The most common techniques for joining parts are soldering, brazing and welding. However, such 'brute force' heating methods often cause heating, not only of the solder or braze, but also of the parts to be joined, which may lead to dimensional distortion and changes in physical and/or mechanical properties.
In an attempt to provide more precise heating, methods of using AMFs to induce a flow of current and/or generate magnetic hysteresis losses within a joining material have been developed. However, each of these mechanisms has practical limitations when applied to conventional joining materials. For example, induction heating requires that a joining material be conductive and arranged to provide a conduction path. For this reason, it is generally not possible to inductively heat powders, which may be physically separated and/or coated with a surface oxide that prevents current flow between particles.
On the other hand, when heating via magnetic hysteresis losses, the maximum achievable temperature is the Curie temperature of the magnetic material. Typically, the Curie temperature of the joining material is sufficient to melt polymers, but not metals, which has limited the types of parts joined by heating via magnetic hysteresis losses. Further, bonds formed between parts may be weakened by exposure to extraneous magnetic fields that can cause unintended reheating of the joining material.
Dartmouth inventors have developed methods of using an alternating magnetic field (AMF) to generate hysteresis losses in nanocrystalline metal-aluminum powders, which may be sprinkled, spread, painted, sprayed, silk-screened or otherwise applied to a surface. When the powders are subjected to an AMF, an exothermic reaction is triggered, which causes the powders to melt. A metal aluminide, which does not exhibit hysteretic behavior and cannot be melted by application of an AMF, solidifies from the melt. This inexpensive and convenient method may be used to provide durable, permanent bonds between similar or dissimilar materials, such as polymers, semiconductors, ceramics and metals.
This technology is claimed in the published PCT Application No. PCT/US09/44547. We are seeking an industrial partner interested in its commercialization. (Ref: J443)
Last Updated: 7/24/12