Sol-gel synthesis of nanometer silicon/silicon suboxide/carbon anode material

A stacked Si/SiO_(x)/C composite anode material with carbon-coated structure was prepared by sol-gel method combined with carbothermal reduction using organic silicon.The results of X-ray diffractometry, scanning electron microscopy, and elemental analysis show that the Si/SiO_(x)/C material is a secondary particle with a porous micronanostructure, and the presence of nanometer silicon does not affect the carbothermal reduction and carbon coating.Electrochemical test results indicate that the specific capacity and first coulombic efficiency of SiO_(x)/C composite with nanometer silicon can be increased to 1 946.05 mAh/g and 76.49%,respectively.The reversible specific capacity of Si/SiO_(x)/C material blended with graphite is 749.69 mAh/g after 100 cycles at a current density of 0.1 C,and the capacity retention rate is up to 89.03%.Therefore, the composite has excellent electrochemical cycle stability.

Multilayer Membranes Based on Ceramic Materials——Sol-gel Synthesis,Characterization and Membrane Performance

In nearly all chemical and petrochemical systems, separation of products generally accounts for more than 50% of the capital cost and the greatest part of the energy consumption. It is generally believed that membrane systems can offer benefits in both reducing the energy consumption of the separation stages and lowering the capital expenditure （CAPEX）. Microporous ceramic membranes have the potential to overcome the limitation in polymer membranes operation, which has been the subject of a large amount of research worldwide in the last two decades. And most of the research has aimed at the production of the asymmetric multilayered membrane based on amorphous oxides by sol-gel techniques. The paper is to give an overview of publications on ceramic membranes, including less common materials of titania, zirconia, which can be used for pervaporation in corrosive media. Commercially available microporous membranes based on these membrane materials and the membrane economics are also summarized.

Sol-gel synthesis and photoluminescence of LaPO_4:Eu^(3+) nanorods

Monoclinic LaPO4 nanostructures with uniform rod shape have been successfully synthesized by a simple sol-gel method.The procedure involves formation of homogeneous,transparent,metal-citrate-EDTA gel precursors,followed by calcination to promote thermal decomposition of the gel precursors to yield the LaPO4 nanoparticles.Their morphologies and structures were characterized by XRD,TEM,TG-DSC and HRTEM.The results indicate that single monoclinic phase LaPO4 nanorods are readily obtained at 800 ℃ within 3 h.Furthermore,photoluminescence(PL) characterization of the Eu3+-doped LaPO4 nanocrystals was carried out.The effects of calcination temperatures and Eu3+ doping content on the PL properties were elaborated in detail.Room-temperature photoluminescence(PL) characterization reveals that the optical brightness as well as the intensity ratio of 5D0-7F1 to 5D0-7F2 is highly dependent on the calcination temperature,and the Eu0.05La0.95PO4 nanophosphor shows the relatively promising PL performance with the most intense emission.

Sol-Gel Synthesis of Normal Spinel LiMn_2O_4 and Its Characteristics

Normal spinel LiMn 2O 4 was synthesized by sol-gel method using lithium nitrate,manganese nitrate,citric acid and ethylene glycol as raw materials. LiMn 2O 4 was characterized by XRD,TG-DTA,IR,SEM and AAS.The optimum conditions for the synthesis were explored.Citric acid and ethylene glycol were mixed with molar ratio of 0.25,and the mixture was esterified at 140℃ for 4 hours.Then lithium nitrate and manganese nitrate were added with molar ratio of 0.6. In the system,the total molar of cations was equal to that of citric acid. At last, reflux the system at 105℃ for 2 hours. Dried gel was fired at 600℃ for 8 hours. Particle diameters of raw product were about 100 nm mainly. Further research shows that lithium ion of LiMn 2O 4 is easy to be extracted,and normal spinel λ-MnO 2 can be obtained after lithium ion extraction.

