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

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

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Reactivity of aragonite with dicalcium phosphate facilitates removal of dental calculus
(Springer, 2025) Elhadad, Amir A.; Basiri, Tayebeh; Al-Hashedi, Ashwaq; Smith, Sophia; Moussa, Hanan; Veettil, Sadiya; Pérez-Soriano, Eva María; Tamimi, Faleh; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte
Dental calculus, a main contributor of periodontal diseases, is mostly composed of inorganic calcium phosphate species such as dicalcium phosphate, whitlockite, octa calcium phosphate, and hydroxyapatite. Under physiological pH 7.4, dicalcium phosphates can gradually interact with calcium carbonate to form hydroxyapatite. Therefore, we hypothesized that aragonite (Arg) could react with dental calculus, facilitating its removal. To assess the reactivity of Arg with dental calculus, we examined the changes in surface morphology, composition, and topography of Arg and dental calculus upon exposure to each other in an aqueous environment. The impact of Arg on the removal of dental calculus was assessed by brushing polished sections of dental calculus, enamel, and dentin with slurries of Arg and measuring the depth of abrasion using a stylus profilometer. Our results demonstrate that Arg can react with dental calculus in aqueous environment. This reaction increases calculus surface roughness which in turn facilitate dental calculus removal by brushing. Aragonite could be a promising abrasive for toothpaste design for management of dental calculus.
Enhancing the matrix-fiber bond in ultra-high-performance fiber-reinforced concrete using a high performance plasticizer. Impact on the flowability, physical and mechanical properties
(Elsevier, 2025) Ruiz Martínez, Jaime D.; Ríos Jiménez, José David; Pérez-Soriano, Eva María; Cifuentes Bulté, Héctor; Leiva Fernández, Carlos; Universidad de Sevilla. Departamento de Ingeniería Química y Ambiental; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Ministerio de Ciencia e Innovación (MICIN). España; Universidad de Sevilla. TEP972: Mecánica de Materiales y Estructuras; Universidad de Sevilla. TEP118: Ingeniería de los Transportes; Universidad de Sevilla. TEP123: Metalurgia e Ingeniería de los Materiales; Universidad de Sevilla. TEP142: Ingeniería de Residuos
One of the main problems in the use of ultra-high-performance fiber-reinforced concrete (UHPFRC) with steel fibers is low flowability. The addition of 2,3,4,5,6-Pentahydroxycaproic acid sodium salt (SPS) in small amounts (0.05, 0.1 and 0.15 %wt of the cement content) can significantly increase the flowability and setting time. The effects on porosity, matrix chemical composition and fiber-matrix interaction were examined, as well as its influence on strength. Improving the flowability, pores larger than 50 μm show a significant decrease, while those smaller than 0.1 μm show a significant increase. According to the results of thermo-gravimetric analysis, the production of ettringite with finer grains and staggered symbiosis improves the pore structure of the UHPFRC matrix. An improvement of the adhesion of the steel fibers to the matrix was determined by stereomicroscope images, showing evidence of a relationship between SPS dosage and the expanded concrete area surrounding the fiber. The flexural and compressive strength increased by 10 % and 8 %, respectively, when the plasticizer/cement ratio was 0.15 %.
