Abrasion
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The process of scuffing, scratching, wearing down, marring, or rubbing away. It can be intentionally imposed in a controlled process using an abrasive.
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Acoustic Cavitation
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Cavitation induced by an acoustic field. Microscopic gas bubbles which are generally present in a liquid will be forced to oscillate due to an applied acoustic field. If the acoustic intensity is sufficiently high, the bubbles will first grow in size, and then rapidly collapse. High power ultrasonics usually use the inertial cavitation of microscopic vacuum bubbles for treatment of surfaces, liquids and slurries.
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Adsorption
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A process that occurs when a gas or liquid solute accumulates on the surface of a solid or a liquid (adsorbent), forming a film of molecules or atoms (the adsorbate). Most industrial adsorbents fall into one of three classes: 1. Oxygen-containing compounds (e.g.silica gel and zeolites 2. Carbon-based compounds (e.g. activated carbon and graphite) 3. Polymer-based compounds
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By adsorbing surface contaminants onto an adsorbent material. For example, wiping a surface with a cloth or sponge to remove moisture and/or dirt.
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Brinelling
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Surface fatigue caused by repeated impact or overloading.
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Cavitation
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The formation of vapour bubbles in a flowing liquid in a region where the pressure of the liquid falls below its vapour pressure. Usually divided into two classes of behavior. Inertial (or transient) cavitation occurs when a void or bubble in a liquid rapidly collapses, producing a shock wave. Non-inertial cavitation is the process in which a bubble in a fluid is forced to oscillate in size or shape due to energy input, e.g. acoustic field.
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Combustion
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(or burning) A complex sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat or both heat and light in the form of either a glow or flames. Direct combustion by atmospheric oxygen is a reaction mediated by radical intermediates typically produced as a result of thermal runaway, where the heat generated by combustion is necessary to maintain the high temperature necessary for radical production.
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Conduction (electrical)
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The movement of electrically charged particles through a transmission medium (electrical conductor). The movement of charge constitutes an electric current. The charge transport may result as a response to an electric field, or as a result of a concentration gradient in carrier density, that is, by diffusion .
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Crevice Corrosion
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Corrosion occurring in spaces having limited access to working fluid from the environment, such as gaps and contact areas between parts, under gaskets or seals, inside cracks and seams. Generally occurs due to high concentration of impurities in the crevice (e.g., chlorides, acid, or base), or differential electrolyte chemistry inside and outside the crevice: a single metal part being submerged in two different environments.
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Decomposition (biological)
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The break down of tissue of a formerly living organism into simpler forms of matter.
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Deflagration
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A technical term describing subsonic combustion that usually propagates through thermal conductivity (hot burning material heats the next layer of cold material and ignites it). Most 'fire' found in daily life, from flames to explosions, is technically deflagration. Deflagration is different from detonation (which is supersonic and propagates through shock compression).
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Deformation
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A change in the shape or size of an object due to an applied force. This can be a result of tensile (pulling) forces, compressive (pushing) forces, shear, bending or torsion (twisting). Deformation is often described in terms of strain.
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Depressurisation
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Reduction in pressure. Rapid depressurisation can be used to create pressure differences.
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For example, sunflower seeds are broken open by subjecting them to a high pressure followed by rapid depressurisation. The resulting pressure difference breaks open the husks.
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Desorption
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A phenomenon whereby a substance is released from or through a surface. The process is the opposite of sorption (i.e adsorption and absorption). This occurs in a system being in the state of sorption equilibrium between bulk phase (fluid, i.e. gas or liquid solution) and an adsorbing surface (solid or boundary separating two fluids). When the concentration (or pressure) of substance in the bulk phase is lowered, some of the sorbed substance changes to the bulk state.
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Detonation
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Detonation involves a supersonic exothermic front accelerating through a medium that eventually drives a shock front propagating directly in front of it. Detonations are observed in both conventional solid and liquid explosives, as well as in reactive gases.
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Eddy Currents
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An electrical phenomenon caused when a conductor is exposed to a changing magnetic field due to relative motion of the field source and conductor; or due to variations of the field with time. This can cause eddys of circulating current within the conductor which create electromagnets with magnetic fields that opposes the change of the magnetic field.
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Through inductive heating.
