Luleå University of Technology Publications
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Simultaneous Probe of the Charm and Bottom Quark Yukawa Couplings Using ¯ Events
No full textA search for the standard model Higgs boson decaying to a charm quark-antiquark pair, →¯, produced in association with a top quark-antiquark pair (¯) is presented. The search is performed with data from proton-proton collisions at √ =13 TeV, corresponding to an integrated luminosity of 138 fb−1. Advanced machine learning techniques are employed for jet flavor identification and event classification. The Higgs boson decay to a bottom quark-antiquark pair is measured simultaneously and the observed ¯(→¯) event rate relative to the standard model expectation is 0.91+0.26−0.22. The observed (expected) upper limit on the product of production cross section and branching fraction (¯)ℬ(→¯) is 0.11 (0.13) pb at 95% confidence level, corresponding to 7.8 (8.7) times the standard model prediction. When combined with the previous search for →¯ via associated production with a or boson, the observed (expected) 95% confidence interval on the Higgs-charm Yukawa coupling modifier, , is || <3.5 (2.7), the most stringent constraint to date.Full text license: CC BY</p
On-site residual prestress assessment for service life estimation of prestressed concrete bridges
No full textIn recent decades, assessing the performance of existing structures has become increasingly crucial, especially as many post-war structures approach the end of their design lifespan. Among these, prestressed concrete bridges are particularly concerning because they are inherently vulnerable to deterioration caused by time-dependent prestress losses. Recent inspections of prestressed concrete bridges with internally grouted tendons have uncovered hidden defects beneath a seemingly intact and robust exterior, raising concerns about their structural integrity. Notable bridge collapses, including the Koror–Babeldaob Bridge (1996), Nanfang’ao Bridge (2019), the Polcevera Viaduct (Morandi bridge, 2018) and Carola Bridge (2024) highlight the critical need for accurately assessing the structural condition of aging bridges. These cases underscore vulnerabilities in prestressing systems and underline key gaps in understanding degradation mechanisms, long-term performance, and failure factors in prestressed concrete structures. Conventional investigation techniques and visual inspections often fail to capture the true condition of these structures, necessitating specialized evaluation methods. As a result, there is a pressing need for reliable, user-friendly, and nondestructive techniques to assess their structural performance throughout their life cycle. Such assessments play a vital role in early diagnostics, helping to prevent cracking and deflections that could jeopardize a bridge’s structural integrity and safety. A major challenge in evaluating the structural performance of existing prestressed concrete bridges is assessing the time-dependent loss of prestress. This loss serves as both an indicator and a warning sign of potential structural deterioration. However, accurately measuring prestress loss is difficult due to uncertainties in material properties, environmental conditions, and long-term degradation processes. Simplified code-conforming models fail to account for the combined effects of environmental wear and fatigue, leading to discrepancies between measured and predicted prestress losses. This study examines various testing methods for estimating residual prestress, highlighting their features and experimental approaches through a case study of the Kalix Bridge, a 66-year-old prestressed box-girder bridge in northern Sweden. This bridge posed unique challenges due to the complexity of its prestress system, the non-homogenous concrete curing process induced by due to multiple construction stages and the long-term deformations at the pendulum joint associated with creep. A numerical model was developed and calibrated using proof-loading test data and material characterization from extracted concrete cores. This updated model was later used to calculate residual prestress, which was then compared with predictions from standard formulations. Advanced probabilistic methods, including Bayesian updating and time-dependent reliability analysis, were also employed to refine residual prestress estimations and improve longterm reliability assessments. These methods allowed for the probabilistic analysis of uncertainties in estimating the service life of bridges, particularly when updating prestress levels retrieved through testing. By incorporating uncertainties related to material properties, environmental conditions, and degradation processes, these approaches enhance the accuracy of predictions about how long a bridge can remain serviceable after prestress updates. This refined approach provided valuable insights for optimizing maintenance strategies and ensuring extended service life and durability of prestressed concrete structures
Development of 3D printable thermoplastic polymer composites for tribological applications
