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⋅K−1 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.
The latest graphene thermal news:
South Korea-based Graphene Square, developer and distributor of graphene materials and films, has announced that it is preparing for an IPO to fuel global expansion. It will select the underwriter this year and plans its Kosdaq listing in 2022 through the Technology Special Listing program, a system introduced in 2005 to allow promising startups to list the local bourse based on a technology evaluation conducted by Korea Exchange-designated institutions.
Graphene Square’s competitive edge is said to be found in its proprietary chemical vapor deposition (CVD) method used for the production of graphene. The method is based on the research of Professor Hong Byung-hee of Seoul National University on the synthesis of large-area graphene. In fact, Graphene Square itself was established in 2012 as a spin-off of chemistry professor Hong Byung-hee’s lab at Seoul National University.
Our friend Dr. Khasha Ghaffarzadeh, a well respected graphene market analyst, is launching a new service called TechBlick that is a subscription-based online and all-year round event focused on advanced materials such as graphene, 2D materials, CNTs, boron nitrides, QDs, and more.
Graphene-Info partnered with TechBlick, to provide our readers an exclusive 25% discount on the TechBlick subscription. We took advantage of this launch to discuss the graphene market and industry with Dr. Ghaffarzadeh and also discuss the new service.
Hello Kasha. How do you see the graphene market shaping up in 2021?
I have closely followed and examined the graphene industry for a full decade. The landscape has certainly changed. Many companies have come and gone, and many once considered revolutionary applications are now ruled out, but overall, the industry is now at a tipping point.
We think 2021/2022 will be a turning point, setting the industry on its growth path, despite the delays caused these past 12 months due to Covid. For some, these delays have been painful as projects were pushed back or partners or customers dropped graphene to focus on other core areas. Many undershot their growth expectations, and some had difficult cash flow situations.
STEK Automotive, a U.S-based film technology developer, has launched a premium nano-ceramic window film, NEX, that contains graphene as well as tungsten and antimony tin oxide.
The graphene-enhanced nano-ceramic window films are said to provide crystal clarity as well as UV and glare reduction, and is said to effectively prevent heat from reaching vehicle interiors. Its metal-free structure also reportedly guarantees signal freedom, ensuring the continuous connectivity of all electronic devices. By blocking up to 95% of visible interior light, NEX additionally offers exceptional passenger privacy, while its 92% sun glare reduction rate dramatically reduces eye strain. With a 98% IR rejection rate, NEX's steady regulation of UV transmittance keeps windows cool, significantly reducing the level and intensity of deterioration.
Billabong's Furnace range of wet-suites, enhanced with graphene materials, are now shipping. Billabong is offering a full range of Furnace suits which are all made from recycled nylon fibers infused with graphene to increase warmth and performance.
The suits are now shipping globally, starting at around $175 for the Men's 3/2 Absolute Back Zip Wetsuit.
Researchers at Sweden-based Chalmers University of Technology, in collaboration with researchers in China and Italy, have found that graphene-based heat pipes can help solve the problems of cooling electronics and power systems used in avionics, data centers, and other power electronics.
Electronics and data centers need to be efficiently cooled and rid of excess heat in order to function properly. Currently, heat pipes are usually made of copper, aluminum or their alloys. Due to the relatively high density and limited heat transmission capacity of these materials, heat pipes are facing severe challenges in future power devices and data centers.