KSEF RDE: Metallic and Carbon Foam Bonding

Metal and/or carbon foams have been used at a rapidly increasing rate for applications involving structural and/or thermal tasks. An entirely new realm of manufacturing technologies, capable of achieving desired integrity at the micro level, must be introduced to accommodate these new applications. For example, bonding of extended heat transfer surfaces requires composite materials with minimum of up to 5 microns thick clad layers. However, use of such materials in combination with foams fails to offer successful bonding at the macro scale due to an inherent need to form all the joints at spatially macro-distributed micro-locations. Such foam material cannot take an advantage of a surface tension driven molten metal flow along macro capillary paths of bonded mating surfaces because these paths simply do not exist. Our preliminary study of aluminum and copper foam bonding has demonstrated that the topology of foam ligaments at interfaces must be tightly controlled, in addition to other important influential factors, such as the oxide layer destruction, reactions at the substrate, diffusion across the phases' interfaces, and/or the state of the material throughout processing. As a consequence, joint formation during either brazing or soldering (in particular lead-free) of novel foam materials must be considered in detail at the micro level. Our laboratory has developed a unique experimental capability using the hot stage microscopy real-time in situ studies of the joint formation evolution at the micro scale. This research effort is aimed at investigating new bonding solutions based on the use of filler paste made of true alloy macro particles with polymer binders and with/without nano-particle doping. We plan to analyze behavior of molten metal at the micro level and joint formation of foam-substrate structures. The related applications involve automotive, electronics and aero space applications (non-traditional heat exchangers, and electronics cooling).