• Energy Research
• Open Source close
• Embargo close
• US close
• ES close
• EU close

Abstract The effect of high temperatures as a degrading factor of rock materials is investigated in this study. Valdieri Marble samples, collected in a quarry in North-western Italian Alps, were subjected to thermal cycles (ranging from 105° to 600 °C) and to subsequent non-destructive and destructive laboratory tests with the aim of evaluating the variation of physical and mechanical properties as a function of temperature variations. Physical and mechanical measurements were complemented with microscopic observations on thin sections. The increase of crack density with temperature and the consequent porosity increases were found to be the main causes of degradation of physical and mechanical properties. In general, density, ultrasonic pulse velocity, wet electrical resistivity, uniaxial compressive strength and Young's moduli decrease as temperature increases. By contrast, peak strain and porosity increase. Correlations between temperature and physical-mechanical properties were proposed and compared to other relationships already established in scientific literature. A damage parameter to quantify the degradation of mechanical properties with temperature is also proposed.

El propòsit de la tesi va ser explorar mitjançant estudis empírics l'evolució de l'ús de les eines Lean a les empreses manufactureres europees i el seu vincle amb les tecnologies de la Indústria 4.0 i les pràctiques green. En primer lloc, es va investigar l'adopció i la internalització de les eines Lean i el seu impacte en el rendiment productiu a les empreses manufactureres espanyoles. Tot seguit, es va analitzar la influència de la internalització de les eines Lean en l'adopció de tecnologies de la Indústria 4.0 a les empreses manufactureres europees. I, finalment, es va examinar la relació entre l'ús conjunt d'eines Lean i les pràctiques green associat a l'exercici mediambiental a les empreses manufactureres espanyoles. La metodologia emprada al llarg dels estudis presentats es va basar en l'anàlisi de dades extretes de la European Manufacturing Survey The purpose of the thesis was to explore through empirical studies the evolution of the use of lean tools in European manufacturing firms and their link with Industry 4.0 technologies and green practices and Circular Economy. First, the adoption and internalisation of lean tools and their impact on production performance in Spanish manufacturing firms were investigated. Next, the influence of the internalisation of Lean tools on the adoption of Industry 4.0 technologies in European manufacturing firms was analysed. Finally, the relationship between the joint use of Lean tools and green practices associated with environmental performance in Spanish manufacturing firms was examined. The methodology employed throughout the studies presented was based on the analysis of data extracted from the European Manufacturing Survey Programa de Doctorat Interuniversitari en Dret, Economia i Empresa

AbstractMountain treelines are thought to be sensitive to climate change. However, how climate impacts mountain treelines is not yet fully understood as treelines may also be affected by other human activities. Here, we focus on “closed‐loop” mountain treelines (CLMT) that completely encircle a mountain and are less likely to have been influenced by human land‐use change. We detect a total length of ~916,425 km of CLMT across 243 mountain ranges globally and reveal a bimodal latitudinal distribution of treeline elevations with higher treeline elevations occurring at greater distances from the coast. Spatially, we find that temperature is the main climatic driver of treeline elevation in boreal and tropical regions, whereas precipitation drives CLMT position in temperate zones. Temporally, we show that 70% of CLMT have moved upward, with a mean shift rate of 1.2 m/year over the first decade of the 21st century. CLMT are shifting fastest in the tropics (mean of 3.1 m/year), but with greater variability. Our work provides a new mountain treeline database that isolates climate impacts from other anthropogenic pressures, and has important implications for biodiversity, natural resources, and ecosystem adaptation in a changing climate.

