Papers by Keyword: Sol-Gel Process

Abstract: P-doped titania was synthesized by a one step hydrothermal method and sol-gel method, which is characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The samples prepared by hydrothermal method demonstrate higher photocatalytic activity toward the degradation of methylene blue under xenon lamp which has similar spectra to solar light, and also is much superior to that of the commercial P25. The as prepared P-doped titania shows a small particle size (the minimum reaches to 4.5 nm). In addition, the samples prepared by hydrothermal treatment could severely influence the crystal lattice structure. Morever, P-doped titania can further enhacnce the photocatalytic activity effectively, and hydrothermal treatment is a very suitable method for the synthesis of P-doped titania. This excellent performance could endow the as-prepared P-doped titania potential in purifying wastewater.

Abstract: Pb_0.97La_0.02Zr_0.95Ti_0.05O₃ (PLZT) antiferroelectric thin films were prepared on Pt (111)/ Ti/SiO₂/Si (100) substrates by a sol-gel process. The influences of annealing temperature on the structures and dielectric properties of the PLZT antiferroelectric thin films were investigated. And the phase structure and crystal orientation were studied by X-ray diffraction analyses (XRD). The antiferroelectric characterization of the PLZT thin films annealed at different temperature was demonstrated by P(polarization)-E(electric field) and C(capactitance)-E(electric field) curves. The maximum polarizations for the films annealed at 650°C, 700°C and 750°C were 35μC/cm², 42μC/cm² and 47μC/cm², respectively. The temperature dependent of the dielectric constant and loss was measured under the frequency 1, 10, 100 and 1000 kHz. The films annealed at 700°C have high (100)-preferred orientation and excellent dielectric properties.

Abstract: In order to improve the barrier property of the biaxially oriented polypropylene (BOPP) film, the PVA/SiO₂ organic-inorganic hybrid coating on BOPP film was prepared by the sol–gel method. And the structure and properties of the hybrid composite films were characterized. The results showed that, the oxygen barrier property of the composite films was enhanced with the increase of PVA content, while the water vapor barrier property of the composite films was dropped. As the mass ratio of PVA increased to 80%, the oxygen barrier property of the composite films was 308 times that of the pure BOPP film, however, water vapor barrier character was half of the BOPP film.

Abstract: A novel copper and phosphorus codoped TiO₂ photocatalyst was synthesized by modified sol–gel method using tetrabutyl titanate, Cu(NO₃)₂ and H₃PO₄ as precursors. The samples were characterized by XRD, TEM, TGA, EDX. The TGA indicated the calcination temperature is 450°C. The XRD results showed undoped and Cu, P-codoped TiO₂ nanoparticles only include anatase phase, and the temperture of crystalline phase transform for Cu, P codeped TiO₂ had changed compared with undoped. The TEM analysis revealed the doping of Cu and P suppressed the growth of TiO₂ grains. The photocatalytic activity of samples was tested for degradation of 20 mg·L⁻¹ methyl orange (MO) solutions. The results showed photocatalytic activity of the catalysts with 0.5% Cu, 0.375% P-codoped TiO₂ was higher than pure TiO₂ under ultraviolet (UV).

Abstract: TiO₂ and Sn⁴⁺-doped TiO₂ were prepared by sol-gel method and characterized by the techniques such as XRD, SEM and DRS. The photocatalytic degradation of methylene blue (MB) in aqueous solution was used as a probe reaction to evaluate their photocatalytic activity. The matrix distortion of TiO₂ increases after Sn⁴⁺ doping and a blue-shift of the absorption profile are clearly observed. The results show that doped Sn⁴⁺ inhibits the phase transformation of TiO₂ from anatase to rutile, decreases the diameter of TiO₂ and significantly enhance the photocatalytic activity of TiO₂. The Sn⁴⁺-doped into TiO₂ exert a synergistic effect on their photocatalytic activity.

