Capítulos (Física de la Materia Condensada)

URI permanente para esta colecciónhttps://hdl.handle.net/11441/10870

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A procedure to obtain the parameters of Curie temperature distribution from thermomagnetic and magnetocaloric data
(Elsevier, 2019) Manchón Gordón, Alejandro F.; Moreno Ramírez, Luis Miguel; Ipus Bados, Jhon Jairo; Blázquez Gámez, Javier Sebastián; Conde Amiano, Clara Francisca; Franco García, Victorino; Conde Amiano, Alejandro; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Agencia Estatal de Investigación. España; European Union (UE)
We propose a procedure for the determination of the parameters of the Curie temperature distribution (TCD)in a compositionally inhomogeneous ferromagnetic material. Assuming a Gaussian TCD and using a mean field approach based on the Brillouin function, we report that with respect to the average value of the distribution: a)both inflection point of magnetization, Tinf, and temperature at maximum magnetic entropy change curves, Tpk MCE, shift to lower temperatures and b)temperature at maximum paramagnetic susceptibility, Tpk χ, shifts to higher temperatures. Using these evolutions as a function of the TCD broadening and fitting them to a second order polynomial function, a self-consistent procedure to determine the parameters of the distribution is supplied. These predictions have been experimentally tested for a ball milled Fe70Zr30 amorphous alloy using thermomagnetic and magnetocaloric measurements. The obtained parameters using the proposed procedure agree with those directly measured using Mössbauer spectrometry.
Accommodation Response Variations in University Students under High Demand for Near-Vision Activity
(Multidisciplinary Digital Publishing Institute (MDPI), 2022) Hita Cantalejo, María Concepción de; Benítez Rodríguez, María de los Ángeles; Sánchez González, María del Carmen; Bautista Llamas, María José; Sánchez González, José María; Universidad de Sevilla. Departamento de Física de la Materia Condensada
The objective of this study was to investigate accommodation changes and visual discomfort in a university student population after a period of high demand for near-vision activity. A total of 50 university students aged between 20 and 22 years were recruited. The tests performed involved positive relative accommodation (PRA), negative relative accommodation (NRA), accommodation amplitude (AA), and monocular and binocular accommodative facility (MAF and BAF). Visual discomfort was measured on a scale involving a visual discomfort questionnaire (VDQ). All accommodative variables underwent changes during the exam period; specifically, regarding NRA and PRA, 30.4% and 15.1% of the studied population, respectively, appeared to be below average. Moreover, 42.3% of the population exhibited values below average in the second measure of AA. On the other hand, a small percentage of the population was below average in MAF and BAF measurements: 3% in the monocular right eye test, 6% in the left eye test, and 9.1% in the binocular facility test. Finally, the VDQ score did not reveal a statistically significant difference between the two measurements. Prolonged near-distance work, such as a university exams period, changed all accommodation systems (amplitude of accommodation, relative accommodation, and accommodation facility). These changes influence an accommodation excess that results in blurred vision, headache, and problems with focusing.
An Electrochemical Evaluation of Nitrogen-doped Carbons as Anodes for Lithium Ion Batteries
(Elsevier, 2020) Gomez Martin, A.; Martínez Fernández, Julián; Ruttert, Mirco; Winter, Martin; Placke, Tobias; Ramírez Rico, Joaquín; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Ministerio de Economía y Competitividad (MINECO). España; Ministerium fur Wirtschaft, Innovation, Digitalisierung und Energie des Landes Nordrhein-Westfalen (Germany)
New anode materials beyond graphite are needed to improve the performance of lithium ion batteries (LIBs). Chemical doping with nitrogen has emerged as a simple strategy for enhancing lithium storage in carbon-based anodes. While specific capacity and rate capability are improved by doping, little is known about other key electrochemical properties relevant to practical applications. This work presents a systematic evaluation of electrochemical characteristics of nitrogen-doped carbons derived from a biomass source and urea powder as anodes in LIB half- and full-cells. Results show that doped carbons suffer from a continuous loss in capacity upon cycling that is more severe for higher nitrogen contents. Nitrogen negatively impacts the voltage and energy efficiencies at low charge/discharge current densities. However, as the charge/discharge rate increases, the voltage and energy efficiencies of the doped carbons outperform the non-doped ones. We provide insights towards a fundamental understanding of the requirements needed for practical applications and reveal drawbacks to be overcome by novel doped carbon-based anode materials in LIB applications. With this work, we also want to encourage other researchers to evaluate electrochemical characteristics besides capacity and cycling stability which are mandatory to assess the practicality of novel materials.
