Showing papers on "Sodium silicate published in 2004"

Morphological Control of Rod- and Fiberlike SBA-15 Type Mesoporous Silica Using Water-Soluble Sodium Silicate

Abstract: Well-defined rodlike and fiberlike SBA-15 mesoporous silicas have been selectively synthesized from an aqueous reaction mixture consisting of a commercial sodium silicate solution, P123 triblock copolymer and HCl. The morphologies and physicochemical properties of the products were found to be greatly affected by the shearing stress exerted by cylindrical silicated-surfactant micelles in a flowing solution, referred to hereafter as “shearing flow”. Monodispersed rodlike particles ca. 0.5-μm wide and ca. 1−2-μm long were formed under static reaction conditions, whereas continuous stirring of the reaction mixture led to the formation of fiberlike silicas with lengths of several hundred micrometers and a relatively uniform width of ca. 10 μm. The effects of the synthesis conditions, such as the initial ratio of the reactants, time, temperature, and the acid source, in addition to shearing flow, on particle morphologies were investigated. Fiberlike silicas of various lengths were obtained from a relatively wi...

Preparation and formation mechanism of silica microcapsules (hollow sphere) by water/oil/water interfacial reaction

Abstract: Silica microcapsules (hollow spheres) were readily prepared by an interfacial reaction using a water/oil/water (W/O/W) emulsion system. A W/O emulsion consisting of an aqueous solution of sodium silicate (WP-1) and an n-hexane solution of Tween 80 and Span 80 (OP) was added to another aqueous solution of a precipitant (WP-2). The reaction of sodium silicate with a precipitant to form silica on this W/O/W emulsion system (WP-1/OP/WP-2) forms the hollow structure spontaneously. Therefore, no core material often utilized in silica hollow sphere fabrication was required in this process. The formation and the particle size of the silica microcapsule depended on the precipitant employed. When NH4HCO3 was used as precipitant, the particle size of the silica microcapsule was successfully controlled by the volume ratio of WP-1/OP/WP-2, the rotation number of the homogenizer, and the concentration of sodium silicate in WP-1. However, this control of the particle size was not achieved when other precipitants such as...

First-Principles Calculation of 17O, 29Si, and 23Na NMR Spectra of Sodium Silicate Crystals and Glasses

Abstract: This paper presents results of first-principles calculations of nuclear magnetic resonance (NMR) parameters: the chemical shielding tensor and the electric field gradient tensor, of some crystalline and amorphous sodium silicate systems. The calculations have been performed using the recently introduced gauge including projector augmented wave (GIPAW) method, which was especially devised for periodic systems. It provides an attractive alternative to the cluster approximation, used in the previous NMR theoretical studies of silicates systems. Moreover, within the GIPAW formalism, amorphous systems can be efficiently described via a supercell approach as demonstrated in this work. Five reference crystalline compounds of known structure (α-quartz, α-cristobalite SiO2, and the sodium silicates Na2SiO3, α-Na2Si2O5, and β-Na2Si2O5) and two molecular dynamics models of the sodium tetrasilicate glass Na2Si4O9 (NS4) have been studied. The NS4 glass models were generated by a combination of classical and Car-Parrin...

Channel Formation and Intermediate Range Order in Sodium Silicate Melts and Glasses

Abstract: We use inelastic neutron scattering and molecular dynamics simulation to investigate the interplay between the structure and the fast sodium ion diffusion in various sodium silicates. With increasing temperature and decreasing density the structure factors exhibit an emerging prepeak around 0.9 A(-1). We show that this prepeak has its origin in the formation of sodium rich channels in the static structure. The channels serve as preferential ion conducting pathways in the relative immobile Si-O matrix. On cooling below the glass transition this intermediate range order is frozen in.