Enrichment Methods for Metal Recovery from Waste from Electrical and Electronic Equipment: A Brief Review
(MDPI, 2025) Chicardi Augusto, Ernesto; López-Paneque, Antonio; Gallardo García-Orta, Victoria Humildad; Sepúlveda Ferrer, Ranier Enrique; Gallardo Fuentes, José María; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; EIT Raw Materials
The growing global demand for minerals and metals, coupled with fluctuations in pricing and market disruptions, has emphasised the critical role of these resources in sustaining the global economy. Waste from Electrical and Electronic Equipment (WEEE) has emerged as a promising source of raw materials, particularly for metal recycling and the valorisation of plastic fractions. In 2022, approximately 62 million metric tons of e-waste were generated worldwide, with projections indicating a rise to 74 million metric tons by 2030. Despite the significant volume of WEEE, only 17.4% was collected and recycled, which reveals a considerable opportunity for resource recovery. This review highlights the composition of metals in WEEE, which includes valuable precious metals, such as gold, silver, and palladium, alongside base metals, such as copper and aluminium. The review also discusses current methodologies for metal recovery and focuses on mechanical size-reduction techniques and various physical separation methods, including a shaking table, magnetic, electrostatic, and eddy current separation, flotation, and the use of a hydrocyclone. These technologies play a vital role in enhancing recovery efficiencies, thereby contributing to sustainable practices in the recycling industry. Thus, the works evaluated in this paper reveal the possibility of recovering more than 90 wt.% of precious (Ag, Au, Pd, Pt) and main metals (Cu, Sn, Al, Fe, Ni) by a combination of these mechanical size-reduction and physical separation methods.
Efect of nano silicon nitride on the microstructural characteristics and mechanical properties of ultra‑high‑performance steel fber reinforced concrete
(Springer Nature, 2025) Ruiz Martínez, Jaime D.; Ríos Jiménez, José David; Pérez-Soriano, Eva María; Cifuentes-Bulté, Héctor; Leiva Fernández, Carlos; Universidad de Sevilla. Departamento de Ingeniería Química y Ambiental; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Ministerio de Ciencia e Innovación (MICIN). España; Universidad de Sevilla. TEP142: Ingeniería de Residuos; Universidad de Sevilla. TEP123: Metalurgia e Ingeniería de los Materiales; Universidad de Sevilla. TEP972: Mecánica de Materiales y Estructuras
This study investigates the incorporation of an innovative nano-reinforcement, nano silicon nitride (NSIN), to enhance the workability and mechanical performance of ultra-high-performance fber reinforced concrete. The addition of NSIN at dosages of 0.25, 0.5, 0.75, and 1.5 wt% of cement was analyzed to evaluate its impact on the distribution and interaction between steel fbers and the cementitious matrix. Experimental analyses, including thermogravimetric analysis (TGA), transmission electron microscopy (TEM), and scanning electron microscopy (SEM), were conducted to establish a relationship between the microstructural modifcations, fber-matrix interactions, and the resulting mechanical behavior. The fndings revealed that NSIN increased workability and extended setting time, enabling improved steel fber dispersion and interaction
Influence of the processing variables on the microstructure and properties of gelatin-based scaffolds by freeze-drying
(Wiley, 2019-02-23) Pérez-Puyana, Víctor Manuel; Félix Ángel, Manuel; Romero García, Alberto; Guerrero Conejo, Antonio Francisco; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Universidad de Sevilla. Departamento de Ingeniería Química; Ministerio de Economía, Industria y Competitividad, España; Universidad de Sevilla; Universidad de Sevilla. TEP229: Tecnología y Diseño de Productos Multicomponentes
In the last few years, the field of tissue engineering has suffered an exponential growth, and although it is true that the processing parameters affect the properties of the scaffolds, only a few studies have investigated that statement. For that reason, the influence of different parameters involved in the freeze-drying process (container, freezing temperature, pH, and solvent used) on the mechanical and structural properties of gelatin-based scaffolds was analyzed in this study. Thus, rheological measurements and porosity analyses were performed to evaluate the scaffolds obtained. Results indicate that the parameters evaluated modify the mechanical properties of the scaffold, highlighting the option of a plastic mold to contain an acidic protein solution produced using a weak acid (acetic acid) at low concentration (0.05 M) as solvent. On the contrary, only the pH and the freezing temperature led to significant differences in the porosity of these scaffolds, obtaining values higher than 95% for all the systems studied. These results are useful to demonstrate that the control of the different parameters implied in the processing technique allows designing a scaffold with specific properties suitable for different applications.
