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Kirkendall Effect
The Kirkendall effect is the motion of the interface between two metals that occurs due to the difference in diffusion rates of the metal atoms. The effect can be observed, for example, by placing insoluble markers at the interface between a pure metal and an alloy containing that metal, and heating to a temperature where atomic diffusion is reasonable for the given timescale; the boundary will move relative to the markers. This process was named after Ernest Kirkendall (1914–2005), assistant professor of chemical engineering at Wayne State University from 1941 to 1946. The paper describing the discovery of the effect was published in 1947. The Kirkendall effect has important practical consequences. One of these is the prevention or suppression of voids formed at the boundary interface in various kinds of alloy-to-metal bonding. These are referred to as Kirkendall voids. History The Kirkendall effect was discovered by Ernest Kirkendall and Alice Smigelskas in 1947, in the cours ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diffusion
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 (Molecular diffusion, particle diffusion), chemistry, biology, sociology, economics, statistics, data science, and finance (diffusion of people, ideas, data and price v ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Flux
Flux describes any effect that appears to pass or travel (whether it actually moves or not) through a surface or substance. Flux is a concept in applied mathematics and vector calculus which has many applications in physics. For transport phenomena, flux is a vector quantity, describing the magnitude and direction of the flow of a substance or property. In vector calculus flux is a scalar quantity, defined as the surface integral of the perpendicular component of a vector field over a surface. Terminology The word ''flux'' comes from Latin: ''fluxus'' means "flow", and ''fluere'' is "to flow". As '' fluxion'', this term was introduced into differential calculus by Isaac Newton. The concept of heat flux was a key contribution of Joseph Fourier, in the analysis of heat transfer phenomena. His seminal treatise ''Théorie analytique de la chaleur'' (''The Analytical Theory of Heat''), defines ''fluxion'' as a central quantity and proceeds to derive the now well-known expre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gold
Gold is a chemical element; it has chemical symbol Au (from Latin ) and atomic number 79. In its pure form, it is a brightness, bright, slightly orange-yellow, dense, soft, malleable, and ductile metal. Chemically, gold is a transition metal, a group 11 element, and one of the noble metals. It is one of the least reactivity (chemistry), reactive chemical elements, being the second-lowest in the reactivity series. It is solid under standard temperature and pressure, standard conditions. Gold often occurs in free elemental (native state (metallurgy), native state), as gold nugget, nuggets or grains, in rock (geology), rocks, vein (geology), veins, and alluvial deposits. It occurs in a solid solution series with the native element silver (as in electrum), naturally alloyed with other metals like copper and palladium, and mineral inclusions such as within pyrite. Less commonly, it occurs in minerals as gold compounds, often with tellurium (gold tellurides). Gold is resistant to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ultrasonic Welding
Ultrasonic welding is an industrial process whereby high-frequency ultrasonic acoustic vibrations are locally applied to work pieces being held together under pressure to create a solid-state weld. It is commonly used for plastics and metals, and especially for joining dissimilar materials. In ultrasonic welding, there are no connective bolts, nails, soldering materials, or adhesives necessary to bind the materials together. When used to join metals, the temperature stays well below the melting point of the involved materials, preventing any unwanted properties which may arise from high temperature exposure of the metal. History Practical application of ultrasonic welding for rigid plastics was completed in the 1960s. At this point only hard plastics could be welded. The patent for the ultrasonic method for welding rigid thermoplastic parts was awarded to Robert Soloff and Seymour Linsley in 1965. Soloff, the founder of Sonics & Materials Inc., was a lab manager at Branson Ins ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aluminium
Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has a great affinity towards oxygen, passivation (chemistry), forming a protective layer of aluminium oxide, oxide on the surface when exposed to air. It visually resembles silver, both in its color and in its great ability to reflect light. It is soft, magnetism, nonmagnetic, and ductility, ductile. It has one stable isotope, 27Al, which is highly abundant, making aluminium the abundance of the chemical elements, 12th-most abundant element in the universe. The radioactive decay, radioactivity of aluminium-26, 26Al leads to it being used in radiometric dating. Chemically, aluminium is a post-transition metal in the boron group; as is common for the group, aluminium forms compounds primarily in the +3 oxidation state. The aluminium cation Al3+ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Semiconductor Devices
A semiconductor device is an electronic component that relies on the electronics, electronic properties of a semiconductor material (primarily silicon, germanium, and gallium arsenide, as well as organic semiconductors) for its function. Its conductivity lies between conductors and insulators. Semiconductor devices have replaced vacuum tubes in most applications. They electrical conductivity, conduct electric current in the solid-state electronics, solid state, rather than as free electrons across a vacuum (typically liberated by thermionic emission) or as free electrons and ions through electric discharge in gases, an ionized gas. Semiconductor devices are manufactured both as single discrete devices and as integrated circuit (IC) chips, which consist of two or more devices—which can number from the hundreds to the billions—manufactured and interconnected on a single semiconductor wafer (electronics), wafer (also called a substrate). Semiconductor materials are useful beca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reliability (statistics)
