3. Producción
Browse
7 results
Search Results
- Some of the metrics are blocked by yourconsent settings
Item type:Publication, Metallurgical failure analysis of a welded drive beam of a vibrating screen(Elsevier, 2020-12-01)A metallurgical failure analysis investigation was performed to evaluate the influence of the weld detail on the high cycle fatigue failure of a drive beam of a vibrating screen from the mining industry. The built-up drive beam was composed of three low alloy steel I-type beams joined by longitudinal butt welds. Carbon steel supporting plates for the exciters were transversally welded on the drive beam, with fillet lap welds that overlapped the longitudinal beads, generating a particular weld detail. The drive beam fractured at its mid span after 60 days under regular operating conditions, with the origin of the crack located at the weld beads overlapping. The weld detail was subjected to a metallurgical characterization by means of macro analysis, metallography and hardness testing. Its influence on the fatigue strength of the drive beam was analyzed using a recommended design guideline for structures operating in the giga-cycle regime, stress concentrator considerations and reported maximum stress values for deck and drive beams of vibrating screens operating at similar conditions. The overlapping of the weld beads generated a critical geometrical stress concentrator that served as a crack nucleation point; the crack propagated by a high cycle fatigue mechanism, diminishing the fatigue strength of the drive beam and producing its rupture. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Bandgap engineering of hydrogenated a-SiC:H thin films for photoelectrochemical water splitting applications(IOP Publishing Ltd, 2020-12-15)Abstract Bandgap engineering of a-SiC:H thin films was carried out to assess the material light absorption without compromising its photoelectrochemical water splitting capabilities. The tailoring was performed by varying the hydrogen concentration in the semiconductor and by post-deposition isochronical annealing treatments from 100 °C to 700 °C. Bandgap values were obtained by fitting the fundamental absorption region of the absorption coefficient using three different models. Differences among bandgap values extracted by these methods and its correlation with the a-SiC:H structure, demonstrate that structural features, rather than a hydrogen rearrangement or depletion, would be responsible for annealing induced optical bandgap increment. These features are taking in advantage for the bandgap engineering of a-SiC:H without changing Si-C stoichiometry. Optical bandgap values for p-doped a-SiC:H samples gradually increased from 2.59 to 2.76 eV upon performing each annealing step until 600 °C. Temperature at which an enhancement in the electric performance is observed. We believe, these results will help on the design of monolithic tandem solar cells for water splitting applications. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Improvement of mechanical properties of hydroxyapatite composites reinforced with i-Al64Cu23Fe13 quasicrystal(SAGE Publishing, 2020-10-15)Mechanical behavior of hydroxyapatite-based composites (HAp) was studied as a function of the reinforcement concentration of the quasicrystalline (QC) Al 64 Cu 23 Fe 13 alloy. The synthesis of the HAp matrix was carried out by sol-gel method, while the synthesis of the QC was performed by an arc furnace with a subsequent thermal treatment. The composites were made by powder metallurgy and cold compacted to form test pieces that were sintered with a constant flow of argon. The materials were characterized using X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy and Fourier transform Raman spectroscopy. The study of mechanical strength was carried through compression tests. The biocompatibility of the composites was tested using an in-vitro cytotoxicity assay. The mechanical resistance of HAp/QC composites increased with the concentration of quasicrystalline reinforcement. Young’s modulus and compressive strength increased in 43% and 21%, respectively, with a 10 wt% QC reinforcement, which demonstrates an hybrid behaviour of the composite due to the inclusion of reinforcing particles in the pores of the matrix. This composite did not show cytotoxicity at any of the QC concentrations. A fabrication route is proposed as a fast, easy and high efficiency alternative for applications in the biomedical industry because of its high scalability potential. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, The earliest adobe monumental architecture in the Americas(National Academy of Sciences, 2021-11-30)Adobe bricks, or mud bricks, are construction elements which have defined major architectural traditions in the Andes over thousands of years. From Moche pyramids and the ancient city of Chan Chan in pre-Hispanic times, to Spanish casonas of the colonial period and rural houses in contemporary South America, adobe has been a central component in Andean architecture. Discovery of the remains of an early monumental building constructed primarily of adobes at Los Morteros (lower Chao Valley, north coast of Peru) places the invention of adobe architecture before 5,100 calendar years B.P. The unique composition, internal structure, and chronology of the adobes from Los Morteros show the beginnings of this architectural technique, which is associated with El Niño rainfall and the construction of the earliest adobe monumental building in the Americas. We propose that adobe architecture became a major Andean tradition after a long period of technical evolution and experimentation with both shape and composition. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Analysis of the physical and photoelectrochemical properties of c-Si(p)/a-SiC:H(p) photocathodes for solar water splitting(IOP Publishing Ltd, 2021-05-13)The photoelectrochemical (PEC) properties of sputtered aluminum doped hydrogenated amorphous silicon carbide thin films grown on p-type crystalline silicon substrates were investigated in 1 M H 2 S O 4 solution under chopped light illumination. Optical and structural properties of the top absorber layer were systematically assessed after post-deposition isochronical annealing treatments. Samples exhibited a noticeable improvement of the opto-electronic properties after thermal treatments. In addition, an abrupt enhancement of the photocurrent was observed reaching a saturation value of 17 mA cm −2 at −1.75 V vs. Ag/AgCl (3.5 M KCl). In this research we propose that this enhancement effect is associated to a charge transfer kinetic mechanism influenced by surface states and the p-type substrate. The latter most likely due to the space charge region extending beyond the absorber layer reaching the substrate. Current density-potential and electrochemical impedance spectroscopy measurements in dark revealed a reduction of the S i O 2 native layer at cathodic potentials higher than −1 V vs. Ag/AgCl (3.5 M KCl), which contributes to the high charge transfer kinetic of the system. We believe that these results will contribute to understand the substrate influence in the PEC performance of top absorber layers in multilayer structures for solar water splitting. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Localized surface states influence in the photoelectrocatalytic performance of Al doped a-SiC:H based photocathodes(Elsevier Ltd, 2022-06-01)In this work we evaluate the role of a-SiC:H(p)/SiO2 localized surface states (SS) in the Photoelectrochemical Water Splitting reaction. The analysis was carried out in three steps. First, retrieving the a-SiC:H(p) SS, energy distribution and density, by Electrochemical Impedance Spectroscopy techniques. Second, relating these results with direct measurements over the a-SiC:H(p)/SiO2 surface using X-ray Photoelectron spectroscopy. Finally, assessing the SS influence in the photo-induced hydrogen reduction by testing the a-SiC:H(p) photocathode with Linear Sweep Voltammetry. The whole analysis was done after subjecting the a-SiC:H(p) surface to different annealing treatments, i.e. 600 °C and 700 °C, necessary to obtain the required ohmic contacts. We believe that the participation of SS in an indirect electron charge transfer to the electrolyte, is kinetically feasible to take place in an a-SiC:H surface with relatively low SS density, ∼0.3×1012 cm-2. Whilst higher SS densities, in the range of ∼1.48×1014 cm-2, would trigger undesired charge carrier recombination. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Indirect excitation and luminescence activation of Tb doped indium tin oxide and its impact on the host's optical and electrical properties(IOP Publishing Ltd, 2022-05-26)The effect of adding terbium to indium tin oxide (ITO) thin films on the electrical, optical and light emission properties was investigated. The films were prepared by radio frequency dual magnetron sputtering, maintaining a high optical transmittance in the ultraviolet and visible spectral regions, and a low electrical resistivity ranging from 5 × 10 − 3 Ω ⋅ cm to 0.3 Ω ⋅ cm . Terbium-related luminescence is achieved after annealing at 470 ∘C in air at atmospheric pressure. Electrical resistivity and optical transmittance were measured after each annealing step to evaluate the compromise between the achieved light emission intensity, electrical and optical properties. Additionally, temperature dependence of Tb-related luminescence quenching was assessed by temperature-dependent photoluminescence measurements, from 83 to 533 K, under non-resonant excitation. Thermal quenching activation energies suggest an effective energy transfer mechanism from the ITO host to the rare-earth (RE) ions. This indirect excitation mechanism was modeled using a spherical potential-well and a tight-binding one-band approximation approaches, describing a short-range charge trapping process and subsequent formation of bound excitons to RE ion clusters.