Magnetocaloric Effect and Magnetostriction in a Ni<Subscript>49.3</Subscript>Mn<Subscript>40.4</Subscript>In<Subscript>10.3</Subscript> Heusler Alloy in AC Magnetic Fields

The magnetocaloric effect (MCE) and the magnetostriction in the Ni_49.3Mn_40.4In_10.3 Heusler alloy have been measured in ac magnetic fields to 8 T. It is shown that the contributions of the magnetic and structural subsystems to MCE have opposite signs; in this case, the contribution of the magnetic subsystem is dominant. The anomalous temperature dependence of the magnetostriction during the magnetostructural phase transition (PT) is explained by competition of the processes of growing austenite phase nuclei and the striction processes in them.     

Magnetocaloric Effect in Alloy Fe49Rh51 in Pulsed Magnetic Fields up to 50 T

Physics of the Solid State - Magnetocaloric effect (MCE) in pulsed magnetic fields up to 50 T was directly studied in alloy Fe49Rh51. An inverse MCE ΔT ≈ –8 K is observed at...     

Magnetocaloric and Shape Memory Effects in the Mn2NiGa Heusler Alloy

Physics of the Solid State - The results of investigation of functional characteristics of the Mn2NiGa Heusler alloy prepared by argon-arc melting are presented. Its electric resistance,...     

Magnetic,thermal, and electrical properties of an Ni<Subscript>45.37</Subscript>Mn<Subscript>40.91</Subscript>In<Subscript>13.72</Subscript> Heusler alloy

The magnetization, the electrical resistivity, the specific heat, the thermal conductivity, and the thermal diffusion of a polycrystalline Heusler alloy Ni_45.37Mn_40.91In_13.72 sample are studied. Anomalies, which are related to the coexistence of martensite and austenite phases and the change in their ratio induced by a magnetic field and temperature, are revealed and interpreted. The behavior of the properties of the alloy near Curie temperature T_C also demonstrates signs of a structural transition, which suggests that the detected transition is a first-order magnetostructural phase transition. The nontrivial behavior of specific heat detected near the martensite transformation temperatures is partly related to a change in the electron density of states near the Fermi level. The peculiar peak of phonon thermal conductivity near the martensitic transformation is interpreted as a consequence of the appearance of additional soft phonon modes, which contribute to the specific heat and the thermal conductivity.     

Direct measurement of magnetocaloric effect in metamagnetic Ni43Mn37.9In12.1Co7 Heusler Alloy

The magnetocaloric effect in the metamagnetic Ni₄₃Mn_37.9In_12.1Co₇ Heusler alloy is directly studied experimentally under the adiabatic and quasi-isothermal conditions in a magnetic field with induction of up to 14 T.     

In Situ TEM Study of Phase Transformations in Nonstoichiometric Ni46Mn41In13 Heusler Alloy

Physics of the Solid State - This paper presents a study of the metamagnetostructural transition of the martensitic type in the Ni46Mn41In13 alloy with magnetic shape memory and inverse...     

Degradation of the Magnetocaloric Effect in Ni49.3Mn40.4In10.3 in a Cyclic Magnetic Field

Physics of the Solid State - The direct measurements of the magnetocaloric effect ΔTad in the Heusler alloy Ni49.3Mn40.4In10.3 have been carried out in cyclic magnetic fields with amplitudes...     

Stoichiometry of uranyl hydrolysis reaction in acidic aqueous solutions from the evidence of oxygen exchange kinetics

The kinetics of uranyl oxygen exchange with water molecules in aqueous solutions was studied in the pH range 1–4 and uranium concentration range 10^–4–0.1 M. It was confirmed that the exchange is stimulated by hydrolyzed uranyl species. From the evidence of data on the kinetics of uranyl oxygen exchange the reaction stoichiometry of uranyl hydrolysis was determined. The scheme of uranyl hydrolysis involving formation of (UO₂)₂(OH)₂²⁺, (UO₂)₂(OH)₃⁺, and other hydrolyzed species was proposed. To cite this article: L.G. Mashirov et al., C. R. Chimie 336 (2004).

Résumé

Étude de l'hydrolyse de l'uranium hexavalent en milieu acide par échange isotopique de l'oxygène. L'échange isotopique de l'oxygène de l'ion uranyle avec les molécules d'eau a été étudié dans le domaine de pH de 1 à 4 et de concentration en uranium de 10^–4 à 0,1 M. Cet échange a lieu par l'intermédiaire d'espèces hydrolysées de U(VI). La stoechiométrie des formes hydrolysées de U(VI) est déduite des vitesses d'échange isotopique. En particulier, les espèces (UO₂)₂(OH)₂²⁺ et (UO₂)₂(OH)₃⁺ ont été clairement identifiées. Un schéma d'hydrolyse est proposé. Pour citer cet article : L.G. Mashirov et al., C. R. Chimie 336 (2004).