obtained at pH > 3. As SDS and NP-204 were used as the disperse agent, the sizes of the particles were independent on the pH of the solution and found to be about 8 nm. The morphology variation of titanium oxide was studied under basic solutions. The morphologies of the products were dependent on the concentration of NaOH solutions. A sheet-shaped powder was obtained as TiO2 was treated with 5 M NaOH solution. A tube-shaped powder was formed by refluxing TiO2 in 10 M NaOH at 150 ℃ for 20 hrs. The long (600 nm) and hollow nanotubes were produced. The inner diameter of the tubes was about 5 nm. The wall of the tubes was composed of a few layers, with the distance between each layer about 0.7 nm.