Nitinol is widely used in the production of medical devices, especially the ones that are designed for minimally invasive treatment, such as stents to restore vascular patency, stent grafts to eliminate aneurysms, and cava filters to trap blood clots. One of the most important characteristics that determines the reliability of the functioning of such products in the human body is the state of the surface layer. The higher the surface quality, the less negative impact is on the circulatory system, the walls of blood vessels and the higher the biological compatibility of the product. Electrochemical polishing methods are mainly used to improve the surface quality of nitinol products. The disadvantage of the applied electrochemical methods is the need to use aggressive electrolytes that contain toxic components, such as hydrofluoric acid, sulfuric acid, perchloric acid, nitric acid, methanol. As an alternative to the existing methods of electrochemical polishing, we have developed electrolytic-plasma polishing (EPP), a new highly efficient process for improving the surface quality of nitinol products. The most important advantage of the method over traditional electrochemical polishing is the use of aqueous salt solutions with a concentration of 4 % as electrolytes. Based on the results of the studies performed, the most rational EPP mode was established, the use of which during polishing of nitinol provides surface cleaning from scale, polishing with a decrease in the roughness parameter Ra by 0.344 µm and an increase in pitting potential by 33 %.
Thermal relaxation differential spectrometry (TRDS) was used to study the thermal parameters of samples with various design features for heat removal -a powerful LED lamp (150 W) used in industrial and street lighting, low power LED lamps (4 W) with filament emitters, as well as SMD emitter. It is shown that the method of thermal relaxation differential spectrometry is effectively applicable to the study of the structure of thermal parameters of both high-power and low-power LED devices. The method is informative and allows to study in the distribution of thermal resistance and heat flux over the volume and layers of the LED device detail. The use of the TRDS method allows the optimization of the thermal design of LED devices to reduce the overheating temperature of their active regions, and, therefore, to reduce the degradation of LED devices.
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