Ralf Thomann | Albert-Ludwigs-University of Freiburg (original) (raw)

Papers by Ralf Thomann

Zenodo (CERN European Organization for Nuclear Research), Jan 24, 2022

This is a method and application note, in which we present one of our works on the characterizati... more This is a method and application note, in which we present one of our works on the characterization of interior structures via µ-CT (micro-computed tomography) and FIB/SEM (focused ion beam/scanning electron microscopy). As an example, we selected the characterization of a microfluidic device (probe). Both µ-CT (micro-tomography) and FIB/SEM cross sectioning methods are applied.

Zenodo (CERN European Organization for Nuclear Research), Jan 24, 2022

This is a method and application note, in which we present one of our works on the characterizati... more This is a method and application note, in which we present one of our works on the characterization of interior structures via µ-CT (micro-computed tomography) and FIB/SEM (focused ion beam/scanning electron microscopy). As an example, we selected the characterization of a microfluidic device (probe). Both µ-CT (micro-tomography) and FIB/SEM cross sectioning methods are applied.

Advanced Engineering Materials, Apr 21, 2023

Tungsten is an important material for high‐temperature applications due to its high chemical and ... more Tungsten is an important material for high‐temperature applications due to its high chemical and thermal stability. Its carbide, that is, tungsten carbide, is used in tool manufacturing because of its outstanding hardness and as a catalyst scaffold due to its morphology and large surface area. However, microstructuring, especially high‐resolution 3D microstructuring of both materials, is a complex and challenging process which suffers from slow speeds and requires expensive specialized equipment. Traditional subtractive machining methods, for example, milling, are often not feasible because of the hardness and brittleness of the materials. Commonly, tungsten and tungsten carbide are manufactured by powder metallurgy. However, these methods are very limited in the complexity and resolution of the produced components. Herein, tungsten ion‐containing organic–inorganic photoresins, which are patterned by two‐photon lithography (TPL) at micrometer resolution, are introduced. The printed structures are converted to tungsten or tungsten carbide by thermal debinding and reduction of the precursor or carbothermal reduction reaction, respectively. Using TPL, complex 3D tungsten and tungsten carbide structures are prepared with a resolution down to 2 and 7 μm, respectively. This new pathway of structuring tungsten and its carbide facilitates a broad range of applications from micromachining to metamaterials and catalysis.

Advanced Engineering Materials, Apr 21, 2023

Tungsten is an important material for high‐temperature applications due to its high chemical and ... more Tungsten is an important material for high‐temperature applications due to its high chemical and thermal stability. Its carbide, that is, tungsten carbide, is used in tool manufacturing because of its outstanding hardness and as a catalyst scaffold due to its morphology and large surface area. However, microstructuring, especially high‐resolution 3D microstructuring of both materials, is a complex and challenging process which suffers from slow speeds and requires expensive specialized equipment. Traditional subtractive machining methods, for example, milling, are often not feasible because of the hardness and brittleness of the materials. Commonly, tungsten and tungsten carbide are manufactured by powder metallurgy. However, these methods are very limited in the complexity and resolution of the produced components. Herein, tungsten ion‐containing organic–inorganic photoresins, which are patterned by two‐photon lithography (TPL) at micrometer resolution, are introduced. The printed structures are converted to tungsten or tungsten carbide by thermal debinding and reduction of the precursor or carbothermal reduction reaction, respectively. Using TPL, complex 3D tungsten and tungsten carbide structures are prepared with a resolution down to 2 and 7 μm, respectively. This new pathway of structuring tungsten and its carbide facilitates a broad range of applications from micromachining to metamaterials and catalysis.

Macromolecules, Nov 25, 2019

Nacre-mimicking layered organic/inorganic hybrid materials exhibiting ultrahigh stiffness and str... more Nacre-mimicking layered organic/inorganic hybrid materials exhibiting ultrahigh stiffness and strength frequently require multistep processing that is restricted to polar and even water-soluble polymers. Herein, nacre-mimetic hydrocarbon composites were fabricated by single-step injection molding. The key intermediates are organophilic ultrathin γ-Al(OH)3 (O-gibbsite) single-crystal nanoplatelets and all-hydrocarbon composites (All-PE) containing aligned, extended-chain ultrahigh-molecular-weight polyethylene (UHMWPE) as one-dimensional (1D) nanostructures embedded in a polyethylene (PE) matrix. This formation of flow-induced UHMWPE 1D nanostructures mimics chitin nanofibers in nacre and drives the alignment of O-gibbsite nanoplatelets to assemble bricks. Unprecedented high contents of up to 70 wt % O-gibbsite nanoplatelets are tolerated in injection molding. As verified by focused ion beam-scanning electron microscopy (FIB-SEM), the resulting brick-and-mortar architectures contain aligned O-gibbsite as b...

