Papers by Keyword: Rutile TiO₂

Abstract: In this paper, a simple and pollution-free low temperature hydrothermal method for preparing rutile phase TiO₂ film was proposed. When TiCl₄ solution hydrolyzed in ice-water mixed DI water, rutile TiO₂ can be prepared at a low temperature 70 °C, which is much lower than those of conventional Sol-Gel methods and hydrothermal process. XRD was carried out to analyze the crystal structure and confirmed the TiO₂ film we prepared was pure rutile phase. The surface morphology was characterized using AFM. And XPS was also carried out to illustrate the chemical state of the elements.

Abstract: Effects of annealing treatment on growth of rutile TiO₂ nanorods on structural, morphological and optical properties of TiO₂ nanorods were investigated. The nanorods were fabricated on p-type (111)-oriented silicon substrates and, all substrates were seeded with a TiO₂ seed layer synthesized by radio-frequency reactive magnetron sputtering system. Chemical bath deposition (CBD) was carried out to grow rutile TiO₂ nanorods on Si substrate at different annealing temperatures (350, 550, 750, and 950 °C). Raman spectroscopy, X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) analyses showed the tetragonal rutile structure of the synthesized TiO₂ nanorods. Optical properties were examined by photoluminescence spectroscopy. The spectra exhibit one strong UV emission peak which can be seen at around 390 nm for all of the samples. In the visible region, TiO₂ demonstrated two dominant PL emissions centered at around 519 and 705 nm. The experimental results showed that the TiO₂ nanorods annealed at 550 °C exhibited the optimal structural properties. Moreover, the CBD method enabled the formation of photosensitive, high-quality rutile TiO₂ nanorods with few defects for future optoelectronic nanodevice applications.

Abstract: Sintering reactions and fine structure of a biocomposite fabricated from hydroxyapatite (HA) powder, glass-ceramic (GC) powder and titanium mesh by dip coating method were investigated. A dense GC coating was initially deposited onto 3D Ti-mesh, which is to seal off the Ti-mesh. Then, a microporous HA-GC coating was deposited on the top of the dense GC coating to promote bone regeneration. Interfacial reactions play the key role for the coatings/substrate adhesion. During the fabrication process, the Ti substrate reacted with O₂ and produced the TiO₂ (rutile phase). Ti_xSi_y was detected in the GC coating/Ti substrate interfacial region. The average bonding strength between dense GC coating and Ti substrate was 27.1 MPa.

Abstract: In order to apply nanofluids to ammonia-water absorption refrigeration, several groups of nanofluids mixing with rutile TiO₂(r-TiO₂) and ammonia-water were perpared by an optimizing method. Observation tests were carried out to investigate the effects of the kind and mass fraction of dispersant, mass fraction of ammonia-water basefluid and durations of supersonic vibration on the dispersion stability of nanofluids. The results show that, all three factors have influences on the dispersion. The optimal dispersing condition of 0.1wt% r-TiO₂ nanofluids was 0.1% of PAA in 25% ammonia water basefluid with 10 minutes of ultrasonic vibration.

Abstract: Rutile Ti_1xSn_xO₂ (0.2x<1) solid solutions had been prepared using a sol-hydrothermal method, which combined the conventional sol-gel process with hydrothermal method. Hybrid alkoxides of Ti⁴⁺ and Sn⁴⁺ were used as precursors in the sol-gel process and Sn⁴⁺ served as crystal-inducing agent during the formation of rutile crystal lattice in the hydrothermal process at 200°C. The microstructures and morphologies of nanoparticles were detected with XRD and TEM. Rutile Ti_1xSn_xO₂ solid solutions nanoparticles with well-distributed crystallite sizes about 10nm were obtained with Sn⁴⁺ content above 20mol% without any high temperature calcination. The oxygen sensitivity properties of Ti_1xSn_xO₂ solid solutions had also been investigated. It is proved Ti_1xSn_xO₂ solid solutions exhibited higher oxygen responses than single TiO₂ or SnO₂. A typical sample of Ti_0.5Sn_0.5O₂ presented the best sensitivity is approximately 6 under 400°C.

Abstract: A new methodology was developed to synthesize uniform rutile TiO₂ nanorods. Rutile (TiO₂) nanorods of length L200-300nm and diameter D15-20nm have been synthesized through a seed-mediated growth process by the additional thermohydrolysis of SnCl₄ in concentrated acid aqueous solutions. The XRD show that the additional SnCl₄ can accelerate the crystallization of the rutile due to the SnO₂ acted as the nuclear, avoiding the slow processing of self-nucleation of the rutile TiO₂. The HRTEM suggest that the crystal growth is preferential in the [11 direction resulting the formation of rod-like nanocrystals.

Abstract: The crystal structure, electronic structure and ferromagnetic properties of the transition metals M (where M=Co, Ag) doped rutile TiO₂ are studied by using first-principles calculations based on the density functional theory (DFT) and projector augmented wave (PAW) pseudo-potentials (PP) method. In the doped system M₂Ti₁₄O₃₂, the two doping atoms tend to align along c axis in the stablest configuration state. When M represents Co atom, the ferromagnetic state is favorable with magnetic moments of 0.99μB per Co atom, while Ag₂Ti₁₄O₃₂ has no magnetic moment. Doping atoms induce new energy level, which reduces band gap, decreases Fermi energy level and thus considerably affects the optical absorption and photocatalytic activities of TiO₂ under visible light irradiation.

Abstract: A single-step sonochemical method to directly prepare rutile nanocrystal TiO₂ has been developed. TiO₂ nanaoparticles were synthesized by the hydrolysis of TiCl4 in the presence of water and ethanol under ultrasonic irradiationat 70 °C for 3 h. The crystalline forms and crystallite sizes of the produts were characterized by X-ray diffraction, transmission electron microscopy and thermogravimetry-differential thermal analysis. The TEM images showed the morphology of as-prapared TiO₂ was pinnate in shape and the average sizes were ca. 4/12 nm (W/L). The columnar particles were linked together each other at the certain principle, forming the shape like dendrite crystal. The formation mechanism of the dendrite crystal nanocrystalline TiO₂ was also discussed.