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High entropy alloys (HEAs) are considered as a new class of alloys containing at least 5 elements with concentrations between 5 and 35 atomic percent. There has been a growing interest in HEAs in the material research field in recent years. Due to their adjustable composition, which enables the modifications of mechanical properties (such as hardness, strength and ductility etc) and their stability at high temperatures, HEAs have been the focus of various studies.
Especially the corrosion behavior of HEAs has been a wide research interest. Since the grazing exit X-ray fluorescence (GEXRF) offers a non-destructive way to collect notable information regarding the high temperature oxidation, we consider it as a useful method to investigate how HEAs behave in corrosive environments.
The main idea of grazing geometry is to enhance the fluorescence signal of the surface. This enables highly sensitive surface analyses of thin protective film on surface in sub-micrometer scale. Position-sensitive area detectors provide information regarding the signal emitted from the sample as a function of emission angle and thus allow depth-sensitive analysis. Furthermore, the data collected from samples of an incidence energy which lays within a specific energy range provides XANES data to determine oxidation states. Moreover, since GEXRF profiles can also be simulated through physical models (Urbach 1999), they enable us to determine the layer thickness of a given sample in a non-destructive way.
In this contribution, we present the preliminary results of a conceptual study regarding layer properties of CrCoNi medium entropy alloy. The successful implementation of such methodological concept will pave the way for the investigation of more complex alloys with multiple layers, which is planned for the later phases of the project.
High entropy alloys (HEAs) are considered as a new class of alloys containing at least 5 elements with concentrations between 5 and 35 atomic percent. There has been a growing interest in HEAs in the material research field in recent years. Due to their adjustable composition, which enables the modifications of mechanical properties (such as hardness, strength and ductility etc) and their stability at high temperatures, HEAs have been the focus of various studies.
Especially the corrosion behavior of HEAs has been a wide research interest. Since the grazing exit X-ray fluorescence (GEXRF) offers a non-destructive way to collect notable information regarding the high temperature oxidation, we consider it as a useful method to investigate how HEAs behave in corrosive environments.
The main idea of grazing geometry is to enhance the fluorescence signal of the surface. This enables highly sensitive surface analyses of thin protective film on surface in sub-micrometer scale. Position-sensitive area detectors provide information regarding the signal emitted from the sample as a function of emission angle and thus allow depth-sensitive analysis. Furthermore, the data collected from samples of an incidence energy which lays within a specific energy range provides XANES data to determine oxidation states. Moreover, since GEXRF profiles can also be simulated through physical models (Urbach 1999), they enable us to determine the layer thickness of a given sample in a non-destructive way.
In this contribution, we present the preliminary results of a conceptual study regarding layer properties of CrCoNi medium entropy alloy. The successful implementation of such methodological concept will pave the way for the investigation of more complex alloys with multiple layers, which is planned for the later phases of the project.
This research group has been demonstrating the significant advantages of using Nb2O5 coatings for functionalizing titanium, aluminium, and stainless steels. Regarding the biomedical sector and considering Ti-6Al-4V alloy, the reactive sputtering technique improved the cell viability, the osteogenic performance of cells involved in the osseointegration process as well as the ability to delay bacterial proliferation. The characteristics of the Nb2O5 coatings were assessed before by using standard methods, which provide information only a few tens of nanometers depth. Given that the Nb2O5 coating fabricated in this work exhibits a thickness of approximately 300 nm, the GE-XANES technique emerges as the most suitable method for this analysis. Additional information was provided with the aid of nanoindentation load-depth (P-h) curves. GE-XANES results indicated the formation of a homogeneous layer of Nb2O5 coating on the Ti-6Al-4V surfaces. The deposition process improved the surface hardness of the Ti-6Al-4V alloy (4.38 GPa versus 5.62 GPa) considering the 2 mN load.
Time is the most valuable parameter in synchrotron experiments. This is costly and some of the experiments suffer from low efficiency due to low counting statistics. With today's high processing power long experiments are run in a shorter time and increase efficiency. With optimization algorithms time in "counting-hungry" experiments reduced by factor of 10. Our project is to develop a new method to analyze the chemical properties of complex materials non-destructively and efficiently, such as high entropy materials subjected to corrosion processes. A better understanding of the corrosion process will help to develop corrosion-resistant materials and reduce the cost of corrosion damage, which averages around 2.5 trillion USD annually.
The components that are used in structural and in high temperature applications generally face significant challenges with respect to oxidation behaviours and metalworking processes. In most of the cases, harsh environmental conditions lead materials to degrade due to corrosion. To thoroughly investigate the corrosion processes and to determine oxidation states of metal components within the reaction products, we need special analytical tools. Grazing exit X-ray fluorescence (GEXRF) offers a non-destructive way to collect this information in sub-micrometre depth range.
In order to obtain structural information, such as regarding oxidation states or atomic/molecular geometric arrangement, the GEXRF approach can also be combined with the X-ray absorption spectroscopy (XAS) method. The position and energy sensitive detector, with 264x264 pixel detector area, provides information regarding the signal emitted from the sample as a function of the emission angle and thus allows depth-sensitive analysis. Furthermore, the data collected from samples of an incidence energy which can be controlled with a resolution of 0.5 eV provides XANES data to determine oxidation states.
