Luleå University of Technology Publications
Not a member yet
39356 research outputs found
Sort by
Highly selective and permeable DDR membranes for CO2/CH4 separation in a wide temperature range
No full textA thin-film (700 nm) DDR zeolite disc membrane was evaluated for separating a 1/1 CO2/CH4 mixture in a wide temperature range (−35 to 180 °C). The highest selectivity of 2325 paired with a high CO2 permeance of 34 × 10−7 mol/(m2·s·Pa) was observed at −30 °C and a feed pressure of 3 bar. At the same feed pressure, the highest CO2 permanence was recorded at + 10 °C reaching 44 × 10−7 mol/(m2·s·Pa), while selectivity remained remarkably high at 1118. High permeance and selectivity were also observed at higher feed pressures. These results surpass all previously published data on CO2/CH4 separation using DDR zeolite membranes and indicate that the membranes have strong potential for upgrading natural gas and biogas. A model describing mass transfer while considering adsorption, surface barrier, and surface diffusion was fitted to experimental single gas permeation data and showed that it can accurately describe the mass transfer in the zeolite pores while indicating that the limiting step was the surface barrier. These findings highlight the potential of DDR membranes for industrial gas purification across a broad range of temperatures and feed pressures.Validerad;2025;Nivå 2;2025-09-25 (u4);Fulltext license: CC BY-NC</p
Development and Identification of Amine-based Deep Eutectic Solvents for CO2 Capture
No full textAmine-based deep eutectic solvents (DESs) are promising alternatives to conventional amines for CO2 capture; however, the molecular design principle to achieve practical performance remains unclear. In response to this challenge, this licentiate thesis aims to develop DES-based solvents that achieve balanced performance in 30 wt% aqueous solutions, including high absorption capacity, efficient desorption, good thermal stability, and manageable viscosity, with ethanolamine (MEA) used as the reference. In the first part of this work, ethylenediamine (EDA) and diethylenetriamine (DETA) were selected as hydrogen-bond donors (HBD), while a series of hydrogen-bond acceptors (HBAs) were varied to evaluate their effects on CO2 absorption and desorption behaviors. The solvents were evaluated for absorption capacity and absorption rate at 22 °C and 1 bar, for desorption and cyclic loading at 110 °C, and for thermal stability using thermogravimetric (TG) and derivative thermogravimetric (DTG). From this side-by-side comparison, 30 wt% aqueous [TrizCl][DETA] was identified as the most practical candidate. It achieves a CO2 absorption capacity of 0.164 g-CO2/g-solvent and an absorption rate of 0.183 g-CO2/(g-solvent·min), provides the largest cyclic loading of 0.091 g-CO2/g-solvent, and exhibits an onset decomposition temperature (Tonset) of approximately 178.7 °C. Although EDA-based DESs demonstrate the highest capacity and rapid absorption, for example, a 30 wt% aqueous [N-1,2,4-TrizCl][EDA] solution reaches 0.203 g-CO2/g-solvent, they exhibit limited thermal stability. Building on these findings, the second part of the study focused on structure-property relationships by fixing [TrizCl] as the HBA and varying the amine-based HBDs, including diamines, triamines, and alkanolamines. The comparison revealed that the balanced performance of [TrizCl][DETA] arises from the optimal combination of the triazolium-based HBA and the triamine HBD, which provides sufficient basicity and hydrogen-bonding capacity for CO2 activation. Additionally, [TrizCl][DETA] maintains workable viscosity after CO2 absorption at about 7.5 mPa·s, and exhibits stable absorption-desorption behaviors. Corrosion, oxidative degradation, and mechanistic analyses confirm its stability and explain the rise of moderate viscosity via carbamate and bicarbonate formation, indicating strong potential for CO2 capture and solvent recycling
Tempering of press hardening steels PHS1500 and PHS2000: characterization and influence on fracture toughness
