Particles nickel sulfide

The synthesis of nanosized nickel sulfide particles through a microemulsion-based method is reported in this paper. We used a UV-spectrophotometer to monitor the growth process of the particles and used TEM to confirm the sizes of the particles. By changing W, Ni/S molar ratios and the concentration of reactants, the effects of reaction conditions on particles have been investigated and we put forward the mechanism of growth of NiS particles. 

The inner core of microemulsion can dissolve water to form water core called water pool [1], Little water pools of microemulsion surrounded by the single molecule interface formed by surfactants and co-surfactants can form particles whose sizes are from tens to hundreds of A [2], In this paper, a microemulsion-based method, and the formation conditions and growth mechanism of nanosized nickel sulfide particles are reported. This research is the base of application of ultrafme NiS particles on catalysis and optics. 

Ultrafme nickel sulfide particles have been synthesized in Triton X-100/ n-hexane/ cyclohexane/ water microemulsion. The experimental results indicate that careful control of the water to surfactant molar ratio W and ion occupancy number is vital in forming NiS particles. 

In nickel smelting particles of nickel sulfide ore are first oxidized. 

The form of nickel in particles from different industries varies. The mineralogical composition, chemical content, and form of dusts from nine industries in Cracow, Poland, were examined (Rybicka 1989). The chemical form of a particle-associated heavy metal that was assessed by a five-step extraction scheme classified the metal as exchangeable, easily reducible (manganese oxides, partly amorphous iron oxyhydrates and carbonates), moderately reducible (amorphous and poorly crystallized iron oxyhydrates), organically bound or sulfidic, and residual. Dusts from power plants had a silicate characteristic with quartz and mullite predominant. Approximately 90% of the nickel from these... 

Dai Z. R. and Bradley J. P. (2001) Iron nickel sulfides in anhydrous interplanetary dust particles. Geochim. Cosmo-chim. Acta 65, 3601-3612. 

On the other hand, when the content of sulfur in the gas was sufficiently high (1000-2(X)0 ppmv) for bulk nickel sulfide (NijSj) formation (ascertained by X-ray diffraction analysis), the distribution of sulfur in the catalyst bed was fairly even in different parts of the bed (Table 1) and also within catalyst particles. According to SEM/EDS analysis the content of sulfur on the surface ranged from 4.0 to 7.5 wt% and in the middle of particles from 5.3 to 9.3 wt%. However, nickel forms a liquid sulfide product at temperatures above 635 C [18, 19]. According to the SEM analysis of the firesh and spent catalyst particles, no liquid formation on the catalysts was detected. 

The earlier stages of the attack on Ni36Al are shown in Fig. 12. Local pock like attack occurs from the surface of the specimen. On top of these pocks, spherical particles of nickel sulfide are often found. The cross-section in Fig. 12 shows the dark alumina phase growing into the matrix. At the front of attack the p-NiAl phase of the alloy changed to y -NijAl because of the A1 consumption. In this area small Al-rich sulfides were found. 

Inhalation of airborne nickel powder at 15.0 mg Ni/m air causes an increased frequency of lung anaplastic carcinomas and nasal cancers in rodents and guinea pigs, especially when the particles are less than 4.0 xm in diameter. Rats exposed to airborne dusts of metallic nickel at 70.0 mg Ni/m air for 5h daily, 5 days weekly over 6 months had a 40% frequency of lung cancers the latent period for tumor development was 17 months. A similar case is made for nickel sulfide and nickel oxide. In Canada, however, metallic nickel is considered unclassifiable with respect to carcinogenicity due to the limitations of... 

Figure S. Stoichiometry of nickel sulfide as a function of particle size.

A similar situation can be encountered for internal sulfidation, which is often focused at grain boundaries (Stroosnijder et al., 1991). In this case, crack initiation and even crack growth are stimulated again due to the presence of weak sulfide particles, or in nickel-based alloys due to the formation of... 

A major problem in the catalytic hydrodesulfurization of residual oils is the deactivation of the catalyst by metal-containing asphaltenic species in the feed. As can be seen from the results of a typical desulfurization experiment presented in Fig. 1, the catalyst shows a rapid initial decline which is attended with a fast build-up of coke on the catalyst. At a relatively low catalyst age 0, as defined in Section IV, a stationary coke level is reached. In contrast, the deposition of the inorganic remnants of the hydro-cracked asphaltenes (mainly vanadium and nickel sulfides) continues and gradually clogs the pores in the outer zone of the catalyst particles, as confirmed by electron microprobe analyses of spent catalyst samples (see Fig. 2). This causes a slow further loss in desulfurization activity over a longer period of time. Ultimately, the catalyst becomes totally inactive for desulfurization because the - still active - inner core has become completely inaccessible to the sulfur-bearing molecules. 

Ageing of glass may also be observed because of the physical transformation of internal defects like metastable nickel sulfide (NiS) inclusions. These imdergo a slow transformation at room temperature from a dense to a less dense phase. These inclusions can be of different compositions, namely NiS, Nii or M7S6 (Barry and Ford, 2001 Yousfi et al., 2010), with sizes in the range 1-100 pm (Barry et ah, 1998). S comes from the raw materials and combustion, while Ni comes from the abrasion of the tools used for batching (Chapter 10). In fact, it remains impossible to eliminate these NiS inclusions. Their content is estimated at about 1 particle for 10 tons of glass. 

Metals less noble than copper, such as iron, nickel, and lead, dissolve from the anode. The lead precipitates as lead sulfate in the slimes. Other impurities such as arsenic, antimony, and bismuth remain partiy as insoluble compounds in the slimes and partiy as soluble complexes in the electrolyte. Precious metals, such as gold and silver, remain as metals in the anode slimes. The bulk of the slimes consist of particles of copper falling from the anode, and insoluble sulfides, selenides, or teUurides. These slimes are processed further for the recovery of the various constituents. Metals less noble than copper do not deposit but accumulate in solution. This requires periodic purification of the electrolyte to remove nickel sulfate, arsenic, and other impurities. 

CatalyticaHy Active Species. The most common catalyticaHy active materials are metals, metal oxides, and metal sulfides. OccasionaHy, these are used in pure form examples are Raney nickel, used for fat hydrogenation, and y-Al O, used for ethanol dehydration. More often the catalyticaHy active component is highly dispersed on the surface of a support and may constitute no more than about 1% of the total catalyst. The main reason for dispersing the catalytic species is the expense. The expensive material must be accessible to reactants, and this requires that most of the catalytic material be present at a surface. This is possible only if the material is dispersed as minute particles, as smaH as 1 nm in diameter and even less. It is not practical to use minute... 

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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