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UPCommons - E-prints UPC Universitat Politècnica de Catalunya (63.328 recursos)
E-prints UPC cobreix dues finalitats: per una banda, és el dipòsit institucional de la UPC que recull els articles de revista, les comunicacions de congrés i els reports de recerca generats en les activitats de recerca del personal docent i investigador de la universitat; per l'altra, és una eina que permet accelerar la producció científica, allotjant versions de documents prèvies a la publicació en una revista o a les actes d’un congrés.

Articles de revista

Mostrando recursos 1 - 20 de 355

1. Small punch test on the analysis of fracture behaviour of PLA-nanocomposite films - Rodríguez González, Cristina; Arencón Osuna, David; Belzunce Varela, F. Javier; Maspoch Rulduà, Mª Lluïsa
The analysis of the fracture behaviour of polymeric films involves the determination of the specific essential work of fracture, which requires preparation, testing and evaluation of a large number of notched specimens. All these tasks demand significant time and costs; therefore, the use of alternative testing procedures that offer savings of both materials and time are becoming increasingly attractive options. Recently, the Small Punch Test (SPT) has experienced significant development as an alternative to conventional testing procedures in the field of steels and some metallic alloys. This work considers the applicability of SPT to the fracture characterisation of polylactide acid...

2. In-vitro response of pre-osteoblastic MG63 cells on Ni-free Ti shape memory substrates - Arciniegas, Milena; Peña Andrés, Javier; Gil Mur, Francisco Javier; Manero Planella, José María
Ni-free Ti alloys are a potential strategy to overcome the risk of Ni-adverse reactions and rigidity mismatch for implant materials. Here, we report the biological behavior induced for two promising candidate alloys—Ti19.1Nb8.8Zr (MS temperature of 46°C and elastic modulus of 74 GPa) and Ti41.2Nb6.1Zr (elastic modulus of 67 GPa)—on cultured MG63 cells, as well as their physical and chemical properties. Contact angle results revealed the hydrophobic character of the former alloy (59.02° ± 2.35°) attributed to the presence of the martensitic phase, while the latter one presented a hydrophilic response (67.77° ± 2.78°). Results showed also that the cell adhesion...

3. Fibrinogen nanofibers for guiding endothelial cell behavior - Gugutkov, Dencho; Gustavsson, Johan; Ginebra Molins, Maria Pau; Altankov, George Petrov
This paper describes the biological consequences of presenting electrospun fibrinogen (FBG) to endothelial cells as a spatially organized nanofibrous matrix. Aligned and randomly oriented FBG nanofibers with an average diameter of less than 200 nm were obtained by electrospinning of native FBG solution. Electrophoretic profiling confirmed that the electrospun FBG resembled the native protein structure, and fluorescent tracing of FITC-labeled FBG showed that electrospun fibers withstood immersion in physiological solutions reasonably well for several days. With respect to cellular interactions, the nanofibrous FBG matrix provided better conditions for initial recognition by human umbilical vein endothelial cells compared to pre-adsorbed FBG...

4. Microstructural and calorimetric analysis of ZK60 alloy processed by ECAP - Dumitru, Florina Diana; Ghiban, Brândusa; Cabrera Marrero, José M.; Higuera Cobos, Oscar Fabián; Gurau, Gheorghe; Ghiban, Nicolae
In the last years many research efforts have been made in order to extend the application of wrought magnesium to structural components. One of the methods to improve the mechanical properties of the processed materials is through severe plastic deformation (SPD). ZK60 magnesium alloy samples were subjected to 6 passes of equal-channel angular pressing (ECAP) decreasing the temperature after the fourth pass, following an alternative route A. The structural characterization was realized by microstructural evolution using Oriented Image Microscopy (OIM) and XRD analysis. Differential Scanning Calorimetry (DSC) was used to estimate the stored energy and the recrystallization temperature after each...

