Showing papers on "Sodium silicate published in 2002"

Interactions of amino-containing peptides with sodium silicate and colloidal silica: A biomimetic approach of silicification

Abstract: The influence of poly(lysine) and poly(arginine) on silicate solutions and silica sols has been investigated. In both cases, solid formation could be observed that appeared to depend on the polymer chain length. Polyelectrolytes induced gelation of diluted sodium silicate solutions. Studies of the silicic acid content using the colorimetric molybdosilicate method suggested that polymers act as gelating agents of silica oligomers via electrostatic interactions that favor condensation. In the case of silica sols, quasi-elastic light scattering measurements indicate that particles are first adsorbed on the polymer chain to form aggregates that then flocculate in the presence of additional peptides. Structural characterizations of the solids obtained in both cases were consistent with the proposed models. These results are discussed in the frame of biogenic silica formation at the protein/silica interface.

Structural Design of Mesoporous Silica by Micelle-Packing Control Using Blends of Amphiphilic Block Copolymers

Abstract: The formation of mesoporous silica materials has been studied using blends of diblock (CnH2n+1(OCH2CH2)xOH, CnEOx, n = 12 − 18 and x = 2−100) and Pluronic triblock (EOxPO70EOx, x = 5−100) amphiphilic block copolymers as the structure-directing agents and sodium silicate as the silica source. The mesostructure of the silica materials thus obtained, as determined by X-ray diffraction and transmission electron microscopy, changes as the volume of the hydrophilic EO group of the surfactant increases, from lamellar to two-dimensional hexagonal (p6mm), three-dimensional hexagonal, a cubic phase, and another cubic phase with Im3m symmetry. Particle morphologies of the mesoporous silica materials are correspondingly changed from sheetlike to irregular, facetted cubic shapes depending on the periodic mesoscale symmetry of the structure. It is reasonable that the structural transformations are due to the changes in hydrophobic surface curvatures, which can be controlled readily and precisely by using polymer blend...

Synthesis of silica aerogels from waterglass via new modified ambient drying

Abstract: A new modified ambient drying process for synthesizing silica aerogels cost-effectively from waterglass has been developed. Crack-free silica aerogels were obtained via solvent exchange/surface modification of wet gels using IPA/TMCS/n-Hexane solution. Silica aerogels were heated at different temperatures. The effects of heating temperature on chemical bonding state of aerogels were investigated by means of DTA and FTIR. The surface characteristic of the aerogel was hydrophobic when heat-treated under 350°C. The porosities, densities, and specific surface areas of the silica aerogels were in the range of 93–94%, 0.12–0.15 g/cm3, and ∼630 m2/g, respectively. Distinct spring back phenomena were observed in surface modified wet gels during drying.

Characterization of Fly-Ash-Based Geopolymeric Binders Activated with Sodium Aluminate

Abstract: Properties and characteristics of sodium silicate activated fly-ash-based geopolymers have been extensively investigated, but the utilization of sodium aluminate activation has received little attention. The present work, therefore, examines the properties of the starting materials and sodium aluminate solutions and their effect on the final material properties and microstructure of fly-ash-based geopolymers. To achieve this, starting sodium aluminate solutions were characterized with ATR-FTIR and 27Al NMR spectroscopies to determine the coordination state of aluminum as a function of solution concentration and [OH]/[Al] ratio. Various fly-ash-based geopolymeric matrixes were synthesized utilizing fly ash, kaolinite, K-feldspar, and slag as the mineral aluminum sources. The matrixes were activated with alkali silicate or alkali aluminate solutions as a function of pH, concentration, and alkali ion (Na+ or K+). FTIR and XRD studies combined with compressive strength tests demonstrated that in certain cases...

Synthesis of large-pore silica with cage-like structure using sodium silicate and triblock copolymer template

Abstract: Silicas with large (about 10 nm in diameter), uniform, cage-like pores were synthesized from sodium silicate and poly(ethylene oxide)−poly(butylene oxide)−poly(ethylene oxide) B50-6600 triblock copolymer template (EO39BO47EO39) under acidic conditions The synthesis procedure was analogous to that reported by others for FDU-1 silica with highly ordered cubic Im3m structure, but in our study, an expensive tetraethyl orthosilicate (TEOS) was successfully replaced by cost-efficient sodium silicate Adsorption and thermogravimetric properties of the silicas synthesized from sodium silicate were found to closely resemble those of FDU-1 silicas synthesized from TEOS, but the pore volumes and specific surface areas of the former were found to be lower in most cases The uniform cage-like structures assembled from sodium silicate formed at room temperature and 318 K, but no ordered structure was obtained at 333 K, whereas in the case of TEOS, an ordered structure formed also at 333 K The sample synthesized at ro

Role of framework sodium versus local framework structure in determining the hydrothermal stability of MCM-41 mesostructures.

