http://hdl.handle.net/2117/3161 Thu, 23 May 2013 17:49:14 GMT 2013-05-23T17:49:14Z webmaster.bupc@upc.edu Universitat Politècnica de Catalunya. Servei de Biblioteques i Documentació no http://hdl.handle.net/2117/18633 Title: Tomography of indentation cracks in feldspathic dental porcelain on zirconia Authors: Rueda Arango, Astrid Oasis; Seuba, Jordi; Anglada Gomila, Marcos Juan; Jiménez Piqué, Emilio Abstract: Objectives The objective of this work is to study the crack produced by spherical and sharp indentation on veneering feldspathic dental porcelain in order to understand the morphology of the cracks in the surface and beneath the indentation using a tomographic technique. The geometry of cracks produced under contact loading are directly related to the structural integrity and reliability of dental prosthesis. Methods Monotonic Hertzian contact loading and nanoindentation tests were performed on feldspathic porcelain (VITA-VM9) coatings. Residual imprints and the cracks produced by the indentations were characterized by 3-dimensional reconstruction using focused ion beam tomography. Results Under nanoindentation, the propagating crack deflects due to the interaction with the leucite particles resulting in a crack with a complex morphology. Under spherical contact loading, multiple ring cracks were observed at the surface, with a conical shape beneath the residual imprint. Significance These results will help to improve the mechanical performance of these materials by detecting potential causes of failure for the long term structural integrity and reliability of the prosthesis. Fri, 05 Apr 2013 09:43:59 GMT http://hdl.handle.net/2117/18633 2013-04-05T09:43:59Z Rueda Arango, Astrid Oasis; Seuba, Jordi; Anglada Gomila, Marcos Juan; Jiménez Piqué, Emilio no Objectives The objective of this work is to study the crack produced by spherical and sharp indentation on veneering feldspathic dental porcelain in order to understand the morphology of the cracks in the surface and beneath the indentation using a tomographic technique. The geometry of cracks produced under contact loading are directly related to the structural integrity and reliability of dental prosthesis. Methods Monotonic Hertzian contact loading and nanoindentation tests were performed on feldspathic porcelain (VITA-VM9) coatings. Residual imprints and the cracks produced by the indentations were characterized by 3-dimensional reconstruction using focused ion beam tomography. Results Under nanoindentation, the propagating crack deflects due to the interaction with the leucite particles resulting in a crack with a complex morphology. Under spherical contact loading, multiple ring cracks were observed at the surface, with a conical shape beneath the residual imprint. Significance These results will help to improve the mechanical performance of these materials by detecting potential causes of failure for the long term structural integrity and reliability of the prosthesis. http://hdl.handle.net/2117/17583 Title: GREDIQ-RIMA: The evolution of a teaching project of experimentation in chemistry Authors: Grau Vilalta, Maria Dolors; Guaus Guerrero, Ester; Martínez Martínez, María del Rosario; Calvet Tarragona, Aureli; Farran Marsà, Adriana; Salán Ballesteros, Maria Núria; Álvarez del Castillo, María Dolores; Gorchs Altarriba, Roser; Almajano Pablos, María Pilar; Morillo Cazorla, Margarita; Garrido Soriano, Núria Abstract: Authors of this project belong to the Resources Chemistry Teaching Group (GReDiQ) involved in RIMA (Research and innovation in learning methodologies). The audiovisual and multimedia material productions realized have been grouped into three themes: Basic Techniques of Experimentation in Chemistry, Safety in Chemistry Laboratories and Advanced Techniques of Experimentation in Chemistry. This work has been awarded a prize of the Universitat Politècnica de Catalunya (UPC–BARCELONATECH), one of the Autonomous Region of Catalunya and another one of a State scope Tue, 05 Feb 2013 15:33:21 GMT http://hdl.handle.net/2117/17583 2013-02-05T15:33:21Z Grau Vilalta, Maria Dolors; Guaus Guerrero, Ester; Martínez Martínez, María del Rosario; Calvet Tarragona, Aureli; Farran Marsà, Adriana; Salán Ballesteros, Maria Núria; Álvarez del Castillo, María Dolores; Gorchs Altarriba, Roser; Almajano Pablos, María Pilar; Morillo Cazorla, Margarita; Garrido Soriano, Núria no Authors of this project belong