Papers by Keyword: Sol-Gel Method

Abstract: In this work, the Sol-Gel dip-coating technique is used to report the effect of thickness and annealing temperature on structural and optical properties of TiO₂ thin films. To study the effect of the annealing temperature, the prepared samples were annealed at different temperatures: 300, 400, and 500 °C for 1 h. By increasing the annealing temperature, an amelioration of the crystalline quality is observed. The best crystalline quality was obtained at 500 °C. Additionally, the band gap value E_g, evaluated from transmission spectra, does not vary with the increasing of the annealing temperature. All the films with different thicknesses present crystalize in the Anatase structure, and the crystallite size value does not practically change with thickness increase. It was also found that the TiO₂ film band gap value decreases with the film thickness increase, demonstrating the possibility of band gap tuning by varying the TiO₂ film thickness.

Abstract: This work is focused on the preparation and characterization of poly (vinyl alcohol)/silica gel/Nano-TiO₂, and the study of titanium dioxide (TiO₂) nanoparticles (from 1 to 5%) on the properties of poly (vinyl alcohol) (PVA)/silica films. This new material was prepared by the sol-gel method using poly (vinyl alcohol) powder with Tetraethyl Orthosilicate (TEOS) as a precursor source of silica. TEOS was hydrolyzed and condensed in water and ethanol in the presence of hydrochloric acid (HCl) used as a catalyst. Fourier transform infrared (FT-IR), water absorption, water contact angle, ultraviolet-visible spectrometry (UV-VIS), and thermogravimetric analysis (TGA) were used to characterize the hybrid films obtained. The PVA/SiO₂/Nano-TiO₂ films were successfully synthesized. Owing to the FT-IR Analysis, the chemical bonds have clearly shown that the PVA backbone is linked to the (SiO₂-TiO₂) network. UV-VIS tests indicated that the hybrid films' UV shielding properties were drastically enhanced as a result of the addition of TiO₂. According to the TGA tests, the hybrid films are more heat tolerant than neat PVA films. The water contact angle results revealed that TiO₂ nanoparticles used as a doping compound possess an important influence on the hydrophilicity of PVA/SiO₂ as thin films. The film's water resistance has also been enhanced.

Abstract: Industries such as electroplating, mining etc. produce wastewater that, as it includes various heavy metals such as lead, cadmium, has a potential threat to our environment. If this wastewater is left untreated, soil and water supplies would be polluted. The release of heavy metals into the natural world, has resulted in a number of heavy metals that can cause serious harm to humans and marine life even at trace levels. Thus, this research address the synthesis of oil palm frond (OPF) based mesoporous silica nanoparticle (MSN) which intended for the removal of heavy metal. The MSN were synthesised from OPF via sol-gel method and later utilised as adsorbent to removed lead (Pb) from the aqueous solution. The FTIR results of OPF-based MSN exhibit similar peak with commercially available silica. The MSN adsorbent was then investigated for Pb removal under different parameter including pH, contact time, dosage, concentration, and temperature and analysed using Atomic Absorption Spectroscopy (AAS). The optimum condition was obtained at pH 7, 45 mins of contact time, 0.4 g/L adsorbent dosage under 10 ppm of Pb concentration at 303 K that aid in enhancing Pb removal by the OPF-based MSN. At this condition, MSN successfully removed up to 89% of Pb in aqueous solution with adsorption capacity of the adsorbent is within the range of 22.3 mg/g. This result demonstrates the potential application of MSN from OPF as an adsorbent in Pb removal from wastewater.

Abstract: Dispersions of molybdenum-tungsten blues are promising precursors for the preparation of carbide catalysts by the sol-gel method. Stable systems were synthesized using ascorbic acid as a reducing agent at various molar ratios (Mo) :( W) = 100; 95: 5; 90:10; 80:20; 50:50. To study the properties of colloidal systems, UV / Vis spectroscopy, dynamic light scattering and electrophoretic light scattering were used. It was found that molybdenum-tungsten blue particles with different molar ratios of molybdenum and tungsten have a constant hydrodynamic radius equal to 2.0 nm. In the pH range (0.8 - 3.0) molybdenum-tungsten blue particles are negatively charged; the absolute values of the ζ-potential do not exceed 25 mV.

Abstract: The effect of fire-retardant compositions based on organo-inorganic SiO₂ sols without the use of flame retardants on increasing the fire resistance of cotton-containing textile materials has been studied. Previous studies have shown that the combined use of silicate coatings and flame retardants of simple structure prevents the ignition of impregnated samples of cotton-containing fabric and the proposed chemistry of this process. These studies did not use flame retardants to obtain more information on the effect of the composition and concentration of experimental organo-inorganic SiO₂ sols on the fire resistance of treated tissues. The compositions were prepared by the sol-gel method using a technical product – liquid glass – with a silicate modulus of 2,5 and acetic acid solution. The influence of sols concentration in terms of conditioned SiO₂ on their rheological features has been studied. It was found that the optical density, fluidity and survivability of experimental sols depend on the concentration of SiO₂ in the sol. The compositions were applied to the fabric by the bath method in layers: each layer of the coating was fixed on the surface of the fabric by thermal shock in an oven at temperatures of 80-100 °C. Untreated cotton fabric caught fire under the influence of fire after 7 seconds. Impregnated tissue samples did not ignite under the action of fire, but gradually charred. To determine the effect of coating thickness and SiO₂ concentration in the sol on the fire resistance of impregnated fabric samples, fire tests at a gas pressure of 0,2 MPa were performed for 8 s and the area of damage to the reverse side of the fabric was determined. Prolonged exposure to the flame resulted in a crack in the center of the charred spot. In the absence of flame retardants in the fire-retardant composition after removal of the fire source, decay was observed. The time for which a crack is formed in the sample under the action of fire was determined at the time of onset of tissue destruction. It is shown that in the case of using a sol of 10% concentration it is necessary to apply three layers of coating, which doubles the fire resistance (from 7 s for untreated fabric to 15 s for impregnated fabric), the start time of destruction increases 5 times (from 1 min to 5,5 min). The area of damage to the reverse side of the fabric not treated and impregnated with the experimental coating is reduced from 632 mm² to 0, respectively.

