Dresden 2014 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 30: Topical Session: Thermodynamics at the nano scale III - Novel experimental and theoretical approaches
MM 30.4: Vortrag
Dienstag, 1. April 2014, 16:30–16:45, BAR 205
Low temperature specific heat of pure titanium made nanocrystalline by severe plastic deformation — •Martin Peterlechner1, Jochen Fiebig2, and Gerhard Wilde1 — 1Institute of materials physics, WWU Münster, Germany — 2Department of Chemical Engineering and Materials Science, UC Davis, USA
In the last decades it was shown that severe plastic deformation can be used to obtain bulk nanostructured materials. In the present work, pure titanium was processed by equal channel angular pressing and subsequently annealed to obtain fairly dislocation free bulk nanostructured samples. The arising structures were analyzed using electron microscopy. Specific heat measurements using the two-tau method were conducted in the temperature range between 1.9 and 300 K, to obtain data sets of nanocrystalline titanium and its coarse grained counterpart. Using the Debye model for the lattice-vibrational contribution to the low temperature specific heat (<5K), and using the Sommerfeld model for the contribution of the electrons to the specific heat a function g*T+a*T^3 was fitted to obtain the Sommerfeld coefficient g and the Debye temperature. It is concluded, that in nanocrystalline titanium the contribution of electrons to the specific heat is increased due to the high number of grain boundaries. There is an indication that the Debye temperature slightly decreases and, moreover, the total enthalpy of the nanocrystalline phase increases. Based on the results thermodynamic properties of grain boundaries are deduced, and the limits of the applied models are discussed.