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Papers by Willem Quadakkers

Fresenius' Journal of Analytical Chemistry, 1993

Attempts to obtain a quantitative analysis of depth profiles of oxide films on iron-based ODS-all... more Attempts to obtain a quantitative analysis of depth profiles of oxide films on iron-based ODS-alloys using MCs+-SIMS and e-beam SNMS are presented. Since the oxide films of the alloys consist mainly of alumina, implantation standards in A1203(sapphire) were used for the quantification of the measured depth profiles. The so-called matrix effect, normally present in SIMS analysis, is strongly reduced by recording the MCs+-secondary ions. Over a wide concentration range, agreement between SIMS and SNMS data is obtained within a factor 2-3. The evaluated concentration profiles for the main alloying elements in combination with 180 tracer-experiments have been used to give an interpretation of the growth processes of the oxide films for Fe-based ODS-alloys, with and without the addition of an yttria dispersion. The results show that the addition of yttria dispersion is responsible for the dramatic change observed in the oxide growth mechanism.

Fresenius' Journal of Analytical Chemistry, 1993

The oxidation behaviour of a number of FeCrA1based oxide dispersion strengthened (ODS) alloys of ... more The oxidation behaviour of a number of FeCrA1based oxide dispersion strengthened (ODS) alloys of the type MA 956 was investigated at temperatures between 1100 °C and 1200 ° C. The main emphasis was placed on the effect of alloy yttria content on scale composition and structure. Studies of three model alloys with various alloy yttria contents in the range 0.02-0.7% showed an increase in the oxide growth rate with increasing yttria content. Alumina scales on alloys with 0.17% and 0.7% yttria grow almost exclusively by oxygen diffusion, whereas the scale on the alloy with 0.02% yttria exhibits a significant contribution from cation diffusion. By using SIMS depth-profiling and SIMS-imaging it was found that the oxygen diffuses through the alumina scale via oxide grain boundaries. TEM-studies revealed that the yttria is incorporated in the scale grain boundaries as precipitations and as a segregation layer. This behaviour of the yttrium is believed to be responsible for its influence on scale growth mechanisms, A mathematical model has been developed which describes the alumina scale growth by oxygen diffusion through grain boundaries. The model accounts for the observed increase in aluminium oxide grain size in scale growth direction.

Journal of Physics: Condensed Matter, 2000

Measurements by x-ray diffraction, secondary ion mass spectrometry and atomic force microscopy ar... more Measurements by x-ray diffraction, secondary ion mass spectrometry and atomic force microscopy are reported for single crystalline KTaO3 after thermal treatment under oxidizing conditions in the temperature range of 700 to 1100 °C. The formation of a series of new phases KO*(KTaO3)n of Ruddlesden-Popper type is observed. Atomic force microscopy of (100) surfaces reveals corresponding dramatic changes in the surface morphology. Secondary ion mass spectrometry gives evidence of a redistribution of material leading to an enrichment of K with respect to Ta close to the surface and a corresponding depletion in deeper parts of the near-surface region. The results are in strong contrast to standard point defect models. Instead, our experimental observations have to be interpreted in terms of an evolving chemical inhomogeneity due to segregation processes in the near-surface region of the crystals and intergrowth of KO, which results in the formation of the Ruddlesden-Popper phases. The additional effect of K2O evaporation above 900 °C is discussed and the corresponding topographical changes induced are documented.

Mikrochimica Acta, 1992

Composition and growth phenomena of alumina scales on a conventional wrought alloy Fe-20Cr-5Al an... more Composition and growth phenomena of alumina scales on a conventional wrought alloy Fe-20Cr-5Al and an yttria containing ODS alloy with the same base composition were investigated. The alloys were oxidized in a twostage oxidation process at 1000 °C in air and air containing18O-tracer. By using secondary neutrals and secondary ion mass spectrometry in combination with RBS, the in-depth concentration of main and minor alloying elements as well as the oxygen isotope distribution in the alumina scale could be determined. It is shown, that the difficulties in deriving the exact growth processes of the scales from the oxygen tracer profiles can be overcome by using the time dependance of the iron and chromium distribution in the alumina. From these results it could be derived that growth of the oxide scales formed on the ODS and the conventional alloy mainly differ in the relative contribution of aluminium diffusion. The mechanisms which lead to these differences in scale growth phenomena will be discussed.

