Artículos (Ingeniería y Ciencia de los Materiales y del Transporte)

URI permanente para esta colecciónhttps://hdl.handle.net/11441/11377

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2D magnesium phosphate resorbable coating to enhance cell adhesion on titanium surfaces
(Elsevier, 2024-04) Elhadad, Amir A.; Mezour, Mohamed A.; Abu Nada, Lina; Shurbaji, Samar; Mansour, Alaa; Smith, Sophia; Moussa, Hanan; Lee, Lisa; Pérez-Soriano, Eva María; Murshed, Monzur; Chromik, Richard; Tamimi, Faleh; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Universidad de Sevilla. TEP123: Metalurgia e Ingeniería de los Materiales
Titanium and its alloys are essential metals for orthopedic implant manufacturing due to their exceptional mechanical properties and biocompatibility, used extensively for treating various orthopedic conditions. However, Titanium (Ti) implants have a disadvantage due to lack of bioactivity, potentially affecting osseointegration and osteoconductive capabilities, and may take several months to integrate with bone tissue. In this work, we prepared a layer of 2D magnesium phosphate (MgPi) coating on the surface of titanium surfaces via the spin-coating technique. Various techniques were used to study the phase composition of the coatings, including FTIR, Raman spectroscopy, NMR, and XRD analysis. Morphology and chemical analysis were performed using Atomic force microscopy and SEM/EDX. Nano-scratch test and water contact angle measurements were used to measure adhesion strength and wettability. In addition, in vitro cell assays were used to assess cell adhesion and viability to determine how the MC3T3-E1 osteoblast-like cells reacted to the different treated Ti substrates. AFM results showed that the surface roughness became lower after coatings. MgPi-coated samples showed higher hydrophilicity, protein adsorption, and cell viability than uncoated samples. The nano-scratch test showed that the MgPi coating showed better adherence to chemically and thermally treated samples compared to untreated samples. The deposited MgPi coating has good adhesion to the Ti-substrates. Most significantly, compared to uncoated control (Ti) (p < 0.005) and chemically treated coated samples CT-MgPi (p < 0.005), MC3T3-E1 cell proliferation was significantly increased on thermochemical coated surfaces. These findings point to resorbable two-dimensional MgPi coatings as a potential candidate for promoting Ti implant osseointegration.
A boundary element numerical scheme for the two-dimensional convection–diffusion equation
(John Wiley & Sons, 2008-12) Romero Pérez, Luis Miguel; García Benítez, Francisco; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte
In this study, the theoretical and numerical fundamentals of BIEM techniques for the two-dimensionalconvection–diffusion problem are presented. After an extended presentation of the basic integral formu-lation, the discretizing and iterative processes for its resolution are introduced. Interesting remarks ongeneral expressions versus previously published particularized results are worth mentioning. A numericalsolution scheme is provided, which has been completely developed and designed to the physical problemposed. A novel scheme based in the simultaneous solving of the potential and the gradient of the potentialboundary integral equations is included. A diversity of problems is tested to prove the possibilities of themethod.
A machine learning methodology to predict alerts and maintenance interventions in roads
(Taylor & Francis, 2021) Morales Sánchez, Francisco José; Reyes Gutiérrez, Antonio; Caceres, Noelia; Romero Pérez, Luis Miguel; García Benítez, Francisco; Morgado, Joao; Duarte, Emanuel; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; European Union (UE). H2020; Ministerio de Economía y Competitividad (MINECO). España; Programa Torres Quevedo (PTQ); Universidad de Sevilla. TEP118: Ingeniería de los Transportes
This contribution is about predicting maintenance alerts in roads and selecting the most appropriate type of interventions recommended for preventing the occurrence of future failures. The objective is aligned with that covered by pavement maintenance decision support systems (PMDSS), though the methodology presented can be applied to other non-pavement road linear assets. The purpose is to summarise the main findings in the development of an approach based on testing the four most extended machine learning techniques (ML), namely Decision Trees (DT), K-Nearest Neighbourhood (KNN), Support Vector Machines (SVM) and Artificial Neural Networks (ANN), using data from the historical inventory of inspections and maintenance interventions of a case study to illustrate the potential that such approach can offer to road maintenance managers. The correlation process embodies supervised and unsupervised training of models. The maintenance predictions are presented and compared over various segments corresponding to the real maintenance interventions conducted on an existing road network of a geographical zone.
