Low Temperature Bonding of Pd/Ni Assembly for Hydrogen Purifier

Abstract

-For manufacturing a Pd cell for hydrogen purification, a key technology is the bonding of a Pd fine tube with a stainless steel grasp. In this study, the SLID method has been employed to join Pd sheet and Ni plate to evaluate the bendability between a Pd tube and a Ni coated stainless steel grasp. The results indicated that directly inserting a Sn interlayer with a thickness of 8.5μm between the Pd sheet and Ni plate caused the formation of Ni3Sn4 and PdSn4 intermetallic compounds, respectively. However, certain Sn interlayer remained after SLID bonding and low shear strength of 5.3 MPa was obtained. Furthermore, the remaining of low melting point Sn interlayer cannot withstand the operating temperature (above 350 ºC) of SLID assembled Pd cell for hydrogen purification. Reducing the Sn interlayer thickness to 3 μm led to the complete exhausting of Sn interlayer. Unfortunately, a long crack appeared at the Ni3Sn4/PdSn4 interface and a low bonding strength was resulted. Adding an Ag thin layer between the Sn coated Pd sheet and Ni plate caused an Ag3Sn intermetallic compound to form between the Ni3Sn4 and PdSn4 layers, and cracking of the Pd/Ni joint was prevented. This improvement led to satisfactory bonding strengths ranging from 10.6 to 17.3 MPa. High temperature storage at 400ºC for 100 hr did not degrade the bonding interfaces or bonding strengths.