Graphene and related 2D materials (GR2M) can help reduce greenhouse gas emissions from the production of advanced materials. Using GR2M nanoplates in applications such as reinforcing concrete or improving battery performance will require a dramatic increase in production. As production of GR2Ms increases, the ability to effectively and efficiently measure the material properties of nanoplates, both in the final product and as part of process control systems, will become critical.

Instruments used for linear measurements are likely to have lower resolution than research-grade laboratory instruments. The effect this has on the resulting metrics must be understood to ensure confidence in the results reported to clients.

Currently, Raman spectroscopy is used to monitor the material properties of nanoplates, but this requires sampling and additional preparation to make it suitable for analysis, slowing the process and incurring additional storage costs.

Ideally, measurements would be obtained on-line to sample a much larger portion of a batch, with results reported in real-time to enable more responsive adjustments to process parameters. Therefore, faster and easier-to-use measurement methods are needed. It is extremely important that the results generated by these tools are reliable, which can be done by referring to existing standardized methods.

The solution

To address this challenge, the UK’s National Physical Laboratory (NPL) is working with Thomas Swan & Co. Ltd., a UK-based specialty chemicals company, to demonstrate the feasibility of measuring graphene nanosheets in an industrial setting. A portable Raman spectrometer was installed in the company’s pilot-scale manufacturing facility and set up to obtain measurements from materials during a production run. During the GR2M process, platelets are exfoliated from graphite in a liquid. The results showed that the Raman scattered light signal obtained from the in-line measurements is affected by the conditions in the production line, such as pipeline pressure. Changes in typical Raman metrics based on peak intensity ratios were also identified during the process. By taking samples for off-line analysis, changes in measured spectra can be validated against standardized methods and shown to reflect changes in material properties during manufacturing.

The influence

Using the portable Raman spectrometer to make these measurements demonstrates the feasibility of linear measurements using relatively inexpensive instruments. This offers a solution for companies producing a range of advanced materials using GR2M nanosheets for net-zero applications, helping to achieve net-zero carbon targets.

While demonstrating the feasibility of the method for monitoring material properties, NPL also identified metrological challenges in interpreting changes in measured spectra. By continuing to understand and address these issues, users will gain increased confidence in implementing embedded Raman as a quality control method.

NPL works with several other companies and Graphene Engineering Innovation Center at the University of Manchester to expand the range of Raman spectroscopy applications for process measurements. By understanding how measurement challenges vary in different settings, NPL develops additional measurement tools that can be implemented in-line or on-line to improve process control. Combining information from several different measurement methods means that a more complete characterization of the production material can be obtained. This will benefit manufacturers who need fast, near-instantaneous, on-board material characterization and help reduce costs, reduce wastage and improve product quality.

Summarizing the project, Dr Keith Payton, NPL Senior Scientist, said: “This was a fantastic opportunity to demonstrate embedded Raman spectroscopy in an industrial setting. Raman spectroscopy is widely used to characterize graphene, so it is exciting to be able to expand its use in this way. As production rates for industrial materials manufacturers increase, in-line measurements will become both more important and more widespread, and so it is important that measurement challenges are understood and addressed early in the process.”

“The opportunity to characterize graphene nanoplatelets (GNPs) in-line during the exfoliation process is exciting for Thomas Swann. The onboard Raman spectrometer not only has the potential to expand our capabilities to study the exfoliation process, but can also make GNP production more efficient by improving quality control capabilities,” commented Dr Marco Visconti, Head of Research, Thomas Swan & Co.

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Developing In-Line Quality Control of Advanced Materials for Net-Zero Applications