Tesis Doctorals - Departament - Ciència dels Materials i Química Física

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Characterization of protein conformational ensembles from Förster resonance energy transfer simulations
(Universitat de Barcelona, 2025-04-02) Gonzalo Palao, Daniel; Curutchet Barat, Carles E.; Universitat de Barcelona. Departament de Ciència dels Materials i Química Física
[eng] This thesis focuses on the study of partially disordered proteins (IDPs), using calmodulin (CaM) as the system under study. Calmodulin is a crucial protein involved in numerous physiological processes, and its well-documented structure and function make it an ideal candidate for this research. The primary aim is to explore the conformational ensembles of calmodulin through molecular dynamics (MD) simulations, using two distinct force fields: Amber ff14SB, widely used for proteins, and a99SB-disp, specifically refined for disordered proteins like CaM. By generating and analyzing FRET observables, the study evaluates which force field better reflects the dynamic behavior of calmodulin. A central component of this work is the application of Förster Resonance Energy Transfer (FRET) to gain insights into protein conformational dynamics. Advanced computational methods, including TrESP-MMPol and QM/MMPol, are employed to model the energy transfer process and assess how environmental factors affect FRET observables. A particular emphasis is placed on environmental screening, which describes how interactions between the chromophores and their surroundings such as solvent molecules or protein structures modify energy transfer. This screening effect addresses limitations in traditional models, offering a more accurate representation of real-world systems. In addition to environmental screening, this thesis explores key factors influencing FRET, such as Coulombic dipole interactions and orientational anisotropy between the chromophores. A novel screening function is also introduced to study how environmental effects depend on distance, enhancing our understanding of energy transfer in complex biological systems. By connecting theoretical models with experimental data, this research deepens our understanding of calmodulin's confirmational and functional behavior. Through the integration of computational simulations and FRET methodologies, this work advances our ability to study partially disordered proteins and contributes valuable insights to the broader field of protein dynamics and energy transfer.
Recobriments d'or: avançant cap a una tecnologia més sostenible
(Universitat de Barcelona, 2025-07-21) Amazian El Moussaoui, Mohamed; Sarret i Pons, Maria; Andreu Arbella, Teresa; Universitat de Barcelona. Departament de Ciència dels Materials i Química Física
[cat] En la indústria dels recobriments decoratius destaca l'ús d'aliatges d'or. Aquests recobriments es fabriquen majoritàriament mitjançant l’electrodeposició, una tècnica que requereix temps de treball reduïts i que permet controlar amb precisió les propietats del material. L'aliatge ternari AuCuIn és un dels més utilitzats, i disposa d'un procediment comercial establert i reproduïble. Tot i això, la seva electrodeposició presenta certs reptes industrials, com la baixa estabilitat de l’electròlit utilitzat, o l'ús d'espècies químiques perilloses per al medi ambient i la salut humana, com el cianur i certs additius orgànics. En aquest context, aquesta tesi doctoral té com a objectiu abordar els punts febles associats al sistema d’obtenció de l’aliatge AuCuIn per electrodeposició. Inicialment, s’ha dissenyat un electròlit amb una composició controlada i estable, que resol els problemes associats a la precipitació de l’indi en medis alcalins cianurats. Per aconseguir-ho, s’ha realitzat un estudi experimental-computacional on s’estudia l’efecte estabilitzant de la D-glucosa. A continuació, es descriu el procés d’electrodeposició utilitzant l’electròlit cianurat dissenyat, prescindint dels additius que contenen les formulacions comercials. En el seu lloc, s’ha emprat l’electrodeposició per corrent polsant i corrent polsant revers obtenint recobriments amb propietats semblants a les dels comercials. Els bons resultats obtinguts han motivat l’escalat industrial, ajustant els paràmetres operatius de l’obtenció de l’aliatge AuCuIn als processos industrials actuals. Paral·lelament, s’ha desenvolupat un electròlit alternatiu al cianurat per electrodipositar aliatges binaris AuCu, utilitzant citrat de sodi com a agent complexant. Els recobriments obtinguts presenten propietats similars als comercials, així com als electrodipositats mitjançant l’electròlit cianurat estudiat anteriorment. Aquests recobriments també han presentat una millora substancial en les seves característiques quan s’han electrodipositat per corrent polsant. La formulació de l’electròlit de citrat dissenyat és més senzilla i estable que la de l’electròlit cianurat. Finalment, d’acord amb el rerefons de sostenibilitat mediambiental de la tesi, i aprofitant la versatilitat de la tècnica d’electrodeposició, s’han obtingut diversos aliatges, que inclouen or, coure i indi, com a electrocatalitzadors. Els resultats obtinguts confirmen la seva viabilitat en la conversió electrocatalítica de CO2 a altres productes d’interès químic, especialment CO i HCOOH, utilitzant elèctrodes de difusió de gas com a substrat. Els resultats exposats en aquesta tesi doctoral no només contribueixen a la millora de l’obtenció i aplicació de recobriments d’or, sinó que també obren nous camins de recerca en diversos camps d’investigació.
Development and assessment of magnesium phosphate cements by using industrial by-products and wastes
(Universitat de Barcelona, 2025-05-16) Alfocea Roig, Anna; Formosa Mitjans, Joan; Giró Paloma, Jessica; Universitat de Barcelona. Departament de Ciència dels Materials i Química Física
[eng] The construction sector is globally recognized as a significant contributor to environmental pollution, particularly in terms of climate change and the depletion of natural resources. These environmental impacts arise from various factors, including the materials used, the technologies applied, and transportation processes involved. In response, the industry is increasingly prioritizing strategies to reduce its carbon footprint by adopting innovative solutions that minimize environmental impact and promote sustainability. One such approach is the development of alternative cements that valorise industrial by-products and wastes. These efforts aim to conserve natural resources, protect the environment, and promote sustainable construction practices. Among these alternatives, magnesium phosphate cement (MPC) has gained recognition as a promising option. MPC is typically composed of a magnesium oxide (MgO) source and a phosphate source. However, due to the high carbon dioxide emissions associated with the production of pure magnesium oxide, identifying sustainable alternatives is essential to minimizing their environmental impact. This PhD thesis explores the feasibility of using industrial by-products and wastes as substitutes for pure magnesium oxide in the production of MPC. Specifically, it focuses on tundish deskulling waste (TUN), a waste of the steel industry, and low-grade magnesium oxide (LG-MgO; LG), a by-product derived from magnesite calcination. This approach aligns with principles of the circular economy, promotes efficient wastes management, and contributes to the achievement of sustainable development goals (SDGs), particularly in addressing climate change. The research began with a comprehensive evaluation of the global landscape of alternative magnesium oxide sources, offering valuable context while identifying existing opportunities and challenges. Following, a detailed investigation was conducted into the properties of TUN, marking its first-ever application as a raw material for MgO-based cements. The analysis assessed its suitability for cement formulations, its performance in mortar development, and, finally, its environmental impact through a life cycle assessment (LCA). Subsequent chapters focused on the characterization of cements incorporating TUN and LG-MgO. The first study examined the synergistic effects of combining these materials, emphasizing their compatibility and mutual benefits. The second study shifted attention solely on LG-MgO, exploring its versatility and potential for innovative applications in the construction sector. The present doctoral thesis highlights the transformative potential of alternative secondary sources, such as TUN and LG-MgO, as sustainable raw materials for MPC production. By minimizing the environmental footprint of conventional cement formulations, this research offers a pathway for a greener and more sustainable construction industry, emphasizing the pivotal role of industrial by-products and wastes in the advancement of cementitious materials.
