scispace - formally typeset
Search or ask a question
Journal ArticleDOI

Preparative Aspects of Sol-derived Oxide Glass Coatings

01 Jan 1983-Transactions of The Indian Ceramic Society (Indian Ceramic Society)-Vol. 42, Iss: 2, pp 44-47
TL;DR: In this paper, thin, transparent coatings of amorphous Si02 and Al203 were deposited on soda lime glass substrates by the dip technique, using organometallic precursor sols.
Abstract: Thin, transparent coatings of amorphous Si02 and Al203 were deposited on soda lime glass substrates by the dip technique, using organometallic precursor sols. The water content of the sol was found to influence its wetting behaviour, low values of H20: Si(OC2H6), being preferred for Si02 and high values of H20: AI(OC, H9B)3 for Al20a coatings of sufficient uniformity and clarity. Expulsion of volatiles and polycondensation of the coated material were allowed to take place via (i) an initial baking step at 90°-l00°C and (ii) a final heating step at 350°-500°C according to the sol composition. The procedure yielded homogeneous, highly transparent coatings, showing 84-93 transmission of the visible runge of wavelengths. © 1983 Taylor and Francis Group, LLC.
Citations
More filters
Journal ArticleDOI
TL;DR: In this article, the thicknesses of the liquid films deposited by the dip-coating method were calculated from those of the heat treated coatings and related to the withdrawal speed and to the properties of the solutions by means of the theoretical equations and the empirical approaches described in the literature.
Abstract: Silica coatings on glass slides were prepared from solutions of the same concentration, but with different H 2 O/TEOS ratios. The thicknesses of the liquid films deposited by the dip-coating method were calculated from those of the heat treated coatings and related to the withdrawal speed and to the properties of the solutions by means of the theoretical equations and the empirical approaches described in the literature. A modified empirical method was derived to fit the experimental thicknesses of heat treated layers. It was shown that the H 2 O/TEOS ratio scarcely affect the flow behavior of the solutions and differences in thickness arise from their different viscosities. Films deposited in a higher alcohol content environment exhibited smaller thickness values.

77 citations

Journal ArticleDOI
TL;DR: In this article, the authors showed that the rate of evolution of the volatiles from the gel-forming compositions could play a vital role in determining the nature of the product.
Abstract: It has recently been shown by Ganguli and Kundu [1] that amorphous and transparent coatings of pure ZrO 2 could be prepared by controlled hydrolysis of zirconium propoxide and subsequent polymerization by using a non-polar solvent like cyclohexane instead of the usual alcoholic solvents employed for preparing coatings and monoliths [2-7] The non-polar, hydrophobic solvent was used to avoid precipitation caused by the high rate of hydrolysis of Zr(OC3H7)4 The present work is a continuation of the above study, leading to the preparation of pure, transparent and amorphous zirconia gels (including monoliths), using zirconium propoxide and cyclohexane It was observed during this work that the rate of evolution of the volatiles from the gel-forming compositions could play a vital role in determining the nature of the product This has also been systematically examined Technical grade zirconium n-propoxide (Fluka) and Analar grade cyclohexane (BDH) were used for preparing the zirconia gels The cyclohexane was thoroughly dried before use by repeated contact under stirring with activated silica gel and molecular sieve 4A Solutions of the propoxide in cyclohexane (in the range 4 to 10 equivalent wt % ZrO2) were prepared in

42 citations

Journal ArticleDOI
TL;DR: Conditions de preparation and proprietes de transmission optique des revetements transparents et amorphes de ZrO 2 des substrats de verres sodocalciques as discussed by the authors.
Abstract: Conditions de preparation et proprietes de transmission optique des revetements transparents et amorphes de ZrO 2 des substrats de verres sodocalciques

35 citations

Journal ArticleDOI
TL;DR: In this article, the most dramatic improvements in unfired coating quality were obtained by adding titanium alkoxide to the sol. This improvement is explained in terms of a sol/substrate charging mechanism.
Abstract: In this study several types of coating sol to substrate wetting behaviors were observed. These wetting behaviors, which influence final coating quality, are a complicated function of sol and substrate chemistry. Coating quality could be altered considerably by the choice of substrate, sol additives, or sol ageing. The most dramatic improvements in unfired coating quality were obtained by additions of titanium alkoxide to the sol. This improvement is explained in terms of a sol/substrate charging mechanism.