A Method to Determine the Electrical Resistance of a Metallic Powder Mass under Compression
(MDPI, 2017-11-06) Montes Martos, Juan Manuel; Gómez Cuevas, Francisco de Paula; Ternero Fernández, Fátima; Astacio López, Raquel; Sánchez Caballero, Eduardo; Cintas Físico, Jesús; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Ministerio de Economía y Competitividad (MINECO). España; Universidad de Sevilla. TEP123: Metalurgia e Ingenieria de los Materiales
In this paper, a phenomenological model to predict the value of the electrical resistance of a compressed metal powder mass is proposed. The model, based on the experimental compressibility and resistivity-porosity curves, is useful in the field of the electrical resistance consolidation. In this area is often required to find out whether a certain mass of powder inside a die of specified inner section, and subjected to a certain compression, reaches a sufficiently small resistance value so that it can be consolidated by electrical means. The model also predicts the electrical resistance value of the powder mass in case of powders with no oxide layers, or after removing them mechanically or electrically by a previous activation process. The model predictions have been successfully validated through direct measurements of electrical resistance in powder aggregates both in as-received state and after electrical activation.
A multidisciplinary perspective on the latest trends in artificial cartilage fabrication to mimic real tissue
(Elsevier, 2022-12) Elhadad, Amir A.; Alcudia Cruz, Ana; Begines Ruiz, Belén; Pérez-Soriano, Eva María; Torres Hernández, Yadir; Universidad de Sevilla. Departamento de Química Orgánica y Farmacéutica; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Universidad de Sevilla. FQM135: Carbohidratos y Polímeros; Universidad de Sevilla. TEP123: Metalurgia e Ingeniería de los Materiales
Articular cartilage (AC) has a low ability for endogenous repair, and current treatments are not completely efficient in generating strong and healthy repair tissue. As a result, there is a great deal of interest in cartilage repair and recovery of joint function due to the aging population and the increasing frequency of cartilage degradation and osteoarthritis. Thus, the search for better and more efficient strategies to regenerate articular cartilage to repair the joints in patients with osteoarthritis is a critical motivation. Biomaterials, which are made of natural or synthetic polymers, or a mixture of the two, serve as a scaffold for tissue regeneration. Cartilage tissue engineering (TE) seeks to develop a treatment that can effectively repair damaged AC caused by trauma or disease. In cartilage TE, scaffolds that provide a 3D environment like native articular cartilage for cells to proliferate, attach, and hence ensure tissue regeneration success are needed. For optimal cell activities, which is associated with proper cartilage regeneration, these scaffolds must meet all necessary criteria, including adequate architectural, physicochemical, and biological properties. This study briefly explores the evolution of scaffolds constructed of synthetic polymers and hybrid materials for cartilage tissue engineering. Initially, general information on AC is presented, as well as a review of medical approaches to treating cartilage injuries or disease. Following that, the requirements for scaffolds in tissue regeneration, specific materials, and techniques for producing them are briefly discussed.
