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Faculty of Management Sciences

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Author: search.filters.author.Bharuth-Ram, Krish

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    Mössbauer spectroscopy analysis of valence state of iron in historical documents obtained from the National Library of South Africa
    (Elsevier, 2014-07-09) Dzinavatonga, Kaitano; Bharuth-Ram, Krish; Medupe, Thebe R.
    Documents of historical and cultural value are under constant risk of deterioration by acid hydrolysis and catalytic oxidation. The assessment of this risk of degradation is necessary in order to prepare for the conservation and preservation of such documents. The risk of oxidative degradation of four histor-ical documents obtained from the National Library of South Africa and one sample from the Timbuktu manuscripts was assessed by determining the valence states of Fe in the samples using Mössbauer Spec-troscopy (MS). The pH levels of the samples were also determined using the Abbey pH pen. It was found that all the samples were acidic, indicating that acid hydrolysis is occurring in all samples. One sample (Wildsport of Africa) had both Fe2+ (21%) and Fe3+ (79%); all the other samples had only Fe3+. The detec-tion Fe2+ in the Wildsport of Africa sample shows that oxidative degradation is also occurring in this document. The results also show for the first time ever that MS can be used to determine the valence state of trace amount of iron in paper.
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    Mössbauer spectroscopy study of surfactant sputtering induced Fesilicide formation on a Si surface
    (Elsevier, 2015) Beckmann, C.; Zhang, Kun; Hofsäss, Hans; Brüsewitz, C.; Vetter, U.; Bharuth-Ram, Krish
    The formation of Fe silicides in surface ripple patterns, generated by erosion of a Si surface with keV Ar and Xe ions and simultaneous co-deposition of Fe, was investigated with conversion electron Mössbauer spectroscopy, atomic force microscopy and Rutherford backscattering spectrometry. For the dot and rip-ple patterns studied, we find an average Fe concentration in the irradiated layer between 6 and 25 at.%. The Mössbauer spectra clearly show evidence of the formation of Fe disilicides with Fe content close to 33 at.%, but very little evidence of the formation of metallic Fe particles. The results support the process of ion-induced phase separation toward an amorphous Fe disilicide phase as pattern generation mecha-nism. The observed amorphous phase is in agreement with thermodynamic calculations of amorphous Fe silicides.
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    Characterization of Fe states in dilute 57 Mn implanted SnO 2 film
    (Springer Link, 2014-04) Gunnlaugsson, H.P.; Nomura, K.; Mølholt, Torben Esmann; Shayestehaminzadeh, S.; Johnston, K.; Mantovan, R.; Masenda, H.; Ncube, M.; Bharuth-Ram, Krish; Gislason, H.; Langouche, G.; Naidoo, D.; Ólafsson, S.; Weyer, G.
    States of dilute Fe in SnO2 have been monitored using 57Fe emission Mössbauer spectroscopy following implantation of 57Mn (T 1/2 = 85.4 s) in the temperature range from 143 K to 711 K. A sharp annealing stage is observed at ~330 K where the Fe3 + /Fe2 +  ratio shows a marked increase. It is suggested that this annealing stage is due to the dissociation of Mn-VO pairs during the lifetime of 57Mn; the activation energy for this dissociation is estimated to be 0.9(1) eV. Fe3 +  is found in a paramagnetic state showing spin-lattice relaxation rates consistent with an expected T 2 dependence derived for a Raman process. In addition, a sharp lined doublet in the Mössbauer spectra is interpreted as due to recoil produced interstitial Fe.