A И-Shaped Curve of Hot Tearing Susceptibility in Magsimal®-59-Based Alloys

The hot tearing susceptibility of Al-6Mg-xSi (x = 0-6.0 wt.%) alloys was studied using constrained rod casting. Addition of Si content resulted in double ternary eutectic reactions and then changed the freezing range and eutectic liquid fraction greatly, which made the hot tearing susceptibility show a И-curve with the increasing of Si content. The И-curve was obviously different from the λ-curve that supported by most researchers.

Stretchable, Rehealable, Recyclable, and Reconfigurable Integrated Strain Sensor for Joint Motion and Respiration Monitoring

Cutting-edge technologies of stretchable, skin-mountable, and wearable electronics have attracted tremendous attention recently due to their very wide applications and promising performances. One direction of particular interest is to investigate novel properties in stretchable electronics by exploring multifunctional materials. Here, we report an integrated strain sensing system that is highly stretchable, rehealable, fully recyclable, and reconfigurable. This system consists of dynamic covalent thermoset polyimine as the moldable substrate and encapsulation, eutectic liquid metal alloy as the strain sensing unit and interconnects, and off-the-shelf chip components for measuring and magnifying functions. The device can be attached on different parts of the human body for accurately monitoring joint motion and respiration. Such a strain sensing system provides a reliable, economical, and ecofriendly solution to wearable technologies, with wide applications in health care, prosthetics, robotics, and biomedical devices.

Interfacial strength and microstructure of AlN/Cu joints produced by a novel brazing method facilitated by porous-copper layer and Ag foil

The reliability of wide-bandgap (WBG) semiconductors used as power electronics is closely related to the high thermal conductivity of AlN-metalized substrates. Thus, the bonding of AlN ceramics with metals is a key issue for the production of reliable AlN-metalized substrates. This paper reports on a new method for producing AlN/Cu joints by employing a novel film-metallization production process, which involves a porous network of Cu layer and Ag foil. The microstructure and the phases formed at the interface of the AlN/Cu joints produced at various brazing temperatures and times, were analyzed by scanning electron microscopy and X-ray diffraction analysis. Strong joints with shear strength of 48.5 MPa were produced after brazing at 850 °C for 10 min. The typical microstructure at the interfacial reaction zone was Cu / Ag(s) + Cu(s) / CuAlO2 + Al2O3 + Cu(s) / AlN. The experimental results manifest the crucial role of the Ag-Cu eutectic liquid phase, formed by the reaction between the Cu layer and the Ag foil, and of the porous network of the Cu layer deposited on the surface of the AlN ceramic substrate, since both of them effectively favor the reduction of the residual thermal stresses in the joint and result in strong ceramic/metal joins.

Effect of CeO2 Nanoparticles on Interface of Cu/Al2O3 Ceramic Clad Composites

Cu/Al2O3 ceramic clad composites are widely used in electronic packaging and electrical contacts. However, the conductivity and strength of the interfacial layer are not fit for the demands. So CeO2 nanoparticles 24.3 nm in size, coated on Al2O3 ceramic, promote a novel CeO2–Cu2O–Cu system to improve the interfacial bonded strength. Results show that the atom content of O is increased to approximately 30% with the addition of CeO2 nanoparticles compared with the atom content without CeO2 in the interfacial layer of Cu/Al2O3 ceramic clad composites. CeO2 nanoparticles coated on the surface of Al2O3 ceramics can easily diffuse into the metallic Cu layer. CeO2 nanoparticles can accelerate to form the eutectic liquid of Cu2O–Cu as they have strong functions of storing and releasing O at an Ar pressure of 0.12 MPa. The addition of CeO2 nanoparticles is beneficial for promoting the bonded strength of the Cu/Al2O3 ceramic clad composites. The bonded strength of the interface coated with nanoparticles of CeO2 is increased to 20.8% compared with that without CeO2; moreover, the electric conductivity on the side of metallic Cu is 95% IACS. The study is of great significance for improving properties of Cu/Al2O3 ceramic clad composites.