Abstract

Nanopowdered alloys of Pd100-xFex, with x=4, 6, 8, and 12, have been prepared by ultrasound assisted electrochemistry. The composition of the individual particles, as determined by x-ray fluorescence, and the bulk composition, as determined by atomic absorption, are in agreement within experimental error. Transmission electron microscopy indicates that the nanopowders consist of agglomerates of small grains with a radius of approximately 5 nm, a radius which is confirmed by the broadening of the reflections in the x-ray powder diffraction patterns. X-ray fluorescence analysis of individual grains indicates a homogeneous distribution of palladium and iron throughout the grains. The x-ray diffraction patterns indicate that solid solutions of iron in palladium show no evidence of any pure palladium, any pure iron, or any other PdFe compound. The 78 K iron-57 Mössbauer spectra of these nanopowders reveal the presence of one magnetic sextet assigned to slowly relaxing superparamagnetic particles of Pd100-xFex and one weak doublet, which is assigned to rapidly relaxing superparamagnetic particles of Pd100-xFex. The hyperfine fields of 29.0 to 31.0 T are typical of iron in a metallic alloy and correspond to a magnetic moment of approximately 2µB per iron atom. The hysteresis curves obtained at 4.2, 100, and 295 K with a vibrating sample magnetometer are typical of superparamagnetic particles with saturation magnetization values which are substantially smaller than those observed for the bulk. The fit of the magnetization curves with a Langevin function yields estimates of the particle radii which are in good agreement with those obtained both by transmission electron microscopy and by the broadening of the x-ray diffraction peaks.

Department(s)

Chemistry

Keywords and Phrases

Atomic Absorption; Bulk Compositions; Experimental Errors; Homogeneous Distribution; Hyperfine Field; Hysteresis Curve; Individual Particles; Iron Atoms; Langevin Functions; Magnetic Sextet; Magnetization Curves; Metallic Alloys; Mössbauer; Nano Powders; Particle Radii; Pure Iron; Small Grains; Superparamagnetic Particles; Vibrating Sample Magnetometer; X Ray Fluorescence; X Ray Fluorescence Analysis; Diffraction Patterns; Electrochemistry; Interferometry; Iron; Iron Alloys; Magnetic Moments; Magnetic Properties; Molybdenum; Nanostructured Materials; Saturation Magnetization; Superparamagnetism; Transmission Electron Microscopy; Ultrasonics; X Ray Diffraction; X Ray Powder Diffraction; Palladium

International Standard Serial Number (ISSN)

218979

Document Type

Article - Journal

Document Version

Final Version

File Type

text

Language(s)

English

Rights

© 2002 American Institute of Physics (AIP), All rights reserved.

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Chemistry Commons

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