Graphene has applications in composites, biomaterials, energy electrodes, printing inks, gas barriers, and heat dissipation. In Korea, the areas expected to see rapid application include composites and energy electrodes. In foreign countries, applications for ink and anti-static properties are being made, and it is spreading to the energy field.

▲ The Electronics and Telecommunications Research Institute (ETRI) has developed a flexible display transparent electrode using graphene.

To commercialize graphene, six issues must be addressed: shortening synthesis time, recovery rate, purity/impurity control, size control, eco-friendly manufacturing process, and continuous production.

According to an online seminar by KETI Senior Researcher Yang Woo-seok held on the 10th at eewebinar, graphene exhibits diverse properties depending on the exfoliation method. The graphene materials team explained that they have improved upon the problems with the widely used chemical exfoliation method, the Hummers method. The Hummers method is not suitable for mass production because it fails to meet three conditions.

Focus on solving mass production problems of the Hummer's Method.

Graphite becomes graphene oxide when acid is added to it, causing its layers to separate. This process, called the Hummus process, involves a long synthesis time of over 24 hours between the graphite and acid. Furthermore, the high viscosity of graphene makes it difficult to remove the acid, generating a large volume of wastewater. Furthermore, production volume is determined by vessel size, requiring significant investment in space and facilities, making it difficult to meet commercialization requirements.

Woo-Seok Yang, a senior researcher at KETI's graphene materials team, said, "The Taylor reactor we developed can create a vortex layer and control pressure by using the speed of the rotating shaft. “This allows for the separation of graphite layers in just 15 minutes, and allows for the production of low-concentration graphene, which reduces wastewater and allows for the reuse of sulfuric acid, lowering manufacturing costs,” he said. “It improves on the problems of previous methods and satisfies all six conditions for commercialization.”

Presenting a technology that is differentiated from existing methods

During the exfoliation process, washing the graphene oxide with sulfuric acid is crucial. If impurities like acid remain on the graphene, its application in various applications is limited. The graphene materials team developed a floating washing method that floats the graphene without clogging the filter, improving upon the existing filter press method, which allows for large-scale washing.

"Separating graphene into similar sizes improves quality," said Yang Woo-seok, a senior researcher. "Rather than separating graphene after it's been created, we set the size when it's first created and maintain that original size throughout the process." He added, "Using a Taylor reactor, we can apply shear stress, allowing us to produce a large quantity of graphene oxide with a uniform size."

Research is underway to develop a sensor for detecting hazardous chemicals using graphene.

KETI has manufactured a paste by combining graphene and polymers, and is currently testing it to create a sensor for detecting hazardous chemicals through coating.

Currently, acid, alkali, and oil tanks located outside the factory are connected by pipes, making leaks frequent. Therefore, sensors are needed to detect hazardous substances. Existing sensors utilize pointers, bands, cables, and film sensors. However, these sensors also have the drawback of reacting to water.

KETI differentiated itself from the start by using materials to solve the problem of reacting to water. The sensor is designed to react by increasing resistance when exposed to water and decreasing resistance when exposed to acid. Testing with sulfuric acid demonstrated detection at low concentrations, and it can also detect nitric, hydrochloric, and hydrofluoric acids. The sensor has also undergone immersion and temperature testing.

Senior Researcher Yang Woo-seok said, "The lab has a Taylor reactor that makes graphene, dispersion equipment that can make paste and ink, and measuring equipment, so we are building an infrastructure that can respond from material manufacturing to application." He added, "Using this technology, we are conducting research to mass-produce graphene materials at low prices and with high quality that companies can utilize, and to create intermediate materials such as ink, paste, and master batches that can be applied to various applications." He stated that they are one step closer to mass production of high-quality graphene.