to the Resources Chemistry Teaching Group (GReDiQ) involved in RIMA (Research and innovation in learning methodologies). The audiovisual and multimedia material productions realized have been grouped into three themes: Basic Techniques of Experimentation in Chemistry, Safety in Chemistry Laboratories and Advanced Techniques of Experimentation in Chemistry. This work has been awarded a prize of the Universitat Politècnica de Catalunya (UPC–BARCELONATECH), one of the Autonomous Region of Catalunya and another one of a State scope http://hdl.handle.net/2117/17115 Title: Revealing crack profiles in polycrystalline tetragonal zirconia by ageing Authors: García Marro, Fernando; Camposilvan, Erik; Anglada Gomila, Marcos Juan Abstract: Exposure to hot water vapour is shown to be useful for staining indentation crack profiles in doped zirconia polycrystals. This is illustrated here in 3Y-TZP with two different grain sizes, for which Vickers indentation cracks are of Palmqvist type, as well as in 3Y-TZP with 2.5 wt.% cerium oxide, for which indentation cracks are half-penny. The crack profile is clearly revealed on the fracture surface after biaxial flexural testing in all the specimens previously exposed to hot water vapour. The contrast in 3Y-TZP is induced by t–m transformation caused by hydrothermal degradation, which induces an intergranular fracture zone in front of the initial position of the indentation crack tip. The biaxial strength and apparent fracture toughness of 3Y-TZP increase substantially with the time of exposure at a rate that depends on the grain size. On the contrary, in 3Y-TZP doped with ceria no signal of t–m transformation is found and the flexure biaxial stress remains practically constant, but the initial position of the indentation crack is also clearly revealed by an intergranular fracture zone in front of the initial position of the crack tip. In this case, this is associated to environmentally assisted slow crack growth under the indentation residual stress during exposure to hot water vapour in autoclave. Wed, 12 Dec 2012 10:41:01 GMT http://hdl.handle.net/2117/17115 2012-12-12T10:41:01Z García Marro, Fernando; Camposilvan, Erik; Anglada Gomila, Marcos Juan no Exposure to hot water vapour is shown to be useful for staining indentation crack profiles in doped zirconia polycrystals. This is illustrated here in 3Y-TZP with two different grain sizes, for which Vickers indentation cracks are of Palmqvist type, as well as in 3Y-TZP with 2.5 wt.% cerium oxide, for which indentation cracks are half-penny. The crack profile is clearly revealed on the fracture surface after biaxial flexural testing in all the specimens previously exposed to hot water vapour. The contrast in 3Y-TZP is induced by t–m transformation caused by hydrothermal degradation, which induces an intergranular fracture zone in front of the initial position of the indentation crack tip. The biaxial strength and apparent fracture toughness of 3Y-TZP increase substantially with the time of exposure at a rate that depends on the grain size. On the contrary, in 3Y-TZP doped with ceria no signal of t–m transformation is found and the flexure biaxial stress remains practically constant, but the initial position of the indentation crack is also clearly revealed by an intergranular fracture zone in front of the initial position of the crack tip. In this case, this is associated to environmentally assisted slow crack growth under the indentation residual stress during exposure to hot water vapour in autoclave. http://hdl.handle.net/2117/17019 Title: Influencia de la degradación hidrotérmica en la resistencia mecánica y comportamiento al desgaste de 3Y-TZP Authors: Mestra Rodríguez, Álvaro Miguel; García Marro, Fernando; Kiran Chitapalli, Ravi; Armas Sancho, Zamir de; Anglada Gomila, Marcos Juan Abstract: En este trabajo se realiza un estudio comparativo de la influencia de la degradación hidrotérmica a baja temperatura de circona tetragonal estabilizada con el 3% molar de Itria (3Y-TZP) en la resistencia mecánica a flexión y en el comportamiento bajo cargas de indentación esférica. Se presentan resultados de resistencia mecánica a flexión y de indentación esférica monotónica así como de ensayos de rayado en probetas artificialmente degradadas durante diferentes períodos de tiempo. Se pone de manifiesto que la resistencia mecánica a flexión es poco sensible a la degradación; por el