TiO2有序分级结构的制备条件对其形貌和光电转换性能的影响

采用水热法,在钛箔表面成功制备出TiO2纳米线-纳米粒子分级结构光阳极.利用XRD、SEM等表征方法系统研究了制备条件对TiO2有序分级结构物相和微观形貌的影响,讨论了TiO2纳米结构和其光电转换性能之间的关系.结果表明:由于二次水热反应将初级TiO2纳米线阵列转变为纳米线-纳米粒子分级结构,使其比表面积和光电转换性明显提高.然而晶体生长时间过长或水热反应前驱液的浓度较高,都使得生长的纳米结构相互团聚在一起,从而减少其比表面积,降低光电转换性能.最佳的条件是第一步水热反应时间10 h,草酸钛钾溶液浓度0.0075mol/L,第二步水热反应时间6h,TiC14处理液浓度0.05 mol/L,分级结构的光电转换效率达到2.01;.     

热处理过程对纳米TiO2结构和性能的影响

以钛酸丁酯为钛源,采用溶胶-凝胶法制备纳米TiO2,结合TG-DTA,XRD,TEM等分析了不同热处理温度对纳米TiO2的晶型结构、晶粒粒径及微观形貌的影响.以甲基橙溶液为目标降解物,探讨了热处理温度对纳米TiO2光催化活性影响.利用Eastman的粒子生长理论对晶粒生长的动力学过程进行初步分析.研究表明:随着热处理温度升高,TiO2粒径逐渐从11.2 nm增大到78.6 nm;热处理温度为450～ 550℃时,纳米TiO2晶粒以锐钛矿为主,温度升至650℃时,出现了锐钛矿和金红石的混合相(质量比A∶R =9∶1),此时晶粒对甲基橙的降解率达到97.75;.而煅烧温度高于850℃后,TiO2几乎完全为金红石相,光催化活性显著下降.50;锐钛矿型TiO2转变金红石型TiO2的温度约为730℃,锐钛矿和金红石相晶粒表观活化能分别18.15 kJ/mol和42.56 kJ/mol;晶粒生长最快温度分别为546℃和1280℃.     

钒掺杂纳米二氧化钛的制备及光催化活性研究

以钛酸四丁酯为钛前驱体,偏钒酸铵为掺杂离子给体.采用溶胶-凝胶法制备了V掺杂纳米二氧化钛粉体;并使用TGA-DSC、XRD、BET、SEM对其晶化温度与结构进行了表征.结果表明:V掺入促进锐钛矿相向金红石相转变、抑制晶粒长大、增大比表面积,纳米粉体颗粒呈分布较均匀的类球形晶粒.以亚甲基蓝为模型反应,考察了V掺杂量、煅烧温度对催化剂光催化性能的影响,结果表明:V掺杂的TiO2 粉体降解亚甲基蓝符合一级反应动力学规律;晶格中V4+能够作为电荷转移物种,有效的抑制光生电子与空穴的复合,增加了表面空穴浓度,提高TiO2 纳米粉体的光催化活性,当掺杂量为1.5 mol;,煅烧温度为450 ℃时,TiO2 具有最佳的光催化性能.     

稀土Gd3+掺杂TiO2纳米带的制备及其光催化性能研究

以水热法制备出的钛酸盐纳米带为原料,利用二次水热反应制备了Gd3+掺杂TiO2纳米带.采用XRD、TEM和N2吸附-脱吸等手段对样品的晶型、微观形貌及比表面积进行了表征,讨论了Gd3+掺杂浓度、二次水热温度对材料结构及性能的影响.研究结果表明,Gd3+的掺杂没有影响原有样品的晶型,样品保持了锐钛矿相,但二次水热温度过高会破坏纳米带的形状,掺杂提高了样品的光催化活性,最佳掺杂量为5.O;.以掺杂量为5.0;、二次水热温度为180°C制备出的样品为光催化剂降解甲基橙,在光照180min后,甲基橙的降解率可达68;.     

炭黑吸附水热法制备纳米TiO2粉体及其光催化降解甲基橙

利用炭黑吸附钛酸异丙酯水热法制得锐钛矿型TiO2纳米粉体.采用热重/差热分析(TG-DTA)、X-射线衍射(XRD)、扫描电镜(SEM)、比表面积吸附(BET)和紫外-可见光谱(Uv-vIS)等分析方法对不同煅烧机制下所得粉体的物相、颗粒度、分散性和光吸收性能进行表征.同时利用纳米TiO2粉体对甲基橙进行了光催化降解,研究了其光催化性能.结果表明,炭黑的吸附阻止了纳米TiO2超细颗粒的团聚和烧结,制得的颗粒分散均匀、具有单一锐钛矿晶型结构的TiO2纳米粉体.经500℃煅烧获得的TiO2粉体粒径约为15 nm,比表面积为76.31 g/m2.在紫外灯照射下,由于炭黑的吸附和纳米TiO2的光催化形成协同效应,甲基橙的光催化降解率在6min达到99;.     