No full textWith the continuous development of the automobile industry, the use of advanced high-strength steel in vehicles has become increasingly prevalent. Press hardening steels, known for their ultra-high strength, are gaining significant traction in this domain. Components manufactured using press hardening exhibit high dimensional accuracy and minimal spring back. The press hardening components are produced by heating the steel blank at the austenitization temperature, followed by hot forming and rapid cooling using pressing dies. However, despite the advancement in press hardening technologies and the widespread adoption of ultra-high-strength steels, certain challenges remain in further improving the performance of these materials, particularly in understanding the effect of processing treatments. This work studies the behavior of two ultra-high strength press hardening steels (PHS2000 and PHS1500) after undergoing heat treatment methods, specifically focusing on low-temperature tempering and press hardening. The objective is to increase the understanding of microstructure evolution and its influence on mechanical performance. The first method involved quenching the steels in oil followed by tempering at four temperatures in the range of 180-300 °C, while the second utilized die quenching to targeted temperatures, followed by air cooling to induce auto-tempering. Tensile properties, hardness, and microstructure changes were tested to understand how these treatments affect the steels' mechanical properties. The tensile properties of the steels investigated are influenced by the auto-tempering of martensite that occurs during the processes of oil quenching and die cooling. This phenomenon allows the steel to attain an optimal balance, demonstrating ultra-high strength exceeding 1900 MPa and good elongation at fracture, reaching around 8% or slightly higher. The tensile tests and microstructure analysis implied that low-temperature tempering (180-200 °C) could improve the yield strength of the steel as well as the elongation with a small reduction in the strength of the steel, in which the tempering effect caused precipitation strengthening and reducing of residual stresses in the microstructure. It was found that tempering at 300 °C promotes the formation and coarsening of cementite carbide, which led to a deterioration in the tensile elongation of the steels. The fracture toughness and bending properties of the steels were evaluated following oil quenching, press hardening, and a combination of press hardening with subsequent bake hardening. PHS2000 displayed brittle fracture characteristics and lower fracture toughness, while PHS1500 exhibited ductile fracture behavior and higher fracture toughness, with similar trends observed in three-point bending results. STEM and EDS analyses identified precipitates of varying compositions and morphologies, with coarse precipitates acting as key factors that limit grain refinement and contribute to stress concentration, thereby influencing fracture toughness and bending properties
DesignWise : Design Principles for Smart Applications targeting Internet of Things Services
No full textAs Internet of Things (IoT) has developed, the number of connected entities has increased, allowing systems to interact with users and their environments in smart ways. For example, presence and environmental sensors enable the system to be aware of the user's state and environment, allowing it to provide helpful information for users. The connected entities include not only IoT devices for data acquisition and actuation but also interaction modalities for communication between users and systems. Multimodal interaction (MI) and augmented reality (AR) are enablers for enhanced user experience (UX) for IoT services. However, combining an IoT-enabled system with MI and AR without careful consideration may hinder the benefits of these technologies. Thus, understanding the technologies and target user group's characteristics depending on the application's context is essential. Design principles allow people—who are interested in UX and user interface (UI) development of IoT-enabled mobile AR applications—to gain knowledge about UX/UI design that considers both the technology and user aspects.This thesis aims to identify, propose, and validate design principles for mobile applications within IoT-enabled smart city domains, especially healthcare and energy management services. We identified the requirements and needs of MI and AR through a systematic literature review. We also found that studies of design principles for IoT-enabled mobile AR applications are limited. We designed, developed, and analyzed three IoT-enabled mobile AR applications along with their UX. From the state-of-the-art research, we compiled and categorized 26 existing design principles into seven categories. We derived and evaluated five new design principles based on the analysis of our developed applications. As a practical realization of the identified design principles, we provided examples of design principles through user interface mockups, which represent the re-designed interfaces of the applications. We expect that our findings will give insight into the UX/UI design of IoT-enabled mobile AR applications for researchers, educators, and practitioners interested in UX/UI development
