Abstract
Impact fragmentation can be used to disperse nanoparticle-agglomerates. While the fragmentation of openly structured (fractal dimension Df < 2) agglomerates during perpendicular impaction was the subject of several investigations, the fragmentation during oblique impaction is not experimentally investigated so far. During oblique impaction a tangential velocity component acts on the agglomerates leading to an increased fragmentation for the investigated agglomerate structures (with Df = 1.6, 1.8, 2.3, 2.6 and 3.0). For the agglomerates with Df = 1.6. 1.8, 2.3 and 2.6 the degree of fragmentation can be described with the Weibull-statistics using the tangential impact velocity. This shows that the fragmentation during oblique impaction is determined by the tangential velocity component. The reason for the differing behavior of spherical agglomerates could not be elucidated but it is hypothesized, that a transition from sliding to rolling during the impact occurs affecting the fragmentation behavior.The breakage pattern is obtained by analyzing the fragment size distribution as a function of the impact energy. For agglomerates with fractal dimensions of Df = 1.6, 1.8, 2.3 and 2.6 a broad size distribution is observed containing small clusters/primary particles, bigger fragments and intact agglomerates at low impact energies. Increasing the impact energy shifts the whole fragment size distribution to smaller sizes. A nearly total disintegration at high impact energies is reached. The spherical agglomerates fracture into nearly equal sized fragments resulting in a narrower size distribution, which is shifted to smaller sizes at higher impact energies.
Published Version
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