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Tailoring the chemical structures of a precursor polymer for carbon nanofibers (CNFs) produced by thermal treatment of electrospun nanofibers was studied to prepare the electrodes for electrochemical double layer capacitors (EDLCs). To improve energy storage performance of CNF electrodes, 6FDA-durene nanofibers were crosslinked by a vapor crosslinking method, and subsequently carbonized. Chemical modification via crosslinking was confirmed by FTIR spectra while the conversion of crosslinked 6FDA-durene into carbon was done by Raman spectroscopy. Electrochemical performance of these CNF electrodes was evaluated by assembling coin cells, and the CNFs derived from crosslinked 6FDA-durene nanofibers showed higher specific capacitances, energy densities and cycling stability than those from non-crosslinked ones. It was also shown that CNFs prepared using 1 min crosslinking exhibit the highest energy storage performances, a specific capacitance of 301 F g−1 (at 10 mV s−1), and the maximum energy density of 11.1 Wh kg−1 (at 0.5 A g−1) and power density of 1.8 kW kg−1 (at 6 A g−1). Surface area and porosity of CNFs, which is critical for the performance of EDLC electrodes, were studied by nitrogen adsorption/desorption measurements, and it was clearly seen that surface crosslinking of precursor polymers improved surface properties of the resultant CNFs.

The effect of crosslinking on vapor permeation behavior of polyelectrolyte membranes was studied. Poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPS) membranes were crosslinked by using crosslinkers with different lengths between the reactive ends. Crosslinked membranes with a longer crosslinking length showed lower water vapor permeability due to the lower sorption coefficient. It was also shown that the permeation behavior of PAMPS membranes was more affected by sorption than diffusion. For chemical protection applications, the ratio of water over chemical warfare agent permeability (i.e., selectivity) was measured. Due to the high water solubility of polyelectrolytes, crosslinked PAMPS allowed for the selective permeation of water over harmful chemical vapor, showing a selectivity of 20. The addition of electrospun nylon nanofibers in the membranes significantly improved the selectivity to 80, since the embedded nanofibers effectively reduced both diffusion and sorption coefficients of chemical warfare agents.

The effect of TiO₂ additive concentration and sintering temperatures on the densification of alumina (Al₂O₃ ) ceramics were investigated. Densified alumina specimens were prepared by uniaxial pressing at a pressure of 60 MPa followed by isothermal heating at either 1400, 1500, or 1600 o C for 2 h. The relative density, microstructure, crystallinity, and hardness were investigated, and the correlation between properties and structure was discussed in relation to TiO₂ addition and sintering temperature. The densities of the 0.05wt%-TiO₂ specimens sintered at 1500 and 1600 o C had higher values than the pure alumina specimens. Adding more than 5.0wt% TiO₂ lowered the relative density. The maximum achieved density was 99.7% at 0.05wt% TiO₂ addition. Shrinkage and hardness analyses confirmed that the sintering temperature for the Al₂O₃ insulator could be lowered by adding TiO₂. The optimal concentration to obtain a dense alumina with high hardness for insulator use was determined to be in the range of 0.05 to 1.0 wt% of TiO₂ . These results provide fundamental composition and process optimization data for the development of high-dielectric alumina insulators.

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