Dosage de quelques impuretés dans le gallium par activation neutronique

Neutron activation is suggested for the determination of Pt, Au, Hg, Sc, Zn and Sn in high purity gallium. Pt, Hg and Au are reduced to metals, gallium is extracted and then Sc, Zn, and Sn are separated on Dowex 1×8 ion exhanger. All components except Sn are determined by substoichiometric methods in the form of chelate complexes. Sn is extracted with oxine into chloroform, and the chemical yield measured by spectrophotometry.      

Analyse systematique des elements traces dans l'eau de mer par activation neutronique

The trace elements in sea water, particularly the pollutant elements (Cu, Cd, As, Zn, Hg and Cr) are present in very low concentrations (in the order of 10^?9 g/ml). For the determination of the concentration of these elements the neutron activation analysis has been used successfully. The separation of the impurities has been studied using radioactive tracers by coprecipitation with carriers and on ion exchange resins. The preconcentration technics applied before the irradiation introduces too large “blank” values, which can be reduced by etching the containers with HF—EDTA. In order to have representative samples, the water must be quickly frozen after taking out from the sea. With these precautions, the method developed allows to analyse samples of 3 ml volumes. The results of sea water sample analyses from different areas are presented.     

Analyse destructive de traces de rubidium dans des echantillons mineralogiques par radioactivation au moyen de neutrons de 14 MeV

Increasing interest is devoted in geochemistry to the determination of minor elements in rocks and minerals with the best analytical precision. The use of different methods is quite useful to point out and overcome the systematic and specific interferences of the geological matrix. 14 MeV neutron activation analysis can be used for such a purpose as an additional check method. A successful attempt has been made in the determination of rubidium in different geochemical standards. A sensitivity of 100 ppm can be reached with a 5% precision without any interference problem.     

Determination du bore dans le zirconium,par activation au moyen de deutons

The determination of boron in zirconium by activation analysis using the¹⁰B(d, n)¹²C reaction with the chemical separation of¹¹C is described. The method was applied to industrial zirconium samples as zircalloy.

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Collaborateur temporaire de thèse au CEA.     

Le dosage de traces d'argent dans le zinc extra-pur par activation neutronique

Below the p.p.m. level, the determination of silver in zinc by non-destructive γ-spectrometry is no longer feasible due to the activation of the matrix element. The activated zinc is dissolved in nitric acid, sulfamic acid and silver carrier are added, and ^110mAg (253 d) is obtained in a radiochemically pure state after two successive electrolyses on gold cathodes.After two days of irradiation in a thermal neutron flux of the order of 3.10¹³ n/cm²/sec (BR₂-Mol), 30 ng of silver can easily be evaluated with an error of 5%. Data obtained by integral γ-counting or by γ-spectrometry are compared.     

Determination non destructive du profil profond de repartition de traces de fluor. Application a l'email dentaire

A non-destructive method is proposed for the determination of fluorine in dental enamel. The detection of the prompt gamma-rays emitted by bombarding with 3 MeV protons lead to the solution of an equation system giving the average fluorine content in the successive layers of the sample. The mathematical treatment of this system is discussed as well as its improvement and generalization.      

Etude par RMN d'une inversion de cycle de quelques benzodiazépinones

The NMR spectra of five benzodiazepinones are determined over a range of temperature. They indicate that the seven ring has a twist-boat shape, which inverts more or less rapidly according to the nature of substituents. The activation parameters and the rates of inversion are determined and the substituent effects are discussed.     

Determinations de traces dans les semi-conducteurs par activation neutronique

Résumé On décrit la détermination de traces dans le germanium, le silicium et le sélénium. En appliquant des techniques gamma spectrométriques, précédées ou non de séparations chimiques il est possible de doser les éléments suivants dans (1) germanium: As, Cu, Au, Ga, Zn, Hg, Cr, Sn, Sb, Co, In, Ni, Ir, Se, Sc, Ag, Ta, Hf et U; (2) silicium: P, Au, Sb, Ga, Fe, K, Cr, Mo, Sn, As, Co, In, Zn, Cu, W, Ta, Na, Eu, Sm, La, Sc et T1; (3) sélénium: Cl, Br, I, P, S, Te, Na, K, Cr, Fe, Co, Cu, Zn, Ga, Sc, Ag, Cd, La, W, Au et Tl. Les concentrations et ou limites de détections varient de quelques parties par million à 10⁻³ parties par milliard.     