Applied Surface Science, 1991

The composition and growth phenomena of alumina scales on a conventional wrought alloy Fe-20Cr-SA... more The composition and growth phenomena of alumina scales on a conventional wrought alloy Fe-20Cr-SAI and on an yttria containing ODS alloy of similar base composition were investigated. The oxide scales were formed during two-stage oxidation at temperatures between 900 and 1100 o C in air and in air containing I80 tracer. The in-depth concentration profiles of the various elements as well as the oxygen isotope distributions in the oxide scales were determined by secondary neutrals mass spectrometry (SNMS). It was found that detailed knowledge about the time and temperature dependence of scale composition is necessary for deriving unequivocal information on the scale growth process from the oxygen isotope distributions. It appeared that the growth of the oxide scales mainly occurs on the scale/alloy and the scale/gas interface. The existence of growth within the scale could not clearly be confirmed although some results indicated that this effect might have occurred. The scales on the ODS alloy and the conventional alloy differed mainly in the relative contributions of cation diffusion to the overall growth process.

Ceramic Engineering and Science Proceedings, 2004

ABSTRACT Solid oxide fuel cell (SOFC) development work at Forschungszentrum Juelich (FZJ) is exte... more ABSTRACT Solid oxide fuel cell (SOFC) development work at Forschungszentrum Juelich (FZJ) is extensive, ranging from fundamental materials' design through to near-commercial prototype CHP systems. Considerable advances have been demonstrated in the past years concerning the improvement of device performance by identifying performance degradation mechanisms and reducing or eliminating those problems, and in designing, developing and manufacturing core SOFC components. At the time of this writing, the first, fully integrated SOFC combined heat and power generation prototype system is awaiting completion. FZJ is involved in significant national and international programs and coordinates major international projects.

Mikrochimica Acta, 1995

ABSTRACT

Scripta Metallurgica et Materialia, 1995

ABSTRACT

Surface and Coatings Technology, 1996

ABSTRACT

Oxidation of Metals, 1995

The oxidation behavior of the titanium aluminides has been investigated in Ar + 20%02 and in air ... more The oxidation behavior of the titanium aluminides has been investigated in Ar + 20%02 and in air at 900~ Thermogravimetric studies in combination with structural analyses using optical metallography, SEM/EDX and X-ray diffraction show a marked influence of nitrogen on the composition and growth rate of the oxide scales. For a more detailed study concerning the effect of nitrogen on the scale-growth kinetics, thermogravimetrical analyses were carried out during which the gas atmosphere was changed from air to Ar-02, and vice versa, without intermediate cooling of the specimen. The results show, that nitrogen adversely affects the formation of the initially formed alumina scale and that it enhances the growth rate of the rapidly growing Ti-rich oxide. This effect was observed in both alloys investigated, although the thermogravimetric results at first sight indicated an opposite effect for the Nb-containing alloy. This apparent contradiction is caused by internal oxidation which occurs in this alloy during exposure in Ar-02.

Oxidation of Metals, 1996

... to be related to a direct decrease of anion and cation transport in the mixed alumina titania... more ... to be related to a direct decrease of anion and cation transport in the mixed alumina titania scale ... Effect of Niobium Ion Implantation ... MF Stroosnijder, JD Sunderk6tter, and VAC Haanappel, in Design Fundamentals of Composites, Intermetallics and Metal-Ceramics Systems, RY ...

International Journal of Applied Ceramic Technology, 2006

ABSTRACT The SOFC group at Forschungszentrum Juelich has assembled and tested more than 220 SOFC ... more ABSTRACT The SOFC group at Forschungszentrum Juelich has assembled and tested more than 220 SOFC stacks during the last 10 years, rated between 100 W and 15 kW. The topics of high-performance materials, corrosion, materials compatibility, and cost-effectiveness, including manufacturing processes, etc., are being continuously addressed. Large stacks of 5 kW and above have been operated since 2002 and have also been successfully delivered to other institutions. In parallel, lightweight stacks have been developed in the “cassette” design line for SOFC-APU. Several 1–20 kW SOFC laboratory systems are in preparation.

