Refractory metals distribution

It is found that the atomic arrangement, or a vacancy network, in a depleted zone in a refractory metal or a dilute alloy of a refractory metal, created by bombardment of an ion can be reconstructed on an atomic scale from which the shape and size of the zone, the radial distribution function of the vacancies, and the fraction of monovacancies and vacancy clusters can be calculated. For example, Wei Seidman108 studied structures of depleted zones in tungsten produced by the bombardment of 30 keV ions of different masses, W+, Mo+ and Cr+. They find the average diameters of the depleted zones created by these ions to be 18,25 and 42 A, respectively. The fractions of isolated monovacancies are, respectively, 0.13,0.19and0.28,andthe fractions of vacancies with more than six nearest neighbor vacancies (or vacancy clusters) are, respect-... 

Electron Beam Rotating Disk Atomization (EBRD) <700 Narrow size distribution Refractory, reactive metals and alloys such asTi >103 -5.5 -0.5 Relatively high EE Coarse (flaky) particles, Relatively low capacity throughput... 

For airbursts the form of the distribution functions is still under investigation. All particles consist of metal oxide spheres produced by condensation from the vapor state of the device materials. The number of population components may be related to the number of major condensable components of the device. Large particles are enriched in refractory isotopes, small particles in volatile. The interisotopic relationships may be expressed best as power functions. 

The particle size of a fission aerosol, and the distribution of fission products between particulate and vapour phases, depends on the mechanism of release to the atmosphere. In a weapons explosion, some physicochemical fractionation of radionuclides may occur, particularly if the explosion is near the ground. Everything in the vicinity is vapourised by the heat of the explosion, but within less than a minute the fireball cools to a temperature in the range 1000-2000°C, and refractory materials such as metal oxides and silicates condense to form particles (Glasstone Dolan, 1977). Refractory fission products, and plutonium, are incorporated in these particles. 

For opaque materials the reflectance p is the complement of the absorptance. The directional distribution of the reflected radiation depends on the material, its degree of roughness or grain size, and, if a metal, its state of oxidation. Polished surfaces of homogeneous materials are specular reflectors. In contrast, the intensity of the radiation reflected from a perfectly diffuse or Lambert surface is independent of direction. The directional distribution of reflectance of many oxidized metals, refractory materials, and natural products approximates that of a perfectly diffuse reflector. A better model, adequate for many calculation purposes, is achieved by assuming that the total reflectance is the sum of diffuse and specular components pD and ps, as discussed in a subsequent section. 

Of the 80 or so scarce elements, many occur in solid solution in major rock-forming minerals (e.g., rubidium, strontium, vanadium, germanium, gallium, scandium, rare earth elements (REEs)), or in solid solution in widely distributed, refractory, or low-solubility accessory phases (e.g., hafnium). Some elements, such as zirconium and phosphorus, form their own minerals. Others, like the base metals (e.g., copper, lead, zinc), semi-metals (arsenic, antimony, bismuth), and... 

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