臺灣博碩士論文加值系統

本實驗利用平板火焰化學氣相沉積法，成功的製備出在可見光下具有光催化效應的混相二氧化鈦粉末。首先我們發現使用不同的穩壓氣體種類會影響相結構的組成。由於氮氣的比熱比氬氣高，在粉末製程中較能蘊涵熱量維持高溫，有助於rutile的形成。而此時也認知到混相結構會讓光催化效應的提升。間隙距離的增加，會延長粉末在此區間的加熱和碰撞次數時間，使得rutile的含量提升。接著我們固定乙炔的流量比分別為600 sccm和800 sccm，並變化乙炔/氧氣流量比為1：3、1：4、1：5和1：6，調控此比例的同時也會影響相結構的組成。我們發現在低溫和缺氧的條件下，所形成的rutile是以可見光的光吸收中心為成核點，這會造成可見光吸收強度下降。而在高溫和富氧的環境下，合成的大顆粒rutile為小顆粒的anatase經碰撞後聚集形成。於TEM的實驗中，我們觀察到粉末中大部分是微小的anatase細晶粒，而rutile則呈現不規則的大顆粒狀散佈在anatase中。這種混相結構的粉末不論在可見光的吸收能力和亞甲基藍的降解，都呈現出最優異的結果。綜合實驗分析，我們認為因碳摻雜或碳所造成的缺陷形成了新的缺陷能階於混相的anatase相中，促使二氧化鈦得以吸收可見光。而混相在此的功用為延緩電子電洞對的再複合時間，藉此提升光催化效應。

In this study, we have successfully prepared the dual phase TiO2 nanopowder as visible-light photocatalyst using flat-flame chemical vapor condensation method. First, we found that the type of buffer gas has significant effect on the phase transformation. Due to higher specific heat of nitrogen than that of argon, nitrogen is more capable of maintaining particles at high temperature, and to promote the rutile formation. We also realized that the dual phase formation by partial phase transformation from anatase to rutile is critical in the enhancement of photocatalytic reaction. Second, the increase of gap distance increases the heating time and collision time for the particles, thus increases the rutile content of the particles. Third, we managed to proceed our experiment by fixing the acetylene flow rate at either 600 sccm or 800 sccm, while vary the acetylene/oxygen flow ratio for 1:3, 1:4, 1:5, and 1:6, for the flame. We found that at low temperature and oxygen-deficient condition, the rutile formation is at the expense of visible-light photonic center, while at high temperature and oxygen-rich condition, the rutile formation does not interfere with its visible-light absorption. At high temperature and oxygen-rich condition, the rutile formation is promoted by thermal energy, and does not necessarily need the nucleation agent, such as visible-light photonic center. From the TEM observation, this powder consists of majorly fine anatase particles and some scattered large rutile particles. The nanopowder produced under this condition has the highest visible-light absorption capability as well as methylene blue photocatalytic decomposition reactivity. Finally, we concluded that the defect level in anatase formed by carbon doping and related effect is responsible for the visible-light absorption, and the dual phase is responsible for the reduction of the electron-hole recombination. With both carbon doping and dual-phase formation, the visible-light photocatalytic ability of our powder is greatly enhanced.

摘要 1
Abstract 3
目錄 5
表目錄 8
圖目錄 9
第一章 序論 13
1.1前言 13
1.2 研究動機與目標 15
第二章 文獻回顧 17
2.1二氧化鈦光觸媒簡介 17
2.1.1二氧化鈦之物理性質 17
2.1.2 二氧化鈦的光催化原理 24
2.1.3二氧化鈦光觸媒文獻回顧 27
2.2火焰合成法相關探討 32
第三章 實驗系統與研究方法 39
3.1實驗規劃 39
3.2實驗前置準備 40
3.3實驗設備 41
3.3.1燃燒器系統 42
3.3.2氣體流量與燃料輸送系統 43
3.3.3前驅物裝置與產生原理 44
3.3.4體壓力控制迴路系統 44
3.3.5真空抽氣系統 45
3.3.6間隙距離定義 46
3.4實驗參數與操作流程 46
3.5分析方法 53
3.5.1 X-ray 繞射分析(XRD) 53
3.5.2紫外光 / 可見光吸收光譜分析儀 (UV-visible) 53
3.5.3電子順磁共振儀(EPR) 54
3.5.4光觸媒粉末分解亞甲基藍實驗 55
3.5.5穿透式電子顯微鏡(Transmission Electron Microscope) 58
第四章 實驗結果與討論 61
4.1在全氮和全氬氣氛下製備二氧化鈦粉末 61
4.1.1探討氮氣和氬氣的差別 66
4.2固定穩壓稀釋氣體為氮氣，改變載流氣體為氬氣 68
4.3探討促使rutile的形成方式 69
4.4 改變間隙距離從28mm至35mm 70
4.5改變乙炔(600 sccm)與氧氣火焰燃燒的比例 72
4.6 改變乙炔(800 sccm)與氧氣火焰燃燒的比例 79
4.7 TEM穿透式電子顯微鏡分析 87
4.7.1 乙炔流量600 sccm 88
4.7.2 乙炔流量800 sccm 93
第五章 結論 101
未來工作 105
參考資料 107

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