Sascha Sebastian Riegler - Academia.edu (original) (raw)
Papers by Sascha Sebastian Riegler
Advanced engineering materials, Jun 30, 2024
Advanced engineering materials, May 30, 2024
Advanced engineering materials, Apr 23, 2024
Free-standing Ni/Al multilayer films with a planar morphology, a bilayer thickness of 20 nm, and ... more Free-standing Ni/Al multilayer films with a planar morphology, a bilayer thickness of 20 nm, and an average composition of Ni 50Al 50 (at%) deposited by direct current magnetron sputtering are investigated by nanocalorimetry and conventional calorimetry. Both the novel fast differential scanning calorimeter (FDSC) Flash DSC 2þ from Mettler–Toledo (MT) and conventional calorimeter MT DSC 3 are used to cover a range of heating rates from 0.1 to 10 4 K s-1. A quantitative kinetic study of the interdiffusion and phase reaction sequence is performed via a Kissinger analysis covering five orders of magnitude of heating rates. Using the calorimetric data, the derived apparent activation energies suggest monotonic reaction kinetics over the entire range of heating rates applied. To correct the thermal lag at the highest heating rates with the FDSC for nonadhered free-standing films, a new methodology for its correction is used. Overall, this work extends the application of commercial FDSC to nonadhered films.
Advanced engineering materials, Apr 16, 2024
arXiv (Cornell University), Mar 18, 2024
Advanced Engineering Materials, 2024
Free-standing Ni/Al multilayer films with a planar morphology, a bilayer thickness of 20 nm, and... more Free-standing Ni/Al multilayer films with a planar morphology, a bilayer
thickness of 20 nm, and an average composition of Ni 50Al 50 (at%) deposited by
direct current magnetron sputtering are investigated by nanocalorimetry and
conventional calorimetry. Both the novel fast differential scanning calorimeter
(FDSC) Flash DSC 2þ from Mettler–Toledo (MT) and conventional calorimeter
MT DSC 3 are used to cover a range of heating rates from 0.1 to 10 4 K s-1. A quantitative kinetic study of the interdiffusion and phase reaction sequence is
performed via a Kissinger analysis covering five orders of magnitude of heating
rates. Using the calorimetric data, the derived apparent activation energies
suggest monotonic reaction kinetics over the entire range of heating rates
applied. To correct the thermal lag at the highest heating rates with the FDSC for
nonadhered free-standing films, a new methodology for its correction is used.
Overall, this work extends the application of commercial FDSC to nonadhered
films.
Physical Review Letters, Jul 27, 2020
We present a detailed investigation of the wave vector dependence of collective atomic motion in ... more We present a detailed investigation of the wave vector dependence of collective atomic motion in Au49Cu26.9Si16.3Ag5.5Pd2.3 and Pd42.5Cu27Ni9.5P21 supercooled liquids close to the glass transition temperature. Using x-ray photon correlation spectroscopy in a precedent uncovered spatial range of only few interatomic distances, we show that the microscopic structural relaxation process follows in phase the structure with a marked slowing down at the main average inter-particle distance. This behavior is accompanied by dramatic changes in the shape of the intermediate scattering functions which suggest the presence of large dynamical heterogeneities at length-scales corresponding to few particle diameters. A ballistic-like mechanism of particle motion seems to govern the structural relaxation of the two systems in the highly viscous phase, likely associated to hopping of caged particles in agreement with theoretical studies.
Materials
A two-dimensional numerical model for self-propagating reactions in Al/Ni multilayer foils was de... more A two-dimensional numerical model for self-propagating reactions in Al/Ni multilayer foils was developed. It was used to study thermal properties, convective heat loss, and the effect of initial temperature on the self-propagating reaction in Al/Ni multilayer foils. For model adjustments by experimental results, these Al/Ni multilayer foils were fabricated by the magnetron sputtering technique with a 1:1 atomic ratio. Heat of reaction of the fabricated foils was determined employing Differential Scanning Calorimetry (DSC). Self-propagating reaction was initiated by an electrical spark on the surface of the foils. The movement of the reaction front was recorded with a high-speed camera. Activation energy is fitted with these velocity data from the high-speed camera to adjust the numerical model. Calculated reaction front temperature of the self-propagating reaction was compared with the temperature obtained by time-resolved pyrometer measurements. X-ray diffraction results confirmed ...
