Microstructure of Carbon Encapsulated Superparamagnetic Co Nanoparticles

2001 ◽  
Vol 704 ◽  
Author(s):  
Xiang-Cheng Sun ◽  
J. Reyes-Gasga ◽  
X. L. Dong
Keyword(s):  
Electron Microscopy ◽  
Arc Discharge ◽  
Stacking Faults ◽  
Good Evidence ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Lattice Images ◽  
Co Nanoparticles ◽  
Discharge Method

AbstractCarbon encapsulated magnetic Co nanoparticles have been synthesized by modified arc-discharge method. Both high-resolution transmission electron microscopy (HREM) and powder x-ray diffraction (XRD) profiles reveal the presence of 8-15nm diameter crystallites coated with 1-3 carbon layers. Specially, HREM images indicate that the intimate and contiguous carbon fringe around those Co nanoparticles is good evidence for complete encapsulation by carbon shell layers. The encapsulated phases are identified as hcp (α)-Co, fcc (β)-Co and cobalt carbide (Co3C) nanocrystals by using x-ray diffraction, electron diffraction and energy dispersive x-ray analysis. However, some fcc (β)-Co particles with a significant fraction of stacking faults are observed by HREM and confirmed by means of numerical Fourier transform (FFT) of HREM lattice images. In particular, the carbon encapsulation formation and growth mechanism are also reviewed.

Synthesis of troilite by the arc-discharge method

2000 ◽  
Vol 64 (1) ◽  
pp. 143-147
Author(s):  
Chen Daizhang ◽  
Yang Xiang
Keyword(s):  
Electron Microscopy ◽  
Arc Discharge ◽  
Carbon Fibres ◽  
X Ray Diffraction ◽  
Solid Reaction ◽  
X Ray ◽  
Reducing Conditions ◽  
Transmission Electron ◽  
Hollow Carbon ◽  
Discharge Method

AbstractTroilite is a sulfide that occurs commonly in meteorites. In the laboratory, it can be synthesized by gas-solid reaction of metallic Fe and H2S-H2 gas mixtures. In this research, the arc-discharge method was used to synthesize troilite. The resulting spherules are up to 2–3 mm in diameter and composed of troilite, pyrrhotite and metallic Fe. Nanometer-sized hollow carbon fibres and balls occur on the surface of the spherules. The features and coexisting relationships of the constituents of the spherules were studied by X-ray diffraction (XRD), energy-dispersive X-ray spectrometry (EDS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the phenomenon of transformation of pyrite (FeS2) into pyrrhotite (Fe1-xS), troilite (FeS) and metallic Fe under arc-discharge reducing conditions were examined.

Characterization of Fe–Ni(C) nanocapsules synthesized by arc discharge in methane

1999 ◽  
Vol 14 (5) ◽  
pp. 1782-1790 ◽  
Author(s):  
X. L. Dong ◽  
Z. D. Zhang ◽  
S. R. Jin ◽  
W. M. Sun ◽  
X. G. Zhao ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Photoelectron Spectroscopy ◽  
Arc Discharge ◽  
Carbon Layer ◽  
Magnetization Measurement ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Energy Disperse Spectroscopy

Ultrafine Fe–Ni(C) particles of various compositions were prepared by arc discharge synthesis in a methane atmosphere. The particles were characterized by x-ray diffraction, transmission electron microscopy, energy disperse spectroscopy, chemical analysis, x-ray photoelectron spectroscopy, Mössbauer spectroscopy, and magnetization measurement. The carbon atoms solubilizing at interstitial sites in γ–(Fe, Ni, C) solution particles have the effects of forming austenite structure and changing microstructures as well as magnetic properties. A carbon layer covers the surface of Fe–Ni(C) particles to form the nanocapsules and protect them from oxidization. The mechanism of forming Fe–Ni(C) nanocapsules in the methane atmosphere was analyzed.

Stacking Faults in SiC Nanowires

2008 ◽  
Vol 8 (7) ◽  
pp. 3504-3510 ◽  
Author(s):  
K. L. Wallis ◽  
M. Wieligor ◽  
T. W. Zerda ◽  
S. Stelmakh ◽  
S. Gierlotka ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Stacking Faults ◽  
Multiwall Carbon Nanotubes ◽  
Structural Defects ◽  
X Ray Diffraction ◽  
Ir Spectrometry ◽  
X Ray ◽  
Sic Nanowires ◽  
Transmission Electron ◽  
Multiwall Carbon

SiC nanowires were obtained by a reaction between vapor silicon and multiwall carbon nanotubes, CNT, in vacuum at 1200 °C. Raman and IR spectrometry, X-ray diffraction and high resolution transmission electron microscopy, HRTEM, were used to characterize properties of SiC nanowires. Morphology and chemical composition of the nanowires was similar for all samples, but concentration of structural defects varied and depended on the origin of CNT. Stacking faults were characterized by HRTEM and Raman spectroscopy, and both techniques provided complementary results. Raman microscopy allowed studying structural defects inside individual nanowires. A thin layer of amorphous silicon carbide was detected on the surface of nanowires.