In statistics and psychometrics, reliability is the overall consistency of a measure. A measure is said to have a high reliability if it produces similar results under consistent conditions:It is the characteristic of a set of test scores that relates to the amount of random error from the measurement process that might be embedded in the scores. Scores that are highly reliable are precise, reproducible, and consistent from one testing occasion to another. That is, if the testing process were repeated with a group of test takers, essentially the same results would be obtained. Various kinds of reliability coefficients, with values ranging between 0.00 (much error) and 1.00 (no error), are usually used to indicate the amount of error in the scores. For example, measurements of people's height and weight are often extremely reliable.The Marketing Accountability Standards Board (MASB) endorses this definition as part of its ongoinCommon Language: Marketing Activities and Metrics Pr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RCA Corporation
RCA Corporation was a major American electronics company, which was founded in 1919 as the Radio Corporation of America. It was initially a patent trust owned by General Electric (GE), Westinghouse, AT&T Corporation and United Fruit Company. In 1932, RCA became an independent company after the partners were required to divest their ownership as part of the settlement of a government antitrust suit. An innovative and progressive company, RCA was the dominant electronics and communications firm in the United States for over five decades. In the early 1920s, RCA was at the forefront of the mushrooming radio industry as a major manufacturer of radio receivers, and the exclusive manufacturer of the first superheterodyne sets. The company also created the first nationwide American radio network, the National Broadcasting Company (NBC). RCA was also a pioneer in the introduction and development of television, both black and white and especially color television. Throughout most o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Annealing (metallurgy)
In metallurgy and materials science, annealing is a heat treatment that alters the physical and sometimes chemical properties of a material to increase its ductility and reduce its hardness, making it more workable. It involves heating a material above its recrystallization temperature, maintaining a suitable temperature for an appropriate amount of time and then cooling. In annealing, atoms migrate in the crystal lattice and the number of dislocations decreases, leading to a change in ductility and hardness. As the material cools it recrystallizes. For many alloys, including carbon steel, the crystal grain size and phase composition, which ultimately determine the material properties, are dependent on the heating rate and cooling rate. Hot working or cold working after the annealing process alters the metal structure, so further heat treatments may be used to achieve the properties required. With knowledge of the composition and phase diagram, heat treatment can be used t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Porosity
Porosity or void fraction is a measure of the void (i.e. "empty") spaces in a material, and is a fraction of the volume of voids over the total volume, between 0 and 1, or as a percentage between 0% and 100%. Strictly speaking, some tests measure the "accessible void", the total amount of void space accessible from the surface (cf. closed-cell foam). There are many ways to test porosity in a substance or part, such as industrial CT scanning. The term porosity is used in multiple fields including pharmaceutics, ceramics, metallurgy, materials, manufacturing, petrophysics, hydrology, earth sciences, soil mechanics, rock mechanics, and engineering. Void fraction in two-phase flow In gas-liquid two-phase flow, the void fraction is defined as the fraction of the flow-channel volume that is occupied by the gas phase or, alternatively, as the fraction of the cross-sectional area of the channel that is occupied by the gas phase. Void fraction usually varies from location to l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Boltzmann–Matano Analysis
The Boltzmann–Matano method is used to convert the partial differential equation resulting from Fick's law of diffusion into a more easily solved ordinary differential equation, which can then be applied to calculate the diffusion coefficient as a function of concentration. Ludwig Boltzmann worked on Fick's second law to convert it into an ordinary differential equation, whereas Chujiro Matano performed experiments with diffusion couples and calculated the diffusion coefficients as a function of concentration in metal alloys. Specifically, Matano proved that the diffusion rate of A atoms into a B-atom crystal lattice is a function of the amount of A atoms already in the B lattice. The importance of the classic Boltzmann–Matano method consists in the ability to extract diffusivities from concentration–distance data. These methods, also known as ''inverse methods'', have both proven to be reliable, convenient and accurate with the assistance of modern computational techniques. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fick's Laws Of Diffusion
Fick's laws of diffusion describe diffusion and were first posited by Adolf Fick in 1855 on the basis of largely experimental results. They can be used to solve for the diffusion coefficient, . Fick's first law can be used to derive his second law which in turn is identical to the diffusion equation. ''Fick's first law'': Movement of particles from high to low concentration (diffusive flux) is directly proportional to the particle's concentration gradient. ''Fick's second law'': Prediction of change in concentration gradient with time due to diffusion. A diffusion process that obeys Fick's laws is called normal or Fickian diffusion; otherwise, it is called anomalous diffusion or non-Fickian diffusion. History In 1855, physiologist Adolf Fick first reported* * his now well-known laws governing the transport of mass through diffusive means. Fick's work was inspired by the earlier experiments of Thomas Graham, which fell short of proposing the fundamental laws for which ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
