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Joint homogenization during transition metal carbides ceramic bonding has attracted much attention as a technique to increase the service temperature and relieve the residual stress for various high-temperature applications. In this work, homogeneous joints of ZrC0.85 ceramic were obtained by diffusion bonding using single Nb and multiple Ti/Nb/Ti as the interlayer. The effect of interlayer composition, bonding temperature and holding time on the microstructure of the joints was investigated. The effect of Nb and Ti on the composition homogeneity and the formation of Kirkendall voids in the ZrC0.85 joints was also discussed. When using single Nb as the interlayer, the homogenization of the joints can be achieved at a bonding temperature of ∼1500 °C and holding for 1 h and no Kirkendall voids were observed when further increasing the bonding temperature to 1600 °C because of the good mutual solubility of NbCx and ZrCx and the relative moderate diffusion rate of Nb. However, severe Kirkendall effects were observed at a higher temperature of 1700 °C, which would deteriorate the high-temperature performance of the joints. The adoption of Ti/Nb/Ti further minished the diffusion rate difference of the interfacial elements through the formation of TiCx phase. As a result, only a few Kirkendall voids were formed at 1700 °C. Nano-hardness of the resultant homogeneous joints was comparable to that of the ZrC0.85 ceramic due to their similar composition. This study shows that active diffusion bonding based on interlayer design for homogeneous joints could pave a new way to join transition metal carbides.

The wettability and high-temperature mechanical properties of porous BN/Si3N4 ceramics brazed with SiTi22 (wt. %) filler were studied. It is manifested that SiTi22 filler presents remarkable wetting and spreading capabilities on the porous BN/Si3N4 ceramic surface. An interfacial reaction layer is generated at the interface, and the thickness of the reaction layer initially grows and subsequently remains constant with the escalation of temperature. Carbon coating modification is beneficial to the wettability and high-temperature mechanical properties of porous BN/Si3N4 ceramics. The wetting driving force is mainly controlled by the interfacial reaction at the three-phase line of the wetting front. The mechanical properties of the carbon-coated joints are significantly enhanced in comparison with uncoated joints. The joint strength attains a maximum value of roughly 73 MPa in the shear test implemented at 800 °C. The strength of the joint is significantly enhanced mainly due to the TiN0.7C0.3 particles that consume energy by changing the crack propagation direction, and the SiC nanowires strengthen the connection by bridging.

Joining of dissimilar superalloys is indispensable in the field of advanced manufacture, achieving a high-quality joint while minimizing thermal damage to substrates during diffusion bonding is a critical but challenging pursuit. A low-temperature and rapid diffusion bonding strategy enabled by pulsed current was proposed to resolve this challenge. Attributed to the enhanced interfacial plastic-deformation and carbide-precipitation, pulsed current rapidly achieved a nanovoid-free and tight joint of GH3536 and GH5188 superalloys at a low temperature of 850 °C for 5 min. Meanwhile, the rapid joining process prevented the interfacial carbides from coarsening and allowed their elimination in a short-term heat-treatment. The carbide dissolution, recrystallization of highly-deformed grain and cross-interface grain growth during heat-treatment significantly enhanced the joint performance, the heat-treated joint exhibited a high ultimate strain of 25.5 % and a tensile strength comparable to the raw GH3536.

With the swift advancement of wearable electronics and artificial intelligence, the integration of electronic devices with the human body has advanced significantly, leading to enhanced real-time health monitoring and remote disease diagnosis. Despite progress in developing stretchable materials with skin-like mechanical properties, there remains a need for materials that also exhibit high optical transparency. Supercapacitors, as promising energy storage devices, offer advantages such as portability, long cycle life, and rapid charge/discharge rates, but achieving high capacity, stretchability, and transparency simultaneously remains challenging. This study combines the stretchable, transparent polymer PEDOT:PSS with MnO2 nanoparticles to develop high-performance, stretchable, and transparent supercapacitors. PEDOT:PSS films were deposited on a PDMS substrate using a spin-coating method, followed by electrochemical deposition of MnO2 nanoparticles. This method ensured that the nanosized MnO2 particles were uniformly distributed, maintaining the transparency and stretchability of PEDOT:PSS. The resulting PEDOT:PSS/MnO2 nanoparticle electrodes were gathered into a symmetric device using a LiCl/PVA gel electrolyte, achieving an areal capacitance of 1.14 mF cm−2 at 71.2% transparency and maintaining 89.92% capacitance after 5000 cycles of 20% strain. This work presents a scalable and economical technique to manufacturing supercapacitors that combine high capacity, transparency, and mechanical stretchability, suggesting potential applications in wearable electronics.

