X-Ray Spectrochemical Determination of Niobium and Tantalum in High-Alloy and Stainless Steel
In alloys for nuclear applications, tantalum must be maintained at low levels to avoid neutron loss and induced radioactivity. Since varying amounts of tantalum generally will be present in alloys containing niobium, the chemist needs a method of determining tantalum in the presence of niobium, or else he must perform the tedious job of quantitatively separating them. An X-ray spectrochemical method was developed for the determination of niobium and tantalum in a variety of high-temperature alloys and steels. A curved crystal spectrometer with a tungsten target tube and lithium fluoride crystals is employed. The earth acids are separated by dissolving the alloy in aqua regia, evaporating with perchloric acid, boiling with sulfurous acid, and then filtering. After ignition the oxides are blended with cellulose and iron oxide. A pellet is briquetted for the X-ray analysis. The iron oxide serves to reduce the background and scattered radiation from the Compton effect. Niobium and tantalum are run simultaneously on the scanners with the lithium fluoride crystals. Silicon could not be determined accurately on the pellets because of the varying absorption effects from different amounts of niobium and tantalum. Silicon can be determined by the conventional wet chemical method—volatilizing with hydrofluoric acid. The niobium and tantalum can then be reprecipitated and determined by X-ray. Since the niobium and tantalum are separated from most of the alloy matrix, it is possible to analyze these elements from one curve for nearly all types of alloys.
KeywordsLithium Fluoride Compton Effect Target Tube Pheny Lhydroxy Lamine Lithium Fluoride Crystal
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