Showing papers on "Sodium silicate published in 2000"

The importance of intumescent systems for fire protection of plastic materials

Abstract: A review of recent developments in the applications and actions of intumescent fire-retardance is given. An attempt has been made to classify the main systems of importance such as melamine, ammonium polyphosphate, melamine phosphate, pentaerythritol phosphate, sodium silicate, vermiculite, expandable graphite and microbeads. They are defined in terms of the Berthelot number which is the product of heat of vaporization or decomposition and volume of gases evolved. In principle, only two kinds of gases are produced from this group, namely water vapour and ammonia (from melamine). The heats of decomposition are readily calculated from heats of formation. An important aspect which is not included in the Berthelot number is the ignition residue in the shape of glassy foam or a cellular enamel.

Fluoride sites in aluminosilicate glasses: High-resolution 19F NMR results

Abstract: We present here high-resolution, 19 F NMR spectra, collected with sample spinning rates to 25 kHz, for sodium and calcium silicate and aluminosilicate glasses. Several distinct fluoride ion sites are well resolved and can be assigned to various coordination environments based on clear similarities to crystalline model compounds. In aluminosilicates, fluoride with one Al and several Na or Ca neighbors predominate, but silicon-fluoride groups may also be significant. Small concentrations of the latter can also be detected in sodium silicate glasses, suggesting a possible role in reduction of viscosity. Fluoride sites with no Si neighbors are, however, predominant in Al-free sodium silicates and probably in Ca silicates as well.

Synthesis of Mesoporous MSU-X Materials Using Inexpensive Silica Sources

Abstract: MSU-X materials are a family of ordered mesoporous silica obtained through an assembly mechanism between nonionic poly(ethylene oxide)-based surfactants and silica precursors. Until now, among many advantages, the main drawback of this synthesis was the cost of the silica source, a silicon alkoxide that prevented any application where large amounts of material are required. We report that a new two-step synthesis pathway implying first the stabilization of a microemulsion made of both nonionic surfactants and a silica source and then the silica condensation through a fluoride-helped catalysis can be extended to cheaper silica sources than the silicon alkoxide usually used. Both sodium silicate or colloidal silica lead to sodium- and fluoride-free materials that exhibit exactly the same structures and properties as those previously reported [Boissiere et al. J. Chem. Soc. Chem. Commun. 1999, 20, 2047]. In addition, with the process occurring in slightly acidic aqueous medium, at moderate temperatures, and ...

Complexes of Cu(II) with polyvinyl alcohol as precursors for the preparation of CuO/SiO2 nanocomposites

Abstract: Cupric oxide (CuO) nanoparticles have been prepared in amorphous SiO2 matrix using a novel variant of sol-gel technique. The method is based on the polycondensation of a silica source (sodium silicate) in the presence of an aqueous solution containing complex of Cu(II) with polyvinyl alcohol (CuPVA). After gelation, polymeric complexes containing several thousands Cu atoms each are incorporated into the silica network forming a precursor, which is then annealed in oxygen to get rid of organic components. The formation of CuO nanoparticles was confirmed by electron diffraction studies. The size of nanoparticles can be controlled by varying [Cu2+]/[PVA] ratio in the precursor. Thus prepared CuO/SiO2 nanocomposites are characterized by high specific surface area as measured by capillary adsorption of nitrogen, suggesting their possible use in catalysis.

Sodium Silicate Based Thermal Interface Material for High Thermal Contact Conductance

Abstract: Sodium silicate based thermal interface pastes give higher thermal contact conductance across conductor surfaces than polymer based pastes and oils, due to their higher fluidity and the consequent greater conformability. Addition of hexagonal boron nitride particles up to 16.0 vol. percent further increases the conductance of sodium silicate, due to the higher thermal conductivity of BN. However, addition beyond 16.0 vol. percent BN causes the conductance to decrease, due to the decrease in fluidity. At 16.0 vol. percent BN, the conductance is up to 63 percent higher than those given by silicone based pastes and is almost as high as that given by solder. Water is almost as effective as sodium silicate without filler, but the thermal contact conductance decreases with time due to the evaporation of water. Mineral oil and silicone without filler are much less effective than water or sodium silicate without filler. @S1043-7398~00!00402-3#

Sodium silicate based thermal interface material for high thermal contact conductance

