Regensburg 2004 – wissenschaftliches Programm
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MA: Magnetismus
MA 6: Magnetische Partikel / Cluster
MA 6.10: Vortrag
Montag, 8. März 2004, 17:30–17:45, H10
Equation of State of Fe3C nanoparticles — •E. Duman, M. Acet, T. Hülser, and E.F. Wasserman — Experimentalphysik, AG Farle, Universität Duisburg-Essen
Fe3C, which incorporates only Fe as a metallic element with valence electron concentration e/a = 8, is an Invar material [1]. The p electrons of the interstitial carbon atoms hybridize with the d-band of the metal, so that the electron concentration per Fe atom becomes 8.67 for Fe3C, which fits into the Invar composition range. We have measured the pressure dependence up to 30 GPa of the lattice parameters of Fe3C nanoparticles (∼ 40 nm) at room temperature and at 550 K using energy dispersive X-ray diffraction. The pressure-volume data was analysed with the third order Birch-Murnaghan equation and the isothermal bulk modulus of both samples were obtained at room temperature and 550 K. The bulk modulus of Fe3C nanoparticles at room temperature (Bo=201 GPa) was found to be approximately %14 smaller than that of the value at 550 K (Bo= 235 GPa). This difference is comparable with the relative difference in the bulk modulus of Fe65Ni35 Invar in a similar temperature range [2]. No pressure or temperature induced phase transition was observed. Supported by DFG (SFB 445) [1]W. Pepperhof, M. Acet, Constitution and Magnetism of Iron and its Alloys, Springer- Verlag, Berlin-Heidelberg, 2001 [2]Philippe Renaud, Ph. D Thesis, Universite de Lausanne, Faculte des Sciences, 1988