Novel inorganic pigment containing calcium carbonate, aqueous suspension containing same, and uses thereof

Abstract: The present invention relates to the technical field of inorganic pigments containing a material formed in situ by a double and/or multiple reaction between a calcium carbonate and one or more products of a reaction between said carbonate and one or more medium- to high-strength H3O+ ion donors and one or more products of a reaction between said carbonate and gaseous CO2 formed in situ and/or supplied from an external source, and at least one aluminium silicate and/or at least one synthetic silica and/or at least one calcium silicate and/or at least one silicate of a monovalent salt such as sodium silicate and/or potassium silicate and/or lithium silicate, and/or at least one aluminium hydroxide and/or at least one sodium and/or potassium aluminate, containing less than 01 wt % of the monovalent salt silicate such as sodium, potassium or lithium silicate or mixtures thereof, based on the dry weight of the calcium carbonate, having a pH higher than 75 at 20 °C, and the uses thereof in paper-making applications such as adding a filler to and/or coating paper, particularly raw printing stock for offset printing in particular, or digital printing such as ink jet and/or laser printing

Fire-resistant panel and method of manufacture

Abstract: A highly fire-resistant and environmentally-friendly panel of 2 mm to 28 mm may be manufactured by a blending of magnesium compounds, sodium silicate, kaolin, fillers, and additives to form the core materials, reinforced by 4 layers of fire-resistant glass fiber meshes and fabrics. Using a proprietary ITC process that accelerates the chemical reactions of the ingredients to generate sufficient heat without external supply of energy, the panels may be completely cured within 24 hours instead of 10 days. The use of waste materials, energy-saving curing system and no gas emission manufacturing process combined to make this panel an eco-friendly product which offers the world's highest-rated fire resistance of 5 hours, high flexural strength, low density, durability and effective water-resistance.

Simple Synthesis of Uniform Mesoporous Carbons with Diverse Structures from Mesostructured Polymer/Silica Nanocomposites

Abstract: Uniform-sized mesoporous carbons having high surface areas and various structures were synthesized directly by the carbonization of P123 triblock copolymer/phenol−resin/silica nanocomposites, which were prepared from the sol−gel polymerization of silica in the presence of Pluronic P123 triblock copolymer and phenol and subsequent silica removal. Mesoporous carbon, with uniform 5.6 nm wormhole-like pores, was synthesized using sodium silicate as a silica source. When the amount of phenol relative to block copolymer was reduced in the synthesis, mesocellular carbon foams with bimodal pore structures were obtained. In addition, mesoporous carbons were synthesized using TEOS (tetraethyl orthosilicate) as a silica source. The pore size of the mesoporous carbons was controlled by varying the ratio of phenol and P123 triblock copolymer. At an optimal molar ratio of phenol to block copolymer, mesoporous carbon with a nanofiber morphology was obtained. The mesoporous carbons were successfully used as the electrode...

One-Step Preparation of Porous Silica Spheres from Sodium Silicate Using Triblock Copolymer Templating

Abstract: Mesoporous and microporous monodispersed silica spheres have been prepared using a simple one-step synthetic procedure from an aqueous reaction mixture consisting of a commercial sodium silicate solution, various Pluronic triblock copolymers, and HCl or HNO3. The formation of porous silica spheres 130−225 μm in diameter was observed over a moderately wide range of reaction conditions. The pore structures of the resultant spheres lacked any long-range order, although they did exhibit outer textural uniformity. We concluded that the well-defined spherical morphology and pore sizes were the result of a combined effect of the EO/(EO + PO) block ratio and molecular weight of the Pluronics and the counteranions of the acid source.

Synthesis of high-quality MCM-48 mesoporous silica using gemini surfactant dimethylene-1,2-bis(dodecyldimethylammonium bromide)

