Samarium impurity

Seccand example - In the production of samariumcobalt permanent magnets impurities have practically only a dilution effect. One can therefore use instead of a 99.9 % pure samarium metal a significantly cheaper 90 %, perhaps even 80 % pure metal vdth the balance other rare earths. In any case, it is necessary in this instance that the conposition of the other rare earth elements be held constant, vdiich is not always quite so siitple. 

It has been found that in the preparation of pure europium the starting materials need not be extremely pure. The common impurity viz. samarium is completely eliminated in the above process because samarium is less volatile than europium, and the reduction of Sn Os to the metal requires a higher temperature than the EU2O3 reduction. Commeri-cal lanthanum turnings can also be used for the reduction in place of more expensive very pure lanthanum metal. Extreme care should be taken to ensure that the reactants contain no calcium as it appears as an impurity in the final product if present in the charge. 

Properties Pink crystals. Soluble in water. Technical grade contains 75% neodymium salt, principal impurities praseodymium and samarium compounds. 

Samarium-153 has relatively high neutron capture cross-sections (with a thermal capture cross-section of 206 b and an epithermal capture cross-section of 3000 b), thus enabling production of high specific activity with minimal long lived radionuclidic impurities. The activities of various samarium targets obtained post-irradiation in PARR-I are given in Table 12.4. 

Samarium (II) iodide [32248-43-4] M 404.2, m 520°, b 1580. A possible impurity is Sml3 from which it is made. If present, grind the solid to a powder and heat it in a stream of pure H2. The temperature ( 500-600°) should be below the m ( 628°) of Sml3, since the molten compounds react very slowly. [WetzelmHandbookof Preparative Inorganic Chemistry (Ed. Brauer) Acadercac Press Vol II pp 1149, 1150 1965.]... 

There are two ways to produce a pure radionuclide not contaminated with any other radioactivity. An extremely pure target can be used with a reaction path which is unique. Alternatively, the radioactive products can be purified after the end of the bombardment. For example, a 10 g sample of zinc irradiated for one week with 10 n cm s yields a sample of Zn (ti 244 d) with 7.1 X 10 Bq. If, however, the zinc target is contaminated with 0.1% of copper, in addition to the zinc activity, 3.0 x 10 Bq of Cu (ti 12.7 h) is formed. In another example element 102 believed to be discovered initially in a bombardment of a target of curium by carbon ions. The observed activity, however, was later found to be due to products formed due to the small amount of lead inq)urity in the target. Similarly, in neutron activation of samarium it must be very free of europium contamination because of the larger europium reaction cross-sections. Handbooks of activation analysis oftra contain information on the formation of interfering activities from impurities. 

In addition to the above-mentioned losses which are inherently a part of the nuclear chain reaction process impurities present in both the slowing material and the uranium add a very important neutron loss factor in the rhaiti. The effectiveness of various elements as neutron absorbers varies tremendously. Certain elements such as boron, cadmium samarium gadolinium and some others, if present even in a few parts per million could prevent a self-sustaining chain reaction from taking place. 

In his opinion, a new previously unknown element contained in didymium was responsible for the appearance of the new lines in the spectrum. He named it decipium from the Latin to deceive, to stupefy and the name proved to be ironical decipium turned out to be a mixture of several REEs both known and unknown ones. Decipium was debunked in 1879 by L. de Boisbaudran of France who played a prominent role in the discovery of new REEs. In the next chapter we shall tell you how he discovered gallium predicted by Mendeleev. Boisbaudran extracted didymium from samarskite and thoroughly studied the sample by spectroscopy. Boisbaudran was a much more skillful experimenter than Delafontaine and he succeeded in separating the impurity from didymium . He named the new element samarium after samarskite, being unaware that samarium was also a mixture of elements. Boisbaudran s discovery was immediately confirmed by Marignac who, after multiple recrystallizations of samarium , separated two fractions which he marked Y and Yp (not to be confused with the symbol of yttrium Y ). The spectrum of the second fraction was identical to the spectrum of samarium . As to the first fraction, we shall have a look at it a little later. 

Fig. 8.28. Temperature dependence of the tensile properties of samarium. Owen and Scott (1971) worked and annealed less than 1530 ppm impurities including 106 ppm oxygen mixed (30 to 230 /urn) grain size. Love (1959) as-cast contained 200 ppm oxygen.

Recently, a novel rf-laser double resonance method for optical heterodyne detection of sublevel coherence phenomena was introduced. This so-called Raman heterodyne technique relies on a coherent Raman process being stimulated by a resonant rf field and a laser field (see Fig.l(a)). The method has been applied to impurity ion solids for studying nuclear magnetic resonances at low temperature3 5 and to rf resonances in an atomic vapor /, jn this section we briefly review our results on Raman heterodyne detection of rf-induced resonances in the gas phase. As a specific example, we report studies on Zeeman resonances in a J=1 - J =0 transition in atomic samarium vapor in the presence of foreign gas perturbers. 

Lundin (1970), in an investigation of the formation of samarium-type structure in intra rare earth binary alloys included six compositions in the lanthanum-scandium system ranging from 10 to 85at% La. Lundin prepared his alloys using 99.8(wt )% pure lanthanum metal (major impurities, 330 ppm other rare earths, 510 ppm O, 50 ppm each Si, Mg and Zn) and 99 -F (wt )% pure scandium for which there were no details given on the impurities. Lundin found two-phase inuniscibility at low temperatures in the lanthanum-scandium system and, since no samarium-type structure was found, he concluded that scandium behaves more like the neighboring transition elements than it does as a rare earth metal. 

The samarium and gadolinium metals were reported to include no more than 0.1 wt% total impurities in either metal, but a detailed chemical analysis was not reported. Alloys were prepared by standard arc-melting techniques, and since samarium has a high vapor pressure, the alloys were analyzed by X-ray fluorescence to assess loss of samarium. Loss of gadolinium was not a problem in the alloy preparation since the vapor pressure of gadoUnium is at least four orders of magnitude less than that of samarium. The phase relations in this system were established by metallography. X-ray diffraction, thermal analysis, density and microhardness measurements and effusion experiments. 

Lundin and Yamamoto formed their alloys from metals of select purity . Major impurities in their samarium were < 0.038 wt% O, 0.02 wt% Ca, 0.005 wt% each Ce, Nd, Pr, B, Si and Zn and 0.003 wt% Zr. Their yttrium metal contained 0.037 wt% O, 0.01 wt% each Er and Tb and 0.005 wt% each Ce, Ho, Tb, Pr, B and Si. Alloys were prepared at 10 at% intervals and melted in sealed tantalum crucibles. Three or more melting cycles, well above the melting temperature, were performed before the thermal analysis of each alloy was carried out. 

Ge et al. from our group, used NAA as a non-destructive standard method to quantify metallic impurities in carbon nanotubes (CNTs). Considerable amounts of iron, nickel, molybdenum, and chromium in the CNTs were found, which implies that these elements were dominantly used in the synthesis process. Small amounts of other impurity elements like manganese, cobalt, copper, zinc, arsenic, bromine, antimony, lanthanum, scandium, samarium, tungsten, and thorium are also found, which are presumed to have come from sources in chemical and physical manipulations used during the production process or in the precursors of the synthesis (Table 11.1). Although these commercial CNTs have been processed to reduce metal and amorphous carbon, even these as-purified samples still contain significant quantities of residual metals, which maybe contribute to the potential toxicological effects of CNTs. 

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