Struvite precipitation in municipal wastewater treatment plants using a magnesium oxide by-product
(Universitat de Barcelona, 2025-09-09) Aguilar Pozo, Verónica-Belén; Chimenos Ribera, Josep Ma.; Astals Garcia, Sergi; Universitat de Barcelona. Departament de Ciència dels Materials i Química Física
[eng] Phosphorus has been classified as a critical raw material by the European Union (EU) due to its economic importance, price volatility, and supply risks. This has driven research into alternative secondary sources for phosphorus recovery, particularly in wastewater treatment plants (WWTPs), where the majority of phosphorus losses occur. In the EU, approximately 54 % of imported phosphorus is lost through wastewater. Recovering phosphorus from these streams aligns with circular economy principles and enhances resource recovery. Struvite precipitation is a promising approach for phosphorus recovery, with the potential to supply nearly 13 % of the EU’s phosphorus fertiliser demand. Additionally, phosphorus recovery can reduce its concentration in wastewater streams, leading to cost savings related to (i) chemical dosing for phosphorus removal and (ii) maintenance issues caused by uncontrolled struvite scaling in pipelines and equipment. In recent years, there has been a significant increase in full-scale phosphorus recovery facilities. North America leads in struvite production, while the EU has the highest number of operational full-scale struvite recovery units. Currently, over 80 full-scale plants worldwide recover phosphorus from industrial and municipal wastewater, employing technologies such as PHOSPAQ®, ANPHOS®, NeReSys®, Struvia™, PHOSNIX®, Ostara Pearl®, and PhosphoGREEN. These processes use MgCl2, MgO, or Mg(OH)2 as magnesium sources and they primarily increase pH by CO2 stripping or by adding NaOH. However, reagent costs pose a major limitation, as magnesium and alkaline agents account for approximately 75 % of operating expenses, particularly in streams with low phosphorus concentrations. This thesis investigates the feasibility of using an industrial by-product, low-grade magnesium oxide (LG-MgO), as a single reagent for phosphorus recovery via struvite precipitation. When added to anaerobic digestion supernatant, LG-MgO releases both magnesium and hydroxide ions, acting simultaneously as a magnesium source and an alkaline reagent. Phosphorus recovery yields ranged from 50 to 90 %, primarily influenced by the P:Mg molar ratio, the phosphorus concentration in the supernatant, and the reactivity of the LG-MgO used. The resulting precipitates consisted mainly of struvite, with a purity between 72 and 88 wt%. Significantly, the findings support struvite precipitation in streams with low phosphorus concentrations when struvite seed is added, as these conditions promote particle growth. Moreover, the use of LG-MgO reduces operating costs. An economic analysis showed that the reagent cost to produce one tonne of struvite was significantly lower when using LG-MgO (73 €) compared to MgCl2·6H2O and NaOH (940 €) at a phosphorus recovery efficiency of approximately 90 %. These findings highlight LG-MgO as a cost-effective alternative to conventional magnesium sources for struvite precipitation. Its application not only reduces operational costs but also adds value to an industrial by-product, promoting resource efficiency and advancing the circular economy.
Métodos químico-físicos para despintar parachoques de coche para su revalorización en automoción mediante reciclaje
(Universitat de Barcelona, 2025-07-21) Zambrano Membrives, Carla; Barreneche, Camila; Universitat de Barcelona. Departament de Ciència dels Materials i Química Física
[spa] El sector de la automoción es uno de los principales contribuyentes a la contaminación ambiental, no solo por las emisiones generadas durante la vida útil de los vehículos, sino también por el impacto ambiental asociado a la fabricación de sus materiales y la generación de residuos plásticos. El reciclaje mecánico de estos residuos es hoy en día la solución más extendida para maximizar la tasa de reutilización de estos materiales para la fabricación de las mismas piezas (upcycling) o de otros productos con requisitos menos estrictos (downcycling). Los parachoques se han convertido en una de las piezas más aprovechables del vehículo, ya sea en el final de su vida útil (posconsumo) o formando parte de rechazos de producción (posindustrial). Esta pieza suele estar compuesta en base termoplástica de polipropileno con elastómeros o refuerzos minerales, materiales fácilmente reciclables. No obstante, en muchos casos, esta pieza llega pintada para su reciclaje en distintos colores. En los materiales posconsumo especialmente, la pintura puede presentar formulaciones diversas, muchas veces desconocidas. Además, su naturaleza puede ser tanto de tipo termoestable como termoplástica, dificultando los procesos de extrusión y de inyección de los polímeros preparados para el reciclaje por su incompatibilidad térmica. Tras la extrusión, este recubrimiento genera tensiones localizadas en el material, reduciendo sus propiedades mecánicas, además de defectos estéticos. Por lo tanto, los parachoques pintados reciclados, suelen destinarse a aplicaciones de menor valor en lugar de reincorporarse completamente a la fabricación de nuevos parachoques, limitando el upcycling dentro del sector. A pesar de los numerosos intentos durante años por desarrollar un método de despintado viable, económico y con un bajo impacto ambiental, hasta la fecha no se ha logrado una solución efectiva que se haya podido implantar con éxito en la industria. La presente tesis doctoral pretende abordar la problemática de la presencia de pintura en los parachoques reciclados hechos con base de polipropileno, evaluando diferentes estrategias de despintado químico y físico-mecánico. Se estudian los mecanismos de acción involucrados para el establecer las bases de un nuevo método de despintado viable a escala industrial, con el objetivo de mejorar la calidad del material reciclado y aumentar su reincorporación en la fabricación de nuevas piezas de automoción. Se caracterizan los materiales procedentes de parachoques reciclados en función de variables como la presencia de pintura, el efecto del despintado, la distribución del tamaño de partícula y las condiciones del procesado, evaluando su influencia en las propiedades críticas para un correcto procesamiento en etapas propias del reciclaje mecánico. También se presentan varias estrategias para poder evaluar la eficacia de estos métodos de despintado experimentados durante la tesis y diferentes procedimientos de muestreo representativo. Para un correcto despintado industrial de estos materiales es necesario implantar procesos posteriores para hacer efectiva la correcta separación de esta pintura desprendida del sistema. Por ello, se presentan también pruebas experimentales a nivel laboratorio y se presentan alternativas para solventar problemáticas relacionadas con el proceso de despintado. Finalmente, se emplea un enfoque analítico basado en la priorización de criterios para determinar la factibilidad de los métodos probados, identificando la estrategia más adecuada bajo los criterios escogidos. En conclusión, esta tesis doctoral pretende dar las bases para el desarrollo de un nuevo método o sistema de despintado de poliolefinas termoplásticas recicladas, con el fin de mejorar su valorización y reducir la dependencia de polímeros vírgenes en la fabricación de parachoques y otras piezas de automoción, contribuyendo así a la reducción del impacto ambiental del sector. De esta forma, el reaprovechamiento de este residuo plástico pintado fomenta la economía circular, las políticas de residuo cero, así como los criterios medioambientales y de sostenibilidad, contribuyendo a alcanzar los Objetivos de Desarrollo Sostenibles (ODS), especialmente aquellos destinados a combatir el cambio climático y sus impactos.