Abstract: Sodium silicate based thermal interface pastes give higher thermal contact conductance across conductor surfaces than polymer based pastes and oils, due to their higher fluidity and the consequent greater conformability Addition of hexagonal boron nitride particles up to 160 vol percent further increases the conductance of sodium silicate, due to the higher thermal conductivity of BN However, addition beyond 160 vol percent BN causes the conductance to decrease, due to the decrease in fluidity At 160 vol percent BN, the conductance is up to 63 percent higher than those given by silicone based pastes and is almost as high as that given by solder Water is almost as effective as sodium silicate without filler, but the thermal contact conductance decreases with time due to the evaporation of water Mineral oil and silicone without filler are much less effective than water or sodium silicate without filler @S1043-7398~00!00402-3#

A new method for free fatty acid reduction in frying oil using silicate films produced from rice hull ash

Abstract: Sodium silicate films were produced from rice hull ash silica, and their application in reducing free fatty acid (FFA) in frying oil was investigated. Sodium hydroxide concentration of these films was 32, 28, 24, and 20% with silica concentration of 45, 50, 55, and 60%, respectively. Moisture contents of these films were 20–23%. Adsorption performance of the films was investigated in frying oil at 80°C for 10–40 min. FFA content gradually decreased with treatment time for all films. There were no significant differences in FFA content among films for treatments up to 30 min. Treatment with 45 and 50% silica films for 40 min led to significantly larger reduction in FFA compared to treatment with 60% silica film. Differences between the FFA content of oil treated for 40 min with 55% silica and the FFA content of oils treated with other silica films were insignificant. FFA content of oil decreased from 0.8 to 0.55, 0.55, 0.57, and 0.59% after 40 min treatment with 45, 50, 55, and 60% silica film, respectively. Peroxide values (PV) of treated oils slightly increased from 48 to about 60 meq/kg for films with 45, 50, and 55% silica. Treatment with 60% silica led to a decrease in PV values to 42 meq/kg. Soap content of oil increased from 51 to over 100 ppm as a result of silicate film treatment.

Silica xerogels from rice hull ash: structure, density and mechanical strength as affected by gelation pH and silica concentration

Abstract: Silica xerogels were produced from rice hull ash (RHA), and the structure, density and mechanical strength of the gels were investigated. Silica was extracted as sodium silicate from RHA using 1M NaOH. This silicate solution was concentrated by volume reduction and used to obtain silica concentrations of 0.04, 0.06, 0.08, 0.10, and 0.12 g cm−3. The pH values of these silicate solutions were adjusted to 9.0, 10.0, 10.5, or 11.0 to produce silica gels. The silica gels produced were then dried at 80 °C for 24 h. X-ray diffraction demonstrated the amorphous nature of silica gels. Diffuse reflectance Fourier Transform Infrared (FTIR) spectroscopy was used to investigate the effect of gelation pH, and silica concentration on the chemical structure of the xerogel and concomitant effect on density and mechanical strength of the xerogel. The FTIR spectra demonstrated that at higher pH of gelation, siloxane bonding was the primary network in the xerogel. As the pH of gelation decreased, the structural silica gel network became the major interaction in the silica xerogel. At each gelation pH, the silica gel network increased with increase in silica concentration. The higher pH led to condensed glassy solids, while higher silica concentration produced highly porous silica xerogel. Hence, gelation pH and silica concentration of gel-forming solution had significant effects on the density and the mechanical strength of xerogels produced from rice hull silica. © 2000 Society of Chemical Industry

Inorganic binders employing waste glass

Abstract: The present invention relates to a binder composition comprising a glass powder with a particle size of at least less than 0.15 mm and an alkali activator containing at least one alkali metal and at least one silicate. Preferably, a sodium silicate with a SiO2:Na2O weight ratio between about 1.6:1 to about 2.0:1. Mixed with water, the binder composition can be cured at ambient temperature, but rapidly yields a very high strength at an elevated temperature between about 40°C to about 120°C, preferably, between about 70°C to about 90°C. The invention further provides a method of making artificial stone using glass as a sole binder and aggregate.

Sol-gel particle growth studied using fluorescence anisotropy: An alternative to scattering techniques

Abstract: There can be few more important materials than silica and water. The former constitutes the most abundant material in the earth’s crust and the latter occupies most of the surface of the earth. The properties of the two are inextricably linked in the search for a better understanding of the molecular dynamics responsible for sol to gel phase transitions. Few techniques permit the study of both, but in this paper we report the results of an approach that gives independent, simultaneous, and in situ characterization of the aqueous phase and silica particle size during sol-gel polymerization. The sol-gel process is a room temperature inorganic polymerization involving a series of hydrolysis and condensation steps to produce a rigid network. It owes its origins to the pioneering work of Ebelman, Mendeleyev, and Graham in the 19th century @1#. The sol to gel transition is characterized by a gel point, after a time t g , at which a fine silica network spans the containing vessel. Of all the possible syntheses, the mixing of concentrated sulfuric acid and sodium silicate ~i.e., water glass! to produce silica gel, through the formation of siloxane ~—Si—O—Si—! bonds, has the largest industrial significance owing to the large scale production of silica gel for everyday applications such as an abrasive, filling, and refining agent. Hence, although possessing an

