Umeå University's logo

umu.sePublications
Change search
Refine search result
1 - 20 of 20
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Babaahmadi, Arezou
    et al.
    Chalmers University of Technology, Gothenburg, Sweden.
    Figueira, João
    Umeå University.
    Chloride binding in slag containing composite cements2023In: International RILEM conference on synergising expertise towards sustainability and robustness of cement-based materials and concrete structures: SynerCrete’23 - volume 1 / [ed] Agnieszka Jędrzejewska; Fragkoulis Kanavaris; Miguel Azenha; Farid Benboudjema; Dirk Schlicke, Cham: Springer, 2023, 1, , p. 13p. 645-657Chapter in book (Refereed)
    Abstract [en]

    Higher availability of grand granulated blast furnace slag compared to coal fly ash has attributed lots of attention to this supplementary cementitious material in recent years, especially with respect to applications in infrastructure. Therefore, further research on long term performance of slag containing binders in chloride containing environments is promoted. In this article chloride binding in a high slag containing composite binder (70% substitution) with respect to the changes in structure of CSH gel prior and after exposure to chlorides and its effect on chemical and physical chloride binding is accounted for. The changes in the structure of CSH are accounted by NMR analysis and the effect of these changes on chloride binding is addressed through adsorption tests. The results are compared with a ternary binder of cement-silica fume-metakaolin, given the relatively similar chemical composition between these two composite binders, as well as a reference Portland cement binder. The results infer that the slag containing binder exhibits higher chloride binding capacity compared to the metakaolin-silica fume containing. Moreover, a higher share of chemically bound chloride (meaning a lower physical binding) in SCM containing binders is foreseen compared to pure Portland cement system, due to the increased C(-A)-S-H chain length and Al/Si molar ratio in these binders. Furthermore, it is shown that exposure to NaCl causes a higher share of chemically bound chlorides compared to the CaCl2 exposure while the total bound chloride content increases upon exposure to CaCl2.

  • 2.
    Boulanger, Nicolas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Barbero, David R.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    [Cover picture] Carbon Nanotubes: Ordered and Highly Conductive Carbon Nanotube Nano-Networks in a Semiconducting Polymer Film by Solution Processing (Adv. Electron. Mater. 5/2015)2015In: Advanced Electronic Materials, E-ISSN 2199-160X, Vol. 1, no 5Article in journal (Refereed)
  • 3.
    Dahlberg, Tobias
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Stangner, Tim
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Hanqing, Zhang
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wiklund, Krister
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Lundberg, Petter
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Andersson, Magnus
    Umeå University, Faculty of Science and Technology, Department of Physics.
    3D printed water-soluble scaffolds for rapid production of PDMS micro-fluidic flow chambers2018In: Scientific Reports, E-ISSN 2045-2322, Vol. 8, no 1, article id 3372Article in journal (Refereed)
    Abstract [en]

    We report a novel method for fabrication of three-dimensional (3D) biocompatible micro-fluidic flow chambers in polydimethylsiloxane (PDMS) by 3D-printing water-soluble polyvinyl alcohol (PVA) filaments as master scaffolds. The scaffolds are first embedded in the PDMS and later residue-free dissolved in water leaving an inscription of the scaffolds in the hardened PDMS. We demonstrate the strength of our method using a regular, cheap 3D printer, and evaluate the inscription process and the channels micro-fluidic properties using image analysis and digital holographic microscopy. Furthermore, we provide a protocol that allows for direct printing on coverslips and we show that flow chambers with a channel cross section down to 40 x 300 μm can be realized within 60 min. These flow channels are perfectly transparent, biocompatible and can be used for microscopic applications without further treatment. Our proposed protocols facilitate an easy, fast and adaptable production of micro-fluidic channel designs that are cost-effective, do not require specialized training and can be used for a variety of cell and bacterial assays. To help readers reproduce our micro-fluidic devices, we provide: full preparation protocols, 3D-printing CAD files for channel scaffolds and our custom-made molding device, 3D printer build-plate leveling instructions, and G-code.

