Tag Archives: Sebastian Volz

Dissipating heat with graphene-based film

As the summer approaches here in the Northern Hemisphere I think longingly of frost and snow and so readers may find more than the usual number of stories about ‘cooling’. On that note, Chalmers Technical University (Sweden) is announcing some new research into cooling graphene-based films, from an April 29, 2016 news item on ScienceDaily,

Heat dissipation in electronics and optoelectronics is a severe bottleneck in the further development of systems in these fields. To come to grips with this serious issue, researchers at Chalmers University of Technology have developed an efficient way of cooling electronics by using functionalized graphene nanoflakes. …

“Essentially, we have found a golden key with which to achieve efficient heat transport in electronics and other power devices by using graphene nanoflake-based film. This can open up potential uses of this kind of film in broad areas, and we are getting closer to pilot-scale production based on this discovery,” says Johan Liu, Professor of Electronics Production at Chalmers University of Technology in Sweden.

An April 29, 2016 Chalmers Technical University press release (also on EurekAlert), which originated the news item, describes the work in more detail,

The researchers studied the heat transfer enhancement of the film with different functionalized amino-based and azide-based silane molecules, and found that the heat transfer efficiency of the film can be improved by over 76 percent by introducing functionalization molecules, compared to a reference system without the functional layer. This is mainly because the contact resistance was drastically reduced by introducing the functionalization molecules.

Meanwhile, molecular dynamic simulations and ab initio calculations reveal that the functional layer constrains the cross-plane scattering of low-frequency phonons, which in turn enhances in-plane heat-conduction of the bonded film by recovering the long flexural phonon lifetime. The results suggested potential thermal management solutions for electronic devices.

In the research, scientists studied a number of molecules that were immobilized at the interfaces and at the edge of graphene nanoflake-based sheets forming covalent bonds. They also probed interface thermal resistance by using a photo-thermal reflectance measurement technique to demonstrate an improved thermal coupling due to functionalization.

“This is the first time that such systematic research has been done. The present work is much more extensive than previously published results from several involved partners, and it covers more functionalization molecules and also more extensive direct evidence of the thermal contact resistance measurement,” says Johan Liu.

Here’s a link to and a citation for the paper,

Functionalization mediates heat transport in graphene nanoflakes by Haoxue Han, Yong Zhang, Nan Wang, Majid Kabiri Samani, Yuxiang Ni, Zainelabideen Y. Mijbil, Michael Edwards, Shiyun Xiong, Kimmo Sääskilahti, Murali Murugesan, Yifeng Fu, Lilei Ye, Hatef Sadeghi, Steven Bailey, Yuriy A. Kosevich, Colin J. Lambert, Johan Liu, & Sebastian Volz. Nature Communications 7, Article number: 11281  doi:10.1038/ncomms11281 Published 29 April 2016

This is an open access paper.

Feel the vibe on Nanophonics Day

Officially, Nanophonics Day was held on May 26, 2014 but it’s never too late to appreciate good vibrations. Here’s more about the ‘day’ and nanophonics from a May 27, 2014 news item on Azonano (Note: A link has been removed),

The Nanophononics Day, collocated with the European Materials Research Society Spring Meeting (Lille, 26-30 May), aims to raise awareness about this emergent research area and the EUPHONON Project. ICREA Prof Dr Clivia Sotomayor, Group Leader at ICN2, coordinates this initiative.

A phonon is a collective excitation of atoms or molecules, a vibration of matter which plays a major role in physical properties of solids and liquids. Nanophononics is the science and engineering of these vibrations at the nanometre scale. Applications of the knowledge generated in the field might include novel devices aiming to decrease the power consumption for a low-power information society. It also includes phonon lasers and phenomena involving ultra-fast acoustic processes, or exceeding the limits of mass and pressure detections in membranes which might have an impact in safety and technology standards. Nanophononics links classical and quantum physics and translates this knowledge into everyday applications.

A May 26, 2014 Institut Català de Nanociència i Nanotecnologia (ICN2) news release, which originated the news item, provides more details about European research into nanophonics,

The EUPHONON project aims to amalgamate the activities on phonon science and technology in Europe to establish a strong community in this emerging research field. It started in November 2013, coordinated by Prof. Sebastian Volz from CNRS – École Central Paris. ICREA Prof Dr Clivia M Sotomayor Torres, Phononic and Photonic Nanostructures (P2N) Group Leader at the Institut Català de Nanociència i Nanotecnologia (ICN2), is among the 7 members of the consortium. She is the coordinator of the Nanophononics Day, intended to raise awareness about this emergent research area and the EUPHONON Project.

The Nanophononics Day is celebrated in May 26th 2014, collocated with Symposium D of the European Materials Research Society (E-MRS) Spring Meeting 2014 in Lille, entitled “Phonons and Fluctuation in Low Dimensional Structures” and with ICREA Prof Dr Clivia M Sotomayor Torres again among its organizers. It is probably the largest nanophononic event in Europe and a perfect context for a lively discussion about the most recent theoretical and experimental findings.

The Nanophononics Day includes conferences by leading scientists about recent breakthroughs in nano-scale thermal transport and how the recent achievements constitute solid base for nanophononics. Prof Gang Chen (MIT, USA) and Prof Olivier Bourgeois (CNRS Inst. Neel) will cover phonons in solid materials while phonons in biological matter will be addressed by Prof Thomas Dehoux (University of Bordeaux). Experimental methods using scanning probes will be illustrated by Prof Oleg Kolosov (Lancaster University) and Prof Severine Gomez (University of Lyon).

I wish you a belated Happy Nanophonics Day!