TiO_2对α-Fe_2O_3纳米微粒拉曼散射效应的影响

选取α Fe2O3和TiO2研究一种氧化物对另一种氧化物的拉曼散射效应。采用Sol gel方法制备纳米α Fe2O3/TiO2复合微粒,α Fe2O3粒径及含量分别为20nm、150nm和3%、6%、12%。制备过程中调节水解时的pH值和热处理温度,得到掺杂α Fe2O3粒子的不同晶型的TiO2纳米颗粒。Raman测量结果显示,α Fe2O3粒径越小、含量越高,TiO2对其散射效应的影响越大。不同的TiO2晶型对α Fe2O3纳米粒子的拉曼增强效应也不同。锐钛矿型及金红石型TiO2对α Fe2O3有一定的拉曼增强作用,当水解pH值较小时,得到板钛矿型TiO2,由于部分板钛矿型TiO2振动声子模的峰位与α Fe2O3的重叠,所以尚难观察它对α Fe2O3的拉曼增强效应。     

不锈钢丝网上薄膜TiO2光催化剂的Raman光谱研究

用Raman光谱方法来研究用Sol Gel法负载于金属丝网的薄膜TiO2 光催化剂的物相结构、厚度以及粒径大小。研究结果显示 ,薄膜达到一定厚度能够阻止基底Fe元素向薄膜表层的扩散 ;在 4 0 0℃下灼烧制得的薄膜TiO2 光催化剂具有锐钛矿晶型 ,而高于 4 0 0℃时 ,将出现金红石相TiO2 ;锐钛矿晶型TiO2 的Raman特征峰产生偏移 ,表明薄膜粒径的变化 ,通过计算表明 ,薄膜TiO2 的粒径为 10nm左右 ,TEM的分析结果也与之一致。     

大气可吸入颗粒物中锐钛矿的发现及意义

激光拉曼微探针(laser Raman microprobe,简称LRM)能将激光聚焦在1 μm2的极小区域进行分子成分和结构的微区分析,是一种可靠的物相鉴定手段,非常适用于单个微小颗粒物的物相鉴定。文章利用LRM对北京市大气可吸入颗粒物(PM₁₀)进行单颗粒物相分析 将实验图谱与Renishaw矿物与无机材料拉曼光谱数据库中标准图谱进行对比,通过简正坐标分析对谱带进行指认和对各谱峰分子类型及振动模进行归属,首次在PM₁₀中发现了锐钛矿型TiO₂,其实验图谱具有638 cm-1处的较强峰以及398和517 cm-1处中等强度峰,为O—Ti—O特征振动,确认了大气中富Ti颗粒的矿物物相为锐钛矿型TiO₂。锐钛矿型TiO₂是一种重要的光催化剂,锐钛矿与其他矿物颗粒(尤其是含Ca碳酸盐)的聚集能够加剧非均相反应的发生。锐钛矿的晶体结构及所处大气环境的相对湿度和pH值对其光催化反应有重要影响。     

Sb掺杂纳米TiO2光催化剂的晶体结构与光催化性能

用溶胶-凝胶法将纳米TiO2:Sb薄膜沉积在玻璃基板上．通过XRD、Raman光谱研究了Sb掺杂量对薄膜的晶体结构和晶相转变的影响．结果表明:纯TiO2薄膜中,TiO2不仅以无定型态存在,而且还以板钛矿和锐钛矿的形式存在．掺入适量的Sb后,由于Sb替代了TiO2的部分Ti形成Sb-O-Ti结构,改变了TiO2的晶格结构,改善了薄膜的结晶效率,使锐钛矿结构的TiO2:Sb含量明显提高．掺杂0．2％Sb时,薄膜的结晶效率最高．254 nm光源照射时,掺杂0．2％Sb的电极的阳极光电流密度可达42．49μA／cm2,是用同种方法制备的纯TiO2薄膜电极的近11倍;对亚甲基蓝具有最高分解性能,其一级反应速率常数为0．171 h／cm2,是未掺杂的纯TiO2薄膜的近2倍．     

TiO2花状纳米结构的制备及光催化性能

用Ti片和H2O2在较低的温度下通过控制反应时间制备了不同形貌的纳米TiO2.在80℃下反应10 min得到了和Ti片黏附较好的多孔纳米结构,延长反应时间先后得到了类花状和类棒状纳米结构．在80℃下反应4 h得到的纳米结构样品为非晶态,而反应10 h制备出以锐钛矿相为主的结晶态纳米结构．通过300℃退火得到的几乎是纯锐钛矿相的纳米TiO2．用紫外光照射降解RhB溶液的方法研究了纳米TiO2的光催化性能．结果表明7 cm2的退火后的类花状纳米TiO2降解染料分子的光催化效率是仅用紫外光降解的29．8倍．     

