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:
MSI, a global computer hardware manufacturer, has revealed that it is utilizing graphene composites in its RTX 3000 series GPUs.
It seems that the graphene composite parts are replacing the backplate, traditionally made of plastic, and provide greater heat dissipation performance and better stiffness to handle the weight of the entire card while still weighing less than plastics.
The International Graphene Awards (IGA) was initiated by the Chinese Graphene Industry Association (CGIA) in collaboration with 50 graphene experts from all over the world.
In 2020 the IGA committee offered 5 different awards: for best graphene products, best graphene firm, industry promotion, industry demonstration and honorary award for the most contribution people in graphene industry.
Researchers led by Professor Tony McNally, from WMG, at the University of Warwick, in partnership with Senergy Innovations, have launched the first nanomaterial enabled all polymer solar thermal cell. This achievement was supported by funding from BEIS (Department for Business, Energy & Industrial Strategy).
The thermal properties of the polymers that were used were modified to enable heat from sunlight to be transferred with high efficiency to heat water in a low cost and sustainable way. The modular design of the cells reportedly allows for the rapid construction of a solar thermal cell array on both domestic and industry roofing.
Xiaomi recently launched a crowdfunding campaign for its new graphene-based smart heating mattress. The graphene layer in the mattress is used to generate heat, and according to the company the graphene enables uniform heating without the overheating or overcooling problems that are inherent in traditional heating mattress.
Xiaomi offers two kinds of graphene blankets - a single mattress at 299 Yuan (about $43) and a double one at 499 Yuan (about $73). The crowdfunding campaign has already attracted over 3,500 supporters and raised over 1.5 million Yuan.
Haydale has announced that, following the announcement on March 2020 regarding its graphene nano-platelets having been incorporated into iCraft’s cosmetic face mask sheet, a contract is now in place for 1 metric tonne of graphene nano-platelets (GNP-02-STD) in the first year, 2 metric tonnes in the second year, and three metric tonnes in the third year. This is an exclusive agreement for the mask application within the APAC region, excluding Thailand.
Haydale has signed a worldwide exclusivity contract to supply functionalized graphene nano-platelets for use in these sheet masks that are face-shaped sheet fabrics which utilize the thermal and electrical conductivity of graphene to help the skin absorb its contents through bioelectric currents. In addition, Haydale said it has completed a GBP3.0 million equity raise.