Metal powders 670 INDEX

A Carr index less than 21 for a powder mixture indicates good flow, while one between 21 and 25 suggests a marginal flow property. A more commonly used term is the Hausner ratio, which is simply p,/pb, or the tapped density divided by bulk density. This ratio was introduced by Hausner in 1967 to characterize metal powders,58 but is commonly used today for pharmaceutical powders. The higher the Hausner ratio, the poorer the flow. The Hausner ratio varies from about 1.2 for a free-flowing powder to 1.6 for cohesive powder. 

Thus far we have been concerned almost exclusively with low index surfaces of single crystals of pure metals, for good reason. In the older work on metal powders and films, their polycrystalline nature forbade the drawing of conclusions about surface geometry, and their doubtful cleanliness was a continual worry. Only the work on FEM and FIM produced results of comparable importance, although these techniques are now rarely used. There have however been a number of studies of stepped surfaces. The behaviour of chemisorbed hydrogen on Ni(997), which is a stepped version of Ni(l 11), is dominated by the plane areas, but the order-disorder transition from the (2 x 2)2H phase to the randomly located lattice gas was raised by about 40 K by the presence of the steps, which stabilise the ordered structure. 

The task of predicting a reasonable structure for this alloy was carried out with no information about the powder X-ray diffraction pattern except that one group of investigators had said that it could not be indexed by any Bravais lattice. The prediction of the structure was made entirely on the basis of knowledge of the effective radii of metal atoms and the principles determining the structure of metals and intermetallic compounds. 

Colorless cubic crystals or white granular powder saline taste odorless hygroscopic does not melt but sublimes on heating at 340°C vapor pressure 48.75 torr at 250°C and 251.2 torr at 300°C density 1.5274 g/cm at 25°C refractive index 1.642 readily dissolves in water, solubihty 229 g and 271 g/L solution at 0°C and 20°C, respectively solubdity lowered by alkah metal chlorides and HCl dissolution lowers the temperature of the solution sparingly soluble in alcohols (6 g/L at 19°C) and soluble in hquid NH3 insoluble in acetone and ether. 

White crystalline powder sharp metallic taste orthorhombic structure refractive index 1.5452 density 4.20 g/cm very hygroscopic melts at 394°C vaporizes at 650°C highly soluble in water 447g/100 mL at 20°C aqueous solution acidic very soluble in alcohol, ether, and acetone soluble in alkali hydroxides and ammonia solution. 

No structure analyses on transition metal compounds NasMeFe have been performed yet, but recently Vollmer 316) indexed a powder diagram... 

Immediately after the isolation of macroscopic quantities of Cgo solid [298], highly conducting [299] and superconducting [141] behaviors were verified for the K-doped compounds prepared by a vapor-solid reaction (Haddon, Hebard, et al.). Crystallographic study based on the powder X-ray diffraction profile revealed that the composition of the superconducting phase is KsCeo and the diffraction pattern can be indexed to be a face-centered cubic (fee) structure with a three-dimensional electronic pathway [300]. The lattice parameter (a = 14.24 A) is apparently expanded relative to the undoped cubic Ceo = 14.17 A). The superconductivity has been observed for many A3C60 (A alkali metal), e.g., RbsCeo (Tc = 29 K... 

The Surlyn A ionomers (E. I. du Pont de Nemours Co.) are believed to be derived from copolymers of ethylene with minor amounts of methacrylic acid which are treated subsequently, so that substantial amounts of the carboxylic acid are converted to the sodium or other metal carboxylate. Resins similar to the one studied in this work contain about 10 weight % methacrylic acid. The ash (sodium carbonate) indicates about 40% neutralization. This resin, which contains 0.05% Santo-white Powder (Monsanto Chemical Co.), a phenolic antioxidant, is of medium molecular weight—i.e., probably corresponding to an ethylene homopolymer with a melt flow index around 20 (17). The molecular weight distribution is broad (17). 

The Pico abrader is specified in D222857. This device uses a pair of tungsten carbide knives which rub the test piece whilst it rotates on a turntable. The direction of rotation is reversed at intervals throughout a test and a dusting powder is fed to the test piece surface, which doubtless helps to avoid stickiness. The apparatus is calibrated by the use of no less than five standard rubbers and the result also expressed as an abrasion index. Force on the test piece and speed of rotation can be varied and, presumably, different abradant geometries could be used, although the distinctive feature of the Pico is the use of blunt metal knives in the presence of a powder. 

Single-crystal precession data indicate orthorhombic symmetry with the crystallographic space group Fddd. This system is not isostructural with any other known metal oxyfluoride or metal dioxide. The cell dimensions, determined from Guinier data, are a = 8.370 1 A. b = 10.182 1 A. and c = 7.030 1 A. The indexed powder data are given in reference 6. 

X-ray Diffraction of Pure MoFe, High Temperature Form. X-ray diffraction powder photographs of MoFe taken at 10 °C. can be indexed on the basis of a body-centered cubic unit cell with a lattice constant, a = 6.23 zb 0.01 A. The similarity of the MoFe diffraction pattern to that of molybdenum metal indicates that the molybdenum atoms in the hexafluoride, as in the metal, are located at the body center and comers of a cube. 

Clear diamonds, occasionally in coloured form, are used as gems because the high index of refraction 2.42) enhances internal reflexion and brilliance in the cut stone. Diamond powder, much now manufactured industrially, is an abrasive for arming grinding and cutting wheels larger opaque, natural diamonds are mounted in tools for cutting metal and rock. 

Properties Soft, blue-white, malleable metal or grayish-white powder. D 8.642, mp 320.9C, bp 767C,refr index 1.13, Mohs hardness 2.0. Soluble in acids, especially nitric, and in ammonium nitrate solution. Lowers melting point of certain alloys when used in low percentages. Tarnishes in moist air. Corrosion resistance poor in industrial atmo-... 

Properties Colorless, odorless, nontoxic, water-soluble powder or granules. D 1.59, refr index 1.51, tensile strength 8000-15,000 psi, pH (1% solution) 6.5-8.0, stable in pH range 2-10. Viscosity of 1% solution varies from 5 to 2000 cP, depending on the extent of etherification. Insoluble in organic liquids. Reacts with heavy-metal salts to form films that are insoluble in water, transparent, relatively tough, and unaffected by organic materials. Many of its colloidal properties are superior to those of natural hydrophilic colloids. It also has thixotropic properties and functions as a polyelectrolyte. 

I push out the corner with my index finger. The comer of the bag is covered with white powder. I sucked on the comer of the bag and get a very powerful metallic slam in the back of my throat. I visualize the bag turning into a breast. 

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