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Electroplasticity
Electroplasticity, describes the enhanced plastic behavior of a solid material under the application of an electric field. This electric field could be internal, resulting in current flow in conducting materials, or external. The effect of electric field on mechanical properties ranges from simply enhancing existing plasticity, such as reducing the flow stress in already ductile metals, to promoting plasticity in otherwise brittle ceramics. The exact mechanisms that control electroplasticity vary based on the material and the exact conditions (e.g., temperature, strain rate, grain size, etc.). Enhancing the plasticity of materials is of great practical interest as plastic deformation provides an efficient way of transforming raw materials into final products. The use of electroplasticity to improve processing of materials is known as electrically assisted manufacturing. History Electroplasticity was first discovered by Eugene S. Machlin, who reported in 1959 that applying an el ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plastic
Plastics are a wide range of synthetic or semi-synthetic materials that use polymers as a main ingredient. Their plasticity makes it possible for plastics to be moulded, extruded or pressed into solid objects of various shapes. This adaptability, plus a wide range of other properties, such as being lightweight, durable, flexible, and inexpensive to produce, has led to its widespread use. Plastics typically are made through human industrial systems. Most modern plastics are derived from fossil fuel-based chemicals like natural gas or petroleum; however, recent industrial methods use variants made from renewable materials, such as corn or cotton derivatives. 9.2 billion tonnes of plastic are estimated to have been made between 1950 and 2017. More than half this plastic has been produced since 2004. In 2020, 400 million tonnes of plastic were produced. If global trends on plastic demand continue, it is estimated that by 2050 annual global plastic production will reach over 1,1 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Direct Current
Direct current (DC) is one-directional flow of electric charge. An electrochemical cell is a prime example of DC power. Direct current may flow through a conductor such as a wire, but can also flow through semiconductors, insulators, or even through a vacuum as in electron or ion beams. The electric current flows in a constant direction, distinguishing it from alternating current (AC). A term formerly used for this type of current was galvanic current. The abbreviations ''AC'' and ''DC'' are often used to mean simply ''alternating'' and ''direct'', as when they modify '' current'' or '' voltage''. Direct current may be converted from an alternating current supply by use of a rectifier, which contains electronic elements (usually) or electromechanical elements (historically) that allow current to flow only in one direction. Direct current may be converted into alternating current via an inverter. Direct current has many uses, from the charging of batteries to large po ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Covalent Bond
A covalent bond is a chemical bond that involves the sharing of electrons to form electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs. The stable balance of attractive and repulsive forces between atoms, when they share electrons, is known as covalent bonding. For many molecules, the sharing of electrons allows each atom to attain the equivalent of a full valence shell, corresponding to a stable electronic configuration. In organic chemistry, covalent bonding is much more common than ionic bonding. Covalent bonding also includes many kinds of interactions, including σ-bonding, π-bonding, metal-to-metal bonding, agostic interactions, bent bonds, three-center two-electron bonds and three-center four-electron bonds. The term ''covalent bond'' dates from 1939. The prefix ''co-'' means ''jointly, associated in action, partnered to a lesser degree, '' etc.; thus a "co-valent bond", in essence, means that the atoms share "valence" ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ionic Bonding
Ionic bonding is a type of chemical bonding that involves the electrostatic attraction between oppositely charged ions, or between two atoms with sharply different electronegativities, and is the primary interaction occurring in ionic compounds. It is one of the main types of bonding along with covalent bonding and metallic bonding. Ions are atoms (or groups of atoms) with an electrostatic charge. Atoms that gain electrons make negatively charged ions (called anions). Atoms that lose electrons make positively charged ions (called cations). This transfer of electrons is known as electrovalence in contrast to covalence. In the simplest case, the cation is a metal atom and the anion is a nonmetal atom, but these ions can be of a more complex nature, e.g. molecular ions like or . In simpler words, an ionic bond results from the transfer of electrons from a metal to a non-metal in order to obtain a full valence shell for both atoms. It is important to recognize that ''clean'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oxide
An oxide () is a chemical compound that contains at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion of oxygen, an O2– (molecular) ion. with oxygen in the oxidation state of −2. Most of the Earth's crust consists of oxides. Even materials considered pure elements often develop an oxide coating. For example, aluminium foil develops a thin skin of Al2O3 (called a passivation layer) that protects the foil from further corrosion.Greenwood, N. N.; & Earnshaw, A. (1997). Chemistry of the Elements (2nd Edn.), Oxford:Butterworth-Heinemann. . Stoichiometry (the measurable relationship between reactants and chemical equations of a equation or reaction) Oxides are extraordinarily diverse in terms of stoichiometries and in terms of the structures of each stoichiometry. Most elements form oxides of more than one stoichiometry. A well known example is carbon monoxide and carbon dioxide.Greenwood, N. N.; & Earnshaw, A. (1997). Chemist ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aluminium
