Currently, the overheating detection of electric system components is performed using thermal imaging devices, which depend on on-site regulation parameters, require skilled operators and suitable weather conditions. The development and application of innovative technologies to monitor hotspots has highlighted the use of sensors based on thermosensitive materials. In this study, a temperature sensor with thermochromic coating was developed. Thermochromic sensors covered with a varnish layer and nano-titanium oxide, in addition to thermochromic paint, were produced. A 23 experimental design was established to assess the performance of thermochromic sensors under artificial weathering conditions. Color measurements of the coatings were performed using the CIELAB method. Fourier-transform infrared (FTIR), UV-Vis (Ultraviolet-Visible), (thermogravimetric TGA, and Differential Scanning Calorimetry (DSC) analyses were performed on the sensors exposed to photodegradation to detect changes in the thermochromic coatings. The sensors exposed to thermodegradation, and salt spray weathering showed ΔE (total color difference) values below 1.50 points in the presence of TiO2. In comparison, the sensors exposed to photodegradation showed ΔE values above 10 points, and UV-Vis analysis revealed changes in the chemical structure of the coatings. These results demonstrate that the varnish layer and TiO2 can help minimize the degradation effects of temperature, light, and salinity.

Abstract The microstructures of steels are altered when exposed to high working temperatures for long periods, which results in varied physical and chemical proprieties. This study evaluates the erosive wear behavior of ASTM A106 steel after it is exposed to high temperatures for long durations. Samples of normalized ASTM A106GrB steel were placed in a muffle furnace at 530 and 630 °C for 50, 100, and 200 h. The erosive wear test was conducted at a speed of 20 m/s for 30 min at 450 °C with an incidence angle of 30°. Irregular alumina was used as the erodent material. The surface characterization was performed using scanning electron microscopy to determine the distribution homogeneity, morphological conditions, quantity, and spheroidization degree of the carbides. The erosive wear test results indicated that there was no volume loss after 50 h of heat treatment at 530 °C. The maximum spheroidization degree was 0.71 after 200 h at 630 °C, which decreased the hardness from 220 to 140 HV. Additionally, the volume loss reached 2.52 cm3. Therefore, the use of the ASTM A106GrB steel at working temperatures higher than 530 °C for more than 50 h decreased the mechanical behavior and the wear resistance, thereby decreasing the lifetime of the system.

Connectors used in electrical power distribution systems should allow the passage of electricity continuously and without interruption. However, this does not always occur due to failure caused by improper assembly and/or corrosion of the materials employed, which reflects the quality of service. Notable among the new detection technologies that have been studied to facilitate the identification of defects is the use of thermochromic materials, which allow the easy identification of "hot spots", without the need for specialized equipment and personnel. In this context, in this study, the performance of a thermochromic liquid crystal was evaluated with the aim of developing a temperature sensor for connectors used in electrical power distribution networks. For the evaluation of the performance, thermal and ultraviolet radiation degradation tests were conducted, as well as analysis using spectroscopic (FTIR, FTIR-HATR, UV-Vis, 1H NMR) and thermal (DSC, PLM) techniques. The results indicated that the liquid crystal and the associated components showed no degradation under the test conditions, as well as a good color stability was observed, verifying the viability of the use of these materials for the construction of a temperature sensor. A field test was performed with the devices and was effective for the suggested application.

The influence of alternating electric field (AC) in the structure and dynamics of giant unilamellar vesicles (GUVs) comprised of 1,2-dilauroyl-sn-glycero-3-phosphatidylcholine (DLPC) is reported. The investigations were conducted by using optical fluorescence microscopy as the method of analysis. The lipid membrane of the DLPC GUVs at the fluid phase can be deformed and they migrate towards the electrodes under AC electric field. Nevertheless, membrane disruption or vesicle fusion was never noticed. The addition of concentrated glucose solution influences the osmotic pressure of the system leading to the formation of filaments at the outer region of the GUVs. These long flexible cylinders do not retract spontaneously. However, the application of AC electric field (20 V/mm, 20 Hz) enables the filaments to be retracted back to the GUVs membrane at a calculated speed of 0.18 µm.s-1

Mixtures of ethyl(hydroxyethyl)cellulose (EHEC) and Sodium Dodecyl Sulfate (SDS) were investigated using surface tension, conductivity and viscosity measurements in aqueous solutions. The parameters of the surfactant to polymer association processes such as the critical aggregation concentration (cac) and saturation of the polymer by SDS (psp) were determined from the plots of surface tension and specific conductivity versus surfactant concentration. Through the final results we see that there was no specific link of polymer with the surfactant, implying therefore a phenomenon of only cooperative association.