Mesosphere of Carbon-Shelled Copper Nanoparticles with High Conductivity and Thermal Stability via Direct Carbonization of Polymer Soft Templates.

Copper nanoparticle (Cu NP) is a promising replacement for noble metal nanoparticles due to its high electrical conductivity and low cost. However, Cu NPs are relatively active compared to noble metals, and current ways of protecting Cu NPs from oxidation by encapsulation have severe drawbacks, such as a long reaction time and complicated processes. Here, a facial and effective method to prepare the mesosphere of carbon-shelled copper nanoparticles (Cu@MC) was demonstrated, and the resulting Cu@MC was both highly electrically conductive and thermally stable. Cu@organic (100 nm) was first synthesized by the reduction of Cu ions with poly (vinyl pyrrolidone) (PVP) and sodium poly ((naphthalene-formaldehyde) sulfonate) (Na-PNFS) as soft templates. Then, the carbon shells were obtained by in situ carbonization of the polymer soft templates. The Cu@organic and Cu@MC showed an anti-oxidation ability up to 175 and 250 °C in the air atmosphere, respectively. Furthermore, the Cu@MC exhibited excellent volume resistivity of 7.2 × 10-3 Ω·cm under 20 MPa, and showed promising application potential in electric sensors and devices.

In Situ Observation of the Tensile Deformation and Fracture Behavior of Ti-5Al-5Mo-5V-1Cr-1Fe Alloy with Different Microstructures.

The plastic deformation processes and fracture behavior of a Ti-5Al-5Mo-5V-1Cr-1Fe alloy with bimodal and lamellar microstructures were studied by room-temperature tensile tests with in situ scanning electron microscopy (SEM) observations. The results indicate that a bimodal microstructure has a lower strength but higher ductility than a lamellar microstructure. For the bimodal microstructure, parallel, deep slip bands (SBs) are first noticed in the primary α (αp) phase lying at an angle of about 45° to the direction of the applied tension, while they are first observed in the coarse lath α (αL) phase or its interface at grain boundaries (GBs) for the lamellar microstructure. The ß matrix undergoes larger plastic deformation than the αL phase in the bimodal microstructure before fracture. Microcracks are prone to nucleate at the αp/ß interface and interconnect, finally causing the fracture of the bimodal microstructure. The plastic deformation is mainly restricted to within the coarse αL phase at GBs, which promotes the formation of microcracks and the intergranular fracture of the lamellar microstructure.

Precipitation hardening and microstructure evolution of the Ti-7Nb-10Mo alloy during aging.

A biomedical ß titanium alloy (Ti-7Nb-10Mo) was designed and prepared by vacuum arc self-consumable melting. The ingot was forged and rolled to plates, followed by quenching and aging. Age-hardening behavior, microstructure evolution and its influence on mechanical properties of the alloy during aging were investigated, using X-ray diffraction, transmission electron microscopy, tensile and hardness measurements. The electrochemical behavior of the alloy was investigated in Ringer's solution. The microstructure of solution-treated (ST) alloy consists of the supersaturated solid solution ß phase and the ωath formed during athermal process. The ST alloy exhibits Young's modulus of 80 GPa, tensile strength of 774 MPa and elongation of 20%. The precipitation sequences during isothermal aging at different temperatures were determined as ß+ωath→ß+ωiso (144 h) at Taging=350-400 °C, ß+ωath→ß+ωiso+α→ß+α at Taging=500°C, and ß+ωath→ß+α at Taging=600-650 °C, where ωiso forms during isothermal process. The mechanical properties of the alloy can be tailored easily through controlling the phase transition during aging. Comparing with the conventional Ti-6Al-4V alloy, the Ti-7Nb-10Mo alloy is more resistant to corrosion in Ringer's solution. Results show that the Ti-7Nb-10Mo alloy is promising for biomedical applications.

Theoretical prediction of impurity effects on the internally oxidized metal/oxide interface: the case study of S on Cu/Al2O3.

A detrimental sulfur effect on adhesion is known for iron- and nickel-oxide interfaces, but has never been reported on copper-oxide interfaces. Here we present a first-principles based study on the effects of temperature, interfacial stoichiometry, Al activity, and S segregation on the internally oxidized Cu/α-Al(2)O(3) interface. The calculated "interfacial phase diagram" for temperatures of interest suggests that the equilibrium interface structure is near the transition between Al-rich and stoichiometric phases. The Al-rich type interface is significantly stronger than the stoichiometric counterpart. The S effect on the Cu/α-Al(2)O(3) interface is obvious: S strongly segregates to both types of interface, degrades the adhesion (by ∼65%) and also reduces the size stability of alumina particles in Cu.

[Cytotoxicity of a new biomedical titanium alloy Ti-25Nb-10Ta-1Zr-0.2Fe].

OBJECTIVE: To evaluate the cytotoxicity of a new type of titanium alloy Ti-25Nb-10Ta-1Zr-0.2Fe by studying the induced proliferation of L929 cells in contrast with other titania widely used in clinical practice. METHODS: The cell line was treated with extracting liquid containing different concentrations of titanium alloys. The number and morphology of cells was observed under an inverted phase contrast microscope. MTT was used to measure the relative growth rate (RGR) and judge the cytotoxicity grade. Flow cytometry was used to observe cell cycle progression. RESULTS: The RGR of TNTZ group cells at the 3 time points was (93.7±0.8), (100.6±0.4), and (106.4±0.3); the cytotoxicity grade was 1, 0 and 0 after treating for 1, 3 and 5 days; with influence on neither the cell morphology nor the cell cycle. The flow cytometry showed that the sequence of S phase cells was Ti>TNTZ>TC4>blank control >TC4ELI, with no significant difference (P>0.05). None of the 4 materials inhibited the cell proliferation. CONCLUSION: The cell morphology and proliferation are not affected by TNTZ. The new titaniu alloys shows good cyto-compatibility. The cytotoxicity is grade 0, meeting the clinical application standard.