A new manual wheelchair propulsion system with self-locking capability on ramps
(Copernicus, 2018-11-08) Rodríguez Jiménez, Gaspar; Rodríguez Salgado, David; Alonso, Francisco Javier; Castillo Granados, José María del; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte
A wheelchair user faces many difficulties in their everyday attempts to use ramps, especially those of some length. The present work describes the design and build of a propulsion system for manual wheelchairs for use in ascending or descending long ramps. The design is characterized by a self-locking mechanism that activates automatically to brake the chair when the user stops pushing. The system consists of a planetary transmission with a self-locking capacity coupled to a push rim with which the user moves the system. Different transmission ratios are proposed, adapted to the slope and to the user’s physical capacity (measured as the power the user can apply over ample time periods). The design is shown to be viable in terms of resistance, and approximate dimensions are established for the height and width of the propulsion system. Also, a prototype was built in order to test the self-locking system on ramps.
A Novel, Simple and Highly Efficient Route to Obtain PrBaMn2O5+δ Double Perovskite: Mechanochemical Synthesis
(MDPI, 2021-02) García-García, Francisco J.; Sayagués de Vega, María Jesús; Gotor Martínez, Francisco José; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER); Junta de Andalucía
In this work, a mechanochemical route was proposed for the synthesis of the PrBaMn2O5+ (PMBO) double layered perovskite phase. The mechanochemical reaction between Pr6O11, BaO2, and MnO powders with cationic stoichiometric ratios of 1/1/2 for Pr/Ba/Mn was performed using highenergy milling conditions in air. After 150 min of milling, a new phase with perovskite structure and cubic symmetry consistent with the A-site disordered Pr0.5Ba0.5MnO3 phase was formed. When this new phase was subsequently annealed at a high temperature in an inert Ar atmosphere, the layered PrBaMn2O5+ phase was obtained without needing to use a reducing atmosphere. At 1100 C, the fully reduced layered PrBaMn2O5 phase was achieved. A weight gain was observed in the 200–300 C temperature range when this fully reduced phase was annealed in air, which was consistent with the transformation into the fully oxidized PrBaMn2O6 phase. The microstructural characterization by SEM, TEM, and HRTEM ascertained the formation of the intended PrBaMn2O5+ phase. Electrical characterization shows very high electrical conductivity of layered PBMO in a reducing atmosphere and suitable in an oxidizing atmosphere, becoming, therefore, excellent candidates as solid oxide fuel cell (SOFC electrodes).
A Structural Comparison of Ordered and Non-Ordered Ion Doped Silicate Bioactive Glasses
(MDPI, 2020-02) Schmitz, Seray; Beltrán, Ana M.; Cresswell, Mark; Boccaccini, Aldo R.; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Universidad de Sevilla. TEP123: Metalurgía e Ingeniería de los Materiales
One of the key benefits of sol-gel-derived glasses is the presence of a mesoporous structure and the resulting increase in surface area. This enhancement in textural properties has a significant e ect on the physicochemical properties of the materials. In this context the aim of this study was to investigate how sol-gel synthesis parameters can influence the textural and structural properties of mesoporous silicate glasses. We report the synthesis and characterization of metal ion doped sol-gel derived glasses with di erent dopants in the presence or absence of a surfactant (Pluronic P123) used as structure-directing templating agent. Characterization was done by several methods. Using a structure directing agent led to larger surface areas and highly ordered mesoporous structures. The chemical structure of the non-ordered glasses was modified to a larger extent than the one of the ordered glasses due to increased incorporation of dopant ions into the glass network. The results will help to further understand how the properties of sol-gel glasses can be controlled by incorporation of metal dopants, in conjunction with control over the textural properties, and will be important to optimize the properties of sol-gel glasses for specific applications, e.g., drug delivery, bone regeneration, wound healing, and antibacterial materials.