This are the main raw data and derived data for the publication "Ultrafast formation of sing... more This are the main raw data and derived data for the publication "Ultrafast formation of single B2 phase AlCoCrFeNi high entropy alloy films by combustion of a reactive Ni/Al multilayer as heat source". Abstract High entropy alloy films of AlCoCrFeNi B2-ordered structure are formed during an ultrafast heating process by reactive Ni/Al multilayers. The self-propagating high-temperature reaction occurring in reactive Ni/Al multilayers after ignition represents an ultrafast heat source which is used for the transformation of a thin films Al/CoFe/CrNi multilayer structure into a single phase high entropy alloy film. The materials design of the combined multilayers thus determines the phase formation. Conventional rapid thermal annealing transforms the multilayer into a film with multiple equilibrium phases. Ultrafast combustion synthesis produces films with ultrafine-grained single-phase B2-ordered compound alloy. The heating rates during the combustion synthesis are in the ord...
Journal of Alloys and Compounds, 2022
Materials & Design, 2021
Abstract High entropy alloy films of AlCoCrFeNi B2-ordered structure are formed during an ultrafa... more Abstract High entropy alloy films of AlCoCrFeNi B2-ordered structure are formed during an ultrafast heating process by reactive Ni/Al multilayers. The self-propagating high-temperature reaction occurring in reactive Ni/Al multilayers after ignition represents an ultrafast heat source which is used for the transformation of a thin films Al/CoFe/CrNi multilayer structure into a single-phase high entropy alloy film. The materials design of the combined multilayers thus determines the phase formation. Conventional rapid thermal annealing transforms the multilayer into a film with multiple equilibrium phases. Ultrafast combustion synthesis produces films with ultrafine-grained single-phase B2-ordered compound alloy. The heating rates during the combustion synthesis are in the order of one million K/s, much higher than those of the rapid thermal annealing, which is about 7 K/s. The results are compared with differential scanning calorimetry experiments with heating rates ranging from about 100 K/s up to 25000 K/s. It is shown that the heating rate clearly determines the phase formation in the multilayers. The rapid kinetics of the combustion prevents long-range diffusion and promotes the run-away transformation. Thus, multilayer combustion synthesis using reactive Ni/Al multilayers as heat source represents a new pathway for the fabrication of single phase high-entropy alloy films.
Applied Sciences, 2021
Reactive multilayer systems represent an innovative approach for potential usage in chip joining ... more Reactive multilayer systems represent an innovative approach for potential usage in chip joining applications. As there are several factors governing the energy release rate and the stored chemical energy, the impact of the morphology and the microstructure on the reaction behavior is of great interest. In the current work, 3D reactive microstructures with nanoscale Al/Ni multilayers were produced by alternating deposition of pure Ni and Al films onto nanostructured Si substrates by magnetron sputtering. In order to elucidate the influence of this 3D morphology on the phase transformation process, the microstructure and the morphology of this system were characterized and compared with a flat reactive multilayer system on a flat Si wafer. The characterization of both systems was carried out before and after a rapid thermal annealing treatment by using scanning and transmission electron microscopy of the cross sections, selected area diffraction analysis, and differential scanning ca...
Materials & Design, 2021
• LPBF-formed AMZ4 metallic glass provides enough thermal stability for thermoplastic forming wit... more • LPBF-formed AMZ4 metallic glass provides enough thermal stability for thermoplastic forming without harsh crystallization. • With adequate process parameters, thermoplastic forming has no influence on the mechanical properties of LPBFformed AMZ4. • Thermoplastic forming allows to massively reduce the surface roughness of additively formed metallic glass specimen. • Finely structured surface pattern can be imprinted on additively formed metallic glass parts via thermoplastic forming.
