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標題: | 燃燒合成銳鈦礦二氧化鈦奈米顆粒之研究 A Study of Anatase Titania Nanoparticles Synthesized in Premixed and Diffusion Flames |
作者: | Hsiung-An Yang 楊雄安 |
指導教授: | 馬小康 |
關鍵字: | 甲烷火焰,燃燒合成,銳鈦礦,金紅石,預混燃燒器,擴散燃燒器, Titanium tetra-isopropoxide,TiO2 nanoparticles,Synthesize,Premixed flame,Diffusion flame, |
出版年 : | 2010 |
學位: | 博士 |
摘要: | 本研究是以鈦系化合物Ti[OCH(CH3)2]4 (TTIP)做為前置物取代傳統的 TiCl4(較具毒性且昂貴), TTIP蒸氣於甲烷火焰中燃燒合成二氧化鈦奈米粉末,使用平板式預混燃燒器、本生式預混燃燒器與改良式 Hencken擴散燃燒器三種燃燒器做比較,針對火焰溫度、前置物濃度、氧氣與氮氣比例,對於產物晶相進行研究,探討燃燒合成二氧化鈦銳鈦礦(anatase)和金紅石(rutile)之差異。藉由穿透式電子顯微鏡(TEM)和 X-ray光譜儀(XRD)觀察合成產物之形態、二氧化鈦晶相純度,和顆粒尺寸,並利用氮氣吸附法(BET)測定其比表面積,再根據 BJH(Barrett-Joyner-Halenda)公式計算孔徑分布,最後,進行光觸媒活性分析以顯示其於奈米科技技術上應用之價值。因為本生式燃燒器火焰較長且較不穩定,反應時間會較長,進而改用平板式燃燒器,雖然平板式燃燒器火焰具有較短且穩定的特性,但是二氧化鈦晶相控制不佳,希望改良 Hencken擴散燃燒器能獲得更廣大範圍的可控氧氮比例,擴散式燃燒器所形成短小本生式火焰,改善平板式燃燒器因多孔性材料所造成的擾曲路徑,進一步得到均勻且粒徑較小的奈米微粒。此外。並配合 ANASYS 12.0 FLUENT軟體,來模擬甲烷擴散火焰溫度場以及燃燒合成之二氧化鈦粒徑分布。在研究中,調整氧化劑的氧氣濃度皆可有效的控制二氧化鈦晶相純度;而火焰溫度和收集產物高度將促使二氧化鈦顆粒尺寸發生改變,當收集高度降低時,使得二氧化鈦顆粒在火焰中的反應時間和相互碰撞頻率減少,造成產物粒徑縮小。 Previous studies have shown that titanium tetra-isopropoxide (TTIP) can be a substitute in the production of non-poisonous and inexpensive titania (TiO2) nanoparticles. This study discusses the combustion characteristics of synthesized titania obtained while adding TTIP into the premixed methane/air flames via premixed flame from a Bunsen burner and a porous flat burner. In the meanwhile, a modified Hencken burner was used to synthesize smaller titania nanoparticles via short diffusion flames. ANSYS 12.0 FLUENT computational fluid dynamics (CFD) code is used to simulate diffusion turbulent flames and coagulation of particles using a user-defined function (UDF). The results show that the frequency of collisions among particles would decrease and reduce titania nanoparticle size in a short diffusion flame height. The crystalline structure of the synthesized nanoparticles was characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), Barrett-Joyner-Halenda (BJH) and Brunauer-Emmett-Teller (BET) measurements. The characteristic properties of titania nanoparticles synthesized from a modified Hencken burner were compared with the results from a Bunsen burner and commercial titania (Degussa P25). The results showed that the average particle size of 6.63 nm from BET method was produced by a modified Hencken burner which was smaller than the titania in a Bunsen burner and commercial titania. Also, the size of titania nanoparticles was highly dependent on the TTIP loading and the collecting height in the flame. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/48537 |
全文授權: | 有償授權 |
顯示於系所單位: | 機械工程學系 |
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