Introduction

Due to the many superlative properties of graphene and related 2D materials, there are many application areas where these nanomaterials could be disruptive, areas such as flexible electronics, nanocomposites, sensing, filtration membranes and energy storage.

There are barriers to commercialisation that are impeding the progress of products containing graphene, which need to be overcome. One of these crucial barriers is answering the question “What is my material?”. End-users of the raw materials containing graphene should be able to rely on the advertised properties of the commercial graphene on the global market, instilling trust and allowing worldwide trade. Reliable and repeatable measurement protocols are required to address this challenge.

This document provides a set of flow-charts for analysts to follow in order to determine the structural properties of graphene from powders and liquid dispersions (suspensions). Initially, a quick check should be undertaken to determine if graphene and/or graphitic material is present. If it is, then further detailed analysis is required to determine if the samples contain a mixture of single-layer graphene, bilayer graphene, few-layer graphene, graphene nanoplatelets and graphite particles. Depending on the methods used, the samples are typically analysed after deposition on a substrate. The document describes how to assess what measurements are required depending on the type of sample and includes decision trees and flow diagrams to aid the user. This document describes a selected set of measurands that are needed, namely:

a) the number of layers/thickness of the flakes;
b) the lateral dimensions of flakes;
c) layer alignment;
d) the level of disorder;
e) the estimated number fraction of graphene or few-layer graphene;
f) the specific surface area of the powder containing graphene.

The above physical properties of the material can change during its processing and lifetime, for example, the samples can become more agglomerated, obtain different surface functionalities. The above measurand list for the initial material defines their inherent characteristics that, along with the chosen manufacturing processes, will determine the performance of real-world products. Generally, different material properties can be important in different application areas, depending on the functional role of the material.

The document provides methods for structural characterization of individual flakes of graphene, bilayer graphene, graphene nanoplatelets and graphite particles isolated from powders and/or liquid dispersions. It does not provide methods for determination of whether the powders and/or dispersions are composed solely of these materials. No recommendation is provided as to when or how often to measure samples, although it is not expected this would be for every batch of the same material. It is up to the user to determine when, how often and which characterization routes described in this document to take. As with all microscopical investigations, care is needed in drawing statistical conclusions dependant on representative sampling.

A set of annexes provide example protocols on how to prepare and analyse the samples, sources of uncertainty and how to analyse the data. The methods used are Raman spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM) and the BET (Brunauer–Emmett–Teller) method.

PD ISO/TS 21356-1:2021

Nanotechnologies. Structural characterization of graphene - Graphene from powders and dispersions

Current

Published:

31 Mar 2021