Development of a solder paste with ultrafine conditioned powder for the active brazing of ceramics

Because of its high reactivity, ultrafine powder of the alloy Zr (16 wt.%)-Fe (9 wt.%), which is used for the production of a solder paste for the brazing of ceramics, must be conditioned for a safe handling. The conditioning methods, hydrogenation, defined oxidation and adsorption of organic solvents, which were used alone or in combination, were performed in a special reaction vessel. The efficacy of the methods was studied by measuring the inflammation temperature, the oxidation resistance, the wetting angle and the tensile strength of bonded ceramic parts. The optimum oxygen content, which is high enough to protect the powder by a thin surface layer and low enough to have only a small influence on the properties of the brazer, was determined. Suitable organic solvents for pastes were elaborated. The reactions taking place during brazing are described.