A Track Geometry Measuring System Based on Multibody Kinematics, Inertial Sensors and Computer Vision
(MDPI, 2020-01) Escalona Franco, José Luis; Urda Gómez, Pedro; Muñoz Moreno, Sergio; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Universidad de Sevilla. Departamento de Ingeniería Mecánica y de Fabricación; Universidad de Sevilla. TEP -111: Ingeniería Mecánica; Universidad de Sevilla. TEP-123: Metalurgia e Ingeniería de los Materiales
This paper describes the kinematics used for the calculation of track geometric irregularities of a new Track Geometry Measuring System (TGMS) to be installed in railway vehicles. The TGMS includes a computer for data acquisition and process, a set of sensors including an inertial measuring unit (IMU, 3D gyroscope and 3D accelerometer), two video cameras and an encoder. The kinematic description, that is borrowed from the multibody dynamics analysis of railway vehicles used in computer simulation codes, is used to calculate the relative motion between the vehicle and the track, and also for the computer vision system and its calibration. The multibody framework is thus used to find the formulas that are needed to calculate the track irregularities (gauge, cross-level, alignment and vertical profile) as a function of sensor data. The TGMS has been experimentally tested in a 1:10 scaled vehicle and track specifically designed for this investigation. The geometric irregularities of a 90 m-scale track have been measured with an alternative and accurate method and the results are compared with the results of the TGMS. Results show a good agreement between both methods of calculation of the geometric irregularities.
Absence of the core–rim microstructure in TixTa1 − xCyN1 − y-based cermets developed from a pre-sintered carbonitride master alloy
(Elsevier, 2012) Chicardi Augusto, Ernesto; Córdoba Gallego, José Manuel; Sayagués de Vega, María Jesús; Gotor Martínez, Francisco José; Universidad de Sevilla. Departamento de Química Inorgánica; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Gobierno de España
(Ti,Ta)(C,N) solid solution-based cermets with cobalt as the binder phase were synthesised by a two-step milling process. The titanium–tantalum carbonitride solid solution (the ceramic phase) was obtained via a mechanically induced self-sustaining reaction (MSR) process from stoichiometric elemental Ti, Ta, and graphite powder blends in a nitrogen atmosphere. Elemental Co (the binder phase) was added to the ceramic phase, and the mixture was homogenised by mechanical milling (MM). The powdered cermet was then sintered in a tubular furnace at temperatures ranging from 1400 °C to 1600 °C in an inert atmosphere. The chemical composition and microstructure of the sintered cermets were characterised as ceramic particles grown via a coalescence process and embedded in a complex (Ti,Ta)–Co intermetallic matrix. The absence of the typical core–rim microstructure was confirmed.
Adjustment of Origin-Destination Matrices Based on Traffic Counts and Bootstrapping Confidence Intervals
(SAGE Publications, 2013-01) García Benítez, Francisco; Romero Pérez, Luis Miguel; Cáceres, Noelia; Castillo Granados, José María del; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Ministerio de Obras Públicas (MOP). España
Mobility studies require, as a preliminary step, that a survey of a sample of users of the transportation system be conducted. The statistical reliability of the data determines the goodness of the results and the conclusions that can be inferred from the analyses and models generated. Because of the high costs of collection, data are partially reused in either a disaggregated or an aggregated manner. In the first case, statistical reliability is not always guaranteed; this condition affects the results that will be derived from projections and estimates of future hypothetical scenarios. A methodology is presented: it is based on bootstrapping techniques and is used for robust statistical estimation of mobility matrices. Confidence intervals of travel between origin–destination pairs defined by each matrix cell derived from a survey are generated. The result is applicable to defining the dimensions of certainty for matrix cells and subsequent adjustment by techniques based on aggregate data (e.g., traffic counts, cordon line matrices, paths). A statistically reliable data mobility study conducted in Spain at a regional level is used. Results derived from disaggregating data at an interprovincial level are presented, along with an application to the posterior mobility matrix adjustment based on traffic count data. The study results demonstrate the potential of the methodology developed and the usefulness of the conclusions.