Abstract: Two mesostructured MCM-41 silicas that differ dramatically in hydrothermal stability have been examined by 29 Si MAS NMR spectroscopy and pair distribution function (PDF) analysis of synchrotron X-ray scattering data. The less stable mesostructure assembled from sodium silicate and the substantially more stable derivative made from fumed silica possess equivalent local framework wall structures, as judged by NMR and PDF methods. Approximately 80% of the SiO4 tetrahedra are fully cross-linked as Q 4 (Si- (OSi)4) units in both calcined samples. Additionally, the structural correlation distances for the two materials are nearly identical, having values of 1.62(1), 2.60, and 3.09(1) A for the Si -O, O-O, and nearest neighbor Si-Si distances in the framework. Sodium ions in the framework play a crucial role in limiting the hydrothermal stability of the mesostructure. Residual sodium (0.05-0.10% Na2O) is retained in the MCM- 41 made from sodium silicate, even after two ion exchange reactions with ammonium ions in more than 300 - fold excess. The entrapped framework sodium ions catalyze the collapse of the mesopores upon exposure to 20% steam at 800 °C for 5 h. The sodium - free mesostructure assembled from fumed silica retains an open framework under the same hydrothermal conditions. The stability of the fumed silica derivative, however, is greatly compromised when doped with as little as 0.10% Na2O, thus confirming the deleterious effect of sodium on hydrothermal stability.

Investigation of a synthetic aluminosilicate inorganic polymer

Abstract: A melt-quenched of mixture of alumina and silica (46 wt% Al2O3 or Al2O3(SiO2)2) was found to react with an alkaline silicate solution (Na2O)(SiO2)1.2(H2O)9.5) at low-temperatures to form a synthetic aluminosilicate inorganic polymer. The as-quenched material consisted of a mixture of amorphous and crystalline phases with a range of aluminium coordination environments. Upon reaction with the alkaline silicate solution, solid-state aluminium and silicon magic-angle spinning nuclear magnetic resonance (SS 27Al and 29Si MAS NMR) indicated that a conversion to four-fold aluminium coordination environments occurred, consistent with the formation of a three-dimensional cross-linked inorganic polymer comprised of NaAlO4 and SiO4 tetrahedra. Mechanical testing showed the compressive strength of the inorganic polymer increased as the Na2O/Al2O3 molar ratio decreased. Solution studies indicated that 73% of the aluminosilicate starting material was reactive. Scanning electron microscopy (SEM) showed the inorganic polymers had a porous nanoscale grain structure. Open porosity was confirmed by relatively high specific surface area values. Energy dispersive spectroscopy (EDS) and elemental x-ray composition mapping showed that the high-strength specimens had a composite microstructure consisting of 40% unreacted Al2O3(SiO2)2 and an inorganic polymer binder Na2O · Al2O3(SiO2)3.4. The high compressive strengths have been rationalized by this in-situ particle reinforced composite structure, consisting of ∼10 μm agglomerates of unreacted starting material bonded within a sub-micron aluminosilicate/inorganic polymer matrix.

FCC catalysts for feeds containing nickel and vanadium

Abstract: A fluid catalytic cracking catalyst made from microspheres that initially contain kaolin, a dispersible boehmite alumina and a sodium silicate or silica sol binder. The kaolin portion contains hydrous kaolin and a particular kaolin which has been calcined through its characteristic exotherm and which produces a catalyst having a novel morphology comprising a macroporous matrix and crystallized zeolite freely coating the walls of the pores of the matrix. Calcination of the hydrous kaolin to metakaolin and formation of in-situ zeolite by treatment with sodium silicate yields a catalyst containing Y-faujasite and transforms the dispersible boehmite into a transitional alumina. The catalyst can be used to crack resid or resid-containing feeds as the alumina phase formed from the dispersible boehmite passivates nickel and vanadium contaminants.

