Papers by Keyword: Copper (Cu)

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Authors: Frank Lüthen, Claudia Bergemann, Ulrike Bulnheim, Cornelia Prinz, Hans Georg Neumann, Andreas Podbielski, Rainer Bader, Joachim Rychly
Abstract: To stimulate bone regeneration, the design of bioactive implants is a great challenge in current orthopedic research. We reasoned that implants should be suitable both to stimulate osteogenic differentiation of mesenchymal stem cells and prevent infections at the site of implantation. Therefore, we focus on copper ions, which are known to exert antimicrobial effects. On the other hand, copper is essential for the cell physiology, including the formation of the extracellular matrix. We studied the influence of copper ions on mesenchymal stem cells at various concentrations and identified the limits of copper concentrations for cell survival. Below the critical concentration for cell survival we analysed proliferation and osteogenic differentiation of the cells in the presence of copper ions. We found that copper stimulated the proliferation of the mesemchymal stem cells at 0.1 mM. Osteogenic differentiation decreased after 14 days at a concentration of 0.05 - 0.1 mM copper ions in osteogenic medium measured by the expression of osteogenic proteins, like alkaline phosphatase (ALP), bone sialoprotein (BSP) and collagen I (COL). We argue that at the implant surface a higher concentration of copper could prevent biofilm formation of bacteria and physiological concentrations in the vicinity of the implant would stimulate stem cell expansion. Together, copper is an interesting agent to control both bacteria and stem cells in the field of implant technology.
Authors: Yan Chen, Hai Ying Zhu, Yan Hua Lei, Wei Wei Sun, Yun Ping Liu, Shou Gang Chen
Abstract: A 3, 4-dihydroxyphenethylamine (dopamine) polymer film has been prepared on copper surface from 2.0g/L dopamine solution in tris(hydroxymethyl)aminomethane hydrochloride (Tris-HCl) buffer solution at pH 8.5 by a simple solution-immersion method. The dopamine self-polymerized and adhered to the copper surface firmly in aqueous environment. The film surface was evaluated through SEM, EDS, XPS and contact angle measurement. The results have shown that the film was indeed formed on copper surface. And this research offers a versatile approach for the surface modification.
Authors: Ikunori Yokoi, Geun Min Choi, Yoshio Yamazaki, Tadahiro Ohmi
Authors: V.G. García, Jose María Cabrera, Jose Manuel Prado
Abstract: Modelling hot flow stress during grain refinement operations of fcc metals has largely included the use of an Avrami type equation to describe the decrease in stress due to Dynamic Recrystallization (DRX). However when refining large-grained copper, the processing temperatures and strain rates often produce a multi peak behaviour, which is not predictable by an Avrami equation alone. If an initial grain size, D0, is greater than the stable dynamically recrystallized grain size, Drex, which is a function of the Zener-Hollomon Parameter, Z, then the material will tend to refine. However if the current the Zener-Hollomon value, given by current temperature and strain rate conditions, is lower than a critical value, Zc, which depends on D0, then a multi peak stress behaviour is expected while refining. The latter Relative-Grain-Size model (i.e. the D0-Zc and Drex-Z relationships plotted on the same log-log graph) is a practical model that allows determination of whether a material will grain coarsen or refine and whether the dynamic recrystallization behaviour will be monotonic or with multi peaks. The present authors devised a dynamic recrystallization algorithm to measure the stress due to the diminishing initial grain volume and to measure the correction stress due to recrystallizing grains. Analysis on the hot (600°C-950°C) compression data of a 99.9% pure copper inductively lead to the use of an Avrami type equation to describe the stress contribution produced by the deformation of the remaining initial grain volume and a damped cosine equation to describe the stress contribution of the synchronized volume of new grains. This work discusses the experimental evidence and analytical findings that inductively support the mathematical description of the stress-strain curve given by a Damped Cosine Avrami Model for discontinuous DRX.
Authors: Yuan Tong Gu, Prasad K.D.V. Yarlagadda
Abstract: This paper presents a concurrent multiscale study for the deformation mechanism of monocrystalline copper under dynamic uniaxial tension. The multiscale simulation is based on the coupled meshless and molecular dynamic (MD) method. Using it, the size of computational model can be extended to a large dimension (in micrometer) with an atomistic resolution. The pure MD simulation is difficult to reach this microscopic dimension because the number of atoms will be too large. In this study, it has been revealed that the deformation behavior and mechanism of the copper is sensitive to its size, geometry, and loading strain rate. In addition, the Young’s modulus is found to be independent of the cross-sectional size and the strain rate range considered in this study. On the other hand, the yield stress decreases with specimen length and increases with the loading strain rate.
Authors: Rodica Wenkert, I. Bunia, V. Neagu, I. Sârghie
Abstract: Copper and its alloys are part of common used metals in the microelectronic industry. Copper uses, in microelectronic industry include interconnection and electronic packaging. The presence of copper in different alloys creates galvanic cells, which causes rising in corrosion rates. This rising leads to failure of microelectronic devices. The ability of controlling the amount of copper ions Cu (II) bath system has been carried out. The sorption of Cu (II) ions depends on pH, being maximum (73%) at pH=5 and pH=10. In solution of pH 5, the Cu (II) sorption capacity increases with the increase of copper initial concentration, leading to the conclusion that the chelating ion exchanger under study could be used in processes of Cu (II) separation and preconcentration. The Cu (II) ions equilibrium distribution between solution phase and sorbent phase has been described by means Langmuir isotherm model. The calculated value of Gibbs free energy (ΔG=-13.975 KJmol), confirms the affinity of the ion exchange resin with hydroxamic acid and amidoxime groups towards Cu (II) ions. The type of corrosion mechanism and its rate of attach depend on the exact nature of the environment (air, soil, water) in wich the corrosion takes place.
Authors: Kazuki Abe, Akira Izumi
Abstract: Cu has been used as interconnection and lead frame in ULSIs. However, the oxidation and contamination of Cu are not easily avoided. As a result, a thin layer of Cu2O, CuO and carbon contaminations are formed at the Cu surface and these resistances are increased. Therefore, Cu cleaning is necessary. There are some reports to remove Cu oxide layers. Chemical processes such as H2 and NH3 plasma reduction are being investigated [1-5]. These methods have the problem of the plasma damage. Lee et al. proposed Cu oxide reduction using vacuum annealing [6]. However, it seems not suitable for the ULSI process, because the heat-treatment of 400oC is necessary. Therefore, low temperature Cu cleaning without plasma assist is strongly desired. In our previous work, we proposed novel low temperature atomic hydrogen or NH3 decomposed species cleaning generated by heated catalyzer [7,8]. However, in the method it is used 100% hydrogen gas. From the view point of safety, hydrogen gas diluted below explosion limit is preferred to use. In this paper we proposed a novel Cu cleaning method by atomic hydrogen generated on a heated tungsten catalyzer using diluted hydrogen as a cleaning gas.
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