Observation of nonlocal orbital transport and sign reversal of dampinglike torque in Nb/Ni and Ta/Ni bilayers
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We study the efficiencies of dampinglike and fieldlike torques in Nb/Ni and Ta/Ni bilayers and compare them with $\mathrm{Nb}/{\mathrm{Ni}}_{81}{\mathrm{Fe}}_{19}$(Py) and Ta/Py as a function of the thickness of a ferromagnet. In both these systems, we observe that the sign of the dampinglike torque is negative for Py whereas it is positive for nickel. The negative sign of the dampinglike torque in Nb/Py and Ta/Py is consistent with the negative sign of the spin Hall effect in niobium and tantalum. The sign reversal of the dampinglike torque in Nb/Ni and Ta/Ni suggests a strong generation of the orbital current from niobium and tantalum, which is converted into the spin current inside nickel and produces the orbital torque. We also find that both the dampinglike and fieldlike efficiencies change signs when nickel is replaced by Py.A spectrochemical method for the determination of small quantities of niobium and tantalum in rocks was developed including a preliminary chemical concentration with the use of phenyl-arsonic acid for the precipitation of the elements together with titanium followed by a spectrographic analysis of the products of concentration. The determination of niobium and tantalum is possible when their concentration in rocks is not less than 5 x 10/sup -5/%; the probable experimental error is about 7% for niobium and 9% for tantalum. (auth)
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Measurements have been made of far-infrared absorption in bulk samples of superconducting niobium and tantalum at 1.41 °K. The results indicate a gap width 2Δ of 23.8 ± 0.2 cm −1 for niobium and 10.3 ± 0.2 cm −1 for tantalum. The measured values of the critical temperature, T c , for these samples are 9.38 ± 0.04 °K for niobium and 4.33 ± 0.02 °K for tantalum. In terms of these values of T c , 2Δ is 3.66 ± 0.05 kT c for niobium and 3.43 ± 0.08 kT c for tantalum. These values of 2Δ are in good agreement with those obtained by other methods, unlike earlier far-infrared absorption measurements on bulk niobium and tantalum that indicated anomalously low values of 2Δ.
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Abstract Die Reaktion des Ta‐Komplexes (IIa) mit Phosphinen liefert nur bei PPh3 und Tricyclohexylphosphin isolierbare Produkte (I).
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This paper describes a new technology which is used to recover tantalum and niobium from tungsten residues with the method of acid treatment,which includes diluted acid treatment for desilication,concentrated acid treatment for iron and manganese removal,HF acid leaching of tantalum and niobium and evaporation concentration.Using this method,the tungsten residues containing 0.14% tantalum and 0.59% niobium can be processed.The optimal technical conditions are ensured by experiments.Under the optimal condition,HF acid solution containing 8.0 g/L Ta2O5 and 35.4 g/L Nb2O5 can be obtained which can be used in the production of tantalum-niobium industry and the recovery rate of tantalum and niobium can reach above 80%.With this method,the recovery of tantalum,niobium and silicon in the tungsten residues can be realized and the environmental pollution caused by large amounts of tungsten residues can be decreased.
Residue (chemistry)
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The present state of tantalum and niobium containing raw materials and recovering methods of tantalum and niobium from secondary materials were introduced,and the urgency and importance of recovering tantalum and niobium from these materials were pointed out in this article.
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Abstract : Content: Properties of tantalum and niobium; Properties of the principal compounds of tantalum and niobium; Applications of tantalum, niobium, and their principal compounds; Economics of tantalum and niobium; Minerals, ores, and concentrates of tantalum and niobium; Metallurgy of tantalum and niobium; Mechanical working and heat treatment of tantalum and niobium. Manufacture of products. Welding; Coatings of tantalum and niobium on base materials; Brief data on characteristic reactions and chemical determination of tantalum and niobium; Two-component alloys of tantalum and niobium; Three- component alloys containing tantalum and niobium; Quaternary and higher alloys containing tantalum and niobium.
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A. R. Powell and W. R. Schoeller, Analyst, 1925, 50, 485 DOI: 10.1039/AN9255000485
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Spectrophotometry
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The ferro-alloys of niobium and tantalum have come to be used frequently in adding them to steels. The determination of niobium and tantalum in the ferro- alloys. as well as in the steels. has thus become a problem for the steelmaker. Existing chemical methods for separation of the Nb- Ta group and for separation of the two are long. dlfficult. and delicate. Research is reported on simplification of the problem. A method was sought which involved simple determination of Ta + Nb first and then the proportions of the two elements. In addition to its application in chemical analysis. the method should be of use in the metallurgy of treatment of tantalum and niobium ores to obtain a very pure mixture of the two. (T.R.H.)
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