Papers by Keyword: Electrical Resistivity

Abstract: Continuous monitoring of additively manufactured structures is essential for understanding their mechanical behavior and durability. This study investigates the electromechanical behavior of additively manufactured PETG specimens reinforced with continuous carbon fiber, with a particular focus on the influence of reinforcement geometry on strain-sensing performance. Specimens were fabricated using Fused Filament Fabrication and designed with four different reinforcement configurations: a reference single-layer layout, an extended-length reinforced region, a wider reinforced region, and a double-layer reinforcement. A total of twelve specimens were experimentally characterized. Electrical resistivity measurements were conducted under unloaded conditions and during bending induced by a low applied load of approximately 1.6 N. The initial electrical resistivity was found to depend on reinforcement geometry, with average values of approximately 523 Ω for the reference configuration, 888 Ω for the extended-length reinforcement, 1066 Ω for the wider reinforcement, and 285 Ω for the double-layer configuration. Under mechanical loading, the relative resistance variation remained below 0.6% for all specimens, indicating that the induced strain was very small. To further quantify strain sensitivity, the gauge factor was calculated for each configuration. Low average gauge factor values were obtained for the reference (K ≈ 0.1), extended-length (K ≈ 0.38), and wider (K ≈ 0.5) configurations. In contrast, the double-layer reinforcement exhibited a higher average gauge factor of approximately 2.24. These results indicate that reinforcement architecture affects the electromechanical sensitivity under low applied loads and offer insights for the design of multifunctional additively manufactured composite structures.

Abstract: A vacuum-assisted thermal evaporation method for the preparation of undoped and Zn-doped erbium sesquiselenide Er₂Se₃ thin films on various substrates using independent elementary sources is developed. The electrophysical parameters, such as electrical resistivity and thermo-electromotive force of the films, are measured from 77 up to 650 K.

Abstract: Sr-doped CaMnO₃ materials have wide applications due to their thermal and electrical properties. The importance of the synthesis of Sr-doped CaMnO₃ material for various applications encourages researchers to evaluate and refine the synthesis process. In this study, Ca_1-xSr_xMnO₃ (x = 0; 0.05; 0.1; 0.15; 0.2) system has been prepared by sol-gel method followed by conventional sintering process at 850°C for 8 hr. A thorough discussion has been made on the outcomes derived from the investigation on the structural, electrical, and thermal properties of Sr-doped CaMnO₃ system using powder x-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, DC fourprobe method, thermal expansion studies, and thermoelectric power analyses. The XRD patterns of all prepared samples exhibited single phase with orthorhombic crystal structure (space group Pnma). Rietveld refinements were performed for all the patterns by using Fullprof software to extract the structural properties. The values of unit cell volume of samples tend to increase with the increment of dopant concentration, whereas the crystallite size values were decreased with dopant concentration. The microstructures of all the samples were studied using SEM, and elemental compositions were confirmed from the EDS results. Linear thermal expansion coefficients of all the samples were found to have moderate values in the temperature range from 30°C to 800°C. The electrical properties of all the system of samples were studied in the temperature range from 30°C to 400°C using DC fourprobe conductivity setup. It was found that all the samples exhibited semiconductor nature. Sr-content on the A-site suppress the electrical resistivity up to 10% of concentration and 5% dopant content exhibited the lowest electrical resistivity. The values of Seebeck coefficient found to vary from -160 µV/K to -124 µV/K with the increase of dopant content in the parent compound.

Abstract: The aim of this study is discussing the results achieved on undoped and Ni-doped bulk LaCoO₃ samples synthesized by solid-state reaction. The crystal structures of the samples were analyzed by x – ray diffraction (XRD) and Rietveld refinement of the XRD patterns was used to test the quality of the samples, the results of this procedure confirmed a single phase of LaCo_1-xNi_xO₃ for (x=0 and 0.05) with rhombohedral crystal structure (space group :). The main interest in this class of materials is the possibility of improving the values of Seebeck coefficient and electrical resistivity through chemical doping. The Seebeck coefficient and electrical resistivity were investigated from room temperature (RT) to 450 K, near RT the LaCoO₃ system showed a large negative Seebeck coefficient, but it changed to positive value with increasing temperature while the LaCo_0.95Ni_0.05O₃ composition showed a positive Seebeck coefficient throughout all the temperature range. Hence, within this study the Ni substitution led to decrease the electrical resistivity of the samples to one order of magnitude as a result of the partial substitution of Co³⁺ in LaCoO₃ by Ni²⁺. LaCoO₃ was chosen for this thermoelectric test because cobalt oxides have extensive applications.

