The impacts on the morphological, electrical and hardness properties of thermoplastic polyurethane (TPU) plates using multi-walled carbon nanotubes (MWCNTs) as reinforcing fillers have been investigated, using MWCNT loadings between 1 and 7 wt%. Plates of the TPU/MWCNT nanocomposites were fabricated by compression molding from extruded pellets. An X-ray diffraction analysis showed that the incorporation of MWCNTs into the TPU polymer matrix increases the ordered range of the soft and hard segments. SEM images revealed that the fabrication route used here helped to obtain TPU/MWCNT nanocomposites with a uniform dispersion of the nanotubes inside the TPU matrix and promoted the creation of a conductive network that favors the electronic conduction of the composite. The potential of the impedance spectroscopy technique has been used to determine that the TPU/MWCNT plates exhibited two conduction mechanisms, percolation and tunneling conduction of electrons, and their conductivity values increase as the MWCNT loading increases. Finally, although the fabrication route induced a hardness reduction with respect to the pure TPU, the addition of MWCNT increased the Shore A hardness behavior of the TPU plates.

Thermoplastic polyurethane (TPU) doped with multi-walled carbon nanotubes (MWCNTs) at 1, 3, 5, and 7 wt% has been studied. The effect of MWCNTs on thermal, viscoelastic, and electric properties in the TPU matrix was characterized by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and by impedance spectroscopy. The results show that the thermal, electrical, and viscoelastic properties, such as the glass transition temperature, shifted towards high temperatures. The melting temperature decreased, and the conductivity and the storage modulus increased by 61.5 % and 58.3 %. The previously observed behavior on the films is due to the increase in the mass percentage of carbon nanotubes (CNTs) in the TPU matrix. Also, it can be said that the CNTs were homogeneously dispersed in the TPU matrix, preventing the movement of the polymer chains, and generating channels or connections that increase the conductivity and improve the thermal properties of the material.

Gold nanostructures (AuNSs) were used to fabricate surface-enhanced Raman spectroscopy (SERS) substrates. These AuNSs were produced using the solid-state dewetting method from thin films. The fragmentation process was studied at 300 °C, with durations of thermal treatment of 1, 3, 6, and 12 h. These SERS substrates were then employed to detect Rhodamine B (RhB) as the model analyte, simulating a contaminant in the water at a concentration of 5 ppm. The morphology of the AuNSs was examined using SEM, which revealed a spheroidal shape that began to coalesce at 12 h. The size of the AuNSs was estimated to range from 22 ± 7 to 24 ± 6 nm, depending on the annealing time. The localized surface plasmon resonance of the AuNSs was determined using absorption spectroscopy, showing a shift as the annealing time increased. The SERS signals of RhB adsorbed on the AuNS substrates were validated by performing a 10 × 10 point map scan over each sample surface (1, 3, 6, and 12 h), and a comparative analysis showed no significant differences in the positions of the bands; however, variations in intensity enhancement ranged from 5 to 123 times at 6 and 1 h, respectively.

High-purity TiO₂ and CuO powders were synthesized by the Pechini method, an inexpensive and easy-to-implement procedure to synthetize metal oxides. The variables of synthesis were the ethylene glycol:citric acid molar ratio and the pH. High reproducibility of the anatase and tenorite phase was obtained for all synthesis routes. The degree of purity of the powders was confirmed by XRD, FTIR, UV-Vis absorption and XPS spectra. SEM and TEM images revealed the powders are composed of micrometer grains that can have a spherical shape (only in the TiO₂) or formed by a non-compacted nanocrystalline conglomerate. FTIR spectra only displayed vibrational modes associating TiO₂ and CuO with nanoparticle behavior. UV-Vis absorption spectra revealed the values of maximum absorbance percentage of both systems are reached in the ultraviolet region, with percentages above 83% throughout the entire visible light spectrum for the CuO system, a relevant result for solar cell applications. Finally, XPS experiments allow the observation of the valence bands and the calculation of the energy bands of all oxides.

Gold nanostructures (AuNSs) were used to fabricate surface-enhanced Raman spectroscopy (SERS) substrates. These AuNSs were produced by the solid-state dewetting method from thin films. The fragmentation process was studied at 300 °C, considering the duration of the thermal treatment for 1, 3, 6, and 12 hours. These SERS substrates were then employed to detect Rhodamine B (RhB) as a model analyte, simulating a contaminant in water at a concentration of 5 ppm. The morphology of the AuNSs was examined using SEM, which revealed a spheroidal shape beginning to coalesce after 12 hours. The size of the AuNSs was estimated to range from 22 ± 7 to 24 ± 6 nm, depending on the annealing time. The surface plasmon resonance of the AuNSs was determined using absorption spectroscopy, showing a shift as the annealing time increased. The SERS signals of RhB adsorbed on the AuNS substrates were studied, and a comparative analysis showed no significant differences in the positions of the bands; however, variations in intensity enhancement ranged from 20 to 90 times for 6 and 3 hours, respectively. Three new vibrational modes, observed at 1683, 1720, and 1789 cm–1, have been identified and reported.

In this work, a bibliometric study was carried out to perform a scientific and technological analysis of exchange-spring magnets, an alternative permanent magnet synthesized by reducing or eliminating the use of critical raw materials, such as rare earths. The bibliometric analysis utilized the Scopus database, Orbit-Intellixir, VOSviewer, Orbit-Intelligence and Loglet Lab 4 software for maturity analysis, keyword network representations, charts and graphs for scientific articles and/or patents. A special analysis was performed on nanocomposite and thin-films systems based on Nd-Fe-B, SmCo₅ and Mn–Al–C alloys, either mixed or layered with a soft magnetic phase, where relevant information on their magnetic parameters was compilated in tables, highlighting the nanostructured systems that have been exhibited the best permanent magnet properties. The bibliometric analysis revealed that the primary production of scientific articles is concentrated in industrialized countries, and they are predominantly published in journals dedicated to magnetism. A patents analysis showed that Nissan motors is by far the main applicant, with most of its patents is focused on technological domains related to electrical machinery, apparatus, energy and metallurgy. On the other hand, the S-curve of maturity for scientific articles indicated that the study of exchange-spring magnets is entering a mature state. In contrast, patent production, following a bi-logistic model, is in a saturation stage for the second S-curve. Maturity analyses, employing S-curve, bi-logistic and multi-logistic models, were performed on nanocomposites and thin films based on Nd-Fe-B, SmCo₅ and Mn–Al–C alloys, respectively. We found that the investigation in Nd-Fe-B-based alloys is close to enter to a scientific saturation stage, while an average growth stage is observed for the SmCo₅ and Mn–Al–C-based alloys. This suggests that research on alternative magnets, capable of fulfilling technological applications where a Nd-Fe-B magnets are commonly used, is a topic of significant interest.