Thermal And Mechanical Properties Of Epoxy Composites Reinforced By A Natural Hydrophobic Sand

If a low weight percentage of crude fine fillers can improve properties of polymer materials directly without complicated chemical treatment process involved, it will be significant for many industrial applications. Our previous study indicated that a kind of Cancun natural sand could be an effective filler material for polymer composites. In this current work, the epoxy composites reinforced by this kind of natural sand particles were prepared and thermal and mechanical properties of the composites containing up to 5 wt % of the sand particles were characterized. Results showed that the highest flexural strength appears in the epoxy composite containing 1 wt % sand particles. A damage model was used to interpret the flexural properties, which showed an acceptable agreement with the experimental results. The glass transition temperature, high temperature storage modulus, and dimensional stability of the sand/epoxy composites monotonically increased with the addition of the sand particles. The sand particle/epoxy composites also displayed a noticeable enhancement in thermal conductivity. Theoretical analysis showed that in addition to conduction, other heat transport mechanisms played roles in the improved heat transmission through the composites. As a natural porous micron-scale material, Cancun sand has the potential for applications in cost-effective composites with enhanced mechanical and thermal properties. © 2008 Wiley Periodicals, Inc

Nanoparticle Silver Catalysts That Show Enhanced Activity for Carbon Dioxide Electrolysis

Electrochemical conversion of CO₂ has been proposed both as a way to reduce CO₂ emissions and as a source of renewable fuels and chemicals, but conversion rates need improvement before the process will be practical. In this article, we show that the rate of CO₂ conversion per unit surface area is about 10 times higher on 5 nm silver nanoparticles than on bulk silver even though measurements on single crystal catalysts show much smaller variations in rate. The enhancement disappears on 1 nm particles. We attribute this effect to a volcano effect associated with changes of the binding energy of key intermediates as the particle size decreases. These results demonstrate that nanoparticle catalysts have unique properties for CO₂ conversion