微乳法制备纳米TiO2 /SiO2的结构及光催化研究

Nanosized TiO₂ and TiO₂/SiO₂ particles were prepared by hydrolysis of tetrabutyl titanate (TBOT) and tetraethyl orthosilicate (TEOS) in the TX-100 reverse microemulsion. These particles were characterized by TG-DSC, XRD, FTIR, TEM，N₂ adsorption-desorption. Their photocatalytic activity was tested by degradation of methyl orange. The result shows that TiO₂/SiO₂ nanoparticles are with a monodispersed spherical phase and a uniform size distribution，and TiO₂ particles are dispersed on the surface of SiO₂. The band for Ti-O-Si vibration in FTIR was observed, the Ti-O-Si bond increased the stability of anatase TiO₂, suppressed the phase transformation of titania from anatase to rutile. And due to the addition of SiO₂, the average size of titania decreased from 38 nm in pure TiO₂ to 5 nm in TiO₂/SiO₂. It was found, under UV light irradiation, TiO₂/SiO₂ particles showed higher activity than pure TiO₂, and TiO₂/SiO₂(1/1) particles showed the highest photocatalytic activity on the photocatalytic decomposition of methyl orange, which was influenced by crystal structure, particle size, crystallinity and Surface area Characteristics.     

乙烯在纳米催化剂InVO4-TiO2上的可见光降解

The InVO₄-TiO₂ nano-crystalline photocatalyst was prepared by sol-gel method and characterized by DRS, FTIR, Raman and XRD. The photocatalytic activities of the prepared sample were investigated by photocatalytic degradation of ethylene in the gaseous phase under visible light irradiation (λ>450 nm). The results indicate that both of pure TiO₂ and InVO₄ or their simple mixture show no photocatalytic activities for degradation of ethylene under visible light irradiation. However, as-synthesized InVO₄-TiO₂ catalyzes the degradation of ethylene into CO₂ under visible light irradiation. In addition, the interaction between InVO₄ and TiO₂ results in some structural distortion to all the crystal forms of TiO₂ in as-synthesized catalyst InVO₄-TiO₂.     

锐钛矿型TiO2水溶胶的低温制备及其表征

Anatase titanium dioxide hydrosol was prepared at low temperature by a simple method. The title material was characterized by TEM, XRD, FTIR and BET, respectively. The photocatalytic activity of the as-prepared TiO₂ was evaluated by the degradation of methyl orange solution under sunlight and the photocatalytic oxidation of acetone in air. The results showed that the titanium dioxide hydrosol was composed of anatase phase with average grain size of about 7 nm, and the crystallinity became more perfect with the increase of temperature. The BET surface areas were more than 220 m²·g^-1 for these samples. It is found that the photocatalytic activity was much better for the higher heat processing temperature. Especially, the photocatalytic activity of the sample with a heat treatment of 110 ℃ was better than that of P25. In addition, TiO₂ hydrosol also possessed good photocatalytic activity under the sunlight illumination.     

掺钇锆酸锶-TiO2复合光催化剂的制备及性能研究

SrZrO₃ particles were prepared by a co-precipitation method and Sr(Zr_1-xY_x)O_3-δ -TiO₂ composite particles were then synthesized by Sr(Zr_1-xY_x)O_3-δ and titanium dioxide. The composite particles were characterized by XRD, SEM, FTIR and TG-DTA techniques. The photocatalytic degradation of methylene blue (MB) in aqueous solution was used as a probe reaction to evaluate the photocatalytic activity of the composite particles. The effect of the preparation method for SrZrO₃, doping content of yttrium and TiO₂ amount in the composite particles on the photocatalytic activity of composite particles was also discussed. The results show that the methylene blue solution could be completely degraded by Sr(Zr_1-xY_x)O_3-δ -TiO₂ composite particles under UV-light or visible light irradiation. The photocatalytic activity of composite particles was higher than that of pure TiO₂. The fast recombination of photogenerated electrons and holes were restrained by the heterojunction formed in composite particles. The particle of SrZrO₃ prepared by co-precipitation was small, and the photocatalytic activity of composite particles prepared from this kind of SrZrO₃ was higher than that of particles prepared by solid sintering method. The best doping content of yttrium is 5%. The optimal content of TiO₂ in composite particles is 90wt%, 70wt%, respectively under UV-light and visible light irradiation, the degradation rates of MB are 98.8% and 93.5% , respectively after 50 min irradiation.     

