Showing papers on "Sol-gel published in 1983"

Preparation of High‐Silica Glasses from Colloidal Gels: III, Infrared Spectrophotometric Studies

Abstract: The gel process for making silica was studied by infrared spectrophotometry of solid samples in various stages of dehydration. Spectra were recorded in the high-frequency overtone region (2500 to 8000 cm-1) as well as in the region of fundamental absorption (200 to 4000 cm-1), depending on the nature of the sample. Molecular water was distinguished from silanol groups and the effects of hydrogen bonding were observed. Drying and heat treatment of gels at low temperatures ( 800°C). Hydration of siloxane groups on pore surfaces and attachment of water molecules by hydrogen bonding to these surface silanol groups is reversible for heat treatments up to 1025°C. At higher temperatures (>1025°C), active sintering takes place, converting the porous structure into a homogeneous silica network. In this process, surface silanol groups become isolated within the silica network, giving rise to vibrational frequencies characteristic of internal -OH groups. Also, at the higher temperatures silanol groups react to form siloxane groups with loss of H2O. A model is presented for formation of a gel in which hydrogen bonding initiates association of colloidal particles, followed by strengthening through interparticle solid silica precipitation.

Tin Oxide Films On Glass Substrates By A SOL-GEL Technique

Abstract: The novel sol-gel technique has been implemented to deposit electroconductive tin oxide films to be used as transparent electrodes, mainly for display applications. Thin films of antimony-doped tin oxide were deposited on several types of glass substrates (soda-lime-silica, borosilicate and fused silica) using a dip-coating procedure. Alcoholic solutions of tin and antimony organometallic compounds were prepared under controlled conditions. The dipcoating procedure is described° in detail as well as subsequent thermal treatments under controlled atmosphere and temperatures up to 630 C. The optical and electrical characteristics of the films were studied as a function of the process parameters, firing conditions and number of coatings. After the subsequent thermal treatments, 2film resistances of about 200 ohms square could be measured corresponding to resistivities of about 10 ohm cm. The films optical transmission was above 80 percent.© (1983) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Carbon-containing monolithic glasses prepared by a sol-gel process

Abstract: What is disclosed is a method of preparing carbon-containing monolithic glassy ceramics from organosilsesquioxanes, metal oxides and metal alkoxides through pyrolysis of their gels. Also disclosed are certain gel compositions used in the method and the glassy ceramics.