Copper Sandwich Research Articles

Effect of thin-wall copper on the mechanical properties of ultra-light 3D-printed polymeric sandwich panels

In this study, a portion of an ultra-light polymeric sandwich panel was produced by additive manufacturing with a dimension of 25 × 25 × 37 mm as a precursor. Then, the precursor was covered with a thin-walled copper through electroforming deposition as a portion of a copper sandwich panel. The weight of the polymeric sandwich panel increased from 2–4 g to 9–13 g for the copper sandwich panel during the electroforming process. Compressive strength and energy absorption density of the polymeric and the copper sandwich panels with open-cell cores measured for 4, 5 and 6 PPI. The results shown that the ultra-light polymeric and copper sandwich panels with 6 PPI have the best mechanical performance in terms of yield stress, energy absorption density and energy absorption efficiency. Moreover, the abovementioned characteristics are 0.09 MPa, 0.11 MJ . m − 3 and 80% for the polymeric sandwich panels, and 1.74 MPa, 0.98 MJ . m − 3 and 70% for the copper sandwich panels, respectively. Therefore, the addition of 9.01 g copper as a reinforcing around the core’s polymeric ligaments caused an increase in the yield stress for 20 times and in the energy absorption density for 9 times. Comparing to Ashby diagram, and previous studies, the sandwich panel portions of this study could develop the industry of sandwich panels by using the metallic shells as a reinforcement to ultralight polymeric sandwich structures.

Comparative Study of Metal Substrates for Improved Carbonization of Electrospun PAN Nanofibers.

Carbon nanofibers are used for a broad range of applications, from nano-composites to energy storage devices. They are typically produced from electrospun poly(acrylonitrile) nanofibers by thermal stabilization and carbonization. The nanofiber mats are usually placed freely movable in an oven, which leads to relaxation of internal stress within the nanofibers, making them thicker and shorter. To preserve their pristine morphology they can be mechanically fixated, which may cause the nanofibers to break. In a previous study, we demonstrated that sandwiching the nanofiber mats between metal sheets retained their morphology during stabilization and incipient carbonization at 500 °C. Here, we present a comparative study of stainless steel, titanium, copper and silicon substrate sandwiches at carbonization temperatures of 500 °C, 800 °C and 1200 °C. Helium ion microscopy revealed that all metals mostly eliminated nanofiber deformation, whereas silicone achieved the best results in this regard. The highest temperatures for which the metals were shown to be applicable were 500 °C for silicon, 800 °C for stainless steel and copper, and 1200 °C for titanium. Fourier transform infrared and Raman spectroscopy revealed a higher degree of carbonization and increased crystallinity for higher temperatures, which was shown to depend on the substrate material.

Maskless atmospheric pressure PECVD of SiOx films on both planar and nonplanar surfaces using a flexible atmospheric microplasma generation device

AbstractThis paper presents the use of a simple‐arranged, low‐cost, and flexible atmospheric pressure microplasma generation device (μPGD) with controlled gas discharge to achieve maskless atmospheric plasma‐enhanced chemical vapor deposition (PECVD) of SiOx films on both planar and nonplanar surfaces. The μPGD is mainly composed of a copper–polyimide–copper sandwich structure with predefined microfluidic channels. Uniform microplasmas of different shapes and dimensions were generated in the open air. SiOx films were masklessly deposited with well‐defined edges and good feature transfer fidelity. The SEM, EDS, XPS, and FTIR spectra of the deposited film confirm the SiOx structure. These results indicate that μPGD is able to achieve maskless PECVD of SiOx films in the open air, especially micropatterning on nonplanar surfaces.

Heat transfer at dielectric - metallic interfaces in the ultra-low temperature range

In the framework of the AEgIS project a series of steady state and dynamic heat transfer measurements at ultra-low temperatures was conducted in the Central Cryogenic Laboratory at CERN. Two sandwich setups, simulating the behaviour of ultra-cold AEgIS electrodes, were investigated and compared, namely: a sapphire — indium — copper and a sapphire — titanium — gold — indium — copper sandwich. The total thermal resistivity of both sandwich setups was evaluated as a function of the influence of normal and superconducting thin layers and multiple dielectric — metallic interfaces in terms of Kapitza resistance. The resulting limitations of the electrode’s design are presented.

