Carbon in zirconium

The interaction between carbon and zirconium is in some way similar to that between carbon and titanium. The solubility is however lower in zirconium than it is in titanium in a zirconium it is very low, in p zirconium, even at 1000°C, it is only 0.1 at.% (130 fig/g) (1). 

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ASTM (46) also recommends this procedure to determine carbon in zirconium. Chips or similar forms with a diagonal length of 7 mm maximum are used. 

Fig. V-3 Results of BCR round robins for carbon in zirconium metal (90)...

Hexafluorozirconic acid [12021 -95-3]], H2ZrP, is formed by dissolving freshly prepared oxide, fluoride, or carbonate of zirconium in aqueous HP. This acid is produced commercially in a concentration range of 10 to 47%. The acid can be stored at ambient temperatures in polyethylene or Teflon containers... 

Carbonates. Basic zirconium carbonate [37356-18-6] is produced in a two-step process in which zirconium is precipitated as a basic sulfate from an oxychloride solution. The carbonate is formed by an exchange reaction between a water slurry of basic zirconium sulfate and sodium carbonate or ammonium carbonate at 80°C (203). The particulate product is easily filtered. Freshly precipitated zirconium hydroxide, dispersed in water under carbon dioxide in a pressure vessel at ca 200—300 kPa (2—3 atm), absorbs carbon dioxide to form the basic zirconium carbonate (204). Washed free of other anions, it can be dissolved in organic acids such as lactic, acetic, citric, oxaUc, and tartaric to form zirconium oxy salts of these acids. 

An extension of the reduction-chlorination technique described so far, wherein reduction and chlorination occur simultaneously, is a process in which the oxide is first reduced and then chlorinated. This technique is particularly useful for chlorinating minerals which contain silica. The chlorination of silica (Si02) by chlorine, in the presence of carbon, occurs above about 1200 °C. However, the silica present in the silicate minerals readily undergoes chlorination at 800 °C. This reaction is undesirable because large amounts of chlorine are wasted to remove silica as silicon tetrachloride. Silica is, therefore, removed by other methods, as described below, before chlorination. Zircon, a typical silicate mineral, is heated with carbon in an electric furnace to form crude zirconium carbide or carbonitride. During this treatment, the silicon in the mineral escapes as the volatile oxide, silicon monoxide. This vapor, on contact with air, oxidizes to silica, which collects as a fine powder in the furnace off-gas handling system ... 

T. Curtius and A. Darapsky prepared a basic salt, lanthanum hydroxyazide, La(0H)(N3)2l H20, by boiling a soln. of lanthanum nitrate and sodium azide. The white, slimy mass of basic lanthanum azide is obtained by evaporating the mixed soln. in vacuo, or by treatment of the soln. with a mixture of alcohol and ether. They also made rose-coloured didymium hydroxyazide, Dy(OH)(N3)2, by evaporating a soln. of didymium carbonate in hydrazoic acid. Freshly precipitated yttrium hydroxide dissolves in hydrazoic acid, forming a soluble yttrium hydroxyazide boiling a soln. of yttrium sulphate and sodium azide gives a precipitate of yttrium hydroxide. L. M. Dennis found that zirconium hydroxide is precipitated when a soln. of zirconium salt is treated with potassium azide. 

Zirconium Carbide, ZrC grey pdr, not attacked by w, NH or HC1 even when heated. It is harder than quartz but softer than ruby. Was first prepd by Moissan et al on heating a mixt of Zr oxide with carbon in an electric furnace... 

The addition of zirconium to activated carbon may substantially increase the removal of arsenic from water (Daus, Wennrich and Weiss, 2004 Schmidt et al., 2008). (Daus, Wennrich and Weiss, 2004) used batch and column tests to evaluate the ability of five materials (activated carbon, zirconium-loaded activated carbon, zerovalent iron, granulated Fe(III) hydroxide, and a commercial product, Absorptionsmittel 3 ) to sorb As(III) and As(V) from water. The GAC had grain sizes between 1.0 and 1.5 mm. The material was primarily chosen as a comparison with the zirconium-loaded sample. The zirconium-loaded activated carbon contained 28 mg zirconium g 1 activated carbon and was produced by shaking activated carbon in a solution of zirconyl nitrate (Zr0(N03)2). The zerovalent iron (Fe(0)) primarily had particle sizes of 1.2-1.7 mm. Absorptionsmittel 3 is a mixture of calcite, brucite, fluorite, and iron hydroxides. The granular iron hydroxides consisted of mostly amorphous Fe(III) hydroxide coatings on sand grains (particle sizes of 3-4mm) (Daus, Wennrich and Weiss, 2004, 2950). 

