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The interfacial behaviors and mechanism of ZrC–SiC and Ti system under pulsed electric current were systematically analyzed in this study. The results showed that the dominant products of Ti and ZrC–SiC composite interface were TiC x and Ti 3 Zr 3 Si 3. The former was originated from the interaction of Ti and interfacial ZrC, while the latter resulted from the grain-boundary diffusion of inner Si and Zr atoms towards Ti interlayer. Meanwhile, the reaction of Ti and interfacial SiC produced TiC x and Ti 5 Si 3 C, and Ti 5 Si 3 C would transform into Ti 5 Si 3 and TiC x in the Ti-enriched environment. More interestingly, pulsed current could significantly promote the interfacial reactions, the combination of experimental analysis and theoretical calculation indicated that the current-related mechanisms involved (i) quick grain-boundary diffusion of Zr and Si benefited from the local joule-heating, (ii) strengthened volume diffusion of C element by the increasing lattice defects and (iii) additional diffusion flux towards Ti interlayer induced by the temperature gradient in micro-scale. Additionally, the coupled influence of skin effect and electromigration were studied, the results revealed the skin effect caused a local high current density at the sample edge, which triggered the directional movement of carbon vacancies thus the preferential growth of TiC x phase in the anode, but the microstructure was homogenous in the majority area due to the exponential distribution of current. • Interfacial behaviors and mechanism of ZrC–SiC and Ti under pulsed current were revealed. • Reaction pathways of ZrC–SiC and Ti were disclosed via TEM analysis. • Reaction kinetic was improved by several current-related mechanisms. • High current density at sample edge caused preferential growth of TiC x. [ABSTRACT FROM AUTHOR]

[Display omitted] • Computationally analyze atomic diffusion in transient liquid phase bonding joints. • Design a composite filler via the supercooling and chemical potential gradients. • Study the mechanism of progressive solidification around the Si-absorber phases. • Make the joint produced at 430–490 °C for 30 min to be effective at 600 °C. 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. [ABSTRACT FROM AUTHOR]

A direct method to construct a gradient interfacial structure was developed for the Ni-based superalloy (GH3039) and SiC f -SiC composite brazed joint using a high-temperature and ductile AuCuV filler. The interfacial structure and reaction products under different brazing temperature, as well as their effect on the joint mechanical properties were studied. Compared with the SiC fiber, the SiC matrix exhibited a rapid kinetical characteristic when reacted with the active elements dissolved from GH3039. As the temperature reached 1050 °C, the quick and selective decomposition of SiC matrix provided an artificial channel for the infiltration of molten alloy, and with the further increase of temperature, the SiC fibers in infiltration region gradually converted into the fiber-like Cr 3 C 2 phase. As a result, a joint interface with multi-layer structure was formed in one step. Through forming a reinforced interfacial structure, the maximum shear strength of joint at room temperature and 700 °C reached 44.3 ± 5.8 MPa and 38.7 ± 4.5 MPa, respectively, which are nearly 3.5 and 2.5 times of that with a mono-layer structure. The enhancement in joint performance was attributed to the increased bonding area, enhanced pinning effect and reduced thermal stresses benefited from the gradient interface. • A gradient brazed joint of SiC f -SiC and Ni-based superalloy was directly constructed. • The SiC matrix exhibited a rapid reaction kinetic than the SiC fibers. • SiC matrix decomposition and liquid infiltration led to a multi-layer joint structure. • Gradient joint showed an excellent shear strength at ambient and high temperature. • Reduced residual stress and enhanced interfacial bonding contributed to joint performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new low-temperature magnetic 56Bi 2 O 3 -12CoO-12Fe 2 O 3 -20B 2 O 3 (BCFB) glass was designed to join yttrium iron garnet (YIG) ferrite. • The formation process of nano-scale and micro-scale CoFe 2 O 4 crystals were revealed. • The microstructure evolution and formation process of yttrium iron garnet (YIG/YIG) joint were systematically studied. • The saturation magnetization of the glass heat-treated at 775 °C reached 5.0 emu/g and the joint shear strength reached 85.2 MPa. A new low-temperature magnetic Bi 2 O 3 -CoO-Fe 2 O 3 -B 2 O 3 (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. CoFe 2 O 4 nuclei were gradually formed, growing up into nano-scale CoFe 2 O 4 crystals in the glass seam. Meanwhile, some CoFe 2 O 4 crystals grew up excessively by swallowing nano CoFe 2 O 4 , reaching microns. YBO 3 reaction layer was formed and grew into YBO 3 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. [ABSTRACT FROM AUTHOR]

