Preparation of Titanium Oxide by Chemical Vapor Deposition and Hydrolysis Methods using Titanium Tetrakisisopropoxide as a Precursor
Prof. Hsin-Tien Chiu
Prof. Chi-Young Lee
|關鍵字:||二氧化鈦;化學氣相沉積;水解;Titanium Oxide;Chemical Vapor Deposition;Hydrolysis|
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。
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.
|Appears in Collections:||Thesis|