Eco-Friendly Recovery and Alloying of Metals from Spent Lithium-ion Batteries
No full textWith growing environmental concerns and the critical need for sustainable resources, metal recovery from secondary sources has gained importance. Among the techniques applied for this purpose, pyrometallurgy, which involves high-temperature processing, is a widely used method. However, this method faces challenges when recovering elements from spent Li-Ion Batteries (LIBs). Black Mass (BM), the residue left after mechanical shredding and physical separation of spent LIBs, is rich in valuable elements such as Co, Ni, and Li. This study investigates the pyrometallurgical recycling of BM from various types of LIBs. Initially, the high-temperature behavior of BM was examined to identify the critical reduction temperatures. A temperature of 600 °C was identified as critical. This temperature ensures the complete transformation of the cathode material into its constituent metal oxides (MeOs). Additionally, thermodynamic modeling indicated that up to 600 °C Li is present as Li2O or Li2CO3, while at higher temperatures, it forms LiAlO2 by reacting with Al. A temperature of 800 °C was found to fully reduce Co and Ni oxides to their metallic forms. Furthermore, it was also observed that heating the BM up to 700 °C, regardless of the atmosphere's oxidizing properties, resulted in evaporation of less than 10 % of the F in the BM. After investigating the high-temperature behavior of BM, in-situ alloying was introduced as an approach for recovering Co and Ni as alloying elements. This was achieved by the addition of Fe2O3/CuO to the BM, and consequently, the production of Fe/Cu-based alloys. The effect of mechanical activation on BM reduction and in-situ alloying was also examined, revealing varying effects across different BMs. While ball milling showed no effect on some BM samples, it enhanced the reduction rate in others by decreasing particle size. The variation in BM susceptibility to ball milling may result from the technique employed in producing the BM or the rate-influencing factors in its reduction. In samples where the reduction rate improved, ball milling resulted in lower C consumption and, consequently, reduced CO2 emission. In the final phase of this study, slag was incorporated into the in-situ alloying system, and Li and F evaporation were tracked under various slag conditions. Basicity was found to be a significant parameter, with a linear positive effect on Li evaporation and a quadratic effect on F evaporation.
High-Entropy Oxides for Thermoelectric Application
No full textHigh-entropy oxides (HEOs) are a new class of single-phase inorganic materials with a high specific capacity, high structural stability, and super-electronic conductivity and exhibit a wide range of useful properties. HEOs are better semiconductor materials compared to traditional ones due to their lattice distortion. Because parameters, such as crystal symmetry, different lattice parameters, etc., have a significant influence on the thermal conductivity of the material, lowering it via phonon-phonon or phonon-electron scattering. The entropy stabilization produces the high stability of the phase but also can result in interesting properties of the materials due to the contribution of different elements through four main effects: high-entropy effect, severe lattice distortion, sluggish diffusion effect, and cocktail effect. This thesis identified potential HEOs with the chemical composition Co-Cr-Fe-Mn-Ni-O by doing a thorough literature review. During the research, we have focused on the synthesis process and electrical properties of the HEOs (Co0.33Cr0.22Fe0.22Mn0.11Ni0.11)3O4, (Co0.33Cr0.22Fe0.22Mn0.11Cu0.11)3O4, and (Co0.2Cr0.2Fe0.2Mn0.2Cu0.2)3O4. Oxides were synthesized via Spark Plasma Sintering and Solid-State Reaction resulting in obtaining two or more phases with different crystal structures for the materials (Co0.33Cr0.22Fe0.22Mn0.11Ni0.11)3O4, and single-phased for the (Co0.33Cr0.22Fe0.22Mn0.11Cu0.11)3O4 and (Co0.2Cr0.2Fe0.2Mn0.2Cu0.2)3O4 at specific synthesis conditions. As expected, obtained single-phased materials exhibit higher values of electrical