A mathematical model based on the Lucas-Washburn equation has been developed to address the relationships between capillary height,capillary radius and heat flux in a capillary loop.The stability criteria at the interface are studied in detail by introducing a small perturbation to the interfaces of the capillary loop.The formulae deduced as a consequence are used to analyze the influence of height of the capillary wick and the stability in a capillary loop undergoing phase changes.
Nafion/Silicon oxide composite membranes were produced via in situ sol-gel reaction of tetraethylorthosilicate (TEOS) in Nafion membranes. The physicochemical properties of the membranes were studied by FT-IR,TG-DSC and tensile strength. The results show that the silicon oxide is compatible with the Nafion membrane and the thermo stability of Nafion/Silicon oxide composite membrane is higher than that of Nafion membrane. Furthermore,the tensile strength of Nafion/Silicon oxide composite membrane is similar to that of the Nafion membrane. The proton conductivity of Nafion/Silicon oxide composite membrane is higher than that of Nafion membrane. When the Nafion/Silicon oxide composite membrane was employed as an electrolyte in H2/O2 PEMFC,a higher current density value (1 000 mA/cm2 at 0.38 V) than that of the Nafion1135 membrane (100 mA/cm2 at 0.04 V) was obtained at 110 ℃.