Journal of Alloys and Compounds, 2020
Abstract The thermodynamic and kinetic properties of Cu45.6Zr45.3Al9.1, Cu47.5Zr45.1Al7.4, and Cu... more Abstract The thermodynamic and kinetic properties of Cu45.6Zr45.3Al9.1, Cu47.5Zr45.1Al7.4, and Cu47.3Zr45.8Al6.4Sn0.5 bulk metallic glasses are investigated to help understanding the origin of the glass-forming ability in the Cu–Zr–Al(–Sn) glass-forming system. The thermodynamic driving force for crystallization is determined by using specific heat capacity data and several thermodynamic parameters, e.g., enthalpies and entropies, measured via differential scanning calorimetry and differential thermal analysis. Moreover, a thermomechanical analyzer and a custom-built Couette rheometer were used to measure shear viscosity and to determine the fragilities in the low- and high-temperature regimes, close to the glass transition and in the stable melt respectively. For each alloy, the thermodynamic driving force and low-temperature fragility exhibit good correlation with the critical casting diameter. Melt viscosity was measured up to approximately 150 K above the liquidus temperature, i.e., from 1100 K to 1350 K. At temperature above 1350 K, reactions between the graphite crucible and the melt were observed to occur and may interfere with the viscosity measurement. Considerable differences in fragility between the stable melt and the deeply supercooled liquid were observed and discussed in terms of a fragile-to-strong crossover.
Acta Materialia, 2019
Abstract The low temperature viscosities of Cu47.5Zr45.1Al7.4 glass-forming liquid are measured b... more Abstract The low temperature viscosities of Cu47.5Zr45.1Al7.4 glass-forming liquid are measured by thermomechanical analysis in three-point beam bending mode. The experimental equilibrium values are fitted with the Vogel-Fulcher-Tammann (VFT) function, and the fragility parameter of the supercooled liquid is determined to be D* = 20.6. Viscosity measurements during isothermal annealing at 710 K show an initial relaxation from the glassy state into the supercooled liquid, followed by an anomalous viscosity increase of about two orders of magnitude. In-situ transmission electron microscope (TEM) and spherical aberration-corrected TEM investigations reveal that the effects of primary crystallization, nanoscale decomposition and structural ordering might be responsible for the anomalous viscosity behavior. The change in dynamic properties of the supercooled liquid, which is reflected by the larger VFT fitting parameter D* = 41.9 of the new annealed state reached before the final crystallization, is suggested to be not only related to the nanoscale structure change, but may also be caused by the change in chemical composition of the new annealed glass due to the primary crystallization. Furthermore, possible mechanisms for the nanoscale phase separation and the formation of atomic clusters are discussed based on the results of high-resolution TEM experiments.
Nature Communications, 2023
Reducing the sample size can profoundly impact properties of bulk metallic glasses. Here, we syst... more Reducing the sample size can profoundly impact properties of bulk metallic glasses. Here, we systematically reduce the length scale of Au and Pt-based metallic glasses and study their vitrification behavior and atomic mobility. For this purpose, we exploit fast scanning calorimetry (FSC) allowing to study glassy dynamics in an exceptionally wide range of cooling rates and frequencies. We show that the main α relaxation process remains size independent and bulk-like. In contrast, we observe pronounced size dependent vitrification kinetics in micrometer-sized glasses, which is more evident for the smallest samples and at low cooling rates, resulting in more than 40 K decrease in fictive temperature, T f , with respect to the bulk. We discuss the deep implications on how this outcome can be used to convey glasses to low energy states.
Materials & Design, 2021
h i g h l i g h t s The flowability of ZrCuAlNb powder improves with flow aid and coarser particl... more h i g h l i g h t s The flowability of ZrCuAlNb powder improves with flow aid and coarser particles. Preexisting crystals in the powder feedstock vanish during laser powder bed fusion. The O 2 content within the powder impacts the applicable parameter range. ÁThe Laser power predominantly fosters crystallization compared to the scan speed. An O 2 contamination >1600°mg/g drastically decreases the flexural strength.
