Graphene thermal conductivity

Thermal transport in graphene is a thriving area of research, thanks to graphene's extraordinary heat conductivity properties and its potential for use in thermal management applications.

The measured thermal conductivity of graphene is in the range 3000 - 5000 W/mK at room temperature, an exceptional figure compared with the thermal conductivity of pyrolytic graphite of approximately 2000 W⋅m−1⋅K−1 at room temperature. There are, however, other researches that estimate that this number is exaggerated, and that the in-plane thermal conductivity of graphene at room temperature is about 2000–4000 W⋅m−1⋅K1 for freely suspended samples. This number is still among the highest of any known material.

Graphene is considered an excellent heat conductor, and several studies have found it to have unlimited potential for heat conduction based on the size of the sample, contradicting the law of thermal conduction (Fourier’s law) in the micrometer scale. In both computer simulations and experiments, the researchers found that the larger the segment of graphene, the more heat it could transfer. Theoretically, graphene could absorb an unlimited amount of heat.

The thermal conductivity increases logarithmically, and researchers believe that this might be due to the stable bonding pattern as well as being a 2D material. As graphene is considerably more resistant to tearing than steel and is also lightweight and flexible, its conductivity could have some attractive real-world applications.

But what exactly is thermal conductivity?

Heat conduction (or thermal conduction) is the movement of heat from one object to another, that has a different temperature, through physical contact. Heat can be transferred in three ways: conduction, convection and radiation. Heat conduction is very common and can easily be found in our everyday activities - like warming a person’s hand on a hot-water bottle, and more. Heat flows from the object with the higher temperature to the colder one.

Thermal transfer takes place at the molecular level, when heat energy is absorbed by a surface and causes microscopic collisions of particles and movement of electrons within that body. In the process, they collide with each other and transfer the energy to their “neighbor”, a process that will go on as long as heat is being added.

The process of heat conduction mainly depends on the temperature gradient (the temperature difference between the bodies), the path length and the properties of the materials involved. Not all substances are good heat conductors - metals, for example, are considered good conductors as they quickly transfer heat, but materials like wood or paper are viewed as poor conductors of heat. Materials that are poor conductors of heat are referred to as insulators.

How can graphene’s exciting thermal conduction properties be put to use?

Some of the potential applications for graphene-enabled thermal management include electronics, which could greatly benefit from graphene's ability to dissipate heat and optimize electronic function. In micro- and nano-electronics, heat is often a limiting factor for smaller and more efficient components. Therefore, graphene and similar materials with exceptional thermal conductivity may hold an enormous potential for this kind of applications.

Graphene’s heat conductivity can be used in many ways, including thermal interface materials (TIM), heat spreaders, thermal greases (thin layers usually between a heat source such as a microprocessor and a heat sink), graphene-based nanocomposites, and more.

Latest Graphene Thermal Conductivity news

G3 and Lanka Graphite enter agreement to develop graphene-enhanced products

Apr 19, 2017

Global Graphene Group (G3), a holding company for subsidiaries like Angstron Materials, has signed Heads of Agreement with Lanka Graphite, a graphite exploration company. The joint venture entity (LGR 50%, G3 50%) will develop a range of commercial graphene projects.

G3 is reportedly scaling a broad range of commercial platforms of graphene applications in several , areas like energy storage, coatings, and thermal management. Lanka Graphite will supply vein graphite product into the joint venture in addition to assisting with sourcing investment, marketing and administration. G3 proposes to supply its experience in developing IP and research grants, commercialization planning and manufacturing infrastructure.

JTX demonstrates its graphene filament LED lighting

Apr 16, 2017

JTX (officially Shandong Prosperous Star Optoelectronics Co) demonstrated its graphene-enhanced LED lighting bulbs at the Hong Kong lighting fair. These LED lighting devices use graphene coating that aid in heat dissipation and thus contribute to longer lifetime and better efficiency.

JTX graphene bulbs, Hongkong lighting fair 2017 photo

JTX is a relatively new company (established in May 2014 in China) that is involved with the entire LED lighting value chain (from LED chips and filaments to complete light bulbs). In July 2016 JTX was merged with Graphene Lighting PLC that developed the graphene lighting technology in collaboration with Manchester University and the NGI.

Graphene Handbook

Researchers from Singapore's SUTD design a graphene-based high-efficiency energy harvesting device

Apr 09, 2017

Researchers from the Singapore University of Technology and Design (SUTD) have proposed a high-efficiency energy harvesting device based on graphene electrodes and 2D transition metal dichalcogenide materials.

Graphene-TMDs TEC device image

Inspired by the concept of multilayer thermionic devices, the team designed a solid-state thermionic device using van der Waals (vdW) heterostructure sandwiched between two graphene electrodes, to achieve high energy conversion efficiency in the temperature range of 400 to 500 K. The technology enables performance (8% above) of devices comparable to or even better than state-of-art thermoelectric devices around room temperature. This novel design may boost interest in thermionic emission-based energy conversion and pave the way towards another alternative to solutions to low-grade waste heat harvesting.

Manchester U team shows the influence of pre- and post-dispersion on the properties of GNP-enhanced epoxy

Mar 23, 2017

Researchers from The University of Manchester have conducted a study that presents a review of the three steps of manufacturing graphene/epoxy nano-composites. The possible pre-treatments of nanoparticles before dispersion are introduced, and their influence on the final nanocomposite properties discussed.

SEM images of fracture surface of aligned GNP based epoxy compositeSEM images of fracture surface of aligned GNP based epoxy composite

The study stresses interesting results, among which are improvements in various characteristics via the use of GNPs. For instance, an improvement of the thermal diffusivity of 220% was seen when compared to a non-oriented GNP epoxy sample. The work demonstrates how the addition of functionalized graphene platelets to an epoxy resin will allow it to act as electrical and thermal conductor rather than as insulator. The mechanical properties of functionalized GNP/epoxy composites show improvement of the interfacial bond.