Selective CO2 capture using MOF/Graphene Oxide Materials
(Universitat de Barcelona, 2025-07-17) Martínez Medina, Elizabeth; Xuriguera Martín, María Elena; Martínez López, Mònica; Universitat de Barcelona. Departament de Ciència dels Materials i Química Física
[eng] In recent years, climate change has become a central concern in the scientific community, primarily caused by greenhouse gas emissions; carbon dioxide (CO2) being one of the most significant contributors. Among the proposed strategies to mitigate its impact, porous materials have emerged as a potential solution to capture these harmful gases that present a risk to both society and the environment. Among these, Metal Organic Frameworks (MOFs) stand out due to their exceptional properties, such as thermal stability, large specific surface area, high porosity and tunable functionality, all of which are crucial for efficient gas sorption. There is notable variability in measuring CO₂ capture using MOFs in the literature, which are mostly performed at low temperatures and/or high pressures, where most porous materials perform better. These conditions are not usual in emission sources like industrial chimneys or vehicle exhausts and, to overcome this, this study explores enhancing CO2 adsorption performance and properties of MOF materials, specifically at 25ᵒC and up to 1.3 atmospheres. The present thesis explores the development, characterization, and performance of HKUST-1 and their hybrid combination with graphene-based materials, specifically graphene oxide (GO) and reduced graphene oxide (rGO), for CO2 capture. The research aims to address urgent environmental concerns through the design of efficient adsorbents capable of capturing CO₂. Firstly, this work focuses on the synthesis of HKUST-1/GO hybrid materials by adding GO at several concentrations, ranging from 0.15% up to 9% w/w of GO. Using Mixed- Solvent Methods (MSM), commonly used in the synthesis of MOFs, the study identifies the optimal content of GO that enhances CO2 adsorption performance at 25ᵒC and up to 1.3 atmospheres. Additionally, a novel methodology, named here as Reverse Quantification (RQ); has been developed to quantify the experimental GO content in the hybrids, addressing inconsistencies often found in literature. As a result, it is determined that the theoretical amount of GO used during synthesis is not entirely incorporated into the HKUST-1 samples. A deviation from the ideality is observed across 0 to 9% GO range, generally resulting in lower experimental GO content than theoretically added. Since RQ is employed in all syntheses of this study, it proves, through different trends, the deviation from the ideal behavior in all cases. In this instance, the sample containing 0.25% w/w of experimental GO obtained via MSM exhibits the highest CO2 adsorption performance, with a specific value of 5.33 ± 0.16 mmol CO2/g at 1.3 atm, achieving up to 80% greater CO2 uptake compared to pristine HKUST-1. Additionally, the major focus of the research is to optimize the method of synthesis, developing a more environmentally friendly synthesis method. HKUST-1 materials are commonly synthesized by MSM using harmful and ecotoxic solvents, such as dimethylformamide, at high temperatures (85ᵒC). Consequently, mechano-chemical synthesis through the liquid-assisted grinding (LAG) method using ball milling (BM) is explored. The results confirm that this method offers a more sustainable alternative while maintaining material performance. Two synthesis scales are investigated: small-scale (sBM) and medium-scale (bBM), with GO concentrations between 0.15–2.5% w/w, based on prior results obtained by MSM. sBM samples achieved CO₂ adsorption up to 4.93 ± 0.28 mmol/g at 0.48–0.55% of experimental GO content, comparable to MSM results. In contrast, bBM samples reached 3.77 ± 0.07 mmol/g at 0.25–0.30% w/w of experimental GO, though with less correlation between GO content and performance. Overall, mechano-chemical synthesis using ball milling proves effective, potentially scalable, and environmentally friendly. Another important aspect is the cyclability of the synthesized material, since HKUST-1/GO hybrid material presents a notable regeneration capability over multiple adsorption-desorption cycles. Hence, the incorporation of reduced graphene oxide (rGO) into the HKUST-1 synthesis is investigated. As rGO offers potential for CO₂ desorption via electrical heating, the main goal is to synthesize hybrid HKUST-1/rGO and HKUST-1 with mixtures of the graphenic materials (GM): rGO and GO, HKUST-1/GM; and check their CO2 adsorption properties. As a result, HK-rGO samples showed slightly lower CO₂ adsorption than GO-based ones, and a maximum of 5.10 mmol/g is achieved at 0.80% w/w of experimental rGO. In contrast, HK-GM samples (rGO/GO mixtures) expose a better performance, reaching 6.00 mmol CO2/g with the best result at 0.60% GM (1:3 ratio of rGO/GO mixtures, respectively). These findings suggest that combining rGO and GO can enhance the adsorption of pure GO-based materials, making them a promising candidate for cyclable adsorption processes, with CO2 desorption via electrical heating. Finally, this thesis also explores the interaction between water (humidity) and CO₂ during adsorption processes when using HKUST-1/GO samples, both for samples obtained via mechano-chemical methods and MSM. Further analysis explores the competition of H₂O with CO₂ during adsorption processes under post-combustion conditions, using streams of 15 % CO2 and 50% RH. Specifically, this part of the research focuses on the behavior of H2O and CO2 adsorption processes by using different characterization techniques, such as Infrared Spectroscopy (IR), Dynamic Vapor Sorption (DVS), Breakthrough Analysis (BTA) and Solid-State 13C Nuclear Magnetic Resonance (13C NMR). A competition is observed between H₂O and CO₂ for the material's adsorption sites, with H₂O molecules exhibiting a higher affinity. The results suggest that H2O adsorption is produced mainly in carboxylate and aromatic functional groups, while CO2 molecules only show preference for aromatic functional groups. The experiments also confirm that CO₂ has higher adsorption kinetics than H₂O, aligned with RMN and IR experiments. It is also determined that the incorporation of GO increases the number of favorable adsorption sites for CO₂, such as aromatic carbon, and partially blocks H2O adsorption near copper nuclei, reducing the sample degradation. As a result, HKUST-1/GO that exhibits higher CO₂ uptake also indicates enhanced cycling behavior than pure HKUST-1. On the contrary, CO₂ adsorption under humid conditions is significantly reduced, highlighting that HKUST-1/GO materials are most effective in dry environments. Additionally, the interaction with water is studied using colorimetric sensors, as the color of HKUST-1/GO changes from light to dark blue upon drying, indicating structural changes confirmed by X-ray diffraction, linked to water content. CO₂ exposure also induces color changes that correlate with CO₂ adsorption behavior. These initial results highlight the similarity between CO₂ adsorption and colorimetry in HK-GO samples, with HKUST-1 showing color changes upon interaction with CO₂, enabling detection of adsorbed CO₂ under dry conditions. Overall, this work contributes to the field of sustainable materials for gas capture by combining advanced synthesis techniques, aligned with the principles of green chemistry, with emerging hybrid systems. The findings support the potential of HKUST-1-graphenic materials as effective and versatile CO2 adsorbents.
Recobriments d'or: avançant cap a una tecnologia més sostenible
(Universitat de Barcelona, 2025-07-21) Amazian El Moussaoui, Mohamed; Sarret i Pons, Maria; Andreu Arbella, Teresa; Universitat de Barcelona. Departament de Ciència dels Materials i Química Física
[cat] En la indústria dels recobriments decoratius destaca l'ús d'aliatges d'or. Aquests recobriments es fabriquen majoritàriament mitjançant l’electrodeposició, una tècnica que requereix temps de treball reduïts i que permet controlar amb precisió les propietats del material. L'aliatge ternari AuCuIn és un dels més utilitzats, i disposa d'un procediment comercial establert i reproduïble. Tot i això, la seva electrodeposició presenta certs reptes industrials, com la baixa estabilitat de l’electròlit utilitzat, o l'ús d'espècies químiques perilloses per al medi ambient i la salut humana, com el cianur i certs additius orgànics. En aquest context, aquesta tesi doctoral té com a objectiu abordar els punts febles associats al sistema d’obtenció de l’aliatge AuCuIn per electrodeposició. Inicialment, s’ha dissenyat un electròlit amb una composició controlada i estable, que resol els problemes associats a la precipitació de l’indi en medis alcalins cianurats. Per aconseguir-ho, s’ha realitzat un estudi experimental-computacional on s’estudia l’efecte estabilitzant de la D-glucosa. A continuació, es descriu el procés d’electrodeposició utilitzant l’electròlit cianurat dissenyat, prescindint dels additius que contenen les formulacions comercials. En el seu lloc, s’ha emprat l’electrodeposició per corrent polsant i corrent polsant revers obtenint recobriments amb propietats semblants a les dels comercials. Els bons resultats obtinguts han motivat l’escalat industrial, ajustant els paràmetres operatius de l’obtenció de l’aliatge AuCuIn als processos industrials actuals. Paral·lelament, s’ha desenvolupat un electròlit alternatiu al cianurat per electrodipositar aliatges binaris AuCu, utilitzant citrat de sodi com a agent complexant. Els recobriments obtinguts presenten propietats similars als comercials, així com als electrodipositats mitjançant l’electròlit cianurat estudiat anteriorment. Aquests recobriments també han presentat una millora substancial en les seves característiques quan s’han electrodipositat per corrent polsant. La formulació de l’electròlit de citrat dissenyat és més senzilla i estable que la de l’electròlit cianurat. Finalment, d’acord amb el rerefons de sostenibilitat mediambiental de la tesi, i aprofitant la versatilitat de la tècnica d’electrodeposició, s’han obtingut diversos aliatges, que inclouen or, coure i indi, com a electrocatalitzadors. Els resultats obtinguts confirmen la seva viabilitat en la conversió electrocatalítica de CO2 a altres productes d’interès químic, especialment CO i HCOOH, utilitzant elèctrodes de difusió de gas com a substrat. Els resultats exposats en aquesta tesi doctoral no només contribueixen a la millora de l’obtenció i aplicació de recobriments d’or, sinó que també obren nous camins de recerca en diversos camps d’investigació.
