The knowledge of the thermal conductivity variation as a function of temperature for the hydrogen storage materials is fundamental in the planning and development of the storage tank and its heating system. Really, the thermal conductivity of the solid material is an important parameter to evaluate how long it will take to get the materials to an equilibrium temperature at which they will begin releasing hydrogen. Anyway, up to now, very few data are available in literature. Moreover, the thermal conductivity strongly varies as a function of the physical form of the material (loose powders, pellets with different density): also this factor is to be taken into account in the design of the tank. In this work, the thermal conductivity dependence by temperature of loose powders and pellets is measured for a wide range of metallic and complex hydrides and for some reactive hydride composites from room temperature up to 200 °C by modified transient plane source method. In particular, binary metallic hydrides, alanates and borohydrides are considered. The measurements are performed under Ar atmosphere in a glove box to avoid powder oxidation – reaction during heating. The values for the pellets result higher than those for the loose powders. A linear trend is evident for all the explored materials. Physical transitions as polimorphic transphormations or melting are evident in the thermal conductivity vs temperature graphs since the straight line corresponding to the room temperature stable phase changes into a plateau followed by a line with different slope, corresponding to the new stable physical form. The temperature of the phase transformations are in very good agreement with the values reported in literature an/or obtained by us through differential scanning calorimetry.

Thermal conductivity as a function of temperature for the most common metallic and complex hydrides

MILANESE, CHIARA;MARINI, AMEDEO
2012-01-01

Abstract

The knowledge of the thermal conductivity variation as a function of temperature for the hydrogen storage materials is fundamental in the planning and development of the storage tank and its heating system. Really, the thermal conductivity of the solid material is an important parameter to evaluate how long it will take to get the materials to an equilibrium temperature at which they will begin releasing hydrogen. Anyway, up to now, very few data are available in literature. Moreover, the thermal conductivity strongly varies as a function of the physical form of the material (loose powders, pellets with different density): also this factor is to be taken into account in the design of the tank. In this work, the thermal conductivity dependence by temperature of loose powders and pellets is measured for a wide range of metallic and complex hydrides and for some reactive hydride composites from room temperature up to 200 °C by modified transient plane source method. In particular, binary metallic hydrides, alanates and borohydrides are considered. The measurements are performed under Ar atmosphere in a glove box to avoid powder oxidation – reaction during heating. The values for the pellets result higher than those for the loose powders. A linear trend is evident for all the explored materials. Physical transitions as polimorphic transphormations or melting are evident in the thermal conductivity vs temperature graphs since the straight line corresponding to the room temperature stable phase changes into a plateau followed by a line with different slope, corresponding to the new stable physical form. The temperature of the phase transformations are in very good agreement with the values reported in literature an/or obtained by us through differential scanning calorimetry.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11571/570247
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