Advanced titanium scaffolds obtained by directional freeze-drying: on the influence of processing conditions
(Frontiers, 2016) Pavón Palacio, Juan José; Trueba Muñoz, Paloma; Rodríguez-Ortiz, José Antonio; Torres Hernández, Yadir; Alonso Álvarez, Esteban; Hurtado, A.; Dunand, D.C.; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Universidad de Sevilla. Departamento de Química Analítica; Ministerio de Ciencia e Innovación (MICIN). España; Junta de Andalucía; Universidad de Sevilla. TEP123: Metalurgia e Ingeniería de los Materiales; Universidad de Sevilla. FQM344: Análisis Químico Industrial y Medioambiental
Alloy exsolution in co-doped PrBaMn₂₋ₓTMₓO₅+δ (TM = Co and/or Ni) obtained by mechanochemistry
(Elsevier, 2024-12) Gotor Martínez, Francisco José; Sayagués de Vega, María Jesús; Zamudio-García, Javier; Marrero López, David; García-García, Francisco J.; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Ministerio de Ciencia e Innovación (MICIN). España; European Commission. Fondo Social Europeo (FSO); Universidad de Sevilla. TEP123: Metalurgia e Ingeniería de los Materiales
Doped- PrBaMn₂₋ₓTMₓO₅+δ samples with TM = Co and/or Ni were synthesized by a mechanochemical route from stoichiometric oxide precursor mixtures (Pr₆O₁₁, BaO₂, MnO, NiO and CoO) using a planetary mill at 600 rpm for 150 min. A disordered ABO₃ pseudocubic perovskite phase was obtained after the milling process that was transformed, as established by XRD, into the double layered AA’B₂O₅+δ perovskite phase after annealing at 900 ◦C in a reducing atmosphere (10%H₂/Ar). The microstructural characterization by SEM, TEM, and HRTEM ascertained that this reducing treatment induced the exsolution of Ni and Co metallic nanoparticles from the doped samples. Ni-Co alloys were even exsolved when the layered manganite phase was co-doped with both transition metals. It was confirmed that the exsolution process was reversible by switching the working atmosphere from reducing to oxidizing. Polarization resistance values of the doped samples determined in symmetrical cells in air and H₂, as well as the electrochemical performance of electrolyte LSGM-supported planar cells suggested that these samples can be used as symmetrical electrodes in SOFCs.
Alumina doped Fe2O3 foams by freeze-casting for redox cycling applications
(Elsevier, 2022-10) Lloreda Jurado, Pedro Javier; Balu, Krishnakumar; Hernández-Saz, Jesús; Chicardi Augusto, Ernesto; Ferrari, Begoña; Sepúlveda Ferrer, Ranier Enrique; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Universidad de Sevilla. TEP973: Tecnología de polvos y corrosión
Hydrogen is the next energy vector for a decarbonization society but industrial production is still methane-based. The Steam Iron Process (SIP) could provide a carbon-free production and safety storage option. Here, we show that a Fe2O3-3 wt% of Al2O3 foams created by freeze-casting withstand 10 redox cycles at different temperatures with no reduction in performance or pore shrinking. The use of stearic acid as a dispersant agent/binder produces the porous structure enhancement of the foam and promotes the early reduction of the hematite phase during foam sintering. The Al2O3 incorporation was detected as a solid solution in the Fe2O3 phase at the particle surface. This result is relevant as correlated the positive values of the zeta potential observed. Freeze-casted foams could improve long-term redox performances combining a unique tailored interconnected pore structure with a specific chemical composition.
Amorphous Al-Ti Powders Prepared by Mechanical Alloying and Consolidated by Electrical Resistance Sintering
(MDPI, 2019-10) Urban, Petr; Ternero Fernández, Fátima; Caballero Sánchez, Eduardo; Nandyala, Sooraj; Montes Martos, Juan Manuel; Gómez Cuevas, Francisco de Paula; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Universidad de Sevilla. TEP971: Ingeniería de Materiales Avanzados
A novel processing method for amorphous Al50Ti50 alloy, obtained by mechanical alloying and subsequently consolidated by electrical resistance sintering, has been investigated. The characterisation of the powders and the confirmation of the presence of amorphous phase have been carried out by laser diffraction, scanning electron microscopy, X-ray diffraction, differential scanning calorimetry and transmission electron microscopy. The amorphous Al50Ti50 powders, milled for 75 h, have a high hardness and small plastic deformation capacity, not being possible to achieve green compacts for conventional sintering. Moreover, conventional sintering takes a long time, being not possible to avoid crystallisation. Amorphous powders have been consolidated by electrical resistance sintering. Electrically sintered compacts with different current intensities (7–8 kA) and processing times (0.8–1.6 s) show a porosity between 16.5 and 20%. The highest Vickers hardness of 662 HV is reached in the centre of an electrically sintered compact with 8 kA and 1.2 s from amorphous Al50Ti50 powder. The hardness results are compared with the values found in the literature.
