52 research outputs found
Temperature dependence on the mass susceptibility and mass magnetization of superparamagnetic MnāZnāferrite nanoparticles as contrast agents for magnetic imaging of oil and gas reservoirs
The mass susceptibility (Ļmass) and mass magnetization (Mmass) were determined for a series of ternary manganese and zinc ferrite nanoparticles (MnāZn ferrite NPs, MnxZn1āxFe2O4) with different Mn:Zn ratios (0.08 ā¤ x ā¤ 4.67), prepared by the thermal decomposition reaction of the appropriate metal acetylacetonate complexes, and for the binary homologs (MxFe3āxO4, where M = Mn or Zn). Alteration of the Mn:Zn ratio in MnāZn ferrite NPs does not significantly affect the particle size. At room temperature and low applied field strength the mass susceptibility increases sharply as the Mn:Zn ratio increases, but above a ratio of 0.4 further increase in the amount of manganese results in the mass susceptibility decreasing slightly, reaching a plateau above Mn:Zn ā 2. The compositional dependence of the mass magnetization shows less of a variation at room temperature and high applied fields. The temperature dependence of the mass magnetization of MnāZn ferrite NPs is significantly less for Mn-rich compositions making them more suitable for downhole imaging at higher temperatures (>100 Ā°C). For non-shale reservoirs, replacement of nMag by Mn-rich MnāZn ferrites will allow for significant signal-to-noise enhancement of 6.5Ć over NP magnetite
Magnetism and phase transformation of Cu-Fe composite oxides prepared by the sol-gel route
Magnetism and phase transformation of Cu-Fe composite oxides prepared by the sol-gel rout
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