Reactive air brazing of YSZ ceramic with novel Al2O3 nanoparticles reinforced Ag-CuO-Al2O3 composite filler: Microstructure and joint properties

The YSZ ceramic coatedwith a copper layer (similar to 5 mu m) was successfully reactive air brazed using novel Al2O3 nanoparticles (NPs) reinforced Ag-CuO-Al2O3 composite filler. The effects of Al2O3 NPs content on the interfacial microstructure and joint properties were investigated. When the content of Al2O3 NPs was 8 wt.%, YSZ joints obtained fine interfacial microstructure and optimal mechanical properties. The coefficient of thermal expansion of composite filler was calculated to be 16.26 x 10(-6) K-1, presenting a decline of 12.1% compared to that of AgCuO base filler. The hardness and modulus values of braze joint slightly increased to 2.6 GPa and 164 GPa, respectively, possessing a better ability to resist deformation. Consequently, the YSZ joint possessed a maximum shear strength of 60 MPa, which was 25 MPa (similar to 71%) higher than that of the joints brazed using Ag-CuO base filler. The leakage rate of YSZ-tube/AgCuO-8Al(2)O(3)/YSZ-block samples was measured to be 3.2 +/- 0.9 x 10(-10) Pa m(3) s(-1), which met the leakage rate requirements for vacuum tight components (less than 10(-9) Pa m(3) s(-1)). It implied that this novel method was an effective way to obtain hermetic YSZ joints. (C) 2016 Elsevier Ltd. All rights reserved.