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For alumina (Al2O3) powder produced by corrosion of aluminum, we investigated the effect of the solvent composition (C2H5OH/H2O of 100:0, 80:20, 60:40, 40:60, 20:80, and 0:100 v/v) on the particle size distribution. The powders were calcined at 1473K and identified as α-Al2O3. The particle size of alumina powder obtained with H2O as the solvent was 0.3-100 µm. As the volume fraction of H2O in the solvent mixture increased, the particle size of the alumina powder also increased. With the increase in the H2O volume fraction, agglomeration of the obtained alumina particles was observed by scanning electron microscopy. [ABSTRACT FROM AUTHOR]

Summary: NiCo2O4 nanoparticles (5‐10 nm) were prepared by a simple sol‐gel method and evaluated in the Li/Na‐cell as an anode. The anode exhibited excellent lithium storage capacity (1050 and 860 mAh g−1 at specific currents of 0.1 and 0.5 A g−1, respectively) and outstanding cycling performance of over 200 cycles. However, it showed a moderate sodium storage capacity with poor cycle retention. A clear comparison of the structural stability of the electrode determined via the cross‐sectional scanning electron microscopy (SEM) micrographs indicates swelling and extensive volume expansion in the Na cell. The investigations conducted using in situ X‐ray diffraction (XRD) and ex situ X‐ray absorption spectroscopy (XAS) reveal the limited reduction of Co and Ni oxidation states and a minimal degree of conversion during Na uptake. This study highlights the ability of NiCo2O4 nanoparticles to withstand high mechanical stress during the conversion reaction with Li, thus providing excellent performance. Conversely, the NiCo2O4 anode with Na could not be overcome massive volume expansion and irreversibility by reducing the size of particles in nano‐dimension. [ABSTRACT FROM AUTHOR]

We present here a technology to microencapsulate drugs by the sol–gel process, and cryo-SEM methodology that allows the nanostructural characterization of the formed capsules in their native state without any artifacts, related to their drying prior to imaging. The methodology utilizes three signals generated by the electron beam scanning the specimen: Secondary electrons, backscattered electrons, and x-rays. The first gives topographical information of the fracture-surface of the thermally-fixed specimen, the second gives contrast between elements of different atomic numbers, and the third allows the identification of those elements. Combined, the three signals provide full microstructural characterization of the studied specimen. Using this methodology, we were able to demonstrate that the sol–gel technology does indeed enable the encapsulation of two hydrophobic active molecules with a silica shell. This technology allows the active ingredient in the drug product to slowly migrate from the microcapsule onto the skin, thus obtaining the desired effect with minimal side-effects, as was exhibited in several clinical studies. The successful application of the cryo-SEM methodology in this case, demonstrates that it can be used to characterize a wide range of liquid-phase suspensions, in their native state, with minimal specimen preparation or imaging artifacts. [ABSTRACT FROM AUTHOR]

In this work, a wide and highly sensitive chemiresistive sensor has been developed based on the AZO nanocolumn array film. This is meant for the room detection of H 2 O 2 under UV illumination. A cost-effective one step multi-layers growth process was adopted for the synthesis of the AZO nanocolumn array. The experimental studies were done by scanning electron microscopy (SEM), transmission and electron microscopy (TEM).Then X-ray diffraction confirmed that the AZO column array was closely packed, connected, vertically aligned, and polycrystalline, with a high surface area. This structure ensures better electrical conduction over random and separated nanostructures. The hall-effect measurement indicates that the AZO film was n-type, with high conductivity (3.60 × 103 Ωcm), high carrier density (11.3 × 1020cm−3) and with acceptable mobility (0.95 cm2/Vs). The x-ray photoemission spectroscopy suggests that the AZO film consists of a large amount of adsorbed oxygen-related species at the sheath layer of the thin-film, which is vital for sensors. By the UV light activation, sensors based on the AZO nanocolumn array exhibited enhanced H 2 O 2 detection properties at room temperature. At a concentration from 15 μM to 30 mM, H 2 O 2 sensitivity evaluated by relative response was remarkably increased from 15% to 36%. The operation under ambient conditions and wide range sensing shows that this chemiresistive AZO sensor is adequate for biomedical and environmental applications. [ABSTRACT FROM AUTHOR]

