Silica

14,000,000 Leading Edge Experts on the ideXlab platform

Scan Science and Technology

Contact Leading Edge Experts & Companies

Scan Science and Technology

Contact Leading Edge Experts & Companies

The Experts below are selected from a list of 893577 Experts worldwide ranked by ideXlab platform

Andrzej Krysztafkiewicz - One of the best experts on this subject based on the ideXlab platform.

  • influence of selected alkoxysilanes on dispersive properties and surface chemistry of spherical Silica precipitated in emulsion media
    Materials Chemistry and Physics, 2010
    Co-Authors: Teofil Jesionowski, Filip Ciesielczyk, Andrzej Krysztafkiewicz
    Abstract:

    Abstract The process of Silicas formation in emulsion system in the reaction of precipitation from water solutions of sodium Silicate and hydrochloric acid has been studied. The effects of Silica surface modifications with silane coupling agents from the group of alkoxysilanes with different functional groups have been determined. Both unmodified and modified Silicas have been thoroughly characterised by scanning electron microscopy (SEM) and dynamic light scattering (DLS) and other methods. The effect of alkoxysilanes on the diameter distribution of the modified Silica is insignificant; the presence of silane coupling agents causes a small increase in the particle diameter and a small increase in the tendency towards agglomeration, moreover the particles of silicon dioxide precipitated are characterised by spherical shape. The course of the electrokinetic curves depends mainly on the proton affinity of the modifiers. Significant changes in the stability of Silica dispersions have been found as a result of modification with N-2-(aminoethyl)-3-aminopropyltrimethoxysilane. This compound causes the greatest increase in the tendency towards agglomeration of the primary particles. The modification mechanism has been established to be chemisorption, as indicated by the 13C and 29Si CP MAS NMR spectra. The products have been shown to have typical mesoporous structure. The surface area of the unmodified Silica is 133 m2/g, while those for the modified Silicas vary from 115 to 182 m2/g.

  • adsorption of the selected organic dyes on the functionalized surface of precipitated Silica via emulsion route
    Dyes and Pigments, 2005
    Co-Authors: Teofil Jesionowski, Slawomir Binkowski, Andrzej Krysztafkiewicz
    Abstract:

    Abstract Physicochemical analysis was performed on Silicas precipitated according to a novel method, in an emulsion system. Substrates for the process involved solutions of sodium metaSilicate and sulphuric acid while the organic phase consisted of cyclohexane and non-ionic emulsifiers. The Silicas were used to obtain hybrid structures of the formed inorganic pigments. For this purpose, the adsorption of organic dyes on the Silica surface was preceded by modification of the surface with silane coupling agent containing amine groups. Specific surface area (BET) and porous structure of the raw Silicas were estimated. The Silicas and pigments were subjected to studies on surface morphology, zeta potential, particle size and distribution of particle diameters were also established. Effects of modification with the aminosilane were appraised using FTIR and 29 Si CP MAS NMR techniques. Stable pigments were obtained on Silica core, the surface of which was modified with N -2-(aminoethyl)-3-aminopropyltrimethoxysilane. Particles of the obtained pigment manifested a spherical shape and particle size distribution proved that no agglomerate structures were present. High stability of the obtained pigments proved that the organic dye was chemically bound to the modified Silica surface. Mechanisms of inorganic–organic hybrid formation were also suggested.

  • Studies on precipitation of highly dispersed Silica from sodium metaSilicate–sodium hydrogencarbonate system
    Journal of Chemical Technology & Biotechnology, 2002
    Co-Authors: Jolanta Żurawska, Teofil Jesionowski, Andrzej Krysztafkiewicz
    Abstract:

    A novel procedure is presented for precipitation of highly dispersed Silica from sodium metaSilicate solution using sodium hydrogencarbonate. In the course of Silica precipitation, hydrophobicity-inducing agents were introduced to the reactor, including derivatives of saturated and unsaturated higher fatty alcohols and nonylphenylpolyoxyethyleneglycol ethers. Silicas of variable physicochemical characteristics were obtained. Analysis of the principal physicochemical properties of the Silicas was performed, their surface morphology was examined using scanning electron microscopy while particle size distribution, polydispersity and tendency to form the agglomerate structures were estimated by the dynamic light scattering technique. The zeta potential was also measured by estimation of electrophoretic mobility. Sodium hydrogencarbonate solution was found to be a very good Silica-precipitating agent in solutions of sodium metaSilicate. The hydrated Silica obtained demonstrated low bulk density and a high capacity to absorb paraffin oil. © 2002 Society of Chemical Industry

  • preparation of the hydrophilic hydrophobic Silica particles
    Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2002
    Co-Authors: Teofil Jesionowski, Andrzej Krysztafkiewicz
    Abstract:

