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Scientists devise a way to determine the viability of predicted 2D materials

Posted By Graphene Council, Friday, May 29, 2020
An international team of researchers from Russia, Sweden and South Korea has proposed a new way to test the structural stability of predicted 2D materials. The testing revealed a number of materials erroneously proposed earlier. The scholars believe that the use of the new method will further help to avoid mistakes in the development of two-dimensional nanomaterials that are in high demand in the modern world. The results were published in the international journal Physical Chemistry Chemical Physics.

The existence of two-dimensional structures, which are the thinnest films consisting of one layer of the crystal lattice of atoms, has been widely discussed since the mid 20th century. Scientists had been heatedly discussed for several decades until such possibility was proved by theoretical conclusions and confirmed experimentally later by the synthesis of graphene -- crystalline carbon with a thickness of one atom. Since then, attention to two-dimensional materials with unexpected properties -- high strength (hundreds of times stronger than metal), lightness, thermal conductivity -- has grown significantly, and today the number of experimentally obtained 2D materials comes in dozens.

It is worth noting that most of the early materials were discovered mainly by trial and error. With the advent of sufficient computer power and theoretical methods of prediction, however, scholars now are discovering materials even before their synthesis. Modern high-performance algorithms and methods can be used for mass scanning of new 2D materials among already known compounds. Moreover, with their help, we can create previously unknown materials with designed properties. Nevertheless, it is necessary to calculate the stability of such predicted materials in order to make them desired for the production and have future prospects for adopting into the reality.

'We discovered that the existing and widely used methods for checking the stability of theoretically-known 2D materials have a serious drawback, which allows bypassing the generally accepted criteria and, virtually, in some cases leads to a false prediction of the stability of a 2D material. To put it simpler, such materials merely should not exist, there is practically no chance to get them experimentally, and the discovery of such materials is just an error of the method used,' said Artyom Kuklin, a research engineer at the Laboratory for Fundamental Scientific Research, Department of Science and Innovation, SibFU.

The scholar explained that the main disadvantage of the common method applied nowadays is the model of representation of the material.

'When modelling, researchers use conditional material of some kind, which is an infinitely repeating pattern consisting of the so-called unit cells -- minimal fragments of the structure. It looks like cells recurring on a notebook sheet. Moreover, information about one cell gives information about the entire sheet. The model assumes that all these cells are rigidly interconnected and that they cannot be bent along this connection. In other words, we knowingly get a perfectly even infinite sheet, which, of course, lines up weakly with the reality,' explained Artyom Kuklin.

The authors of the study propose to disregard an infinite model of a material, but instead, to consider its portion of a finite size as an additional criterion for the stability of two-dimensional nanomaterials, as this part has no strict restrictions on the connection between separate fragments of the structure. If under these conditions, the material remains the same as it was in the periodic model, then there are no internal stresses in it. If the material significantly distorts (for example, folds up), then the internal stress in such structure will become a marker of instability, and hence realizability of this material will be dubious in reality.

'Using the proposed method, our team demonstrated the structural stability of the recently synthesized 2D material of Palladium diselenide (PdSe2) and the instability of several previously proposed two-dimensional materials with a similar structure. We consider this approach effective enough to theoretically study materials which are promising for the future technology. By the way, as for another criterion for assessing the absence of internal stresses in a 2D material, we have proposed to study its stability with respect to nanotubes of the same material. In this case, a two-dimensional material should be more stable than nanotubes.

We hope that the scientific community will turn their attention to the mentioned problem and improve the existing algorithms to avoid similar errors in the future,' summed up the researcher.

Tags:  2D materials  Artyom Kuklin  Graphene  Laboratory for Fundamental Scientific Research 

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Nanopatterning electronic properties of twisted 2D semiconductors using twist

Posted By Graphene Council, Friday, May 29, 2020
A team of researchers at the National Graphene Institute, have demonstrated that atomic lattices of slightly twisted 2D transition metal dichalcogenides undergo extensive lattice reconstruction, which can pattern their optoelectronic properties on nanometre length scale.

Since the isolation of graphene in 2004, researchers have identified a multitude of 2D materials, each with specific and often exciting properties.