No full textThe growing interest in environmental sustainability aims to improve resource efficiency and minimize energy consumption throughout material manufacturing, usage, end-of-life handling, and recycling aspect. Energy loss due to friction and wear of materials is the major challenge in machine components. Therefore, reducing friction and improving wear resistance with an appropriate selection of surface materials is the most direct route to reducing energy loss via reduced frictional forces, which contributes directly to sustainable development in the field of tribology and machine components. In that regard, polymer-based materials (PBM) are widely used as load-carrying components, such as bearings in tribological applications. In recent years, additive manufacturing (AM), also known as 3D printing, has gained widespread interest in the functional prototyping of PBM. 3D printing of polymers enables time-efficient processing with weight reduction and energy savings, addressing the sustainable development goals (such as SDG 9, 11, and 12) associated with the manufacturing of engineering materials. Additionally, the ability of in-field fabrication at the time of need increases the potential implementation of decentralized manufacturing with AM, reducing the resource depletion related to logistics and transportation. Therefore, AM/3D printing of PBM holds significant potential to provide a major enhancement to the current manufacturing capabilities with environmental and economic benefits. Fused filament fabrication (FFF) is an extrusion-based 3D printing technique with increasing popularity for the manufacturing of thermoplastic polymers. The printing technique, processing parameters, material selection, part characteristics, and final application are some of the factors affecting the sustainability and performance of 3D printed PBM. It should be noted that surface finish and internal defects are two of the most important challenges within the FFF method. In addition, the requirement of high thermal processing conditions for high-performing thermoplastic matrices often complicates the processability in FFF. Therefore, this research project aims to identify and optimize the important printing parameters in the FFF method, and to understand the mechanism and formation of internal defects, bulk properties, and tribological performance of 3D printed PBM. Initially, the key process parameters affecting the quality of 3D printed PBM are identified by employing commercially available filaments. The interrelationship between processing-induced defects and their impact on the material properties is explored. Moreover, novel polymeric composite filaments based on the polyether-ether-ketone (PEEK) matrix are developed in-house. Composite filaments are printed and evaluated as load-bearing components. To develop in-house self-lubricating filaments, microscale short carbon fibers (SCF) and nanoscale silicon dioxide (SiO2) particles are incorporated with the PEEK matrix using melt compounding and fabricated with FFF 3D printing. 3D printed parts are evaluated for their thermal, mechanical, and tribological performance. The characteristics of internal porosity and their impact on the material properties of these composites are investigated in this thesis. 3D printed PBM are examined using fractography and tomography to identify the impact of printing parameters on the bulk structure. Raster angle orientation and printing speeds impacted the location and shape of internal voids. Filament fillers were distributed along the material deposition path during the printing process. Adding micro-SCF in the PEEK matrix negatively influenced the formation of voids and interlayer adhesion, while nano-SiO2 improved the fiber-matrix interfacial bonding, reducing the internal porosity. Moreover, the mechanical properties of 3D printed composites significantly increased compared to neat PEEK. Similarly, the crystallization behavior and thermal decomposition temperatures of PEEK were positively influenced by the presence of fillers. Furthermore, 3D printed components were compared with conventional injection/compression molded samples, and the results showed similar tribological performance for both processing methods. The experimentally developed self-lubricating PEEK-based composites exhibited significant improvement in friction reduction and wear resistance compared to commercially available filament options. The multiscale composites showed superior tribological performance in dry sliding, exhibiting up to 50% friction reduction and reduction of specific wear rates by an order of magnitude (at 10-7 mm3/Nm) compared to printed neat PEEK. Analysis of wear mechanisms indicated that neat PEEK and SCF‑PEEK suffered severe abrasion and fiber-matrix debonding with increasing contact pressures, respectively. On the contrary, SiO2-SCF-PEEK composites showed improved wear resistance with smoother surfaces due to the polishing effect of nanoparticles and enhanced stress transfer from the matrix to reinforcements. The increased tribo-contact area with a larger polymer sample size adversely impacted friction characteristics with stick-slip, however, the effect on specific wear rates remains remarkably low. Water lubrication effectively improved tribological performance by reducing running-in duration and fluctuations during the evolution of friction coefficients. In this thesis, 3D printed self-lubricating PEEK composites were successfully fabricated and exhibited comparable friction coefficients and wear resistance to their corresponding compression-molded composites. The findings are evidence that FFF 3D printing can be explored as an alternative technique for the sustainable manufacturing of PEEK-based materials for tribological applications
Sustainable solid-state polymer electrolyte based on PEO-Xanthan gum blend for enhanced lithium-metal batteries
