Graphite had already been extensively studied. German physicist Martin Dienwiebel was therefore extremely surprised when he discovered a completely new effect in this well-known lubricant. During research into the frictional properties of the material, he discovered that the frictional force almost completely disappeared at a certain moment.
Dienwiebel only intended to test the new friction force microscope he had developed. The Tribolever is a raster microscope which can measure frictional forces of just a few picoNewtons in three spatial dimensions. With his new instrument Dienwiebel first of all studied the frictional properties of graphite.
Graphite consists of carbon atoms arranged in layers one above another. The carbon atoms in a graphite layer form a sort of undulating landscape, which is similar to an egg box. The different layers can slide over each other. However, resistance can occur during the sliding process if the hills of one layer fit exactly into the valleys of another layer. Yet if the two layers are rotated with respect to each other, there are always points within the contact surface where the hills touch each other. As a result of this the two layers cannot collapse into each other and the resistance is overcome. The researcher has termed this phenomenon superlubrication.
Nalinie Moerlie | alfa
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A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.
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