More importantly, these atomically thin crystals can be stacked together, similarly to stacking Lego bricks, in order to create artificial materials with desired properties, known as heterostructures.

The mutual rotation of adjacent crystals in such heterostructures, or twist, plays an important role in their resulting properties, but so far these studies have largely been limited to graphene and hexagonal boron nitride.

In the report, published in Nature Nanotechnology, the team have described that for small twist angles atomic lattices of transition metal dichalcogenides adjust locally to form perfectly stacked bilayer islands, separated by grain boundaries which accumulates the resulting strain. Using atomic resolution transmission electron microscopy (TEM) they have demonstrated that stacking the two monolayers nearly parallel to each other (twist angle close to 0°) and anti-parallel (twist angle close to 180°) produces strikingly different periodic domain patterns.

“A fundamental understanding of the evolution of crystal structure in twisted transition metal dichalcogenides is critical to the study of their exciting electronic and optical properties and was missing in the field Astrid Weston„

The electronic properties of 2D materials are expected to depend on the local atomic stacking configuration and such periodic domain networks can open an avenue to pattern material properties with nanometre precision. To that end, the team have found that domain in nearly-parallel bilayers demonstrate intrinsic asymmetry of electronic wavefunctions previously unseen in other 2D materials.

In anti-parallel bilayers, the resulting domain structure produces strong piezoelectric textures detected by conductive atomic force microscope, which will govern motion of electrons, holes an excitons in this system.

This work demonstrates that the “twist” degree of freedom in heterostructure design can allow the creation of new exciting quantum systems, such as controllable periodic arrays of quantum dots and single photon emitters.

Astrid Weston, who authored the paper said: “A fundamental understanding of the evolution of crystal structure in twisted transition metal dichalcogenides is critical to the study of their exciting electronic and optical properties and was missing in the field.”

Dr Roman Gorbachev, who led the team said: “The twist will have ground-breaking impact on the field of 2D materials, and our work is an important milestone on this path.”

Tags:  2D materials  Astrid Weston  Graphene  National Graphene Institute  Nature Nanotechnology  Roman Gorbachev 

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Two-dimensional MXene as a novel electrode material for next-generation display

Posted By Graphene Council, Wednesday, May 27, 2020
Researchers in the US and Korea reported the first efficient flexible light-emitting diodes with a two-dimensional titanium carbide MXene as a flexible and transparent electrode. This MXene-based light-emitting diodes (MX-LED) with high efficiency and flexibility have been achieved via precise interface engineering from the synthesis of the material to the application (Advanced Materials,2020, 2000919).

Flexible displays have been developing with a high pace and the global flexible display market has been expanding quickly over the years. Development of flexible transparent conducting electrodes (TCEs) with outstanding flexibility and electrical conductivity is one of the key requirements for the next-generation displays because indium tin oxide (ITO), the conventional TCE, is brittle. Diverse materials such as graphene, conducting polymers and metal nanowires have been suggested but their insufficient electrical conductivity, low work function and complicated electrode fabrication limited their practical use.

MXenes, a new family of two-dimensional materials

MXenes, a new class of two-dimensional materials discovered at Drexel University in 2011, consist of few-atoms-thick layers of transition metal carbides or nitrides. They have shown impressive properties such as metal-like electrical conductivity and tunable surface and electronic properties, offering new possibilities to the various fields of technology. Since their discovery, their use has been explored in a number of areas, such as metal ion batteries, sensors, gas and electrochemical storage, energy devices, catalysts and medicine. MXenes have exhibited potential as flexible electrodes because of their superior flexibility. However, exploration of MXenes in flexible electrodes of optoelectronic devices just started recently because the conventional MXene films do not meet the requirements of work function and conductivity in LEDs and solar cells and can degrade when they are exposed to the acidic water-based hole injection layer (HIL).

MXene for flexible LED application

An international team of scientists from Seoul National University and Drexel University, led by Tae-Woo Lee and Yury Gogotsi focused on the surface and interface modulation of the solution-processed MXene films to make an ideal MXene/HIL system. They tuned the surface of the MXene film to have high work function (WF) by low-temperature vacuum annealing and the HIL is designed to be pH-neutral and be diluted with alcohol, preventing detrimental surface oxidation and degradation of the electrode film. The MXene/HIL system suggested by the team provides advantages to the device efficiency due to efficient injection of holes to the emitting layer by forming a nearly ideal Ohmic contact.

