Fabrication of Ta-Nb-Al2O3 seal composites by laser radiation

Ceramic-metal (Al2O3-Nb) sealing was performed by melting an Al2O3 capillary using neodymium-doped yttrium aluminum garnet (Nd:YAG) laser irradiation. However, voids existed in the melting region. Since voids are the most important factor affecting the mechanical strength of seals, attempts were made to remove them by introducing annealing as an additional cooling step after the melting step during the sealing process with Nd:YAG laser irradiation. Simultaneously, a Ta mesh foil was used, wrapped around the surface of the Al2O3 capillary as a grain-growth inhibitor. In addition, another important factor affecting the mechanical strength of the sealing is control of the seal length. In this study, the influence of various Ta mesh foil form factors (hole area, space between holes, and Ta area) on the seal length in the melted A2O3 capillary for Al2O3-Nb seals was therefore investigated in order to elucidate the optimal factors to increase the seal length. It was found that both the Ta area and space between holes should be decreased to increase seal length. Moreover, as the ratio of the Ta area to the space between holes increased, the seal length increased as well.