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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

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.

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.