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:
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.
A team of researchers from the University of Oxford, Delft University and IBM Zurich has demonstrated that graphene can be used to build sensitive and self-powering temperature sensors. The findings could pave the way for the design of highly sensitive thermocouples, which could be integrated in nanodevices and even living cells.
On-chip temperature sensors that are scalable, reliable and installable into nanodevices are essential for future thermal management in CPUs. By determining the local heating in certain segments of a CPU through the distribution of temperature monitors along critical points, feedback can be provided to a control system. In response, thermal management could allow for the redistribution of the thermal load through spot cooling or load distribution, for instance among different computing cores, avoiding hot spots and enabling a longer device lifetime as well as saving energy. Such temperature sensors should have a small footprint, high accuracy, consume a minimum amount of power and be compatible with established nanofabrication techniques.
Huawei has launched its Huawei P40 flagship phone family, that includes three different devices: the Huawei P40, Huawei P40 Pro and, a new addition to the line-up for 2020, the Huawei P40 Pro Plus.
After many rumors about this line sporting a graphene battery - which were later disproved - it appears that Huawei's new P40 phones are using a graphene film cooling technology for heat management purposes (Huawei's SuperCool system), much like the Mate 20X and P30 line that preceded the P40.
Researchers from Swinburne University developed a graphene-based highly efficient solar absorbing film that absorbs sunlight with minimal heat loss. The film rapidly heats up in an open environment and has great potential in solar thermal energy harvesting systems - in addition to other applications such as thermophotovoltaics (directly converting heat to electricity), solar seawater desalination, light emitters and photodetectors.
This is the 2nd-generation material developed by the same group - now with a thickness of only 30 nm and improved performance and longer lifetime. The researchers have now created a first prototype and also suggest a scalable low-cost manufacturing process.