Carbon atoms can stack extremely fast and in an irregular manner. Scientists from FOM Institute DIFFER have observed this in experiments with intense bombardments of charged particles. The stacking of carbon atoms results in porous structures and is similar to the game Tetris played at the fastest level.
The stacking of the carbon atoms is indeed very similar to the game Tetris. According to the researchers, just like in the computer game the atoms have too little time to order themselves. In the plasma experiment Pilot-PSI, the beam of charged particles (plasma) is so intense that each carbon atom on the besieged surface is hit every microsecond by the incoming protons and electrons. The atoms do not have enough time to dissipate this energy. The material therefore remains in a state of flux and arranges itself in unique structures.
Ultra-rapid Tetris causes cavities
Displaced carbon atoms are quickly pushed back to the material by the plasma. The atoms preferably seek irregularities in the surface as these disturb the local electric field. The carbon atoms are deposited so quickly that they do not have time to nestle deep in the material. They therefore grow on protrusions. Consequently, just like in a game of Tetris played too fast, cavities develop in the material.
During the experiments the researchers discovered a sponge-like network of several micrometres in size that contained regular cavities at the nanoscale. As such a network has grown extremely quickly the atoms do not fit together perfectly. In the open spaces there is room for new atoms or molecules. Scientists are investigating whether they can store the greenhouse gas carbon dioxide in the open spaces. First of all though they want to allow nitrogen to pass through the material, as it bonds well with both carbon atoms and carbon dioxide gas.
The researchers can also use the extreme plasmas to test computer models for molecular dynamics. Up until now the models and the reality were always far apart. The models are simpler than the reality as otherwise the calculation time would get out of hand. The models approximate a few atoms and many collisions. And that is exactly what seems to happen in Pilot-PSI. The researchers therefore hope that they can at last bring model and reality closer together.