contrario, los ensayos superficiales ponen claramente de manifiesto la presencia de degradación en sus etapas iniciales. Se constata la fuerte sensibilidad de la resistencia al desgaste y de la fatiga por contacto a la presencia de degradación hidrotérmica a baja temperatura. Los resultados se analizan en términos de la capa degradada de estructura monoclínica que se forma durante la degradación. Mon, 26 Nov 2012 10:32:26 GMT http://hdl.handle.net/2117/17019 2012-11-26T10:32:26Z Mestra Rodríguez, Álvaro Miguel; García Marro, Fernando; Kiran Chitapalli, Ravi; Armas Sancho, Zamir de; Anglada Gomila, Marcos Juan no En este trabajo se realiza un estudio comparativo de la influencia de la degradación hidrotérmica a baja temperatura de circona tetragonal estabilizada con el 3% molar de Itria (3Y-TZP) en la resistencia mecánica a flexión y en el comportamiento bajo cargas de indentación esférica. Se presentan resultados de resistencia mecánica a flexión y de indentación esférica monotónica así como de ensayos de rayado en probetas artificialmente degradadas durante diferentes períodos de tiempo. Se pone de manifiesto que la resistencia mecánica a flexión es poco sensible a la degradación; por el contrario, los ensayos superficiales ponen claramente de manifiesto la presencia de degradación en sus etapas iniciales. Se constata la fuerte sensibilidad de la resistencia al desgaste y de la fatiga por contacto a la presencia de degradación hidrotérmica a baja temperatura. Los resultados se analizan en términos de la capa degradada de estructura monoclínica que se forma durante la degradación. http://hdl.handle.net/2117/16941 Title: Yield strength, Shear Stress and Toughness of YBCO samples textured by Bridgman technique Authors: Roa Rovira, Joan Josep; Jiménez Piqué, Emilio; Capdevila, X.G.; Martínez, M.; Segarra, M. Abstract: Mechanical properties of the orthorhombic phase of YBa2Cu3O7-δ (Y-123) at room temperature have been investigated at different applied loads using nanoindentation technique. The study was carried out for several monodomains on the (001) planes for textured Bridgman samples with dispersed Y2BaCuO5 (Y-211) particles as pinning centers. The yield strength (σys), shear stress (τm) and toughness (KIC) of Y123/Y211composite was determined at different applied loads. First and second mechanical properties have been calculated though the Hertz equations and the last one with Lawn et al. equations. Finally, the ultra-low imprints obtained by nanoindentation have been correlated with parameters obtained by Field Emission Scanning Electron Microscope (FE-SEM). Mon, 19 Nov 2012 09:18:50 GMT http://hdl.handle.net/2117/16941 2012-11-19T09:18:50Z Roa Rovira, Joan Josep; Jiménez Piqué, Emilio; Capdevila, X.G.; Martínez, M.; Segarra, M. no Mechanical properties of the orthorhombic phase of YBa2Cu3O7-δ (Y-123) at room temperature have been investigated at different applied loads using nanoindentation technique. The study was carried out for several monodomains on the (001) planes for textured Bridgman samples with dispersed Y2BaCuO5 (Y-211) particles as pinning centers. The yield strength (σys), shear stress (τm) and toughness (KIC) of Y123/Y211composite was determined at different applied loads. First and second mechanical properties have been calculated though the Hertz equations and the last one with Lawn et al. equations. Finally, the ultra-low imprints obtained by nanoindentation have been correlated with parameters obtained by Field Emission Scanning Electron Microscope (FE-SEM). http://hdl.handle.net/2117/16814 Title: High hardness, low youngs modulus and low friction of nanocrystalline ZrW 2 laves phase and Zr 1-xW x thin films Authors: Horwat, David; Jiménez Piqué, Emilio; Pierson, J.F.; Migot, S.; Dehmas, M.; Anglada Gomila, Marcos Juan Abstract: Zr1−xWx nanocrystalline films of Zr-W solid solutions and ZrW2 Laves phase were synthesized by magnetron co-sputtering. Large values of the H/E ratio up to 0.09 are observed for grain sizes in the nanometer range along with a hardness above 10 GPa and Young's modulus below 230 GPa. H/E values are correlated with the developed surface of grain boundaries suggesting an elastic deformation mostly handled by the grain boundaries. This is associated to friction coefficients comparable to those of metallic glass surfaces. In contrast to fragile bulk Laves phases, no cracks were detected at the film surface after