Metal-dust particles

Indium metal dust, particles, and vapors are toxic if ingested or inhaled, as are most of the compounds of indium. This requires the semiconductor and electronics industries that use indium compounds to provide protection for their workers. 

As the demand for higher energy densities increases, it is desirable to minimize the total quantity of all inert materials in a battery. With a separator thickness of only 20-25 jm, any small intrusion of metallic dust particles can have devastating consequences. High rate cells are looking toward even thinner separators within the range of 9-16 pm to minimize the separator-incurred resistance. Even gel spots (binder particles agglomerates) or bumps in the electrode... 

But they all oxidise very rapidly indeed (see Table 21.2), and are utterly useless without coatings. The problem with coated refractory metals is, that if a break occurs in the coating (e.g. by thermal fatigue, or erosion by dust particles, etc.), catastrophic oxidation of the underlying metal will take place, leading to rapid failure. The unsafeness of this situation is a major problem that has to be solved before we can use these on-other-counts potentially excellent materials. 

The term, metal dusting, was first used about this time to describe the phenomenon associated with hydrocarbon processing. Butane dehydrogenation plant personnel noted how iron oxide and coke radiated outward through catalyst particles from a metal contaminant which acted as a nucleating point. The metal had deteriorated and appeared to have turned to dust. The phenomenon has been called catastrophic carburization and metal deterioration in a high temperature carbonaceous environment, but the term most commonly used today is metal dusting. 

This approach has not been tested for any dusts that burn heterogeneously (A-6-1.2), such as some metal dusts. The equation should not be applied for gas concentrations greater than the LEE [11] otherwise extrapolation might be made into region Q shown on Eigure 6-1.3.1, where the predicted HMIE is greater than the gas MIE. The MIE of dust, D, must be determined by test using a conservatively fine dust sample to represent particles in the hybrid mixture. Values for G and Cg can be found in Appendix B. Where G is not... 

Group E. Atmospheres containing combustible metal dusts, including aluminum, magnesium, and their commercial alloys, or other combustible dusts whose particle size, abrasiveness, and conductivity present similar hazards in the use of electrical equipment. 

This concept may be invoked to account for electrolyte formation in microcracks in a metal surface or in the re-entrant angle formed by a dust particle and the metal surface. More importantly, it can also explain electrolyte formation in the pores of corrosion product and hence the secondary critical humidity discussed earlier. Ferric oxide gel is known to exhibit capillary condensation characteristic and pore sizes deduced from measurements of its adsorptive capacity are of the right order of magnitude to explain a secondary critical relative humidity as70 7o for rusted steel . 

Dust particles may be removed from air by passing the air through an electrical discharge and then between a pair of oppositely charged metal plates. Explain how this removes the dust. 

Almost all the materials which are being considered as components in automobile exhaust catalyst are somewhat toxic (74)- Most of the compounds considered are low vapor pressure solids which can only escape from the exhaust system as very fine airbone dust particles formed by catalyst attrition. A few compounds, such as the highly toxic metal carbonyls and ruthenium tetroxides, are liquid under ambient conditions and have boiling points less than 100 °C. These compounds are not present in... 

Mining and industrial activities produce large quantities of volatiles and dust particles and increase concentrations of trace elements and heavy metals in soils, waters, and vegetation. When mineral deposits containing concentrated trace elements and heavy metals are exposed at the earth s... 

During aerial transportation by wind the dust particles are enriched in heavy metal and other pollutant species, especially during transport over east and southeast industrial areas of China. Further dry and wet deposition leads to human and ecosystem exposure to this pollution and a related increase of environmental risk. 

Despite the quantitative variability of salts and silicate dust particles in the plants of Arid ecosystems, we can easily discern a trend towards the selective uptake of trace elements. The calculation of coefficient of biogeochemical uptake (Cb) shows the rates of exposure to heavy metals in biogeochemical food webs. One can see that the elements contained in the plant species of both Steppe and Desert ecosystems are in equal measure susceptible to the influence of environmental factors. The most extensively absorbed are Sr, Cu, Mo, and Zn. Their values of Cb are more than unit. The group of other elements, like Ti, Zr, and V, are poorly taken up, with their values of Cb often dropping below 0.1 (see Figures 4 and 5). 

Inorganic and organic compounds are often present in the environment in complex forms. Levels of contaminating metals and molecules are variable, depending on the natural conditions and anthropogenic activities. The contaminants may be airborne as vapour, droplets or dust particles, and in the soil in aqueous or particulate forms. In the case of aqueous systems, they can exist as emulsions, as dissolved ions or molecules and as suspended or sedimentary particles. Environmental particles have been reviewed in the first two volumes of this series [1,2]. 

A shadow-mask technique has been applied for the local metal deposition to exclude metal residues on other designs processed on the same wafer (Fig. 4.2b). Such metal residues may be caused by imperfections in the patterned resist due to topographical features on the processed CMOS wafers or dust particles. The metal film is only deposited in those areas on the wafer, where it is needed for electrode coverage on the microhotplates. This also renders the lift-off process easier since no closed metal film is formed on the wafer, so that the acetone has a large surface to attack the photoresist. Another advantage of the local metal lift-off process is its full compatibility with the fabrication sequence of chemical sensors based on other transducer principles [20]. 

Both fossil fuels and hazardous waste fuels used in Southdown cement kilns contain metals. The raw materials (limestone, clay, sand) used to make cement clinker also contain metals. In fact, certain metals, such as iron and aluminum, are essential components of the final product. While metals cannot be destroyed, the Southdown cement kiln process effectively manages them in the following ways (a) cement kiln operators limit emissions by carefully restricting the metals content in wastes accepted for recycling (b) dust particles containing metals are returned to the kUn through closed-loop mechanisms, where metals are chemically bonded into the cement clinker (c) particles not returned to the kiln are captured in state-of-the-art pollution control devices and (d) small amounts are emitted from the stack in quantities strictly hmited by USEPA s BIF mle. 

Electrostatic precipitators and baghouses are used to catch dust particles containing metals. Electrostatic precipitators use an electrical field to remove the particles. Baghouses use fiberglass filters, similar to vacuum cleaner bags, to catch them. The majority of theses particles, called cement kiln dust (CKD), are trapped by this equipment and returned to the kiln for incorporation into the cement clinker. Under USEPA s BIF rule. Southdown tests its cement kiln dust to judge whether it is hazardous. If the CKD does not meet the standards set under the BIF rule, it must be disposed of in accordance with USEPA s strict hazardous waste regulations. For that reason. Southdown does not accept fuels that would cause the waste CKD to fail this test. 

The time-resolved studies of the cluster formation achieved by pulse radiolysis techniques allow one to better understand the main kinetic factors which affect the final cluster size found, not only in the radiolytic method but also in other reduction (chemical or photochemical) techniques. Generally, reducing chemical agents are thermodynamically unable to reduce directly metal ions into atoms (Section 20.4) unless they are complexed or adsorbed on walls or dust particles. Therefore, we explain the higher sizes and the broad dispersity obtained in this case by in situ reduction on fewer sites. A classic... 

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