Abstract: Using the Gemini surfactant [C12H25N+(CH3)(2-)N+(CH3)(2)-N+(CH3)(2)-C12H25](.)2Br(-) (abbreviated as C12-2-12) with the short spacer group (s = 2) as structure-directing agent and sodium silicate as precursor, high-quality ordered cubic mesoporous silica (space group Ia3d) was prepared through the S+I- route (S denotes surfactant, I precursor). The samples were characterized by small-angle X-ray diffraction, transmission electron microscopy, and N-2 adsorption-desorption techniques. Results showed that the pore structure of the resulting mesoporous silica belonged to the cubic structure (space group Ia3d). The high-quality cubic mesoporous structure was formed at 1:0.33 (molar ratio of sodium silicate to C12-2-12), 2:1 (ethyl acetate to sodium silicate), and at 30 degreesC. The formation conditions of MCM-48 with C12-2-12 were milder than those with the corresponding monovalent surfactants, such as alkyltrimethylammonium bromide. N-2 adsorption-desorption curves revealed type IV isotherms and H1 hysteresis loops; Brunauer-Emmet-Teller (BET) surface areas increased with the decrease of the molar ratio of sodium silicate to C12-2-12 and of ethyl acetate to sodium silicate as well as of the hydrothermal temperatures.

Inhibition of pyrite oxidation by a phospholipid in the presence of silicate.

Abstract: The influence of sodium silicate on the ability of a diacetylene-containing phospholipid (23:2 diyne PC) to inhibit the oxidation of pyrite at pH 2 and pH 6 was investigated. The phospholipid used has previously been reported to show up to 80% suppression of pyrite oxidation and to show excellent stability down to at least pH 2. Pyrite was leached with a solution containing Fe3+ but no coating agent and three different solutions or treatments: a lipid treatment, a silicate treatment, and a lipid + silicate treatment. Pyrite oxidation was based on iron (Fe3+, Fe2+) leached out of a continuous-flow porous-bed reactor system. The results show that at pH 6 the silicate and lipid both bind strongly to the pyrite surfaces, providing a barrier that inhibits the production and subsequent release of oxidation products. The lipid is superior to the silicate in suppressing pyrite oxidation at both pH 2 and pH 6. Also, the presence of silicates decreased the ability for the lipid to suppress pyrite oxidation, both at pH 2 and pH 6. The reaction mechanism for pyrite oxidation at pH 2 is first order for pyrite leached by solutions containing only ferric, ferric together with silicate, and ferric combined with silicate and lipid. The only treatment that effectively prevented pyrite oxidation at pH 2 was the lipid treatment. The Fe speciation results are supported by both SEM images and EDS calculations.

The study of formation colloidal silica via sodium silicate

Abstract: The process parameters of the formation colloidal silica via sodium silicate had been investigated in this article. Sodium ion of sodium silicate was removed by ion-exchanging to obtain the active silicic acid which was titrated to the solution of potassium hydroxide (KOH) to form the colloidal silica. In this study, the results showed the mean particle size of colloidal silica was influenced by the KOH concentration, formation temperature and titration rate of active silicic acid. High KOH concentration, high formation temperature and low titration rate of active silicic acid would help the particle growth to form the larger particle size of colloidal silica. Unfortunately, the colloidal silica formed at theses conditions were unstable.

Thermal protective coating

Abstract: A coating, method of coating and substrates coated thereby, wherein the coating contains an inorganic adhesive such as an alkali/alkaline earth metal silicate such’as sodium silicate, potassium silicate, calcium silicate, and magnesium silicate; a filler such as a metal oxide for example silicon dioxide, aluminum oxide, titanium dioxide, magnesium oxide, calcium oxide and boron oxide; and one or more emissivity agents such as silicon hexaboride, carbon tetraboride, silicon tetraboride, silicon carbide, molybdenum disilicide, tungsten disilicide, zirconium diboride, cupric chromite, or metallic oxides such as iron oxides, magnesium oxides, manganese oxides, chromium oxides and copper chromium oxides, and derivatives thereof. In a coating solution, an admixture of the coating contains water. A stabilizer such as bentonite, kaolin, magnesium alumina silicon clay, tabular alumina and stabilized zirconium oxide may be added.

