The Synthesis of Superparamagnetic Cobalt Nanoparticles Encapsulated in Carbon Through High‐pressure CVD

Abstract

Superparamagnetic nanocomposites of carbon-coated cobalt (Co@C) nanoparticles are synthesized through CVD by the use of cobaltocene and an additional hydrocarbon as the precursor. The nanocomposite is characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy (RS), and superconducting quantum interference device (SQUID) magnetometry. The cobalt nanoparticles exhibit face-centered cubic (fcc) structure and an average size of about 4 nm within a narrow size distribution of 3-5 nm. They are tightly embedded in the carbon matrix in core/shell structures and well protected against oxidation. Magnetic results reveal superparamagnetic behavior with blocking temperature T B $ 140 K and a room temperature saturation magnetization of 79 emu g À1 . We evaluate synthesis parameters such as decomposition temperature, pressure, and ratio of cobalt to carbon in the gaseous precursor and show that they strongly affect the characteristics of the C matrix, the size of cobalt particles, and thus the magnetic properties of the nanocomposite.

Sonochemical synthesis, structural inspection and semiconductor behavior of three new nano sized Cu(II), Co(II) and Ni(II) chelates based on tri‐dentate NOO imine ligand as precursors for metal oxides

“…The data also affirm that the synthesized materials are CuO, Co 3 O 4 and NiO, that all the diffraction peaks agreed with the reported standard data; no characteristic peaks were manifested other than metal oxides. The mean granule size (D) of the particles was predestined from the XRD line broadening measurement plying the Scherrer Equation : where λ is the wavelength (1.5406 Å), β is the full breadth at the half‐ maximum of the CuO, Co 3 O 4 and NiO line and θ is the diffraction angle. Average crystallite size in the domain of 16‐46 nm were predestined for the CuO, Co 3 O 4 and NiO nanoparticles.…”

“…The data also affirm that the synthesized materials are CuO, Co 3 O 4 and NiO, that all the diffraction peaks agreed with the reported standard data; no characteristic peaks were manifested other than metal oxides. The mean granule size (D) of the particles was predestined from the XRD line broadening measurement plying the Scherrer Equation [43][44][45][46][47][48]:…”

Large Scale Synthesis of Superparamagnetic Face-centered Cubic Co/C Nanocapsules by a Facile Hydrothermal Method and their Microwave Absorbing Properties

“…The ratio of I D /I G can represent the quality or crystallinity of the carbon in the nanocomposites. The I D /I G ratio exceeds 1, revealing the amorphous nature of C in the present nanocomposites 14 .…”

“…Furthermore, since C is on the shell of the nanocapsules, it is also difficulty to detect its XRD pattern because of breaking down of the periodic boundary condition (translation symmetry) along radial direction 7 . The inset of Figure 1 shows the Raman spectrum of the products, which can provide more detailed information about the structure of the carbon 14 . It is obviously seen that there are two peaks in the spectrum.…”

High saturation magnetization superparamagnetic Fe/Ni core/shell microparticles for chromium removal

“…Currently, the modied liquid-phase chemical reduction method 4,10 has been used to prepare Fe/Ni composite, but the samples prepared by this method are prone to agglomeration, which limit application development. Because the samples prepared by the chemical vapor deposition (CVD) method have high crystallinity and fewer defects, 13 here we report a CVD method for the synthesis of core/shell Fe/Ni MPs. We use NiO and Fe 3 O 4 particles (based on our earlier work) 5,6,8 as precursors, and the Fe 3 O 4 particles are prepared through a solvothermal reaction.…”