indentation and scratch test of nanocrystalline ZrW2. The friction coefficient of such films against diamond tip was in the range 0.08–0.15, similarly to metallic glass surfaces. Mon, 29 Oct 2012 15:24:16 GMT http://hdl.handle.net/2117/16814 2012-10-29T15:24:16Z Horwat, David; Jiménez Piqué, Emilio; Pierson, J.F.; Migot, S.; Dehmas, M.; Anglada Gomila, Marcos Juan no Zr1−xWx nanocrystalline films of Zr-W solid solutions and ZrW2 Laves phase were synthesized by magnetron co-sputtering. Large values of the H/E ratio up to 0.09 are observed for grain sizes in the nanometer range along with a hardness above 10 GPa and Young's modulus below 230 GPa. H/E values are correlated with the developed surface of grain boundaries suggesting an elastic deformation mostly handled by the grain boundaries. This is associated to friction coefficients comparable to those of metallic glass surfaces. In contrast to fragile bulk Laves phases, no cracks were detected at the film surface after indentation and scratch test of nanocrystalline ZrW2. The friction coefficient of such films against diamond tip was in the range 0.08–0.15, similarly to metallic glass surfaces. http://hdl.handle.net/2117/16773 Title: Martensitic transformation during fatigue testing of an AISI 301LN steel Authors: Mateo García, Antonio Manuel; Fargas Ribas, Gemma; Zapata Dederle, Ana Cristina Abstract: The plastic deformation accumulated during fatigue testing can induce the transformation of austenite to martensite in metastable austenitic stainless steels. To analyze this issue, a metastable austenitic stainless steel grade AISI 301 LN was studied in two different conditions, i.e. annealed and cold rolled. In the first case, the steel was fully austenitic, whereas cold rolled material had almost 30% of martensite. High cycle fatigue tests at a stress ratio of 0.8 were carried out on flat specimens from both steel conditions. Several characterization techniques, including optical microscopy, X-ray diffraction (XRD) and electron back scattered diffraction (EBSD), were used to detect and quantify the martensite induced by the cyclic deformation. Mon, 22 Oct 2012 10:45:27 GMT http://hdl.handle.net/2117/16773 2012-10-22T10:45:27Z Mateo García, Antonio Manuel; Fargas Ribas, Gemma; Zapata Dederle, Ana Cristina no The plastic deformation accumulated during fatigue testing can induce the transformation of austenite to martensite in metastable austenitic stainless steels. To analyze this issue, a metastable austenitic stainless steel grade AISI 301 LN was studied in two different conditions, i.e. annealed and cold rolled. In the first case, the steel was fully austenitic, whereas cold rolled material had almost 30% of martensite. High cycle fatigue tests at a stress ratio of 0.8 were carried out on flat specimens from both steel conditions. Several characterization techniques, including optical microscopy, X-ray diffraction (XRD) and electron back scattered diffraction (EBSD), were used to detect and quantify the martensite induced by the cyclic deformation. http://hdl.handle.net/2117/16761 Title: Contact fatigue damage of monolayer and bilayer ceramic coatings deposited on cemented carbides Authors: Mateo García, Antonio Manuel; Llanes Pitarch, Luis Miguel; Jiménez Piqué, Emilio Abstract: En este trabajo se estudia el comportamiento a fatiga bajo solicitaciones de contacto de un carburo cementado WC-Co recubierto con dos películas cerámicas distintas: TiN y WC/C, ya sea como monocapas o bicapas, mediante técnicas de indentación. Los resultados obtenidos en ensayos de indentación esférica indican que la nucleación de fisuras circulares en las capas es un criterio más apropiado que la delaminación interfacial para definir las condiciones de daño crítico en los sistemas investigados. Desde esta perspectiva, se encuentra que los carburos cementados recubiertos son susceptibles a ser degradados mecánicamente bajo solicitaciones de contacto cíclicas, aunque la sensibilidad a fatiga y el escenario de daño efectivos difieren en cada caso, en función de la naturaleza cerámica (cristalina/amorfa) y la arquitectura (mono- o bicapa) del recubrimiento. Fri, 19 Oct 2012 11:05:28 GMT http://hdl.handle.net/2117/16761 2012-10-19T11:05:28Z Mateo García, Antonio Manuel; Llanes Pitarch, Luis Miguel; Jiménez Piqué, Emilio no En este trabajo se estudia el comportamiento a fatiga bajo solicitaciones de contacto de un carburo cementado