• Industrial-Scale Graphene Nanoplatelets & Dispersions
    Jan 10, 2018 | ACS MATERIAL LLC Download PDF

    Graphene is typically produced with either a top-down or bottom-up approach; however, manufacturing a vast amount of the material is beneficial in technical industries. Creating high-quality and high-yield graphene, such as graphene nanoplatelets and dispersions, can push forward its use in a variety of industrial applications such as electronics, touchscreens and light-emitting diodes. This report will explain the different methods used to synthesize a large amount of these graphene materials and its benefits in industrial applications. 

    Introduction

    Graphene is a one-atom-thick, honeycomb lattice structure that was extracted from graphite as shown in Figure 1, below. Apart from graphene’s excellent electrical and thermal conductivities, inertness and ability to absorb a large portion of white light, other attributes that are found most attractive for structural applications are the excellent mechanical and flexible properties of this unique two dimensional (2D) material.1 This unique nanostructure holds great promise for potential applications in many technical fields such as nanoelectronics, sensors, nanocomposites, batteries, supercapacitors, and hydrogen storage.2-7

    Graphene

    Figure 1. Graphene is made of carbon atoms with a hexagonal structure.

    Synthesis

    Currently, various methods have been proposed to prepare graphene by two main categories: top-down (exfoliation of graphite) and bottom-up (chemical synthesis).8 Top-down methods typically include mechanical exfoliation of highly ordered pyrolytic graphite (HOPG), chemical oxidation/exfoliation of graphite followed by reduction of graphene oxide (GO) and solution-based exfoliation of graphite intercalation compounds.9-11 The bottom-up approaches for graphene synthesis include epitaxial growth on metallic substrates by means of CVD, thermal decomposition of SiC, and organic synthesis based on precursor molecules.12-14 However, developing a method for producing high-quality graphene in large quantities is essential for further investigation of its properties and applications.

    Industrial applications are likely to require large-scale, high-throughput processing methods.15 The direct liquid-phase exfoliation of graphite to produce graphene is a convenient method for generating ideal graphene samples in large quantities. In the past few years, significant efforts have been devoted to the low-cost liquid-phase exfoliation of graphite to produce high-quality, pristine graphene.16 Thus, the immaculately obtained graphene and its derivatives has proven to exhibit highly desirable properties and performances in numerous applications.17

    Liquid-phase exfoliation is a widely used method to make colloidal dispersions of graphene in a variety of solvents. Exfoliating reagents such as benzyl benzoate, 1-methyl-2-pyrrolidinone (NMP), N,N-dimethylacetamide (DMA), N-vinyl- 2-pyrrolidone (NVP), N,N-dimethylformamide (DMF), ethanol, acetone, water and so on.16 High temperature or microwave treatments have been employed to expand graphite for better liquid-phase exfoliation.18 Graphite intercalation compounds (GICs) are also widely used as starting materials for exfoliation.19

    The concentrations of the graphene dispersions and the yields of the single-layered graphene sheets vary under different exfoliation conditions and can be adjusted or optimized by changing the sonication time, centrifugal rotational speed, amount of graphite added to the media and more.16 Water is an ideal solvent for numerous compounds, especially biological ones, owing to its high degree of compatibility and nontoxicity.20, 21 On the other hand, organic solvents have many serious drawbacks associated with them: they are toxic, expensive, difficult to remove, and not very biocompatible.22 Thus, water can be a better choice as a medium for graphite exfoliation.16 

    Applications

    Parameters such as chemical stability, mechanical tolerances, flexibility and thermal conductivity need to be considered in order to meet industry requirements. With excellent electrical properties, graphene is highly beneficial in fields like batteries and electronics. Industrial applications of graphene electrodes are also realized in the form of organic light-emitting diodes (OLEDs), touchscreens and LCD displays.24 Batch or continuous production processes are industrially very relevant and are used, for example, in the production of light-emitting diodes (LEDs), transistors and solar cells.23 Much like graphene dispersions, graphene nanoplatelets can be manufactured as a free-standing, powder-like material and in large quantities which makes them especially suitable for large-volume dispersion in paints, coatings, composites, films, adhesives, lubricants and functional fluids.23

    Conclusion

    TEM graphene nanoplatelet TEM graphene nanoplatelet

    Figure 2. TEM images (a and b) of ACS Material graphene nanoplatelets.

    ACS Material used a simple but effective method to produce huge quantities of graphene nanoplatelets including large, industrial scales to be used in multiple applications. The diameters range between 1-2 nm, 1-5 nm and 2-10 nm with diameters of approximately 5 µm, 5-10 µm and 5 µm, respectively. The interlayer cleavage (liquid-phase exfoliation from expanded graphite, water as exfoliating reagent) method was used to obtain high-quality and high-yield graphene nanoplatelets with an industrial quantity. TEM images of ACS Material graphene nanoplatelets can be seen in Figure 2. In addition, we also provide graphene nanoplatelet-based oily and aqueous slurry, such as graphene dispersion in NMP/water, that is metal ion-free, possesses a high electrical conductivity and can be widely applied in battery slurry as a conductive agent to improve the high rate charge-discharge capacity. 

    ACS Material Products:

    Graphene Powder:

    Graphene Slurry:

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