Query: FeCo

title: FeCo Fe2CoO4/Co3O4 nanocomposites: Phase transformations as a result of thermal annealing and practical application in catalysis
abstract: The results of the synthesis and subsequent phase transformations of FeCo nanowires depending on the annealing temperature are presented. An annealing temperature range of 200 800 degC was chosen to initialize the processes of annihilation of point defects at low temperatures, as well as phase transformations as a result of oxidation of nanostructures at high annealing temperatures. In the course of the research, a three stage process of phase transformations was established, accompanied by oxidation of the structure followed by the formation of oxide phases of the spinel type Fe2CoO4 and Co3O4. It was found that at temperatures of 400 degC and 600 degC, the introduction of oxygen occurs nonuniformly along grain boundaries with the subsequent formation of oxide compounds, and in the case of annealing at a temperature of 800 degC, the oxygen distribution in the structure of nanowires becomes uniform, which indicates the complete oxidation of nanowires with isotropic the formation of oxide phases in the entire volume of nanowires. The prospects of using oxide biphasic nanowires for catalytic reduction reactions para nitroaniline para phenyldiamine are shown.

title: Facile synthesis of FeCo layered double oxide/raspberry like carbon microspheres with hierarchical structure for electromagnetic wave absorption.
abstract: Transition metal compositions (Fe, Co and Ni) have always been promising candidates for electromagnetic wave (EMW) absorbers. In this study, the FeCo layered double hydroxide (LDH) supported on raspberry like carbon spheres (RCs) was synthesized by a simple hydrothermal method and the spontaneous electrostatic self assembly process. The surface FeCo LDH is then transformed into FeCo layered double oxide (LDO) with different compositions after calcination treatment (650 degC and 700 degC) forming a typical hierarchical structure. The sample calcined at 700 degC exhibited an ultra wide effective absorption bandwidth (fe) (RL 10 dB) of 7.4 GHz (from 10.6 to 18.0 GHz) at the matched thickness of 2.2 mm. The remarkable EM wave absorption properties are attributed to the strong interface polarization due to the various phase boundaries in LDO shell as well as sufficient heterointerfaces between LDO shell and RCs. It should be emphasized that LDH is rarely used for EMW absorption, and the use of LDH positively charged characteristics to fabricate hierarchical materials is a meaningful attempt and confirms the potential of LDH in EMW absorbing materials.

title: High performance bifunctional oxygen electrocatalysts for zinc air batteries over mesoporous Fe/Co N C nanofibers with embedding FeCo alloy nanoparticles
abstract: Mesoporous Fe/Co N C nanofibers with embedding FeCo nanoparticles (denote as FeCo@MNC) have been prepared from electrospun Fe/Co N coordination compounds with bicomponent polymers consisting of polyvinylpyrrolidone (PVP) and polyacrylonitrile (PAN) The as fabricated hybrid nanofibers exhibited one dimensional mesoporous morphology, a large BET surface area and uniformly distributed active sites (e.g FeCo alloy, Fe/Co N) It elucidated that the co existence of FeCo alloy and Fe/Co N active sites could promote the catalytic activity of ORR and OER simultaneously. Essentially, the unique one dimensional of nanofiber with observable porous morphology has indispensable contribution to charge transportation and exposure of active sites to O2 adsorption when assembled into a rechargeable zinc air battery. As a result, FeCo@MNC exhibited a low discharge charge voltage gap (e.g. 0.9 V, discharge charge at 20 mA cm 2) higher power density (e.g. 115 mW cm 2, at 143 mA cm 2) and stability.

title: Carbon coated FeCo nanoparticles as sensitive magnetic particle imaging tracers with photothermal and magnetothermal properties
abstract: The low magnetic saturation of iron oxide nanoparticles, which are developed primarily as contrast agents for magnetic resonance imaging, limits the sensitivity of their detection using magnetic particle imaging (MPI) Here, we show that FeCo nanoparticles that have a core diameter of 10 nm and bear a graphitic carbon shell decorated with poly(ethylene glycol) provide an MPI signal intensity that is sixfold and fifteenfold higher than the signals from the superparamagnetic iron oxide tracers VivoTrax and Feraheme, respectively, at the same molar concentration of iron. We also show that the nanoparticles have photothermal and magnetothermal properties and can therefore be used for tumour ablation in mice, and that they have high optical absorbance in a broad near infrared region spectral range (wavelength, 700 1,200 nm) making them suitable as tracers for photoacoustic imaging. As sensitive multifunctional and multimodal imaging tracers, carbon coated FeCo nanoparticles may confer advantages in cancer imaging and hyperthermia therapy. FeCo nanoparticles with a graphitic carbon shell decorated with poly(ethylene glycol) have photothermal and magnetothermal properties and are sensitive tracers for magnetic particle imaging, magnetic resonance imaging and photoacoustic imaging.

