In this research, the structure changes along the depth of gradient layers of nickel-titanium substrate, after etching with NaOH and subsequent thermal treatment at various temperatures between 300 and 800 °C, were investigated by XRD, FTIR and AES. Particularly, the changes of Ni-Ti substrate after etching with NaOH, subsequent ionic exchange of Na+ with Ca2+ ions and thermal treatment at 700 °C were analysed. Due to this approach, it was possible to get insight into the chemical changes and changes of Ti oxidation states and consequent phase analysis, along the depth of the titanium oxide coatings. In addition, Secondary Electron Imaging (SEI) showed very interesting nanotopology of all samples. Particularly interesting topology, consisting of very thin nano-designed walls between mutually interconnected pores, was observed for the sample in which Na+ were replaced with Ca2+ ions. This structure might be suitable for deposition of hydroxyapatite by biomimetic or plasma methods and as an appropriate scaffold for cell adhesion and proliferation.
COBISS.SI-ID: 17537814
This work presents the results of the microstructure observation of six different NiTi orthodontic wires by using Transmission Electron Microscopy (TEM). Within these analyses the chemical compositions of each wire were observed in different places by applying the EDS detector. Namely, the chemical composition in the orthodontic wires is very important because it shows the dependence between the phase temperatures and mechanical properties. Microstructure observations showed that orthodontic wires consist of nano-sized grains containing precipitates of Ti2Ni and/or TiC. The first precipitated Ti2Ni are rich in Ti, while the precipitated TiC is rich in C. Further investigation showed that there was a difference in average grain size in the NiTi matrix. The sizes of grains in orthodontic wires are in the range from approximately 50 to 160 nm and the sizes of precipitate are in the range from 0.3 μm to 5 μm.
COBISS.SI-ID: 17828374
In this paper the results of a microstructural analysis before and after fracture along with the mechanical properties and hardness of the CuAlNiMn shape-memory alloy are presented. The melting of the alloy was carried out in a vacuum-induction furnace in a protective atmosphere of argon. The alloy was cast into an ingot of 15 kg. After casting the alloy was forged and rolled into rods with a diameter of approximately 10 mm. A microstructural characterization was performed with light microscopy (LM) and scanning electron microscopy (SEM) equipped with energy-dispersive spectrometry (EDS). Martensitic microstructure was observed in the rods after the deformation. The fractographic analysis of the samples after the tensile testing revealed some areas with intergranular fracture. However, the greater part of the fracture surface indicated the pattern of transgranular brittle fracture. The results of the tensile tests showed the tensile strength of 401.39 MPa and elongation of 1.64 %. The hardness of the CuAlNiMn alloy is 290.7 HV0.5.
COBISS.SI-ID: 1483871