Using the MXene/HIL system, the team fabricated high-efficiency green organic LEDs (OLEDs) exceeding 100 cd/A, which agrees well with the theoretical maximum values and is quite comparable with that of the conventional ITO-based devices. Finally, flexible MXene-LEDs on a plastic substrate show outstanding bending stability while the ITO-LEDs could not stand the bending stress. It is the first report that demonstrates highly efficient OLEDs using a single layer of 2D titanium carbide MXene as a flexible electrode.

This progressive research is published in the prominent journal 'Advanced Materials' (IF: 25.809). The authors explain further: "The results of interface engineered MXene film and the MXene electrode-based flexible organic LEDs show the strong potential of the solution-processed MXene TCE for use in next-generation optoelectronic devices that can be manufactured using a low-cost solution-processing technology."

Tags:  Drexel University  Graphene  LED  optoelectronic  Yury Gogotsi 

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Kirigami/origami: Unfolding the new regime of advanced 3D micro-/nanofabrication with 'folding'

Posted By Graphene Council, Wednesday, May 27, 2020
3D micro-/nanofabrication holds the key to build a large variety of micro-/nanoscale materials, structures, devices, and systems with unique properties that do not manifest in their 2D planar counterparts. Recently, scientists have explored some very different 3D fabrication strategies such as kirigami and origami that make use of the science of cutting and folding 2D materials/structures to create versatile 3D shapes. Such new methodologies enable continuous and direct 2D-to-3D transformations through folding, bending and twisting, with which the occupied space can vary "nonlinearly" by several orders of magnitude compared to the conventional 3D fabrications. More importantly, these new-concept kirigami/origami techniques provide an extra degree of freedom in creating unprecedented 3D micro-/nanogeometries beyond the imaginable designs of conventional subtractive and additive fabrication.

In a new paper published in Light: Science & Applications, Chinese scientists from Beijing Institute of Technology and South China University of Technology made a comprehensive review on some of the latest progress in kirigami/origami in micro-/nanoscale. Aiming to unfold this new regime of advanced 3D micro-/nanofabrication, they introduced and discussed various stimuli of kirigami/origami, including capillary force, residual stress, mechanical stress, responsive force and focused-ion-beam irradiation induced stress, and their working principles in the micro-/nanoscale region. The focused-ion-beam based nano-kirigami, as a prominent example coined in 2018 by the team, was highlighted particularly as an instant and direct 2D-to-3D transformation technique. In this method, the focused ion beam was employed to cut the 2D nanopatterns like "knives/scissors" and gradually "pull" the nanopatterns into complex 3D shapes like "hands". By utilizing the topography-guided stress within the nanopatterns, versatile 3D shape transformations such as upward buckling, downward bending, complex rotation and twisting of nanostructures were precisely achieved.

As discussed in this review, the unprecedented micro-/nanoscale geometries created by kirigami/origami have brought about extensive potentials for the reshaping of 2D materials, as well as in biological, optical, and reconfigurable applications. Moreover, 3D transformations of emerging 2D materials (such as graphene, MoS2, MoS2, WSe2 and PtSe2), for example, were briefly introduced and the associated new electrical and mechanical properties were uncovered.

"Advanced kirigami/origami provides an easily accessible approach for the modulation of mechanical, electrical, magnetic and optical properties of existing materials, with remarkable flexibility, diversity, functionality, generality and reconfigurability", they said. "These key features clearly differentiate the facile kirigami/origami from other complicated 3D nanofabrication techniques, and make this new paradigm technique unique and promising for solving many difficult problems in practical applications of micro/nano-devices."

