ABSTRACT
Ferromagnetic FeCo nanocrystals with high coercivity have been synthesized using a reductive decomposition method. The sizes and shapes of the nanocrystals were found to be dependent on reaction parameters such as the surfactant ratio, the precursor concentration and the heating rate. Synthesized nanocrystals have a body-centered cubic crystal structure for both particles and nanowires and the (110) crystalline direction is along the long axis of the nanowires. The coercivity and magnetization of the FeCo nanocrystals are found to be dependent on morphology. Nanowires of Fe60Co40 with saturation magnetization of 92 emu g(-1) and coercive force of 1.2 kOe have been obtained in this study.
ABSTRACT
We report here a novel synthetic method to prepare monodisperse air-stable FeCo nanoparticles with average sizes of 8, 12 and 20 nm. CoFe2O4 nanoparticles of different sizes were first synthesized by a chemical solution method. The as-synthesized CoFe2O4 nanoparticles were then mixed with ball-milled NaCl powders and heated to 400-500 ° C in forming gas (Ar 93%+H2 7%). The salt powder worked as a separating medium that prevents the CoFe2O4 nanoparticles from agglomerating during the heat treatment while the forming gas reduces the CoFe2O4 nanoparticles to FeCo nanoparticles. Monodisperse FeCo nanoparticles were recovered by dissolving the NaCl in water and subsequently washing with ethanol and acetone. Structural analyses confirmed that FeCo nanoparticles retained the same size as their oxide precursors. The size of the FeCo nanoparticles can be well tuned by controlling the size of the CoFe2O4 nanoparticles. The saturation magnetization of FeCo nanoparticles is size dependent and increases with size.
ABSTRACT
Scrolling of niobate nanosheets (NSs) in the presence of magnetic nanoparticle (NP) chains can lead to peapodlike structures. Surface functional groups on both the NSs and NPs are important in directing the assembly and subsequent NS convolution. The dimensions of the peapods are typically dictated by the diameters of the NPs and the length of the NP chains.
Subject(s)
Cobalt/chemistry , Magnetics , Metal Nanoparticles/chemistry , Nanoshells/chemistry , Niobium/chemistry , Particle Size , Surface PropertiesABSTRACT
Fe(x)Pt(y)Au(100-x-y) nanoparticles of size 3.5 nm were prepared by polyol reduction of platinum acetylacetonate and gold acetate and the thermal decomposition of iron pentacarbonyl. The as-synthesized nanoparticles with disordered fcc structure were then heat treated to transform to the L1(0) structure with high magnetocrystalline anisotropy. By tuning the stoichiometry of the Fe(x)Pt(y)Au(100-x-y) nanoparticles, the phase transition temperature was reduced by more than 200 degrees C. After the annealing 500 degrees C, for instance, the highest coercivity of 18 kOe was obtained from the Fe51Pt36Au13 nanoparticles which is substantially higher compared to 2 kOe for Fe51Pt49 nanoparticles annealed at the same temperature. In addition to the high coercivity, the saturation magnetization value obtained from Fe51Pt36Au13 nanoparticles was 47 emu/g which is similar to that for the Fe51Pt49 nanoparticles, indicating that there is no trade-off between the coercivity and the saturation magnetization upon Au doping.
ABSTRACT
Mixed spinel hydrophobic ZnxFe1-xO x Fe2O3 (up to x = 0.34) nanoparticles encapsulated in polymeric micelles exhibited increased T2 relaxivity and sensitivity of detection over clinically used Feridex.
Subject(s)
Contrast Media/chemistry , Ferric Compounds/chemistry , Magnetic Resonance Imaging/methods , Metal Nanoparticles/chemistry , Zinc Compounds/chemistry , Hydrophobic and Hydrophilic InteractionsABSTRACT
FePt nanorods and nanowires have been synthesized by the reduction of Pt(acac)(2) and the thermal decomposition of Fe(CO)(5) in the presence of solvents/surfactants by simply controlling the sequence of addition of surfactants. The as-synthesized FePt nanorods and nanowires have a face centered cubic structure with average diameter of 3 nm. Length of nanorods and nanowires can be adjusted in the range of 15-150 nm by varying reaction parameters. Nanocrystalline L1(0) FePt phase with coercivity up to 24 kOe was obtained after heat treatments.