Joining single crystal superalloy with polycrystalline superalloy has important applications in the aerospace industry. Here, the IC10 single crystal superalloy to GH536 polycrystalline superalloy was diffusion brazed using a BNi-2 filler alloy. The effects of bonding temperature and time on the microstructure evolution and mechanical properties of the GH536/IC10 joints were investigated in detail. The results elucidated that the joint brazed at a lower temperature and time (i.e., 1050 °C/30min) was composed of diffusion affected zone (DAZ), athermal solidification zone (ASZ), and isothermal solidification zone (ISZ). The secondary precipitates formed in DAZ were Cr-rich borides, Cr–Mo borides, and Cr–Mo–W borides. The ASZ was made up of Cr-rich borides, Ni-rich borides, Ni–Cr borides, and Ni-based solid solutions. These borides with high hardness were the potential source of cracks and caused the joints to fracture under a lower load. Raising bonding temperature and time gradually eliminated Ni-rich borides in ASZ and Cr-rich borides in DAZ, and improved the shear strength.

In the evolving landscape of portable electronics, there is a critical demand for components that meld stretchability with optical transparency, especially in supercapacitors. Traditional materials fall short in harmonizing conductivity, stretchability, transparency, and capacity. Although poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) stands out as an exemplary candidate, further performance enhancements are necessary to meet the demands of practical applications. This study presents an innovative and effective method for enhancing electrochemical properties by homogeneously incorporating Ru(III) into PEDOT:PSS. These Ru(III) PEDOT:PSS complexes are readily synthesized by dipping PEDOT:PSS films in RuCl3 solution for no longer than one minute, leveraging the high specific capacitance of Ru(III) while minimizing interference with transmittance. The supercapacitor made with this Ru(III) PEDOT:PSS complex demonstrated an areal capacitance of 1.62 mF cm−2 at a transmittance of 73.5%, which was 155% higher than that of the supercapacitor made with PEDOT:PSS under comparable transparency. Notably, the supercapacitor retained 87.8% of its initial capacitance even under 20% tensile strain across 20,000 cycles. This work presents a blueprint for developing stretchable and transparent supercapacitors, marking a significant stride toward next-generation wearable electronics.

AgCu+TiH2+Nb filler was newly-designed to braze Ti2AlNb and SiBCN. The Ag–Cu melt firstly filled the interfacial gaps and then solidified into refractory Ag(s,s) via Ti–Cu interaction, while Nb refined the brittle compounds and relieved the residual stresses well. The obtained joint exhibited a shear strength of 73 ± 10.2 MPa and 81.7 ± 9.5 MPa at room temperature and 600 °C respectively, which is 3.1 and 1.7 times of that with AgCu. No softening occurred at 600 °C and the strength remained 24 ± 1.4 MPa at 800 °C. The proposed method provides a new strategy for preparing high-temperature joint at low temperature, to address the issues of poor thermal resistance as well as huge residual stresses and excessive formation of brittle phases.

Ultrasonic Impact Treatment (UIT) was performed to improve the corrosion resistance of 2219 aluminum alloy friction stir welding (FSW) joints. Results showed that the coarse grains on near surface of FSW joints were obviously modified and refined after UIT, and the thickness of the modified layer of different sub-regions was ranged from 90 to 120 μm. UIT increased intergranular corrosion resistance of 2219 aluminum alloy FSW joints in salt spray corrosion atmosphere. Free-corrosion potential of heat-affected zone (HAZ), which presented the worst corrosion resistance, was increased from −0.653 to −0.628 V, and the corrosion current density was decreased from 7.48 to 6.18 mA cm−2. The sensitivity index of stress corrosion cracking (SCC) of the joints was decreased from 0.139 to 0.129 in 3.5% NaCl solution after UIT, and the risk of crack initiation during SCC process was significantly inhibited. UIT improved the SCC resistance of 2219 aluminum alloy FSW joints by surface plasticity improvement, grain refinement and precipitates dissolution and redistribution.

