Massive metals

The toxicity of a metal in powder form may vary from that of the massive metals in that fine particles can be ingested or inhaled more readily (41). The metal powder producing or consuming industries must conform to OSHA requirements. The limits of airborne particulates are set by NIOSH. 

Thorium metal alloys readily with a large number of metals, including Fe, Co, Ni, Cu, Au, Ag, B, Pt, Mo, W, Ta, Zn, Bi, Pb, Hg, Na, Be, Mg, Si, Se, and Al. Like many electropositive metals, finely divided thorium metal is pyrophoric in air, and bums to give the oxide. Massive metal, chips, and turnings... 

Owing to the fact that iron Ka has a much lower excitation potential than the corresponding line of either silver or zirconium, it is not possible here to excite the substrate Ka without exciting iron Ka as well. Following are estimated Ka counting rates (counts per second) for the massive metals under the experimental conditions employed iron, 200,000 zirconium, 32,000 silver, 8100. Clearly, Method I would fail here if Ka lines were used Meftiod III is successful because the analyzing crystal eliminates interference by iron Ka. 

Der Absolutwert des Temperaturkoeffizienten des elektrischen Widerstandes muB wenigstens der GroBenordnung nach mit dem Wert fiir das massive Metall ubereinstimmen. 

Finally, the presence of ultrasound in the electrodeposition of metals can produce both massive metal and metal colloid [75]. The reduction of AuCLt- at polycrystalline boron-doped diamond electrodes follows two pathways forming... 

Current density, which ranges from 2,000 to 300,000 Am 2, has been probed as an important operational variable for the sonoelectrodeposition process of massive metals [70], sonoelectrodeposition of oxide metals [80], sonoelectrosynthesis of gases [54] and also nanomaterials synthesis [96], where current density can affect crystal size in at least two opposing directions. A smaller size would be expected, on the basis of the small amount of material deposited at a lower current. On the other hand, lower current density allows more time for atomic diffusion processes to occur which can lead to larger crystal size. However, the former effect is dominant [85]. 

Although the massive metal is relatively inert, when powdered it becomes very reactive. The dry powder may react explosively at elevated temperatures with nitrogen, phosphorus, oxygen, sulfur and other non-metals. The halogens react similarly, and in contact with hot cone, nitric acid and other oxidants it may explode (often after a delay with nitric acid). The powder is pyrophoric and readily ignitable by friction, heat or static sparks, and if dry bums fiercely. Presence of... 

Finely divided calcium may ignite in air, and the massive metal ignites on heating in air, and bums vigorously at 300°C in oxygen. Strontium and barium behave similarly. 

Storage of uranium foil in closed containers in presence of air and water may produce a pyrophoric surface [1], Uranium must be machined in a fume hood because, apart from the radioactivity hazard, the swarf is easily ignited. The massive metal ignites at 600-700°C in air [2]. The finely divided reactive form of uranium produced by pyrolysis of the hydride is pyrophoric [3], while that produced as a slurry by reduction of uranium tetrachloride in dimethoxyethane by potassium-sodium alloy is not [4],... 

At 750°C interaction is so rapid that ignition will occur with the finely divided metal, and at 800°C the massive metal will ignite. 

Thick fringe-free polycrystalline Pt film, deposited 273°C massive metal 0.37 5.0 8.4 22 7.5... 

In this microcalorimeter, the heat sink is not a massive metal block but is divided into several parts which are mobile with respect to each other. Each thermoelectric element (E) and a cell guide (D) are affixed to a fluxmeter holder (C). The holder (C) is mobile with respect to a massive arm (B) which, in turn, rotates around a vertical axle (A). All parts of the heat sink are made of brass. Surfaces in contact are lubricated by silicone grease. Four thermoelectric elements (E) are mounted in this fashion. They enclose two parallelepipedic calorimetric cells, which can be made of glass (cells for the spectrography of liquids are particularly convenient) or of metal (in this case, the electrical insulation is provided by a very thin sheet of mica). The thermoelectric elements surrounding both cells are connected differentially, the Petit microcalorimeter being thus a twin differential calorimeter. 

Heating is most often achieved using electrical resistive devices to heat a relatively massive metal block. This ensures that the temperature... 

Thorium metal also can he prepared hy thermal reduction of its hahdes with calcium, magnesium, sodium, or potassium at elevated temperatures (950°C), first in an inert atmosphere and then in vacuum. Fluoride and chloride thorium salts are commonly employed. Berzehus first prepared thorium by heating tetrachloride, ThCh, with potassium. Magnesium and calcium are the most common reductant. These metals are added to thorium halides in excess to ensure complete reduction. Excess magnesium or calcium is removed by heating at elevated temperatures in vacuum. One such thermal reduction of hahdes produces thorium sponge, which can be converted into the massive metal by melting in an electron beam or arc furnace. 

The fundamental hydrodynamic theory of deton refers to a chge of infinite diam or a cylindrical chge encased in a perfectly rigid tube. Of course, ideal lateral confinement can never be realized completely since even massive metal tubes are compressible under the internal pressure developed during deton... 

As a first approximation to the influence of structure on the vibrational frequencies, we shall concentrate on the M-H-M tri-atomic array. For a linear M-H-M unit, the normal modes are very simple. There is a Raman-active symmetric M-H-M stretch (Structure 9) that only involves motion of the massive metal and therefore occurs at much lower frequencies than the B-B and M-B stretching modes discussed in a previous section. In an intermediate frequency region, a doubly degenerate M-H deformation mode occurs that involves hydrogen motion (Structure 10), and at high frequencies, an asymmetric ir-active stretching vibration (Structure 11) should be observed. 

Here we will discuss G/L/S reactors with S solid catalysts (almost always a supported or massive metal). 

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