Synthesis of high magnetization FeCo alloys prepared by a modified polyol process

High magnetization, soft ferromagnetic FeCo alloy nanoparticles were synthesized at various Fe to Co ratios using a modified polyol process. Transmission electron microscopy images revealed that Fe-rich particles had a cubic shape with a mean particle size of 100 nm, while Co-rich particles had a spherical shape. A maximum saturation magnetization of 212 emu/g was recorded for both Fe60Co40 and Fe75Co25 particles. X-ray diffraction scans at room temperatureof synthesized particles were characteristic of body-centered-cubic single-phase FeCo. Variabletemperature x-ray diffraction scans under N2 gas revealed an order–disorder transition at 600 °C and a transition to a face-centered-cubic crystal structure at 1000 °C

Characterization of oxidation resistant Fe@M (M=Cr, Ni) core@shell nanoparticles prepared by a modified reverse micelle reaction

Iron-based nanoparticles are the forerunners in the field of nanotechnology due to their high magnetizationsaturation and biocompability which affords them use in a variety of applications. However, iron-based nanoparticles, due to a high surface-to-volume ratio, suffer from oxidation and limit its practicality by lowering the magnetic moment significantly. To avoid this oxidation, the surfaces of the particles have to be passivated. One such way to accomplish this passivation is to synthesize core@shell nanoparticles that have a surface treatment of chromium or nickel. These core@shell nanoparticles have been synthesized using a reverse micelle technique. The Cr and Ni passivated ironnanoparticles were characterized by x-ray diffraction, transmission electron microscopy, vibrating sample magnetometry, and x-ray photoelectron spectroscopy to determine their phase, morphology, surface properties, and magnetizationsaturation. A high magnetizationsaturation of 160 and 165 emu/g for Cr and Ni passivated iron core@shell nanoparticles was achieved

High magnetization aqueous ferrofluid: A simple one-pot synthesis

A one-step polyol method was utilized to prepare a stable aqueous iron/iron oxide ferrofluid. The dried powders were characterized by x-ray diffraction, electron microscopy, x-ray absorption spectroscopy, and vibrating sample magnetometry for the determination of phase, morphology, and magnetic properties. To show its potential for imaging applications, the ferrofluid was also investigated as a magnetic resonance imaging contrast agent

Nonclassical crystallization of amorphous iron nanoparticles by radio frequency methods

Amorphousironnanoparticles were synthesized using an aqueous reduction in iron(II) sulfate with sodium borohydride and sodium citrate. Various radio frequency (rf) exposure times were investigated in order to determine trends in nonclassical crystallization. RF times from 15 to 300 s revealed an increase in crystallite size from 5 to 60 nm, as determined by powde rx-ray diffraction. Also, solvent optimization revealed that ethanol produced the largest trends for increasing crystallite size without total oxidation of the samples. Magnetic characterization by room temperature vibrating sample magnetometry and high resolution transmission microscopy was performed to verify magnetic properties and particle morphology

Understanding improved electrochemical properties of NiO-doped NiF2-C composite conversion materials by X-ray absorption spectroscopy and pair distribution function analysis.

The conversion reactions of pure NiF2 and the NiO-doped NiF2-C composite (NiO-NiF2-C) were investigated using X-ray absorption spectroscopy (XAS) and pair distribution function (PDF) analysis. The enhanced electronic conductivity of NiO-NiF2-C is associated with a significant improvement in the reversibility of the conversion reaction compared to pure NiF2. Different evolutions of the size distributions of the Ni nanoparticles formed during discharge were observed. While a bimodal nanoparticle size distribution was maintained for NiO-NiF2-C following the 1st and 2nd discharge, for pure NiF2 only smaller nanoparticles (∼14 Å) remained following the 2nd discharge. We postulate that the solid electrolyte interphase formed upon the 1st discharge at large overpotential retards the growth of metallic Ni leading to formation of smaller Ni particles during the 2nd discharge. In contrast, the NiO doping and the carbon layer covering the NiO-NiF2-C possibly facilitate the conversion process on the surface preserving the reaction kinetics upon the 2nd discharge. Based on the electronic conductivity and surface properties, the resulting size of the Ni nanoparticles is associated with the conversion kinetics and consequently the cyclability

Large-scale synthesis of high moment FeCo nanoparticles using modified polyol synthesis

