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Contribution to the study of porous or very finely divided alumina; Contribution a l'etude des alumines poreuses ou tres finement divisees

Abstract

An amorphous porous alumina having a large surface area can be made non-stoichiometric by a treatment at 500 - 700 deg C in a vacuum. The oxygen deficit after a treatment at 500 deg C, and the aluminium deficit after a treatment at 700 deg C, give rise to semiconductor properties successively of type n and of the type p. A crystallized {delta}-alumina in the form of non-porous spherical grains compressed at a pressure of 1 to 5 metric tons/cm{sup 2} is also non-stoichiometric with a deficit of oxygen or of aluminium. None of these phenomena could be observed with a sample which had not been compressed. The favorable influence of oxygen on the recrystallization process of amorphous alumina, and on the {delta}-{alpha}, transformation of crystallized alumina has been demonstrated. Furthermore, the strains produced by the compression of the {delta}-alumina make possible its transformation in air into a at a temperature lower than the temperature necessary to observe this phenomenon with non-compressed {delta}-alumina. Amorphous alumina undergoes an intergranular sintering at 500 deg C and an intergranular sintering at 1 000 deg C. Only the latter occurs in the case of spherical alumina grains. For these, the strains brought about by  More>>
Authors:
Juillet, F [1] 
  1. Commissariat a l'Energie Atomique, Saclay (France). Centre d'Etudes Nucleaires
Publication Date:
Dec 15, 1961
Product Type:
Thesis/Dissertation
Report Number:
CEA-R-2257
Resource Relation:
Other Information: TH: These sciences; 56 refs
Subject:
36 MATERIALS SCIENCE; ALUMINIUM OXIDES; AMORPHOUS STATE; CRYSTAL-PHASE TRANSFORMATIONS; ELECTRIC CONDUCTIVITY; N-TYPE CONDUCTORS; P-TYPE CONDUCTORS; POROUS MATERIALS; PRESSURE DEPENDENCE; SINTERING; SPECIFIC SURFACE AREA; STOICHIOMETRY; TEMPERATURE DEPENDENCE
OSTI ID:
20804951
Research Organizations:
CEA Saclay, 91 - Gif-sur-Yvette (France); Feculte des Sciences de l'Universite de Lyon, 69 (France)
Country of Origin:
France
Language:
French
Other Identifying Numbers:
TRN: FR06R2257107173
Availability:
Available from INIS in electronic form
Submitting Site:
FRN
Size:
56 pages
Announcement Date:
Dec 29, 2006

Citation Formats

Juillet, F. Contribution to the study of porous or very finely divided alumina; Contribution a l'etude des alumines poreuses ou tres finement divisees. France: N. p., 1961. Web.
Juillet, F. Contribution to the study of porous or very finely divided alumina; Contribution a l'etude des alumines poreuses ou tres finement divisees. France.
Juillet, F. 1961. "Contribution to the study of porous or very finely divided alumina; Contribution a l'etude des alumines poreuses ou tres finement divisees." France.
@misc{etde_20804951,
title = {Contribution to the study of porous or very finely divided alumina; Contribution a l'etude des alumines poreuses ou tres finement divisees}
author = {Juillet, F}
abstractNote = {An amorphous porous alumina having a large surface area can be made non-stoichiometric by a treatment at 500 - 700 deg C in a vacuum. The oxygen deficit after a treatment at 500 deg C, and the aluminium deficit after a treatment at 700 deg C, give rise to semiconductor properties successively of type n and of the type p. A crystallized {delta}-alumina in the form of non-porous spherical grains compressed at a pressure of 1 to 5 metric tons/cm{sup 2} is also non-stoichiometric with a deficit of oxygen or of aluminium. None of these phenomena could be observed with a sample which had not been compressed. The favorable influence of oxygen on the recrystallization process of amorphous alumina, and on the {delta}-{alpha}, transformation of crystallized alumina has been demonstrated. Furthermore, the strains produced by the compression of the {delta}-alumina make possible its transformation in air into a at a temperature lower than the temperature necessary to observe this phenomenon with non-compressed {delta}-alumina. Amorphous alumina undergoes an intergranular sintering at 500 deg C and an intergranular sintering at 1 000 deg C. Only the latter occurs in the case of spherical alumina grains. For these, the strains brought about by the compression cause a lowering of 100 deg C in the threshold sintering temperature, with respect to the temperature required to produce the phenomena in a non-compressed sample. The amount of sintering in a crystallized alumina pellet depends, as well, on the rate of rise of temperature. This study tends to show that new properties, or at least unusual solid-state properties, can be observed on disorganised solids or on solids which are crystallized but which have a large surface area and a certain amount of strain. (author) [French] Une alumine poreuse amorphe de grande surface specifique peut etre rendue non-stoechiometrique par traitement sous vide pousse a 500-700 deg C. Le deficit en oxygene apres chauffage a 500 deg C, puis le deficit en aluminium apres traitement a 700 deg C entrainant l'apparition des proprietes de semi-conducteur n puis p. Une alumine cristallisee delta sous forme do grains spheriques non poreux soumise a une compression de 1 a 5 t/cm{sup 2} presente egalement une non-stoechiometrie a deficit d'oxygene ou d'aluminium. Aucun de ces phenomenes n'a pu etre enregistre avec l'echantillon non soumis a la compression. L'influence favorable de l'oxygene dans le processus de recristallisation de l'alumine amorphe et dans la transformation delta-alpha de l'alumine cristallisee a ete mise en evidence, De plus, les contraintes developpees par compression de l'alumine delta permettent sa transformation en phase alpha dans l'air a une temperature inferieure a celle necessaire pour observer le meme phenomene dans l'alumine delta non comprimee. L'afumine amorphe subit un frittage intragranulaire des 500 deg C et un frittage intergranulaire a 1 000 deg C. Seul ce dernier s'observe pour l'alumine en grains spheriques. Pour cette derniere les contraintes developpees par la compression abaissent de 100 deg C le seuil de ce frittage par rapport a la temperature necessaire pour observer ce phenomene avec l'echantillon non comprime. Le taux de frittage d'un comprime d'alumine cristallisee depend, en plus, de la vitesse de la mise en temperature. L'ensemble de cette etude tend a montrer que des proprietes nouvelles, ou du moins inhabituelles de l'etat solide peuvent etre observees s'il est fait appel a des solides desorganises ou encore cristallises mais dotes d'une importante surface specifique et soumis a des contraintes. (auteur)}
place = {France}
year = {1961}
month = {Dec}
}