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Abstract: The evolution of nanoclusters in sequentially ion-implanted Cu/Ag into silica glasses has been studied. Third-order nonlinear optical properties of the nanoclusters were measured at 1064nm excitations using the Z-scan technique. Results of the investigation of nonlinear refraction by the off-axis Z-scan configuration were presented and the mechanisms responsible for the nonlinear response were discussed. The innovative point of this paper is that we carried out curve fitting analysis, which is based on MATLAB features, for Cu/Ag optical limiting experiment. Our results showed that Cu/Ag mixture nanoclusters have refractive optical limiting effect at 1064nm. [Copyright &y& Elsevier]

By additions of Cu and Sn elements, we have synthesized nanocrystalline Au–Cu and Au–Cu–Sn materials with a minimum grain size down to ∼3nm. Tensile measurements of these nanocrystalline materials indicate that the Hall–Petch scaling law is maintained to the smallest length scale. Though Cu and Sn solid solutions are observed to have little effect on the strength of nanocrystalline Au, they substantially enhance the thermal stability of these alloys. Abnormal grain growth no longer becomes the characteristic feature of alloyed nanocrystalline Au. [Copyright &y& Elsevier]

The present paper is concerned with the formation of the Cu-based Cu–Zr–Al bulk metallic glasses (BMGs). Composition optimization for BMG formation was realized by using an ‘e/a-variant criterion’ that had been successfully applied in the Zr–Al–Ni and Zr–Al–Co systems. This criterion was incorporated into the ternary phase diagram by constructing a composition line (Cu61.8Zr38.2)1-xAlx, which was defined by linking the optimum binary composition (Cu61.8Zr38.2, a deep eutectic in this case) and the third element. BMGs were obtained within an e/a span from 1.24 to 1.3 along this composition line. Thermal analysis results indicate that these BMGs manifest increased thermal stability and glass forming ability (GFA) with increasing e/a ratios. The maximum appears in Cu58.1Zr35.9Al6 with the e/a value of 1.3 which is the highest among our samples. The characteristic thermal parameters of this BMG are Tg=760K, Tg/Tl=0.648, which are all superior to those reported for the known Cu55Zr40Al5 BMG. [Copyright &y& Elsevier]

In nanostructured metals with grain sizes of the order of 100 nm, dislocation mechanisms remain dominant in controlling plastic deformation. These materials, similar to their coarse-grained counterparts that have been subjected to heavy cold work, can no longer go through the several strain hardening stages of normal metals and are hence susceptible to plastic instabilities such as necking in tension. For processing and applications, it is obviously important and often necessary to control such inhomogeneous plastic deformation. Here we demonstrate three strategies to achieve relatively large stable tensile deformation in nanostructured metals, using the pure Cu processed by equal channel angular pressing as a model. The first approach uses an in situ formed composite-like microstructure, such as a bimodal grain size distribution, to impart strain hardening to the material and attain large uniform tensile strains while maintaining the majority of the strengthening brought forth by nanostructuring. In the second route, deformation is conducted at low temperatures, such as 77 K. The material regains the ability to work harden due to suppressed dynamic recovery. Uniform elongation is achieved as a result, together with an elevated strength at the cryogenic temperature. The third method takes advantage of the elevated strain rate sensitivity of the flow stress of the nanostructured Cu, especially at slow strain rates. Using the stabilizing effects of strain rate hardening on tensile deformation, nearly uniform strains can be acquired in absence of strain hardening. We also discuss the deformation mechanisms involved in these approaches to assess their applicability to nanocrystalline metals with grain sizes well below 100 nm, where normal dislocation activities become severely suppressed. [Copyright &y& Elsevier]

The tensile properties of nanocrystalline copper with grain sizes <100 nm produced by surface mechanical attrition treatment have been characterized using a microsample testing technique. The nanocrystalline copper exhibits a yield strength as high as 760 MPa, with a small elongation to failure. Factors leading to the high strength and low ductility are discussed. [Copyright &y& Elsevier]

