For two different types of poly(N-isopropylacrylamide) (PNIPA) hydrogels, i.e., nanocomposite type PNIPA hydrogels (NC gel) and conventional chemically cross-linked PNIPA hydrogels (OR gel), the effects of cross-linker contents on various physical properties were investigated. In NC gels composed of a unique organic (PNIPA)/inorganic (clay) network, the inorganic clay acts as a multifunctional crosslinker in place of an organic cross-linker (BIS) as used in OR gels. In NC gels, which generally exhibit extraordinary mechanical toughness, the tensile moduli and tensile strengths are almost proportional to the clay content (C clay), while the elongation at break tends to decrease slightly with increasing Cclay. On the other hand, in OR gels, which always exhibit weak and brittle natures, there was no detectable change in properties on altering the concentration of BIS (C BIS). The deswelling rate was affected markedly by the cross-linker content in both gels though in opposite directions. On increasing cross-linker contents NC gels exhibit decreases and OR gels exhibit increases in rates of deswelling. In NC gels, high deswelling rates and high structural homogeneities (transparencies) were achieved simultaneously. Also, volume changes related to the phase transition of PNIPA at LCST were also inclined to decrease on increasing cross-linker contents in both gels, although swelling ratios at temperatures below LCST were generally larger in NC gels than those in OR gels. As for transparency changes at LCST, in OR gels changes in transparency decrease on increasing C BIS, because below the LCST the transmittances themselves decrease steeply with increasing CBIS. On the contrary, NC gels exhibit large transparency changes regardless of Cclay and show a tendency to increase their transmittances above LCST in the high Cclay region. All results obtained were consistent with the proposed model structure for NC gels. On the basis of the theory of rubber elasticity and using tensile mechanical data, the number of effective cross-links and the molecular weight between cross-linking points were evaluated for all NC gels.

Due to improved kinetics and reduced CO poisoning effects, higher temperature alcohol fuel cells have been shown to have higher activity and increased performance output when compared to lower temperature alcohol fuel cells. In this work, the Direct Alcohol Phosphoric Acid Fuel Cell (DAPAFC) with methanol and ethanol as reactant fuels, and Pt and PtRu as catalysts is studied. The electrolyte/separator consists of Phosphoric Acid in a Silicon Carbide (SiC) matrix and replaces conventional polymer electrolyte or PBI membranes. Comprehensive studies are conducted to demonstrate the performance effects of the Gas Diffusion Layer (GDL), Micro-porous Layer (MPL) and such parameters as the stream pressures, higher temperature operation (120-180 • C), and the thickness of the SiC separator, etc. Results show that at the same operating conditions, the cell performance is comparable to that of a vapour fed Nafion membrane based fuel cell. Structure improvement of the Phosphoric Acid Electrode Assembly (PAEA) and reactant vapor composition can significantly improve durability. This type of fuel cell demonstrates performance improvement and stability in a higher temperature range than is possible with the conventional PEMFC.

Rechargeable zinc-air redox flow batteries have been reported as an energy storage technology that has high energy density, uses abundant low-cost raw materials, and has low environmental impact [1, 2]. Due to these characteristics, zinc-air batteries are attractive for both portable and smart-grid energy storage applications [1, 2]. However, the limited cycle life has been identified as a major problem for commercialization of zinc-air batteries [2].Flooding of the electrolyte within alkaline electrode pores is reported as one of the major causes of degradation and performance loss of the air cathode in these devices [1, 3]. To prevent the ingress of electrolyte in the zinc-air cathode, modifying the hydrophobicity and conductivity of the catalyst layer has been reported [4]. The ratio of carbon/binder has impact on ionic conductivity and gas transport in the electrode. In addition, it is observed that degradation of performance of the electrode without binder is faster than that with binder [4].In this study, degradation of the air cathode in the zinc air flow battery was investigated by measuring the variation in the cell voltage at a constant current density. The air cathode consisted of a sintered active layer (AL) composed of platinum nanoparticles supported on carbon (Pt/C), a carbon / PTFE backing layer (BL), and a nickel mesh current feeder. The experimental setup used a 6 M KOH electrolyte, with a zinc wire reference and nickel counter electrode. A control system for real time control of the operating temperature, pressure, and inlet air humidity was implemented to maintain stable operating conditions and record the data. Post-mortem (PM) analysis was conducted on the tested samples. The sample preparation method was carefully evaluated for the PM study to make sure that the KOH present in the pores is preserved during imaging.No significant degradation in the performance of the air cathode was observed after 148 hours at baseline operating conditions (current density of 200 mA cm-2 and 21% oxygen). In order to enable rapid evaluation of electrode durability, conditions for accelerated degradation of the air cathode were investigated. Under conditions of low oxygen stoichiometry (achieved by 50% drop in oxygen stoichiometry) and high current density (400 mA cm-2), the rate of degradation was accelerated and the lifetime of the air cathode was less than 24 hours. The lifetime of the air cathode was estimated based on significant increase in the potential loss ca. 0.3 V, while performing oxygen reduction from an air feed at baseline operating conditions. Polarization studies were performed on the air cathode after a significant performance loss during the accelerated degradation experiments. The results indicate that the air cathode degradation accelerated under conditions of oxygen mass transfer limitation. The increased potential loss is likely due to flooding of electrolyte inside the pores of the active layer of the electrode, which increases the mass transfer resistance for oxygen transport [5, 6]....