Experimental study of the use of a transfer function to find rail corrugation from axle-box accelerations
(Elsevier, 2025-05) Yu, Xinxin; Muñoz Moreno, Sergio; Urda Gómez, Pedro; Fernández Aceituno, Javier; Rodríguez Gómez, Miguel; Escalona Franco, José Luis; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Universidad de Sevilla. Departamento de Ingeniería Mecánica y Fabricación; Consejería de Economía, Ciencia, Empresa y Universidades. Junta de Andalucía; Ministerio de Ciencia, Innovación y Universidades (MICIU). España; Universidad de Sevilla. TEP111: Ingeniería Mecánica; Universidad de Sevilla. TEP123: Metalurgia e Ingeniería de los Materiales
This investigation uses a scale vehicle-track experimental facility to study the calculation of rail corrugation using vertical accelerations measured in the axle-box of rail vehicles and a transfer function (TF). The rail corrugated profile is machined in the rail heads of the scale track following a periodic function with four harmonics. Experiments are performed with a scale bogie-like vehicle at different forward velocities in the range inspection velocities. Two simple analytical forms of the TF are studied: the kinematic TF, that assumes that the axle box follows the rail profile, and the TF of a 2-dof model of the vehicle-track system. For the vehicle response analysis, this work proposes to normalize the measured acceleration with the square of the forward velocity of the vehicle, that is assumed to be approximately constant. This normalized acceleration reduces the effect of the forward velocity on the TF. Experimental results show that the kinematic TF can be used to measure the track corrugation for moderate forward velocities providing reasonable but not accurate results. The limitation of the kinematic TF is mainly due to free flights and wheel rail curvature incompatibility. The measured axle-box accelerations may include frequency peaks that are not excitation frequencies and can distort the rail profile measurement. Results show that linear elastic models like the assumed 2-dof model do not explain the appearance of these non-excitation peaks.
Silk-Sericin Release from Polymeric Scaffold as Complementary Dermocosmetic Treatment for Acne
(MDPI, 2025-03-14) Vargas González, Arianna; Pérez Ramos, Patricia; Pérez-Soriano, Eva María; Sola Dueñas, Francisco Javier; Pérez Almazán, Denise; García Couce, Jomarien; Fuentes Estévez, Gastón; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Universidad de Sevilla. TEP123: Metalurgia e Ingeniería de los Materiales
Currently, acne therapy relies not only on specific drugs but also on complementary treatments, such as dermocosmetics. Several studies have reported the use of chitosan and alginate in scaffolds for drug delivery systems. These materials can be loaded with a product that exhibits anti-acne properties such as silk sericin, a protein with antioxidant, photoprotective, and moisturizing properties. Therefore, this study proposes the development of a chitosan/alginate scaffold, loaded with sericin, to serve as a dermocosmetic platform complementing the pharmacological treatment of acne. The moisture content of the alginate and chitosan was determined as 14.7 and 21%, respectively; the ash content, which is similar for both polymers, was approximately 5%. The employed chitosan had a deacetylation degree of 82%, as determined by infrared spectrometry and corroborated by potentiometry. This technique was also used to determine the mannuronic/guluronic ratio of the alginate [M/G = 1.3] and confirm the identity of each one of the polymers in the raw materials and the resulting scaffolds. The molecular weights of alginate, chitosan, and sericin were 85, 5.1, and 57.4 kDa, respectively. The pH [6.31] and total protein concentration of the sericin solution [c(SER) = 6.1 mg/mL] were determined using UV-visible spectrophotometry. Swelling and release studies indicated that, although there were varying degrees of cross-linking and certain variables to control, the mechanism that defines the nature of both processes (otherwise complementary) is the relaxation of the polymer chains.
