Graphene is the thinnest, strongest material known to man. Graphene is a single layer of carbon atoms, tightly bound in a honeycomb crystal lattice that’s the basic structural element of industrial and manufacturing applications of carbon, including graphite, charcoal, and carbon nanotubes.
Graphene applications include lightweight, thin, flexible electric and photonics circuits, solar cells, as well as an input for products with applications in medical, chemical, and industrial processes.
Graphene is a form of carbon that consists of a single layer of atoms in a two-dimensional hexagonal lattice. Each vertex of the lattice is made up of one atom. It is the basic structural element of other isotopes including graphite, charcoal, carbon nanotubes and fullerenes. It has a unique set of properties. For its thickness, it is approximately 100 times stronger than steel. It conducts heat and electricity efficiently while being almost transparent.
For centuries, graphene may have been produced unknowingly in small quantities through the use of pencils and other similar graphite applications. It was isolated and characterised in 2004. By 2012, the global market for graphene was reported to have reached $9 million, with most of the R&D demand in semiconductor, electronics, battery energy and composite applications. There are now many different methods of producing graphene. Scientists have found that the first method of producing single and few-layer graphene is mechanical exfoliation using tape technology. This article looks at some of the more popular methods of manufacturing graphene, but new methods are still being researched.
How is graphene made from graphite?
Graphite is one of three naturally occurring isomers or forms of carbon. The other two are amorphous carbon and diamond. As graphene is found in graphite, usable graphene can be made by obtaining graphite and applying one of the following methods to it.
One common method is called chemical vapour deposition (CVD). Carbon atoms are extracted from a carbon-rich source by reduction. One problem with this technique is finding a suitable substrate on which to grow the graphene layer, which is complex, and an effective method of removing the graphene layer from the substrate without damaging or modifying the atomic structure of the graphene is still being developed.
Other methods of making graphene are: growth from a stable carbon source (using thermal engineering), cutting carbon nanotubes, carbon dioxide reduction and graphite oxide reduction. Reduction uses heat generated by atomic force microscopy or lasers to reduce graphite oxide to graphene. It has received some publicity due to the lowest production costs. However, the quality of graphene produced so far is below the theoretical potential and has not yet been perfected.
Graphene exfoliation
Exfoliation is considered to be the method for producing graphene with the lowest number of defects and the highest electron mobility. There are various methods of exfoliating graphite in order to produce graphene. Adhesive tape is one of the more commonly used methods. It has been used to split graphite into graphene. Obtaining a single layer of graphene usually requires multiple exfoliation steps, each of which produces a smaller layer of slices until only one layer remains. After exfoliation, the flakes are placed on a silicon wafer. Microcrystals larger than one millimetre and visible to the naked eye can be obtained using this method of peeling with tape.
By using a liquid medium to disperse the graphite, graphene can be produced by sonication, i.e. the application of acoustic energy to stir up the behaviour of the particles. Graphene is also separated from the graphite by centrifugation. The graphene content manufactured by this method is very low, as there is nothing to prevent the sheets from restacking. The addition of surfactant to the solvent prior to sonication prevents restacking and produces a higher concentration of graphene, but the removal of the surfactant requires chemical treatment.
The following is a brief step-by-step guide on how to make injection moulded parts from graphene:
1. Graphene preparation: Firstly, high-quality graphene material needs to be prepared. Common preparation methods include chemical vapour deposition, mechanical exfoliation and chemical exfoliation. Choose the method that suits your experimental conditions and needs for preparation.
2. Preparation of graphene-reinforced composites: To improve the mechanical properties of graphene, graphene can be prepared with base materials such as polymers to form graphene-reinforced composites. This can be achieved by homogeneously dispersing graphene into a polymer matrix and performing steps such as mixing, dispersing and compounding.
3. Mould design: The design and manufacture of a suitable injection mould according to the desired shape and size of the injection moulded part. Injection moulds are usually made of metal and are able to withstand high temperatures and pressures in the injection moulding process.
4. Injection moulding: The graphene-reinforced composite is heated to a molten state and the molten material is injected into the injection mould. During the injection moulding process, the thermal conductivity of graphene helps to transfer heat evenly, allowing the injection moulded part to be filled and cooled uniformly.
5. Cooling and curing: During the injection moulding process, the molten material cools rapidly and cures in the mould to the desired shape. The control of the cooling time is essential to ensure the quality of the injection moulded part.
6. Mould release and processing: Once the injection moulding process is complete, the injection moulded part can be removed from the mould. Further processing, such as trimming the edges, polishing the surface, etc., may be required, depending on the need.
It is important to note that the process of making injection moulded parts from graphene is complex and requires highly sophisticated equipment and process control. In addition, the cost of graphene is high and its application in practical production is still in the research and development stage. Therefore, adequate experiments and process optimisation are required to ensure the performance and reliability of graphene injection moulded parts prior to practical application.
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