    Download full text (pdf)
    fulltext
  • 4.
    Gong, Hanmo
    et al.
    State Key Laboratory of Modern Optical Instrumentation, Department of Optical Engineering, Zhejiang University, Hangzhou, China.
    Yang, Yuanqing
    State Key Laboratory of Modern Optical Instrumentation, Department of Optical Engineering, Zhejiang University, Hangzhou, China.
    Chen, Xingxing
    State Key Laboratory of Modern Optical Instrumentation, Department of Optical Engineering, Zhejiang University, Hangzhou, China.
    Zhao, Ding
    State Key Laboratory of Modern Optical Instrumentation, Department of Optical Engineering, Zhejiang University, Hangzhou, China.
    Chen, Xi
    School of Information and Communication Technology, KTH Royal Institute of Technology, Electrum 229, Kista, Sweden.
    Chen, Yiting
    School of Information and Communication Technology, KTH Royal Institute of Technology, Electrum 229, Kista, Sweden.
    Yan, Min
    School of Information and Communication Technology, KTH Royal Institute of Technology, Electrum 229, Kista, Sweden.
    Li, Qiang
    State Key Laboratory of Modern Optical Instrumentation, Department of Optical Engineering, Zhejiang University, Hangzhou, China.
    Qiu, Min
    State Key Laboratory of Modern Optical Instrumentation, Department of Optical Engineering, Zhejiang University, Hangzhou, China; School of Information and Communication Technology, KTH Royal Institute of Technology, Electrum 229, Kista, Sweden.
    Gold nanoparticle transfer through photothermal effects in a metamaterial absorber by nanosecond laser2014In: Scientific Reports, E-ISSN 2045-2322, Vol. 4, no 1, article id 6080Article in journal (Refereed)
    Abstract [en]

    A non-complicated, controllable method of metallic nanoparticle fabrication at low operating light power is proposed. The method is based on laser-induced forward transfer, using a metamaterial absorber as the donor to significantly enhance the photothermal effect and reduce the operating light fluence to 35 mJ/cm2, which is much lower than that in previous works. A large number of metallic nanoparticles can be transferred by one shot of focused nanosecond laser pulses. Transferred nanoparticles exhibit good size uniformity and the sizes are controllable. The optical properties of transferred particles are characterized by dark-field spectroscopy and the experimental results agree with the simulation results.

    Download full text (pdf)
    fulltext
  • 5.
    Kaitainen, Salla
    et al.
    Department of Applied Physics, University of Eastern Finland, Kuopio, Finland.
    Mähönen, Anssi
    Institute of Biomedicine, University of Eastern Finland, Kuopio, Finland.
    Lappalainen, Reijo
    Department of Applied Physics, University of Eastern Finland, Kuopio, Finland.
    Kröger, Heikki
    Department of Orthopaedics and Traumatology, Kuopio University Hospital, Kuopio, Finland.
    Lammi, Mikko
    Institute of Biomedicine, University of Eastern Finland, Kuopio, Finland; Biocenter Kuopio, University of Eastern Finland, Kuopio, Finland.
    Qu, Chengjuan
    Institute of Biomedicine, University of Eastern Finland, Kuopio, Finland; Biocenter Kuopio, University of Eastern Finland, Kuopio, Finland.
    TiO2 coating promotes human mesenchymal stem cell proliferation without the loss of their capacity for chondrogenic differentiation2013In: Biofabrication, ISSN 1758-5090, Vol. 5, no 2, p. 025009-, article id 23592549Article in journal (Refereed)
    Abstract [en]

    Human mesenchymal stem cells (hMSCs) are used in applications, which may require a large amount of cells; therefore, efficient expansion of the cells is desired. We studied whether TiO2 coating on plastic cell culture dishes could promote proliferation of hMSCs without adverse effects in chondrogenic differentiation. TiO2-films were deposited on polystyrene dishes and glass coverslips using an ultrashort pulsed laser deposition technique. Human MSCs from three donors were expanded on them until 95% confluence, and the cells were evaluated by morphology, immunocytochemistry and quantitative RT-PCR (qRT-PCR). The chondrogenic differentiation in pellets was performed after cultivation on TiO2-coated dishes. Chondrogenesis was evaluated by histological staining of proteoglycans and type II collagen, and qRT-PCR. Human MSC-associated markers STRO-1, CD44, CD90 and CD146 did not change after expansion on TiO2-coated coverslips. However, the cell number after a 48h-culture period was significantly higher on TiO2-coated culture dishes. Importantly, TiO2 coating caused no significant differences in the proteoglycan and type II collagen staining of the pellets, or the expression of chondrocyte-specific genes in the chondrogenesis assay. Thus, the proliferation of hMSCs could be significantly increased when cultured on TiO2-coated dishes without weakening their chondrogenic differentiation capacity. The transparency of TiO2-films allows easy monitoring of the cell growth and morphology under a phase-contrast microscope.

