Fabrication and performance evaluation of nickel-rich conductive coating for carbon steel grounding grids in saline-alkali soil solution

A nickel-rich conductive anti-corrosive coating (CACC) was fabricated to improve the corrosion resistance of the carbon steel grounding materials. The coating was tested using surface contact resistance measurement, electrochemical impedance spectroscopy (EIS) and surface characterization. The results indicate that the increase of the nickel powder content in the coating induces its electrical conductivity enhancement; the surface contact resistance is as low as 0.05 Ω/cm2 when the nickel powder content is 20%. The EIS data show that the anti-corrosive performance of the coating with 20% nickel powder content in three soil saline-alkali solutions (mild, moderate and severe) is higher than that with 40% nickel powder content, and the impedance of the coating decreases with the increase of the salt concentration. It is detected that 20% nickel powder content can achieve a good balance between low surface contact resistance and high corrosion resistance of the coating.

Realizing the nanoscale quantitative thermal mapping of scanning thermal microscopy by resilient tip–surface contact resistance models

Quantitative assessment of thermal properties by scanning thermal microscopy (SThM) is a demanded technology, but still not yet available due to the presence of unpredictable thermal contact resistance (TCR) at the tip/substrate interface.

Analysis on Influencing Factors of Bus Bar Contact Resistance

Contact resistance is one of the key parameters of main bus bar. The bus performance is decided by the value of Contact resistance. By test of the typical rectangular copper bus-bar, it is analyzed that the effects of force on DC contact resistance. The results show that metal surface contact resistance decreases with the increment of pressure. The resistance is mental nature property, which is determined by material’s performance. At the same time the effect of contact distance is studied in detail.

Measuring Conductivity With Scanning Probe Microscopes

There are two kinds of conductivity measurements possible with scanning probe microscopy (SPM). In the first case, the specific resistance of material directly below the tip is probed. In the second case, SPM probes local potential induced by the lateral current applied through macroscopic contacts, thus providing the information on the mesoscopic transport properties of the sample.The first set of techniques is invariably based on measuring tip-surface current in contact or intermittent tapping mode. If the tip-surface contact resistance is small (good contact), the current will be limited by the spreading resistance of the sample from which specific resistance can be calculated, assuming that the contact area is known.

Three-Dimensional Thermal Model of Resistance Spot Welding in Aluminum

A 3-D thermal model for resistance spot welding in aluminum is presented. The numerical model, validated with experimental findings, considers phase change and the associated weld-pool convection. A parametric study is performed to determine the influence of welding features such as faying surface (work-piece contact surface) contact resistance, current, electrode-work-piece surface-thermal-contact-conductance and electrode tip diameter. These parameters have significant effects on the nugget and heat-affected-zone geometry. The phase change morphology, including melting and solidification rates and weld pool dynamics, is also significantly influenced by the parameters studied. The strongest convection was observed at the center of the molten pool in a plane aligned with gravity. Although two prominent convection cells develop, the phase change morphology is not significantly affected due to the short welding time (less than 0.05 seconds) and low fluid velocity (smaller than 1 × 10−2 mm/s). The nugget grows nonlinearly with increasing current and faying surface contact resistance while diminishing with increasing electrode work-piece surface-thermal-contact-conductance. The influence of faying surface contact resistance on nugget size is less than that of the other parameters. Optimum selection of electrode tip diameter provides the best possible nugget. The duration of weld pool existence increases with the increasing current but decreases with the increasing electrode work-piece surface-thermal-contact-conductance.