Some HREM observations on silicon small particles

1988 ◽  
Vol 46 ◽  
pp. 1010-1011
Author(s):  
Sumio Iijima
Keyword(s):  
Small Particle ◽  
Particle Production ◽  
Atomic Level ◽  
Small Particles ◽  
Evaporation And Condensation ◽  
Development Corporation ◽  
The Many ◽  
Ar Gas ◽  
Physical And Chemical ◽  
Chemical Anomaly

In recent years, small particles have attracted the attentions of by some researchers for their physical and chemical anomaly as well as technological application to ceramics and catalyst industries. For these studies, morphological investigations on small particles seem to be important. HREM methods are the most direct approach to obtain particle crystal structures at atomic level resolution. This talk reviews some of the works on small particle research that have been done as a part of the fine particle research project by Japanese Research development Corporation (fully government-supported project). Among the many TEM observations on small particles that have been done, some specific problems using Si particles are presented.Small particle production Small particles of Si were prepared by a gasevaporation method which utilizes the evaporation and condensation of Si vapors in an Ar gas at 300Torr. The Si vapors were obtained by heating Si rods by an arc discharge1.

SREM observation of the interaction between the in-situ deposited Pd small particles and MgO cleavage surface

1986 ◽  
Vol 44 ◽  
pp. 382-383
Author(s):  
H.-J. Ou
Keyword(s):  
Electron Microscopy ◽  
Small Particle ◽  
Small Particles ◽  
Cleavage Surface ◽  
Metallic Particles ◽  
Microscopy Technique ◽  
Ceramic Surfaces ◽  
Reflection Electron Microscopy ◽  
New Perspective

The understanding of the interactions between the small metallic particles and ceramic surfaces has been studied by many catalyst scientists. We had developed Scanning Reflection Electron Microscopy technique to study surface structure of MgO hulk cleaved surface and the interaction with the small particle of metals. Resolutions of 10Å has shown the periodic array of surface atomic steps on MgO. The SREM observation of the interaction between the metallic particles and the surface may provide a new perspective on such processes.

scholarly journals Coordinated programs for comet Halley

1986 ◽  
Vol 118 ◽  
pp. 223-235
Author(s):  
Michael F. A'Hearn
Keyword(s):  
Chemical Processes ◽  
Complete Understanding ◽  
The Many ◽  
Comet Halley ◽  
Physical And Chemical ◽  
Optical Telescopes ◽  
Infrared Telescopes

Because comets are so difficult to observe, it is essential to coordinate observations from a variety of telescopes in order to fully understand their behavior. The apparition of Comet Halley represents a unique opportunity for coordinated programs because this is the only predictable comet which is routinely bright enough for the many observational programs desired. The International Halley Watch is playing an advocacy and coordinating role in the observations of Halley. Coordinated photographic observations will provide a record of the development of jets in the coma and of the motion of features in the tail. Coordinated photometry will provide both the heliocentric variation in vaporization and also the details of the outbursts thought to occur in most comets. Coordination with larger optical telescopes and with radio and infrared telescopes will allow a more complete understanding of the physical and chemical processes occurring in comets. Examples, of course, must still be drawn from observations of previous comets but they illustrate the results expected from Halley.

scholarly journals NANOTECHNOLOGIES IN CONSTRUCTION

2021 ◽  
pp. 7-14
Author(s):  
O.S. BALAN
Keyword(s):  
Food Packaging ◽  
Building Materials ◽  
Chemical Properties ◽  
Practical Significance ◽  
Construction Sector ◽  
Long Term Effects ◽  
Daily Lives ◽  
Building Product ◽  
The Many ◽  
Physical And Chemical

