时间：2011-03-11 23:13来源：蓝天飞行翻译 作者：admin 点击：次
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metal. A fusible, ductile, lustrous material. Fusible means it can be melted, ductile means its shape can be changed by drawing or stretching, and lustrous means it reflects light evenly without sparkling. Nearly all metals are good conductors of electricity and heat, and all metals readily lose electrons to form positive ions. metal-film resistor (electrical component). A type of electrical resistor made by depositing an extremely thin film of metal on a ceramic form. The thickness and type of metal film determines the resistance and the power-dissipating ability of the resistor. metal foil (electrical capacitor component). A very thin sheet of metal used as an electrode in electrolytic capacitors. The use of foil allows a large-area electrode to be contained in a small physical space. metal-ion concentration-cell corrosion. A type of concentration-cell corrosion that forms in the metal skin of an aircraft along the edges of a lap joint where moisture can be trapped. When trapped water absorbs oxygen from the air, it attracts electrons from the metal and forms negative hydroxide ions. When electrons are taken from the metal, positive metallic ions are left, and these positive ions collect in the stagnant moisture trapped between the skins in the lap joint. The positive ions attract electrons from the metal along the edges of the lap joint and cause the metal to unite with the hydroxide ions in the moisture to form a salt. This salt is corrosion. metallic pigment. Thin flakes of aluminum or copper that are mixed with a liquid vehicle to serve as the pigment for paint. When the paint is applied to a surface, these tiny flakes spread out to form a solid, opaque covering. metallic ring test (test for bonded-structure delamination). A very simple test for delamination in a bonded structural component. The material is tapped with a coin, and the sound is noted. If the sound is a clear metallic ringing, the material is good, and there is no delamination. But if the tapping produces a dull thudding noise, there is a good possibility that the laminations of which the material is made have begun to separate. metal oxide rectifier. A form of electrical rectifier that operates on the principle that electrons can flow from a base metal through a film of oxide, but cannot flow through the oxide into the base metal. Copper oxide and selenium oxide rectifiers have both been used in the past, but they have been replaced, to a great extent, by silicon or germanium semiconductor diode rectifiers. metal oxide semiconductor capacitor. See MOS capacitor. metal oxide semiconductor field effect transistor. See MOSFET. |
