Liquid metal infiltration

Reactive fibers, 9 486-489 Reactive flame retardants, 11 474-479 brominated, ll 475-477t Reactive gases, 13 456 Reactive groups, types of, 9 178 Reactive hot melt butyl sealants, 22 44 Reactive hot melt polyurethanes, 22 37-38 Reactive hot melt silicones, 22 35 Reactive ion-beam etching (RIBE), 22 184 Reactive ion etching (RIE), 20 278 22 183 of lotus effect surfaces, 22 120 Reactive lead alloys, 14 779 Reactive liquid metal infiltration process, 16 168... 

Parts produced having a gradient in porosity could be used to fabricate composites with a gradient in composition. For graded ceramic-ceramic composites, the graded porosity in a partially sintered compact could be filled with a suitable liquid precursor to produce composites by the infiltration processing route [6, 7]. In the case of metal-ceramic composites, liquid metal infiltration of the sintered ceramic piece could be employed to introduce the metal phase [8],... 

Carbon fibers have been successfully used to reinforce Pb alloys [107] using liquid metal infiltration and used for the positive electrode of rechargeable lead acid batteries. 

Figure 16.8 Liquid metal Infiltration under gas pressure, (a) Insert preform and close die (b) evacuate air (c) apply gas pressure and maintain during solidification. Source Reprinted with permission from Matthews FL, Rawlings RD, Composite Materials, CRC Press, Boca Raton, 78-117, 2000. Copyright 2000, CRC Press, Boca Raton, Florida.

Fabrication techniques include diffusion coating and electroplating, followed by hot-pressing and liquid-metal infiltration. In some cases, the carbon fibers are coated by electroplating copper. A carbon tow is used instead of a twisted bundle to facilitate infiltration. This is followed by plasma-spraying of additional copper and hot-pressing.f 1... 

Cross section of a grophile/aluininuin com- posile in 6061 alloy matrix. The fibers were precoated with titanium and Ixvon. Fiber bundles were impregnated by liquid-metal infiltration with 6061. The composite was consolidated by diffusion bonding with 6061 foil. 

Lanxide process (a) infiltration of preform (b) wicking of liquid metal along grain boundaries (reproduced by permission of Woodhead Publishing Limited)74. 

Liquid-phase infiltration of preforms has emerged as an extremely useful method for the processing of composite materials. This process involves the use of low-viscosity liquids such as sols, metal- or polymer-melts. Using this infiltration process, it is possible to design new materials with unique microstructures (e.g. graded, multiphase, microporous) and unique thermomechanical properties (graded functions, designed residual strains and thermal shock). 

The heating started after the pressure of the order of 8 GPa was created. In 0.5 s after the heating starts, current force and heating power in the system become constant. In this case, a formation and migration of the liquid from the centre to the heater take place. As soon as the liquid metal reaches the heater inner surface, the current in the system increases abruptly as an electric circuit with a lower electrical resistance is connected parallel to the heater. The distance covered by the liquid for this period is assessed from the thickness of an infiltrated diamond coampact recovered of the HPA. 

J. T. Blucher, Discussion of a liquid metal pressure infiltration process to produce metal matrix composites. J. Mater. Proc. Technol. 30, 381-390 (1992). 

The range of processing techniques that can be employed to produce FGMs is also broad [1]. Vapor-phase methods e.g., CVD, CVI, and PVD methods), liquid-phase methods e.g., electrodeposition, sol-gel, plasma spraying and molten metal infiltration methods), and a variety of solid-phase methods based on powder metallurgy are available. The solid-state methods include powder stacking techniques, powder infiltration techniques, slurry techniques e.g., sedimentation... 

LIQUID PENETRANT INSPECTION - A type of nondestructive inspection that locates discontinuities that are open to the surface of a metal by first allowing a penetrating dye or fluorescent liquid to infiltrate the discontinuity, removing the excess penetrant, and then applying a developing agent that causes the penetrant to seep back out of the discontinuity and register as an indication. 

LCM liquid composite molding LMI hquid metal infiltration... 

The main type of corrosion damages in liquid Pb, Bi and Pb-Bi is the dissolution of structural materials (steels) and their components in these coolants. The kinetics of dissolution processes can be of different nature. For example, in some cases the dissolution is localized on boundaries of grain, causing interstructure infiltration of liquid metal (Pb, Pb-Bi) into steel. 

Closer in concept to the DMO process is the infiltration of aluminum alloys in nitrogen to yield Al-AIN composites. Low temperatures (<1000°C) and high magnesium or strontium eontent promote the spontaneous infiltration of liquid metal with a small concurrent nitridation to yield dispersions of AIN [34]. Similar alloys may be infiltrated at higher temperatures, resulting in nitride contents that increase with temperature to yield AlN-matrix composites [35-38]. This process can result in particulate loadings of up to 75%. The mechanical properties of these aluminum nitride composites have been extensively characterized [39]. 

Preform infiltration This process usually involves the infiltration of a preform of fibers or particulate reinforcement with a liquid metal. Depending on the wetting characteristics and the type of alloy, either pressureless or pressure-assisted infiltration can be used. 

Metal particle catalyzed chemical vapor infiltration Liquid metal and/or liquid metal alloy droplets 0 Silicon nitride fibers with high strength, 0 Uniform SiN microcoils... 

Figure 16.9 depicts liquid infiltration where the molten metal is evacuated and forced into the preform chamber under pressure, where it infiltrates the perform. The pressure is maintained until solidification has occurred. Yang and Chung [159] and also Chiou and Chung [160] used vacuum infiltration of a liquid metal in an inert gas under pressure. 

Jeng-Maw Chiou, Chung DDL, Characterization of metal-matrix composites fabricated by vacuum infiltration of a liquid metal under an inert gas pressure, J Mater Sci, 26, 2583-2589, 1991. 

Many metals are naturally brittle at room temperature, so must be machined when hot. However, particles of these metals, such as tungsten, chromium, molybdenum, etc., can be suspended in a ductile matrix. The resulting composite material is ductile, yet has the elevated-temperature properties of the brittle constituents. The actual process used to suspend the brittle particles is called liquid sintering and involves infiltration of the matrix material around the brittle particles. Fortunately, In the liquid sintering process, the brittle particles become rounded and therefore naturally more ductile. 

Curing primarily refers to the process of solidification of polymer matrix materials. Metal matrix materials are simply heated and cooled around fibers to solidify. Ceramic matrix and carbon matrix materials are either vapor deposited, mixed with fibers in a slurry and hardened, or, in the case of carbon, subjected to repeated liquid infiltration followed by carbonization. Thus, we concentrate here on curing of polymers. 

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