Synthesis and Characterization of Microporous Silica Prepared with Sodium Silicate and Organosilane Compounds

Abstract: Microporous silica gels were prepared in the pH range of 3–4 using sodium silicate as a silica source. Surface polarity of these gels was modified by grafting hydrophobic groups into the silica gel matrix with the help of hydrophilic solvents (acetone, acetonitrile, ethanol and methanol) and alkoxysilane compounds containing nonhydrolyzable alkyl groups. The porous framework and hydrophobicity of the silica gels were evaluated using nitrogen adsorption/desorption and water adsorption measurement techniques. All the measured isotherms were found to be type I which is indicative of microporosity. The surface area and microporosity of these samples were estimated by analyzing the measured nitrogen adsorption/desorption data using BET, Langmuir and Dubinin-Radushkevich (D-R) adsorption isotherms. The micropore size distribution was determined from their nitrogen adsorption isotherms using the slit-pore model of the Horvath-Kawazoe equation. Silica gels with high surface area (over 500 m2/g) as well as high microporosity (over 0.2 cc/g) were obtained at gelation pH of 3.50 from the water-solvent system.

Epoxy resin composition

Abstract: PROBLEM TO BE SOLVED: To provide an epoxy resin composition providing excellent adhesion of a silica filler to a resin after curing of the composition and excellent mechanical characteristics of the cured product as well as having sufficient curability even without using a curing accelerator by including a reactive silica particle having a silanol group of at least a certain concentration and a curable epoxy resin SOLUTION: A reactive silica particle to be used has a silanol group of at least 6 μmol/g, and preferably from at least 6 μmol/g to not more than 5 mmol/g The reactive silica particle having a silanol group of at least 6 μmol/g is obtained by gelatinizing sodium silicate or an alkyl silicate under wet conditions, and then calcining the resulting gel (sol-gel method spherical silica) at a relatively low-controlled calcining temperature A particle diameter of the reactive silica particle is preferably an average diameter of 001-30 μm, and more preferably 01-10 μm

Synthesis of Mesostructured Nickel Oxide with Silica

Abstract: Mesostructured nickel oxide was formed with nickel sulfate and cationic surfactant cetyltrimethylammonium bromide (CTAB) X-ray diffraction (XRD) peaks at low scattering angles and transmission electron microscopy (TEM) indicated that a mesostructure was formed However, these XRD patterns disappeared after calcination The addition of sodium silicate in the precursor solutions produced a mesostructure, which is stable against calcination Surface areas as high as 530 m2/g can be obtained for the nickel silicate mesophase TEM-EDXS showed that the Si/Ni molar ratio in the mesophase is ∼05, independent of the initial Si/Ni ratio in the precursor

Synthesis of submicron silicalite-1 crystals from clear solutions

Abstract: Discrete and monodisperse submicron crystals of silicalite-1 with a mean size of 0.3 μ m were synthesized from clear crystallization solutions. The effects of silica content, alkalinity of batch and the nature of silica source on the product yield, crystal morphology and particle size distribution were investigated. The crystal shape was sphere-like or hexagonal twinned disks when silicic acid was the silica source. Change of silica source to sodium silicate solution leads to the formation of rounded-edged-hexahedron crystals. Silica content of batch does not influence crystal morphology. Alkalinity of clear crystallization solution has a strong effect both on the particle size distribution and yield of product. Increase of alkalinity caused bimodal particle size distribution and decrease of yield.

Synthesis of Crystalline Layered Sodium Silicate from Amorphous Silicate for Use in Detergents

Abstract: The synthesis of crystalline layered sodium silicates from amorphous sodium silicate has been investigated. Different synthesis process variables have been studied to synthesize products of a suitable quality for their use as builders in detergent formulations. Two different experimental processes have been used: a furnace (discontinuous process) and a pilot-plant rotary tubular oven (continuous process). The capacity to remove calcium and magnesium ions from water directly depends on the crystallinity and the δ phase content of the samples. The presence of about 20 wt % crystalline seeds and a reaction temperature of around 685 °C are needed to synthesize highly crystalline δ layered silicates. Differential thermal analysis measurements confirmed that amorphous silicate undergoes a crystallization process (exothermic step at 685 °C) which is attributed to the formation of the crystalline δ phase. The increase in the crystallization rate produced by agitation in the rotary tubular oven resulted in shorte...

