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  • 1.
    Babaahmadi, Arezou
    et al.
    Chalmers University of Technology, Department of Architecture and Civil Engineering, Gotenburg, Sweden.
    Machner, Alisa
    Technical University of Munich, TUM School of Engineering and Design, Department of Materials Engineering, Professorship for Mineral Construction Materials, Munich, Germany.
    Kunther, Wolfgang
    Technical University of Denmark, Department of Environmental and Resource Engineering, Kongens Lyngby, Denmark.
    Figueira, Joao
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Hemstad, Petter
    Norwegian University of Science and Technology, NTNU, Department of Structural Engineering, Trondheim, Norway.
    De Weerdt, Klaartje
    Norwegian University of Science and Technology, NTNU, Department of Structural Engineering, Trondheim, Norway.
    Chloride binding in Portland composite cements containing metakaolin and silica fume2022In: Cement and Concrete Research, ISSN 0008-8846, E-ISSN 1873-3948, Vol. 161, article id 106924Article in journal (Refereed)
    Abstract [en]

    This paper investigates how the composition of Portland composite cements affects their chloride-binding properties. Hydrated cement pastes prepared with a reference Portland cement and composite Portland cements containing metakaolin and/or silica fume were exposed to NaCl or CaCl2 solutions. Chloride-binding isotherms were determined and the hydrate assemblage was investigated using TGA, XRD, 27Al NMR, 29Si NMR and thermodynamic modelling. Compared to the reference Portland cement paste, silica fume replacement did not alter the chloride-binding capacity. The metakaolin replacement resulted in the highest chloride-binding capacity. When combining silica fume with metakaolin, the chloride binding is similar to the reference Portland cement. In this study the differences in chloride binding were linked not only to changes in the AFm content, but also to alterations in the Al-uptake and chain length of the C(-A)-S-H.

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  • 2.
    Buckland, Philip I.
    et al.
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    Hammarlund, Dan
    Lund University.
    Hjärthner-Holdar, Eva
    Swedish National Historical Museums.
    Lidén, Kerstin
    Stockholm University.
    Lindahl, Anders
    Lund University.
    Palm, Fredrik
    Umeå University, Faculty of Arts, Humlab.
    Possnert, Göran
    Uppsala University.
    The Strategic Environmental Archaeology Database: a resource for international, multiproxy and transdisciplinary studies of environmental and climatic change2015Conference paper (Refereed)
    Abstract [en]

    Climate and environmental change are global challenges which require global data and infrastructure to investigate. These challenges also require a multi-proxy approach, integrating evidence from Quaternary science and archaeology with information from studies on modern ecology and physical processes among other disciplines. The Strategic Environmental Archaeology Database (SEAD http://www.sead.se) is a Swedish based international research e-infrastructure for storing, managing, analysing and disseminating palaeoenvironmental data from an almost unlimited number of analysis methods. The system currently makes available raw data from over 1500 sites (>5300 datasets) and the analysis of Quaternary fossil insects, plant macrofossils, pollen, geochemistry and sediment physical properties, dendrochronology and wood anatomy, ceramic geochemistry and bones, along with numerous dating methods. This capacity will be expanded in the near future to include isotopes, multi-spectral and archaeo-metalurgical data. SEAD also includes expandable climate and environment calibration datasets, a complete bibliography and extensive metadata and services for linking these data to other resources. All data is available as Open Access through http://qsead.sead.se and downloadable software.

     

    SEAD is maintained and managed at the Environmental Archaeology Lab and HUMlab at Umea University, Sweden. Development and data ingestion is progressing in cooperation with The Laboratory for Ceramic Research and the National Laboratory for Wood Anatomy and Dendrochronology at Lund University, Sweden, the Archaeological Research Laboratory, Stockholm University, the Geoarchaeological Laboratory, Swedish National Historical Museums Agency and several international partners and research projects. Current plans include expanding its capacity to serve as a data source for any system and integration with the Swedish National Heritage Board's information systems.