紫外光下纳米TiO2薄膜亲水性机理的电化学研究

利用溶胶 凝胶方法在透明导电玻璃ITO (SnO2 ∶In)表面制备纳米TiO2 薄膜 ,XRD谱图表明TiO2 是锐钛矿晶型 ,AFM (Atomic Force Microscope)测得薄膜表面粒子约为 10 0nm .研究了ITO表面纳米TiO2 薄膜的光致亲水性变化 .通过循环伏安技术测定TiO2 薄膜电极在 2 5 3.7nm的紫外光照射后的电化学行为推测光致亲水性机理 .发现在紫外光照射一定时间后 ,TiO2 薄膜电极的循环伏安图在 +0 .0 35V处出现新的氧化峰 ;且随光照时间的增加 ,氧化峰的峰电流增大 ,溶液中的溶解氧对峰电流的大小有明显影响 .实验表明 ,在紫外光照下电极表面有Ti3 + 产生 ,证实了TiO2 薄膜的光致亲水性转变过程与Ti3 + 的生成导致的表面结构变化有关     

γ-Al2O3高温相变的XRD和Raman光谱比较研究

采用XRD和Raman光谱研究了γ-Al2O3的高温相变.Raman结果表明,位于1 175,1 241 cm-1和1 370,1 400 cm-1的2组谱峰是杂质Fe3 和(或)Cr3 在θ-Al2O3和α-Al2O3环境中产生的荧光光谱,用这2组峰来指认θ-Al2O3和α-Al2O3物相比XRD更灵敏.因此,Raman技术能高灵敏地表征γ-Al2O3的高温相变过程.结果表明γ-Al2O3从800 ℃开始发生相变,γ-Al2O3同时向θ-Al2O3和α-Al2O3转变,随着温度的升高最终完全转变成α-Al2O3.相变温度与样品本身有关.     

低温拉曼光谱研究二氧化钛纳米晶的相变

本文通过对二氧化钛纳米晶在-190℃温度的低温拉曼光谱的研究,得到了在二氧化钛纳米晶聚集体中,可以发生锐钛矿到板钛矿然后到金红石和/或直接到金红石的相变;也可发生板钛矿到锐钛矿然后到金红石和/或直接到金红石的相变。     

Cu掺杂SnO_2/TiO_2复合薄膜的制备及性能研究

制备Cu掺杂的纳米Sn O2/Ti O2溶胶,采用旋涂法在载玻片上镀膜,经干燥、煅烧制得Cu掺杂的Sn O2/Ti O2薄膜,通过对比实验探讨掺杂比例、条件、复合形式等对结构和性能的影响。采用XRD、SEM、EDS、UVVis等测试手段对样品进行表征,并以甲基橙为探针考察了其光催化降解性能。XRD测试结果显示薄膜的晶型为锐钛矿型,结晶度较高。SEM谱图显示薄膜表面无明显开裂,粒子分布均匀,粒径约为20 nm。EDS测试结果表明薄膜材料中含有Cu元素,谱形一致。UV-Vis吸收光谱表明Cu掺杂以及Sn O2/Ti O2的复合使得在近紫外区的光吸收比纯Ti O2明显增强。光催化实验表明Cu掺杂后使得Sn O2/Ti O2复合薄膜对甲基橙的光催化降解效率进一步提高,Sn O2/Ti O2复合薄膜的光催化活性在10%Cu掺杂时达到最高。     

采用紫外光照法在磷酸盐玻璃中合成CdS/Ag复合微粒

掺杂有Ⅱ-Ⅵ族半导体纳米颗粒(如CdS)或者过渡金属(如Ag)的玻璃由于其较大的非线性光学效应而引起人们的极大兴趣,而同时掺杂有半导体/金属的复合微粒则可以进一步增强玻璃的三阶非线性效应,因此成为目前的研究热点。我们利用玻璃沉淀技术及随后的热处理和紫外光还原技术制备了含高浓度(1%)Ag微粒的玻璃,并采用X射线衍射分析了其物相,用高分辨扫描电镜分析了其形貌,以及测试了其吸收和发光性能。从CdS/Ag复合微粒的扫描照片可以发现晶粒均匀分布在玻璃中,尺寸约为1μm。X射线衍射发现经过热处理和紫外光照的样品衍射峰中含有CdS和Ag,而只进行热处理的样品则只含有CdS,未处理的样品则显非晶态。CdS/Ag复合微粒的吸收峰呈现典型的表面等离子共振峰(420nm)以及CdS的峰(600nm),只含有CdS微粒的样品的吸收峰则在480nm附近,未处理的样品在320nm附近有一个吸收峰,这可能是由于样品在快速冷却过程中的微小晶化造成的。只含有CdS微粒的样品有三个明显的发光峰,然而CdS/Ag复合微粒的发过峰则消失。我们提出了共振能量转移机制来解释该现象。讨论了紫外光照还原Ag微粒的机制。可以认为通过紫外光照,CdS表面的电子被激发出来还原Ag+,从而形成银颗粒,伴随着空穴则被表面缺陷所捕获。     