5. Printed circuit boards: a review on the perspective of sustainability - Cabrera Marrero, José M.; Canal Marques, André; Malfatti, Célia de Fraga
Modern life increasingly requires newer equipments and more technology. In addition, the fact that society is highly consumerist makes the amount of discarded equipment as well as the amount of waste from the manufacture of new products increase at an alarming rate. Printed circuit boards, which form the basis of the electronics industry, are technological waste of dif fi cult disposal whose recycling is complex and expensive due to the diversity of materials and components and their dif fi cult separation. Currently, printed circuit boards have a fi xing problem, which is migrating from traditional Pb e Sn alloys to lead-free alloys without de fi nite choice. This replacement is an attempt to minimize the problem of...

6. Estudio macro-micro en un acero de bajo contenido de carbono obtenido con el proceso de colada continua - Acevedo, Jorge; Cabrera Marrero, José M.
En una palanquilla de acero (0.075%C, 0.017%Si, 1.186%Mn, 0.052%P, 0.271%S y 0.075%Cr) fabricada con el proceso de colada continua, se simula con el método de los elementos finitos la transferencia de calor y la microestructura de solidificación. Las temperaturas que enmarcan los límites de la solidificación son obtenidas en función de la composición química del material. Con una formulación macro-micro se relaciona la transferencia de calor con la microestructura de solidificación. Los espaciados dendríticos primarios y secundarios se simulan con modelos analíticos en función de los parámetros termo-físicos M y N, que son ajustados linealmente entre resultados numéricos y experimentales....

7. Microstructure influencing physical and mechanical properties of electrolytic tough pitch copper produced by equal channel angular pressing - Higuera Cobos, Oscar Fabián; Cabrera Marrero, José M.
Samples of electrolytic tough pitch (ETP) copper were subjected to equal-channel angular pressing (ECAP) for up to 16 passes at room temperature following route Bc. The microstructural evolution was followed by Oriented Image Microscopy (OIM) and Differential Scanning Calorimetry (DSC) was used to estimate the activation energy and the recrystallization temperature after each ECAP pass. Also, mechanical properties after each pass were evaluated by tensile tests. Finally, electrical properties were analyzed. Results show that the stored energy increases on increasing ECAP deformation, while the recrystallization temperature decreases signi¿cantly. From a mechanical point of view a stable state is attained after 4...

8. Effect of boron on the hot ductility behavior of a low carbon advanced ultra-high strength steel (A-UHSS) - Mejía, Ignacio; Altamirano, G.; Bedolla Jacuinde, Arnoldo; Cabrera Marrero, José M.
This research work studied the effect of boron additions (14, 33, 82, 126, and 214 ppm) on the hot ductility behavior of a low carbon advanced ultra-high strength steel. For this purpose, specimens were subjected to a hot tensile test at different temperatures [923 K, 973 K, 1023 K, 1073 K, 1173 K, and 1273 K (650 °C, 700 °C, 750 °C, 800 °C, 900 °C, and 1000 °C)] under a constant true strain rate of 10-3 s-1. The reduction of area (RA) of the tested samples until fracture was taken as a measure of the hot ductility. In general,...

9. Texture analysis in ultrafine grained copper processed by equal channel angular pressing - Higuera Cobos, Oscar Fabián; Cabrera Marrero, José M.
Electrolytic tough pitch (ETP) and fire refined high conductivity (FRHC) copper samples were severely deformed at room temperature by equal channel angular pressing (ECAP) up to 16 passes (e ~ 1 per pass), following route Bc. The effect of the initial texture on the evolution of texture after the ECAP process for both materials was analyzed. The annealed materials present a marked anisotropy, with a texture controlled by the <110> fiber. According to the orientation distribution function (ODF), this initial behavior allows the presence of a strong C ({001} <110>) component after the first two ECAP passes in both coppers....

