Showing papers on "Sol-gel published in 2018"

Sol–Gel Synthesis of Fe-Doped TiO 2 Nanocrystals

Abstract: Fe-doped TiO2 powders were synthesized by the sol–gel method using titanium (IV) isopropoxide (TTIP) as the starting material, ethanol as solvent, and ethylene glycol (EG) as stabilizer. These prepared samples were characterized by x-ray diffractometer (XRD), field emission scanning electron microscope (FESEM), Fourier-transform infrared (FTIR) spectroscopy, diffuse reflection spectroscopy (DRS), energy-dispersive x-ray spectroscopy (EDX), and photoluminescence (PL) analyses to study their structure, morphology, and optical properties. The particle size of Fe-doped TiO2 was in the range of 18–39 nm and the minimum crystallite size was achieved for 4 mol.% of Fe. The XRD result of the samples that were doped with Fe showed a tetragonal structure. It also revealed the coexistence of the anatase and rutile phases, and showed that their ratio changed with various molar concentrations of Fe dopant. FTIR spectroscopy showed the presence of the Ti-O vibration band in the samples. PL analysis revealed the PL property in the UV region. Visible irradiation and the intensity of PL spectra were both reduced by doping TiO2 with 3 mol.% of Fe as compared to the pure variety. The spectra from the DRS showed a red shift and a reduction of 2.6 eV in the band gap energy for 4 mol.% Fe-doped TiO2. The optimum level of impurity (4 mol.%) for Fe-doped TiO2 nanoparticles (NPs), which improve the optical and electrical properties by using new precursors and can be used in solar cells and electronic devices, was determined. The novelty of this work consists of: the Fe/TiO2 NPs are synthesized by new precursors from sol–gel synthesis of iron and TTIP using acetic acid-catalyzed solvolysis (original idea) and the optical properties optimized with a mixture of phases (anatase/rutile) of Fe-doped TiO2 by this facile method.

The Preparation of TiO2 Film by the Sol-Gel Method and Evaluation of Its Self-Cleaning Property

Abstract: TiO2 sol was produced by the sol-gel method through the hydrolysis and the aging of tetrabutyl titanate and the TiO2 film was obtained by dipping and uniform lifting of the acid-treated and ultrasound-treated clean glass slides into the TiO2 sol followed by aging, drying, and calcination. The effect of the hydrolysis control agents to the formed sol was researched and the crystalline state, the morphology, and the photocatalytic properties of the products after calcination were characterized. The structural morphology, the contact angles before and after illumination, and the self-cleaning properties of the TiO2 film were characterized as well. The results showed that by using acetylacetone as the hydrolysis control agent, the formed TiO2 sol had relatively high stability. The product after the calcination of the TiO2 sol was of single anatase type with crystalline size of 18–20 nm and it could degrade nearly 100% of methylene blue after 90 min illumination. The formed TiO2 film is compact, continuous, smooth, and had the properties of super-hydrophilicity (after 30 min illumination due to its contact angle decreasing from 21° to nearly 0°) and anti-fogging capability, which indicated its excellent self-cleaning property.

Structure and properties of epoxy-siloxane-silica nanocomposite coatings for corrosion protection.

Abstract: Hypothesis The fraction of the silica/siloxane phase is a crucial parameter, which determines the structure and thus the properties of epoxy-siloxane-silica hybrid coatings. A careful adjustment of the colloidal precursor formulation allows tuning the nanostructure towards a highly condensed and cross-linked hybrid nanocomposite, suitable as an efficient anticorrosive coating. Experiments Novel epoxy-siloxane-silica hybrids have been prepared through the curing reaction of poly(bisphenol A-co-epichlorohydrin) (DGEBA) with diethyltriamine (DETA) and (3-glycidoxypropyl)methyltriethoxysilane (GPTMS), followed by hydrolytic condensation of tetraethoxysilane (TEOS) and GPTMS. At a constant proportion of the organic phase, the effects of the varying molar proportions of siloxane (GPTMS) and silica (TEOS) on the film properties have been investigated. Findings A detailed structural analysis suggests for intermediate TEOS to GPTMS ratios a structure of highly condensed silica-siloxane domains covalently bonded to the embedding epoxy phase. The homogeneous distribution of the quasi-spherical sub-nonmetric silica-siloxane nodes is in agreement with low surface roughness ( 300 °C), strong adhesion to steel substrate and excellent barrier property in saline solution, with corrosion resistance in the GΩ cm2 range.

