Materials powder

The znortcu should be provided with a tightly fitting rubber cover to protect the powdered material from oxidation in air. 

Note 1. Prepared from the commercial products by heating the powdered materials in round-bottomed flasks at 16Q°C/Q.5-0.1 mmHg. 

Calcination. Calcination involves a low (<1000° C) temperature soHd-state chemical reaction of the raw materials to form the desired final composition and stmcture such as perovskite for BaTiO and PZT. It can be carried out by placing the mixed powders in cmcibles in a batch or continuous kiln. A rotary kiln also can be used for this purpose to process continuously. A sufficiendy uniform temperature has to be provided for the mixed oxides, because the thermal conductivity of powdered materials is always low. 

A modified method of estimating the OI for fibrous or finely divided ceUulosic materials has been developed (53). The fibers or powdered materials are first pressed iato disks, then the OI is measured ia the usual way. 

Niobium BaseMlloy Powders Material Safety Data Sheet, No. 516, Teledyne Wab Chang Corp., Albany, Oieg., 1992. 

Some finely powdered materials, such as carbon black, contain much air. If possible they should be compacted or wet out before being added to the mix. If a sufficient quantity of hght solvent is a part of the formula, it may be used to wet the powder and drive out the air. If the powder cannot be wet, it may be possible to densify it somewhat by mechanical means. Removal of adsorbed gas under vacuum is sometimes necessary. 

Multiwall Paper Bags These bags (Fig. 21-40), made from plies of kraft paper or from combinations of kraft and special-purpose papers and plastics, are the most common packages For almost any pelleted or powdered material as well as for briquettes or bats of such solids as synthetic rubber, waxes, and insulation. 

X-RAY FLUORESCENCE INTENSITY ELEMENTS OE MULTICOMPONENT POWDER MATERIAL WITH CONTINUOUS GRAIN SIZE DISTRIBUTION OE COMPONENTS... 

The existing models for emitting x-ray fluorescence intensity of elemental analytical lines from heterogeneous samples are limited in practical applications, because in most publications the relations between the fluorescence intensity of analytical lines elements and the properties of powder materials were not completely studied. For example, particles distribution of components within narrow layer of irradiator which emitted x-ray fluorescence intensity of elements might be in disagreement with particles distribution of components within whole sample. 

If powdered materials are being handled, does the site evaluate dust explosion issues ... 

Two hundred grams of eleaned and dried crab shells (Note 1) ground to a fine powder is placed in a 2-1. beaker, and an excess of dilute (approximately 6 N) commercial hydrochloric acid is added slowly to the powdered material until no further action is evident. Much frothing occurs during the addition of the acid, and care must be exercised to avoid loss of material due to foaming over the sides of the beaker. After the reaction has subsided, the reaction mixture is allowed to stand from 4 to 6 hours to ensure complete removal of calcium carbonate. The residue is then filtered, washed with water until neutral to litmus, and dried in an oven at 50-60°. The weight of dried chitin is usually about 70 g., but with some lots of crab shells it may be as low as 40 g. 

Fillers are often employed to reduce the surface tack of the final product. Examples are talc and china clay. If powdered materials are added directly to a latex they compete for the emulsion stabiliser present and tend to coagulate the latex. They are therefore added as an aqueous dispersion prepared by ball milling the filler with water and a dispersing agent, for example a naphthalene formaldehyde sulphonate at a concentration of about 1% of the water content. Heat and light stabilisers which are solids must be added in the same way. 

For dealing with other powdered materials that are additives to cement slurries, the absolute volume must be used. The absolute volume (gal) is... 

For a long period of time, molten salts containing niobium and tantalum were widely used for the production by electrolysis of metals and alloys. This situation initiated intensive investigations into the electrochemical processes that take place in molten fluorides containing dissolved tantalum and niobium in the form of complex fluoride compounds. Well-developed sodium reduction processes currently used are also based on molten salt media. In addition, molten salts are a suitable reagent media for the synthesis of various compounds, in the form of both single crystals and powdered material. The mechanisms of the chemical interactions and the compositions of the compounds depend on the structure of the melt. 

The contaminated powdered material usually causes problems during crystal growth and degraded the electric and optic properties of the final products. 

Even the sampling of solids must not be casually undertaken, and the operator should always use a face mask as a protection until it is established that the powdered material is not hazardous. 

Perhaps the first practical application of carbonaceous materials in batteries was demonstrated in 1868 by Georges Le-clanche in cells that bear his name [20]. Coarsely ground MnO, was mixed with an equal volume of retort carbon to form the positive electrode. Carbonaceous powdered materials such as acetylene black and graphite are commonly used to enhance the conductivity of electrodes in alkaline batteries. The particle morphology plays a significant role, particularly when carbon blacks are used in batteries as an electrode additive to enhance the electronic conductivity. One of the most common carbon blacks which is used as an additive to enhance the electronic conductivity of electrodes that contain metal oxides is acetylene black. A detailed discussion on the desirable properties of acetylene black in Leclanche cells is provided by Bregazzi [21], A suitable carbon for this application should have characteristics that include (i) low resistivity in the presence of the electrolyte and active electrode material, (ii) absorption and retention of a significant... 

Occurrence of the temperature inhomogeneity along a film during its heating was reported recently (45f). Different results were obtained when temperature measurement and control were effected only in one point, and in three points of the desorption cell, which illustrates that caution should be observed in this respect when studying thermodesorption from the films. This caution is obviously yet more essential when working with powdered materials. 

The analysis of experimental data is clearly rather difficult in this approach. Therefore, an experimental arrangement on which the derived expressions are based is rarely used in practice for the quasi-equilibrium measurements. For powdered materials, a different experimental design advanced by Amenomiya and Cvetanovic (47-49) is widely employed. 

Size, Particle Size Distribution, and Packed Density of Powdered Materials , MIL-STD-1233 (March 1962) 3) Anon, EngDesHdbk, Pro-... 

SHARPLESMICROMEROGRAPH- A commercially available air sedimentation device introduced in 1953 (Ref 6) that provides rapid particle size distribution determinations for powdered materials by the application of Stokes law for particles falling thru a static column of gas... 

Johnson, Christian, and Tiedemann (Ref 27) evaluated the Sorptometer vs the Micromero-graph and the microscope for particle size and surface area determinations to characterize powdered materials used in solid propints. Table 12 compares the surface area of A1 powder samples calculated from Micromerograph and microscopic data with that measured using a Sorptometer... 

In this paper we attempt a preliminary investigation on the feasibility of catalytic combustion of CO/ H2 mixtures over mixed oxide catalysts and a comparison in this respect of perovskite and hexaaluminate type catalysts The catalysts have been characterized and tested in the combustion of CO, H2 and CH4 (as reference fuel). The catalytic tests have been carried out on powder materials and the results have been scaled up by means of a mathematical model of the catalyst section of the Hybrid Combustor. 

FT-IR spectra were recorded at RT on a Perkin-Elmer 1760-X spectrophotometer equipped with a cryodetector, at a resolution of 2 cm-" (number of scans -100). In the 1070-960 cm- region, band integration and curve fitting were carried out by Curve fit, in Spectra Calc. (Galactic Industries Co.). Powdered materials were pelleted in self-supporting discs of 25-50 mg cm-2 and 0.1-0.2 mm thick, placed in an IR cell allowing thermal treatments in vacuo or in a controlled atmosphere. 

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