Capítulos (Física de la Materia Condensada)

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

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Modern rare-earth-containing magnetocaloric materials: Standing on the shoulders of giant Gd5Si2Ge2
(Elsevier, 2023) Law, Jia Yan; Franco García, Victorino; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Ministerio de Ciencia e Innovación (MICIN). España; Agencia Estatal de Investigación. España; Air Force Office of Scientific Research; European Commission (EC)
The magnetocaloric effect (MCE) is a phenomenon where varying magnetic fields cause temperature changes in magnetic materials, primarily near their thermomagnetic phase transitions. Its first observation was the induced temperature change of 0.7 K (for 1.5 T at 630 K) in a nickel sample near its thermomagnetic phase transition, but the heart of modern magnetocaloric materials research was shaped by Vitalij K. Pecharsky's and Karl A. Gschneidner Jr.'s discovery of the giant magnetocaloric effect (GMCE) in the famous Gd5Si2Ge2. Significant MCE values are achieved when structural transformations coincide with magnetic transitions. This chapter focuses on rare-earth (RE)-containing magnetocaloric compounds that stand on the shoulders of the "giant Gd5Si2Ge2", i.e., whose MCE values meet the GMCE threshold and pays attention to their material criticality assessment. It highlights recent breakthroughs related to first-order thermomagnetic phase transitions (FOMT) and magnetocalorics, including the quantitative criteria to identify FOMT and the critical point at which FOMT crossovers to second-order thermomagnetic phase transition (SOMT). The chapter examines the massive magnetocaloric materials library, including lanthanide metals, binary lanthanide-metalloid compounds, binary lanthanides-transition metals, ternary intermetallics, RE oxides, and alloys with multiple principal elements (known as high entropy alloys). The book chapter also discusses a directed search strategy for designing intermetallics with multi-principal elements exhibiting FOMT and GMCE, which can largely balance criticality and enable a combination of properties with mechanical stability if it is properly applied when searching for and developing modern magnetocaloric materials containing highly critical rare-earth elements.
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.
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.
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
Trabajo cooperativo de formulación de preguntas y evaluación como forma de profundizar en las experiencias prácticas en el laboratorio de Termodinámica
(Universidad de Sevilla, 2022) Miranda Muñoz, José María; Universidad de Sevilla. Departamento de Física de la Materia Condensada
El presente trabajo describe el diseño, implementación y evaluación de un Ciclo de Mejora en el Aula (CIMA) (Delord, Hamed y otros, 2020) para su aplicación en el Laboratorio de Termodinámica, asignatura del segundo año de las titulaciones de Grado en Física, Doble Grado en Física e Ingeniería de Materiales y Doble Grado en Física y Matemáticas. El CIMA persigue promover un aprendizaje colaborativo, así como fomentar la capacidad de los estudiantes para plantear cuestiones a las que necesiten dar respuestas para solucionar un problema dado. Además, la metodología facilita a los estudiantes obtener una idea general de los fenómenos que estudiarán a lo largo del cuatrimestre en el laboratorio. El CIMA se ha diseñado también con el objetivo de fomentar la preparación de las prácticas de forma previa al acceso al laboratorio, lo que se pondrá de manifiesto en el trabajo de formulación de cuestiones. La metodología empleada combina la realización práctica de las experiencias con rondas de pregunta-respuesta que los estudiantes deberán formular, responder y evaluar.
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».
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.
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.
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.
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.
Microstructure and Thermal Conductivity of Si-Al-C-O Fiber Bonded Ceramics Joined to Refractory Metals
(Elsevier, 2020) Vera García, María del Carmen; Martínez Fernández, Julián; Singh, M.; Casalegno, V.; Balagna, C.; Ramírez Rico, Joaquín; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Ministerio de Economía y Competitividad (MINECO). España
We explore joining Si-Al-C-O fiber-bonded ceramics to Cu-clad-Mo using an Ag-Ti-Cu brazing alloy. A temperature of 900 °C and times in the range of 10–20 min are required to obtain sound joints irrespectively of the fiber orientation. The reaction layer is 1–2 μm thick and free of pores and defects. The thermal conductivity of the joined samples is well described considering that the metal and the ceramic are in series for thermal resistance. This implies that the joint is highly conductive and forms an almost perfect thermal interface between the two materials, confirming the quality of the obtained brazing layer.
Mg2SiO4-MgAl2O4 Directionally Solidified Eutectics: Hardness Dependence Modelled Through an Array of Screw Dislocations
(Elsevier, 2020) Moshtaghion, Bibi Malmal; Gómez García, Diego; Peña, Jose I.; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Ministerio de Economía y Competitividad (MINECO). España; Gobierno de Aragón; Junta de Andalucía
Mg2SiO4-MgAl2O4 eutectic ceramics have been fabricated by means of the laser floating zone (LFZ) technique. The microstructure has revealed as an unusual one at lower growth rate, composed of broken lamellae of MgAl2O4 distributed randomly along one matrix, composed of Mg2SiO4. At higher growth rates, a cell structure with intra-cell lamella structure is dominant. Contrary to most eutectic systems, hardness is not dependent upon the inter-spacing, but it does depend on one characteristic length of lamellae: their perimeter. One simple model based upon the dislocation is proposed, which successfully accounts for such extraordinary hardness law. Accordingly, Mg2SiO4-MgAl2O4 eutectic ceramics fabricated at 50 mm/h growth rate with the smallest MgAl2O4 lamella perimeter favorably showed more elevated hardness (13.4 GPa from Vickers indentation and 15.3 GPa from nanoindentation) and strength (∼430 MPa) than those found in the monolithic Mg2SiO4 matrix.
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.
Temperature-FORC Analysis of a Magnetocaloric Heusler Alloy Using a Unified Driving Force Approach (T*FORC)
