|
Electron Diffraction
Electron diffraction is a generic term for phenomena associated with changes in the direction of electron beams due to elastic interactions with atoms. It occurs due to elastic scattering, when there is no change in the energy of the electrons. The negatively charged electrons are scattered due to Coulomb forces when they interact with both the positively charged atomic core and the negatively charged electrons around the atoms. The resulting map of the directions of the electrons far from the sample is called a diffraction pattern, see for instance Figure 1. Beyond patterns showing the directions of electrons, electron diffraction also plays a major role in the contrast of images in electron microscopes. This article provides an overview of electron diffraction and electron diffraction patterns, collective referred to by the generic name electron diffraction. This includes aspects of how in a general way electrons can act as waves, and diffract and interact with matter. It a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gas Electron Diffraction
Gas electron diffraction (GED) is one of the applications of electron diffraction techniques. The target of this method is the determination of the structure of gaseous molecules, i.e., the geometrical arrangement of the atoms from which a molecule is built up. GED is one of two experimental methods (besides microwave spectroscopy) to determine the structure of free molecules, undistorted by intermolecular forces, which are omnipresent in the solid and liquid state. The determination of accurate molecular structures by GED studies is fundamental for an understanding of structural chemistry. Introduction Diffraction occurs because the wavelength of electrons accelerated by a potential of a few thousand volts is of the same order of magnitude as internuclear distances in molecules. The principle is the same as that of other electron diffraction methods such as LEED and RHEED, but the obtainable diffraction pattern is considerably weaker than those of LEED and RHEED because the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Austenite ZADP
Austenite, also known as gamma-phase iron (γ-Fe), is a metallic, non-magnetic allotropes of iron, allotrope of iron or a solid solution of iron with an alloying element. In plain-carbon steel, austenite exists above the critical eutectoid temperature of 1000 K (727 °C); other alloys of steel have different eutectoid temperatures. The austenite allotrope is named after Sir William Chandler Roberts-Austen (1843–1902). It exists at room temperature in some stainless steels due to the presence of nickel stabilizing the austenite at lower temperatures. Allotrope of iron From alpha iron undergoes a phase transition from body-centered cubic (BCC) to the face-centered cubic (FCC) configuration of gamma iron, also called austenite. This is similarly soft and ductile but can dissolve considerably more carbon (as much as 2.03% by mass at ). This gamma form of iron is present in the most commonly used type of stainless steel for making hospital and food-service equipment. Mater ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polycrystalline Pattern
A crystallite is a small or even microscopic crystal which forms, for example, during the cooling of many materials. Crystallites are also referred to as grains. Bacillite is a type of crystallite. It is rodlike with parallel longulites. Structure The orientation of crystallites can be random with no preferred direction, called random texture, or directed, possibly due to growth and processing conditions. While the structure of a single crystal is highly ordered and its lattice is continuous and unbroken, amorphous materials, such as glass and many polymers, are non-crystalline and do not display any structures, as their constituents are not arranged in an ordered manner. Polycrystalline structures and paracrystalline phases are in between these two extremes. Polycrystalline materials, or polycrystals, are solids that are composed of many crystallites of varying size and orientation. Most materials are polycrystalline, made of a large number crystallites held together by th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plane Waves, Wavevectors And Reciprocal Lattice
Plane most often refers to: * Aero- or airplane, a powered, fixed-wing aircraft * Plane (geometry), a flat, 2-dimensional surface * Plane (mathematics), generalizations of a geometrical plane Plane or planes may also refer to: Biology * Plane (tree) or ''Platanus'', wetland native plant * ''Planes'' (genus), marsh crabs in Grapsidae * '' Bindahara phocides'', the plane butterfly of Asia Maritime transport * Planing (boat), where weight is predominantly supported by hydrodynamic lift * ''Plane'' (wherry), a Norfolk canal boat, in use 1931–1949 Music *"Planes", a 1976 song by Colin Blunstone *"Planes (Experimental Aircraft)", a 1989 song by Jefferson Airplane from ''Jefferson Airplane'' *"Planez", originally "Planes", a 2015 song by Jeremih *"The Plane", a 1987 song on the '' Empire of the Sun'' soundtrack *"The Plane", a 1997 song by Kinito Méndez Other entertainment * Plane (''Dungeons & Dragons''), any fictional realm of the D&D roleplaying game's multiverse * ''Plan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reflection High-energy Electron Diffraction (RHEED)
Reflection high-energy electron diffraction (RHEED) is a technique used to characterize the surface of crystalline materials. RHEED systems gather information only from the surface layer of the sample, which distinguishes RHEED from other materials characterization methods that also rely on diffraction of high-energy electrons. Transmission electron microscopy, another common electron diffraction method samples mainly the bulk of the sample due to the geometry of the system, although in special cases it can provide surface information. Low-energy electron diffraction (LEED) is also surface sensitive, but LEED achieves surface sensitivity through the use of low energy electrons. Introduction A RHEED system requires an electron source (gun), photoluminescent detector screen and a sample with a clean surface, although modern RHEED systems have additional parts to optimize the technique. The electron gun generates a beam of electrons which strike the sample at a very small angle relat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Low-energy Electron Diffraction (LEED)
