Regensburg 2022 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 10: Poster Session 1

MM 10.32: Poster

Montag, 5. September 2022, 18:00–20:00, P2

Electrophysical properties of titanium-thermo-expanded graphite composites which can used in low-temperature thermionic converters — •Iryna Galstian, Halyna Mykhailova, Mykola Yakymchuk, Oleksij Tereshchenko, Mykhaylo Rud, Yevgen Tsapko, Olexandr Gerasimov, and Evgen Len — G. V. Kurdyumov Institute for Metal Physics of the N.A.S.U.

Development of nanophysics and nanotechnologies has made it possible to overcome the main disadvantage of thermionic converters - their high operating temperatures. As shown in our work, when using composite materials based on titanium and thermally expanded graphite (TEG), the electron emission onset temperature can be lowered to 500 K. The disclosure of the mechanisms of this effect requires additional studies of this composite material, which is the subject of this work. By resistometric and electron microscopic methods were used to study the change in the structural state and electronic properties of a nanostructured material based on metal and TEG during its vacuum annealing in a furnace and in a solar energy concentrator. By comparing the experimental and theoretical values of electrical conductivity for different densities of the powder material, it is shown that the mixture of hydrogenated Ti + 0.53 wt. % TEG can form a composite, the electrophysical properties of which differ significantly from those for a simple mixture and its pure components. The reason for this is the important role of interfaces between the components of the composite, in particular, the total contact area and their type, the thickness of the oxide layer and deformation of the metal particulars and the amount of adsorbate at the nanocarbon component of the composite, the charge transfer through these interfaces. It was found that a short-term increase of temperature significantly and irreversibly changes the structure of each component of the composite and its electrical conductivity, but in the composition of the composite its components do not show significant irreversible changes during such heating. The result is the stabilization of the composite material electrophysical properties under the action of temperature and solar radiation.