Aprendizaje basado en el planteamiento de casos clínicos en contactología
(Editorial Universidad de Sevilla, 2019) Bautista Llamas, María José; Universidad de Sevilla. Departamento de Física de la Materia Condensada
Este artículo describe la puesta en práctica de un ciclo de mejora en el aula aplicado en la asignatura Contactología II, que se imparte de ma- nera conjunta en el Grado en Óptica y Optometría y en el Doble Grado en Farmacia y en Óptica y Optometría de la Facultad de Farmacia de la Universidad de Sevilla. Este ciclo de mejora se centra en la docen- cia correspondiente a la selección de pacientes y la lente de contacto adecuada para cada uno de ellos, así como las complicaciones deri- vadas de las mismas. El modelo metodológico se basa en el planteamiento de una pregunta sobre el tema que se pretende aprender por parte del profesor, y que esa pregunta obtenga respuesta a través de la resolución de un pro- blema o caso práctico planteado y desarrollado por los alumnos, y ex- puesto en clase para discutir y extraer conclusiones sobre el mismo.
CaO–MgO–SiO2–P2O5- based multiphase bio-ceramics fabricated by directional solidification: Microstructure features and in vitro bioactivity studies
(Elsevier, 2021) Díaz Pérez, María; Grima, Lorena; Moshtaghion, Bibi Malmal; Peña, José Ignacio; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Universidad de Zaragoza; Ministerio de Ciencia e Innovación (MICIN). España; Junta de Andalucía
In vitro activity is important when considering the choice of a multiphasic bioceramic scaffold as phases can dissolve or transform at different rates. The aim of this study is focused on the synthesis and in vitro analysis of multiphasic ceramics obtained from the melt by directional solidification. Depending on the growth rate of the new composition different bioactive phases coexist in the same sample: akermanite, monticellite, tricalcium phosphate and Nurse’s A phase, all of them with potential in the medical area as implant for bone or dental repair. With the knowledge of what and how phases dissolve first, it was possible to design materials to get porous scaffolds or more stable ceramics.
Casimir-Lifshitz Force Based Optical Resonators
(American Chemical Society, 2019) Esteso Carrizo, Victoria; Carretero Palacios, Sol; Míguez García, Hernán Ruy; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Ministerio de Ciencia, Innovación y Universidades (MICINN). España
We theoretically investigate the building of optical resonators based on the levitation properties of thin films subjected to strong repulsive Casimir-Lifshitz forces when immersed in an adequate medium and confronted with a planar substrate. We propose a design in which cavities supporting high Q-factor optical modes at visible frequencies can be achieved by means of combining commonly found materials, such as silicon oxide, polystyrene or gold, with glycerol as a mediating medium. We use the balance between flotation and repulsive Casimir-Lifshitz forces in the system to accurately tune the optical cavity thickness and hence its modes. The effects of other forces, such as electrostatic, that may come into play are also considered. Our results constitute a proof of concept that may open the route to the design of photonic architectures in environments in which dispersion forces play a substantial role and could be of particular relevance for devising novel microfluidic optical resonators.