A novel two-step joining technology (pyrolysis and C-Si reaction bonding) was used to prepare the SiC/SiC joints with SiC nanowire reinforcements. The microstructure and phase composition of joining layers and joints were characterized, and the effects of pyrolysis temperature, SiC particle size, polycarbosilane content and filler ratio (C/SiC) were investigated. The results indicated that when the temperature was lower than melting point of catalyst, the formation mechanism of SiC nanowires was vapor-solid growth (VS); conversely, the formation mechanism was vapor-liquid-solid growth (VLS). With the increase of SiC particle size, the quantity and diameter of SiC nanowires increased and the thickness of interlayer was slightly smaller. The higher the polycarbosilane content, the thinner the as-prepared interlayer would be. The phases of joints consisted of 6H-SiC and the mixture of 3C-SiC and free Si. The highest flexural strength of joined samples can reach 289 ± 60 MPa and 368 ± 44 MPa at room temperature and 1200 °C, respectively. [Display omitted] • SiC ceramics were successfully joined using SiC nanowires reinforced C-Si reaction bonding technology. • SiC nanowires were in-situ incorporated into SiC/SiC joints using preceramic polymer slurry. • The flexural strength of the joints with SiC nanowire reinforcement can reach 289 ± 60 MPa and 368 ± 44 MPa at room temperature and 1200 °C, respectively. [ABSTRACT FROM AUTHOR]

Bismuth-based glasses doped with different CoO contents were designed to realize the in-situ growth of Co 2 FeO 4 whiskers in YIG/YIG joint. The microstructure, mechanical and dielectric properties of the joints were systematically investigated. The optimized processing joint with 23 mol% CoO doping, brazed at 725 °C for 15 min, under bonding pressure of 6 kPa was achieved. And the shear strength of joint reached a maximum of 72 MPa, which is attributed to the increased number and optimized spatial distribution of Co 2 FeO 4 whiskers. The in-situ Co 2 FeO 4 whiskers acted as effective hard phases in the glass matrix. The shear strength of YIG/YIG joint was enhanced by the crack propagation deflection and pulling out result from Co 2 FeO 4 whiskers. The dielectric constant of YIG joints decreased from 16.2 to 15.3 at the frequency of 10 MHz, which is closer to that of the original YIG material with the CoO doping increasing. The dielectric loss tangent increased slightly with the growth of Co 2 FeO 4 whiskers due to the hole hopping between Co3+⇔Co2+ ions. The effective bonding of YIG materials has broad application prospects for the integration of ferrite microwave devices. • Bismuth-based glass doped with different CoO nanoparticles content is designed to realize the in-situ growth of Co 2 FeO 4 whiskers. • The effect of the CoO doping on the microstructure, mechanical and dielectric properties of YIG ferrite joint are systematically investigated. • The processed joint with maximized CoO doping, minimized bonding temperature and optimized Co 2 FeO 4 spatial distribution is achieved. • The strengthening mechanism of Co 2 FeO 4 whiskers is revealed. [ABSTRACT FROM AUTHOR]