Structural, optical and electrical properties of Ni-doped Co3O4 prepared via Sol-Gel technique

Abstract: In this article, Nickel doped Cobalt oxide thin films and powders have been prepared on glass substrates using sol gel based dip coating process in order to investigate their optical, structural and electrical properties. The Ni concentration was changed from 0 to 9 wt(%).The synthesized samples were characterised by Ultraviolete visible analysis, X-ray diffraction, Fourier transform infrared spectroscopy and Complex impedance spectroscopy to depict the optical, structural, vibrational and electrical properties. Our structural results show that the obtained samples were composed of (Co3O4) polycrystalline with spinel-type preferentially oriented in the (311) plane. Our optical results show that the films have high transparency over the visible region (85% for Co3O4 and ∼ 60-75% for all doped samples). The optical band gaps were found to be (Eg1 = 1.50 eV, Eg2 = 2.20 eV) and (Eg1 = 1.42 eV, Eg2 = 2.07 eV) for the case of (pure Co3O4 and 9% Ni-doped Co3O4) respectively. The complementary phase information is provided by FT-IR spectroscopy. FT-IR spectra confirms the presence of Co2+-O and Co3+-O vibrations in the spinel lattice. The Nyquist plots suggests that the equivalent circuit of our films is an parallel circuit RpCp. It was found that the resistance Rp decreases whereas the capacity Cp increases with increasing doping levels.

Hybrid sol–gel coatings based on GPTMS/TEOS containing colloidal SiO2 and cerium nitrate for increasing corrosion protection of aluminium alloy 7075-T6

Abstract: One of the promising candidates to replace the chromate conversion coatings for corrosion protection of aluminium alloy AA7075 are the hybrid sol–gel coatings. In the present work hybrid silica sol–gel coatings doped with cerium nitrate were prepared and characterized. Tetraethoxysilane (TEOS) and 3-glycidoxypropyl-trimethoxysilane (GPTMS) were used as precursors. Silica SiO2 (Ludox) particles were added to achieve a barrier properties of coating, while Ce(NO3)3·6H2O was added in order to obtain an active corrosion protection. Optimization of sol synthesis was based on the results of ATR-FTIR spectroscopy and UV–vis–NIR spectroscopy. Opening of epoxy rings and completion of hydrolysis and the condensation reactions during the synthesis process were confirmed. Coatings were characterized through thickness, water contact angle, roughness, adhesion, electrochemical properties (potentiodynamic and electrochemical impedance spectroscopy) and the response to prolonged immersion time in 0.1 M NaCl. The high degree of cross-linking of Si–O–Si network structure and high density was achieved during the synthesis of the sol. Moreover, the results showed that the curing process and the incorporation of cerium nitrate into the hybrid sol–gel coating affected to the corrosion properties of the coating. The observed enhancement in corrosion protection properties is attributed to the combination of the barrier properties of the silica matrix with the active protection of the cerium nitrate.

