WETTING WHEN JOINING

The carbon monoxide prevents reoxidation of the hot copper. A further temperature rise to about 900°C results in the copper and gold (or silver) at the surface of the parts interacting to form a eutectic. The eutectic melts and runs freely, wetting the surface as well as the attached wires or granules. When the assemblage is finally cooled, the eutectic solidifies, firmly joining the wires or granules to the now decorated surface. 

This special class of brazes reacts chemically with the surfaces of ceramic components to produce wettable products with metallic characteristics, such as TiO, TiC x or TiN x as described in Sections 6.3 and 7.2. Thus the wetting is due to an in situ metallization . By definition, the brazes must contain chemically reactive elements such as Ti that are often added to eutectic brazes similar to those developed for joining metal components. Many sessile drop experiments have shown that active metal brazes can wet a wide range of ceramics when a suitable inert environment is used. Particularly high standards of environmental inertness... 

---