Copper Lattice Research Articles

The influence of cutting conditions and cutting tool geometry on the atomistic modeling of precision cutting

In this paper a molecular dynamics simulation of nano-metric cutting of copper with a diamond tool is presented. MD simulations require the determination of the interaction of the involved atoms through a function of potential for the materials involved in the analysis and the accurate topography of the studied area, leading to high demand of computational time. The models presented are taking into account the cubic lattice of copper, test two different potential functions and at the same time control the computational cost by introducing small models at realistic cutting conditions. This is realized by a novel code developed and allows focusing on the influence of several processes and modeling parameters on the outcome of the simulations. Models with and without thermostat atoms are investigated and the influence of cutting conditions and cutting tool geometry on chip morphology, cutting forces and cutting temperatures are studied.

Modifications of the Response of Materials to Shock Loading by Age Hardening

The shock response of two age-hardened alloys, aluminum 6061 and copper-2 wt pct beryllium (CuBe), has been investigated in terms of their microstructual state; either solution treated or age hardened. While age hardening induces large increases in strength at quasi-static strain rates, age hardening does not produce the same magnitude of strength increase during shock loading. Examination of the shocked microstructures (of 6061) indicates that the presence of a fine distribution of precipitates throughout the microstructure hinders the motion and generation of dislocations and hence reduces the strain-rate sensitivity of the aged material, thus allowing the properties of the solution-treated state to approach those of the aged. It has also been observed that the shear strength of solution-treated CuBe is near identical to that of pure copper. It is suggested that this is the result of two competing processes; large lattice strains as beryllium substitutes onto the copper lattice inducing a high degree of solution strengthening acting against a reduction in shear strength caused by twinning in the alloy.

Vortices and charge order in high-Tcsuperconductors

We theoretically investigate the vortex state of the cuprate high-temperature superconductors in the presence of magnetic fields. Assuming the recently derived nonlinear $\sigma$-model for fluctuations in the pseudogap phase, we find that the vortex cores consist of two crossed regions of elliptic shape, in which a static charge order emerges. Charge density wave order manifests itself as satellites to the ordinary Bragg peaks directed along the axes of the reciprocal copper lattice. Quadrupole density wave (bond order) satellites, if seen, are predicted to be along the diagonals. The intensity of the satellites should grow linearly with the magnetic field, in agreement with the result of recent experiments.

Production of Cu-TiC Nanocomposite Using Mechanical Alloying Route

In this study, Cu-TiC nanocomposites were produced by high energy ball milling of elemental powders and in-situ formation of TiC in the copper matrix. Cu-40wt% Ti powder mixture were milled for 60 h, then graphite powder was added, subsequently milling was continued for further 10 h. Based on theoretical calculations, at this composite, the amount of TiC as reinforcement should be 60.25vol% (45.47wt%). The effect of milling time on solution progress of titanium in the copper lattice was studied by X-Ray diffraction analysis (XRD) with CuKα radiation. Considering XRD of Cu-40wt%TiC after 60 h milling data and Williamson-Hall relation, crystallite size and lattice strain of copper were determined 12nm and 1.04% respectively. To ensure the formation of titanium carbide, XRD analysis was performed after pressing at 300MPa and sintering at 900oC for an hour and heating rate of 2.5oC/min. XRD pattern was indicated the formation of TiC,CuTi3and TiO2phases in Cu matrix.

Self-organized and cu-coordinated surface linear polymerization.

We demonstrate a controllable surface-coordinated linear polymerization of long-chain poly(phenylacetylenyl)s that are self-organized into a “circuit-board” pattern on a Cu(100) surface. Scanning tunneling microscopy/spectroscopy (STM/S) corroborated by ab initio calculations, reveals the atomistic details of the molecular structure, and provides a clear signature of electronic and vibrational properties of the poly(phenylacetylene)s chains. Notably, the polymerization reaction is confined epitaxially to the copper lattice, despite a large strain along the polymerized chain that subsequently renders it metallic. Polymerization and depolymerization reactions can be controlled locally at the nanoscale by using a charged metal tip. This control demonstrates the possibility of precisely accessing and controlling conjugated chain-growth polymerization at low temperature. This finding may lead to the bottom-up design and realization of sophisticated architectures for molecular nano-devices.