We designed a composite filler beginning with becoming light elements to be the main diffusing elements and (ii) controlling the diffusion of the light elements. It was achieved by establishing chemical potential and supercooling gradients and shortening the diffusion distance. As a result, a transient liquid phase bonding (TLP) composite joint with hedgehog-like reinforcements and a ductile matrix was obtained. The room-temperature (RT) shear strength of the joint produced at 460 °C for 30 min was up to 84 MPa, and it had a strength of 30 MPa at 600 °C. The hedgehog-like” reinforcements with finer or longer whiskers can provide a better load transfer effect. The progressive phase formation around NiTi was induced by the large supercooled liquid, wherein either the fastest-solidified region or the deepest-supercooled liquid served as a barrier for metallic atoms. Consequently, the lower supercooling and higher Si chemical potential in the farther region enable Si to directionally diffused towards the NiTi. This study offered a novel filler feasible for most ceramic/metal systems with the goals of low-temperature joining and high-temperature using and controllable product distribution; and this idea can be extended to develop other systems.

In this study, we proposed a new method to prepare yttrium iron garnet/yttrium iron garnet (YIG/YIG) functional joint via in-situ synthesis of novel Co2FeO4 needle-like phases. It is found that the formation of the Co2FeO4 needle-like phases was controlled by “two-step heterogeneous nucleation”: (i) CoO nanoparticles acted as the preliminary heterogeneous nucleation particle, reacting with O2 to form Co3O4 phase; (ii) The surface of Co3O4 phase acted as the subsequent heterogeneous nucleation interface, atoms stacked along the (220) crystal plane of Co3O4 to form Co2FeO4 phase. Fe3+ diffused into the glass matrix which is rich in O2−, participating in the reaction with Co3O4 and CoO. The Co2FeO4 nuclei grew into needle-like phases along the [001] orientation. The Co2FeO4 needle-like phases exhibited favourable mechanical property and magnetism according to the nanoindentation and magnetic force microscopy (MFM) analysis. And the shear strength of YIG/YIG joint reinforced by Co2FeO4 needle-like phases could reach 72 MPa. The investigation supplies a new synthetic idea of Co2FeO4 magnetic needle-like phases, which has significant application potential for the structural and functional integration in electromagnetic field.

Bismuth-borate glass, 40Bi2O3–60B2O3 (mol.%), was prepared and acted as a braze to join sapphire in air. Ahead of brazing, basic properties of glass were investigated, including structure and thermal parameters. The thermal expansion test showed that CTE of glass was 8.4 × 10−6/°C in period from 20 to 450 °C, suggesting a good thermal compatibility with sapphire. Bi45BO69 was the main crystalline phase in glass according to DSC analysis [BiO6], [BO3] and [BO4] were major units in 40Bi2O3–60B2O3 glass on the basis of FT-IR spectra analysis.In addition, the wetting behavior of the 40Bi2O3–60B2O3 glass on the sapphire substrate was favourable. Thereafter, sapphire plates were joined at 700 °C for 0 and 20 min, respectively. The results showed that Al4B2O9 whiskers grew in joint when holding for 20 min due to a reaction between 40Bi2O3–60B2O3 glass braze and sapphire. The shear strength was improved greatly as a result of Al4B2O9 whiskers’ appearance.

Uniform and fine in-situ short-fiber/particle hybrid reinforcements were obtained in a SiCf/SiC composite/Ni-based superalloy joint by using a novel AuCuTiB/Mo/AuCuTiB composite filler. The growth of in-situ phases showed a strong dependence on the numbers of nucleation sites and metal atoms on the ceramic side. Inadequate brazing conditions adversely affected the formation of indirect TiB whiskers, and excessive brazing conditions induced an accumulation of metal atoms. As a result, the in-situ phases switched from Ti5Si3 + TiC to Ti5Si3 + Ni + TiB + TiC, and to (Ni, Ti)-(Si, C) + TiB with increasing brazing conditions. The size, type, and composition of the in-situ phases were effectively controlled by adjusting the brazing conditions (B content, brazing temperature, and holding time). In light of this, the shear strength of the joint was optimized at 124.9 MPa. The excellent mechanical performance was ascribed to (i) a suitable interfacial layer and (ii) the effective stress relief of in-situ phases and ductile/rigid/ductile multiple layers. Moreover, the joint exhibited mechanical stability at 973 K because the in-situ phases can serve as a high-temperature resistant second structure.

