High-purity tungsten

As an example, it was possible by isotope dilution analysis to determine 15ppq of uranium in an ultrapure tungsten sample. This corresponds to 15 x 10 %. These 

FIGURE 5.38. Ultrahigh-purity tungsten improvement in purity from 1988 to 1994 (target data) production takes place under clean room conditions [5.96]. 

FIGURE 5.39. Production methods for high-purity tungsten. 

Of all impurity elements, in particular uranium and thorium contents must be extremely low. These naturally radioactive elements cause soft errors in memory circuits due to a-particle emission. 

The diverse production methods for high-purity tungsten are summarized in Fig. 5.39. The raw material is always APT with different purity depending on the uranium and thorium content. It depends on the ore deposit whether these two elements are present or not. If the concentrations are unacceptably high after dissolution, a selective solvent extraction process removes the main portion of these two elements. 

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Use Source of high purity tungsten disulfide for catalysts, lubricants, semiconductors. 

Hornung D. and Krivan V. (1999) Solid sampling electrothermal atomic absorption spectrometry for analysis of high-purity tungsten trioxide and high-purity tungsten blue oxide, Spectrochim Acta, Part B 54 1177— 1191. 

Twinning. Twirming is a less dominant deformation mechanism and occurs in high-purity tungsten only. Twins are mainly formed on [112 planes in [111] direction. Twins have been observed in tension below 0°C and, after rolling, compressing, swaging, and explosion deformation, up to 1500°C. 

FIGURE 1.12. Critical flow stress (a) vs. tempeiatuie of a high-purity tungsten single crystal ((110)) [1.48] tensile deformation rate, 1.6 x 10 s . 

FIGURE 1.19. Temperature dependence of the thermal conductivity X of well-annealed high-purity tungsten [1.35] source [1.81]. 

Yoshiki Doi, Characteristics and Application of High Purity Tungsten and Chemical Vapor Deposited Tungstein, paper presented at the Annual ITIA Meeting, Huntsville, USA transcript of papers ITIA, London (1994). 

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