Incommensurate SDW in cuprates

The incommensurate antiferromagnetism (AF) in metallic underdoped cuprates is interpreted with several complementary approaches, unified by a consistent disambiguation of the copper and oxygen degrees of freedom. Collinear (with respect to the copper lattice) peaks in the neutron response at low frequency are due to the oxygen-dominated arcs, while the diagonal peaks at high frequency or low doping come from the copper-dominated vH points. The latter switch from collinear to diagonal as the frequency increases. The direct O–O overlap induces an AF which is weaker and thermodynamically preferred to the AF of strongly localized copper sites, and which coexists with Fermi arcs. A theoretical understanding of the strongly k-dependent AF gap observed in ARPES and STM measurements is proposed.

Decoupling of CVD graphene by controlled oxidation of recrystallized Cu

Large-area graphene grown by chemical vapour deposition (CVD) is promising for applications; however, the interaction between graphene and the substrate is still not well understood. In this report, we use a combination of two non-destructive characterization techniques, i.e., electron backscatter diffraction (EBSD) and Raman mapping to locally probe the interface between graphene and copper lattices without removing graphene. We conclude that the crystal structure of the Cu grains under graphene layers is governed by two competing processes: (1) graphene induced Cu surface reconstruction favoring the formation of Cu(100) orientation, and (2) recrystallization from bulk Cu favoring Cu(111) formation. The underlying Cu grains, regardless of reconstruction or recrystallization, induce a large hydrostatic compression to the graphene lattice. Interestingly, the strong interaction could be decoupled by allowing the intercalation of a thin cuprous oxide interfacial-layer. The Cu2O layer is mechanically and chemically weak; hence, graphene films can be detached and transferred to arbitrary substrates and the Cu substrates could be re-used for graphene growth.

SYNTHESIS OF NANO-CRYSTALLINE Cu-Cr ALLOY BY MECHANICAL ALLOYING

In this paper, the influence of toluene as the process control agent (PCA) and pre-milling on the extension of solid solubility of 7 wt.% Cr in Cu by mechanical alloying in a high energy ball mill was investigated. The structural evolution and microstructure were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques, respectively. The solid solution formation at different conditions was analyzed by copper lattice parameter change during the milling process. It was found that both the presence of PCA and pre-milling of Cr powder lead to faster dissolution of Cr . The mean crystallite size was also calculated and showed to be about 10 nm after 80 hours of milling.

Influence of copper crystal surface on the CVD growth of large area monolayer graphene

We study the influence of the surface structure of copper single crystals on the growth of large area monolayer graphene by chemical vapor deposition (CVD) in ultra-high vacuum (UHV). Using atomic-resolution scanning tunneling microscopy (STM), we find that graphene grows primarily in registry with the underlying copper lattice for both Cu(111) and Cu(100). The graphene has a hexagonal superstructure on Cu(111) with a significant electronic component,whereas it has a linear superstructure on Cu(100). Graphene on Cu(111) forms a microscopically uniform sheet, the quality of which is determined by the presence of grain boundaries where graphene grains with different orientations meet. Graphene grown on Cu(100) under similar conditions does not form a uniform sheet and instead displays exposed nanoscale edges. Our results indicate the importance of the copper crystal structure on the microstructure of graphene films produced by CVD.

On the mechanism of nucleation of copper precipitates upon aging of Fe-Cu alloys

Structure of the Fe-5.5% Cu alloy has been studied after aging at 500°C to show that the lattice of copper precipitates changes with increasing time of holding at a temperature from bcc to 9R to fcc. The free energy of the solid solutions and the phase-separation diagrams of the bcc and fcc phases of copper have been calculated. Barriers for the nucleation of copper particles with the bcc and fcc lattices have been evaluated. Factors that favor the appearance of intermediate structural forms of copper, which precede the formation of the stable fcc phase, are discussed.

Step-by-step growth of epitaxially aligned polythiophene by surface-confined reaction

One of the great challenges in surface chemistry is to assemble aromatic building blocks into ordered structures that are mechanically robust and electronically interlinked--i.e., are held together by covalent bonds. We demonstrate the surface-confined growth of ordered arrays of poly(3,4-ethylenedioxythiophene) (PEDOT) chains, by using the substrate (the 110 facet of copper) simultaneously as template and catalyst for polymerization. Copper acts as promoter for the Ullmann coupling reaction, whereas the inherent anisotropy of the fcc 110 facet confines growth to a single dimension. High resolution scanning tunneling microscopy performed under ultrahigh vacuum conditions allows us to simultaneously image PEDOT oligomers and the copper lattice with atomic resolution. Density functional theory calculations confirm an unexpected adsorption geometry of the PEDOT oligomers, which stand on the sulfur atom of the thiophene ring rather than lying flat. This polymerization approach can be extended to many other halogen-terminated molecules to produce epitaxially aligned conjugated polymers. Such systems might be of central importance to develop future electronic and optoelectronic devices with high quality active materials, besides representing model systems for basic science investigations.