Spectroscopic Study of CuO/CoO Catalysts Supported by Si-Al-Y Zeolite Matrices Prepared by Two Sol-Gel Methods

Abstract: Two different sol-gel methods for silica-aluminates have been used for catalyst preparation, one based on inorganic precursors, aluminum nitrate and sodium silicate, and a second based on alkoxides, aluminum tri-sec-butoxide (ATB) and tetra-ethoxy-silane (TEOS). A third element, Y-zeolite was incorporated in both of the gel matrices during the process, in order to alter the acid properties of the catalyst. Although the final compound has approximately the same chemical composition, the crystalline structures of the two catalysts are substantially different. The support made from inorganic precursor yielded a more hydroxylated surface, whereas the support based on organic precursors readily incorporated the metals into the network. The support from organic precursors showed almost total dehydroxylation. The Co-Cu complexes formed at the catalyst surface differ greatly, depending on the preparation method.

Dust core having high electric resistance and its manufacturing method

Abstract: PROBLEM TO BE SOLVED: To provide a dust core in which the lowering of permeability is hardly generated or is slight even in a high frequency region because distortion in metallic powder is eliminated sufficiently by annealing at a high temperature and electric resistance is improved remarkably in the dust core obtained by compression-molding the powder of a soft magnetic metal together with an insulating binder. SOLUTION: The water-spray powder of an Fe-Si alloy, an Fe-Si-Al alloy or an Fe-Ni alloy is treated by phosphate and films are formed on the surfaces of powder, powder on which the films are formed is mixed with the aqueous solution of a sodium silicate, a mixture is compression-molded and molded in a core shape, and a molded form is annealed at 500-1000 deg.C such as 650 deg.C, thus manufacturing the dust core. The crystallization temperature of phosphate is increased by the working of the sodium silicate, and electric resistance does not lower even when an annealing temperature is increased.

Crystal nucleation rates in a Na2O–SiO2 glass

Abstract: Nucleation of sodium metasilicate crystals in sodium silicate glass of composition 43Na2O–57SiO2 is investigated. Two-stage isothermal heating and optical microscopy techniques are utilized to determine the steady-state nucleation rates at temperatures between 390°C and 455°C. The results of this investigation are compared to the results we obtained for the temperature dependence of the nucleation rate in these glasses via a DTA technique which we presented in a previous study. It is found that the results of the two techniques are in agreement within experimental error. It is observed that the peak nucleation rate for this composition occurs near 410°C, which is about 50°C lower than that reported for nucleation in the 46Na2O–54SiO2 glass composition.

Sorbent, method of making the sorbent, and method of using the sorbent in fixed bed applications

Abstract: A sorbent contains an acid-leached clay and a binder. The acid-leached clay may be attapulgite, kaolin, bentonite, montmorillonite, or a combination thereof. The binder may be colloidal silica sol, sodium silicate, sodium di-silicate, hydrated alumina, starch, sucrose, or a combination thereof. Sorbent particles may contain 40 to 95 wt. % of the acid-leached clay and 5 to 30 wt. % of the binder. The sorbent has high dry and wet crush strengths and good water stability.

Liquid feedstuff additives and preparation thereof

Abstract: A functional liquid feedstock additive that has conspicuous advantages of increasing the productivity of livestock, activating immune competent cells to enhance the immunity of livestock against diseases, and improve meats of livestock into unsaturated fatty acid-rich ones. It is prepared by homogeneously dissolving a composition comprising 5-12 g of calcium alumina silicate (CaOSiO 2 Al 2 O 3 ), 5-12 g of sodium alumina silicate (Na 2 OAl 2 O 3 SiO 2 ), 300-900 g of sodium silicate (Na 2 OSiO 2 ), 400-1,200 g of potassium silicate (K 2 OSiO 2 ), 200-600 g of sodium bicarbonate (NaHCO 3 ), 350-1,100 g of potassium carbonate (K 2 CO 3 ), 250-800 g of sodium carbonate (Na 2 CO 3 ), 10.8-2.5 g of zinc oxide, 0.4-4.5 g of germanium dioxide and 900-1,800 g of a reducing sugar in 1 liter of water under a flow of nitrogen gas with a redox potential being maintained in the range of −25 to 25 mV to give a gel phase and diluting the gel five-ten folds in water, and aging the gel at 20-35° C. for about 1-2 days under a flow of nitrogen gas with a redox potential being maintained in the range of −30 to 30 mV.