Abstract: According to the well-known concept of multicomponent high-entropy alloys, high entropy of mixing can stabilize the formation of solid solutions (simple bcc or fcc crystal structure) during solidification. Stabilization of the solid solution and prevention of the formation of intermetallic phases during solidification is provided by the high entropy of mixing in the solid and liquid states. High-entropy alloys have increased strength, high hardness, thermal stability in combination with good resistance to oxidation and corrosion. These properties allow to significantly expand the scope of these alloys. In this work, the electrical resistivity, thermoelectric power and surface tension of binary Cu–Sn, Cu–Ga and Cu–Bi alloys, which are the sub-system components of model low-temperature high-entropy Bi–Cu–Ga–Pb–Sn alloys, have been studied in a wide temperature range including solid and liquid states. The lack of the surface tension data of the above-mentioned alloys is compensated by the model predicted values.

Abstract: In this research, different types of Mg-Zn based intermetallics that appear in the Mg-Zn alloy system were synthesized by conventional casting route. Consequently, the structural, mechanical, electrical, and magnetic properties of these Mg-Zn intermetallics were thoroughly studied. Every casting underwent a trivial loss of Mg by oxidation which resulted in slightly higher weight percentages of Zn. X-ray Diffraction (XRD) analysis confirmed the coexistence of several intermetallics in each sample. The morphology of the samples was studied under Optical and Field Emission Scanning Electron Microscopes and the phases were identified by Energy Dispersive Spectroscopy (EDS). Differential Scanning Calorimetry (DSC) analysis further confirmed many of the available phases found. Mainly five intermetallics i.e., Mg₅₁Zn₂₀, MgZn, Mg₄Zn₇, MgZn₂ and Mg₂Zn₁₁ were observed in the structures. The cast sample which is rich in Mg₂Zn₁₁ showed the highest compressive strength (122.6 MPa) and electrical conductivity of 10.47 S/m. From Vibrating Sample Magnetometry (VSM) analysis it was found that three of the samples are soft ferromagnets whereas only the samples abundant in MgZn₂ content showed paramagnetic behavior with maximum magnetization of 0.66 emu/gm.

Abstract: Measuring humidity in building materials is of great importance in assessing the condition of materials and also in building diagnostics, as the presence of humidity affects their physical and thermal insulation properties. In the construction industry, the use of non-destructive electrical measurement methods for testing the physico-chemical properties of materials is common and especially the electrical conductivity of materials is significantly affected by humidity.

Abstract: This article shows the results of the modulus of rupture test for concrete specimens added with PET fibers and also with polypropylene, with the objective of giving a second use to this waste through recycling, and its incorporation into concrete to improve its mechanical properties. The samples were tested with different fiber contents, and the results showed an increase in the modulus of rupture at 90 days with respect to a normal sample (1-3%). Specimens with PET and polypropylene fibers had a poor performance (<18%).

Abstract: The diagrams of isothermal transformation based on kinetic curves R = (τ) for retained austenite in high-strength alloy low-carbon at overcooling have been built. It is shown that the temperature of quenching influences the stability at overcooling and resistance to isothermal transformation of austenite at sub-zero temperatures.

Abstract: We investigated the kinematic viscosity and electrical resistivity of the multicomponent Fe₇₄Cu₁Nb_1.5Mo_1.5B_8.5Si_13.5 melt during three heating–cooling cycles. The temperature dependence of kinematic viscosity and electrical resistivity have the anomalous zones in the same temperature range and they are associated with the liquid–liquid structure transition (LLST). The anomalies were explained by changes in the activation energy and the cluster size. As the cluster size decreases, the activation energy decreases, but the viscosity and electrical resistance increase. LLST begins with the cluster dissolution, and as a result, the Arrhenius plot becomes nonlinear in the transition temperature range. After three cycles of heating–cooling, the temperature dependences of the kinematic viscosity and electrical resistance did not qualitatively change, and this allows us to conclude that LLST is thermoreversible. With an increase in the number of thermal cycles, the activation energy of viscous flow decreases, as well as the onset temperature and temperature range of LLST.