Nickel valve metals

The passive films formed by the addition of sufficient amounts of valve metals to amorphous nickel-valve-metal alloys are exclusively composed of valve-metal oxyhydroxides or oxides such as TaOjCOH) , Nb02(OH) or TajO,. Consequently, amorphous alloys containing strongly passivating elements, such as chromium, niobium and tantalum, have a very high ability... 

Kumagai K., Samata Y., Kawashima A., Asami K. and Hashimoto K. (1987) Anodic characteristics of amorphous nickel-valve metal alloys containing small amounts of platinum group elements in 0.5 M NaCl. J. appl. J. electrochem. 17, 347-356. 

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... 

Nickel boride with the same composition as the above one has been investigated in the amorphous state (see Section 4.8). Borides and nitrides of other transition metals, in particular the valve metals Zr, Nb, Ta, and W, have not shown any interesting activity for hydrogen evolution [436]. 

Ni(C0)4 is a volatile, extremely toxic liquid that must be handled with great caution. It was first observed in Mond s study of the reaction of CO with nickel valves. Because the reaction can be reversed at high temperature, coupling of the forward and reverse reactions has been used commercially in the Mond process for obtaining purified nickel from ores. Other binary carbonyls can be obtained from direct reaction of metal powders with CO, but elevated temperatures and pressures are necessary. 

Metals are used in the cardiovascular area including heart valves, heart pacemaker leads, and heart pacemaker cases. These metals include titanium, titanium aUojrs, cobalt-chromium alloys, and cobalt-nickel alloys. Metals used for aneurism clips include cobalt-chromium-molybdenum alloys, cobalt-nickel-chromium-molybdenum allojfs, and, previously, stainless steels were used. Metal seeds are used for fractionated hyperthermia treatment of prostate disease, and corrosion analysis showed the alloy, PdCo may be suitable for the seed implants [52],... 

Solids materials that are insoluble in hydrocarbon or water can be entrained in the crude. These are called bottom sediments and comprise fine particles of sand, drilling mud, rock such as feldspar and gypsum, metals in the form of minerals or in their free state such as iron, copper, lead, nickel, and vanadium. The latter can come from pipeline erosion, storage tanks, valves and piping systems, etc. whatever comes in contact with the crude oil. 

Methyl bromide, when dry (<100 ppm water), is inert toward most materials of constmction. Carbon steel is recommended for storage vessels, piping, pumps, valves, and fittings. Copper, brass, nickel, and its alloys are sometimes used. Aluminum, magnesium, zinc, and alloys of these metals should not be used because under some conditions dangerous pyrophoric compounds may be formed. Many nonmetallic materials are also useful for handling methyl bromide, but nylon and polyvinyl chloride should be avoided. 

As for storage tanks, stainless steel and lacquer-lined mild steel are suitable materials of constmction for pipe lines. For pumps, valves, etc, various alloys are suitable, including phosphor bronze, gun metal. Monel, stainless steel, and certain nickel steel alloys. Alloys with high proportions of ziac and tin together with copper and aluminum are not recommended. 

For the more vigorous reactions, a twin-cell calorimeter was devised (188). It consisted of two nickel cylinders connected by a stainless steel needle valve and tubing and held rigidly to a metal top-plate. The cylinders and connections were immersed in a wide-necked Dewar vessel containing carbon tetrachloride which would react mildly with any BrF3 that escaped. Bromine trifluoride contained in one cylinder was transferred to the solid contained in the other cylinder by opening the valve and applying controlled suction. All measurements were made externally on probes in the carbon tetrachloride. 

Pure nickel is a hard, silvery-white metal, which has properties that make it very desirable for combining with other metals to form mixtures called alloys. Some of the metals that nickel can be alloyed with are iron, copper, chromium, and zinc. These alloys are used in making metal coins and jewelry and in industry for making items such as valves and heat exchangers. 

Fig. 10.15, Metal vacuum systems for handling fluorine and reactive fluorides, (a) A design used extensively at Argonne National Laboratory constructed of nickel tubing and Monel valves (A) with cone joints (illustrated in Fig. 10.13) (D) nickel U-trap (E) Monel Bourden gauge (0-1000 ion) (F) 130-mL nickel reactor can (Fig. 10.17) (G) 1,500-mL nickel storage or measuring can, (H) 85-mL nickel can, (i) brass valve (K) soda-lime trap to protect vacuum pumps (L) Monel valve. (Reproduced by permission of the copyright holder, The University of Chicago Press, from Nobel Gas Compounds, H. H. Hyman (Ed.), Chicago, 1963.)...

The apparatus consists of a simple vacuum manifold similar to that shown in Fig. 4. The vacuum manifold should be fabricated from nickel or Monel metal, with silver-soldered or Swagelok connections. Valves should be of Monel metal, and the traps and scrubber, the function of which is to remove hydrogen fluoride vapor from the C103 F product, may be constructed conveniently of poly(chlorotrifluoroethylene) (Kel-F) tubing. A nickel cylinder of 500-ml. or 1-1. capacity serves as a reaction vessel, and a 500-ml. Monel bulb or similar vessel may be used as a product receiver. The scrubber (about 1-in. o.d.) is charged with pellets of sodium fluoride prepared in a separate operation by heating sodium... 

Apparatus in which fluorine is to be handled at room temperature may be made from a number of metals. Platinum, copper, nickel, magnesium, monel metal, brass, steel, and German silver are all known to be satisfactory. Most of these become coated with a film of fluoride which prevents further corrosion. If the metal is in contact not only with fluorine but also with a liquid such as water or hydrogen fluoride, corrosion frequently becomes troublesome. Under such circumstances, platinum usually behaves in the most satisfactory manner. With the gas alone, brass needle valves may be used with success, but the packing is eventually ruined. Fabrication of apparatus is best accomplished by welding, brazing, or silver soldering. Solder made from lead and tin does not resist attack. 

The properties of the interface metal/solution. Cast iron corrodes because of exposure of its graphite to the surface (graphitic corrosion), which is cathodic to both low-alloy and mild steels. The trim of a valve must always maintain dimensional accuracy and be free of pitting and hence it should stay cathodic to the valve body. Hence, in aggressive media, valve bodies are frequently chosen of steel rather than cast iron. Because of increased anodic polarization, low-alloy steel (Cr and Ni as noble components) is cathodic to normal steel in most natural media. Accordingly, steel bolts and nuts coupled to underground mild steel pipes, or a weld rod used for steel plates on the hull of a ship, should always be of a low-nickel, low chromium steel or from a similar composition to that of the steel pipe.7... 

The apparatus used is shown diagrammatically in Fig. 14. The vacuum line is made from f-in. nickel or Monel tubing. The metal valves can be of the bel-... 

Containment of Materials. All experimental work with hexafluorides was carried out in a metal manifold constructed of nickel tubing and fittings which could be evacuated by both mechanical and diffusion pumps. The manifold incorporated Monel diaphragm valves and a number of 1 in. diameter valves with brass bodies. Monel bellows, and Teflon seats. The hexafluorides were transferred between vessels in the manifold by vacuum distillation at room temperature. 

The noble-metal fluorides were stored in welded nickel bottles joined to the main line through Hoke A431 valves. Xenon was fed from a glass storage bulb into the metal system through a similar valve. 

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