Relation entre la morphologie des précurseurs et la microstructure de la céramique WO3 frittée

Relationship between the morphology of precursors and the microstructure of sintered WO₃ ceramics. The aim of this study is to perfect an elaboration process of ceramic WO₃, to control the main parameters, to understand the nature and the role of the precursors and to establish a relationship between the morphology of the powder and the microstructure of the final ceramic. © 2000 Académie des sciences / Éditions scientifiques et médicales Elsevier SASpowder / granulometric / microstructure / precursors / sintering / ceramics     

Propriétés de transport de membranes échangeuses d'anions en présence d'ions organiques. Partie I. Influence de la longueur de la chaı̂ne aliphatique

Transport properties of anion exchange membranes in contact with organic ions. Part I. Influence of the length of the aliphatic chain. The physico-chemical properties of an anion-exchange membrane (AMV, Asahi Glass) were studied in aqueous solutions containing both a mineral salt (NaCl) and an organic salt at the same concentration (10^–1 M). The organic salt was a sodium carboxylate with an aliphatic chain varying from C₁ to C₈. Measurements of ion exchange, water content, electric resistance, self-diffusion and electrodiffusion fluxes were performed. Changes in the membrane parameters were related to the increase in the hydrophobic character of the organic ion.     

Microdosage colorimétrique de la cystéïne et de la cystine

Thiofluorescein is bleached in alkaline medium by light but reforms its colour on reaction with —SH groups. This can be used for the colorimetric determination of cystine and cysteine in the micromolar range.     

Microanalyse fonctionnelle organique basée sur la détermination des constantes physiques. Identification des acides aminés

Résumé Le présent travail, tout en s'inscrivant comme contribution aux microdéterminations des constantes physiques des corps organiques, est en même temps une contribution à la microanalyse fonctionnelle organique, en ce sens qu'il préconise l'emploi de deux constantes physiques: la température de fusion eutectique et l'indice de réfraction pour identifier les acides aminés.Toutes les déterminations se font en une minute et sur un cristal. Cette méthode est extensible à d'autres classes de composés et susceptible de rendre de grands services dans le contrôle industriel et biochimique.La méthode préconisée ici pour l'identification des corps organiques concurrence avantageusement celle de préparation des dérivés des substances organiques et permettrait en outre d'accélérer les déductions de l'analyse qualitative organique classique, basées sur les différences, de solubilité (méthode deStaudinger, Kamm, Shriner, etc.). Ces nouvelles techniques se prêtent aussi à une extension quantitative.

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Summary This study, though entitled as a contribution to the microdetermination of the physical constants of organic compounds, is at the same time a contribution to functional organic microanalysis, in the sense that it involves the use of two physical constants: the eutectic fusion temperature and the index of refraction for identifying amino acids.All the determinations can be made in one minute and on only one crystal. This method may be extended to other classes of compounds and is capable of rendering great service in industrial and biochemical control.The method given here for the identification of organic compounds competes advantageously with that of preparing derivatives of organic materials and furthermore it permits speeding up the deductions of classical qualitative organic analysis based on the differences in solubility (method ofStaudinger, Kamm, Shriner, etc.). Quantitative developments are being studied.

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Zusammenfassung Die vorliegende Arbeit ist sowohl ein Beitrag zur Mikrobestimmung physikalischer Konstanten organischer Stoffe, wie gleichzeitig auch ein Beitrag zur funktionellen organischen Mikroanalyse. Es wird vorgeschlagen, die Bestimmung zweier physikalischer Konstanten, nämlich der eutektischen Temperatur und des Brechungsindex zur Identifizierung von Aminosäuren zu verwenden.Diese Bestimmungen sind in einer Minute an nur einem Kristall ausführbar. Die Methode ist auch auf andere Arten von Verbindungen übertragbar und geeignet, bei der Untersuchung technischer und biochemischer Produkte gute Dienste zu leisten.Die vorgeschlagene Methode ist vorteilhafter als die Identifizierung organischer Stoffe über den Weg der Herstellung von Derivaten. Außerdem läßt sich mit ihrer Hilfe die Ausführung des klassischen organischen Analysenganges nach dem Prinzip der Löslichkeitsunterschiede (Staudinger, Kamm, Shriner u. a.) beschleunigen. Die quantitative Auswertung der angegebenen Verfahren ist in Aussicht genommen.

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Ce travail a été subsidié par leFonds national de la recherche scientifique de Belgique.     

Etude structurale par RMN 29Si—V. Dérivés de la quinoléine et de l'isoquinoléine

A series of silylated compounds obtained from quinoline or isoquinoline were studied by ²⁹Si NMR using the selective polarization transfer (SPT). Both silicon chemical shifts and ²⁹Si, ¹H coupling constants have been measured. These results are the first example of coupling through siliconnitrogen bonds.     