Macromolecules, Nov 25, 2019

Nacre-mimicking layered organic/inorganic hybrid materials exhibiting ultrahigh stiffness and str... more Nacre-mimicking layered organic/inorganic hybrid materials exhibiting ultrahigh stiffness and strength frequently require multistep processing that is restricted to polar and even water-soluble polymers. Herein, nacre-mimetic hydrocarbon composites were fabricated by single-step injection molding. The key intermediates are organophilic ultrathin γ-Al(OH)3 (O-gibbsite) single-crystal nanoplatelets and all-hydrocarbon composites (All-PE) containing aligned, extended-chain ultrahigh-molecular-weight polyethylene (UHMWPE) as one-dimensional (1D) nanostructures embedded in a polyethylene (PE) matrix. This formation of flow-induced UHMWPE 1D nanostructures mimics chitin nanofibers in nacre and drives the alignment of O-gibbsite nanoplatelets to assemble bricks. Unprecedented high contents of up to 70 wt % O-gibbsite nanoplatelets are tolerated in injection molding. As verified by focused ion beam-scanning electron microscopy (FIB-SEM), the resulting brick-and-mortar architectures contain aligned O-gibbsite as b...

Crystal Growth & Design, Dec 10, 2020

Crystal Growth & Design, Dec 10, 2020

Journal of Functional Biomaterials, Nov 11, 2022

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Journal of Functional Biomaterials, Nov 11, 2022

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Macromolecular Symposia, 2000

Macromolecular Symposia, 2000

Batteries & Supercaps

Upon immersion of a lithium (Li) anode into a diluted 0.05 to 0.20 M dimethoxyethane‐solution of ... more Upon immersion of a lithium (Li) anode into a diluted 0.05 to 0.20 M dimethoxyethane‐solution of the phosphoric acid derivative (CF3CH2O)2P(O)OH (HBFEP), an artificial solid electrolyte interphase (SEI) is generated on the Li‐metal surface. Hence, HBFEP reacts on the surface to the corresponding Li salt (LiBFEP), which is a Li‐ion conducting inorganic coordination polymer. This film exhibits – due to the reversibly breaking ionic bonds – self‐healing ability upon cycling‐induced volume expansion of Li. The presence of LiBFEP as the major component in the artificial SEI is proven by ATR‐IR and XPS measurements. SEM characterization of HBFEP‐treated Li samples reveals porous layers on top of the Li surface with at least 3 μm thickness. Li−Li symmetrical cells with HBFEP‐modified Li electrodes show a three‐ to almost fourfold cycle‐lifetime increase at 0.1 mA cm−2 in a demanding model electrolyte that facilitates fast battery failure (1 M LiOTf in TEGDME). Hence, the LiBFEP‐enriched la...

Batteries & Supercaps

Upon immersion of a lithium (Li) anode into a diluted 0.05 to 0.20 M dimethoxyethane‐solution of ... more Upon immersion of a lithium (Li) anode into a diluted 0.05 to 0.20 M dimethoxyethane‐solution of the phosphoric acid derivative (CF3CH2O)2P(O)OH (HBFEP), an artificial solid electrolyte interphase (SEI) is generated on the Li‐metal surface. Hence, HBFEP reacts on the surface to the corresponding Li salt (LiBFEP), which is a Li‐ion conducting inorganic coordination polymer. This film exhibits – due to the reversibly breaking ionic bonds – self‐healing ability upon cycling‐induced volume expansion of Li. The presence of LiBFEP as the major component in the artificial SEI is proven by ATR‐IR and XPS measurements. SEM characterization of HBFEP‐treated Li samples reveals porous layers on top of the Li surface with at least 3 μm thickness. Li−Li symmetrical cells with HBFEP‐modified Li electrodes show a three‐ to almost fourfold cycle‐lifetime increase at 0.1 mA cm−2 in a demanding model electrolyte that facilitates fast battery failure (1 M LiOTf in TEGDME). Hence, the LiBFEP‐enriched la...

