Article
Materials Science, Multidisciplinary
L. Abou-Khalil, Z. Thompson, G. Reinhart, T. Stan, L. Sturz, G. Zimmermann, P. W. Voorhees, N. Mangelinck-Noel, H. Nguyen-Thi
Summary: Three-dimensional reconstruction of the microstructure of Al - 7 wt.% Si samples solidified in microgravity conditions on the International Space Station revealed that the number of dendrite fragments depends on the dendrite network configuration. Samples with multiple dendrites with different orientations had more fragments compared to samples with well-aligned dendrites. The highest number of fragments was found in the region corresponding to an incipient grain boundary where dendrites with different orientations compete, indicating that dendrite misorientation during solidification leads to the formation of dendrite fragmentation.
Article
Materials Science, Multidisciplinary
Xudong Liu, Qingfeng Zhu, Cheng Zhu, Yubo Zuo, Haichang Jiang
Summary: This study investigated the mechanisms involved in the grain refinement of a 2024 aluminum alloy prepared through the direct-chill (DC) casting process with the introduction of intensive melt shearing. The experiments and theoretical analyses demonstrated that shear stress between the stator and rotor can break the dendrite arms. The experimental results showed that the cooling rate of the melt during intensive melt shearing casting is higher than that in conventional DC casting, leading to improved grain refining effect when shearing is processed at a lower position with a higher rotation speed.
METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE
(2022)
Article
Materials Science, Multidisciplinary
V. T. Witusiewicz, L. Sturz, A. Viardin, C. Pickmann, G. Zimmermann
Summary: This study investigated the interaction of melt flow with solidification microstructures during the directional solidification process of a succinonitrile-2.2wt.%(d)camphor alloy. The results showed that the intensity of melt flow affected the morphology, spacing, and growth direction of the microstructures, leading to transitions between dendritic and seaweed-type structures. Additionally, oscillations of dendrite tip positions were observed within a specific parameter range.
Article
Materials Science, Multidisciplinary
Luwei Yang, Neng Ren, Chinnapat Panwisawas, Jun Li, Mingxu Xia, Hongbiao Dong, Jianguo Li
Summary: This study combines the cellular automaton-finite volume approach and the displacement-based finite element method to simulate dendrite growth, fluid flow, and flow-induced mechanical deformation in Al-4.5 wt%Cu alloy. The results show that fluid flow can cause visible mechanical bending of dendrites, and the stress increases with the enhancement of fluid flow. The primary dendritic trunk is the primary location of deformation under parallel fluid flow. The bridging of secondary dendrites impedes the development of stress concentrations.
JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T
(2023)
Article
Engineering, Chemical
Wataru Hikita, Shodai Hirayama, Chihiro Inoue, Zhenying Wang, Makoto Nakaseko, Takuya Takashita
Summary: This study investigates the fragmentation and solidification processes during the production of metal powders. The experiments reveal that fragmentation is controlled by capillarity, while solidification and viscosity have no influence. Additionally, the study finds that the circularity of the produced metal powder is size-dependent, with larger particles being less spherical.
Article
Materials Science, Multidisciplinary
Luwei Yang, Neng Ren, Chinnapat Panwisawas, Jun Li, Mingxu Xia, Hongbiao Dong, Jianguo Li
Summary: This paper combines the cellular automaton-finite volume approach and finite element method to study the flow-induced dendritic deformation in alloy solidification. The simulation results show that dendrites can undergo mechanical fracture in the solidification of Al-Cu alloy. The root of the primary dendrite is not the location of maximum stress due to secondary dendritic bridging and uneven radius of the primary dendritic trunk. Corresponding deformation and fracture mechanisms of dendrites are suggested in the paper.
METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE
(2023)
Article
Materials Science, Multidisciplinary
Xuesong Xu, Hongsheng Ding, Haitao Huang, He Liang, Ruirun Chen, Jingjie Guo, Hengzhi Fu
Summary: In this study, the factors affecting the columnar to equiaxed transition (CET) in high-Nb TiAl alloys were investigated by fabricating Ti46Al7Nb0.4W0.6Cr0.1B alloy using cold crucible directional solidification (CCDS) technique. Results showed that the increase in pulling rate and fulfillment of heterogeneous nucleation conditions were the main factors influencing CET.
JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T
(2021)
Article
Mathematics, Applied
Dmitri V. Alexandrov, Peter K. Galenko
Summary: The analytical solution to the boundary integral equation is obtained for the growth of angled dendrites and arbitrary parabolic/paraboloidal solid/liquid interfaces in two and three dimensions. The undercooling of a binary melt and solute concentration at the phase transition boundary are determined. This theory potential can be useful in describing more complex growth shapes and interfaces.