     

    SEAD is partnered with the Neotoma palaeoecology database (http://www.neotomadb.org) and a new initiative for building cyberinfrastructure for transdisciplinary research and visualization of the long-term human ecodynamics of the North Atlantic funded by the National Science Foundation (NSF).

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  • 3.
    Carlborg, Markus
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Backman, Rainer
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Landälv, Ingvar
    Characterization of spent spinel-based refractory lining from a 3 MW black liquor gasifierManuscript (preprint) (Other academic)
    Abstract [en]

    Black liquor gasification is dependent on minimizing heat loss to the surroundings and thus needs to be well insulated. In combination with the high temperature and basic black liquor, a very corrosive environment is created on the hot face of such a reactor. Therefore the wall system is required to be chemically and thermally stable at the same time as it has insulating properties. These cannot easily be combined in the same material and therefore layers with different properties can be used in combination. Penetration of species through the lining can lead to further reactions with other construction materials, less suited for chemical resistance, corrosion of the pressure shell is an example with catastrophic consequences. This paper investigates two castable and one fused cast spinel (MgAl2O4) refractory after about 1 600 hours, and one fused cast material used for 15 000 hours of operation in a 3 MWth black liquor gasifier. Infiltration of Na, followed by destruction of microstructure, and extensive formation of NaAlO2 was observed throughout the whole castable materials, while it was mainly restricted to the hot face of the fused cast materials. Formation of NaAlO2 leads to a volumetric expansion which eventually lead to an increased pressure on the steel shell. In addition, the expansion of the bricks can cause stress and by that spallation and material loss.

  • 4.
    Carlborg, Markus
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Kannabiran, Sankar
    Höganäs Bjuf AB.
    Backman, Rainer
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Interaction between ash forming elements in woody biomass and two high alumina refractories part 1: effects on morphology and elemental distributionManuscript (preprint) (Other academic)
    Abstract [en]

    To gain more knowledge about possibly destructive effects of ash-forming elements in woody biomass on refractory materials in entrained flow gasification, an exposure study was performed on two high alumina refractories. The materials, a pre-fired castable consisting of about 63 weight-% Al2O3, and a phosphate bonded brick with 83 weight-% Al2O3 was exposed to synthetic ash mixtures at 1050°C and 1 atm CO2 for 7 days. This paper presents distribution of ash-forming elements and morphology of the samples microstructure, while identification and distribution of crystalline compounds is presented in a separate paper. In the samples, potassium (K) had infiltrated the materials and reacted with different components, while calcium (Ca) did not seem to have any direct effect during these conditions. The matrix of the castable absorbed much K, became clogged and produced a distinct border between reacted and unaffected matrix. The coarser matrix of the phosphate bonded brick retained much of its porosity and had ash transported further into the material without a clear distinction between reacted and unaffected matrix. Grains with >30 atomic-% Si, formed a layer enriched in K, with a thickness up to 40 µm and cracks propagating through it. Grains mainly consisting of Al2O3 seemed unaffected by the exposure. When the ash was rich in SiO2, a melt was produced that restricted the attack on the refractories to the surface and coarser pores.

  • 5.
    Carlborg, Markus
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Kannabiran, Sankar
    Höganäs Bjuf AB.
    Backman, Rainer
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Interaction between ash forming elements in woody biomass and two high alumina refractories part 2: transformation of crystalline compoundsManuscript (preprint) (Other academic)
    Abstract [en]

