Continuously operating thermo-electrochemical cells (thermocells) are of interest for harvesting low-grade waste thermal energy because of their potentially low cost compared with conventional thermoelectrics. Pt-free thermocells devised here provide an output power of 12 W m for an interelectrode temperature difference (ΔT) of 81 °C, which is sixfold higher power than previously reported for planar thermocells operating at ambient pressure.

A method has been developed for removing chromium from alkaline high-level radioactive tank waste. Removing chromium from these wastes is critical in reducing the volume of waste requiring expensive immobilization and deep geologic disposition. The method developed is based on the oxidation of insoluble chromium(III) compounds to soluble chromate using ferrate. This method could be generally applicable to removing chromium from chromium-contaminated solids, when coupled with a subsequent reduction of the separated chromate back to chromium(III). The tests conducted with a simulated Hanford tank sludge indicate that the chromium removal with ferrate is more efficient at 5 M NaOH than at 3 M NaOH. Chromium removal increases with increasing Fe(VI)/Cr(II) molar ratio, but the chromium removal tends to level out for Fe(VI)/ Cr(III) greaterthan 10. Increasingtemperature leadsto better chromium removal, but higher temperatures also led to more rapid ferrate decomposition. Tests with radioactive Hanford tank waste generally confirmed the simulant results. In all cases examined, ferrate enhanced the chromium removal, with a typical removal of around 60-70% of the total chromium present in the washed sludge solids. The ferrate leachate solutions did not contain significant concentrations of transuranic elements, so these solutions could be disposed as low-activity waste.

We have fabricated thin-film combinatorial gas sensor libraries based on doped semiconducting SnO 2 thin films. Combinatorial pulsed-laser ablation was used to deposit compositionally varying arrays of sensor elements onto a prepatterned device electrode configuration. Using multiplexing electronics, we have demonstrated the detection of chloroform, formaldehyde, and benzene gases at concentrations down to 12.5 ppm through pattern recognition of signals from the arrays of sensors. This technique of fabricating gas sensor arrays as combinatorial libraries can be applied to the manufacturing of portable electronic noses.

Scanning tunneling microscopy has been used to study polycrystalline iron in borate buffer. The effect of oxidation and reduction processes on the electrode surface has been studied in situ. The initiation of oxide formation appears to start in the form of patches or clusters, which fuse together in time.