Graphene CVD sheets - updates and market status - Page 19

Researchers from NASA are developing nano-sized sensors based on graphene. The potential applications are chemical sensors (detecting atmosphere atomic traces of oxygen and other elements) and strain sensors (for detecting strains in airplane wings or spacecrafts buses). The researchers are fabricating relatively large and high quality graphene using CVD and are now applying these to sensors.

The team wants to develop small, low mass and low-power chemical detectors that could measure the amount of atomic oxygen in the upper atmosphere - for its role in creating atmospheric drag (which can cause orbiting spacecraft to lose altitude prematurely and plunge to Earth). When graphene oxidizes it changes the electrical resistance - and this can be used to measure oxygen density. Graphene could also be used to measure methane, carbon monoxide and other gases.

Researchers from Rice University discovered a way to create Bernal-stacked bi-layer graphene sheets. These kinds of structures (in which every other carbon atom in the six-carbon rings of the top graphene layer sits over the middle of the hexagonal space created by a six-carbon ring of the bottom layer) exhibit a small band gap.

To create these sheets with controlled thickness on copper substrates, the researchers used pressure-tuned CVD chambers, while keeping constant the pressure ratio of hydrogen to methane. The higher the pressure, the thicker the graphene film. They created all sorts of sheets, and the bi-layer ones indeed were Bernal-stacked. They created a transistor and checked the electronic properties to make sure there's a band gap.

Japan based iTRIX Corporation, a local supplier of graphene materials has spun-off a new company called Graphene Platform to handle worldwide sales. The new company is fully equipped for large-scale production of graphene materials with two 4 thermal CVD systems and one 6 thermal CVD system.

Graphene Platform currently offers CVD grown graphene (single layer on copper foil and multilayer on nickel foil), and also also graphene on PET, Glass and SiO2 (single layer and multilayer). The company produces its graphene in Japan and includes multipoint Raman spectra data with all samples. They promise to deliver standard products within a week.

Researchers from Purdue University discovered a while that using silver nanowires can dramatically increased graphene's conductivity. The nanowires are used to bridge defects and crystal boundaries. Now researchers from the University of Texas demonstrated how this works.

When making large graphene sheets, there are many defects (ripples, folds and tears) and also large graphene sheets are currently made from many small crystals, and the boundaries between the crystals scatter the electrons. The Texas researchers grew graphene on copper foil using CVD. This sheet had a resistance of over 1,000 ohms. Transferring a film of silver nanowires to the graphene sheet lowered the resistance to 64 ohms. The sheet still retained good transparency (94%). A bi-layer graphene-silver-nanowire sheet resulted in lower resistance (24 ohms) - and 91% transparency.

Graphenea has launched an online store, and the company now offers several graphene materials including CVD graphene films (on SiO₂, copper and any substrate that the customer provides), graphene oxide and reduced graphene oxide. The company is also building a distribution network in main graphene markets (such as the US, Japan and Korea).

Graphenea has a pilot line with a capacity of 50,000 cm²/year and they plan to expand it during 2013. Graphenea says that their customer list includes Nokia, Philips, Corning and ASML.

Researchers from MIT and the Oak Ridge national Laboratory (ORNL) developed a promising new graphene-based membrane that can be useful to filter microscopic contaminants from water or for drug delivery. The membrane features high flux and tunability (i.e. it can quickly filter fluids but also be easily tunable to let certain molecules through while stopping others).

To develop the membrane, the team fabricated a 25 square millimeter graphene sheet using CVD. They managed to transfer the sheet to a polycarbonate substrate dotted with holes. They thought that the graphene will be totally impermeable, but experiments proved that salts can flow through the membrane.

Nobel Prize-winner (together with Andre Geim) Professor and Kostya Novoselov Professor Volodya Falko from Lancaster University have released a graphene roadmap. The roadmap discusses the different possible applications for graphene and also the different ways to produce the material.

The authors says that the first key application is conductors for touch-screen displays (replacing ITO), where they expect can be commercialized within 3-5 years. They also see rollable e-paper displays soon - prototypes could appear in 2015. Come 2020, we can expect graphene-based devices such as photo-detectors, wireless communications and THz generators. Replacing silicon and delivering anti-cancer drugs are interesting applications too - but these will only be possible at around 2030.

PlanarTech is now offering graphene samples and Korean-made thermal CVD equipment. PlanarTech is targeting corporate and academic R&D labs.

Its graphene samples include graphene on copper foil, SiO2, PET, PI, glass and other substrates, graphene on UV tape, large-area single-crystal graphene and other custom samples.

Researchers from Monash University and Rice University developed a thin graphene film anti-corrosion coating. Their new coating can maker copper more resistant to corrosion - almost 100 times better than uncoated copper. According to the researchers, that's the best graphene-based anti-corrosion material developed yet.

The researchers are now looking at different metals to coat, and are also investigating ways of applying the coating at lower temperatures (currently they use CVD at temperatures between 800 and 900 degrees).

Sony has developed a new graphene producing process that use a roll-to-roll method. They have built a machine that can produce graphene sheets up to 100 meters in length (23 cm width), and the resulting sheet is the largest area graphene sheet in the world by far (the previous record was Samsung's 40" sheet from back in 2011).

Sony's new process integrates CVD and roll-to-roll, at a temperature of 1,000°C. The idea is to directly apply a current to a copper (Cu) foil that is the catalyst of graphene and a substrate for the CVD method so that only the Cu foil is heated. As a result, the thermal load on the entire machine was drastically reduced.