Friction Drilling of Cast Aluminum Alloy A380 Without Significant Petal Formation and Radial Fracture

Cast aluminum alloy A380 is one of the most commonly specified alloys that has light weight and exhibits excellent resistance to hot cracking, which makes it necessary in many industrial applications. An idea is investigated to generate a cylindrical bushing without significant petal formation and radial fracture that are expected to be obtained by friction drilling of cast metals. Three materials; namely, 316 stainless steel, Al6060 aluminum alloy, and red copper alloy are used in which each of them is located on the upper and lower surfaces of A380 workpiece, so achieving the idea of the functionally graded material. The process parameters were studied for reducing the resultant axial force, the gap between surfaces, and achieving a longer bushing without petal formation and radial fracture. Lower feed rate achieves minimum axial force and gap thickness with maximum bushing length for all material sandwiches. An optimized decision making by the help of fuzzy logic techniques is performed, revealing that red copper sandwich exhibits the optimal multiple performance characteristic index based on axial force, bushing length, gap thickness, and gap divergence.

Heat transfer at a sapphire – indium interface in the 30 mK – 300 mK temperature range

Within the framework of the AEgIS (Antimatter Experiment: Gravity, Interferometry, Spectroscopy) project a direct measurement of the Earth’s gravitational acceleration on antihydrogen will be carried out. In order to obtain satisfactory precision of the measurement, the thermal movement of the particles should be reduced. Therefore a Penning trap, which is used to trap antiprotons and create antihydrogen, will be placed on a mixing chamber of an especially designed dilution refrigerator. The trap consists of 10 electrodes, which need to be electrically insulated, but thermally anchored. To ensure that the trap remains at a temperature below 100 mK, the heat transfer at the metallic-dielectric boundary is investigated. A copper – indium – sapphire – indium – copper sandwich setup was mounted on the CERN Cryolab dilution refrigerator. Keeping the mixing chamber at a constant low temperature in the range of 30 mK to 300 mK, steady-state measurements with indium in normal conducting and superconducting states have been performed. Obtained results along with a precise description of our setup are presented.

Copper–gold sandwich structures on PE and PET and their SERS enhancement effect

In this paper we have investigated the SERS effect of gold–copper sandwich structures i.e. the coupling between surface plasmon polaritons supported by the gold grating and localized surface plasmons excited on the grafted copper nanoparticles.

Copper–graphite–copper sandwich: superior heat spreader with excellent heat-dissipation ability and good weldability

Cu–graphite–Cu sandwich heat spreaders with high thermal conductance and low density present outstanding ability of heat dissipation, which have potential application in smart and wearable electronics cooling.

An accurate technique for pre-yield characterization of MR fluids

This study is concerned with the characterization of two types of magnetorheological (MR) fluids (MR 122EG and MR 132DG) in the pre-yield region. A phenomenological model is proposed for characterizing the complex shear modulus of the MR fluids as a function of both the magnetic flux density and the excitation frequency using the experimental data acquired for both the fluids. The experiments were conducted with a sandwich beam structure with an aluminum face layer and MR fluid as the core layer. A nearly uniform magnetic field was applied across the sandwich beam using two ceramic permanent magnet bars. The frequency response characteristics of the sandwich cantilevered beam were subsequently measured under harmonic excitations swept in the 0 to 500 Hz frequency range considering different densities of the applied magnetic flux, ranging from 0 to 90 mT. Dynamic responses of the structure were also obtained through analysis of a finite element (FE) model developed using the classical plate theory. The frequency and field-dependent complex shear moduli of the two MR fluids were identified from both the experimental data and the FE model results. The validity of the proposed methodology is demonstrated by comparing the FE model results with the experimental data for a copper sandwich structure comprising the two MR fluids.

