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A specialized CaO–Al 2 O 3 –SiO 2 (CAS) glass-ceramic was innovated to join SiC ceramics. The crystallization kinetics of the CAS glass was studied, revealing distinct anorthite precipitates in the CAS glass-ceramic. The impact of process parameter variations on microstructure and mechanical properties was studied. It revealed that post-joining crystallization heat-treatment could change the size and the content of crystals and significantly improve the shear strength of the joint. It was duly observed that a remarkable shear strength of 86 MPa was achieved when the joint was formed at the temperature of 1450 °C and treated at 1050 °C for crystallization. Notably, this exceptional mechanical endurance remained impressively high, maintaining a value of 85 MPa at 800 °C. Based on density functional theory calculations, it was confirmed that glass/C–SiC (0001) has a stronger interface bond than glass/Si–SiC (0001), resulting in a reliable joining at the glass/C–SiC (0001) interface for CAS glass and SiC. [ABSTRACT FROM AUTHOR]

Joining of SiC ceramics with a pre-oxidized or unoxidized surface and the subsequent mechanical properties have been studied using Y 2 O 3 –Al 2 O 3 –SiO 2 glass bonding method, and the mechanism of interface bonding was revealed. The joining parameter of interest was temperature from 1400 °C to 1500 °C for a dwell time 10 min. The microstructure, compositions, and interfacial properties were characterized via electron microscopy and X-ray diffractometry. A multiphase glass-ceramic interlayer mainly consisting of Y 2 Si 2 O 7 and mullite was formed in the joint, which possessed good thermal matching with the SiC substrate. Moreover, the softening temperature of glass-ceramic could exceed to 1200 °C. The joint obtained from the pre-oxidized SiC substrate exhibited a more reliable interface bonding than the unoxidized surface. A preferable shear strength of 48 MPa was achieved within 10 min at 1420 °C. The elemental diffusion at the interface and the chemical bonding between glass-ceramic and SiC contributed to a reliable SiC–SiC joint. [ABSTRACT FROM AUTHOR]

• A novel glass-ceramic interlayer was developed to join porous Si 3 N 4 to dense Si 3 N 4 ceramics. • The β-LiAlSi 2 O 6 /Mg 2 SiO 4 glass-ceramic interlayer and the dense infiltration layer were formed in the joint. • The shear strength of the joint reached 78 MPa, and it could still maintain 74 MPa up to 850 °C. In this work, we developed a new β-LiAlSi 2 O 6 /Mg 2 SiO 4 glass-ceramic interlayer to join dense Si 3 N 4 and porous Si 3 N 4 ceramics for high-temperature applications. The microstructure and phases of the joint were investigated using systematic analysis methods and the mechanism for the interfacial bonding was proposed. The double crystalline phases of β-LiAlSi 2 O 6 and Mg 2 SiO 4 precipitated in the joint seam during the joining process, forming a novel glass-ceramic interlayer with high crystallinity. Due to the good wettability of liquid glass on porous Si 3 N 4 , a gradient and dense infiltration layer was formed in porous Si 3 N 4 and reinforced it, which improved the mechanical strength of the whole joint. In this case, the shear strength of the joint reached 78 MPa, and it could still maintain 74 MPa up to 850 °C, which fully demonstrated the high-temperature resistance of the joint. [ABSTRACT FROM AUTHOR]

A novel CaO-Li 2 O-Al 2 O 3 -SiO 2 (CLAS) glass was developed for the joining of porous Si 3 N 4 and dense Si 3 N 4. A multiphase interlayer consisting of CaAl 2 Si 2 O 8 , LiAlSi 2 O 6 and CaSiO 3 phases was formed in joint, which possessed matched CTE with the Si 3 N 4 substrates. In addition, the infiltrated layer with bilayer structure in the porous Si 3 N 4 substrate was observed. The effects of joining temperature and cooling rate on microstructure, phase evolution and shear strength of joints were studied carefully. The results showed that the kinds of precipitated phases remained invariable with the joining temperature increased, but the crystallinity in the interlayer was improved remarkably as the cooling rate reduced. The maximum shear strength of 45 MPa was obtained when the joining temperature and cooling rate were 1100 °C and 5 °C/min, respectively. Moreover, fracture during the shear test occurred mainly within porous Si 3 N 4 side, indicating superior joining of dense Si 3 N 4 /glass-ceramic/porous Si 3 N 4. [ABSTRACT FROM AUTHOR]

