Cold joining of fused silica: Bonding pressure and surface roughness effects

Abstract Isostatic pressure of 300 MPa promoted the formation of strong bonds between fused silica pieces. The joining was performed using a 5 mol/l NaOH solution at room temperature for 20 minutes with and without an isostatic pressure. The as-received materials (with a roughness of 13.4 nm) joined with pressure resulted in a ∼ 40% increase of the shear strength (from 12.3 MPa to 17.73 MPa). An even more significant effect, 70% increase, was found for the sample with a higher surface roughness of 0.10 µm where the shear strength was as high as 15.21 MPa. Fourier-transform infrared spectroscopy analysis and SEM suggested that the applied pressure promoted the formation of a strong bond. Unlike pressure-less joining, the joints produced with pressure retained their integrity after being exposed at 1000 °C