Zirconium oxide boiling point

Table 3 (3) shows the influence of branching of the alkyl group on volatility and complexity, usiag titanium and zirconium amyl oxides as examples. Table 3. Boiling Points and Molecular Complexities of Amyloxides of Titanium and of Zirconium...

If uniform mixing of the fission product vapors and volatilized materials results, the recondensed particles might be expected to have a constant specific activity of elements having similar boiling points. Note parenthetically that studies of fission-product incorporation into the metal and oxide products of vaporized iron wires (in which iron-metal spheres and iron-oxide irregulars are formed) indicate no simple relationship between specific activity and size. For example, a refractory element like zirconium is found most enriched in particles of intermediate size. This is probably in part caused by a concentration effect—i.e.y in these experiments the zirconium represented a mole fraction of about 10"9. As indicated earlier, the fission products are a minor constituent in the fireball, and a very complex pattern of incorporation can be anticipated, especially if coagulation with melted but unvaporized particles ensues. 

Metal salts may be used in the treatment of wool. Flame methods for the determination of aluminium [185], barium, chromium, copper, mercury, strontium, tin, zinc [186] and zirconium [187] in wool have been published. Standard additions to wool cleaned by soaking and washing it with disodium EDTA (800 ml of 0.5 M for 30g wool with soaking for 3 days and double washing) was used as the calibration technique. This compensated for interferences from hydrochloric acid and amino-acids. The samples were equilibrated to a constant humidity for 24 h and then 0.3 g sealed with 5 ml of constant boiling point hydrochloric acid in a glass tube. The tubes were placed in an oven at 110UC for 20 h. The nitrous oxide/acetylene flame was used for the determination of aluminium and zirconium. Sulphate, phosphate, citrate and silicate have been found to interfere in the determination of titanium and zirconium in fire-proofed wool [188], These flame... 

Figure 10.2 shows clearly that at about 1000°C sodium oxide can oxidize stainless steel (the dashed line represents liquid sodium above its normal boiling point). A diagram of this kind shows not only that sodium can cause material transport of oxygen from a point of external contamination, but also that metallic zirconium is able to hot-trap the oxygen from the sodium stream. 

Zirconium (Zr, CAS 7440-67-7, atomic number 40, atomic mass 91.22) has a melting point of 1852 °C and a boiling point of 4377 °C. It is a hard, lustrous, silvery metal, in contrast to fine zirconium powder, which is black. Zirconium belongs to Subgroup IV of the Periodic Table of the elements, between the elements titanium and hafnium - two metals with which it is often found in nature. Zirconium has oxidation states ranging from II to IV, of which the tetravalent is relatively stable and abundant (Venugopal and Luckey 1979). Zirconium is very corrosion-resistant and is unaffected by alkalis or acids (except for HF). 

The reactions of metals to form stable halides are important for various reasons. The metal halides generally have low boiling points and high volatiUty. For this reason, they are used in several important processes for the production and refining of metals, such as the reactive metals titanium and zirconium. These metals are produced using the Kroll process, in which the metal oxide is converted to metal chloride or fluoride, which is then reduced to metal. This route avoids several formidable difficulties involved in the reduction of the oxides of these metals. Details of these processes can be found in extractive-metallurgy textbooks. 

Tantalum and niobium are, like zirconium and titanium, reactive metals, that is, they rely on an oxide film for corrosion protection. The corrosion behavior of tantalum is similar to that of glass, that is, it can withstand most acids, but not hydrofluoric acid and caustic solutions. Tantalum is inert to nitric acid at all concentrations up to the boiling point and is resistant to hydrochloric acid at all concentrations up to 190 °C (Schussler and Pokross, 1987). There is only one commercially important tantalum alloy (Ta-2.5% W-0.15% Nb) which has corrosion resistance equivalent to that of tantalum (Hunkeler, 1997). When tantalum is coupled with other metals in any industrial application tantalum would generally become cathodic. When exposed to nascent hydrogen tantalum readily absorbs hydrogen and it is very sensitive to hydrogen embrittlement (HE) (Dillon, 1994). The corrosion behavior of niobium is similar to that... 

Zirconium shows excellent corrosion resistance to hydrochloric acid and is superior to any other engineering metal for this application, with a corrosion rate of less than 0.125 mm y" at all concentrations and temperatures well in excess of the boiling point. Aeration does not affect its corrosion resistance, but the presence of oxidizing impurities such as cupric or ferric chlorides in relatively small amoimts will decrease it. Therefore, either these ions should be avoided, or suitable electrochemical protection should be provided. Zirconium also shows excellent corrosion resistance to nitric acid in all concentrations up to 90% and temperatures up to 200°C, with only platinum being equal to it for this service. Welded zirconium and its alloys retain this high corrosion resistance. In concentrated nitric acid, zirconium may exhibit SCC at nitric acid concentrations above 70%, if under high tensile stress. ... 

Figure 10.2 Ellingham free energy diagram showing possibility of corrosion of stainless steel fuel cans by sodium oxide near 1250 K. Liquid sodium coolant may be kept free of oxygen by zirconium metal, which has greater affinity for oxygen. (The letter M, B or T represents the melting, boiling or transition point for the element. A circumscibed O denotes the oxide.)...

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