A novel two-step joining method was adopted to achieve the reliable bond of dense Si 3 N 4 (D-Si 3 N 4) with porous Si 3 N 4 (P-Si 3 N 4) components for high temperature applications using Li 2 O-MgO-Al 2 O 3 -SiO 2 -B 2 O 3 glass-ceramic as interlayer. The joining process involved a pre-oxidation of D-Si 3 N 4 in air for a good wettability, followed by a joining process at 1240 °C–1300 °C for 10 min in vacuum. The microstructure evolution, interface structure, fracture characteristics and joining mechanism of the joints were elucidated. The β-spodumene solid solution based glass-ceramic was formed in the seam, which could effectively moderate the thermal expansion mismatch between interlayer and Si 3 N 4 substrates and ensure the high-temperature resistance of joint. Compared with one-step joining , two-step joining method could obtain more reliable D-Si 3 N 4 /glass-ceramic/P-Si 3 N 4 joints. A favorable shear strength of 43 MPa was achieved within 10 min at 1280 °C, which was 15 MPa (~54%) higher than that of the joints by one-step joining method. As a result, good CTE match as well as strong bonding to Si 3 N 4 substrates made the investigated glass-ceramic a suitable candidate for joining Si 3 N 4 ceramics. Unlabelled Image • Porous Si 3 N 4 was firstly joined with dense Si 3 N 4 using Li 2 O-Al 2 O 3 -SiO 2 -B 2 O 3 glass-ceramic interlayer; • Dense Si 3 N 4 was pre-fabricated a oxidation coating for the wettability and compatibility with glass-ceramic interlayer; • β-spodumene based glass-ceramic interlayer contributed to high-temperature resistance and appropriate CTE for the joint; • The room-temperature and high-temperature (850 °C) shear strengths were ~43 MPa and ~54MPa, respectively. [ABSTRACT FROM AUTHOR]

Brazing of Ti 2 AlC ceramics has been successfully performed using a pure Al filler metal, in the temperature range 1023 K–1173 K and with holding time ranging from 0 to 30 min. The microstructure of the Ti 2 AlC joints was studied, and the mechanical properties of the joints were evaluated by shear strength test. It is observed that the Al filler has weak effect on the stability of Ti 2 AlC substrate, and only a small amount of decomposition products including the TiC x and TiAl 3 compounds can be observed in the joints. In addition, the formation of an inter-diffusion layer in the Ti 2 AlC substrate is considered as the major brazing mechanism. The maximum shear strength of the Ti 2 AlC joints using the pure Al filler metal is 95 MPa, with an electrical conductivity of 2.21×10 6 S m −1 , after holding the sample at 1123 K for 10 min. [ABSTRACT FROM AUTHOR]

The microstructure evolution of Si 3 N 4 /316 L joint brazed with AgCuTi/Ag composite filler is investigated, and the typical microstructure of Si 3 N 4 /316 L joint is Si 3 N 4 /TiN+Ti 5 Si 3 /Ag-rich/Cu-rich+Fe 2 Ti, NiTi+Ag-rich+Fe-rich/316 L. Further research on the corrosion resistance of the joint is warranted to build the relationship between microstructure and corrosion behavior. It is noteworthy that corrosion behavior is more likely to occur at the interface of seam/316 L by SEM analysis. The residual stress on the 316 L substrate is also concentrated on this region, playing an important catalytic role in corrosion behavior. The joint presents a shear strength of 100 MPa and excellent corrosion resistance when it is brazed at 900°C for 15 min. Moreover, the diffusion kinetic process of Fe element in the interface of filler/316 L is studied based on the Boltzmann-Matano model, and the activation energy is obtained for about 468 kJ/mol. Although the addition of the Ag layer into the seam decreases the non-corrodibility of the 316 L substrate, however, the non-corrodibility of the joint is improved by transforming galvanic corrosion to uniform corrosion with the prolonged immersion time. Fig. 14. Residual stress distribution in the filler/316 L interface of Sample-T. [Display omitted] • The AgCuTi/Ag as composite filler is designed to braze Si 3 N 4 to 316 L, relieving the residual stress of joints. • The diffusion kinetic process of Fe element in the interface of filler/316 L is studied based on the Boltzmann-Matano model. • The relationship between microstructure evolution and corrosion behavior in the joint was investigated. • The corrosion mechanism is changed from the pitting of Cu to the uniform corrosion of 316 L. [ABSTRACT FROM AUTHOR]