Synthesis and Optimisation of Layered Hybrid Organic-Inorganic Perovskites as Solid-State Thermal Energy Storage Materials
(Universitat de Barcelona, 2024-12-11) Salgado Pizarro, Rebeca; Fernández Renna, Ana Inés; Barreneche, Camila; Universitat de Barcelona. Departament de Ciència dels Materials i Química Física
[eng] The effective use of thermal energy storage (TES) systems has demonstrated their ability to enhance energy efficiency and sustainability across various sectors. These systems play a critical role in facilitating the integration of renewable energy sources and enhancing the overall efficiency of heating and cooling systems, thereby contributing to environmental conservation and energy savings. Among the different TES technologies, latent heat thermal energy storage (LHTES) has gained attention due to its ability to store and release large amounts of energy through phase change materials (PCMs). The necessity of effective thermal management in electronic devices has become increasingly critical due to the tendency to develop thinner devices and increase their power density, which has led to significant challenges in dissipating excess heat. Overheating can severely affect electronic components’ performance, reliability, and lifespan. Current cooling technologies, such as passive heat sinks and active cooling systems, are often limited by size, weight, and energy consumption. This doctoral thesis aims to develop novel solid-solid phase change materials (SS-PCMs) based on layered hybrid organic-inorganic perovskites (LHOIPs) for use in electronic devices. The implementation of these materials has the potential to significantly reduce heat peaks and thereby improve the efficiency and lifetime of electronic devices. This dissertation is presented as a collection of publications consisting of five papers that have been published or submitted to prestigious scientific journals. Each scientific publication includes relevant details of the outputs obtained from the synthesis to the characterisation of the selected SS-PCMs. The thesis begins by outlining the energy storage (ES) and TES technologies, followed by a thorough analysis of the state-of-the-art of SS-PCMs focused on LHOIPs. The introduction concludes with an overview of existing technologies for managing thermal energy in electronic devices. This leads to the core of the thesis, starting with the evaluation of the synthesis of the bis(alkylammonium) tetrahalometallates. In the first part of the thesis, the synthesis mechanism of the bis(alkylammonium) tetrahalometallates was investigated and optimised specifically for TES applications. This study established a new synthesis protocol, which significantly reduced the required time and the waste generated during the process. Additionally, the use of mechanical energy through ball milling was explored. Through this process, the synthesis was accelerated and optimised while enhancing the overall sustainability and opening the door to scaling up the process. Following the synthesis evaluation, the characteristics of selected bis(alkylammonium) tetrahalometallates were analysed, and their tailoring properties were investigated. The research findings demonstrated that SS-PCMs can be customised for specific applications by modifying the length of the carbon chain. The results indicated that the core mechanism of the polymorphic transitions resides in the reorganisations of the organic chain. This outcome led to the final section of the investigation, where the movement of the organic chain was evaluated. Various reordering mechanisms of the organic chains during phase transitions were proposed. The present PhD thesis shows the potential of bis(alkylammonium) tetrahalometallates as alternative SS- PCMs. The optimisation and sustainability of the materials synthesis have been addressed, as well as the understanding of the polymorphic mechanism.
Clot-in-a-Chip and Innovative Programmable Materials
(Universitat de Barcelona, 2024-12-12) Herrera Restrepo, Ramón Santiago; Puigmartí-Luis, Josep; Ignés i Mullol, Jordi; Universitat de Barcelona. Departament de Ciència dels Materials i Química Física
[eng] Stroke is a medical condition in which vessel or artery obstruction leads to tissue damage due to a lack of nutrients and oxygen in the affected area. In the past decade, stroke has become the most common circulatory disease in the European Union (EU) and one of the leading causes of death and disability globally, ranking second and third in 2019 and 2020, respectively. The research presented in this thesis was conducted as part of the European-funded ANGIE project (magnetically steerable wireless nanodevices for targeted delivery of therapeutic agents in any vascular region of the body, HORIZON 2020). This thesis contributes to ANGIE by developing novel technologies for producing submillimeter-sized blood clots and investigating innovative materials for programming micrometer-sized robotics to dissolve blood clots. We propose technical approaches for creating blood clots within microfluidic devices that will support future research on magnetically guided entities that promote lytic processes in complex environments. This thesis comprises multiple chapters that contain experimental results. Initially, we developed a microfluidic device with five inlets for controlled generation of blood clots containing tissue factor. The device flow conditions facilitated precise manipulation of the straight blood clot dimensions by adjusting the flow rates of the side streams. This experimental setup enabled the production of both heterogeneous and homogeneous blood clots, which were used to investigate the variation in thrombolytic agent efficacy based on the clot composition. Quake valve systems were employed as a secondary approach for the formation of free interface diffusion between whole blood and tissue factors. The reaction under diffusive mass transport facilitated the formation of homogeneous blood clots with volumes on the order of nanoliter. The latter acquired a semi-hemispherical shape as determined by the channel contour. Dissolution studies revealed a correlation between blood clot size and the injected volume of the thrombolytic agent. As a third approach, the mass transport phenomena through an in situ produced PDMS membrane was investigated. Blood clots were generated within the control chambers, separated by a thin membrane from the fluidic channel carrying thrombogenic agents. The blood clots assumed complex morphologies determined by chamber geometry, and structural alterations were contingent on the concentration of the thrombogenic agent. The generated blood clots were used to develop a high-throughput printing system for drug testing in future research. This study introduces a novel method for creating programmable robots using polymeric meshes for dissolution treatments. This process integrates Liquid Crystal Elastomers and hydrogels via sequential photopolymerization. A tailored photopolymerization setup was devised to control hydrogel alignment via Lyotropic Chromonic Liquid-Crystal templating regulated by a permanent magnetic field during polymerization. High-temperature water applications have demonstrated composite actuation. In addition, the setup allows the printing of complex designs.
Electronic Structure and machine learning protocols for pre-screening of near-room temperature spin-crossover materials
(Universitat de Barcelona, 2024-11-20) Vidal Ramon, Daniel; Ribas Ariño, Jordi; Cirera Fernández, Jordi; Universitat de Barcelona. Departament de Ciència dels Materials i Química Física
[eng] Spin-crossover (SCO) is a phenomenon observed in certain transition metal complexes, particularly d4–d7 metals, where a reversible transition between high-spin (HS) and low-spin (LS) electronic states occurs in response to external stimuli like temperature, pressure, or light. This switch alters magnetic, optical, and structural properties, making SCO materials attractive for applications in molecular electronics, data storage, sensors, and smart devices. Among transition metal complexes, FeIII SCO complexes are widely studied because of their distinct electronic configurations and stability. The transition between HS and LS states is governed by the metal-ligand interaction, specifically the ligand field strength. A stronger ligand field stabilizes the LS state, while a weaker one favours the HS state, influencing the system's magnetic properties. These transitions, characterised by changes in magnetic moment and colour, make FeIII complexes a key focus for material design. This thesis investigates the SCO behaviour of FeIII complexes through computational and machine learning (ML) techniques, with a focus on ligand functionalization, benchmarking of density functional theory (DFT) methods, and studying dinuclear and polynuclear systems. The research begins with a systematic benchmark analysis of different DFT functionals to determine the best-suited computational approaches for predicting the spin state energetics and transition temperatures of FeIII complexes. The results show that while certain functionals provide accurate predictions of SCO properties, the accuracy depends heavily on the specific characteristics of the FeIII systems being studied. A key contribution of the research is the exploration of ligand design and its impact on SCO behaviour. By altering ligand substituents, the electronic environment around the metal ion can be fine-tuned, providing control over the transition temperature (T(1/2) and other SCO properties. For instance, electron-donating groups on the ligand tend to lower T(1/2) , while electron-withdrawing groups increase it. These ligand-induced modifications are particularly important in FeIII complexes, as both electronic and steric factors play critical roles in governing the spin state transition. The study demonstrates how strategic ligand design can be used to tailor SCO properties for specific applications. In addition to mononuclear FeIII complexes, the thesis examines dinuclear systems, where the presence of two metal centres introduces additional complexity. In these systems, the interaction between metal centres results in cooperative SCO behaviour, such as two-step transitions or the stabilization of intermediate spin states. The research highlights the need for more sophisticated computational models to accurately capture these complex behaviours in dinuclear and polynuclear systems. The findings contribute to the growing understanding of how intermetallic interactions can be leveraged to design SCO materials with specific magnetic properties, which are critical for potential applications in sensors and molecular electronics. Machine learning (ML) models, particularly Kernel Ridge Regression (KRR) and Gaussian Processes (GP), are introduced as complementary tools to traditional computational methods. These ML models are trained on datasets generated from DFT calculations and are used to predict SCO properties such as transition temperatures and spin state energetics. The ML models offer a scalable and efficient approach to studying larger and more complex systems, significantly reducing computational costs while maintaining high accuracy. Feature importance analysis reveals key molecular descriptors that drive SCO behaviour, providing valuable insights into which molecular modifications are likely to result in desirable SCO properties. This approach accelerates the discovery and design of new SCO materials. The integration of machine learning, ligand design, and advanced computational methods in this thesis presents a comprehensive framework for understanding and predicting SCO behaviour in FeIII complexes. The combination of these approaches enables the development of customizable materials for a range of technological applications, including molecular switches, sensors, and memory devices.