温度对TiO2-B纳米纤维的结晶度和稳定性的影响

本文以锐钛矿相二氧化钛纳米颗粒和NaOH溶液为前驱物,通过水热反应和退火处理制备了TiO2-B纳米纤维.用XRD、HRTEM和EDS对样品的结构、形貌及其演化进行了表征.讨论了水热反应温度和退火温度对TiO2 -B纳米纤维的结晶度、形貌和热稳定性的影响.结果表明:在160℃、180℃和200℃温度下水热反应,分别得到H2Ti4O9、H2Ti3O7和H2Ti4O9与H2Ti3O7混合的纳米纤维,400℃退火后,无论是H2Ti4O9还是H2Ti3O7纳米纤维都转化为TiO2-B纳米纤维,但从180℃水热反应得到的H2Ti3O7纳米纤维转化的TiO2-B纳米纤维具有较高结晶度和热稳定性.     

温度对钛酸盐纳米管水热转化的TiO_2纳米晶形貌演变的影响机制

钛酸纳米管水热转化是制备晶相组成和形貌可调控TiO2纳米晶的工艺易控及成本低且收率高的途径。本文研究了两种pH值体系中,水热处理温度对钛酸纳米管水热转化的TiO2纳米晶形貌演变的影响。当钛酸悬浮液的pH值为2.0时,钛酸纳米管水热转化为锐钛矿相纳米晶,且随着水热温度的升高,纳米晶的形貌向规则的双锥形演变;对于pH为0.5的强酸性体系,钛酸纳米管水热转化为金红石相纳米棒,并随着水热温度的升高,其形貌向带有两锥形尖端的长方体纳米棒演变。最后,结合TEM和HRTEM分析,探讨了钛酸纳米管向不同晶相组成和形貌的TiO2纳米晶的水热转化及其形貌演变机制。     

微波水热法制备ZnO纳米晶

采用微波水热(microwave hydrothermal,M-H)法在MDS-6型温压双控微波水热反应仪中成功地制备出平均晶粒尺寸为30 nm且呈现棒状形貌的ZnO纳米晶.并在一定的水热温度和反应时间下系统研究了微波水热反应过程中[Zn2+]离子浓度、反应釜填充比、反应物浓度比[Zn2+]/[OH]等工艺因素对ZnO纳米晶的晶粒尺寸及形貌的影响.采用X射线衍射仪(XRD)、场发射扫描电子显微镜(FE-SEM)和透射电子显微镜(TEM)对所制备的ZnO纳米晶进行表征.结果表明:所制备ZnO的平均晶粒尺寸约为30 nm,ZnO纳米晶呈现棒状形貌.随着[Zn2+]离子浓度的增加,ZnO纳米晶的晶粒尺寸先减小后增大;随着反应釜填充比和反应物浓度比[Zn2+]/[OH]的增大,ZnO纳米晶的晶粒尺寸先减小后增大,并逐渐趋于稳定.制备ZnO纳米晶的最佳反应条件为:[Zn2+]=1.6 mol·L-1;反应釜填充比=70;;[Zn2+]/[OH]=1/2.     

H2O/HAc对纳米TiO2/硅藻土复合材料TiO2晶相和性能的影响

以硅藻土为载体,钛酸四丁酯为前驱体,采用溶胶-凝胶法制备了纳米TiO2/硅藻土复合材料.在750下对复合材料煅烧晶化,以罗丹明B为降解对象检测了材料的光催化性能.并结合XRD、BET、SEM等表征手段,探究了H2O/HAc比例对复合材料晶型、比表面积和光催化性能的影响.结果表明,H2O/HAc比例对TiO2/硅藻土复合材料中TiO2的晶相组成和光催化性能有很大影响.当H2O/HAc=6时,二氧化钛颗粒均匀地负载在硅藻土表面,样品具有较大的比表面积和较好的光催化效果,同时锐钛矿晶型比例为80.2;.     

花状TiO2的制备及光催化性能研究

采用溶剂热法合成了花状TiO2,运用SEM、XRD和N2物理吸附-脱附等对其形貌、结构、比表面积和孔径进行了表征,并以甲基橙为模拟污染物研究了它们的光催化性能.结果表明,花状TiO2结构为锐钛矿相,是由纳米晶定向聚集形成纳米棒组成的3D花状结构,花状结构的直径在0.7～1.5 μm,平均直径在1.1μm,细小纳米晶聚集形成的纳米棒的直径在20～25 nm,长度100～ 150 nm.该样品具有较高的比表面积,表现出良好的光催化活性.     

