Calculation of the density relies on the assumption of presence of a bulk of material (either liquid or solid) in which the mass is distributed evenly through a given volume. In this regard, Graphene, that is by definition single separate sheets of graphite does not meet the requirements of "density" since if you accumulate and compress them they will not be single separate sheets, but instead, they will stick to gather and reform Graphene multilayers or in in fact, tiny graphite flakes. Moreover, like any other powder, the more you compress and densify them, the higher the density you'll measure, that does not have any thing to do with the Graphene density.

Finally, I think the definition of density is not applicable to Graphene.

Calculation of the density relies on the assumption of presence of a bulk of material (either liquid or solid) in which the mass is distributed evenly through a given volume. In this regard, Graphene, that is by definition single separate sheets of graphite does not meet the requirements of "density" since if you accumulate and compress them they will not be single separate sheets, but instead, they will stick to gather and reform Graphene multilayers or in in fact, tiny graphite flakes. Moreover, like any other powder, the more you compress and densify them, the higher the density you'll measure, that does not have any thing to do with the Graphene density.

Finally, I think the definition of density is not applicable to Graphene.

Thanks for your answer

you mean that there is no way to measure it, but some scientists mentioned a number for density of graphene in articles. I attached it below.

What is mentioned in the paper is not density, but the “packing density”. By definition, packing density is the fraction (η) of a volume filled by a given collection of solids. So, it should be a dimensionless number. However, in the paper you sent, they’re reporting (g cm–3) units for the packing density that is not literally right. In fact, they are reporting the density of a packed powder. So the density they’ll measure depends strongly on the packing conditions they have used (most important of which, packing pressure, if that is the case for their used method). I couldn’t however find any info about the packing condition or the method used to measure the “packing density” in their report that is a pity. Anyways, you can try to see if you can find the authors in RG or elsewhere to ask them. But in the current condition, it does not give enough sight.

I’d suggest having a look at literature on density measurement of packed powders if you’re interested in them. Few examples:

http://www.sciencedirect.com/science/article/pii/0032591086800584

http://www.sciencedirect.com/science/article/pii/S003259100800079X#

http://www.usp.org/sites/default/files/usp_pdf/EN/USPNF/revisions/m99375-bulk_density_and_tapped_density_of_powders.pdf

www.quantachrome.com/articles_pdf/tablets_capsules.pdf

I agreed with Dr @ Mazdak Hashempour.

This called packing density not density nor specific gravity. However, it is considered as a method to determine the electrode materials apparent density related behaviors by using fixed parameters of preparation and fixed volume followed by measuring the weight and from which the packing density can be calculated. This is just a simple method to realize the difference when fabricating nano-structured films or other nanodesigned structures. As the fabrication technologies are going to more advancements so this issue is still growing up.

Sometime the effective parameter is not only packing pressure , this depend on the fabrication process its self.

For example the fabrication or annealing time and/or temperature affect as shown in the following paper

Size and Density of Graphene Domains Grown with Different Annealing Times

hopefully my answer could help you

regards

Ahmed