    Abstract Silicas of high dispersion degree were obtained. The process included formation of Silica particles and their aggregation. Glycerin solution was used in precipitation process, resulting in a partial blocking of the Silica surface hydroxyl groups (silanol groups) and, thus, in a decreased hydrophilicity of Silica. Studies on the surface modification of Silicas using silane coupling agents are described. The best modifiers were selected, which induced a change of the Silica surface from the hydrophilic to the hydrophobic one. Basic physicochemical analyses of the obtained Silicas were performed. Near infrared spectroscopy (NIR) was used to determine the degree of condensation of Silica surface silanol groups. The degree of hydrophobization of Silica surface was determined by a calorimetric method. Moreover, zeta potential, size distribution of primary particles, aggregates and agglomerates structures were determined by ZetaPlus instrument using electrophorectic (ELS) and dynamic (DLS) light scattering techniques.

  • Surface properties and dispersion behaviour of precipitated Silicas
    Journal of Materials Science, 2002
    Co-Authors: Teofil Jesionowski, Jolanta Żurawska, Andrzej Krysztafkiewicz
    Abstract:

    Silicas of highly dispersion degree were obtained using the precipitation technique with sodium metaSilicate solution and sulphuric acid. This process includes formation of Silica particle and their aggregation. Studies on the surface modification of Silicas using silane coupling agents are described. Application of these compounds results in the change of the hydrophilic character to the hydrophobic one. Basic physicochemical analyses of the obtained Silica were presented. Moreover, studies on morphology and microstructure using scanning electron microscopy (SEM) were performed. The zeta potential, polydispersity and changes in the tendency to form agglomerates and aggregates of the particles were also described. Silicas modified with any of the examined silanes manifest a decreased tendency to secondary agglomerate formation and in many cases uniform Silicas were obtained.

Teofil Jesionowski - One of the best experts on this subject based on the ideXlab platform.

  • influence of selected alkoxysilanes on dispersive properties and surface chemistry of spherical Silica precipitated in emulsion media
    Materials Chemistry and Physics, 2010
    Co-Authors: Teofil Jesionowski, Filip Ciesielczyk, Andrzej Krysztafkiewicz
    Abstract:

    Abstract The process of Silicas formation in emulsion system in the reaction of precipitation from water solutions of sodium Silicate and hydrochloric acid has been studied. The effects of Silica surface modifications with silane coupling agents from the group of alkoxysilanes with different functional groups have been determined. Both unmodified and modified Silicas have been thoroughly characterised by scanning electron microscopy (SEM) and dynamic light scattering (DLS) and other methods. The effect of alkoxysilanes on the diameter distribution of the modified Silica is insignificant; the presence of silane coupling agents causes a small increase in the particle diameter and a small increase in the tendency towards agglomeration, moreover the particles of silicon dioxide precipitated are characterised by spherical shape. The course of the electrokinetic curves depends mainly on the proton affinity of the modifiers. Significant changes in the stability of Silica dispersions have been found as a result of modification with N-2-(aminoethyl)-3-aminopropyltrimethoxysilane. This compound causes the greatest increase in the tendency towards agglomeration of the primary particles. The modification mechanism has been established to be chemisorption, as indicated by the 13C and 29Si CP MAS NMR spectra. The products have been shown to have typical mesoporous structure. The surface area of the unmodified Silica is 133 m2/g, while those for the modified Silicas vary from 115 to 182 m2/g.

  • synthesis and characterization of spherical Silica precipitated via emulsion route
    Journal of Materials Processing Technology, 2008
    Co-Authors: Teofil Jesionowski
    Abstract:

    Abstract The reaction of precipitation of amorphous silicon dioxide from aqueous solution of sodium Silicate and hydrochloric acid in cyclohexane medium has been studied. The effects of experimental conditions on the dispersity and adsorptive character of the obtained Silicas have been established on the basis of the particle size, polydispersity, specific surface area and pore characteristics. The effect of the dispersion–induction technique on the physicochemical characterization of the obtained Silicas has been estimated. The application of homogenization has been found to lead to SiO2 particles of the most favourable dispersion and morphological character, while the application of a top propeller stirrer might be an alternative technique. The modification of the reaction involving precipitation of Silica from sodium Silicate emulsion dosed directly into hydrochloric acid has been shown to give SiO2 particles of a defined shape, provided that no exposure to ultrasound was employed. The Silicas precipitated using a homogenizer and ultrasound bath have shown much higher specific surface area (ABET) than that of the obtained Silica using the top propeller stirrer. The Silica of the most favourable physicochemical parameters contained particles of the size of 400 nm, polydispersity of 0.005, and surface area of 466 m2/g.

