Thermophysical and Magnetic Properties of Carbon Beads Containing Cobalt Nanocrystallites |
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Authors: | M Izydorzak A Skumiel M Leonowicz M Kaczmarek-Klinowska A D Pomogailo G I Dzhardimalieva |
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Affiliation: | (1) Faculty of Materials Science and Engineering, Warsaw University of Technology, Woloska, 141, 02-507 Warsaw, Poland;(2) Institute of Problems of Chemical Physics, 142432 Chernogolovka, Moscow Region, Russia |
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Abstract: | Magnetic Co-beads were fabricated in the course of a three-step procedure comprising preparation of a metal–acrylamide complex,
followed by frontal polymerization and finally pyrolysis of the polymer. The composites obtained were composed of cobalt nanocrystallites
stabilized in a carbon matrix built of disordered graphite. The crystallite size, material morphology, fraction of the magnetic
component, and thus the magnetic properties can be tailored by a proper choice of the processing variables. The samples were
subjected to an alternating magnetic field of different strengths (H = 0 to 5 kA · m−1) at a frequency of f = 500 kHz. From the calorimetric measurements, we concluded that the relaxation processes dominate in the heat generation
mechanism for the beads pyrolyzed at 773 K. For the beads pyrolyzed at 1073 K, significant values of magnetic properties,
such as the coercive force and remanence give substantial contribution to the energy losses for hysteresis. The specific absorption
coefficient (SAR) related to the cobalt mass unit for the 1073 K pyrolyzed beads (SAR = 1340 W ·g-1 cobalt){({\it SAR} = 1340 \, \, {\rm W} \cdot {\rm g}^{-1 }_{\rm cobalt})} is in very good conformity with the results obtained by other authors. The effective density power loss, caused by eddy currents,
can be neglected for heating processes applied in magnetic hyperthermia. The Co-beads can potentially be applied for hyperthermia
treatment. |
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