Thermodynamic stability of nanocrystalline palladium
- Georg-August Univ. Goettingen (Germany). Inst. fuer Metallphysik
- GKSS-Forschungszentrum Geesthacht GmbH (Germany). Inst. fuer Werkstofforschung
- Univ. des Saarlandes, Saarbruecken (Germany). Inst. fuer Werkstoffwissenschaften
The physical properties of nanostructured materials are determined by the extremely high density of grain or interface boundaries. Therefore, nanocrystalline materials can be viewed as novel type of solids in which defects such as grain and interface boundaries represent up to 50% of the volume. With respect to technological application of these materials, it is important to determine their thermodynamic and kinetic stability. From the thermodynamic point of view the atomically disordered grain boundaries influence the configurational and vibrational entropy as well as the enthalpy of the system. A possible thermodynamic stabilization of the grain boundaries by their high vibrational and configurational entropy in nanocrystalline materials can best be evaluated by EMF measurements at elevated temperatures. In this letter the authors focus on the question whether an unrelaxed grain boundary structure exhibits a lower Gibbs energy state with respect to the relaxed grain boundary. For these investigations nanocrystalline Pd was chosen because of its high purity and its unambiguous electrochemical behavior with respect to the electrolyte used for the experiments. The samples were prepared by an inert gas condensation technique and subsequent compaction of the nanocrystalline particles at low temperatures. Thereby unrelaxed grain boundary structures were formed. Besides the investigation of the thermodynamic stability of the nanocrystalline materials, these samples allow also to monitor the relaxation behavior of the grain boundary structure by the EMF measurements during an annealing treatment.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 382479
- Journal Information:
- Scripta Materialia, Journal Name: Scripta Materialia Journal Issue: 7 Vol. 35; ISSN XZ503X
- Country of Publication:
- United States
- Language:
- English
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