Laser Spot Welding and Electric Contact Points Using Copper/Single-Walled Carbon Nanotube Nanocomposite Synthesized by Laser Surface Implanting

In our previous studies, we have developed a wet process, denoted as laser surface implanting (LSI), to synthesize a copper/single-walled carbon nanotube (Cu–SWCNT) metal nanocomposite. The nanostructure of this Cu–SWCNT composite was shown to contain discernable SWCNT clusters in nanosizes inside the copper matrix. Its hardness could achieve up to three times that of pure copper, verified by micro-hardness and nano-hardness tests. A focus ion beam bombardment test and a plane strain compression test show 2.5 times toughness improvement for the Cu-SWCNT composite. Based on these strength improvements, two potential applications for the Cu-SWCNT nanocomposite are proposed and their feasibilities are verified using specially design test rigs. The first application is related to creating long lasting electric contacts. The result shows that the Cu-SWCNT nanocomposite is highly wear-resistant. The contact area of the simulated electric contacts increases after repeated impact loading, which potentially could lower the contact resistance. The second application is to use the Cu-SWCNT implants as high strength spot weld for joining copper foils. A smaller weld with a higher strength reduces the power requirement of the laser and, consequently, the thermal distortion for higher-dimensional precision. The specially designed test rig for the weld strength characterization is a new contribution, providing a new testing capability for small and non-homogeneous samples not suitable for a standard tensile test machine.

Near-IR transparent conductive amorphous tungsten oxide thin layers by non-reactive radio-frequency magnetron sputtering

Key assets for transparent electric contacts in optoelectronic applications are high conductivity and large transparency over extended spectral range. Indium-Tin-Oxide and Aluminium-doped-Zinc-oxide are commercial examples, with their electrical conductivity resembling those of metals, despite, their transparency being limited up to 1.5µm. This work introduces smooth and compact amorphous thin films of n-type semiconducting WO3-x prepared by RF-sputtering followed by annealing in dry air, as optical layers of tailorable dielectric properties. We evaluate Figure of Merit, combining electrical conductivity and optical transparency, and rate the performances as a transparent conductive layer.

A Combinatory Package for Diamond Anvil Cell Experiments

In this work, we introduce the Architecture Tech for High-Pressure Experiments Net Assembly (ATHENA) package based on diamond anvil cells, combining both the deposition of specimens as well as the detection of probes on anvils layer by layer. The specimens are typically ~1 μm in thickness and very hard to manipulate with traditional hand skills. ATHENA represents an all-in-one package by accurately synergizing chip-like networks prepared using magnetic sputtering methods and guaranteeing well-designed dimensions, positions and perfect electric contacts. We apply ATHENA successfully to the study of lanthanum metal above 60 GPa, showing very sharp pressure-enhanced superconductivity and parabolic critical temperature (Tc) evolution as a function of pressure with pressure-enhanced itinerant behavior at normal state.

Change in Electric Contact Resistance of Low-Voltage Relays Affected by Fault Current

Contact resistance is an important maintenance parameter for electromagnetic switches, including low-voltage relays. The flow of significant current through electric contacts may influence the contact surface and thus the value of the electric contact resistance (ECR). The change in ECR is influenced not only by the value of current but also by the current phase. Therefore, the impact of the switching short-circuit current’s phase on the ECR was analyzed in this paper. Significant changes in the resistance after each switching cycle were observed. The ECR decreased significantly after each make operation, and a correlation with current amplitude, total let-through energy, and short-circuit time was not observed.

Tribological properties of metallic nanoparticles as lubricant additives under the applied electric currents

Purpose This paper aims to clarify the effects of metallic nanoparticles (NPs) additives and room temperature ionic liquids (ILs) on the tribological performance of electric contacts. Design/methodology/approach Tribological properties of copper (Cu) and silver (Ag) NPs as lubricant additives in different lubricants of ILs or polyalphaolefin (PAO) oils under applied electric currents were investigated. After tribological tests, morphologies of worn surfaces were observed; meanwhile, lubrication and anti-wear properties were analyzed. Findings The mixture solution of the IL and Cu NPs showed desirable lubrication and anti-wear properties due to the reduction of electrocorrosion and the enhancement of rolling effects of particles in the contact region. The anti-wear performance of Cu NPs is better than that of Ag NPs due to the difference in the particle size. The PAO oil with the Cu NPs additives showed poor lubrication properties due to the low solubility of the particles in the oil. When the direction of applied current was changed, the friction of the lubricant with better conductivity was more stable in the variation trend. Originality/value This paper begins with a study of tribological properties of Cu and Ag NPs as lubricant additives in different lubricants of IL or PAO oils under applied electric currents. The authors then propose several methods and possible solutions which could be implemented to improve the tribological performance of electric contacts.