Problem statement. Cosmetics, clothing, and even food packaging: nanomaterials have invaded our daily lives. The construction and construction sector is no exception, and is undoubtedly one of the largest users of this technology. It is difficult to know if a building product contains nanomaterials. Indeed, unlike certain products, such as cosmetics, food or biocides (insecticides, detergents), no regulations establish special labeling. However, they are very widespread and are used to improve the properties of most materials: cement, plaster, glass, tiles, insulation metals, paints, etc. The benefits of using nanoparticles in construction are huge, promising extraordinary physical and chemical properties for modified building materials. Among the many different types of nanoparticles, titanium dioxide, carbon nanotubes, silicon dioxide, copper, clay, and aluminum oxide are the most widely used nanoparticles in the construction sector [1]. The purpose of this article is to analyze the use of nanoparticles in the construction industry to illustrate the benefits of using nanoparticles and address the short − and long-term effects of nanoparticles on the environment and human health in the microcosm of industry, so that the results can be generalized. Results. The use of nanotechnologies in construction and their properties are analyzed. Scientific novelty and practical significance. The problem of using nanothenologies in construction is analyzed.

scholarly journals Pitfalls in Calculating Scattering by Small Particles

1989 ◽  
Vol 135 ◽  
pp. 329-336
Author(s):  
Donald R. Huffman
Keyword(s):  
Small Particle ◽  
Interstellar Dust ◽  
Optical Constants ◽  
Particle Systems ◽  
Graphitic Carbon ◽  
Laboratory Work ◽  
Small Particles

Comparisons between measured extinction on small particle systems and the same quantity derived from scattering calculations using bulk optical constants often show substantial disagreements. Based on such comparisons, certain pitfalls which have been recognized in such a process, as it applies to the modelling of interstellar dust properties, are pointed out. Illustrations are taken from laboratory work on SiC, graphitic carbon, and olivine-type silicates.

Diversity of Freshwater Ecosystems and Global Distributions

2018 ◽  
pp. 3-19
Author(s):  
G. Randy Milton ◽  
C. Max Finlayson
Keyword(s):  
Freshwater Ecosystems ◽  
Longitudinal Distribution ◽  
General Distribution ◽  
Large Fluctuations ◽  
Global Mapping ◽  
Global Coverage ◽  
Karst Systems ◽  
The Many ◽  
Standing Waters ◽  
Physical And Chemical

Freshwater ecosystems are found on all continents comprising many different types and sizes; and defined and classified in different ways. The hydrologic regime influences the many physical and chemical features of freshwater ecosystems and has temporal and dynamic dimensions for flowing (rivers—lotic systems) and standing waters (lakes and ponds—lentic systems) and others that may experience permanent flooding or large fluctuations in water depths. The water balance is commonly used to understand a system’s hydrology and provide insights into the key processes determining its functioning. Widely distributed, global mapping initiatives provide a general distribution of types, document latitudinal and longitudinal distribution, and provide a global coverage estimate of 12.5–14.4 × 106 km2. However, a comprehensive inventory and global map for these ecosystems still does not exist. Information on the specific features of rivers and streams, lakes and ponds, swamps and marshes, peatlands, and freshwater karst systems is provided.

Experimental and Numerical Investigation of Small Particle Erosion in Gas Dominated Multiphase Flow

2021 ◽  
Author(s):  
G. Haider ◽  
M. Othayq ◽  
S. A. Shirazi
Keyword(s):  
Multiphase Flow ◽  
Small Particle ◽  
Hot Spots ◽  
Flow Behavior ◽  
Petroleum Engineering ◽  
Small Particles ◽  
Particle Erosion ◽  
Sand Particles ◽  
Pass Through ◽  
Paint Removal

Abstract Sand production is a significant challenge in petroleum engineering, and specifically in multiphase gas condensate wells where small amount of liquid is present with the gas. Sand particles entrained in multiphase flow can severely affect the integrity of fluid transportation structures such as pipelines, elbows, and reducers. Traditionally, sand management techniques such as sand screens and gravel packs are used to control sand. However, small particles can pass through these controls. Furthermore, small particles can block a part of the sand screen, causing high velocities in other sections which can cause erosion of the sand screen openings allowing larger particles to pass through which in turn cause more erosion. Furthermore, these small particles are highly susceptible to turbulent regions of flow and can cause severe erosion in these regions. Hence, it is critically important to understand the erosion caused by small particles. This study investigates the effect of small particles on erosion. Small particle erosion is more severe in gas dominated multiphase flows such as annular and mist flows than liquid dominated bubbly and slug flows. A 90-degree standard elbow is used in the experimental and numerical analyses because of its high erosion vulnerability and its importance in pipeline applications. This is because the flow changes direction in this geometry which has complex implications on erosion. This study follows the below mentioned research method: 1) Flow Visualization Study: To understand the flow behavior in bend. 2) Paint-Removal Study: To visualize the progress of paint-removal pattern and to identify the erosion hot spots caused by sand particles. 3) Multiphase Erosion Experiments: To determine the wall thickness loss on identified hot spots using fix-mounted temperature compensated ultrasonic measurement technique. 4) Computational Fluid Dynamics (CFD) Study: To compare erosion patterns with CFD simulations of multiphase flow. Furthermore, the effects of particle size on erosion ratio and its distribution in pipe bends are discussed. The CFD results of larger particles agree better with experimental data than for smaller particles using existing erosion models.

