Two series of TiO2 thin films were prepared based on soluble precursor powders: The first run originated directly from an alcohol-based coating solution whereas for the second batch the aqueous precursor powder sol had previously undergone a hydrothermal treatment. The respective microstructures were characterized by electron microscopy, the phase evolution was monitored by X-ray diffraction. Ellipsometric porosimetry (EP) was employed to reveal changes of porosity and pore size induced by thermal treatment of the films.
Soluble TiO2 precursor powders were hydrothermally treated to yield coating solutions. Films from these sols were compared with those directly obtained by dissolving the precursor powders. Results indicate that crystallization to anatase is induced under hydrothermal conditions and the resulting films mostly maintain their porosity throughout thermal treatment. In contrast to that coatings processed from as-dissolved precursor powders undergo more extensive densification
Bismuth ferrite (BiFeO3) nanopowder have been successfully synthesized for the first time via a microwave-assisted sol-gel combustion method by using citric acid as fuel. The resulting nanopowder was characterized using FT-IR, TG-DTA, XRD, EDX, VSM, SEM, and UV-Vis DRS. A ferromagnetic hysteresis loop with a saturation magnetization (MS) of 0.66?emu?g?1 has been observed at room temperature in the sample. The optical properties of the nanosized BiFeO3 showed its small band gap (=2.08?eV) indicates a possibility of utilizing much visible light for photocatalysis.
The aim of this work was an investigation of structural and electrical properties of ZnO/Zn2-xFexTiO4 (x?=?0.7, 1, 1.4) powders. The compounds obtained by sol-gel method are characterized by several techniques: X-ray diffraction (XRD), N2 adsorption–desorption isotherms, scanning and transmission electron microscopy (SEM and TEM), X-ray photoelectron spectroscopy (XPS), electrical and dielectrical measurements. The XRD, SEM and XPS analysis confirmed the formation of ZnFeTiO4 inverse spinel structure. The electrical and dielectrical properties of ZnO/Zn2-xFexTiO4 (x?=?0.7, 1, 1.4) were measured by impedance spectroscopy, revealing a decrease in the electrical conductivity and the dielectric constant with Fe content.
Nanocomposites of reduced graphene oxide (rGO) coupled gadolinium doped ZnFe2O4 (GZFG) have been successfully one pot in-situ synthesized adopting low temperature solution process from zinc nitrate, iron nitrate, gadolinium acetate and graphene oxide with varying concentrations of gadolinium (upto 10% Gd with respect to Zn) in the precursor medium. X-ray diffraction and transmission electron microscopy studies confirm the presence of single phase cubic spinel structure of ZnFe2O4 that uniformly distributed over the rGO layers. With increasing Gd doping concentration in precursor medium, the average crystallite size of ZnFe2O4 diminishes gradually from ~11 to ~5.5?nm. Raman and X-ray photoelectron spectral analyses confirm an existence of interaction between rGO and ZnFe2O4 in GZFG samples. Using antibiotic levofloxacin in water, the drug removal capacity (DRC) of GZFG has been performed by optimization of parameters such as gadolinium doping concentration in precursor medium, solution pH, etc. However, the gadolinium doping leads to an improvement in DRC of the nanocomposite and the 5% Gd doped sample shows about 86% DRC at the optimized condition. This simple strategy can be utilized in the synthesis of rGO coupled Gd doped other metal oxide nanocomposites for DRC application.
In this work, sol–gel-based non-stick ceramic coating formulations were prepared and coated onto aluminum panels in order to investigate their surface properties. The effect of the addition of optimal amount of fluorine-containing silane compound (FAS) on the surface and adhesion properties were also investigated. The morphology, structure, and elemental chemical composition of the coatings were characterized by scanning electron microscopy, atomic force microscopy (AFM), energy dispersion spectrum (SEM/EDAX), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS), respectively. Moreover, several properties of the coatings such as cross-cut adhesion, hardness, gloss, and contact angle (CA) were determined. When fluorine was introduced, the pencil hardness was increased to 6H. Fluorinated non-stick ceramic coatings were found to have good adhesion on the aluminum substrates.