The wetting and brazing of Y3Fe5O12 (YIG) ceramics with a Ag–8CuO–2TiO2 filler was investigated for the first time. For comparison, the wettability of a Ag–10CuO filler on YIG ceramics was similarly investigated. The Ag–8CuO–2TiO2 filler has an equilibrium contact angle of approximately 31 °C on the YIG substrate at 1000 °C; thus, its wettability is excellent. Moreover, its wettability exceeds that of Ag–10CuO. The microstructure and the interfacial structure between the filler and the substrate were determined using scanning electron microscopy, X-ray diffraction, EPMA and transmission electron microscopy. The liquid Ag–8CuO–2TiO2 filler can react with the YIG substrate by forming continuous Y2Ti2O7 layers with dotted CuFe2O4 and promote the wetting behavior and bonding performance. The average shear strength could exceed 30 MPa for the joints at a brazing temperature of 1000 °C. As rupture occurred adjacent to the seam at the ceramic side, the strengths of the interfaces were characterized via nanoindentation. The hardness of the interface with doped TiO2 exceeds that of Ag–10CuO, which is strengthened by the dotted CuFe2O4 among Y2Ti2O7.

Borate based glass, 25Bi2O3–75B2O3 (mol.%), was employed as a braze to join sapphire in an atmospheric environment. The crystallization behaviour as well as the crystallization kinetics of the glass during the heating process were investigated in a variety of ways. Wetting tests were conducted to research the wetting and spreading performances of the glass on the surface of sapphire prior to joining. Furthermore, sapphire joints were reliably obtained under various joining parameters. The dependence of the microstructural evolution and mechanical performance of sapphire joints on temperature and dwell time were also explored. The research results indicate that 25Bi2O3–75B2O3 glass possesses outstanding glass-forming ability and excellent wettability on the surface of sapphire. Bi6B10O24 crystalline phases were produced in the seam. The width of the joint as well as the quantity of Bi6B10O24 crystals increased at first and then decreased with the extension of dwell time. Simultaneously, the shear strength of the joints had a tendency to improve gradually and then diminish with the rise in brazing temperature. The maximum strength of the joints (49.3 MPa) was obtained by brazing at 700 °C for 20 min.

A new low-temperature magnetic Bi2O3-CoO-Fe2O3-B2O3 (BCFB) glass was designed to acquire magnetic yttrium iron garnet (YIG/YIG) joint. This paper investigated the thermal behavior of BCFB glass and its wettability on YIG. The microstructural evolution, mechanical and electromagnetic properties of YIG/YIG joint were systematically studied. CoFe2O4 nuclei were gradually formed, growing up into nano-scale CoFe2O4 crystals in the glass seam. Meanwhile, some CoFe2O4 crystals grew up excessively by swallowing nano CoFe2O4, reaching microns. YBO3 reaction layer was formed and grew into YBO3 whiskers at the interface of YIG/glass with the brazing temperature increasing. The joint shear strength increased, reaching a maximum of 85.2 MPa at 775 °C under the collaborative reinforcement of well-integrated interface and glass-ceramic seam, then declined due to the aggravative reaction. The dielectric constant of YIG/YIG joints decreased with the brazing temperature increasing, varying from 18.5 to 16.6 at the frequency of 10 MHz. AFM/MFM and VSM analyses indicate that the glass seam performed magnetic property. The saturation magnetization of BCFB glass reached about 4.2 emu/g and 5.0 emu/g heat-treated at 750 °C and 775 °C, respectively, which could effectively enhance the magnetism of the glass seam.

5A06 aluminum alloy bar was brazed by temperature gradient transient liquid phase diffusion welding (TG-TLP). The effects of brazing temperature on the microstructure and the tensile strength of the brazing joints were investigated. Three typical brazing filler alloys (1# Al-20Cu-6Si-2Ni, 2# Al-10Cu-10Si-3Mg-1Ga, and 3# Al-6Cu-10Si-2Mg-10Zn) were prepared by smelting, and TG-TLP diffusion bonding was carried out at different brazing temperatures (550 °C~590 °C). The results show that with the increase in brazing temperature, the oxide films at the brazing junction are easier to be broken and dispersed, but the oxidation extent will also increase. The oxidation products enriched were mainly Al2O3 and SiO2 at the brazing junction. There are different optimal brazing temperatures corresponding to the different filler alloys. For 1#, the optimal temperature is 570 °C; for 2# is 580 °C; for 3# is 580 °C. For 1# brazing joints, the maximum tensile strength was 113 MPa, and for 2# was 122.4 MPa. Under the experimental conditions of this study, the maximum tensile strength of the TG-TLP joint is 147.4 MPa of 3# brazing sample (at 580 °C), which has increased by 30% and 20% compared to 1# and 2# respectively. The nickel-rich phase at the interface (of 1# brazing filler) could form a brittle fracture, which was unfavorable for interface bonding. For TG-TLP brazing of 5A06, the filler alloy with high Al:Cu ratio (12:1 wt.%) needs a sufficient temperature gradient to exert the film-breaking effect, while the filler alloy with low Al:Cu ratio (3.6:1 wt.%) needs to accurately control its brazing temperature to avoid excessive oxidation. There are many research gaps in the influence of brazing material composition and brazing temperature on the microstructure and mechanical properties of 5A06 aluminum alloy TG-TLP joints. The research results can provide a theoretical basis for formulating the TG-TLP brazing specification of 5A06 aluminum alloy.