Mechanical activation of clays as an alternative to thermal activation for ternary blended cement production
(Universitat de Barcelona, 2024-10-01) Mañosa Bover, Jofre; Chimenos Ribera, Josep Ma.; Maldonado Alameda, Alex; Universitat de Barcelona. Departament de Ciència dels Materials i Química Física
[eng] The construction industry significantly contributes to climate change and global warming, especially due to the environmental footprint of Portland cement (PC) production, which is the second most widely used material worldwide. PC manufacture involves CO2 emissions from the limestone reaction during calcination and the fossil fuel burning to reach the high temperatures needed to produce clinker, the main component of PC. Although several strategies are being implemented to decarbonise the PC industry, the most promising short-term solution is partially replacing clinker with supplementary cementitious materials (SCMs). SCMs can replace clinker in blended cement, improving its long-term properties. However, SCMs can only replace clinker to a limited extent without affecting cement performance. Nevertheless, combining two or more SCMs to produce ternary blended cement allows for higher clinker replacements. One of the most promising ternary blended cement is limestone calcined clay cement (LC3), which uses widely available SCMs like clay and limestone, thereby reducing the environmental impact and cost of production and enabling local production of LC3. However, clays require a prior activation process to enhance their reactivity, typically achieved by calcining them in industrial rotary kilns that burn fossil fuels and emit a significant amount of CO2 during the thermal activation process. In contrast, mechanical activation is an electrically driven milling process that induces the amorphisation of clay minerals by breaking the chemical bonds within the crystalline structure, improving their reactivity. This process has the potential to reduce the carbon footprint associated with clay activation. The main goal of this PhD thesis is to explore the potential of using mechanically activated clay in ternary blended cements, aligning with the need for sustainable and affordable solutions to decarbonise the cement and construction industries. This thesis is presented as a compendium of articles, comprising a total of seven papers published, under review, or submitted to high-impact scientific journals. These scientific papers provide detailed descriptions of the results obtained from the mechanical activation of clays and the formulation of alternative ternary blended cements, consistently comparing them with those of LC3 containing metakaolin. In this regard, the first step of this thesis involved evaluating the current status of LC3 technology through a bibliometric analysis. The analysis confirmed the potential of LC3 to reduce the carbon footprint of the cement industry, especially in developing countries needing affordable and locally produced materials. The experimental work initially focused on evaluating the effect of mechanical activation on kaolinitic and muscovitic clays, which were selected due to their high and limited reactivity after thermal activation, respectively. The research revealed that the clays were successfully activated under optimal milling conditions, leading to increased reactivity and changes in particle size and morphology. The reactivity of mechanically activated kaolinitic clay was comparable to that of thermally activated kaolinitic clay, while the reactivity of mechanically activated muscovitic clay showed superior reactivity compared to its thermally activated counterpart. The promising results validated the potential of using mechanically activated clays as SCM or alternative cementitious materials precursors. Following the activation process evaluation, mechanically activated clays were introduced into ternary blended cements, replacing thermally activated clays in LC3. The resulting ternary blended cements exhibited properties comparable to traditional LC3 containing thermally activated kaolinitic clay and superior to those of LC3 containing thermally activated muscovitic clay. Furthermore, the incorporation of mechanically activated clay improved the workability of alternative ternary blended cements and induced an acceleration of hydration kinetics, enhancing early age performance. This PhD thesis outlines the potential of mechanical activation as an alternative method for producing activated clay SCMs, contributing to the reduction of the environmental impact associated with ternary blended cements.
Economía circular de la Guadua angustifolia Kunth (GaK) como una alternativa de construcción sostenible
(Universitat de Barcelona, 2024-07-17) Torres Ruilova, Bismark Osmany; Segarra Rubí, Mercè; Universitat de Barcelona. Departament de Ciència dels Materials i Química Física
[spa] La presente tesis doctoral se centra en el aprovechamiento sostenible de la Guadua angustifolia Kunth (GaK), una especie de bambú predominante en las regiones tropicales y subtropicales, especialmente en América Latina. Esta investigación se desarrolla bajo un marco de economía circular y propone la utilización de la GaK como una alternativa ecológica y viable para la construcción. El estudio persigue tres objetivos principales: el desarrollo de tratamientos para mejorar la durabilidad de la GaK, la evaluación de su sostenibilidad mediante el análisis de ciclo de vida (ACV) y la innovación en la creación de materiales compuestos a partir de sus residuos. En primer lugar, se analizan tratamientos térmicos y termoquímicos, incluyendo la ebullición a presión atmosférica y la aplicación de soluciones de bórax y ácido bórico. Estos tratamientos están diseñados para mejorar la durabilidad del bambú, manteniendo al mismo tiempo sus propiedades mecánicas esenciales e incrementando su resistencia a condiciones adversas, como la exposición al fuego. El propósito de estos tratamientos es alterar la composición química y estructural del bambú de manera que se optimicen su durabilidad y funcionalidad para aplicaciones en el sector de la construcción. El segundo objetivo se centra en realizar un ACV detallado de los tableros de bambú producidos en Santa Elena, Ecuador. Este análisis puerta a puerta no solo identifica los impactos ambientales significativos asociados con la producción de bambú, sino que también propone mejoras basadas en los hallazgos. Se consideran dos escenarios de: uno que representa el proceso actual y otro que incluye mejoras en la gestión de residuos y recursos, destacando una reducción significativa de los impactos ambientales en el escenario optimizado. En cuanto al tercer objetivo, se investiga la viabilidad de desarrollar materiales compuestos integrando fibras de bambú en matrices poliméricas. Este enfoque no solo busca valorizar los residuos de bambú, sino también evaluar las propiedades mecánicas y térmicas de los compuestos desarrollados para su posible aplicación en construcción. La metodología empleada incluye avanzadas técnicas de caracterización química, morfológica, térmica y mecánica para analizar las modificaciones en las propiedades de la guadua y los materiales compuestos resultantes. Este enfoque integral permite una evaluación detallada de los tratamientos y procesos propuestos, asegurando que las soluciones sean prácticas y científicamente validadas. Se espera que los resultados de esta investigación proporcionen nuevas perspectivas sobre la optimización del uso del bambú, mejorando su aplicación en la construcción y otros campos, y promoviendo prácticas de desarrollo sostenible. Al abordar tanto las limitaciones actuales como las potencialidades de la guadua, este trabajo contribuye al avance de conocimientos en el área de materiales sostenibles y ofrece soluciones prácticas que pueden beneficiar tanto a la comunidad científica como a la industria local y global del bambú. En síntesis, esta tesis representa un esfuerzo por mejorar la comprensión y utilización de GaK en aplicaciones sostenibles, apoyando su adopción en prácticas de construcción innovadoras y ecológicas que alinean las necesidades industriales con los imperativos ambientales, especialmente en comunidades en vías de desarrollo
Optimal Selection, Characterization, and Life Cycle Assessment of Sustainable Materials for Thermal Energy Storage in Concentrating Solar Power: A Circular Economy Approach
(Universitat de Barcelona, 2024-07-02) Majó Robles, Marc; Barreneche, Camila; Calderón Díaz, Alejandro; Universitat de Barcelona. Departament de Ciència dels Materials i Química Física
[eng] The world's energy dilemma, balancing supply and demand, finds a potential solution in energy storage technologies. Energy storage systems store excess energy during low-demand periods for later use. This approach enhances grid stability, integrates renewable sources like solar and wind power cost-effectively, and reduces reliance on fossil fuel-based thermal power plants, thus lowering greenhouse gas emissions. One prominent and cost-effective technology is Thermal Energy Storage (TES) systems integrated into Concentrated Solar Power (CSP) plants. These plants utilize molten salts both as TES material and Heat Transfer Fluid (HTF). By storing solar heat and then generating electricity through a heat exchanger, it is possible to enable continuous electricity production, mitigating the "duck effect." To advance this technology and increase its competitiveness, the use of sustainable low-cost materials has been proposed to work as TES material in solar tower configurations, aiming to achieve a higher operating temperature. This translates into higher efficiency in converting heat to electricity, lower cost and environmental impact, and better compatibility with the structure. The main objective of this thesis is to provide a proven alternative material for the TES tanks in the next generation of CSP plants. With a selection of sustainable materials, testing and characterization of their properties and stability, and an environmental evaluation and comparison with conventional technology through a newly proposed Summary methodology to complete a Life Cycle Assessment (LCA) of alternative materials, a comprehensive evaluation of several sustainable materials from different origins will be completed. Two concepts will be evaluated throughout the thesis work: one involves the integration of sustainable materials with conventional technology to enhance stability and reduce compatibility issues, while the other presents insight into the new strategy of using solid particle materials for TES without molten salts. Additionally, several challenges faced during the testing of the materials have led the study to the need for a specific device to conduct thermal cycles with controlled heating and cooling ramps. This is addressed in the last chapter of the thesis, where a self-developed device capable of automatically completing thermal cycles of materials is presented. Throughout all tests and characterizations, a complete validation of alternative sustainable materials from different origins has been assessed and presented as candidates for TES applications in various technologies. The incorporation of these materials will help increase competitiveness by reducing the environmental impact and cost of electricity production.