Cation-driven electrical conductivity in Ta-doped orthorhombic zirconia ceramics
(Elsevier, 2021) Moshtaghion, Bibi Malmal; Laguna Bercero, Miguel Ángel; Peña, José I.; Gómez García, Diego; Domínguez Rodríguez, Arturo; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Ministerio de Ciencia e Innovación (MICIN). España; Junta de Andalucía; Gobierno de Aragón; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER)
This paper is devoted to the study of the electrical conductivity of tantalum-doped zirconia ceramics prepared by spark plasma sintering. In this study, the temperature dependence of conductivity in as-prepared specimens and in those previously annealed in air is determined and compared. A semi-empirical model, which is based on the oxidation states of the cations, has been developed and successfully assessed. According to this, the conductivity is basically controlled by the diffusion of tetravalent zirconium cations in both cases, although the concentration of these species varies drastically with the amount of induced oxygen vacancies. This is a quite unexpected fact, since conductivity is normally controlled by anionic diffusion in zirconia ceramics. This option is forbidden here due to the presence of substitutional pentavalent cations. Therefore, conductivity values are much lower than those reported in trivalent or divalent substitutional cation doped zirconia ceramics.
Complications of Small Aperture Intracorneal Inlays: A Literature Review
(Multidisciplinary Digital Publishing Institute (MDPI), 2023) Sánchez González, María del Carmen; Gutiérrez Sánchez, Estanislao; Sánchez González, José María; Hita Cantalejo, María Concepción de; Piñero Rodríguez, Ana María; González Cruces, Timoteo; Capote Puente, Raúl; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Universidad de Sevilla. Departamento de Cirugía
Presbyopia can be defined as the refractive state of the eye in which, due to a physiological decrease in the ability to accommodate, it is not possible to sustain vision without fatigue in a prolonged manner, along with difficulty focusing near vision. It is estimated that its prevalence in 2030 will be approximately 2.1 billion people. Corneal inlays are an alternative in the correction of presbyopia. They are implanted beneath a laser-assisted in situ keratomileusis (LASIK) flap or in a pocket in the center of the cornea of the non-dominant eye. The purpose of this review is to provide information about intraoperative and postoperative KAMRA inlay complications in the available scientific literature. A search was conducted on PubMed, Web of Science, and Scopus with the following search strategy: ("KAMRA inlay" OR “KAMRA” OR “corneal inlay pinhole” OR “pinhole effect intracorneal” OR “SAICI” OR “small aperture intracorneal inlay”) AND (“complication” OR “explantation” OR “explanted” OR “retired”). The bibliography consulted shows that the insertion of a KAMRA inlay is an effective procedure that improves near vision with a slight decrease in distance vision. However, postoperative complications such as corneal fibrosis, epithelial iron deposits, and stromal haze are described.
Creación de una lente de contacto basándose en la investigación del mercado y sus aplicaciones como método de aprendizaje
(Editorial Universidad de Sevilla, 2021) Bautista Llamas, María José; Universidad de Sevilla. Departamento de Física de la Materia Condensada
Deuteration effect on tricritical phase transition of triglycine selenate: Calorimetric and dielectric measurements analyzed in the framework of Landau theory
(AIP Publishing, 2010) Romero Landa, Francisco Javier; Gallardo Cruz, María del Carmen; Martín Olalla, José María; Cerro González, Jaime del; Universidad de Sevilla. Departamento de Física de la Materia Condensada
The ferroelectric phase transition of three single crystals of TGSe1−x DTGSex has been described by using specific heat, latent heat, and dielectric permittivity measurements. Pure, half-deuterated, and highly-deuterated TGSe single crystals were analyzed. Transition temperature and latent heat increase with increasing deuteration. Irrespective of the degree of deuteration, a 2-4-6 Landau model is suitable to describe the phase transition. The fourth-rank prefactor in Landau potential is found to be very sensitive to deuteration while the second-rank and the sixth-rank prefactors smoothly change with composition. The pyroelectric figure of merit for these materials has also been derived from the theoretical model.