电沉积HA/TiO2复合涂层的结合强度和热稳定性研究

HA/TiO₂ composite coating were fabricated via adding TiO₂ powder in the electrolyte by electrodeposition. The influence of current density and deposition time on the content of TiO₂ in the coating, the influence of the content of TiO₂ in the coating on the bonding strength of coating and the influence of sintering temperature on the structure and the bonding strength of coating were investigated. The experiment results show that the content of TiO₂ in the coating increase with reducing the current density and prolonging the deposition time, the bonding strength improve with increasing the content of TiO₂ in the coating, which can obtain 18.7 MPa when the weight percent TiO₂ in the coating attain 72.2 %. The addition of TiO₂ in the coating reduces the thermal expansion coefficient of the coating, improves the bonding strength of coating and changes the fracture mechanism of the coating from adhesion failure to cohesive failure. HA in the composite coatings is decomposed by the catalysis reaction of TiO₂ at the temperature of sinter 850 ℃. Differential scanning calorimetry and X-ray diffractometry analyses showed that the chemical reaction between HA and TiO₂ lead to the product are α-TCP and CaTiO₃ at the temperature of sinter 1200 ℃. In order to prevent the coating from decomposing and attain hign bonding strength, the sintering temperature should be less than 820 ℃.     

湿法水解制备可见光催化剂N/TiO2

The N/TiO₂ was prepared by wet hydrolyzation method. The photocatalytic decomposition of benzoic acid solution was carried out under simulated sun light; the photocatalytic activity was 2.47 times of TiO₂. The products were characterized by XRD, SPS, EFISPS and XPS, respectively. The results of XRD showed that the N could restrain the crystallization transformation of TiO₂ from anatase to rutile. The N/TiO₂ was still n-type semiconductor, and the absorbance wavelength appeared red-shifted by N-doping. The band gap of N/TiO₂ was decreased to 2.7 eV. The amount of doped-N is about 0.94at.%. The binding energy of N1s are 396.62 eV (Ti-N bonds, β-N) and 400.87 eV (N-N bonds, γ-N₂), respectively, and the photocatalytic activity of N/TiO₂ under visible light is related to the β-N. The N atoms replace the O of the TiO₂ and form the Ti-N bonding.     

正钛酸胶溶法制纳米TiO2薄膜及性能表征

The Nanometer TiO₂ thin film was prepared by sol method with titanic acid precursor from industrial TiOSO₄ solution. The characters of the sol and the factors affecting sol formation were investigated by ζ electricity potential. The crystalline structure, particle size, appearance shape and photo-catalytic activity were characterized by XRD, SEM, TEM and spectrophotometer. The study show: (1) pH value and HNO₃concentration effected importantly on the forming process and stability of the sol. The thermodynamic condition for forming sol is pH=0.5～1.5. The lower the HNO₃concentration,the more stable the sol. The ζ electricity potential of the sol, with 5% HNO₃as gluing reagent, was up to 48 mV, and shelf life of the sol could more than 10 months. (2) The film, made from the sol and crystallized at 400 ℃, had the characters of anatase structure and crystal size of 18.5 nm by XRD analysis. The SEM imagines show that TiO₂ film was with the characteristics of tight surface structure, The TEM imagine showed the mean particle size is about 20 nm. The photo-degrading test data indicate that the photo-degrading rate to methyl orange solution of 20 mg·L^-1 was more than 84% in 5 hours.     

