Advantages Of Sol Research Articles

Improved Design Guidelines for Pipelines Subjected to Vertical Fault Movement in Dry Sand

AbstractPracticing engineers use the uncertain bilinear soil spring methodology recommended by engineering guidelines to predict soil loads acting on buried pipelines. Even though more advanced sol...

An advanced sol–gel strategy for enhancing interfacial reactivity of iron oxide nanoparticles on rosin biochar substrate to remove Cr(VI)

The application of iron oxide nanoparticles (IONs) is often limited by agglomeration and low loading. Here, we presented a facile phase change material (PCM) -based sol-gel strategy for the fabrication of α-Fe2O3 nanoparticles. Rosin was used as the PCM in the sol-gel process and the carbon-based substrate of α-Fe2O3 nanoparticles in the thermal process. The α-Fe2O3 nanoparticle embedded rosin-derived biochar(α-Fe2O3@HrBc)were highly dispersed. The dispersity of α-Fe2O3 nanoparticle could be regulated by the weight ratios of rosin to FeCl3·6H2O during the preparation, as evidenced by the scanning electron microscope (SEM) spectrum and the sorption capacity results. Among a series of α-Fe2O3@HrBc nanocomposites, the one with the weight ratios of 1/1.5 rosin/FeCl3·6H2O had the highest capacity for hexavalent chromium (Cr(VI)) sorption. This phenomenon can be ascribed to a remarkably enhanced interfacial reactivity due to an increase in the dispersity of α-Fe2O3 nanoparticle. In addition, SEM showed that the majority of α-Fe2O3 nanoparticles was dispersed on and inside the biochar substrate. Batch adsorption experiments revealed that the α-Fe2O3@HrBc adsorbed 90% Cr(VI) within one minute, and the maximum capacity was up to 166 mg·g−1 based on the Langmuir model. The FTIR and XPS spectra revealed that the adsorbed Cr(VI) species were partially reduced to less toxic Cr(III). Considering that α-Fe2O3 nanoparticles provided important sorption sites, the newly formed Cr(III) and the remaining Cr(VI) ions could be adsorbed on α-Fe2O3@HrBc via the formation of FeCr coprecipitation.

Immobilization engineering – How to design advanced sol–gel systems for biocatalysis?

An immobilization engineering approach using bioinformatics and experimental design tools was applied to improve the sol–gel enzyme entrapment methodology.

Sintering and Microstructural Modification of Seeded and Neodymium Doped Lanthanum Hexaaluminate

The effect of (i) heterogeneous nucleation by seeding or (ii) doping with neodymium on the formation of lanthanum hexaaluminate was studied during sol to gel conversion. The resultant dried gels were calcined at various temperatures starting from 1100°C to 1600°C for 2 h to study the phase evolution and microstructure.The combined effects of advanced sol gel processing and heterogeneous nucleation promoted the formation of lanthanum hexaaluminate phase at lower temperature (1200°C) than the conventional routes (1300°C). Lanthanum hexaaluminate phase was detected at 1200°C and 1300°C in seeded gel (SG) and unseeded gel (UG), respectively. Heterogeneous nucleation of SG decreases the temperature of formation of lanthanum hexaaluminate by 100°C. Single phase lanthanum hexaaluminate was formed at 1600°C in seeded gel whereas trace of lanthanum monoaluminate phase was still present in UG even at 1600°C.On the doped ones, randomly grown platelets of lanthanum magnesium hexaaluminate form a porous interlocking structure. Presence of various percentages of neodymium oxide significantly modifies the porous interlocking microstructure into self-reinforced, card-house like microstructure. Platelets of rare earth rich magnesium hexaaluminate were grown preferentially more than the stoichiometric rare earth magnesium hexaaluminate at elevated temperature greater than 1450°C. Rare earth rich magnesium hexaaluminate platelets formed the skeleton of a card house structure and the tiny platelets of stoichiometric rare earth magnesium hexaaluminate fill the rest. Lattice parameters of the hexagonal unit cell (c and a) decrease, relative density increases and pore size distribution remained almost unaltered with the increment of doping concentration.