A series of poly(N,N-dimethylacrylamide)-l-polyisobutylene (PDMAAm-l-PIB) amphiphilic conetworks ... more A series of poly(N,N-dimethylacrylamide)-l-polyisobutylene (PDMAAm-l-PIB) amphiphilic conetworks were synthesized from two incompatible polymers, i.e. hydrophilic PDMAAm and strongly hydrophobic PIB in a wide range of composition (38-80 m/m % PIB). Swelling experiments were carried out to determine the equilibrium swelling ratios which proved the amphiphilic nature of these new materials, and are in correlation with composition. Thermal analysis (DSC), small angle X-ray scattering (SAXS) and atomic force microscopy (AFM) measurements were carried out. Results show special phase separated morphology, where the size of the phases are in the nanometer range in all cases. Furthermore, the nanophases of the conetworks have composition dependent spatial arrangement. Successful synthesis of silver nanoparticles was achived inside of the conetwork’s hydrophilic phases resulting in a novel organic-inorganic nanohybrid material.

A series of poly(N,N-dimethylacrylamide)-l-polyisobutylene (PDMAAm-l-PIB) amphiphilic conetworks ... more A series of poly(N,N-dimethylacrylamide)-l-polyisobutylene (PDMAAm-l-PIB) amphiphilic conetworks were synthesized from two incompatible polymers, i.e. hydrophilic PDMAAm and strongly hydrophobic PIB in a wide range of composition (38-80 m/m % PIB). Swelling experiments were carried out to determine the equilibrium swelling ratios which proved the amphiphilic nature of these new materials, and are in correlation with composition. Thermal analysis (DSC), small angle X-ray scattering (SAXS) and atomic force microscopy (AFM) measurements were carried out. Results show special phase separated morphology, where the size of the phases are in the nanometer range in all cases. Furthermore, the nanophases of the conetworks have composition dependent spatial arrangement. Successful synthesis of silver nanoparticles was achived inside of the conetwork’s hydrophilic phases resulting in a novel organic-inorganic nanohybrid material.

Catalysis Science & Technology, 2020

Influencing stability and performance through directing nitrogen-doping in carbon support materials.

Catalysis Science & Technology, 2020

Influencing stability and performance through directing nitrogen-doping in carbon support materials.

Magyar Kémiai Folyóirat, 2018

Magyar Kémiai Folyóirat, 2018

Zenodo (CERN European Organization for Nuclear Research), Jan 24, 2022

This is a method and application note, in which we present one of our works on the characterizati... more This is a method and application note, in which we present one of our works on the characterization of interior structures via µ-CT (micro-computed tomography) and FIB/SEM (focused ion beam/scanning electron microscopy). As an example, we selected the characterization of a microfluidic device (probe). Both µ-CT (micro-tomography) and FIB/SEM cross sectioning methods are applied.

Zenodo (CERN European Organization for Nuclear Research), Jan 24, 2022

This is a method and application note, in which we present one of our works on the characterizati... more This is a method and application note, in which we present one of our works on the characterization of interior structures via µ-CT (micro-computed tomography) and FIB/SEM (focused ion beam/scanning electron microscopy). As an example, we selected the characterization of a microfluidic device (probe). Both µ-CT (micro-tomography) and FIB/SEM cross sectioning methods are applied.

Advanced Engineering Materials, Apr 21, 2023

Tungsten is an important material for high‐temperature applications due to its high chemical and ... more Tungsten is an important material for high‐temperature applications due to its high chemical and thermal stability. Its carbide, that is, tungsten carbide, is used in tool manufacturing because of its outstanding hardness and as a catalyst scaffold due to its morphology and large surface area. However, microstructuring, especially high‐resolution 3D microstructuring of both materials, is a complex and challenging process which suffers from slow speeds and requires expensive specialized equipment. Traditional subtractive machining methods, for example, milling, are often not feasible because of the hardness and brittleness of the materials. Commonly, tungsten and tungsten carbide are manufactured by powder metallurgy. However, these methods are very limited in the complexity and resolution of the produced components. Herein, tungsten ion‐containing organic–inorganic photoresins, which are patterned by two‐photon lithography (TPL) at micrometer resolution, are introduced. The printed structures are converted to tungsten or tungsten carbide by thermal debinding and reduction of the precursor or carbothermal reduction reaction, respectively. Using TPL, complex 3D tungsten and tungsten carbide structures are prepared with a resolution down to 2 and 7 μm, respectively. This new pathway of structuring tungsten and its carbide facilitates a broad range of applications from micromachining to metamaterials and catalysis.

