Metallic powder dusting

Refs 1) I. Hartman H.P. Greenwald, The ExplosiMlity of Metal-Powder Dust Clouds , Mining Metallurgy 26, 331 (1954) 2) M. 

Solid Zr is not hazardous but any high surface form of Zr metal (powder, dust, etc.) is hazardous because of its easy ignition in air and the exothermic (often explosive) reactions with many other elements and compounds. 

Solid materials that can support an explosion include chemicals, pharmaceuticals, dyestuffs, coal, plastics, wood, foods, agricultural products, and metal powders. Dusts of these materials in air can be explosive, and diere are some substances that do not even need air (e.g., some metal powders in nitrogen or carbon dioxide). 

Many finely divided metal powders in suspension in air are potential e] losion hazards, and causes for ignition of such dust clouds are numerous [Hartmann and Greenwald, Min. MetalL, 26, 331 (1945)]. Concentration of the dust in air and its particle size are important fac tors that determine explosibility. Below a lower Umit of concentration, no explosion can result because the heat of combustion is insufficient to propagate it. Above a maximum limiting concentration, an explosion cannot be produced because insufficient oxygen is available. The finer the particles, the more easily is ignition accomplished and the more rapid is the rate of combustion. This is illustrated in Fig. 20-7. 

Compiled from the following reports of the U.S. Department of Interior, Bureau of Mines Rl 5753, The Explosibility of Agricultural Dusts Rl 6516, Explosibility of Metal Powders Rl 5971, Explosibility of Dusts Used in the Plastics Industry Rl 6597, Explosibility of Carbonaceous Dusts Rl 7132, Dust Explosibility of Chemicals, Drugs. Dyes and Pesticides and Rl 7208, Explosibility of Miscellaneous Dusts.)... 

Jacobson, A.R. Cooper J. Nagy, Exploability of Metal Powders , BuMines Rept 6516 (1964) 3) J. Nagy, A.R. Cooper J.M. Stuper. Pressure Develdpment in Laboratory Dust Explosions , BuMines Rept 6561 (1964). 4) J. Nagy, H.G. 

Because of the many examples of such activation of metal powders by TCS 14 only a limited and arbitrary number will be discussed here. The Clemmensen-type reduction of ketones such as cyclohexanone with Zn powder in the presence of TCS 14 affords, via 2082, 2084, and 2085, cyclohexene and, via 2082, O-silylated pinacol 2083 [19, 20]. Ketones such as 5a-cholestan-3-one 2086 are reduced by Zn dust-TCS 14 in TFIF, in ca 65-70% yield, to give 5a-cholest-2-ene 2087 and ca 5% 5a-cholest-3-ene [21] (Scheme 13.8). 

Thermal infusion is the process of applying fused zinc, cadmium, or other metal coatings to a ferrous workpiece by imbuing the surface of the workpiece with metal powder or dust in the presence of heat. 

Pyrophoricity and detonation behaviour of titanium hydride powders of various particle sizes were studied in comparison with those of titanium metal powders [1]. Maximum dust explosion pressures of 8.2 bar, with a maximum rate of rise of 816 bar/s have been recorded [2]. 

Solutions to similar problems of achieving catalytic turnover [22] in McMurry couplings [23], Nozaki—Hiyama reactions [24], and pinacol couplings [25] have been reported by Fiirstner and by Hirao. The key step in these reactions is the in situ silylation of titanium and vanadium oxo species with Me3SiCl and reduction of the metal halides by suitable metal powders, e. g. zinc and manganese dust, as shown in Scheme 12.13. 

Standard for Combustible Metals, Metal Powders, and Metal Dusts... 

Reaction [6] generates iron powder or dust, thus explaining how bulk metal is converted to metallic powder. A schematic representation of the Hochman mechanism has been given by Grabke4. 

Molybdenum hexacarbonyl usually is made by treating molybdenum pen-tachloride with zinc dust in carbon monoxide under high pressure (90 to 120 atm). Also, it can be prepared by direct combination of molybdenum metal powder with carbon monoxide under pressure. 

Othmer, ChemProcessEng 45(4), 165-74(1964) (A dust-explosion test app is described and exptl data are reported) 51) M. Jacobson et al, USBurMines Rl 6516(1964) (Explosibility of metal powders) 52) J. Nagy et al, USBurMines Rl 6597(1965) (Explosibility of carbonaceous dusts) 53) J.P. Gillis, InstEnvironSciAnnuTechMeet,Proc 1965,... 