  • adsorption of the selected organic dyes on the functionalized surface of precipitated Silica via emulsion route
    Dyes and Pigments, 2005
    Co-Authors: Teofil Jesionowski, Slawomir Binkowski, Andrzej Krysztafkiewicz
    Abstract:

    Abstract Physicochemical analysis was performed on Silicas precipitated according to a novel method, in an emulsion system. Substrates for the process involved solutions of sodium metaSilicate and sulphuric acid while the organic phase consisted of cyclohexane and non-ionic emulsifiers. The Silicas were used to obtain hybrid structures of the formed inorganic pigments. For this purpose, the adsorption of organic dyes on the Silica surface was preceded by modification of the surface with silane coupling agent containing amine groups. Specific surface area (BET) and porous structure of the raw Silicas were estimated. The Silicas and pigments were subjected to studies on surface morphology, zeta potential, particle size and distribution of particle diameters were also established. Effects of modification with the aminosilane were appraised using FTIR and 29 Si CP MAS NMR techniques. Stable pigments were obtained on Silica core, the surface of which was modified with N -2-(aminoethyl)-3-aminopropyltrimethoxysilane. Particles of the obtained pigment manifested a spherical shape and particle size distribution proved that no agglomerate structures were present. High stability of the obtained pigments proved that the organic dye was chemically bound to the modified Silica surface. Mechanisms of inorganic–organic hybrid formation were also suggested.

  • Studies on precipitation of highly dispersed Silica from sodium metaSilicate–sodium hydrogencarbonate system
    Journal of Chemical Technology & Biotechnology, 2002
    Co-Authors: Jolanta Żurawska, Teofil Jesionowski, Andrzej Krysztafkiewicz
    Abstract:

    A novel procedure is presented for precipitation of highly dispersed Silica from sodium metaSilicate solution using sodium hydrogencarbonate. In the course of Silica precipitation, hydrophobicity-inducing agents were introduced to the reactor, including derivatives of saturated and unsaturated higher fatty alcohols and nonylphenylpolyoxyethyleneglycol ethers. Silicas of variable physicochemical characteristics were obtained. Analysis of the principal physicochemical properties of the Silicas was performed, their surface morphology was examined using scanning electron microscopy while particle size distribution, polydispersity and tendency to form the agglomerate structures were estimated by the dynamic light scattering technique. The zeta potential was also measured by estimation of electrophoretic mobility. Sodium hydrogencarbonate solution was found to be a very good Silica-precipitating agent in solutions of sodium metaSilicate. The hydrated Silica obtained demonstrated low bulk density and a high capacity to absorb paraffin oil. © 2002 Society of Chemical Industry

  • preparation of the hydrophilic hydrophobic Silica particles
    Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2002
    Co-Authors: Teofil Jesionowski, Andrzej Krysztafkiewicz
    Abstract:

    Abstract Silicas of high dispersion degree were obtained. The process included formation of Silica particles and their aggregation. Glycerin solution was used in precipitation process, resulting in a partial blocking of the Silica surface hydroxyl groups (silanol groups) and, thus, in a decreased hydrophilicity of Silica. Studies on the surface modification of Silicas using silane coupling agents are described. The best modifiers were selected, which induced a change of the Silica surface from the hydrophilic to the hydrophobic one. Basic physicochemical analyses of the obtained Silicas were performed. Near infrared spectroscopy (NIR) was used to determine the degree of condensation of Silica surface silanol groups. The degree of hydrophobization of Silica surface was determined by a calorimetric method. Moreover, zeta potential, size distribution of primary particles, aggregates and agglomerates structures were determined by ZetaPlus instrument using electrophorectic (ELS) and dynamic (DLS) light scattering techniques.

Shinyoung Kaang - One of the best experts on this subject based on the ideXlab platform.

  • influence of thermal treatment of nano scaled Silica on interfacial adhesion properties of the Silica rubber compounding
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2005
    Co-Authors: Soojin Park, Sungyeol Jin, Shinyoung Kaang
    Abstract:

    Abstract In this work, the effect of thermal treatment on crosslink density and adhesion properties of nano-scaled Silica/rubber compounding are investigated. The chemical structures and surface properties of modified Silicas are studied in terms of Fourier transform-IR (FT-IR), solid-state 29 Si-NMR spectroscopy, and surface free energy, respectively. Also, the mechanical interfacial properties of the Silica/rubber compounding are determined by the crosslink density and tearing energy ( G IIIC ). As a result, it was found that the thermally treated Silicas became hydrophobic in nature, due to the condensation of surface hydroxyls and the formation of siloxane bond. From which, the increase of the siloxane bond on the Silica surfaces led to an improvement of the dispersion of Silicas in a rubber matrix, finally resulting in improving the tearing energy in a compounding system.

Jiří Čejka - One of the best experts on this subject based on the ideXlab platform.