Furthermore, they discussed the current challenges in kirigami/origami-based 3D micro-/nanofabrication, such as the limited strategies of stimuli and reconfigurations, and the difficulties in on-chip and large-scale integration. "When these challenges are met and the advantages are fully adopted," they envisioned, "micro-/nanoscale kirigami/origami will greatly innovate the regime of 3D micro-/nanofabrication. Unprecedented physical characteristics and extensive functional applications can be achieved in wide areas of optics, physics, biology, chemistry and engineering. These new-concept technologies, with breakthrough prototypes, could provide useful solutions for novel LIDAR/LADAR systems, high-resolution spatial light modulators, integrated optical reconfigurations, ultra-sensitive biomedical sensors, on-chip biomedical diagnosis and the emerging nano-opto-electro-mechanical systems."

Tags:  2D materials  Beijing Institute of Technology  Graphene  nanofabrication  South China University of Technology 

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Researchers Obtain 2D Magnetism in Both Carbon and Polyradical Nanosheets

Posted By Graphene Council, Wednesday, May 27, 2020
Chinese scientists from High Magnetic Field Laboratory, Hefei Institutes of Physical Science reported that they have obtained edge-induced room-temperature ferromagnetism in both carbon nanosheets and two-dimension (2D) organic antiferromagnetic polyradical nanosheets.

Magnetism has broad applications in living organisms as well as in energy harvesting, data storage, and medical diagnosis. Moreover, the ability to knit such magnetic order in atomically thin flatlands would foster vast opportunities for integrated, flexible, and biocompatible devices.

According to recent studies, apart from mechanical exfoliation of bulk van der waals magnetic crystals, 2D magnetism has also been achieved by defect engineering (based on vacancies, adatoms, boundaries, and edges) in non-magnetic 2D materials.

In their first study, the researchers prepared the scalable carbon nanosheets (CNs) without magnetic impurities through a one-stepWurtz reaction and the CNs had amorphous structure with crystallized graphene nanocrystals inside.

The zigzag edges of those nanocrystals in CNs could show ferromagnetic coupling even above room temperature and yielded a saturation magnetization of ~0.22 emu/g which was 2 orders of magnitude larger than reported values in defective graphite.

Moreover, the results from both first-principle calculation and controllable experiments showed that the magnetic properties of CNs were dominated by the distance between zigzag edges.

With decreasing interedge distance from 3.6 to 0.8 nm, the ferromagnetism descended and even disappeared, implying a switch of magnetic coupling between zigzag edges from ferromagnetic to the antiferromagnetic configuration.

In their work, freestanding 2D organic magnetic polyradical (OMP) nanosheets were successfully synthesized using the polymerization of tris (2,3,5,6-tetrachloro-4-ethynylphenyl) methyl radicalsat a liquid/liquid interface.

The OMP obtained had a 2D sheet-like morphology and possessed triarylmethylradicals after polymerization, which could act as spin centers. With the magnetic exchange coupling between radicals, the OMP showed an antiferromagnetic behavior with a Neel temperature of 42.5 K.

The results were published in Journal of Physical Chemistry C and Polymer Chemistry (supplementary journal cover).

The works are supported by the National Key R&D Program of China and the National Natural Science Foundation of China.

Tags:  2D Materials  Graphene  Hefei Institutes of Physical Science  nanosheets 

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High-speed femtosecond laser plasmonic lithography of graphene oxide film

Posted By Graphene Council, Wednesday, May 27, 2020
Graphene analogues, such as graphene oxide (GO) and its reduced forms (rGO), are fascinating carbon materials due to the complementary properties endowed by the sp3-sp2 interconversion, revealing the substitutability and potential for industrialization of integrated graphene devices. Appropriate micro/nanostructural design of GO and rGO for controlling the energy band gap and surface chemical activity is important for developing strategic applications. The femtosecond laser plasmonic lithography (FPL) technology is a qualified candidate for generating the required structures due to its efficiency, high-quality, flexibility and controllability. However, as both the theoretical and experimental explorations of this method are still in their infancy, micro/nanoprocessing of graphene materials using FPL has not been realized. The feasibility of implementing the technique in practical applications is still questionable because most related studies only highlight the characteristics of the structure obtained from the processing but often ignore the complementary changes in the properties of the material itself.