Structural organization and thermal properties of crystalline copper(II) N,N-cyclo-hexamethylenedithiocarbamate: A manifestation of coordination polymerism

The first representative of copper(II) dithiocarbamate complexes with an unusual type of structural organization is synthesized. According to the X-ray diffraction data, the layers of noncentrosymmetric mononuclear [Cu{S2CN(CH2)6}2] and centrosymmetric binuclear [Cu2⨑ub;S2CN (CH2)6⫂ub;4] molecules alternate in the crystalline lattice of copper(II) N,N-cyclo-hexamethylenedithiocarbamate. The mononuclear and binuclear forms of the complex are observed in the 2: 1 ratio. The thermal properties of the synthesized compound are studied by thermogravimetry and differential scanning calorimetry. The final product of the thermal destruction of the complex is CuS.

Ambulatory Device for Urinary Incontinence Detection in Female Athletes

Urinary incontinence (UI) has been known as a prevalent concern among parous and elderly women. However, recent studies have shown an unexpectedly high occurrence of UI in young physically fit female athletes who are actively participating in vigorous physical activities. Those study results motivated us to explore the relationship between daily intensive exercise and the occurrence of UI. As the first step to advance our understanding of this problem, an ambulatory device was developed for recording urological response to the intense force levels to which female athletes are subjected. The device consists of three types of wearable sensors, including 1) a +/– 25g tri-axial accelerometer, 2) a 360° biaxial inclinometer and 3) a urinary leakage detector or ULD. It also contains a compact data logger for real-time data recording with high frequency and precision (125 Hz, 16-bit A/D converter). The accelerometer and inclinometer help to determine the force levels developed in the body during physical activities at which urinary leakage occurs. Two types of ULD sensors have been designed: (1) copper lattice ULD, and (2) thermistor array ULD. Copper lattice ULD senses the UI based on the fact that urine drops reduce the resistance of the copper lattice resulting in a voltage change. The thermistor array ULD makes use of the finding that leaked urine is warmer than the surface of the skin, such that the integrated thermal components respond to urine leakage differently. In addition, a thermoelectric cooler is applied to produce a constant reference temperature. The entire device is small, lightweight, nonintrusive, and can be worn comfortably by subjects on their wrists or low back for at least 3 hours of continuous data recording. The test results from the recruited female athletes show that the three sensors can simultaneously record the intensity of activity and the corresponding urine leakage. However, for the copper lattice ULD, substantial sweat developed during the vigorous activity which produced an artifact and prevented the device from detecting the occurrence of urine leakage. The recently designed thermistor array ULD is less sensitive to sweat, resulting a more reliable sensor than is provided by the copper lattice ULD. The wearable sensor based device enables us to determine if urinary incontinence in female athletes occurs during vigorous physical activities or as a result of the fatigue caused by these activities. This conclusion facilitates the understanding of the mechanism of UI and assists trainers and coaches with the design of an appropriate training program that reduces the occurrence of UI in these female athletes.

Statistical thermodynamics of low-concentration gold melts in copper

The Wagner interaction parameter ɛ Au Au and first-order enthalpy parameter η Au Au in Cu-Au melts at 1550 K were calculated in terms of the lattice solution model and statistical theory of low-concentration melts. The h i potential of the approach of two gold atoms in the face-centered cubic lattice of copper was used. The theoretical parameter ɛ Au Au = 3.2 was satisfactorily close to the experimental value ɛ Au Au = 3.7, whereas the theoretical enthalpy parameter agreed with its experimental value only in sign and the order of magnitude.

Copper valence, structural separation and lattice dynamics in tennantite (fahlore): NMR, NQR and SQUID studies

Electronic and magnetic properties of tennantite subfamily of tetrahedrite-group minerals have been studied by copper nuclear quadrupole resonance (NQR), nuclear magnetic resonance (NMR) and SQUID magnetometry methods. The temperature dependences of copper NQR frequencies and line-width, nuclear spin-lattice relaxation rate T 1 −1 and nuclear spin-echo decay rate T 2 −1 in tennantite samples in the temperature range 4.2–210 K is evidence of the presence of field fluctuations caused by electronic spins hopping between copper CuS3 positions via S2 bridging atom. The analysis of copper NQR data at low temperatures points to the magnetic phase transition near 65 K. The magnetic susceptibility in the range 2–300 K shows a Curie–Weiss behavior, which is mainly determined by Fe2+ paramagnetic substituting ions.