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Electric Arc
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An electrical breakdown of a gas which produces an ongoing plasma discharge, resulting from a current flowing through normally nonconductive media such as air
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Electrolysis
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A method of separating chemically bonded elements and compounds by passing an electric current through them. Electrolysis involves the passage of an electric current through an ionic substance that is either molten or dissolved in a suitable solvent, resulting in chemical reactions at the electrodes.
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Through electrolytic erosion at electrodes.
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Electromagnetic Induction
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The generation of electromotive force (EMF) in a current-carrying conductor exposed to a changing magnetic field
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Through inductive heating.
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Electron Impact Desorption
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Desorption arising from electron-impact induced adsorbate surface bond breaking. Molecules on surfaces may also be chemically converted to other species by electron impact
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Electrostatic Discharge
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The sudden and momentary electric current that flows between two objects at different electrical potentials
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Entropic Explosion
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An explosion in which the reactants undergo a large change in volume without releasing a large amount of heat.
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Enzyme
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Proteins that catalyze (i.e., increase the rates of) chemical reactions. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates sufficient for life. Enzymes differ from most other catalysts in that they are highly specific for their substrates
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Erosion
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The process of weathering and transport of solids (sediment, soil, rock and other particles) in the natural environment or their source and deposits them elsewhere. It usually occurs due to transport by wind, water, or ice; by down-slope creep of soil and other material under the force of gravity; or by living organisms, such as burrowing animals, in the case of bioerosion.
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Explosion
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A sudden increase in volume and release of energy in an extreme manner, usually with the generation of high temperatures and the release of gases.
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Fatigue
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The progressive and localised structural damage that occurs when a material is subjected to cyclic loading. The maximum stress values are less than the ultimate tensile stress limit, and may be below the yield stress limit of the material.
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Fermentation
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In an industrial context, fermentation refers to the breakdown of organic substances and re-assembly into other substances. Somewhat paradoxically, fermenter culture in industrial capacity often refers to highly oxygenated and aerobic growth conditions, whereas fermentation in the biochemical context is a strictly anaerobic process.
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Fluidisation
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A process similar to liquefaction whereby a granular material is converted from a static solid-like state to a dynamic fluid-like state. This process occurs when a fluid (liquid or gas) is passed up through the granular material. When fluidized, a bed of solid particles will behave as a fluid, like a liquid or gas.
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Force
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That which can cause an object with mass to accelerate. Force has both magnitude & direction, i.e. it's a vector quantity. An object with constant mass will accelerate in proportion to the net force acting upon it and in inverse proportion to its mass (or the net force on an object is equal to the rate of change of momentum it experiences). Forces acting on objects may cause them to rotate or deform, or result in a change in pressure.
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Freezing
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A phase change in which a liquid turns into a solid when its temperature is lowered below its freezing point. Colloquially it is applied to water, but technically it applies to any liquid. All known liquids, except liquid helium, freeze when the temperature is lowered enough.
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For example, frost damage in the case of water which has a negative coeficcient of thermal expansion at temperatures below 4 °C.
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Friction
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The force resisting the relative motion of two surfaces in contact or a surface in contact with a fluid (e.g. air on an aircraft or water in a pipe).
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Hydrodynamic Cavitation
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The process of vaporisation, bubble generation and bubble implosion which occurs in a flowing liquid as a result of a decrease and subsequent increase in local pressure.
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Hydrolysis
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A chemical reaction during which one or more water molecules are split into hydrogen and hydroxide ions which may go on to participate in further reactions.
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Hydrophile
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A physical property of a molecule that can transiently bond with water (H2O) through hydrogen bonding. This is thermodynamically favorable, and makes these molecules soluble not only in water, but also in other polar solvents.
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Impact Force
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A high force or shock applied over a short time period. Such a force or acceleration can sometimes have a greater effect than a lower force applied over a proportionally longer time period.
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Incandescence
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The emission of light (visible electromagnetic radiation) from a hot body due to its temperature.
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Infrared Radiation
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Infrared (IR) radiation is electromagnetic radiation whose wavelength is longer than that of visible light (400-700 nm), but shorter than that of terahertz radiation (3-300 µm) and microwaves (~30,000 µm). Infrared radiation spans roughly three orders of magnitude (750 nm and 1000 µm).
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From energy of incident infrared radiation.