We prepared aluminum-doped zinc oxide (ZnO:Al, AZO) films by a sol–gel method and investigated the effect of doping on the electrical properties of AZO films in the Al doping concentration range of 0.5–3.0 at.%. The negative effect of Al dopants on the carrier mobility counteracted their positive effect on the carrier concentration and the resistivity of the films remained almost constant at the optimum Al doping level of 0.5 at.%. Moreover, the doping efficiency of Al dopant decreased with increasing doping level and the maximum efficiency was not higher than 50% even at the optimum doping concentration. The microstructure and chemical composition of the films were examined by X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy to elucidate the mechanism behind the low doping efficiency of Al dopant in the sol–gel-derived AZO films. The reason was attributed to the passivation of the dopant in two forms, defect complex nAlZn–VZn originating from the dopant–defect reaction in the ZnO grains and aluminum oxide phase segregating at the ZnO grain boundaries. [ABSTRACT FROM AUTHOR]

Hollow silica nanospheres (HSNs) were synthesized via sol–gel method followed by calcination, using positively charged polystyrene (PS) as a hard template, and the tetraethoxysilane as precursor. The inner diameter and shell thickness of the HSNs can be expediently controlled by adjusting the particle size of PS and the amount of ammonia, respectively. The average inner diameters of HSNs increased from 153 nm to 255 nm along with the increasing PS particle size from 150 nm to 300 nm. The shell thickness of HSNs decreased from 20 nm to 12 nm with the increasing amount of ammonia from 1.5 mL to 3.0 mL. The structure of HSNs was verified by Fourier-transform infrared, thermogravimetric, scanning electron microscopy, and transmission electron microscopy characterization. The prepared thermal insulation coating comprised of HSNs shows good temperature retention and thermo-insulating properties, which indicate that the as-prepared HSNs are potentially used as an inorganic filler for thermal insulation coating. [ABSTRACT FROM AUTHOR]

The bioactive glass (BG) system of 60SiO 2 –4P 2 O 5 –31CaO-xSrO-(5-x) ZnO (0 ≤ x ≤ 5 %mol) was synthesized by sol-gel route. The role of zinc contents and strontium on the in-vitro formation of hydroxyapatite (HA), antibacterial properties, and cell viability of BGs were investigated. XRD (X-ray diffraction analysis), SEM (Scanning electron microscopy) and FTIR (Fourier transform infrared spectroscopy) were utilized to study the HA morphology, its functional groups and obtained phases, respectively. The results established the formation of HA on the surface of strontium and zinc-containing BGs. The 3-(4,5 dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay after one day immersion in SBF, implied that the viability of samples containing 4 %mol Sr and 1 %mol Zn (S4-Z1) and 3 %mol Sr and 2 %mol Zn (S3-Z2) increases by increasing immersion time, while the sample containing 1 %mol Sr and 4 %mol Zn (S1-Z4) showed a statistically significant increase in osteoblast G292 proliferation. Furthermore, the antibacterial tests showed that all Zn containing BGs created clear inhabitation zones. The zone of clearance around the bioactive glasses demonstrated that sufficient Zn ion was released to create an antibacterial activity around the bioactive glasses. [ABSTRACT FROM AUTHOR]

The study presents the synthesis of TiO2/SiO2 membrane materials using sol–gel method by hydrolysis of tetrabutyl titanate (TBOT) with ethanol and water mixture as titania source, tetraethylorthosilicate (TEOS) and methyltriethoxysilane (MTES) as silica source. The microstructure of the composites were characterized by X-ray diffraction (XRD), fourier transform infrared (FTIR) spectra, scanning electron microscopy (SEM), energy dispersive spectrum (EDS), N2 absorption–adsorption measurement and thermogravimetric-differential thermogravimetric (TG-DTG) analysis. The as obtained TiO2/SiO2 membrane materials showed the existence of Si–O–Ti, which indicates that the SiO2 is chemically bonded with the TiO2 particles. The TiO2 nanoparticles have entered into the channels of SiO2 network. The TiO2-doping decreased the mean pore diameter, and increased the surface area and porosity of SiO2 materials. The TiO2/SiO2 membrane materials with Ti/Si molar ratio of 0.4 exhibit a large BET surface area (up to 284.04 m2/g) and total pore volume (up to 0.272 cm3/g), as well as a mean pore diameter of about 2.49 nm. [ABSTRACT FROM AUTHOR]

Surrogate glasses were fabricated by the sol–gel process aiming to produce compositions similar to naturally occurring tektite. The volatile species in the xerogel samples were removed by heat treatments. All products were characterized by thermal analysis, scanning electron microscopy, X-ray diffraction and energy dispersive spectroscopic techniques. The elemental distribution in the surrogates was found to be more homogeneous than the one observed in natural materials. This work presents an alternative to generate target materials for the validation of techniques aimed to comminute samples in the nuclear forensics field, making the comparison between the pre and post-treatments more viable. [ABSTRACT FROM AUTHOR]

