ISSN:
1662-9752
Source:
Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Ni-Ti SMA are smart materials undergoing first order martensitic transformations drivenby temperature and/or stress. In the form of film they are very attractive candidates for microelectro-mechanical system (MEMS) applications. Future directions include the production offunctionally graded films by changing deliberately the ratio Ti/Ni across their thickness. However,for the successful development of this type of films, it is important to characterize, model andcontrol the variations in composition, crystalline structure and transformation temperatures. Ourapproach is in-situ XRD study of the actual growth of the films of varying composition along thethickness carried out using a deposition chamber installed at a synchrotron radiation beamline.These studies were complemented with ex-situ analysis techniques. The results achieved on a Ni-Tifilm co-sputtered from Ni-Ti and Ti targets on a TiN buffer layer are presented in this paper. Thedeposition started by using optimised parameters for a near equiatomic composition. After 1 h(≈330 nm thick film), the Ti power was increased from 20 to 25 W, leading to the precipitation ofTi2Ni. The evolution of the lattice parameter values of the B2 phase, calculated from thecorresponding XRD data, is clearly linked with the increase of the Ti power. The depth profile ofthe atomic concentrations determined by Auger Electron Spectroscopy (AES) is in agreement withthe in situ XRD results. The temperature dependence of the electrical resistivity was used to monitorphase transformations, Scanning Electron Microscopy (SEM) has shown the presence of twinnedmartensite on the film’s surface at room temperature
Type of Medium:
Electronic Resource
URL:
http://www.tib-hannover.de/fulltexts/2011/0528/02/19/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.587-588.672.pdf
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