Devitrification of Mechanically Alloyed Fe-Nb System: Mössbauer Study of the Intermetallic Phases
(Springer Nature, 2020) Manchón Gordón, Alejandro F.; Svec, P.; Ipus Bados, Jhon Jairo; Kowalczyk, M.; Blázquez Gámez, Javier Sebastián; Conde Amiano, Clara Francisca; Conde Amiano, Alejandro; Svec, P.; Kulik, T.; Universidad de Sevilla. Departamento de Física de la Materia Condensada; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER)
Intermetallic phases in the Fe-Nb system have been obtained as products of the devitrification of a homogeneous amorphous Fe70Nb30 alloy prepared by mechanical alloying. Besides Fe2Nb Laves and Fe7Nb6 intermetallic phases, α-Fe phase has been detected by X-ray diffraction (XRD). Hyperfine parameters for both Fe2Nb and Fe7Nb6 intermetallics have been obtained from Mössbauer spectroscopy in correlation with phase identification from XRD results. Thermomagnetic measurements show changes in the Curie temperatures of the amorphous and Fe2Nb phases during the crystallization, due to compositional variations related to the developing of the α-Fe phase. Kinetics of the crystallization process has been analyzed using the classical Johnson-Mehl-Avrami-Kolmogorov kinetic theory in both isothermal and non-isothermal regimes.
Does grain size have an influence on intrinsic mechanical properties and conduction mechanism of near fully-dense boron carbide ceramics?
(Elsevier, 2019) Moshtaghion, Bibi Malmal; Laguna Bercero, Miguel Ángel; Gómez García, Diego; Peña, José I.; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Ministerio de Economía y Competitividad (MINECO). España
This work is concentrated on getting a reply to the following question: how does the grain size of boron carbide specimens influence on their mechanical and electrical response? It is a common issue that both essential properties are usually affected by the grain boundaries. To this purpose, a set of near fully-dense boron carbide specimens were prepared by spark plasma sintering. In order to reduce residual porosity and grain-size effects, nanoindentation tests at room temperature were conducted. DC conductivity was measured through four-point test technique from room temperature up to 800 °C. The results show that hardness can reach values as high as ∼60 GPa and plasticity onset takes place at around 23 GPa by dislocation nucleation. Regarding the conductivity, it is found that grain boundaries can block the mobility of bipolarons in an effective way. A simple additive law is provided to account for the resistivity of boron carbide polycrystals.
Effect of the crystal chemistry on the hydration mechanism of swelling micas
(Elsevier, 2017) Pavón González, Esperanza; Alba Carranza, María Dolores; Castro Arroyo, Miguel Ángel; Osuna, Francisco J.; Pazos, M. Carolina; Universidad de Sevilla. Departamento de Química Inorgánica; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Junta de Andalucía; Ministerio de Economía y Competitividad (MINECO). España; European Union (UE)
Swelling and dehydration under minor changes in temperature and water vapor pressure is an important property that clays and clay minerals exhibit. In particular, their interlayer space, the solid-water interface and the layers’ collapse and re-expansion have received much attention because it affects to the dynamical properties of interlayer cations and thus the transfer and fate of water and pollutants. In this contribution, the dehydration and rehydration mechanism of a swelling high-charge mica family is examined by in situ X-ray Diffraction. The effect of the aluminosilicate layer charge and the physicochemical properties of the interlayer cations on these processes are analyzed. The results showed that the dehydration temperature and the number of steps involved in this process are related to the layer charge of the silicate and the physicochemical properties of the interlayer cations. Moreover, the ability to adsorb water molecules in a confined space with high electric field by the interlayer cations does not only depend on their hydration enthalpy but also on the electrostatic parameters of these cations.
