Niobium oxide coatings

Cathodic Protection Systems. Metal anodes using either platinum [7440-06 ] metal or precious metal oxide coatings on titanium, niobium [7440-03-17, or tantalum [7440-25-7] substrates are extensively used for impressed current cathodic protection systems. A prime appHcation is the use of platinum-coated titanium anodes for protection of the hulls of marine vessels. The controUed feature of these systems has created an attractive alternative... 

Good results are obtained with oxide-coated valve metals as anode materials. These electrically conducting ceramic coatings of p-conducting spinel-ferrite (e.g., cobalt, nickel and lithium ferrites) have very low consumption rates. Lithium ferrite has proved particularly effective because it possesses excellent adhesion on titanium and niobium [26]. In addition, doping the perovskite structure with monovalent lithium ions provides good electrical conductivity for anodic reactions. Anodes produced in this way are distributed under the trade name Lida [27]. The consumption rate in seawater is given as 10 g A ar and in fresh water is... 

The impressed current method with metal oxide-coated niobium anodes is usually employed for internal protection (see Section 7.2.3). In smaller tanks, galvanic anodes of zinc can also be used. Potential control should be provided to avoid unacceptably negative potentials. Pure zinc electrodes serve as monitoring and control electrodes in exposed areas which have to be anodically cleaned in the course of operation. Ag-AgCl electrodes are used to check these reference electrodes. 

Precious metals and oxides platinised titanium, platinised niobium, platinised tantalum, platinised silver, solid platinum metals, mixed metal oxide-coated titanium, titanium oxide-based ceramics. 

Canister anodes consist of a spirally wound galvanised steel outer casing containing a carbonaceous based extender which surrounds the primary anode element which may be graphite, silicon iron, magnetite, platinised titanium, mixed metal oxide-coated titanium or platinised niobium, etc. 

The most recently developed anode for the cathodic protection of steel in concrete is mixed metal oxide coated titanium mesh The anode mesh is made from commercially pure titanium sheet approximately 0-5-2mm thick depending upon the manufacturer, expanded to provide a diamond shaped mesh in the range of 35 x 75 to 100 x 200 mm. The mesh size selected is dictated by the required cathode current density and the mesh manufacturer. The anode mesh is supplied in strips which may be joined on site using spot welded connections to a titanium strip or niobium crimps, whilst electrical connections to the d.c. power source are made at selected locations in a suitably encapsulated or crimped connection. The mesh is then fitted to the concrete using non-metallic fixings. 

Calcination is performed in crucibles made of platinum or related metals. Tantalum or niobium oxide can be successfully used in the manufacturing of such crucibles. Frolov et al. [505, 506] developed a method for coating various ceramic materials with tantalum or niobium oxide using an optical furnace. 

The nozzle of original design was fabricated from a niobium alloy coated with niobium silicide and could not operate above 1320°C. This was replaced by a thin shell of rhenium protected on the inside by a thin layer of iridium. The iridium was deposited first on a disposable mandrel, from iridium acetylacetonate (pentadionate) (see Ch. 6). The rhenium was then deposited over the iridium by hydrogen reduction of the chloride. The mandrel was then chemically removed. Iridium has a high melting point (2410°C) and provides good corrosion protection for the rhenium. The nozzle was tested at 2000°C and survived 400 cycles in a high oxidizer to fuel ratio with no measurable corrosion.O l... 

Niobium is a soft grayish-silvery metal that resembles fresh-cut steel. It is usually found in minerals with other related metals. It neither tarnishes nor oxidizes in air at room temperature because of a thin coating of niobium oxide. It does readily oxidize at high temperatures (above 200°C), particularly with oxygen and halogens (group 17). When alloyed with tin and aluminum, niobium has the property of superconductivity at 9.25 Kelvin degrees. 

L. Yoimg, "Anodic Oxide Films 4. The Interpretation of Impedance Measurements on Oxide Coated Electrodes on Niobium," Transactions of the Faraday Society, 51 (1955) 1250-1260. 

Lactate dehydrogenase (LDH) has been immobilized on silica gel coated with niobium oxide carbon paste electrode for the development of lactate biosensor. This biosensor shows good sensitivity allows lactate estimation upto 6.5 x 10-6 mol L-1. Moreover, the biosensor shows linear range from 0.1 to 14 mmol L-l for lactate. [111]. 

The DSA-type anodes are inert , coated anodes made of a valve metal (titanium, niobium, or tantalum) base coated with an electrochemically active coating. The active coating is made either of noble metals or of mixed metal oxides. Noble metals in active coatings are usually platinum or platinum alloys. Mixed metal-oxide coatings contain active oxides and inert oxides the active components are usually ruthenium dioxide (R.UO2) and iridium dioxide (IrC>2) and the inert components are mostly titanium dioxide (TiC>2) and other oxides such as tantalum... 

The surface of Mo disc opposite to the emitter is covered with NbOx (Niobium oxide) layer coated by a sputtering method. NbOx surface, which shows low work function in Cs vapor, can reduce the energy loss of electron condensing in to collector. 

L-lactate Lactate oxidase and meldola s blue adsorbed on Si02 particles coated with niobium oxide and dispersed in a cartxm paste electrode Bio- and electro- catalysis [205]... 

NbC powder is prepared by the reaction of niobium oxide with carbon at 1700°C in hydrogen. The reaction of niobium metal or niobium hydride with carbon under vacuum is also used. NbC coatings are deposited by CVD, reactive evaporation, or sputtering (see Chs. 14 and 15). 

Oxides of transition metals, such as niobium, tantalum, or titanium, are suitable as waveguiding layers on optical (grating coupler) waveguides due to their high refractive index and transparency. Therefore, oxide-coated chips are used as sensing devices in technology based on the interaction of a laser-induced evanescent field with analyte constituents adsorbed on or immobilized at the waveguide/ fluid interface. ... 

---