Abstract: Sea urchin zinc oxide (SU-ZnO) nanostructures were successfully synthesized using the sol-gel method and characterized by various analytical techniques. The present work reports a facile and straightforward route for synthesizing sea urchin ZnO nanostructures consisted of self-assembled ZnO nanorods with sharp tips yielding the sea urchin-like shape. The SU-ZnO nanostructures were characterized using Scanning electron microscopy and Energy dispersive X-ray spectroscopy (SEM-EDS), Fourier transform infrared (FTIR) spectroscopy, particle size analysis (dynamic light scattering technique), and ultraviolet-visible (UV-vis) spectroscopy. The result of energy dispersive X-ray spectroscopy shows that the SU-ZnO nanostructure contains 77.30% zinc and 22.70% oxygen content. Scanning electron microscopy shows that the synthesized ZnO exhibits a sea urchin-like structure with a homogeneous and consistent size. FTIR spectroscopy confirmed the structural features and functional groups that are present in ZnO nanostructures. The particle size analysis shows that the synthesized SU-ZnO nanostructures have an average particle size of 812.62 ± 55.92 nm. The growth of SU-ZnO nanostructure was also investigated by recording the UV-Vis absorption spectra at different reaction times.

Abstract: Heterogeneous fenton , although offering promises for large scale wastewater treatment, is still hindered in its practicality due to its modest catalytic activity. The usage of catalyst supportas been demonstrated previously toecrease the overall particle size to improve its catalytic performance. In this demonstration, fenton catalysts were prepared using the sol-gel method and bacterial cellulose (BC) as catalyst support, with varying sodium hydroxide (NaOH) concentrations (0.01; 0.1 and 1 M). NaCl impurities' presence was successfully eliminated by reducing NaOH concentration relative to the previous 4 M concentration. Lower NaOH concentration leads to a more favorable condition for the formation of smaller non-agglomerated particles and magnetite (Fe₃O₄) as its main crystalline phase. It was found that the best performing catalyst was produced using 1 M NaOH and was able to degrade Methylene blue solution up to 53.8% remaining dye concentration within two hours.

Abstract: Nanoparticles of La₂CuO₄ (LCO) with different particles and crystallite size have been synthesized by the sol-gel method. The samples have been sintered at 600, 650, and 700°C. The sintering process have been performed in atmospheric pressure and vacuum pressure. The structural and morphological properties of the samples have been investigated by the X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), and Transmission Electron Microscope (TEM). The XRD patterns of the samples have shown that all samples crystallize in orthorhombic structure with Bmab space group. Additionally, Rietveld refinement process have shown that higher sintering temperature, as well sintering process under vacuum pressure, can improve both phase purity and the crystallinity of the samples. SEM and TEM results have also shown that higher sintering temperature results in a sample with larger particle size.

Abstract: ZnO:Graphene Oxide composite nanopowders have been successfully prepared by sol-gel method. The study of composite preparation is discussed in this paper. Graphene oxide was added in two ways in order to study the mixed behaviour especially in photocatalytic properties. The degradation of methylene blue (MB) concentration in water was used to evaluate the photocatalytic property under low UV-light irradiation (14 μW/cm²). The results showed that all varian ZnO-GO composite samples have spherical morphology and hexagonal wurtzite crystal structure. An addition of graphene oxide (GO) in ZnO precursor solution during preparation shows a better photocatalytic property that related to reducing in particle size, thereby produce a large surface area and formed a better interfacing with GO/rGO. The existence of GO around ZnO nanoparticles gives some advantageous due to presences of hydroxyl component that directly relate to the increments in photocatalytic behavior. The photodegradation rate of MB in water using ZnO-GO composite as catalyst is significantly increase compared with pure ZnO.

Abstract: The article presents the results of studies on preparation of amorphous zirconium dioxide from zirconium nitrate by its hydrolysis in the presence of oxalic acid. It is determined that the balance of reagents taken for synthesis (1 ml 0,025 M ZrO(NO₃)₂ is 1.35 ml 4 M HOOC-COOH), and the optimum temperature of the received gel drying, which is 230 ̊С, is established, too. Morphology of the obtained ZrO₂ samples was explored. It has been found that the calcining temperature is independent of the size and shape forming irregular agglomerates, consisting of smaller spherical particles, whose diameter varies between 50 and 300 nm. The X-ray analysis of the sample is represented, which showed a low degree of crystallinity of the substance. IR spectroscopy data showed the presence of zirconium dioxide-characteristic peaks on the IR spectrum. The same spectrum reflects the presence of a large amount of sorbed water in the obtained sample, as well as peaks characteristic of the gas adsorbed by the sample from the environment.