Thermal resistance of indium coated sapphire–copper contacts below 0.1 K

High thermal resistances exist at ultra-low temperatures for solid–solid interfaces. This is especially true for pressed metal–sapphire joints, where the heat is transferred by phonons only. For such pressed joints it is difficult to achieve good physical, i.e. thermal contacts due to surface irregularities in the microscopic or larger scale. Applying ductile indium as an intermediate layer reduces the thermal resistance of such contacts. This could be proven by measurements of several researchers. However, the majority of the measurements were performed at temperatures higher than 1K. Consequently, it is difficult to predict the thermal resistance of pressed metal–sapphire joints at temperatures below 1K.In this paper the thermal resistances across four different copper–sapphire–copper sandwiches are presented in a temperature range between 30mK and 100mK. The investigated sandwiches feature either rough or polished sapphire discs (Ø 20mm×1.5mm) to investigate the phonon scattering at the boundaries. All sandwiches apply indium foils as intermediate layers on both sides of the sapphire. Additionally to the indium foils, thin indium films are vapour deposited onto both sides of one rough and one polished sapphire in order to improve the contact to the sapphire.Significantly different thermal resistances have been found amongst the investigated sandwiches. The lowest total thermal resistivity (roughly 26cm2K4/W at 30mK helium temperature) is achieved across a sandwich consisting of a polished sapphire with indium vapour deposition. The thermal boundary resistance between indium and sapphire is estimated from the total thermal resistivity by assuming the scattering at only one boundary, which is the warm sapphire boundary where phonons impinge, and taking the scattering in the sapphire bulk into account. The so derived thermal boundary resistance agrees at low temperatures very well with the acoustic mismatch theory.

Metal–Graphene–Metal Sandwich Contacts for Enhanced Interface Bonding and Work Function Control

Only a small fraction of all available metals has been used as electrode materials for carbon-based devices due to metal-graphene interface debonding problems. We report an enhancement of the bonding energy of weakly interacting metals by using a metal-graphene-metal sandwich geometry, without sacrificing the intrinsic π-electron dispersions of graphene that is usually undermined by strong metal-graphene interface hybridization. This sandwich structure further makes it possible to effectively tune the doping of graphene with an appropriate selection of metals. Density functional theory calculations reveal that the strengthening of the interface interaction is ascribed to an enhancement of interface dipole-dipole interactions. Raman scattering studies of metal-graphene-copper sandwiches are used to validate the theoretically predicted tuning of graphene doping through sandwich structures.

Synthesis, Structure and Magnetic Properties of a Novel Hexanuclear Copper Methylsiloxane Complex

AbstractA new hexanuclear copper(II) sandwich complex based on two 12‐membered macrocyclic methylsiloxanolate ligands, [Cu6{(MeSiO2)6}2]·6DMF, was synthesized and characterized by single‐crystal X‐ray diffraction analysis and magnetic measurements. The cluster compound crystallizes in the monoclinic system, space group P21/n (No. 14), with a = 13.3728(5) Å, b = 15.4281(7) Å, c = 17.4335(7) Å, β = 98.932(3)° and Z = 2. The unit cell contains two identical molecular clusters, each consisting of six interacting Cu2+ (S = ${1 \over 2}$) ions. Within the cluster the six oxygen‐bridged Cu2+ ions are arranged in an almost regular hexagon. An analysis of the high‐temperature part of the magnetic susceptibility reveals that the complex has a strong average ferromagnetic Cu–Cu exchange interaction of |Jav/kB| = (50.4 ± 1) K with a high‐spin S = 3 ground state. A satisfactory fit for the magnetic susceptibility and the magnetization in the whole accessible temperature range is obtained from a Heisenberg model with nonuniform exchange couplings within a ring, corresponding to a system of two weakly coupled trimers with a ferromagnetic intratrimer exchange coupling of |J/kB| = 72.5 K and a ferromagnetic intertrimer exchange coupling of |J′/kB| = 7 K. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Synthesis, Structure and Magnetic Properties of a Novel Linear CuII‐Trimer Complex

AbstractA new hexanuclear copper(II) sandwich complex based on two 10‐membered macrocyclic phenylsiloxanolate ligands, {Cu6[(C6H5SiO2)5]2(OH)2(C10H8N2)2}·4(DMF)·3(H2O) (1), was synthesized and characterized by single‐crystal X‐ray diffraction and measurements of the magnetic susceptibility and isothermal magnetization. The cluster compound crystallizes in the triclinic system, space group P$\bar {1}$ (No. 2), with a = 14.925(3) Å, b = 16.745(2) Å, c = 23.053(3) Å, α = 83.079(9)°, β = 84.836(13)°, γ = 65.019(17)°, and Z = 2. The unit cell contains two identical molecules, each consisting of six interacting Cu2+ (S = 1/2) ions. Within the molecule, the six Cu2+ ions are arranged in two almost linear, parallel trimers. While pairs of oxygen atoms link the Cu2+ ions within the trimers, single oxygen atoms residing at the ends of the trimers provide the strongest intertrimer bonds. Magnetic measurements reveal an antiferromagnetic intratrimer exchange interaction, J/kB = 85 K, as the dominant magnetic coupling of the complex. By introducing a weak antiferromagnetic intertrimer coupling, J′/kB = 3.5 K, a satisfactory description of the magnetic behavior over a wide range of temperature and magnetic field is obtained. The departure of the model curves from the data at the lowest available temperature indicates the presence of additional, weak intra‐ and/or intermolecular interactions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Dissolution from electrodeposited copper–cobalt–copper sandwiches