Influence on the properties of TMCs of ceramic and intermetallic composite reinforcements (B₄C, TiₓAly and TiₓSiy) fabricated by inductive hot pressing
(Elsevier, 2024-09-30) Arévalo Mora, Cristina María; Montealegre-Meléndez, Isabel; Neubauer, Erich; Kitzmantel, Michael; Lascano, Sheila; Pérez-Soriano, Eva María; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Universidad de Sevilla. TEP123: Metalurgia e Ingeniería de los Materiales
Ambitious and competitive, the aerospace industry continuously demonstrates to be one of the leading engineering sectors either at exigence and new technologies development. As lightning the weight of aircrafts is one of the main targets, the spotlight is usually on material research by which new ones may be produced to pursue this aim and still offer the necessary performances. The combination of the properties of titanium and other materials as reinforcements provides really interesting results as titanium matrix composite materials, also known as TMCs. Various samples of titanium matrix composite materials with different reinforcements have been under study to determine the influence of the reinforcements and their respective proportions on the properties of the material. These samples composed of grade 1 commercially-pure titanium as matrix and B₄C, TiₓAly and TiₓSiy as reinforcements, have been manufactured through powder metallurgy in the same conditions of temperature and pressure via Inductive Hot Pressing (IHP). A total of eight composite materials have been arranged in several different groups to confront their compositions. Thus, this analysis reports results for the influence of the powder size of the matrix and the ceramic reinforcement, the effect of varying the volumetric composition of B₄C, and the selection of different intermetallic reinforcements. These tests and the obtained information serve for a project in which the main goal is to determine which compositions of the studied composite materials reach a high enough specific stiffness for a suitable application in the aerospace industry.
Alloy exsolution in co-doped PrBaMn₂₋ₓTMₓO₅+δ (TM = Co and/or Ni) obtained by mechanochemistry
(Elsevier, 2024-12-15) Gotor Martínez, Francisco José; Sayagués de Vega, María Jesús; Marrero-López, D.; García García, Francisco José; García García, Francisco José; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Ministerio de Ciencia e Innovación (MICIN). España; European Commission (EC); 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.
Enabling low molecular weight electrospinning through binary solutions of polymer blends
(Elsevier, 2025-01) Pérez-Puyana, Víctor Manuel; Romero García, Alberto; Guerrero Conejo, Antonio Francisco; Moroni, Lorenzo; Wieringa, Paul; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Universidad de Sevilla. Departamento de Ingeniería Química; Ministerio de Economía y Competitividad (MINECO). España; Universidad de Sevilla. TEP229: Tecnología y Diseño de Productos Multicomponentes
The formation of nanofibrous membranes via electrospinning is typically restricted to high molecular weight polymers in an appropriate solvent, correlated with the necessary formation of polymer chain entanglements that are needed to achieve successful production of electrospun fibers. The present work extends the electrospinning of low molecular weight polymers by investigating the electrospinning of a binary solution system consisting of two different low molecular weight polymers, using as a model system polycaprolactone (PCL) and gelatin in different ratios. The viscosities of the polymer solutions were characterized as a proxy for polymer chain entanglement and the resulting fibers were morphologically characterized by SEM imaging and further assessed water contact angle and molecular composition to determine the impact and homogeneity of the binary mixtures. We found that unitary solutions of either PCL or gelatin failed to generate proper fibers despite indications of chain entanglement. In contrast, binary solutions of low molecular weight PCL and gelatin generated different fiber quality and size distributions, depending on the ratio used, with direct correlations between fiber properties and the PCL:Gelatin ratio. It was discovered that the ratio of PCL to gelation was most predictive for successful fiber generation, with effective electrospinning occurring only for a define intermediate range of high blend ratios while both low and high blended binary solutions resulted in poor fiber production. Our study confirmed that this behavior was independent from absolute polymer concentration, indicating a unique interaction between these binary species which exists only under specific ratio concentrations and indicates promising new avenues to process low molecular weight polymers solutions.