title: Carbon nanofibers supported by FeCo nanocrystals as difunctional magnetic/dielectric composites with broadband microwave absorption performance
abstract: Lightweight, strong and broadband microwave absorbents are urgently demanded for practical applications. Exploring magnetic/dielectric composites by anchoring magnetic nanostructures on lightweight dielectric carbon is an effective way, due to their possible good impedance matching condition. Herein, one dimensional FeCo/C nanofibers are fabricated by electrospinning method and subsequent anoxic annealing treatment, which are used as difunctional magnetic/dielectric microwave absorbents. The nanofibers have a large aspect ratio, in which tiny magnetic FeCo nanocrystals are uniformly decorated in the amorphous dielectric C nanofibers. Benefiting from good impedance matching condition, enhanced microwave attenuation ability and synergistic effect between ferromagnetic FeCo and dielectric C, the FeCo/C nanofibers exhibit boosting microwave absorption performance, which is related to the absorber thickness and filling ratio. The optimal FeCo/C/paraffin composites with 40 wt% of functional fillers show a minimum reflection loss value of 59.9 dB with broad effective absorption bandwidth of 6.0 GHz at 13.2 GHz when the absorber thickness is only 2.6 mm. The FeCo/C nanofibers have a small density of only about 1.1 g/cm3, much smaller than the bulk FeCo (7.4 7.6 g/cm3) Owing to the characteristics of low density, strong absorption and broad effective absorption bandwidth, the FeCo/C nanofibers are promised to be good candidates as microwave absorbents.

title: Broadband and multilayer core shell FeCo@C@mSiO2 nanoparticles for microwave absorption
abstract: The core shell composite of FeCo alloy coated with amorphous carbon and mesoporous silica (mSiO2 for short) has been successfully fabricated through liquid phase reduction, hydrothermal reaction as well as high temperature calcination, forming nanoparticles around 400 nm in size. The alloy core provides strong magnetic loss and keeps stable under the protection of the shell, while the carbon shell reduces density and promotes dielectric loss. The outer layer of mSiO2 provides a larger specific surface area for multiple reflections, and meanwhile effectively adjusting the impedance matching, resulting in a better absorption. With a thickness of 3.5 mm, the maximum RL of the composite reaches 46.79 dB at 11.84 GHz, and the effective absorption bandwidth with the RL below 10 dB is up to 8.8 GHz (from 9.2 to 18.0 GHz) Hence, FeCo@C@mSiO2 composite is potential to become an excellent candidate in the field of microwave absorption.

title: Core shell FeCo@carbon nanoparticles encapsulated in polydopamine derived carbon nanocages for efficient microwave absorption
abstract: Rational manipulation on chemical composition and microstructure is evolving as a powerful approach to reinforce the electromagnetic (EM) functions of magnetic carbon based composites. With FeCo Prussian blue analogs (FeCo PBAs) as the nucleation sites, we conduct the polymerization of dopamine (DA) on their surface and then convert the precursor into desirable FeCo alloy/carbon composites. PDA coating is greatly helpful to suppress the microstructure collapse of FeCo PBAs during high temperature pyrolysis, resulting in a unique hierarchical configuration of core shell FeCo@C nanoparticles encapsulated in PDA derived carbon nanocages. The formation of carbon nanocages not only adjusts the relative carbon content, but also affects EM properties of these composites. In particular, the dielectric loss can be significantly enhanced, which further accounts for an improvement in overall attenuation ability toward incident EM waves. When the weight ratio of DA to FeCo PBAs reaches 0.75, the obtained composite will exhibit excellent microwave absorption performance thanks to its decent attenuation ability and matched characteristic impedance. The strongest reflection loss intensity is located at 67.8 dB at 15.8 GHz, and the effective bandwidth covers 11.0 16.3 GHz with the thickness of 2.00 mm. The advantages in microstructure are also established by parallel comparison with a disordered counterpart.

