In situ micromechanics during hydrogen charging: Case study of diffusible hydrogen in bcc iron alloys

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Hydrogen‐microstructure interactions in bcc FeCr alloys by in‐situ nanoindentation

Environment sensitive failure, such as hydrogen embrittlement, of metallic alloys and particularly steels is a longstanding problem causing large annual economical loses. A deeper understanding of the individual mechanisms leading to the final material breakdown is highly demanded. Hydrogen can be incorporated into the material from different liquid or gas sources, during material processing or in operation conditions; the mechanisms leading to the material failure depend on the absorbed hydrogen interaction with trap binding sites or defects, as it is the case of dislocations. Please click Additional Files below to see the full abstract

In situ micromechanics during hydrogen charging: Effect of diffusible hydrogen on BBC Fe-based alloys and hydrogen protection through hydrogen barrier coatings

Hydrogen is a strong candidate to be the energy carrier of the future; however it also represents a challenge as it might cause material degradation through hydrogen embrittlement. To mitigate the negative effects of hydrogen and propose new strategies to protect structural materials it is necessary to understand which embrittlement mechanism is dominant and its specific causes. This can be reached by studying individual hydrogen-microstructure interactions, thereby targeting analyses at the nano-/microscale during hydrogen exposure. In this talk, we will present our novel electrochemical cell design developed for this purpose (Fig. 1a). In this “back-side” charging approach, the analyzed front surface is never in contact with the solution, avoiding unwanted corrosion, and the observed effects are only due to hydrogen [1]. Please click Download on the upper right corner to see the full abstract

Hydrogen induced hardening effect and the diffusion behavior in bcc Fe-Cr alloys by in situ nanoindentation

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Hydrogen-microstructure interactions by novel back-side hydrogen charging during in situ nanoindentation

To understand how hydrogen interacts with different features (e.g. dislocations, grain boundaries, precipitates, etc.) in alloys and composites is essential either to control and benefit from the hydrogen technology, or to prevent the destructive outcome of hydrogen embrittlement. Failure mechanisms initiate at the atomic scale with hydrogen absorption and further interaction with trap binding sites or defects. Nanoindentation and related techniques are valuable tools to study independently such mechanisms due to the small volume probed. Even more, in situ testing while charging the sample with hydrogen can prevent the formation of concentration gradients due to hydrogen desorption. Two custom electrochemical cells were built for in situ hydrogen charging during nanoindentation of the sample (Figure 1): “front-side” charging with the sample and indenter tip immersed into the electrolyte, and “back-side” charging where the analyzed region is never in contact with the solution and therefore the observed effects are only due to hydrogen. We discuss the advantages and disadvantages of both approaches during the study of the hydrogen effect on the mechanical behavior and incipient plasticity in bcc FeCr alloys. A reduction in the pop-in load indicating the yield point with the increase of hydrogen content and formation of multiple pop-ins during nanoindentation provided evidence for the decrease in the resolved shear stress and enhanced dislocations nucleation. This behavior is consistent with multiscale simulations of homogeneous dislocation nucleation where the reduced critical shear stress can be explained as an effective decrease of the dislocation line energy due to the interaction with diffusible hydrogen. Please click Additional Files below to see the full abstract

Global economic burden of unmet surgical need for appendicitis

Background There is a substantial gap in provision of adequate surgical care in many low- and middle-income countries. This study aimed to identify the economic burden of unmet surgical need for the common condition of appendicitis. Methods Data on the incidence of appendicitis from 170 countries and two different approaches were used to estimate numbers of patients who do not receive surgery: as a fixed proportion of the total unmet surgical need per country (approach 1); and based on country income status (approach 2). Indirect costs with current levels of access and local quality, and those if quality were at the standards of high-income countries, were estimated. A human capital approach was applied, focusing on the economic burden resulting from premature death and absenteeism. Results Excess mortality was 4185 per 100 000 cases of appendicitis using approach 1 and 3448 per 100 000 using approach 2. The economic burden of continuing current levels of access and local quality was US $92 492 million using approach 1 and$73 141 million using approach 2. The economic burden of not providing surgical care to the standards of high-income countries was $95 004 million using approach 1 and$75 666 million using approach 2. The largest share of these costs resulted from premature death (97.7 per cent) and lack of access (97.0 per cent) in contrast to lack of quality. Conclusion For a comparatively non-complex emergency condition such as appendicitis, increasing access to care should be prioritized. Although improving quality of care should not be neglected, increasing provision of care at current standards could reduce societal costs substantially

Global economic burden of unmet surgical need for appendicitis

Background There is a substantial gap in provision of adequate surgical care in many low- and middle-income countries. This study aimed to identify the economic burden of unmet surgical need for the common condition of appendicitis. Methods Data on the incidence of appendicitis from 170 countries and two different approaches were used to estimate numbers of patients who do not receive surgery: as a fixed proportion of the total unmet surgical need per country (approach 1); and based on country income status (approach 2). Indirect costs with current levels of access and local quality, and those if quality were at the standards of high-income countries, were estimated. A human capital approach was applied, focusing on the economic burden resulting from premature death and absenteeism. Results Excess mortality was 4185 per 100 000 cases of appendicitis using approach 1 and 3448 per 100 000 using approach 2. The economic burden of continuing current levels of access and local quality was US $92 492 million using approach 1 and$73 141 million using approach 2. The economic burden of not providing surgical care to the standards of high-income countries was $95 004 million using approach 1 and$75 666 million using approach 2. The largest share of these costs resulted from premature death (97.7 per cent) and lack of access (97.0 per cent) in contrast to lack of quality. Conclusion For a comparatively non-complex emergency condition such as appendicitis, increasing access to care should be prioritized. Although improving quality of care should not be neglected, increasing provision of care at current standards could reduce societal costs substantially