2023-06-21 04:00:02
Researchers from the international LIMMS laboratory and the University of Tokyo have identified the conditions under which heat can flow like a fluid through graphite. These results, which make it possible to envisage highly efficient heat removal devices, are published in the journal Nature Communications. a) Hydrodynamic flow of phonons in purified graphite, heat flux showing a characteristic parabolic profile (red arrows).
b) Scanning electron microscopy images of graphite ribbons of different widths.
c) Diagram of the contactless measurement of thermal conductivity by a Time-domain thermoreflectance (TDTR) technique, using an excitation laser beam (pump) and a measurement beam (probe).
© LIMMS.
Under certain conditions, heat can propagate through a material by behaving like a liquid: phonons – the particles associated with the propagation of vibrations in the network crystalline – flow like a fluid in a pipe. But this hydrodynamic flow of phonons was still poorly understood by the theory, and difficult to confirm experimentally. Published in Nature Communications, a theoretical study and experimental carried out by the Laboratory for Integrated Micro Mechatronics Systems (LIMMSCNRS/University of Tokyo) and the Institute of industrial science of the’UniversitĂ© of Tokyo makes it possible to better understand this phenomenon, and to elucidate the conditions in which it occurs.
The researchers studied the propagation of heat in graphite, a material already identified as being able to give rise to a hydrodynamic flow of phonons. Specifically, they used purified graphite, which contains only 0.02% of the carbon-13 isotope – compared to 1.1% in natural graphite. Indeed, the theoretical model predicts that the hydrodynamic flow of phonons is destroyed by their interaction with the C13 isotope. There geometry of the material also plays a key role in the occurrence of the phenomenon.
To experimentally confirm the predictions of the theoretical model, graphite micro ribbons were fabricated, 30 microns long and 5.5 microns maximum width. Samples were made in natural graphite and in purified graphite. By taking measurements over a wide range of temperaturefrom 10 K (-263°C) to 300 K (27°C), the researchers demonstrated that the conductivity thermal purified graphite could reach a value twice that of natural graphite. The hydrodynamic flow regime is observed in ribbons up to 90 K.
These results could eventually lead to very efficient heat removal devices, for example to cool the “hot spots” of increasingly dense micro or nanoelectronic circuits. Provided materials are found in which the hydrodynamic flow of heat occurs at temperatures compatible with the intended applications. For their part, the researchers are continuing the study with purified graphite, in order to deepen different aspects of the analogy with the flow of a fluid, and are interested in other types of specific phonon propagation regimes. in materials.
References
Observation of phonon Poiseuille flow in isotopically purified graphite ribbons
Xin Huang, Yangyu Guo, Yunhui Wu, Satoru Masubuchi, Kenji Watanabe, Takashi Taniguchi, Zhongwei Zhang1, Sebastian Volz, Tomoki Machida & Masahiro Nomura.
Nature Communications, 19 avril 2023.
Article searchable on the basis of open archives Arxiv
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