Molecules Coining Patterns into a Metal: The Hard Core of Soft Matter

Using scanning tunneling microscopy (STM), we demonstrate that deposition of a monolayer of perylene (C20H12), a planar aromatic molecule, on a Cu(110) substrate leads to the formation of a periodic pattern of nanostripes. High-resolution STM data indicate that the driving force for this unexpected surface restructuring caused by such nonreactive hydrocarbons is a lock-in mechanism due to a close registry of the molecular carbon frame with respect to the underlying copper lattice which leads to an enhanced adsorption energy.

Electron density analysis of the layered antiferromagnetic compoundCu2(OH)3NO3: Relationship with the magnetic interaction mechanism

The electronic properties of the antiferromagnetic layer compound copper hydroxonitrate $[{\mathrm{Cu}}_{2}(\mathrm{OH}{)}_{3}{\mathrm{NO}}_{3}]$ are investigated by high-resolution single-crystal x-ray diffraction at $114\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. A pseudoatomic multipolar model is used to reconstruct the experimental electron density (ED) distribution, whose quantitative analysis is performed through the quantum theory of atoms in molecules. The topological properties of the ED indicate indirect $\mathrm{Cu}\ensuremath{\cdots}\mathrm{Cu}$ bonds mediated by the hydroxo and nitrate ions among the two-dimensional (2D) copper lattice. A mean charge transfer of 0.4 electrons from the copper atoms to the hydroxo groups and of 0.76 electrons to the nitrate ion is determined via numerical integration of the ED over the atomic basins. Low but nonetheless significant $\mathrm{Cu}\text{\ensuremath{-}}\mathrm{O}$ partial covalent bonds do also exist. Interplane interaction pathways are furthermore localized and characterized.

A Study of the Behavior of Cobalt in Carbonylation of Copper-Nickel Metallurgical Half-Products at Medium Pressure of the Reaction Gas

Dependences of the cobalt recovery into the carbonyl gas phase on the content of sulfur and carbon in sulfidized copper-nickel metallurgical half-products subjected to carbonylation were studied at a medium pressure of the reaction gas (70 gage atm). The behavior of cobalt was examined by means of metallographic analysis of the residue formed in carbonylation. A mechanism of solid-phase interaction of cobalt with copper sulfide and a method for calculation of the volume self-diffusion coefficient of cobalt in the crystal lattice of metallic copper deformed after removal of nickel were suggested.

Metal–insulator transition in a layer adsorbed on a metal electrode

The properties of a layer of metal atoms adsorbed on a metal electrode are investigated as a function of the coverage, focusing on metal–insulator transitions of the Mott–Hubbard type. For this purpose a model Hamiltonian is set up which incorporates the interaction of the adsorbate with the metal and with the solvent, and approximate solutions for the adsorbate Green's functions are derived. The presence of the solvent has a strong effect both on the onsite Coulomb repulsion and on the adsorbate–adsorbate interactions. Metallization requires both a finite density of states near the Fermi level and a mean free path for the electrons exceeding the lattice spacing. Explicit model calculations have been performed for a regular lattice of copper on Au(1 1 1). With increasing coverage, the adsorbate passes from an insulating to a conductive state, then back to an insulating phase before becoming conductive again near full coverage.

Magnetoelastic stress inCu∕Ni∕Cu∕Si(100)epitaxial thin films

The magnetoelastic (ME) stresses for a series of $\mathrm{Cu}∕\mathrm{Ni}({t}_{\mathrm{Ni}})∕\mathrm{Cu}∕\mathrm{Si}(001)$ epitaxial films are reported. The direct measurement of the stresses in the (001) plane allows determination of the irreducible ME stress ${B}_{\mathrm{eff}}^{\ensuremath{\gamma},2}$ that accounts for the breaking of the in-plane square symmetry. ${B}_{\mathrm{eff}}^{\ensuremath{\gamma},2}$ has been determined as a function of the applied magnetic field $(\ifmmode\pm\else\textpm\fi{}15\phantom{\rule{0.3em}{0ex}}\mathrm{kOe})$ and the temperature $(300--10\phantom{\rule{0.3em}{0ex}}\mathrm{K})$ for ${t}_{\mathrm{Ni}}$ ranging from 5 to $15\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$. The temperature dependence of ${B}_{\mathrm{eff}}^{\ensuremath{\gamma},2}$ is proportional to the square power of the reduced magnetization and the $0\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ value increases with the internal stress. These experimental observations are explained considering the tetragonal distortion of the nickel caused by the epitaxial strain that the copper lattice introduces in the nickel layers.