Synthesis and Characterization of Cobalt Nanoparticles Prepared by Arc Discharge Method Using an Ultrasonic Nebulizer

2018 ◽  
Vol 52 ◽  
pp. 88-101 ◽  
Author(s):  
Ahmed M. El-Khatib ◽  
Mohamed S. Badawi ◽  
Gamal D. Roston ◽  
Alaa M. Khalil ◽  
Ramy M. Moussa ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Electron Microscope ◽  
Ac Conductivity ◽  
Arc Discharge ◽  
Spherical Shape ◽  
X Ray Diffraction ◽  
Ultrasonic Nebulizer ◽  
Transmission Electron ◽  
Co Nanoparticles ◽  
Discharge Method

Magnetic cobalt nanostructured was synthesized by a two-stage method. First, a solution of cobalt precursor droplets was prepared by an ultrasonic nebulizer. Second, the arc discharge method between two electrodes in an inert gas at atmospheric pressure is used to obtain the nanostructured cobalt powder. The sample obtained was characterized by X-ray diffraction (XRD). Scanning electron microscope (SEM), High Resolution Transmission Electron Microscope (HR-TEM), UV-Vis Spectrophotometry, zeta potential (ZP) and vibrating sample magnetometer (VSM). The dielectric constant, and AC conductivity of the prepared sample was determined in the frequency range of 4 Hz to 8 MHz. The investigations showed that the Co nanoparticles prepared in this way have smaller and homogeneous nanoparticles with spherical shape morphology with good stability and unique magnetic properties as compared with the bulky one. The dielectric properties analysis shows an enhancement in the dielectric constant and the AC conductivity of the Co nanoparticles.

High-density stacking faults in a supersaturated nitrided layer on austenitic stainless steel

2016 ◽  
Vol 49 (6) ◽  
pp. 1967-1971 ◽  
Author(s):  
Ke Tong ◽  
Fei Ye ◽  
Honglong Che ◽  
Ming Kai Lei ◽  
Shu Miao ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Nitrided Layer ◽  
Stacking Faults ◽  
High Density ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron

The nitrogen-supersaturated phase produced by low-temperature plasma-assisted nitriding of austenitic stainless steel usually contains a high density of stacking faults. However, the stacking fault density observed in previous studies was considerably lower than that determined by fitting the X-ray diffraction pattern. In this work, it has been confirmed by high-resolution transmission electron microscopy that the strip-shaped regions of about 3–25 nm in width observed at relatively low magnification essentially consist of a series of stacking faults on every second {111} atomic plane. A microstructure model of the clustered stacking faults embedded in a face-centred cubic structure was built for these regions. The simulated X-ray diffraction and transmission electron microscopy results based on this model are consistent with the observations.

scholarly journals Parameters and properties for the preparation of Cu nanocolloids containing polyvinyl alcohol using the electrical spark discharge method

2021 ◽  
Vol 11 ◽  
pp. 184798042110351
Author(s):  
Kuo-Hsiung Tseng ◽  
Han-Chiao Ke ◽  
Hsueh-Chien Ku
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Zeta Potential ◽  
Polyvinyl Alcohol ◽  
Suspension Stability ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Discharge Method ◽  
Electrical Spark Discharge Method

Through the use of an electric discharge machine, this study performed the electrical spark discharge method in deionised water under normal temperature and pressure for Cu nanocolloid (CuNC) preparation. The CuNCs had a zeta potential of 12.3 mV, indicating poor suspension stability. The suspension stability was effectively increased (zeta potential 32.5 mV) through the addition of polyvinyl alcohol (PVA) to form PVA-containing CuNCs PVA/CuNCs. Next, the following pulse-width modulation (Ton:Toff) parameters were tested to determine the optimal setting for PVA/CuNC preparation: 10:10, 30:30, 50:50, 70:70 and 90:90 µs. The optimal preparation parameter was then determined according to the absorbance, zeta potential and size distribution results. Finally, the surface properties and crystal structure of the PVA/CuNCs were characterised through transmission electron microscopy (TEM) and X-ray diffraction (XRD). When the Ton:Toff was set to 30:30 µs, preparation efficiency was optimal, as was suspension stability, as indicated by the absorbance value (0.534), zeta potential (32.5 mV) and size distribution (85.47 nm). Transmission electron microscopy revealed that Cu nanoparticles that were more dispersed in the PVA/CuNCs had a diameter smaller than 10 nm and a crystal line width of 0.2028 nm. X-ray diffraction showed that the PVA/CuNCs contained intact Cu crystal structures.

