Hydrogen transport by dislocations

A kinetic model is presented for the transport of hydrogen, as Cottrell atmospheres on dislocation, at a rate appreciably in excess of that for lattice diffusion. The particular destinations for the hydrogen which are modeled here are ductile fracture initiation sites such as inclusions and microvoids. The functional predictions of the mechanism are shown to be consistent with available experimental evidence on ductile fracture behavior in the presence of hydrogen.     

Determination of phase equilibria in the system Si-Al-Zr/N-O by experiment and thermodynamic calculation

The phase relations in the system Si-Al-Zr/N-O are studied by experiment and by thermodynamic calculations. The results show the conditions under which such ceramics can exist and thereby explain contradictions between earlier results. The knowledge of these phase equilibria makes it possible to choose suitable material compositions in order to apply the toughening effects of ZrO₂ on a SiAlON matrix.     

Deposition of Brownian particles in packed beds

An analysis is presented to describe the deposition of Brownian particles from suspensions flowing through granular media. The constricted tube porous media model recently proposed by Payatakes et al.[8] was used to characterize the media and the deposition process was assumed to be controlled by convective diffusion as well as the nature of the surface interaction between the media grains and the Brownian particles. Three different tube configurations were considered and the differences among the results were found to be relatively unimportant. Agreement between the analysis and available experimental data was found to be reasonably good for the limiting case when the surface effect is favorable.     

Polymer/graphite oxide composites as high-performance materials for electric double layer capacitors

A single graphene sheet represents a carbon material with the highest surface area available to accommodating molecules or ions for physical and chemical interactions. Here we demonstrate in an electric double layer capacitor the outstanding performance of graphite oxide for providing a platform for double layer formation. Graphite oxide is generally the intermediate compound for obtaining separated graphene sheets. Instead of reduction with hydrazine, we incorporate graphite oxide with a poly(ethylene oxide)-based polymer and anchor the graphene oxide sheets with poly(propylene oxide) diamines. This polymer/graphite oxide composite shows in a “dry” gel-electrolyte system a double layer capacitance as high as 130 F g⁻¹. The polymer incorporation developed here can significantly diversify the application of graphene-based materials in energy storage devices.     

A New Finite-Difference Representation for the Vorticity at a Wall with Suction

Abstract

In two-dimensional convective transport, the vorticity at a wall is usually not well specified. There exist several representations to relate the vorticity at a wall to the stream function and interior vorticity values. These are shown to be inadequate when suction occurs at the wall. A new representation is proposed and shown to be significantly superior to the existing ones. The analysis can also be applied to heat transfer calculations at a wall with suction.