Sol-gel Synthesis and Photoluminescence of InP Nanocrystals Embedded in Silica Glasses

III-Vsemiconductor nanocrystals rarely exist as spherical inclusions inside glasses, due to difficulties during their preparation, such as high toxic reagents or fast oxidation under usual glass technology temperatures. In this article a sol-gel method for synthesis of InP nanocrystals embedded in silica glasses was described. Gels were synthesized by hydrolysis of a complex solution of Si(OC 2 H 5 ) 4 , InCl 3 4H 2 O and PO(OC 2 H 5 ) 3 . Then, the gels were heated at 600 o C in the presence of H 2 gas to form fine cubic InP crystallites. Raman spectrum showed InP longitudinal-optic mode (342cm -1 ) and transverse-optic mode (303cm -1 ). The size of InP nanocrystals was found to be from 2 to 8 nm in diameter by transmission electron microscopy. A strong photoluminescence with peaks at, 606, 730nm 856 nm was observed from 3InP/100SiO 2 nanocompositions. The temperature-and excitation power-dependent PL spectra from the nanocomposition are measured in order to confirm the origin of the PL spectra. These behaviors of the three peaks emissions suggest that 606, 733, and 856 nm emissions do not have the same origin. The PL with peak at 856nm arise from the cubic InP nanocrystallites embedded in the SiO 2 gel glasses. The 605 and 732 nm emissions may arise from the SiO 2 gel glass matrix or the interface between the InP crystallite core and SiO2 glass matrix.

Sol-gel synthesis and photoluminescence properties of BaSO_4/Y_2O_3:Eu^(3+) core-shell submicrospheres

Europium-doped nanocrystalline Y2O3 phosphor layers were coated on the surface of preformed submicron BaSO4 spheres via the sol-gel process.The obtained BaSO4/Y2O3:Eu3+ core-shell phosphors were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),energy dispersive spectroscopy(EDS) and photoluminescence spectra.The results showed that the obtained BaSO4/Y2O3:Eu3+ core-shell phosphors consisted of well-dispersed submicron spherical particles with na...

Effects of chelating agents on the sol-gel synthesis of nano-zirconia:Comparison of the Pechini and sugar-based methods

This study focused on the comparison of the Pechini and sugar-based combustion synthesis methods to produce nano-zirconia. Zirconium hydroxide was utilized as metal precursor and citric acid, sucrose, and fructose were used as chelating agents, followed by calcination at 500, 600, and 700°C in air, respectively. Characterization was conducted by thermal analysis, specific surface area measurement, Fourier transform infrared spectroscopy, X-ray diffraction, and scanning and transmission electron microscopy. When sucrose and citric acid were used as chelating agents during synthesis, mixtures of monoclinic and tetragonal phases were formed after calcination at 600 and 700°C. In the fructose samples, the tetragonal structure was the unique characterized phase. The tetragonal parameters in the fructose samples were determined using the diffraction data and the lattice parameter ratio was proven to increase with the temperature increase. Compared with the citrate and sucrose samples, the largest specific surface area(27 m2·g-1) and smallest particle size(39.1 nm) were obtained for the fructose sample after calcination at 700°C. The study revealed the formation of single-phase stabilized tetragonal zirconia using fructose as chelating agent after calcination at 500°C, and the presence and formation mechanism of stabilized tetragonal phase were also discussed on the basis of the X-ray and electron diffraction studies.

Sol-gel synthesis and photoluminescence characterization of La_2Ti_2O_7:Eu^(3+) nanocrystals

Eu3＋ doped La2Ti2O7 nanocrystals with pure monoclinic phase and size of about 100 nm were prepared by a citric acid （CA） assisted sol-gel method. Techniques of thermo-gravimetric （TG） and differential scanning calorimetry （DSC）, X-ray diffraction （XRD）, as well as transmission electron microscopy （TEM） were employed to characterize the as-synthesized nanoparticles. Furthermore, photoluminescence （PL） performances of the Eu3＋ doped La2Ti2O7 nanocrystals were evaluated with focus on the effects of calcination temperature and Eu3＋ doping concentration on the photoluminescence properties.

Synthesis and electrochemical performance of Li_3V_2(PO_4)_3 by optimized sol-gel synthesis routine

Li3V2（PO4）3 samples were synthesized by sol-gel route and high temperature solid-state reaction. The influence of Li3V2（PO4）3 as cathode materials for lithium-ion batteries on electrochemical performances was investigated. The structure of Li3Va（PO4）3 as cathode materials for lithium-ion batteries and morphology of Li3V2（PO4）3 were characterized by X-ray diffractometry （XRD） and scanning electron microscopy （SEM）. Electrochemical performances were characterized by charge/discharge and AC impedance measurements. Li3V2（PO4）3 with smaller grain size shows better performances in terms of the discharge capacity and cycle stability. The improved electrochemical properties of Li3V2（PO4）3 are attributed to the refined grains and enhanced electrical conductivity. AC impedance measurements also show that the Li3V2（PO4）3 synthesized by sol-gel route exhibits significantly decreased charge-transfer resistance and shortened migration distance of lithium ions.

