The Effects of Mechanical Alloying of C 60 with Metals (II): Al and Mg.
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XIN-YU ZHANGa"d, RAFAEL Q. HIDALGOa", RICHARD J. MURPHY', ROBERT S. MARKIEWICZCd AND BILL C. GIESSEN'd aDepartment of Chemistry, bMechanical Engineering Department, cDepartment of Physics, dBarnett Institute of Chemical Analysis and Materials Science, Northeastern University, 360 Huntington Avenue, Boston, MA 02115, USA
ABSTRACT C60 has been subjected to multiple micro-alloying passes by co-rolling together with Al and Mg. Complete amorphization has been found in samples of C60 with Al. However, the structural changes in the C60/Mg combination were more complex. Here, a chemical reaction occurred during which the C60 molecules were apparently broken up into amorphous carbon-like materials, while a Mg-containing oxidation reaction product formed.
INTRODUCTION Interest in the chemical and physical properties of fullerenes has continued to grow, following their synthesis in macroscopic amounts [1] and the reports of superconductivity of doped fullerenes. [2] Much effort has been put into intercalating metals or other species into the C60 lattice, [3,4] while there is also a report on the dispersion of fiillerenes in metals. [5] In a previous study of mechanically alloyed metal-fullerene combinations, [6] (of which the present report is a continuation), we have observed major crystal structural changes in mixed C 6 0 /C 7 0 fullerenes co-rolled with several transition metals and Al in multiple micro-alloying passes.
In
the present work, we have studied phase formation in pure C60 co-rolled with Al and Mg, with a strong focus on the C60-Mg combination. The stability and reactivity of C60 exposed to this processing method were explored.
EXPERIMENTAL METHODS The preparation technique used in this study consisted of cold rolling metal-fullerene sandwich structures, as described in detail in our previous report. [6] This method had been found to be effective in producing metastable alloying effects in metal-metal combinations. [7,8] The fullerenes used were C60 (99.9%) obtained from MER Corp.; 99.9+% metal foils (Al and Mg) were obtained from Alfa/AESAR. Samples were examined at various stages of the multiple rolling process by X-ray diffraction (XRD) on a Siemens D-5000 diffractometer (Cu-Koc radiation) with pole figure attachment.
437 Mat. Res. Soc. Symp. Proc. Vol. 359 01995 Materials Research Society
RESULTS Co.•_ : The XRD pattern of pure C60 before rolling is shown for comparison in Fig. 1 (a). Fig. 1 (b) shows the XRD pattern of C60 co-rolled with Al in six deformation passes. All C6 0 peaks have broadened, indicating progressive grain refinement (see [6]); also, incipient (110) rolling texture formation [6] is evidenced by the enhanced intensity of the (220) reflection at 20 -17.80. Furthermore, a broad background appears, indicating the formation of an amorphous Fig. 1(c) shows its XRD pattern after 8 phase. The sample was cold-rolled further; The peaks due to grain-refined (but still crystalline) C60 have now deformation passes. disappeared; instead, three broad maxima (at 20 -9.5, 19 and 30") are now clea
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