Advanced engineering materials, Jun 30, 2024
Advanced engineering materials, May 30, 2024
Advanced engineering materials, Apr 23, 2024
Free-standing Ni/Al multilayer films with a planar morphology, a bilayer thickness of 20 nm, and ... more Free-standing Ni/Al multilayer films with a planar morphology, a bilayer thickness of 20 nm, and an average composition of Ni 50Al 50 (at%) deposited by direct current magnetron sputtering are investigated by nanocalorimetry and conventional calorimetry. Both the novel fast differential scanning calorimeter (FDSC) Flash DSC 2þ from Mettler–Toledo (MT) and conventional calorimeter MT DSC 3 are used to cover a range of heating rates from 0.1 to 10 4 K s-1. A quantitative kinetic study of the interdiffusion and phase reaction sequence is performed via a Kissinger analysis covering five orders of magnitude of heating rates. Using the calorimetric data, the derived apparent activation energies suggest monotonic reaction kinetics over the entire range of heating rates applied. To correct the thermal lag at the highest heating rates with the FDSC for nonadhered free-standing films, a new methodology for its correction is used. Overall, this work extends the application of commercial FDSC to nonadhered films.
Advanced engineering materials, Apr 16, 2024
arXiv (Cornell University), Mar 18, 2024
Advanced Engineering Materials, 2024
Free-standing Ni/Al multilayer films with a planar morphology, a bilayer thickness of 20 nm, and... more Free-standing Ni/Al multilayer films with a planar morphology, a bilayer
thickness of 20 nm, and an average composition of Ni 50Al 50 (at%) deposited by
direct current magnetron sputtering are investigated by nanocalorimetry and
conventional calorimetry. Both the novel fast differential scanning calorimeter
(FDSC) Flash DSC 2þ from Mettler–Toledo (MT) and conventional calorimeter
MT DSC 3 are used to cover a range of heating rates from 0.1 to 10 4 K s-1. A quantitative kinetic study of the interdiffusion and phase reaction sequence is
performed via a Kissinger analysis covering five orders of magnitude of heating
rates. Using the calorimetric data, the derived apparent activation energies
suggest monotonic reaction kinetics over the entire range of heating rates
applied. To correct the thermal lag at the highest heating rates with the FDSC for
nonadhered free-standing films, a new methodology for its correction is used.
Overall, this work extends the application of commercial FDSC to nonadhered
films.
Physical Review Letters, Jul 27, 2020
We present a detailed investigation of the wave vector dependence of collective atomic motion in ... more We present a detailed investigation of the wave vector dependence of collective atomic motion in Au49Cu26.9Si16.3Ag5.5Pd2.3 and Pd42.5Cu27Ni9.5P21 supercooled liquids close to the glass transition temperature. Using x-ray photon correlation spectroscopy in a precedent uncovered spatial range of only few interatomic distances, we show that the microscopic structural relaxation process follows in phase the structure with a marked slowing down at the main average inter-particle distance. This behavior is accompanied by dramatic changes in the shape of the intermediate scattering functions which suggest the presence of large dynamical heterogeneities at length-scales corresponding to few particle diameters. A ballistic-like mechanism of particle motion seems to govern the structural relaxation of the two systems in the highly viscous phase, likely associated to hopping of caged particles in agreement with theoretical studies.
Materials
A two-dimensional numerical model for self-propagating reactions in Al/Ni multilayer foils was de... more A two-dimensional numerical model for self-propagating reactions in Al/Ni multilayer foils was developed. It was used to study thermal properties, convective heat loss, and the effect of initial temperature on the self-propagating reaction in Al/Ni multilayer foils. For model adjustments by experimental results, these Al/Ni multilayer foils were fabricated by the magnetron sputtering technique with a 1:1 atomic ratio. Heat of reaction of the fabricated foils was determined employing Differential Scanning Calorimetry (DSC). Self-propagating reaction was initiated by an electrical spark on the surface of the foils. The movement of the reaction front was recorded with a high-speed camera. Activation energy is fitted with these velocity data from the high-speed camera to adjust the numerical model. Calculated reaction front temperature of the self-propagating reaction was compared with the temperature obtained by time-resolved pyrometer measurements. X-ray diffraction results confirmed ...
