Nickel oxide thin films

Figure 8.5 Change in transmittance (upper part) and deflection angle variation (lower part) associated with galvanostatic (1= 21 pAcm" ) insertion-deinsertion cycles of a lithiated nickel oxide thin-film electrode. The vertical bar corresponds to a stress variation of 0.5 GPa. Sample thickness 2000A. Counter-electrode Li foil. Electrolyte iM LiC104-PC. From [26] by permission of Elsevier Science Publishers, Amsterdam.

F. Decker, S. Passerini, R. Pileggi, and B. Scrosati [1992] The Electrochromic Process in Non-Stoichiometiic Nickel Oxide Thin Film Electrodes. Electrochim. Acta 37, 1033-1038. 

Williams P.A, Jones A.C., Bickley J.F., Steiner A., Davies H.O., Leedham T.J., Impey SA., Garcia J., Allen S., Rougier A., Blyr A. Synthesis and crystal structures ofdimethylaminoethanol adducts of Ni(ll) acetate and Ni(II) acetylacetonate. Precursors for the sol-gel deposition of electrochromic nickel oxide thin films, J. Mater. Chem. 2001, 11 2329 Yanovskaya M.L, Kotova N.M., Golubko N.V., Turova N.Ya. Reactions of magnesium and titanium alkoxides. Preparation and characterization of alkoxy-derived magnesium titanate powders and ceramics, J. Sol-Gel Sci. Tech. 1998 11 23... 

Cere KoroSec, Bukovec P., Pihlar B., Padeznik Gomilsek. The role of thermal analysis in optimization of the electrochromic effect of nickel oxide thin films, prepared by the sol-gel method. Part I. Thermochim. Acta 2003 402 57-67... 

Miki T., Yoshimura K., Tai Y., Tazawa M., Jin P., Tanemura S. Electrochromic properties of nickel oxide thin films prepared by the sol-gel method, Proc. SPIE, 1995 2531 135-142 Monk P.M.S., Mortimer R.J., Rosseinsky D.R. Electrochromism-Fundamentals and Applications VCH, Weinheim, 1995... 

Examples for electrochromic behavior upon electrochemical oxidation can be found among group VIII metal oxides. Thin films of transparent hydrated iridium oxide turn blue-black, whereas nickel oxide switches from pale green to brown-black, possibly due to the absorbance of Ni3+ centers [26]. The systems are much less thoroughly investigated and a detailed mechanistic explanation is not known. However, proton extraction and anion insertion have been suggested. 

F. Artnso, E. Bonino, E. Decker, A. Lourenco, and E. Masetti [2002] Study of Lithium Diffusion in RE Sputtered Nickel-Vanadium Mixed Oxides Thin Films. Electrochim. Acta 47,... 

Nonferrous alloys account for only about 2 wt % of the total chromium used ia the United States. Nonetheless, some of these appHcations are unique and constitute a vital role for chromium. Eor example, ia high temperature materials, chromium ia amounts of 15—30 wt % confers corrosion and oxidation resistance on the nickel-base and cobalt-base superaHoys used ia jet engines the familiar electrical resistance heating elements are made of Ni-Cr alloy and a variety of Ee-Ni and Ni-based alloys used ia a diverse array of appHcations, especially for nuclear reactors, depend on chromium for oxidation and corrosion resistance. Evaporated, amorphous, thin-film resistors based on Ni-Cr with A1 additions have the advantageous property of a near-2ero temperature coefficient of resistance (58). 

The current-potential relationship ABCDE, as obtained potentiosta-tically, has allowed a study of the passive phenomena in greater detail and the operational definition of the passive state with greater preciseness. Bonhoeffer, Vetter and many others have made extensive potentiostatic studies of iron which indicate that the metal has a thin film, composed of one or more oxides of iron, on its surface when in the passive state . Similar studies have been made with stainless steel, nickel, chromium and other metals... 

The reaction channels were made in silicon by several photolithographic steps, followed by potassium hydroxide etching [13,14]. Silicon oxide was thermally grovm over the silicon. Nickel thin films were vapor-deposited. Pyrex was anodically bonded to such a modified micro structured silicon wafer. 

A novel polysiloxane, containing the isocyanide group pendent to the backbone, has been synthesized. It is observed to react with the metal vapors of chromium, iron and nickel to afford binary metal complexes of the type M(CN-[P])n, where n = 6, 5, 4 respectively, in which the polymer-attached isocyanide group provides the stabilization for the metal center. The product obtained from the reaction with Fe was found to be photosensitive yielding the Fe2(CN-[P])q species and extensive cross-linking of the polymer. The Cr and Ni products were able to be oxidized on exposure of thin films to the air, or electrochemically in the presence of an electron relay. The availability of different oxidation states for the metals in these new materials gives hope that novel redox-active polymers may be accessible. 

The electrochemical behavior of thin-film oxide-hydroxide electrodes containing chromium, nickel and cobalt compounds was investigated. Experimental results have shown that such compounds can be successfully used as active cathodic materials in a number of emerging primary and secondary battery applications. 

Figure 3. Microphotograph of a thin-film Figure 4. Microphotograph of a thin-film nickel oxide representing sample 4. nickel oxide representing sample 6.

Thin films of a composite nickel-iron (9 1 Ni/Fe ratio) and iron-free oxyhydroxides were deposited from metal nitrate solutions onto Ni foils by electroprecipitation at constant current density. A comparison of the cyclic voltammetry of such films in 1M KOH at room temperature (see Fig. 6) shows that the incorporation of iron in the lattice shifts the potentials associated formally with the Ni00H/Ni(0H)2 redox processes towards negative potentials, and decreases considerably the onset potential for oxygen evolution. The oxidation peak, as shown in the voltammo-gram, is much larger than the reduction counterpart, providing evidence that within the time scale of the cyclic voltammetry, a fraction of the nickel sites remains in the oxidized state at potentials more negative than the reduction peak. 

At a nickel metal surface in alkaline aqueous medium a thin film of Ni(II) hydroxide is formed. At + 0.63 V (vs NHE) the film is oxidized to Ni(III) oxide hydroxide (a). After adsorption of the substrate at this surface (b) hydrogen atom abstraction at the a-carbon of the substrate occurs in the rate determining step (c). The intermediate radical is then further oxidized either directly (d) or indirectly (e) to the product. 

Kuan-Xin, H., et ah, Electrodeposition of nickel and cobalt mixed oxide/carbon nanotube thin films and their charge storage properties. Journal of The Electrochemical Society, 2006. 153(8) p. A1568-A1574. 

It has been observed that solid oxide fuel cell voltage losses are dominated by ohmic polarization and that the most significant contribution to the ohmic polarization is the interfacial resistance between the anode and the electrolyte (23). This interfacial resistance is dependent on nickel distribution in the anode. A process has been developed, PMSS (pyrolysis of metallic soap slurry), where NiO particles are surrounded by thin films or fine precipitates of yttria stabilized zirconia (YSZ) to improve nickel dispersion to strengthen adhesion of the anode to the YSZ electrolyte. This may help relieve the mismatch in thermal expansion between the anode and the electrolyte. 

---