The Mechanism of Sol-Gel Synthesis of Normal Spinel LiMn_2O_4 with Chelation of Citric Acid

The sol-gel process of citric acid chelating with metal cations for the synthesis of normal spinel LiMn 2O 4 and the reaction mechanism were investigated by means of XRD,IR,TG-DTA, and SEM.The results show that at the beginning lithium citrate and chelate compound of citric acid with manganese ions formed,and then with heating the esterification and condensation reactions occured between them and glycol.The products obtained are polymers in which metal cations are distributed homogeneously on atomic scale that ensure high reactivity to cations of Li + and Mn 2+.Firing the gel prepared by this process,the lattice diffusions of solid reactant ions caused by non-homogeneity of reactants are eliminated and avoided.At 400℃ phase-pure LiMn 2O 4 with nanometer scale crystallization having precise stoichiometry and perfect crystallization can be obtained.The model of chelate coordinate of double-molecule between citric acid and Mn 2+ in the gel network is proposed.It is important for explaining the dispersion state of Mn 2+ and the formation process of gel by this model.

Comparison of Hydrothermal and Sol-Gel Synthesis of Nano-Particulate Hydroxyapatite by Characterisation at the Bulk and Particle Level

Hydrothermal and sol-gel synthesis methods have been used to prepare nano-particulate hydroxyapatite (HA) powders for detailed characterisation. Bulk elemental analysis data are compared from X-ray diffraction, X-ray fluorescence and Fourier transform infrared spectroscopy. These show the presence of secondary phases in the sol-gel powders which can be attributed to evaporative loss of precursor phosphite phases during specimen preparation and breakdown of the primary HA phase during calcination. Only the primary HA phase is detected in the hydrothermally prepared powder. In addition, Ca/P ratios of each powder are determined at the particle level using transmission electron microscopy with energy dispersive X-ray spectroscopy (TEM-EDX), having first established a threshold electron fluence below which significant electron-beam-induced alteration of the composition of HA does not occur. The TEM-EDX results show a greater compositional variability of particles from the sol-gel preparation route compared to the hydrothermal route. Overall it is the combination of the analysis techniques that shows the hydrothermal synthesis route produces near- stoichiometric, single phase, hydroxyapatite.

Microwave-assisted sol-gel synthesis of hydroxyapatite nanoparticles

A rapid sol-gel method for preparing hydroxyapatite nanoparticles(nHAP) has been developed. Three different sets of experimental conditions, in terms of solvents(water and ethanol), synthesis temperatures(25, 40 and 60℃), and microwave irradiation(on and off) were explored. Crystal phase composition, functional groups and morphology of the products were characterized by thermogravimetric analysis(TGA), X-ray diffraction(XRD), Fourier transform infrared spectroscopy(FT-IR), scanning electron microscopy(SEM) and transmission electron microscopy(TEM). The solvent and temperature were optimized based on product properties. Most importantly, the microwave-assisted method(with little to no ageing necessary) was much faster than the conventional methods(with slow ageing processes needing from hours to days), while affording pure nHAP with virtually identical morphological and structural properties. This study represents a practical application of the powerful microwave technique in synthesis of nHAP, offering guidance on the selection of optimum experiment conditions.

Effect of Co substitution on the structural,electrical,and magnetic properties of Bi_(0.9)La_(0.1)FeO_3 by sol-gel synthesis

Cobalt （Co）-doped Bi0.9La0.lFeO3 multiferroics were synthesized by a sol-gel method based on the auto- combustion technique. As-synthesized powder was examined using various characterization techniques to explore the effect of Co substitution on the properties of Bi0.9La0.1FeO3. X-ray diffraction reveals that Co-doped Bi0.9La0.1FeO3 preserves the perovskite-type rhombohedral structure of BiFeO3, and the composition without Co preserves the original structure of the phase; however, a second-phase Bi2Fe409 has been identified in all other compositions. Surface morphological studies were performed by scanning electron microscopy. Temperature-dependent resistivity of the samples reveals the characteristic insulating behavior of the multiferroic material. The resistivity is found to decrease with the increase both in temperature and Co content. Room temperature frequency-dependent dielectric measurements were also reported. Magnetic measurements show the enhancement in magnetization with the increase in Co content.

