| Conglomerates formed out of aggregated nanodiamond particles have been successfully covered with magnetic Co-containing nanoparticles by means of thermal destruction of metal-containing compounds in a hot mixture of mineral oil and detonation nanodiamonds. The samples produced were studied using TEM, XRD, and element analysis. The average sizes of the cobalt-containing particles are 5-7 nm. Magnetic studies of Co-containing samples have been performed. In order to detect if metallic cobalt phase really existed in the material, we used "NMR-in-magnetic" technique also known as the "spin-echo" method. The main peak of NMR spectra at ca. 227 MHz can be ascribed to the hcp form of metallic cobalt and confirms unambiguously the presence of metallic core in the nanoparticles. There is no clear evidence of signals which may correspond to the fcc metallic cobalt phase. The room temperature magnetization curves demonstrate high magnetization and large coercivity of the material confirming presence of metallic Co nanoparticles. |
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