A mathematic model is established to simulate the effects of methanol crossover on the DMFC. The transport and reactions of both oxygen and methanol at the cathode are described and the theory of “parallel electrode reactions” is applied to calculate the cathode over‐potential caused by methanol crossover. The influence of methanol concentration, fuel cell temperature, oxygen pressure, and membrane properties on the cathode over‐potential is evaluated. Simulation results show that methanol crossover considerably increases the cathode over‐potential at low current density, but its effect is significantly reduced when the current density is increased to reasonable values. It also shows that of the two parameters characterizing a polymer electrolyte membrane, proton conductivity and methanol permeability, the former has more impact on the performance of a DMFC.

The effect of flow bed design on the performance of a liquid feed direct methanol fuel cell was studied experimentally. The flow beds were designed and manufactured with different channel densities, channel depths, and ridge widths. The flow beds were machined on stainless steel polar plates. The experimental results showed that ridge width affects the slope of the ohmic polarization curve. A ridge width of 3.30 mm provided the highest peak power. When the contact surface area between the flow bed and electrode was constant, the effect of channel density on cell performance was minimal, under the experimental conditions of this paper. The channel depth had a considerable influence on cell performance with a 2 mm deep channel achieving the best performance. The mechanism of the experimental phenomena was analyzed in this paper.

A new kind of hollow titania spheres-chitosan (hTiO 2 -CS) hybrid membranes was prepared by a physical blending method. hTiO 2 spheres were found to disperse well in the as-prepared hTiO 2 -CS hybrid membranes. Their incorporation can reduce the chitosan crystallinity and enhance slightly its hydrophilicity and thermal stability. Subsequently, hTiO 2 -CS/PAN composite membranes comprising of the hTiO 2 -CS hybrid membrane as separation layer and a polyacrylonitrile (PAN) membrane as support layer were fabricated. Compared to the CS/PAN membrane, all of them exhibit a much better flux and separation factor for a 90 wt % aqueous solution of isopropanol at 80°C. This promising kind of composite membranes may find potential application in the dehydration of alcohols.

Calcium–magnesium–alumina–silicate (CMAS) attack is a crucial issue for thermal–environmental barrier coatings (T/EBCs) with the ever-increasing operating temperature of turbine engines. In this study, CeO2 has been demonstrated as a promising protective material for T/EBCs against CMAS attack. At 1300 °C, CeO2 powder kept excellent phase and structural stability in molten CMAS; there were some CMAS constituents dissolved into the CeO2 lattice to form a solid solution. With higher CeO2 contents and longer duration time, more CeO2 solid solution particles were formed, which acted as the nucleating agent for CMAS crystallization. As a result, apatite, anorthite and wollastonite crystalline products were easily generated. At 1300 °C for 10 h, CeO2 pellets covered with CMAS powder had limited degradation, which was attributed to the rapid crystallization of molten CMAS due to the excellent nucleating agent effect of the precipitated CeO2 solid solution.

No abstract