Metals purification

Metal Purification. Depending on the relative boiling points, purification may be carried out by RE distHlation, aHoying element distHlation, or 2one melting. 

The basic electrorefining process is now being used on a production scale for the purification of non-specification plutonium metal. The technology is sufficiently well developed to permit 24-hour unattended operation of the electrorefining cells, and the quality of the product metal is highly consistent. This technology is rapidly replacing aqueous chemistry for plutonium metal purification. 

In addition there are two principle metal purification processes ... 

Figure 1. Pyrochemical vs. aqueous flowsheet for metal purification.

This process of metal purification is of particular interest in that it involves the application of principles of both chemistry and chemical engineering and necessitates the cost evaluation of alternatives. 

There are several processes for extracting and refining niobium from its ores. (Payton, P.H. 1981. Niobium and Niobium Compounds. In Kirk-Othmer Encyclopedia of Chemical Technology, 3 . ed., Vol, 15, pp. 820-827. New York Wiley Interscience). The process of choice depends on nature of the ore and end use intended for the metal. Some common steps in these recovery processes involve ore preconcentration, breaking or opening the ore, obtaining pure niobium compounds, reduction of niobium compounds to niobium metal, purification or refining metal and fabrication. If niobium is extracted from a niobium-tantalum ore, the most important step is separation of niobium from tantalum, both of which are chemically very similar. 

Pulse ultrasonic relaxation method, 32 18 Pump-and-probe techniques, 46 137 Purification, of actinide metals, see Actinide, metals, purification XjPj Purified protein, 36 94 Purple acid phosphatases, 40 371, 376, 43 362, 395-398, 44 243-245 biological function, 43 395 homology, 43 397... 

Reductive nitrosylation, transition metal nitrosyl complexes, 34 296-297 ReFejSj cluster, 38 41-43 self-assembly system, 38 41-42 Refining, of actinide metals, see Actinide, metals, purification Refractory compounds heat treatment of solids, 17 105-110 crystal growth, 17 105, 106 decomposition, 17 107,-110 spheroidization, 17 106, 107 preparation of, using radio-frequency plasma, 17 99-102... 

CVD can be performed in a so-called closed or open system. In closed CVD, both reactants and products are recycled for reuse within an enclosure [11], The closed reactor CVD method is primarily used for metal purification and protection coating for aero-engine blades (e.g. pack cementation for aluminising, chromising, etc.). In most cases, CVD happens in an open state which is described in Chapter 1 and Figure 1.1. 

In other cases, the use of the oxygen pumps carries out in galvano-stalic mode, that is, at the constant current in circuit (4.43). Let us consider the main calculated characteristics of such pumps, which can be represented by the speed and depth of the liquid metal purification from oxygen as well as by the oxygen flow and by the time of the attainment of the set deepness of purification. 

The speed of the liquid metal purification from oxygen can be expressed by the following equation [71] ... 

Deepness of the liquid metal purification from the traces of oxygen by the electrochemical cell (4.43) at = 1 can be determined from Equation (4.46) as the relative quantity of oxygen removed to the time. After substitution of (4.54) or (4.55) into (4.46) with consideration of conditions (4.63), the following equation yields for... 

The achievable deepness of the liquid metal purification from the oxygen by the solid electrolyte can be determined from Equation (4.73). For example, in the case of Fq = 0.15, the following equality, (x) = 2(1 ) mid consequently. 

It is seen that at v Eq, ttj = 1 and ct2= 1, that is, both flow and purification speed are independent on the pump voltage. The deepness of the liquid metal purification from oxygen can be found from (4.110) for Fq > 0.1 as... 

Consequently, the maximum deepness of molten metal purification from oxygen can be determined from Equation (4.122) with Equation (4.129). 

After about four years of quite interesting and educational service, I was extremely fortunate to receive a recommendation that promoted me to the professional staff of the Lamp Development Laboratory. It was there that I was assigned to a group working on the development of the quartz heat lamp. While working there, I happened to read about the van Arkel cycle that involved a regenerative iodine cycle in a metal purification system. This knowledge, coupled with my familiarity with the CRC Handbook, enabled me to see a new possible application for that process. 

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