HREM image simulations for supported metal particle catalysts

1993 ◽  
Vol 51 ◽  
pp. 736-737 ◽  
Author(s):  
Ming-Hui Yao ◽  
David J. Smith
Keyword(s):  
Fine Particles ◽  
Amorphous Material ◽  
Chemical Properties ◽  
Morphological Features ◽  
Metal Particles ◽  
Plan View ◽  
Profile View ◽  
Imaging Conditions ◽  
Image Simulations ◽  
Supported Metal

The chemical properties of catalysts often depend on the size, shape and structure of the supported metal particles. To characterize these morphological features and relate them to catalysis is one of the main objectives for HREM study of catalysts. However, in plan view imaging, details of the shape and structure of ultra-fine supported particles (<2nm) are often obscured by the overlapping contrast from the support, and supported sub-nanometer particles are sometimes even invisible. Image simulations may help in the interpretation at HREM images of supported particles in particular to extract useful information about the size, shape and structure of the particles. It should also be a useful tool for evaluating the imaging conditions in terms of visibility of supported particles. P. L. Gai et al have studied contrast from metal particles supported on amorphous material using multislice simulations. In order to better understand the influence of a crystalline support on the visibility and apparent morphological features of supported fine particles, we have calculated images of Pt and Re particles supported on TiO2(rutile) in both plan view and profile view.

A method for direct measurement of specimen noise in HREM images

1993 ◽  
Vol 51 ◽  
pp. 458-459
Author(s):  
Sidnei Paciornik ◽  
Roar Kilaas ◽  
Ulrich Dahmen ◽  
Michael Adrian O'Keefe
Keyword(s):  
Random Noise ◽  
Image Interpretation ◽  
Thin Foil ◽  
High Resolution Electron Microscopy ◽  
Black Dot ◽  
Atomic Column ◽  
Amorphous Oxide ◽  
Resolution Electron ◽  
Imaging Conditions ◽  
Image Simulations

High resolution electron microscopy (HREM) is a primary tool for studying the atomic structure of defects in crystals. However, the quantitative analysis of defect structures is often seriously limited by specimen noise due to contamination or oxide layers on the surfaces of a thin foil.For simple monatomic structures such as fcc or bcc metals observed in directions where the crystal projects into well-separated atomic columns, HREM image interpretation is relatively simple: under weak phase object, Scherzer imaging conditions, each atomic column is imaged as a black dot. Variations in intensity and position of individual image dots can be due to variations in composition or location of atomic columns. Unfortunately, both types of variation may also arise from random noise superimposed on the periodic image due to an amorphous oxide or contamination film on the surfaces of the thin foil. For example, image simulations have shown that a layer of amorphous oxide (random noise) on the surfaces of a thin foil of perfect crystalline Si can lead to significant shifts in image intensities and centroid positions for individual atomic columns.

Surface Study of Supported Metal Particles by129XeNMR

1995 ◽  
Vol 74 (16) ◽  
pp. 3277-3280 ◽  
Author(s):  
A. Bifone ◽  
T. Pietrass ◽  
J. Kritzenberger ◽  
A. Pines ◽  
B. F. Chmelka
Keyword(s):  
Metal Particles ◽  
Surface Study ◽  
Supported Metal

Structural Investigation of Photoluminescent Porous Si by Transmission Electron Microscopy

1992 ◽  
Vol 281 ◽  
Author(s):  
S. Shih ◽  
K. H. Jung ◽  
D. L. Kwong
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Sample Preparation ◽  
Structural Investigation ◽  
Amorphous Material ◽  
Porous Si ◽  
Plan View ◽  
Mesh Structure ◽  
Transmission Electron ◽  
Minimal Damage

ABSTRACTWe have developed a new, minimal damage approach for examination of luminescent porous Si layers (PSLs) by transmission electron microscopy (TEM). In this approach, chemically etched PSLs are fabricated after conventional plan-view TEM sample preparation. A diffraction pattern consisting of a diffuse center spot, characteristic of amorphous material, is primarily observed. However, crystalline, microcrystalline, and amorphous regions could all be observed in selected areas. A crystalline mesh structure could be observed in some of the thin areas near the pinhole. The microcrystallite sizes were 15–150 Å and decreased in size when located further from the pinhole.