Effect of different solvents on the key structural, optical and electronic properties of sol–gel dip coated AZO nanostructured thin films for optoelectronic applications

Abstract: Transparent conducting aluminum (i.e. 2 at.%) doped zinc oxide (AZO) thin films were prepared on glass substrates by sol–gel dip coating technique using different solvents. This inexpensive dip coating method involves dipping of substrate consecutively in zinc solution and tube furnace for required cycles. Prepared films were investigated by XRD, SEM, PL, Raman spectroscopy optical and electrical studies. From the XRD studies, it confirmed the incorporation of aluminum in ZnO lattice. The prepared samples are polycrystalline nature, and these films reveal hexagonal wurtzite arrangement with (002) direction. The structural parameters such as crystallite size, dislocation density, micro strain, texture coefficient and lattice constant were investigated. SEM study showed well defined smooth and uniformed ganglia shaped grains are regularly distributed on to the entire glass substrate without any pinholes and cracks, and the average grain size is 75 nm. From the optical studies, the observed highest transmittance is 93% in the visible range and the band gap (Eg) is 3.26 eV. Room temperature PL spectra exhibited strong UV emission peak located at 386 nm for all the films. The electrical properties of the AZO thin films were studied by Hall-Effect measurements and found as n-type conductivity with high carrier concentrations (n), 2.76 × 1019 cm− 3 and low resistivity (ρ), 7.56 × 10− 3 Ω cm for the film deposed using methanol as solvent.

Impact of silica nanoparticles on the morphology and mechanical properties of sol-gel derived coatings

Abstract: Although corrosion resistance and mechanical properties of sol-gel coatings have been studied independently, there are limited studies that consider both collectively. However, since any form of mechanical damage could impair the protective function of the coating, it is prudent to consider the mechanical durability of coatings as well as their corrosion resistance. The present work considers the impact of silica nanoparticles on the morphology and mechanical properties of a sol-gel derived coating. The relationships between the results obtained from tests such as atomic force microscopy (AFM), nanoindentation or erosion test with previously reported corrosion results obtained via salt spray or electrochemical impedance spectroscopy (EIS) are discussed. Results show that reinforcing a sol-gel coating with silica nanoparticles and, particularly, functionalised silica nanoparticles led to coatings with improved mechanical properties and enhanced erosion impact resistance. The role of nanoparticles on improving mechanical properties and corrosion resistance, which is of importance within the coating industry, is discussed.

Physical Properties of Copper Oxide Thin Films Prepared by Sol–Gel Spin–Coating Method

Abstract: In this study, copper oxide thin films prepared by the sol–gel method, have been deposed onto glass substrates by the spin coating technique Our target was to study their properties and improve them for photovoltaic use These properties were optimized by varying the temperature annealing and the molar concentration of the precursor solutions The effects of the annealing temperature on the structural and optical properties of the thin films are studied It was found that the film treated at 550°C shows a higher absorbance Then by using this optimized temperature, CuO thin films of various molar concentrations, were deposited at the same experimental conditions The structural analysis by X- ray diffraction (XRD) shows that all the samples are polycrystalline with monoclinic crystal structure Raman scattering measurements of all thin films confirms the structure of CuO The optical properties of the films were characterized by UV–Visible–NIR spectrophotometry, which shows that the films show high absorbance in the visible region Their optical band gap decreases from 368 to 244 eV when the molar concentration of precursor solutions increases from 01 to 05 M The electrical measurements show that the resistivity of the films varies slightly from 84 Ω cm to 124 Ω cm as the molar concentration increases

Acetic acid sensing of Mg-doped ZnO thin films fabricated by the sol–gel method

Abstract: Acetic acid vapor thin film gas sensor was developed by synthesizing Mg-doped ZnO nanoparticles using a low cost and facile sol–gel route and were characterized using field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy and photoluminescence analysis. Morphological characterizations showed the formation of well-defined and highly crystalline ZnO nanoparticles on Si(100)/SiO2 substrate. Gas sensing characterization of dip coated Mg-doped ZnO thin films were performed in temperature range of 150–400 °C at different acetic acid vapor concentrations. At 300 °C, the sensitivity for pure ZnO, Zn0.98Mg0.02O and Zn0.94Mg0.06O samples at concentration of 200 ppm of acetic acid were 124, 78 and 67%, respectively. The highest sensitivity for Zn0.96Mg0.04O sample was 136% at the same vapor concentration and temperature. It showed a fast response time and recovery time (145 and 110 s, respectively).