Effect of seeding on the formation of lanthanum hexaaluminates synthesized through advanced sol gel process

Advanced sol gel processing was used to synthesize high purity lanthanum hexaaluminate powders. The effect of seeding on the formation of lanthanum hexaaluminate was also studied by seeding the gel. Dry gel was calcined at various temperatures starting from 1100°C to 1600°C for 2h to study the phase evolution. The combine effects of advanced sol gel processing and the presence of seeds promoted the formation of lanthanum hexaaluminate phase at lower temperature than the conventional routes. Lanthanum hexaaluminate phase was detected at 1201°C and 1300°C in seeded and un-seeded gels, respectively. The presence of seed decreases the temperature of formation of lanthanum hexaaluminate by 99°C. Single phase lanthanum hexaaluminate was formed at 1600°C in seeded gel whereas trace of lanthanum monoaluminate phase still present in un-seeded gel even at 1600°C.

Structure–Activity Relationships in Bulk Polymeric and Sol–Gel-Derived Carbon Nitrides during Photocatalytic Hydrogen Production

Photocatalytic hydrogen evolution rates and structural properties as well as charge separation, electron transfer, and stabilization have been analyzed in advanced sol–gel-derived carbon nitrides (SG-CN) pyrolyzed at different temperatures (350–600 °C) and in bulk polymeric carbon nitride reference samples (CN) by XRD, XPS, FTIR, UV–vis, Raman, and photoluminescence as well as by in situ EPR spectroscopy. SG-CN samples show about 20 times higher H2 production rates than bulk CN. This is due to their porous structure, partial disorder, and high surface area which favor short travel distances and fast trapping of separated electrons on the surface where they are available for reaction with protons. In contrast, most of the excited electrons in bulk polymeric CN return quickly to the valence band upon undesired emission of light, which is responsible for their low catalytic activity.

Effect of 200 MeV Ag+15 ion irradiation on magnetic and dielectric properties of nanocrystalline Zn–Cr ferrite

Nanocrystalline samples of ZnCr0.4Fe1.6O4 ferrite were synthesized by the advanced sol–gel method to investigate the effect of 200 MeV Ag+15 ion irradiation on the cation distribution, magnetic and dielectric properties. Rietveld profile refinement of the X-ray diffraction (XRD) patterns confirms the single-phase cubic spinel structure of the specimens. The irradiated sample retains the cubic spinel structure with a slight increase in the lattice parameters and the average crystallite size. Temperature- and field-dependent dc magnetization studies show an appreciable enhancement in the saturation magnetization and blocking temperature of the irradiated samples, which could be attributed to the slight increase in the particle size due to the heat evolved during irradiation. Subsequently, the rearrangement of cations in the lattice structure and the ion-induced modifications on the surface states of the nanoparticles could be accountable. The room temperature dielectric constant and the loss tangent in the frequency range 75 kHz–10 MHz revealed the normal frequency dispersion. The increase in ϵr and tan δ on irradiation could be attributed to the slight crystal growth and hence the availability of the sufficient number of Fe2+ and/or Zn3+ ions particularly at the octahedral site on the grain boundaries, showing a fair agreement with the magnetization results.

TEMPERATURE DEPENDENT DIELECTRIC BEHAVIOR OF NANOCRYSTALLINE Ca FERRITE

Dielectric behaviour of Nanocrystalline CaFe2O4 ferrite synthesized by advanced sol- gel method has been investigated as a function of frequency at different temperatures. Rietveld profile refinement of the XRD pattern confirms formation of cubic spinel structure of the specimen.The dispersion in dielectric behavior of CaFe2O4 ferrite sample has been observed in the temperature range of 100-250˚C as a function of frequency in the range 75 kHz to 10 MHz Both the real value of dielectric constant (ɛ′) and the dielectric loss factor (tanδ) decrease with frequency. This decrease in the values of ɛ′ and tanδ could be explained on the basis of available ferrous, i.e. Fe2+ , ions on octahedral sites such that beyond a certain frequency of applied electric field the electronic exchange between the ferrous and ferric ions i.e. Fe2+↔Fe3+ cannot follow the applied alternating electric field.