Synthesis and Analysis of Mn3O4@Graphene Nanocomposites for Supercapacitors

2017 ◽  
Vol 26 (1) ◽  
pp. 096369351702600 ◽  
Author(s):  
Mingfu Zhu ◽  
Ruimin Fu
Keyword(s):  
Arc Discharge ◽  
Electrochemical Behaviour ◽  
Electronic Conduction ◽  
Graphene Sheets ◽  
X Ray Diffraction ◽  
Graphene Nanocomposites ◽  
X Ray ◽  
Transmission Electron ◽  
Morphology And Structure ◽  
Discharge Method

An easy arc discharge method was developed to synthesize nanocomposites composed of Mn3O4 nanoparticles loaded on graphene sheets. The morphology and structure of the obtained nanocomposites were analysed via X-ray diffraction, Raman spectroscopy, and transmission electron microscopy. The electrochemical behaviour of the product was evaluated via cyclic voltammetry and alternating current impedance. Results showed that Mn3O4 was dispersed homogeneously on the surface of graphene. The supercapacitor constructed by graphene/Mn3O4 as the positive electrode showed both high capacitance and good electronic conduction, which may lead to the development of nanocomposites with great potential for applications in biosensors and electrode material analysis.

scholarly journals Ferromagnetic Property and Synthesis of Onion-Like Fullerenes by Chemical Vapor Deposition Using Fe and Co Catalysts Supported on NaCl

2011 ◽  
Vol 2011 ◽  
pp. 1-6
Author(s):  
Yongzhen Yang ◽  
Xuguang Liu ◽  
Yanxing Han ◽  
Wenfang Ren ◽  
Bingshe Xu
Keyword(s):  
Electron Microscopy ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
X Ray Diffraction ◽  
Ferromagnetic Property ◽  
X Ray ◽  
Co Catalysts ◽  
Transmission Electron ◽  
Morphology And Structure ◽  
Co Nanoparticles

Metal-encapsulating onion-like fullerenes (M@OLFs) were synthesized by CVD at relatively low temperature (420C∘) using Fe and Co nanoparticles impregnated into NaCl as catalyst. The morphology and structure of the products were characterized by field emission scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, and Raman spectroscopy. The results show that Fe@OLFs and Co@OLFs with stacked graphitic fragments were prepared using Fe/NaCl or Co/NaCl as catalysts; after Co@OLFs were immersed in concentrated HCl for 48 hours, Co nanoparticles encapsulated by carbon shells were not removed, meaning that carbon shells can protect the encapsulated Co cores against environmental degradation. The coercivity value (750.23 Oe) of Co@OLFs showed an obvious magnetic property.

Formation of U-type hexaferrites

2004 ◽  
Vol 19 (8) ◽  
pp. 2462-2470 ◽  
Author(s):  
Darja Lisjak ◽  
Darko Makovec ◽  
Miha Drofenik
Keyword(s):  
Crystal Structure ◽  
Electron Microscopy ◽  
Stacking Faults ◽  
High Energy ◽  
Structural Defects ◽  
X Ray Diffraction ◽  
X Ray ◽  
Calcination Temperatures ◽  
Intermediate Phases ◽  
Transmission Electron

The formation of U-type hexaferrites with the composition Ba4B2Fe36O60 (B = Co, Ni, Zn) was studied. Samples were characterized by means of x-ray diffraction, electron microscopy (with energy-dispersive spectroscopy), and thermogravimetric and thermomagnetic analyses. U-hexaferrites are formed from the intermediate phases M-hexaferrite (BaFe12O19) and Y-hexaferrite (Ba2B2Fe12O22), which at the same time represent units in the U-hexaferrites’ crystal structure. The preparation of monophase U-hexaferrites was made possible by combining high-energy milling or chemical coprecipitation with a calcination at 1250–1300 °C. Structural defects, such as stacking faults, were observed in monophase samples with a high-resolution transmission electron microscope. The observed defects can be regarded as seeds for the formation of other hexaferrite phases after prolonged calcination times or higher calcination temperatures.

Preparation, Characterization and Magnetic Property of MFe2O4 (m=Mn, Zn, Ni, Co) Nanoparticles

2013 ◽  
Vol 842 ◽  
pp. 35-38 ◽  
Author(s):  
Li Xia Yang ◽  
Sha Li ◽  
Jing Zhang ◽  
Zhou Chen ◽  
Shi Cheng Xu
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Magnetic Properties ◽  
Room Temperature ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Basic Source ◽  
Co Nanoparticles ◽  
Zn Nanoparticles

MFe2O4 (M=Mn, Co, Ni, Zn) Nanoparticles with diameters from 5nm to 30nm have been prepared through a hydrothermal method. In this system, ethanolamine was used as a basic source instead of NaOH. The as-prepared ferrites were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). In addition, the magnetic properties of the obtained ferrites have been studied at room temperature, showing that the magentic properties of ferrites closely depended on the chemical composition of M2+.

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