Amorphous Phase Formation and Heat Treating Evolution in Mechanically Alloyed Ti–Cu Alloy for Biomedical Applications
(Springer, 2022-12) Urban, Petr; Astacio López, Raquel; Ternero Fernández, Fátima; Náhlík, L.; Cintas Físico, Jesús; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Universidad de Sevilla; Universidad de Sevilla. TEP971: Ingeniería de Materiales Avanzados
The present work aims to produce TixCu100-x (x=90, 80, 70, and 60) amorphous alloys by using high energy ball mill. The microstructure and possible formation of amorphous phases were characterized employing laser granulometry, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray difraction (XRD). The amorphous-crystalline transformation at high temperatures was studied according to diferential scanning calorimetry (DSC) and XRD. The Ti80Cu20 alloys were obtained in an amorphous state after 30 h of mechanical alloying, and the amorphous phase is stable up to 340 °C. At higher temperatures, this alloy crystallizes, forming the intermetallic compound Ti2Cu, and a substitutional solid solution Ti(Cu).
An alternative procedure to measure railroad track irregularities. Application to a scaled track
(Elsevier, 2019-04) Fernández Aceituno, Javier; Chamorro Moreno, Rosario; Muñoz Moreno, Sergio; Escalona Franco, José Luis; Universidad de Sevilla. Departamento de Ingeniería Mecánica y de Fabricación; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Ministerio de Ciencia, Innovación y Universidades (MICINN). España; Universidad de Sevilla. TEP111: Ingeniería Mecánica; Universidad de Sevilla. TEP123: Metalurgia e Ingeniería de los Materiales
In this paper an alternative procedure to accurately measure static railroad track irregularities is proposed and applied to a scaled railroad track. The purpose of this work is the determination of highly-precise measured data in short track segments that needs to be used as input in the validation of railroad computational models that are used for on-board railroad track measurement systems. The procedure consists of the use of a topographic total station combined with a postprocessing of the measured data that reduces misalignment errors and provide the analytical ideal geometry of the track together with its irregular geometry characterized in terms of the magnitudes of track gauge, vertical profile, alignment and cross level. Experimental results are compared to standard magnitudes of full scale tracks showing that real track geometry can differ from PSD-based predicted one. This supports the application of the proposed procedure for an accurate geometric determination of short track segments.
An approach using highly sensitive carbon nanotube adhesive films for crack growth detection under flexural load in composite structures
(Elsevier, 2019-09) Sánchez Romate, Xoan F.; Moriche Tirado, Rocío; Jiménez Suárez, Alberto; Sánchez Martínez, María; Güemes, Alfredo; Ureña Fernández, Alejandro; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Ministerio de Economía y Competitividad (MINECO). España; Gobierno de la Comunidad de Madrid
Sensing capabilities of carbon nanotube (CNT)doped adhesive films under bending conditions were investigated. Standard Mode-II coupons and skin-stringer sub-elements were manufactured while their electrical resistance was monitored. Mode-II energy fracture was improved when adding CNTs in comparison to neat adhesive joints due to their toughening effect. Electrical monitoring showed a stable increase of the electrical resistance with crack length with lower sensitivity than Mode-I testing due to a lower crack opening effect. A good agreement was observed by comparing to theoretical estimations, indicating a uniform adhesive distribution inside the joint, confirmed by SEM analysis. Monitoring tests on skin-stringer sub-elements subjected to bending load showed a similar behavior but some sharp increases were observed, especially in the last stages of the test, due to a less uniform adhesive distribution in the central region. Therefore, the proposed technique shows a high potential and applicability for Structural Health Monitoring of composite structures.