Strategies to synthesize carbon-supported elctrocatalysts with reduced Pt content and increased activity for use in low temperature fuel cells
(Universitat de Barcelona, 2023-12-04) Garcia Cardona, Júlia; Cabot Julià, Pere-Lluís; Sirés Sadomil, Ignacio; Universitat de Barcelona. Departament de Ciència dels Materials i Química Física
[eng] Conventional catalysts for polymer electrolyte fuel cells are based on Pt supported on porous carbons, generally carbon blacks. However, Pt is expensive and scarce and is poisoned by CO, which is present in the hydrogen obtained by reforming natural gas and it is also generated as an intermediate in the oxidation of methanol. In addition, carbon blacks have some drawbacks, such as their microporosity, impurities, and low electrochemical and thermal stability. In this thesis, nanoparticle catalysts with a core- shell structure have been synthesised and characterised, with the Ni or Cu core and the Pt shell supported on advanced carbons, in order to reduce the amount of Pt used and increase its catalytic activity against the reduction of oxygen and the oxidation of methanol and CO, as well as its stability. Different procedures have been used to synthesize the catalysts, with initial deposition of Ni or Cu nanoparticles by chemical reduction on different carbons and subsequent galvanic exchange with Pt. The catalysts have been characterised by transmission electron microscopy, X-ray photoelectron spectroscopy, voltammetry cyclic and linear scanning voltammetry on rotating disk electrode. The results of the structural and electrochemical analyses, supported by computational calculations of model atomic clusters, are consistent with the formation of nanoparticles with a diameter of 2-5 nm, a nucleus enriched with Ni or Cu and an essentially Pt shell. They presented greater tolerance to CO than the commercial Pt/C, due to the electronic effect of the metallic nucleus on the Pt, which enhanced the desorption of CO. The calculation of the CO adsorption energies on different active centres showed that the presence of surface defects could affect the CO tolerance of the catalysts, which could be critical for nanoparticles that are too small, as observed experimentally. In the case of PtNi, the two anodic peaks observed in the oxidation of CO suggest the presence of two distinct structural domains on the catalyst surface, probably Pt in Ni-rich hexagonal domains and in Pt-rich cubic domains, without forming a solid solution between Ni and Pt. Its activity against methanol oxidation is also greater than that of Pt/C due to the ligand effect of Ni on Pt, which also increases with the incorporation of Ru species due to its bifunctional effect. Contrary to the case of PtNi, a solid solution of Cu is formed in Pt, attributable to its compatibility of size and crystallization system, cubic (hexagonal in the case of Ni). Also, in the case of PtCu, better catalytic activity is observed against the oxidation of methanol than for commercial Pt/C, due to the geometric and ligand effects of Cu on Pt. This makes them interesting for the reduction of oxygen in the cathodes of direct methanol fuel cells, since it decreases the negative effect of methanol transport through the membrane. The dispersion of PtCu nanoparticles on commercial carbon nanofibers and nanotubes, as well as commercial and synthetic mesoporous carbons, also leads to catalysts that are more tolerant to CO than commercial Pt/C, due to the electronic effects of Cu on Pt discussed above. Better activities for oxygen reduction than on commercial Pt/C, both mass and specific, are achieved on various supports, while its relative stability is increased with respect to the latter. Mesoporous carbon supports synthesised from chitosan are of special interest, since chitosan is an abundant, non-toxic, nitrogen-rich natural polysaccharide present in crustacean shells. Also taking into account that P20 silicon oxide was used as a template in the synthesis procedure, the mesoporous carbon obtained was low cost and of great added value. Adjusting the microporosity-mesoporosity ratio of the carbons through different synthetic procedures, specific activities against oxygen reduction and methanol oxidation were obtained with mesoporous carbons derived from chitosan, greater than those of Pt/C and that of PtCu catalysts supported on commercial mesoporous carbons.
Prediction of partition coefficients for systems of micelles using DFT
(Universitat de Barcelona, 2023-10-30) Saranjam, Leila; Madurga Díez, Sergio; Universitat de Barcelona. Departament de Ciència dels Materials i Química Física
[eng] A compound’s solvent−water partition coefficient (log P) measures the equilibrium ratio of the compound’s concentrations in a two-phase system: as two solvents in contact or a system of micelles in an aqueous solution. In this thesis, the partition coefficient of three groups of small compounds (alcohol, ether, and hydrocarbons) in 10 different solvents (benzene, cyclohexane, hexane, n-Octane, toluene, carbon tetrachloride, heptane, trichloroethane, and octanol) was computed used DFT and B3LYP method with 6.31G(d), 6.311+G** and 6.311++G** basis sets. It is obtained that the partition coefficient of alcohol solutes in various solvents using the 6.31G(d) basis set indicates a satisfactory correlation with experimental values. The correlation between the experimental value and the partition coefficient of ether solutes in different solvents using the 6.311++G** basis set shows high agreement. The experimental data displayed a high correlation with the partition coefficient computed for hydrocarbon compounds in various solvents using all three basis sets: 6.31G(d), 6.311+G**, and 6.311++G**. In addition, we have studied the correlation of the experimental partition coefficients in Sodium Dodecyl Sulfate (SDS), Hexadecyltrimethylammonium bromide (HTAB), Sodium cholate (SC), and Lithium perfluoro octane sulfonate (LPFOS) micelles with ab initio calculated partition coefficients in 15 different organic solvents. Specifically, the partition coefficients of a series of 63 molecules in an aqueous system of SDS, SC, HTAB, and LPFOS micelles are correlated with the partition coefficient in heptane/water, cyclohexane/water, n-dodecane/water, pyridine/water, acetic acid/water, octanol/water, acetone/water, 1-propanol/water, 2-propanol/water, methanol/water, formic acid/water, diethyl sulfide/water, decan-1-ol/water, 1-2 ethane diol/water and dimethyl sulfoxide/water systems. All calculations were performed using the Gaussian 16 Quantum Chemistry package. Molecular structures were generated in the more extended conformation using Avogadro, and geometries of all molecules were optimized using Density Functional Theory (DFT) B3LYP and MO6-2X with 6-31++G** basis set by the continuum solvation model based on density (SMD). The obtained results show that calculated partition coefficients in the alcohol/water mixture give the best correlation to predict the experimental partition coefficients in SDS, SC, and LPFOS micelles. With respect to HTAB micelle systems, a new selection of molecules is created, excluding those containing N atoms and Urea atom groups. Interestingly, the partition coefficient of these chosen molecules exhibits a strong correlation with the experimental partition coefficient. Finally, the partition coefficient of flexible molecules was studied by the same protocol for two solvent combinations, octanol/water and cyclohexane/water. The calculated values were compared with the experimental partition coefficients. The average partition coefficient in octanol solvent exhibited a high correlation with the experimental data. However, for the 16 compounds in the cyclohexane solvent, their partition coefficients do not exhibit significant agreement with the experimental partition coefficients.
