Computed tomography assists in optimising the internal material structures of tablets and catalysts

How should tablets, pellets and briquettes be composed to prevent them from breaking during transport? Which microstructure should have an industrial filter to show the highest solid separation efficiency? How long can chemical catalysts withstand high mechanical loads in a high-pressure reactor? Kaiserslautern researchers are investigating these questions with a computed tomograph system that can recognise the smallest material structures non-destructively. The technique may be used in various areas of application. The team will be presenting its work at the Process Industry Trade Fair Achema in Frankfurt from 10 to 14 June at the Rhineland-Palatinate research stand (Stand E51, Hall 6.0).

Prof Sergiy Antonyuk (left), Dr Kai Nikolaus and Yannik Sinnwell (at the back of the picture) are researching the mechanical properties of so-called agglomerates such as tablets. Credit: RPTU, Koziel

Tablets combine the active substance with fillers and binders (e.g. microcrystalline cellulose and lactose) into a dosage form. This is usually a so-called agglomerate, i.e. a mixture of bound fine particles of the active ingredient and filler components. Professor Dr Sergiy Antonyuk’s research team from the Institute of Partcile Process Engineering at the University of Kaiserslautern-Landau (RPTU) is working on this research topic. The team is analysing the mechanical properties of such a structure. “This is important for the strength of tablets, for example. We are interested in finding out where potential fracture points are located, as well as when and why a fracture occurs,” explains Antonyuk.

To do so, the researchers use a computed tomography (CT) scanner to capture the material structures in high resolution. To investigate the fracture behaviour of particle agglomerates, the working group uses a second measuring device that is operated in the tomograph during the CT measurement. “We use what is known as an in-situ compression/tension unit to directly load the samples with a certain force and check at which position a fracture or crack occurs. We investigate how the composition and microstructure influence the strength. The distribution of the components in the agglomerate and how the individual particles stick to each other in contacts also play a role here,” the professor continues.

This is important for the storage and transport of tablets, for example. Antonyuk: “The fracture processes reduce the product quality and cause the dust formation. This means that a tablet produced with a press agglomeration process must have a high strength. At the same time, however, it must not be pressed overly so that it can dissolve in water, for example, based on a high porosity needed for a quick dissolution.” Based on the CT results, the researchers are working on optimising the internal structure of such agglomerates.

CT technology is also suitable for catalysts and filters

The device can also be used to analyse chemical catalysts. Researchers are focussing on the question of whether and at which positions catalyst particles can break. “In many industrial processes, they are exposed to high loads in reactors and can lose their function over time due to breakage processes or increase the flow resistance,” explains Antonyuk. One of the things the engineers are investigating is the extent to which mechanical stress impairs the function of catalytic converters and when they need to be replaced.

The working group also uses the system to analyse certain filter materials. These are used in industry, for example, to separate solids from fluids. “We look at the exact arrangement of such composite filters, which consist of several materials,” Antonyuk continues. They are structured as follows: A membrane is applied to a fabric, which adheres to it via adhesive dots. “It’s like a water-repellent functional jacket, but in reverse,” he explains. “The water penetrates through the filter material, but the membrane prevents air from passing through.” This type of mechanical dehumidification is used in industry for the recovery of solid recyclable materials. The advantage of this process is that it saves energy compared to other methods. The team is focussing on the adhesive dots. Antonyuk: “We investigate the distribution of the adhesive dots over the surface to find out how this affects the filtration process and the mechanical stability of the filter material during operation of a filter system.”

The device can also be used to analyse the efficiency or protective effect of medical and FFP face masks. “We first test the filter efficiency for different wearing scenarios with a test aerosol, a mixture of gas or fine liquid, on a test head,” explains the professor. The CT images can then be used to generate a 3D model of the entire test head with mask and to analyse the microstructure of the face masks. This data is used to calculate the flow during the breathing process. The aim is to optimise the filter efficiency and ageing of the face masks.

Technical details of the computed tomography scanner

The TomoScope L computed tomography (CT) scanner from Werth Messtechnik GmbH can be used very flexibly to examine different sample sizes (< 300 millimetres) and material densities thanks to its 400 millimetres, high-resolution 4K area detector and two X-ray tubes. The measuring device enables this flexibility thanks to a microfocus tube with 240 kilovolts and a nanofocus tube with 160 kilovolts, which can be used depending on the sample properties. The maximum proven structural resolution of the measuring device is one micrometre with a minimum voxel size of 500 nanometres.

The acquisition of the CT system was funded as part of a large-scale research equipment programme of the Deutsche Forschungsgemeinschaft [German Research Foundation, DFG]. The institute has opened its laboratory for this device since 2021.  Dr Kai Nikolaus from the Institute of Particle Process Engineering is in charge of the laboratory. The CT system can also be used to precisely analyse the shapes and size distributions of particles in the lower micrometre range, surface structures of components and even biological structures from human connective tissue cells.

At Achema, Antonyuk and his team are presenting various computed tomography results, providing an insight into the microstructures and fracture processes of different materials.

Questions can be directed to:
Professor Dr-Ing. Sergiy Antonyuk
Department of Mechanical Process Engineering
University of Kaiserslautern-Landau (RPTU)
E-mail:     sergiy.antonyuk[at]mv.rptu.de
Phone: +49 631 205-3524

Klaus Dosch, Department of Technology, Innovation and Sustainability, is organizing the presentation of the researchers of the University Kaiserslautern-Landau at the fair. He is the contact partner for companies and, among other things, establishes contacts to science. Contact: Klaus Dosch, E-mail: klaus.dosch[at]rptu.de, Phone: +49 631 205-3001