Analysis of the Influence of Starting Materials and Processing Conditions on the Properties of W/Cu Alloys
(MDPI, 2017) Montealegre-Meléndez, Isabel; Arévalo Mora, Cristina María; Pérez-Soriano, Eva María; Neubauer, Erich; Rubio Escudero, Cristina; Kitzmantel, Michael; Universidad de Sevilla. Departamento de Lenguajes y Sistemas Informáticos; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Junta de Andalucía
In this work, a study of the influence of the starting materials and the processing time used to developW/Cu alloys is carried out. Regarding powder metallurgy as a promising fabrication route, the difficulties in producingW/Cu alloys motivated us to investigate the influential factors on the final properties of the most industrially demanding alloys: 85-W/15-Cu, 80-W/20-Cu, and 75-W/25-Cu alloys. Two different tungsten powders with large variation among their particle size—fine (Wf) and coarse (Wc) powders—were used for the preparation ofW/Cu alloys. Three weight ratios of fine and coarse (Wf:Wc) tungsten particles were analyzed. These powders were labelled as “tungsten bimodal powders”. The powder blends were consolidated by rapid sinter pressing (RSP) at 900 C and 150MPa, and were thus sintered and compacted simultaneously. The elemental powders andW/Cu alloys were studied by optical microscopy (OM) and scanning electron microscopy (SEM). Thermal conductivity, hardness, and densification were measured. Results showed that the synthesis ofW/Cu using bimodal tungsten powders significantly affects the final alloy properties. The higher the tungsten content, the more noticeable the effect of the bimodal powder. The best bimodalWpowder was the blend with 10 wt % of fine tungsten particles (10-Wf:90-Wc). These specimens present good values of densification and hardness, and higher values of thermal conductivity than other bimodal mixtures.
Analysis of the microstructure and mechanical properties of Titanium-based composites reinforced by secondary phases and B4C particles produced via direct hot pressing
(MDPI, 2017) Montealegre-Meléndez, Isabel; Arévalo Mora, Cristina María; Ariza Galván, Enrique; Pérez-Soriano, Eva María; Rubio Escudero, Cristina; Kitzmantel, Michael; Neubauer, Erich; Universidad de Sevilla. Departamento de Lenguajes y Sistemas Informáticos; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Junta de Andalucía
In the last decade, titanium metal matrix composites (TMCs) have received considerable attention thanks to their interesting properties as a consequence of the clear interface between the matrix and the reinforcing phases formed. In this work, TMCs with 30 vol % of B4C are consolidated by hot pressing. This technique is a powder metallurgy rapid process. Incorporation of the intermetallic to the matrix, 20 vol % (Ti-Al), is also evaluated. Here, the reinforcing phases formed by the reaction between the titanium matrix and the ceramic particles, as well as the intermetallic addition, promote substantial variations to the microstructure and to the properties of the fabricated composites. The influences of the starting materials and the consolidation temperature (900 C and 1000 C) are investigated. By X-ray diffraction, scanning and transmission electron microscopy analysis, the in-situ-formed phases in the matrix and the residual ceramic particles were studied. Furthermore, mechanical properties are studied through tensile and bending tests in addition to other properties, such as Young’s modulus, hardness, and densification of the composites. The results show the significant effect of temperature on the microstructure and on the mechanical properties from the same starting powder. Moreover, the Ti-Al addition causes variation in the interface between the reinforcement and the matrix, thereby affecting the behaviour of the TMCs produced at the same temperature.

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