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11. Correlative characterization of plasma etching resistance of various aluminum garnets.

Author

Stern, Christian, Schwab, Christian, Kindelmann, Moritz, Stamminger, Mark, Weirich, Thomas E., Park, Inhee, Hausen, Florian, Finsterbusch, Martin, Bram, Martin, and Guillon, Olivier

Subjects
SECONDARY ion mass spectrometry, PLASMA etching, ATOMIC force microscopy, TRANSMISSION electron microscopy, SEMICONDUCTOR manufacturing, YTTRIUM aluminum garnet, GARNET
Abstract

Plasma etching is a crucial step in semiconductor manufacturing. High cleanliness and wafer‐to‐wafer reproducibility in the etching chamber are essential in order to successfully achieve nanometer‐sized integrated functions on the wafer. The trend toward the application of more aggressive plasma compositions leads to higher demands on the plasma resistance of the materials used in the etching chamber. Due to its excellent etch resistance, yttrium aluminum garnet Y3Al5O12 (YAG) is starting to replace established materials like SiO2 or Al2O3 in this kind of application. In this study, reactive spark plasma sintering (SPS) was used to manufacture highly dense YAG ceramics from the respective oxides. In addition, yttrium was replaced with heavier lanthanoids (Er, Lu), intending to investigate the role of the A‐site cation in the garnet type structure on the plasma erosion behavior. The produced materials were exposed to fluorine‐based etching plasmas mimicking the conditions in the semiconductor manufacturing apparatus and the erosion behavior was characterized by atomic force microscopy (AFM), secondary ion mass spectrometry (SIMS), transmission electron microscopy (TEM), and profilometry. The induced chemical gradient in the samples is limited to a few nanometers below the surface, which makes its characterization challenging. For advanced analysis, we developed a correlative characterization method combining SIMS and scanning TEM (STEM)–energy‐dispersive spectroscopy (EDS) enabling us to examine the structural and chemical changes in the reaction layer locally resolved. In the case of lanthanoid aluminates, an altered reaction layer and reduced fluorine penetration compared to YAG were found. However, a correlation between the characteristics of the induced chemical gradient and the determined physical erosion rates was not evident. [ABSTRACT FROM AUTHOR]

Published
2024
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12. Effect of Yttrium and Yttria Addition in Self-Passivating WCr SMART Material for First-Wall Application in a Fusion Power Plant.

Author

Chen, Jie, Tejado, Elena, Rasiński, Marcin, Litnovsky, Andrey, Nguyen-Manh, Duc, Prestat, Eric, Whitfield, Tamsin, Pastor, Jose Ygnacio, Bram, Martin, Coenen, Jan Willem, Linsmeier, Christian, and Gonzalez-Julian, Jesus

Subjects
FLEXURAL strength, SMART materials, FRACTURE toughness, CRYSTAL grain boundaries, FRACTURE strength, MECHANICAL alloying
Abstract

The self-passivating yttrium-containing WCr alloy has been developed and researched as a potential plasma-facing armour material for fusion power plants. This study explores the use of yttria (Y2O3) powders instead of yttrium elemental powders in the mechanical alloying process to assess their applicability for this material. Fabricated through field-assisted sintering, WCr-Y2O3 ingots show Y2O3 and Cr-containing oxides (Cr-O and Y-Cr-O) dispersed at grain boundaries (GBs), while WCrY ingots contain Y-O particles at grain boundaries, both resulting from unavoidable oxidation during fabrication. WCr-Y2O3 demonstrates higher flexural strength than WCrY across all temperature ranges, ranging from 850 to 1050 MPa, but lower fracture toughness, between 3 and 4 MPa·√m. Enhanced oxidation resistance is observed in WCr-Y2O3, with lower mass gain as compared to WCrY during the 20-hour oxidation test. This study confirms the effectiveness of both yttria and yttrium in the reactive element effect (REE) for the passivation of WCr alloy, suggesting the potential of Y2O3-doped WCr for first wall applications in a fusion power plant. [ABSTRACT FROM AUTHOR]

Published
2024
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13. Flash‐induced defects in single‐crystal 8YSZ characterized by TEM, XRD, and Raman spectroscopy.

Author

Jo, Seohyeon, Kindelmann, Moritz, Jennings, Dylan, Balice, Luca, Sohn, Yoo Jung, Scheld, Walter Sebastian, Bram, Martin, Guillon, Olivier, Mayer, Joachim, and Raj, Rishi

Subjects
RAMAN spectroscopy, X-ray diffraction, CRYSTAL defects, ELECTRON energy loss spectroscopy, TRANSMISSION electron microscopy, CRYSTAL surfaces
Abstract

We present direct evidence, for the first time, for the flash‐induced generation of crystal defects in single‐crystal cubic zirconia. The defects are characterized by multiple techniques. The crystals were flashed and then cooled down to ambient temperature in Ar atmosphere to preserve the electronic conductivity from the steady state of flash. Transmission electron microscopy revealed colonies of defects. The crystal structure, the non‐stoichiometry, and the electronic structure of oxygen ions within these colonies were characterized. They consist of oxygen‐depleted compositions. Selected area electron diffraction revealed the structure of these zirconia suboxides to be epitaxially coherent with the parent cubic structure but with a smaller lattice parameter. Electron energy loss spectroscopy spectra showed the peak near 25 mV to shift toward metallic zirconium. The electronic conductivity of the flashed cubic zirconia is attributed to this suboxide phase. The phase also gave rise to new peaks in Raman spectroscopy. A surprising finding was the presence of a distinct, ∼30 nm thick layer of the suboxide on the surface of the crystal. The surface layer showed a high degree of oxygen deficiency. It was also epitaxial, but with an even smaller lattice parameter than the defect colonies underneath the surface. Mechanical polishing of the crystal to remove this surface layer gave a broad view of the interconnected network of defects across the entire specimen; the length scale of this network was about 0.2 mm. Recent work, where an overlay of a magnetic field caused the flash to migrate from a flashing surface into a free‐standing workpiece, suggests the presence of evanescent plasma, which may have a connection to this surface layer. [ABSTRACT FROM AUTHOR]