表面活性剂辅助水热合成氧化钛纳米针溶胶

TiO₂ nanoneedles sol with particle size of 10～15 nanometer was synthesized by hydrothermal method using peroxo titanic acid as the precursor, cetyltrimethyl ammonium bromide(CTAB) as the surfactant. The product was characterized by XRD, TEM, HRTEM and selected area electron diffraction(SAED). The results show that the as-prepared products have high crystallinity and grow along the c-axis, with homogeneous morphology and good monodispersity. In addition, TiO₂ hydrosol possessed good photocatalytic activity for the photocatalytic degradation of methyl orange aqueous solution under the sunlight illumination.     

可见光催化剂S/TiO2的制备与表征

The sulfur-doped titanium dioxide (S/TiO₂) was prepared by calcinations. The photocatalytic decomposition of benzoic acid solution was carried out under simulated sun light; the photocatalytic activity is 2.7 times of TiO₂. The results of XRD show that the sulfur can restrain the crystallization transformation of TiO₂ from anatase to rutile, although the calcinations temperature has attained 500 ℃, the crystallization still is anatase entirely. The responsive wavelength range of S/TiO₂ was shifted; it has obvious absorption in the region from 320 to 550 nm. The S (S⁶⁺) substituted for some of the lattice titanium atoms in S/TiO₂. At the same time the XRF also prove the formation of S⁶⁺ and the atomic content is 2.13%.     

纳米二氧化钛粉末的溶胶-凝胶法合成及晶相转化

Nanosized TiO₂ powder with anatase and rutile structures was synthesized by a sol-gel method using TiCl₄ ethanol solution as a precursor.The grain size of TiO₂ powder was about 63nm after the precursor was calcined at 600℃ for 2 hours .The experimental techniques of XRD,TEM and Particle Distribution were used to characterize the synthesized specimens. Various special effects were investigated for their contribution to crystal structure and the size of TiO₂ powder .The formation of anatase as well as the rutile phase of TiO₂ was indicted from the XRD when the reaction temperature was above 30℃ and when the sol was irradiated by infrared rays .However, an anatase TiO₂ powder formed after the heat treatment of the dried gel in a temperature range from 300℃ to 500℃.Under the vacuum drying and with the calcined time below 3hours ,the anatase phase was gained .As well as with the increase of gelatinizing time, the anatase TiO₂ powder was obtained.     

TiO2/蒙脱石纳米复合物中TiO2的结构相变

以钛酸丁酯和季铵盐改性有机蒙脱石为原料,采用原位水解法和原位脱羟法制备了TiO2/蒙脱石纳米复合物。采用X射线衍射(XRD)、拉曼光谱(Raman)表征了不同焙烧温度下TiO2/蒙脱石纳米复合物中TiO2的结构相变,并与不同焙烧温度下纯TiO2的结构相变进行对比。结果发现TiO2/蒙脱石纳米复合物中TiO2从锐钛矿相开始转变为金红石的最低温度要比纯TiO2从锐钛矿开始相转变为金红石的最低温度高200℃,且在焙烧温度1 200℃时还存在锐钛矿相,而纯TiO2在焙烧温度800℃时就全部转换为金红石相。TiO2/蒙脱石纳米复合物中TiO2和纯TiO2的平均晶粒度都随焙烧温度升高而增大,但TiO2/蒙脱石纳米复合物中TiO2的平均晶粒度要小于相同温度下焙烧纯TiO2的平均晶粒度。表明蒙脱石结构层的硅氧结构抑制了TiO2晶型由锐钛矿相向金红石相的转变,进而使相变温度升高,同时阻碍了晶体的生长。     