WC-Co recubierto con dos películas cerámicas distintas: TiN y WC/C, ya sea como monocapas o bicapas, mediante técnicas de indentación. Los resultados obtenidos en ensayos de indentación esférica indican que la nucleación de fisuras circulares en las capas es un criterio más apropiado que la delaminación interfacial para definir las condiciones de daño crítico en los sistemas investigados. Desde esta perspectiva, se encuentra que los carburos cementados recubiertos son susceptibles a ser degradados mecánicamente bajo solicitaciones de contacto cíclicas, aunque la sensibilidad a fatiga y el escenario de daño efectivos difieren en cada caso, en función de la naturaleza cerámica (cristalina/amorfa) y la arquitectura (mono- o bicapa) del recubrimiento. http://hdl.handle.net/2117/16660 Title: Corrosion induced degradation of textured YBCO under operation in high humidity conditions Authors: Roa Rovira, Joan Josep; Jiménez Piqué, Emilio; Díaz, Jordi A.; Morales, Manuel; Calleja Lázaro, Albert; Segarra, M. Abstract: The early stages of aggressive degradation at 85% of humidity for 24 h of single crystals of YBa2Cu3O7 − δ textured by Bridgman technique have been analyzed by means of atomic force microscopy, X-ray photoelectron spectroscopy, nanoindentation and focused ion beam. The results show that the initial formation of barium hydroxide and the non-superconducting green phase, Y2BaCuO5, induces the surface degradation and the loss of the mechanical properties as a consequence of the mechanical transformation after the degradation process due to an embrittlement of the superficial layer. Fri, 05 Oct 2012 11:30:03 GMT http://hdl.handle.net/2117/16660 2012-10-05T11:30:03Z Roa Rovira, Joan Josep; Jiménez Piqué, Emilio; Díaz, Jordi A.; Morales, Manuel; Calleja Lázaro, Albert; Segarra, M. no Atomic force microscopy, Bridgman technique, Corrosion, Nanoindentation, Superconductor The early stages of aggressive degradation at 85% of humidity for 24 h of single crystals of YBa2Cu3O7 − δ textured by Bridgman technique have been analyzed by means of atomic force microscopy, X-ray photoelectron spectroscopy, nanoindentation and focused ion beam. The results show that the initial formation of barium hydroxide and the non-superconducting green phase, Y2BaCuO5, induces the surface degradation and the loss of the mechanical properties as a consequence of the mechanical transformation after the degradation process due to an embrittlement of the superficial layer. http://hdl.handle.net/2117/16659 Title: Processing and characterization of high-density zirconia-carbon nanotube composites Authors: Chintapalli, R.K.; García Marro, Fernando; Milsom, Ben; Reece, Michel; Anglada Gomila, Marcos Juan Abstract: Addition of multiwall carbon nanotubes (MWCNTs) to polycrystalline ceramics is currently considered as a potential method for improving their mechanical properties, mainly their fracture toughness. High density composites produced by the addition of relatively small volume fractions of MWCNTs (0–2 vol.%) to 3 mol% yttria doped zirconia (3Y-TZP) have been produced by spark plasma sintering, resulting in a homogeneous distribution of MWCNTs with a small average matrix grain size in the range 153–182 nm. The influence of transformation toughening is found to be very weak for this small grain size by measuring the extent of phase transformation in the crack wake. Also, no hydrothermal degradation takes place after more than 200 h at 131 °C either in the monolithic ceramic or in the composites. The study of the influence of MWCNTs on the microstructure and mechanical properties of 3Y-TZP shows that in the composites there is a very slight decrease in hardness, while the elastic modulus does not practically change. By fitting the crack opening displacement in the near crack tip region to the Irwin parabola, the intrinsic fracture toughness is found to be approximately the same in the matrix and in the 2 vol.% composites. In spite of the observation of some crack bridging by nanotubes, from the measurement of the crack opening displacement (δ) along the crack faces, it is concluded that there is hardly any change in δ in 3Y-TZP by the addition of 2 vol.% of MWCNTs not only in the crack tip region but also in all the range studied. However, the indentation fracture toughness is nearly 15% higher in 2 vol.