We address the feasibility of our setup and provide a new optimization procedure (Bayesian Optimization and Gaussian Regression) to decrease measuring time. The results settle on a conceptual study on a reference sample (Cr-Oxide layer (300nm) on Cr layer (500nm) on Si wafer).
The components that are used in structural and in high temperature applications generally face significant challenges with respect to oxidation behaviours and metalworking processes. In most of the cases, harsh environmental conditions lead materials to degrade due to corrosion. To thoroughly investigate the corrosion processes and to determine oxidation states of metal components within the reaction products, we need special analytical tools. Grazing exit X-ray fluorescence (GEXRF) offers a non-destructive way to collect this information in sub-micrometre depth range.
In order to obtain structural information, such as regarding oxidation states or atomic/molecular geometric arrangement, the GEXRF approach can also be combined with the X-ray absorption spectroscopy (XAS) method. The position and energy sensitive detector, with 264x264 pixel detector area, provides information regarding the signal emitted from the sample as a function of the emission angle and thus allows depth-sensitive analysis. Furthermore, the data collected from samples of an incidence energy which can be controlled with a resolution of 0.5 eV provides XANES data to determine oxidation states.
We address the feasibility of our setup and provide a new optimization procedure (Bayesian Optimization and Gaussian Regression) to decrease measuring time. The results settle on a conceptual study on a reference sample (Cr-Oxide layer (300nm) on Cr layer (500nm) on Si wafer).
Compositionally complex alloys (CCAs) are a new class of alloys containing at least 5 elements with concentrations between 5 and 35 atomic percent. Due to their adjustable composition, which enables modifications of mechanical properties (such as hardness, strength and ductility etc) and their stability at high temperatures, CCAs have been the focus of various studies [1,2]. Especially the corrosion behavior of CCAs has been a wide research interest.
However, there are only few studies that deals with the degradation process on such materials, which is highly relevant for the safety aspect for future component design. To thoroughly investigate the corrosion processes and to determine oxidation states of metal components within the reaction products, we need special analytical tools. Since the grazing exit X-ray fluorescence (GEXRF) offers a non-destructive way to collect notable information regarding the high temperature oxidation, we consider it as a useful method to investigate how CCAs behave in corrosive environments.
The main idea of grazing geometry is to enhance the fluorescence signal of the surface. This enables highly sensitive surface analyses of thin protective film on surface in sub-micrometer scale [3]. When compared to a conventional CCD-based camera, the advantage and most important feature of the detector system (Color X-Ray Camera (CXC)) is that each pixel is an energy sensitive detector. The position and area sensitive detector, with 264x264 pixel detector area, provides information regarding the signal emitted from the sample as a function of the emission angle and thus allows depth-sensitive analysis. Furthermore, the data collected from samples of an incidence energy which can be controlled with a resolution of 0.5 eV provides XANES data to determine oxidation states.
In this contribution, we address the feasibility of our setup and new optimization procedure (Bayesian Optimization and Gaussian Regression). The results of a conceptual study regarding layer properties of the reference sample (Cr-Oxide layer (300nm) on Cr layer (500nm) on Si wafer) and CrCoNi (Cr-Oxide (>1µm) layer on CrCoNi substrate) medium entropy alloy.
In materials science, traditional techniques for analyzing layered structures are essential for obtaining information about local structure, electronic properties and chemical states. While valuable, these methods often require high vacuum environments and have limited depth profiling capabilities. The grazing exit x-ray absorption near-edge structure (GE-XANES) technique addresses these limitations by providing depth-resolved insight at ambient conditions, facilitating in situ material analysis without special sample preparation. However, GE-XANES is limited by long data acquisition times, which hinders its practicality for various applications. To overcome this, we have incorporated Bayesian optimization (BO) into the GE-XANES data acquisition process. This innovative approach potentially reduces measurement time by a factor of 50. We have used a standard GE-XANES experiment, which serve as reference, to validate the effectiveness and accuracy of the BO-informed experimental setup. Our results show that this optimized approach maintains data quality while significantly improving efficiency, making GE-XANES more accessible to a wider range of materials science applications.
In the field of materials science, there is a critical need for efficient and effective characterization techniques, especially in the investigation of corrosion processes of compositionally complex alloys (CCAs) or the analysis of layered structures. This talk presents an advanced approach that combines grazing-exit X-ray absorption near-edge structure spectroscopy (GE-XANES) with Bayesian optimization (BO) to significantly improve the efficiency of data acquisition while retaining the depth-resolved, element-specific analysis capabilities that are critical for studying these materials under ambient conditions. Using a non-destructive, scan-free GE-XANES setup coupled with a pnCCD detector and grazing exit X-ray fluorescence spectroscopy (GE-XRF) geometry, our method enables precise analysis at sub-micrometer depths without the need for high vacuum environments or extensive sample preparation. The integration of BO reduces experimental time by a factor of 50, overcoming the practical limitations of conventional GE-XANES and increasing its applicability in the study of surface catalysis and corrosion processes. We validate this optimized approach through comparative studies on a CrCoNi alloy and a reference layered sample, demonstrating its potential to revolutionize materials analysis by increasing both efficiency and accessibility.