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Ionisation
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The physical process of converting an atom or molecule into an ion by adding or removing charged particles such as electrons or other ions.
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Jet
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A coherent stream of fluid (e.g. gas or liquid) that is projected into a surrounding medium, usually from some kind of a nozzle or aperture. Jets can travel long distances without dissipating.
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Joule Heating
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The process by which the passage of an electric current through a conductor releases heat. Heat generated is a function of current, resistance and time. Also known as the Joule-Lenz effect, Ohmic heating or resitive heating.
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Light
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Light is electromagnetic radiation of a wavelength that is visible to the human eye (in a range from about 380 or 400 nanometres to about 760 or 780 nm)
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Using a high-power light source or a target susceptible to light.
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Mechanical Force
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A mechanical influence that causes a free body to undergo an acceleration.
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Nuclear Fission
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The splitting of the nucleus of an atom into parts (lighter nuclei) often producing free neutrons and other smaller nuclei, which may eventually produce photons (in the form of gamma rays). Fission of heavy elements is an exothermic reaction which can release large amounts of energy both as electromagnetic radiation and as kinetic energy of the fragments (heating the bulk material where fission takes place).
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Oxidation
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A chemical reaction that involves the loss of electrons or an increase in the oxidation state by a molecule, atom or ion.
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Phase Change
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The transformation of a thermodynamic system from one phase to another. Most commonly used to describe transitions between solid, liquid and gaseous states of matter, in rare cases including plasma.
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Photo-oxidation
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Oxidation facilitated radiant energy such as UV or artificial light. This process is often the most significant component of weather degradation of polymers.
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Photodissociation
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A chemical reaction in which a chemical compound is broken down by photons. Any photon with sufficient energy can affect the chemical bonds of a chemical compound. Since a photon's energy is inversely proportional to its wavelength, electromagnetic waves with the energy of visible light or higher, such as ultraviolet light, x-rays and gamma rays are usually involved in such reactions.
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Plasma
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A partially ionized gas, in which a certain proportion of electrons are free rather than being bound to an atom or molecule. The ability of the positive and negative charges to move somewhat independently makes the plasma electrically conductive so that it responds strongly to electromagnetic fields. Plasma therefore has properties quite unlike those of solids, liquids or gases and is considered to be a distinct state of matter.
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Pressure Drop
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Pressure is an effect which occurs when a force is applied on a surface. Pressure is transmitted to solid boundaries or across arbitrary sections of fluid normal to these boundaries or sections at every point. Rapid pressure drop is a useful technique for applying force or breaking objects apart.
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For example, the breaking apart of sunflower seed shells by sudden pressure drop.
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Pyrolysis
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A thermochemical decomposition of organic material at elevated temperatures in the absence of oxygen. Pyrolysis typically occurs under pressure and at operating temperatures above 430 °C (800 °F). Pyrolysis is a special case of thermolysis.
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Pyrophoricity
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A pyrophoric substance ignites spontaneously in air at or below 55 degrees centigrade. The creation of sparks from metals is based on the pyrophoricity of small metal particles. The sparking mechanism in cigarette lighters is an example. Some liquids and gases are phyrophoric.
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Radiation
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A process in which energetic particles or waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing.
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Radioactive Decay
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The process in which an unstable atomic nucleus spontaneously loses energy by emitting ionizing particles and radiation.
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Redox Reactions
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Redox (shorthand for oxidation-reduction) reactions describe all chemical reactions in which atoms have their oxidation number (oxidation state) changed. This can be either a simple redox process, such as the oxidation of carbon to yield carbon dioxide (CO2) or the reduction of carbon by hydrogen to yield methane (CH4), or a complex process such as the oxidation of sugar(C6H12O6) in the human body through a series of complex electron transfer processes.
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Reduction
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A chemical reaction that involves the gain of electrons or a decrease in the oxidation state by a molecule, atom or ion.
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Regelation
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The phenomenon of melting under pressure and freezing again when the pressure is reduced. Occurs only for substances, such as ice, that have the property of expanding upon freezing, for the melting points of those substances decrease with increasing external pressure.
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Resonance
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The tendency of a system to oscillate with larger amplitude at some frequencies than at others. These are known as the system's resonant frequencies. At these frequencies, even small periodic driving forces can produce large amplitude oscillations, because the system stores vibrational energy.