Analyse de la réduction passive de la traînée laminaire

A theoretical multi-layer model is used to describe the influence of wall perturbations on the boundary layer flow. The originality and interest of the method lies in the use of non-regular second-order asymptotic expansions arising from the presence of two longitudinal length scales. From the lower deck canonical problem, the influence of wall perturbations on laminar drag reduction is inferred.     

Simulation numérique déterministe de la turbulence

We first present techniques of large-eddy simulation (LES) in physical und Fourier spaces. We show how LES allows vortex control in mixing layers, and good prediction of velocity statistics in a turbulent channel. We study also in a developed boundary layer the dynamics of high- and low-speed streaks at the wall, and the associated pressure fluctuations. Following this, we show in rotating shear flows a universal behaviour ol the mean velocity in regions whosw local Rossby number is sirictly inferior to — 1. Finally, we present for LES of compressible flows a formalism based on Favre averages.     

Sur la réaction colorimétrique de l'aluminium avec la quinalizarine

The reaction between aluminium and quinalizarin has been studied, and some modifications have been made to the analytical procedure usually followed.The absorption curve of the Al-quinalizarin compound and that of quinalizarin alone have been drawn. We applied the continuous variations method in order to determine the structure and composition of the reaction product. The spectrophotometric readings have shown that the constituents of the coloured compound are bound in a definite ratio. 2:3.     

Détermination de la dissipation caractéristique dans la propagation d'un front de recristallisation

We study the displacement of the boundary between the two grains of an ideal two-dimensional bicrystal having a hexagonal lattice within the plane. The boundary we deal with is a discontinuity straight line for the lattice orientation function that may move at a different velocity from the underlying matter; hence dissipation occurs, eventually equal to the rate of released energy. We estimate the characteristic dissipation in the propagation of the discontinuity.     

Emploi de la thermogravimétrie et de la spectrophotométrie infrarouge pour suivre les réactions à l'état solide

Résumé L'auteur indique sur des exemples variés comment on peut combiner les indications de la thermobalance et du spectromètre infrarouge pour suivre les réactions à l'état solide, qu'il se dégage ou non un produit gazeux: action de la strontiane sur les pyrophosphates, polymérisation spontanée des métaborates, adsorption du permanganate par le sulfate de baryum, combinaison supposée SiO₂ + 12 MoO₃, action de l'iode sur la magnésie. Ensuite, il étudie plus longuement la synthèse des chromites et la mise en solution par l'oxylithe des oxydes métalliques; cette dernière réaction s'effectue suivant quatre mécanismes différents illustrés par des exemples concrets.

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Summary The writer shows by means of varied examples how the information furnished by the thermobalance may be combined with that derived from the infra red spectrometer in following solid state reactions, which may or may not produce gaseous products. Examples are: action of strontium oxide on the pyrophosphates, spontaneous polymerization of metaborates, adsorption of permanganate by barium sulfate, alleged compound SiO₂ + 12 MoO₃, action of iodine on magnesia. The investigation also included a lengthy study of the synthesis of chromites and the solution of metal oxides by sodium peroxide. The latter reaction, effected by four different mechanisms, is illustrated by concrete examples.

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Zusammenfassung An Hand verschiedener Beispiele wird gezeigt, wie man mit Hilfe der Thermowaage und des IR-Spektrophotometers Festkörperreaktionen mit oder ohne Gasentwicklung verfolgen kann. Als solche Beispiele werden angeführt: die Einwirkung von Strontiumoxyd auf Pyrophosphat, die Spontanpolymerisation von Metaboraten, die Absorption von Permanganat durch Bariunisulfat, die Bildung des Gemisches SiO₂ + 12 MoO₃ durch Erhitzen von Oxin-Silicomolybdat, Einwirkung von Jod auf Magnesiumoxydhydrat. Weiters wird die Synthese von Chromiten und die Auflösung von Metalloxyden mit Natriumperoxyd ausfuhrlich erörtert. Der letztgenannte Vorgang verläuft nach vier verschiedenen Reaktionsmechanismen, die an konkreten Beispielen erklärt werden.

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Conférence prononcée le 25 avril 1961, au Congrès de chimie analytique de Budapest.     

Phénomènes Transitoires et Influence de la Nature du Substrat dans la Déformation de la Surface Libre d'un Liquide Isolant Chargé

Abstract

On étudie l'établissement du régime final dans l'évolution électrohydrodynamique d'un liquide isolant soumis à un flux de charges dans le cas d'un substrat conducteur et dans le cas d'un substrat plus ou moins isolant; le cas d'un substrat ferroélectrique est envisagé plus particulièrement. Dans le cas d'un substrat isolant on étudie des mouvements latéraux du liquide. On montre que l'analyse de la déformation du liquide permet des études de substrats.

