【正文】 基本相同。 在此首先向朱院長致以深切的感謝及敬意 ! 恩師淵博的學(xué)識、嚴(yán)謹(jǐn)?shù)闹螌W(xué)態(tài)度、孜孜不倦的教誨以及科學(xué)的工作方法給了我極大的幫助和影響。C is required, and this will result in the dramatic growth of the particle sizes. However, titania for photocatalytic activity is dependent on both particle size and degree of crystallinity . In this work, nanocrystalline anatase and rutile TiO2 particles with crystallite size ranging from 7 to 14 nm have been derived via sol gel precipitation of alkoxides followed by calcination. The effect of pH towards the development of titania nanocrystal structure and their performance as photocatalyst is investigated. II EXPERIMENTAL SECTION Synthesis. TiO2 nanocrystal were prepared by sol gel hydrolysis precipitation of titanium (IV) isopropoxide (Ti(OC3H7)4) (Sigma Aldrich, 97%), followed by calcination treatment. A specific amount of titanium isopropoxide was dissolved in isopropyl alcohol ( Merck, 95%) solution and the solution was dropped slowly into distilled water, pH was adjusted by HNO3 for acidic condition and NaOH for basic condition. Molar ratio of water to alkoxide was 110. Upon dropping, white precipitates of hydrous oxide were produced instantly, and the mixture was stirred vigorously for 4 hours at room temperature. The precipitates were centrifuged and were redispersed in ethanol to minimize agglomeration. This process was repeated five times. The resulting materials were then dried and annealed at 400176。 corresponding to anatase phase (110). In this case, it is found that high acidity in medium solution will favor the formation of rutile phase while lower acidity will favor anatase formation [11, 12]. The results show high acidity favor formation of rutile. This mechanism may be explained using the concept of partial charge model [13]. According to this model, hydrolysis of titanium cation is occurred at strong acidity condition. In this condition, a stable species of [Ti(OH)(OH2)5]3+ will form, but due to the positive charge of hydroxo group , these species are not able to condense. When acidity is not sufficiently low to stabilize these precursor, deprotonation will takes place forming new species of [Ti(OH)2(OH2)5]2+. However, these species also do not condense probably because of spontaneous intramolecular oxolation to [TiO(OH2)5]2+ [14]. Condensation to both anatase and rutile starts when the solution activity is sufficient enough to allow further deprotonation to [TiO(OH)(OH2)4]+, which can undergo intramolecular of deoxolation [TiO(OH)3(OH2)3]+ depending in exact pH. In lower pH region, deoxolation does not happen and oxolation leads to linear growth along the equatorial plane of cations. This reaction leads to rutile formation due to oxolation between resulting linear chains. Meanwhile, in higher pH values, when deoxolation occurs, condensation can proceed