Interfacial strengthening and antibacterial behavior in an ultrafine-graine d Zn-Ag-base d biocomposites fabricated by the Cu_(2)O-induced in situ wetting approach

Nowadays,Zinc(Zn)-based biocomposites as biodegradable implant materials have been recognized as a promising approach to overcome the insufficient mechanical performance of Zn matrix and to endow the Zn-based materials with biofunctionality.However,the strengthening effect on Zn-based matrix compos-ite remains far from expectation mainly due to the poor interfacial bonding between the reinforcement and Zn matrix,and the relatively coarse grain size of the Zn matrix.Herein,we have developed a novel in situ wetting strategy to ameliorate the interfacial bonding and mechanical performance of Zn-Ag-based composites using cuprous oxide-modified graphene oxide(Cu_(2)O-GO)sheets as reinforcement.The en-hanced interfacial bonding between GO sheets and Zn matrix owing to the in situ generated ZnO inter-layer and the ultrafine microstructure with an average grain size of 360 nm were simultaneously achieved in the hot extruded(HEed)1 wt%Cu_(2)O-GO/Zn-2 wt%Ag biocomposites.Consequently,HEed biocompos-ites possessed excellent tensile properties,including ultimate tensile strength(UTS)of 344.0±2.4 MPa,yield stress(YS)of 314.0±4.8 MPa,and elongation at failure of 15.5%±1.3%.Ultrafine and uniform microstructure of the HEed biocomposites resulted in a relatively uniform corrosion morphology and a degradation rate of 0.195±0.004 mm y^(−1) in simulated body fluid(SBF)solution.The 2-fold diluted extract of the HEed biocomposites exhibited satisfying cytocompatibility with MC3T3-E1 pre-osteoblast comparable to that of Ti-6Al-4 V ELI alloys.More importantly,the synergistic effect of metallic ions,Ag-rich nanoparticles,and GO sheets contributed to the remarkable antibacterial activity of the experimental biocomposites against both S.aureus and E.coli.These results demonstrated that the 1Cu_(2)O-GO/Zn-2Ag biocomposites should be anticipated as a promising biodegradable material for orthopedic applications.

High-entropy rare-earth zirconate ceramics with low thermal conductivity for advanced thermal-barrier coatings

The high-entropy rare-earth zirconate((La_(0.2)Nd_(0.2)Sm_(0.2)Gd_(0.2)Yb_(0.2))_(2)Zr_(2)O_(7),5RE_(2)Zr_(2)O_(7)HEREZs)ceramics were successfully prepared by a new high-speed positive grinding strategy combined with solid-state reaction method.The microstructure,crystal structure,phase composition,and thermophysical and mechanical properties of the samples were systematically investigated through various methods.Results indicate that the samples have a single-phase defect fluorite-type crystal structure with excellent high-temperature thermal stability.The as-prepared samples also demonstrate low thermal conductivity(0.9–1.72 W·m^(−1)·K^(−1)at 273–1273 K)and high coefficient of thermal expansion(CTE,10.9×10^(−6)K^(−1)at 1273 K),as well as outstanding mechanical properties including large Young’s modulus(E=186–257 GPa)and high fracture toughness(KIC).Furthermore,the formation possibility of the as-prepared samples was verified through the first-principles calculations,which suggested the feasibility to form the 5RE_(2)Zr_(2)O_(7)HE-REZs in the thermodynamic direction.Therefore,in view of the excellent multifunctional properties exhibited by the as-prepared 5RE_(2)Zr_(2)O_(7)HE-REZs,they have great potential applications in next-generation thermal-barrier coatings(TBCs).

In vitro and in vivo biocompatibility of Mg–Zn–Ca alloy operative clip

At present,titanium(Ti)and its alloys are most commonly use in hemostasis clip clinical applications.However,the Ti Clip cannot be absorbed in human body and produce artifacts on computed tomography(CT),and induce clinically relevant hypersensitivity in patients.In order to overcome the drawbacks of the non-degradable Ti clips,an Mg-Zn-Ca alloy operative clip was fabricated by combining hot extrusion and blanking processing.In vitro and in vivo biocompatibility of Mg-Zn-Ca alloy operative clip were evaluated by L-929 Cells and SD rat model respectively.It was found that Mg-Zn-Ca alloy exhibited non-cytotoxic to L929 cells.In vivo implantation showed that the newly designed Mg-Zn-Ca clip can successfully ligated carotid artery and no blood leakage occurred post-surgery.During the period of the clip degradation,a small amount of H2 gas formation and no tissue inflammation around the clips were observed.The degradation rate of the clip near the heart ligated the arteries faster than that of clip far away the heart due do the effect of arterial blood.Histological analysis and various blood biochemical parameters in rat serum samples collected at different times after clip implantation showed no tissue inflammation around the clips.