(American Institute of Physics, 2020) Franco García, Victorino; Universidad de Sevilla. Departamento de Física de la Materia Condensada; European Commission (EC). European Commission (FEDER); Junta de Andalucía; Army Research Laboratory
Temperature-first order reversal curve (FORC) distributions of thermomagnetic phase transitions are a fingerprinting tool to identify features of the phase transformations of the material. However, they have two major limitations: Qualitative character, due to the shift of the loops with increasing driving forces, and long experimental time. The use of an effective temperature that takes into account the different driving forces affecting the transformation allows for a more quantitative comparison of the features of the FORC distributions, as it eliminates the need for an ad hoc selection of the origin of the distribution axes. At the same time, experimental measurements as a function of this effective temperature are significantly faster than purely temperature loops, hinting at a future possibility of time and cost efficient FORC characterization of temperature dependent transitions.
Phosphogypsum waste lime as a promising substitute of commercial limes: A rheological approach
(Elsevier, 2019) Romero Hermida, Isabel; Borrero-López, Antonio María; Alejandre Sánchez, Francisco Javier; Flores Alés, Vicente; Santos, A.; Franco, J. M.; Esquivias Fedriani, Luis María; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Universidad de Sevilla. Departamento de Construcciones Arquitectónicas II (ETSIE)
This paper presents the rheological properties of three types of lime putty, specifying the influence of their origin. The study aims to compare a special lime putty prepared from phosphogypsum with a commercial lime powder and an aged lime putty. The results obtained in terms of chemical composition, crystalline structure, grain size and rheological characterization, (linear viscoelasticity, shear rate and time-dependent flow behaviour) are presented in the study. Putties studied present a similar rheological response, which mainly depends on the particle size and water content. Lower values of the linear viscoelastic functions and viscosity were found for the phosphogypsum lime putty, in agreement with the higher particle size. Transient flow tests reveal a predominant elastic response with no significant shear-induced structural perturbations. However, either a thickening phenomenon over time, i.e. rheopexy, favoured at low shear rates, or a viscosity decrease, i.e. thixotropy, favoured at high shear rates, was observed.
Novel Procedure for Laboratory Scale Production of Composite Functional Filaments for Additive Manufacturing
(Elsevier, 2020) Díaz García, Álvaro; Law, Jia Yan; Cota Reguero, Agustín; Bellido-Correa, A.; Ramírez Rico, Joaquín; Schäfer, R.; Franco García, Victorino; Universidad de Sevilla. Departamento de Física de la Materia Condensada; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER); Junta de Andalucía
Successful 3D printing by material extrusion of functional parts for new devices requires high quality filaments. Uniform homogeneity and good dispersion of particles embedded in filaments typically takes several cycles of extrusion or well-prepared feedstock by injection molding, industrial kneaders or twin-screw compounding. These methods need specific production devices that are not available in many laboratories non-specialized in polymer research, such as those working on different material science and technology topics that try to connect with additive manufacturing. Therefore, laboratory studies are usually limited to compositions and filler concentrations provided by commercial companies. Here, we present an original laboratory scale methodology to custom-prepare the feedstock for extruding magnetic composite filaments for fused filament fabrication (FFF), which is attainable by a desktop single-screw extruder. It consists in encapsulating the fillers in custom made capsules that are used as feedstock and reach the melting area of the extruder maintaining the same concentration of fillers. Results have shown that our approach can create smooth and continuous composite filaments with good homogeneity and printability with fine level of dimensional control. We further show the good dispersion of the particles in the composite filament using X-Ray Tomography, which enabled a 3D reconstruction of the spacial distribution of the embedded magnetic particles. The major advantage of this new way of preparing the composite feedstock is that it avoids the hassle of multiple extrusion runs and industrial machinery, yet providing uniform filaments of well controlled filler concentration, which is predictable and reproducible. The proposed methodology is suitable for different polymer matrices and applicable to other functional particle types, not just limited to magnetic ones. This opens an avenue for further laboratory scale development of novel functional composite filaments, useful for any community. This democratization of complex filament preparation, including consumers preparing their own desired uniform novel filaments, will facilitate to unify efforts nearing 3D printing of new functional devices.
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.
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.
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.
Tribological behavior of graphene nanoplatelet reinforced 3YTZP composites
(Elsevier, 2019) Gutiérrez Mora, Felipe; Morales Rodríguez, Ana; Gallardo López, Ángela María; Poyato Galán, Rosalía; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Ministerio de Economía y Competitividad (MINECO). España
The tribological behavior of graphene nanoplatelet (GNP) reinforced 3 mol% yttria tetragonal zirconia polycrystals (3YTZP) composites with different GNP content (2.5, 5 and 10 vol%) was analyzed and discussed. Their dry sliding behavior was studied using a ball-on-disk geometry with zirconia balls as counterparts, using loads between 2 and 20 N at ambient conditions and compared to the behavior of a monolithic 3YTZP ceramic used as a reference material. The composites showed lower friction coefficients and higher wear resistance than the monolithic 3YTZP. An outstanding performance was achieved at 10 N, where the friction coefficient decreased from 0.6 to 0.3 and the wear rates decreased 3 orders of magnitude in comparison with the monolithic ceramic. A layer adhered to the worn surface was found for all the composites, but it did not acted as a lubricating film. The composites with the lowest GNP content showed an overall improved tribological behavior.

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