The effect of boron addition on texture and structure of NiMo/Al2O3 catalysts

The effect of support (Al₂O₃) modification with borate ions and the effect of their concentration on the texture and structure of nickel-molybdena catalysts were studied. The surface area and pore volume of the samples were determined using the BET method, whereas pores distribution – besides the BET method also by mercury porosimetry. FT-IR, derivatographic, and diffractometric studies were also performed. Modification with borate ions does not bring about any change in the type of the support pores, nor does it change its crystallic structure. However, a considerable decrease in the surface area of the support was observed. It was shown that modification with borate ions leads to a decrease in thermal stability of catalysts, yet increase in concentration of borate ions raises the thermal stability of the samples. It was found that on the catalyst surface borate ions form a well-dispersed monolayer structure.     

水热法制备二氧化锡/钨酸铋复合光催化材料及其催化活性研究

本文用水热法制备了正交晶系的纳米球状结构的二氧化锡和正交晶系的由片状聚集成球状结构的钨酸铋,并且对二者进行了复合,制备出了二氧化锡/钨酸铋复合光催化材料。采用X射线衍射(XRD)、扫描电子显微镜(SEM)、比表面积测试仪(BET)、紫外可见分光光度计等技术对复合样品的结构、形貌、比表面积、孔容孔径和光学性质进行了表征。用碘钨灯模拟太阳光,分别以二氧化锡、钨酸铋和二氧化锡/钨酸铋复合材料为催化剂降解罗丹明B(RhB),研究所制备的二氧化锡/钨酸铋复合材料的光催化活性。光催化90 min时二氧化锡、钨酸铋和二氧化锡/钨酸铋对罗丹明B的降解率分别是9%、22%和30%。实验结果表明,在可见光下,二氧化锡/钨酸铋复合材料的光催化活性要高于单一的二氧化锡和钨酸铋。     

Effects of carbon structure orientation on the performance of glucose sensors fabricated from electrospun carbon fibers

High-performance enzyme-based glucose sensors were prepared by electrospinning carbon fibers. The efficiency of the glucose sensor was assessed based on efficient enzyme immobilization and electrical resistance transfer by examining improved porosity and electrical properties, respectively. The porosity of the electrospun carbon fiber electrode was improved by physical activation to increase the immobilization sites of the glucose oxidase enzyme. The electrical properties were improved by a thermal treatment, which caused carbon orientation effects because of the high thermal energy. The glucose oxidase enzyme immobilization was developed based on improved specific surface area and pore volume, which were studied by pore structure and image analyzers. The glucose sensor was evaluated by amperometric measurements and cyclic voltammetry. The measured current increased with higher glucose concentrations based on the effects of the developed pore structure and the electrical properties. The enzymatic kinetics were also studied using the Lineweaver–Burk equation. The sensitivity of the glucose sensor was improved significantly with increased maximum current, whereas the GOD enzyme activity was diminished by efficient GOD immobilization. It is concluded that a high-performance glucose sensor was obtained using electrospun carbon fibers based on the effects of efficient GOD enzyme immobilization and electrical resistance transfer.     

Zn2+掺杂高岭石基纳米TiO2光催化材料的表面特性研究

基于高岭石表面是以Si-O键为主的亲水表面且具有巨大比表面积,易于复合光催化优异的TiO2膜.以高岭石为基材,溶胶-凝胶法制备了具有光催化活性的Zn2掺杂TiO2/高岭石复合光材料.采用XRD、FrIR、Raman、XPS等技术对材料的晶体结构、分子结构、表面元素组成及化学态、纳米TiO2晶体膜的覆盖面积进行表征分析.结果表明:Ti-O与高岭石结构的Si-O发生化学键合,在高岭石表面形成Si-O-Ti键合的纳米TiO2晶体膜,占高岭石表面积的91.35;.掺杂的Zn2只是在TiO2晶体表面复合氧化成红锌矿,而不能进入TiO2晶格.物理化学复合增加了基材高岭石表面晶体缺陷,有利于TiO2晶体表面光生载流子的增生和传输.     