10. Large linear anhysteretic magnetoelectric voltage coeficients in CoFe2O4/polyvinylidene ¿uoride 0–3 nanocomposites - Martins, Pedro; Moya, Xavier; Caparrós Vázquez, Cristina Maria; Fernandez Gonzalez, Javier; Mathur, N.D.; Lanceros Méndez, Senentxu
Free-standing flexible magnetoelectric 0–3 composite films comprising CoFe2O4 non-spherical ferromagnetic nanoparticles with strong magnetic anisotropy in soft polyvinylidene fluoride matrices with significant void ratios have been prepared at low temperatures by solvent casting, melt crystallization and mechanical stretching. Magnetoelectric voltage coefficients increase linearly with applied dc magnetic field bias up to 5 kOe. At this field, a maximum magnetoelectric voltage coef¿cient of 11.2 mV cm-1 Oe-1 was obtained for samples with 10 wt% ferrite at *50-kHz resonance. The observed linear magnetoelectric response is attributed to a linear gradient of magnetostriction with respect to magnetic field for H B 5 kOe.

11. Effect of sandblasting and residual stress on strength of zirconia for restorative dentistry applications - Kiran Chintapalli, Ravi; Mestra Rodríguez, Álvaro Miguel; García Marro, Fernando; Anglada Gomila, Marc
Sandblasting is a commonly used surface treatment technique for dental crowns to improve the adhesion of the mating parts of a restoration. The goal of this work is to study the effect of different sandblasting conditions on the mechanical properties of 3 mol% yttria stabilized tetragonal zirconia (3Y-TZP), such as biaxial strength, surface elastic modulus, contact hardness and residual stresses induced by sandblasting. The specimens were sandblasted considering two different particle sizes (110, 250 μm), two pressures (2 and 4 bar) and two impact angles (30° and 90°). Biaxial strength of 3Y-TZP increases when sandblasted with 110 µm particles while...

12. Biomimetic treatment on dental implants for short-term bone regeneration - Gil Mur, Francisco Javier; Manzanares, Norberto; Badet de Mena, Armando; Aparicio, Conrado; Ginebra Molins, Maria Pau
Objectives The main purpose of this work was to assess the short-term bone regenerative potential of new osteoconductive implants. The novelty of the study lies in the analysis of the effectiveness of a novel two-step treatment which combines shot-blasting with a thermo-chemical treatment, at very short times after implant placement in a minipig model. Materials and methods Three hundred twenty implants with four different surface treatments, namely bioactivated sur- faces, micro-rough grit-blasted, micro-rough acid-etched and smooth as-machined titanium implants were placed into the bone of 20 minipigs. The percent of bone-to-implant contact was determined 3 days, 1, 2, 3 and 10 weeks after implant placement by histomorphometric analysis. Surface composition, topography and wettability of the...

13. Nanoindentation and nanoscratch properties of mullite-based environmental barrier coatings: Influence of chemical composition - Al/Si ratio - Botero, Carlos; Jiménez Piqué, Emilio; Martin, R; Kulkarni, Tushar; Sarin, Vinod K.; Llanes Pitarch, Luis Miguel
The mechanical properties and structural integrity of mullite (3Al2O3·2SiO2) environmental barrier coatings (EBCs) are key factors towards the implementation of these systems in real applications. By using chemical vapor deposition, the chemical composition of mullite in these coatings may be tailored to obtain high Al/Si ratios in the outer surface, for an optimum corrosion protection in gas turbine environments. In this work, the influence of such Al/Si ratio on the mechanical properties and structural integrity of different Al-rich mullite coatings is evaluated by means of nanoindentation and nanoscratch tests. It is found that hardness and elastic modulus of the coating...

14. Magnesium phosphate cements for endodontic applications with improved long-term sealing ability - Mestres Beà, Gemma; Aguilera, F. S.; Manzanares, N; Sauro, S; Osorio, R; Toledano, M; Ginebra Molins, Maria Pau
To characterize three radiopaque Magnesium Phosphate Cements (MPCs) developed for endodontic purposes

