Journal ArticleDOI
New insight in the role of modifying ligands in the sol-gel processing of metal alkoxide precursors: A possibility to approach new classes of materials
Vadim G. Kessler,Gerald I. Spijksma,Gerald I. Spijksma,Gulaim A. Seisenbaeva,Sebastian Håkansson,David H.A. Blank,Henny J.M. Bouwmeester +6 more
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In this article, the authors summarized recent literature data and presented new experimental data on the mechanisms of chemical modification, hydrolysis and polycondensation of the alkoxides and demonstrates possibilities to approach new classes of materials, exploiting these mechanisms.Abstract:
This paper summarizes recent literature data and presents new experimental data on the mechanisms of chemical modification, hydrolysis and polycondensation of the alkoxides and demonstrates possibilities to approach new classes of materials, exploiting these mechanisms. Low reactivity of silicon alkoxides is improved by either basic catalysis exploiting an SN2 mechanism or acidic catalysis facilitating a proton-assisted SN1 mechanism as well as by modification with chelating ligands. Metal alkoxides are much stronger Lewis bases compared to silicon alkoxides and the acidity of water is strong enough to achieve their rapid hydrolysis via proton-assisted SN1 pathway even in the absence of additional catalysts. Introduction of the modifying chelating ligands is leading generally to increased charge distribution in the precursor molecules. Modifying chelating ligands are also appreciably smaller than the alkoxide ligands they replace. The modification with chelating ligands is thus facilitating the kinetics of hydrolysis and polycondensation. The size and shape of the primary particles formed in sol-gel treatment of metal alkoxides are defined not by kinetic factors in their hydrolysis and polycondensation but by the interactions on the phase boundary, which is in its turn directed by the ligand properties. The products of the fast hydrolysis and condensation sequence consist of micelles templated by self-assembly of ligands (mainly oxo-species). This concept provides explanations for commonly observed material properties and allows for the development of new strategies for the preparation of materials. We discuss the formation of inverted micelles, obtained by the appropriate choice of solvents, which allows for the formation of hollow spheres. The modifying β-diketonate ligands act as the surfactant and form an interface between the hollow sphere and the solvent. Retention of ligands inside the gel particles is possible only if ligands possessing both chelating and bridging properties are applied. Application of such ligands, for example, diethanolamine, permits to prepare new transition metal oxide based microporous membranes.read more
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Sol-gel based materials for biomedical applications
Gareth J Owens,Rajendra K. Singh,Farzad Foroutan,Mustafa Alqaysi,Cheol-Min Han,Chinmaya Mahapatra,Hae-Won Kim,Jonathan C. Knowles,Jonathan C. Knowles +8 more
TL;DR: A more detailed description of the biomedical areas where sol-gel materials have been explored and found to hold significant potential is given in this paper, where a generalized description of various solgel methods available and how these chemistries control the bulk properties of the end products is presented.
Journal ArticleDOI
High surface area crystalline titanium dioxide: potential and limits in electrochemical energy storage and catalysis.
Thomas Fröschl,U. Hörmann,Pierre Kubiak,Gabriela Kučerová,Manuel Pfanzelt,Clemens K. Weiss,Rolf Jürgen Behm,Nicola Hüsing,Ute Kaiser,Katharina Landfester,Margret Wohlfahrt-Mehrens +10 more
TL;DR: The present work critically reviews the formation of crystalline nanoscale titania particles via solution-based approaches without thermal treatment, with special focus on the resulting polymorphs, crystal morphology, surface area, and particle dimensions.
Journal ArticleDOI
FTIR study of the sol–gel synthesis of cementitious gels: C–S–H and N–A–S–H
TL;DR: In this article, the compatibility between Portland cement hydration and the main product of the alkali activation of fly ash was explored, and the results relating to the joint synthesis of the two (C−S−H and N−A−S-H) gels were not conclusive.
Patent
System and apparatus for flowable deposition in semiconductor fabrication
Jonathan D. Mohn,Harald Te Nijenhuis,Shawn M. Hamilton,Kevin Madrigal,Ramkishan Rao Lingampalli +4 more
TL;DR: In this article, a semiconductor fabrication chamber is described, which is configured to maintain a single semiconductor wafer at a temperature near 0°C. while maintaining most other components within the fabrication chamber at temperatures on the order of 5-10°C or higher than the wafer temperature.
Journal ArticleDOI
Organic-Inorganic Hybrid Polymers as Adsorbents for Removal of Heavy Metal Ions from Solutions: A Review.
TL;DR: The adsorption characteristics of heavy metals of organic-inorganic hybrid polymers, including different kinds of functional groups, selectivity of them for heavy metals, effect of pH and synthesis conditions on Adsorption capacity, are studied.
References
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Book
Sol-Gel Science: The Physics and Chemistry of Sol-Gel Processing
TL;DR: Gel-Derived and Conventional Ceramics: as discussed by the authors Theoretical analysis of deformation and flow in gels and a comparison of gel-derived and conventional ceramics.
Journal ArticleDOI
Recent advances in the liquid-phase syntheses of inorganic nanoparticles.
TL;DR: The development of novel materials is a fundamental focal point of chemical research; and this interest is mandated by advancements in all areas of industry and technology.
Journal ArticleDOI
Sol-gel chemistry of transition metal oxides
TL;DR: In this paper, the preparation of a colloidal colloidal by un procede sol gel is described, and a procedure for determination des proprietes electriques et electrochimiques is described.
Journal ArticleDOI
Sol-gel transition in simple silicates II☆
TL;DR: In this article, a range of conditions in which the rate of hydrolysis was varied from fast to slow with respect to condensation were discussed, and it was shown that higher temperatures were sufficient to densify fine gels by a process which was postulated to consist of polymer relaxation followed by condensation and pore collapse.
Journal ArticleDOI
Sol-gel chemistry
Jacques Livage,Clément Sanchez +1 more
TL;DR: The chemical reactivity of metal alkoxides toward hydrolysis, condensation and complexation mainly depends on the electronegativity of the metal atom, its coordination number and the steric hindrance of alkoxide groups.