Millikelvin magnetic relaxation measurements of alpha-Fe2O3 antiferromagnetic particles

In this paper we report magnetic relaxation data for antiferromagnetic alpha-Fe2O3 particles of 5 nm mean diameter in the temperature range 0.1 K to 25 K. The average spin value of these particles S=124 and the uniaxial anisotropy constant D=1.6x10^-2 K have been estimated from the experimental values of the blocking temperature and anisotropy field. The observed plateau in the magnetic viscosity from 3 K down to 100 mK agrees with the occurrence of spin tunneling from the ground state Sz = S. However, the scaling M vs Tln(nu t) is broken below 5 K, suggesting the occurrence of tunneling from excited states below this temperature.Comment: 4 pages (two columns), 4 figure

Thermodynamic assessment of the Ca–Pb system

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Thermodynamic assessment on the Pb–Ca–Sn ternary system

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Pb-based composites materials for grids of acid battery

International audienceNewlead-based materials that should use as acid battery electrodes were synthesised by metallurgy powder. The effect of experimental conditions as well as temperature, applied stress, grain size and volume fraction of ceramic additive on the sintering process has been characterized. The higher densification rate, i.e. about 98% of the theoretical value, was reached when 0.5 vol.% of titanium dioxide was added to lead powder. It clearly appeared that the best mechanical properties were reached when the sintered materials were elaborated. The hardness value (about 14 HV) of Pb/0.5 vol.%TiO2 composite slightly fluctuated for long time of treatment at room temperature. From compression tests performed at lower stress (1.4MPa), the creep rate, measured in stationary conditions, of sintered lead was lower of two order of magnitude with regards to that of as-cast lead. The electrochemical corrosion of sintered materials in simulated overcharge conditions was achieved from weight loss measurements and i = f(t) curves. By pumping the electrolyte solution, the residual open porosity of sintered materials led to a severe intergranular corrosion and, consequently, to the grain scaling off

On the Bi2O3-Al2O3-PbO system

39th Edition of the Joint European Days on Equilibrium between Phases (JEEP), Nancy, FRANCE, MAR 19-21, 2013International audienceThe present work is dedicated to the description of the pseudo - binary Al 2 O 3 - Bi 2 O 3 and the isothermal section at 600°C of the system Al 2 O 3 - Bi 2 O 3 - PbO according to a Calphad approach. It takes part of the complete description of the complex system Pb - Bi - Fe - (Al,Cr) - O. Such study is of hig h interest for the nuclear community that aims to develop protective coatings for the MEGAPIE s pa l lation t arget to prevent the T91 steel from corrosion due to contact with lead - bismuth eutectic liquid

The Pb-Ca-Sn system : experimental investigations for x(Ca)≤0.25 composition and thermodynamic modelling

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Experimental study and modelling of Pb-Bi-Hg system

As a first step, an experimental study of the Pb-Bi-Hg system was performed from calorimetric, XRD and EPMA measurements. Results indicated the presence of a ternary intermetallic compound i.e. Pb$_{\rm 0.549\pm\Delta x}$B$_{\rm 0.307\pm\Delta y}$ Hg$_{\rm 0.144\pm\Delta z}$ with a narrow homogeneity domain. This phase decomposes peritectically above 45$^{\circ}$C. In a second step, all the experimental phase diagram data collected during the present study in the ternary system and the thermodynamic quantities (enthalpies of mixing and activities) given in the literature mainly for binary borders were taken into account in a thermodynamic modelling which used the CALPHAD (CALculation PHAse Diagram) approach. It appeared that two peritectic invariants exist at 37 and 82$^{\circ}$C. Otherwise, the calculation of the isopleth section x(Pb)/x(Bi) = 0.45/0.55 versus mercury content which is especially interesting for nuclear applications, suggested the rapid decrease of liquidus temperature even with minor mercury additions (inferior to 1 wt.%)

Thermodynamic description of the Cr–Nb–Si isothermal section at 1473K

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Thermodynamic description of the Cr–Nb–Si isothermal section at 1473 K

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