SnO_2改性TiO_2对V_2O_5-WO_3/TiO_2催化剂结构和SCR性能影响

采用共沉淀法将SnO_2组分掺入到V_2O_5-WO_3/TiO_2催化剂载体TiO_2中,并通过多种物理化学手段,考察了不同SnO_2掺入量时对催化剂结构,表面分散物种和SCR性能影响.结果表明,SnO_2掺入到TiO_2中,元素Sn与Ti以Sn—O—Ti键形式相互作用,促进锐钛矿型TiO_2向金红石型TiO_2转变.在特定条件下,VO_x与WO_x物种和SnTi氧化物之间以V—O—Ti(Sn)和W—O—Ti(Sn)键形式相互作用,提高了VO_x物种可还原能力、促进了具有更多B酸酸量四面体WOx物种和V~(5+)物种生成.VW/SnTi催化剂表面VO_x物种与WO_x物种之间的相互作用更强.因此,VW/SnTi催化剂具有更好的SCR活性.     

Catalytic oxidation of no to NO2 over Cr/TiO2 and Cu/TiO2 under oxidizing atmosphere

The catalytic activity of Cr/TiO₂ and Cu/TiO₂ for the oxidation of NO under an oxidizing atmosphere has been examined. Both catalysts had excellent ability for the oxidation of NO to NO₂ in the temperature range of 350–400°C.     

TiO_2纳米带光催化二氧化碳甲烷化

研究了在常温常压下TiO2纳米带光催化CO2催化加氢气反应。在紫外光照射下,二氧化碳的加氢还原产物为甲烷。利用高分辨TEM,XRD,UV-Vis DRS,低温氮吸附-脱附,TG等考察了催化剂与甲烷产率的构效关系。结果表明,在600℃焙烧时得到的双晶材料具有最佳的光催化活性。优异的光催化活性主要得益于TiO2双晶脱水纳米带(DNR Bicrystalline dehydratednanoribbon)。上面形成的纳米晶界能够提高催化剂在紫外区的光吸收能力,TiO2(B)和锐钛矿独特的双晶间隔结构也提高了界面电荷分离的效率。担载贵金属Pt显著地提高了反应速率。     

Effect of TiO2 crystallite size on the dispersion of Co on nanocrystalline TiO2

Nanocrystalline TiO₂ powders with average crystallite sizes of 9–15 nm were synthesized by the solvothermal method and employed as supports for Co catalysts. The value of H₂ chemisorption/specific surface area of Co/TiO₂ increased significantly with increasing TiO₂ crystallite size. It was suggested that the higher amount of Ti³⁺ surface defects on the larger crystalline TiO₂ resulted in a stronger interaction between Co and TiO₂, hence, higher dispersion of Co was obtained.     

TiO2/SnO2复合光催化剂的耦合效应

采用改进的sol gel技术制备TiO2/SnO2耦合型半导体光催化剂,利用XRD、气相色谱 仪、粒度仪和表面光电压装置等研究了耦合型半导体光催化机理和光催化效率的影响因素, 并通过降解甲醛探讨其在空气污染治理中的作用.实验结果表明,添加20 ％(mol) SnO2的复 合半导体光催化剂,其光催化效率比纯TiO2高一倍以上.据实验结果和粒子紧密堆积原理,提 出强耦合效应和弱耦合效应的光催化反应模型,并用此模型较好地解释了TiO2/SnO2复合型半 导体光催化剂的光催化效率随SnO2含量变化规律.     

CeO2改性Ag-V2O5/TiO2催化剂的甲基吡啶氧化脱甲基性能

以锐钛矿TiO_2为载体,考察了CeO_2改性对Ag-CeO_2-V_2O_5/TiO_2催化3-甲基吡啶氧化脱甲基性能的影响,并优化了催化剂组成与制备条件.结果表明:Ce掺杂改性不仅能够与V物种作用形成Ce VO_4,而且促进V_2O_5分散,改善活性组分的氧化还原性能,从而提高3-甲基吡啶脱甲基转化率与选择性,改善Ag-V_2O_5/TiO_2催化性能.适宜的催化剂组成为V_2O_5负载量15%,Ce/V的摩尔比0.33,Ag质量分数1.0%.过高的焙烧温度将导致TiO_2载体向金红石型转变,Ag-CeO_2-V_2O_5/TiO_2适宜制备条件为450℃焙烧4 h.     

