NUS researchers offer solution in fight against fake <span style='color:red'>graphene</span>
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NUS researchers offer solution in fight against fake graphene

　　A lack of quality control in the graphene market has led to inferior products being touted as high-grade. In response, a National University of Singapore (NUS) research team has developed what it says is a reliable way to test graphene quality.　　Ever since the isolation of graphene was first achieved in 2004, there has been an explosion in graphene-related research and development, with hundreds of business opportunists producing graphene to capitalise on this rapidly expanding industry. However, a new study by researchers from the NUS has uncovered a major problem – a lack of production standards has led to many cases of poor quality graphene from suppliers. Such practices can impede the progress of research that depend fundamentally on the use of high-quality graphene.　　“It is alarming to uncover that producers are labelling black powders as graphene and selling them for top dollar, while in reality, they contain mostly cheap graphite," said Professor Antonio Castro Neto, Director of the NUS Centre for Advanced 2D Materials, who led the study.　　"There is a strong need to set up stringent standards for graphene characterisation and production to create a healthy and reliable graphene market worldwide."　　Graphene is typically produced by exfoliating graphite into a powder, submerging this into a liquid, and then separating the tiniest graphene flakes by using sound energy to vibrate the mixture. The aim of this synthesis is to produce the thinnest graphene possible. Pure graphene would be just one atomic layer thick, however the International Organization for Standardisation (ISO) states that stacks of graphene flakes up to ten layers thick can still behave like graphene.　　With this in mind, Prof Castro Neto and his team set out to develop a systematic and reliable method for establishing the quality of graphene samples from around the world. They were able to achieve this by using a wide range of analytical techniques and tested samples from many suppliers.　　Upon analysing samples from over 60 different providers from the Americas, Asia and Europe, the NUS team discovered that the majority contained less than 10 per cent of what can be considered graphene flakes. The bulk of the samples was graphite powder that was not exfoliated properly.　　“Whether producers of the counterfeit graphene are aware of the poor quality is unclear. Regardless, the lack of standards for graphene production gives rise to bad quality of the material sold in the open market. This has been stalling the development of the future applications,” elaborated Prof Castro Neto.　　Graphite powder and graphene have wildly different properties, so any research conducted under the pretext that the sample was pure graphene would give inaccurate results. In addition, just one of the samples tested in the study contained more than 40 per cent of high-quality graphene. Some samples were even contaminated with other chemicals used in the production process. These findings mean that researchers could be wasting valuable time and money performing experiments on a product that is falsely advertised, says NUS.　　“This is the first ever study to analyse statistically the world production of graphene flakes. Considering the important challenges related to health, climate, and sustainability that graphene may be able to solve, it is crucial that research is not hindered in this way,” explained Prof Castro Neto.　　With this discovery, and the development of a reliable testing procedure, graphene samples may now be held to a higher standard.　　“We hope that our results will speed up the process of standardisation of graphene within ISO as there is a huge market need for that. This will urge graphene producers worldwide to improve their methods to produce a better, properly characterised product that could help to develop real-world applications,” said Prof Castro Neto.　　In addition, NUS believes that testing graphene using a universal and standardised way has the potential to ensure easy quantitative comparisons between data produced from different laboratories and users around the world.
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Release time：2018-12-03 00:00 reading：8535 Continue reading>>
New process to 3D print <span style='color:red'>graphene</span> developed
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New process to 3D print graphene developed

　　Researchers from Virginia Tech and Lawrence Livermore National Laboratory have developed an innovative method to 3D print graphene, which until now has only been available in 2D sheets or basic structures.　　According to engineers at Virginia Tech, they have been able to 3D print graphene objects at a resolution and an order of magnitude greater than ever before, unlocking the ability to, in theory, create any size or shape of graphene.　　Graphene is extremely strong and has high thermal and electricity conductivity. 3D printed graphene objects would be welcomed by a number of industries, including batteries, aerospace, separation, heat management, sensors, and catalysis.　　A single layer of carbon atoms organised in a hexagonal lattice, when graphene sheets are neatly stacked on top of each other and formed into a three-dimensional shape, it becomes graphite. Because graphite is simply packed-together graphene, it has fairly poor mechanical properties. But if the graphene sheets are separated with air-filled pores, the three-dimensional structure can maintain its properties. This porous graphene structure is called a graphene aerogel.　　"Now a designer can design three-dimensional topology comprised of interconnected graphene sheets," said Xiaoyu "Rayne" Zheng, assistant professor with the Department of Mechanical Engineering in the College of Engineering and director of the Advanced Manufacturing and Metamaterials Lab. "This new design and manufacturing freedom will lead to optimisation of strength, conductivity, mass transport, strength, and weight density that are not achievable in graphene aerogels."　　Zheng, also an affiliated faculty member of the Macromolecules Innovation Institute, has received grants to study nanoscale materials and scale them up to lightweight and functional materials for applications in aerospace, automobiles, and batteries.　　Researchers have printed graphene using an extrusion process, but that technique could only create simple objects.　　"With that technique, there's very limited structures you can create because there's no support and the resolution is quite limited, so you can't get freeform factors," Zheng explained. "What we did was to get these graphene layers to be architected into any shape that you want with high resolution."　　To create these complex structures graphene oxide sheets, a precursor to graphene, is crosslinked to form a porous hydrogel. Breaking the graphene oxide hydrogel with ultrasound and adding light-sensitive acrylate polymers, micro-stereolithography is used to create a solid 3D structure with the graphene oxide trapped in the long, rigid chains of acrylate polymer. The 3D structure is then placed in a furnace to burn off the polymers and fuse the object together, leaving behind a pure and lightweight graphene aerogel.　　"We've been able to show you can make a complex, three-dimensional architecture of graphene while still preserving some of its intrinsic prime properties," Zheng said. "Usually when you try to 3D print graphene or scale up, you lose most of their lucrative mechanical properties found in its single sheet form."
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Release time：2018-09-18 00:00 reading：2826 Continue reading>>

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