The effect of the sintering temperature on the formation of secondary phases and ferroelectric properties of Bi0.5(Na0.8K0.2)0.5TiO3 ceramics has been studied. Ceramic powders were prepared by the sol-gel method and sintered at different temperatures. Samples were characterized by X-ray diffraction (XRD), Raman microspectroscopy, scanning electron microscopy, impedance spectroscopy and ferroelectric hysteresis loops. Through XRD and Raman results, the perovskite structure was detected, and the formation of secondary phases was registered. As the sintering temperature was increased, the secondary phase composition was modified. Moreover, dielectric properties were influenced by the resulting grain size and the secondary phase amount. [ABSTRACT FROM AUTHOR]

SiO2 and Pd/SiO2 nanocomposites were prepared using sol-gel method and characterized by X-ray diffraction, Fourier transform infrared spectra, scanning electron microscopy and different heating rate thermogravimetric-differential thermogravimetric analysis. The apparent activation energies (Ea) were calculated using the Kissinger's and Ozawa's methods. The most probable kinetic mechanism functions were obtained by master plot method. The entropy (ΔS≠), enthalpy (ΔH≠) and activation free energy (ΔG≠) were calculated using three methods. The results demonstrated that the thermal decomposition processes of both materials are the three-step reactions. After thermal condition in air atmosphere, the introduced hydrophobic Si-CH3 group in Pd/SiO2 gel materials was completely decomposed into inorganic composition, and the Pd element was transformed into PdO and metallic Pd. The Ea values obtained by Kissinger's method are close to those by Ozawa's method. The Pd-doping can increase the thermal decomposition activation energies and improve the thermal stability of SiO2 material. The decomposition mechanisms for the three stages are the assumed random nucleation and its subsequent growth, irrespective of the Pd-doping. Compared with SiO2 material, the thermal decomposition of Pd/SiO2 requires more energy due to the increasing ΔH≠. The ΔH≠ values calculated by method II are nearly equal to the Ea values from the Kissinger's and Ozawa's methods, which indicated that the thermodynamic parameters obtained by method II are the most accurate. [ABSTRACT FROM AUTHOR]

We present a two-step method to prepare a hydrophobic cellulosic membrane involving a SiO 2 sol-gel process, to increase surface roughness, followed by grafting of hexadecyltrimethoxysilane groups to chemically enhance the membrane’s water repellency. The modification processes induced morphological and chemical changes as observed by scanning electron microscopy and infrared spectroscopy, respectively. The hydrophobic membrane was used to separate immiscible oil/water mixtures with efficiencies over 99%. In addition, we tested the material for breaking an asphaltene–stabilized water in oil emulsion and registered separation efficiencies from 75% to 95%. The demulsification process depends on membrane surface hydrophobicity, emulsion viscosity and dispersed droplet size. The hydrophobic/oleophilic cellulose membrane was efficiently reused over 18 times to break a water/oil (50% water) emulsion. This facile solution for breaking low viscosity w/o emulsions and immiscible water/oil mixtures could be easily scalable and used to develop efficient separation methods driven solely by gravity. [ABSTRACT FROM AUTHOR]

This paper presents a study on attempting to substitute Gd into a Ca-Ba M-type hexaferrite (Ca0.5Ba0.5GdxFe12−xO19, where x = 0, 0.05, 0.1, 0.15, 0.2, 0.25) using the sol-gel method. The structural, magnetic and microwave properties of the resultant material were investigated. Since Gd has a much larger ionic radius than Fe, substitution is not straightforward as revealed by the structural analysis. X-ray diffraction (XRD) patterns revealed some substitution into the M-type phase due to a changing lattice parameter; however, significant quantities of additional phases of hematite (α-Fe2O3) and gadolinium orthoferrite started to form at concentrations of up to Gd = 0.10 and at higher Gd concentrations, respectively. High-resolution transmission electron microscopy of selected compositions showed d-spacings corresponding to the three phases observed in XRD, confirming the incomplete substitution of Gd. Scanning electron microscopy showed platelet-shaped grains. Vibrating sample magnetometry at room temperature showed varied results owing to a myriad of interactions from the hexaferrite and secondary phases. The microwave complex permittivity and permeability in the frequency range of 2-11 GHz showed little frequency dependence with nominal values for the complex permeability. All the compositions exhibit low magnetic losses with frequency except Gd = 0.10. Such type of materials can be used for microwave devices in the low-GHz range and as well as permanent magnets. [ABSTRACT FROM AUTHOR]