Low-energy electron diffraction (LEED) is a technique for the determination of the surface structure of single-crystalline materials by bombardment with a collimated beam of low-energy electrons (30–200 eV) and observation of diffracted electrons as spots on a fluorescent screen. LEED may be used in one of two ways: # Qualitatively, where the diffraction pattern is recorded and analysis of the spot positions gives information on the symmetry of the surface structure. In the presence of an adsorbate the qualitative analysis may reveal information about the size and rotational alignment of the adsorbate unit cell with respect to the substrate unit cell. # Quantitatively, where the intensities of diffracted beams are recorded as a function of incident electron beam energy to generate the so-called I–V curves. By comparison with theoretical curves, these may provide accurate information on atomic positions on the surface at hand. Historical perspective An electron-diffract ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electron Backscatter Diffraction
Electron backscatter diffraction (EBSD) is a scanning electron microscopy (SEM) technique used to study the Crystallography, crystallographic structure of materials. EBSD is carried out in a scanning electron microscope equipped with an EBSD detector comprising at least a Phosphorescence, phosphorescent screen, a compact lens and a low-light Charge-coupled device, camera. In the microscope an incident beam of electrons hits a tilted sample. As backscattered electrons leave the sample, they interact with the atoms and are both elastically Electron diffraction, diffracted and lose energy, leaving the sample at various scattering angles before reaching the phosphor screen forming Kikuchi lines (physics), Kikuchi patterns (EBSPs). The EBSD spatial resolution depends on many factors, including the nature of the material under study and the sample preparation. They can be indexed to provide information about the material's grain Crystal structure, structure, grain Electron crystallogr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
In A Scanning Electron Microscope
IN, In or in may refer to: Dans * India (country code IN) * Indiana, United States (postal code IN) * Ingolstadt, Germany (license plate code IN) * In, Russia, a town in the Jewish Autonomous Oblast Businesses and organizations * Independent Network, a UK-based political association * Indiana Northeastern Railroad (Association of American Railroads reporting mark) * Indian Navy, a part of the India military * Infantry, the branch of a military force that fights on foot * IN Groupe, the producer of French official documents * MAT Macedonian Airlines (IATA designator IN) * Nam Air (IATA designator IN) * Office of Intelligence and Counterintelligence, sometimes abbreviated IN Science and technology * .in, the internet top-level domain of India * Inch (in), a unit of length * Indium, symbol In, a chemical element * Intelligent Network, a telecommunication network standard * Intra-nasal (insufflation), a method of administrating some medications and vaccines * Integrase, a retr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
4D STEM
4D or 4-D primarily refers to: * 4-dimensional spacetime: three-dimensional space of length, width, and height, plus time * Four-dimensional space It may also refer to: Computers and photography * 4D (software), a complete programming environment including database and web server ** 4D SAS, developers of 4D and Wakanda ** 4D Inc, a US-based subsidiary of 4D SAS * 4D BIM, a term used in computer aided design * 4D printing * Cinema 4D, a commercial cross platform 3D graphics application * SGI IRIS 4D, a line of workstations from Silicon Graphics * 4D, a photo print size for digital cameras Arts and entertainment * ''4D'' (album), a 2010 album by Matthew Shipp * "4-D" (''The X-Files''), an episode of ''The X-Files'' * 4D Audio Recording system, an audio recording system developed by Deutsche Grammophon * 4D film, a high technology film experience augmented with physical or environmental effects * 4DTV, a satellite TV broadcasting technology from Motorola * 4DX, a 4D film form ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Precession Electron Diffraction
Precession electron diffraction (PED) is a specialized method to collect electron diffraction patterns in a transmission electron microscope (TEM). By rotating (precessing) a tilted incident electron beam around the central axis of the microscope, a PED pattern is formed by integration over a collection of diffraction conditions. This produces a quasi-kinematical diffraction pattern that is more suitable as input into direct methods (crystallography), direct methods algorithms to determine the crystal structure of the sample. Overview Geometry Precession electron diffraction is accomplished utilizing the standard instrument configuration of a modern Transmission electron microscope, TEM. The animation illustrates the geometry used to generate a PED pattern. Specifically, the beam tilt coils located pre-specimen are used to tilt the electron beam off of the optic axis so it is incident with the specimen at an angle, φ. The image shift coils post-specimen are then used to til ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Convergent Beam Electron Diffraction
Convergent beam electron diffraction (CBED) is an electron diffraction technique where a convergent or divergent beam (conical electron beam) of electrons is used to study materials. History CBED was first introduced in 1939 by Kossel and Möllenstedt. The development of the Field Emission Gun (FEG) in the 1970s, the Scanning Transmission Electron Microscopy (STEM), energy filtering devices and so on, made possible smaller probe diameters and larger convergence angles, and all this made CBED more popular. In the seventies, CBED was being used for the determination of the point group and space group symmetries by Goodman and Lehmpfuh, and Buxton, and starting in 1985, CBED was used by Tanaka et al. for studying crystals structure. Applications By using CBED, the following information can be obtained: *parameters of the crystal lattice, sample thickness *strain distribution * defects such as stacking faults, dislocations, grain boundaries, three-dimensional deformations, lattice ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diffuse Scattering
Diffusion is the net movement of anything (for example, atoms, ions, molecules, energy) generally from a region of higher concentration to a region of lower concentration. Diffusion is driven by a gradient in Gibbs free energy or chemical potential. It is possible to diffuse "uphill" from a region of lower concentration to a region of higher concentration, as in spinodal decomposition. Diffusion is a stochastic process due to the inherent randomness of the diffusing entity and can be used to model many real-life stochastic scenarios. Therefore, diffusion and the corresponding mathematical models are used in several fields beyond physics, such as statistics, probability theory, information theory, neural networks, finance, and marketing. The concept of diffusion is widely used in many fields, including physics (particle diffusion), chemistry, biology, sociology, economics, statistics, data science, and finance (diffusion of people, ideas, data and price values). The central i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