Synopsis Climate change is accelerating the increase of temperatures across the planet and resulting in the warming of oceans. Ocean warming threatens the survival of many aquatic species, including squids, and has introduced physiological, behavioral, and developmental changes, as well as physical changes in their biological materials composition, structure, and properties. Here, we characterize and analyze how the structure, morphology, and mechanical properties of European common squid Loligo vulgaris sucker ring teeth (SRT) are affected by temperature. SRT are predatory teethed structures located inside the suction cups of squids that are used to capture prey and are composed of semicrystalline structural proteins with a high modulus (GPa-range). We observed here that this biological material reversibly softens with temperature, undergoing a glass transition at ∼35°C, to a MPa-range modulus. We analyzed the SRT protein nanostructures as a function of temperature, as well as microscale and macroscale morphological changes, to understand their impact in the material properties. The results suggested that even small deviations from their habitat temperatures can result in significant softening of the material (up to 40% in modulus loss). Temperature changes following recent global climate trends and predictions might affect environmental adaptation in squid species and pose emerging survival challenges to adapt to increasing ocean temperatures.

For layered oxide cathodes, aluminum doping has widely been shown to improve performance, particularly at high degrees of delithiation. While this has led to increased interest in Al-doped systems, including $\mathrm{LiNi_{0.8}Co_{0.15}Al_{0.05}O_{2}}$ (NCA), the aluminum surface environment has not been thoroughly investigated. Using hard x-ray photoelectron spectroscopy measurements of the Al 1s core region for NCA electrodes, we examined the evolution of the surface aluminum environment under electrochemical and thermal stress. By correlating the aluminum environment to transition metal reduction and electrolyte decomposition, we provide further insight into the cathode-electrolyte interface layer. A remarkable finding is that Al-O coatings in LiPF$_6$ electrolyte mimic the evolution observed for the aluminum surface environment in doped layered oxides. ECS transactions 80(10), 197 - 206 (2017). doi:10.1149/08010.0197ecst Published by Pennington, NJ

Synopsis The biological structures that fill the environment around us are derived from materials produced by organisms. These biological materials are key to the mechanical function of organisms. The pathways and growth processes that produce biological materials can influence the mechanical properties of the materials, which can in turn shape the higher level function of the system into which the materials are incorporated. Characterizing a biological system requires thorough knowledge of the underlying materials, including their mechanical function, diversity, evolution, and sensitivity to the environment. Anthropogenic activity is driving rapid and widespread changes to the natural environment and global climate, which are influencing organismal growth and physiology in myriad ways. Here, we briefly introduce a collection of articles that focus on the intersection of anthropogenic activity and the mechanical function of biological materials, as part of the “Global Change in a Material World” bundle for Integrative and Comparative Biology. In addition, we provide an analysis of the current scientific literature in this field, highlighting an urgent need to better understand how changes to our world, driven by human activity, are influencing the fundamental architecture and mechanical performance of organisms across the globe.

The data used in "Assessing a Fuel Subsidy: Dynamic Effects on Retailer Pricing and Pass-Through to Consumers" by J. Balaguer and J. Ripollés.

The optical and photovoltaic properties of Si NCs / SiC multilayers (MLs) are investigated using a membrane-based solar cell structure. By removing the Si substrate in the active cell area, the MLs are studied without any bulk Si substrate contribution. The occurrence is confirmed by scanning electron microscopy and light-beam induced current mapping . Optical characterization combined with simulations allows us to determine the absorption within the ML absorber layer, isolated from the other cell stack layers. The results indicate that the absorption at wavelengths longer than 800 nm is only due to the SiC matrix. The measured short-circuit current is significantly lower than that theoretically obtained from absorption within the ML absorber, which is ascribed to losses that limit carrier extraction. The origin of these losses is discussed in terms of the material regions where recombination takes place. Our results indicate that carrier extraction is most efficient from the Si NCs themselves, whereas recombination is strongest in SiC and residual a-Si domains . Together with the observed onset of the external quantum efficiency (EQE) at 700-800 nm, this fact is an evidence of quantum confinement in Si NCs embedded in SiC on device level.