conductivity, which is probably due to the less electron-phonon scattering. Two types of semiconductors are needed for thermoelectric applications: p- and n-type. Due to the different synthesis temperatures, materials with Ni were obtained in both types. This can lead to the production of the Peltier module with the same chemical composition inside. With the Ni-Cu substitution, it became easier to produce single-phased materials, probably due to the melting point of the reagents. These materials also presented higher electrical properties, which the changes in carrier concentration can explain due to the differences in the electronic structures. All obtained samples exhibit low values of the electronic part of thermal conductivity, which can lead to low values of total thermal conductivity. It shows that the main contributor to the thermal conductivity will be from the phonons (lattice thermal conductivity). Overall, the expected thermal conductivity for these materials should be lower compared to the traditional semiconductor materials due to the crystal distortion, which can lead to higher phonon-phonon and phonon-electron scattering. Furthermore, this research shows that HEOs with unequal content of metals can be produced as single-phase materials and have even better or similar electrical properties compared to known compositions. Also, these oxides with impurities still exhibit promising electrical properties
Membrane technologies for treatment of urban wastewater streams and resource recovery
No full textStormwater and blackwater are two urban wastewater streams with potential as valuable resources. The stormwater quality varies depending on catchment, actual rain pattern, pollutants sources, etc. Blackwater contains nutrients and energy that can be recovered. In addition, it contains organics, metals, micropollutants and microorganisms which might affect the efficiency of downstream processes. Efficient removal of contaminants from both stormwater and blackwater is essential for their reuse and recovery of resources, including water and nutrients. Membrane technology offers an advanced solution to improve the quality of stormwater and blackwater. While a number of studies have explored the application of membranes for stormwater treatment, the varying quality of stormwater raises questions about membranes’ efficiency in separating pollutants from different qualities of stormwater. More research is needed to understand the reusability of treated stormwater using membranes as well as the recovery of metals in the concentrate. The overall aim of this study is to improve the quality of stormwater and source-separated blackwater, which has a direct impact on the reusability of stormwater as water resource and of struvite as a biofertilizer. Nutrient recovery from blackwater after membrane treatment is a new concept requiring further attention. Membrane cleaning is essential for maintaining membrane efficiency. For stormwater, regular backwashing with different durations and chemical combinations were tested, and the fouling layer on the membrane was analyzed, using a scanning electron microscope. Backwash water was characterised. For blackwater, the membrane cleaning method used included backwashing combined with aeration, raising the question about its adequacy. The ultrafiltration membrane was able to separate total suspended solids, oil, particulate metals, total phosphorus, turbidity and microorganisms from stormwater and effectively reduced organic compounds. After hygenisation, ultrafiltratered stormwater has a significant potential for non-potable uses, and its quality approaches potable standards, based on Swedish Food Agency. The struvite produced from membrane treated digestate resulted in struvite with more uniform struvite crystals, free of organic substances and metals (As, Ca, Cr, Cu, Pb and Si) stepping towards reusing this struvite as biofertilizer. The optimal backwash duration after stormwater treatment, for these set of experiments was 45 s considering membrane productivity. Chemical cleaning with sodium hydroxide, and with or without sodium hypochlorite followed by hydrochloric acid were compared which indicated that addition of sodium hypochlorite did not improve the efficiency of chemical cleaning. Analyses of the backwash water showed a high metal concentration which might indicate the potential for metal recovery. Combinations of backwash and aeration was an efficient method to preserve membrane initial flux after digestate blackwater treatment.