International Journal of Applied Ceramic Technology, 2006

ABSTRACT The SOFC group at Forschungszentrum Juelich has assembled and tested more than 220 SOFC ... more ABSTRACT The SOFC group at Forschungszentrum Juelich has assembled and tested more than 220 SOFC stacks during the last 10 years, rated between 100 W and 15 kW. The topics of high-performance materials, corrosion, materials compatibility, and cost-effectiveness, including manufacturing processes, etc., are being continuously addressed. Large stacks of 5 kW and above have been operated since 2002 and have also been successfully delivered to other institutions. In parallel, lightweight stacks have been developed in the “cassette” design line for SOFC-APU. Several 1–20 kW SOFC laboratory systems are in preparation.

Bansal/Solid Oxide, 2007

ABSTRACT: Solid Oxide Fuel Cell (SOFC) stacks as developed by Forschungszentrum Jiilich (FZJ) are... more ABSTRACT: Solid Oxide Fuel Cell (SOFC) stacks as developed by Forschungszentrum Jiilich (FZJ) are based on nickel-cermet anode supported cells. The planar anode supported design offers high performance at lower temperatures thanks to an extremely thin ...

ECS Transactions, 2013

ABSTRACT The SOFC group at JULICH works on the development of materials, cell and stack since the... more ABSTRACT The SOFC group at JULICH works on the development of materials, cell and stack since the early 90s, strongly supported by post-operational analysis. Important achievements are e. g. the development of ferritic chromium steels which are now commercially available and anode substrate cells with power densities exceeding 2 W/cm(2) at 0.7 V and 700 degrees C. Special highlights are long term tests with short stacks of which one has reached 50,000 h of continuous operation. In the year 2000 also systems and system components development has been started. In 2012 a 20 kW system, based on four 5 kW stacks, was successfully set into operation. The envisaged 20 kW were achieved and the system has been operated for about 4,000 h up to now.

Oxidation of Metals, 2015

Fresenius' Journal of Analytical Chemistry, 1993

Attempts to obtain a quantitative analysis of depth profiles of oxide films on iron-based ODS-all... more Attempts to obtain a quantitative analysis of depth profiles of oxide films on iron-based ODS-alloys using MCs+-SIMS and e-beam SNMS are presented. Since the oxide films of the alloys consist mainly of alumina, implantation standards in A1203(sapphire) were used for the quantification of the measured depth profiles. The so-called matrix effect, normally present in SIMS analysis, is strongly reduced by recording the MCs+-secondary ions. Over a wide concentration range, agreement between SIMS and SNMS data is obtained within a factor 2-3. The evaluated concentration profiles for the main alloying elements in combination with 180 tracer-experiments have been used to give an interpretation of the growth processes of the oxide films for Fe-based ODS-alloys, with and without the addition of an yttria dispersion. The results show that the addition of yttria dispersion is responsible for the dramatic change observed in the oxide growth mechanism.

Fresenius' Journal of Analytical Chemistry, 1993

The oxidation behaviour of a number of FeCrA1based oxide dispersion strengthened (ODS) alloys of ... more The oxidation behaviour of a number of FeCrA1based oxide dispersion strengthened (ODS) alloys of the type MA 956 was investigated at temperatures between 1100 °C and 1200 ° C. The main emphasis was placed on the effect of alloy yttria content on scale composition and structure. Studies of three model alloys with various alloy yttria contents in the range 0.02-0.7% showed an increase in the oxide growth rate with increasing yttria content. Alumina scales on alloys with 0.17% and 0.7% yttria grow almost exclusively by oxygen diffusion, whereas the scale on the alloy with 0.02% yttria exhibits a significant contribution from cation diffusion. By using SIMS depth-profiling and SIMS-imaging it was found that the oxygen diffuses through the alumina scale via oxide grain boundaries. TEM-studies revealed that the yttria is incorporated in the scale grain boundaries as precipitations and as a segregation layer. This behaviour of the yttrium is believed to be responsible for its influence on scale growth mechanisms, A mathematical model has been developed which describes the alumina scale growth by oxygen diffusion through grain boundaries. The model accounts for the observed increase in aluminium oxide grain size in scale growth direction.