In a new paper published in Light Science & Application, scientists from the State Key Laboratory of Applied Optics, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, China, and co-workers presented a high-quality, efficient and large-area periodic micro/nanoripple manufacturing (~680 nm period) and photoreduction of GO films (~140 nm thickness) on a silicon substrate by using the FPL method. Interestingly, unlike most of the reported laser-induced periodic surface structures (LIPSS) in which the pattern alignment is perpendicular to the polarization of the incident light, they are found to have the extraordinary uniform distribution with orientation parallel to each other in this case. Such a phenomenon cannot be explained by the conventional theory of LIPSS, i.e., the interference between the incident light with TM mode and the excited surface plasmon (SP) wave. The analysis demonstrated that the laser-induced gradient reduction of GO film from its surface to the interior plays a key role, and it leads to an inhomogeneous slab with the maximum dielectric permittivity (DP) at the surface and a smaller DP in the interior that allows excitation of TE-mode surface plasmons (TE-SPs) and the subsequent uncommon interference. Due to the diverse physical mechanisms involved in the laser-rGO interaction, the LIPSS formation also exhibited unique characteristics such as strong robustness against a range of perturbations. Because the microprocessing contains no assistant operations, such as chemical etching, the properties of the graphene material are retained, which allows them for optoelectronic applications. As a matter of fact, through modulation of the photoreduction degree and structural design of the rGO surface, they realized the enhanced light absorption (~ 20%), thermal radiation (> 10°C) and anisotropic conductivities (anisotropy ratio ~ 0.46) from this film material. Based on it, they designed an on-chip, broadband photodetector with stable photoresponsivity (R ~ 0.7 mA W-1) even when exposed to light with the low power (0.1 mW). The authors of the paper summarize the significance of this work as follows:

"(1) The FPL technology is used for the first time to realize the preparation of high-quality, efficient and large-scale periodic micro/nanostructures on the surface of graphene materials; (2) The physical mechanisms of the laser-material interaction involved in FPL technology is further improved; (3) Both the structural characteristics and the properties of the processed material itself are taken into account in the application of photoelectric devices."

"Compared to laser direct writing adopting the same incident laser parameters, our FPL strategy takes only ~1/14000 of the time to process a centimetre-sized sample (1×1.2 cm2). At the same time, due to the possible nonlinear optical property, the FPL strategy induces an obvious 'self-repairing' phenomenon, which can effectively guarantee the processing quality. For example, we can prepare rGO-LIPSS films on different substrates and nondestructively transfer them onto other substrates."

"Our explanation of the experimental phenomena is markedly different from most of the principles at present. This will give us a clearer understanding of the relevant physical processes and lay a solid foundation for the further development of FPL technologies."

"The structured graphene materials by FPL technology present excellent photoelectric performance. The photoresponsivity is numerically comparable to the response of the samples obtained by other reduction methods (e.g., chemical and thermal) and is much larger than that of typical photoreduced ones. The anisotropy ratio is even larger than that of some natural anisotropic crystals. Our work combines the experimental exploration with the in-depth understanding of high-speed micro/nanopatterning of the regular rGO-LIPSS, which not only benefits fundamental physics but also facilitates the practical development of graphene analogues on the industrial scale. "

Tags:  Graphene  graphene oxide  photonics 

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Battery anode agreement with Farasis Energy

Posted By Graphene Council, Wednesday, May 27, 2020

Australian battery anode provider Talga Resources Ltd is pleased to advise the Company has entered an agreement with Farasis Energy Europe GmbH (“Farasis”), a subsidiary of Farasis Energy Inc, one of the world’s leading manufacturers of lithium-ion batteries.

Talga is building a European anode production facility for lithium-ion batteries using the Company’s proprietary material technologies, wholly owned Swedish carbon source and 100% electricity from renewable energy sources. As part of the agreement between Talga and Farasis (“Agreement”), Talga will supply coated (‘active’) anode products for evaluation in Farasis batteries and assessment of potential business development opportunities, primarily in Europe.

Talga Managing Director, Mr Mark Thompson: “Following successful initial tests, we are very pleased to continue this progress in collaboration with the experienced Farasis team. Talga is making substantial progress in commercialising its European lithium-ion battery anode products, and demand is growing rapidly, particularly in the EV market. We look forward to working together with Farasis to advance our anode materials for their innovative energy storage solutions.”