  • 6.
    Lander, Bror
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Optimering av betongrecept med ballast av bergkross2021Independent thesis Basic level (professional degree), 180 HE creditsStudent thesis
    Download full text (pdf)
    fulltext
  • 7. Ma, Chunyan
    et al.
    Wang, Nan
    Chen, Yifeng
    Khokarale, Santosh Govind
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Bui, Thai Q.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Weiland, Fredrik
    Lestander, Torbjörn A.
    Rudolfsson, Magnus
    Mikkola, Jyri-Pekka
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Åbo Akademi University, Industrial Chemistry & Reaction Engineering, Johan Gadolin Process Chemistry Centre, Åbo-Turku, Finland .
    Ji, Xiaoyan
    Towards negative carbon emissions: Carbon capture in bio-syngas from gasification by aqueous pentaethylenehexamine2020In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 279, article id 115877Article in journal (Refereed)
    Abstract [en]

    In this work, an aqueous pentaethylenehexamine (PEHA) solution was studied for CO2 removal from bio-syngas for the first time. Firstly, pure CO2 absorption in aqueous PEHA solution under different conditions was conducted, and 20 wt% PEHA solution was identified as the best option. Secondly, the capture of CO2 was tested with synthetic syngas from a gas cylinder, and the species other than CO2 showed a negligible impact on CO2 removal. Finally, to evaluate the practical feasibility of using aqueous PEHA solution on the downstream CO2 capture, the pilot experiments of gasification with boreal forest-based biomasses were designed to provide real syngas with a realistic distribution in composition for further testing. The results showed that the operating conditions and the type of feedstocks affected the distribution in the bio-syngas composition. Among these feedstocks, at the optimal oxygen supply, using spruce needles generated the highest yields of CO and H2 and, meanwhile, gave rise to similar yields of other gases such as CO2, CH4, etc. The influence of the species other than CO2 for CO2 removal was negligible. Additionally, aqueous PEHA solution was tested as a biomass pretreatment agent, showing that no significant changes could be identified by the ultimate analysis (except for increased nitrogen content), but the yields of CO were affected negatively. On the other hand, when using the pretreated biomass by the aqueous PEHA solution, the NH3 concentration in bio-syngas reached to the highest (4000 parts per million), which slightly affected the CO2 absorption capacity and initial absorption rate of 20 wt% PEHA solution in a positive way.

  • 8.
    Maccaferri, Nicolò
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics. Department of Physics and Materials Science, University of Luxembourg, Luxembourg, Luxembourg.
    Gabbani, Alessio
    Department of Chemistry and Industrial Chemistry, University of Pisa, Pisa, Italy.
    Pineider, Francesco
    Department of Chemistry and Industrial Chemistry, University of Pisa, Pisa, Italy.
    Kaihara, Terunori
    CIC nanoGUNE BRTA, Tolosa Hiribidea, Donostia-San Sebastian, Spain.
    Tapani, Tlek
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Vavassori, Paolo
    CIC nanoGUNE BRTA, Tolosa Hiribidea, Donostia-San Sebastian, Spain; IKERBASQUE, Basque Foundation for Science, Bilbao, Spain.
    Magnetoplasmonics in confined geometries: current challenges and future opportunities2023In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 122, no 12, article id 120502Article in journal (Refereed)
    Abstract [en]