Synthesis of nanosized ZSM‐5 using different alumina sources

Alumina sources can influence different aspects of ZSM‐5 crystallization and it leads to change in the properties of the final product. The crystallinity of nanosized ZSM‐5 zeolite from precursors mixtures containing different alumina sources, e.g. sodium aluminate, aluminum sulphate, aluminum hydroxide and alumina has been studied. The produced samples were investigated using XRD, SEM, FT‐ IR and BET surface area. The product obtained by sodium aluminate and aluminum sulphate was ZSM‐5 phase. Whereas, the product obtained by aluminum hydroxide and alumina was the albit phase. As‐synthesized ZSM‐5 was prepared by sodium aluminate, as alumina source was the highest crystallinity. It was found that the average crystallite size increased in the following order; alumina <aluminum hydroxide < aluminum sulphate < sodium aluminate. The surface area increased in the following order; aluminum sulphate < sodium aluminate < aluminum hydroxide < alumina due to increasing in crystallinity percentage of ZSM‐5. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Nanostructured materials obtained under conditions of hierarchical self-assembly and modified by derivative forms of fullerenes

Gas-sensitive nanocomposites, based on silicon dioxide–metal oxide systems, were obtained via self-assembly using the sol–gel method. Surface morphology diagnostics of nanomaterials, synthesized from sol solutions in a precursor medium based on tetraethoxysilane, were made using atomic force microscopy. The main evolution stages of nanocomposites based on two-component systems were determined. Specific surface area measurements of nanocomposites were made using a Sorbi analytical instrument by the thermal desorption method. A method for increasing the specific surface area and gas-sensitivity of nanomaterials by modifying them using fullerenols is suggested.     

Effects of organic content and H2O/TEOS molar ratio on the porosity and pore size distribution of hybrid naphthaleneaminepropylsilica xerogel

The hybrid naphthaleneaminepropylsilica material was obtained by a sol-gel route, varying the organic loading and the water/TEOS molar ratio. Infrared spectroscopy was used to identify the organic and inorganic phases. The morphology of the hybrid material was studied by using scanning electron microscopy and N₂ adsorption-desorption isotherms. It was observed that the increase in the organic content produces a decrease in the size and volume of the pores as well as in the surface area of the xerogel. The best porosity was obtained for water/TEOS molar ratio between 4 and 6.     

Highly efficient photocatalytic degradation of methyl orange and Rhodamine B by hierarchical BiOBr microspheres

Hierarchical BiOBr microspheres were successfully synthesized via a solvothermal method by using the diethylene glycol(DEG) as the solvent and soft‐template. The as‐obtained products were characterized by X‐ray powder diffraction (XRD), scanning electron microscopy (SEM), selected area electron diffraction (SAED), high resolution transmission electron microscopy (HRTEM), N₂ adsorption–desorption and UV–Vis diffuse reflectance spectroscopy(DRS) techniques. The formation mechanism for the growth of hierarchical BiOBr microspheres has been studied. The possible mechanism of photocatalysis has been discussed. Remarkably, the as‐prepared BiOBr microspheres has a large specific surface area, which can reach a maximum surface area of 55.9307 m²/g. In addition, the superior enhanced photocatalytic activities of BiOBr microspheres were evaluated by the photodegradation of methyl orange (MO) and Rhodamine B (RhB) under visible‐light illumination, which presented the efficiency up to 98.10% just within 50 min and 98.64% within 30 min, respectively. BiOBr microspheres can be a promising candidate as highly efficient photocatalyst for decompositing of organic contaminants for environmental remediation.     

Thermal stability and optical property of ormocers (organically modified ceramics) nanoparticles produced from copolymerization between amino-silanes and tetraethoxysilane

The effect of heat treatment on the optical activity of ormocers (aminopropyl-modified silica) is studied using photoluminescence and ultraviolet diffuse reflectance spectroscopy techniques. The thermal stability of the modified silica is also investigated by X-ray diffraction and thermogravimetric analyses. Great withstanding of aminopropyl group located inside the silica network is found at high temperature. Distinct blue and green bands are observed in the modified silica nanoparticles after heat treatment using different temperatures, whereas some optical activities in the area of near-ultraviolet and infrared relating to the OH-related and carbon-related species and non-bridging oxygen hole center, respectively, diminished. The decrease in the band intensity besides band shift was evidences for changing the structural defect owing to releasing and decomposing of aminopropyl group from the nanoparticle surface. Some ultraviolet bands were detected because of the existence of oxygen-related defect.     

临江高品位硅藻土的物理化学提纯

采用超声、酸浸和煅烧结合的物理化学法对临江高品位硅藻土进行处理,分析不同的硫酸浓度、酸浸处理方式(水浴、水热)以及煅烧温度对其形貌、比表面积、吸附量及各成分含量的影响,并利用红外光谱仪分析了硅藻土提纯前后谱图的变化,最终确定了最佳酸浸和煅烧提纯条件.其中,水浴酸浸采用28;硫酸处理后500℃煅烧,精硅藻土比表面积值为27.79 m2·g-1,非晶质SiO2含量为93.42;,对罗丹明B吸附量为1.94 mg·g-1;水热酸浸采用28;硫酸处理后500℃煅烧,精硅藻土比表面积值为25.10 m2·g-1,SiO2含量93.52;,对罗丹明B吸附量为1.84 mg·g-1.