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Rethinking Sintering: Superfast, Flexible and Energy Saving from a Batch Size of 1

At the Annual Meeting of the German Ceramic Society – DKG – in March 2023, Lukas Porz (TU Darmstadt and Illutherm GmbH) presented a new technology in a keynote entitled “Blacklight Sintering – a Disruptive Technology for Ceramic Processing?“ For his work, he had been awarded the DGM Prize for Young Talents in autumn 2022. Will these new findings from basic research replace to any extent existing sintering technologies in future or even squeeze them completely out of the market for certain applications? If yes, this will open up great potential for saving energy, time and costs. We were able to ask Lukas Porz (LP) about his current plans and obtain an abstract of his work (E 21).

cfi: How did you get to the topic of blacklight sintering? 

LP: As an employee at the Technical University of Darmstadt, in Prof. Jürgen Rödel’s Ceramics Group, I was involved in a Koselleck project funded by the DFG. Its objective was to develop a new generation of ceramics that were not optimised based via doping and optimising their microstructure, but by means of dislocations, as known from metals. Line defects are deliberately incorporated into the crystal lattice so that half planes are missing in the otherwise regular crystal lattice of the ceramics. These dislocations lead to a range of interesting, potentially useful changes in properties, like, for example, improved plasticity, conductivity or catalytic activity. Once we understood that these dislocations can be formed as a result of ultrafast sintering, we looked into fast sintering methods. We identified photonic high-power energy input as the most promising future method as it is precise, flexible and scalable. It was clear to us: With light as the energy medium, the use of photon energy that is greater than the band gap of the ceramic (blacklight) is essential for good absorption and high efficiency. 

cfi: Is that model more suitable for research or can we expect an application in industry? 

LP: It is only recently that sufficiently powerful short wave light sources have become available. Over the last five years, photonics (light technology) has developed very rapidly. Thanks to the large number of recent optical applications (lasers, sensors and imaging), it is one of the largest growth markets. This is also driven by trends like smart manufacturing. At the focus of photonics is the use of light with all its possibilities. From light control through laser technologies to data transfer, photonics is applied in many fields, such as the medical sector, industry, astronomy, microscopy or traffic safety. So we are expecting a rapid increase in the availability of systems on the market, which will then be offered at more attractive prices and enable industrial applications on a greater scale. So far, we have been working with novel blue diode lasers and xenon flash lamp systems. 

cfi: Is the process suitable for all ceramics? 

LP: We have tested a wide range of materials (e.g. oxide ceramics). And these tests have shown that blacklight is universally usable, even if not every material system is likely to be suitable. Graded materials are also possible. We place the dried (in some cases debinded) components on an insulated base surface, e.g. made of expanded graphite or porous ceramic, and irradiate the ceramic components for a few seconds. Using thermal simulation techniques, we can find out which temperature distribution results on interaction between the components to be sintered and the base material, and how long we have to treat the parts. Within seconds, we can obtain sintering curves from 1200–1800 ÆC – or even higher if required. With coordinated light conditions (geometry of the components, material of the components and base), we achieve excellent sintered densities, and consequently good material properties. With optimised systems, microcracks could not be detected. It is feasible to work with moveable bases if that is expedient with regard to the component geometry. In our view, energy transfer by means of light offers a wider range of application than other new sintering techniques, e.g. flash sintering. 

cfi: What limits does the process have? 

LP: At present, we are working with relatively small components with a cross-section measuring a few centimetres and wall thicknesses of several millimetres. The limitation comes from the penetration depth while the lateral size is limited by the power of the commercially available light sources. 

cfi: Where do you see the key advantages of blacklight sintering? 

LP: It works from a batch size of one and can be easily extended as part of a modular concept. Investment costs are lower because no furnaces, the size of which would have to be defined in advance, are needed. The rapid speed of the process enables low energy costs, and its flexibility – you can change over programs shortly after each other – offers additional cost efficiency. As results are available fast, it is possible to get working quickly on any further optimization, meaning development time and costs can be reduced considerably. 

cfi: How are you planning your further work on this? 

LP: Just in February 2023, three of us set up the company Illutherm in order to work with more interested companies. Thanks to start-up support from SPRIN-D of over EUR 200 000 and EUR 50 000 from the ESA, we have been able to lease premises in the HUB 31 technology and start-up centre in Darmstadt and use the technical facilities at LAB3 e. V. With regard to specific analytics, we shall certainly get further support from TU Darmstadt. For that reason, the close proximity is a huge advantage. If we are successful in the first year, there is the chance to receive support amounting to one or even double-figure millions annually in a second phase over five years. Important for us is that we also get help with non-technical aspects, e.g. business or legal issues, through SPRIN-D. It was amazing that for our application we only had to fill out a two-page form, and do two online interviews before we received a prompt decision on the investment. The SPRIN-D package provides indispensable and valuable support. 

cfi: Thank you for talking to us.

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