Mot cirkulär ekonomi för rymd: Satellitåteranvändningens roll
No full textDriven by innovation and cost reductions, the space industry is experiencing rapid growth. The proliferation of human-made objects launched into Earth orbits presents significant environmental challenges. If not properly addressed, continued growth at the current rate could lead to negative impacts both in space and on Earth. The space industry has begun exploring sustainable practices, though most efforts focus on addressing issues that are related to the space environment. This neglects the impact on Earth and its atmosphere. Progress has been made in reuse of rocket bodies, however the benefits of satellite reuse remain largely disregarded. For example, the environmental impact of satellite constellations that are currently designed with large amounts of single use satellites, is still underexplored. This underscores the critical research gap in understanding the fast-growing space industry’s impact on the environment and advancing knowledge related to satellite reuse. Therefore, the objective of this thesis is to explore satellite reuse and its contribution to space sustainability. The research starts by exploring how the fast-growing space industry impacts the environment and then examines if satellite reuse could help mitigate this impact. It ends with asking why satellite reuse is not yet widespread. The research in this thesis employs a mixed-method approach, starting with industry expert interviews to gain insight into the current state of practice for satellite reuse. Building upon these interviews, two scoping studies were conducted to further the understanding on how satellite reuse could be achieved. The findings emphasize the importance for the space industry to initiate an industrial transformation and develop sustainability-driven innovation rather than having a focus on mostly commercial gains. The absence of necessary practices and technologies for satellite reuse have been identified in three critical building blocks: (1) reverse logistics systems to retrieve and process satellites for reuse, (2) design practices that enable reuse, and (3) business models that ensure financial viability. Focusing on these three areas can advance sustainable practices in the space industry and could contribute to the mitigation of its negative environmental impact. The presented findings can provide valuable insights for policymakers and industry stakeholders, to rethink practices and to prioritize sustainability in space activities.Drivet av innovation och minskade kostnader upplever rymdindustrin en snabb tillväxt. Den ökande spridningen av mänskligt skapade objekt i omloppsbanor runt jorden medför betydande miljöutmaningar. Om detta inte hanteras kan den fortsatta tillväxten medföra betydande negativ miljöpåverkan, både i rymden och på jorden. Rymdindustrin har börjat arbeta med hållbarhet, men mestadels fokuseras frågor kopplade till rymdmiljön. Det innebär att miljömässig påverkan på jorden och atmosfären i stort sett bortses ifrån. Framsteg har gjorts inom återanvändning av raketdelar, men fördelarna med att återanvända satelliter har till stor del ignorerats. Exempelvis är miljöpåverkan från satellitkonstellationer, som idag ofta designas med stora mängder engångssatelliter, fortfarande ett relativt outforskat område. Detta framhäver ett kritiskt forskningsgap: en brist på förståelse för hur den snabbt växande rymdindustrin påverkar miljön och ett behov av fördjupad kunskap om återanvändning av satelliter. Syftet med denna avhandling är att utforska hur satellitåteranvändning kan bidra till rymdhållbarhet. Forskningen inleds med en undersökning av hur rymdindustrins tillväxt påverkar miljön och huruvida satellitåteranvändning kan mildra denna påverkan. Den avslutas med att undersöka varför återanvändning av satelliter ännu inte är utbrett.Studien använder en blandad forskningsmetodik, och inleddes med intervjuer av industriexperter för att få inblick om nuläget för satellitåteranvändning. Baserat på dessa intervjuer genomfördes två förstudier för att ytterligare förstå hur återanvändning av satelliter kan möjliggöras. Resultaten betonar vikten av att rymdindustrin genomgår en industriell omvandling och utvecklar hållbarhetsdriven innovation, i stället för att enbart fokusera på kommersiella mål. Tre viktiga områden identifierades som avgörande för att möjliggöra återanvändning av satelliter: (1) returlogistiksystem för att samla in och bearbeta satelliter för återanvändning, (2) designpraktik som möjliggör återanvändning, och (3) affärsmodeller som säkerställer ekonomisk bärkraft. Genom att prioritera dessa områden kan rymdindustrin främja hållbara metoder och minska sin miljöpåverkan. Resultaten kan ge värdefulla insikter för beslutsfattare och industrins aktörer, med möjlighet att förändra praxis och prioritera hållbarhet i rymdaktiviteter
Materialkaraktärisering och processmodellering av varmformning av ultrahöghållfast stål för chassikomponenter i tunga fordon