Anode Market Background and Agreement Details
Talga is a developing lithium-ion battery anode producer in Sweden, utilising vertical integration and wholly owned technology to supply cost competitive and high-quality anode to European battery markets. The Company’s operations in northern Sweden use fossil free hydroelectricity, enabling Talga’s position as a low-emission leader in anode production and a secure local partner for the emerging European battery supply chain.

Europe is undergoing unprecedented growth in the demand for lithium-ion batteries, driven by the move to electric vehicles and renewable energy storage. This creates new demand for sustainable and locally sourced battery anode materials, such as Talga’s. In addition, global EV battery demand is forecast to grow 14-fold by 2030, which would require approximately 1.7 million tonnes of anode material per annum1.

Under the non-binding Agreement Talga agrees to supply Farasis with lithium-ion battery anodes in quantities as mutually agreed and required, with no contractually obligated minimum quantity, for evaluation and business development purposes. The Agreement is valid until 2024 and either party can choose to withdraw at any time via standard termination clauses, not constituting binding commercial terms. All of Talga’s intellectual property rights remain unaffected by the Agreement

The Company is unable to quantify the economic benefits to Talga arising from the Agreement at this stage. Further terms, including quantity and pricing, are subject to negotiations throughout evaluation and development, and in the event commercially binding contracts are entered into Talga will inform the market. However, Talga recognises Farasis commercial relationships, particularly with European automotive manufacturers2, to be well aligned with its developing Swedish anode business.

Tags:  Battery  energy storage  Farasis Energy Europe GmbH  Graphene  Li-ion batteries  Mark Thompson  Talga Resources 

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First Graphene’s Ability to Supply High-Quality Graphene at Volume Secures a Supply Contract

Posted By Graphene Council, Wednesday, May 27, 2020
First Graphene Ltd, the leading global producer of advanced graphene products, has signed an exclusive supply agreement with planarTECH (Holdings) Ltd, a global leader in graphene process equipment and graphene-enabled products.  First Graphene will supply high-quality PureGRAPH® nanoplatelets in large-scale volumes for use in planarTECH’s coating formulation for face masks and PPE.  

Under the supply contract, planarTECH will exclusively source graphene additives from First Graphene over a 2-year term with the agreed initial minimum quantity to be 1000kg in the first year.  A further 2 terms to follow the initial term included in the contract.

First Graphene recently partnered with planarTECH to develop a robust supply chain for the manufacture of innovative graphene-enhanced personal protective equipment.  Initial testing of PureGRAPH® has been completed and planarTECH will use this product in their proprietary coating to provide anti-static and bacteria-resistant properties to their range of face masks.

planarTECH has been experiencing increased demand for these products as world populations seek protection from airborne infection.

First Graphene has a well-established and robust supply chain for the manufacture of their high performing PureGRAPH® graphene products and have an already proven successful formulation that disperses uniformly into polymer coatings.

Craig McGuckin, Managing Director for First Graphene Ltd., said, “planarTECH have moved very quickly to test and commercialise their new range of graphene face masks and we are delighted to enter this contract to support the growth of their business.  Clearly, further opportunities exist in the development of planarTECH’s other PPE equipment.”

Ray Gibbs, Chairman for planarTECH (Holdings) Ltd., said, “We have experienced substantial, rapid and qualified enquiries for the graphene mask.  The 35 or so we are pursuing all require a fast turnaround of 2-3 weeks where potential orders could be very significant.  This increasing demand has meant we needed to secure a robust graphene supply to ensure we met the known market demand.  We have been impressed with the speed of response and high quality, consistent product from First Graphene which is crucial in urgently supplying this much needed product across the world.”

Tags:  coatings  Craig McGuckin  FIrst Graphene  Graphene  planarTECH  polymer  Ray Gibbs 

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Leading the Industry in Graphene Product Quality

Posted By Graphene Council, Tuesday, May 26, 2020
Updated: Tuesday, May 26, 2020

First Graphene Ltd. is a graphene manufacturing company that leads the industry in product quality measurement and process control. The company is determined to provide its customers with the high-performing and high-quality raw materials that their products demand.