Protecting the MoSi 2 healing particles for thermal barrier coatings using a sol-gel produced Al 2 O 3 coating

Abstract: A successful sol-gel process to encapsulate molybdenum di-silicide MoSi2 particles with a closed and thermally stable Al2O3 layer using aluminium tri-sec-butoxide as a precursor is presented. The processing conditions such as precursor selection and temperature were optimized through analysing the interaction of the MoSi2 particles with the sol. The application of the sol-gel based coating was followed by calcining the coated particles at temperatures between 900 and 1200 °C in Ar. The shell composition and the mechanical stability of the microcapsule were analysed by means of X-ray diffraction, scanning electron microscopy and thermogravimetric analysis. Upon calcining at 1200 °C in Ar, the MoSi2 core remains intact as it is, covered by an α - alumina shell with a thickness of about 0.6 μm. The stability tests proved that the encapsulate particles are about five times more oxidation resistant than the uncoated MoSi2 particles.

STUDIES ON STRUCTURAL, SURFACE MORPHOLOGICAL, OPTICAL, LUMINESCENCE AND UV PHOTODETECTION PROPERTIES OF SOL–GEL Mg-DOPED ZnO THIN FILMS

Abstract: Undoped and magnesium-doped zinc oxide thin films were prepared by the sol–gel method. Results from X-ray diffraction indicated that the films exhibited a hexagonal wurtzite structure and were high...

High-Performance and Simply-Synthesized Ladder-Like Structured Methacrylate Siloxane Hybrid Material for Flexible Hard Coating.

Abstract: A high performance ladder-like structured methacrylate siloxane hybrid material (LMSH) was fabricated via simple hydrolytic sol–gel reaction, followed by free-radical polymerization. A structurally ordered siloxane backbone, the ladder-like structure, which is an essential factor for high performance, could be achieved by a short period of sol–gel reaction in only 4 h. This results in superior optical (Transmittance > 90% at 550 nm), thermal (T5 wt % decomposition > 400 ℃ ), mechanical properties(elastic recovery = 0.86, hardness = 0.6 GPa) compared to the random- and even commercialized cage-structured silsesquioxane, which also has ordered structure. It was investigated that the fabricated ladder-like structured MSH showed the highest overall density of organic/inorganic co-networks that are originated from highly ordered siloxane network, along with high conversion rate of polymerizable methacrylate groups. Our findings suggest a potential of the ladder-like structured MSH as a powerful alternative for the methacrylate polysilsesquioxane, which can be applied to thermally stable and flexible optical coatings, even with an easier and simpler preparation process.

Effect of pH and annealing temperature on the properties of tin oxide nanoparticles prepared by sol–gel method

Abstract: Tin oxide (SnO2) nanoparticles were synthesized employing simple sol–gel method. Modification in the structural, morphological and optical properties of the as-synthesized tin oxide nanoparticles due to various solution pH (6–12) and thermal annealing at 400 °C (Experiment 1) was studied. X-ray diffraction results of the tin oxide nanoparticles prepared from the precursor solution pH 8 and annealed at 400 °C showed the formation of tin oxide tetragonal phase (SnO2-t) and the surface morphology of the SnO2-t nanoparticles studied by scanning electron microscope revealed the formation of spherical shaped agglomerations. Hence, the tin oxide nanoparticles prepared from the solution pH 8 were annealed at 200, 400, 600 and 800 °C in order to study the effect of annealing at various temperatures on the structural, morphological, optical and vibrational properties of tin oxide nanoparticles (Experiment 2). When the annealing temperature was increased to 600 and 800 °C, mixed phases of SnO2-t and tin oxide orthorhombic system (SnO-o) were formed. Various solution pH and annealing temperatures influenced the direct band gap value. SnO2-t phase synthesized from the solution pH 8 and annealed at 400 °C showed a direct band gap of ~4.50 eV. The tin oxide samples annealed at various temperatures showed a slight shift in the fluorescence peak observed at ~327 nm. Raman studies of the samples obtained from Experiment 1 and Experiment 2 showed a slight shift in the vibrational frequency. I–V studies carried out to investigate the electrical properties of the SnO2 thin film formed by simple drop casting method revealed better ohmic contact and its suitability for gas sensing applications.