Advanced Engineering Materials, Apr 21, 2023

Tungsten is an important material for high‐temperature applications due to its high chemical and ... more Tungsten is an important material for high‐temperature applications due to its high chemical and thermal stability. Its carbide, that is, tungsten carbide, is used in tool manufacturing because of its outstanding hardness and as a catalyst scaffold due to its morphology and large surface area. However, microstructuring, especially high‐resolution 3D microstructuring of both materials, is a complex and challenging process which suffers from slow speeds and requires expensive specialized equipment. Traditional subtractive machining methods, for example, milling, are often not feasible because of the hardness and brittleness of the materials. Commonly, tungsten and tungsten carbide are manufactured by powder metallurgy. However, these methods are very limited in the complexity and resolution of the produced components. Herein, tungsten ion‐containing organic–inorganic photoresins, which are patterned by two‐photon lithography (TPL) at micrometer resolution, are introduced. The printed structures are converted to tungsten or tungsten carbide by thermal debinding and reduction of the precursor or carbothermal reduction reaction, respectively. Using TPL, complex 3D tungsten and tungsten carbide structures are prepared with a resolution down to 2 and 7 μm, respectively. This new pathway of structuring tungsten and its carbide facilitates a broad range of applications from micromachining to metamaterials and catalysis.

Macromolecules, Nov 25, 2019

Nacre-mimicking layered organic/inorganic hybrid materials exhibiting ultrahigh stiffness and str... more Nacre-mimicking layered organic/inorganic hybrid materials exhibiting ultrahigh stiffness and strength frequently require multistep processing that is restricted to polar and even water-soluble polymers. Herein, nacre-mimetic hydrocarbon composites were fabricated by single-step injection molding. The key intermediates are organophilic ultrathin γ-Al(OH)3 (O-gibbsite) single-crystal nanoplatelets and all-hydrocarbon composites (All-PE) containing aligned, extended-chain ultrahigh-molecular-weight polyethylene (UHMWPE) as one-dimensional (1D) nanostructures embedded in a polyethylene (PE) matrix. This formation of flow-induced UHMWPE 1D nanostructures mimics chitin nanofibers in nacre and drives the alignment of O-gibbsite nanoplatelets to assemble bricks. Unprecedented high contents of up to 70 wt % O-gibbsite nanoplatelets are tolerated in injection molding. As verified by focused ion beam-scanning electron microscopy (FIB-SEM), the resulting brick-and-mortar architectures contain aligned O-gibbsite as b...

Macromolecules, Nov 25, 2019

Nacre-mimicking layered organic/inorganic hybrid materials exhibiting ultrahigh stiffness and str... more Nacre-mimicking layered organic/inorganic hybrid materials exhibiting ultrahigh stiffness and strength frequently require multistep processing that is restricted to polar and even water-soluble polymers. Herein, nacre-mimetic hydrocarbon composites were fabricated by single-step injection molding. The key intermediates are organophilic ultrathin γ-Al(OH)3 (O-gibbsite) single-crystal nanoplatelets and all-hydrocarbon composites (All-PE) containing aligned, extended-chain ultrahigh-molecular-weight polyethylene (UHMWPE) as one-dimensional (1D) nanostructures embedded in a polyethylene (PE) matrix. This formation of flow-induced UHMWPE 1D nanostructures mimics chitin nanofibers in nacre and drives the alignment of O-gibbsite nanoplatelets to assemble bricks. Unprecedented high contents of up to 70 wt % O-gibbsite nanoplatelets are tolerated in injection molding. As verified by focused ion beam-scanning electron microscopy (FIB-SEM), the resulting brick-and-mortar architectures contain aligned O-gibbsite as b...

Crystal Growth & Design, Dec 10, 2020

Crystal Growth & Design, Dec 10, 2020

Journal of Functional Biomaterials, Nov 11, 2022

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Journal of Functional Biomaterials, Nov 11, 2022

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Macromolecular Symposia, 2000