No full textThe European Commission has set a target to reduce greenhouse gas (GHG) emissions from road transport by 60\% compared to 1990 levels by 2050, as outlined in the Transport White Paper. In 2012, passenger cars accounted for about 60\% of GHG emissions from the road transport sector, a figure expected to decline to 45\% by 2030. Meanwhile, heavy-duty vehicles (HDVs), including trucks, buses, and coaches, contribute around 26\% of total CO emissions in the European Union, with trucks alone responsible for over 85\% of this share. To achieve the 2050 goal, the European Commission has identified key strategies, including improving vehicle efficiency, developing sustainable propulsion systems, and using advanced lightweight material solutions. A promising approach to reduce fuel consumption and increase payload capacity in HDVs is to reduce vehicle weight. One method is the integration of ultra-high strength steels (UHSS) into chassis structures, enabling thinner, lighter components. However, the limited ductility of UHSS in cold-forming requires exploring alternative forming techniques. Warm forming of thick-walled UHSS sheets presents a viable solution. This thesis focused on the mechanical characterisation of WARMLIGHT-980, a novel 7~mm thick UHSS grade (UTS 980~MPa), developed for warm forming in the 430–580\textdegree C range. The goal of the forming process is to produce lightweight components with high stiffness and fatigue resistance, specifically for HDVs. The elastoplastic and ductile failure properties of this UHSS grade were investigated at elevated temperatures to support numerical simulations of warm-forming processes. Failure strains under various stress triaxialities and specimen geometries were determined by digital image correlation. Due to the thickness of the material, conventional full-scale specimens were impractical; thus, scaled-down 1.2~mm specimens were tested and validated against full-thickness tensile tests. Inductive heating was used to reach target-forming temperatures, with thermal photography confirming uniform distribution. A modified Mohr-Coulomb ductile failure model, calibrated at 3D stress states, was used to predict crack formation during forming. The thermo-mechanical simulation model was validated through three-point bending tests by comparing force-displacement responses. Thickness distribution from simulations was also compared with demonstrator components. Findings indicate UHSS can be effectively warm-formed into complex components at elevated temperatures. The calibrated material model accurately describes material behaviour, with simulation results closely matching experimental force measurements. This research supports the development of lightweight, high-performance HDV structures through improved forming processes and material modelling
Mechanical Characterization and Modeling of Heterogeneous Brittle Materials in Comminution Processes
No full textThe steel industry has been an asset in society’s development; therefore, the worldwide production of crude steel has shown a growing trend. Following the sustainability principles reflected by the World Steel Association, incorporating pyrometallurgical by-products into a circular economy framework is of great interest to maximize the efficient use of resources throughout the life cycle of steel products and to help reduce CO2 emissions. Thus, research to optimize the supply chain of raw materials has increased, and there is a need to address the energy consumption of the highly demanding mechanical processes related to it, such as crushing. This PhD research focuses on the development of a framework that facilitates the optimization of comminution processes for secondary raw materials and enhances the value of material data for modeling breakage processes in the upscaling and evaluation of crushing at an industrial scale. This investigation was divided into two primary components. First, an experimental framework was developed and implemented to characterize the tensile and compressive responses of electric arc furnace (EAF) manganese slag under both quasi-static and dynamic conditions. In the first study, manganese slag, a highly heterogeneous material, was examined, providing insights into the methodologies and challenges associated with sample manufacturing, quasi-static testing using simple loading schemes, and processing of mechanical and optical data. In the second study, the macro-response of slag under dynamic conditions was investigated, providing pertinent information regarding processing and crushing in relation to rate-dependent behavior, as well as energy expenditure during the fragmentation processes. The second part of this research focused on evaluating a numerical framework to upscale the fracture processes in crushing applications. Simulations of the fracture process of quasi-brittle materials employing finite element methods (FEM) were implemented and evaluated for mineral and secondary raw materials, enhancing the knowledge regarding the calibration of material models to simulate complex geometries with a high level of detail in the crack patterns and the accuracy of the failure loads. Finally, a fourth research article demonstrated the viability of employing an established material model to simulate slag from a macroscopic perspective.