X‐ray Photoelectron Spectroscopy Study on the Process of Apatite Formation on a Sodium Silicate Glass in Simulated Body Fluid

Abstract: The process of apatite formation on the surface of Na2O–SiO2 glass in a body environment was investigated, mainly by X-ray photoelectron spectroscopy, as a function of soaking time in a simulated body fluid (SBF). The glass was found to release Na+ ions via exchange with H3O+ ions in the SBF to form Si—OH groups on its surface. These Si—OH groups induced apatite formation indirectly, by forming calcium silicate and amorphous calcium phosphate. The formation of the calcium silicate and amorphous calcium phosphate is attributed to electrostatic interactions between the Si—OH groups on the glass surface and the calcium and phosphate ions in the SBF.

Lithium Doped Polyethylene-Glycol-Based Thermal Interface Pastes for High Thermal Contact Conductance

Abstract: Polyethylene-glycol-based thermal interface paste containing trifluoroacetic acid lithium salt (1.5 wt. percent optimum) and boron nitride particles (;18.0 vol. percent optimum), as well as water and N, N-dimethylformamide for helping the dissociation of the salt to release Li ions, gives thermal contact conductance that is almost as high as that given by Sn-Pb solder, similar to that given by boron nitride particle filled sodium silicate, and much higher than that given by boron nitride particle filled silicone. @DOI: 10.1115/1.1477191#

Catalysts Based on Fiberglass Support: IV. Platinum Catalysts Based on Fiberglass Support in Oxidation of Hydrocarbons (Propane and n-Butane) and Sulfur Dioxide

Abstract: Platinum catalysts (0.003–0.52% Pt) based on leached sodium silicate and boron silicate fiberglass supports are studied in the complete oxidation of hydrocarbons (n-butane and propane) and high-temperature SO2 oxidation. It was shown that platinum localized in the bulk of the glass matrix show a higher activity and thermal stability than metal particles supported on the outer surface of fiberglass. The experimental results for hydrocarbon oxidation on platinum-containing fiberglass gauzes at short contact times are discussed.

Etude de la synthese des zeolites 4A et HS a partir de produits naturels

Abstract: The crystallization of the zeolite HS was studied during the synthesis of the zeolite 4A using several raw materials like diatomite, kaolin and bentonite. First, these three materials were activated mainly by melting in the presence of caustic soda. The comparison with the pure reagents (solution of sodium silicate and sodium aluminate) as a reference allowed to deduce that an appearance of the zeolite HS during the synthesis is observed with most of the raw materials. Its formation takes place when the concentration of aluminium decreases below the value corresponding to the pure products in the liquid phase. This situation takes place when the reactant gel is heterogeneous, which is characteristic of all the raw materials studied. This seems to be the reason for the formation of zeolite HS.

Cell adhesion and proliferation on biomimetic calcium-phosphate coatings produced by a sodium silicate gel methodology

Abstract: The present study describes a methodology to produce bioactive coatings on the surface of starch based biodegradable polymers or other polymeric biomaterials. As an alternative to the more typical bioactive glass percursors, a sodium silicate gel is being employed as a nucleating agent, for inducing the formation of a calcium-phosphate (Ca-P) layer. The method has the advantage of being able to coat efficiently both compact materials and porous 3D architectures aimed at being used on tissue replacement applications and as bone tissue engineering scaffolds. This treatment is also very effective in reducing the incubation periods, being possible to observe the formation of an apatite-like layer, only after 6 h of immersion in a simulated body fluid (SBF). The influence of the SBF concentration on the formation of the apatite coating was also studied. The apatite coatings formed under different conditions were analyzed and compared in terms of morphology, chemical composition and structure. After the first days of SBF immersion, the apatite-like films exhibit the typical cauliflower like morphology. With increasing immersion times, these films exhibited a partially amorphous nature and the Ca/P ratios became very closer to the value attributed to hydroxyapatite (1.67). The obtained results are very promising for pre-calcifying bone tissue engineering scaffolds. Therefore, in order to study cell behavior and response to these apatite coatings, adhesion, morphology, and proliferation of a human osteoblast cell line (SaOS-2) was also analyzed after being cultured in the coatings formed after 15 days of immersion in SBF. Results indicate a good correlation between crystallinity of the apatite like coatings formed in these conditions and respective cell spreading and morphology. In general, higher cell proliferation was observed for higher crystalline Ca-P coatings.

Composition of materials for production of acid resistant cement and concrete and methods thereof

Abstract: A cement composition for use in acidic environment containing liquid alkali silicate, vitreous silicate setting agent, lime containing material and inert filler and building materials made therefrom as well as the method of making such building materials. The liquid alkali silicate may include sodium silicate or potassium silicate. The vitreous silicate setting agent may include soda-lime glass powder or coal fly ash. The lime containing material refers to the materials containing more than 20% lime and may include quicklime, hydrated lime, Portland cement, blast furnace slag or steel slag. The inert fillers include ground quartz, ground ceramic, and/or clay.

