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Tribological test was carried out using a pin-on-disc geometry with fabricated SKD11 pin on bearing steel disc, under sliding in paraffin oil. Fabrication has been made with various angles and widths of crosshatch pattern. The effects of geometrical parameters on friction were mainly examined in mixed and elastohydrodynamic lubrication. The result shows that friction control could achieve by fabricating micro-grooved crosshatch pattern on contact surface. It is observed that each geometrical parameter of texture influence on friction, especially decrease of groove aspect ratio and increases of groove sliding length show friction reduction performance. Crucial parameter G l was proposed for micro-grooved crosshatch texture.

Remarkable advances have recently been made in the thermocell array with series or parallel interconnection, however, the output power from the thermocell array is mainly limited by the electrolyte performance of an n-type element. In this work, we investigate iron (II/III) perchlorate electrolytes as a new n-type electrolyte and compared with the ferric/ferrous cyanide electrolyte at its introduction with platinum as the electrodes, which has been the benchmark for thermocells. In comparison, the perchlorate electrolyte (Fe 2+ /Fe 3+ ) exhibits a high temperature coefficient of redox potential of +1.76 mV/K, which is complementary to the cyanide electrolyte (Fe(CN) 6 3− /Fe(CN) 6 4− ) with the temperature coefficient of −1.42 mV/K. The power factor and figure of merit for the electrolyte are higher by 28% and 40%, respectively, than those for the cyanide electrolyte. In terms of device performance, the thermocell using the perchlorate electrolyte provides a power density of 687 mW/m 2 that is 45% higher compared to the same device but with the cyanide electrolyte for a small temperature difference of 20 °C. The advent of this high performance n-type electrolyte could open up new ways to achieve substantial advances in p-n thermocells as in p-n thermoelectrics, which has steered the way to the possibility of practical use of thermoelectrics.

Characterization of very high cycle fatigue (VHCF) performance is of significant issue for ensuring long‐term durability and reliability of machinery and structural components due to the growing industrial demands and significant requirements of the advanced systems. In this study, VHCF characteristics of nanocrystallized skins (nanoskin) on JIS SCM435 (AISI 4137) steels were investigated as three different nanoskins on the surface, which was fabricated by altering the static load of ultrasonic nanocrystal surface modification (UNSM) treatment. The fatigue characterization, which shows linearly proportional correlation in the range of 80–120 µm depth of subsurface, was subjected to severe plastic deformation by altering the static loads of UNSM treatment to 40, 70 and 100 N, respectively. The fatigue strength increased up to 30% in the regime of VHCF. The improved strength mainly resulted from the generation of nanocrystalline structure, the enhanced surface uniformity, hardness and residual stress.

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