Simple fabrication of rutile titanium dioxide whiskers

Rutile TiO₂ whiskers with a length of 30 μm and a diameter of 1.5 μm were prepared via a facile sintering technique with H₂Ti₄O₉^.0.25H₂O as a precursor under strong acidic condition. Scanning electron microscopy images showed that the whiskers have a uniform shape and a straight rod morphology with a square cross section. X-ray diffraction and transmission electron microscopy combined with a selected-area electron diffraction pattern showed that the TiO₂ whiskers are single crystalline rutile structures grown along the [002] direction and the circumferential faces have four equivalent (110) planes. Compared with rutile microparticles, rutile whiskers exhibit higher activity for the photocatalytic degradation of methylene blue.     

Anatase–rutile transformation of TiO2 sol–gel coatings deposited on different substrates

Titanium dioxide is widely used in a lot of applications. The properties of TiO₂ strongly depend on its phase composition. The transformation temperature between phases is influenced by a lot of factors. One of them is a type of substrate under the TiO₂ film. In presented work, thin films of TiO₂ were deposited by the sol–gel method on silicon, stainless steel (304 L) and Co–Cr–Mo alloy (Vitallium). The process of anatase–rutile phase transformation was investigated by Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD) studies of deposited coatings. The results were compared with anatase–rutile transformations temperature of TiO₂ powders obtained by analogous sol–gel process. The temperature of anatase–rutile phase transformation changed in the range of 700–1000 °C and strongly depends on a kind of substrate. It was found that anatase–rutile transformation of TiO₂ coating proceeded at a higher temperature than rutilization of titania powders.     

Low temperature stabilized rutile phase TiO2 films grown by sputtering

The deposition of rutile phase TiO₂ films on unheated substrates by radio frequency magnetron sputtering is elaborated. The effect of total pressure and O₂/Ar flow ratio on the growth of rutile film on different substrates has been studied thoroughly. The development of crystalline phase along with film deposition rate, surface morphology, optical transmission and band gap were also investigated for various growth conditions. It was found that the rutile phase crystallinity increased with decrease in total pressure and increase in O₂ flow. In addition, the grown rutile films have interesting optical characteristics such as high transmittance (~ 85%) and high refractive index (~ 2.7) with a band gap about 3.2 eV.     

Effect of TiO2 Crystalline Phase on Performance of Flux Assisted GTA Welds

Rutile and anatase TiO₂ fluxes were used to investigate the influence of the powdered oxides on the joint penetration ability (JPA) and solidification cracking susceptibility (SCS) in the gas tungsten arc (GTA) welding of type 316L stainless steel (SS). The mechanisms underlying the increase in JPA of GTA welds made with various crystalline phases of TiO₂ were also identified. The results indicate that GTA welding with rutile TiO₂ (R-TiO₂) or anatase TiO₂ (A-TiO₂) forms a viscous slag over the surface of the weld. The R-TiO₂ is more thermodynamically stable than the A-TiO₂, leading to a greater improvement in JPA of GTA weld made with A-TiO₂. The welding arc action can be ignored and only the convection of the molten pool should be considered in the underlying mechanism for the increase in JPA of GTA weld made with R-TiO₂ or A-TiO₂. Moreover, the TiO₂ assisted GTA welding of type 316L SS was effective in decreasing the SCS.     

工作气压对TiO2薄膜结构的影响

用射频磁控溅射方法以纯金属钛做靶材在氩氧混合气体中制备了TiO2薄膜，Raman光谱测量表明，工作气压从0．2Pa变化到2Pa时，TiO2薄膜的结构由金红石相变化到锐钛矿相，厚度对TiO2薄膜结构没有明显影响．     

河南某地金红石矿选矿研究

试验结果表明,选前脱泥对提高原矿品位,改善浮选环境、降低药耗和提高低品位细粒嵌布金红石的选矿回收率至为重要。试验发现,浮选药剂的选用和药剂间的组合搭配,对浮选结果影响也很大。中间试结果表明所选用的浮选工艺是合理的。     

金红石加碳氯化的热力学

运用HSC软件对金红石构成的多元、多相、多反应的复杂体系进行还原平衡组分的计算与分析。通过热力学计算,所得的结果表明：金红石在200℃的较低温条件下可完全转化。金红石加碳氯化反应随着温度的升高和配碳量的增加,体系中CO／CO2摩尔比值增大。只要维持理论配碳量和氯气用量,金红石即可完全转化。     

硫酸法制取金红石型钛白粉的新工艺研究

通过系统试验,用筛选出的最佳晶型转化剂直接加入到硫酸氧钛水解的产物中,在最佳工艺条件下,经过煅烧和处理后,可生产出金红石型钛白粉。该工艺可为传统硫酸法制取钛白粉技术改革提供重要依据。     

Synthesis and Characterization of Rutile TiO2 Nanopowders Doped with Iron Ions

Titanium dioxide nanopowders doped with different amounts of Fe ions were prepared by coprecipitation method. Obtained materials were characterized by structural (XRD), morphological (TEM and SEM), optical (UV/vis reflection and photoluminescence, and Raman), and analytical techniques (XPS and ICP-OES). XRD analysis revealed rutile crystalline phase for doped and undoped titanium dioxide obtained in the same manner. Diameter of the particles was 5–7 nm. The presence of iron ions was confirmed by XPS and ICP-OES. Doping process moved absorption threshold of TiO₂ into visible spectrum range. Photocatalytic activity was also checked. Doped nanopowders showed normal and up-converted photoluminescence.     

The effect of particle shape on the activity of nanocrystalline TiO2 photocatalysts in phenol decomposition

Nanosized TiO₂ photocatalysts were synthesized via hydrogen–air flame hydrolysis. X-ray diffraction (XRD) measurements revealed that the TiO₂ samples thus prepared consisted mainly of anatase (79–98 wt%) and the rest is rutile. Average particle diameters from TEM measurements were found to vary between 48 and 63 nm. The specific surface area of the samples was found to be practically independent of the synthesis parameters employed (20–32 m² g⁻¹). Photocatalytic activity of the catalysts was studied by using various model compounds. In spite of their very similar properties, the initial decomposition rate of phenol and methanol showed up to threefold variations within the series of the samples, and it was significantly higher for the best catalyst than that determined for Degussa P25. Our TEM measurements demonstrated that in the less active catalysts the dominant morphology of the particles is spherical, while polyhedral (cubic or hexagonal) shapes predominate in the samples with superior photocatalytic activity. From these observations, we concluded, that the shape of the primary particles (both in the case of our home made ones and in various batches of Degussa P25) strongly influence the photocatalytic activity of titania nanoparticles.