Dispersion measurement, aluminum

The explosive dispersion of aluminum or the release of trimethyl aluminum at high altitude leads to formation of the lower oxide AlO that emits a blue glow useful for temperature measurements. Other studies with different goals involve the release of ammonia or nitric oxide. The subject is lucidly treated, with individual references, in an article by Rosenberg, ... 

The effect of particle size, and hence dispersion, on the coloring properties of aluminum lake dyes has been studied through quantitative measurement of color in compressed formulations [47], It was found that reduction in the particle size for the input lake material resulted in an increase in color strength, and that particles of submicron size contributed greatly to the observed effects. Analysis of the formulations using the parameters of the 1931 CIE system could only lead to a qualitative estimation of the effects, but use of the 1976 CIEL m v system provided a superior evaluation of the trends. With the latter system, the effects of dispersion on hue, chroma, lightness, and total color differences were quantitatively related to human visual perception. 

The wavelength-dispersive x-ray spectroscopy method (ASTM D6376) provides a rapid means of measuring metallic elements in coke and provides a guide for determining conformance to material specifications. A benefit of this method is that the sulfur content can also be used to evaluate potential formation of sulfur oxides, a source of atmospheric pollution. This test method specifically determines sodium, aluminum, silicon, sulfur, calcium, titanium, vanadium, manganese, iron, and nickel. 

By modifying the procedure described above to explode a wire in the water sphere while the system was under compression, they did attain explosions. Measuring the rebound of the cylinder and the loss of aluminum, they could estimate the work produced by the event. Assuming the maximum energy transfer to the water would occur by constant volume heating to the aluminum temperature, foUowed by an isothermal, reversible expansion, they estimated an efficiency of about 25%. Clearly the exploding wire led to an immediate and effective dispersal of the water. 

Taking into consideration a) the specific properties of organoaluminum compounds, especially lower aluminumtrialkyls, and their hydride-, halo-gene- and alkoxy derivatives, which are highly flammable in air and explode at contact with water b) the use of hydrogen, ethylene, isobutene, ethylene, isobutene, ethylchloride, sodium and aluminum (finely dispersed and active, which can self-inflame in air), the production of organoaluminum compounds can be considered one of the most dangerous chemical productions. Therefore, safety measures and fire prevention are especially important. 

Surface plasmons (SPs) are surface electromagnetic waves that propagate parallel along a metal/dielectric interface. For this phenomenon to occur, the real part of the dielectric constant of the metal must be negative, and its magnitude must be greater than that of the dielectric. Thus, only certain metals such as gold, silver, and aluminum are usually used for SPR measurements. The dispersion relation for surface plasmons on a metal surface is ... 

Kepler et al. (1995) measured electron and hole mobilities of tris(8-hydroxyquinoline)aluminum (Alq). Alq is of interest for electroluminescent devices. The photocurrent transients for both carriers were highly dispersive. Transit times could be resolved only from double logarithmic transients. The electron mobilities were approximately two orders of magnitude higher than hole mobilities. Figure 46 compares the room temperature electron and hole mobilities. The dashed line represents electron mobilities reported by Hosokawa et al. (1994). At 4 x 105 V/cm, the electron and hole mobilities are 1.4 x 10-6 cm2/Vs and 2.0 x 10-8 cm2 Vs. The activation energy for the electron mobility was reported as 0.56 eV. Later results of Lin et al. (1996) were in excellent agreement with the hole mobilities reported by Kepler et al. 

H30 per liter, but for a solid acid such as acid-activated clay a sharp distinction must be made between soluble acidity and local acid strength . The soluble acidity can be readily measured by convential techniques such as titration or gas volumeter analysis. As to titration, the clay can be dispersed in water, and any acidity thus liberated can be neutralized. On this basis, Thomas, Hickey, and Stecker [89] found that raw montmorillonite yielded 0.41 milliequivalents of acid per gram of dry clay, while after acid treatment (removal of half of the aluminum) this value rose to only 1 milliequivalent per gram. If the clay were a liquid with the density of water, these results would mean hydrogen ion concentrations of 0.41 x 10 and 1 X 10 mole per liter, which corresponds to pH values of 6.39 and 6.00, respectively. Thus, even for the acid-activated clay the soluble acidity is extremely small, and cannot possibly explain the proven catalytic effect of this material. It does, however, explain the fact that TONSIL can be swallowed without harm. 

The deactivated catalyst was studied by several methods scanning electron microscopy (SEM)-energy dispersive spectroscopy (EDS), infrared spectroscopy (IR), and by extracting water-insoluble phosphorus. The SEM-EDS studies gave no useful results. IR absorption was measured on samples that were mulled in mineral oil. Comparisons of IR spectra were made with samples of y -alumina and aluminum phosphate. Determination of total P in the deactivated sample, presumed to be present as water-insoluble aluminum phosphate, was made by standard wet chemical analysis dissolution in hot, dilute HCl followed by colorimetric determination of phosphate. ... 

It would be expected that chromia-alumina catalysts prepared by coprecipitation techniques should differ from impregnated catalysts, and this difference has been demonstrated by Eischens and Selwood (5) who measured the magnetic susceptibility of a chromia-alumina catalyst (35 wt % Cr) prepared by coprecipitation with ammonium hydroxide from a solution of aluminum nitrate and chromium nitrate. The susceptibility of the reduced catalyst indicated a much greater dispersion of the chromium than was characteristic of the impregnated catalysts. This was attributed to the presence of a three-dimensional dispersion of the chromium in the coprecipitated catalysts, as compared to a two-dimensional dispersion in the case of the impregnated catalysts. 

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