Synthesis and Characterisation of Polyvinyl alcohol (PVA)/Silica Hybrid Composites Derived Through the Sol-Gel Method in Aqueous Medium: Effect of Acid Content, Silica Content and Viscosity of PVA on the Dispersion Characteristics of Silica and the Physical Properties of the Composites

Abstract: A cheap and environment friendly route towards the synthesis of Polyvinyl alcohol/silica hybrid composites is presented. Polyvinyl alcohol/silicate hybrid materials were synthesised in aqueous medium by the sol-gel method using dil HCl (0.5 N) as catalyst and a cost-effective silica source sodium silicate. The synthesis method was aimed at enhancing the rate of co-condensation of silica within the polyvinyl alcohol matrix. Transparent and flexible hybrid films of homogenous thickness were obtained after gelation at 45°C for 24 h and extended drying for another 48 h. The hybrid composites were characterised by fourier transform infrared spectroscopy (FTIR), scanning electron microscopoy (SEM), thermogravimeric analysis (TGA), tensile strength, elongation at break and water uptake measurements. SEM micrographs revealed that silica was dispersed in the PVA matrix without the large aggregation of particles for a molar composition of 0.0004 PVA:0.048 Sodium silicate: 0.004 HCl.

The fused silicate route to protoimogolite and imogolite

Abstract: The formation of imogolite from protoimogolite from fused sodium silicate and aluminum perchlorate has been investigated. It is shown that the initial solutions prepared by this method are different from those from hydrolyzed solutions of tetraethoxysilane, so the mechanism of protoimogolite formation is different. Species with isolated silicon tetrahedral (Q33Al) are present much earlier in the fused silicate process than in the tetraethoxysilane reaction. Kinetic studies do show however that once protoimogolite is formed the two reaction mixtures crystallize imogolite in the same way.

Inert failure strain studies of sodium silicate glass fibers

Abstract: The inert failure strains of glass fibers with the molar compositions x Na 2 O · (1 − x )SiO 2 , where 0 ⩽ x ⩽ 0.35, were measured under liquid nitrogen (77 K) using a two-point bending technique. Failure strain increases with increasing Na 2 O content, from 17.7% for x = 0.00–23.5% for x = 0.35. The inert failure strain depends on the face-plate velocity ( V fp ) of the two-point bending test, increasing with increasing V fp for silica and decreasing with increasing V fp for the sodium silicate glasses. The magnitude of the latter ‘inert delayed failure effect’ increases with increasing x . The addition of Na 2 O to a silicate glass weakens the glass network through the formation of non-bridging oxygens, and the weaker network distorts more at high strains and slower V fp .

Novel degradable superabsorbent materials of silicate/acrylic‐based polymer hybrids

Abstract: Novel superabsorbent materials, inorganic–organic hybrids, were synthesized by polymerizing acrylic acid or acrylamide with sodium silicate without any other crosslinking agent. The crosslinking bonds of SiOC form through the reaction of carboxyl groups with silanol groups (SiOH) existing in reaction system. Results of FTIR, swelling, and degrading experiments show that the crosslinking degree increased as the mol ratio of silicate increased in a certain range. The hybrids possess the properties of high absorbency and high absorption rate in both distilled water and normal saline solution. Because of the hydrolysis of SiOC bonds in aqueous solution, the hybrid hydrogels can degrade in days, and maybe beneficial to environment protection. This property is quite different from those superabsorbent polymer crosslinked with organic crosslinking agent. By monitoring the temperature of the reaction system, sodium silicate was also found to facilitate the trommsdorff effect in polymerization process. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 936–940, 2004

Hydrothermally synthesized high silica mordenite as an efficient catalyst in alkylation reaction under liquid phase condition

Abstract: High silica mordenite (HSM) samples have been synthesized hydrothermally by using low aluminum contents (Si/Al molar ratios 40 and 60) with the synthesis gel in the presence of orthophosphoric acid as promoter at 443 K. Sodium silicate and aluminum sulfate were used as Si and Al precursors, respectively. Solid yield and particle size of these materials have been improved considerably over the conventional synthesis method for aluminous mordenite apart from high Si/Al molar ratios of the product and hydrothermal stability. These high silica mordenite samples showed excellent catalytic activity in the alkylation of benzene under liquid phase reaction conditions together with high selectivity towards linear alkyl benzenes. This catalytic performance suggested the presence of strong acid sites in this HSM material.