Hydrogels and Nanogels: Pioneering the Future of Advanced Drug Delivery Systems
(MDPI, 2025-02-07) Delgado-Pujol, Ernesto J.; Martínez Muñoz, Guillermo; Casado Jurado, David; Vázquez Cabello, Juan; León-Barberena, Jesús; Rodríguez Lucena, David; Torres Hernández, Yadir; Alcudia Cruz, Ana; Begines Ruiz, Belén; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Universidad de Sevilla. Departamento de Química Orgánica y Farmacéutica; Universidad de Sevilla. Departamento de Química Orgánica; Ministerio de Ciencia e Innovación (MICIN). España; Universidad de Sevilla. TEP123: Metalurgia e Ingeniería de los Materiales; Universidad de Sevilla. FQM408: Química Farmacéutica Aplicada
Conventional drug delivery approaches, including tablets and capsules, often suffer from reduced therapeutic effectiveness, largely attributed to inadequate bioavailability and difficulties in ensuring patient adherence. These challenges have driven the development of advanced drug delivery systems (DDS), with hydrogels and especially nanogels emerging as promising materials to overcome these limitations. Hydrogels, with their biocompatibility, high water content, and stimuli-responsive properties, provide controlled and targeted drug release. This review explores the evolution, properties, and classifications of hydrogels versus nanogels and their applications in drug delivery, detailing synthesis methods, including chemical crosslinking, physical self-assembly, and advanced techniques such as microfluidics and 3D printing. It also examines drug-loading mechanisms (e.g., physical encapsulation and electrostatic interactions) and release strategies (e.g., diffusion, stimuli-responsive, and enzyme-triggered). These gels demonstrate significant advantages in addressing the limitations of traditional DDS, offering improved drug stability, sustained release, and high specificity. Their adaptability extends to various routes of administration, including topical, oral, and injectable forms, while emerging nanogels further enhance therapeutic targeting through nanoscale precision and stimuli responsiveness. Although hydrogels and nanogels have transformative potential in personalized medicine, challenges remain in scalable manufacturing, regulatory approval, and targeted delivery. Future strategies include integrating biosensors for real-time monitoring, developing dual-stimuli-responsive systems, and optimizing surface functionalization for specificity. These advancements aim to establish hydrogels and nanogels as cornerstones of next-generation therapeutic solutions, revolutionizing drug delivery, and paving the way for innovative, patient-centered treatments.
Simulation of the electrical resistance sintering process by means of fnite diference in a spreadsheet
(Springer, 2025) Montes Martos, Juan Manuel; Ternero Fernández, Fátima; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Ministerio de Ciencia e Innovación (MICIN). España; Agencia Estatal de Investigación. España; European Union (UE)
In this work, a theoretical model for the metal powder consolidation technique known as Electrical Resistance Sintering (ERS) is proposed and validated. This technique consists of the consolidation of a mass of metal powder by the simultaneous action of pressure and the passage of a high intensity electric current. This electric current heats the powder mass by the Joule effect, while softening it so that the imposed pressure causes its densification. The proposed model meets the set objective of seeking the greatest possible simplicity, without ignoring the key aspects of the technique. In line with this simplicity, the proposed model has a one-dimensional character and is solved numerically by means of Finite Difference through a simulator implemented in the Microsoft Excel™ spreadsheet environment, programming in VBA, with computation times not exceeding 5 min. The adopted strategy takes into account the strong electrical–mechanical-thermal coupling present in the process. The sensors incorporated in the ERS equipment allow the recording of the data necessary to construct the evolution curves of the global porosity and the thermal energy released. The theoretical predictions provided by the simulator have been compared with experimental curves obtained from the electrical consolidation experiments with commercially pure iron powder. Discrepancies between experimental and theoretical values for final global porosity are around 5% (although approaching 20% in the vicinity of critical conditions) and those for final specific thermal energy do not exceed 7%. The reasonable agreement between the experimental and theoretical curves gives confidence that the model, despite its simplifications, reproduces the main characteristics of the process.
Porosity efect on the thermal conductivity of sintered powder materials
(Springer, 2025-02) Montes Martos, Juan Manuel; Gómez Cuevas, Francisco de Paula; Cintas Físico, Jesús; Ternero Fernández, Fátima; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Ministerio de Ciencia e Innovación (MICIN). España; Agencia Estatal de Investigación. España; European Union (UE)
In this work, the effective thermal conductivity of sintered powder materials is studied. The extensive literature related to the proposed models about this property in all kind of porous materials is reviewed, and a new equation is proposed as a function of the fully dense material conductivity, the porosity of the material and the tap porosity of the starting powder. This equation covers the porosity range of powder aggregates from the tap porosity to zero porosity, and also applies to sintered powders. The proposed equation has been experimentally validated by fitting to experimental data of metallic sintered powder materials measured at room temperature, resulting very good agreements. Also, alternative models proposed by other authors have been fitted to the same experimental data to check the relative goodness of the proposed model. The results allow to conclude that a percolation model can describe the behaviour of the effective thermal conductivity of sintered powder materials with low and medium porosity levels.