大尺寸TiO2/SiO2大孔材料的制备及光降解性能

先以三维骨架聚合物为整体型模板,利用硅酸酯原位溶胶-凝胶过程并结合高温烧结的方法制备出大尺寸大孔径的SiO2载体,然后通过钛酸丁酯溶液浸渍、原位水解、煅烧制备出大尺寸的TiO2/SiO2大孔材料并用SEM、TEM、FTIR、XRD和XPS对其表征,结果表明SiO2载体具有三维连续的超薄层,TiO2以纳米薄层方式均匀地沉积在SiO2的三维超薄层上,形成TiO2/SiO2/TiO2三层夹心结构,层与层界面存在Si-O-Ti键,同时复合结构提高了TiO2由锐钛矿相向金红石相的转变温度.以甲基橙为目标降解物考察不同条件下制备的复合材料的光催化活性,采用复合材料吸入甲基橙溶液的方式,并借助甲醇萃取手段研究光降解动力学过程.结果表明,该复合材料具有较好的光降解催化活性,当焙烧温度为600℃和TiO2的负载量为54.5wt%时,其活性最大且降解速率常数达到1.78 h-1.     

The release of TiO2 and SiO2 nanoparticles from nanocomposites

There is a growing interest in the development of nanocomposites consisting of organic polymers and TiO₂ or amorphous SiO₂ nanoparticles. These nanoparticles may be released from nanocomposites. There is evidence that amorphous SiO₂ and TiO₂ nanoparticles can be hazardous. Thus, in the design of nanocomposites with such nanoparticles, hazard reduction extending to the full nanocomposite life cycle would seem a matter to consider. Options for hazard reduction include: changes of nanoparticle surface, structure or composition, better fixation of nanoparticles in nanocomposites, including persistent suppression of oxidative damage to polymers by nanoparticles, and design changes leading to the release of relatively large particles.     

Preparation and photocatalytic activity of ZnO/TiO2/SnO2 mixture

ZnO/TiO₂/SnO₂ mixture was prepared by mixing its component solid oxides ZnO, TiO₂ and SnO₂ in the molar ratio of 4?1?1, followed by calcining the solid mixture at 200-1300 °C. The products and solid-state reaction process during the calcinations were characterized with powder X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG-DTA), UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS) and Brunauer-Emmett-Teller measurement of specific surface area. Neither solid-state reaction nor change of crystal phase composition took place among the ZnO, TiO₂ and SnO₂ powders on the calcinations up to 600 °C. However, formation of the inverse spinel Zn₂TiO₄ and Zn₂SnO₄ was detected at 700-900 and 1100-1200 °C, respectively. Further increase of the calcination temperature enabled the mixture to form a single-phase solid solution Zn₂Ti_0.5Sn_0.5O₄ with an inverse spinel structure in the space group of . The ZnO/TiO₂/SnO₂ mixture was photocatalytically active for the degradation of methyl orange in water; its photocatalytic mass activity was 16.4 times that of SnO₂, 2.0 times that of TiO₂, and 0.92 times that of ZnO after calcination at 500 °C for 2 h. But, the mass activity of the mixture decreased with increasing the calcination temperature at above 700 °C because of the formation of the photoinactive Zn₂TiO₄, Zn₂SnO₄ and Zn₂Ti_0.5Sn_0.5O₄. The sample became completely inert for the photocatalysis after prolonged calcination at 1300 °C (42 h), since all of the active component oxides were reacted to form the solid solution Zn₂Ti_0.5Sn_0.5O₄ with no photocatalytic activity.