General Graphene manufactures graphene using the Chemical Vapor Deposition (CVD) technique. This “bottom-up” graphene synthesis method is enabled by a controlled processes that consistently delivers high quality graphene.
In this process, hydrocarbon gases decompose at high temperature, on a transition metal foil, such as copper or nickel. The reaction causes the carbon to deposit on the metal surface, and the growing graphene crystals merge together as the foil moves through the roll-to-roll conveyor to form a continuous single or multi-layer atomic structure.
Unlike exfoliated graphene and reduced graphene oxide that are in a form of powders and used as additives in plastics and coatings, General Graphene’s single or multi-layer continuous graphene sheets remain on a metal substrate, or are transferred to a substrate of interest (polymers, metals, ceramics, etc.). Our large-area continuous CVD graphene provides distinct advantages for barriers and films in comparison to graphene in a powder form. The resulting graphene is produced in 4 main forms:
Single layer graphene is 1 atom thick. Sometimes referred to as monolayer or single-layer graphene.
Bilayer graphene consists of two well-defined stacked graphene layers, grown as 2 single stacked layers or as 1 two layer sheet.
Few layer graphene consists of three to ten well-defined stacked graphene (FLG), grown as multiple single layers, which are transferred and stacked, or grown as a single multiple layer sheet.
Multilayer graphene consists of more than 10 graphene layers and properties become more like graphite materials. Multilayer graphene can be grown from single sheets which are transferred and stacked, or as 1 multi-layer sheet.
General Graphene uses a patented and proprietary atmospheric CVD process to produce high volume, roll to roll graphene sheets. The process is broken down into 2 main steps:
Step 1: Metal Substrate Pre-treatment
Step 2: Graphene Growth
Graphene growth is initiated during conveyance of the metal catalyst substrate through the furnace by the introduction of a hydrocarbon gas mixture at high temperature and atmospheric pressure. The hydrocarbon gas adsorbs on the catalyst surface where dehydrogenation occurs, leaving elemental carbon adsorbed on the catalyst surface. The carbon atoms diffuse on the catalyst surface attaching to nucleated hexagonal graphene crystals until the individual crystal edges meet each other, covering the whole catalyst surface in a single, continuous graphene sheet.
The graphene crystal size, number of layers and defect density can be tuned by accurately controlling our process conditions, such as the catalyst composition, catalyst pre-treatment steps, hydrocarbon gas mixture, growth temperature, and retention time of the substrate under heat.
The graphene-coated foil is rolled up as a substrate ready for use by industry. Alternatively, the graphene is transferred onto a suitable substrate, such as a polymer, inorganic substance or other customer substrates, as described in the next step.
General Graphene has focused on the development of processes to rapidly transfer graphene onto customer substrates, components and devices. Typically, General Graphene conducts the transfer of graphene by either (1) wet-transfer method or (2) dry-transfer.
The industry standard wet-transfer method works by first generating graphene on a catalyst, typically a thin metal foil. The catalyst substrate is then chemically etched away to isolate the graphene and enable its transfer onto almost any surface. The wet-transfer technique is a robust method that can be used to transfer high-quality graphene onto relatively small-to-moderate sized objects.
For the dry-transfer technique, graphene is also first generated on a metal catalyst. The graphene and catalyst substrate undergoes a proprietary treatment to loosen the graphene from the surface of the catalyst material. After applying a thin coating of polymer, the graphene can then be peeled from the surface of the catalyst in a roll-to-roll manner and transferred onto a variety of surfaces or objects. In another dry transfer method, graphene is transferred onto an adhesive film, which the customer can use for roll-to-roll application of graphene to products in their own process line.
General Graphene has techniques to apply graphene to almost any surface, and the expertise to find a graphene transfer solution for your specific application requirements.