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 it will be collaborating with Cadent Gas and the Energy Innovation Centre to develop graphene ink-based heaters for low-power hot water. The £135,000 three-stage project will run for an initial 15 months.
The graphene solution has the potential to offer a low-power way to heat water when there is an interruption to the gas supply. Currently, the provision of fan heaters and hot plates to vulnerable customers without a gas supply can be expensive and challenging, particularly for elderly or disabled customers.
At the recent CES event, South Korea-based Graphene Square presented its 'kitchen styler' - a transparent toaster that uses graphene.
In addition to tracking the level of toasting of the bread, the device is also said to offer 50% less power consumption and enable outdoor cooking with rechargeable batteries. The device is also foldable and expandable to dual cooking/warming plates and connects to mobile devices for recipe download/control.
realme has announced its new GT 2 series, marking the company’s first steps into the premium segment. The GT 2 series, equipped with various top-notch gear and AMOLED panels, is also said to be sporting a graphene-based cooling system.
SmartIR, a spin-out of the University of Manchester, is working on a graphene-based smart coating for satellites, to allow them to control thermal radiation on demand, depending on whether a satellite’s surface is Earth’s shadow or on the side closest to the Sun.
This graphene technology is said to be a far more optimal solution as it is lightweight, has a low power consumption, can respond quickly to temperature changes, operates across the infrared spectrum, and involves no moving parts.
Sweden-based graphene fabric developer Grafren launched a new graphene-coated textile, branded G-HEATEX. The company says that this is the world's first active heating fabric.
According to Grafren, G-HEATEX fabrics supply powerful and uniform heat, while being soft, flexible, breathable and ultralightweight.