Characterization of Ferromagnetic Nanoparticles Produced by A Carbon Arc

1994 ◽  
Vol 359 ◽  
Author(s):  
E. M. Brunsman ◽  
S. Anna ◽  
S. A. Majetich ◽  
M. E. Mchenry
Keyword(s):  
Fine Particles ◽  
Weight Percent ◽  
Buffer Gas ◽  
Switching Field ◽  
Interparticle Interactions ◽  
Carbon Coated ◽  
Carbon Arc ◽  
Co Nanoparticles ◽  
Percent Cobalt

ABSTRACTThe effect of increasing metal fraction on carbon arc nanoparticle production is examined for 10–50 weight percent cobalt starting materials. With 500 Torr of helium buffer gas, the carbon arc process yields carbon-coated FCC Co nanoparticles of similar sizes throughout this range. The saturation magnetization is believed to scale linearly with the relative abundance of Co. The variation in the coercivity with abundance is small compared to the dramatic changes which can arise from changes in the size of fine particles. The approach to magnetic saturation is more rapid in high abundance samples. This is attributed to interparticle interactions which align the easy axes when the nanoparticles crystallize within interconnected carbon shells. The switching field distribution as a function of Co abundance arises from both rotational barriers and from barriers due to the particle size distribution.

Cryomicroscopy of multiphase latices

1991 ◽  
Vol 49 ◽  
pp. 1060-1061
Author(s):  
O. L. Shaffer ◽  
M.S. El-Aasser ◽  
C. L. Zhao ◽  
M. A. Winnik ◽  
R. R. Shivers
Keyword(s):  
Electron Microscopy ◽  
Radiation Damage ◽  
Freeze Fracture ◽  
Particle Morphology ◽  
Second Stage ◽  
Transmission Electron ◽  
Important Approach ◽  
Carbon Coated ◽  
Preparation Techniques

Transmission electron microscopy is an important approach to the characterization of the morphology of multiphase latices. Various sample preparation techniques have been applied to multiphase latices such as OsO4, RuO4 and CsOH stains to distinguish the polymer phases or domains. Radiation damage by an electron beam of latices imbedded in ice has also been used as a technique to study particle morphology. Further studies have been developed in the use of freeze-fracture and the effect of differential radiation damage at liquid nitrogen temperatures of the latex particles embedded in ice and not embedded.Two different series of two-stage latices were prepared with (1) a poly(methyl methacrylate) (PMMA) seed and poly(styrene) (PS) second stage; (2) a PS seed and PMMA second stage. Both series have varying amounts of second-stage monomer which was added to the seed latex semicontinuously. A drop of diluted latex was placed on a 200-mesh Formvar-carbon coated copper grid.

Characterization of interfaces in CVD-coated nicalon fiber-reinforced SiC

1989 ◽  
Vol 47 ◽  
pp. 556-557
Author(s):  
K.L. More ◽  
R.A. Lowden
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Chemical Vapor ◽  
Chemical Vapor Infiltration ◽  
Frictional Stress ◽  
Fiber Reinforced ◽  
Pull Out ◽  
Carbon Coated ◽  
Fiber Matrix

The mechanical properties of fiber-reinforced composites are directly related to the nature of the fiber-matrix bond. Fracture toughness is improved when debonding, crack deflection, and fiber pull-out occur which in turn depend on a weak interfacial bond. The interfacial characteristics of fiber-reinforced ceramics can be altered by applying thin coatings to the fibers prior to composite fabrication. In a previous study, Lowden and co-workers coated Nicalon fibers (Nippon Carbon Company) with silicon and carbon prior to chemical vapor infiltration with SiC and determined the influence of interfacial frictional stress on fracture phenomena. They found that the silicon-coated Nicalon fiber-reinforced SiC had low flexure strengths and brittle fracture whereas the composites containing carbon coated fibers exhibited improved strength and fracture toughness. In this study, coatings of boron or BN were applied to Nicalon fibers via chemical vapor deposition (CVD) and the fibers were subsequently incorporated in a SiC matrix. The fiber-matrix interfaces were characterized using transmission and scanning electron microscopy (TEM and SEM). Mechanical properties were determined and compared to those obtained for uncoated Nicalon fiber-reinforced SiC.

scholarly journals Size-resolved characterization of organic aerosol in the North China Plain: new insights from high resolution spectral analysis

2021 ◽  
Author(s):  
Weiqi Xu ◽  
Chun Chen ◽  
Yanmei Qiu ◽  
Conghui Xie ◽  
Yunle Chen ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
North China Plain ◽  
North China ◽  
Fine Particles ◽  
Large Fraction ◽  
Organic Aerosol ◽  
Size Distributions ◽  
The North ◽  
The Impact