In this paper, we reported the design and preparation of a double-layer antireflective (AR) coating, which possessed relatively high transmittance at 351, 527, and 1053?nm. The refractive indices and film thicknesses of the under layer and upper layer of the simulated AR coating were determined as 1.27, 95?nm and 1.18, 106?nm, respectively. The under layer of the double-layer coating dip-coated from a mixture of base-catalyzed and acid-catalyzed silica sols had a refractive index of 1.27. The upper layer fabricated by the deposition of methylated silica nanoparticles by simply adding methyltriethoxysilane into the base-catalyzed silica sols possessed a refractive index of 1.18. The hydrophobicity of coatings could be dramatically improved with the water contact angle increasing from 23.4° to 150.0°, and the refractive indices of the pure base-catalyzed silica coatings were easily decreased from 1.20 to 1.12 through the surface treatment of silica nanoparticles. Thus, we have successfully prepared a double-layer AR coating, which had a high transmittance of 99.8%, 96.1%, and 99.7% at 351, 527, and 1053?nm, respectively.
Novel La-doped Bi2WO6 composites were successfully prepared via a facile solvothermal method and well characterized by X-ray diffraction, Brunner?Emmet?Teller measurements, scanning electron microscopy, transmission electron microscopy/high-resolution, energy dispersive spectrometry, X-ray photoelectron spectroscopy, ultraviolet–visible spectroscopy, and Fourier transform infrared spectroscopy. The photocatalytic activity of modified catalysts was evaluated by degrading tetracycline hydrochloride under visible light (450?W Xe lamp irradiation). It was found 5%La-Bi2WO6 had the highest light-absorption ability, great morphology, and microstructures. The La dopant enlarged surface area and increased crystal defects, which may enhance the optical absorption activity and inhibit the recombination of the photo-generated charge carrier, respectively. After 150?min illumination, the photocatalysts that 5%La-Bi2WO6 and pure Bi2WO6 exhibited the best and worst photocatalytic performance, respectively (96.25% vs. 88.92%).
Phase pure, mesoporous, and crystalline V2O5 is synthesized by acid hydrolysis technique and subsequently heat treatment is carried out at 450, 500, 550, and 600?°C in air. The as-synthesized and heat-treated powders are thoroughly studied by X-ray diffraction, electron microscopy, dynamic light scattering, and spectroscopic techniques. A unique morphological tuning of V2O5 powders from as small as ~80?nm tiny nanorod to as large as a ~2.5?μm hexagonal grain as microstructural unit blocks is observed. A qualitative mechanism is suggested for particle growth. Further, the powders are pelletized and subsequently sintered in air at the same temperatures of 450, 500, 550, and 600?°C at which the powders were heat treated. Finally, nanomechanical properties of bulk pelletized V2O5 such as nanohardness and Young’s modulus are also evaluated by nanoindentation technique at nine different loads e.g., 10, 30, 50, 70, 100, 300, 500, 700, and 1000?mN.
Superhydrophilic surfaces without the need of other stimuli are usually realized by constructing a rough morphology. However, constructing rough surfaces usually require specialized equipment or complicated processing. Besides, rough surfaces can cause undesirable scattering, which strongly limits the use in optical devices. In this article, we prepared superhydrophilic TiO2 films with ultra-smooth surfaces using simple sol-gel dip-coating method. The hydrophilicity of the TiO2 films varied with different post-heat treatments. The films heat-treated at 400?°C exhibited a durable superhydrophilicity and anti-fogging property. This superhydrophilicity was attributed to the decrease of surface hydrophobic alkoxy groups and the formation of point defects, i.e., Ti3+ and oxygen vacancies, which are favourable for dissociative water adsorption. The amount of surface organic groups was influenced by autophobicity effects, further hydrolysis and decomposition of residual alkoxy groups. Additionally, the wettability behaviours of the films were also explained from the perspective of the surface energy. These results can benefit the design and manufacture of anti-fogging and self-cleaning superhydrophilic TiO2 films.
Light-activated antimicrobial coatings were obtained by the covalently immobilizing photo-sensitizers in a hybrid organic/inorganic matrix. These coatings were deposited via sol-gel chemistry using epoxy and methyl functional silanes. The light-activated chromophores used in this study were Methylene Blue, Toluidine Blue O, and Rose Bengal. The immobilized photo-sensitizers did not leach from the coatings. The mechanically durable hybrid coatings comprising 2.5% by weight of Rose Bengal had a good adhesion to the glass surface. These coatings were tested for the photo-deactivation of Escherichia coli and Staphylococcus aureus using illumination by a commercial fluorescent lamp. Log reduction of E. coli and S. aureus were >4 when illuminated by the fluorescent lamp in 1 and 3?h, respectively. Due to its high mechanical durability and chemical resistance, such light-activated hybrid coatings are promising candidates for indoor applications in healthcare facilities.
