3D CVDGraphene™ Material Production Scale-up Process using Ni Powders
Karlheinz Strobl, Mathieu R. Monville, Subarna Banerjee, Shihsheng Chang
CVD Equipment Corporation, 1860 Smithtown Ave, Ronkonkoma, NY 11779, USA
Graphene, a 2D sp2-hybridized carbon sheet with one-atom thickness, has attracted increasing attention in recent years because of its unique structure and special properties. Recently several research publications have described the synthesis of 3D CVD graphene continuous networks1,2 grown on Ni foam substrates and their utilization for various novel products and application developments such as high sensitive gas sensor3, electrode or electrode additive for solar cells4 and ultra capacitors.5
The commercially available Ni foam substrate which is used as a sacrificial template for CVD graphene growth in these publications is typically 1 to 2 mm thick, has a density of ~0.3 g/cm3 and a surface area in the order of 1 m2/g. This results in the growth of around 0.3 m2 of graphene per cm3 of Ni foam used. However, higher density 3D graphene material is desired in applications (sensors, batteries, ultracapacitors, etc.) where more graphene material per mass/volume of active material is required to achieve better performance.
In addition, one way to achieve higher yield per batch in a coating process is to use particles instead of flat substrates to exploit the increased surface area available for CVD. This path was already explored to achieve bulk growth of high-quality mono- to few-layer graphene sheets on nickel particles.6
We improved upon these prior concepts to produce 10-100 higher batch quantity of 3D CVDGraphene™ material by starting with a micron size filamentary Ni powder (Fig.1) and filling it into multiple, specially designed porous molds that allow the precursor gas to enter the Ni powder easily. This resulted in highly porous sintered Ni pellets (5mm tall, 16mm in diameter, Fig.2), uniformly covered with a graphene skin, as can be observed on the corresponding cross-sectional SEM images (Fig.3). Fig.4 shows the free standing 3D graphene network after Ni is etched away.
This novel way to synthesize graphene on 3D interconnected Ni sintered powder allows to create macroscopic custom 3D structures of CVD3DGraphene™ which can be further customized by using other 3D shapes and sizes of molds and other types (spherical instead of filamentary) and sizes (nm to μm) of Ni powders. The CVD graphene batch yield can thus be 10-100 times improved (larger quantities and/or denser 3D CVD graphene can be achieved per oven volume) and its cost dramatically reduced.
References Chen Z., Ren W., Gao L., Liu B., Pei S., Cheng H-M., Nature Materials 10 (2011), 424-428.
 Monville M.R., Strobl K., Stolyarov D., Polyakova E., MRS Fall (2011), Poster AA5.15.
 Yavari F., Chen Z., Abhay V.T., Ren W., Cheng H-M., Koratkar N., Scientific Reports 1 (2011), #166.  Bi H., Huang F., Liang J., Tang Y., Lü X., Xie X., Jiang M., J. Mater. Chem. 21 (2011) 17366-17370.
 Cao X., Shi Y., Lu G., Huang X., Yan Q., Zhang Q., Zhang H., Small 7 (2011), 3163-3168.
 Chen Z., Ren W., Liu B., Gao L., Pei S., Wu Z-S, Zhao J., Cheng H-M., Carbon 48 (2010) 3543.
Presented at Graphene 2012 International Conference in Brussels, Belgium