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- ItemThe influence of mean strain on the high-cycle fatigue of Nitinol with application to medical devices(Amsterdam : Elsevier, 2020) Cao, H.; Wu, M.H.; Zhou, F.; McMeeking, R.M.; Ritchie, R.O.One of the contentious issues associated with the high-cycle fatigue of Nitinol, a nominally equiatomic alloy of nickel and titanium, is the claim that increasing the applied mean strain can increase, or at least have no negative impact, on the fatigue lifetime, in conflict with reported behavior for the vast majority of other metallic materials. To investigate this in further detail, cyclic fatigue tests in bending were carried out on electropolished medical grade Nitinol at 37 °C for lives of up to 400 million cycles of strain involving various levels of the mean strain. A constant life model was developed through statistical analysis of the fatigue data, with 90% reliability at a confidence level of 95% on the effective fatigue strain. Our results show that the constant life diagram, a plot of strain amplitude versus mean strain, is monotonic yet nonlinear for lives of 400 million cycles of fatigue loading. Specifically, we find that in contradiction to the aforementioned claim, the strain amplitude limit at zero mean strain is 0.55% to achieve a 400 million cycle lifetime, at 90% reliability with 95% confidence; however, to achieve the same lifetime, reliability and confidence level in the presence of a 3% or more mean strain, the required strain amplitude limit is decreased by over a factor of three to 0.16%. Moreover, for mean strains from 3% to 7%, the strain amplitude limit that allows a 400 million cycle lifetime, at 90% reliability with 95% confidence, is ~ 0.16%, and essentially independent of mean strain. We conclude that the debatable claim that an increase in the applied mean strain can increase the fatigue life of Nitinol components is not supported by the current data.
- ItemHigh-performance ion removal via zinc–air desalination(Amsterdam : Elsevier, 2020) Srimuk, P.; Wang, L.; Budak, Ö.; Presser, V.Electrochemical processes enable a new generation of energy-efficient desalination technologies. While ion electrosorption via capacitive deionization is only suitable for brackish water with low molar strength, the use of Faradaic materials capable of reversible ion intercalation or conversion reactions allows energy-efficient removal of ions from seawater. However, the limited charge transfer/storage capacity of Faradaic materials indicates an upper limit for their desalination applications. Therefore, a new electrochemical concept must be explored to exceed the current state-of-the-art results and to push the desalination capacity beyond 100–200 mgNaCl/gelectrode. In this proof-of-concept work, we introduce the new concept of using metal–air battery technology for desalination. We do so by presenting performance data for zinc–air desalination (ZAD) in 600 mM NaCl. The ZAD cell provides a desalination capacity of 0.9–1.0 mgNaCl/cm2 (normalized to the membrane area; corresponding to 1300 mgNaCl/gZn) with a charge efficiency of 70% when charging/discharging the cell at 1 mA/cm2. The energy consumption of ZAD is 68–92 kJ/mol.
- ItemSafe-by-Design part I: Proposal for nanospecific human health safety aspects needed along the innovation process(Amsterdam : Elsevier, 2020) Dekkers, S.; Wijnhoven, S.W.P.; Braakhuis, H.M.; Soeteman-Hernandez, L.G.; Sips, A.J.A.M.; Tavernaro, I.; Kraegeloh, A.; Noorlander, C.W.Safe-by-Design aims to reduce uncertainties and/or increase the human health and environmental safety from already early in the innovation process onwards and will thereby contribute to increased innovation efficiency, economic viability, interdisciplinary collaboration, consumers trust and improve sustainability. Since most innovators or designers are neither toxicologists nor risk assessors, considering human health safety aspects within their innovation process may be challenging. This paper provides sets of questions that can help innovators to assess nanospecific human health safety aspects of their product or material along the various stages of the innovation process. Addressing these questions will facilitate innovators to identify which type of information may support decisions on how to address potential human health risks in the innovation process. The identified information on the human health safety aspects can help innovators to decide if further investments in the product or material are beneficial. It may allow them to rank, prioritize and choose safer alternatives early in the innovation process. This may enable innovators to better anticipate on potential safety issues in an early stage, preventing these safety issues to become an innovation killer in a later stage of the innovation process. This approach to identify potential nanospecific human health risks should be considered as complementary to current regulations. The applicability of this approach was evaluated using a few industrial case studies. To determine if the approach is applicable to the innovation of a broader group of nanomaterials and nano-enabled products, more experience within various industrial sectors is needed.
- ItemPre and post-treatments to improve weldability and mechanical properties of aluminum-polyamide laser welded specimens(Amsterdam : Elsevier, 2020) Elahi, Mahdi Amne; Koch, Marcus; Heck, Mike; Plapper, PeterThe laser polishing surface treatment is a prerequisite for enhanced weldability that is enabled by superior adhesion between the weldments. The paper describes the laser polishing process of the aluminum surface to develop a relatively thick and porous artificial aluminum oxide layer. Microscopic observation shows the laser polishing process significantly improves the adhesion of molten polyamide to the aluminum surface. Besides, the shear load of the pretreated joints is much higher than that of as-received ones. However, for the majority of the welded samples, the failure happens at the polyamide near the interface of aluminum/polyamide due to the thermal effect and structural changes of polyamide during the welding process. By applying the post-treatment of the welded specimens with different cycles, the mentioned failure mechanism is not observed anymore. Therefore, the mechanical properties of the joint will be improved and reach to the limits of the base materials.