Heat transmission effects of hetero-material (Al-PZT) direct bonding on an in-pipe micro inspection machine

Direct bonding between Al and PZT {Pb(Zr,Ti)O₃} was made possible by the formation hydrogen bonds at the interface. The strength of the bond and the structure of the interface were investigated. This technique was applied to the direct bonding between a PZT stacked actuator and an Al radiator plate on an in-pipe micro inspection machine, and the heat transmission effects of direct bonding on the PZT stacked actuator have been compared with the adhesive bonding. First, the Al and the PZT were treated so that their surfaces were hydrophilic, then OH groups were adsorbed by a physical reaction in which the surfaces are bombarded with ions produced by passing the steam through an ion source. The surfaces were then placed in contact with each other in air, then heated above 250°C in a vacuum to remove the residual water molecules from the bonding interface. The bonding strength of Al-PZT was above 10 MPa after the 5 hours heat treatment at above 250°C. The observation with a thermo-viewer shows that the saturated temperature of the PZT stacked actuator at the driving frequency of 1 kHz is suppressed below 93°C by the direct bonding of the Al radiator plate as compared with 110°C of adhesive bonding