3D Printing Improves X-Ray Diffraction Experiments

I was never very good at chemistry experiments in school, and now that I’ve just heard the word mechanochemistry for the first time, I’m starting to get nervous all over again, as if I’m approaching a set of beakers back in high school. But if you break it down, the concept is pretty interesting – mechanochemistry is basically an interface between mechanical engineering and chemistry. It’s the combination of mechanical and chemical phenomena on a molecular scale, and includes molecular machines and shock wave chemistry. A team of researchers with the Université catholique de Louvain (UCL) in Belgium is working on this interesting field of study, and using 3D printing technology to improve their experiment.

As mechanochemistry has spread across all areas of chemistry, it’s been able to synthesize multiple materials when what’s known as the typical ‘wet chemistry’ process isn’t working. But the downside is that the characterization of the reaction mixture is far less accessible than it is in solutions. Both X-ray diffraction and Raman spectroscopy, a technique which typically provides an identification ‘fingerprint’ for molecules in chemistry, were recently used to achieve in situ observations of mechanochemical reactions.

It’s possible to track solid-state reactions during synthesis, including material transformations and phase transitions, in what’s called a ball milling jar. But, because of scattering from its walls, as the X-rays go through the jar, the diffraction patterns offer a high background. Additionally, it’s expected that the sample will present broad diffraction peaks, due to the probing of a large sample area that covers the whole jar, and an extra complexity shows up as a result of diffraction on the milling balls. This technique has gained popularity in many of the various fields of mechanochemistry, but isn’t foolproof.

This image shows a thin-walled jar with a groove; isometric view with a cut (left) and cross section (right). [Image: UCL research team]

The research team recently published a paper on their efforts, titled “3D-printed jars for ball-milling experiments monitored in situ by X-ray powder diffraction,” in the Journal of Applied Crystallography; co-authors included UCL researchers Yaroslav Filinchuk; Nikolay Tumanov, also with the Department of Chemistry at Belgium’s University of Namur; Voraksmy Ban, also with the MS Group of the Swiss Light Source with the Paul Scherrer Institut in Switzerland; and Agnieszka Poulain, who is with the European Synchrotron Radiation Facility in France.

According to the abstract, “Mechanochemistry is flourishing in materials science, but a characterization of the related processes is difficult to achieve. Recently, the use of plastic jars in shaker mills has enabled in situ X-ray powder diffraction studies at high-energy beamlines. This paper describes an easy way to design and manufacture these jars by three-dimensional (3D) printing. A modified wall thickness and the use of a thin-walled sampling groove and a two-chamber design, where the milling and diffraction take place in two communicating volumes, allow for a reduced background/absorption and higher angular resolution, with the prospect for use at lower-energy beamlines. 3D-printed polylactic acid jars show good mechanical strength and they are also more resistant to solvents than jars made of polymethyl methacrylate.”

In the paper, the research team details how 3D printing was used to quickly make the ball milling jars, and optimize them to achieve improved absorption and angular resolution, and a better, less high background, for their X-ray powder diffraction experiments. As we know, 3D printing technology allows for low-cost, on-demand production of customized objects, and the UCL team’s 3D printed jars were manufactured to be more resistant to solvents, when compared to typical acrylic jars. 3D printing has been used for experiments in the growing materials science field before, and judging by the success of the UCL researchers, I’m sure other institutes will also turn to the technology for help. Discuss in the Mechanochemistry forum at 3DPB.com.