The Effect and Mechanism of Nano-Cu Lubricating Additives on the Electroless Deposited Ni-W-P Coating

The coating and deposition process with excellent anti wear and suitable for industrial application were developed, and the optimum bath composition and process were obtained by studying the influence of the bath composition, temperature and pH value on the deposition rate and the plating solution stability. Moreover, the tribological properties of nano-Cu lubricating additives and electroless deposited Ni-W-P coating as well as their synergistic effect are researched using ring-block abrasion testing machine and energy dispersive spectrometer. Research results show that Ni-W-P alloy coating and nano-Cu lubricating additive have excellent synergistic effect, e g, the wear resistance of Ni-W-P alloy coating （with heat treatment and the oil with nano-Cu additives） has increased hundreds times than 45 steel as the metal substrate with the basic oil, and zero wear is achieved, which breaks through the bottleneck of previous separate research of the above-mentioned two aspects.

Excellent Terahertz shielding performance of ultrathin flexible Cu/graphene nanolayered composites with high stability

Electromagnetic interference(EMI)shielding at Terahertz(THz)frequency range attracts increasing attention due to the rapid development of THz science and technologies.EMI shielding materials with small thickness,high shielding effectiveness(SE),good flexibility and stability are highly desirable.Herein,an ultrathin flexible copper/graphene(Cu/Gr)nanolayered composite are prepared,which can reach the average EMI SE of 60.95 dB at 0.1–1.0 THz with a thickness of only 160 nm,indicating that more than 99.9999%of the THz wave power can be shielded.Furthermore,the Cu/Gr nanolayered composite also exhibits excellent oxidation resistance,with a 93.09%maintenance rate for EMI SE value after heating at 120℃for 3 h in air,far higher than that of the bare Cu film(62.15%).Besides,the Cu/Gr nanolayered composite exhibits good mechanical flexibility and flexural fatigue resistance.The EMI SE value of the Cu/Gr nanolayered composite shows a maintenance rate of 98.87%even after 1500 times bending cycles,obviously higher than that of multilayer Cu film(93.07%).These results demonstrate that the ultrathin flexible Cu/Gr nanolayered composites with excellent shielding performance and good stability have a broad application prospect in THz shielding for wearable devices and next generation mobile communication equipment.

Shear strength of LED solder joints using SAC-nano Cu solder pastes

The addition of Cu nanoparticles into the solder pastes by mechanical mixing method creates a positive effect on the microstructure refinement of the LED solder joints. The grain size of β-Sn and Cu6Sn5 decrease obviously due to the increasing concentration of the nanoparticles in the solder pastes. However, the addition of nanoparticles facilitates the formation of voids in the solder joints, especially when the concentration of nanopar- ticles is higher than 0.5 wt% in the solder pastes. Both the microstructure refinement and void percentage affect the shear strength of the solder joints. Since the increase of the void percentage is limited when the concentration of nanoparticles increases from 0 to 0.5 wt%, the microstructure refinement shows a dominant effect on the shear performance and thus improves the shear strength of the solder joints from 49.8 to 55 MPa. Further addition of nanoparticles in the solder pastes leads to a sharp increase of the void percentage. Consequently, the shear strength of the solder joints decreases from 55 to 48.8 MPa when the concentration of doped particles increases from 0.5 to 1 wt% in the solder pastes.

New insight in the O_(2) activation by nano Fe/Cu bimetals:The synergistic role of Cu(0) and Fe(Ⅱ)

This study demonstrated that as-synthesized nano Fe/Cu bimetals could achieve significant enhancement in the degradation of diclofenac(DCF),as compared to much slow removal of DCF by Cu(Ⅱ) or zero valent iron nanoparticles(nZVI),respectively.Further observations on the evolution of O_(2) activation process by nano Fe/Cu bimetals was conducted stretching to the preparation phase(started by nZVI/Cu2+).Interesting breakpoints we re observed with obvious sudden increase in the DCF degradation efficiency and decrease in solution pH,as the original nZVI just consumed up to Fe(Ⅱ) and Cu(II) appeared again.It suggested that the four-electrons reaction of O_(2) and Cu-deposited nZVI would occur to generate water prior to the breakpoints,while Cu(0) and Fe(Ⅱ) would play most important role in activation of O_(2) afterwards.Through the electron spin resonance(ESR) analysis and quenching experiments.·OH was identified as the responsible reactive species.Further time-dependent quantifications in the cases of Cu(0)/Fe(Ⅱ) systems we re carried out.It was found that the ’OH accumulation was positively and linearly correlated with nCu dose,Fe(Ⅱ) consumption,and Fe(II) dose,respectively.Since either Cu(O) or Fe(Ⅱ)would be inefficient in activating oxygen to produce ·OH,a stage-evolution mechanism of O_(2) activated by nano Fe/Cu bimetals was proposed involving:(a) Rapid consumption of Fe(0) and release of Fe(Ⅱ) based on the Cu-Fe galvanic corrosion,(b) adsorption and transformation of O_(2) to O_(2)2 at the nCu surface,and(c) Fe(Ⅱ)-catalyzed activation of the adsorbed O_(2)2 to ·OH.

Heat Transfer Analysis of MHD Power Law Nano Fluid Flow through Annular Sector Duct

Flow and heat transfer analysis of an electrically conducting MHD power law nano fluid is carried out through annular sector duct,under the influence of constant pressure gradient.Two types of nano particles(i.e.Cu and TiO2)are used in power law nano fluid.Strongly implicit procedure,(SIP)is used to simulate the discretized coupled algebraic equations.It has been observed that volume fraction of nano particles,ϕand magnetic field parameter,Ha are favourable for the heat transfer rate,however,both resist the fluid flow.Impact of applied uniform transverse magnetic field exceeds in the case of shear thickening fluids(i.e.n>1)by increasing the value of Ha as compared to that in shear thinning fluids(i.e.n<1).Therefore,enhancement in heat transfer rate is comparably more in shear thickening fluid.Furthermore,comparable limiting case study with published result is also carried out in this research paper.