Sol-Gel Synthesis and Luminescent Characteristic of Doped Eu~ 3+ Silicate-Silica Phosphor

Eu-doped silicate complex gel nano-particles was obtained by sol-gel process and characterized with TEM, XRD, PL, etc. The well dispersed particles have particle size about 60 - 70 nm with specific surface area 98.3 m^2· g^- 1 The complex gel phosphor gives a broad and strong luminescent emission originating from Eu^2＋ ions centered at 425 nm. The emission band shifts to shorter wavelengths with the increase of the ion radius of the alkali earth metals, but the band becomes red-shifted gradually with the increase of the ion radius of the alkali metals（except Li ^＋ ）. These divalent Eu^2＋ ions originate in inequivalent substitution of the alkaline earth ions. The presence of alkaline ions is favorable for the increasing emission intensity of the Eu^2 ＋ and lowering crystalline temperature of the silicate complex gel.

Sol-Gel Synthesis and Structure-Property Relations in Nd4-xCs2（1＋x）Fe5-xZnxO14＋δ（0≤x≤1.0） Oxide Systems

Synthesis of composite oxides in the series Nd4-xCs2（1＋x）Fe5-xZnxO14＋δ（0≤x≤1.0） （B1-B5： x= 0.0, 0.25, 0.5, 0.75, 1.0） is performed by sol-gel method via nitrate-acetate precursor route. Analysis of the powder x-ray diffraction （XRD） patterns show tetragonal unit cell with lattice parameters a = 8.6545, 8.2520, 7.7645, 9.8952, 8.2863 A; b = 8.9800, 11.5788, 15.6305, 8.4766, 11.6465 A in B1-B5, respectively. The average crystallite sizes in the samples are found to be in the range 69.56-119.48 A. Energy dispersive analysis of x-rays （EDAX） result shows the presence of Fe, Nd, Cs and O, and Fe, Nd, Zn, Cs and O in B 1 （x=0） and B2（x=0.25）-B5（x= 1.0）, respectively. The IR results at 300 K show the presence of octahedral [NdO6/2]^3- （asymmetric stretch： 410-416 cml） and [FeO6/2]^3-（symmetric stretch： 562-572 cm^-1） units in the samples. Observed magnetic moments versus magnetic field plots in the range -10 kG to ＋10 kG exhibit hysteresis loops with average magnetic susceptibility values in the range 3.46 × 10^-5 -7.05 × 10^-5 emu/gG in B1-B5 shows fairly strong ferromagnetic nature of the samples. The observed EPR lineshapes at 300 and 77 K with giso=2.01-2.03 and giso=2.01-2.03, respectively is ascribed to the octahedral [FeO6/2]^3- coordination of Fe^3＋ （3d^5） ion. The optical absorption spectra show the transition of ^4I9/2→^4F7/2→^ 4S3/2 （750 nm） of optically active Nd^3＋ ions in samples.

SOL-GEL SYNTHESIS AND LUMINESCENCE OF GREEN LIGHT EMITTING PHOSPHORS ZN_2SIO4/MN^(2+)

Mn^2＋ doped Zn2SiO4 phosphors were synthesized by sol-gel method, and the influence of zinc source, Mn^2＋ dopant concentration and annealing temperature were investigated. Results show that zinc nitrate based precursor with strong green emission intensities is better than zinc acetate based precursor. The intensity of green light emission reaches a peak at 254 nm when the Mn^2＋ dopant concentration is about 5%（ molar percentage）. Structural details of the phosphors were examined through X-ray diffractometry, thermogravimetric and differential thermal analysis. The result indicates that they are both rhombohedral structures, which remain amorphous below 700 ℃ and crystallize completely around 1000 ℃. The luminescent properties of Zn2SiO4/Mn^2＋ phosphors were characterized by excitation and emission spectra.

Sol-Gel Synthesis and Structure-Property Relations in Silver Nanoparticles-Dispersed in GeO2 Matrix