To combine the advantages of ductile fillers and composite fillers and alleviate residual stress in joints between ZrB 2 -SiC ceramics (ZS) and TC4-TiB w 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. Unlabelled Image • SiC particles clustered away from both substrates in joint. • Ductile layers without SiC particles bordered on both substrates. • Multi-layered joint architecture was achieved. • Multi-layered architecture mitigated residual stress in joints. • This design combined advantages of ductile fillers and composite fillers. [ABSTRACT FROM AUTHOR]

• Longer time intervals increased the contents of lath martensite in DLD 12CrNi2. • Optimized time intervals restrained the formation of a Widmannstätten structure. • The relationship between time intervals and microstructure were obtained. • Optimized time intervals enhanced layer strength via martensitic strengthening. Nuclear power emergency diesel engine crankshafts are commonly fabricated using 12CrNi2 low-alloy steel. Direct laser deposition (DLD) may address conventional manufacturing issues associated with cost, long lead time, and design complexity. The idle time between deposited layers significantly affects the mechanical properties of the deposited materials. To date, the influence of inter-layer idle time on microstructural evolution and mechanical properties of DLD 12CrNi2 steel has not been studied in detail. In this study, we have designed different idle times between deposited layers or tracks to investigate the effect of idle time on the microstructural evolution and mechanical properties of DLD 12CrNi2 samples. The results indicate that sample S3 fabricated using a scanning strategy consisting of 10 s dwelling between tracks with 2 min between layers presented the most optimum combination of ultimate tensile strength (1007 MPa) and elongation (19.3%). This is mainly because sample S3 had a higher proportion of martensite due to the higher cooling rate of the upper layers than other samples. This paper provides experimental data and analysis to understand how the microstructural evolution and mechanical properties of DLD 12CrNi2 steel are impacted by different idle times between layers or tracks. [ABSTRACT FROM AUTHOR]

Bismuth-based glasses doped with MgO nanoparticles were designed to realize the in situ growth of MgFe 2 O 4 whiskers with the aim of improving the mechanical and magnetic properties of YIG/YIG joints. The microstructure of the joints and the formation mechanism of MgFe 2 O 4 whiskers were systematically investigated, as well as the mechanical and magnetic properties. The MgFe 2 O 4 nuclei grew along the [001] orientation to form MgFe 2 O 4 whiskers. The shear strength of YIG/YIG joints increased with an increase in doping of MgO nanoparticles, reaching a maximum of 67.5 MPa for the joint brazed with Bi25-21MgO. It indicated that MgFe 2 O 4 whiskers play an important role in strengthening the joints. The magnetic force microscopy (MFM) and vibrating sample magnetometer (VSM) results indicated that the magnetic properties of the brazing seam improved with the growth of in situ magnetic MgFe 2 O 4 whiskers. The magnetism of YIG/YIG joints could be intensified by brazing with Bi25-21MgO composite glass. • Bismuth-based glass doped with MgO nanoparticles is designed to realize the in situ growth of MgFe 2 O 4 whiskers. • The formation mechanism of MgFe 2 O 4 whiskers is revealed. • Mechanical and magnetic properties of YIG ferrite joint are both enhanced by the magnetic MgFe 2 O 4 whiskers. [ABSTRACT FROM AUTHOR]

Magnetic hydrogels have received extensive attention in various research fields due to their excellent controllability and responsiveness. In this work, we constructed a magnetic biocompatible hydrogel based on PAAm-SAlg (polyacrylamide and sodium alginate) system. The crosslinking network of this magnetic hydrogel is constructed by two kinds of chemical bonds. Magnetic particles with cores of Fe 3 O 4 are embedded in hydrogel networks by physical and chemical bindings. The addition of magnetic particles has different effects on the properties of hydrogels. Firstly, compared to hydrogels without magnetic particles, the tensile strength of magnetic hydrogels increases by 40 % from 0.035 MPa to 0.049 MPa, however, the swelling property is slightly reduced. In addition, magnetic hydrogels retain the characteristics of shear thinning and excellent superparamagnetism, and the magnetic response is slightly weakened than pure magnetic particles. The printed hydrogel fiber has a diameter of 100 μm and the magnetic particles are evenly distributed in the fiber. Moreover, increasing the air pressure of printing will cause irregular bumps on the surface of the printed hydrogel. [ABSTRACT FROM AUTHOR]

