Search results for "Sol-gel"

Hydrogen-Related Paramagnetic Centers in Ge-Doped Sol-Gel Silica Induced by γ-Ray Irradiation

2006

We have studied the generation mechanisms of H(II) paramagnetic centers in Ge-doped silica by investigating up to 104 mol ppm sol-gel Ge-doped silica materials. We have considered materials with the same concentrations of Ge but that are produced by two different densification routes that give rise to different concentrations of Ge-related oxygen deficient centers (GeODC(II)). These centers are characterized by an optical absorption band at ∼5.2 eV (B2 β band) and two related emissions at ∼3.2 eV and ∼4.3 eV. The GeODC(II) content was estimated by absorption and emission measurements. The H(II) centers were induced by room temperature γ-ray irradiation and their concentration was determined…

Scale-up low-cost synthesis of bimodal mesoporous silicas

2005

Porous pure and doped silicas with pore sizes at two length scales (meso/macroporous) have been prepared through a large scale one-pot surfactant assisted reproducible procedure by using a simple template agent and starting from non-expensive sodium silicate as silicon source. Together with the relative low-cost of the reagents we have used, the simplicity of this method, which moreover is scalable and provides high yields, could be a strong argument for considering its suitability for the production of bimodal porous silicas. Additionally, we present a simple chemical scheme that allows directing the synthesis towards different related materials including both bimodal nanoparticulated meso…

Cobalt aluminate spinel-mullite composites synthesized by sol-gel method

1997

Abstract CoAl 2 O 4 spinel-mullite composites were prepared by double substitution of Al by Ti and Ni in stoichiometric 3:2 mullite. Gels with compositions 3(Al 2 − 2 x Co x Ti x O 3 )·2SiO 2 (x = 0.025, 0.05 and 0.2) and 3(Al 2 − 2 x M x O 3 )·2SiO 2 (x = 0.05; M = Co 2+ or Ti 4+ ) were synthesized by sol-gel techniques. The structure of the gels was investigated by infra-red spectroscopy. Heating gels at 750 °C produced an amorphous silicoaluminate network. The reaction sequence was investigated by differential thermal analysis, X-ray diffraction and ultraviolet-visible spectroscopy. All samples crystallized at temperatures lower than 1000 °C from the amorphous state. Al-Si spinel and/or …

Sol-gel assisted molten-salt synthesis of novel single phase Y3–2xCa2xTaxAl5−xO12:1%Eu garnet structure phosphors

2022

Strong absorption and emission are the key the features of any phosphor. The results obtained during this study demonstrate the difficulty of the incorporation of tantalum ions into the garnet structure and reveal that only the combination of Sol-Gel synthesis method together with Molten-Salt technique enable to obtain a single-phase cubic garnet structure. Note that, the Sol-Gel synthesis assisted by further processing by Molten-Salt technique can be a potentially new way of material preparation reported in literature. This work also proves that this combination of synthesis methods is much more capable of incorporating ions with large ionic radii into the garnet structure as compared to t…

Antimicrobial Properties of the Modified Cotton Textiles by the Sol-Gel Technology

2015

Comparison of the antimicrobial properties of textiles with amorphous coatings containing Zn and Si obtained by the sol-gel technology against microorganismsPseudomonas fluorescens,Saccharomyces cerevisae,Trichoderma viridethat can cause cotton textile destruction was made. Modified textile were evaluated using scanning electron microscopy, energy dispersive x-ray spectroscopy. Investigation of antimicrobial properties of the cotton fabric samples treated with different zinc acetate dihydrate concentration sols and various thermal post-treatments was made. Strong inhibition of microbial growth was detected for all cotton textile samples treated via sol-gel method according all tests microor…

Characterization and photoactivity of coupled ZnO-ZnWO4 catalysts prepared by a sol-gel method

2014

Abstract ZnO–ZnWO4 nanocomposites were synthesized by a novel sol–gel method and characterized through X-ray diffraction, BET specific surface area analysis, UV–Vis diffuse reflectance spectroscopy, scanning electron microscopy and transmission electron microscopy. The photocatalytic activity of the samples was evaluated using the degradation of 4-nitrophenol under UV light as probe reaction. The ZnO/ZnWO4 molar ratio was varied in order to study its influence on the photoefficiency of the mixed samples. The ZnO–ZnWO4 nanocomposites showed higher photoactivity than ZnO and ZnWO4. The high efficiency of the mixed samples was explained by the coupling and the intimate contact of two different…

Influence of Sn Low Doping on the Morphological, Structural and Optical Properties of ZnO Films Deposited by Sol Gel Dip-Coating

2014

In this work, Undoped Zinc Oxide (ZnO) and Sndoped Zinc Oxide (ZnO:Sn) films have been deposited by sol-gel dip coating method, where the Sn/Zn atomic ratio was 3% and 5% in the solution. The effects of Sn incorporation on morphological, structural and optical properties of ZnO films were investigated. The Scanning Electron Microscopy (SEM) showed that the morphological surface of the films was affected by Sn low doping. The X-Ray Diffraction (XRD) patterns showed that all films have polycrystalline structures, and the doping incorporation has not lead to substantial changes in the structural characteristics of ZnO films. The crystallite size was calculated using the well-known Scherrer’s f…

A Review of using spray pyrolysis through Sol-gel materials in the synthesis of cathode materials for lithium-ion batteries

2016

Over the years, new synthesis routes of the cathode electrochemical active material for lithium-ion batteries have improved remarkably to optimize their capacity and cycle life performance. This review study focused on the use of some techniques to synthesize the common cathode materials (LiCoO2, LiMn2O4, LiFePO4). The most common and simplest synthesis method was the mixing of powders in their solid-state form and heating them at relatively high temperatures over long periods. Other methods included the formation of sol-gel products that could be either heat-treated more or could be used directly by means of a spray pyrolysis method producing the desired active material. The spray pyrolysi…

Microcapsule sol-gel dopate per applicazioni industriali ecocompatibili

2012

Photocatalytic activity of binary and ternary SnO2–ZnO–ZnWO4 nanocomposites

2015

Binary and ternary SnO2-ZnO-ZnWO4 nanocomposites were prepared by a sol-gel route. The photocatalytic activity of the samples was evaluated through the decomposition of 4-nitrophenol and partial oxidation of 4-methoxybenzyl alcohol to p-anisaldehyde. All the mixed catalysts revealed higher photoactivity than bare ZnO, SnO2 or ZnWO4 and the best performances were exhibited by the binary nanocomposites. The high photocatalytic activity was explained by the presence of heterojunctions among different semiconductors that enhance the separation of the photogenerated electron-hole pairs, hindering their recombination. As a general consideration, an essential role was played by the electronic feat…