Cellulose nanofibers (CNFs) are synthesized by unraveling cellulose made from wood. CNFs have attracted significant attention among biomass materials owing to their excellent mechanical properties and wide range of applications. This study aims to elucidate the effects of CNFs as a lubricating additive. In order to accomplish this, CNFs were dispersed in water at densities of 0.02-1.0 mass%, and friction tests were performed using a ball-on-plate friction tester with a reciprocating motion configuration. Stainless steel (JIS-SUS304) and polyoxymethylene (POM) were used as sliding plates, while various materials were used for sliding balls. On both the SUS304 and POM plates, friction reductions were observed by adding only a small amount of CNFs (0.02 mass%). Although wear on the SUS304 plate reduced by 0.02 mass%, the water dispersion of CNFs was not distinct; it was observed only at densities of CNFs that were more than 0.2 mass%. On the POM plate, wear was induced by adding 0.02 mass% of CNF water dispersion. Adverse effects may arise with the addition of more than 0.2 mass% CNF. A distinctive feature observed in the water dispersion lubrication of CNFs was that a tribofilm is not formed due to the chemically inert nature of CNFs. It appears highly probable that in the water dispersion lubrication of CNFs, the physical effects of these fibers are much stronger than their chemical effects. These effects include rolling and/or sliding, which occurred in fullerene and carbon nanotubes.

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ABASTRACT:A thermoelectric device consisting of the porous part and the bulk part was proposed. Increase of heat exchange area due to porous medium will improve the efficiency of heat exchange between heating/cooling sources and the device. Estimation based on physical properties of FeSi2 indicated that generated power of the partially porous device per unit area can be several times higher than that of the bulk one in case of gas heating / cooling system. The partially porous thermoelectric devices were produced. In measurement of power, it has been confirmed that generated power per unit area of the partially porous FeSi2 devices was roughly 10 times higher than that of the conventional device. The proposed porous device will exhibit its advantage in the case of low heat transfer coefficient between the device and the heating / cooling sources.