Copper Nanotubes Research Articles

Changes in the structure and conducting properties of copper nanotubes as a result of bombardment with O3+ ions

The results of targeted modification of the structure and properties of copper nanotubes by accelerated O3+ ions at a fluence of 1 × 109 to 5 × 1011 cm−2 with an energy of 1.75 MeV/nucleon are reported. XHray diffraction methods have been used to study the dynamics of changes in the crystallite shape, dislocation density, and the orientation of copper nanotubes before and after irradiation. It has been shown that irradiation with accelerated ions has a significant effect on the change in texture coefficients and dislocation density. At a fluence of 1 × 1010 cm−2 or higher, the accumulation of oxygen in the nanotube structure is observed, which leads to the appearance of oxide compounds.

Thermal annealing-induced modification of the structure and electrical conductivity of metallic nanotubes embedded in PET track-etched membranes

This work is dedicated to developing a simple methodology that allows for the application of a thermal annealing process, which can improve the conductivity of metallic nanostructures, embedded in porous track-etched membranes based on polyethylene terephthalate (PET TeMs), but at the same time, does not compromise the mechanical properties. Zinc, copper, and cobalt nanotubes (NTs) prepared by electrochemical deposition in PET TeMs were annealed at 200 °C for different time periods. The effects of annealing treatment on the structural and electrical properties were investigated by scanning electron microscopy, X-ray diffraction, and room-temperature resistance measurements. Choosing the appropriate annealing time for Zn or Cu-NTs allows controlling the formation of an oxide phase in these nanostructures. The presence of the oxide phase in an amount of no more than 10–15 wt% led to a decrease in the resistivity and an increase in the conductivity. Thermal annealing of Co-based NTs changed intensities of the metastable fcc β-Co and stable hcp α-Co phases. The metastable β-Co phase caused additional defects due to a change in the crystallite size after 90 min of thermal annealing.

From morphology of attrited copper/MWCNT hybrid fillers to thermal and mechanical characteristics of their respective polymer‐matrix composites: An analytical and experimental study

ABSTRACTSynergistic effect of copper and multiwalled carbon nanotube on thermal and mechanical properties of high‐density polyethylene (HDPE)‐matrix composite was evaluated. Attrition mill was employed to prepare the hybrid powder. Reinforcing the polymer‐matrix was carried out using different contents of simultaneously (Sim) and separately (Sep) milled powders as hybrid fillers. X‐ray diffraction and microscopy results show different trends of particle size for Sep and Sim affected by both milling time and volume fraction ratio. Thermal characterization indicates that conductivity was enhanced by 90% and thermal expansion was reduced to 53% of neat HDPE. Young's modulus and tensile strength were improved by 7.8 and 1.22 times of neat HDPE, respectively. Also, characteristics of Sim‐reinforced composites exhibited better correlated relation with milling time compared with erratic behavior of Sep. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45397.

First-principles study of the stability, magnetic and electronic properties of Fe and Co monoatomic chains encapsulated into copper nanotube

By using first-principles calculations based on density-functional theory, the stability, magnetic and electronic properties of Fe and Co monoatomic chains encapsulated into copper nanotube are systematically investigated. The binding energies of the hybrid structures are remarkably higher than those of corresponding freestanding TM chains, indicating the TM chains are significantly stabilized after encapsulating into copper nanotube. The formed bonds between outer Cu and inner TM atoms show some degree of covalent bonding character. The magnetic ground states of Fe@CuNW and Co@CuNW hybrid structures are ferromagnetic, and both spin and orbital magnetic moments of inner TM atoms have been calculated. The magnetocrystalline anisotropy energies (MAE) of the hybrid structures are enhanced by nearly fourfold compared to those of corresponding freestanding TM chains, indicating that the hybrid structures can be used in ultrahigh density magnetic storage. Furthermore, the easy magnetization axis switches from that along the axis in freestanding Fe chain to that perpendicular to the axis in Fe@CuNT hybrid structure. The large spin polarization at the Fermi level also makes the hybrid systems interesting as good potential materials for spintronic devices.

Effect of pH on enhancement of hydrogen storage capacity in carbon nanotubes on a copper substrate

Electrochemical storage of hydrogen in Cu–CNTs (copper and carbon nanotubes) electrodes was studied by Chronopotentiometry technique. In this project effective absorption factors in atomic hydrogenation by CNTs such as charge/discharge (C&D) cyclic number, current and also different pHs were studied. Acidic method was used for purifying and functionalizing the CNTs, and the outputs were characterized using XRD spectroscopy. The CNTs were deposited on copper foam with nano metric porosity by electrophoretic method (EPD). By comparing the results of different experiments in different charge and discharge cycles, it was observed that multi-wall carbon nanotubes in the current of 3mA with pH=5.4 have a maximum discharge capacity ‎about 10,000mAh/g.

Analytical Study and Experimental Validation of Copper II Sulfate and Potassium Ferri/Ferrocyanide Thermocells Using Onsager Flux Equations

Thermocells convert heat energy directly into electrical energy through charge-transfer reactions at the electrode–electrolyte interface. To perform an analytical study on the behavior of thermocells, the Onsager flux relationship was applied to thermocells, which used aqueous copper II sulfate and aqueous potassium ferri/ferrocyanide as the electrolyte. The transport coefficient matrices were calculated for each electrolyte and applied to several simulations, which were subsequently validated through experimental testing and comparison to previous literature results. The simulation is shown to correctly predict the short circuit current, maximum power output, and power conversion efficiency. Validation demonstrates that the simulation model developed, using the Onsager flux equations, works for thermocells with different electrode materials (platinum, copper, charcoal, acetylene black, and carbon nanotube), electrode spacing, and temperature differentials. The power dependence of the thermocell on concentration and electrode spacing, with respect to the Seebeck coefficient, maximum power output, and relative efficiency, is also shown.

Prediction of metallic nanotube reactivity for H2O activation.

The reactivity of metallic nanotubes toward the catalysis of water dissociation, a key step in the water gas shift reaction (WGSR), was analyzed through density functional theory (DFT) calculations. Water dissociation was studied on surfaces of nanotubes based on copper, gold and platinum, and also on platinum doped copper and gold nanotubes. Gold and copper nanotubes present activities that are similar to those of their corresponding extended surfaces but, in the case of the Pt(5,3) nanotube, a significant improvement in the activity is found when compared with the extended surfaces. In fact, the calculations predict the water dissociation to be spontaneous on Pt(5,3) with a low activation energy barrier. The platinum doping of gold and copper nanotubes leads to contrasting effects, i.e., with a slight increase of activity found on gold and a slight decrease of activity in the case of copper. The consideration of a Brönsted-Evans-Polanyi (BEP) relationship to estimate the activation energy barriers for the O-H bond break leads to a satisfactory agreement between estimated and explicitly calculated values which suggests the validity of the BEP relationship for qualitative predictions of the activities of metal nanotubes towards the water dissociation reaction.

Breaking the electrical barrier between copper and carbon nanotubes.

Improving the interface between copper and carbon nanotubes (CNTs) offers a straightforward strategy for the effective manufacturing and utilisation of Cu-CNT composite material that could be used in various industries including microelectronics, aerospace and transportation. Motivated by a combination of structural and electrical measurements on Cu-M-CNT bimetal systems (M = Ni, Cr) we show, using first principles calculations, that the conductance of this composite can exceed that of a pure Cu-CNT system and that the current density can even reach 1011 A cm-2. The results show that the proper choice of alloying element (M) and type of contact facilitate the fabrication of ultra-conductive Cu-M-CNT systems by creating a favourable interface geometry, increasing the interface electronic density of states and reducing the contact resistance. In particular, a small concentration of Ni between the Cu matrix and the CNT using either an "end contact" and or a "dot contact" can significantly improve the electrical performance of the composite. Furthermore the predicted conductance of Ni-doped Cu-CNT "carpets" exceeds that of an undoped system by ∼200%. Cr is shown to improve CNT integration and composite conductance over a wide temperature range while Al, at low voltages, can enhance the conductance beyond that of Cr.

Exergetic analysis of plate evaporator using hybrid nanofluids as secondary refrigerant for low-temperature applications

The brine-based hybrid nanofluids are proposed as a secondary refrigerant in counter-flow corrugated plate evaporator for low-temperature applications. Different types of alumina hybrid nanofluids containing different nanoparticles (copper, silver and multi-walled carbon nanotube) in equal volume with the total volume concentration of 0.8% dispersed in different brines have been assessed for certain cooling load. Various exergetic performance parameters-based comparison has been performed with brines and related hybrid nanofluids for milk chilling, ice making and fish freezing applications. Some energy-exergy relationships have been established as well. Exergetic performance decreases with a decrease in application temperature. The maximum reduction in irreversibility and non-dimensional exergy destruction, and maximum increase in irreversibility distribution ratio (IDR) and exergetic efficiency have been obtained for propylene glycol brine-based alumina multi-walled carbon nanotube hybrid nanofluid. The study reveals that the brine-based hybrid nanofluids may be the suitable substitute as a secondary refrigerant.

Изменение структурных характеристик нанотрубок меди под воздействием ионизирующего излучения

Изменение структурных характеристик нанотрубок меди под воздействием ионизирующего излучения

Mechanical and thermal properties of graphene–carbon nanotube-reinforced metal matrix composites: A molecular dynamics study

Single layer graphene sheets and carbon nanotubes have resulted in the development of new materials for a variety of applications. Though there are a large number of experimental and numerical studies related to these nanofillers, still there is a lack of understanding of the effect of geometrical characteristics of these nanofillers on their mechanical properties. In this study, molecular dynamics simulation has been used to assess this issue. Two different computational models, single layer graphene sheets–copper and carbon nanotube–copper composites have been examined to study the effect of nanofiller geometry on Young’s modulus and thermal conductivity of these nanocomposites. Effect of increase in temperature on Young’s modulus has also been predicted using molecular dynamics. The effect of nanofiller volume fraction ( Vf) on Young’s modulus and thermal conductivity has also been studied. Results of thermal conductivity obtained using molecular dynamics have been compared with theoretical models. Results show that with increase in Vf the Young’s modulus as well as thermal conductivity of single layer graphene sheets–Cu composites increases at a faster rate than that for carbon nanotube–Cu composite. For the same Vf, the Young’s modulus of single layer graphene sheets–Cu composite is higher than carbon nanotube–Cu composite.

PdCu alloy nanoparticle-decorated copper nanotubes as enhanced electrocatalysts: DFT prediction validated by experiment

In order to combine the advantages of both 0D and 1D nanostructured materials into a single catalyst, density functional theory (DFT) calculations have been used to study the PdCu alloy NP-decorated Cu nanotubes (PdCu@CuNTs). These present a significant improvement of the electrocatalytic activity of formic acid oxidation (FAO). Motivated by our theoretical work, we adopted the seed-mediated growth method to successfully synthesize the nanostructured PdCu@CuNTs. The new catalysts triple the catalytic activity for FAO, compared with commercial Pd/C. In summary, our work provides a new strategy for the DFT prediction and experimental synthesis of novel metal NP-decorated 1D nanostructures as electrocatalysts for fuel cells.

Thermal radiation energy due to SWCNTs on MHD nanofluid flow in the presence of seawater/water: Lie group transformation

Abstract An investigation of the boundary layer nanofluids flow over a porous wedge in the presence of uniform transverse magnetic field and thermal radiation energy has been analyzed. Water and seawater based nanofluid containing copper, aluminum oxide and Single Walled Carbon nanotubes (SWCNTs) is taken into consideration. The governing equations in terms of ODEs are solved using fourth–fifth order Runge–Kutta–Fehlberg method with shooting technique. Approximate solution of temperature, velocity, the rate of heat transfer and the shear stress at the wedge are illustrated graphically for several values of the pertinent parameters. Thermal conductivity enhancements of water and seawater in the presence of single-walled carbon nanotubes (SWCNTs) are presented. The thermal boundary layer of SWCNTs–water is compared to SWCNTs–seawater on absorbing the incident thermal energy radiation and transmitting it to the nanofluid by convection. Momentum and thermal boundary layer thickness for SWCNTs–seawater is stronger than SWCNTs–water with increase of the radiation parameter because of low thermal conductivity of seawater. The rate of heat transfer of Cu–seawater is significantly stronger than all the other mixtures in the flow regime because of the combined effects of density of copper and seawater.

Thermal radiation energy on squeezed MHD flow of Cu, Al2O3 and CNTs-nanofluid over a sensor surface

The squeezed MHD flow of water, ethylene glycol and engine oil based metallic nanoparticles over a sensor surface in the presence of thermal radiation energy have been investigated. The physical significance of the problem is water, ethylene glycol and engine oil based on the geometry and the interaction of copper (Cu), alumina (Al2O3) and carbon nanotubes (SWCNTs and MWCNTs). The governing partial differential equations of momentum and energy are transformed to similarity equations (ODEs) for certain families of the controlling parameters. The numerical and analytical solutions of the resulting ODEs are solved using fourth or fifth order Fehlberg method with shooting technique and optimal homotopy asymptotic method (OHAM) and it is also found that there is no significance difference between them. It is investigated that in squeezing flow phenomena, SWCNTs-engine oil in the presence of thermal radiation energy gives approximately more than 30% enhancement in the heat transfer as compared to the water based SWCNTs and MWCNTs.

Interaction between copper and carbon nanotubes triggers their mutual role in the enhanced photodegradation of p-chloroaniline.

Copper (Cu, 1-5 wt%) was loaded onto carbon nanotubes (CNTs) by a simple electrochemical method. The physicochemical properties of catalysts (Cu/CNTs) were characterized by using X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen (N2) adsorption-desorption, Fourier transform infra-red spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and electron spinning resonance (ESR). The results showed that the Cu was distributed well on the CNT surface by the interaction of Cu(2+) ions with -OH and -COOH groups on the CNT surface, which preferentially occurred at the defect sites along the CNT backbone. The Cu-O-C bonds formed were found to play an important role in enhancing the photoactivity of the catalysts. The highest number of Cu-O-C bonds possessed by 3 wt% Cu/CNTs demonstrated the best performance in the degradation of p-chloroaniline (96%) under UV light irradiation within 5 h of reaction at 27 °C and under neutral pH conditions. Kinetic studies showed that the degradation followed the pseudo-first order model and the surface reaction was the controlling step. It is believed that these results could contribute to the synthesis of various supported catalysts for various applications.

Growth of copper oxide nanocrystals in metallic nanotubes for high performance battery anodes.

A rational integration of 1D metallic nanotubes and oxide nanoparticles has been demonstrated as a viable strategy for the production of both highly stable and efficient anodes for lithium ion batteries. We encapsulated copper oxide (CuO) nanoparticles in ultra-long metallic copper nanotubes with engineered interspaces, and explored their electrochemical properties. Such a hierarchical architecture provides three important features: (i) a continuous nanoscale metallic Cu shell to minimize electronic/ionic transmitting impedance; (ii) a unique quasi-one-dimensional structure with a large aspect ratio to reduce self-aggregation; (iii) free space for volume expansion of CuO nanoparticles and stable solid-electrolyte interphase (SEI) formation. The anode materials with such hierarchical structures have high specific capacity (around 600 mA h g-1 at a current density of 0.1 A g-1), excellent cycling stability (over 94% capacity retention after 200 cycles) and superb reversible capacity of 175 mA h g-1 at a high charging rate of 15 A g-1.

