| Four types of cement mortars without and with a small amount of magnetic nanoparticles of fcc-nickel and a-iron encapsulated in carbon were prepared. The samples were investigated by the ferromagnetic resonance (FMR) and compressive strength methods. The FMR spectra of the following samples were recorded: cement mortar in powder form, cement mortar powder/nanoparticles and cement mortar powder/nanoparticles/water. No difference was observed in the FMR spectra in the two former types. Samples containing magnetic nanoparticles showed a wide and intense almost symmetrical FMR line, while a sample with additional water molecules displayed an essentially lower intensity spectrum. A compressive strength study of samples with and without carbon encapsulated nickel nanoparticles showed an increase of over 15% for the former sample while an opposite effect was observed for concrete with a-iron nanoparticles. The presence and interaction of magnetic nanoparticles embedded in non-magnetic materials could significantly change some of their physical properties. A possible explanation for the obtained results is discussed. The role of the size of nanoparticles agglomerates in enhancing the mechanical properties of cement mortars is emphasized. |
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