纳米TiO_2薄膜的结构与光电特性

用射频磁控溅射方法制备出厚度大约15-225nm的TiO2薄膜。Raman光谱测量显示,TiO2薄膜主要是金红石结构(含少量板钛矿相)。紫外可见光吸收光谱表明,在纳米厚度(100nm)范围内,TiO2薄膜的带隙宽度随着薄膜厚度的变化而变化。室温下测量TiO2薄膜的电阻率发现,随着厚度的增加TiO2薄膜的电阻率先后在导体、半导体和绝缘体范围变化。     

Investigation on the sonocatalytic degradation of acid red B in the presence of nanometer TiO2 catalysts and comparison of catalytic activities of anatase and rutile TiO2 powders

Here, the nanometer anatase and rutile titanium dioxide (TiO(2)) powders were introduced to act as the sonocatalysts during the ultrasonic degradation of azo dye-acid red B which was chosen as model compound. The ultrasound of low power was used as an irradiation source to induce TiO(2) particles performing catalytic activity. It was found that the processes of sonocatalytic degradation were different between nanometer anatase TiO(2) and nanometer rutile TiO(2). For nanometer anatase TiO(2) catalyst, the acid red B was mainly oxidated by the holes on the surface of nanometer anatase TiO(2) particles, so that the decolorization and degradation happened at the same time. For the nanometer rutile TiO(2) catalyst, the acid red B was mainly oxidated by the *OH radicals from the ultrasonic cavitation, so that the decolorization of azo bond takes place primarily, and then the degradation of naphthyl ring does. The intermediates of acid red B in the presence of nanometer anatase and rutile TiO(2) powders have been monitored by UV-vis spectra and high performance liquid chromatography (HPLC), respectively. All experiments indicated that the degradation effect of acid red B in the presence of nanometer anatase TiO(2) powder was obviously better than that in the presence of nanometer rutile TiO(2) powder. Hence, the method of sonocatalytic degradation for organic pollutants in the presence of nanometer anatase TiO(2) powder is expected to be promising as an advisable choice for the treatment of organic wastewaters in future.     

Sonocatalytic degradation of methyl orange in the presence of TiO2 catalysts and catalytic activity comparison of rutile and anatase

Rutile and anatase titanium dioxide (TiO(2)) powders were used as sonocatalysts for the degradation of methyl orange which was used as a model compound. Ultrasound was used as an irradiation source. It was found that the sonocatalytic degradation ratios of methyl orange in the presence of TiO(2) powder were much better than ones without any TiO(2), but the sonocatalytic activity of rutile TiO(2) particles was obviously higher than that of anatase TiO(2) particles. Although there are many factors influencing sonocatalytic degradation of methyl orange, the experimental results show that the best degradation ratio of methyl orange can be obtained when the experimental conditions of the initial methyl orange concentration of 10 mg/l, rutile TiO(2) added amount of 500 mg/l, ultrasonic frequency of 40 kHz, output power of 50 W, pH=3.0 and 40 degrees C within 150 min were adopted. In addition, the catalytic activity of reused rutile TiO(2) catalyst was also studied and found to be better than new rutile TiO(2) catalyst sometimes. All experimental results indicated that the method of the sonocatalytic degradation of organic pollutants in the presence of TiO(2) powder was an advisable choice for treating non- or low-transparent organic wastewaters.     

光催化剂SO2- 4/TiO2和TiO2 的光谱行为比较

用ＩＲ、Ｒａｍａｎ和ＤＲＳ光谱研究了ＳＯ＾２－４／ＴｉＯ２光催化剂和ＴｉＯ２光催化剂的光谱行为差别。结果表明,ＴｉＯ２光催化剂的表面只有Ｌ酸中心,而ＳＯ＾２－４／ＴｉＯ２光催化剂表面既有Ｌ酸中心也有Ｂ酸中心。ＴｉＯ２的硫酸化有效地抑制了晶相转变和晶粒度的增加。与ＴｉＯ２相比,ＳＯ＾２－４／ＴｉＯ２光催化剂的锐钛矿相含量较多、晶粒较小、光谱吸收边蓝移,从而增大了光吸收阈值,增强了光生空穴和电子的氧化     

Anatase TiO<Subscript>2</Subscript> nanoparticles for lithium-ion batteries

Anatase TiO₂ nanoparticles were prepared by a simple sol-gel method at moderate temperature. X-ray powder diffraction (XRD) and Raman spectroscopy revealed the exclusive presence of anatase TiO₂ without impurities such as rutile or brookite TiO₂. Thermogravimetric analysis confirmed the formation of TiO₂ at about 400 °C. Particle size of about 20 nm observed by transmission electron microscopy matches well with the dimension of crystallites calculated from XRD. The electrochemical tests of the sol-gel-prepared anatase TiO₂ show promising results as electrode for lithium-ion batteries with a stable specific capacity of 174 mAh g^?1 after 30 cycles at C/10 rate. The results show that improvement of the electrochemical properties of TiO₂ to reach the performance required for use as an electrode for lithium-ion batteries requires not only nanosized porous particles but also a morphology that prevents the self-aggregation of the particles during cycling.