Crystal bar zirconium

Attention was focused on the crystal bar zirconium made by the iodide route in addition to the Kroll magnesium reduction process. The iodide decomposition route gives a superior product, but at a higher cost. 

Other materials. Crystal-bar zirconium was tested in several loop and autoclave experiments. Observed corrosion rates were in near agreement with those for Zircaloy-2. 

Chemically polished specimens of Zircaloy-2 and crystal-bar zirconium corroded at rates about 10% lower than the as-machined specimens. 

Total hafnium available worldwide from nuclear zirconium production is estimated to be 130 metric tons annually. The annual usage, in all forms, is about 85 t. The balance is held in inventory in stable intermediate form such as oxide by the producers Teledyne Wah. Chang (Albany, Oregon) and Western Zirconium in the United States Ce2us in France Prinieprovsky Chemical Plant in Ukraine and Chepetsky Mechanical Plant in Russia (crystal bar). 

In this way rods, or crystal bars, of compact, ductile zirconium or hafnium have been prepared. The usual crystal bar is 0.25 to 0.4 in in diameter in lengths up to 2 ft, but Westinghouse and Battelle Memorial Institute have produced zirconium bars as large as 1.7 in in diameter and 50 ft overall length [HI]. 

Iodide compounds are not very stable, so heating them can result in an easy recapture of the metal elements in the compound. For example, the van Arkel-de-Boer process (or crystal bar process) is used to purify zirconium. This is done by passing the heated gas (Zrl ) over a white hot tungsten filament, and over time the metals form on the tungsten. 

Hage, H. R. and Shapiro, Z. M. Preparation of Cheap Alternative Feed Material for the Manufacture of Zirconium Crystal Bar. U.S.A.E.C. Report, WAPD-TD-51... 

Zirconium, atomic number 40 and atomic weight 91.22, was identified by the German chemist, Klaproth, in 1789. However, the metal itself was not isolated imtil 1824, when Berzelius produced a brittle, impure metal powder by the reduction of potassium fluorozirconate with potassium. One himdred years later, van Arkel and de Boer developed the iodide decomposition process to make a pure, ductile metal in Einhoven, Holland. The "iodide crystal bar" process continues to be used today as a method of purifying titanium, zirconium, and hafnium, even though it is slow and expensive. 

For zirconium production, the Van Arkel-de Boer process [1] and the Kroll process [2] are the two main processes applied in the industry. The Van Arkel-de Boer process is also known as the iodide process or the crystal bar process, developed by the Dutch chemists Van Arkel and De Boer in 1925 [1]. It is the first industrial process for the commercial production of pure ductile metallic zirconium, and is still in use for the production of small quantities of ultra-pure titanium and zirconium. The Van Arkel-de Boer process involves the use of elemental iodine and crude metal, in the form of a sponge or alloy scrap, to form a volatile metal iodide at a low temperature. At a high temperature, the metal iodide will thermally decompose into pure metal and gaseous iodine. The Kroll process is a process used to produce titanium metal [2], developed in 1945 by... 

Fig. 4.20. XRD traces of active sample derived from milled glassy iron-zirconium alloy after 20 h (top) and 450 h of activation under 9 bar of a 3 1 mixture of hydrogen and nitrogen at 700 K [4.44], The top inset shows a high-resolution scan over the Fe (222) reflection, which consists of two doublets arising from the CuK /CuK. splitting. The central inset compares the Fe (200) reflection of a sample exposed to in situ activation for 60 h (a) and of a sample crystallized thermally in an inert gas atmosphere (b)...

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