The electrochemical behaviour of electrodeposited Co–Cu/Cu multilayers from citrate electrolytes was investigated using cyclic voltammetry and stripping techniques at a rotating ring disc electrode. Copper and cobalt–copper alloy sandwiches were deposited from an electrolyte containing 0.0125 M CuSO4, 0.250 M CoSO4 and 0.265 M trisodium citrate at two different pHs, 1.7 and 6.0. The Cu/Co–Cu/Cu sandwich is representative of a single layer in a Co–Cu/Cu multilayer deposit, which is known to exhibit unusual physical and magnetic properties. Results from cyclic voltammetry and detection of dissolving species at the ring showed that cobalt is stripped from a Cu/Co–Cu/Cu sandwich even when a copper layer as thick as 600 nm covers the Co–Cu alloy. Scanning electron microscopy showed that cobalt can dissolve from the deposit easily because the copper layer covering the Co–Cu alloy is porous. A separate series of experiments with Cu/Co–Ni–Cu/Cu sandwich showed that cobalt does not dissolve from these deposits because the addition of nickel stabilises cobalt in the Co–Ni–Cu alloy.

Fabrication of magnetic rings for high density memory devices

A new technique has been developed to fabricate magnetic ring elements. The technique is based on pre-patterning of silicon ring structures and subsequently epitaxial growth of copper–cobalt–copper sandwich film on top of silicon rings. In contrast to conventional methods of making magnetic elements, no damage to the magnetic layer structure is introduced by the patterning process. Unlike conventional magnetic structures, there are a number of challenges in patterning ring geometry by electron beam lithography and by reactive ion etching. Electron beam lithography process has been optimised for patterning ring structures of sub half micrometer dimension. Both conventional RIE and deep RIE techniques have been tried for transferring resist ring structure to silicon substrates. Large arrays of magnetic rings have been fabricated by the prepatterning techniques. Magnetic measurement by MOKE method has demonstrated the new onion state for magnetic switching, which is in agreement with computer simulation results.

Different degree of reduction and sliding phenomenon study for three-dimensional hot rolling with sandwich flat strip

Symmetric rolling of 3D sandwich flat strips with thermal-elastic–plastic coupled model was studied under the assumption of an elastic roller and the condideration of heat transfer. Aluminum–copper sandwich flat strips were used in this study. The numerical model of symmetric rolling for 3D sandwich flat strip with thermal-elastic–plastic coupled model was developed based on the large deformation–large strain theory, the update Lagrangian formulation and the incremental principle. Besides, flow stress was considered as the function of strain, strain rate and temperature. The theoretical model of finite element method containing the two-order strain rate formulation acted as the basis for determining the convergence of simulation results. The contact surface between the aluminum and copper for the sandwich flat strip was also discussed. First of all, the contact face between the aluminum and copper was assumed that it would be fixed without sliding. Symmetric hot rolling of the aluminum and copper sandwich flat strip was analyzed. A slide criterion was then introduced to study the shear stress states of the contact face between aluminum and copper of sandwich strip, which was used to compare the relation between the maximum shear stress and the yielding shear stress on the contact face. If the maximum shear stress of aluminum or copper is smaller than the yielding stress of aluminum or copper respectively, sliding does not occur on the contact face. On the contrary, the sliding may occur on the contact face between aluminum and copper. Three different degrees of reduction were simulated in this study to analyze the states of shear stress on the upper aluminum strip and lower copper strip close to the contact face. Finally, it finds that the sliding on the contact face between aluminum and copper may occur around certain degree of reduction. The average rolling force of the simulation result was compared with experimental data [8] to verify the simulation results.