Ion beam induced secondary electron tomography of acrylonitrile-styrene-acrylate/polycarbonate polymer blends for fused filament fabrication and injection moulding
(Nature Portfolio, 2025) Hernández-Saz, Jesús; Moreno Sánchez, Daniel; Valencia Liñán, Luisa María; Gómez, Y.; Molina Rubio, Sergio Ignacio; Herrera Collado, Miriam; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Junta de Andalucía; European Union (UE)
Polymer blending is an interesting strategy to broaden the combination of properties available for a variety of applications. To understand the behaviour of the new materials obtained as well as the influence of the fabrication parameters used, methods to analyse the distribution of polymers in the blend with resolution below the micrometer are required. In this work, we demonstrate the capability of focused ion beam (FIB) tomography to provide 3D information of the polymer distribution in objects obtained by blending acrylonitrile-styrene-acrylate (ASA) with polycarbonate (PC) (50 wt%), fabricated by Fused Filament Fabrication (FFF) and by Injection Moulding (IM). For this, ion beam induced secondary electron (iSE) images show the capability to distinguish unequivocally the two phases in the blend, providing enough contrasts to perform the 3D experiment. Additionally, Monte Carlo simulations show that the lateral spread for incident electrons in PC is 61.7 nm and for Ga+ ions of 26.2 nm, evidencing a better spatial resolution in iSE imaging. The sputtering rate under the ion beam has been quantified for both neat ASA and neat PC to find optimal parameters for the iSE tomography, resulting in a current of 0.05 nA and a dwell time of 3 µs. Our results reveal significant differences in the morphology of ASA/PC blends depending on the fabrication method. Blends obtained by FFF exhibit strong directionality and a co-continuous morphology, whereas IM objects present a droplet-matrix structure. Also, the interface area between the ASA and PC is quantified to be of 3200 μm² for the FFF sample and 1400 μm² for the IM sample, approximately double in FFF than in IM. The reasons for the different morphologies obtained in the studied blends and possible effects in their mechanical properties are discussed.
Compositional and microstructural study of joining methods in archaeological gold objects
(John Wiley and Sons Ltd, 2017-03) Scrivano, Simona; Gómez-Tubio, Blanca María; Ortega-Feliú, Inés; Ager Vázquez, Francisco José; Paúl Escolano, Antonio; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; Universidad de Sevilla. Departamento de Física Aplicada III; Universidad de Sevilla. Departamento de Física Aplicada I; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Ministerio de Economía y Competitividad (MINECO). España
This work arises in response to the need to understand the production techniques of pre-roman gold jewels, starting from the systematic characterization of the different methods of metal joining used in antiquity to produce these objects. To meet this requirement, different procedures used in antiquity were reproduced by means of experimental archaeology. These models correspond to three metal-joining methods reported by ancient recipes: solid-state diffusion with copper salt, brazing and autogenous welding. These techniques were studied by different analytical methods in order to characterize them at both compositional and microstructural level (SEM-EDS, metallography, μ-XRF and μ-PIXE). The results obtained show that the solid-state diffusion bonding with copper salt presents a crystal hexagonal structure without phase changes in the joining point, where only a variation in the grain size is observed. At the compositional level, this soldering method is characterized by a local increase in copper concentration and a small decrease in gold content. In contrast, brazing shows a dendritic-porous structure due to the superposition of the soldering alloy and the crystal structure of the original foils. Besides, the compositional analysis revealed an increment of silver and copper concentrations and a simultaneous reduction of gold concentration. Finally, in the autogenous welding, no changes at the microstructural and compositional levels were observed. The results obtained have also demonstrated the usefulness of a portable μ-XRF system for the in-situ characterization of ancient jewels.