Nitrate and Pesticide Removal from Groundwater Using Different Electrochemical Reactors
(Universitat de Barcelona, 2023-10-23) Oriol López, Roger; Sirés Sadornil, Ignacio; Universitat de Barcelona. Departament de Ciència dels Materials i Química Física
[eng] Groundwater has been traditionally considered a reliable source of freshwater. However, the low replenishment rates and the increasing contamination due to different anthropogenic activities, such as the use of pesticides and fertilizers to increase crop production, the spread of manure and urban and industrial discharge effluents have affected the water quality in these underground reservoirs around the globe. The different nature of the discharged contaminants in this natural water body adds complexity for its treatment, owing to their different chemical properties. The electrochemical processes for GW treatment have emerged as viable alternatives to the conventional methods. Moreover, the low conductivity and high hardness of these water matrices are drawbacks that must be conveniently addressed beforehand. In this Thesis, different strategies to overcome the major drawbacks have been used in order to remove model pesticides spiked from softened groundwater by electro-oxidation (EO) and/or the nitrate concentration present in the actual water matrix, which was higher than the recommended limit established by the WHO, by electroreduction (ER). Two different softening methods have been used in order to remove the alkaline-earth ions from the groundwater, avoiding the precipitation of calcium and magnesium carbonates and hydroxides on the cathode surface. This would lead to an increase of the electrical resistance of the system and hence, the treatment cost. One process was based on sodium-charged zeolites and the other consisted in forcing the precipitation of the alkaline-earth ions. The cell configuration and the materials employed as electrodes are critical in order to develop a system able to remove specific pollutants. Two pesticides, imidacloprid and terbuthylazine, were removed by either direct or indirect EO using DSA® and boron-doped diamond (BDD) anodes. In the presence of chloride in the water matrix, this species was oxidized to active chlorine, which was able to oxidize organic pollutants in the bulk of the solution increasing the pesticide removal rate. Higher mineralization degrees were achieved when the BDD anode was employed, owing to its superior oxidant power, although chlorinated oxyanions as chlorate and perchlorate were accumulated in solution. A post-treatment based on a Purolite® A532E resin has been considered to remove such by-products generated along the electrochemical treatment. Different iron-based steel materials were also used as cathodes to study the nitrate electrochemical removal by electroreduction in different water matrices. Mild steels have shown superior electrocatalytic activity for the nitrate removal with complete conversion towards ammonia while stainless steel showed poor activity achieving worse nitrate removals at analogous conditions. This reaction has been electrochemically characterized using a mild steel rotating disk electrode (RDE) through a Koutecky-Levich analysis. The number of electrons involved in nitrate ER over a mild steel cathode has been determined (n = 8) as well as the heterogeneous charge transfer kinetic constant (kh) at different cathode potentials (Ecath). The role of atom hydrogen (•H) as a reducing agent, generated on the cathode surface as a hydrogen evolution by-product, has also been studied. Simultaneous removal of a pesticide by electro-oxidation and nitrate by electroreduction has been assessed, alongside the effect of using different anode-cathode combinations. Furthermore, a mild steel rotating cylinder electrode (RCE) reactor has been employed in galvanostatic and potentiostatic conditions in order to enhance the mass transport towards a mild steel cylinder electrode. The diffusion-convection mass transport of this system has been characterized by obtaining the following Sherwood-Reynolds-Schmidt correlation: Sh = 0.7Re0.46Sc0.356 aiming at a future scale-up. The same RCE reactor system has been modeled in order to predict its behavior upon use of a suitable electrocatalytic RCE for nitrate removal. The developed mathematical model has been validated by comparing the simulations obtained by computational fluid dynamics (CFD) with the experimental trends.
Evolución de las propiedades de tuberías de PP-R en servicio
(Universitat de Barcelona, 2023-09-06) Ferrer, Josep Mª; Fernández Renna, Ana Inés; Barreneche, Camila; Universitat de Barcelona. Departament de Ciència dels Materials i Química Física
[spa] Esta tesis está enfocada en la búsqueda de hitos y nuevos conceptos que permitan la mejora de un producto que actualmente está dominando el mercado en su nicho de negocio español: las tuberías de PP-RCT. La empresa Italsan, actual líder del sector lleva más de 30 años ofreciendo las mejores soluciones a sus clientes. Mediante el diseño y construcción de una planta piloto disruptiva desde el punto de vista de la versatilidad y del cumplimiento de los objetivos establecidos, se ha conseguido establecer un entorno prácticamente idéntico al de los circuitos de fontanería en los edificios. Se reproducen las mismas condiciones de presión, temperatura y fluido para evidenciar aspectos críticos en la vida útil de las tuberías de PP-R. El objetivo es realizar un seguimiento de las primeras etapas de su envejecimiento prematuro, presentando evidencias, por ejemplo, sobre la necesidad de una actualización en la normativa o una mejora en la formulación de su materia prima. También se realiza un estudio factorial sobre las características de las tuberías de PP-R en el mercado, obteniendo resultados que evidencian claros aspectos mejorables en la predicción de la vida útil después de haber superado con éxito los ensayos certificados de envejecimiento acelerado. Si bien la tesis se centra en un solo polímero, los datos obtenidos son extrapolables a todas aquellas formulaciones basadas en los mismos principios. Además, los resultados se trasladan al nuevo enfoque legislativo: entre 2022 y 2023 se actualiza la legislación relativa a la calidad del agua y a la desinfección para protegernos de la legionelosis, aumentando los requisitos fisicoquímicos de los materiales con los que se realizan los circuitos de fontanería.
Aleación nanoestructurada de alta entropía FeAlNiCuCo: diseño, síntesis y caracterización
(Universitat de Barcelona, 2023-05-03) López Jiménez, Isabel; Llorca i Isern, Núria; Universitat de Barcelona. Departament de Ciència dels Materials i Química Física
[spa] Durante los últimos años el estudio de las aleaciones de alta entropía, o high entropy alloys (HEA), ha sido un tema en auge. Las HEA presentan de cinco a más elementos en proporción equimolar y una microestructura de solución sólida. Aunque, la comunidad científica no ha llegado a una definición clara de cuáles son los criterios que deben cumplir estas aleaciones. Las aleaciones HEA presentan propiedades excelentes y sus óptimas características las están haciendo muy interesantes para aplicaciones estructurales en la industria aeronáutica, en aplicaciones relacionadas con la energía y en la industria química de la catálisis, entre otras. Gracias a la aleación mecánica (MA) es posible obtener soluciones sólidas de sistemas termodinámicamente inmiscibles y materiales nanoestructurados. Este método se ha empleado durante años para la producción de multitud de materiales y piezas de pulvimetalúrgia. Esta tesis doctoral plantea la síntesis de tres aleaciones HEA donde la proporción de los elementos no es equiatómica. Los elementos han sido Fe, Al, Ni, Cu y Co en diferentes proporciones. Las aleaciones convencionales de estos elementos muestran de por si propiedades sobresalientes y gran variedad de aplicaciones. La síntesis de la aleación FeAlNiCuCo pretende contribuir al debate de la obtención de una HEA con solución sólida, a pesar de que su proporción de elementos no sea equimolar. En el trabajo se plantea encontrar las condiciones óptimas de síntesis de estas nuevas aleaciones mediante MA y estudiar sus propiedades. Esta investigación parte de una primera etapa de búsqueda y evaluación de los parámetros que las hacen únicas. Se realiza un estudio bibliográfico de los indicadores termodinámicos que debe cumplir una HEA. También se evalúan las diferentes técnicas de síntesis utilizadas actualmente, considerando las ventajas y desventajas que presentan. La primera etapa de estudio bibliográfico ha permitido obtener toda la información necesaria para plantear un diseño de la aleación FeAlNiCuCo que cumpla con todos los parámetros termodinámicos fijados para la obtención de una solución sólida. Seguidamente, se ha decidido una síntesis con aleación mecánica. A continuación, se efectúa la síntesis de la aleación HEA y se optimizan las condiciones para la obtención de una solución sólida. Una segunda etapa de caracterización de las aleaciones ha permitido un estudio en profundidad de las aleaciones. Las técnicas de caracterización de microscopía electrónica de barrido (FESEM-EDS), difracción de rayos X (DRX) y espectroscopia Mössbauer juegan un papel clave en la determinación de la microestructura y la red cristalina de las HEAs. A su vez, permiten evaluar los cambios de la muestra durante varios puntos del procesado, como son la síntesis mecánica y la sinterización a diferentes temperaturas. Otras técnicas como XPS, picnometría de helio o la calorimetría diferencial de barrido (DSC) también han aportado datos fundamentales para la interpretación de los resultados. Igualmente se han estudiado propiedades físico-químicas de las tres aleaciones. Los análisis se han centrado en la variación de la microestructura de las muestras a diferentes temperaturas, su área superficial BET y su porosidad, su comportamiento magnético, su resistencia a la corrosión y su microdureza. En último lugar, con todos los datos reunidos, se han evaluado en conjunto las tres aleaciones FeAlNiCuCo obtenidas. Se han valorado las diferencias y similitudes entre ellas y se ha considerado cuál presenta las mejores propiedades y estabilidad. De igual manera, se ha determinado que la microestructura para las tres aleaciones es de solución sólida, a pesar de que no presentan una proporción equiatómica como alguna definición de las aleaciones de alta entropía requiere. La ruta de síntesis de aleación mecánica se ha validado como adecuada para esta obtención y se ha planteado las posibles aplicaciones de las aleaciones HEA.
