Porous tungsten oxide films were deposited onto a sensor substrate with a Si bulk-micromachined hotplate, by drop-coating isopropyl alcohol solution of highly crystalline tungsten oxide $\left(\mathrm{W}{\mathrm{O}}_{2.72}\right)$ nanorods with average $75\mathrm{nm}$ length and $4\mathrm{nm}$ diameter. The temperature-dependent gas sensing characteristics of the films have been investigated over the mild temperature range from $20\text{to}250°\mathrm{C}$ . While the sensing responses for ammonia vapor showed increase in electrical conductivity at temperatures above $150°\mathrm{C}$ as expected for $n$ -type metal oxide sensors, they exhibited the opposite behavior of unusual conductivity decrease below $100°\mathrm{C}$ . Superb sensing ability of the sensors at room temperature in conjunction with their anomalous conductivity behavior might be attributed to unique nanostructural features of very thin, nonstoichiometric $\mathrm{W}{\mathrm{O}}_{2.72}$ .

An electrochemical quartz crystal microbalance is used in an investigation of the corrosion of aluminum in electrolytes appropriate for lithium batteries. The electrolytes are solutions of LiN ( CF 3 SO 2 ) 2 , LiC ( CF 3 SO 2 ) 3 , LiCF 3 SO 3 , LiPF 6 , LiBF 4 , and LiClO 4 , singly or in a limited number of combinations, in propylene carbonate (PC) and polyethylene glycol dimethyl ether. Aluminum that is scratched or abraded in an inert atmosphere (so that a protective surface film does not reform) undergoes significant corrosion in PC containing LiN ( CF 3 SO 2 ) 2 , LiC ( CF 3 SO 2 ) 3 , LiCF 3 SO 3 , and LiClO 4 , but forms a protective film in PC containing LiPF 6 , or LiBF 4 . A mechanism of corrosion of aluminum in LiN ( CF 3 SO 2 ) 2 / PC is proposed. © 2000 The Electrochemical Society. All rights reserved.