Development of Inspection Machine that Detect Small Particles Added on Surface with Precise Pattern by Capturing Backwards Scattered Polarized Light

2012 ◽  
Vol 6 (6) ◽  
pp. 781-791 ◽  
Author(s):  
Tsuyoshi Nomura ◽  
◽  
Tatsuo Nagasaki ◽  
Masami Ito
Keyword(s):  
Optical System ◽  
Small Particle ◽  
Laser Light ◽  
Polarized Light ◽  
Ccd Camera ◽  
Horizontal Line ◽  
Small Particles ◽  
The Real ◽  
Inspection Machine

The paper discusses the development of inspectionmachine to detect small particle by capturing backwards scattered polarized light. The proposed optical system consists of very low angle (2°) horizontal line laser light withSpolarized characteristics and angle 150° backwards line CCD Camera to capturePpolarized light from particles on wafer or glass and so on. This system is confirmed to apply the real production of wafer or glass.

scholarly journals The Volatile Composition of Comets

1989 ◽  
Vol 8 ◽  
pp. 387-393 ◽  
Author(s):  
H. A. Weaver
Keyword(s):  
Molecular Data ◽  
Detailed Knowledge ◽  
Volatile Composition ◽  
Cometary Nuclei ◽  
The Status ◽  
Chemical Conditions ◽  
The Many ◽  
Physical And Chemical ◽  
Cometary Comae ◽  
Excitation Conditions

ABSTRACTComets may be our best probes of the physical and chemical conditions in the outer regions of the solar nebula during that crucial period when the planets formed. The volatile composition of cometary nuclei, in particular, can be used to decide whether comets are the product of a condensation sequence similar to that invoked to explain the compositions of the planets and asteroids, or if comets are simply agglomerations of interstellar grains which have been insignificantly modified by the events that shaped the other bodies in the solar system. Although cometary nuclei are not generally accessible to observation, observations of cometary comae can illuminate at least some of the mysteries of the nuclei provided one has a detailed knowledge of the excitation conditions in the coma and also has access to basic atomic and molecular data on the many species present in comets. This paper examines the status of our knowledge of the volatile composition of cometary nuclei and discusses how these data are obtained.

Phonon States in Sic Small Particles

1989 ◽  
Vol 164 ◽  
Author(s):  
Y. Sasaki ◽  
C. Horie ◽  
Y. Nishina
Keyword(s):  
Particle Size ◽  
Small Particle ◽  
Particle Surface ◽  
Minor Role ◽  
Phonon Confinement ◽  
Small Particles ◽  
Temperature Dependent ◽  
Damping Term ◽  
Surface Phonon Polariton ◽  
A Minor

AbstractSize dependence of optical phonon frequencies and that of phonon dampings of SiC small particles have been studied by analysing their Raman data. The particle size ranges from 30 nm to 1000 nm. Decrease in the TO-phonon frequency as well as the LT-splitting (the splitting between the LO- and TO-phonon) with decrease in the particle size are much larger than that expected from the spatial correlation model or that from the phonon confinement model. The phonon damping for the small particle consists of the usual temperature-dependent term and an excess damping term, which is independent of temperature. These results suggest that the scattering of the phonon at the particle surface plays a major role in determining the phonon states of the small particle. Our experimental data suggest that the surface phonon-polariton mode at the interface between the crystallites plays a minor role in the Raman spectrum of particles consisting of a number of crystallites.

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