[eng] Aqueous zinc ion batteries (AZIBs) have garnered significant research attention due to their remarkably high-volume energy density, reaching up to 5,851 mAh mL-1. This surpasses the capabilities of state-of-the-art lithium-ion batteries (LIBs), making AZIBs a promising candidate for advanced energy storage technology. Additionally, the natural abundance, low cost, and non-toxic nature of zinc offer economic advantages and environmental sustainability, particularly beneficial for large-scale applications. One notable advantage of AZIBs is their ability to be fabricated in an air atmospheric environment, thanks to the air stability of the AZIBs system. This characteristic significantly simplifies the fabrication process, further enhancing the attractiveness of AZIBs for widespread adoption. However, the practical implementation of AZIBs still suffers from several intractable technical challenges, such as limited energy density and inadequate cycle life, which seriously hinder this technology from yielding practically viable energy density and cyclability. Selecting appropriate cathode materials and implementing rational structural design engineering can effectively overcome the aforementioned challenges. In Chapter 1, I summarize the state of the art on advanced cathode materials for AZIBs and particularly detail structural engineering strategies to achieve high energy density and extended cycle life. In Chapter 2, I detail my work on the design and engineering of K+ pre-intercalated MnO2 nanorods (K-MnO2-NR) as an efficient cathode to overcome the limitations of AZIBs. The K-MnO2-NR is synthesized by a facile one-step chemical method with a size of less than 10 nm. Their unique structure provides a large surface area, abundant active sites for ion storage, and a short diffusion path for ion transport. The intercalation of K+ also improves the conductivity of the electrode and stabilizes the tunnel structure. Consequently, this K-MnO2-NR configuration delivers a high capacity of 285 mAh g-1 at 0.1 A g-1, while retaining 222 mAh g-1 at 2 A g-1. Kinetic reaction analysis reveals that even under high charging/discharging rates, ion diffusion-controlled capacity plays a crucial role, which is beneficial for achieving high capacity under such conditions. Assembled pouch cells with K-MnO2-NR also exhibit promising application prospects. This work has been accepted for publication in the journal Ceramics International and it is already available online (https://doi.org/10.1016/j.ceramint.2024.04.324). However, the capacity of the enhanced MnO2 still falls short of expectations, hampering its practical application. The primary reason for this limitation is that the prepared crystalline MnO2 possess few defects, resulting in a reduced ion storage capacity. Hence, there arises a necessity to devise a novel defect engineering methodology to address this issue and obtain materials with high-density active sites, thereby enhancing their performance. In Chapter 3, to further improve MnO2-based cathodes, I introduce a method to obtain manganese oxide materials with high-density active sites through the in situ phase transformation of MnSe, thereby regulating the defect structure. I detail my work on the structural engineering of reduced graphene oxide (rGO)-coated MnSe nanoparticles (MnSe@rGO) as a cathode material for AZIBs. The introduction of rGO provides a surface-confining effect against morphological evolution, thus preventing structural failure of the electrode. Furthermore, the intrinsically high electronic conductivity of rGO facilitates the MnSe phase transition, enabling the utilization of its full capacity potential. The optimized MnSe@rGO-3 cathode demonstrates a significant specific capacity of 290 mAh g-1 at 0.1C and retains a specific capacity of 178 mAh g-1 even at 5C. Through quantitative electrochemical analyses, first-principles calculations, and in situ characterization, the enhanced capacitive zinc-ion storage behavior and phase transformation mechanism of MnSe@rGO cathode materials are elucidated. Moreover, the mechanical stability of rGO ensures the successful electrohydrodynamic (EHD) jet printing of flexible ZIBs into a flexible integrated functional system. As an illustration, a flexible touch-controlled light-emitting diode (LED) array system incorporating as-fabricated MnSe@rGO-3-based ZIBs is developed. This approach showcases effective performance in both flat and bent configurations, offering the added advantages of enhanced safety and environmental