[Display omitted] • The surface of SiC substrate was fabricated a ~ 2 μm thick oxidation coating by heat treatment; • The CLAS glass solder exhibited excellent wettability on the surface-oxidized SiC substrates, with contact angles of 33°; • A glass–ceramic interlayer with a micro-nano structure was formed in the joint seam after the joining process; • The joints showed an excellent mechanical property, with an optimal shear strength of 127 MPa at room temperature. A novel strategy was developed to join SiC ceramics via a two-step method (i.e., SiC surface was modified by pre-oxidation treatment before bonding) using CaO-Li 2 O-Al 2 O 3 -SiO 2 (CLAS) glass as the joining material. The wetting behavior, joint microstructure, bonding strength, fracture characteristics, and joining mechanism were investigated. Due to the formation of the SiO 2 layer on the SiC surface by the pre-oxidation, the wettability of CLAS glass solder on the SiC matrix was significantly improved and the interfacial bonding was also enhanced. The microstructure of the joint revealed that the nanoscale eutectic structure composed of wollastonite and spodumene and the rod-shaped anorthite with micron-size were the main products in the joint seam. Besides, the content and size of anorthite in the joints increased with the increase of the joining temperature. Compared with one-step joining, the two-step method can obtain more reliable SiC/SiC joints due to the strong interfacial bonding. As a result, the optimal shear strength of 127 MPa was achieved at a joining temperature of 1240 °C, which was 119% higher than that obtained by the one-step joining method. [ABSTRACT FROM AUTHOR]

The joint between C/C composites and liquid silicon infiltrated-C/SiC composites was achieved using a Si 10Zr (at. %) eutectic filler. The microstructure and mechanical properties of joints at different brazing temperature and holding time were characterized. The results showed that the melting filler infiltrated along the carbon fiber bundle gaps and formed SiC reaction layers at both interfaces. On the side of C/SiC composites, the residual silicon in the original base material dissolved into the molten Si 10Zr alloy during the brazing procedure. The phenomenon resulted in intense infiltration of the liquid filler into C/SiC composites, which formed a unique C/SiC-Si-ZrSi 2 multiphase-ceramic gradient structure. Excessive filler was squeezed out around the joint seam to form a fillet. The shear strength of the joint reached up to 37 MPa, with fracture occurrence in both substrates and the joint seam. Reliable bonding between C/C and C/SiC dissimilar composites was finally achieved. • The melting filler infiltrated along the carbon fiber bundle gaps and formed SiC reaction layers at both interfaces. • A unique C/SiC-Si-ZrSi 2 multiphase-ceramic gradient structure was formed on the side of C/SiC composites through reactive infiltration. • The shear strength of the joint reached up to 37 MPa, with fracture occurrence in both substrates and the joint seam. [ABSTRACT FROM AUTHOR]

• A novel of Zr-24Ni (at.%) filler was proposed to achieve the joining of SiC ceramic and Zircaloy-4. • The wetting behavior and interfacial reaction between the Zr-Ni filler and SiC substrate were characterized. • The effect of brazing temperature on the microstructure and shear strength of the SiC/Zircaloy-4 joint was discussed. • He ion irradiation behavior in SiC/brazing seam interface was studied for the first time using TEM. SiC ceramic was successfully brazed to Zircaloy-4 using Zr-24Ni (at.%) filler alloy for nuclear application. The wetting behavior and interfacial reaction between the Zr-Ni filler and SiC substrate were studied. The results showed that the Zr-Ni filler possessed excellent wettability (wetting angle ∼ 4°) on the SiC substrate, and the interfacial reaction products of ZrC and Zr 2 Si were formed. The effect of brazing temperature on the microstructure and shear strength of the SiC/Zircaloy-4 joint were investigated. When the brazing temperature was lower than 1060 °C, the interface reaction of the joint was weak and the joint was mainly composed of SiC/ZrC/Zr 2 Ni +Zr-based solid solution/Zircaloy-4. When the brazing temperature was higher than 1060 °C, the interface reaction was enhanced and the Zr 2 Si phase appeared in the joint. The maximum shear strength of the joint was 110 MPa at a brazing parameter of 1060 °C for 15 min due to the moderate interface reaction between filler and substrates. Moreover, the experiment of He ion irradiation on the joint at room temperature showed that no significant irradiation damage appeared for SiC, ZrC and Zr 2 Ni in the joints when the irradiation fluence was lower than 1 × 1016 ions/cm2. However, when the irradiation fluence was higher than 5 × 1016 ions/cm2, the transformation of SiC and Zr 2 Ni from crystalline into amorphous state was observed. As the irradiation fluence increased, microcracks appeared in SiC and ZrC due to the uncoordinated irradiation swelling between them. [ABSTRACT FROM AUTHOR]