水热法制备稀土掺杂TiO2薄膜及光催化降解性能研究

采用水热法,以载玻片为基片制备了稀土掺杂Ti O2薄膜。以紫外光区吸光度值为指标,确定最佳制备条件为:90℃保温2h,Ti(SO4)2溶液和尿素溶液摩尔比为10∶1,稀土掺杂量为1 mL0.5 mol/L稀土盐溶液,掺杂稀土镧Ti O2薄膜有较好的光吸收性能。利用X-射线粉末衍射法(XRD)、扫描电子显微镜(SEM)及电子能谱法(EDS)对Ti O2薄膜的结构及表面特性进行表征,结果表明制备的稀土掺杂Ti O2薄膜为锐钛矿型。以紫外灯为光源,降解率为指标,罗丹明B溶液降解为模型反应,考察稀土掺杂Ti O2薄膜光催化性能,结果表明,稀土掺杂Ti O2薄膜具有较高光催化活性且明显大于纯Ti O薄膜,该薄膜对罗丹明B的光催化降解率达87%以上。     

Photocatalytic reduction of NO with NH3 using Si-doped TiO2 prepared by hydrothermal method

A series of Si-doped TiO2 (Si/TiO2) photocatalysts supported on woven glass fabric were prepared by hydrothermal method for photocatalytic reduction of NO with NH3. The photocatalytic activity tests were carried out in a continuous Pyrex reactor with the flow rate of 2000mL/min under UV irradiation (luminous flux: 1.1x10(4)lm, irradiated catalyst area: 160cm2). The photocatalysts were characterized by X-ray diffraction (XRD), BET, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) spectrophotometer, transmission electron microscopy (TEM), photoluminescence (PL) and temperature-programmed desorption (TPD). The experiment results showed that NO conversion on Si/TiO2 at 323K could exceed 60%, which was about 50% higher than that on Degussa P25 and pure TiO2. With the doping of Si, photocatalysts with smaller crystal size, larger surface area and larger pore volume were obtained. It was also found that Ti-O-Si bands were formed on the surface of Si/TiO2 and that the surface hydroxyl concentration was greatly increased. As a result, total acidity and NH3 chemisorption amount were enhanced for Si/TiO2 leading to its photocatalytic activity improvement.     

Photocatalytic ozonation of dimethyl phthalate with TiO2 prepared by a hydrothermal method

TiO(2) was prepared by a hydrothermal method at a low temperature and used to degrade and mineralize dimethyl phthalate (DMP). TiO(2) was characterized by XRD, TEM, BET and UV-vis techniques. The characteristics of TiO(2) prepared by a hydrothermal method (h-t TiO(2)) included a good crystalline anatase phase, greater surface area, stronger absorption to UV light wavelength and lower agglomeration than TiO(2) prepared by a classic sol-gel method (s-g TiO(2)). The photocatalytic activity of h-t TiO(2) prepared under optimal hydrothermal condition (180°C for 10h) was 2.5 times higher than that of s-g TiO(2) in degrading DMP. The process of photocatalysis combined with UV irradiation and ozonation (TiO(2)/UV/O(3)) considerably improved the mineralization and degradation of DMP compared to photocatalysis combined with UV irradiation (TiO(2)/UV), ozonation combined with UV irradiation (UV/O(3)), and ozonation alone (O(3)). A kinetic study showed the mineralization in TiO(2)/UV/O(3) followed the Langmuir-Hinshelwood model.     

Template-free hydrothermal synthesis of macroporous TiO2 microspheres on a large scale

Macroporous TiO₂ microspheres have been synthesized on a large scale by a facile hydrothermal process using titanium tetrachloride (TiCl₄) as the titanium source, ammonium fluoride (NH₄F) and hydrogen peroxide (H₂O₂) as the etchant. X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscope (TEM) studies show that the anatase TiO₂ microspheres are well-crystalline with an average diameter of 5.43 μm. N₂ adsorption–desorption and mercury intrusion porosimetry analysis reveal that the as-prepared TiO₂ microspheres are composed of numerous pore networks with an average pore diameter of 274 nm and porosity of 39.8%. In addition, the formation mechanisms of macroporous TiO₂ microspheres were also investigated.     

用水基憎水剂在预处理的金属表面制备超憎水膜

探讨了一种新型水基憎水剂的制备和成膜工艺,并分析了预处理金属表面超憎水膜的形成机理.将这种以聚四氟乙烯和硅溶胶为基础组分的水基憎水剂在化学镀镍膜和磷化膜上进行憎水处理,与工业上常用的有机硅氧烷类憎水剂进行对比,表明这种憎水剂获得的膜层具有憎水效果优异、附着力好、耐磨性好、制备工艺简单等优点.利用扫描电镜、接触角测试仪等对这种憎水膜层的微观形貌和成分、憎水角等进行了表征分析.结果表明,这种水基憎水剂在化学镀镍膜和磷化膜表面形成憎水膜层的憎水角分别为155～157°和146～148°,膜层增重分别为0.81和0.54mg/cm2.     