    Plasmonics represents a unique approach to confine and enhance electromagnetic radiation well below the diffraction limit, bringing a huge potential for novel applications, for instance, in energy harvesting, optoelectronics, and nanoscale biochemistry. To achieve novel functionalities, the combination of plasmonic properties with other material functions has become increasingly attractive. In this Perspective, we review the current state of the art, challenges, and future opportunities within the field of magnetoplasmonics in confined geometries, an emerging area aiming to merge magnetism and plasmonics to either control localized plasmons, confined electromagnetic-induced collective electronic excitations, using magnetic properties, or vice versa. We begin by highlighting the cornerstones of the history and principles of this research field. We then provide our vision of its future development by showcasing raising research directions in hybrid magnetoplasmonic systems to overcome radiation losses and novel materials for magnetoplasmonics, such as transparent conductive oxides and hyperbolic metamaterials. Finally, we provide an overview of recent developments in plasmon-driven magnetization dynamics, nanoscale opto-magnetism, and acousto-magnetoplasmonics. We conclude by giving our personal vision of the future of this thriving research field

    Download full text (pdf)
    fulltext
  • 9.
    Nordenström, Andreas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Boulanger, Nicolas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Iakunkov, Artem
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Li, Gui
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Mysyk, Roman
    Centre for Cooperative Research on Alternative Energies (CIC energiGUNE), Basque Research and Technology Alliance (BRTA), Alava Technology Park, Vitoria-Gasteiz, Spain.
    Bracciale, Gaetan
    Thales Research & Technology, Palaiseau, France.
    Bondavalli, Paolo
    Thales Research & Technology, Palaiseau, France.
    Talyzin, Aleksandr V.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    High-surface-area activated carbon from pine cones for semi-industrial spray deposition of supercapacitor electrodes2022In: Nanoscale Advances, E-ISSN 2516-0230, Vol. 4, no 21, p. 4689-4700Article in journal (Refereed)
    Abstract [en]

    High surface area carbons are so far the best materials for industrial manufacturing of supercapacitor electrodes. Here we demonstrate that pine cones, an abundant bio-precursor currently considered as a waste in the wood industry, can be used to prepare activated carbons with a BET surface area exceeding 3000 m2 g−1. It is found that the same KOH activation procedure applied to reduced graphene oxide (rGO) and pine cone derived biochars results in carbon materials with a similar surface area, pore size distribution and performance in supercapacitor (SC) electrodes. It can be argued that “activated graphene” and activated carbon are essentially the same kind of material with a porous 3D structure. It is demonstrated that the pine cone derived activated carbon (PC-AC) can be used as a main part of aqueous dispersions stabilized by graphene oxide for spray deposition of electrodes. The PC-AC based electrodes prepared using a semi-industrial spray gun machine and laboratory scale blade deposition of these dispersions were compared to pellet electrodes.

    Download full text (pdf)
    fulltext
  • 10.
    Sandström, Robin
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Innovations in nanomaterials for proton exchange membrane fuel cells2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Hydrogen technologies are rapidly receiving increased attention as it offers a renewable energy alternative to the current petroleum-based fuel infrastructure, considering that continued large-scale use of such fossil fuels will lead to disastrous impacts on our environment. The proton exchange membrane fuel cell should play a significant role in a hydrogen economy since it enables convenient and direct conversion of hydrogen into electricity, thus allowing the use of hydrogen in applications particularly suited for the transportation industry. To fully realize this, multiple engineering challenges as well as development of advanced nanomaterials must however be addressed.

    In this thesis, we present discoveries of new innovative nanomaterials for proton exchange membrane fuel cells by targeting the entire membrane electrode assembly. Conceptually, we first propose new fabrication techniques of gas diffusion electrodes based on helical carbon nanofibers, where an enhanced three-phase boundary was noted in particular for hierarchical structures. The cathode catalyst, responsible for facilitating the sluggish oxygen reduction reaction, was further improved by the synthesis of platinum-based nanoparticles with an incorporated secondary metal (iron, yttrium and cobalt). Here, both solvothermal and high-temperature microwave syntheses were employed. Catalytic activities were improved compared to pure platinum and could be attributed to favorably shifted oxygen adsorption energies as a result of successful incorporation of the non-precious metal. As best exemplified by platinum-iron nanoparticles, the oxygen reduction reaction was highly sensitive to both metal composition and the type of crystal structure. Finally, a proton exchange membrane based on fluorine and sulfonic acid functionalized graphene oxide was prepared and tested in hydrogen fuel cell conditions, showing improvements such as lowered hydrogen permeation and better structural stability. Consequently, we have demonstrated that there is room for improvement of multiple components, suggesting that more powerful fuel cells can likely be anticipated in the future.

