Discharged energy properties of PbO–SrO–Na2O–Nb2O5–SiO2 glass‐ceramics with crystallization time from 1 to 1000 min were investigated by measuring their hysteresis loops (described as quasi‐static measuring method) and pulse‐discharge current‐time curves (described as dynamic measuring method). The results show the same trend for both measuring methods: With the increment of crystallization time, the discharged energy density increases gradually, while the energy efficiency decreases. The highest energy efficiencies were obtained in the sample with crystallization time of 1 min, which are 96.3% and 82.4%, corresponding quasi‐static and dynamic measurement, respectively. The reduction of energy efficiency with crystallization time is attributed to combined effect of ferroelectric polarization and interfacial polarization, and part of the corresponding energy could not release in the pulse‐discharge process. 相似文献
Bromate by-product formation during ozonation of bromide-containing potable water has aroused widespread concern. In this study, cetylpyridinium chloride was selected to modify two different kinds of granular activated carbon (GAC) to improve their bromate adsorption capacity. The adsorption characteristics of modified GAC were studied by batch and column tests, with results suggesting greatly improved bromate adsorption ability: the saturation capacities for bromate were >7 times for modified GAC than for GAC under the experimental conditions used. This enhancement in adsorptive capacity is likely due to an increase in basic functional groups, because the saturated adsorption capacity of bromate on the GAC is positively correlated with the basic functional groups. The increase of the basic functional groups accelerates OH- dissociation from the GAC surface and protonation of the GAC surface, thus resulting in the enhancement in adsorptive capacity. The modified GAC was relatively immune to the impact of pH change over a broad range. Both the Yoon-Nelson model and the Thomas model fit well the breakthrough curves of bromate adsorbed by modified and unmodified GAC under different conditions. Our results provide insight into the sorption process of bromate onto modified GAC. 相似文献
A general protocol for the chemoselectivity‐controlled C C and C S coupling reactions of di(hetero)aryl disulfides with Grignard reagents catalyzed by ferrocene and palladium acetate has been developed. Ferrocene favored the formation of C S coupled products at low temperature, whereas C C bond couplings were favored when palladium acetate was used. All the reactions proceeded with excellent chemoselectivity and in good yields under mild conditions, and a library of molecules with pyridine and pyrimidine scaffolds was produced.