This are the main raw data and derived data for the publication "Ultrafast formation of sing... more This are the main raw data and derived data for the publication "Ultrafast formation of single B2 phase AlCoCrFeNi high entropy alloy films by combustion of a reactive Ni/Al multilayer as heat source". Abstract High entropy alloy films of AlCoCrFeNi B2-ordered structure are formed during an ultrafast heating process by reactive Ni/Al multilayers. The self-propagating high-temperature reaction occurring in reactive Ni/Al multilayers after ignition represents an ultrafast heat source which is used for the transformation of a thin films Al/CoFe/CrNi multilayer structure into a single phase high entropy alloy film. The materials design of the combined multilayers thus determines the phase formation. Conventional rapid thermal annealing transforms the multilayer into a film with multiple equilibrium phases. Ultrafast combustion synthesis produces films with ultrafine-grained single-phase B2-ordered compound alloy. The heating rates during the combustion synthesis are in the ord...
Journal of Alloys and Compounds, 2022
Materials & Design, 2021
Abstract High entropy alloy films of AlCoCrFeNi B2-ordered structure are formed during an ultrafa... more Abstract High entropy alloy films of AlCoCrFeNi B2-ordered structure are formed during an ultrafast heating process by reactive Ni/Al multilayers. The self-propagating high-temperature reaction occurring in reactive Ni/Al multilayers after ignition represents an ultrafast heat source which is used for the transformation of a thin films Al/CoFe/CrNi multilayer structure into a single-phase high entropy alloy film. The materials design of the combined multilayers thus determines the phase formation. Conventional rapid thermal annealing transforms the multilayer into a film with multiple equilibrium phases. Ultrafast combustion synthesis produces films with ultrafine-grained single-phase B2-ordered compound alloy. The heating rates during the combustion synthesis are in the order of one million K/s, much higher than those of the rapid thermal annealing, which is about 7 K/s. The results are compared with differential scanning calorimetry experiments with heating rates ranging from about 100 K/s up to 25000 K/s. It is shown that the heating rate clearly determines the phase formation in the multilayers. The rapid kinetics of the combustion prevents long-range diffusion and promotes the run-away transformation. Thus, multilayer combustion synthesis using reactive Ni/Al multilayers as heat source represents a new pathway for the fabrication of single phase high-entropy alloy films.
Applied Sciences, 2021
Reactive multilayer systems represent an innovative approach for potential usage in chip joining ... more Reactive multilayer systems represent an innovative approach for potential usage in chip joining applications. As there are several factors governing the energy release rate and the stored chemical energy, the impact of the morphology and the microstructure on the reaction behavior is of great interest. In the current work, 3D reactive microstructures with nanoscale Al/Ni multilayers were produced by alternating deposition of pure Ni and Al films onto nanostructured Si substrates by magnetron sputtering. In order to elucidate the influence of this 3D morphology on the phase transformation process, the microstructure and the morphology of this system were characterized and compared with a flat reactive multilayer system on a flat Si wafer. The characterization of both systems was carried out before and after a rapid thermal annealing treatment by using scanning and transmission electron microscopy of the cross sections, selected area diffraction analysis, and differential scanning ca...
Materials & Design, 2021
• LPBF-formed AMZ4 metallic glass provides enough thermal stability for thermoplastic forming wit... more • LPBF-formed AMZ4 metallic glass provides enough thermal stability for thermoplastic forming without harsh crystallization. • With adequate process parameters, thermoplastic forming has no influence on the mechanical properties of LPBFformed AMZ4. • Thermoplastic forming allows to massively reduce the surface roughness of additively formed metallic glass specimen. • Finely structured surface pattern can be imprinted on additively formed metallic glass parts via thermoplastic forming.
