Cobalt impurity element

Other impurities levels are quite low as exemplified in Table 9.2.4 for cobalt. Impurities such as Ca, Fe, or Na, which may be present as cations in the precursor, are considerably lower because these elements can not be reduced to the zero-valence state by the polyol and then are retained in the solution. 

The purified cobalt solution was removed the organics impurity and concentrated following by electrolytic deposition. The electrolysis temperature was 60°C.The cathode current density was 300A.m. The high purity electrolytic cobalt which total content of the impurity elements was proved to be smaller than lOmg-kg by GDMS was obtained. 

In most cases, as a fluence monitor small disks or wires of an Al-Co alloy with 0.1 to 1% Co are used by such a dilution of the monitor substance, self-shielding and flux depression effects are avoided. In general, since interfering radionuclides produced in the diluting element are small, chemical separations before activity measurement of Co are normally not needed. Frequently, the cobalt impurities in stainless steels, which are in the range of 100 to 1000 ppm, can be directly used as a fluence monitor in such cases, however, the accurate cobalt concentration in the material has to be additionally determined by chemical analysis. 

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. 

Germanium tetrachloride refined for use in making optical fibers is usually specified to contain less than 0.5 to 5 ppb of each of eight impurities vanadium, chromium, manganese, iron, cobalt, nickel, copper, and zinc. Limits are sometimes specified for a few other elements. Also of concern are hydrogen-bearing impurities therefore, maximum limits of 5 to 10 ppm are usually placed on HCl, OH, CH2, and CH contents. 

The most common ores of nickel include pentlandite, pyrrhotite, and garnierite. The element also occurs as an impurity in ores of iron, copper, cobalt, and other metals. 

The zinc salt solutions, which currently mainly come from zinc and copper smelters, contain impurities which have to be completely removed prior to use, because all heavy metals form colored sulfides. For the purification step the solution is oxidized with chlorine (pH 4), which precipitates most of the iron and manganese as the oxide-hydrate and part of the cobalt, nickel and cadmium present as their hydroxides. In the second step, the elements nobler than zinc (Ni, Co, Cd, In, Tl, Pb, Cu, Ag) are precipitated as their metals by adding zinc dust and the metals returned to the copper smelters for noble metal extraction. After purification the solutions are adjusted to a particular zinc content. Mixtures of zinc sulfate and zinc chloride solutions are used for manufacturing lithopone types with more than 30% ZnS. 

As a result of the diminution in the range of oxidation states which has already been mentioned, the number of oxides formed by these elements is less than in the preceding groups, being confined to two each for cobalt (CoO, C03O4) and rhodium (RhiOB, RhOi) and to just one for iridium (IrOi) (though an impure sesquioxide IriOs has been reported — see below). No trioxides are known. 

At first chemists were disinclined to accept the view that nickel was a new element. Cronstedt s specimen was impure and many believed that it was merely a more or less unholy mixture of cobalt, arsenic, iron, and possibly copper. But in 1775 Torbern Bergman, Cronstedt s famous Swedish contemporary, confirmed the existence of nickel, of which he prepared a fairly pure sample, and showed that no alloy of copper, iron, cobalt, and arsenic would behave like it. 

Corrosion of Magnesium in Neutral and Alkaline Solutions Magnesium is highly susceptible to galvanic corrosion. Small amounts of impurities in the alloy can have a tremendous influence on the corrosion susceptibility. In Fig. 30, the influence of various elements is demonstrated. Small additions of copper, iron, nickel, and cobalt have an extremely negative effect on the corrosion resistance. The tolerance Kmit for iron is 0.015%, for nickel 0.0005%, and for copper 0.1% [35]. Because of the low solid solubility of these elements, they precipitate as inclusions. These act as active cathodic sites for the... 

A further characteristic of metals that is usually given is that, in the solid state, they are malleable (easily hammered into sheets) and ductile (easily drawn into wires). By contrast, nonmetals in the solid state are brittle and easily powdered. In practice, however, while the majority of elements that are metallic according to the above criteria are indeed malleable and ductile, there are a few that do not have this property, even when ultra-pure. (Slight traces of impurity can produce brittleness in metals. Thus, ordinary commercial tungsten is so brittle that it can only be worked with difficulty, whereas the ultra-pure metal can be cut with a hacksaw, turned, drawn, or extmded.) Since the exceptional elements include some whose metallicity has never been questioned - e.g. manganese, cobalt, and zinc - it seems better not to make malleability and ductility a characteristic of metals, but rather a property possessed by most of them. 

The success of this method depends on the rapid diffusion of the impurities in the rare earth metal in a strong electric field. Most of the non-metallic elements (carbon, nitrogen and oxygen) and the small interstitial-like transition metals (iron, cobalt, nickel and copper) migrate from the cathode towards the anode, purifying the cathode portion of the rod. After 100 to 1000 hours a steady-state condition is built-up after which the forward diffusion from the cathode to the anode due to the electric field is equal to the backward diffusion due to the chemical concentration difference, and no further purification is realized. 

The usual alloying additions to aluminum in order to improve physical properties include Cu, Si, Mg, Zn, and Mn. Of these, manganese may actually improve the corrosion resistance of wrought and cast alloys. One reason is that the compound MnAle forms and takes iron into solid solution. The compound (MnFe)Alg settles to the bottom of the melt, in this way reducing the harmful influence on corrosion of small quantities of alloyed iron present as an impurity [27]. No such incorporation occurs in the case of cobalt, copper, and nickel, so that manganese additions would not be expected to counteract the harmful effects of these elements on corrosion behavior. 

Results from patch tests performed with impure preparations and with an insufficient number of controls for irritancy imply that some anecdotal reports on contact allergy to metals, such as antimony, iron, lead, silver, manganese, and zinc, may be questioned. Scientifically, as well as from a clinical point of view, it is somewhat challenging that nickel, chromium, and cobalt are so dominant, while the other metals in the periodic table of elements play such a minor role. 

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