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:
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.
Xiaomi's upcoming smartphone, the high-end Mi 10 Ultra, will reportedly be sporting "the first mass-produced 120W graphene battery".
Xiaomi claims the 4,500mAh “graphene-based lithium-ion” battery packs 1,000 times greater conductivity than traditional “carbon black” batteries. The brand was also quoted as saying that the battery remained at over 90% capacity after 800 charge and discharge cycles.
Huawei continues the use of graphene heat dissipation technology, which started with the use of graphene film in Huawei Mate 20X and continues with later versions, with its Huawei MatePad Pro 5G launched earlier in 2020. The MatePad is a 5G tablet, equipped with ultra-thick 3D graphene heat dissipation technology.
For this technology, graphene is used as raw material, in the form of oriented thermal conductive films embedded in several layers of graphene with good mechanical properties, high thermal conductivity, lightweight, thin material, and high flexibility.
U.S-based motorcycle maker Indian Motorcycle has launched a new graphene-based technology Called ClimaCommand Classic Seat, which aims to deliver both heating and cooling to riders and passengers. The thermo-electric technology reportedly raises the bar on cooling, providing a much more effective solution than HVAC convection systems.
A critical performance benefit of the ClimaCommand technology is that it actually produces a surface that’s cold to the touch, rather than merely pushing cool air through perforations in the surface in the manner that HVAC system offerings operate.
It has been reported that Honor will introduce the Honor X10 at the end of this month, and that it will feature a graphene-based cooling system.
The phone is expected to be the cheapest 5G model to come from Huawei, so it may get a little warmer than regular smartphones. Thanks to the graphene-based cooling system, the phone will have better heat protection.