Abstract: We have prepared Cu powders with nanocrystalline grain sizes via ball milling at liquid nitrogen temperature. An in situ consolidation technique was used to produce fully dense nanocrystalline Cu samples centimeters in lateral dimensions and about one millimeter in thickness. We report a much improved combination of tensile strength and ductility, over the tensile properties of other nanocrystalline Cu materials documented in the literature. We also demonstrate the elevated strain rate sensitivity and strong temperature dependence of the flow stress and explain the results in terms of the thermally activated deformation mechanisms operative in the nanocrystalline grains. The nearly perfectly plastic behavior and shear localization observed are discussed and compared with the strain hardening behavior and deformation modes known for other nanocrystalline metals. [Copyright &y& Elsevier]

Heavy ion beam lost on the accelerator vacuum wall will release quantity of gas molecules and make the vacuum system deteriorate seriously. This phenomenon is called dynamic vacuum effect, observed at CERN, GSI and BNL, leading to the decrease of beam lifetime when increasing beam intensity. Heavy ion-induced gas desorption, which results in dynamic vacuum effect, becomes one of the most important problems for future accelerators proposed to operate with intermediate charge state beams. In order to investigate the mechanism of this effect and find the solution method for the IMP future project High Intensity heavy-ion Accelerator Facility (HIAF), which is designed to extract 1 × 1 0 11 uranium particles with intermediate charge state per cycle, two dedicated experiment setups have been installed at the beam line of the CSR and the 320 kV HV platform respectively. Recently, experiment was performed at the 320 kV HV platform to study effective gas desorption with oxygen-free copper target irradiated with continuous Xe 10 + beam and O + beam in low energy regime. Gas desorption yield in this energy regime was calculated and the link between gas desorption and electronic energy loss in Cu target was proved. These results will be used to support simulations about dynamic vacuum effect and optimizations about efficiency of collimators to be installed in the HIAF main synchrotron BRing, and will also provide guidance for future gas desorption measurements in high energy regime. [ABSTRACT FROM AUTHOR]

Atomic-scale simulations are performed to study atomic motion on Cu surfaces to illustrate the effect of the scanning tunneling microscopy tip on mass transport (MT) in the surfaces and on top of the Co island in heteroepitaxial Co/Cu(0 0 1) and Co/Cu(1 1 1) systems. First we investigate tip-induced atomic motion of Co atoms embedded in the Cu(0 0 1) surface at zero bias voltage. With the help of the tip, the Co atom in the surface can freely diffuse toward its nearby vacancy site. So-called vacancy mechanism is used to interpret this phenomenon. Then tip-mediated atomic motion of Co adatoms on the Co islands supported by a Cu(1 1 1) surface is studied. It is revealed that the tip has a significant effect on the diffusion of adatoms on the islands and interlayer mass transport at the island edge. Interlayer mass transport at the island edge is found to depend strongly on the tip height and the lateral distance from the tip. By calculating the diffusion barriers, it is found that the jumping diffusion barrier on the island can be zero by the tip vertical manipulation while the Ehrlich–Schwoebel diffusion barrier at the island edge can be reduced by the tip lateral manipulation. Thus, the quality of thin films can be improved by controlling MT in and/or on the surface. [ABSTRACT FROM AUTHOR]

The single and joint effects of Cu2+ and cypermethrin (CPM) on the seed germination and the elongation of root and shoot of Pakchoi were investigated. The results showed that in solution low concentrations of Cu2+ could accelerate the germination rate of Pakchoi, whereas high concentrations of Cu2+ could inhibit it. CPM could strongly inhibit the germination of Pakchoi in solution. However, in the joint toxicity effect, CPM reduced the phytotoxicity of Cu2+ on the germination of Pakchoi seeds under solution conditions. In the single-factor experiments and joint effect tests of CPM and copper on the seedling growth, it was found that there were significant liner relationships between concentrations of pollutants and root elongation (P <0.05). Copper and CPM had synergic effects on root elongation of Pakchoi in solution cultivation test. However, in soil culture test, these synergistic effects were not significant (P <0.05). Meanwhile, the joint toxicity was more dependent on the effect of copper than that of CPM. The toxicity of the pollutants to seed germination, shoot and root elongation is in the following sequence: root elongation>shoot elongation>germination rate. [Copyright &y& Elsevier]