    Two high alumina refractories, one brick and one pre fired castable was exposed to pure K2CO3, K2CO3 + CaCO3, and K2CO3 + CaCO3 + SiO2 at 1050°C and a CO2 atmosphere. A stratified investigation of crystalline phases was made with polycrystalline x-ray diffraction, and thermodynamic equilibrium calculations were performed to explore possible formation paths. A monoclinic polymorph of KAlSiO4 was formed to a large extent in both materials exposed to pure K2CO3. Throughout the affected part of the castable and a small layer close to the surface of the brick, a solid solution between KAlO2 and KAlSiO4 formed, K1-xAl1-xSixO2, x = 0.19. The affected area of the castable had 30-50 %wt new phases and made a sharp transition to unaffected material. The concentration of new phases in the brick was decreasing at an even rate from about 40 to 15%wt throughout the whole material thickness of 14 mm. Exposure to K2CO3 and CaCO3 showed the same phases and behavior, but no Ca-bearing phases could be detected. The mixture containing K2CO3, CaCO3 and SiO2 did not penetrate far into the material but formed the same phases in the affected areas. Wollastonite (CaSiO3) formed in the slag on top of these materials. The major mechanism for formation of new phases is suggested to be the formation of an initial melt composed of K2O and SiO2. This liquid is then dissolving refractory components and forms a liquid in equilibrium with KAlSiO4 and K1-xAl1-xSixO2.

  • 6. Kang, Yuqiong
    et al.
    Guo, Xingang
    Guo, Zhiwu
    Li, Jiangang
    Zhou, Yunan
    Liang, Zheng
    Han, Cuiping
    He, Xiangming
    Zhao, Yun
    Tavajohi Hassan Kiadeh, Naser
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Li, Baohua
    Phosphorus-doped lithium- and manganese-rich layered oxide cathode material for fast charging lithium-ion batteries2021In: Journal of Energy Chemistry, ISSN 2095-4956, E-ISSN 2096-885X, Vol. 62, p. 538-545Article in journal (Refereed)
    Abstract [en]

    Owing to their high theoretical specific capacity and low cost, lithium- and manganese-rich layered oxide (LMR) cathode materials are receiving increasing attention for application in lithium-ion batteries. However, poor lithium ion and electron transport kinetics plus side effects of anion and cation redox reactions hamper power performance and stability of the LMRs. In this study, LMR Li1.2Mn0.6Ni0.2O2 was modified by phosphorus (P)-doping to increase Li+ conductivity in the bulk material. This was achieved by increasing the interlayer spacing of the lithium layer, electron transport and structural stability, resulting in improvement of the rate and safety performance. P5+ doping increased the distance between the (003) crystal planes from ∼0.474 nm to 0.488 nm and enhanced the structural stability by forming strong covalent bonds with oxygen atoms, resulting in an improved rate performance (capacity retention from 38% to 50% at 0.05 C to 5 C) and thermal stability (50% heat release compared with pristine material). First-principles calculations showed the P-doping makes the transfer of excited electrons from the valence band to conduction band easier and P can form a strong covalent bond helping to stabilize material structure. Furthermore, the solid-state electrolyte modified P5+ doped LMR showed an improved cycle performance for up to 200 cycles with capacity retention of 90.5% and enhanced initial coulombic efficiency from 68.5% (pristine) or 81.7% (P-doped LMR) to 88.7%.

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  • 7.
    Kumar Wagri, Naresh
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Assessment of bio-based fuel ash effects on magnesia refractory materials in quicklime production kilns2023Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Limestone is calcined into quicklime in lime kilns at temperatures above 1000°C. Heat is supplied through combustion inside the kilns, which are insulated with a lining of refractory bricks to mitigate heat loss and to protect the kiln from the hot, chemically aggressive, and mechanically abrasive environment. While magnesia bricks have proven to be effective lining materials, they are still susceptible to extensive wear in lime kilns, especially in the burn zone. Refractory corrosion, in particular, can occur when melted fuel ash infiltrates the refractory materials through pores and small cracks. This resultant wear can lead to high maintenance and operational costs, often due to unplanned kiln shutdowns.

