Volume 641, September 2020
|Number of page(s)||9|
|Section||Planets and planetary systems|
|Published online||24 September 2020|
Collisions between amorphous carbon nanoparticles: phase transformations
Physics Department and Research Center OPTIMAS, University Kaiserslautern,
2 Centro de Investigación DAiTA Lab, Facultad de Estudios Interdisciplinarios, Universidad Mayor, Santiago, Chile
3 Center for the Development of Nanoscience and Nanotechnology CEDENNA, Avda. Ecuador 3493, Santiago 9170124, Chile
4 Centro de Nanotecnología Aplicada, Facultad de Ciencias, Universidad Mayor, Santiago 8580745, Chile
5 CONICET and Facultad de Ingeniería, Universidad de Mendoza, Mendoza 5500, Argentina
Accepted: 29 July 2020
Context. Collisions of nanoparticles (NPs) occur in dust clouds and protoplanetary disks.
Aims. Sticking collisions lead to the growth of NPs, in contrast to bouncing or even fragmentation events and we aim to explore these processes in amorphous carbon NPs.
Methods. Using molecular-dynamics simulations, we studied central collisions between amorphous carbon NPs that had radii in the range of 6.5–20 nm and velocities of 100–3000 m s−1, and with varying sp3 content (20–55%).
Results. We find that the collisions are always sticking. The contact radius formed surpasses the estimate provided by the traditional Johnson-Kendall-Roberts model, pointing at the dominant influence of attractive forces between the NPs. Plasticity occurs via shear-transformation zones. In addition, we find bond rearrangements in the collision zone. Low-sp3 material (sp3 ≤ 40%) is compressed to sp3 > 50%. On the other hand, for the highest sp3 fraction, 55%, graphitization starts in the collision zone leading to low-density and even porous material.
Conclusions. Collisions of amorphous carbon NPs lead to an increased porosity, atomic surface roughness, and changed hybridization that affect the mechanical and optical properties of the collided NPs.
Key words: planets and satellites: formation / protoplanetary disks / methods: numerical
© ESO 2020
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