/pdf/the-surface-chemistry-of-amorphous-silica-zhuravlev-model-4kfs2lx66q.pdf

The surface chemistry of amorphous silica. Zhuravlev model

https://web.iitd.ac.in/~arunku/files/CEL311_Y13/Adsorption%20Theory%20to%20practice_Dabrowski.pdf

Adsorption — from theory to practice

Preface. 1. Introductory Remarks. 2. Fundamental Factors for Designing Adsorbent. 3. Sorbent Selection: Equilibrium Isotherms, Diffusion, Cyclic Processes, and Sorbent Selection Criteria. 4. Pore Size Distribution. 5. Activated Carbon. 6. Silica Gel, MCM, and Activated Alumina. 7. Zeolites and Molecular Sieves. 8. &pi -Complexation Sorbents and Applications. 9. Carbon Nanotubes, Pillared Clays, and Polymeric Resins. 10. Sorbents for Applications. Author Index. Subject Index.

/pdf/adsorbents-fundamentals-and-applications-2732spmgdj.pdf

Adsorbents: Fundamentals and Applications

Application of silica nanoparticles as fillers in the preparation of nanocomposite of polymers has drawnmuch attention, due to the increased demand for new materials with improved thermal, mechanical, physical, and chemical properties. Recent developments in the synthesis of monodispersed, narrow-size distribution of nanoparticles by sol-gel method provide significant boost to development of silica-polymer nanocomposites. This paper is written by emphasizing on the synthesis of silica nanoparticles, characterization on size-dependent properties, and surface modification for the preparation of homogeneous nanocomposites, generally by sol-gel technique. The effect of nanosilica on the properties of various types of silica-polymer composites is also summarized.

/pdf/synthesis-of-silica-nanoparticles-by-sol-gel-size-dependent-4pexez08bs.pdf

Synthesis of silica nanoparticles by sol-gel: size-dependent properties, surface modification, and applications in silica-polymer nanocomposites — a review

Surface modification of natural halloysite clay nanotubes with γ-aminopropyltriethoxysilane (APTES) was investigated. Untreated and modified samples were characterized by nitrogen adsorption, X-ray diffraction, elemental analysis, thermogravimetry, transmission electron microscopy, atomic force microscopy, MAS nuclear magnetic resonance (29Si, 13C, 29Al), and Fourier transform infrared spectroscopy. The modification mechanism was found to include not only the direct grafting of APTES onto the hydroxyl groups of the internal walls, edges and external surfaces of the nanotubes but other processes in which oligomerized APTES condensed with the directly grafted APTES to form a cross-linked structure. The thermal and evacuation pretreatment conditions were found to play an important role in controlling the extent and mechanism of the modification. The extent of modification is also strongly affected by the morphological parameters of the original clay samples. This study demonstrates that the surface chemistry...

Functionalization of Halloysite Clay Nanotubes by Grafting with γ-Aminopropyltriethoxysilane

Part 1 The silica surface: silica - preparation and properties physical characterization of the silica surface the surface chemistry of silica quantification of the silanol number the distribution of the silanol types and their desorption energies the effect of surface morphology on the dehydroxylation behaviour related materials - silicates Part 2 Chemical modification of the silica surface: chemical modification of silica - applications and procedures modification with silicon compounds mechanistic studies modification with boron compounds modification with other compounds ammoniation of modified silica - introduction of functional groups Part 3 Chemical surface coating: coating techniques chemical surface coating Appendices - surface analysis techniques: FTIR-PAS, fourier transform infrared spectroscopy with photoacoustic detection XPS, X-Ray photoelectron spectroscopy 29Si CP MAS NMR, Cross polarization magic angle spinning nuclear magnetic resonance surface science techniques

Characterization and Chemical Modification of the Silica Surface

Surface modification of silica gels with aminoorganosilanes

Three mesoporous silica gels with variable pore size were modified with γ-aminopropyltriethoxysilane. The degree of surface hydration and hydroxylation and the available specific surface area were varied by a variation of pretreatment temperature. The effect of surface and structural properties of the silica substrate on both chemical and physical interaction of the silane with the silica were characterized using spectrophotometric and elemental analysis data. Total deposition is governed by the degree of hydration and the specific surface area of the substrate. Hydration causes hydrolysis and polymerization of the grafted molecules. On the dehydrated but hydroxylated substrate, a coating layer with a coverage of 2.05 molecules/nm2 is formed. The degree of chemical bonding is controlled by the number of surface hydroxyls if a relative excess of silane over surface silanols is used. On dehydroxylated silica a diverging reaction behavior is observed. The relative amount of physisorption increases largely. If the average pore radius r ⩽ 20 A steric hindrance lowers the surface coverage value.

Surface and Structural Properties of Silica Gel in the Modification with γ-Aminopropyltriethoxysilane

Yoshinaga et al. ( J. Colloid Interface Sci. 153, 207 (1992)) have reported in this journal a method to determine the silanol number (α OH ) on silica gel, using a chemical modification with dimethylchlorosilane. This method is appreciated as a fast and convenient way to determine α OH . However, three important cautions should be taken into account: (1) Chlorosilanes can also react with bridged hydroxyl groups. (2) The possibility of side reactions exists. (3) Sterical hindrance will not allow quantitative α OH determination above approximately 3 OH/nm 2 .

P. Van Der Voort

Papers

Characterization and Chemical Modification of the Silica Surface

Surface modification of silica gels with aminoorganosilanes

Surface and Structural Properties of Silica Gel in the Modification with γ-Aminopropyltriethoxysilane

Some precautions when determining the silanol number, using chemical modification with methylchlorosilanes