along apical direction and leads to the skewed chain of anatase structure. Therefore, based on this study, it is believe that the determination of resulting crystal structure is affected by pH values [13,15]. The higher acidity promotes rutile formation and lower acidity will lead to anatase formation. Figure 1. XRD patterns of nanocrystalline titania samples prepared by sol gel method with various pH condition as (a) pH 9, (b) pH 7, (c) pH 5, (d) pH 3 and (e) pH 1. The crystallite size was determined by Scherrer equation and summarized in Table 1. It was found the crystallite size vary from 7 to 14 nm and specific surface area ca. ranging from 112 to 194 m2g1Table 1. Crystallite size and specific surface area of sam。朱院長是我們恩師，同時(shí)也是我們的親人、朋友！ 在此，謹(jǐn)向朱 院長 表示衷心的感謝。因此其催化劑載體、紫外線吸收劑、高效光敏催化劑、防曬 護(hù)膚化妝品、塑料薄膜制品、水處理、精細(xì)陶瓷、生態(tài)陶瓷及氣敏傳感器元件等領(lǐng)域具有廣泛和潛在的應(yīng)用前景。 20 30 40 50 60 70 802 T h e t a ( 176。 不同 溶液 PH 值 對晶體結(jié)構(gòu)的影響 按照試驗(yàn)工藝步驟， 水浴 反應(yīng)溫度為 50℃ ， 水浴加熱時(shí)間為 1h，煅燒溫度為 500℃ ，煅燒 時(shí)間 為 4h，控制變量 為 溶液 PH 值 ，在不同 溶液 PH值 、 、 下制得樣品 對應(yīng) 如下： TO TO TO6。、 176。、 176。05010 015 020 025 030 035 040 045 0Intensity(Counts)[ z hao x unn aT O 5. ra w ] 1 2032 1 1 2 7 2 A n a t a s e T i O 2 圖 42 煅燒溫度為 500℃條件下制備樣品 TO5 的 XRD 衍射圖譜 Anatase(101)Anatase(103)Anatase(004)Anatase(112)Anatase(200)Anatase(105)Anatase(211)Anatase(213)Anatase(204)Anatase(116)Anatase(220)Anatase(107)Anatase(215)Anatase(301)10 20 30 40 50 60 70 802 T h e t a ( 176。論文中采用的是 S4800 型高分辨場發(fā)射掃描電鏡（簡稱 S4800）及其附件 X 射線能譜儀，如圖 32 所示，主 要用其進(jìn)行納米材料的形貌、顆粒度、分散性與表面微區(qū)成分的定性、定量等分析。 X射線衍射儀 (XRD)是利用不同構(gòu)象和晶型的粉末固體對 X射線有其特殊的衍射方向和強(qiáng)度，得到特征衍射譜。在空氣中陳化得到凝膠 。 其中鈦酸四丁酯水解、縮聚主要反應(yīng)如下： 水解： Ti(OC4H9)4+4H2O→ Ti(OH)4+4C4H9OH (1) 縮聚： Ti(OH)4 +Ti(OC4H9)4→ TiO2+ 4C4H9OH (2) Ti(OH)4+Ti(OH)4 → 2TiO2+4H2O (3) 總反應(yīng)是： Ti(OC4H9)4+2H2O→ TiO2+2C4H9OH (4) 其中 冰醋酸與鈦酸四丁酯發(fā)生的螯合反應(yīng) 如下 : Ti(OC4H9)4 + n(CH3COOH)→ (CH3COO)nTi(OC4H9)4 n + nC4H9OH 其中 CH3COO在反應(yīng)中起到配位體的作用。此方法中，反應(yīng)通常在特制的密閉反應(yīng)容器（聚四氟乙烯內(nèi)襯、不銹鋼反應(yīng)釜）中進(jìn)行。微乳液是指一種 液體混合物，具有熱力學(xué)穩(wěn)定性、互不相溶、宏觀均勻但微觀不均勻的特點(diǎn)。 本課題主要的研究目的是探索采用的制備工藝及條件對所制備的納米二氧化鈦的形貌，粒徑、性能等的影響。二氧化鈦的這一特性已經(jīng)被用于建筑物窗戶、鏡子等玻璃表面 自清潔和防霧等方面。此后，很多科研工作者進(jìn)行了這方面的研究，一致認(rèn)為二氧化鈦光催化技術(shù)在污水處理方面有很好的應(yīng)用前景，比如工業(yè)有毒試劑、工業(yè)用燃料、化學(xué)殺蟲劑等皆可使用二氧化鈦光催化劑進(jìn)行降解，并對環(huán)境無害，目前已經(jīng)成為半導(dǎo)體催化研究中最為活躍的領(lǐng)域。而 TiO2 的晶型結(jié)構(gòu)取決于 TiO6 八面體的對稱性和連接方式，其中，銳鈦礦相是 TiO6 八面體共邊構(gòu)成，板鈦礦相和 金紅石相則是由共邊和共定點(diǎn)的TiO6 八面體共同組成。納米二氧化鈦不但具有納米粉體的表面效應(yīng)、體積效應(yīng)、小尺寸效應(yīng)、久保效應(yīng)等，而且具有其獨(dú)特的性能。自 1939 年 Geffcken 和 Berger 的報(bào)道問世以來，這種方法一直備受人們的關(guān)注。二十世紀(jì) 80 年代以前，超細(xì) TiO2的研究開發(fā)目的主要是作為精細(xì)陶瓷原料、催化劑、傳感器等，需求量不大，沒有形成大的生產(chǎn)規(guī)模。 畢業(yè)論文 納米二氧化鈦粉體制備工藝及其性能研究 摘 要 納米二氧化鈦因?yàn)槠涓咝?、無毒、穩(wěn)定、成本較低等優(yōu)點(diǎn)，在半導(dǎo)體材料中脫穎而出，成為應(yīng)用最廣的光催化劑，被廣泛用于廢水廢氣處理、光催化制氫、光電池、抗菌