Organic aerosol (OA), a large fraction of fine particles, has a large impact on climate radiative forcing and human health, and the impact depends strongly on size distributions. Here we...

scholarly journals Morphological, chemical and optical absorbing characterization of aerosols in the urban atmosphere of Valladolid

2005 ◽  
Vol 5 (10) ◽  
pp. 2739-2748 ◽  
Author(s):  
S. Mogo ◽  
V. E. Cachorro ◽  
A. M. de Frutos
Keyword(s):  
Mass Fraction ◽  
Fine Particles ◽  
Aerosol Particles ◽  
Cascade Impactor ◽  
Urban Atmosphere ◽  
Coarse Particles ◽  
X Ray ◽  
Illumination System ◽  
Inverse Power Law

Abstract. Samples of atmospheric aerosol particles were collected in Valladolid, Spain, during the winter of 2003-2004. The measurements were made with a Dekati PM10 cascade impactor with four size stages: greater than 10 µm, between 2.5 to 10 µm, 1 to 2.5 µm and less than 1 µm. The size and shape of the particles were analyzed with a scanning electron microscope (SEM) and elemental analysis was done with an energy dispersive x-ray analysis (EDX). We present an evaluation by size, shape and composition of the major particulate species in the Valladolid urban atmosphere. The total aerosol concentration is very variable, ranging from 39.86 µg·m-3 to 184.88 µg·m-3 with the coarse particles as the dominant mass fraction. Emphasis was given to fine particles (<1 µm), for which the visible (400 nm to 650 nm) light absorption coefficients were measured using the integrating plate technique. We have made some enhancements in the illumination system of this measurement system. The absorption coefficient, σa, is highly variable and ranges from 7.33×10-6 m-1 to 1.01×10-4 m-1 at a wavelength of 550 nm. There is an inverse power law relationship between σa and wavelength, with an average exponent of -0.8.

Synthesis and Structural Characterization of Ferromagnetic Au/Co Nanoparticles

2014 ◽  
Vol 1708 ◽  
Author(s):  
Nabraj Bhattarai ◽  
Subarna Khanal ◽  
Daniel Bahena ◽  
Robert L. Whetten ◽  
Miguel Jose-Yacaman
Keyword(s):  
Quantum Interference ◽  
Magnetic Measurements ◽  
Ferromagnetic Behavior ◽  
Contrast Imaging ◽  
Uniform Size ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Co Nanoparticles ◽  
Z Contrast

ABSTRACTThe synthesis of bimetallic magnetic nanoparticles is very challenging because of the agglomeration and non-uniform size. In this paper, we present the synthesis of monodispersed 3-5 nm sized thiolated bimetallic alloyed Au/Co nanoparticles with decahedral and icosahedral shape, their characterization using Cs-corrected scanning transmission electron microscopy (STEM) and magnetic measurements using superconducting quantum interference device (SQUID) magnetometer. The Z-contrast imaging and energy dispersive X-ray spectroscopy (EDS) mapping showed an inhomogeneous alloying with minor segregation between Au and Co at nanoscale and the SQUID measurement exhibited the ferromagnetic behavior.

scholarly journals Impact of Crystalline Orientation on the Switching Field in Barium Titanate Using Piezoresponse Force Spectroscopy

2014 ◽  
Vol 1652 ◽  
Author(s):  
Nikhil K. Ponon ◽  
Daniel J. R. Appleby ◽  
Erhan Arac ◽  
Kelvin S. K. Kwa ◽  
Jonathan P. Goss ◽  
...  
Keyword(s):  
Electric Field ◽  
Phase Change ◽  
Crystal Orientation ◽  
Force Spectroscopy ◽  
Ferroelectric Domain ◽  
Switching Field ◽  
The Impact ◽  
Non Destructive ◽  
Domain Level

ABSTRACTUnderstanding crystal orientation at the ferroelectric domain level, using a non destructive technique, is crucial for the design and characterization of nano-scale devices. In this study, piezoresponse force spectroscopy (PFS) is used to identify ferroelectric domain orientation. The impact of crystal orientation on the switching field of ferroelectric BaTiO3 is also investigated at the domain level. The preferential domain orientations for BaTiO3 thin films prepared by pulsed laser deposition (PLD) in this study are [001], [101] and [111]. They have been mapped onto PFS spectra to show three corresponding switching fields of 460, 330 and 120 kV/cm respectively. In addition, the electric field at which the enhanced piezoresponse occurs was found to vary, due to a phase change. The polarization reversal occurs via a 2-step process (rotation and switching) for [101] and [111] orientations. The piezoresponse enhancement is absent for the [001] (pure switching) domains. The results demonstrate that an electric field induced phase change causes the [101] and [111] domains to reverse polarization at a lower field than the [001] domain.

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