    To reduce the release of fossil-based carbon dioxide into the atmosphere from lime production kilns, there is a growing interest in introducing bio-based fuels with only relatively minor modifications to the process. Biomass fuels can be sourced from bio-based waste streams from industries or be specifically cultivated for combustion. However, the ash content and properties of bio-based fuels tend to be problematic from an ash chemistry perspective. Therefore, before introducing a new fuel source, it is essential to investigate its potential effects on the kiln lining material. 

    In this thesis work, the interactions between melted olive pomace ash and coal ash with commercially available magnesia refractory materials, primarily composed of periclase (MgO) with minor amounts of spinel (MgAl2O4), were studied. A procedure for quantifying the intrusion depths was described. Refractory samples were exposed to the fuel ashes under a simulated lime kiln atmosphere with high CO2 levels at 1200 and 1400°C for 15 and 60 minutes. Cold crushing strength tests were conducted on refractory samples exposed to coal and olive pomace ash, along with CaO powder, at 1400°C for 96 hours. Additionally, postmortem analyses of spent MgO-based refractory bricks were carried out to investigate their chemical characterization and resistance to slag attack after serving as part of the lining in a quick lime rotary kiln for six months.

    The morphology and elemental compositions of the exposed samples were examined using scanning electron microscopy and energy-dispersive X-ray spectroscopy. Crystalline phases were investigated with powder X-ray diffraction. Thermodynamic equilibrium calculations were performed to further investigate the ash’s melting behavior in contact with the refractories.

    The results indicated that the potassium-rich olive pomace ash exhibited a greater tendency to infiltrate compared to the silicon-rich coal ash, while the latter formed a glassy melt layer on top of the refractory samples. The ash slags primarily infiltrated through the porous matrix and grain boundaries of the refractory materials. Also, refractory phases were observed in both types of ashes, indicating migration of refractory constituents. K2MgSiO4 phase was found in the olive pomace ash residues on top of the samples, both for the 1200°C and 1400°C exposures. Similarly, Al6Si2O13 phase was dominant in the residual coal ash, in both the 1200°C and 1400°C exposed samples. None of these phases were present in the original ashes.

    The results of the postmortem analysis revealed that there was no potassium (K) from the fuel ash present on the hot side of the refractory bricks. However, some K was detected in the middle and back parts of the bricks. On the other hand, some phases, possibly connected to degradation, could be found on the hot side of the bricks, where most of the wear was observed.

    The crushing strengths increased after exposure for all samples, except for those exposed exclusively to coal ash. One possible explanation for this is that the refractory materials exhibited a sintered structure, as a result of their interaction with the ashes and CaO. However, in the samples exposed to coal ash, forsterite (Mg2SiO4) was identified, which can be considered a corrosion product.

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  • 8.
    Kumar Wagri, Naresh
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Carlborg, Markus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Eriksson, Matias
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Ma, Charlie
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Broström, Markus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Andersson, Britt M.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    A postmortem corrosion study of spent MgO-based refractory materials from a lime kilnManuscript (preprint) (Other academic)
  • 9.
    Kumar Wagri, Naresh
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Carlborg, Markus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Eriksson, Matias
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Ma, Charlie
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Broström, Markus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Andersson, Britt M.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Crushing strength of MgO-based refractory after exposure to fuel ashes and quicklime at high temperatureManuscript (preprint) (Other academic)
  • 10.
    Viggh, Erik
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. Cementa AB, Malmö, Sweden.
    Eriksson, Matias
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. Nordkalk AB, Köping, Sweden.
    Wilhelmsson, Bodil
    R and D Cement Cementa AB, Stockholm, Sweden.
    Backman, Rainer
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Early formation of belite in cement clinker raw materials with slag2021In: Advances in Cement Research, ISSN 0951-7197, E-ISSN 1751-7605, Vol. 33, no 6, p. 249-256Article in journal (Refereed)
    Abstract [en]