Combining XRF and GRT for the analysis of ancient silver coins
(Elsevier, 2016-05) Ager Vázquez, Francisco José; Gómez-Tubio, Blanca María; Paúl Escolano, Antonio; Gómez-Morón, A.; Scrivano, Simona; Ortega-Feliú, Inés; Respaldiza Galisteo, Miguel Ángel; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; Universidad de Sevilla. Departamento de Física Aplicada I; Universidad de Sevilla. Departamento de Física Aplicada III; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Ministerio de Economía y Competitividad (MINECO). España
Archaeological silver-copper alloys are usually affected by silver enrichment of the near surface layers, either intentional or fortuitous. In previous studies we have shown that surface composition of archaeological bronzes and leaded copper coins obtained by XRF can be corrected by means of gamma-ray transmission (GRT) to obtain the bulk composition. In the present work, we have studied the applicability of this method to silver-copper alloys and established the most suitable conditions for the GRT correction calculation. The analysis of the microstructure of the core and the corrosion layers of a set of silver roman coins shows that copper could be leached from the surface during corrosion and cleaning treatments, resulting in an apparent silver surface enrichment. After the correction calculations by GRT method, the concentrations of the major elements, Ag and Cu, were found to be in good agreement with the bulk composition obtained by direct analysis of the cut cross-sections of the coins. The GRT method shows to be a useful tool to study metal artefacts having a surface composition modified by corrosion or cleaning treatments.
Camphene/polystyrene solutions: A rheological approach for material processing industry
(John Wiley & Sons Inc., 2019-05-11) Félix Ángel, Manuel; Pérez-Puyana, Víctor Manuel; Paúl Escolano, Antonio; Sepúlveda Ferrer, Ranier Enrique; Universidad de Sevilla. Departamento de Ingeniería Química; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Ministerio de Economia, Industria y Competitividad (MINECO). España
Rheological properties of polymer–camphene solutions are very relevant as they affect their stability, and they have many implications in operation costs. This work elucidates the rheological properties of polystyrene (PS–camphene) solutions with industrial applications. Unfortunately, the assessment of the very low shear viscosities of camphene-based materials (below 0.005 Pa s) is still a challenge with commercial rheometers. Flow curves, stress growth tests, and small amplitude oscillatory shear (SAOS) measurements were carried out as a function of PS concentration (0, 2.5, 5.0, 10, and 20 wt % PS) to understand the rheological behavior of these systems. Results indicate that liquid camphene has a shear-thinning behavior (flow index = 0.99) when the increase of polymer concentration involves changes in the structure of these systems (flow index = 0.10 for 20 wt % PS). An increase in PS concentration leads to a forwarding in the shear-thinning zone, and the Newtonian region (from ∼1 s−1, for 0 wt % PS, to 10−3 s−1 for 20 wt % PS). Eventually, these results evidence the high dependence of η∞ on PS concentration (from ∼1.16 ± 0.01 Pa s, for 0 wt % PS, to 631.5 ± 0.2 Pa s for 20 wt % PS). © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47953.
