Synthesis of nanostructured metal (Fe, Al)-C 60 composites
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Synthesis of nanostructured metal (Fe, Al)-C60 composites I. I. Santana García1, V. Garibay Febles2, H.A. Calderon1 1
ESFM, Instituto Politécnico Nacional, Edif. 9 UPALM D.F. 07738, México
2
LMEUAR, Instituto Mexicano del Petróleo, México D.F. 07730, México
ABSTRACT Composites of M-2.5 mol. % Fullerene C60 composites (where M= Fe or Al) are prepared by mechanical milling and Spark Plasma Sintering (SPS). The SPS technique has been used to consolidate the resulting powders and preserve the massive nanostructure. Results of X-Ray Diffraction and Raman Spectroscopy show that larger milling balls (9.6 mm in diameter) produce transformation of the fullerene phase during mechanical milling. Alternatively smaller milling balls (4.9 mm in diameter) allow retention of the fullerene phase. SEM shows homogeneous powders with different particle sizes depending on milling times. Sintering produces nanostructured composite materials with different reinforcing phases including C60 fullerenes, diamonds and metal carbides. The presence of each phase depends characteristically on the energy input during milling. Transmission Electron Microscopy (TEM) and Raman Spectroscopy show evidence of the spatial distribution and nature of phases. Diamonds and carbides can be identified for the sintered Fe containing composites with a relatively high volume fraction. INTRODUCTION Fullerene phases are of great interest due to their diversity and attractive mechanical and physical properties. Since their discovery, a great deal of attention has been given to their characterization and potential application. A fullerene composite comprises a dispersion of ultrafine particles of fullerene incorporated in a matrix, representing a new class of technologically relevant composites. Recently, the development of fullerene-reinforced composite materials inside a metallic matrix is directed towards the improvement of mechanical properties [1-4]. Mechanical alloying is a very popular method to fabricate materials with novel structures and/or properties. It can be used to produce non equilibrium structures, supersaturated solid solutions, metastable crystalline phases and nanocrystalline materials [5]. Massive nanostructured materials are possible because the process involves repeated deformation, fracture and welding of powder particles. Milling of powders involves a considerable number of impacts, resulting in solid state alloying with a controlled nanostructure [6-7]. In the present case, the selected processing can also promote phase transformations of the involved components so that harder disperse phases can be developed with a corresponding improvement in the mechanical properties of the resulting product. Additionally and to preserve the massive nanostructure developed during milling, a special sintering methods is required. The Spark Plasma Sintering (SPS) technique offers a relatively faster processing that produces a uniformly dense material with very limited grain growth. It makes use of temperature, applied pressures and an electric pulse cur
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