    Download full text (pdf)
    fulltext
    Download (pdf)
    spikblad
    Download (jpg)
    preview image
  • 11.
    Sandström, Robin
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Annamalai, Alagappan
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Boulanger, Nicolas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Ekspong, Joakim
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Talyzin, Aleksandr V.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Mühlbacher, Inge
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Evaluation of Fluorine and Sulfonic Acid Co-functionalized Graphene Oxide Membranes in Hydrogen Proton Exchange Membrane Fuel Cell Conditions2019In: Sustainable Energy & Fuels, E-ISSN 2398-4902, Vol. 3, no 7, p. 1790-1798Article in journal (Refereed)
    Abstract [en]

    The use of graphene oxide (GO) based membranes consisting of self-assembled flakes with a lamellar structure represents an intriguing strategy to spatially separate reactants while facilitating proton transport in proton exchange membranes (PEM). Here we chemically modify GO to evaluate the role of fluorine and sulfonic acid groups on the performance of H2/O2 based PEM fuel cells. Mild fluorination is achieved by the presence of hydrogen fluoride during oxidation and subsequent sulfonation resulted in fluorine and SO3- co-functionalized GO. Membrane electrode assembly performance in low temperature and moderate humidity conditions suggested that both functional groups contribute to reduced H2 crossover compared to appropriate reference membranes. Moreover, fluorine groups promoted an enhanced hydrolytic stability while contributing to prevent structural degradation after constant potential experiments whereas sulfonic acid demonstrated a stabilizing effect by preserving proton conductivity.

    Download full text (pdf)
    fulltext
  • 12.
    Sandström, Robin
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Ekspong, Joakim
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Gracia-Espino, Eduardo
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Oxidatively Induced Exposure of Active Surface Area during Microwave Assisted Formation of Pt3Co Nanoparticles for Oxygen Reduction Reaction2019In: RSC Advances, E-ISSN 2046-2069, Vol. 9, no 31, p. 17979-17987Article in journal (Refereed)
    Abstract [en]

    The oxygen reduction reaction (ORR), the rate-limiting reaction in proton exchange membrane fuel cells, can efficiently be facilitated by properly manufactured platinum catalysts alloyed with late 3d transition metals. Herein we synthesize a platinum:cobalt nanoparticulate catalyst with a 3:1 atomic ratio by reduction of a dry organometallic precursor blend within a commercial household microwave oven. The formed nanoparticles are simultaneously anchored to a carbon black support that enables large Pt surface area. Two separate microwave treatment steps were employed, where step one constitutes a fast oxidative treatment for revealing active surface area while a reductive secondary annealing treatment promotes a Pt rich surface. The resulting Pt3Co/C catalyst (~3.4 nm) demonstrate an enhanced ORR activity directly attributed to incorporated Co with a specific and mass activity of 704 μA cm-2Pt and 352 A g-1Pt corresponding to an increase by 279 % and 66 % respectively compared to a commercial Pt/C (~1.8 nm) catalyst measured under identical conditions. The method´s simplicity, scalability and novelty is expected to further assist in Pt-Co development and bring the catalyst one step closer toward commercialization and utility in fuel cells.

    Download full text (pdf)
    fulltext
  • 13.
    Sandström, Robin
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Gracia-Espino, Eduardo
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Annamalai, Alagappan
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Persson, Per
    Linköping University.
    Persson, Ingemar
    Linköping University.
    Ekspong, Joakim
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Barzegar, Hamid Reza
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Microwave-Induced Structural Ordering of Resilient Nanostructured L10-FePt Catalysts for Oxygen Reduction Reaction2020In: ACS Applied Energy Materials, E-ISSN 2574-0962, Vol. 3, no 10, p. 9785-9791Article in journal (Refereed)
    Abstract [en]

    We show how structurally ordered L10 face-centered tetragonal (fct) FePt nanoparticles are produced by a solid-state microwave-assisted synthesis method. The structural phase as well as the incorporated Fe into the nanoparticles is confirmed by X-ray diffraction and high resolution high-angle annular dark field scanning transmission electron microscopy experiments. The prepared particles exhibit a remarkable resilience toward crystallite growth at high temperatures. Directly correlated to the L10 phase, the best oxygen reduction reaction (ORR) characteristics are achieved for particles with a 1:1 Fe:Pt atomic ratio and an average size of ~2.9 nm where Pt-specific evaluation provided a high mass and specific activity of ~570 A/gPt and ~600 μA/cm2Pt respectively. Our results demonstrate that well-structured catalysts possessing activities vastly exceeding Pt/C (~210 A/gPt & ~250 μA/cm2Pt), can be synthesized through a fast and highly eco-friendly method. We note that the achieved mass activity represent a significant leap toward the theoretical maximum for fully ordered FePt nanoparticles.