% composites as compared to their monolithic counterparts. Fri, 05 Oct 2012 11:21:41 GMT http://hdl.handle.net/2117/16659 2012-10-05T11:21:41Z Chintapalli, R.K.; García Marro, Fernando; Milsom, Ben; Reece, Michel; Anglada Gomila, Marcos Juan no Carbon nanotubes, Mechanical properties, Processing, Toughness, Zirconia Addition of multiwall carbon nanotubes (MWCNTs) to polycrystalline ceramics is currently considered as a potential method for improving their mechanical properties, mainly their fracture toughness. High density composites produced by the addition of relatively small volume fractions of MWCNTs (0–2 vol.%) to 3 mol% yttria doped zirconia (3Y-TZP) have been produced by spark plasma sintering, resulting in a homogeneous distribution of MWCNTs with a small average matrix grain size in the range 153–182 nm. The influence of transformation toughening is found to be very weak for this small grain size by measuring the extent of phase transformation in the crack wake. Also, no hydrothermal degradation takes place after more than 200 h at 131 °C either in the monolithic ceramic or in the composites. The study of the influence of MWCNTs on the microstructure and mechanical properties of 3Y-TZP shows that in the composites there is a very slight decrease in hardness, while the elastic modulus does not practically change. By fitting the crack opening displacement in the near crack tip region to the Irwin parabola, the intrinsic fracture toughness is found to be approximately the same in the matrix and in the 2 vol.% composites. In spite of the observation of some crack bridging by nanotubes, from the measurement of the crack opening displacement (δ) along the crack faces, it is concluded that there is hardly any change in δ in 3Y-TZP by the addition of 2 vol.% of MWCNTs not only in the crack tip region but also in all the range studied. However, the indentation fracture toughness is nearly 15% higher in 2 vol.% composites as compared to their monolithic counterparts. http://hdl.handle.net/2117/16622 Title: Focused ion beam tomography of zirconia degraded under hydrothermal conditions Authors: Jiménez Piqué, Emilio; Ramos, A.; Muñoz Tabares, José Alejandro; Hatton, A.; Soldera, Flavio; Mucklich, F.; Anglada Gomila, Marcos Juan Abstract: Three-dimensional tomography was performed on hydrothermal degraded zirconia by sequential focussed ion beam (FIB) sectioning and field emission scanning electron microscopy (FE-SEM) observation. By means of image analysis the distribution of microcracks produced under the surface was reconstructed and characterized. Results show a microcrack network preferentially oriented parallel to the surface, and a gradient in microcrack density from the surface, which is coherent with other measurements that reveal a decrease in monoclinic phase. The elastic properties of the reconstructed volume are simulated, showing that the deterioration of mechanical properties of degraded zirconia can be mainly attributed to microcracking, with a minor contribution of the phase transformation. Wed, 03 Oct 2012 11:58:04 GMT http://hdl.handle.net/2117/16622 2012-10-03T11:58:04Z Jiménez Piqué, Emilio; Ramos, A.; Muñoz Tabares, José Alejandro; Hatton, A.; Soldera, Flavio; Mucklich, F.; Anglada Gomila, Marcos Juan no Defects, Fracture, Mechanical properties, Tomography, ZrO 2 Three-dimensional tomography was performed on hydrothermal degraded zirconia by sequential focussed ion beam (FIB) sectioning and field emission scanning electron microscopy (FE-SEM) observation. By means of image analysis the distribution of microcracks produced under the surface was reconstructed and characterized. Results show a microcrack network preferentially oriented parallel to the surface, and a gradient in microcrack density from the surface, which is coherent with other measurements that reveal a decrease in monoclinic phase. The elastic properties of the reconstructed volume are simulated, showing that the deterioration of mechanical properties of degraded zirconia can be mainly attributed to microcracking, with a minor contribution of the phase transformation. http://hdl.handle.net/2117/16491 Title: Influence of substrate microstructure on the contact fatigue strength of coated cold-work tool steels Authors: Llanes Pitarch, Luis Miguel; Ramirez, Giselle; Mestra Rodríguez, Álvaro Miguel; Casas, B.; Valls, Isaac; Martinez, R.; Bueno, R.; Goez, Alexey; Mateo García, Antonio Manuel Abstract: The contact fatigue behavior of three microstructurally