Sol-gel processing - a versatile concept for special glasses and ceramics

The various parameters related to sol-gel processing are discussed with special reference to those which usually attract less attention but depending on the final product in mind, can play important roles. The versatility of the sol-gel technique in materials preparation is demonstrated by discussing the various products developed at the author's laboratory by using this processing method

Sol-gel glasses - some recent trends

The basic experimental steps in the preparation of sol-gel glass as developed in recent times, and their relevance have been discussed taking high purity silica glass as an example. Current developments in sol-gel derived ultra-low expansion glasses, rare earth doped laser glasses, semiconductor-doped non-linear glasses, gradient index lenses, microoptics and organic molecule-doped (mainly dyes) glasses for sensor and other applications have been discussed in brief

Sol-gel processing of materials for electronic and related applications

Various techniques of sol gel processing for the preparation of electronic and related materials are described and reviewed. Typical examples are chosen from thin films and coatings of gels, crystalline materials and glasses as also bulk glasses to illustrate the variations in processing parameters and material properties

Sol-gel electrochromic coatings and devices: A review

A brief updated review is made on sol-gel-derived electrochromic films (some of which used as ion storage films) of different chemical systems. Performances of selected films measured in electrochemical cells or in devices are discussed and the degradation problems experienced by different authors enumerated

Sol-gel preparation of silica glass

This paper is a preliminary report on the preparation of silica glass containing very low amount of hydroxyl by the sol-gel processing technique. Gels were prepared from optimized amounts of tetraethyl orthosilicate, fumed silica and water. Acids and bases in small quantities were added for catalysing hydrolysis and adjusting the pH. Dried gels were heated up to 1400-degrees-C in various atmospheres to obtain transparent silica glass of the required density and very low (< 5 ppm) hydroxyl content

Plasma spraying of an indigenous yttria stabilized zirconia powder prepared by the sol-gel technique

An indigenous sol-gel derived yttria-partially stabilized zirconia (Y-PSZ) powder has been characterized and its suitability for plasma spraying applications evaluated. The powder, determined to have about 5.1% yttria content, predominantly consisted of spherical particles with an average equivalent particle diameter close to 25 mum. Furthermore, it was found that the powder did not contain any particles > 50 mum, which is considered the ideal upper size limit for spray-grade ceramic powders in order to ensure complete melting during spraying. The sol-gel produced powder exhibited good flow characteristics and the plasma sprayed coatings developed using this powder were also found to have excellent thermal shock resistance. The corresponding results obtained using an imported Y-PSZ powder are also presented for the purpose of comparison

Inorganic particle synthesis via macro and microemulsions: a micrometer to nanometer landscape

"Nanotechnology" is now very well known as one of the most important key technologies in science and industry. In the field of material science and engineering, nanoparticles should be unit materials, as well as atoms and molecules, to build ceramics, devices, catalysts, and machines, and the "nanoparticle technology" is thus attracting. This novel technology includes various methodologies for nanoparticles: preparation, surface-modification via chemical and/or physical treatments, immobilization and arrangement on supports or substrates, to achieve high performance for luminescence properties in light emitting devices, and high efficiency for catalytic and photocatalytic reactions in chemical synthesis, chemical decomposition, and artificial photosynthesis, etc. It should be needless to say that the preparation of nanoparticles, having precisely controlled particle size, size distribution, chemical composition, and surface properties, is essentially important to realize "true nanoparticle technology". This book, written by Dr. Dibyendu Ganguli and Dr. Munia Ganguli, deals with the preparation methodologies for inorganic nanoparticles using macro- and microemulsions as "microreactor". There are several differences between these two emulsions, in addition to water droplet size: thermodynamic stability, and fusion-redispersion dynamics of the droplets. The properties of the nanoparticles prepared in these emulsion systems are seriously influenced and controlled by the selection of dynamic and static conditions

Cationic radius ratio and formation of K2NiF4-type compounds

A survey of known compounds which can assume K2NiF4-type structure at least over a certain P, T range was made. The cationic radius ratios rA rB of this family of compounds were found to vary over a relatively narrow range of values around 2.00, in contrast to the much wider ranges known for other important A2BX4 structure groups, e.g., β-K2SO4, thenardite, olivine, etc., providing thereby a constraint on the crystal chemical variabilities in this group of compounds. Usefulness of the simple size parameter rA(IX) rB(VI) in predicting formation of new K2NiF4-type compounds is discussed. © 1979

Sol-emulsion-gel synthesis of ceramic particles

The basic characteristics of the sol-emulsion-gel (SEG) process are described as derived from water-in-oil type emulsions when `water' is replaced by an aqueous sol and `oil' indicates water-immiscible organic liquids. The main roles of a surfactant in emulsion formation are discussed. Steps in the generation of ceramic particles from the SEG process through a variety of experimental options are explained. Relevant examples are described where control of surfactant contents (below and above the working range of critical micelle concentration) in a sol-emulsion can lead to oxide particles of different sizes and shapes. Attempts are made to correlate the products of high-surfactant emulsions with micelles and mesophase structures known to form by surfactant molecules in large concentrations