The establishment of the final behaviour is studied concerning the electrohydrodynamical evolution of an insulating liquid submitted to a flux of charges, for a conducting and for an insulating substrate of variable resistivity. In the case of an insulating substrate, lateral movements of the liquid are studied. One shows that analysis of the deformation of the liquid allows studies of substrates.     

Etude,par thermogravimétrie et spectrographie d'absorption infrarouge,de quelques sulfates doubles de la série magnésienne. I. Courbes de thermolyse

Résumé L'auteur étudie le comportement thermique des sulfates doubles du type M₂M(SO₄)₂ · 6 H₂O, avec M=K et NH₄ et M=Ni, Co, Mg, Zn et Fe.

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Summary A study was made of the thermal behavior of double sulfates of the type M₂M(SO₄)₂ · 6 H₂O where M=K or NH₄ and M=Ni, Co, Mg, Zn, Fe.

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Zusammenfassung Das thermische Verhalten der Doppelsulfate vom Typus M₂M(SO₄)₂ · 6 H₂O wurde untersucht. In dieser Formel steht M für K oder NH₄, M für Ni, Co, Mg, Zn oder Fe.

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En l'honneur du Prof.A. A. Benedetti-Pichler, respectueusement.     

Applications analytiques de la phénothiazine

Spot tests carried out with the help of phenothiazine as reagent permit the detection of silver on a drop plate or on paper. D = 10^-5 or even 6.7.IO^-6 with a little less certainty. The reactions obtained are described in detail in the case of palladium, gold and platinum. Use of the reagent allows the detection of iron in presence of uranium (0.15γ iron in 0.053 ml in the presence of 107 times its weight of uranium). It also enables mercury to be detected in the presence of silver, even in the case of silver which is practically free from mercury. Finally, by the combined use of phenothiazine and diphcnylcarbazide it is possible to detect 0.54γ of silver in the presence of 100 times its weight of mercury.     

Dosage colorimétrique précis de la silice applications

A method is described for the colorimetric determination of silica as silicomolybdate. Conditions have been established for determining major amounts of silica with an accuracy of about 0.5%.The method has been applied to the analysis of compounds rich in silica and for the determination of silica in compounds containing fluorine.     

Un réactif spécifique du germanium: la phénylfluorone

Based on the action of methyl fluorone on Ge(IV) the use of this reagent for the detection of germanium is described. It is necessary to treat with 6N HCl to make this reaction specific.However, another derivative of fluorone, namely phenyl fluorone, is still better for identifying Ge(IV). By placing a drop of the solution under test, previously strongly acidified (3 N to 6N in HCl), on a phenyl fluorone reagent paper and adding 2 or 3 drops of 6 N HNO₃, a. sensitive and specific reaction for germanium is obtained.The only interfering ions are those of strong oxidising agents (Ce⁺⁴, Cr⁺⁶, Mn⁺⁷, etc.) which destroy the reagents and must be eliminated in the first place.Other ions and ions of the group of the sulphides soluble in alkalisulfides do not interfere, even in the proportion of 100 parts by weight, to 1 of Ge. The limit of dilution is about 10^-5.5.     

Decontamination chimique. II. Oxydation de composés soufrés en milieu micellaire: rôle de la lipophilie des substrats

Chemical decontamination of toxic compounds (warfare agents and pesticides) is of increasing importance. Oxidation of sulphur-containing model toxic agents in micellar media (in water or binary systems) was investigated through the relationship between the reactivity/ selectivity and the lipophilicity (log P)) of the model.Two substrates with lipophilicities close to that of mustard seem to be the best suited for miming the degradation of the toxin. The micellar medium composed of cetylpyridinium chloride and of the binary system water/ formamide (1:1; vol/vol) gave the best results: quantitative yield with over 90 % of the product in the form of sulphoxide.     

Étude de la compatibilité d'un système polyamide/phase caoutchoutique modifiée par l'anhydride maléique—I. Étude de la modification de la phase caoutchoutique par l'anhydride maléique

The study deals with the variation of physical properties of a blend (50/50 polyethylene/terpolymer ethylene-propylene-diene monomer) due to chemical modification by maleic anhydride. This compound is generally used as a rubbery domain in polyamide resins. The chemical modification induces cross-linking the amount of which is clearly revealed by the variation of the elastic modulus and the residual deformation of the samples. The crystallization ratio of the polyethylene, measured by differential scanning calorimetry, is also related to the chemical modification. This effect may be due to an increase in the miscibility of the two constituents of the blend.