Sustainable Graphene Production and Graphene's Potential in the Automotive Industry

Graphene, a two-dimensional material one atom thick with remarkable mechanical, electrical, thermal and optical properties, has opened new horizons in science. Due to its unique characteristics, it is defined as "the Material of the 21st Century". Graphene layers were first separated from graphite in 2004 by Konstantin Novoselov and Andre Geim, researchers at Manchester University, using micromechanical exfoliation (scotch tape method) [1]. This work was awarded the Nobel Prize in Physics in 2010. Since its discovery, graphene has shown great potential as a reinforcing element in polymers and polymer composites used in energy, electronics, aviation, automotive and construction sectors, increasing interest in commercializing graphene-based products. Graphene has significant effects on the mechanical performance, flame retardancy, thermal and electrical conductivity properties of composite materials. Due to its large surface area and strong interface interactions, it is an ideal additive material providing better load transfer within the polymeric matrix. With minimal graphene usage (less than 1% by weight), significant improvements can be achieved in the performance of thermoset and thermoplastic-based composites. The greatest barriers to commercializing graphene are large-scale production and high production costs. Many initiatives exist to increase graphene capacity and meet market needs.

Graphene Production from Waste Tires

Looking at graphene production methods, three techniques are commonly used: arc plasma, chemical vapor deposition (CVD) and chemical exfoliation. Among these methods, the CVD technique allows production of large surface area, defect-free graphene at high costs. CVD graphene is used in common electronic and photonic applications. Chemical exfoliation technique enables large-scale bulk graphene production (Figure 1 shows electron microscopy images of graphene layers produced from graphite). Considering cost and production capacity, chemical exfoliation technique offers advantages. In the chemical exfoliation technique, strong oxidants are used to break the bonds between graphene layers in the graphite structure and separate the layers [2, 3]. Moreover, the strong oxidizers used during oxidation (potassium permanganate and sulfuric acid) complicate the process and carry explosion risk [4], while long production and purification times also increase costs. For this reason, shifts toward alternative methods in graphene production have begun. [caption id="attachment_104456" align="aligncenter"] Figure 1. Electron microscopy image of graphene nanolayers[/caption] Instead of graphite used in graphene synthesis, various laboratory-scale studies exist using lignocellulosic biomass or coals produced from oxygen-rich precursors. This enables production of environmentally friendly, sustainable and cost-effective high value-added nanomaterials from waste. In this context, Nanografen, established in 2013 with support from Sabancı University and TÜBİTAK Technology Entrepreneurship Capital Support Program (BiGG) (1512), began work on environmentally friendly graphene production from sustainable sources. Nanografen converts carbon black obtained from waste tire pyrolysis into graphene nanolayers through an advanced transformation technique it developed. Additionally, through its partnership with Gan Pyrolysis Facility, it has established a production line with a 6-ton production capacity. This facility provides a solution to the growing waste problem in our country while opening the way for production of high value-added products and pioneering this field globally. Graphene Market: Since 2015, graphene has been one of the fastest-growing nanomaterials in the market with a 42.8% growth rate. This rate is expected to remain constant until 2020, creating approximately EUR 234 million market opportunity [5]. Graphene demand is estimated to reach 1,321.1 tons annually by 2022. Market size is expected to increase to EUR 445 million by 2025. Automotive applications have a very small share in the graphene market. Demand for Lightweight Vehicles: The automotive sector accounts for approximately one-third of global energy demand, which is a major source of pollution and greenhouse gas emissions in urban areas. At this point, lightweight vehicle design is key to improving fuel efficiency and vehicle performance while reducing adverse environmental impacts. In line with decisions taken by authorities in the European Union, the goal is to transition to a competitive low-carbon economy by reducing CO2 emissions to 75 g/km by 2050. In next-generation vehicles, vehicle weight is reduced through composite parts used in interior and exterior equipment, thereby reducing fuel consumption. Use of materials such as carbon/glass fiber-reinforced composites in vehicles provides significant weight reduction. Currently used fiber-reinforced composites have been adopted by the automotive industry because they offer advantages such as 50-60% weight reduction compared to steel, ease of manufacturing, design flexibility, reduced processing costs and better mechanical and corrosion resistance. In 2013, BMW became the first company to initiate major change in automotive production by adding carbon fiber composites to its electric i3 model for urban use. However, due to the high cost of carbon fiber, vehicle manufacturers continue searching for materials that will have the desired impact on cost, safety, risk, weight, market size and vehicle emissions. Graphene has great potential in weight reduction while maintaining the structural integrity of the composite and simultaneously improving mechanical, electrical and thermal properties. Use of graphene-based polymer composites as multifunctional structural materials has significant potential to impact the automotive sector. Given the expected future demand for lightweight vehicles, the automotive industry is also expected to be the largest user of graphene-modified polymeric composite materials in various applications. Recently, automotive giant Ford announced that starting in 2018 with the Mustang and F-150, it would begin using graphene parts in its vehicles [6]. Ford and its partners tested graphene-reinforced foam caps for noisy components such as fuel rails in front of engines, pumps, belt-driven pulleys and chain-driven gears. In these tests, graphene-reinforced parts demonstrated better performance being 17% quieter, 20% stronger and 30% more heat-resistant. The use of graphene in automotive manufacturing has opened the door to a new era in the sector as it paves the way for commercialization of nanointegrated parts. However, the matrix of parts commercialized by Ford is thermoset-based. Graphene currently cannot be used in thermoplastic commodity products due to high costs. According to a new report by Grand View Research, Turkey's automotive plastic compound market is expected to reach USD 390.8 million by 2025. In terms of volume, this market, estimated at 102.39 kilotons in 2015, is projected to reach 183.80 kilotons by 2025. Particularly when considering the potential of graphene's use in the plastic materials market, it is seen that it will create a very large market. Moreover, graphene has usage potential not only in structural parts but in various interior and exterior sections of vehicles (Figure 2) [7]. [caption id="attachment_104457" align="aligncenter"] Figure 2. Potential graphene-based automotive applications[/caption]   In the 2017 Automotive Sector's "Turkey Automotive Industry Competitiveness and Domestic Market Expectations for 2020 from the Perspective of Demand Dynamics" report, it was stated that Turkey's main automotive industry has comparative advantage in the automobile segment and a high level of competitive strength in the truck and bus segments compared to other vehicle-producing countries. Turkey's total vehicle production (excluding tractors) increased from 431,000 units in 2000 to 1,359,000 units in 2015, with an average production growth rate of 12.7% over the 16-year period. In 2015, Turkey ranked 5th in Europe and 15th globally in vehicle production rankings. However, Turkey is Europe's largest commercial vehicle manufacturer. For this reason, innovative approaches in this field will increase our competitiveness in the market. Moreover, Turkey's automotive sector is expected to witness tremendous growth in the near future despite the slowdown and stagnation in the European automotive sector.