Journal of Physics: Condensed Matter, 2000

Measurements by x-ray diffraction, secondary ion mass spectrometry and atomic force microscopy ar... more Measurements by x-ray diffraction, secondary ion mass spectrometry and atomic force microscopy are reported for single crystalline KTaO3 after thermal treatment under oxidizing conditions in the temperature range of 700 to 1100 °C. The formation of a series of new phases KO*(KTaO3)n of Ruddlesden-Popper type is observed. Atomic force microscopy of (100) surfaces reveals corresponding dramatic changes in the surface morphology. Secondary ion mass spectrometry gives evidence of a redistribution of material leading to an enrichment of K with respect to Ta close to the surface and a corresponding depletion in deeper parts of the near-surface region. The results are in strong contrast to standard point defect models. Instead, our experimental observations have to be interpreted in terms of an evolving chemical inhomogeneity due to segregation processes in the near-surface region of the crystals and intergrowth of KO, which results in the formation of the Ruddlesden-Popper phases. The additional effect of K2O evaporation above 900 °C is discussed and the corresponding topographical changes induced are documented.

Mikrochimica Acta, 1992

Composition and growth phenomena of alumina scales on a conventional wrought alloy Fe-20Cr-5Al an... more Composition and growth phenomena of alumina scales on a conventional wrought alloy Fe-20Cr-5Al and an yttria containing ODS alloy with the same base composition were investigated. The alloys were oxidized in a twostage oxidation process at 1000 °C in air and air containing18O-tracer. By using secondary neutrals and secondary ion mass spectrometry in combination with RBS, the in-depth concentration of main and minor alloying elements as well as the oxygen isotope distribution in the alumina scale could be determined. It is shown, that the difficulties in deriving the exact growth processes of the scales from the oxygen tracer profiles can be overcome by using the time dependance of the iron and chromium distribution in the alumina. From these results it could be derived that growth of the oxide scales formed on the ODS and the conventional alloy mainly differ in the relative contribution of aluminium diffusion. The mechanisms which lead to these differences in scale growth phenomena will be discussed.

Applied Surface Science, 1991

The composition and growth phenomena of alumina scales on a conventional wrought alloy Fe-20Cr-SA... more The composition and growth phenomena of alumina scales on a conventional wrought alloy Fe-20Cr-SAI and on an yttria containing ODS alloy of similar base composition were investigated. The oxide scales were formed during two-stage oxidation at temperatures between 900 and 1100 o C in air and in air containing I80 tracer. The in-depth concentration profiles of the various elements as well as the oxygen isotope distributions in the oxide scales were determined by secondary neutrals mass spectrometry (SNMS). It was found that detailed knowledge about the time and temperature dependence of scale composition is necessary for deriving unequivocal information on the scale growth process from the oxygen isotope distributions. It appeared that the growth of the oxide scales mainly occurs on the scale/alloy and the scale/gas interface. The existence of growth within the scale could not clearly be confirmed although some results indicated that this effect might have occurred. The scales on the ODS alloy and the conventional alloy differed mainly in the relative contributions of cation diffusion to the overall growth process.

Ceramic Engineering and Science Proceedings, 2004

ABSTRACT Solid oxide fuel cell (SOFC) development work at Forschungszentrum Juelich (FZJ) is exte... more ABSTRACT Solid oxide fuel cell (SOFC) development work at Forschungszentrum Juelich (FZJ) is extensive, ranging from fundamental materials' design through to near-commercial prototype CHP systems. Considerable advances have been demonstrated in the past years concerning the improvement of device performance by identifying performance degradation mechanisms and reducing or eliminating those problems, and in designing, developing and manufacturing core SOFC components. At the time of this writing, the first, fully integrated SOFC combined heat and power generation prototype system is awaiting completion. FZJ is involved in significant national and international programs and coordinates major international projects.