TiO2/WO3 nanocomposite with nanodisk morphology was prepared and successfully used as a photocatalyst. The nanocomposite was obtained via sonochemical and hydrothermal methods, using pomegranate juice as a capping agent. The products were characterized by FE-SEM imaging, BET, EDAX spectroscopy, X-ray diffraction, DRS, and FT-IR spectroscopy. TiO2/WO3 nanocomposite showed high sensitivity to absorb visible light in compared to TiO2. In an optimized condition, the yield of the aerobic photocatalytic oxidation of benzyl alcohol derivatives reached to 65% for the TiO2/WO3 nanocomposite, while the conversion percent of the derivatives was less than 8% and 50% on the TiO2 and WO3 nanoparticles, respectively. Experimental results were supported by density functional theory (DFT) calculations. The DFT results in several solvents of different dielectric constants, confirmed the strong dependence of light absorption and photocatalytic activity to adsorption energy of the substrates on the surface of the nanoparticles (Ead). In addition, the theoretical results showed an inverse correlation between the adsorption energy of benzyl alcohol and its conversion percent, accordance to the experimental trend.
Dual-network aerogels (HPSA) with improved mechanical property and thermal insulation were prepared by vacuum impregnation of HNTs/PVA aerogels (the first network aerogel, HPA) in tetraethoxysilane (TEOS). Scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, and N2 adsorption–desorption analysis were used to study micromorphology and microstructure of HPSA, while compression tests and thermal conductivity tests were used to investigate related properties. The results showed that the dual-network frame was successfully constructed, this enabled HPSA to display enhanced compressive properties with increased HNTs content. The addition of silica sol improved the mesoporous characteristics including specific surface area and pore volume and also reduced the thermal conductivities. The first network made it possible for HPSA to possess good mechanical property, while SiO2 aerogel allowed HPSA greater thermal insulation. The obtained aerogel samples exhibited a high compressive strength (i.e., 1.36?MPa) and a low thermal conductivity (i.e., 0.022?W/(m?K)). HNTs/SiO2 dual-network aerogels with improved strength and thermal insulation could show great potential in a wide variety of applications.
Boron Nitride (BN) particles were functionalized with vinyl-trimethoxysilane (VTMS) and incorporated into a hybrid polymer (ORMOCER®) resin. The thermal conductivity and mechanical properties of the resulting composite were compared to materials prepared using unmodified particles. Results indicate that the chemical bonding between grain surface and ORMOCER® matrix has a pronounced effect on the final performance of the respective compounds.
The surface of BN particles was functionalized prior to their incorporation into a hybrid polymer (ORMOCER®) matrix, thermal, electrical and mechanical properties of the resulting composites were characterized.
ZrC–ZrO2 composite ceramic microspheres were prepared by internal gelation combined with carbothermic reduction using fructose as a chelating agent and carbon source. Fructose in the precursor solution formed complex with zirconium ions, which was conducive to the refining of the microstructure of the sintered composite. ZrC–ZrO2 composite with ZrC content as high as 60?wt% could be prepared.
In this paper, fructose was used as a chelating agent and an organic carbon source to prepare ZrCO microspheres by internal gelation and carbothermic reduction. The fructose in the precursor solution could form complex with zirconium ions, which was conducive to the refining of the microstructure of the sintered composite. ZrC–ZrO2 composite with crystal size of ZrO2 and ZrC in nanometer range and ZrC content as high as 60?wt% could be successfully prepared.
A new chemical approach for the fabrication of Fe3O4 embedded ZnO magnetic semicondutctor composite is reported. The method consists in increasing the pH of the synthesis solution by the thermal decomposition of urea instead of using common alkaline agents, such as NaOH and NH4OH. The material (Fe3O4@ZnO) was used as a platform for the fabrication of highly dispersed gold nanoparticles (~5?nm). The catalytic efficiency of the material, Fe3O4@ZnO@Au, was tested in the photodegradation of Rhodamine-B solutions, and prominent catalytic efficiency, stability, and recycling were achieved. A single portion of the catalyst could be used up to five times without significant loss of activity and its photodegradation efficiency was considered high even after the 12th cycle (56%). Catalyst separation after each batch could be easily achieved because of the intrinsic magnetic property of the material. Leaching monitoring of free Zn species during the fabrication of the catalyst suggests that the use of urea decreased substantially the formation of non-magnetic-semiconducting species and provided a higher mass yield of the magnetic composite compared to an analogous protocol using NaOH. The catalyst was also characterized by detailed structural and chemical analyses, such as transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and vibration sample magnetometer (VSM).