Conformal TiO₂ Aerogel-Like Films by Plasma Deposition: from Omniphobic Antireflective Coatings to Perovskite Solar Cell Photoelectrodes
(American Chemical Society, 2024-07-20) Obrero Pérez, José M.; Contreras Bernal, Lidia; Aparicio Rebollo, Francisco Javier; Rojas, Teresa C.; Ferrer Troyano, Francisco Javier; Orozco, Noe; Saghi, Zineb; Czermak, Triana; Pedrosa, José María; López Santos, Carmen; Ostrikov, Kostya Ken; Borrás Martos, Ana Isabel; Sánchez Valencia, Juan Ramón; Barranco Quero, Ángel; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Universidad de Sevilla. Departamento de Lenguajes y Sistemas Informáticos; Universidad de Sevilla. Departamento de Física Aplicada I; Ministerio de Ciencia e Innovación (MICIN). España; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER); Junta de Andalucía; Universidad de Sevilla; European Union (UE). H2020; Universidad de Sevilla. TEP123: Metalurgia e Ingeniería de los Materiales
The ability to control the porosity of thin oxide films is a key factor determining their properties. Despite the abundance of dry processes for synthesizing oxide porous layers, a high porosity range is typically achieved by spin-coating-based wet chemical methods. Besides, special techniques such as supercritical drying are required to replace the pore liquid with air while maintaining the porous network. In this study, we propose a new method for the fabrication of ultraporous titanium dioxide thin films at room or mild temperatures (T ≤ 120 °C) by a sequential process involving plasma deposition and etching. These films are conformal to the substrate topography even for high-aspect-ratio substrates and show percolated porosity values above 85% that are comparable to those of advanced aerogels. The films deposited at room temperature are amorphous. However, they become partly crystalline at slightly higher temperatures, presenting a distribution of anatase clusters embedded in the sponge-like open porous structure. Surprisingly, the porous structure remains after annealing the films at 450°C in air, which increases the fraction of embedded anatase nanocrystals. The films are antireflective, omniphobic, and photoactive, becoming superhydrophilic when subjected to ultraviolet light irradiation. The supported, percolated, and nanoporous structure can be used as an electron-conducting electrode in perovskite solar cells. The properties of the cells depend on the aerogel-like film thickness, which reaches efficiencies close to those of commercial mesoporous anatase electrodes. This generic solvent-free synthesis is scalable and applicable to ultrahigh porous conformal oxides of different compositions, with potential applications in photonics, optoelectronics, energy storage, and controlled wetting.
Design, processing and characterization of advanced titanium scaffolds with controlled radial porosity: a new sequential compaction device
(Elsevier, 2016) Pavón, Juan; Trueba Muñoz, Paloma; Rodríguez, José Antonio; Torres Hernández, Yadir; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Ministerio de Ciencia e Innovación (MICIN). España; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER); Universidad de Sevilla. TEP123: Metalurgia e Ingeniería de los Materiales
Biological systems like those that are involved in many human tissues are perhaps one of the most exciting and inspiring examples of graded highly anisotropic hierarchical materials. In this work, we are initially focused on phenomenological relationships between bone structure, its mechanical properties and most frequent damages. Current status of biomedical materials for bone replacement clearly indicates that titanium (Ti) and some of its alloys are still the better metallic material clinically used to that purpose. The stiffness mismatch between Ti and bone, around one-order magnitude (~110 GPa against ~20GPa), is one of those current challenges that require to be overcome; the associated stress shielding is main the cause of the clinically observed bone resorption around Ti implants. This is an ideal scenario in which functionally graded materials (FGMs) become a powerful alternative to offer new alternatives for better bone implants. The aim of this work is the development of a novel compaction device that responds to necessity of fabricating new components with controlled graded radial porosity.
Effect of Copper Addition on Pitting Corrosion of MA-Al
(Polish Academy of Sciences, 2016-04) Aranda, B.; Cuevas, F. G.; Cintas Físico, Jesús; Herrera García, Marta; Urban, Petr; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Ministerio de Ciencia, Innovación y Universidades (MICIU)
This paper is intended to highlight the effect of copper addition on the pitting corrosion resistance of aluminium-base powder metallurgy parts. Results obtained on these mechanically alloyed (MA) specimens are compared with parts of MA-Al without added copper, as well as with commercial aluminium alloys. Immersion tests from 2 to 96 hours in 3.5% NaCl solutions, and potentiostatic techniques, were used to study the pitting corrosion. It was concluded that copper addition, in a similar way that in commercial aluminium alloys, produces a negative effect on the pitting corrosion resistance, because of the formation of Al2Cu. These precipitates produce galvanic cells that favour the specimen pit. Therefore, increasing the copper content of MA-Al, although improving their ductility, worsens the pitting corrosion resistance of these alloys.

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