No abstract

Shape memory alloys are known for their ability to return to their original shape under the influence of external factors (temperature, magnetic field and mechanical stress). Although NiTi-based alloys come to mind first when the shape memory effect is mentioned, CuAl-based alloys are very popular alternatives. The low cost of copper-based alloys is the biggest reason to study. In this study, the heat treatment effects of Cu-Al-X (X: Cr, Ti) (% weight) on some thermodynamic parameters, crystal structure and microstructure of shape memory alloy were investigated at three different temperatures (973 K, 1073 K and 1173 K). The changes in the thermal transformation of the samples were determined by DSC (Differential Scanning Calorimetry) and the changes in the crystal structure were determined by X-ray diffraction (XRD), Scanning Electron Microscope (SEM) and optical microscope device. According to DSC measurement, the temperature hysteresis of the samples decreased after the heat treatment. Besides, as the entropy change decreased, the thermal stability of the samples increased. It can be seen that the particle size of the CuAlCr alloy decreased with increasing temperature. The particle size of the CuAlTi alloy increased with increasing temperature. SEM and optical images showed that chromium (Cr) was more dissolved in the alloy compared to titanium (Ti) into CuAl alloy.

In this study, the spectral and optical properties of organic spectacle lenses used as visual aids were analyzed using Jasco V-730 UV/VIS spectrophotometer device in the ultraviolet and visible light wavelength ranges. The results obtained showed that the light transmittance in the wavelength (550nm) range to which the human eye is most sensitive in the lens samples examined was over 80% and that Polycarbonate (A3) lenses had a maximum value of 97.87%. The largest cut off edge wavelength value was found to be 390nm for the A3 lens. At 550 nm for all lenses, the absorption spectrum was below 0.07. In terms of visual quality, it is expected that the visible light transmittance is high and the ultraviolet light transmission is minimal. Our eyes are exposed to ultraviolet rays almost every day, and these rays cause damage to the ocular tissues. The degree of damage caused by the amount of ultraviolet light absorption increases. This situation is especially worrisome for young people and affluent individuals. Among the organic lenses with ultraviolet protection coating, the protection of the A3 lens was relatively higher. Furthermore, optical band gap energies were found to range from 3.145 – 4.155 and 2.994 – 3.936 for direct and indirect transitions, respectively. The highest optical band gap values were found to be those of the B1 and C1 organic lenses, respectively. The results will contribute to the awareness of spectacle wearers about eye health from an optical point of view, the selection of coatings applied to vision instruments for various purposes and the selection of lenses used in other optical areas.