title: Implanting FeCo/C nanocages with tunable electromagnetic parameters in anisotropic wood carbon aerogels for efficient microwave absorption
abstract: Adjusting the electromagnetic parameters by decorating magnetic particles for improved impedance matching is an important strategy for obtaining lightweight and efficient carbon based electromagnetic wave absorbing materials. In this work, a tomato like hierarchical porous FeCo/C@WC was prepared for efficient microwave absorption, in which a lightweight anisotropic wood carbon aerogel (WC) was used as a structural assistant, and a MOF derived graphitized carbon coated FeCo alloy (FeCo/C) served as a dielectric/magnetic regulator. The tomato like polystage micro nano construction was made up of a "pericarp" left by the parallel channels of natural wood, a "pulp tissue" of the MOF derived nanocage and "seeds" of FeCo nanoalloys embedded in a nanocage. The macroporous wooden shell and mesoporous carbon nanocage gave the composite an excellent hierarchical dielectric coupling network. Meanwhile, the uniformly dispersed FeCo nanoparticles enhanced the magnetic loss to the carbonaceous substrate, allowing for better impedance matching. As a result, the constructed multidimensional FeCo/C@WC exhibited superior wave absorbing ability, in which the maximum reflection loss (RL) reached 47.6 dB and the wide absorption bandwidth was up to 8.9 GHz. These excellent results confirmed that wood based electromagnetic absorption devices may have a good application prospect.

title: Hollow structure engineering of FeCo alloy nanoparticles electrospun in nitrogen doped carbon enables high performance flexible all solid state zinc air batteries
abstract: Hollow structuring of active components is among the most effective strategies for improving the kinetics of oxygen electrode catalysts, benefiting from the much improved active surface area, enhanced accessible active sites, and formation of the desired defects on the exposed surface. Integration of active hollow nanostructures with functionalized carbon nanofibers synergizes the electrochemical performance and mechanical flexibility, which are particularly of interest for all solid state zinc air batteries (FASS ZABs) In the present work, we demonstrate that the electrospinning of Prussian blue analogs can give rise to hollow FeCo alloy nanoparticles assembled in nitrogen doped carbon nanofibers (h FeCo alloy/N CNFs) The h FeCo alloy/N CNFs thus derived exhibit superior bifunctional activities for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) and impressive performance in rechargeable Zn air batteries. When integrated into a rechargeable FASS ZAB, they exhibit a high open circuit voltage of 1.335 V and a stable discharge charge plateau around 1.1 V to 2.0 V, together with a large voltage efficiency of 63.5% under bending conditions.

title: Hierarchical peony like FeCo NC with conductive network and highly active sites as efficient electrocatalyst for rechargeable Zn air battery
abstract: Carbon materials featuring hierarchical pores and atomically dispersed metal sites are promising catalysts for energy storage and conversion applications. Herein, we developed a facile strategy to construct functional carbon materials with a fluffy peony like structure and dense binary FeCo N x active sites (termed as f FeCo CNT) By regulating the metal content in precursors, a three dimensional (3D) interconnected conductive carbon nanotubes network was in situ formed throughout the atomically dispersed FeCo NC matrix during pyrolysis. Taking advantage of rich pore hierarchy and co existence of highly active FeCo N x sites and beneficial FeCo alloy nanoparticles, the f FeCo CNT material exhibited excellent bifunctional performance towards oxygen reduction reaction/oxygen evolution reactions (ORR/OER) with respect to the atomically dispersed FeCo NC (SA f FeCo NC) and commercial Pt/C+RuO 2 mixture, surpassing the SA f FeCo NC with a 20 mV higher ORR half wave potential and a 100 mV lower OER overpotential (at 10.0 mA/cm 2 Remarkably, the f FeCo CNT assembled Zn air battery (ZAB) possessed a maximum specific power of 195.8 mW/cm 2 excellent rate capability, and very good cycling stability at large current density of 20.0 mA/cm 2 This work provides a facile and feasible synthetic strategy of constructing low cost cathode materials with excellent comprehensive ZAB performance.