Microemulsion-mediated hydrothermal synthesis of photocatalytic TiO2 powders

A reverse microemulsion-mediated hydrothermal route has been employed to synthesize photocatalytic titanium dioxide (TiO2) powders. Nano-crystalline monophasic anatase TiO2 powders were successfully prepared when the microemulsion-derived precursors were hydrothermally treated. The advantage of using this microemulsion mediated hydrothermal route is the significant reduction in reaction time and temperatures as compared with the conventional hydrothermal process. The oil/water emulsion ratio significantly affected the particle sizes of the obtained TiO2 powders. The specific surface area of TiO2 powders was increased with the oil/water ratio, thereby leading to enhanced photocatalytic activity of TiO2 powders. As the hydrothermal temperature was elevated, the morphology of the TiO2 particles changed from a rod-like shape into a polyhedral shape. The variation in microstructures decreased the specific surface area of the TiO2 powders and lowered the photocatalytic activity.     

Photovoltaic enhancement of nanostructured boron-doped rutile phase TiO2 nanorods via facile hydrothermal method

Journal of Materials Science: Materials in Electronics - Several doping processes are being investigated for the enhancement and efficient utilization of TiO2 properties with increased focus on the...     

Synthesis and characterization of highly dispersed TiO2 nanocrystal colloids by microwave-assisted hydrothermal method

Anatase TiO₂ nanocrystal colloids with high dispersion and photocatalytic activity were rapidly synthesized from peroxo-titanium-acid precursor by microwave-assisted hydrothermal method within 30?min at low temperature (120–180?°C). The transmission electron microscopy results indicate that the as-prepared TiO₂ have a narrow particle size distribution (25–29?nm) and high dispersion. The crystal structure of all these products are pure anatase phase (XRD, Raman), and they show good crystallinity and large surface area (N₂ adsorption–desorption measurements BET). The results of the UV–Visible absorbance and Fourier transform infrared spectra indicate that the surface peroxo group Ti(O₂) still remains in TiO₂ nanoparticles prepared by microwave-assisted hydrothermal method at 120?°C, and this surface peroxo group can be decomposed effectively by drying at 140?°C. The photocatalytic activity of the as-prepared TiO₂ were evaluated by the degradation of reactive brilliant red X-3B, it is found that the as-prepared TiO₂ exhibited good photocatalytic performance. Moreover, the existence of surface peroxo group greatly suppressed the photocatalytic activity of the TiO₂ nanoparticles.     

TiO2 supported on SiO2 photocatalysts prepared using ultrasonic-assisted sol-gel method

TiO₂-SiO₂ (TiO₂ supported on SiO₂) photocatalysts were prepared using an ultrasonic-assisted sol-gel method. These photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and photoluminescence spectra (PL). Their photocatalytic activities were investigated by the method of methyl orange oxidation. It was found that the photocatalytic activity of TiO₂-SiO₂ was optimal when the molar ratio of hexadecyl trimethyl ammonium bromide to titanium butoxide was 1:10. The average crystallite size of TiO₂-SiO₂ was smaller than that prepared by the stirring method. Furthermore, for pure anatase phase samples, it was shown that the lower the photoluminescence intensity, the higher the photocatalytic activity.     

Prolonging the combustion duration of wood by TiO<Subscript>2</Subscript> coating synthesized using cosolvent-controlled hydrothermal method

Thin TiO₂ coating was grown on wood surface using a cosolvent-controlled hydrothermal method. The surface morphology, chemical composition, and functional groups were examined by the scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDXA), and Fourier transform infrared spectroscopy (FTIR), respectively. The crystalline phase of TiO₂ was investigated by the X-ray diffraction (XRD). The combustion test was carried out on the Dual Analysis Cone Calorimeter, according to the fire testing standard ISO 5660-1. Resulted from the combined analysis of SEM and EDXA, FTIR and XRD, it was demonstrated that the anatase TiO₂ layer accompanying some spheral morphology chemically bonded to wood surface with intact and smooth appearance. The significant differences in combustion parameters between the untreated and the TiO₂ coated wood were observed. In comparison to the untreated wood, the burning time of TiO₂ coated wood was doubled, and the smoke, CO, CO₂ emissions were markedly reduced. As a result, the TiO₂ coating can effectively act as a protective layer to prolong the combustion duration of wood and prevent the harmful gas from spreading.     

