Fragmentation erosion

Use of Radioactivated Metal Discs for Hypervelocity Fragment Erosion Studies (Ref 4)... 

The use of radioactivated discs of aluminum and steel to estimate fragment erosion in solid targets at very high velocities was found to be feasible. Activation of discs was accomplished by slow neutron irradiation in a nuclear reactor at a flux of 8 x 1012 neutrons per cm2 per sec for 3 days for the aluminum discs (4g, 2.5cm diam x 0.3cm thick), and for 4 hrs for the steel discs (5g, 2.5cm diam x 0.15cm thick). Gamma-ray spectrometry indicated the presence of 59Fe (half-life 46 days) and 51Cr (half-life 28 days) in ratios 0.5 for aluminum and 1.3 for steel. The radioactivities in the aluminum arose solely from impurities, whereas in the steel they were contributed by the major component, iron, and only supplemented by the chromium impurity. The radioactivity was found by successive acid soln determinations to be distributed evenly in both metals... 

Shells, clams, wood fragments, and other biological materials can also produce concentration cell corrosion. Additionally, fragments can lodge in heat exchanger inlets, locally increasing turbulence and erosion-corrosion. If deposits are massive, turbulence, air separation, and associated erosion-corrosion can occur downstream (see Case History 11.5). 

A common cause of erosion is partial obstruction of tubes by foreign bodies. At the inlet end, for example, debris such as sticks, glass fragments, and wood chips may lodge in tube ends or be held against the tubes by water flow. The nominal velocity of the water past the obstruction increases according to the degree of obstruction. It can be shown... 

Abrasive wear can be classified into three types. Gouging abrasion is a high stress phenomenon that is likely to be accomplished by high comprehensive stress and impact. Grinding abrasion is a high stress abrasion that pulverizes fragments of the abrasive that become sandwiched between metal faces. And erosion is a low-stress scratching abrasion. 

The small size of daughter partieles and only very small ehanges of the parent erystal size distribution during eaeh run indieate that substantial gross partiele fragmentation does not oeeur. Partiele dispersion oeeurs mainly due to erosion of the erystal surfaee in the inert solutions. 

TOF-SIMS can be applied to identify a variety of molecular fragments, originating from various molecular surface contaminations. It also can be used to determine metal trace concentrations at the surface. The use of an additional high current sputter ion source allows the fast erosion of the sample. By continuously probing the surface composition at the actual crater bottom by the analytical primary ion beam, multi element depth profiles in well defined surface areas can be determined. TOF-SIMS has become an indispensable analytical technique in modem microelectronics, in particular for elemental and molecular surface mapping and for multielement shallow depth profiling. 

One may observe that in plasma deposition of a-C(N) H films, as the nitrogen precursor gas partial pressure is increased, the bombardment of the film surface by N2 ions will certainly occur. As this situation was shown to generate carbon erosion, and evolution of CN molecules, there is no reason to believe that CN fragments from the plasma would survive the bombardment, resting attached to the film. 

Fig. 30. Schematic view of rupture and erosion of particles and the typical size distribution of fragments obtained.

Fig. 35. (a) Size distributions [c (x, q)] obtained for erosion-controlled fragmentation for increasing fragmentation time (q). (b) Comparison of theoretically predicted cumulative size distribution for erosion-controlled fragmentation to experimental data (Hansen and Ot-tino, 1996a). 

Occurs even at low fragmentation numbers, and over long time scales Rate of erosion is directly proportional to the fragmentation number... 

Hansen, S., and Ottino, J. M., Agglomerate erosion A nonscaling solution to the fragmentation equation. Phys. Rev. E S3, 4209-4212 (1996a). 

Environmental Erosion is promoted by the elements - wind, rain, temperature - and by larger animals. Usually, a surface environment phenomenon, and fragments produced may biodegrade. 

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