MATHEMATICAL METHODS IN THE APPLIED SCIENCES
(2021)
Article
Crystallography
Andras Roosz, Arnold Ronafoldi, Yuze Li, Nathalie Mangelinck-Noel, Gerhard Zimmermann, Henri Nguyen-Thi, Maria Sveda, Zsolt Veres
Summary: In this study, solidification experiments were conducted on the International Space Station to investigate the effect of solidification parameters on the grain structure and dendritic microstructure of Al-Si alloy. The analysis also focused on the macrosegregation caused by diffusion and the distribution of eutectic along the solidification direction. The results showed good agreement between the experimental and simulated data.
Article
Materials Science, Multidisciplinary
Luciano Eliezer Ramirez-Vidaurri, Manuel Castro-Roman, Martin Herrera-Trejo, Karla-Leticia Fraga-Chavez
Summary: The solidification evolution of an ASTM F75 alloy during directional cooling was studied, revealing that the solid grows most rapidly in a temperature range of approximately 200 degrees Celsius, reaching a solid fraction of about 0.8-0.9, with the coarsening of Secondary Dendrite Arm Spacing (SDAS) mainly occurring during this period.
JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T
(2022)
Article
Crystallography
Junfeng Xu, Peter K. Galenko
Summary: This paper presents a solidification growth model that combines the effect of eutectic transformation and off-eutectic composition, and discusses the influence of model and material parameters on solidification kinetics by comparing them with experimental data. The computational results show that the off-eutectic growth model agrees well with experimental data on the solidification kinetics of Ni-B and Ti-Si alloys.
Article
Optics
Jiawei Wang, Huaming Wang, Xu Cheng, Bo Zhang, Yu Wu, Shuquan Zhang, Xiangjun Tian
Summary: By controlling the processing parameters in laser additive manufacturing, the mechanical properties of titanium aluminum alloy can be modified. The study developed a numerical model to predict solidification microstructure and investigate the effects of laser processing parameters on dendrite arm spacing. Experimental results show that the model is effective in predicting the solidification microstructure. The scanning velocity plays a dominant role in changes in dendrite arm spacing, while the impact of laser power gradually increases with higher scanning velocity.
OPTICS AND LASER TECHNOLOGY
(2022)
Review
Materials Science, Multidisciplinary
Nicholas Cusato, Seyed Amin Nabavizadeh, Mohsen Eshraghi
Summary: Over the past two decades, researchers have been interested in large-scale simulations for analyzing the solidification of alloys. In situ X-ray observations have revealed costly defects in dendrites for manufacturers. These simulations involve various numerical schemes to simulate morphology and solve transport phenomena, such as cellular automaton, phase field, and finite element methods. This paper explores these methodologies in detail and focuses on understanding complex real-world phenomena, including columnar to equiaxed transition, competitive growth, and microsegregation.
Article
Materials Science, Multidisciplinary
Xiaoping Ma, Dianzhong Li
Summary: This study reveals that the base of conventional dendritic arms in the solidification process of M50 bearing steel is formed by a primary semi-solid matrix. The superimposition of temperature fluctuations gives rise to multi-scale dendritic patterns in the primary semi-solid matrix. These findings redefine the essence of multi-scale dendrites and have significant implications for the field of solidification research.
JOURNAL OF MATERIALS SCIENCE & TECHNOLOGY
(2022)
Article
Materials Science, Multidisciplinary
L. Abou-Khalil, K. Sabat da Cruz, G. Reinhart, N. Mangelinck-Noel, H. Nguyen-Thi
Summary: The directional solidification of Al - 14 wt.% Sn alloy was investigated using synchrotron X-radiography. The influence of increasing growth velocity on the fragmentation phenomenon of dendrite arms was studied, and the Columnarto-Equiaxed Transition induced by the fragmentation phenomenon was observed.
Article
Engineering, Environmental
Yorgos Stergiou, Kerstin Eckert, Karin Schwarzenberger
Summary: Hele-Shaw cells are commonly used in various fields, and the flow conditions near the inlet of a radial Hele-Shaw cell can significantly affect its technological applications. This study combines CFD and μPIV to explain the entrance phenomena in radial Hele-Shaw cells, providing valuable insights for future engineering applications.
CHEMICAL ENGINEERING JOURNAL
(2022)
Article
Chemistry, Applied
Barbara Fritzsche, Zhe Lei, Xuegeng Yang, Kerstin Eckert
Summary: Efficient extraction and recycling of rare earth elements are crucial issues, and magnetic separation may offer a promising solution. This study verifies the theory of magnetic separation for various rare earth ions and suggests incorporating magnetic separation into existing hydrometallurgical technology to enhance REE selectivity.