Similar to the catalyst of the catalytic thermometry sensor, the catalytic activity of the CTL-based sensor depends not only on the kind of catalyst material and the surface-to-volume ratio of the powder but also on the preparation procedure of the powder. In considering these conditions, a detailed comparison of the CTL catalytic activity has not been reported so far. The present authors and coworkers observed the CTL emission by ethanol vapor on y-aluminum oxide, barium sulfate, calcium carbonate, and zirconium oxide at a few hundred degrees. On the other hand, CTL emission is not observed during the catalytic oxidation on metal and semiconductive materials, e.g., tin oxide, zinc oxide, and copper oxide. 

Table IV lists specific examples of compounds related through this form of dimensional reduction, By far, the majority of these are zirconium chloride and iodide phases, in which case lower main group and even transition metals have been found to incorporate as interstitial atoms. A few analogues are known with hafnium (135), and very recently it has been shown that nitrogen can be substituted for carbon in tungsten chloride clusters adopting the centered trigonal-prismatic geometry (see Fig. 2) (32). It is hoped that a variability similar to that exposed for the octahedral zirconium clusters will be attainable for such trigonal-prismatic cluster phases.

Table 1(c) on the formation or removal in vacua of carbon dioxide by reaction of the surface oxides with carbon in the metal shows the results of these calculations. The reactions are feasible for tungsten and iron but not for zirconium and magnesium. Chromium presents an intermediate case with an equilibrium pressure of 10-12-46 at 800°C., 10-9,88 at 1000°C., and 10 768 at 1200°C. The reverse reaction is feasible for zirconium and magnesium and for chromium at low temperatures. From a kinetic viewpoint the probability that this reaction will occur is small compared to the reaction to form carbon monoxide gas. In this case zirconium will act as a getter for carbon dioxide, while tungsten, iron, and chromium will be relatively inert to carbon dioxide molecules. 

AUcynylchalcogenato ruthenium complexes react with zirconocene to give rise to heterobimetallic early-late dissymmetrically bridged complexes of family (76) (equation 39). In those specific complexes, the two metal centers are linked by /u.-chalcogenido and /x-a, jr-alkynyl moieties. The acetylenic bridge is unsymmetrical because the terminal carbon of alkynyl is ct-bonded to ruthenium, while zirconium interacts with both alkynyl carbons in a side-on fashion. 

Corrosion studies have been rare. (8), copper, or iron were corroded by carbon tetrachloride when exposed to Co-60 radiation (78). Alkyl halides enhanced the corrosive effect of benzoic acid on iron (79). (1) was found to promote stress-corrosion cracking in zirconium alloys used in nuclear reactors (80). 

Impurities in zirconium and zirconium alloys and compounds are often determined by emission spectroscopy. Both carrier distillation techniques and poiat-to-plane methods are available (91,92). Several metaUic impurities can be determined instantaneously by this method. Atomic absorption analysis has been used for iron, chromium, tin, copper, nickel, and magnesium (93). The interstitial gases, hydrogen, nitrogen, and oxygen are most often determiaed by chromatography (81). Procedures for carbon, chloride, fluoride, phosphorus, siUcon, sulfur, titanium, and uranium in zirconium are given in the hteiatuie (81,94—96). 

Stone and Tilley have shown that the spectral changes which occur on spinel formation can be related to the extent of reaction of the component oxides, although the kinetics were also followed by chemical analysis. Keyser et have studied the reaction of zirconium silicate with calcium oxide by a radio tracer method. Wagenblast and Damask have used internal friction measurements to study the rate of precipitation of carbon in iron. The rate of decrease of the Snoek peak can be related to the growth kinetics of the iron carbon precipi-... 

Compiled in Table 1 are typical carbon-carbon bond distances and NMR shifts of the olefinic carbons in several base-stabilized olefin complexes of zirconium and hafnium. In general, the NMR shifts are consider-... 

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