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Shock Wave
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A type of propagating disturbance. Like an ordinary wave, it carries energy and can propagate through a medium (solid, liquid, gas or plasma) or through a field such as the electromagnetic field. Characterized by an abrupt, nearly discontinuous change in the characteristics of the medium. Associated with rapid rise in pressure, temperature and density of the flow. A shock wave travels through most media at a higher speed than an ordinary wave.
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Solvation
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(commonly called dissolution) The process of attraction and association of molecules of a solvent with molecules or ions of a solute. As ions dissolve in a solvent they spread out and become surrounded by solvent molecules. The bigger the ion, the more solvent molecules are able to surround it and the more it becomes solvated.
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Sonochemistry
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The effect of sonic waves and wave properties on chemical systems. Sonochemistry arises from acoustic cavitation: the formation, growth, and implosive collapse of bubbles in a liquid. This is demonstrated in phenomena such as ultrasound, sonication, sonoluminescence, and sonic cavitation.
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Sonoluminescence
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The emission of short bursts of light from imploding bubbles in a liquid when excited by sound.
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Sorption
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The action of both absorption and adsorption taking place simultaneously, i.e. the effect of gases or liquids being incorporated into a material of a different state and adhering to the surface of another molecule. Absorption is the incorporation of a substance in one state into another of a different state (e.g., liquids absorbed by solid or gas absorbed by liquid). Adsorption is the physical adherence or bonding of ions and molecules onto the surface of another molecule.
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Sound
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A mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard.
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Used in some cleaning applications (e.g. cleaning teeth, especially when coupled using a liquid medium)
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Sputtering
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A process whereby atoms are ejected from a solid target material due to bombardment of the target by energetic ions. It is commonly used for thin-film deposition, etching and analytical techniques
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Sublimation
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The change of the physical state of aggregation (or simply state) of matter directly from solid phase to gaseous phase without passing through an intermediate liquid phase.
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Supercritical Fluid
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Any substance at a temperature and pressure above its critical point. It can diffuse through solids like a gas, and dissolve materials like a liquid. Additionally, close to the critical point, small changes in pressure or temperature result in large changes in density, allowing many properties to be 'tuned'.
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For example: Carbon dioxide is a common supercritical solvent. It is used on a large scale for the decaffeination of green coffee beans, the extraction of hops for beer production.
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Superhydrophilicity
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Under light irradiation, water dropped onto titanium dioxide forms no contact angle (almost 0 degrees). This effect is called superhydrophilicity. Examples of uses: defogging glass, enabling oil spots to be swept away by water, door mirrors for cars, coatings for buildings, self-cleaning glass, etc. Another use is the property of self-cleaning by the photodecomposition of dirt such as organic compounds adsorbed on the surface.
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Tension
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The pulling force exerted by a string, cable, chain, or similar object on another object. It is the opposite of compression.
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Thermal Radiation
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Electromagnetic radiation emitted from the surface of an object due to the object's temperature.
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Thermionic Emission
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Emission of electrons or ions caused by thermal vibrational energy . Also known as the Edison Effect.
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Thermolysis
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(or Thermal decomposition) A chemical decomposition caused by heat. The reaction is usually endothermic as heat is required to break chemical bonds in the compound undergoing decomposition. If decomposition is sufficiently exothermic, a positive feedback loop is created producing thermal runaway and possibly an explosion.
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Torque
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Torque (also called moment or moment of force) is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist. Torque is the rotational analogue of Force.
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Ultrasonic Vibration
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Vibration at ultrasonic frequencies.
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Ultrasound
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Cyclic sound pressure with a frequency greater than the upper limit of human hearing. Although this limit varies from person to person, 20 kHz serves as a useful lower limit in describing ultrasound.
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Vibration
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Mechanical oscillations about an equilibrium point. The oscillations may be periodic such as the motion of a pendulum or random such as the movement of a tire on a gravel road.
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Weathering
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The breaking down of Earth's rocks, soils and minerals through direct contact with the planet's atmosphere. Weathering occurs in situ, or 'with no movement', and thus should not be confused with erosion, which involves the movement of rocks and minerals by agents such as water, ice, wind, and gravity.
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X-Ray
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A form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz (3 × 1016 Hz to 3 × 1019 Hz) and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma rays. In many languages, X-radiation is called Röntgen radiation.
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