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266511

Research outputs

As an application-oriented research organisation, Fraunhofer aims to conduct highly innovative and solution-oriented research - for the benefit of society and to strengthen the German and European economy.

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Projects

Fraunhofer is tackling the current challenges facing industry head on. By pooling their expertise and involving industrial partners at an early stage, the Fraunhofer Institutes involved in the projects aim to turn original scientific ideas into marketable products as quickly as possible.

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Researchers

Scientific achievement and practical relevance are not opposites - at Fraunhofer they are mutually dependent. Thanks to the close organisational links between Fraunhofer Institutes and universities, science at Fraunhofer is conducted at an internationally first-class level.

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Institutes

The Fraunhofer-Gesellschaft is the leading organisation for applied research in Europe. Institutes and research facilities work under its umbrella at various locations throughout Germany.

Recent Additions

  • Publication
    Additive Manufacturing of Side-Coupled Cavity Linac Structures from Pure Copper: A First Concept
    ( 2023)
    Mayerhofer, Michael
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    Brenner, Stefan
    ;
    Helm, Ricardo
    ;
    ; ; ;
    Gold, Gerald
    ;
    Dollinger, Günther
    Compared to conventional manufacturing, additive manufacturing (AM) of radio frequency (RF) cavities has the potential to reduce manufacturing costs and complexity and to enable higher performance. This work evaluates whether normal conducting side-coupled linac structures (SCCL), used worldwide for a wide range of applications, can benefit from AM. A unit cell geometry (SC) optimized for 75 MeV protons was developed. Downskins with small downskin angles 𝛼 were avoided to enable manufacturing by laser powder bed fusion without support structures. SCs with different 𝛼 were printed and post-processed by Hirtisation (R) (an electrochemical process) to minimize surface roughness. The required accuracy for 3 GHz SCCL (medical linacs) is achieved only for 𝛼>45∘. After a material removal of 140 µm due to Hirtisation (R), a quality factor 𝑄0 of 6650 was achieved. This corresponds to 75% of the 𝑄0 simulated by CST®. A 3 GHz SCCL concept consisting of 31 SCs was designed. The effective shunt impedance 𝑍𝑇2 simulated by CST corresponds to 60.13MΩm and is comparable to the 𝑍𝑇2 of SCCL in use. The reduction in 𝑍𝑇2 expected after Hirtisation (R) can be justified in practice by up to 70% lower manufacturing costs. However, future studies will be conducted to further increase 𝑄0. .
  • Publication
    Laser induced reduction of iron ore by silicon
    ( 2023)
    Kaplan, Alexander
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    Fedina, Tatiana
    ;
    ;
    Powell, John
    Iron ore powder accompanied by Si-powder as a reducing agent, was melted using a high-power laser beam. During laser melting of the two different powder beds placed next to each other, silicon merged and diffused into the iron ore, forming a ternary melt phase Fe-O-Si of around 30-60-10 at%. High speed imaging of the laser melting process as well as subsequent SEM-analysis of the generated nuggets showed the formation of droplets that merge with the surrounding Si- or ore-powder and form distinct domains. Under certain circumstances, the solidifying nuggets, of the order of 0.5-5 mm in size, generated numerous small domains, up to 25 µm, of high purity iron, 90 + at%, surrounded by a matrix of the above mentioned slag. Many of these Fe-domains were created in the vicinity of regions of high Si-content.
  • Journal
  • Publication
    Impact of the Carbon Matrix Composition on the S/C Cathode Porosity and Performance in Prototype Li-S Cells
    The lithium-sulfur battery is a promising electrochemical storage solution, especially for aviation and aeronautical applications, due to its high-gravimetric energy density (specific energy) and the abundance of sulfur. In recent years, the number of reported prototype cells and their realized energy have increased. This underlines the progress of technology readiness of the lithium-sulfur system. However, the influence of the cathode porosity as well as the porosity of the carbon material on the performance of prototype cells is still not fully understood. Consequently, in this study, the porosity of solvent-free processed cathodes is investigated, with varying carbon matrix composition, via mercury intrusion porosimetry and synchrotron tomography. Moreover, the swelling behavior of the S/C dry-film cathodes is investigated and mitigated. These cathodes are then electrochemically evaluated at pouch cell level with ether-based electrolytes with varying E/S ratios. The combination of the gained findings in pouch cells enables specific energies of 425 Wh kg-1 and 558 Wh L-1 at cell level.

Most viewed

  • Publication
    Hierarchical Clock Synchronization in MPI
    ( 2018)
    Hunold, S.
    ;
    Carpen-Amarie, A.
    MPI benchmarks are used for analyzing or tuning the performance of MPI libraries. Generally, every MPI library should be adjusted to the given parallel machine, especially on supercomputers. System operators can define which algorithm should be selected for a specific MPI operation, and this decision which algorithm to select is usually made after analyzing bench-mark results. The problem is that the latency of communication operations in MPI is very sensitive to the chosen data acquisition and data processing method. For that reason, depending on how the performance is measured, system operators may end up with a completely different MPI library setup. In the present work, we focus on the problem of precisely measuring the latency of collective operations, in particular, for small payloads, where external experimental factors play a significant role. We present a novel clock synchronization algorithm, which exploits the hierarchical architecture of compute clusters, and we show that it outperforms previous approaches, both in run-time and in precision. We also propose a different scheme to obtain precise MPI run-time measurements (called Round-Time), which is based on given, fixed time slices, as opposed to the traditional way of measuring for a predefined number of repetitions. We also highlight that the use of MPI_Barrier has a significant effect on experimentally determined latency values of MPI collectives. We argue that MPI_Barrier should be avoided if the average run-time of the barrier function is in the same order of magnitude as the run-time of the MPI function to be measured.
  • Publication
    Characterization of self-cleaning properties on superhydrophobic aluminum surfaces fabricated by direct laser writing and direct laser interference patterning
    ( 2020)
    Milles, Stephan
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    Soldera, Marcos
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    ;
    Self-cleaning ability on technical surfaces can increase the added value of a product. A common path to achieve this property is making the surface superhydrophobic so that water droplets can roll down, picking up dirt particles. In this contribution, the self-cleaning efficiency of Al surfaces structured with direct laser writing (DLW), direct laser interference patterning (DLIP) and a combination of both technologies was quantitatively determined. This was performed by developing a characterization method, where the treated samples are firstly covered with either MnO2 or polyamide micro-particles, then tilted by 15° and 30° and finally washed applying up to nine water droplets (10 µl) over the contaminated surfaces. Then, an optical analysis by image processing of the remaining contamination particles on the textured surfaces was realized after each droplet rolled over the surface. The DLIP textures showed the best performance, allowing the removal of more than 90% of the particles after just three droplets were released. High-speed videos and scanning electron microscopy characterization allowed a deeper understanding on the cleaning behavior and on the relationship between surface microstructure and particle size and shape.