Dosage de traces d'hafnium dans l'aluminium par activation neutronique

Three methods are proposed for the assay of traces of hafnium in aluminium metal by neutron activation analysis. In the first method, the isotope ^179mHf (T = 19 s), produced is counted after anionic resin exchange-separation in sulfuric acid medium. The two other methods, which are non-destructive, are based on the formation of ^180mHf (T = 5,5 h) and ^179mHf (T = 19 s). The latter method comprises an instrumental separation.     

Determination de l’oxygene dans le sodium par activation au moyen de protons

The method described may be used to measure traces of oxygen in sodium, whatever the potassium content is. In addition, if the sample is very pure, a non-destructive analysis is possible. Experience shows that nitrogen or boron can be determined in the same way if one of these elements is predominant with respect to the others.      

Determination des taux de deuteriation de molecules organiques par resonance magnetique nucleaire

The accuracy of several methods for deuterium content determination in organic molecules are tabulated. The sample-substitution (using one or two NMR sample tubes) and internal standard (inter- or intra-molecular) processes are discussed and compared. These methods are applied to some examples and the NMR results are confirmed by mass spectrometry.     

Observations par microscopie électronique de traces d'ions lourds dans le triacétate de cellulose

Tracks of heavy charged particles have been observed in cellulose acetate by conventional electron microscopy (100 kV) and by high voltage microscopy (1, 2 MV). The tracks are formed of successive islets following each other at distances of 70-150 Å. With the evolution of the diameter of these zones is shown the existence of a highly perturbed cylindrical volume (diameter 400 Å for the case of krypton) corresponding to regions in which free radicals have been created. The different techniques used do not allow observation of the latent track because of the complications of energetic phenomena: the electron beam current density being limited, the contrast is small and hence the resolution is restricted.     

Analyse non destructive d'impuretes dans Ag,Al et Co en utilisant l'activation par les protons de 11 MeV

Résumé Nous montrons que l'activation par les protons de 11 MeV permet le dosage non destructif de traces d'impuretés dans des échantillons d'Argent, d'Aluminium et de Cobalt. Nous avons pour le moment étudié le dosage de 30 éléments dans Al et Co et de 24 dans Ag. Nous avons choisi les protons car ces particules sont les seules qui permettent d'effectuer un dosage non destructif dans Ag et Co, au niveau des traces sans interférence, et ceci pour de nombreux éléments. Le cas de l'aluminium a été étudié, bien que les neutrons puissent ici être utilisés pour l'analyse non destructive car l'activation dans les protons permet de doser facilement des éléments autres que ceux dosés en irradiant dans les neutrons. Ces premiers résultats nous conduisent à penser que l'activation dans les protons sera très employée dans les cas où l'activation neutronique est en difficulté (exemple de Ag, Co, Ir, HgTe, AsGa, terres rares, etc.).     

Determination de C,N, O,F et de quelques autres elements par activation au moyen des photons gamma

The (γ, n) activation curves for 17 elements were determined as a function of energy between 25 and 42 MeV. From these are deduced the detection sensitivities intrinsically possible for an average beam intensity of 100 μA. Our experimental results are compared with values calculated byG. J. Lutz. The activation curves relative to certain competitive nuclear reactions on N, O and Na, liable to interfere in the measurements of C, N and F, were also determined. It is shown that the relative importance of these competitive nuclear reactions decreases rapidly for energies below 30 MeV and becomes practically negligible at 25 MeV.      

Etude de la conductivite anionique dans quelques fluorures amorphes obtenus par hypertrempe

Fluoride ion conductivity has been investigated in amorphous materials obtained in the BaF₂-ZnF₂, PbF₂-ZnF₂ and BaF₂-MnF₂ systems using both NMR and complex impedance techniques. The activation energies appear to be about 0.53 eV with a good agreement between both methods. Ionic conductivities have been found to be larger than 10^-5ω^-1cm^-1 at 180°C, values which are among the best ones so far obtained for fluorine conducting glasses.     

Determination de l'enthalpie de formation standard du tetrafluorure de tellure par calorimetrie de combustion dans le fluor et par calorimetrie de reaction

The standard enthalpy of formation of tellurium tetrafluoride has been determined: by combustion in fluorine:

by reaction in a normal solution of soda: