nano-Cu Particles Research Articles

Effect of Nano-Cu Particles on the Microstructure and Mechanical Properties of Cu/AZ31 Composites

Effect of Nano-Cu Particles on the Microstructure and Mechanical Properties of Cu/AZ31 Composites

Mass-Produced Cu Nanoparticles as Lubricant Additives to Enhance the Tribological Properties of DLC Coatings

In this paper, Nano copper (Cu) particles with a core-shell structure and good spherical shape were prepared by an innovative method called mass-produced nanoparticles (MPNP). The prepared Cu nanoparticles have good dispersibility and are agglomeration-free in Pao oil. In particular, the effects of nano-Cu particles with different mass fractions on the tribological properties of the steel against diamond-like carbon (DLC) coating were studied systematically. The results showed that the nano-Cu particles with the mass fraction of 0.1 wt.% and the steel/DLC friction pairs had good synergistic lubrication. The friction mechanism of the metal nano-particles and carbon-based coatings mainly depends on the physical effects such as nano-bearing and nano-filling of the nano-particles, which has little correlation with the shear film formation of the metal nano-particles. Therein, the surface polish behaviors of the metal nano-particles and carbon-based coatings are the key to bringing the nano-bearing mechanism of nano-particles into full play. Therefore, the Cu nanoparticles prepared by MPNP show excellent tribological performance and possess broad prospects in the fields of lubricant additives.

Laser powder bed fusion of ultrahigh strength Fe-Cu alloys using elemental powders

Laser powder bed fusion (LPBF) was employed to produce Fe and Fe-(10–50 vol%) Cu immiscible alloys using elemental powders. The addition of 10 vol% Cu to Fe resulted in ultrahigh compressive yield and ultimate strengths of >~ 1000 and ~ 1400 MPa (more than 2 times greater than those in LPBF Fe and 4–6 times than in conventionally processed Fe), respectively, with fracture strain of ~ 20%. However, a further increase in the amount of Cu gave rise to significantly more heterogeneous microstructures with non-uniform distribution of Cu, leading to considerable liquation cracking, large voids and reduced strength and plasticity. Strengthening was primarily attributable to the dispersion of nano-Cu particles of 2–5 nm with spacings of < 10 nm and ultrafine grains (<~ 50–300 nm). The substantial grain refinement in Fe-Cu alloys during LPBF was mainly a result of the confinement of Fe crystals by Cu films, hindering their growth. By analysing microstructures in single laser tracks, single layers, top and middle sections of the LPBF Fe, it was revealed that constitutional undercooling during solidification or the subsequent transformations of γ → α were responsible for the formation of equiaxed, rather than columnar, grains in pure Fe.

Enhancement on the Tribological Properties of the Multilayer RGO/Al Matrix Composites by Cu-Coating Method.

Multilayer reduced graphene oxide (mrGO) was chemically modified by electroless plating of copper on surface to form mrGO-Cu. The scanning electron microscope (SEM) and transmission electron microscope (TEM) analysis revealed that nano-Cu particles were uniformly dispersed on the surface of mrGO. The mrGO-Cu powders were further utilized as reinforcements for aluminum (Al) matrix and the mrGO-Cu/Al composite was successfully fabricated through clad rolling of milled powder. The tribological properties of the mrGO-Cu/Al composites were explored. The tribological results show that the mrGO-Cu could reduce the friction coefficient and wear loss of mrGO-Cu/Al composites, since the mrGO-Cu participated in lubricating processes due to the formation of a transfer layer on the contact surface. Furthermore, it is found that the composition of mrGO-Cu could significantly influence the tribological properties of the mrGO-Cu/Al composites. The composites with 4% of mrGO-Cu for composites exhibited the best tribological behavior, which transformed from adhesive wear to abrasive wear, due to the formation of a graphite lubricating film.

Effect of Dynamic Viscosity on Nanofiber Diameters and Electrical Conductivity of Polyacrylonitrile Nanofibers Doped Nano-Cu Particles

In this study, pure polyacrylonitrile nanofibers in the diameter range of 200-500 nm and PAN / Cu composite nanofibers in 200-600 nm diameter range were produced at applied voltage of 15 kV. The distribution of fiber diameters, the dynamic viscosities of the solutions and the electrical conductivity (EC) of the produced fibers have been examined as a function of copper nanoparticles content (1%, 3% and 5% by weight). Results showed that the dynamic viscosity of the electrospinning solution is an important parameter on the nanofiber morphology as well as on the nanofiber diameter distribution. Taken together, the data analysis showed that the highest EC value was 38x10-2 S/cm, which was obtained from nanofibers produced by electrospinning solution containing %1 Cu nanoparticle having a dynamic viscosity value of 577.7 mPa.s. The addition of Cu nanoparticles increased the EC of pure PAN nanofibers by a factor of 2.37. In addition, further analysis of pure PAN nanofibers and %1 Cu/PAN nanofibers have been performed by XRD, contact angle and TGA devices. Results showed that the TGA degradation curves of both pure PAN and Cu-based PAN nanofibers presented the same behavior. In DSC analysis, the glass transition temperature of pure PAN nanofibers was observed at 112 °C, while no glass transition temperature was observed for PAN nanofibers containing 1% Cu.

Synthesis of Novel Macromolecular Coupling Agent and its Application in Nano-Copper Lubricating Oil

Background: Due to temperature-insensitive and limited tribochemical reaction, nanolubricants have received tremendous focus over the past few years. The addition of nanoparticles in lubricant has been demonstrated to reduce the coefficient of friction and increase the loadcarrying capability of lubricant in coupled surfaces. Much attention has been paid to copper nanoparticles for their perfect friction reduction and wear resistance performances. However, it is difficult to maintain stable dispersion in lubricant oil for the aggregation of copper nanoparticles. Methods: A novel macromolecular coupling agent copolymer, styrene-butyl methacrylate-3- methoxyacryloyl-propyltrimethoxyl silicon was successfully prepared by free radical polymerization. The structure and composition of the copolymer were characterized through X-ray diffractometer, Fourier-transform infrared spectrometer, and nuclear magnetic resonance spectrometer. The loadcarrying capacities and anti-wear properties of the base oil were evaluated on four-ball tester. Results: The average size of the nano-Cu particle was around 40 nm. The modifier, St-MMA-(KH- 570) macromolecular copolymer could improve the dispersibility of nano-Cu particles. The introduction of the nano-Cu particles helped to improve the tribological properties of base oil. Conclusion: The macromolecular coupling agent was synthesized by free radical solution polymerization method. The modifier was able to bond to the nano-Cu via chemical interaction. The modified Cu nanoparticles as the additive were able to greatly improve the anti-wear and extreme pressure properties of base oil. The optimum concentration of modified Cu nanoparticles in base oil was 0.25 wt.%.

Active catalyst construction for CO2 recycling via catalytic synthesis of N-doped carbon on supported Cu

Bridging homogeneous and heterogeneous catalysis is a long-term pursuit in the field of catalysis. Herein, we report our results in integration of nano- and molecular catalysis via catalytic synthesis of nitrogen doped carbon layers on AlOx supported nano-Cu which can finely tune the catalytic performance of the supported copper catalyst. This synthetic catalytic material, which can be generated in situ by the reaction of CuAlOx and 1,10-Phen in the presence of hydrogen, could be used for controllable synthesis of N,N-dimethylformamide (DMF) from dimethylamine and CO2/H2 via blocking reaction pathways of further catalytic hydrogenation of DMF to N(CH3)3. Detailed characterizations and DFT calculations reveal that the presence of N-doped layered carbon on the surface of the nano-Cu particles results in higher activation energy barriers during the conversion of DMF to N(CH3)3. Our primary results could promote merging of homogeneous catalysis and heterogeneous catalysis and CO2 recycling.

New underfill material based on copper nanoparticles coated with silica for high thermally conductive and electrically insulating epoxy composites

With the microelectronics technology going toward its physical limits and the emergence of three-dimensional chip stack architectures, now more than ever there are both needs and opportunities for novel materials to help address some of these pressing thermal management challenges. In this paper, a high-thermal-conductivity insulative SiO2-coated nano-Cu particle is prepared for new-type underfill materials of high-performance microelectronics packaging. It was found that nano-Cu can be successfully coated with SiO2 by using the surface modification between cetyltrimethyl ammonium bromide and silane coupling agent although nano-Cu particles have silicon-disordered property during the coating process of tetraethyl orthosilicate hydrolysis. Moreover, the thermal conductivity of epoxy mixed with nano-Cu@SiO2 as the packaging underfill is dramatically increased from 0.15 W/m K of the pure-EP and 0.60 W/m K of the EP/SiO2 to 2.9 W/m K due to electronic heat transfer, heat network and fast heat transfer center. It effectively releases the heat generated by the IC device, and the service life of the device is significantly improved from 63 min of pure-EP and 350 min of the EP/nano-SiO2 to 1039 min. The new material creates a challenging environment for keeping modern electronic devices cool, a critical factor in determining their speed, efficiency and reliability.

Investigation on mechanism and microwave absorption properties of Ti3SiC2/nano-Cu powders

In this work, Ti3SiC2/nano-Cu powders were synthesized by two different routes: mechanical ball-milling and electroless-plating process. The phase composition was identified by XRD and the microstructure was observed by SEM. Both the real and imaginary parts of complex permittivity for Ti3SiC2/nano-Cu powders prepared by electroless-plating process are higher because of the uniformly dispersing nano-Cu particles. In addition, the influences of concentration on the dielectric and microwave absorption properties were also investigated. As the content of Ti3SiC2/nano-Cu rises from 40 to 70 wt%, the real part of complex permittivity increases from 8.81 to 7.37 to 24.73–20.24, while the imaginary part enhances from 0.78–1.65 to 8.02–7.71 in the frequency range of 8.2–12.4 GHz. The most favorable absorption performance is obtained for the Ti3SiC2/nano-Cu/paraffin mixture containing 60 wt% filler with a thickness of 1.8 mm. The effective absorption bandwidth below − 10 dB is obtained in 9.2–12.2 GHz with a minimum reflection loss of − 20.42 dB at 10.88 GHz.

SiO2-coated Cu nanoparticle/epoxy resin composite and its application in the chip packaging field

A silicon dioxide–copper (SiO2-Cu) epoxy resin composite material for chip packaging was made by a mechanical mixing method with epoxy resin as the base glue and SiO2 coated with nano-Cu (SiO2-Cu) particles as the filler. The dispersion of SiO2-Cu nanoparticles in epoxy resin was studied using scanning electron microscopy and transmission electron microscopy. Meanwhile, the effects of the filler on the coefficient of thermal conductivity, the coefficient of thermal expansion (CTE), and the mechanical properties of the composite material were also studied. The results show that SiO2-Cu nanoparticles disperse well in the epoxy resin, the coefficient of thermal conductivity of SiO2-Cu epoxy resin composites increases with an increase in the SiO2-Cu filler amount, the coefficient of thermal conductivity begins to decline when the filling volume is over 25%, and the suitable amount of SiO2-Cu is 25% of the total volume. With the increase in the filler, the CTE of the composite decreases; when the SiO2-Cu filling amount is 25%, the material has good impact resistance and a long electromigration failure time for chip packaging materials.

Size-dependence of surface thermodynamic functions of nano-Cu by dissolution kinetics

The surface thermodynamics of nanoparticle present an amazing difference compared with their corresponding bulk counterpart, and the difference depends on the size of nanoparticles. Herein, we obtained the size-dependence of surface thermodynamic functions of nanoparticles by dissolution kinetics. The theoretical relations between dissolution kinetic parameters as well as molar surface thermodynamic functions and particle size were derived, respectively. In experiment, taking the dissolution of nano-Cu particles as a system, the dissolution rate constant of nano-Cu with different sizes under different temperatures, the dissolution apparent activation energy and the dissolution pre-exponential factor of nano-Cu with different sizes were obtained, respectively. Finally, the regularities of influence of particle size on surface thermodynamic functions of nanoparticles were derived. The theoretical and experimental results indicate that with the size of nano-Cu decreasing, the molar surface Gibbs energy, the molar surface enthalpy and the molar surface entropy correspondingly increase, which are linearly related to the reciprocal of particle size.

Enhanced electrochemical performances of LiNi0.5Mn1.5O4 by surface modification with Cu nanoparticles

5V spinel LiNi0.5Mn1.5O4 cathode is prepared by traditional solid-state method and nano-Cu particles were derived from a chemical reduction process. The effect of Cu-coating on the electrochemical performances of LiNi0.5Mn1.5O4 cells, in a wide operation temperature range (-10?C, 25?C, 60?C), is investigated systematically by the charge/discharge testing, cyclic voltammograms and impedance spectroscopy, respectively. The results demonstrate that the modified material exhibits remarkably enhanced electrochemical reversibility and stability. Cu-coated material has much lower surface and charge transfer resistances and shows a higher lithium diffusion rate. The Cu coating layer as a highly efficient lithium ion conductor, acted as a highly efficient protector to restrain the contact loss.

Effect of nano Cu coating on porous Si prepared by acid etching Al-Si alloy powder

As a promising anode material for lithium ion battery, nano-Cu coated porous Si powder was fabricated through two stages: first, preparation of porous nano Si fibers by acid-etching Al-Si alloy powder; second, modified by nano-Cu particles using an electroless plating method. The nano-Cu particles on the surface of nano-Si fibers, not only increase the conductivity of material, but also inhibit the fuse process between nano Si fibers during charge/discharge cycling process, resulting in increased cycling stability of the material. In 1M LiPF6/EC: DMC (1:1)+1.5wt% VC solution at current density of 200mAg−1, the 150th discharge capacity of nano-Cu coated porous Si electrode was 1651mAhg−1 with coulombic efficiency of 99%. As anode material for lithium ion battery, nano-Cu coated porous Si nano fiber material is easier to prepare, costs less, and produces higher performance, representing a promising approach for high energy lithium ion battery application.

Performance evaluation of a solar water heater integrated with a PCM nanocomposite TES at various inclinations

The present work presents and analyzes the results acquired from outdoor experimental measurements of a flat plate solar collector integrated with built-in thermal energy storage. Paraffin wax as a PCM and a nanocomposite of paraffin wax with 1.0wt% of 20-nm nano-Cu particles were tested as the energy storage medium for TES. Three cases have been investigated, namely without PCM, with PCM, and with the Cu-PCM nanocomposite, at 10°, 20°, and 30° inclination angles of each case. The system performance was evaluated for water heating. The process involved a total change of the 60-l water tank at 7:00PM and 7:00AM. The use of water circulation of 0.5kg/min and setting the collector at a 10° inclination angle was found to be the best operational condition. The measurement result of the tank water temperature at 7:00AM, after 24h of operation, was 35.1°C when the system operated without TES, while the operation with the PCM and with the Cu-PCM nanocomposite resulted in 40.1°C and 40.7°C tank water temperatures, respectively. The best performances analyzed were at 10°, with efficiencies of 47.6%, 51.1% and 52.0% for the cases without PCM, with PCM and with Cu-PCM nanocomposite, respectively. This indicates that the enhancement of the system using TES with paraffin wax is considerable, while further enhancement is not significant in the case of nanocomposite. Further measurements with various flow rates are recommended to investigate the performance of the developed solar-TES integrated system.

Preparation of Cu/Dickite/LLDPE nanocomposites and synergistic effect of exfoliated dickite and nano-Cu in LLDPE matrix

A novel anticorrosion packaging nanocomposite composed of LLDPE (linear low-density polyethylene), nano-sized Cu, and exfoliated dickite was prepared via melt mixing combined with melt extruding process. X-ray diffraction and transmission electron microscopy (TEM) were employed to characterize the resultant nanocomposite. The results showed that most dickite layers were exfoliated and the nano-Cu particles were distributed uniformly in the polymer matrix. The characteristic properties of the Cu/dickite/LLDPE nanocomposite were investigated using salt spray test, thermogravimetry analysis, mechanical test, and antibacterial test. The salt spray test results showed that exfoliated dickite and nano-Cu improved the anticorrosion properties of the Cu/dickite/LLDPE nanocomposite in simulated ocean environment, respectively. Furthermore, the coexistence of exfoliated dickite and nano-Cu in Cu/dickite/LLDPE nanocomposite produced a synergistic effect on enhancing the anticorrosion properties. Additionally, the co-incorporation of exfoliated dickite and nano-Cu in LLDPE matrix also improved the thermal-oxidative stability and mechanical properties of the polymer matrix. The bactericidal properties evaluation showed that the Cu/dickite/LLDPE nanocomposite had better bactericidal ability because of the presence of nano-Cu in LLDPE matrix. POLYM. COMPOS., 34:1061–1070, 2013. © 2013 Society of Plastics Engineers

Monitoring the performance of innovative and traditional biocides mixed with consolidants and water-repellents for the prevention of biological growth on stone

In this study, some mixtures of consolidants or water-repellent products and biocides developed to prevent biological growth, were tested over time on three stone substrates with different bioreceptivity. The performance of both traditional (tetraethylorthosilicate, methylethoxy polysiloxane, Paraloid B72, tributyltin oxide, dibutyltin dilaurate) and innovative compounds (copper nanoparticles) was assessed using colour measurements, the water absorption by contact sponge method, and observation under stereo and optical microscopes. The application of the mixtures had also the purpose of controlling re-colonization on stone after a conservation treatment. The study site was the archaeological Area of Fiesole; the mixtures were applied in situ to sandstone, marble and plaster which had been cleaned beforehand. An innovative aspect of the study is that, by using non-invasive methods, it also permitted monitoring the mixtures' effectiveness in preventing biological growth. The monitoring results made it possible to assess the bioreceptivity of the treated stones (sandstone, marble, plaster) over a period of almost three years.The results showed that the mixtures of consolidants or water-repellent products with biocides were effective in preventing biological growth on both a substrate with low bioreceptivity like plaster and a substrate with high bioreceptivity such as marble. The innovative mixture of nano-Cu particles with a water-repellent yielded good results in terms of preventing biological colonization. Moreover, they apparently did not affect the substrates' colour. Mixtures of nano-Cu particles with a consolidant and a water-repellent hold great promise for preventing re-colonization of stone after conservation treatment.

The Effect of Nano-Cu Particles on Mechanical Properties of Micro-Joining Joint with Lead-Free Solder

The effect of nano-Cu particles on mechanical bend reliability of micro-joining joint with Sn-3.5Ag lead free solder was studied in this paper. The results show that 0.5% nano-Cu composite lead free solder show significantly better shearing strength and mechanical bend fatigue properties than eutectic Sn-3.5Ag solder paste, 1.0% nano-Cu composites and 1.5% nano-Cu composites. The further analysis shows that adding nano-Cu particles make much effect on intermetallic (IMC) in the interface of micro-joint and the inside of the solder joint. The different interface of micro-joining joint induced different mechanical properties.

利用纳米粒子强化微乳液体系HCFC141b 水合物的生成

Accelerating the formation of gas hydrate is of great significance for the application of gas hydrate technology in the area of cooling storage. To promote the rapid formation and growth of HCFC141b gas hydrate, the thermodynamically stable HCFC141b microemulsion was successfully prepared with aid of Tween 20/lecithin compound surfactants for increasing interface and compatibility between the refrigerant and water. The hydration process of HCFC141b in the microemulsion system was investigated in terms of induction time and supercooling degree and was compared to that in coarse HCFC141b/water mixture systems with or without surfactant in them. The characteristics of hydrate formation in the different systems were revealed. It is indicated that HCFC141b hydrate can form rapidly and uniformly in the microemulsion system. The induction time of HCFC141b hydration in the microemulsion system was shortened by 36% and 52% compared to that in coarse HCFC141b/water mixture with 1wt% Tween 20 and without any surfactant in it, respectively. Then, considering the characteristics of nano-particles in the enhancement of heat transfer, different amount of nano-Cu particles or nano-Al2O3 particles was added to HCFC141b/water microemulsion system and coarse mixture systems aiming to facilitate HCFC141b hydration process. The addition of nano-Cu to the microemulsion system further shortened the induction time and led to reduced supercooling degree of hydration in the microemulsion system, while it did not function in the coarse mixtures. The promotion degree of nano-Cu on decreasing the induction time as welll as the supercooling degree of hydration was increased with an increase in the amount of nano-particles in the system. By adding 0.1wt% nano-Cu in the microemulsion system, the induction time was shortened by 29% and the supercooling degree was reduced by 39%. In all, combining the characteristics of large interfacial area of microemulsion with that of enhanced mass and heat transfer of nano-fluid by adding nano-particles can be an effective way to promote the formation of gas hydrate.

Preparation of Cu/OMMT/LLDPE nanocomposites and synergistic effect study of two different nano materials in polymer matrix

Cu/OMMT (organo-montmorillonite)/LLDPE (linear low-density polyethylene) nanocomposites were prepared via melt mixing combined with melt extruding process. X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectra, scanning electron microscope (SEM), and transmission electron microscopy (TEM) were employed to characterize the resultant nanocomposites. The results showed that the OMMT layers were exfoliated and the nano-Cu particles were distributed uniformly in the polymer matrix. And the introduction of nanofiller into LLDPE matrix had little effect on the crystallinity of the polymer. The salt spray tests showed that OMMT and nano-Cu could improve the anticorrosion properties of LLDPE matrix, respectively. And the coexistence of OMMT and nano-Cu in Cu/OMMT/LLDPE nanocomposites could produce a synergistic effect on enhancing the anticorrosion properties. Furthermore, the co-incorporation of OMMT and nano-Cu into the polymer matrix also increased the thermal-oxidative stability and mechanical properties of LLDPE matrix significantly, as compared with the Cu/LLDPE and OMMT/LLDPE nanocomposites due to the synergistic effect. The bactericidal properties evaluation showed that the bactericidal ability of Cu/OMMT/LLDPE increases with nano-Cu content effectively.

Effects of Copper Nanoparticles on the Development of Zebrafish Embryos

The environmental behavior and the potential toxicity of copper nanoparticles (nano-Cu) in water are major concerns for assessing their environmental safety. The present study was undertaken to characterize the properties of nano-Cu in E3 medium, such as size changes, solubility, zeta-potential and pH, and to test the toxicity of nano-Cu suspension to zebrafish embryos. Dynamic light scattering and solubility experiments showed that three components coexisted in the nano-Cu exposure system, including small nano-Cu aggregates still suspended in E3 medium, large nano-Cu aggregates deposited on the container bottom and dissolved copper species (Cu(dis)). Both the zeta-potential of nano-Cu particles in E3 medium and the pH of the nano-Cu suspension showed no change during a 24 hour period. It is found that nano-Cu retarded the hatching of zebrafish embryos and caused morphological malformation of the larvae, and high concentrations (>0.1 mg/L) of nano-Cu even killed the gastrula-stage zebrafish embryos. Cu2+ ions were used to study the toxicity caused by nano-Cu dissolution. The embryo toxicity of nano-Cu at 0.01 and 0.05 mg/L showed no significant difference from Cu2+ at the corresponding concentrations (0.006 and 0.03 mg/L), but 0.1 mg/L nano-Cu had a greater toxicity than 0.06 mg/L Cu2+.