Abstract: Using tetraethoxysilane, aluminum nitrate and aluminum fluoride as raw materials, the precursor of mullite was prepared by sol-gel process. When the precursor sintered at 1200°C, mullite ceramic was obtained. Differential thermal analysis, X-ray powder diffraction and scanning electron microscope were used to characterize the dried mullite gel and ceramic blocks. The results suggest mullite is synthesized by solid-phase reaction mechanism. X-ray powder diffraction indicates mullite is the main crystals phase in the ceramic specimen. SEM micrograph shows the mullite grains in the shape of short rod with length of 20 um when sintered at 1200 °C for 2 h and the grains grown up to acicular with length of more than 50 um when the treating time under 1200 °C achieved to 4 h.

Abstract: . A series of gels with 3Al2O3•2SiO2 were prepared by Sol-gel method and heated at several temperatures for 2 h to synthesize Ti, Fe-doped mullite. The received powers with highest amount of TiO2 and Fe2O3 additive in range of 3.7-5.6 % and 12.5-15.9 % respectively as starting materials were characterized using X-ray powder diffraction (XRD), scanning electron microscopies (SEM) and energy dispersive spectrometry(EDX). Fe3+ and Ti4+ cation has been incorprated into the crystal lattice of mullite unevenly. The overall trend of Ti, Fe-doped mullite powers with additive amount changing is Δa>Δb>Δc(Except sample 5.6Ti-1350 is Δb>Δa>Δc owing to its excess amount of TiO2), and the relative change of Ti, Fe-doped mullite powers is Δc（%）>Δb（%）>Δa（%）(Except sample 5.6Ti-1350 and 15.9Fe-1350 is Δb（%）>Δc（%）>Δa（%） with the maximum amount of dopant ions).

Abstract: A series of gels with 3Al2O3•2SiO2 were prepared by Sol-gel method and heated at several temperatures for 2 h to synthesize Ti, Fe-doped mullite. The powers were characterized by differential thermal analysis (DSC-TG) and X-ray powder diffraction (XRD). Phase separation was promoted by doping both TiO2 and Fe2O3; with increasing the amount of dopant ions the formation temperature of Si-Al spinel decreased and the formation temperature of mullite increased by TiO2 doping but decreased by Fe2O3 doping. The formation temperature of pure mullite was about 1250-1350 °C.

Abstract: TiO₂ can be used as a photocatalyst because of its semiconductor property. When TiO₂ is doped with transition metal ions, its electronic properties may be modified. In this work, nanosized Sn⁴⁺-doped TiO₂ (TiO₂-Sn⁴⁺) particles have been synthesized by a sol-gel process at different temperature. Their microstructure and crystal structure depending on the calcination temperatures were investigated using XRD and SEM techniques. The photocatalytic degradation of diesel pollutants in seawater was investigated by using Sn⁴⁺-doped nanometer TiO₂ under UV irradiation. In the experiment, the effect of different ratio of Sn⁴⁺ doped into TiO₂, the effect of calcination temperature of Sn-doped nano-TiO₂, the effect of Sn⁴⁺-doped nanometer TiO₂ dosage, pH value and photocatalytic degradation reaction time, respectively, on the removal of diesel pollutants in seawater was investigated. On the basis of the results of these experimental data, the optimal experimental conditions for photocatalytic degradation of diesel are tried through the orthogonal test. The results reveal that when the ratio of Sn⁴⁺ doped into TiO₂ was 3% wt, the calcination temperature of Sn-doped nano-TiO₂ was 400°C, the Sn⁴⁺-doped nanometer TiO₂ dosage was 1 g/L, pH value was 8 and photocatalytic degradation reaction time was 1.5h, respectively, the removal rate of diesel pollutants in seawater was expected to reach 88.00 %.

Abstract: Li₂O-Al₂O₃-P₂O₅-SiO₂ xerogel powders were synthesized by sol-gel route and glass-ceramics were prepared under different forming pressure and sintering temperature. The effects of sintering temperature and forming pressure on coefficient of thermal expansion of prepared glass-ceramics were investigated by means of DTA-TG, TEC and XRD. The results indicate that xerogel powders crystallization begins at 785°C, and the main crystallite phases in the researched specimens are virgilite and cristobalite. The TEC decreases linearly with the forming pressure. When the sintering temperature is 950°C and forming pressure is 40MPa, a low TEC of 0.65×10^-6 °C^-1 can be obtained.