Una forma diferente de abordar el estudio del cálculo de lentes de contacto de hidrogel-silicona a partir de casos clínicos, de las lentes terapéuticas y de los sistemas de limpieza y desinfección, en la asignatura Contactología II
(Universidad de Sevilla, 2022) García Romera, Marta de la Concepción; Universidad de Sevilla. Departamento de Física de la Materia Condensada
Este CIMA se lleva a cabo en la asignatura Contactología II durante el segundo cuatrimestre del curso 2020-21. La duración fue de 12 horas (8 clases) en las que se desarrollan los siguientes contenidos: (1) Adaptación/post-adaptación de lentes de contacto de hidrogel-silicona, (2) lentes de contacto terapéuticas y (3) sistemas de limpieza/desinfección. Las clases han sido seguidas por los alumnos/ as a través de la plataforma virtual Blackboard Collaborate mayoritariamente, lo cual ha sido un gran impedimento. Las líneas metodológicas seguidas han sido el aprendizaje basado en problemas y la clase invertida adaptativa. A parir de la valoración de los cuestionarios parece claro que el trabajo dialogado en clase de los conceptos teóricos ha favorecido el aprendizaje, sin embargo, en el caso de los conceptos más procedimentales, si bien hay una parte que demuestra haber adquirido un buen nivel de conocimientos con el trabajo en clase, no es algo generalizado, pues se requiere un mayor esfuerzo personal por parte de los/as estudiantes. La evaluación general ha sido buena, con mejor valoración de aspectos como, «la motivación para la participación», «nivel de conocimientos de la profesora » y «la aplicación práctica / profesional de los contenidos».
Functional, thermal and rheological properties of polymer-based magnetic composite filaments for additive manufacturing
(Elsevier, 2022-07) Díaz García, Álvaro; Law, Jia Yan; Félix Ángel, Manuel; Guerrero Conejo, Antonio Francisco; Franco García, Victorino; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Universidad de Sevilla. Departamento de Ingeniería Química; AEI/FEDER-UE PID2019-105720RB-I00; US/JUNTA/FEDER-UE US-1260179; Consejería de Economía, Conocimiento, Empresas y Universidad de la Junta de Andalucía P18-RT-746; US Air Force Office of Scientific Research FA8655-21-1-7044; Universidad de Sevilla. FQM121: Sólidos no Cristalinos; Universidad de Sevilla. TEP229: Tecnología y Diseño de Productos Multicomponentes
The design of functional composite filaments for fused filament fabrication requires a suitable polymer composition, functionality of particles, uniform distribution of fillers throughout the filament, and ade- quate printability. Uniform distribution at predictable concentrations is achieved by designing polymeric capsules containing the fillers and using them as feedstock for extrusion. Functionality can be inferred from that of the particles and target concentration. However, suitable conditions for printing strongly depend on polymer type and characteristics/concentration of fillers. Soft magnetic composite filaments were produced from polylactic acid (PLA) capsules filled with 30–52 wt. % maraging steel particles. Composite filaments preserve the soft magnetic character of the fillers. Fillers reduce the transition tem- peratures of the polymer by 5 K and have a profound impact on printability. Rheological characteriza- tion shows that the ‘‘ball bearing effect” of gas-atomized particles reduces the viscosity of the composites by more than one order of magnitude, decreasing printing temperature from 215 °C to 170 °C, associated with the lack of agglomeration of particles achieved by the proposed production method. Rheological experiments allow to detect the required changes in printing conditions without requiring an extensive and costly trial and error process of printing with a large set of printing parameters.
Graphene nanoplatelets for electrically conductive 3YTZP composites densified by pressureless sintering
(Elsevier, 2019) López Pernía, Cristina; Gallardo López, Ángela María; Morales Rodríguez, Ana; Poyato Galán, Rosalía; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Ministerio de Economía y Competitividad (MINECO). España
3 mol% yttria tetragonal zirconia polycrystalline (3YTZP) ceramic composites with 2.5, 5 and 10 vol% graphene nanoplatelets (GNP) were pressureless sintered in argon atmosphere between 1350 and 1450 °C. The effects of the GNP content and the sintering temperature on the densification, microstructure and electrical properties of the composites were investigated. An isotropic distribution of GNP surrounding ceramic regions was exhibited regardless the GNP content and sintering temperature used. Electrical conductivity values comparable to the ones of fully dense composites prepared by more complex techniques were obtained, even though full densification was not achieved. While the composite with 5 vol% GNP exhibited electrical anisotropy with a semiconductor-type behaviour, the composite with 10 vol% GNP showed an electrically isotropic metallic-type behaviour.