水热法制备板钛矿型TiO2纳米材料

0.15mol/L TiCl3的饱和NaCl水溶液加添加剂尿素(尿素/Ti3 摩尔比为1:10)用水热法170℃下反应4h在玻璃基板上制备了TiO2纳米材料(粉末和薄膜),SEM和XRD技术表征结果说明,生成的TiO2为板钛矿型晶体,TiO2粉末是由TiO2纳米棒自组装成的微米球,薄膜则是大面积纳米棒阵列形成.探索了制备TiO2纳米材料的最优条件,并讨论了反应机理.     

以偏钛酸为原料常压水热法合成纳米钛酸钡的研究

系统地研究了以廉价的偏钛酸为原料,经常压水热法一步合成钛酸钡.通过考察不同的钡钛比,反应温度,反应时间,溶液pH等条件下反应产物在浓盐酸溶液中的透射比的变化,得出了最佳的制备条件.当反应原料的钡钛比为1.4,反应温度是100℃,反应时间为6 h,溶液pH为12,所制备出的钛酸钡粉体为立方相,a值约为4.030,粉体一次平均粒径为40.9 nm.     

Synthesis of TiO2-based nanotube on Ti substrate by hydrothermal treatment

TiO2-based titanate nanotube film was directly synthesized by hydrothermal treatment of Ti substrate in NaOH solution. The prepared high aspect ratio nanotubes have diameter of 10 nm and pore size of 5 nm with length of several microns. The nanotubes show the same structure and component characteristics as the nanotubes prepared through hydrothermal treatment of TiO2. Other nanostructured titanate as oriented nanofiber film and translucent film were also prepared by adjusting the hydrothermal conditions. The formation mechanism of nanostructured titanate was discussed.     

Growth and properties of ZnO nanowires synthesized by a simple hydrothermal method

Hexagonal ZnO nanowires were synthesized on pre-seeded silicon (100) substrates by a simple hydrothermal method at a relatively low temperature of 95 °C without any catalyst or template. The pre-seeded layer was produced using the sol–gel spin coating technique with 1 M zinc acetate in ethanol and ethanolamine. The structural properties of the nanowires were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD pattern indicated that the as-grown ZnO nanowires had the single-phase wurtzite structure, formed along the c-axis. SEM revealed that the nanostructure thin film had wire textures and the synthesis processes importantly influence the final size and shape of the ZnO nanowires. High-resolution transmission electron microscopy (HRTEM) provided further insight into the structure of ZnO nanostructures. The obtained HRTEM image was of the tip of an individual nanowire. The ZnO nanowires highly preferentially grew in the (002) crystal plane. The lattice spacing between adjacent (002) lattice planes was calculated to be 0.52 nm. The optical characteristics of the nanowires were determined from cathodoluminescence (CL) spectra. The CL revealed a fairly high surface state density of ZnO nanowires that grew at reaction concentrations of 0.01–0.25 M.     

Effect of Ag doping on structural, electrical and dielectric properties of TiO2 nanoparticles synthesized by a low temperature hydrothermal method

Silver (Ag) doped thermally stable TiO₂ nanoparticles in the anatase phase have been synthesized by a low temperature hydrothermal method. The formation of anatase phase has been investigated by X-ray diffraction. Thermogravimetry and differential scanning calorimetry have been used for thermal studies. Scanning electron microscopy, transmission electron microscopy and energy dispersive spectroscopy have been used for the morphology and composition studies. Surface areas were studied by the Brunauer-Emmett-Teller method. Dielectric properties were studied for dopant levels of 0.25, 0.5 and 1.0?wt% at 300?K in the frequency range of 42?Hz–5?MHz. The crystallite size, alternating current (AC) conductivity and dielectric properties of undoped TiO₂ nanoparticles were greatly affected by doping with Ag. At high frequencies, the materials showed high AC Conductivity and low dielectric constant.     

Synthesis of higher surface area mayenite by hydrothermal method

Mayenite (Ca₁₂Al₁₄O₃₃) is an important material, being used as a transparent conductive oxide (TCO), catalysts for VOCs cleaning and ionic conductor. Unfortunately, the material has a very low BET surface area, generally below 10 m²/g and requires higher calcination temperature for the formation of mayenite phase. In this study, a new synthesis method, namely hydrothermal method, was employed for the synthesis of mayenite with higher BET surface area of about 70 m²/g, and also the calcination temperature decreased from over 1000 to just 400 °C. It was found that mayenite from different method shows different shapes.     

Growth and characterization of hydroxyapatite crystals by hydrothermal method

Hydroxyapatite crystals were grown by hydrothermal method using dicalcium phosphate dihydrate crystals as a starting material. The grown crystals were found to be free from carbonate inclusion. Two distinct morphologies were obtained by following two different growth methods. Controlled slow growth process and rapid growth process results in hexagonal and whisker like morphologies.