Graphene CVD sheets - updates and market status - Page 13

A collaboration between Flagship-affiliated physicists from RWTH Aachen University and Forschungszentrum Jülich, together with colleagues in Japan, devised a method for peeling graphene flakes from a CVD substrate with the help of intermolecular forces. It is an innovative variant on the traditional CVD process, which yields high quality material in a scalable manner, that might significantly narrow the performance gap between synthetic and natural graphene.

The process is heavily based on the strong van der Waals interaction that exists between graphene and hexagonal boron nitride, another 2D material within which it is encapsulated. Thanks to strong van der Waals interactions between graphene and boron nitride, CVD graphene can be separated from the copper and transferred to an arbitrary substrate. The process allows for re-use of the catalyst copper foil in further growth cycles, and minimizes contamination of the graphene due to processing.

Researchers at Oxford University demonstrated how millimeter-sized crystals of high-quality graphene can be made in minutes instead of hours. In about 15 minutes, the method can produce large graphene crystals (around 2-3 millimeters in size) that it would otherwise take up to 19 hours to produce using current chemical CVD techniques.

The researchers took a thin film of silica deposited on a platinum foil which, when heated, reacts to create a layer of platinum silicide. This layer melts at a lower temperature than either platinum or silica, creating a thin liquid layer that smooths out nanoscale 'valleys' in the platinum so that carbon atoms in methane gas brushing the surface are more inclined to form large flakes of graphene.

Oxford University researchers have developed a method for producing graphene in large high-quality sheets. The university's technology commercialization branch, Isis Innovation, states that the researchers had solved a major barrier to the development of the material, making commercial-scale sheets of repeatable and uniform quality graphene ready for production.

The technique, currently in the process of patent application, enables the manufacture of commercial scale graphene sheets using a transition metal substrate combined with an intermediate silicon containing liquid film. The graphene sheets are made using CVD and large, high-quality graphene flakes are produced. Synthesis times are reduced by 50 times, according to Isis, adding that it was looking for commercial partners. 

Researchers at the Korean Institute of Energy Research (KIER) and the University of Oxford in the UK showed that encapsulating platinum nanoparticles with nitrogen-doped graphene layers improves the catalytic activity of the particles, while making them more resistant to degradation. This could lead to better proton exchange membrane fuel cells (PEMFCs) in the future.

The scientists state that without the nitrogen treatment, the Ptgraphene nanoparticle is very resilient to degradation, but it also becomes a rather ineffective catalyst. The nitrogen treatment appears to 'puncture' the graphene shell, allowing the Pt underneath to catalyze reactions while being protected from the acidic electrolyte in a fuel cell. The researchers found that the porous graphene encapsulated Pt nanoparticles were almost as good as bare Pt nanoparticles in terms of catalytic performance (with a peak efficiency of 87% compared to bare Pt) but that they did not degrade compared to the bare particles.

A team of scientists from Columbia, Seoul National University (SNU), and Korea Research Institute of Standards and Science (KRISS) reported the creation of an on-chip visible light source using graphene as a filament. Creating light in small structures on the surface of a chip is crucial for developing fully integrated 'photonic' circuits that do with light what is now done with electric currents in semiconductor integrated circuits.

The scientists attached small strips of graphene to metal electrodes, suspended the strips above the substrate, and passed a current through the filaments to cause them to heat up. The team refers to this design as 'the world's thinnest light bulb', a type of 'broadband' light emitter that can be integrated into chips and may pave the way towards the realization of atomically thin, flexible, and transparent displays, and graphene-based on-chip optical communications.

Researchers at MIT and the University of Michigan developed a new roll-to-roll manufacturing method, that promises to enable continuous production using a thin metal foil as a substrate, in an industrial process where the material is deposited onto the foil as it moves from one spool to another. The resulting size of the sheets would be limited only by the width of the rolls of foil and the size of the chamber where the deposition would take place.

The new process is an adaptation of a CVD method already used at MIT (and additional places) to make graphene. The new system uses a similar vapor chemistry, but the chamber is in the form of two concentric tubes, one inside the other, and the substrate is a thin ribbon of copper that slides smoothly over the inner tube. Gases flow into the tubes and are released through precisely placed holes, allowing for the substrate to be exposed to two mixtures of gases sequentially. The first region is called an annealing region, used to prepare the surface of the substrate; the second region is the growth zone, where the graphene is formed on the ribbon. The chamber is heated to approximately 1,000 degrees Celsius to perform the reaction.

The U.S Naval Research Laboratory (NRL) and University College, London, recently purchased Oxford Instruments' plasma processing Nanofab equipment using CVD, PECVD and ICPCVD techniques. 

The Nanofab enables the fabrication of nanostructured materials such as graphene, carbon nanotubes and other 1D and 2D nanomaterials. It combines several essential features for high performance growth such as a high temperature heater capable of processing up to 200 mm wafers, shower head technology, automatic load lock for wafer handling as well as flexible options for liquid/solid precursor delivery.

Future Markets released a new market report (The Global Market for Graphene to 2025) in which they estimate that the graphene market (mostly raw materials sales) was about $9-12 million in 2013 and $15-20 million in 2014. They estimate the market to grow to around $25-45 million in 2015.

According to the report, there is currently an oversupply situation in the graphene market - especially for low quality graphene. Most graphene sales are of graphene flakes (nanoplatelets) and conductive inks, while larger graphene sheets grown using CVD are used mainly for R&D. The main markets for graphene in the next 5-7 years will be Lithium batteries, conductive inks, sensors, supercapacitors, composites and transparent conductive films.

Researchers at the US Department of Energy's Oak Ridge National Laboratory (ORNL) came up with an innovative large-scale graphene fabrication method. The scientists used CVD to create 2-inch-by-2-inch sheets of graphene, contained in a polymer composite. Layering graphene between polymer sheets is meant to facilitate use in commercial products, according to the scientists.

Common approaches to polymer composite fabrication use graphene flakes, creating flake dispersion and agglomeration problems. This method, however, uses graphene sheets that eliminate these problems and allow for better electrical conductivity with a lower graphene content in the composite. In fact, the scientists claim that they were able to make a nanocomposite laminate that is electrically conductive with graphene loading that is 50 times less compared to other samples.

US-based Carbon Sciences announced that the research project funded by the company at the University of California, Santa Barbara (UCSB), has successfully demonstrated the production of high quality graphene using a low cost chemical vapor deposition (CVD) process.

The UCSB research team has successfully engineered a low cost CVD system that is optimized for graphene production using proprietary processes, catalysts and techniques. The system can also be used to customize doping to create application specific graphene.