2 citations

References
More filters
Journal ArticleDOI
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.
Abstract: Silicate gels were prepared under a range of conditions in which the rate of hydrolysis was varied from fast to slow with respect to the rate of condensation. When hydrolysis was fast, larger, more highly condensed polymers were formed during gelation. Conversely, for slow hydrolysis, smaller, less highly condensed polymers were formed. These gels dried to low density coarse textured and high density fine textured gels, respectively. High temperatures, (>800°C) were required to densify the coarse gels by viscous sintering. Lower temperatures were sufficient to densify fine gels by a process which was postulated to consist of polymer relaxation followed by condensation and pore collapse.

645 citations

Journal ArticleDOI
Bulent E. Yoldas1
TL;DR: In this paper, the authors discuss the requirements for a porous transparent Al2O3 from aluminium alkoxides to retain its integrity during drying and pyrolysis, and show that there is a critical electrolyte concentration at which the gelling volume goes through a pronounced minimum.
Abstract: Formation of a porous transparent Al2O3 from aluminium alkoxides has been previously reported. During the process, alkoxides are hydrolyzed and the resultant hydroxide is peptized to a clear sol. The sol then must be gelled and pyrolyzed to 500° C to obtain the aluminium oxide. This paper discusses the gel state and the requirements for the system to retain its integrity during the drying and pyrolysis. Influence of electrolytes on the sol-gel transformation shows that there is a critical electrolyte concentration at which the gelling volume goes through a pronounced minimum. Deviation in either direction of this electrolyte concentration causes a sharp increase in the relative gelling volume and detrimentally effects the capability of the gel to retain its integrity. The sols that gel at concentrations less than ∼4 g equivalent oxide per 100 ml do not retain their integrity during pyrolysis.

534 citations

Journal ArticleDOI
TL;DR: In this article, the authors investigated the sol-gel transition of Si(OC 2 H 5 ) 4 by measuring the volume, the density, the SiO 2 content, the viscosity and the specific and intrinsic viscosities of the solution.
Abstract: The sol-gel transition of Si(OC 2 H 5 ) 4 was investigated by measuring the volume, the density, the SiO 2 content, the viscosity and the specific and intrinsic viscosities of the solution. The transition behavior of Si(OC 2 H 5 ) 4 solutions with different amounts of water and different catalysts was compared. The measurements indicated that solutions with a small water content were comprised of linear polymer when catalyzed by HCl. Fibers could be easily drawn from such solutions immediately before gelation. Solutions catalyzed by HCl and containing a large amount of water behaved similarly to solutions catalyzed by NH 4 OH, suggesting that a high water content causes the formation of non-linear or network colloidal polymers in hydrolysis-polycondensation. Such solutions did not exhibit spinnability but gelled into elastic bulk masses which were easily converted to bulk glasses.

360 citations

Journal ArticleDOI
TL;DR: In this paper, the technique of preparing oxide glasses from metal alcoholates through hydrolysis, gelling and heating at low temperatures has been reviewed, which makes it possible to produce very high purity and compositions which the conventional melting technique could not give because of immiscibility, crystallization and high melting temperatures.
Abstract: Developments in the technique of preparing oxide glasses from metal alcoholates through hydrolysis, gelling and heating at low temperatures have been reviewed. This technique makes it possible to produce (1) glasses of very high purity and (2) glasses of compositions which the conventional melting technique could not give because of immiscibility, crystallization and high melting temperatures. This technique can provide glasses having various shapes such as fibers, thin coating films, isolated films and bulk glasses. Discussion was made on the microscopic processes leading to fibers and bulk glasses.

321 citations

Journal ArticleDOI
TL;DR: In this paper, the optical and physical properties of various single films and multilayer systems are described and their history, the dip-coating procedure and especially the chemical processes are described.

229 citations