GB/T 42310-2023Nanotechnology—Measurement for specific surface area of graphene powder—Static volumetric method by argon gas adsorption (English PDF)

Foreword

This document is in accordance with the provisions of GB/T 1.1-2020 "Guidelines for Standardization Work Part 1: Structure and Drafting Rules for Standardization Documents" drafting.

Introduction

The specific surface area of graphene powder is one of the key characteristic parameters affecting its application performance. Nitrogen adsorption (Brunauer-Emmett- Teler) method is a common method for testing the specific surface area of solid substances, but its applicable premise is that nitrogen is used as the adsorbate on the surface of solid adsorbent.

The adsorption behavior fits the ideal classical physical adsorption model. There are various types of industrialized graphene powder in my country, and different types of samples contain different Intra-sheet defects, sheet edge dislocations, grain boundaries, etc., make the chemical activity and number of carbon atoms in the above places also exist. difference. In addition, due to different production processes, the functional groups (such as -OH) introduced on the surface of different types of powder samples are also different. nitrogen Gas molecules have a quadrupole moment, and as an adsorbate, they will interact with polar adsorbents to form specific adsorption, which is different from ideal classical physical adsorption.

The molecular arrangement and orientation of the model may cause poor linear correlation of the multi-point BET diagram, so the accuracy and reliability of the specific surface area test results Sex is also poor. The adsorption behavior of different adsorbates on the surface of graphene powder is shown in Appendix A.

Argon molecules are monatomic gas molecules, electrons have been completely paired and there is no bonding orbital, and it is generally considered to have no chemical activity. sex. There is no quadrupole moment for argon molecules, and when adsorbed on the surface of graphene powder materials as an adsorbate, it is sensitive to the surface structure or functional groups of the sample.

The sensitivity is low, and its adsorption behavior conforms to the ideal classical physical adsorption model, so when the specific surface area is measured at the temperature of liquid argon, the classical physical adsorption model can be used.

BET theory for calculations. Since the polarizability and molecular size of argon and nitrogen are very similar, their non-specific adsorption properties are also very similar.

Similarly, on nonpolar adsorbents, the heat of adsorption of nitrogen is almost equal to that of argon. For polar graphene powder materials, argon and nitrogen There is a significant difference in the heat of adsorption of argon and gas (see Appendix B for relevant examples), which further confirms that the use of argon as the adsorbate to determine the graphene powder ratio The science and plausibility of surface area.

1 Scope

This document describes a method for the determination of the specific surface area of graphene powders by the argon adsorption static volumetric method.

This document is applicable to the determination of adsorption isotherms with type II (dispersed, non-porous or macroporous) and type IV (mesoporous, pore size 2nm~50nm)

Specific surface area of graphene powder. Contains a small amount of micropores, and the adsorption isotherm shows a combination of type II and type I or a combination of type IV and type I It is also applicable to the determination of specific surface area of graphene powder. Other types of carbon-based nanomaterials, such as carbon nanotubes, carbon fibers, porous carbon, etc. The determination of the volume refers to the use.

2 Normative references

This document has no normative references.

3 Terms and Definitions

The following terms and definitions apply to this document.