Mössbauer Effect Studies of Materials Prepared by Mechanochemical Methods

Campbell, S. J.; Kaczmarek, Wojciech

doi:10.1007/978-1-4899-1763-8_11

Cited by 15 publications

(9 citation statements)

References 197 publications

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“…Other several methods have recently been used to prepare Ferrites in fine particle form, i.e. co-precipitation method and combustion in urea [2], mechanochemical activation [3] and rf plasma aerosol deposition technique [4].…”

Section: Introductionmentioning

confidence: 99%

Mössbauer spectroscopy study of aluminium substituted nickel-ferrites

2008

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Powders of Al substituted Ni-ferrites (NiAl x Fe 2−x O 4 x = 0, 0.5, 1.0 and 1.5) were prepared using the calcination method. Mössbauer spectroscopy results of all samples show two well defined magnetic sextets corresponding to Fe 3+ ions in the A (tetrahedral) and B (octahedral) sites of the spinel structure. In addition, a quadrupole doublet with quadrupole splitting of (∼0.53 mm/s) starts evolving upon Al substitution. This doublet is associated with a new Fe-Al-oxide phase. The X-ray diffraction patterns show, in addition to the original peaks, new peaks evolve and increase in intensity as the Al concentration increases, confirming the evolution of this new phase.

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Section: Introductionmentioning

confidence: 99%

Mössbauer spectroscopy study of aluminium substituted nickel-ferrites

2008

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“…Mössbauer spectrometry is now commonplace for investigations on Fe-containing nanocrystalline materials, and 119 Sn Mössbauer spectrometry has even become important for studies of nanocrystalline Sn in electrode materials for rechargeable batteries [25,26]. So many results have now been reported on 57 Fe Mössbauer spectrometry studies on nanocrystalline materials prepared by mechanical attrition that this subtopic has been the subject of an extensive review by Campbell and Kaczmarek [27]. The present paper serves to review and extend a number of results from our group on Mössbauer spectrometry studies on grain boundaries of nanocrystalline materials prepared by high energy ball milling.…”

Section: Introductionmentioning

confidence: 99%

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2000

Hyperfine Interactions

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Nanocrystalline materials contain many atoms at and near grain boundaries. Sufficient numbers of Mössbauer probe atoms can be situated in grain boundary environments to make a clear contribution to the measured Mössbauer spectrum. Three types of measurements on nanocrystalline materials are reported here, all using Mössbauer spectrometry in conjunction with X-ray diffractometry, transmission electron microscopy, or small angle neutron scattering. By measuring the fraction of atoms contributing to the grain boundary component in a Mössbauer spectrum, and by knowing the grain size of the material, it is possible to deduce the average width of grain boundaries in metallic alloys. It is found that these widths are approximately 0.5 nm for fcc alloys and slightly larger than 1.0 nm for bcc alloys.Chemical segregation to grain boundaries can be measured by Mössbauer spectrometry, especially in conjunction with small angle neutron scattering. Such measurements on Fe-Cu and Fe 3 Si-Nb were used to study how nanocrystalline materials could be stabilized against grain growth by the segregation of Cu and Nb to grain boundaries. The segregation of Cu to grain boundaries did not stabilize the Fe-Cu alloys against grain growth, since the grain boundaries were found to widen and accept more Cu atoms during annealing. The Nb additions to Fe 3 Si did suppress grain growth, perhaps because of the low mobility of Nb atoms, but also perhaps because Nb atoms altered the chemical ordering in the alloy.The internal structure of grain boundaries in nanocrystalline materials prepared by highenergy ball milling is found to be unstable against internal relaxations at low temperatures. The Mössbauer spectra of the nanocrystalline samples showed changes in the hyperfine fields attributable to movements of grain boundary atoms. In conjunction with SANS measurements, the changes in grain boundary structure induced by cryogenic exposure and annealing at low temperature were found to be somewhat different. Both were consistent with a sharper density gradient between the crystalline region and the grain boundary region.

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“…Stirred ball/bead mills, which can be operated under wet or dry conditions, utilize the impact between balls or beads, container wall, agitator shaft and impellers to realize powder size reduction. There are several variables which influence the high-energy milling process, such as selection of milling media, ballto-powder ratio, milling time, temperature of mill and milling speed (Baláž, 2008;Campbell and Kaczmarek, 1996). As expected, better controlled combinations of variables can result in a superior milling effect (Toraman and Katırcıoglu, 2011).…”

Section: Contents Lists Available At Sciencedirectmentioning

confidence: 92%