Nickel impurity element

A process for the gravimetric determination of mixtures of selenium and tellurium is also described. Selenium and tellurium occur in practice either as the impure elements or as selenides or tellurides. They may be brought into solution by mixing intimately with 2 parts of sodium carbonate and 1 part of potassium nitrate in a nickel crucible, covering with a layer of the mixture, and then heating gradually to fusion. The cold melt is extracted with water, and filtered. The elements are then determined in the filtrate. 

Next, let the example of vanadium, which, in the as-reduced condition, may contain a variety of impurities (including aluminum, calcium, chromium, copper, iron, molybdenum, nickel, lead, titanium, and zinc) be considered. Vanadium melts at 1910 °C, and at this temperature it is considerably less volatile than many of the impurity metals present in it. The vapor pressure of pure vanadium at this temperature is 0.02 torr, whereas those of the impurity elements in their pure states are the following aluminum 22 torr calcium 1 atm, chromium 6 torr copper 23 torr iron 2 torr molybdenum 6 1CT6 torr nickel 1 torr lead 1 torr titanium 0.1 torr and zinc 1 atm. However, since most of these impurities form a dilute solution in vanadium, their actual partial pressures over vanadium are considerably lower than the values indicated. Taking this into account, the vaporization rate, mA, of an element A (the evaporating species) can be approximated by the following free evaporation equation (Langmuir equation) ... 

Radiotracer analysis is particularly effective for tracking the fate of additives, because molecular fragmentation can typically be expected to result in an impurity element distribution different from that of the original molecules. For example, in nickel plating in the presence of thiourea, complete incorporation of the molecule should give a carbon/sulfur ratio of 1.0, while experiments indicate a ratio ranging from 0.01 to 0.7 depending on the deposition conditions [130,131,141,142], As with additive incorporation, the decomposition process can be a sensitive function of the co-adsorbates [145, 149, 150]. 

As reinforcement material for all matrix materials - ceramics, metals, and plastics -SiC platelets offer a similar potential as whiskers, but at lower cost and without any health hazard. Platelets are single-crystal, plate-like a-SiC particles with an aspect ratio of about 8-15. SiC platelets typically range in size from about 5-100 pm in diameter and 1-5 pm in thickness (see Table 4.2). They are produced commercially from inexpensive raw materials (silica and carbon, micron-sized 3-SiC powders) at temperatures of 1900-2100 °C under an inert atmosphere [100]. Due to the presence of the boron and aluminum dopants added, platelet-shaped crystals are formed. Aluminum enhances the growth in the [0001] direction and decelerates the growth perpendicular to the [0001] direction. Boron enhances the growth notoriously perpendicular to the [0001] direction [101]. Aluminum (0.04—0.45 wt%), boron and nickel (each 0.4-0.8 wt%), and free silicon (0.3-3.6 wt%) were identified as impurity elements in SiC platelets produced by Millenium Materials [102]. 

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. 

Ni-Cr-Fe Chloride solutions at and Ni-Cr- elevated temperature Fe-Mo-Cu (Ni approx. <40%) TG 1. Use alloys with higher nickel content 2. Control amounts of minor alloying elements and impurities 3. Remove or reduce Cl in environment if possible... 

The discussion so far has been limited to the structure of pure metals, and to the defects which exist in crysteds comprised of atoms of one element only. In fact, of course, pure metals are comparatively rare and all commercial materials contain impurities and, in many cases also, deliberate alloying additions. In the production of commercially pure metals and of alloys, impurities are inevitably introduced into the metal, e.g. manganese, silicon and phosphorus in mild steel, and iron and silicon in aluminium alloys. However, most commercial materials are not even nominally pure metals but are alloys in which deliberate additions of one or more elements have been made, usually to improve some property of the metal examples are the addition of carbon or nickel and chromium to iron to give, respectively, carbon and stainless steels and the addition of copper to aluminium to give a high-strength age-hardenable alloy. 

The most important undesired metallic impurities are nickel and vanadium, present in porphyrinic structures that originate from plants and are predominantly found in the heavy residues. In addition, iron may be present due to corrosion in storage tanks. These metals deposit on catalysts and give rise to enhanced carbon deposition (nickel in particular). Vanadium has a deleterious effect on the lattice structure of zeolites used in fluid catalytic cracking. A host of other elements may also be present. Hydrodemetallization is strictly speaking not a catalytic process, because the metallic elements remain in the form of sulfides on the catalyst. Decomposition of the porphyrinic structures is a relatively rapid reaction and as a result it occurs mainly in the front end of the catalyst bed, and at the outside of the catalyst particles. 

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