To meet the high demand for ceramic/superalloy composite structural components in various fields, an advanced high-temperature adhesion technique was firstly developed by preparing a novel inorganic/organic hybrid adhesive suitable for ZrO 2 and TC4 . Chemical bonding started to work at ∼600°C, and became the crucial bonding mechanism at elevated temperatures. The formation of ZrSiO 4 and Ti 5 Si 3 at the interfaces of two substrates not only increased the interfacial connection strength , but also formed two gradient layers with a size of ∼2 μm to effectively alleviate the difference of composition and performance between the adhesive and substrates. In the temperature range of 500–900°C, the matching degree of CTE among ZrO 2 , adhesive and TC4 is higher, and the maximum difference does not exceed 3×10 -6 K -1 . Meanwhile, the formation of a composite structure containing various ceramics (ZrO 2 , SiC and ZrB 2 ) and intermetallics (Ni–Si, Al–Ni), and the improvement of structural compactness of adhesive from 500 to 900°C greatly improved the bonding strength to the maximum value of 31.4 MPa at 900°C. Also, the adhesive pretreated at 900°C showed good thermal cycling resistance, and the strength was still higher than 15 MPa after 50 cycles. For cured adhesive, when used directly in an extreme environment, it can provide bonding strength not less than 5 MPa in the whole temperature range, indicating that the adhesive possessed potential emergency repair convenience. This work significantly broadened the application of high-temperature-resistant adhesion technology in the connection of dissimilar ceramics and alloys.
Xiaoyang Wang,Chun Li,Qihan Zhou,Mingshen Li,Mushi Zheng,Junlei Qi,Xiaoqing Si,Jian Cao
One of the critical challenges for the protonic ceramic fuel cell stack is sealing electrolytes and interconnects. However, the traditional Ag CuO sealant will aggravate the oxidation along the interconnect surface and result in brittle compound layers at the BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3- δ (BZCYYb) electrolyte interface. The present work demonstrates that a silver particle interlayer with high dislocation density can be adopted to join BZCYYb electrolyte to the interconnect (AISI 441 stainless) in air instead of traditional Ag CuO sealant. Elevating temperatures result in a sufficient bonding at the Ag/BZCYYb interface, and a defect-free joint is obtained at 950 °C. Atomic bonding at Ag/BZCYYb interface is confirmed by TEM. Also, a dense and thin oxide layer (2–3 μm) is formed along the AISI 441 interface. Ag particles in the interlayer provide the main driving force for the sintering joining. The massive dislocations promote the recovery and recrystallization of the Ag interlayer, as well as the interdiffusion of BZCYYb/Ag. After aging in the wet oxidizing atmosphere at 600 °C for 300 h, joints remain intact and dense, indicating superior oxidation resistance and aging performance. Besides, the joint shear strength (25.3 MPa) is 59 % higher than that of the joint brazed by traditional Ag CuO.
Negative thermal expansion (NTE) materials can offset the high expansion of metal brazing alloys, and play a key role in alleviating the residual stress and improving the mechanical properties of the joint . However, in Sc 2 W 3 O 12 reinforced AgCuTi composite filler, the strong interfacial reaction between active Ti and Sc 2 W 3 O 12 has become a bottleneck restricting the NTE behavior of Sc 2 W 3 O 12 . Herein, a novel strategy is proposed by designing a carbon barrier layer between active filler and Sc 2 W 3 O 12 materials. Under the guidance of experimental results and theoretical analysis, the interface evolution mechanism is proposed. The results show that the carbon barrier layer increases the diffusion path of Ti atoms and weakens the interfacial reaction. With the help of carbon barrier layer, Sc 2 W 3 O 12 gives full play to its NTE behavior during brazing, and the retention rate increases from 65.8% to 97.6%. Consequently, a highest shear strength of ∼77 MPa is achieved in the C/SiC-GH3536 joints by the designed composites filler, which is 1.3 times higher than that without carbon barrier layer and 3.2 times higher than that of AgCuTi filler. Our work opens the way for expanding the application of NTE materials in brazing process, and also provides new insights for the development of low-CTE composites.
危险品化学品经营许可证（带存储）