Para-Nitroaniline-functionalized chromophoric organic–inorganic hybrid materials

An advanced procedure for the one-pot synthesis of organic–inorganic hybrid materials via combination of sol–gel process and nucleophilic aromatic substitution reaction (SNAr) of 4-fluoronitrobenzene and 3-aminopropyltrimethoxysilane is described. With this advanced procedure both SNAr-reaction and sol–gel process can be accomplished in the same reaction vessel due to the sol–gel precursor tetraethoxysilane (TEOS) acting as solvent during the first reaction step. Via extensive NMR spectroscopic studies it is proven for the first time that—contrary to common belief—hydrogen fluoride (HF), which is formed as a by-product in the SNAr-reaction, is not trapped by any bases present but is rather trapped by both of the silane species and serves as a catalyst during the subsequent sol–gel process. The chromophoric system of the resulting xerogels is well protected against aggressive chemicals, i.e. strong acids, by the silica matrix, which predestines these materials for pigment applications. Given that a high chromophore content is highly desirable in these applications, we show that the chromophore content of the final xerogel can be varied by modification of the organosilicon precursor : TEOS ratio or by using trialkoxy-silanes bearing two or three amino functions, whereby the latter option is more favourable. Monodisperse core–shell particles with identical chromophore content but consisting of a pure silica-core and a p-nitroaniline functionalized shell with a diameter of about 200 nm can also be prepared using this advanced procedure.

Advanced sol–gel coatings for practical applications

One of the features of the sol–gel techniques is closeness to the industrial applications. Another feature is the variation of shapes of obtained materials like bulk, fiber, coating film, powder and so on. Among them, the author has focused on research of the sol–gel coatings on various substrates for practical applications as well as the fundamental research under the collaboration with industry. In this review, results of such research will be presented. These include (a) protective coating on metal sheets, (b) micropatterning on glass substrates, (c) water-repellant coating on windshields, (d) colored coating on glass bottles for easy recycling, (e) superhydrophobic and superhydrophilic coating on glass plates, and (f) anti-reflective coating on glass lenses for cameras. Some were highly successful, and some were not, of course. The author also contributed to the foundation of The Japanese Sol–Gel Society in 2003. The activities of The Society in these 8 years are introduced.

Ionic liquid-mediated sol–gel coatings for capillary microextraction

Ionic liquid (IL)-mediated sol–gel hybrid organic–inorganic materials present enormous potential for effective use in analytical microextraction. This opportunity, however, has not yet been explored. One obstacle to materializing this prospect arises from high viscosity of ILs significantly slowing down sol–gel reactions. In this work, we developed a method that overcomes this hurdle and provides IL-mediated advanced sol–gel materials for capillary microextraction (CME). We examined two different ILs: (a) a phosphonium-based IL, trihexyltetradecylphosphonium tetrafluoroborate, and (b) a pyridinium-based ionic liquid, N-butyl-4-methylpyridinium tetrafluoroborate. These ILs were evaluated in conjunction with two types of hydroxy-terminated polymers: (a) two Si–OH terminated polymers (PDMS and BMPO), and (b) two C–OH terminated polymers (PEG and polyTHF) that differ in their sol–gel reactivity. Scanning electron microscopy results demonstrate that ILs can serve as porogenic agents in sol–gel reactions. The IL-mediated sol–gel coatings prepared with silanol-terminated polymers provided up to 28 times higher extractions in off-line CME-GC compared to analogous sol–gel coatings prepared without any IL in the sol solution. Contrary to this, the IL-mediated sol–gel coatings prepared with C–OH terminated polymers provided lower extraction efficiencies compared to their IL-free counterparts. These observations were explained by (a) lower sol–gel reactivity of C–OH groups in PEG and polyTHF compared to Si–OH groups in PDMS and in hydrolyzed alkoxysilane precursors and (b) extremely high viscosity of ionic liquids. This study shows that IL-generated porous morphology alone is not enough to provide effective extraction media: careful choice of the organic polymer and the precursor with close sol–gel reactivity must be made to ensure effective chemical bonding of the organic polymer to the created sol–gel material to be able to provide the desired sorbent characteristics. Additionally, IL-mediated sol–gel PDMS coatings provided run-to-run RSD values of 4.2–5.0% and detection limits ranging from 3.2 ng/L to 17.4 ng/L. PDMS sol–gels prepared without ILs provided RSD values of 2.8–14.1%, and detection limits ranging from 4.9 ng/L to 487.0 ng/L.