Husos horarios españoles: racionalidad frente a leyenda
(Consello da Cultura Galega, 2017-03-22) Martín Olalla, José María; Universidad de Sevilla. Departamento de Física de la Materia Condensada
Se describe la problemática del huso en España y se comparan los horarios españoles con los del resto de Europa para señalar su similitud.
Key Factors in Early Diagnosis of Myopia Progression within Ocular Biometric Parameters by Scheimpflug Technology
(Multidisciplinary Digital Publishing Institute (MDPI), 2023) López Muñoz, Alfredo; Gargallo Martínez, Beatriz; Sánchez González, María del Carmen; Capote Puente, Raúl; Hita Cantalejo, María Concepción de; Romero Luna, Marta; Conejero Domínguez, Juan José; Sánchez González, José María; Universidad de Sevilla. Departamento de Física de la Materia Condensada
The aim of this study was to evaluate the relationship between myopia and ocular biometric variables using the Pentacam AXL® single rotation Scheimpflug camera. This prospective, cross-sectional, single-center study was performed in fifty Caucasian patients aged between 18 and 30 years (24.84 ± 3.04 years). The measured variables included maximum and minimum keratometry (K1 and K2, respectively), anterior chamber depth (ACD), corneal horizontal diameter or white to white (WTW), central corneal thickness (CCT), corneal asphericity (Q), and axial length (AXL). The tomographic and biometric measurements were considered optimal when the quality factor was greater than 95% according to the manufacturer’s software instructions. The AXL presented a significant correlation with the spherical equivalent without cycloplegia (SE without CP), age at onset of myopia (r = −0.365, p = 0.012), mean keratometry (Km) (r = −0.339, p = 0.016), ACD (r = 0.304, p = 0.032), and WTW (r = 0.406, p = 0.005). The eyes with AXL higher than 25 mm had earlier onset; higher SE without CP, AXL, and Q; and a flatter Km. AXL is the biometric variable with the greatest influence on the final refractive state in the adult myopic eye. Ophthalmologists and optometric management must consider these biometric differences in order to identify the most appropriate correction techniques in each case. The use of the Pentacam AXL in ocular biometric measurement is effective, reproducible, and non-invasive.
Laser Dynamics Modelling and Simulation: An application of Dynamic Load Balancing of Parallel Cellular Automata
(Springer, 2010) Guisado Lizar, José Luis; Jiménez-Morales, Francisco de Paula; Guerra Pérez, José Manuel; Fernández de Vega, Francisco; Iskra, Kamil A.; Sloot, Peter M.A.; Lombraña González, Daniel; Universidad de Sevilla. Departamento de Arquitectura y Tecnología de Computadores; Universidad de Sevilla. Departamento de Física de la Materia Condensada
Mechanical properties of ceramics reinforced with allotropic forms of carbon
(Elsevier, 2022) Morales Flórez, Víctor; Domínguez Rodríguez, Arturo; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Junta de Andalucía; Ministerio de Ciencia, Innovación y Universidades (MICINN). España
For decades, enormous investigation effort has been devoted to the fabrication of new ceramic matrix composites with enhanced mechanical properties. One of the most explored strategies is the addition of carbon allotropic phases such as carbon nanotubes, graphene, and carbon nanofibers due to their outstanding properties. In this review, the main fabrication protocols considered for the synthesis of the ceramic composites based on alumina and zirconia are shown, and their mechanical properties and the changes achieved by the addition of carbon allotropes are presented and discussed. Under particular circumstances, significant improvements in properties such as fracture toughness and wear at low temperature, or creep behavior and superplasticity at high temperature have been accomplished. Nevertheless, some critical aspects such as the homogenization of the carbon allotropes within the matrix are still lacking consolidated responses, which suggest that the potentialities of this reinforcing strategy have not yet been completely exploited. In summary, this work collects the fabrication strategies, major results, and main controversies of two decades of scientific research on the improvement of the fabrication methods and mechanical properties of ceramic matrix composites.

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