For electrically conductive adhesives (ECAs), it is critical to ensure high electrical conductivity and good adhesion reliability for practical applications in electronic products. In this study, high conductivity ECAs at low filler content were achieved by fully utilizing the synergistic effect of nano- and micro-scale fillers. Nanosilver-coated copper micronflakes (Ag@Cus) prepared by an electroless plating method were selected as the main conductive fillers. Silver nanowires (AgNWs) made by a simple one-step polyol method were dispersed as auxiliary conductive fillers in Ag@Cus, providing more possibilities for establishing a large number of conductive bridges. Furthermore, the curing process of matrix resin was predicted based on curing kinetics and was verified by corresponding experiments to determine the optimal curing parameters. The results show that the combination of AgNWs and Ag@Cus in ECAs can significantly reduce the bulk resistivity and percolation threshold compared with the single component. In particular, the bulk resistivity of ECAs filled with AgNWs and Ag@Cus (mass ratio 1:9) is as low as 9.42 × 10−5 Ω cm when the filler content is only 60 wt%. • T he combination of AgNWs and Ag@Cus in ECAs could significantly reduce the bulk resistivity and the percolation threshold compared with AgNWs or Ag@Cus individually. • AgNWs as one-dimensional nano-materials has the effect of lowering the percolation threshold, while Ag@Cus as micronflakes has the effect of reducing the bulk resistivity. • Thus, the bulk resistivity of ECAs could reach a low value of 9.42 × 10−5 Ω cm when the filler content was only 60 wt% in bi-compound ECAs filled with AgNWs and Ag@Cus (the mass ratio is 1:9). [ABSTRACT FROM AUTHOR]

High performance multiple-filled X–CoSb 3 skutterudites (X = Yb、Ca、Ba、Al、Ga、In、La、Eu) was prepared by the long term annealing and hot-pressing approaches. Compared with the one-element filling method, multi-elements filling in CoSb 3 can improve their thermoelectric values. The lattice constant of skutterudite filled with multiple types of atoms was increased to 9.076 Å, higher than 9.036 Å of the un-filled one. The electrical conductivity, thermal conductivity and Seebeck coefficient were analyzed from 300K to 823K. The filling fraction of Yb increase with the increasing Fe content in both the Fe-rich phase and the Fe-poor phase. For Ca atoms, a significant phase separation occurs in the Fe-rich phase and the Fe-poor phase, and the Ca filling fraction in the Fe-poor phase is much higher. With the increase of Fe contents, the Al atoms gradually increase in the Fe-poor phase and decrease in the Fe-rich phase. On the contrary, the filled Ga and In atoms have no obvious regularity in this statistical analysis. Compared with the referred Yb 0.5 Co 4 Sb 12 sample, the lattice thermal conductivity is effectively reduced by multi-filling, the multi-filled skutterudite obtained the 47% reduce of the lattice thermal conductivity and the maximum ZT value was reached 1.22 at 823K. • High performance multiple-filled X–CoSb3 skutterudites (X = Yb、Ca、Ba、Al、Ga、In、La、Eu) was prepared by the long term annealing and hot-pressing approaches. • For Ca atoms, a significant phase separation occurs in the Fe-rich phase and the Fe-poor phase, and the Ca filling fraction in the Fe-poor phase is much higher. • Compared with the referred Yb0.5Co4Sb12 sample, the multi-filled skutterudite obtained the 47% reduce of the lattice thermal conductivity and the maximum ZT value was reached 1.22 at 823K. [ABSTRACT FROM AUTHOR]