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Open AccessArticle

Functionalization of the NiTi Shape Memory Alloy Surface by HAp/SiO2/Ag Hybrid Coatings Formed on SiO2-TiO2 Glass Interlayer

1
Refractory Materials Division in Gliwice, ŁUKASIEWICZ Research Network—Institute of Ceramics and Building Materials, Toszecka 99, 44-100 Gliwice, Poland
2
Institute of Materials Engineering, University of Silesia in Katowice, 75 Pulku Piechoty 1A, 41-500 Chorzow, Poland
3
Silesian Center for Education and Interdisciplinary Research, University of Silesia in Katowice, 75 Pulku Piechoty 1A, 41-500 Chorzow, Poland
*
Author to whom correspondence should be addressed.
Materials 2020, 13(7), 1648; https://doi.org/10.3390/ma13071648
Received: 8 March 2020 / Revised: 27 March 2020 / Accepted: 30 March 2020 / Published: 2 April 2020
The surface modification of NiTi shape memory alloys is a method for increasing their multi-functionalities. In our solution, hydroxyapatite powder was mixed with a chemically synthesized silicon dioxide/silver (nSiO2/Ag) nanocomposite in a different weight ratio between components (1:1, 5:1, and 10:1) and then electrophoretically deposited on the surface of the NiTi alloy, under various time and voltage conditions. Subsequently, uniform layers were subjected to heat treatment at 700 °C for 2 h in an argon atmosphere to improve the strength of their adhesion to the NiTi substrate. A change in linear dimensions of the co-deposited materials during the sintering process was also analyzed. After the heat treatment, XRD, Raman, and Scanning Electron Microscopy (SEM) + Energy Dispersive Spectrometer (EDS) studies revealed the formation of completely new composite coatings, which consisted of rutile and TiO2-SiO2 glass with silver oxide and HAp particles that were embedded into such coatings. It was found that spalling characterized the 1:1 ratio coating, while the others were crack-free, well-adhered, and capable of deformation to 3.5%. Coatings with a higher concentration of nanocomposite were rougher. Electrochemical impedance spectroscopy (EIS) tests in Ringer’s solution revealed the capacitive behavior of the material with high corrosion resistance. The kinetics and susceptibility to pitting corrosion was the highest for the NiTi electrode that was coated with a 5:1 ratio HAp/nSiO2/Ag hybrid coating. View Full-Text
Keywords: hybrid coatings; SiO2-TiO2 glass; SiO2/Ag nanocomposite; surface modification; hydroxyapatite (HAp); NiTi shape memory alloy (SMA); pitting hybrid coatings; SiO2-TiO2 glass; SiO2/Ag nanocomposite; surface modification; hydroxyapatite (HAp); NiTi shape memory alloy (SMA); pitting
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MDPI and ACS Style

Dudek, K.; Dulski, M.; Łosiewicz, B. Functionalization of the NiTi Shape Memory Alloy Surface by HAp/SiO2/Ag Hybrid Coatings Formed on SiO2-TiO2 Glass Interlayer. Materials 2020, 13, 1648.

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