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Kim, M.,Jeong, G.,Eom, K.,Cho, E.,Ryu, J.,Kim, H.J.,Kwon, H. Pergamon Press ; Elsevier Science Ltd 2013 INTERNATIONAL JOURNAL OF HYDROGEN ENERGY - Vol.38 No.28
To improve cell performance, the effects of heat treatment time on the electrochemical properties and electrode structure of PTFE-bonded membrane electrode assemblies for PBI-based high-temperature proton exchange membrane fuel cells are investigated. The cell performance is observed to decrease in the high-current-density region rather than in the low-current-density region with increasing heat treatment time at 350 <SUP>o</SUP>C from 1 to 30 min. Microscopic studies reveal remarkable differences in the electrode structure by the agglomeration of dispersed PTFE and adjacent catalyst particles, depending on the heat treatment time. As the heat treatment time increases, only the large pore (secondary pore) volume in the electrode decreases, resulting in increase in mass transport resistance and concentration overpotential in the high-current-density region. Cell performance is not measured without heat treatment because the electrodes are not formed. When the electrodes are heat treated for 1 min at 350 <SUP>o</SUP>C, the best cell performance is obtained, 0.67 V at 200 mA cm<SUP>-2</SUP>.
Probabilistic risk assessment of dietary cadmium in the South Korean population
Kim, M.,Wolt, J.D. Informa UK (TaylorFrancis) 2011 Food additives & contaminants. Part A. Chemistry, Vol.28 No.1
<P>Global interest in the adverse health effects of cadmium (Cd) has focused on dietary exposure as the principal source of Cd exposure to the general population. Common assumptions used in deterministic Cd assessment in global or regional diets have limitations when applied to specific national cases where local variation in food composition and consumption patterns are different than for global or regional norms. Stochastic dietary Cd exposure assessment was conducted for the general South Korean population to understand better Cd dietary intake. Because rice (Oryza sativa) is commonly and highly consumed by Koreans, it was the dominant contributor to Cd in the diet, representing on average 25% of the total dietary exposure for the general population. Hazard index (HI) values were below the level of concern for the 95th percentile of the general population. Sensitivity analyses demonstrated that variation in rice intake and Cd concentration had the greatest influence on the Cd risk estimate for the general population. Changes in food sources, such as the use of imported rice with higher Cd levels, would lead to increased Cd exposure in the diet, thus necessitating continued vigilance as to the status of Cd within the food supply.</P>
Kim, M.,Chae, H.J.,Kim, T.W.,Jeong, K.E.,Kim, C.U.,Jeong, S.Y. Korean Society of Industrial and Engineering Chemi 2011 Journal of industrial and engineering chemistry Vol.17 No.3
SAPO-34 is the most well-known catalyst for MTO (methanol to olefins) reaction because of its good selectivity to light olefins. However, SAPO-34 catalyst is rapidly deactivated by coke, and thus it should be used in circulating fluidized bed (CFB) reactors so that the deactivated catalyst can be continuously regenerated. To apply a catalyst into a CFB reactor, strong mechanical strength of the catalyst as well as good catalytic performance is critical. Therefore, in this study, fluidizable spherical SAPO-34 catalysts to be applied to MTO CFB reactor have been prepared through a spray-drying method, and a formulation composition has been optimized, including binders, matrix materials and additives. In particular, the effects of catalyst phase and acidic solution as an additive have been examined using XRD, N<SUB>2</SUB> isotherm, attrition test, pore size distribution, SEM and TEM.