Electrochemical detection of ammonia solution using tin oxide nanoparticles synthesized via sol–gel route

Abstract: In this work, electrochemical detection of ammonia solution (NH4OH) using sol–gel-synthesized tin oxide (SnO2) nanoparticles is investigated. Structural characteristics were studied using X-ray diffraction, scanning electron microscope and energy-dispersive X-ray spectroscopy that confirmed the formation of tin oxide nanoparticles. Optical characterizations were also studied via UV–Vis–IR spectroscopy and photoluminescence spectroscopy. After successful confirmation of sol–gel synthesis, these tin oxide nanoparticles were deposited on patterned copper substrate via thermal evaporator. Analysis for sensing ammonia solution was carried out using a three electrode system via electrochemical workstation. Electrochemical technique incorporates the results of cyclic voltammetry. The results confirmed that the SnO2-deposited copper (Cu) platform successfully detect the presence of ammonia solution in double-distilled water. These results were further analyzed and compared with each indium tin oxide (ITO)-coated glass and pure copper substrate. Moreover, the tin oxide-deposited copper platform showed better performance than ITO substrate.

Structural and Optical Properties of Zinc Oxide (ZnO) based Thin Films Deposited by Sol-Gel Spin Coating Method

Abstract: The structural and optical properties of ZnO thin films deposited by sol-gel spin coating method have been investigated. The ZnO thin films were deposited on corning glass 7059 substrate from zinc acetate (ZnAc), ethanol, and stearic acid as starting material, solvent and stabilizer were used, respectively. The characteristics of the film were analysed from transmittance spectra obtained by UV-Vis spectroscopy measurement, while the atomic structure of the films analysed from XRD and AFM measurement. The results showed that the characteristics of ZnO thin films were strongly depend on annealing temperature. The XRD measurement indicated that deposited film shows a type of nanocrystalline peak broadening with hexagonal structure and preferential orientation along (002) crystal plane. The transmittance value of the ZnO films was relatively high (75 - 80 %). The optical band gap of ZnO films decreases with increasing in annealing temperature. AFM images showed the annealing temperature effects surface morphology of the films.

Sol-gel preparation of self-cleaning SiO2-TiO2/SiO2-TiO2 double-layer antireflective coating for solar glass

Abstract: Self-cleaning SiO2-TiO2/SiO2-TiO2 double-layer antireflective (AR) coating is prepared by sol-gel process. SiO2 sol is prepared by using tetraethyl orthosilicate (TEOS) as precursor and ammonia as catalyst, while TiO2 sol was prepared by using tetrabutyl orthotitanate (TBOT) as precursor and hydrochloric acid as catalyst. The effect of TiO2 content on refractive index, abrasion-resistance and photo-catalytic activity of SiO2-TiO2 hybrid thin films or powders is systematically investigated. It is found that the refractive index of SiO2-TiO2 hybrid thin films increases gradually from 1.18 to 1.53 as the weight ratio of TiO2 to SiO2 increased from 0 to 1.0. The SiO2-TiO2 hybrid thin film and powder possesses good abrasion-resistance and photo-catalytic activity, respectively, as the weight ratio of TiO2 to SiO2 is 0.4. The degradation degree of Rhodamine B by SiO2-TiO2 hybrid powder is 88.3%. Finally, SiO2-TiO2/SiO2-TiO2 double-layer AR coating with high transmittance, abrasion-resistance and self-cleaning property is realized.