| Research Abstract |
A new concept of reversible interconnection is proposed, by which any material combination can be bonded and separated reversibly. Separation of inorganic materials is important also from the point of view of recycling the materials. Few attempt, however, has been made for designing materials interconnections which can be separated as occasion demands. To demonstrate the concept of the reversible interconnection, two techniques of separation were investigated : weakening bonded interface i) by formation of reaction products and ii) by internal strain induced by hydrogen absorption.
The first case is demonstrated by polycrystalline Al and stainless steel interface. It is difficult to bond them by the conventional technique like diffusion bonding, because a brittle reaction layr is formed during the bonding due to the high process temperature. Their joining was carried out successfully by means of the surface activated bonding (SAB) at room temperature. In the bonding procedure, the surfaces are activated by ion or atom beam irradiation in vacuum and then brought into contact to each other. The tensile strength of the joint reaches as high as 20 Mpa. By heating the joint at 823K for 7.2ksec, Al_<76>Fe_<24>, Al_5Fe_2 FeAl_2 were precipitated at the interface. As a result, the joint could be separated at the interface without applying any external mechanical force. The separation occurred between the reaction layr and Al.
The second separation technique is demonstrated by polycrystalline Cu-, and Al-LaNi_<4.5>Al_<0.5> joint. Also in this case, the bonding is performed by the SAB at room temperature, since degradation of the hydrogen storage alloy might be caused by high temperature of the conventional bonding process. After exposing the joint to hydrogen atmosphere of 20-50atm, separation of the joint at the bonded interface could be observed.
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