sustainability. This work was published in ACS Nano in 2023 (https://doi.org/10.1021/acsnano.3c00672). Despite the significant strides made in enhancing the specific capacity of Mn-based cathode materials through defect engineering, the persisting limitations associated with manganese dissolution and moderate cycle life continue to raise concerns. These issues indeed cast doubt on their viability for high-energy-density applications, particularly in application fields like wearables. In Chapter 4, to increase the energy density of AZIBs, I explain my work on the development of a new cathode material based on a layered metal chalcogenide (LMC), bismuth telluride (Bi2Te3) nanodisks, coated with polypyrrole (PPy) as cathode material for aqueous ZIBs, and then explore its storage mechanism. In situ X-ray diffraction (XRD) analysis, X-ray photoelectron spectroscopy (XPS) measurements, and density functional theory (DFT) calculations are employed to elucidate that the energy storage mechanism of Bi2Te3 is the insertion/extraction of protons rather than Zn ions within the (0 0 6) interlayers, coupled with the formation/deposition of Zn4SO4(OH)6·5H2O on the electrode surface. The PPy coating enhances the ionic conductivity of the LMC while preventing surface oxidation. Consequently, the Bi2Te3@PPy cathode exhibits remarkable rate performance and long-term cycling stability with ultra-long lifespans of over 5,000 cycles. They also present outstanding stability even under bending. This work was published in Advanced Materials in 2023 (https://doi.org/10.1002/adma.202305128). Finally, the main conclusions of this thesis, including a comparison chart of the three cathode materials developed in the thesis, and some perspectives for future work are presented. [spa] Las baterías de iones de zinc en electrolito acuoso (AZIBs) han atraído notable atención por su excelente densidad volumétrica de energía, alcanzando hasta 5,851 mAh mL-1, superando a las baterías de iones de litio (LIB). Además, el zinc es abundante, económico y no tóxico, lo que beneficia aplicaciones a gran escala. Las AZIBs pueden fabricarse en un ambiente atmosférico, simplificando significativamente el proceso de fabricación. Sin embargo, enfrentan desafíos técnicos como densidad de energía limitada y vida útil corta. En el Capítulo 1, se revisa el estado del arte sobre materiales catódicos avanzados para AZIBs, y se detallan estrategias para lograr alta densidad de energía y ciclo de vida extendido. En el Capítulo 2, se presenta el diseño e ingeniería de nanobarras de MnO2 preintercaladas con K+ (K-MnO2-NR) como cátodos. Este material, sintetizado mediante un método electroquímico sencillo, ofrece una alta capacidad de 285 mAh g 1 a 0.1 A g-1 y retiene 222 mAh g-1 a 2 A g-1. La intercalación de K+ mejora la conductividad y estabiliza la estructura, proporcionando una gran superficie y sitios activos para el almacenamiento de iones. Este trabajo se ha publicado en International Ceramics. En el Capítulo 3, se introduce un método para mejorar aún más el cátodo a base de MnO2 mediante la transformación de fase de MnSe, creando materiales con alta densidad de sitios activos. Se diseñaron nanopartículas de MnSe recubiertas con óxido de grafeno reducido (rGO) (MnSe@rGO). El recubrimiento de rGO mejora la conductividad y estabiliza la estructura, evitando fallos estructurales. El cátodo MnSe@rGO-3 demuestra una capacidad específica de 290 mAh g-1 a 0.1 C y retiene 178 mAh g-1 a 5C. Este trabajo fue publicado en ACS Nano. En el Capítulo 4, se explora un nuevo material catódico basado en nanodiscos de telururo de bismuto (Bi2Te3) recubiertos con polipirrol (PPy) para ZIBs acuosas. Mediante análisis XRD in situ, mediciones XPS y cálculos DFT, se dilucida que el mecanismo de almacenamiento de Bi2Te3 implica la inserción/extracción de protones y la formación de Zn4SO4(OH)6·5H2O. El recubrimiento de PPy mejora la conductividad iónica y previene la oxidación. El cátodo Bi2Te3@PPy exhibe excelente rendimiento y estabilidad a largo plazo, con una vida útil de más de 5,000 ciclos, incluso bajo flexión. Este trabajo fue publicado en Materiales Avanzados. A pesar de estos avances, persisten desafíos como la disolución del manganeso y la vida útil limitada, cuestionando su viabilidad para aplicaciones de alta densidad de energía. La tesis concluye con una comparación de los tres cátodos desarrollados y ofrece perspectivas para futuros trabajos. Programa de Doctorat en Nanociències / Tesi realitzada a l'Institut de Recerca en Energia de Catalunya (IREC)