Air Brazing: A New Method of Ceramic-Ceramic and Ceramic-Metal Joining

摘要: A new method of ceramic-ceramic and ceramic-metal joining has emerged over the past several years. Referred to as air brazing, technique was originally designed developed for use in fabricating high-temperature solid-state electrochemical devices such planar SOFCs oxygen hydrogen concentrators. The primary advantage brazing is that a predominantly metallic joint can be formed directly without need an inert cover gas or surface reactive fluxes. resulting bond hermetic, offers excellent room temperature strength, inherently resistant oxidation at high temperature. key developing successful filler metal composition identify oxide wetting agent mutually soluble molten noble solvent. One particular oxide-metal combination appears readily suited this purpose CuOx-Ag, system interest development silver clad cuprate-based superconductors. Studies equilibrium phases studies indicate there are two invariant points pseudobinary CuOx-Ag phase diagram around which braze compositions developed: 1) monotectic reaction 969±1°C, where CuO Ag-rich liquid L1 coexist with second CuOx-rich liquidmore » L2 xAg/(xAg + xCu) = 0.10±0.03 Ag 2) eutectic 942±1°C, 0.99±0.005. Specifically, near-eutectic Ag-CuO have shown good promise electrochemically active ceramics yttria-stabilized zirconia, lanthanum strontium manganite, barium cobalt ferrite, well alumina magnesia. More recently it been found various ternary additions further improve characteristics these metals, increase their potential operating temperatures, and/or strength strength. Here we review basic concept illustrate selection design using example.« less