distinct tool steels coated with a physical vapor deposited TiN film is studied. Substrate microstructural differences come from variations in either chemical composition or processing route. Experimental procedure is based on determining critical applied loads and pressures, under both monotonic and cyclic spherical indentation loading conditions, for emergence and evolution of distinct damage modes at the coating surface: circumferential cracking, cohesive spallation and interfacial decohesion. Experimental results indicate that all coating/substrate systems evaluated are susceptible to mechanical degradation associated with repetitive contact loading. This is clearly discerned from the fact that some damage mechanisms, such as cohesive spallation at the coating and adhesion failure at the interface, are exclusively observed under cyclic loading. Substrate microstructure effects are evidenced by consideration of coating detachment as the critical damage mechanism. In this regard, crack nucleation resistance of primary carbides is pointed out as the main reason for the distinct response against decohesion observed under cyclic contact loads. Hence, finer and tougher, as well as less irregular and more homogeneously distributed primary carbides are pointed out as key microstructural features for enhancing contact fatigue strength of coated cold-work tool steels. Fri, 14 Sep 2012 10:47:00 GMT http://hdl.handle.net/2117/16491 2012-09-14T10:47:00Z Llanes Pitarch, Luis Miguel; Ramirez, Giselle; Mestra Rodríguez, Álvaro Miguel; Casas, B.; Valls, Isaac; Martinez, R.; Bueno, R.; Goez, Alexey; Mateo García, Antonio Manuel no Adhesion failure, Coated tool steel, Fatigue, Spherical indentation The contact fatigue behavior of three microstructurally distinct tool steels coated with a physical vapor deposited TiN film is studied. Substrate microstructural differences come from variations in either chemical composition or processing route. Experimental procedure is based on determining critical applied loads and pressures, under both monotonic and cyclic spherical indentation loading conditions, for emergence and evolution of distinct damage modes at the coating surface: circumferential cracking, cohesive spallation and interfacial decohesion. Experimental results indicate that all coating/substrate systems evaluated are susceptible to mechanical degradation associated with repetitive contact loading. This is clearly discerned from the fact that some damage mechanisms, such as cohesive spallation at the coating and adhesion failure at the interface, are exclusively observed under cyclic loading. Substrate microstructure effects are evidenced by consideration of coating detachment as the critical damage mechanism. In this regard, crack nucleation resistance of primary carbides is pointed out as the main reason for the distinct response against decohesion observed under cyclic contact loads. Hence, finer and tougher, as well as less irregular and more homogeneously distributed primary carbides are pointed out as key microstructural features for enhancing contact fatigue strength of coated cold-work tool steels. http://hdl.handle.net/2117/16486 Title: Nanoindentation of Bridgman YBCO samples Authors: Roa Rovira, Joan Josep; Konstantopoulou, Dimitra; Jiménez Piqué, Emilio; Martín, V.; Segarra, M.; Pastor, J.Y. Abstract: n this study, the mechanical properties of YBa2Cu3O7−x, obtained by the Bridgman technique, were examined using a Berkovich tip indenter on the basal plane (0 0 1). Intrinsic hardness was measured by nanoindentation tests and corrected using the Nix and Gao model for this material. Furthermore, Vickers hardness tests were performed, in order to determine the possible size effect on these measurements. The results showed an underestimation of the hardness value when the tests were performed with large loads. Moreover, the elastic modulus of the Bridgman samples was 128 ± 5 GPa. Different residual imprints were visualised by atomic force microscopy and a focused ion beam, in order to observe superficial and internal fracturing. Mechanical properties presented a considerable reduction at the interface. This effect could be attributed to internal stress generated during the texturing process. In order to corroborate this hypothesis, an observation using transmission electron microscopy was performed. Fri, 14 Sep 2012 08:59:23 GMT http://hdl.handle.net/2117/16486 