    Analytical methods for characterising cement raw meal during heating in different atmospheres were investigated. The effect of replacing limestone with 10 wt% slag on the formation of incipient belite and precursors of the clinker liquid in the temperature range 600–1050°C was quantified using thermogravimetry, X-ray diffraction and equilibrium calculations. The results showed that when calculating the lime saturation factor, slags were favoured to sand, resulting in lower amounts of quartz and C2S in the samples containing slag than the reference sample. This suggests that silicon dioxide in slag minerals did not react in this temperature range. The multi-component equilibrium results supported the phase formation sequence established. Allowing for the possible kinetic influences the potential solids solutions offered with the software was a valuable asset. The results showed that the effect of using slags to reduce the carbonate and sand content in a raw meal on potential amounts of incipient C2S was negative. At present, more detailed knowledge is needed regarding how blast-furnace slag and basic oxygen furnace slag contribute to the formation of intermediary compounds such as incipient C2S, C3A, C2F and C4AF in the solid phase at temperatures over 1050°C and affect the formation of C3S.

  • 11.
    Vikström, Amanda
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Separate Calcination in Cement Clinker Production: A laboratory scale study on how an electrified separate calcination step affects the phase composition of cement clinker2021Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Cement production is responsible for around 7% of the global anthropogenic carbon dioxide emissions. More than half of these emissions are due to the unavoidable release of carbon dioxide upon thermal decomposition of the main raw material limestone. Many different options for carbon capture are currently being investigated to lower emissions, and one potential route to facilitate carbon capture could be the implementation of an electrified separate calcination step. However, potential effects on the phase composition of cement clinker need to be investigated, which is the aim of the present study. Phases of special interest are alite, belite, aluminate, ferrite, calcite, and lime. 

    The phase composition during clinker formation was examined through HT-XRD lab-scale experiments, allowing the phase transformations to be observed in situ. Two different methods of separate calcination were investigated, one method in which the raw meal was calcined separately, and one method where the limestone was calcined separately. The former yielded an alite amount similar to that of the reference experiments, whereas the latter method yielded a lower amount. It could, unfortunately, not be excluded that the difference was due to poor experimental conditions, and additional experiments are needed to investigate the matter further. The study does, however, indicate that a calcined raw meal might be used to produce a clinker of similar phase composition concerning major phases belite, aluminate, ferrite, alite, and free lime. A raw meal containing calcined limestone might, however, need longer residence time at clinkering temperature too obtain similar phase composition. In addition, a raw meal containing calcined limestone was observed to be carbonated to a greater extent upon reheating than a calcined raw meal. Further experiments are needed to fully understand the effects on clinker composition of an electrified separate calcination step, and several improvements to the experimental method are given in the study. 

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  • 12. Zhao, Yun
    et al.
    Wang, Li
    Zhou, Yunan
    Liang, Zheng
    Tavajohi Hassan Kiadeh, Naser
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Li, Baohua
    Li, Tao
    Solid Polymer Electrolytes with High Conductivity and Transference Number of Li Ions for Li-Based Rechargeable Batteries2021In: Advanced Science, E-ISSN 2198-3844, Vol. 8, no 7, article id 2003675Article, review/survey (Refereed)
    Abstract [en]

    Smart electronics and wearable devices require batteries with increased energy density, enhanced safety, and improved mechanical flexibility. However, current state-of-the-art Li-based rechargeable batteries (LBRBs) use highly reactive and flowable liquid electrolytes, severely limiting their ability to meet the above requirements. Therefore, solid polymer electrolytes (SPEs) are introduced to tackle the issues of liquid electrolytes. Nevertheless, due to their low Li+ conductivity and Li+ transference number (LITN) (around 10?5 S cm?1 and 0.5, respectively), SPE-based room temperature LBRBs are still in their early stages of development. This paper reviews the principles of Li+ conduction inside SPEs and the corresponding strategies to improve the Li+ conductivity and LITN of SPEs. Some representative applications of SPEs in high-energy density, safe, and flexible LBRBs are then introduced and prospected.

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