Elastic constants of beta-eucryptite: A density functional theory study

The five independent elastic constants of hexagonal $\beta$-eucryptite have been determined using density functional theory (DFT) total energy calculations. The calculated values agree well, to within 15%, with the experimental data. Using the calculated elastic constants, the linear compressibility of $\beta$-eucryptite parallel to the c-axis, $\chi_c$, and perpendicular to it, $\chi_a$, have been evaluated. These values are in close agreement to those obtained from experimentally known elastic constants, but are in contradiction to the direct measurements based on a three-terminal technique. The calculated compressibility parallel to the c-axis was found to positive as opposed to the negative value obtained by direct measurements. We have demonstrated that $\chi_c$ must be positive and discussed the implications of a positive $\chi_c$ in the context of explaining the negative bulk thermal expansion of $\beta$-eucryptite.Comment: 3 eps figures, submitted for publicatio

Model water disinfection with electrolysis using TinO2n-1 containing ceramic electrodes

Water treatment with electrolysis was performed in a specially made electrolytic cell containing TinO2n-1 ceramic anode and Escherichia coli was used as a model organism for disinfection tests. The results showed that even relatively low energy input (0.5-2.5kWh*m-3, depending on water conductivity) in water samples with chloride ions concentration below 50mg*l-1, TinO2n-1 ceramic electrodes generated active chlorine in the range of 0.4-3.5mg Cl2*l-1, which is the level of chorine used for water disinfection. The results also confirmed that disinfection effect is a result of generation of oxidant species from chlorine rather than effect of electricity per se, or formation of radicals in water. At chloride ion concentration about 7mg*l-1 E. coli is not culturable, not able to divide and not respiring. Results showed that increase of the current above 0.02A at chloride ion concentration of 7mg*l-1 was sufficient to inactivate both culturable and viable but nonculturable (VBNC) E. coli. Notably, the ability of bacteria to divide (DVC positive) was lost more rapidly than their ability to respire. Kinetics of disinfection was studied in water sample which was treated with 0.02A at chloride ion concentration of 7mg*l-1. After about 15 minutes of exposure no culturable or able-to-divide E. coli were detected in the sample. Using the TinO2n-1 electrode in the electrolysis process with the presence of chloride ions, in concentration range which is common in raw waters, one can create a level of active chlorine that kills more than 99% of E. coli within 15 minutes. A practically applicable simple model for prediction of disinfection efficacy with electrolytic cell has been proposed