Synthesis of hermetically-sealed graphite-encapsulated metallic cobalt (alloy) core/shell nanostructures

Zhu, Weimo; Ren, Jiawen; Gu, Xiaoxiong; Azmat, Muhammad Usman; Lu, Guanzhong; Wang, Yanqin

doi:10.1016/j.carbon.2010.12.016

Cited by 27 publications

(24 citation statements)

References 44 publications

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“…The D/G ratio decreases significantly, revealing strong graphitization as the decomposition temperature increases. The production of higher content of amorphous carbon as a subsidiary composition at low temperature syntheses has already been reported by Zhu et al The spectra of the samples synthesized at temperatures higher than 700°C show some peaks in the low frequency region (at 226 and 167 cm −1 ) corresponding to the RBM. The appearance of these features confirms the growth of single‐walled carbon nanotubes (SW)CNTs .…”

Section: Resultssupporting

confidence: 61%

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

Jaumann

Ibrahim

Hampel

et al. 2013

Chemical Vapor Deposition

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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.

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Section: Resultssupporting

confidence: 61%

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

Jaumann

Ibrahim

Hampel

et al. 2013

Chemical Vapor Deposition

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“…[ 7 ] The ratio of G/D-band for the FeCo/GC nanoparticles reduced without and with the salt-matrix is 5.03 and 1.93, respectively, which are higher than previous reports. [ 3,7 ] In both Raman spectra, a shoulder near ≈1620 cm −1 can be seen, which is referred as D′-band and accounts for structural disorder. [ 19 ] The impact of the salt-matrix on the formation of the coreshell structure can be clearly perceived through the transmission electron microscopy (TEM) images ( Figure 2 ).…”

Section: Resultssupporting

confidence: 39%

“…The G/D-band ratio for the synthesized FeCo/GC nanoparticles using the CO fl ow rate of 1, 0.5, and 0.2 SLPM are 2.74, 1.93, and 2.61, respectively, presenting higher graphitization degrees than previous reports. [ 3,7 ] The shoulder at ≈1620 cm −1 (the D′-band) accounting for structural disorder is also observed in all Raman spectra. [ 19 ] TEM ( Figure 5 ) was utilized to see the effect of gas fl ow rate on the morphology and shell thickness of the samples.…”

Section: Resultsmentioning

confidence: 90%

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Tuning Carbon Content and Morphology of FeCo/Graphitic Carbon Core–Shell Nanoparticles using a Salt‐Matrix‐Assisted CVD Process

Azizi

Khosla

Mitchell

et al. 2013

Part & Part Syst Charact

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Large‐scale and tunable synthesis of FeCo/graphitic carbon (FeCo/GC) core–shell nanoparticles as a promising material for multipurpose biomedical applications is reported. The high‐quality graphitic structure of the carbon shells is demonstrated through high‐resolution transmission electron microscopy (HRTEM), X‐ray diffraction (XRD), and Raman spectroscopy. A saturation magnetization of 80.2 emu g−1 is reached for the pure FeCo/GC core–shell nanoparticles. A decrease in the saturation magnetization of the samples is observed with an increase in their carbon content with different carbon morphologies evolved in the process. It is also shown how hybrid nanostructures, including mixtures of the FeCo/GC nanoparticles and multi‐walled carbon nanotubes (MWNTs) or carbon nanorods (CNRs), can be obtained only by manipulation of the carbon‐bearing gas flow rate.

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“…The disorder-induced D band is a consequence of carbon atom vibration (A 1g mode) of defective graphite lattice, disordered carbon particles or amorphous carbon [30]. The G band, characteristic of graphite, is attributed to the stretch vibration (E 2g mode) of sp 2 -hybridized carbon atoms in the graphite layer [31,32]. The width of G band is proportional to the extent of disorder in the graphite [33].…”

Section: Graphitization Degreementioning

confidence: 99%

Magnetic properties of carbon coated Fe, Co and Ni nanoparticles

Xia

Yang

2012

Journal of Alloys and Compounds

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Synthesis of hermetically-sealed graphite-encapsulated metallic cobalt (alloy) core/shell nanostructures

Cited by 27 publications

References 44 publications

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

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

Tuning Carbon Content and Morphology of FeCo/Graphitic Carbon Core–Shell Nanoparticles using a Salt‐Matrix‐Assisted CVD Process

Magnetic properties of carbon coated Fe, Co and Ni nanoparticles

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