Investigadores del Instituto de Ciencias Industriales de la Universidad de Tokio están utilizando grafito purificado con isótopos para estudiar el fenómeno del flujo de calor como fluidos, lo que podría conducir a nuevos dispositivos de disipación de calor para la electrónica. Crédito: Instituto de Ciencias Industriales, Universidad de Tokio

Los investigadores descubrieron que el calor puede moverse como fluidos en el grafito purificado bajo condiciones específicas, lo que resulta en una eliminación de calor más eficiente en los dispositivos electrónicos. Se ha observado que este fenómeno, llamado «flujo de fonones de Poiseuille», es más del doble de la conductividad térmica del grafito natural y tiene aplicaciones potenciales en teléfonos inteligentes, computadoras y LED.

Científicos del Instituto de Ciencias Industriales de la Universidad de Tokio estudiaron el flujo de energía térmica en cintas de grafito purificado y demostraron que el calor puede moverse como un líquido, en lugar de propagarse al azar, bajo ciertas condiciones. Este trabajo puede eliminar el calor de manera más eficiente de los dispositivos electrónicos, incluidos los teléfonos inteligentes, las computadoras y las luces LED.

Antes de la comprensión moderna de la termodinámica, los científicos a veces pensaban en el calor como un fluido llamado calórico. Sin embargo, ahora sabemos que el calor es en realidad la energía cinética aleatoria que poseen los átomos o moléculas en vibración que componen la materia. A veces, las vibraciones pueden considerarse partículas de la física llamadas fonones, que son los principales contribuyentes a la conducción del calor.[{» attribute=»»>semiconductors. In a surprising twist, in certain materials like graphite the phonons may indeed behave in a manner very similar to a fluid. However, this theory has remained relatively obscure.

Now, a team of researchers led by the Institute of Industrial Science at The University of Tokyo has used theoretical and experimental results to better understand the fluid-like nature of phonons. They show that when a sample of graphite is made from isotopically pure carbon, meaning that only carbon-12 atoms are present, heat can be conducted much more rapidly, almost like water flowing through a pipe. This was termed “phonon Poiseuille flow,” based on the theory of viscous fluids flowing in a closed tube. The effect was strongest in graphite at a temperature of about 90 Kelvin. However, natural graphite contains about 1% other isotopes of carbon, particularly carbon-13, which limits this effect in natural samples.

“Our study clarified the theoretical criteria for the formation of phonon Poiseuille flow in graphite, a material that shows strong anisotropy, which had not been clear before,” lead author Dr. Xin Huang says. Graphite, also known as pencil lead, is very inexpensive and easy to produce. As a result, it is already being used for heat dissipation in some electronic devices that produce a lot of waste energy during operation. Using purified graphite that had at most 0.02% carbon-13, the team was able to observe a heat conductivity that was more than double the value of natural graphite. The fact that this enhancement only occurred over a specific temperature range was evidence that fluid-like collective motion of phonons was the mechanism.

“In conventional Poiseuille flow, the velocity is highest near the center, which is what we propose happens with the phonons in our experiments,” senior author Professor Masahiro Nomura says. In addition to graphite, this phenomenon has also been observed in solid helium and black phosphorus. Theoretically, this phenomenon is also possible even at room temperature. This work can help keep sensitive computer processors cool, even as they increase their density inside devices.

Reference: “Observation of phonon Poiseuille flow in isotopically purified graphite ribbons” by Xin Huang, Yangyu Guo, Yunhui Wu, Satoru Masubuchi, Kenji Watanabe, Takashi Taniguchi, Zhongwei Zhang, Sebastian Volz, Tomoki Machida and Masahiro Nomura, 19 April 2023, Nature Communications.
DOI: 10.1038/s41467-023-37380-5

The work is published in Nature Communications as “Observation of phonon Poiseuille flow in isotopically purified graphite ribbons” (DOI: 10.1038/s41467 023 37380 5).