To combine the advantages of ductile fillers and composite fillers and alleviate residual stress in joints between ZrB2-SiC ceramics (ZS) and TC4-TiBw composites, a novel multi-layered joint architecture composed of a layer of clustering SiC at the center of the joint (L-C-SiC) and two ductile layers without SiC particles bordering both substrates (L-DS) was designed. To achieve this, SiC particle skeletons with continuous micro-channels (SSCC) were integrated with AgCu filler as an interlayer. The effects of SSCC porosity and brazing temperature on joint microstructure and mechanical properties were investigated. In particular, the braze/ZS and braze/SSCC interfaces were analyzed through X-ray diffractometry (XRD), transmission electron microscopy (TEM), and wavelength-dispersive spectroscopy (WDS). The residual stress was also evaluated. The results indicate that increasing the brazing temperate improved the infiltration into the SSCC and promoted the SSCC/braze interface reaction (was detrimental to the SiC particle skeleton). Reducing the SSCC porosity changed the thicknesses of the two L-DSs and enhanced the inhomogeneity of the SSCC/braze interface reaction (induced a shear stress in L-C-SiC). For brazing with an interlayer of 30% porosity at 820 °C, the joint shear strength reached a maximum of ~41.2 MPa, mainly due to the construction of the multi-layered joint architecture.

Ni-(3~10) Ta and Ni-(3~10) Y alloys were fabricated by vacuum arc melting. The oxidation resistance of the alloys was studied by cyclic and isothermal oxidation tests at 800 °C in static air. The present work focused on the investigation of the effects of the alloying elements (Ta and Y) on the oxidation behavior of Ni-based alloys. The oxidation behavior of alloys was evaluated by mass gain, composition, as well as the microstructure of oxidized products. The experimental results indicated that Ta at a low content (3 wt %) had a positive role in enhancing oxidation resistance by decreasing the oxygen vacancy concentration of the oxide layer to prevent the inward diffusion of oxygen during oxidation, and the mass gain decreased from 2.9 mg·cm−2 to 1.7 mg·cm−2 (800 °C/200 h), while Y (3~10 wt %) degraded the oxidation resistance. However, it is worth mentioning that the pinning effect of Y2O3 increased the adhesion between the substrate and oxide layer by changing the growing patterns of the oxide layer from a plane growth to fibrous growth. Among the results, the bonding of the substrate and oxide layer was best in the Ni-3Y alloys.

Micron sizes solder metallurgical joints have been applied in a thin film application of anisotropic conductive film and benefited three general advantages, such as lower joint resistance, higher power handling capability, and reliability, when compared with pressure based contact of metal conductor balls. Recently, flex-on-board interconnection has become more and more popular for mobile electronic applications. However, crack formation of the solder joint crack was occurred at low temperature curable acrylic polymer resins after bonding processes. In this study, the mechanism of SnBi58 solder joint crack at low temperature curable acrylic adhesive was investigated. In addition, SnBi58 solder joint cracks can be significantly removed by increasing the storage modulus of adhesives instead of coefficient of thermal expansion. The first approach of reducing the amount of polymer rebound can be achieved by using an ultrasonic bonding method to maintain a bonding pressure on the SnBi58 solder joints cooling to room temperature. The second approach is to increase storage modulus of adhesives by adding silica filler into acrylic polymer resins to prevent the solder joint from cracking. Finally, excellent acrylic based SnBi58 solder joints reliability were obtained after 1000 cycles thermal cycling test.