Macromolecular Symposia, 2000

Batteries & Supercaps

Upon immersion of a lithium (Li) anode into a diluted 0.05 to 0.20 M dimethoxyethane‐solution of ... more Upon immersion of a lithium (Li) anode into a diluted 0.05 to 0.20 M dimethoxyethane‐solution of the phosphoric acid derivative (CF3CH2O)2P(O)OH (HBFEP), an artificial solid electrolyte interphase (SEI) is generated on the Li‐metal surface. Hence, HBFEP reacts on the surface to the corresponding Li salt (LiBFEP), which is a Li‐ion conducting inorganic coordination polymer. This film exhibits – due to the reversibly breaking ionic bonds – self‐healing ability upon cycling‐induced volume expansion of Li. The presence of LiBFEP as the major component in the artificial SEI is proven by ATR‐IR and XPS measurements. SEM characterization of HBFEP‐treated Li samples reveals porous layers on top of the Li surface with at least 3 μm thickness. Li−Li symmetrical cells with HBFEP‐modified Li electrodes show a three‐ to almost fourfold cycle‐lifetime increase at 0.1 mA cm−2 in a demanding model electrolyte that facilitates fast battery failure (1 M LiOTf in TEGDME). Hence, the LiBFEP‐enriched la...

Batteries & Supercaps

Upon immersion of a lithium (Li) anode into a diluted 0.05 to 0.20 M dimethoxyethane‐solution of ... more Upon immersion of a lithium (Li) anode into a diluted 0.05 to 0.20 M dimethoxyethane‐solution of the phosphoric acid derivative (CF3CH2O)2P(O)OH (HBFEP), an artificial solid electrolyte interphase (SEI) is generated on the Li‐metal surface. Hence, HBFEP reacts on the surface to the corresponding Li salt (LiBFEP), which is a Li‐ion conducting inorganic coordination polymer. This film exhibits – due to the reversibly breaking ionic bonds – self‐healing ability upon cycling‐induced volume expansion of Li. The presence of LiBFEP as the major component in the artificial SEI is proven by ATR‐IR and XPS measurements. SEM characterization of HBFEP‐treated Li samples reveals porous layers on top of the Li surface with at least 3 μm thickness. Li−Li symmetrical cells with HBFEP‐modified Li electrodes show a three‐ to almost fourfold cycle‐lifetime increase at 0.1 mA cm−2 in a demanding model electrolyte that facilitates fast battery failure (1 M LiOTf in TEGDME). Hence, the LiBFEP‐enriched la...

A series of poly(N,N-dimethylacrylamide)-l-polyisobutylene (PDMAAm-l-PIB) amphiphilic conetworks ... more A series of poly(N,N-dimethylacrylamide)-l-polyisobutylene (PDMAAm-l-PIB) amphiphilic conetworks were synthesized from two incompatible polymers, i.e. hydrophilic PDMAAm and strongly hydrophobic PIB in a wide range of composition (38-80 m/m % PIB). Swelling experiments were carried out to determine the equilibrium swelling ratios which proved the amphiphilic nature of these new materials, and are in correlation with composition. Thermal analysis (DSC), small angle X-ray scattering (SAXS) and atomic force microscopy (AFM) measurements were carried out. Results show special phase separated morphology, where the size of the phases are in the nanometer range in all cases. Furthermore, the nanophases of the conetworks have composition dependent spatial arrangement. Successful synthesis of silver nanoparticles was achived inside of the conetwork’s hydrophilic phases resulting in a novel organic-inorganic nanohybrid material.

A series of poly(N,N-dimethylacrylamide)-l-polyisobutylene (PDMAAm-l-PIB) amphiphilic conetworks ... more A series of poly(N,N-dimethylacrylamide)-l-polyisobutylene (PDMAAm-l-PIB) amphiphilic conetworks were synthesized from two incompatible polymers, i.e. hydrophilic PDMAAm and strongly hydrophobic PIB in a wide range of composition (38-80 m/m % PIB). Swelling experiments were carried out to determine the equilibrium swelling ratios which proved the amphiphilic nature of these new materials, and are in correlation with composition. Thermal analysis (DSC), small angle X-ray scattering (SAXS) and atomic force microscopy (AFM) measurements were carried out. Results show special phase separated morphology, where the size of the phases are in the nanometer range in all cases. Furthermore, the nanophases of the conetworks have composition dependent spatial arrangement. Successful synthesis of silver nanoparticles was achived inside of the conetwork’s hydrophilic phases resulting in a novel organic-inorganic nanohybrid material.

Catalysis Science & Technology, 2020

Influencing stability and performance through directing nitrogen-doping in carbon support materials.

Catalysis Science & Technology, 2020

Influencing stability and performance through directing nitrogen-doping in carbon support materials.

Magyar Kémiai Folyóirat, 2018

Magyar Kémiai Folyóirat, 2018