Shape and Size Effect on Ultrafine Metallic Particles

1992 ◽  
Vol 272 ◽  
Author(s):  
Keisaku Kimura
Keyword(s):  
Spin Susceptibility ◽  
Metal Particles ◽  
Shape Effect ◽  
View Point ◽  
Metallic Particles ◽  
Crucial Effect ◽  
Strength Based ◽  
Nature Of Chemical Bond ◽  
Theoretical Results ◽  
Small Metal Particles

ABSTRACTThe effect of size and shape on the electronic state of ultrafine metallic particles is described with the critical review of so far proposed experimental and theoretical results. The temperature dependence of the spin susceptibility of small metal particles is presented as function of size, shape, spin-orbit interaction of the elements, and magnetic field strength. Based upon a proposed formula, the spin susceptibility of small Mg particles is precisely analyzed with the view point of shape effect. It is emphasized that the exogenous impurities have crucial effect. on the magnetic properties of small metal particles. It is clarified that the confusion in the magnetic experiments originates from the extrinsic magnetic effect. The deviation of the nature of chemical bond in small size systems from that in bulk is briefly outlined.

NMR IN A SYSTEM OF SMALL METALLIC PARTICLES: A NOVEL MESOSCOPIC PHENOMENON

1993 ◽  
Vol 07 (15) ◽  
pp. 981-997 ◽  
Author(s):  
K.B. EFETOV ◽  
V.N. PRIGODIN
Keyword(s):  
Distribution Function ◽  
Line Shape ◽  
Local Density ◽  
Metal Particles ◽  
Local Density Of States ◽  
Metallic Particles ◽  
Super Symmetry ◽  
Symmetry Method ◽  
Small Metal Particles ◽  
Good Agreement

We consider the NMR line shape for a system of small metal particles. The problem is reduced to calculation of the local density of states distribution function. We present the first exact calculation of this quantity for the mesoscopic system. Using the super-symmetry method, we calculated exactly the whole distribution function which gives the resonance-line shape. It turns out that at low temperatures, the line becomes very broad and asymmetric. The Knight shift defined as the maximum of the line decreases when decreasing the temperature. We found a good agreement of our results with a few experiments done long ago.

Thin foil preparation for AEM study of small metal particles in stony meteorites

1995 ◽  
Vol 53 ◽  
pp. 510-511
Author(s):  
Cheol-Woong Yang ◽  
David B. Williams ◽  
Joseph I. Goldstein
Keyword(s):  
Analytical Electron Microscopy ◽  
Thin Foil ◽  
Metal Particles ◽  
Specimen Preparation ◽  
Silicate Matrix ◽  
Metallic Particles ◽  
Area Of Interest ◽  
Composite Nature ◽  
Transformation Processes ◽  
Small Metal Particles

The phase transformation processes and phase equilibria of the Fe-Ni and Fe-Ni-S system at low temperature can be better understood by characterizing the microstructure and chemistry of metallic particles in stony meteorites using analytical electron microscopy (AEM) techniques. However stony meteorites have a composite nature consisting of metal particles embedded in an inherently brittle silicate matrix, which causes a differential thinning rate. The thin foil preparation of the metal particles for AEM has proved to be very difficult, and we report on the first successful specimen preparation.Materials of this type present particular difficulties in the preparation of thin foil specimens because the area of interest is limited to specific regions within the metal particles. The metal particles are usually less than 500 μm in size and the silicate matrix is inherently brittle. Moreover, the interfaces between metal particles and silicates are weak because of corrosion, depending on cooling, etc.

Electron Microscopy of the Shape of Small Metal Particles

1977 ◽  
Vol 35 ◽  
pp. 300-301
Author(s):  
M. Jose Yacaman
Keyword(s):  
Electron Microscopy ◽  
Metal Particle ◽  
Field Experiments ◽  
Size Range ◽  
Dark Field ◽  
Metal Particles ◽  
Bragg Condition ◽  
Crystal Particle ◽  
Small Metal Particle ◽  
Small Metal Particles

In the Study of small metal particles the shape is a very Important parameter. Using electron microscopy Ino and Owaga(l) have studied the shape of twinned particles of gold. In that work electron diffraction and contrast (dark field) experiments were used to produce models of a crystal particle. In this work we report a method which can give direct information about the shape of an small metal particle in the amstrong- size range with high resolution. The diffraction pattern of a sample containing small metal particles contains in general several systematic and non- systematic reflections and a two-beam condition can not be used in practice. However a N-beam condition produces a reduced extinction distance. On the other hand if a beam is out of the bragg condition the effective extinction distance is even more reduced.

Investigation of cluster layers of small netal particles by TEM, SEM, EELS and by photoacoustic spectroscopy

1990 ◽  
Vol 48 (4) ◽  
pp. 250-251
Author(s):  
H. Seiler ◽  
U. Haas ◽  
K.H. Körtje
Keyword(s):  
Bulk Material ◽  
High Vacuum ◽  
Optical Methods ◽  
Metal Particles ◽  
Silver Particles ◽  
Low Loss ◽  
Plasmon Excitation ◽  
First Results ◽  
Diffraction Patterns ◽  
Small Metal Particles

The physical properties of small metal particles reveal an intermediate position between atomic and bulk material. Especially Ag has shown pronounced size effects. We compared silver layers evaporated in high vacuum with cluster layers of small silver particles, evaporated in N2 at a pressure of about 102 Pa. The investigations were performed by electron optical methods (TEM, SEM, EELS) and by Photoacoustic (PA) Spectroscopy (gas-microphone detection).The observation of cluster layers with TEM and high resolution SEM show small silver particles with diameters of about 50 nm (Fig. 1 and Figure 2, respectively). The electron diffraction patterns of homogeneous Ag layers and of cluster layers are similar, whereas the low loss EELS spectra due to plasmon excitation are quite different. Fig. 3 and Figure 4 show first results of EELS spectra of a cluster layer of small silver particles on carbon foil and of a homogeneous Ag layer, respectively.

Coherent electron nanodiffraction from clean silver nano particles in a UHV STEM

1993 ◽  
Vol 51 ◽  
pp. 1058-1059
Author(s):  
J. Liu ◽  
M. Pan ◽  
G. E. Spinnler
Keyword(s):  
Supported Catalysts ◽  
Imaging Techniques ◽  
Nano Particles ◽  
Metal Particles ◽  
Shape Structure ◽  
Dynamical Simulations ◽  
Small Metal Particles ◽  
Extract Information

Small metal particles have peculiar chemical and physical properties as compared to bulk materials. They are especially important in catalysis since metal particles are common constituents of supported catalysts. The structural characterization of small particles is of primary importance for the understanding of structure-catalytic activity relationships. The shape and size of metal particles larger than approximately 5 nm in diameter can be determined by several imaging techniques. It is difficult, however, to deduce the shape of smaller metal particles. Coherent electron nanodiffraction (CEND) patterns from nano particles contain information about the particle size, shape, structure and defects etc. As part of an on-going program of STEM characterization of supported catalysts we report some preliminary results of CEND study of Ag nano particles, deposited in situ in a UHV STEM instrument, and compare the experimental results with full dynamical simulations in order to extract information about the shape of Ag nano particles.

The optical kerr effect in small metal particles and metal colloids: The case of gold

1988 ◽  
Vol 47 (4) ◽  
pp. 347-357 ◽  
Author(s):  
F. Hache ◽  
D. Ricard ◽  
C. Flytzanis ◽  
U. Kreibig
Keyword(s):  
Kerr Effect ◽  
Metal Particles ◽  
Optical Kerr Effect ◽  
Metal Colloids ◽  
Small Metal Particles
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