Hot rolling of an aluminum–copper sandwich flat strip with the three-dimensional finite element method

The symmetrical rolling of 3D sandwich flat strips with a thermo-elastic–plastic coupled model was studied under the assumption of an elastic roller and the consideration of heat transfer. Aluminum–copper sandwich flat strips were used in this study. The effect of different functions of the flow stress on the strip appearance after rolling were explored. The numerical analytical model of symmetrical rolling for 3D sandwich flat strip with a thermo-elastic–plastic coupled model was developed based on the large-deformation–large-strain theory, the updated Lagrangian formulation and the incremental principle. Further, the flow stress was considered as the function of strain, strain rate and temperature. The theoretical model of the finite element method containing a two-order strain-rate formulation acted as the basis for determining the convergence of simulation results. Before the aluminum–copper sandwich flat strip was simulated first an aluminum–mild steel sandwich flat strip was simulated. The average rolling force of the simulation results was compared with experimental findings to establish that the simulation program proposed in this study is reasonable. In addition, the equivalent strain, and the equivalent strain rate of the aluminum–copper sandwich strip during rolling were analyzed and compared with those for the flat rolling of a single aluminum layer.

The hadron calorimeter of the compact muon solenoid (CMS)

The Hadron Calorimeter of CMS is about 1,000 tons of copper and scintillator sandwich in a 4 tesla magnetic field. It will be built in three segments, the barrel surrounding the central portion and the two end caps. The scintillators will use a tower structure made of grooved megatiles with wavelength shifting (WLS) fibers imbedded inside the grooves. The coverage extends to η = 3.0 and is hermetic with very few gaps. The 1995 test beam data was taken inside a 3 tesla magnet showed that it will work in a magnetic field, but will require a tail catcher inside the muon system.

Influence of KCN treatment on CuInS 2 thin films

Electrical and compositional properties as well as solar cell performances were studied on polycrystalline CuInS 2 films synthesized by sulphurization of copper and indium sandwiches. To study the influence of KCN treatment, each of the samples was divided into two pieces, where one was treated with KCN, and their properties were compared. KCN treatment lowered the initial Cu In composition ratio which ranged between 1 and 2.1 to slightly less than 1. Also, it increased the resistivity by two orders of magnitude, which is due to the reduction of the carrier concentration by three orders of magnitude. The X-ray diffraction line width is narrowed as well. These results indicate that some Cu x S and/or copper are etched during the KCN treatment. Solar cells were fabricated with a chemical bath deposited CdS buffer layer and an atom beam sputtered ZnO window on the CuInS 2 thin films. The solar cell conversion efficiency was increased from η = 2.1% (3.9% after vacuum annealing) to η = 5.8%.

A simple sandwich-cryogen-jet procedure with high cooling rates for cryofixation of biological materials in the native state

We evaluate a method for improved, ice-crystal-free cryofixation of various biological materials (macromolecules, subcellular fractions, whole cells in suspensions or as monolayers) without any chemical pretreatments. The principle of the method (as introduced byPscheid, Schudt, andPlattner 1981 for cell monolayer cultures) is as follows. Firstly, a thin sample layer is sandwiched between a thin copper object holder and a thermally insulating plastic sheet (Thermanox, which is also used as a cell culture substratum); secondly, a jet of melting propane is shot from a simple, inexpensive brass vessel onto the copper object holder. We now ascertained that this simple and inexpensive method allows cooling rates up to > 18,000 °C/sec and, thus, gives better results than comparable but more sophisticated and expensive procedures. The method also avoids all the disadvantages of some other rapid freezing methods. Specifically, the sample mass required is minimal, the sample remains fully hydrated and no changes of ionic or other conditions can occur. There is no hazard of passing a cold gas phase (cooling curves being very steep right at the beginning) or of impairment by mechanical impact (as it could be with “cold metal block freezing”). The expedient of using a thermal insulator as part of a sandwich sample allows cooling rates which are superior or at least equivalent to those obtained with a commercial double propane-jet device (and double copper sandwiches). The reason for this is that in practice a two-side propane jet onto a copper-copper sandwich can not reach both sides precisely at the very same time (as implied from our cooling rate measurements). The tentative transformation of our mono-jet into a double-jet variation (with a branched nozzle piece) did also not improve the results, when compared with a single propane-jet onto a copper-Thermanox sandwich.