scholarly journals Rhombohedral Boron Nitride Epitaxy on ZrB2

2020 ◽  
Author(s):  
Laurent Souqui ◽  
Justinas Palisaitis ◽  
Naureen Ghafoor ◽  
Henrik Pedersen ◽  
Hans Högberg
Keyword(s):  
Electron Microscopy ◽  
Boron Nitride ◽  
Photoelectron Spectroscopy ◽  
Amorphous Material ◽  
Limited Area ◽  
Sem Images ◽  
Plan View ◽  
Minute Amount ◽  
X Ray ◽  
Rhombohedral Boron

<div>Epitaxial rhombohedral boron nitride films were deposited on ZrB<sub>2</sub>(0001)/4H-SiC(0001) by chemical vapor deposition at 1485 °C from the reaction of triethylboron and ammonia and with a minute amount of silane (SiH<sub>4</sub>). X-ray diffraction (XRD) φ-scans yield the epitaxial relationships of 𝑟−𝐵𝑁(0001)∥𝑍𝑟𝐵2(0001) out-of-plane and 𝑟−𝐵𝑁(1120)∥𝑍𝑟𝐵2(1120) in-plane. Cross-section transmission electron microscopy (TEM) micrographs showed that epitaxial break down of r-BN film occurs approximatively after 10 nm, above which epitaxial growth proceeds only in limited area up to 80 nm of film thickness. Both XRD and TEM demonstrate the formation of carbon- and nitrogen-containing cubic inclusions at the ZrB<sub>2</sub> surface. Quantitative analysis from X-ray photoelectron spectroscopy of the r-BN films shows B/N ratios between 1.30 to 1.20 and an O content of 3 to 4 at.%. Plan-view scanning electron microscopy (SEM) images reveal a surface morphology where an amorphous material comprising B, C, and N is surrounding the epitaxial twinned r-BN crystals. SiH<sub>4</sub> exposure prior to growth was found to reduce the amount of the amorphous phase on the surface. Defects such as pitting were also observed on the ZrB<sub>2</sub> template surface.</div><div><br></div>

scholarly journals Experimental study on acidification effect of tailing sand

2021 ◽  
Vol 248 ◽  
pp. 01048
Author(s):  
Wenzhao Chen ◽  
Kai Yang ◽  
Jiaqing Fan ◽  
Xiqi Liu ◽  
Xiaoqing Wei
Keyword(s):  
Fine Particles ◽  
Iron Concentration ◽  
Chemical Properties ◽  
Surface Friction ◽  
Friction Angle ◽  
Immersion Test ◽  
Coarse Particles ◽  
Natural Conditions ◽  
Lead Zinc ◽  
Reaction Processes

Sulfide minerals (mainly FeS2) contained in lead-zinc tailings are easy to be acidified in the air. The acidification mechanism is that the tailing sand generates sulfuric acid and sulfate under the catalysis of oxidant, water and oxygen. The acidic liquid generated by the reaction will continue to react with metal oxides to form an insoluble precipitate.In order to reveal the corresponding changes of chemical properties and physical properties of lead-zinc tailing sand during acidification, a series of reaction processes of tailings under natural conditions were simulated by immersion test in laboratory.It is found through the test that with the deepening of acidification, the coarse particles of tailing sand dissolve, resulting in the decrease of iron concentration in the compound, the increase of fine particles, the increase of specific surface area, the decrease of surface friction and occlusion friction between particles, resulting in the decrease of internal friction angle, and the decrease of the safety of tailings dam. words.

scholarly journals In-situ Study of Coarsening Mechanisms of Supported Metal Particles in Reducing Gas

2015 ◽  
Vol 21 (S3) ◽  
pp. 643-644
Author(s):  
S.Y. Zhang ◽  
Matteo Cargnello ◽  
Christopher B. Murray ◽  
George W. Graham ◽  
Xiaoqing Pan
Keyword(s):  
Metal Particles ◽  
In Situ Study ◽  
Reducing Gas ◽  
Supported Metal
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