Novel electro-optic properties of epitaxially grown (Pb, La)(Zr, Ti)O 3 (PLZT) thin films derived by advanced sol–gel methods

Advanced sol–gel methods using a secondary solvent addition into (Pb, La)(Zr, Ti)O 3 (PLZT) sol–gel solution and a methanol pre-treatment of sapphire substrates are demonstrated. For the secondary solvent addition, the additive affected the crystallinity and electro-optic (EO) property of PLZT films and only methanol addition can improve them. In addition, the methanol pre-treatment is also appeared to be effective to improve film characteristics. Through these optimizations, epitaxially grown PLZT thin films on r-cut sapphire are obtained and a high Pockels coefficient which is comparable to those of bulk PLZTs is achieved. It is believed that these PLZT thin films are applicable for integrated EO devices and open the door for the future data communication systems.

Hetero-atom combination bimodal pore structure supports prepared by inside-pore organized oxide precursors from advanced sol–gel solution

Abstract Hetero-atom combination bimodal pore supports prepared by advanced sol–gel solution realized significantly high catalytic activity in Fischer–Tropsch Synthesis (FTS) due to spatial and hetero-atom combination promotional effects. The obtained bimodal pore supports and catalysts were characterized by N2 physisorption, XRD, H2 chemisorption, H2 TPR.

Simple fabrication process for CeO 2–MgO composite as surrogate for actinide-containing target for use in nuclear fuel

A simple fabrication process for CeO 2–MgO composite as surrogate for actinide-containing target for use in nuclear fuel has been developed. The process is adaptable to present fuel manufacturing technology. The manufactured target has good characteristics, e.g. high density, good appearance, free of reaction phase, etc. In particular, the shape of CeO 2 particles is nearly spherical and their dispersion is homogeneous. Thermal conductivity of the present target can be satisfactorily expressed by using Schulz's equation when CeO 2 spheres are assumed as ideal with no anisotropy. These results indicate that the present simple process gives a composite which is comparable to that fabricated in a complicated process such as an advanced sol–gel supported process.

Silica Xerogel Supported Cobalt Metal Fischer−Tropsch Catalysts for Syngas to Diesel Range Fuel Conversion

Fischer−Tropsch synthesis of diesel range straight-chain hydrocarbons from CO and H2 over a cobalt nanoparticle catalyst supported by a mesoporous silica xerogel is reported. A possible advantage of sol−gel-derived catalyst supports is the tunability of their porosity to favor synthesis of diesel range hydrocarbons. The preparation of the xerogel supports, optimal loading of the supports with cobalt, the percent conversion of syngas to Fischer−Tropsch hydrocarbons, a gas chromatography−mass spectrometry analysis of the diesel range product distribution, and characterization of the catalysts are reported.

Formation of size-controlled micro-pores in amorphous mixed oxides by an advanced sol–gel method

Micro-pores in amorphous mixed oxides can be designed by an advanced sol–gel method using various diols as the pore-forming agents.