In-situ Mossbauer and EXAFS investigations of the structural and magnetic properties of bimetallic $Fe-Ni/SiO_2$ and $Fe-Cu/SiO_2$ catalysts

Rao, CNR and Kulkarni, GU and Kannan, KR and Chaturvedi, Sanjay (1992) In-situ Mossbauer and EXAFS investigations of the structural and magnetic properties of bimetallic $Fe-Ni/SiO_2$ and $Fe-Cu/SiO_2$ catalysts. In: Journal of Physical Chemistry, 96 (18). pp. 7379-7385.

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Abstract

In-situ Mossbauer and EXAFS investigations of $Fe-Ni/SiO_2$ catalysts with different Fe/Ni ratios show that the reducibility of both Fe and Ni is greater in the bimetallic catalysts than in the corresponding monometallic catalysts. Reduced bimetallic catalysts show evidence for the formation of FCC or BCC alloy phases that are superparamagnetic or ferromagnetic depending on the composition as well as the heat treatment given to the precursor. In the Ni-rich composition, Fe(25)-Ni(75), a superparamagnetic alloy is formed, while both ferromagnetic and superparamagnetic alloys are formed in the Fe-rich composition, Fe(75)-Ni(25). In the Fe(50)-Ni(50) catalyst, a ferromagnetic alloy, predominantly in the FCC structure, is formed. The presence of Fe in the FCC, and Ni in the BCC structure is indeed noteworthy. In the case of $Fe-Cu/SiO_2$ catalysts, the promotion effect of Cu on the reduction of Fe is marginal and alloy formation is observed mainly in Fe-rich compositions. Alloy formation and the reducibility of Ni in $Cu-Ni/SiO_2$ catalysts increase with increasing Cu content. It therefore appears that in all these bimetallic catalysts, mutual promotion of the reducibility of the transition metals and alloy formation go hand in hand.

Item Type:	Journal Article
Publication:	Journal of Physical Chemistry
Publisher:	ACS
Additional Information:	Copyright of this article belongs to American Chemical Society.
Department/Centre:	Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Date Deposited:	11 Oct 2006
Last Modified:	19 Sep 2010 04:32
URI:	http://eprints.iisc.ac.in/id/eprint/8775

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