Life Cycle Assessment and Circular Economy:

Lightweighting efforts have significant impact on reducing the automotive sector's carbon footprint. Life Cycle Assessment is a method used for evaluating the environmental aspects of a product or service system throughout all stages of its life cycle, from raw material procurement through production, use, end-of-life processing, using a "cradle-to-grave" approach in a systematic manner. This method is a useful tool for minimizing potential negative environmental impacts that may occur in the process from material development to production. Outputs obtained from Life Cycle Assessment studies will benefit all stakeholders across the value chain, including original equipment manufacturers (OEMs), suppliers, recyclers and end users. With such an approach, it will be possible to identify realistic concepts and examine circular economy applications of technological products.

Other Potential Applications of Graphene:

In conclusion, it is possible to produce reliable and durable composites through integration of graphene layers into the composite matrix. Lightweight graphene-reinforced composites show great promise for use in aircraft fuselages (particularly in wings) because graphene's mechanical properties offer advantages in terms of flexibility. Beyond the gains it provides in composite applications, graphene creates new market potential in various fields such as health, medicine, sensors, energy, electronics and photonics. For example, graphene-based photovoltaics can be integrated into aircraft fuselages, thereby providing direct electric current from solar energy. In the energy sector, transparent organic light-emitting diodes (OLEDs) are used in information displays. Additionally, use of graphene as electrode material in batteries will provide higher power density, longer life and greater recyclability. Figure 3 summarizes the application areas where graphene can be integrated. In the near future, we expect to see graphene-based products manufactured not just in laboratories but at industrial scale. [caption id="attachment_104458" align="aligncenter"] Figure 3. Application areas of graphene[/caption]  

References: [1] Novoselov, K. S., Geim, A. K., Morozov, S. V., Jiang, D., Zhang, Y., Dubonos, S. V., Grigorieva, I. V., Firsov, A. A., 2004. "Electric Field Effect in Atomically Thin Carbon Films", Science, 306, 666-669. [2] Saner, B., Okyay, F., Yürüm, Y. 2010. "Utilization of Multiple Graphene Layers in Fuel Cells. 1. An Improved Technique For the Exfoliation of Graphene-based Nanosheets from Graphite", Fuel, 89(8), 1903-1910. [3] Saner. B., Dinç, F., Yürüm, Y., 2011. "Utilization of Multiple Graphene Nanosheets in Fuel Cells: 2. The Effect of Oxidation Process on the Characteristics of Graphene Nanosheets", Fuel, 90(8), 2609-2616. [4] Hummers, W. S., Offeman, R. E. 1958. "Preparation of Graphitic Oxide", Journal of American Chemical Society, 80(6), 1339-1339. [5] Global Graphene-enhanced Composites Market- Analysis & Forecast (2018-2023) [6] https://www.compositesworld.com/articles/ford-to-integrate-graphene-enhanced-parts-into-its-vehicles [7]https://www.streetinsider.com/SEC+Filings/Form+POS+AM+XG+SCIENCES+INC/14264638.html

    Assoc. Prof. Burcu Saner Okan Founding Partner Nanografen Nanotechnological Products Chemistry Research & Development Consulting Ind. and Trade Ltd. Co. Researcher Sabancı University Integrated Manufacturing Technologies Research and Application Center