【正文】 ase 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。. The crystallite size and peak broadening was determined based on anatase (101) and rutile (110) diffraction using Scherrers equation. Specific surface area of the samples was calculated using formula as : S=6103/ρL (5) Where, S is the specific surface area (m2g1), L is the average crystallite size, and ρ is the density of titania ( gcm3) .The morphologies and particle size of titania particles were examined using a field emission scanning electron microscope (FESEM SUPRA 35VP ZEISS). Photocatalytic degradation studies were performed by mixing g TiO2 powder into 30 ppm methyl orange (MO) in quartz tube and sealed with stopper. The quartz tubes were then irradiated by UV light (Germicidal 36 watt) for 5 hours and samples were collected for every 1 hour. The concentration of the degradated methyl orange was determined using UVVis spectrometer (PerkinElmer Lambda 35). III RESULTS AND DISCUSSION Figure 1 shows the Xray diffraction (XRD) patterns of the powder samples prepared in initial solution with different pH. As seen in figure 1, distinct peaks were noted in the XRD patterns at 176。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。 同時(shí)在找工作的過(guò)程中，我們遇到了很多挫折，朱院長(zhǎng)積極對(duì)我們進(jìn)行就業(yè)指導(dǎo)，幫我們選擇優(yōu)秀且合適的企業(yè)，并且聯(lián)系企業(yè)，向優(yōu)秀企業(yè)推薦我們，讓我們順利實(shí)現(xiàn)就業(yè)。 在此首先向朱院長(zhǎng)致以深切的感謝及敬意 ! 恩師淵博的學(xué)識(shí)、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。 第五章 結(jié)論與展望 二氧化鈦的納米材料是一種新型的無(wú)機(jī)材料，粒徑為 1050nm，相當(dāng)于普通鈦白粉粒徑的 1/10。從圖 38 可以看出 ,不同 PH 值溶液制備的微粉試樣的衍射峰 2θ 的位置和和數(shù)量基本相同。025507510 012 5Intensity(Counts)[ z hao x unn aT O 4. ra w ] 4 78 6 1 1 5 7 A n a t a s e T i 0 . 7 2 O 2 圖 36 溶液 PH 值為 條件下制備樣品 TO4 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。 步長(zhǎng)掃描模式中的 10– 80176。 說(shuō)明隨煅燒溫度的升高 ,晶體發(fā)育趨于完好 ,結(jié)晶度提高。、176。、 176。、 176。從圖 34 可以看出 ,不同不同煅燒溫度條件下制備的微粉試樣的衍射峰 2θ的位置和和數(shù)量基本相同。 為了研究溫度對(duì)產(chǎn)物的結(jié)晶度的影響將不同溫度下制備的產(chǎn)物 XRD 衍射 圖譜疊加在一起進(jìn)行對(duì)比，如圖 44。 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。用 德國(guó)布魯克 D8 系列 X 射線（粉末）衍射儀 ， 用一步為 176。這些信息與樣品表面的幾何形狀以及化學(xué)成分等有很大的關(guān)系。 論文中采用的是CuKα射線源、 D/MAX2500VL/PC 型 X 射線衍射儀， 如圖 31 所示。通過(guò)衍射方法測(cè)定晶體的結(jié)構(gòu)，能夠詳細(xì)了解晶體的對(duì)稱(chēng)性、晶體內(nèi)部三維空間中原子排布情況、晶體中分子的結(jié)構(gòu)式、立體構(gòu)型、鍵長(zhǎng)、鍵角等數(shù)據(jù) [7]。 (4)在 80℃ 的恒溫條件下對(duì)凝膠進(jìn)行干燥 2 h， 得到黃色晶體 ； (5)將晶體研磨后得到白色粉末 ,放入馬弗爐中煅燒 ，以 10℃ /min 的升溫速度進(jìn)行升溫， 將 溫度升 至 預(yù)定溫度， 并保溫 4h， 然后在爐內(nèi)自然冷卻 ,得到白色粉末狀樣品 。 (3)在快速攪拌下 ,將溶液 Ａ 以每分鐘 12 滴的滴速滴到溶液 Ｂ 中得到均勻透明溶液。 第三章 實(shí)驗(yàn)準(zhǔn)備 試驗(yàn)原料 采用 溶膠 凝膠法制備 納米二氧化鈦 粉體 ，實(shí)驗(yàn)過(guò)程中用到的試劑如下表： 表 31 試驗(yàn)原料名稱(chēng)與級(jí)別及其生產(chǎn)商 試劑名稱(chēng) 化學(xué)式 分子量 級(jí)別 生產(chǎn)廠家 鈦酸四丁酯 C16H36O4Ti CP 上海山浦化工有限公司