Atomization method

Lutsko J F ef a/1989 Molecular-dynamic study of lattice-defect-nucleated melting in metals using an embedded-atom-method potential Phys. Rev. B 40 2841... 

Daw M S and M I Baskes 1984. Embedded-atom Method Derivation and Application to Impurities, Surfaces, and Other Defects in Metals. Physical Review B29 6443-6453. 

Miscellaneous Atomization Methods A few elements may be atomized by a chemical reaction that produces a volatile product. Elements such as As, Se, Sb, Bi, Ge, Sn, Te, and Pb form volatile hydrides when reacted with NaBH4 in acid. An inert gas carries the volatile hydrides to either a flame or to a heated quartz observation tube situated in the optical path. Mercury is determined by the cold-vapor method in which it is reduced to elemental mercury with SnCb- The volatile Hg is carried by an inert gas to an unheated observation tube situated in the instrument s optical path. 

The study of the combustion of sprays of Hquid fuels can be divided into two primary areas for research purposes single-droplet combustion mechanisms and the interaction between different droplets in the spray during combustion with regard to droplet size and distribution in space (91—94). The wide variety of atomization methods used and the interaction of various physical parameters have made it difficult to give general expressions for the prediction of droplet size and distribution in sprays. The main fuel parameters affecting the quaHty of a spray are surface tension, viscosity, and density, with fuel viscosity being by far the most influential parameter (95). 

A full-scale treatment of crystal growth, however, requires methods adapted for larger scales on top of these quantum-mechanical methods, such as effective potential methods like the embedded atom method (EAM) [11] or Stillinger-Weber potentials [10] with three-body forces necessary. The potentials are obtained from quantum mechanical calculations and then used in Monte Carlo or molecular dynamics methods, to be discussed below. 

We have used the embedded-atom method (EAM) to develop interatomic potentials suitable for the simulation of iron-nickel alloys. In this method the total energy of the alloys can be written as... 

M.S. Daw and M.I. Baskes, Embedded-atom method Derivation and application to... 

Table 5 Surface energies, calculated from the tight-binding theory (TB), by the embedded-atom method (EAM), or by modified embedded atom method (MEAM), compared to experiment. Energies are given in units of ijm .

X-Ray diffraction from single crystals is the most direct and powerful experimental tool available to determine molecular structures and intermolecular interactions at atomic resolution. Monochromatic CuKa radiation of wavelength (X) 1.5418 A is commonly used to collect the X-ray intensities diffracted by the electrons in the crystal. The structure amplitudes, whose squares are the intensities of the reflections, coupled with their appropriate phases, are the basic ingredients to locate atomic positions. Because phases cannot be experimentally recorded, the phase problem has to be resolved by one of the well-known techniques the heavy-atom method, the direct method, anomalous dispersion, and isomorphous replacement.1 Once approximate phases of some strong reflections are obtained, the electron-density maps computed by Fourier summation, which requires both amplitudes and phases, lead to a partial solution of the crystal structure. Phases based on this initial structure can be used to include previously omitted reflections so that in a couple of trials, the entire structure is traced at a high resolution. Difference Fourier maps at this stage are helpful to locate ions and solvent molecules. Subsequent refinement of the crystal structure by well-known least-squares methods ensures reliable atomic coordinates and thermal parameters. 

In contrast, Skell and co-workers 169) demonstrated that there could be prepared, by the metal atom method, a reasonably well-defined, paramagnetic, yellow TijCCgHgls compound which, in THF, is rapidly reduced with potassium to yield a fairly stable, green solution of the diamagnetic dianion. The H-NMR spectrum and the analytical data were all consistent with the formulation of the green dianion shown, which appears to be the... 

The main handicap of MD is the knowledge of the function [/( ). There are some systems where reliable approximations to the true (7( r, ) are available. This is, for example, the case of ionic oxides. (7( rJ) is in such a case made of coulombic (pairwise) interactions and short-range terms. A second example is a closed-shell molecular system. In this case the interaction potentials are separated into intraatomic and interatomic parts. A third type of physical system for which suitable approaches to [/( r, ) exist are the transition metals and their alloys. To this class of models belong the glue model and the embedded atom method. Systems where chemical bonds of molecules are broken or created are much more difficult to describe, since the only way to get a proper description of a reaction all the way between reactant and products would be to solve the quantum-mechanical problem at each step of the reaction. 

The relative stereochemistry of stephadiamine (16) was clarified by X-ray diffraction analysis, using the direct method, and the absolute configuration was solved by the heavy-atom method, using the N-p-bromobenzoyl derivative (6). Stephadiamine (16), a C-norhasubanan alkaloid, is not regarded as a hasubanan congener in the strict sense, but as a new member of oe-amino acid derivatives (6). 

A complete description of droplet generator and of several atomization methods appears in a previous paper [8]. Simple air-stripping or piezoelectric drop generators were employed. The core liquid typically consisted of a polyanion solution, while the receiving bath contained a polycation(s) solution and, in many instances, a divalent cation. 

In addition to the above-discussed techniques, some other atomization methods have also been developed for specific applications. These include, for example, solution atomization, liquefied gas atomization, and spark-discharge atomization,[881 etc. 

Table 2.5. Comparison of Features of Other Atomization Methods for Melts 5 ...

Water atomization is intrinsically a high volume, low cost process. Therefore, it is generally more cost-effective compared to other commercial atomization methods. However, powder purity,... 

Vacuum atomization is a commercial batch process)180 The development of vacuum atomization started in the mid 1960 s, concurrent with the development of inert gas atomization. In 1970, a patent for the vacuum atomization method was issued to Homogeneous Metals, Inc. Using vacuum atomization, this company routinely produces superalloy powders of fine size without great consumption of argon, giving powders free of inert gas filled porosity. Wentzell1 801 has made detailed description of this proprietary process. 

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