Vanadium pentoxide films

Fig. 5.10 X-ray diffraction patterns of a bare FTO substrate (a), a DG-structured (b) and nontemplated (c) vanadium pentoxide film annealed at 275 °C for 2h. Cu Kq radiation was used and the patterns were matched with the corresponding tetragonal Sn02 (PDF number 046-1088) and orthorhombic V2O5 (PDF number 089-0611)...

The V2O5 System. Vanadium pentoxide films obtained by the sol-gel process have recently received a strong interest for their applications as reversible cathodes for Li batteries (Livage, 1991). Layered structures ofVaOs-l.bHaO xerogel have been shown to be efficient in reversible electrochemical storage of Li+ ions (Araki, 1983), via the reaction ... 

U.S. Stockpile. A U.S. government stockpile goal for vanadium pentoxide of 6985 t contained vanadium was aimounced on May 1, 1980. This is equivalent to 12,470 t of V2O3. At the time of the announcement, the stockpile contained only 4911 of vanadium ia the form of the peatoxide (28). Physical requiremeats are that V2O3 be suppHed as brokea flake, ah. of a size to pass a 2.54-cm screea and not more than 5 wt % to pass a 4.7-mm screen. Packaging ia polyethyleae film iaside 208-L steel dmms and marking of the dmms has been described ia detail (29). 

A colloidal suspension of conductive vanadium pentoxide [130] can be used to perform intercalation, adsorption or encapsulation of electroactive molecules or biomolecules for electrodes or biosensor realization [131]. Encapsulation of glucose oxidase in nanocomposite films made with polyvinyl alcohol and V205 sol-gel matrix or in ferrocene intercalated V2Os sol-gel [132] were envisaged to prepare glucose biosensors. 

Figure 6.14 Cyclic voltammogram obtained for a multiple-electron-transfer system, where a thin film of sputtered V2O5 on a platinum working electrode has been immersed in an electrolyte solution of propylene carbonate containing LiCI04 (1.0 mol dm ). From Cogan, S. F., Nguyen, N. M Perrotti, S. J. and Rauh, R. D Electroctromism in sputtered vanadium pentoxide , SPIE, 1016, 57-62 (1989). Reproduced by permission of the International Society for Optical Engineering (SPIE).

Spectroelectrochemical analysis of charge-insertion nanostructured materials already offers important insight into these systems. These methods were recently exploited to characterize the electrochemical processes of nanostructured manganese oxide ambi-gel and xerogel films. " 6-229 Spectroelectrochemical measurements were used to corroborate electronic state changes with the observed electrochemical response for the insertion of small cations (Li+, Mg2+) and the unexpected insertion of a bulky organic cation (tetrabutylammonium). Vanadium pentoxide exhibits two distinct electrochromic features that can be assigned to the transition at either sto-... 

Thermal treatment of the films was carried out at 300-500 "C during 10-130 min. An oxidation of vanadium films was performed in a stream of Ar+02 gas mixture. A high-temperature processing of the films was carried out in a recovering medium Ar+4%H2 at 350 °C with a goal of the recovery of vanadium pentoxide down to lower phase of vanadium dioxide. 

One should pay attention to the processes taking place in the film after the phase transition, as well. Metallic type of conductance was not observed in our experiment after the phase transition. The conductance continued to increase. This effect could be explained by the presence of small amounts of vanadium pentoxide in the VO2 layer. Co-existence of different conduction mechanisms is possible in that case. 

Equation 3.8 combines the effects of conduction through particles (with characteristic length given by Cdp) and in the stagnant fluid film (with thickness Bdp) in the vicinity of the contact surface between two neighboring particles (with centers distanced hjAdp) as two resistances in series. The reader is referred to the references cited earlier for further details and other expressions [66]. Experimental measurements with air flowing over vanadium pentoxide catalyst are reported in Ref [67]. 

Vinod M.P., Bahnemann D. Materials for all-solid-state thin-film rechargeable lithium batteries by sol-gel processing. J. Solid State Electrochem. 2002 6 498-501 Vivier V., Farcy J., Pereira-Ramos J.P. Electrochemical lithium insertion in sol-gel crystalline vanadium pentoxide thin films. Electrochim. Acta 1998 44 831-839 Wang J., Bell J.M., Skryabin I.L. Kinetics ofcharge injection in sol-gel deposited WO3. Solar Ener. Mater. Solar Cells 1999 56 465-475... 

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