No full textDespite their widespread adoption, LIBs are still facing several challenges, mainly related with safety concerns of conventional electrolytes that are currently limiting their practical use. Solid-state polymer electrolytes (SPEs) represent a promising alternative to produce safer devices, as they offer higher flexibility and energy density, easy processability, non-flammability and improved mechanical strength, even if they often suffer from low ionic conductivity at room temperature. To address the latter issue, the development of novel SPEs based on a blend of polyethylene oxide (PEO) and Xanthan gum (XG), a natural polysaccharide with notable mechanical and rheological properties, is proposed. In this study, the thermal, physical, and electrochemical properties of the PEO-XG blends were investigated, aiming to assess their potential as electrolyte for all solid-state lithium metal batteries. Improved ionic conductivity, electrochemical stability window and cycling stability are achieved, confirming the effectiveness of XG incorporation. The most promising electrolyte formulation was studied using self-diffusion 7Li pulse-field-gradient (PFG) NMR measurements and different temperatures and further evaluated in full-cell configurations employing two olivine-type cathodes (LFP and LMFP). When paired with a lithium manganese iron phosphate (LMFP) cathode and cycled over an extended voltage window of 2.5–4.5 V, the cell demonstrates high specific capacity and excellent capacity retention, maintaining stable performance for at least 750 cycles.Validerad;2025;Nivå 2;2025-11-25 (u5);Full text license: CC BY 4.0;</p
Two-dimensional type-II vdW heterostructure MASnBr3/MoS2 for photovoltaic applications
No full textHerein, we comprehensively investigated the structural, electronic, optical, and photocatalytic properties of van der Waals heterostructure (vdWHs) MASnBr3/MoS2 (MA: CH3NH3). Monolayer MASnBr3 exhibits dynamical stability, as confirmed by phonon spectrum analysis, but suffers from a wide direct bandgap (2.72 eV at the HSE06-SOC (Heyd-Scuseria-Ernzerhof 2006 – Spin Orbit Coupling) level), limiting its photovoltaic efficiency. The formation of heterostructure with MoS2 results in type-II band alignment that facilitates efficient carrier separation, with HSE06-SOC band gaps of 1.89 eV (for AA-configuration) and 1.36 eV (for AB-configuration), aligning optimally with the solar spectrum, while strain engineering further tunes the band gap, extending light absorption into the near-infrared region. The heterostructure exhibits remarkable optoelectronic performance, including a high optical absorption coefficient (8 × 105 cm−1) and a Spectroscopic Limited Maximum Efficiency (SLME) of up to 30 %, exceeding that of conventional lead-based perovskites and monolayer MASnBr3. Favorable valence and conduction band offsets (VBO = 0.48 eV, CBO = 1.6 eV) ensure rapid electron-hole separation, while robust mechanical stability (Young’s modulus ≈ 80 N·m−1) underscores practical viability. These attributes, combined with its potential for photocatalytic hydrogen evolution, position the vdWHs MASnBr3/MoS2 as a promising candidate for sustainable photovoltaics and photocatalysis, offering tunable optoelectronic properties with robust structural stability.Validerad;2025;Nivå 2;2025-11-24 (u4);Funder: Wallenberg Initiative Materials Science (WISE); Ningbo Municipal Government, Zhejiang, China (2024A-434-G; 2024A-176-G); Nottingham Ningbo China Beacons of Excellence Research and Innovation Institute;Fulltext license: CC BY-NC</p
Decentraliserade behandlingssystem för bad-, disk- och tvättvatten: funktion, mikrobiella risker och mikroplaster
No full textGreywater originates from kitchen sinks, dishwashers, handbasins, showers, and laundry. Greywater can account for 70–90% of the domestic wastewater volume and contains organics, nutrients, pathogenic microorganisms, micropollutants, and microplastics. Effective treatment can unlock the potential of greywater for non-potable reuse purposes like urban landscaping or irrigation. The overall aim of this thesis was to investigate on-site greywater treatment systems which included on-site systems, two green walls, and a treatment wetland, and investigate the treatment in terms of organic matter, nitrogen (N), phosphorus (P), pathogenic microorganisms and microplastics (MPs), including the potential resource recovery and safe reuse of greywater. Among the eight on-site systems (1–5 persons) investigated, commercial systems included three type A, two type B, and C system. Type D was a conventional sand filter. After the pre-treatment septic tanks, the treatment unit of type A consisted of a geotextile-fitted trickling filter over a sand bed, type B contained a mineral wool filter, and type C had fine-meshed plastic filters. The two green wall studies were conducted at a testbed facility, RecoLab, which received greywater from a newly developed urban city district (ca 1000 people). The treatment of an indoor vertical flow (VF) green wall with five filter materials (pumice, biochar, hemp fiber, spent coffee grounds, and composted fiber soil (a paper industry byproduct)) was investigated with the flow rates of 4.5, 9, and 18 L/d. The outdoor horizontal flow (HF) green wall with four levels filled with biochar, pumice, and LECA as filter material was investigated for one year, using a subsurface horizontal flow of 430 L/d. A long-term evaluation of the performance of a constructed wetland for treating greywater from a residential building (ca 100 people) in Norway was conducted, using data from the period 2001–2024. The constructed wetland consisted of a biofilter with Filtralite® material and a horizontal subsurface filter with Filtralite®P, for enhanced phosphorus removal. The treatment efficiency of the systems was highly influenced by the filter material and flow rates, while seasonal temperature changes had a low impact. All the systems demonstrated effective treatment of