Search Results

You are looking at 61 - 70 of 273 items for :

  • "solid solution" x
  • All content x
Clear All

Abstract  

The applicability of mechanochemistry to produce uranium–lanthanoid mixed oxides is presented. Phase homogeneous uranium–cerium solid solutions of the type CexU1−xO2 (x = 0.3 ÷ 0.95) and polyphase systems containing LayU1−yO2+x (y = 0.12) were prepared by mechanochemical activation in air of sol–gel produced precursors. The possibility for synthesis of urania–lanthania solid solution by mechanochemical interaction of La2O3 with sol–gel produced U (IV,VI) oxide is established. The crystal structures of the obtained oxides before and after the mechanochemical treatment are analysed by the use of X-ray diffraction method. The size of the crystallites (8–16 nm), lattice parameters, crystallite strains and densities of the oxides are calculated by BRASS program for Rietveld calculation.

Restricted access

Abstract  

The binary system Li2CO3–BaCO3 was studied by means of differential thermal analysis (DTA), thermogravimetry (TG) and X-ray phase analysis. The composition of carbonate and CO2 partial pressure influence on the thermal behavior of carbonate were examined. It was shown that lithium carbonate does not form the substitutional solid solution with barium carbonate, however the possible formation of diluted interstitial solid solutions is discussed. Above the melting temperature the mass loss is observed on TG curves. This loss is the result of both decomposition of lithium carbonate and evaporation of lithium in Li2CO3–BaCO3 system. Increase of CO2 concentration in surrounding gas atmosphere leads to slower decomposition of lithium carbonate and to increase the melting point.

Restricted access

Abstract  

We have studied the solid-liquid equilibrium of the system Sr1–yBayFCl1–xBrx using DTA and X-ray diffraction techniques. The entire composition range in this system yields solid solutions which crystallize in the PbFCl (Matlockite) structure type. The melting points of the entire composition range have been parametrized (within 5°C rms error) using a biquadratic fit of the available data obtained by experiment and from the literature.

Restricted access

Abstract  

The thermoluminescense (TL) behavior of solid solutions of cadmium and manganese doped single crystals under γ-irradiation is reported. Various compositions of single crystals of NaCl doped with Cd2+ and Mn2+ have been irradiated with ionizing radiation. The increase in the glow curve was followed as a function of the F-centers produced by the dose. The analysis shows the potential use of these materials as dosimeters.

Restricted access
Journal of Radioanalytical and Nuclear Chemistry
Authors: E. Ligeon, J. Bugeat, R. Danielou, J. Fontenille, and A. Guivarch

Abstract  

The use of nuclear reaction methods for hydrogen or deuterium analysis and its applications to hydrogen profiling and lattice location by channelling experiments is briefly reviewed. The application of these methods to various problems such as the measurement of surface hydrogen and its stability under ion bombardment, the study of solid solutions of hydrogen metal systems obtained by implantation, and the correlation of the amount of hydrogen with the physical properties of some amorphous semiconductors, is described.

Restricted access

A static method is described for measurement of the equilibrium values of temperature, pressure and composition of the solid phase, and determination of the number of degrees of freedom in heterogeneous systems containing a gaseous phase, including water vapour. With this method, it has been found that in the system formed in the thermal dehydration of CaC2O4·H2O a solid solution of monohydrate and anhydride coexists in equilibrium with water vapour. The composition of the solid solution changes with the temperature and the pressure of water vapour. The dehydration enthalpy of the solid solution referred to 1 mol H2O does not depend on its composition. It was found to be ΔH deh=(69+-3) kJ·mol−1.

Restricted access

Abstract  

The residual fluorine in ammonium uranyl tricarbonate (AUC) cannot be removed, while a large part of residual fluorine in ammonium diuranate (ADU) can be removed, when AUC and ADU are decomposed and reduced under dry hydrogen atmosphere. UO2 was prepared by decomposing and reducing AUC and ADU in dry hydrogen atmosphere. The defluorination kinetics of UO2 at 500–700°C in atmosphere of 50% H2-50% H2O was investigated. The results show that the defluorination kinetics supports the Lindman's assertion that the residual fluorine forms a solid-solution in UO2.

Restricted access

The decay of a monosulphide solid solution (mss) with the composition (Fe1−1Nix)0.96S was investigated by means of differential scanning calorimetry in the temperature range, from 20 to 305‡C. Thermal effects of various natures were detected:i)Ordering-disordering in the Fe-Ni sublattice near 100‡C.ii)Pentlandite exsolution (exothermal peak); the peak temperature varies from 180 to 240‡C and depends on the initial composition; the higher the Ni content, the lower the exsolution temperature.iii)Magnetic-paramagnetic transition. The transition temperature decreases down to 220‡C as the Fe∶Ni ratio is decreased from 10∶0 to 4∶6.

Restricted access

Abstract  

The deleterious interaction of some traditional sulphide artists pigments and copper ions results in the formation of black copper sulphides, in particular, covellite (CuS), and, hence, the discolouration of valuable artworks. In this paper the interaction of malachite, a source of copper(II) ions, with the pigment cadmium yellow, a sulphide pigment comprising of a solid solution of cadmium and zinc sulphides, is investigated by XRD and TG-MS. XRD showed the presence of the copper sulphide and cadmium carbonate phases, produced by a simple ion exchange mechanism. TG-MS showed the complexity of the range of metastable phases produced. The identification of these phases, however, requires further work.

Restricted access

Abstract  

The paper presents the kinetic study of the crystallization processes which take place at the obtaining of some glass ceramics, starting from two basalt glasses with different oxide composition. The activation energies have been calculated using Kissinger's equation and verified with the Ozawa's equation. In this order, the DTA curves have been registered with different heating rates, between 4 and 20C min-1. By X-ray diffraction it was established that the crystalline phase formed in the crystallization process represent a pyroxenic solid solution, Ca(Mg,Fe)SiO3.

Restricted access