Estimation of titanium oxide layer thickness on thermally oxidized NiTi alloy based on color variations

Abstract

This paper studies the estimation of titanium oxide (TiO2) thickness on a thermally oxidized nickel titanium (NiTi) alloy based on its surface color. The NiTi plate specimens were subjected to oxidation at temperatures from 450 °C to 900 °C for different duration to induce the formation of oxide layers of different thicknesses. The oxide thickness of the specimens oxidized from 650 °C to 900 °C was measured by means of scanning electron microscopy. A fitting curve was generated from the measured thicknesses, and further extrapolated to predict the oxide thickness for specimens heated at lower temperature of 450 °C to 600 °C. The oxide thickness estimation was done using thin‐film optical interference, with reference to the observed color of the oxidized surface. The thin‐film optical interference approach showed accurate measurement of oxide thickness as compared to the extrapolated data, highlighting the applicability of this measurement technique.

The Cyclic Stability of Superelasticity in Aged Ti49.3Ni50.7 Single Crystals with Oxide Surface

“…Next, they were aged at 823 K for 1.0 h in helium (marked as without oxide layer) and in air (marked as with oxide layer). Such heat treatment was chosen based on our previous studies and those of other scientific groups [10,[12][13][14]17,19,20]. The samples' surface after aging in helium was mechanically ground and electrolytically polished again to precisely prevent the formation of an oxide film on the surface.…”

“…Also, TiNi alloys have been known to react vigorously with oxygen at elevated temperatures to form titanium oxide TiO 2 (rutile). The formation of titanium oxide on the surface of biomedical TiNi implants improves their corrosion resistance as well as biocompatibility by eliminating nickel from the surface, which is known to be toxic and allergenic in Ni-sensitive patients [8][9][10][11][12][13][14][15][16][17]. Thus, the achievement of optimal SME and SE due to the particles precipitation together with the modification of the NiTi alloys surface with a protective oxide layer is topical to working out the medical TiNi-based materials.…”

“…Most of the previous studies of the TiNi alloy with an oxide layer have concerned medical applications and focused on the identification of oxidation products, oxidation kinetics and corrosion resistance [9][10][11][12][13][14]18]. References [10,[12][13][14]17] show that the oxidation temperature above 873 K is not effective. In this case, the thick oxide layer (more than 100 µm), which consists of a porous phase with a rough aspect, is formed.…”

Analysis of Shape-Memory-Alloy Fiber Interface Strength for Optimization of Self-Healing Composites

“…Unfortunately, connecting NiTi to other materials and structures is a well-known challenge. In air NiTi forms a native inert titanium oxide (TiO2) surface layer on the order of nanometers thick (Ng, Mahmud, Ahmad, Razali, & Liu, 2022) that is notoriously hard to connect to or remove, resulting in weak interfacial shear strength. This week interface strength is detrimental to the overall strength of NiTi reinforced composites as well as the self-healing capability of the system being investigated.…”

Effect of the Surface Oxide Layer on Shape Memory Effect and Superelasticity of [011]-Oriented Ti-50.1Ni Single Crystals

“…Plate rolling and wire production are carried out in the temperature range from 673 K to 1023 K in air. In this case, TiNi alloys interact with oxygen, forming oxide layers [14][15][16][17][18][19][20]. Oxide films of various thicknesses and structures are formed depending on the temperature and exposure time.…”