Synthesis and Characterization of Er(III) and Y(III) Sodium Silicates: Na3ErSi3O9, a New Infrared Emitter

Abstract: The hydrothermal synthesis in mild conditions, and the structural characterizations and luminescence properties, of yttrium and erbium silicates Na3MSi3O9, M = Y(III) and Er(III), has been reported...

Synergistic inhibition of carbon steel corrosion by sodium tungstate and sodium silicate in neutral aqueous media

Abstract: Tungstate inhibitors are seldom used alone in open recirculating cooling water systems due to their low oxidising ability and high cost. The objective of the present work was to develop efficient synergistic inhibitor combinations comprising sodium silicate and very low concentration of sodium tungstate, keeping in view of their application in industrial cooling water system. It was demonstrated in the present study that all the combinations of the inhibitors exhibited synergistic benefit and higher inhibition efficiencies than did either of the individual inhibitors. It was also established that a 4:1 ratio of sodium silicate to sodium tungstate (total 1,000 ppm) was the best overall combination. The FTIR spectra also suggest that tungstate and silicate ions were incorporated in the passivating metal oxide layer formed on the surface of carbon steel in the inhibitor solutions. The effects of excess and depleted concentrations of the individual inhibitor components on overall inhibition behaviour are also discussed.

Effect of Hydrated Sodium Silicates on Cement Paste Hardening

Abstract: The hydration of cement clinker minerals occurs at a high rate in the presence of sodium silicates owing to a decrease in the initial pH of pore solutions of cement pastes and to intensive formation of calcium hydrosilicates.

A multiple-quantum 23Na MAS NMR study of amorphous sodium gallium silicate zeolite precursors

Abstract: Amorphous sodium gallium silicate materials are isolated after short periods of heating a gel of composition Ga2O3 ∶ SiO2 ∶ 4NaOH ∶ 80H2O at 100 °C. On extended heating (periods in excess of 24 hours), the crystalline zeolite gallium hydroxosodalite is produced from the reaction mixture. We have studied the materials using 23Na (I = 3/2) MAS and multiple-quantum MAS (MQMAS) NMR spectroscopy in order to extract information about the local environment of the sodium in the amorphous solids, and thereby gain information about the role of sodium during the crystallisation of the zeolite. The average 23Na isotropic chemical shift, δiso, and the quadrupolar parameter, PQ = CQ(1 + η2/3)½, were evaluated by analysis of the two-dimensional MQMAS spectra. In addition to the sodium gallium silicate materials, a number of crystalline sodium silicates, aluminates and gallates were also studied and their NMR parameters compared with literature values and related to crystallographic data describing the local environment of the sodium atoms. Although no simple correlation is known between 23Na NMR parameters and the coordination number or average sodium–oxygen interatomic distance, a general trend of increasing δiso with decreasing coordination number and interatomic distance is apparent. The data from the amorphous sodium gallium silicates strongly suggest that even after very short periods of heating the local environment of sodium is very similar to that found in the crystalline zeolite product. Additional 71Ga (I = 3/2) MAS NMR spectra were also recorded from the amorphous samples to provide information on the local gallium environment and these show the presence of tetrahedral gallium, as in the crystalline zeolite, even in the samples prepared after the shortest period of heating.

Electrolytic capacitor and separator papers therefor

Abstract: Separator paper comprising paper impregnated with soluble silicate. The soluble silicate may be applied to the separator paper by immersing the paper into an aqueous solution of the soluble silicate or by spraying with an aqueous solution of the soluble silicate. In a preferred embodiment, the soluble silicate is sodium silicate. An electrolytic capacitor comprising an electrolytic solution, at least one anode foil, at least one cathode foil, and separator paper between the at least one anode foil and at least one cathode foil, wherein the separator paper comprises paper impregnated with a soluble silicate.

Water-Based Sodium Borosilicate Sols and Their Gelation-Characterisation by Viscosimetry, UV/VIS- and Infrared Spectroscopy

Abstract: Sodium silicate solutions were mixed with boric acid in order to form sodium borosilicate gels. The gelation process was observed by dynamic oscillatory experiments. The effects of composition and temperature on the gel point are discussed. Furthermore, an indicator of the gel point for the water-based sodium borosilicate gels was found. The turbidity was investigated by UV/VIS spectroscopy and optical microscopy. Infrared spectroscopic measurements were applied to characterise the gelation process, too.