Desarrollo de micro-morteros de cemento de fosfato de magnesio formulados con subproductos y residuos industriales
(Universitat de Barcelona, 2023-02-03) Huete Hernández, Sergio; Formosa Mitjans, Joan; Chimenos Ribera, Josep Ma.; Universitat de Barcelona. Departament de Ciència dels Materials i Química Física
[spa] Con el fin de desarrollar materiales de construcción más sostenibles, los cementos de fosfato de magnesio (MPC) se presentan como una prometedora alternativa al cemento Portland. En concreto, destacan en cuanto a sostenibilidad los cementos de fosfato de magnesio sostenibles (Sust-MPC) formulados con una fuente de fosfato como es el KH2PO4 y óxido de magnesio de baja ley (LG-MgO), el cual es un subproducto industrial procedente del proceso calcinación de la magnesita natural para la producción de MgO. El Sust-MPC despierta un gran interés desde el punto de vista medioambiental, ya que, por sus propiedades encapsulantes, es compatible con la adición de otros subproductos y residuos como agregados, formando morteros e incluso hormigones dependiendo del tamaño de partícula, y mejorando el comportamiento mecánico del conjunto. Además, cabe la posibilidad que los agregados reaccionen con el Sust-MPC dando lugar a productos de hidratación que potencialmente puedan mejorar si cabe más las propiedades mecánicas del material. La presente tesis doctoral desarrolla micro-morteros, denominados así por el tamaño de partícula de los agregados, usando Sust-MPC como matriz conglomerante y un subproducto industrial y un residuo como agregados (o micro-agregados). De esta forma se desarrollan dos tipos de micro- morteros, un primero formulado con el conglomerante Sust-MPC y un residuo procedente del reciclaje del vidrio denominado CSP, del inglés Ceramic, Stone and Porcelain, como micro-agregado. El otro micro-mortero incorpora al conglomerante Sust-MPC un residuo procedente de la industria de reciclaje del aluminio, el PAVAL® (PV). La investigación llevada a cabo tiene como objetivo determinar la mejora del comportamiento mecánico del material final, la reducción del potencial lixiviador de los subproductos, y la posibilidad de que estos micro-agregados formen compuestos de tipo silico-fosfatos, para el CSP, y alumino-fosfatos, para el PV, que puedan contribuir de forma positiva al comportamiento general del micro-mortero. A lo largo de los diferentes capítulos se detallan los resultados para el desarrollo de ambos micro- morteros, los cuales muestran una mejora considerable de las propiedades mecánicas, corroborando la correcta incorporación del subproducto y el residuo en el Sust-MPC. El principal resultado de la tesis doctoral es la observación de la disolución parcial de partículas ricas en Al y Si en la matriz cementante, posiblemente por la formación de nuevos productos de hidratación. Finalmente, se confirma la reducción del potencial lixiviador de metales pesados contenidos inicialmente en el residuo y los subproductos utilizados, gracias a la dilución y acción encapsulante del Sust-MPC. Las mejores formulaciones seleccionadas se basan en un compromiso entre la resistencia mecánica y el potencial lixiviador del material final, promoviendo la economía circular, las políticas de residuo cero y acercando un poco más a la sociedad al cumplimiento de los Objetivos de Desarrollo Sostenible (ODS).
Desenvolupament de nous materials basats en alúmina per fabricació additiva mitjançant estereolitografia
(Universitat de Barcelona, 2023-01-27) Barcelona Pons, Pol; Xuriguera Martín, María Elena; Padilla Sánchez, José Antonio; Universitat de Barcelona. Departament de Ciència dels Materials i Química Física
[cat] La estereolitografia (SLA) és la primera de les tecnologies de fabricació additiva desenvolupada. Aquesta consisteix en la fotopolimerització d’una resina líquida per capes mitjançant la irradiació selectiva de l’àrea que formarà part de l’objecte 3D. Diferents tecnologies basades en SLA s’empraran en aquesta tesi doctoral. S’utilitzaran en el present treball dos equips diferents; un, basat en un sistema de projecció Digital Light Processing (DLP), i un segon, que utilitza una font de LEDs UV i un sistema d’emmascarat per pantalla Liquid-Crystal Display (LCD). La SLA, tot i ser una tecnologia desenvolupada per la fabricació d’objectes a partir de polímers fotosensibles, s’utilitza també per l’obtenció de materials compostos i ceràmics. La metodologia és a nivell teòric senzilla; utilitzar una suspensió estable de partícules embegudes en una matriu polimèrica fotosensible. En el cas dels materials compostos, s’obté directament la peça final. Per peces ceràmiques, s’utilitzen suspensions molt més concentrades i la resina com aglomerant, que després s’eliminarà en tractaments tèrmics posteriors, obtenint així la peça ceràmica final. Tot i això, existeixen problemàtiques habituals associades a la tecnologia. La SLA requereix de suspensions molt fluides, que permetin un bon anivellament de la suspensió i el correcte flux d’aquesta. Per contra, el processat ceràmic necessita de suspensions amb concentracions molt elevades per assegurar una correcta densificació de la peça i evitar l’aparició de defectes. En aquest treball s’ha utilitzat la incorporació de PEG 200 com a diluent no reactiu per millorar l‘eliminació de la part orgànica. S’ha aconseguit una suspensió estable al 77,5 % d’alúmina en pes, imprimible per SLA-DLP i que pot ser tractada tèrmicament per l’obtenció de peces ceràmiques sense esquerdes amb velocitats d’escalfament més ràpides de les habituals. Pel que fa al desenvolupament de materials compostos, l’interès es genera a causa de les baixes propietats mecàniques que presenten les resines acríliques. Aquesta falta de propietats en limita un ús més generalitzat. L’objectiu d’aquesta tesi en aquet sentit és formular i caracteritzar diferents suspensions ceràmiques d’alúmina poc concentrades en partícules, per obtenir materials compostos amb propietats millorades respecte la resina base. Per tal de determinar l’efecte únicament de l’addició de partícules i no en el grau de curat, s’ha emprat un model matemàtic de fotopolimerització frontal per predir el temps d’exposició necessari per cada tinta. El model ha funcionat correctament pel sistema d’impressió per SLA-DLP, però no pel sistema SLA-LCD. Un dels punts clau ha estat la formulació de suspensions suficientment estables per utilitzar-se com a tintes per la impressió de compòsits. Per fer-ho, s'han estudiat diferents sistemes dispersants en funció de la resina base i el tipus de partícula emprada. S’han obtingut suspensions de diferents alúmines amb una concentració màxima del 15 % en pes de pols ceràmica, que presenten mòduls elàstic superiors a la resina base en el rang entre el 5 i el 10 % d’alúmina. Les millores són més notables en les provetes fabricades mitjançant l’equip SLA-DLP, passant de 220 MPa per la resina base a 600 MPa per les provetes reforçades amb un 10 % d’alúmina, que per les provetes fabricades amb l’equip SLA-LCD, que s’aconsegueix un augment de 750 MPa per la resina base fins 890 MPa de mòdul elàstic màxim per les provetes reforçades amb un 5 % d’alúmina. Addicionalment, s’han estudiat sistemes duals epòxid-acrílic com a resina base per la incorporació de partícules de reforç. Aquests sistemes presenten un curat tèrmic addicional a la fotopolimerització inicial, que en millora la rigidesa, augmentant el mòdul elàstic final. Les resines híbrides impreses arriben a mòduls elàstics de 2 GPa.

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