Aluminium (aluminum in AmE, American and CanE, Canadian English) is a chemical element with the Symbol (chemistry), symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It has a great affinity towards oxygen, and Passivation (chemistry), forms a protective layer of Aluminium oxide, oxide on the surface when exposed to air. Aluminium visually resembles silver, both in its color and in its great ability to reflect light. It is soft, Magnetism, non-magnetic and ductility, ductile. It has one stable isotope, 27Al; this isotope is very common, making aluminium the twelfth most common element in the Universe. The radioactivity of Aluminum-26, 26Al is used in Radiometric dating, radiodating. 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+ is small and h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zinc
Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodic table. In some respects, zinc is chemically similar to magnesium: both elements exhibit only one normal oxidation state (+2), and the Zn2+ and Mg2+ ions are of similar size.The elements are from different metal groups. See periodic table. Zinc is the 24th most abundant element in Earth's crust and has five stable isotopes. The most common zinc ore is sphalerite (zinc blende), a zinc sulfide mineral. The largest workable lodes are in Australia, Asia, and the United States. Zinc is refined by froth flotation of the ore, roasting, and final extraction using electricity ( electrowinning). Zinc is an essential trace element for humans, animals, plants and for microorganisms and is necessary for prenatal and postnatal development. It ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Activation Energy
In chemistry and physics, activation energy is the minimum amount of energy that must be provided for compounds to result in a chemical reaction. The activation energy (''E''a) of a reaction is measured in joules per mole (J/mol), kilojoules per mole (kJ/mol) or kilocalories per mole (kcal/mol). Activation energy can be thought of as the magnitude of the potential barrier (sometimes called the energy barrier) separating minima of the potential energy surface pertaining to the initial and final thermodynamic state. For a chemical reaction to proceed at a reasonable rate, the temperature of the system should be high enough such that there exists an appreciable number of molecules with translational energy equal to or greater than the activation energy. The term "activation energy" was introduced in 1889 by the Swedish scientist Svante Arrhenius. Other uses Although less commonly used, activation energy also applies to nuclear reactions and various other physical phenomena. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cavitation
Cavitation is a phenomenon in which the static pressure of a liquid reduces to below the liquid's vapour pressure, leading to the formation of small vapor-filled cavities in the liquid. When subjected to higher pressure, these cavities, called "bubbles" or "voids", collapse and can generate shock waves that may damage machinery. These shock waves are strong when they are very close to the imploded bubble, but rapidly weaken as they propagate away from the implosion. Cavitation is a significant cause of wear in some engineering contexts. Collapsing voids that implode near to a metal surface cause cyclic stress through repeated implosion. This results in surface fatigue of the metal causing a type of wear also called "cavitation". The most common examples of this kind of wear are to pump impellers, and bends where a sudden change in the direction of liquid occurs. Cavitation is usually divided into two classes of behavior: inertial (or transient) cavitation and non-inertial c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Superplasticity
In materials science, superplasticity is a state in which solid crystalline material is deformed well beyond its usual breaking point, usually over about 600% during tensile deformation. Such a state is usually achieved at high homologous temperature. Examples of superplastic materials are some fine-grained metals and ceramics. Other non-crystalline materials (amorphous) such as silica glass ("molten glass") and polymers also deform similarly, but are not called superplastic, because they are not crystalline; rather, their deformation is often described as Newtonian fluid. Superplastically deformed material gets thinner in a very uniform manner, rather than forming a "neck" (a local narrowing) that leads to fracture. Also, the formation of microvoids, which is another cause of early fracture, is inhibited. In metals and ceramics, requirements for it being superplastic include a fine grain size (less than approximately 20 micrometres) and a fine dispersion of thermally stable par ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metallic Bonding
Metallic bonding is a type of chemical bonding that arises from the electrostatic attractive force between conduction electrons (in the form of an electron cloud of delocalized electrons) and positively charged metal ions. It may be described as the sharing of ''free'' electrons among a structure of positively charged ions (cations). Metallic bonding accounts for many physical properties of metals, such as strength, ductility, thermal and electrical resistivity and conductivity, opacity, and luster. Metallic bonding is not the only type of chemical bonding a metal can exhibit, even as a pure substance. For example, elemental gallium consists of covalently-bound pairs of atoms in both liquid and solid-state—these pairs form a crystal structure with metallic bonding between them. Another example of a metal–metal covalent bond is the mercurous ion (). History As chemistry developed into a science, it became clear that metals formed the majority of the periodic tabl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Joule Heating
Joule heating, also known as resistive, resistance, or Ohmic heating, is the process by which the passage of an electric current through a conductor produces heat. Joule's first law (also just Joule's law), also known in countries of former USSR as the Joule–Lenz law, Assuming the element behaves as a perfect resistor and that the power is completely converted into heat, the formula can be re-written by substituting Ohm's law, V = I R , into the generalized power equation: P = IV = I^2R = V^2/R where ''R'' is the resistance. Alternating current When current varies, as it does in AC circuits, P(t) = U(t) I(t) where ''t'' is time and ''P'' is the instantaneous power being converted from electrical energy to heat. Far more often, the ''average'' power is of more interest than the instantaneous power: P_ = U_\text I_\text = I_\text^2 R = U_\text^2 / R where "avg" denotes average (mean) over one or more cycles, and "rms" denotes root mean square. These formulas are valid fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
