Effects of ion implantation on the brazing properties of high purity alumina

In this study, ion implantation was used as a surface modification method for active and inactive brazing of alumina ceramics to metals. Alumina was implanted with Ti ions at acceleration voltages of 35 kV and 55 kV at doses ranging between 2 × 1017 and 1 × 1018 ions/cm2, with Ni ions at an acceleration voltage of 55 kV at doses ranging between 2 × 1016 and 6 × 1017 ions/cm2, and with Al ions at 55 kV with a dose of 2 × 1017 ions/cm2. After implantation, the brazing of alumina to Nb was performed using the active brazing metal Ag70Cu27Ti3 (wt.%) at 850 °C/870 °C and the inactive brazing metal Ag72Cu28 (wt.%) at 830 °C in a vacuum respectively. The surface properties of implanted alumina, e.g., implanted ions depth and concentration distribution, newly formed phases, sheet resistance etc., were studied by Rutherford backscattering (RBS), Glancing X-ray diffraction (GXRD) and four-probe method. Shear strengths of the active and inactive brazing joints were measured. Microstructures of the joints were analyzed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). There is no obvious evidence that Ti and Ni ion implantation can enhance the quality of active brazing joints. However, it has been found that Al ion implantation can significantly increase the shear strengths of active brazing joints to average value 139 MPa, which is 30% greater than in non-ion implantation (107 MPa). It has also been found that ion implantation can improve the shear strengths of alumina–Nb inactive brazing joints. Maximum average shear strength of the inactive brazing joints can reach 43 MPa when Ni ions were used at an acceleration voltage of 55 kV in a dose of 2 × 1017 ions/cm2. Finally, the effects of ion implantation on alumina–Nb active and inactive brazing were discussed.