2012-09-14T08:59:23Z Roa Rovira, Joan Josep; Konstantopoulou, Dimitra; Jiménez Piqué, Emilio; Martín, V.; Segarra, M.; Pastor, J.Y. no Bridgman, Nanoindentation, Superconductor material, YBaCuO n this study, the mechanical properties of YBa2Cu3O7−x, obtained by the Bridgman technique, were examined using a Berkovich tip indenter on the basal plane (0 0 1). Intrinsic hardness was measured by nanoindentation tests and corrected using the Nix and Gao model for this material. Furthermore, Vickers hardness tests were performed, in order to determine the possible size effect on these measurements. The results showed an underestimation of the hardness value when the tests were performed with large loads. Moreover, the elastic modulus of the Bridgman samples was 128 ± 5 GPa. Different residual imprints were visualised by atomic force microscopy and a focused ion beam, in order to observe superficial and internal fracturing. Mechanical properties presented a considerable reduction at the interface. This effect could be attributed to internal stress generated during the texturing process. In order to corroborate this hypothesis, an observation using transmission electron microscopy was performed. http://hdl.handle.net/2117/16484 Title: Nanocharacterization techniques for investigating the durability of wood coatings Authors: Vlad Cristea, Mirela; Riedl, Bernard; Blanchet, Pierre; Jiménez Piqué, Emilio Abstract: Nanocharacterization techniques such as nanoindentation and atomic force microscopy were used to investigate the exterior durability of waterborne coatings improved with inorganic nanosized UV-absorbers. Nanocomposite coatings for exterior uses of wood were formulated with different type of nanoparticles and their performance was evaluated trough artificial aging. Nanoindentation in continuous stiffness mode was used to demonstrate the changes of hardness and Young’s modulus of the coatings after accelerated weathering. The degradation mechanism of the surface coatings was investigated with atomic force microscopy that has provided valuable information on the morphological and microstructural changes of the surface coatings with the artificial aging. Additionally, the glass transition temperature and optical appearance changes were reported. The results obtained have shown that the nanoindentation technique in conjunction with atomic force microscopy can be satisfactorily used for durability investigation and service life prediction of nanocomposite coatings for wood. Fri, 14 Sep 2012 08:42:29 GMT http://hdl.handle.net/2117/16484 2012-09-14T08:42:29Z Vlad Cristea, Mirela; Riedl, Bernard; Blanchet, Pierre; Jiménez Piqué, Emilio no Exterior wood coatings, Nanocomposite coatings, Nanosized UV-absorbers, UV resistance, Nanoindentation, Atomic force microscopy Nanocharacterization techniques such as nanoindentation and atomic force microscopy were used to investigate the exterior durability of waterborne coatings improved with inorganic nanosized UV-absorbers. Nanocomposite coatings for exterior uses of wood were formulated with different type of nanoparticles and their performance was evaluated trough artificial aging. Nanoindentation in continuous stiffness mode was used to demonstrate the changes of hardness and Young’s modulus of the coatings after accelerated weathering. The degradation mechanism of the surface coatings was investigated with atomic force microscopy that has provided valuable information on the morphological and microstructural changes of the surface coatings with the artificial aging. Additionally, the glass transition temperature and optical appearance changes were reported. The results obtained have shown that the nanoindentation technique in conjunction with atomic force microscopy can be satisfactorily used for durability investigation and service life prediction of nanocomposite coatings for wood. http://hdl.handle.net/2117/16183 Title: Comportamiento a fractura de aceros metaestables Authors: Mateo García, Antonio Manuel; Gutierrez, D.; Lara, A.; Zapata Dederle, Ana Cristina; Rodríguez Calvillo, Pablo; Fargas Ribas, Gemma; Calvo Muñoz, Jessica; Casellas Padró, Daniel Thu, 05 Jul 2012 09:39:11 GMT http://hdl.handle.net/2117/16183 2012-07-05T09:39:11Z Mateo García, Antonio Manuel; Gutierrez, D.; Lara, A.; Zapata Dederle, Ana Cristina; Rodríguez Calvillo, Pablo; Fargas Ribas, Gemma; Calvo Muñoz, Jessica; Casellas Padró, Daniel no