If you are a formulator, a plastics extruder or rubber compounder who uses a raw material, we believe we know what is important to you…….an answer to the simple question “what’s in the bag or shipping container?” You want to know the material adds the performance you require and most importantly that a tonne purchased in, say, October performs exactly the same as the tonne you purchased in January. At First Graphene Ltd. we understand this.

Our customers also recognise our focus on quality.  One of our customers, a European based multi-national materials company says, “We have purchased multiple batches of First Graphene’s PureGRAPH® products and have been very pleased with the repeatability and consistency of these materials.”

 Since the isolation of graphene at the University of Manchester in 2004, much effort has been put into developing characterisation methods for the new generation of 2-D materials. This was initially led by academic researchers, who developed new techniques to determine the chemical make-up, size and shape of 2D materials. These techniques have since been adopted by graphene manufacturers and are currently being formalised through the ISO Nanotechnologies Technical Committee (ISO/TC229). Following discussions with Denis Koltsov, chairperson of the ISO 229 committee, Dr. Andy Goodwin of First Graphene Ltd. has agreed to join the BSI and ISO/TC229 working groups for the development of graphene characterisation standards. Ensuring alignment of the company’s quality processes with the emerging international standards.

Denis Koltsov, chairperson ISO 229 committee, says “We are very pleased to see First Graphene joining UK (BSI/NTI/1) and international standards working groups (ISO/TC229) to advance the development of Graphene related standards. Direct involvement of industry players is critical to the development of technical standards. It demonstrates the maturity of industry. It also highlights direct relevance of the standardisation work at ISO/TC229, which currently have 36 standards under development 4 of which are in the Graphene area”.

 As an early adopter in the use of scientific approaches to measurement of graphene materials, First Graphene has pioneered these methods to assure the quality of their PureGRAPH® products. First Graphene’s production and technical team have over 100 years’ experience in the manufacture and supply of high quality speciality chemical products and have used this experience to implement state of the art quality improvement tools such as LEAN and Six Sigma to implement a simple 4 step approach to develop and deliver a consistent and reliable supply to our customers.

4-step approach to high-quality PureGRAPH® products:

1. Representative sampling – whenever possible at-line and quality assurance testing is carried out directly on large aliquots of graphene powder product.
2. At-line and factory laboratory tests have been chosen that are simple and robust but also relate to fundamental material parameters.
3. Statistical process control tools are used to record and monitor all batch data – ensuring full understanding and control of the manufacturing process.
4. Communication to customers – Customer needs are translated into product specifications, with every shipment being accompanied by a certificate of analysis (CoA).

Representative tests have been developed that can be delivered at-line or in a factory quality assurance laboratory – these are directly related to the fundamental properties of the PureGRAPH® products. An example is the implementation of a Raman spectroscopy test method that is unique to First Graphene, using a remote sampling probe to enable representative sampling of product in bulk powder form, meaning that rapid and robust characterisation is available. This method was developed by First Graphene in collaboration with B&W-Tek an equipment supplier and has been accepted for publication in the Spectroscopy journal.

Use of Statistical Process Control Techniques to understand the voice of our process

PureGRAPH® graphene products are currently supplied to global customers from the company’s manufacturing site in Henderson, Western Australia. Minitab® software is routinely used to analyse manufacturing data and produce process control charts at the facility.  The company is manufacturing graphene at tonnage scales and multiple batches of PureGRAPH® products have been analysed. This enables “voice of our process” understanding through process control charts such as those shown below demonstrating a stable production platform, delivering a consistent product.

Figure 1 shows the mean particle size of our PureGRAPH® 10 product, measured using a Malvern 3000 Mastersizer. It’s a clear example of how industry-leading analytical equipment can be combined with Six Sigma concepts to monitor and control product quality.

Figure 2 below shows the Raman data for PureGRAPH® 10 product. A novel at-line Raman measurement technique provides immediate analysis of the quality of PureGRAPH® products.  The statistical analysis again shows consistent product across multiple batches.

Paul Ladislaus, Senior Process Engineer at First Graphene Ltd said: “We have implemented well established quality improvement tools and techniques to ensure we can consistently deliver a high-quality product to our customers.”

Paul Ladislaus added that: “Our process is robust and we can use these tools and techniques throughout our supply chain to reassure our customers that we are capable of reliably delivering the quality of graphene materials that they require.”

