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Contribution to the study of the structure and properties of silica gel (1962); Contribution a l'etude de la structure et des proprietes des gels de silice (1962)

Abstract

The study of the texture of two types of silica gels, xerogels and aerogels, shows that the latter evolve differently on heating. By I.R. spectrography it has been possible to establish that this is due to the existence, in these solids, of a microstructure undetectable by X-rays and which depends on the preparation conditions initially. By using both chemical (thermogravimetry, hydrolysis of diborane) and physical (I.R. spectrography and wide-band N.M.R.) methods we have been able to determine the state of the water of constitution of these gels (water molecules and hydroxyls) and to show that the density, the distribution and the mobility of the protons of this water are very different. For example, the relaxation time T{sub 1} of the protons of a xerogel is about 1 second whilst that of the protons in an aerogel is of the order of a microsecond. Finally, it has been possible by using high resolution N.M.R. to propose a mechanism for the adsorption of formic acid on two types of gel thereby explaining, with the help of previous results, the differences in specificity of these two solids in the decomposition reaction of this acid. (author) [French] L'etude de la texture de deux types  More>>
Authors:
Fraissard, J [1] 
  1. Commissariat a l'Energie Atomique, Saclay (France). Centre d'Etudes Nucleaires
Publication Date:
Apr 15, 1961
Product Type:
Thesis/Dissertation
Report Number:
CEA-R-2129
Resource Relation:
Other Information: TH: These ES sciences physiques; 138 refs
Subject:
36 MATERIALS SCIENCE; ABSORPTION SPECTROSCOPY; ADSORPTION; DECOMPOSITION; DEHYDRATION; FORMIC ACID; HYDROLYSIS; ION EXCHANGE; NUCLEAR MAGNETIC RESONANCE; SILICA GEL; SORPTIVE PROPERTIES; TEXTURE
OSTI ID:
20740248
Research Organizations:
CEA Saclay, 91 - Gif-sur-Yvette (France); Faculte des Sciences de l'Universite de Paris, 75 (France)
Country of Origin:
France
Language:
French
Other Identifying Numbers:
TRN: FR06R2129050064
Availability:
Available from INIS in electronic form
Submitting Site:
FRN
Size:
117 pages
Announcement Date:
Jun 19, 2006

Citation Formats

Fraissard, J. Contribution to the study of the structure and properties of silica gel (1962); Contribution a l'etude de la structure et des proprietes des gels de silice (1962). France: N. p., 1961. Web.
Fraissard, J. Contribution to the study of the structure and properties of silica gel (1962); Contribution a l'etude de la structure et des proprietes des gels de silice (1962). France.
Fraissard, J. 1961. "Contribution to the study of the structure and properties of silica gel (1962); Contribution a l'etude de la structure et des proprietes des gels de silice (1962)." France.
@misc{etde_20740248,
title = {Contribution to the study of the structure and properties of silica gel (1962); Contribution a l'etude de la structure et des proprietes des gels de silice (1962)}
author = {Fraissard, J}
abstractNote = {The study of the texture of two types of silica gels, xerogels and aerogels, shows that the latter evolve differently on heating. By I.R. spectrography it has been possible to establish that this is due to the existence, in these solids, of a microstructure undetectable by X-rays and which depends on the preparation conditions initially. By using both chemical (thermogravimetry, hydrolysis of diborane) and physical (I.R. spectrography and wide-band N.M.R.) methods we have been able to determine the state of the water of constitution of these gels (water molecules and hydroxyls) and to show that the density, the distribution and the mobility of the protons of this water are very different. For example, the relaxation time T{sub 1} of the protons of a xerogel is about 1 second whilst that of the protons in an aerogel is of the order of a microsecond. Finally, it has been possible by using high resolution N.M.R. to propose a mechanism for the adsorption of formic acid on two types of gel thereby explaining, with the help of previous results, the differences in specificity of these two solids in the decomposition reaction of this acid. (author) [French] L'etude de la texture de deux types de gels de silice, les xerogels et les aerogels, montre que ceux-ci evoluent differemment en fonction de la temperature. La spectrographie I.R a permis de preciser que ceci est du a l'existence, dans ces solides, d'une microstructure indecelable aux rayons X, et fonction des conditions initiales de preparation. Par des methodes chimiques (thermogravimetrie, hydrolyse du diborane) et physiques (spectrographie I.R et R.M.N. large bande), nous avons pu determiner l'etat de l'eau de constitution de ces gels (molecules d'eau et hydroxyles) et montrer que la densite, la repartition et la mobilite des protons de cette eau sont tres differentes. Ainsi le temps de relaxation T{sub 1} des protons d'un xerogel est de l'ordre de la seconde, celui des protons d'un aerogel de l'ordre de la microseconde. Enfin, la R.M.N. haute resolution, nous a permis de donner un schema d'adsorption de l'aside formique sur ces deux types de gels, expliquant ainsi, a l'aide des resultats precedents, la difference de specificite de ces deux solides dans la reaction de decomposition de cet acide. (auteur)}
place = {France}
year = {1961}
month = {Apr}
}