Upconversion Sr 2 (Gd .98- x Er .02 Yb x ) 8 Si 6 O 26 (SGSO:2Er 3+ / x Yb 3+ ) phosphor materials were synthesized using a citrate sol-gel process. X-ray diffraction patterns confirmed their hexagonal structure. Field emission scanning electron microscopy images of SGSO:2Er 3+ / x Yb 3+ phosphors depicted submicron particles. The enhanced upconversion luminescence properties of SGSO:2Er 3+ / x Yb 3+ phosphors were analysed as a function of Yb 3+ ion concentration and laser power. The energy transfer induced enhanced emission of the Er 3+ / Yb 3+ ions co-doped SGSO phosphors was ascribed to multi-phonon relaxation. The calculated chromaticity coordinates of the SGSO:2Er 3+ / x Yb 3+ phosphors showed emissions could be tuned by changing Yb 3+ ion concentration. Optimized sample exhibited the chromaticity coordinate values near to the ultra-high definition television standard green emission coordinates. [ABSTRACT FROM AUTHOR]

The paper presents a systematic study of the electrochromic properties of thin films of V 2 O 5 :TiO 2 for a possible utilization as counter-electrode in electrochromic devices. The V 2 O 5 :TiO 2 thin films were prepared by the sol-gel process and deposited on a substrate of fluorine-tin oxide transparent electrode (FTO) using the dip coating technique and heat treatment at 350 °C for 30 min. The films were characterized by chronocoulometry, cyclic voltammetry (CV), UV-Vis, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), atomic force microscopy (AFM), profilometry, and X-ray diffraction (XRD). The best results were obtained for the film of V 2 O 5 with 7.5 mol% of TiO 2 , which presented highest ion storage capacity of ∼106 mC cm −2 and redox reversibility of 1. The diffusion of the Li + ions into the thin films was modeled by solving Fick equations with appropriate boundary conditions for a plane sheet geometry. Besides that, these films showed optical modulation of 35% at 633 nm after coloration and bleaching. The XRD patterns revealed that the films have an orthorhombic crystal structure; the AFM and the profilometry confirmed roughness and thickness of 16.76 and 617 nm, respectively. [ABSTRACT FROM AUTHOR]

New hybrid materials using kaolin and the organosilicas methyl-polysiloxane (MK), methyl-phenyl-polysiloxane (H44), tetraethyl-ortho-silicate (TEOS) and 3 -amino-propyl-triethoxysilane (APTES) were obtained by sol-gel process. These materials presented specific surfaces areas (S BET ) in the range of 20–530 m 2 g −1 . Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed remarkable differences between the kaolin and hybrid structures. Thermogravimetric analysis (TGA) revealed that the hybrid materials presented higher thermal stability when compared with their precursors. The electronic properties of the materials were also studied by Ultraviolet-Visible Diffuse Reflectance Absorption (DRUV) and Diffuse Reflectance spectroscopy (DR), where a new absorption band was observed located around 400–660 nm. In addition, these materials exhibit a decrease in DR from 30% to 70% in the blue-cyan green region and are significantly more transparent in the UV region than the kaolin, which could be useful for photocatalysis applications. These results show that the electronic structure of the final material was changed, indicating a significant interaction between the kaolin and the respective silica derivative. These findings support the main idea of the hybridization afforded by pyrolysis between kaolin and organosilica precursors. In addition, as a proof of concept, these hybrid materials were successfully employed as photocatalyst in the photoreduction of Cr(VI) to Cr(III). [ABSTRACT FROM AUTHOR]

New hybrid materials were synthesized from an inorganic precursor, (tetraethoxysilane: TEOS) and bifunctional organic precursors through the sol-gel process. Indeed, monolithic and transparent hybrid gels were obtained by the reaction of tetraethoxysilicate (TEOS) with 1,2,4-thiadiazole-3,5-diamine(1), 5-amino-1,3,4-thiadiazole-2-thiol(2), and 1H-1,2,4-triazole-3-thiol(3)in ethanol as solvent, using chloric acid (HCl 10−1M) as catalyst. It is shown that TEOS has been cross-linked with bi-functional heterocyclic compounds:(1), (2)and(3)leading to the formation of transparent and colorous gels. The characterization was realized by infrared,29Si and13C CP MAS NMR. The xerogels morphology and texture were studied by scanning electron microscopy (SEM) and Brunauer – Emmet – Teller method (BET). The obtained results show that organic adducts(1), (2)and(3)react with TEOS leading to gels in which Si–N and Si–S bridges were formed. According to N2-physisorption results, xerogels are mesoporous with specific surface area varied from 105 to 312 m2g−1and their isotherms are classified as type IV. The optic and magnetic properties of hybrids were studied respectively by UV-Vis spectroscopy and RPE. This study showed that all materials are paramagnetic semiconductors. [ABSTRACT FROM AUTHOR]