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The friction and wear reducing properties of ammonium thiomolybdate as a water‐soluble lubricant additive were evaluated using a pin‐on‐disck tribometer on a steel‐steel contact. The tribological performance of aqueous solutions of thiomolybdate prepared at concentrations between 0.1 and 0.3 wt% Mo were evaluated at the same load (10 N), entrainment speed, sliding distance and temperature. Although there is a reduction of friction and wear compared with pure water, a significant difference is observed, depending on the additive concentration. SEM/EDAX and Raman spectroscopy analyses of the wear tracks of specimens tested at concentrations below 0.3 wt% Mo reveal the formation of FeS which is responsible for gradually reducing the coefficient of friction from values between 0.30 and 0.5 down to ~0.11. At 0.3 wt% Mo, the analyses indicated the formation of a MoS2 which keeps the coefficient of friction in ~0.05, the lowest recorded value. [ABSTRACT FROM AUTHOR]

In this study, a set of multilayer hard nanocrystalline coatings of Al/AlN with 35, 55 and 75 bilayer were prepared by DC magnetron sputtering on AISI 52100 steel specimens at nitrogen fractions of 35 and 65% in the Ar + N2 discharge. X-ray diffraction analysis indicates a polycrystalline structure of AlN + Al and AlN phases for 35% N2 and 65% N2 fraction, respectively. Nanoindentation tests showed hardness values from 11 to 19 GPa and elastic modulus of ~200 GPa almost independent of the bilayer number for both, 35% N2 and 65% N2. Tribological tests evaluated with a CSM pin-on-disk tribometer showed a reduction in the wear rate compared to AISI 52100 steel specimens. Multilayer coatings deposited at 35% N2 fraction presented a lower friction coefficient than those coatings deposited at 65% N2. The origin of such a decrease in the coefficient of friction was associated with the presence of the Al phase in the coatings deposited at 35% N2. The wear mechanism for both 35 and 65% N2 were different. For the first case, the wear is controlled by plastic flow and abrasive wear, while in the second case, is dominated by adhesive wear. [ABSTRACT FROM AUTHOR]

In the last years, people has become aware of energy saving and thermal comfort requirements for home buildings in hot and cold seasons. In the present study, hybrid multifunctional constructive components made of a reinforced mortar channel filled with cement–soil–sawdust (CL2MSCAL) were evaluated to experimentally determine their thermal performance (thermal conductivity, thermal time lag and decrement factor). The experimental analysis performed in this study was based on dynamic climatology. Measurements of components surface temperature were conducted to determine temperature damping and temperature wave lag. Monthly average temperature and direct solar radiation data of the site was considered. Measurements of real-scale constructive components were conducted on a fully equipped thermal conductive system and thermal chambers (test cells) built for this purpose. Results are compared to concrete components (CCL) that account for approximately 71.6% of the houses built in Mexico and 43.2% in Oaxaca and reinforced mortar (CML) used as prefabricated housing systems. Best results were found for component CL2MSCAL that has a thermal conductivity of 0.81 W·m−1·K−1, a thermal damping of 81.5% (decrement factor of 0.166) and time lag of 7:37 h compared to CCL that present a time lag of 1 h and decrement factor of 0.9. Thus, it is concluded that CL2MSCAL roofing channel components are an alternative for energy saving and thermal comfort. [ABSTRACT FROM AUTHOR]

ABSTRACT Samples of starch−gelatin polymer reinforced with 5% of recycled cellulose were prepared using an extrusion-compression molding process. Nanoindentation and atomic force acoustic microscopy (AFAM) techniques were used to study the effect of reinforcement at nanoscale level. Nanoindentation tests show a 163% increase in hardness and 123% of elastic modulus enhancement after recycled cellulose inclusion. AFAM shows that distribution of recycled cellulose into the polymer matrix is rather homogeneous at nanoscale which improves load transfer. Thermogravimetric analysis indicates an increase in thermal stability of the cellulose reinforced polymer matrix samples. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41787. [ABSTRACT FROM AUTHOR]