Synthesis of Ag nanoparticles dispersed in germanium dioxide （GeO2） matrix was performed via sol-gel route. Analysis of the powder X-ray diffraction （XRD） pattern shows fcc cubic unit cell of Ag with lattice parameters： a = 4.0884 A, space group Fm-3m. Energy dispersive analysis of X-rays （EDAX） results show the presence of only GeO2 and Ag in the sample. The average crystallite sizes of Ag particles determined by Scherrer＇s relation are found to be i 8-47 nm. Observed sharp electron paramagnetic resonance （EPR） lineshapes at 8, 70 and 300 K with g-values of 2.004, 2.004, and 2.004, respectively, show that the Ag （5s~） electrons are localized in the Ag nanoparticles. The calculated value of the magnetic susceptibility is 1.014~ 10-5 emu/gG from the observed magnetic moments data at 300 K, which shows fairly strong paramagnetic nature of the material. Refinement of Ag crystal structure in space group Fm-3m with Ag atoms in 4（a） position shows the agreement bond length as 2.8909 ,＆. Calculated density of states below Fermi factors Rp= 67.22%, Rwp= 75.7%, Rexp= 0.06%, Z = 4 and Ag-Ag energy, EF, from -2 to -8 eV are due to valence d orbitals of Ag.

Sol-Gel Synthesis of SiO₂-CaO-Na₂O-P₂O₅Bioactive Glass Ceramic from Sodium Metasilicate

Bioactive glass ceramic with SiO2-Ca2O-Na2O-P2O5 composition was prepared by the sol-gel method using sodium metasilicate (Na2SiO3) as silica source. The monolith obtained was sintered at 1000?C for 2 hours after which X-ray diffraction (XRD) analysis showed presence of combeite (Na2Ca2Si3O9) as the crystalline phase. In vitro bioactivity test conducted on the material using simulated body fluid (SBF) showed the formation of carbonated hydroxyapatite on its surface. The material during the SBF test was observed to transform from a mechanically strong crystalline phase Na2Ca2Si3O9 to an amorphous phase after incubation for 14 days indicating that the material was biodegradable. Scanning electron microscopy (SEM) was used to investigate the surface morphology, while Fourier transform infrared (FTIR) spectroscopy facilitated the confirmation of hydroxyapatite (HA) formation. The monolith material obtained may be a good candidate for application in tissue engineering scaffolds.

Sol-Gel Synthesis of TiO₂Thin Films from In-House Nano-TiO₂Powder

This paper presents the optimization process in sol-gel technique to synthesize Titanium dioxide (TiO2) thin films using in-house Nano-TiO2 powder. Nano-TiO2 powder was previously synthesized in our lab from ilmenite which is a tin mining byproduct using a modified hydrothermal method. By varying the mass of Nano-TiO2 powder and acetic acid (catalyst) concentration in the sol-gel process, highly transparent TiO2 thin films were obtained. The thin films were characterized by field effect scanning electron microscope (FESEM), atomic force microscopy (AFM), thickness profiler, ultra-violet-visible spectrometer (UV-Vis) and current-voltage (I-V) measurement system. This paper also demonstrates the TiO2 thin films are sensitive towards isopropanol (IPA) solution where the I-V response of the thin films changed sharply as IPA was dropped onto the thin film’s surface. The electrical property shows the thin film has potential applications for chemical sensors and solar cells.

Sol-Gel Synthesis Using Novel Chelating Agent and Electrochemical Characterization of Binary Doped LiMn2O4 Spinel as Cathode Material for Lithium Rechargeable Batteries

LiMn2O4 and LiCuxCryMn2-x-yO4 (x = 0.50;y = 0.05 - 0.50) powders have been synthesized via sol-gel method for the first time using Myristic acid as chelating agent. The synthesized samples have been taken to physical and electrochemical characterization such as thermo gravimetric analysis (TG/DTA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and electrochemical characterization viz., electrochemical galvanostatic cycling studies, electrochemical impedance spectroscopy (EIS) and differential capacity curves (dQ/dE). XRD patterns of LiMn2O4 and LiCuxCryMn2-x-yO4 confirm high degree of crystallinity with good phase purity. FESEM image of undoped pristine spinel lucidly depicts cauliflower morphology with good agglomerated particle size of 50 nm while 0.5-Cu doped samples depict the pebbles morphology. TEM images of the spinel LiMn2O4 and LiCu0.5Cr0.05Mn1.45O4 authenticate that all the synthesized particles via sol-gel method are nano-sized (100 nm) with spherical surface and cloudy particles morphology. The LiMn2O4 samples calcined at 850℃ deliver the high discharge capacity of 130 mA·h/g with cathodic efficiency of 88% corresponds to 94% columbic efficiency in the first cycle. Among all four compositions studied, LiCu0.5Cr0.05Mn1.45O4 delivers 124 mA·h/g during the first cycle and shows stable performance with a low capacity fade of 1.1 mA·h/g cycle over the investigated 10 cycles.