JOURNAL OF RARE EARTHS
(2022)
Article
Electrochemistry
Mengyuan Huang, Katarzyna Skibinska, Piotr Zabinski, Marek Wojnicki, Grzegorz Wloch, Kerstin Eckert, Gerd Mutschke
Summary: This study explores the prospects of using magnetic fields to support the growth of smaller micro-/nano-sized conical structures. Numerical simulations and systematic experiments were conducted to investigate the effects of magnetic fields on electrodeposition. It was found that the support from magnetic fields is limited by viscous friction and concentration changes, and suggestions for improving the structuring effect were proposed.
ELECTROCHIMICA ACTA
(2022)
Article
Materials Science, Multidisciplinary
H. Neumann-Heyme, N. Shevchenko, J. Grenzer, K. Eckert, C. Beckermann, S. Eckert
Summary: This study utilized high-resolution synchrotron radiography and advanced image processing techniques to quantitatively measure the growth process of dendrite tips in solidifying alloys, finding values for dendrite tip shape selection parameter and nonaxisymmetric dendrite tip shape amplitude coefficient.
PHYSICAL REVIEW MATERIALS
(2022)
Article
Physics, Condensed Matter
M. Ziauddin, E. Schleicher, P. Trtik, L. Knuepfer, A. Skrypnik, T. Lappan, K. Eckert, S. Heitkam
Summary: The liquid fraction of foam is crucial for engineering process control and foam rheology interpretation. Existing measurement tools, such as optical measurement and radiography techniques, are mostly limited to laboratory settings, while conductivity-based measurements lack detailed spatial information. In this study, we compare the conductivity-based wire-mesh sensor with neutron radiography and find a linear relationship between the liquid fraction and wire-mesh readings with a deviation of less than 15%. However, the wire-mesh sensor systematically overestimates the liquid fraction due to liquid bridge formation between the wires.
JOURNAL OF PHYSICS-CONDENSED MATTER
(2023)
Review
Chemistry, Multidisciplinary
Mariya E. Ivanova, Ralf Peters, Martin Mueller, Stefan Haas, Martin Florian Seidler, Gerd Mutschke, Kerstin Eckert, Philipp Roese, Sonya Calnan, Rory Bagacki, Rutger Schlatmann, Cedric Grosselindemann, Laura-Alena Schaefer, Norbert H. Menzler, Andre Weber, Roel van de Krol, Feng Liang, Fatwa F. Abdi, Stefan Brendelberger, Nicole Neumann, Johannes Grobbel, Martin Roeb, Christian Sattler, Ines Duran, Benjamin Dietrich, M. E. Christoph Hofberger, Leonid Stoppel, Neele Uhlenbruck, Thomas Wetzel, David Rauner, Ante Hecimovic, Ursel Fantz, Nadiia Kulyk, Jens Harting, Olivier Guillon
Summary: Hydrogen produced from renewables will have a growing impact on global energy dynamics towards sustainability and carbon neutrality. However, the current share of green hydrogen is too low, and there is a rising demand for high-quality hydrogen. This highlights the need for economically viable hydrogen generation technologies. This article evaluates existing technologies for high-quality hydrogen production based on solar energy, considering their current development level, technical limitations, and future potential.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
Article
Chemistry, Physical
Hannes Rox, Aleksandr Bashkatov, Xuegeng Yang, Stefan Loos, Gerd Mutschke, Gunter Gerbeth, Kerstin Eckert
Summary: A novel 3-electrode cell is used to investigate H2 evolution on porous electrodes in an alkaline electrolyte. Electrochemical methods and high-speed optical measurement are applied to characterize the electrodes and bubble dynamics. The size of detached bubbles and the surface coverage of the electrode are significantly influenced by the applied current density. Forced flow reduces the bubble size, while the initial transient is less affected by flow-through.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2023)
Article
Chemistry, Multidisciplinary
Tobias Lappan, Dominic Herting, Muhammad Ziauddin, Julian Stenzel, Natalia Shevchenko, Sven Eckert, Kerstin Eckert, Sascha Heitkam
Summary: In mineral processing, froth flotation is used to recover valuable mineral particles through overflowing froth. However, the velocity profile of the overflowing froth beneath its free surface cannot be observed optically. This study combines X-ray radiography and particle tracking velocimetry to measure local flow velocities within an optically opaque foam at a weir. Tracer particles were used to trace the flow in X-ray image sequences, and the velocity profile above the weir crest was determined.
