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Biocompatible, tough, and photoluminescent hydrogels are highly desirable for biomedical applications in vivo. Herein, hybrid hydrogels prepared from silk fibroin (SF) and polyacrylic acid (PAA) and complexed with europium, named as SF‐PAA‐Eu3+ hydrogels, exhibit good comprehensive properties. Owing to the intensive molecular interactions among SF, PAA, and Eu3+, SF‐PAA‐Eu3+ hydrogels show a greatest tensile strength of 0.58 MPa, elongation of 443%, and work of fracture of 1.65 MJ/m. In vivo imaging experiment in a mouse subcutaneous implantation model revealed excellent and sustained photoluminescence of the SF‐PAA‐Eu3+ hydrogels for 24 h. The work provides a strategy for designing functional SF‐based hydrogels for imaging applications in vivo. [ABSTRACT FROM AUTHOR]

Microstructural observations of cross sections of butt joints of Ti-22Al-25Nb (at.%) alloy manufactured using ultrasonic pulse frequency tungsten inert gas welding method at different welding parameters without and with welding wire, the butt joint at 50 KHz pulse frequency with welding wire has the largest equiaxed crystal zone, finest columnar crystals, and improves damage of dendritic crystals and overburning. The tensile strength, yield strength and elongation of butt joint at 50 KHz welding frequency with welding wire are the highest, compared with those of butt joints at other welding parameters without welding wire, and the fracture of it is ductile fracture mode of dimples. Further, fusion zone composed of α 2  + β/B2 two phases and heat affected zone composed of α 2  + O + β/B2 three phases in the butt joint having the highest tensile strength are determined using X-ray diffraction technology. In this butt joint, the microhardness of heat affected zone is the highest, followed by that of base material, fusion zone lowest. [ABSTRACT FROM AUTHOR]

KD-II SiC fibers were heat treated from 800 °C to 1500 °C in argon and air atmospheres to comparatively analyze the effect of temperature and applied atmosphere on the microstructural evolution and mechanical behaviors of the fibers. The results show that sizes of the β-SiC grains, free carbon clusters, and micropores increase in both atmospheres as the temperature rises. Consequently, the strength of SiC fibers, in general, decreases with the increase in heat treatment temperature. However, SiC fibers responded differently during heat treatment at various temperatures in air compared to argon. The passive oxidation in air could cause more defects in the fibers. At 1200 °C, a lot of oxidation products were formed on the surface of the fibers; at 1400 °C, cracks appeared on the oxidation (silica) scale; and at 1500 °C, spallation of the oxide occurred. The cracking and spallation of the surface oxide may stem from the internal stress produced at the interface between the oxide scale and the unoxidized SiC core, which caused an earlier fiber failure in the air environment. As a result, the fiber strength treated in the air was lower than that treated in argon when the temperature was above 1200 °C. [ABSTRACT FROM AUTHOR]

In order to uniformly disperse graphene in the copper matrix, the complete coating of few-layers high-quality graphene on the surface of the copper powder was realized by chemical vapor deposition, and the graphene coated copper powder is sequentially formed through vacuum hot pressing, hot extrusion, and cold drawing processes. The results show that during the vacuum hot pressing, the metallurgical bonding between original copper powders is hindered by the graphene with a relatively complete structure. And the copper grains are recrystallized and refined in the hot extrusion process, and then stretched into a long and thin fibrous structure during the cold drawing process. Besides, the graphene is partially agglomerated during the hot extrusion process, and is dispersed again during the cold drawing process and gradually oriented along the drawing direction. Finally, the graphene and the copper matrix form a network interpenetrating structure, which improves the mechanical and electrical properties of the composite synergistically. The tensile strength and conductivity of the composite wire drawn to 1 mm reached 573.3 MPa and 5.79 × 107 S/m, respectively, achieving a breakthrough in the performance of copper-based materials. [Display omitted] • Complete coating of few-layers high-quality graphene on Cu powders is realized. • Molding process including severe plastic deformation is well-designed. • The microstructure of composites varies due to severe plastic deformation. • Network interpenetrating structure of fibrous Cu grains and graphene is formed. • Mechanical and electrical properties of composite are synergistically improved. [ABSTRACT FROM AUTHOR]

The dispersion of graphene in copper matrix and their interfacial bonding quality decisively determine the comprehensive performance of graphene/copper composites. To explore the possibility of dispersing the well-bonded graphene evenly in the copper matrix, we tested various processing methods and obtained a unique copper-based composite reinforced by in-situ graphene, achieved by two severe plastic deformation processes of hot extrusion and cold drawing. The experimental results revealed that the in-situ graphene was in the form of shreds and uniformly dispersed in the copper matrix. The abnormal coarsening of copper grains occurred during the graphene depositing process due to high temperature, but the grains were then refined during the following severe plastic deformation process. Graphene can play a role of pinning dislocations and hindering grain boundary slip, thereby improving the strength of the composite. Meanwhile, the network structure of graphene in the copper matrix provides a fast path for electron transmission which can make up for the negative effect of the fine of copper grain structure on the conductivity. The tensile strength and conductivity of the composite reach to 595 MPa and 5.46 × 107 S/m, representing an increase of 23.4% in tensile strength, and similar conductivity (98%) of the original copper matrix. Image 1 • A novel method for preparing high strength and conductivity graphene/copper composite wire is provided. • The graphene is uniformly dispersed inside the copper matrix during the large deformation process for its poorer plasticity. • The copper grains grew abnormally under high temperature, and were refined during the severe plastic deformation process. • The network structure of graphene can make up for the decrease of conductivity caused by refinement of copper grains. [ABSTRACT FROM AUTHOR]