Atomic gases

Fleming, K. N. et al., 1979, A Methodology for Risk Assessment of Major Fires and Its Application to an HTGR Plant, General Atomic GA-A15401. 

The value of k is not universal and depends on the nature of the reactive mixture (for example, fhe value of k may be around 26 for mixtures highly diluted with a mono-atomic gas [29], or around 20 for hydrogen/air mixtures [30]), as well as on the diffraction process at the tube... 

Redfern, P. C., Blaudeau, J.-P., Curtiss, L. A., 1997, Assessment of Modified Gaussian-2 (G2) and Density Functional Theories for Molecules Containing Third-Row Atoms Ga-Kr , J. Phys. Chem. A, 101, 8701. 

The IS process has been studied in United States, Europe, and Japan since 1970s, and some important breakthroughs were attained by General Atomics (GA). So far, the research has been carried out in the following fields ... 

Fig. 23. Schematic representation of the group IV donor-hydrogen complex with hydrogen in AB site. The black spheres represent the group V atoms (As), the large white ones the group III atoms (Ga), the small white one the hydrogen atom and the dotted sphere the impurity. The lone pair on the threefold coordinated group V atom is not represented.

A variety of atomizer designs have been developed in an effort to control the droplet size distribution and to increase the yield of fine powders. Gas atomizers used for the atomization of melts may be loosely classified into two primary categories in terms of the interaction mode between a liquid metal and an atomization gas during atomization, i.e., (1) internal mixing and (2) external mixing. 

For low melting-point metals (for example, solder materials), the liquid metal and the atomization gas may be mixed internally inside the atomizer for both low and high melting point materials, the two fluids can be mixed externally outside the atomizer in the nearnozzle region. 

It has been found that atomization is a pulsating, unsteady process, even if the emerging liquid jet and atomization gas are initially free of oscillation and vibration. 

In both atomization modes, as thin unstable ligaments, and/ or sheets disintegrate into round droplets, atomization gas may plausibly be trapped into the droplets under certain conditions. For alloys with alloying elements which readily react with atomization gas, for example, oxidize to form refractory oxides, solidification may be delayed and spheroidization is prevented so that rough flakes may form. For such alloys, the atmosphere in the spray chamber must be inert and protective to avoid the formation of any refractory and to foster spheroidal shape of droplets. 

While gas atomization of liquid metals is generally viewed as a three-step process, the Kohlswa ultrasonic gas atomization is suggested to be a single-step process.[172] When particles of an atomization gas at extremely high velocities strike a liquid metal... 

In the high-velocity atomization processes, the effect of the compressibility of atomization gas could be quite appreciable. Extending Taylor s analysis 245 for a gas flow over a liquid to a compressible gas flow, Bradley t329 330 developed an expression for the fastest growing wavelength that dominates the disruption at the interface. Supposing that surface tension nips off the crest of the wave into a filament whose diameter is some fraction of the... 

Various correlations for mean droplet size generated by plain-jet, prefilming, and miscellaneous air-blast atomizers using air as atomization gas are listed in Tables 4.7, 4.8, 4.9, and 4.10, respectively. In these correlations, ALR is the mass flow rate ratio of air to liquid, ALR = mAlmL, Dp is the prefilmer diameter, Dh is the hydraulic mean diameter of air exit duct, vr is the kinematic viscosity ratio relative to water, a is the radial distance from cup lip, DL is the diameter of cup at lip, Up is the cup peripheral velocity, Ur is the air to liquid velocity ratio defined as U=UAIUp, Lw is the diameter of wetted periphery between air and liquid streams, Aa is the flow area of atomizing air stream, m is a power index, PA is the pressure of air, and B is a composite numerical factor. The important parameters influencing the mean droplet size include relative velocity between atomization air/gas and liquid, mass flow rate ratio of air to liquid, physical properties of liquid (viscosity, density, surface tension) and air (density), and atomizer geometry as described by nozzle diameter, prefilmer diameter, etc. 

The fundamental issues to be addressed in the process modeling include spray enthalpy, gas consumption, spray mass distribution, microstructure of solidified droplets, and droplet-substrate interactions. The effects of atomization gas chemistry, alloy composition and operation conditions on the resultant droplet properties are also to be investigated in the process modeling. 

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