Tunable synthesis of copper nanotubes

Simple method of tunable synthesis of copper nanotubes based on template synthesis was developed. A comprehensive study of the structural, morphological and electrical characteristics of the obtained nanostructures was carried out. Characterization of structural features was made by methods of scanning electron microscopy, energy dispersive spectroscopy and X-ray diffractometry analysis. Evaluation of wall thickness is made by methods of gas permeability. Electrical conductivity of nanotubes was define in the study of their current-voltage characteristics. The possibility to control of copper nanotubes physical properties by variation of the deposition parameters was shown.

Spacer-Directed Selective Assembly of Copper Square or Hexagon and Ring-Stacks or Coordination Nanotubes.

The use of simple self-assembly methods to direct or engineer porosity or channels of desirable functionality is a major challenge in the field of metal-organic frameworks. We herein report a series of frameworks by modifying square ring structure of [{Cu2(5-dmpy)2(L1)2(H2O)(MeOH)}2{ClO4}4]·4MeOH (1·4MeOH, 5-dmpy = 5,5'-dimethyl-2,2'-bipyridine, HL1 = 4-pyridinecarboxylic acid). Use of pyridyl carboxylates as directional spacers in bipyridyl chelated Cu(II) system led to the growth of square unit into other configurations, namely, square ring, square chain, and square tunnel. Another remarkable characteristic is that the novel use of two isomers of pyridinyl-acrylic acid directs selectively to two different extreme tubular forms-aligned stacking of discrete hexagonal rings and crack-free one-dimensional continuum polymers. This provides a unique example of two extreme forms of copper nanotubes from two isomeric spacers. All of the reactions are performed in a one-pot self-assembly process at room temperature, while the topological selectivity is exclusively determined by the skeletal characteristics of the spacers.

Self‐Supporting Metal Nanotube Networks Obtained by Highly Conformal Electroless Plating

We present a versatile approach for the fabrication of well-defined networks of interconnected metal nanotubes, which applies electroless plating to ion-track-etched polymer templates that enclose designed pore networks. In order to obtain self-supporting structures, the deposition reactions must be optimized to yield conformal nanoscale metal films on microstructured substrates possessing extensive inner surfaces. Using this route, gold, copper, silver, nickel, and platinum nanotube networks are synthesized. The resulting structures can be handled macroscopically and combine a large surface area with continuous mass transport and conduction pathways, rendering them promising for application in, for example, electrocatalysis and sensing. This potential is demonstrated by employing a gold nanotube network for the amperometric detection of hydrogen peroxide, in which excellent sensitivity, catalyst utilization, and stability is achieved.

RESISTIVITY MEASUREMENT TECHNIQUES FOR COMPOSITE MATERIALS

In this article, the theoretical concepts and the experimental techniques for measurements of the volume and surface resistivity of carbon fibre reinforced polymer (CFRP) composite materials have been explained. The purpose of these measurements is to investigate the potential of composite materials as lightning arrestors for an aircraft. In particular, the AC resistivity method and the Delta mode of measurement have been described in detail. A few measurements were carried out using an indigenously designed and fabricated collinear four-probe resistivity measurement tool, for which factors dependent on the dimensions of the samples have to be incorporated, as per the ASTM F390-11 standards. The validity of the two-probe and four-probe methods is also analyzed, along with techniques to minimize errors in measurements. Conductivity measurements on uni-directional laminates have been made in the longitudinal (fibre) direction as well as perpendicular to it, indicating a marked difference in the relative magnitudes. When investigating the potential of materials as lightning arrestors, a very high surface conductivity is desired so that lightning currents (even of the order of kA) pass along the exterior of the aircraft, without penetrating the underlying structure. The effects of the addition of copper nanotubes (CNT) and copper mesh have also been studied. The instruments involved in these experiments have been automated based on the IEEE – 488.2 protocols. The software to program them was developed using Labview. Measurements have also been performed on standard samples to test the accuracy of the data. Currents ranging from 0.1 to 100mA were passed, to deduce the current-dependency of the surface resistivity of these materials.