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shmily5368银虫 (小有名气)
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这是什么制备工艺?
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| gas pressure infiltration |
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shmily5368(金币+2, 翻译EPI+1): 2010-04-19 21:21
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Gas pressure infiltration (GPI) is process for preparation of composite materials where molten matrix material is infiltrated into the pores of preform under the influence of high gas pressure. Technology usually has several steps: evacuation of pressure vessel (some material as Mg are heated under protective gas because of the evaporation which can damage equipment), heating under vacuum until matrix material is melted, immersion of porous preform into the melt, infiltration under high pressure and withdrawal of the sample from the melt (in case of some material systems were wettability is not sufficient, sample solidifies together with matrix in crucible). In some cases bonding between constituents is established due to the chemical reaction at the interface (for example formation of carbides), but sometimes this bond is only mechanical. Cross section of typical gas pressure infiltration equipment showing pressure vessel, insulation of the pressure vessel, heating element and crucible which is used for material melting Steps of gas pressure infiltration process: a) porous preform above matrix material during heating; b) immersion of porous preform into the molten matrix material and inlet of pressurized gas; c) infiltrated sample in molten matrix and d) withdrawal of infiltrated sample from the melt As mentioned before, terms which are very often related with gas pressure infiltration technology are wettability or wetting angle. Wetting is determinated by contact angle between liquid phase and solid substrate. GPI process is used because in some cases wetting angle between molten matrix and solid porous reinforcement is relatively high. To overcome this problem high pressure must be used. If wetting angle is 90° or lower, this is considered as good. Sometime, wetting angle between constituents is so high (pure copper/carbon fibres) that not even extremely high pressure cannot ensure good infiltration results |
2楼2010-04-19 19:38:13
shmily5368
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