  • mgo modified mesoporous Silicas impregnated by potassium carbonate for carbon dioxide adsorption
    Microporous and Mesoporous Materials, 2013
    Co-Authors: Arnost Zukal, Jakub Pastva, Jiří Čejka
    Abstract:

    Abstract Mesoporous adsorbents for carbon dioxide capture were prepared by introducing of magnesium oxide and potassium carbonate into SBA-15, SBA-16 Silicas and MCM-48-like-Silica. In order to avoid destruction of Silica supports, a novel procedure based on the precipitation of magnesium acetate on the Silica surface was developed. Subsequent in situ chemical conversion of magnesium acetate provided magnesium oxalate, while final magnesium oxide was formed by calcination. To introduce potassium carbonate, Silica modified with MgO was impregnated with potassium oxalate followed by its conversion to carbonate. All prepared mesoporous adsorbents preserved characteristic features of mesoporous molecular sieve. The comparison of carbon dioxide isotherms obtained on prepared samples reveals that their adsorption properties are decisively influenced by the type of mesoporous structure. Modified sample of SBA-15 Silica has shown the most steep adsorption isotherm and higher CO 2 adsorption capacity than adsorption capacity of samples prepared from SBA-16 and MCM-48-ls Silicas.

José Miguel Martín-martínez - One of the best experts on this subject based on the ideXlab platform.

  • Comparative Properties of Hydrophilic and Hydrophobic Fumed Silica Filled Two-Component Polyurethane Adhesives
    Journal of Adhesion Science and Technology, 2012
    Co-Authors: Mohammed A. Bahattab, Vanesa García-pacios, Jessica Donate-robles, José Miguel Martín-martínez
    Abstract:

    Two fumed Silicas, one hydrophilic and another hydrophobic, were added to a two-component polyurethane (PU) adhesive and their properties compared. The filled polyurethanes were characterized by thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), transmission electron microscopy (TEM), and water and diiodomethane contact angle measurements. The adhesive strength was evaluated from single lap-shear tests of solvent wiped stainless steel/polyurethane adhesive joints. The fumed Silicas were well-dispersed in the polyurethane matrix as bundles of nanometric spherical Silica particles. However, some micron size agglomerates of fumed Silica appeared in the filled polyurethane. The addition of fumed Silica favoured the degree of phase separation between the hard and the soft segments in the polyurethane. The polyurethanes were not fully cured under the conditions used in this study and the addition of fumed Silica inhibited the curing reaction; the extent of the curing reaction was not a...

  • Thermoplastic polyurethane-fumed Silica composites: influence of the specific surface area of fumed Silica on the viscoelastic and adhesion properties
    Journal of Adhesion Science and Technology, 1999
    Co-Authors: Belén Jaúregui-beloqui, Juan C. Fernández-garcía, M. Mar Mahiques-bujanda, A. César Orgilés-barceló, José Miguel Martín-martínez
    Abstract:

    Fumed Silicas of different specific surface area (90-380 m2/g) were added to a thermoplastic polyurethane (PU) solution. After solvent removal, solid fumed Silica-PU composites were obtained. The viscoelastic properties of PU were improved by adding fumed Silica and only a solid-like behavior in PU-fumed Silica composites was obtained. The increase in the specific surface area of the fumed Silica up to 200 m2 / g increased the moduli of the composites. Fumed Silica-PU interactions were responsible for the improved rheological properties of the composites. The activation energies for viscous flow of the composites were 14-16 kcal/mol and increased as the specific surface area of fumed Silica increased. The glass transition temperature (obtained from DMTA and DSC experiments) and the crystallization rate of fumed Silica-PU composites decreased compared with PU and also decreased with increasing surface area of the fumed Silica. The contact angle values were similar in all the composites and the strength of ...

  • Hydrophobic or Hydrophilic Fumed Silica as Filler of Polyurethane Adhesives
    Journal of Adhesion, 1995
    Co-Authors: T. G. Maciá-agulló, A. M. Torro Palau, A. C. Orgiles Barcelo, Juan C. Fernández-garcía, José Miguel Martín-martínez
    Abstract:

    Abstract Two hydrophilic and two hydrophobic fumed Silicas of different characteristics were added to solvent-based polyurethane adhesives (PU). IR spectroscopy, contact angle measurements and rheology (viscosity measurements, determination of viscoelastic properties) were used to monitor the variation of properties of PU adhesives produced by addition of Silica. Immediate (green) adhesion was determined by T-peel testing of halogenated synthetic rubber/PU adhesive/halogenated synthetic rubber joints. Silica addition produced a noticeable increase in the PU adhesive viscosity which can be related to the variation of viscoelastic properties. Viscosity of PU adhesives containing hydrophilic Silica slightly increased with time after preparation; the increase was less significant in PU adhesives with hydrophilic Silica. In the rheological studies, Silica imparted shear thinning and negative thixotropy to PU adhesives due to a better dispersion of the Silica in the polyurethane during shearing. The addition of...