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Thermomechanical response of Cu-based shape memory alloys suitable for micro-electro-mechanical systems (MEMS) applications: interplay between grain size and sample size effects (SMAMEMS)
Date du début: 1 sept. 2013, Date de fin: 29 févr. 2016 PROJET  TERMINÉ 

"Shape memory alloys (SMA) exhibit unique and useful effects, such as a capacity to cycle a component between two different macroscopic shapes by cycling the temperature. In the recent years MEMS components made of shape memory alloys have attracted considerable interest in the research field as they offer a high output work density and exhibit specific desirable thermomechanical effects. As a consequence, many research studies have been focused on the development of shape memory thin films which could be integrated into the planar technology of microsystems. However, there are few works in the literature where the effects of the grain size (d)/sample size (D) ratio are studied, and those that do exist are insufficient to draw general conclusions.Among the many SMA families that have been reported in the literature, the Cu-based SMAs are attractive because they can exhibit excellent shape memory properties at a substantially lower materials cost relative to the market-dominant Ni-Ti-based alloys. In this project it is proposed to synthesize Cu-based shape memory alloys at the scales relevant to MEMS applications.The first stage of the project comprises the design and production of SMA thin films using electrodeposition methods, with grain sizes ranging from few nanometers to tens of microns, in order to evaluate grain size effects on the thermomechanical behaviour of Cu-based SMA. Furthermore, this step will also permit to optimize the electrodeposition parameters to further carry out the electrodeposition on the pre-patterned surfaces. The second stage aims to produce SMA in the micro- and nano-meter scale dimensions (for example pillars) by means of electron beam lithography and subsequent electrodeposition. The main goal of this part is to study the contribution of the grain size/sample dimensions on its thermomechanical behaviour; i.e., when the grain size is considerably finer than the sample size or when the grain size is close to the sample dimension."