greywater and met the local discharge guideline of 80% BOD reduction and <3mg/L of P in the effluent. However, only the VF green wall and constructed wetland could produce an effluent with <1 mg P/L, a limit for facilities located in sensitive areas. Among the studied filter materials, sand, biochar, and Filtralite® were the most efficient (log10 reduction up to 4) in the bacteria Escherichia coli, enterococci, Clostridium perfringens, Pseudomonas aeruginosa, Legionella spp., and met the European Commission’s guideline for reuse of reclaimed water in agriculture. The quantitative microbial risk assessment (QMRA) on effluent greywater from the constructed wetland, for multiple exposure scenarios (16 exposures/year) of accidental ingestion of 1 mL, indicated safe reuse in a water cascade during the summer season with regard to E. coli and C. perfringens. In addition, using TED-/Py-GC/MS, high variability of MPs was observed in greywater from the different sources of generation, while all the filter material of the respective treatment systems effectively retained the MPs, except for mineral wool and hemp. The findings of this thesis could contribute to the development of a more resource-efficient wastewater management and Water-Food-Energy nexus by demonstrating the potential of decentralized greywater treatment systems
Dual fluorine-free salt electrolytes for medium-to-high voltage lithium metal batteries
No full textFlame-resistant and fluorine-free electrolytes based on (combining) the salts lithium saccharinate (LiSac) and lithium bis(oxalato)borate (LiBOB) in a single solvent triethyl phosphate (TEP) solvent and vinylene carbonate (VC) additive are presented and evaluated for lithium metal battery application. The dual salt electrolyte, 1.5 M LiSac + 0.2 M LiBOB in TEP w. 2 % VC, clearly outperforms the single salt ones in terms of electrochemical performance, especially vs. LiNi0.8Mn0.1Co0.1O2 (NMC811) cathodes, properties that originate in a Li+ cation first solvation shell mainly composed of Sac and BOB anions, promoting formation of a mechanically stable, inorganic-rich cathode electrolyte interphase layer, which by X-ray photoelectron spectroscopy was revealed to comprise Li3N, BxOy and SO32− species. Overall, this also results in stable cycling, and a capacity retention of 86 % in both Li||LiFePO4 and Li||NMC811 cells after 500 cycles at 1C rate – hence offering an intrinsically safer electrolyte that also enables the use of both lithium metal anodes and medium-to-high-voltage cathodes. Full text: CC BY license;For funding information, see: https://doi.org/10.1016/j.jpowsour.2025.239241</p
Advances in amine-based absorption solvent engineering: Co-solvent strategies toward low-energy post-combustion CO₂ capture
No full textThe continuous rise in anthropogenic CO₂ emissions from fossil fuel combustion underscores the urgency of developing efficient carbon capture technologies. Among various methods, post-combustion CO₂ capture using amine-based solvents remains the most mature and industrially viable. However, conventional aqueous-amine systems suffer from high regeneration energy demands, solvent degradation, and operational challenges. This study systematically reviews recent advances in amine-based solvents and co-solvent formulations designed to enhance absorption efficiency and reduce energy consumption. The discussion covers (i) thermodynamic and kinetic fundamentals of amine–CO₂ interactions, (ii) the effects of co-solvent addition on viscosity, mass transfer, and thermal stability, and (iii) the influence of operating parameters on cyclic capacity and regeneration energy. Emerging classes such as water-lean, biphasic, and nanoparticle-enhanced systems are critically compared based on their absorption kinetics, desorption enthalpy, and stability under cyclic operation. Bibliometric analysis is used to map the evolution of research trends in solvent engineering. The review highlights that co-solvents such as glycols, sulfoxides, and glycol ethers can lower reboiler duty by up to 60% relative to aqueous monoethanolamine while maintaining comparable absorption performance. Remaining challenges include viscosity control, long-term solvent degradation, and scalability. Future research should focus on optimizing solvent composition, integrating process intensification techniques, and developing predictive models linking molecular structure to process performance.Full text: CC BY-NC-ND license;</p
From products to smart solutions: A value-creation approach
No full textSmart solutions comprise a synergy of products, services, software, connectivity, data, and intelligence. This study examines the evolution of a manufacturer into a smart solution provider, highlighting the role of value-creation capabilities, activities, and practices. Through a longitudinal, in-depth single-case study of a leading technology provider, we scrutinize the value-creation capabilities, activities, and practices that enable a manufacturer to convert its product-focused capabilities and activities into those of a smart solution provider. Particularly, we uncovered three key value-creation-related capabilities that are crucial for the successful transition, namely: 1) visualization capability, 2) integration capability, and 3) scaling capability to revamp the business model for the adoption of smart solutions logic. The findings highlight the role of sensing, seizing, and transforming in a product manufacturer's transition. For managers, our study provides a framework that helps identify, manage, and alter a firm's capabilities and activities when steering the firm toward smart solutions.Full text license: CC BY</p