Interfacial microstructure and improved wetting mechanism of SiO2f/SiO2 brazed with Nb by plasma treatment. (September 2017)

• Record Type: Journal Article
• Authors: Lin, Jinghuang; Ba, Jin; Liu, Yulin; Wang, Yiheng; Guo, Jiale; Luo, Dalin; Cai, Yifei; Mao, Deshun; Qi, Junlei; Feng, Jicai
• Is Part Of: Vacuum. Volume 143(2017)
• Page Start: 320
• Page End: 328
• Publication Date: 2017-09
• Subjects: Brazing -- Plasma treatment -- Mechanism -- Wettability -- Infiltration -- SiO2f/SiO2; Vacuum -- Periodicals; 621.55
• DOI: 10.1016/j.vacuum.2017.06.041
• Languages: English
• ISSNs: 0042-207X

Abstract

Abstract: Due to the poor wettability with AgCuTi and high residual stress, it is difficult to achieve high-strength brazed joint of SiO2f /SiO2 (quartz fiber reinforced silica) with metals. Herein, plasma treatment as an effective approach was conducted to modify the surface state of SiO2f /SiO2 for better wettability and high-strength brazed joints. Based on SEM, Raman, XPS and wetting experiment analysis, the mechanism of plasma treatment on the improved wettability of SiO2f /SiO2 with AgCuTi is proposed. Plasma treatment can coat thin carbon film and form C-Si bonding on the surface of SiO2f /SiO2, which both show good wettability with AgCuTi. Therefore, the contact angle was notably reduced from 131° to 45° with only 5min plasma treatment on the SiO2f /SiO2 . Afterwards, the effect of plasma treating time on the interfacial microstructure and mechanical property of SiO2f /SiO2 -Nb joints were investigated in detail. It was found that adjusting the plasma treating time can control the distance of brazing alloy infiltration. Further, the shear strength and the fracture morphologies were closely related with the distance of brazing alloy infiltration. The infiltration of AgCuTi at the SiO2f /SiO2 side can significantly increase the bonding areas and reduce residual stress, and thus enhance the mechanical properties of brazed joints. Highlights: Due to the good wettability with carbon or SiC, the addition of C and the formation of C-Si bonding can improve the wettability of SiO2f /SiO2 . Forming brazing alloy infiltration is helpful to enhance the mechanical properties. The maximum shear strength up to 60.5 MPa is achieved.