Journal of Alloys and Compounds, 2020
Abstract The thermodynamic and kinetic properties of Cu45.6Zr45.3Al9.1, Cu47.5Zr45.1Al7.4, and Cu... more Abstract The thermodynamic and kinetic properties of Cu45.6Zr45.3Al9.1, Cu47.5Zr45.1Al7.4, and Cu47.3Zr45.8Al6.4Sn0.5 bulk metallic glasses are investigated to help understanding the origin of the glass-forming ability in the Cu–Zr–Al(–Sn) glass-forming system. The thermodynamic driving force for crystallization is determined by using specific heat capacity data and several thermodynamic parameters, e.g., enthalpies and entropies, measured via differential scanning calorimetry and differential thermal analysis. Moreover, a thermomechanical analyzer and a custom-built Couette rheometer were used to measure shear viscosity and to determine the fragilities in the low- and high-temperature regimes, close to the glass transition and in the stable melt respectively. For each alloy, the thermodynamic driving force and low-temperature fragility exhibit good correlation with the critical casting diameter. Melt viscosity was measured up to approximately 150 K above the liquidus temperature, i.e., from 1100 K to 1350 K. At temperature above 1350 K, reactions between the graphite crucible and the melt were observed to occur and may interfere with the viscosity measurement. Considerable differences in fragility between the stable melt and the deeply supercooled liquid were observed and discussed in terms of a fragile-to-strong crossover.
Acta Materialia, 2019
Abstract The low temperature viscosities of Cu47.5Zr45.1Al7.4 glass-forming liquid are measured b... more Abstract The low temperature viscosities of Cu47.5Zr45.1Al7.4 glass-forming liquid are measured by thermomechanical analysis in three-point beam bending mode. The experimental equilibrium values are fitted with the Vogel-Fulcher-Tammann (VFT) function, and the fragility parameter of the supercooled liquid is determined to be D* = 20.6. Viscosity measurements during isothermal annealing at 710 K show an initial relaxation from the glassy state into the supercooled liquid, followed by an anomalous viscosity increase of about two orders of magnitude. In-situ transmission electron microscope (TEM) and spherical aberration-corrected TEM investigations reveal that the effects of primary crystallization, nanoscale decomposition and structural ordering might be responsible for the anomalous viscosity behavior. The change in dynamic properties of the supercooled liquid, which is reflected by the larger VFT fitting parameter D* = 41.9 of the new annealed state reached before the final crystallization, is suggested to be not only related to the nanoscale structure change, but may also be caused by the change in chemical composition of the new annealed glass due to the primary crystallization. Furthermore, possible mechanisms for the nanoscale phase separation and the formation of atomic clusters are discussed based on the results of high-resolution TEM experiments.
Nature Communications, 2023
Reducing the sample size can profoundly impact properties of bulk metallic glasses. Here, we syst... more Reducing the sample size can profoundly impact properties of bulk metallic glasses. Here, we systematically reduce the length scale of Au and Pt-based metallic glasses and study their vitrification behavior and atomic mobility. For this purpose, we exploit fast scanning calorimetry (FSC) allowing to study glassy dynamics in an exceptionally wide range of cooling rates and frequencies. We show that the main α relaxation process remains size independent and bulk-like. In contrast, we observe pronounced size dependent vitrification kinetics in micrometer-sized glasses, which is more evident for the smallest samples and at low cooling rates, resulting in more than 40 K decrease in fictive temperature, T f , with respect to the bulk. We discuss the deep implications on how this outcome can be used to convey glasses to low energy states.
Materials & Design, 2021
h i g h l i g h t s The flowability of ZrCuAlNb powder improves with flow aid and coarser particl... more h i g h l i g h t s The flowability of ZrCuAlNb powder improves with flow aid and coarser particles. Preexisting crystals in the powder feedstock vanish during laser powder bed fusion. The O 2 content within the powder impacts the applicable parameter range. ÁThe Laser power predominantly fosters crystallization compared to the scan speed. An O 2 contamination >1600°mg/g drastically decreases the flexural strength.