Binary alloys of Fe and Co have among the highest magnetizations of any transition metal alloy systems, but their affinity to form oxides act to reduce the magnetization of nanoparticles as their size is reduced below ∼30 nm. Here, we demonstrate the synthesis of single phase, size-controlled FeCo nanoparticles having magnetization greater than 200 emu/g via a non-aqueous method in which ethylene glycol served as solvent and reducing agent as well as surfactant. Experiments indicated pure-phase FeCo nanoparticles, having saturationmagnetization up to 221 emu/g for sizes of 20–30 nm, in single batch processes resulting in \u3e 2 g/batch. Post-synthesis oxidation of nanoparticles was investigated until very stable nanoparticles were realized with constant magnetization over time

Annealing of amorphous FexCo100-x nanoparticles synthesized by a modified aqueous reduction using NaBH4

FexCo100−x nanoparticles were synthesized by aqueous reduction in iron (II) sulfate and cobalt (II) sulfate using sodium borohydride and sodium citrate. The initial concentrations of iron and cobalt were varied while maintaining an overall metal concentration of 4.60 mM. Increasing the cobalt content from 0 to 100 at. % decreased the magnetization saturation from 152 to 48 emu/g, as determined by room temperature vibrating sample magnetometry. Annealing the samples at 450 and 600 °C showed an increase in crystallite size. Powder x-ray diffraction and transmission electron microscopy was performed to determine the phases and morphology of the materials

Magnetic properties of Co2C and Co3C nanoparticles and their assemblies

Nano-composite material consisting of Co2C and Co3C nanoparticles has recently been shown to exhibit unusually large coercivities and energy products. Experimental studies that can delineate the properties of individual phases have been undertaken and provide information on how the coercivities and the energy product change with the size and composition of the nanoparticles. The studies indicate that while both phases are magnetic, the Co3C has higher magnetization and coercivity compared to Co2C. Through first principles electronic structure studies using a GGA+U functional, we provide insight on the role of C intercalation on enhancing the magnetic anisotropy of the individual phases

Spectrally tunable magnetic nanoparticles designed for distribution/recollection applications

The comprehensive goal of this research is the synthesis and characterization of nanomaterials that are spectrally tunable in terms of their electromagnetic signal, are robust, magnetic (allowing their piloted movement), and have the potential to be functionalized for the detection of CBRNE threats. Various chemical methods were utilized for synthesis of magnetic (iron) and luminescent rare earth (RE) components, and their mixtures. Effects of integrating an iron core into RE luminescent lattices (excited by UV, emit in the VIS) were investigated. The determination of the optimum balances between magnetic and luminescent components such that the magnetism was maximized while maintaining acceptable fluorescence integrity will be discussed. The emphasis of this work is focused on developing a distributed sensor suitable for use in the terrestrial environment. The robust properties of using a RE luminescent shell would allow the particles to be resistant to photobleaching. Additionally the chemical stability of the RE shell would allow operation in a variety of pH conditions. The magnetic core will ultimately allow the distributed particles to be recollected

Quantifying free-roaming domestic cat predation using animal-borne video cameras

Domestic cats (Felis catus) are efficient and abundant non-native predators. Predation by domestic cats remains a topic of considerable social and scientific debate and warrants attention using improved methods. Predation is likely a function of cat behavior, opportunity to hunt, and local habitat. Previous predation studies relied on homeowner reports of wildlife captures from prey returns to the household and other indirect means. We investigated hunting of wildlife by owned, free-roaming cats in a suburban area of the southeastern USA. Specific research goals included: (1) quantifying the frequency of cat interactions with native wildlife, (2) identifying common prey species of suburban cats, and (3) examining predictors of outdoor behavior. We monitored 55 cats during a 1-year period (November 2010–October 2011) using KittyCam video cameras. Participating cats wore a video camera for 7–10 total days and all outdoor activity was recorded for analysis. We collected an average of 38 h of footage from each project cat. Forty-four percent of free-roaming cats hunted wildlife, of which reptiles, mammals, and invertebrates constituted the majority of prey. Successful hunting cats captured an average of 2.4 prey items during 7 days of roaming, with Carolina anoles (Anolis carolinensis) being the most common prey species. Most wildlife captures (85%) occurred during the warm season (March–November in the southern USA). Twenty-three percent of cat prey items were returned to households; 49% of items were left at the site of capture, and 28% were consumed. Our results suggest that previous studies of pet cat predation on wildlife using owner surveys significantly underestimated capture rates of hunting cats