Ostwald ripening of rod-shaped α-Fe particles in a Cu matrix

The coarsening behavior of rod-shaped α-Fe particles in Cu–1.0 wt.% Fe and Cu–1.0 wt.% Fe–1.2 wt.% Sb alloys during aging at 700 °C has been studied by transmission electron microscopy and electric resistivity. The kinetics of the decay of supersaturation with aging time t for both alloys coincide with the t−1/3 law. The coarsening kinetics of the cylindrical radius of the Fe particles obey the t1/3 law. Using the Lifshitz–Slyozov–Wagner theory modified for the case of rod-shaped particles by Speich and Oriani, the maximum value of the Cu/α-Fe interfacial energy γ and the volume diffusivity D of Fe in Cu for the Cu−Fe alloy are independently derived to be 1.3 J/m2 and 3.9×10−16 m2/s. Adding Sb to the Cu−Fe alloy decreases the values of γ and D

Quantitative two-dimensional strain mapping of small core-shell FePt@Fe3O4 nanoparticles

We report a facile one-pot chemical synthesis of colloidal FePt@Fe3O4 core–shell nanoparticles (NPs) with an average diameter of 8.7 ± 0.4 nm and determine their compositional morphology, microstructure, two-dimensional strain, and magnetic hysteresis. Using various state-of-the-art analytical transmission electron microscopy (TEM) characterization techniques—including high resolution TEM imaging, TEM tomography, scanning TEM-high angle annular dark field imaging, and scanning TEM-energy dispersive x-ray spectroscopy elemental mapping—we gain a comprehensive understanding of the chemical and physical properties of FePt@Fe3O4 NPs. Additional analysis using x-ray photoelectron spectroscopy, x-ray diffraction, and superconducting quantum interference device magnetometry distinguishes the oxide phase and determines the magnetic properties. The geometric phase analysis method is effective in revealing interfacial strain at the core–shell interface. This is of fundamental interest for strain engineering of nanoparticles for desirable applications

Rapid Millifluidic Synthesis of Stable High Magnetic Moment FexCy Nanoparticles for Hyperthermia

A millifluidic reactor with a 0.76 mm internal diameter was utilized for the synthesis of monodisperse, high magnetic moment, iron carbide (FexCy) nanoparticles by thermal decomposition of iron pentacarbonyl (Fe(CO)5) in 1-octadecene in the presence of oleylamine at 22 min nominal residence time. The effect of reaction conditions (temperature and pressure) on the size, morphology, crystal structure, and magnetic properties of the nanoparticles was investigated. The system developed facilitated the thermal decomposition of precursor at reaction conditions (up to 265 °C and 4 bar) that cannot be easily achieved in conventional batch reactors. The degree of carbidization was enhanced by operating at elevated temperature and pressure. The nanoparticles synthesized in the flow reactor had size 9–18 nm and demonstrated high saturation magnetization (up to 164 emu/gFe). They further showed good stability against oxidation after 2 months of exposure in air, retaining good saturation magnetization values with a change of no more than 10% of the initial value. The heating ability of the nanoparticles in an alternating magnetic field was comparable with other ferrites reported in the literature, having intrinsic loss power values up to 1.52 nHm2 kg–1

Effects of Preparation Methods and Electronic States of the AuPd Bimetallic Nanoparticles on the Activity for Aerobic Oxidation of Alcohols

Correlations between nanostructure of AuPd active sites synthesized with different preparation methods and their catalytic activities for the oxidation of alcohols were investigated. The catalytic activity strongly depend on the morphology and Au/Pd molar ratio of the AuPd active site, these were attributed by the differences in preparation methods. The Au_Pd_-PVP/HT catalyst prepared with a simultaneous reduction method exhibited the highest activity for aerobic oxidation of alcohol; ex. TON = 395,700, TOF = 207,000 h^ for 1-phenylethanol oxidation.Characterizations with TEM, XPS, XAFS and other analytical techniques suggested that the highly active Au_Pd_-PVP/HT catalyst possessed uniform AuPd nanoalloys and the largest amount of electrons in Au 5d states. These results proposed that formation of the uniform AuPd nanoalloys allowed a big electron transfer from Pd to Au atoms, and which played an important factor for the significant activity of the Au_Pd_-PVP/HT