Purification of TiCI4. The chlorides that are solid at room temperature and the entrained dust can be separated from the TiCl4 by simply evaporating (distilling) this off (j). Dissolved chlorine can be removed by heating or reduction with metal powders (Fe, Cu, or Sn). 

Hartmann and associates (24G-28G) have conducted a great deal of experimental work on the combustion of dust dispersions. Explosions can be caused by particles as large as 700 microns. Many different dusts, including rosins, metal powders, and coal, have been investigated. Zirconium powder is the most explosive. Coal dust explosibility is closely associated with its volatile combustible content. Representative pressure rises as high as 75 pounds per square inch in an enclosed volume are reported. In all cases this maximum pressure is attained at mixture strengths well beyond stoichiometric. 

The limits of flammability of dusts have been investigated (30G, 34G, 35G). Using various metal powders, Boyle and Llewellyn (15G) have found the minimum ignition energy to be proportional to particle size. Browning, Tyler, and Krall (10) report a variation of the lean limit as a function of particle size particles of about 60-micron diameter give the leanest combustible mixtures. 

According to Hart Tomlinson(Ref 11), while the explosibiiity of metal powders depends upon many factors, such as ignition, temperature, particle size, particle size distribution, shape, moisture content, energy required for ignition, etc, the metals may be arranged in decreasing order of explosibiiity of their dusts as follows a)Zr Tifusually shipped under w or ale) b)Mg (less than 200 mesh) c)Mg/Al alloy (less than 200 mesh) d) Al (less than 6 microns) and e)Si... 

There are two reasons why artists are particularly vulnerable to diseases caused by exposure to toxic materials. First of all, artists, by the nature of their work, may have daily, long-term contact with materials that are highly toxic. Second, art materials are used as aerosols, powders, dusts, and in solution, from which maximum physical absorption and adsorption are possible. An artist can inhale aerosols. Powders and dusts are also inhaled and, in addition, can be absorbed through the skin. Solutions and many solvents evaporate into the air for the artist to inhale over long periods of time. This chemical assault, day after day, causes a variety of illnesses. In the following section on artists illnesses, all the chemicals cited are used by artists as they draw and paint, sculpt, work with metals, or develop and print photos—in general, as they engage in any art-associated activity. 

Dusts, silica, metal powder, carbon particles, and particulate matter are collected over membrane filters of appropriate pore size. Filter cassettes are used for this process. A membrane filter having the same diameter as the cassette is placed inside the cassette, one end of which is connected to the sampling pump. A measured volume of air is then sampled. While air can pass through the pores of the filter, the suspended particles get deposited on the filter. 

Metal Powder Wear nitrile rubber gloves, laboratory coat, and eye protection. Avoid breathing dust. Scoop into container for reuse or recycling. 

When you are ready to cut them, use a knife dipped in hot water, wiped clean, to cut the brownies into small squares. If you like, brush on gold or silver metallic powder for an elegant effect, or dust lightly with powdered sugar. 

Melted Chocolate Ganache (recipe follows) Gold metallic powder (see page 238), for dusting... 

Spread the ganache with a small offset spatula. Once chilled, dust with gold metallic powder. 

Besides dusting the ganache with metallic powder, you can simply drizzle melted white chocolate on top of the dark ganache for contrast or after coating the Goldies with the ganache, freeze them for IO minutes and then dip them halfway in warm melted white chocolate—a twist on the black and white cookie. 

The cake decorating industry produces colorful and metallic powders or "dusts for accenting flowers or for painting on cakes. There are three types—petal, luster, and metallic dusts. The powders are all nontoxic, derived from minerals, and can be used as powders or made into a liquid "paint. ... 

Fillers are relatively nonadhesive substances added to the adhesive formulation to improve its working properties, strength, permanence, or other qualities. The improvements resulting from the use of fillers are listed in Table 1.8. Fillers are also used to reduce material cost. By selective use of fillers, the properties of an adhesive can be changed significantly. Thermal expansion, electrical and thermal conduction, shrinkage, viscosity, and thermal resistance are only a few properties that can be modified by the use of fillers. Common fillers are wood flour, silica, alumina, titanium oxide, metal powders, china clay and earth, slate dust, and glass fibers. Some fillers may act as extenders. 

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