Mikrochimica Acta, 1995

ABSTRACT

Scripta Metallurgica et Materialia, 1995

ABSTRACT

Surface and Coatings Technology, 1996

ABSTRACT

Oxidation of Metals, 1995

The oxidation behavior of the titanium aluminides has been investigated in Ar + 20%02 and in air ... more The oxidation behavior of the titanium aluminides has been investigated in Ar + 20%02 and in air at 900~ Thermogravimetric studies in combination with structural analyses using optical metallography, SEM/EDX and X-ray diffraction show a marked influence of nitrogen on the composition and growth rate of the oxide scales. For a more detailed study concerning the effect of nitrogen on the scale-growth kinetics, thermogravimetrical analyses were carried out during which the gas atmosphere was changed from air to Ar-02, and vice versa, without intermediate cooling of the specimen. The results show, that nitrogen adversely affects the formation of the initially formed alumina scale and that it enhances the growth rate of the rapidly growing Ti-rich oxide. This effect was observed in both alloys investigated, although the thermogravimetric results at first sight indicated an opposite effect for the Nb-containing alloy. This apparent contradiction is caused by internal oxidation which occurs in this alloy during exposure in Ar-02.

Oxidation of Metals, 1996

... to be related to a direct decrease of anion and cation transport in the mixed alumina titania... more ... to be related to a direct decrease of anion and cation transport in the mixed alumina titania scale ... Effect of Niobium Ion Implantation ... MF Stroosnijder, JD Sunderk6tter, and VAC Haanappel, in Design Fundamentals of Composites, Intermetallics and Metal-Ceramics Systems, RY ...

International Journal of Applied Ceramic Technology, 2006

ABSTRACT The SOFC group at Forschungszentrum Juelich has assembled and tested more than 220 SOFC ... more ABSTRACT The SOFC group at Forschungszentrum Juelich has assembled and tested more than 220 SOFC stacks during the last 10 years, rated between 100 W and 15 kW. The topics of high-performance materials, corrosion, materials compatibility, and cost-effectiveness, including manufacturing processes, etc., are being continuously addressed. Large stacks of 5 kW and above have been operated since 2002 and have also been successfully delivered to other institutions. In parallel, lightweight stacks have been developed in the “cassette” design line for SOFC-APU. Several 1–20 kW SOFC laboratory systems are in preparation.

International Journal of Applied Ceramic Technology, 2006

ABSTRACT The SOFC group at Forschungszentrum Juelich has assembled and tested more than 220 SOFC ... more ABSTRACT The SOFC group at Forschungszentrum Juelich has assembled and tested more than 220 SOFC stacks during the last 10 years, rated between 100 W and 15 kW. The topics of high-performance materials, corrosion, materials compatibility, and cost-effectiveness, including manufacturing processes, etc., are being continuously addressed. Large stacks of 5 kW and above have been operated since 2002 and have also been successfully delivered to other institutions. In parallel, lightweight stacks have been developed in the “cassette” design line for SOFC-APU. Several 1–20 kW SOFC laboratory systems are in preparation.

Bansal/Solid Oxide, 2007

ABSTRACT: Solid Oxide Fuel Cell (SOFC) stacks as developed by Forschungszentrum Jiilich (FZJ) are... more ABSTRACT: Solid Oxide Fuel Cell (SOFC) stacks as developed by Forschungszentrum Jiilich (FZJ) are based on nickel-cermet anode supported cells. The planar anode supported design offers high performance at lower temperatures thanks to an extremely thin ...

ECS Transactions, 2013

ABSTRACT The SOFC group at JULICH works on the development of materials, cell and stack since the... more ABSTRACT The SOFC group at JULICH works on the development of materials, cell and stack since the early 90s, strongly supported by post-operational analysis. Important achievements are e. g. the development of ferritic chromium steels which are now commercially available and anode substrate cells with power densities exceeding 2 W/cm(2) at 0.7 V and 700 degrees C. Special highlights are long term tests with short stacks of which one has reached 50,000 h of continuous operation. In the year 2000 also systems and system components development has been started. In 2012 a 20 kW system, based on four 5 kW stacks, was successfully set into operation. The envisaged 20 kW were achieved and the system has been operated for about 4,000 h up to now.

Oxidation of Metals, 2015