Degradation of three different endocrine disruptors (EDs) was thoroughly studied on prepared durable thin layers of titanium dioxide with an anatase crystalline structure. Specially constructed laboratory reactors bringing information on all individual processes (photolysis, photocatalysis, sorption) involved in decomposition of the studied EDs (17α-ethynylestradiol, bisphenol A and 4-nonylphenol) were applied. It was found that photolytic removal of EDs is the fastest degradation process; nevertheless, this method may be less effective regarding all indicators including toxicity. It was verified that individual degradation processes (photolysis and photocatalysis) showed a significantly different influence on toxicity of resulting solutions. During the photolytic process, EDs degradation caused increasing toxicity contrary to the photocatalytic process. Obtained results were corroborated by a mathematical model, which showed that a limitation step for photocatalysis is a sorption and for photolysis a toxicity of resulting products.
Systematic studies of silica gels with covalently immobilized thiosemicarbazide and formazan groups under the conditions of competitive sorption from multicomponent systems were conducted. A methodological approach to determine the selectivity of the modified sorption material with regard to Cu(II), Ni(II), Co(II), Cd(II), and Zn(II) was proposed. Solid-phase extraction in equilibrium conditions of Cu(II), Zn(II), Co(II), Cd(II), and Ni(II) on a silica gel with covalently immobilized thiosemicarbazide and formazan groups in the conditions of competitive sorption was studied. The possibility to use the pseudo-second-order kinetic equation for assessment of mutual influence at competitive sorption has been shown. We found that sorption from multicomponent solutions proceeds as a non-additive process under the conditions of an excess of functional groups.
This paper reports a successful preparation of a pure forsterite Mg2SiO4 using the sol–gel approach and its application for the removal of impurities from a Tunisian frying oil. Magnesium nitrate hexahydrate and tetraethylortho-silicate were used as magnesium and silicon precursors, respectively. The synthesis was held at different calcination temperatures for 30?min. The annealed samples were characterized by X-ray diffraction, Fourier transform infrared, scanning electron microscopy, and laser diffraction. The results revealed that the sample calcined at 500?°C was forsterite with unimodal particle size distribution (PSD) centered at 122.8?±?0.3?μm. The dispersion index I (indicator of particle size uniformity) was 1.84. With the temperature increase, well crystallized compounds were obtained. Their PSDs remain unimodal and shift towards smaller particles. A decrease of the dispersion index was also noted, indicating the formation of Mg2SiO4 with more uniform particle size. This study showed that 900?°C could be selected as energy saving temperature suitable for the preparation of a pure and well crystallized Mg2SiO4 within just 30?min of annealing time. The obtained silicate exhibited promoting results for the purification of waste frying oils.
Pure and fine Mg2SiO4 powder with unimodal particle size distribution was prepared by sol gel route under energy saving conditions. The obtained magnesium orthosilicate showed excellent results for waste frying oil purification
Since the late 1960s, ceric hydrogen phosphates have attracted the attention of scientists due to remarkable ion exchange, sorption, proton-conduction and catalytic properties. In this work, through the application of various solvents, we, for the first time, have obtained monolithic aerogels based on ceric hydrogen phosphates with high porosity (~99%) and extremely low density (~10?μg/cm3). The composition and structure of aerogels were thoroughly studied with XRD, TEM, SEM, XPS, low temperature nitrogen adsorption methods, TGA/DSC, Fourier-transform infrared spectroscopy (FTIR) and small-angle neutron scattering (SANS). The aerogels were found to belong to the fibrous macroporous aerogels family.
The behaviour of alginate gel film in response to the tensile load is analysed in this paper. The bubbles of 0.5?mm diameter were embedded in the film by the fluidic method prior to gelation, thus providing uniform voidage over the entire film. Further, the intrinsic porosity of the gel matrix around the voids was varied by removing water through either evaporation under vacuum, or employing lyophilisation. The Poisson’s ratio and the modulus of elasticity were estimated from direct measurements. The viscoelasticity of the gel matrix was characterized from stress-relaxation measurement. The transient response to tensile loading and the evolution of stress contours were studied through numerical simulation in ANSYS. The ultimate strength was studied for the gel films with embedded voids of different sizes. The numerical simulations were validated by experimental measurements.
