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251519

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
    Composition-dependent Photoconductivities in Indium Aluminium Nitride Nanorods Grown by Magnetron Sputter Epitaxy
    ( 2022)
    Kumar, Bangolla Hemanth
    ;
    Siao, Ming-Deng
    ;
    Huang, Yi-Hua
    ;
    Chen, Ruei-San
    ;
    Zukauskaite, Agne
    ;
    Palisaitis, Justinas
    ;
    Persson, Per
    ;
    Hultman, Lars
    ;
    Birch, Jens
    ;
    Hsiao, Ching-Lien
    Photoconduction (PC) properties were investigated for ternary indium aluminium nitride (InxAl1−xN) nanorods (NRs) with different indium composition (x) from 0.35 to 0.68, as grown by direct-current reactive magnetron sputter epitaxy. Cross-sectional scanning transmission electron microscopy (STEM) reveals single-crystal quality of the vertically aligned InxAl1−xN NRs. Single-rod photodetector devices with good ohmic contacts were fabricated using the focused-ion-beam technique (FIB), where In-rich In0.68Al0.32N NR exhibits the optimal photocurrent responsivity at 1400 A/W and photoconductive gain at 3300. A transition from positive photoresponse to negative photoresponse was observed, while increasing the In composition x from 0.35 to 0.57. The negative PC was further enhanced by increasing x to 0.68. A model based on the coexistence and competition of deep electron trap states and recombination centers was proposed to explain the interesting composition-dependent PC in these ternary III-nitride 1D nanostructures.
  • Publication
    A meshfree arbitrary Lagrangian-Eulerian method for the BGK model of the Boltzmann equation with moving boundaries
    ( 2022)
    Tiwari, S.
    ;
    Klar, Axel
    ;
    Russo, G.
    In this paper we present a novel technique for the simulation of moving boundaries and moving rigid bodies immersed in a rarefied gas using an Eulerian-Lagrangian formulation based on least square method. The rarefied gas is simulated by solving the Bhatnagar-Gross-Krook (BGK) model for the Boltzmann equation of rarefied gas dynamics. The BGK model is solved by an Arbitrary Lagrangian-Eulerian (ALE) method, where grid-points/particles are moved with the mean velocity of the gas. The computational domain for the rarefied gas changes with time due to the motion of the boundaries. To allow a simpler handling of the interface motion we have used a meshfree method based on a least-square approximation for the reconstruction procedures required for the scheme. We have considered a one way, as well as a two-way coupling of boundaries/rigid bodies and gas flow. The numerical results are compared with analytical as well as with Direct Simulation Monte Carlo (DSMC) solutions of the Boltzmann equation. Convergence studies are performed for one-dimensional and two-dimensional test-cases. Several further test problems and applications illustrate the versatility of the approach.
  • Publication
    1D multiphysics modelling of PEM water electrolysis anodes with porous transport layers and the membrane
    ( 2022)
    Lin, Nan
    ;
    1D multiphysics modelling of the PEM water electrolysis anode is benefit for detailed investigation of the joint effects of electrochemical performance and multicomponent multiphase flow transport phenomena. Such a model can be effectively applied for the water electrolysis system design and optimization. Recently, the importance of hydraulic effects and dynamic behavior gradually attracts much focus on this specific issue. In this article, a novel 1D dynamic model has been developed for interpreting the multiphysics processes in the PEM water electrolysis anode, which considers the complex fluid dynamics and electrochemistry in the PEM water electrolyzer (PEMWE) components - PEM, the anode catalyst layer and the porous transport layer. As a result, the hydraulic and electrochemical properties of three components were studied for investigation of their effects on the characterization of electrochemical performance and mass transport processes. It concludes that for the improvement of electrolytic performance, the porous transport layer is suggested to be designed for high permeability and low contact angle. The catalyst layer needs to be optimized for its three-phase interface fraction with high coating mass in the membrane assembly.

Most viewed

  • Publication
    Laser structured nickel-iron electrodes for oxygen evolution in alkaline water electrolysis
    ( 2019)
    Koj, M.
    ;
    Gimpel, T.
    ;
    Schade, W.
    ;
    Turek, T.
    In the present work, the ultra-short pulse laser ablation method is applied to create novel surface alloys on NiFe electrodes for the oxygen evolution reaction (OER) in alkaline water electrolysis. The nickel-to-iron ratio in the alloy can be controlled with the ultra-short pulse laser ablation method by varying the thickness of electrochemically deposited iron layers onto the nickel mesh substrate. Besides the application of the additional catalyst, the laser treatment enhances the surface area and a defined micro- and submicrometer structure is created in a single step. The laser structured nickel-iron electrodes show a significantly lower overpotential of 249 mV than an electrochemically deposited Ni-NiFe alloy with 292 mV at 10 mA cm−2, 298 K and 32.5 wt% KOH for the OER, although some loss of iron over time could not be prevented.
  • Publication
    Semantisch unterstützte interaktive Visualisierung von Finanzdaten
    ( 2007)
    Georgi, Matthias
    ;
    Tekusová, Tatiana
    Das Ziel dieser Arbeit ist die Entwicklung eines web-basierten Visualisierungssystems, welches das interaktive Erforschen und Analysieren von hierarchischen Finanzdaten ermöglicht. Hierzu werden verschiedene Darstellungstechniken untersucht und als konfigurierbare Komponenten implementiert, welche von einem Anwender ohne Programmierkenntnisse arrangiert werden können. Um eine effiziente Analyse multidimensionaler Daten zu ermöglichen, wurde ein OLAP-System entworfen, welches über eine multidimensionale Anfragesprache abgerufen werden kann. Wesentliche Kriterien dieser Verfahrensweise sind die einfache Konfigurierbarbeit auf der einen und die einer Vielzahl von Situationen gerecht werdende Anwendbarkeit auf der anderen Seite.