DMFC Performance of Polymer Electrolyte Membranes Prepared from a Graft-Copolymer Consisting of a Polysulfone Main Chain and Styrene Sulfonic Acid Side Chains
Polymer electrolyte membranes (PEMs) for direct methanol fuel cell (DMFC) applications were prepared from a graft-copolymer (PSF- g -PSSA) consisting of a polysulfone (PSF) main chain and poly(styrene sulfonic acid) (PSSA) side chains with various average distances between side chains ( L av) and side chain lengths ( L sc). The polymers were synthesized by grafting ethyl p -styrenesulfonate (EtSS) on macro-initiators of chloromethylated polysulfone with different contents of chloromethyl (CM) groups, and by changing EtSS content in the copolymers by using atom transfer radical polymerization (ATRP). The DMFC performance tests using membrane electrode assemblis (MEAs) with the three types of the PEMs revealed that: a PSF- g -PSSA PEM (SF-6) prepared from a graft copolymer with short average distances between side chains ( L av) and medium L sc had higher DMFC performance than PEMs with long L av and long L sc or with short L av and short L sc. SF-6 had about two times higher PD max (68.4 mW/cm 2 ) than Nafion ® 112 at 30 wt % of methanol concentration. Furthermore, it had 58.2 mW/cm 2 of PD max at 50 wt % of methanol concentration because of it has the highest proton selectivity during DMFC operation of all the PSF- g -PSSA PEMs and Nafion ® 112.
All solid-state polymer electrolytes prepared from a graft copolymer consisting of a polyimide main chain and poly(ethylene oxide) based side chains
Abstract We prepare an all solid-state, liquid-free, polymer electrolyte (ASPE) from a lithium salt and a graft copolymer consisting of a polyimide main chain and poly(ethylene glycol) methyl ether methacrylate side chains using atom transfer radical polymerization method. The ionic conductivity of ASPEs increases with increasing the side chain length. The ionic conductivity of the ASPE whose POEM content = 60 wt% shows 6.5 × 10 −6  S/cm at 25 °C. The ASPEs having shorter average distance between side chains and/or shorter side chain length show higher mechanical strength. The tensile strength of the ASPEs is more than 10 MPa and about 20 times higher than that of the ASPEs in the previous study [Electrochim. Acta, 50 (1998) 3832]; hence, the ASPEs have sufficiently high mechanical strength for a polymer electrolyte of lithium secondary batteries.
ROOM- AND HIGH-TEMPERATURE MAGNETIC PROPERTIES OF Sm(CobalFexCu0.088Zr0.025)7.5 (x=0.30) SINTERED MAGNETS
The effect of Fe content on room- and high-temperature magnetic properties of Sm(CobalFexCu0.088Zr0.025)7.5 (x=0-0.30) sintered magnets, prepared by the conventional powder metallurgy method, has been systematically studied. With increasing Fe content, the remanences BT and maximum energy products (BH)max at room temperature gradually increase and reach optimal values of 1.055 T with x=0.27 for BT, and 205 kJ/m3 with x=0.21 for (BH)max, respectively, and then drop sharply with further Fe increase. An excessive addition of Fe (x≥0.24) results in rapid deterioration of permanent magnetic properties due to the formation of a considerable amount of FeCo soft magnetic phase. It was found that the effect of Fe content on high temperature stability is huge. The lower the Fe content, the smaller the temperature coefficient of coercivity. When x=0.07, a temperature coefficient of coercivity of -0.14%/K (293-723 K) can be achieved, as compared with -0.23%/K for x=0.21. BT of 0.725 T, bHc of 517 kA/m, iHc of 764 kA/m, and (BH)max of 95 kJ/m3 at 723 K were obtained, and the B-H demagnetization curve remains a straight line.