First Graphene intends to stay at the leading edge in terms of controlling the quality of graphene related products. The company continues to invest in its processing capability through measurement and automation and is a Tier 1 Member of the Graphene Engineering Innovation Centre at the University of Manchester with direct access to world-class analytical equipment and techniques and supporting expertise.  The company will continue to invest in analytical methods and process tools to ensure world-leading PureGRAPH® product quality for our customers.

Tags:  2D Materials  Denis Koltsov  First Graphene  Graphene  ISO Nanotechnologies  Paul Ladislaus 

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Nanomaterial bests all others in blocking speeding projectiles

Posted By Graphene Council, Tuesday, May 26, 2020
University of Wisconsin–Madison engineers have fabricated a rubbery nanomaterial that outperforms all other materials, including steel and Kevlar, in protecting against high-speed projectile impacts.

The research provides insights for using nanostructured polymers to develop lightweight, high-performance armor. In the future, these new types of armor could potentially be used as a shield on military vehicles to provide enhanced protection from bullets, as well as on spacecraft to mitigate impacts from meteorite debris.

Ramathasan Thevamaran, a professor of engineering physics at UW–Madison, and postdoctoral research associate Jizhe Cai made ultrathin films only 75 nanometers thick out of a relatively common polymer with a nearly impenetrable name — semicrystalline poly(vinylidene fluoride-co-trifluoroethylene) — and demonstrated that the material was superior at dissipating energy from microprojectile impacts over a wide range of velocities.

They detailed their research in a paper published in the journal Nano Letters.

Materials can exhibit different properties at the nanoscale than at larger sizes. This allows researchers to potentially improve specific properties of a material by working with it at extremely small sizes.

“When we shrunk the polymer down to this nanometer length scale, we found that its internal microstructure completely changed in an unexpected fashion compared to its larger scale,” Thevamaran says. “Surprisingly, the energy-absorbing mechanisms in the material became very prominent, and we found that this particular polymer was performing significantly better than any other material—both large materials and previously reported nanomaterials—at absorbing energy from the projectiles.”

To test their ultrathin polymer films, the researchers used a unique experimental technique called micro-ballistic impact testing. They launched projectile particles of about 10 microns (roughly one-tenth the width of a human hair) in size at the polymer film at velocities ranging from 300 feet per second to 3,500 feet per second — several times the speed of a bullet.

Cai and Thevamaran used an ultrafast imaging system to capture images of the projectiles as they penetrated the polymer film, and then they calculated the penetration energy — the amount of kinetic energy from the projectile that was absorbed by the material, per kilogram of the material.

“We normalized the penetration energy values, which allows us to make comparisons between the performance of these polymer films and different material systems,” Thevamaran says.

In addition, Cai and Thevamaran used scanning electron microscopy techniques to study how the material deformed during and after impact. They observed that the impacts caused extensive stretching and deformation in the material, similar to how a piece of rubber can stretch and snap back into shape.

“The key reason this material is performing better across the broad spectrum of velocity is because of its elastic nature in room temperature,” Thevamaran says. “The organization of the material’s internal structure enables ample stretching and deformation mechanisms, which enhance its ability to dissipate energy.”

Maybe not so much for people, though: Thevamaran says the rubbery nature of this material would make it challenging to use for applications like bulletproof vests, because impacts from bullets would protrude into the material and potentially cause blunt trauma injuries to the wearer.

Instead, Thevamaran says this material could be suitable for developing so-called “ambient armor,” where the armor shields the target, but isn’t applied directly to it.

“For example, with ambient armor positioned a short distance from a spacecraft, meteorite debris would first have to penetrate through several layers of this armor, which would dissipate almost all the energy before the projectile strikes the spacecraft, greatly minimizing any damage,” he says.

Thevamaran says the next steps in this research include further scaling up the material and the projectile sizes.

“We want to test a multi-layered system to make sure the novel properties we discovered in micro-ballistics can still be exploited for performance at a larger scale,” he says.

Tags:  Graphene  Jizhe Cai  Journal Nano Letters  nanomaterials  Ramathasan Thevamaran  University of Wisconsin-Madison 

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