Published
2024
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21. Direct Recycling of Hot‐Deformed Nd–Fe–B Magnet Scrap by Field‐Assisted Sintering Technology

Author

Keszler, Monica, Grosswendt, Felix, Assmann, Anna-Caroline, Krengel, Martin, Maccari, Fernando, Gutfleisch, Oliver, Sebold, Doris, Guillon, Olivier, Weber, Sebastian, Bram, Martin, Keszler, Monica, Grosswendt, Felix, Assmann, Anna-Caroline, Krengel, Martin, Maccari, Fernando, Gutfleisch, Oliver, Sebold, Doris, Guillon, Olivier, Weber, Sebastian, and Bram, Martin

Abstract

Recycling of Nd–Fe–B magnets is an ongoing challenge regarding circular economy. State‐of‐the‐art magnet production methods, such as hot deformation, have limitations with respect to direct recycling of magnet scrap particles that differ from pristine melt‐spun Nd–Fe–B powder. Recent work has shown that a combination of presintering by field‐assisted sintering technology/spark plasma sintering (FAST/SPS) and hot deformation by flash spark plasma sintering (flash SPS) has the potential to directly produce Nd–Fe–B magnets from 100% scrap material. Both processes have the capability to adjust and monitor process parameters closely, resulting in recycled magnets with properties similar to commercial magnets but made directly from crushed and recycled Nd–Fe–B powder that partially or completely replaces pristine melt‐spun Nd–Fe–B powder. Herein, a systematic study is done inserting recycled magnet particles into a flash SPS deformed magnet, considering the effects of different weight percentages of scrap material of varied particle size fractions. In some cases, coercivity HcJ of >1400 kAm⁻¹ and remanence Br of 1.1 T can be achieved with 20 wt% scrap material. The relationship between particle size fraction, oxygen uptake, and percentage of recyclate in a final magnet are all explored and discussed with respect to magnets made from pristine material.

Published
2024

23. Smart Tungsten-based Alloys for a First Wall of DEMO

Author

Litnovsky, Andrey, Schmitz, Janina, Klein, Felix, De Lannoye, Karen, Weckauf, Sophie, Kreter, Arkadi, Rasinski, Marcin, Coenen, Jan W., Linsmeier, Christian, Gonzalez-Julian, Jesus, Bram, Martin, Povstugar, Ivan, Morgan, Thomas, Nguyen-Manh, Duc, Gilbert, Mark, Sobieraj, Damian, and Wróbel, Jan S.

Published
2020
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28. Highly conductive grain boundaries in cold-sintered barium zirconate-based proton conductors

Author

Kindelmann, Moritz, primary, Escolástico, Sonia, additional, Almar Liante, Laura, additional, Vayyala, A., additional, Jennings, Dylan, additional, Deibert, Wendelin, additional, Meulenberg, Wilhelm, additional, Rheinheimer, Wolfgang, additional, Bram, Martin, additional, Serra, Jose Manuel, additional, Mayer, Joachim, additional, and Guillon, Olivier, additional

Published
2024
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36. Tooling in Spark Plasma Sintering Technology: Design, Optimization, and Application.

Author

Laptev, Alexander M., Bram, Martin, Garbiec, Dariusz, Räthel, Jan, van der Laan, Antoine, Beynet, Yannick, Huber, Jens, Küster, Matthias, Cologna, Marco, and Guillon, Olivier

Subjects
SINTERING, TEMPERATURE distribution, THERMAL insulation, HIGH temperatures
Abstract

Spark plasma sintering as the prominent field‐assisted sintering technique (FAST/SPS) is a novel technology for the rapid, pressure‐assisted consolidation of powder materials. The main feature of FAST/SPS is the direct Joule heating of the applied tooling. Tooling is a challenging part of the FAST/SPS setup, which must withstand high pressure at elevated temperatures and ensure a uniform temperature distribution in the sintered part. This review looks at the standard FAST/SPS tooling, the specific tooling for sintering complex‐shaped parts, and for pressureless sintering. A particular focus lies on graphite, the commonly used tooling material, and on alternative materials such as steel, alloys, ceramics, and composites. The review also considers the add‐on tooling elements, such as spacers, foils, and thermal insulation. Furthermore, the article discusses the basics of FAST/SPS modeling, and the computer‐based optimization of FAST/SPS tooling, the procedure used, and the modeling accuracy. The review briefly describes the tooling and equipment for manufacturing upsized parts and large‐scale production. In addition, the article considers the tooling for FAST/SPS sintering under high pressure (up to 1 GPa) and ultra‐high pressure (over 1 GPa). The article concludes with an analysis of the challenges and prospectives for the smart design of FAST/SPS tooling. [ABSTRACT FROM AUTHOR]

Published
2024
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49. Nanocrystalline Nd‐Fe‐B anisotropic magnets by flash spark plasma sintering

Author

Maccari, Fernando, primary, Mishra, Tarini Prasad, additional, Keszler, Monica, additional, Braun, Tobias, additional, Adabifiroozjaei, Esmaeil, additional, Radulov, Iliya, additional, Jiang, Tianshu, additional, Bruder, Enrico, additional, Guillon, Olivier, additional, Molina-Luna, Leopoldo, additional, Bram, Martin, additional, and Gutfleisch, Oliver, additional

Published
2023
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