15. Thermal stability and fire behaviour of flame retardant high density rigid foams based on hydromagnesite-filled polypropylene composites - Redondo Realinho, Vera Cristina de; Haurie Ibarra, Laia; Sousa Pais Antunes, Marcelo de; Velasco Perero, José Ignacio
The present work deals with the development of new rigid polypropylene composite foams filled with high amounts of flame-retardant systems based on synthetic hydromagnesite, a basic magnesium carbonate obtained from an industrial by-product. A partially-interconnected cellular structure with a cell size around 100 μm was obtained for the hydromagnesite-filled PP foams. A 40% reduction of this cell size was observed when a small amount of a combination of montmorillonite and graphene layered nanoparticles was added to the hydromagnesite. The combination of hydromagnesite with an intumescent additive (ammonium polyphosphate) and layered nanoparticles led to improved thermal stability. In particular, the intumescent...

16. Nanoindentation of nanocolumnar TiO2 thin films with single and stacked zig-zag layers - Jiménez Piqué, Emilio; Gonzalez Garcia, Lola; Rico, Victor J.; Rodriguez Gonzalez-Elipe, Agustin
This paper reports a systematic analysis of the mechanical properties of nanocolumnar TiO2 thin films prepared by evaporation at a glancing geometry. A systematic study of the mechanical properties is carried out by comparing the hardness and the Young's modulus determined by nanoindentation for thin films prepared at different deposition angles and characterized by a tilted nanocolumnar structure and others where the nanocolumns are perpendicular to the substrate or are arranged as zig-zag stacked layers. A correlation between mechanical properties and glazing angle geometry is proposed. Differences in the results are discussed in view of the cross section images obtained...

17. Deformation mechanisms induced under high cycle fatigue tests in a metastable austenitic stainless steel - Roa Rovira, Joan Josep; Fargas Ribas, Gemma; Jiménez Piqué, Emilio; Mateo García, Antonio Manuel
Advanced techniques were used to study the deformation mechanisms induced by fatigue tests in a metastable austenitic stainless steel AISI 301LN. Observations by Atomic Force Microscopy were carried out to study the evolution of a pre-existing martensite platelet at increasing number of cycles. The sub-superficial deformation mechanisms of the austenitic grains were studied considering the cross-section microstructure obtained by Focused Ion Beam and analysed by Scanning Electron Microscopy and Transmission Electron Microscopy. The results revealed no deformation surrounding the pre-existing martensitic platelet during fatigue tests, only the growth on height was observed. Martensite formation was associated with shear bands on...

18. Analysis of the misfit of dental implant-supported prostheses made with three manufacturing processes - Fernández Yagüe, Marc-Antoni; Delgado Garoña, Luis María; Molmeneu Trias, Meritxell; García, David; Rodríguez Rius, Daniel
The microgap between implant components has been associated with complications such as screw loosening or adverse biologic responses.

19. Fracture toughness reliability in polycarbonate: notch sharpening effects - Salazar, Alicia; Rodríguez, Jesús; Martínez Benasat, Antonio
The effect of the notch sharpening on the fracture toughness obtained under linear elastic fracture mechanics has been analyzed in an amorphous polycarbonate. The samples for fracture characterization were sharpened via the traditional contact steel razor blade technique and the noncontact femtosecond laser ablation technique. The values of the fracture toughness of the specimens sharpened through femtosecond laser ablation were lower than those measured on samples sharpened using a steel razor blade. Moreover, the former was in plane strain state, but the latter did not verify the size criterion. The damage produced ahead of the crack tip through plastic deformation...

20. Effect of the thermoforming process variables on the sheet friction coefficient - Morales, Rosa Amalia; Candal Pazos, Maria Virginia; Santana Pérez, Orlando Onofre; Gordillo Aubert, Antonio; Salazar, Rubén
The objective of this work was to obtain, through a simple experimental assembly, the real influence of the friction and process conditions in the assisted thermoforming process. The use of simulation tools to optimize this process requires the knowledge of the sheet-plug system friction coefficient [μ], the used temperature and velocity conditions, and due to that, the software does not have a wide database. For this, the users suppose μ with the previous known difference between the simulated and the experimental data. For this reason, the obtaining of μ may allow to achieve more accurate simulations. In this work, a...

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