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:
Versarien has announced its plans to enter an agreement with a large state-owned Chinese aerospace company. The Partner is said to mainly be engaged in the research, design, manufacture and operation of various aerospace systems.
The agreement details the parties' desire to collaborate and ultimately enter into a strategic cooperation covering research, development and manufacturing in order to accelerate the industrialization and market for graphene and other Versarien 2D materials, including Hexotene, in the Chinese aerospace sector. This will include exploring their uses within the fields of, amongst others, microwave and electromagnetic radiation shielding, heat dispersion coatings, 3D printing and flexible wearable devices.
Versarien has announced that it has signed a Memorandum of Understanding ("MOU") with China Tiesiju Civil Engineering Group Co Ltd. ("CTCE"), a subsidiary of China Railway Group Limited ("CRG").
CRG is one of the world's largest construction and engineering contractors and is listed on the Shanghai and Hong Kong Stock Exchanges. CTCE is specifically focused on railway, bridge, tunnel and highway infrastructure engineering. It is active in China and overseas, including in Asia, Africa, Latin America and the Middle East.
US-based graphene developer XG Sciences recently made headlines with a production expansion announcement - and an exciting deal with Ford to supply it with graphene-enhanced parts for the latest the Mustang and F-150 automobiles.
We have reached out to XGS' CEO, Philip Rose, who was kind enough to answer a few questions we had regarding the company's latest materials, plans and business.
In October 2018 Huawei announced its Mate 20 X smartphone, which is a large gaming smartphone that adopts a “graphene film cooling technology” for heat management purposes. Huawei now started shipping the Mate 20 X in China and it can be bought in the US starting at $790 (note: affiliate link to Amazon).
Huawei states that its Mate 20 X features Huawei Supercool - "the world’s first liquid multi-dimensional cooling system with Vapor Chamber (VC) and Graphene Film used in smartphones". It reportedly conducts heat away fast, keeping the device cool even under heavy loads (as the device is touted as a gaming device).
Grahope New Materials (GNM), China-based developer of graphene applications with a special focus on heating applications, has commercialized and is selling several types of graphene-based products, ranging from home textiles and clothes to therapeutic products.
GNM has kindly sent Graphene-Info a pair of "Graphene Physical Therapy Eye Mask" for review. The Company states on its website that the mask "effectively soothes the eyes and alleviates eye fatigue", by heating rapidly and generating "far infra-red waves that are similar to the human body's".