APPLIED SCIENCES-BASEL
(2023)
Article
Nanoscience & Nanotechnology
Lukas Krause, Katarzyna Skibinska, Hannes Rox, Robert Baumann, Mateusz M. Marzec, Xuegeng Yang, Gerd Mutschke, Piotr Zabinski, Andres Fabian Lasagni, Kerstin Eckert
Summary: Emerging manufacturing technologies allow for the design of electrocatalyst morphology on the nanoscale to improve efficiency in electrolysis processes. This study investigates the impact of electrode-attached hydrogen bubbles on electrode performance, depending on surface morphology and wettability. Nickel-based electrocatalysts with hydrophilic and hydrophobic nanostructures are manufactured and their surface properties are characterized. Despite a larger electrochemically active surface area, electrochemical analysis shows that samples with more pronounced hydrophobic properties perform worse at industrially relevant current densities. High-speed imaging reveals larger bubble detachment radii with higher hydrophobicity, indicating that gas blockage outweighs the benefits of nanostructuring. Additionally, a slight decrease in bubble size of 7.5% is observed with an increase in current density in 1 M KOH.
ACS APPLIED MATERIALS & INTERFACES
(2023)
Article
Engineering, Chemical
Aliyar Javadi, Majede Nourizade, Mohammad Rahmani, Kerstin Eckert
Summary: In photocatalytic processes for wastewater treatment, understanding the interactions between the catalyst and pollutant is crucial. This study uses drop profile analysis tensiometry (PAT) to analyze the surface tension and elasticity of dye solutions mixed with catalyst nanoparticles at different pH conditions. The results show that the surface activity of the dye Malachit Green (MG) increases at pH 9 when TiO2 nanoparticles are added. This indicates significant attraction and attachment of MG molecules to the surface of TiO2 nanoparticles, leading to higher degradation efficiency. The same trend is observed for the anionic dye Eriochrom Black-T (EBT) at pH 3.
CHEMICAL ENGINEERING SCIENCE
(2023)
Article
Mechanics
A. Bashkatov, A. Babich, S. S. Hossain, X. Yang, G. Mutschke, K. Eckert
Summary: The dynamics of hydrogen bubbles produced by water electrolysis in an acidic electrolyte are investigated using electrochemical and optical methods. Controlled production of interacting pairs of H2 bubbles is achieved through cyclic modulation of electric potential at a microelectrode. Three scenarios of bubble interactions are identified, with the most prominent one involving a sudden motion reversal of the first detached bubble, its return to the electrode, and eventual coalescence with the second bubble. Contactless motion reversal is explained by the competition between buoyancy and thermocapillary effects, as confirmed by Toepler's schlieren technique.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Yorgos Stergiou, Paszkal Papp, Dezso Horvath, Agota Toth, Kerstin Eckert, Karin Schwarzenberger
Summary: We investigated a convective buoyancy-driven instability that occurs when a denser miscible fluid is injected into a less dense one in a rectilinear geometry. The instability was visualized using shadowgraph technique and quantitative information was obtained using micro-Particle Image Velocimetry. Numerical simulations provided insights into the three-dimensional velocity field. We found that the instability occurs only above a certain Peclet number, depending on the Rayleigh and Schmidt numbers. Scaling laws for the critical time and dimensionless wavelength of the instability were proposed, showing their dependence on Pe and Ra. The interaction of the instability vortices with each other and the geometry boundaries was also investigated.
Article
Chemistry, Physical
Milad Eftekhari, Karin Schwarzenberger, Stoyan I. Karakashev, Nikolay A. Grozev, Kerstin Eckert
Summary: This article focuses on the interaction between oppositely charged nanoparticles and surfactants and their influence on interfacial properties. The findings suggest that the surfactant/nanoparticle ratio primarily determines the interfacial properties, affecting the rheological properties of the interface while not significantly impacting surface tension.
JOURNAL OF COLLOID AND INTERFACE SCIENCE
(2024)
Article
Chemistry, Physical
Aleksandr Bashkatov, Syed Sahil Hossain, Gerd Mutschke, Xuegeng Yang, Hannes Rox, Inez M. Weidinger, Kerstin Eckert
Summary: This study investigates the growth of single hydrogen bubbles at micro-electrodes in an acidic electrolyte. New bubble growth regimes are identified and key features such as bubble radius growth law, dynamics of microbubble carpet, onset time of oscillations, and oscillation frequencies are characterized. The system's response to jumps in cathodic potential is also studied, leading to a hypothesis on the mechanisms underlying the microbubble carpet and oscillations.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2022)
Article
Physics, Fluids & Plasmas
Syed Sahil Hossain, Aleksandr Bashkatov, Xuegeng Yang, Gerd Mutschke, Kerstin Eckert
Summary: This study provides a more accurate analysis of hydrogen evolution in acidic aqueous electrolytes by considering geometric and electrochemical details measured during experiments. It confirms the role of an attractive electrical force caused by the adsorption of hydrogen ions at the bubble interface and improves the understanding of bubble dynamics observed.