    Download full text (pdf)
    fulltext
  • 14.
    Sarmad, Shokat
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Mikkola, Jyri-Pekka
    Umeå University, Faculty of Science and Technology, Department of Chemistry. 2 Industrial Chemistry & Reaction Engineering, Johan Gadolin Process Chemistry Centre, Åbo Akademi University, Åbo-Turku, Finland.
    Vapor-liquid equilibrium of ionic liquids2020In: Encyclopedia of ionic liquids / [ed] Suojiang Zhang, Singapore: Springer, 2020, p. 1-22Chapter in book (Other academic)
  • 15.
    Servin, Martin
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Berglund, Tomas
    Algoryx Simulation AB.
    Mickelsson, Kjell-Ove
    LKAB.
    Rönnbäck, Stefan
    Optimation AB.
    Wang, Da
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Modeling and simulation of a granulation system using a nonsmooth discrete element method2015In: ECCOMAS IV international conference on particle-based methods 2015, 2015Conference paper (Other academic)
    Abstract [en]

    Granulation is the process of forming macroscopic granules, e.g. tablets or pellets, from microscopic particles. A common system for continuous granulation consist of a rotary drum or disc, a sieve and chrusher connected in a circuit by a number of conveyors. The granulation occur in the drum (or disc) and the main mechanisms are nucleation, layering, coalescence and breakage [1]. The process can be controlled by drum velocity and feed rate of fine material, binding agencies and moisture. The geometric design of components affect the material flow and thus the sieving capacity and ultimately the production capacity. Many granulation plants operate well below their capacity and suffer from high recycle rates and dynamic instabilities [2]. The main challenge of modelling and simulation of granulation processes is the occurrence of multiple length and time scales. The traditional approaches are typically focused either the largescale level of processing units or on the microscale level of particles. A complete model of a granulation process need to include also the intermediate scale of granule dynamics [1]. This is, however, a very challenging computational task given the vast number of granules, typically many millions or more. We present a meso-scale approach to modeling and simulating iron ore granulation systems with granules modeled as nonsmooth discrete elements (NDEM) [3-6]. This extend a previous iron ore granule model [7] used for balling drum outlet design simulation [8]. Ore fines and moisture is modeled by a quasiparticle model for slurry [9]. Interaction models for nucleation, layering, coalescence and breakage are proposed and tested in a virtual balling circuit. The computational performance is analysed and different methods for accelerating the NDEM computations are tested.

  • 16.
    Sharifi, Tiva
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics. Department of Material Science and Nanoengineering, Rice University, Houston, Texas, United States.
    Zhang, Xiang
    Costin, Gelu
    Yazdi, Sadegh
    Woellner, Cristiano F.
    Liu, Yang
    Tiwary, Chandra Sekhar
    Ajayan, Pulickel
    Thermoelectricity Enhanced Electrocatalysis2017In: Nano Letters, ISSN 1530-6984, E-ISSN 1530-6992, Vol. 17, no 12, p. 7908-7913Article in journal (Refereed)
    Abstract [en]

    We show that thermoelectric materials can function as electrocatalysts and use thermoelectric voltage generated to initiate and boost electrocatalytic reactions. The electrocatalytic activity is promoted by the use of nanostructured thermoelectric materials in a hydrogen evolution reaction (HER) by the thermoelectricity generated from induced temperature gradients. This phenomenon is demonstrated using two-dimensional layered thermoelectric materials Sb2Te3 and Bi0.5Sb1.5Te3 where a current density approaching ∼50 mA/cm2 is produced at zero potential for Bi0.5Sb1.5Te3 in the presence of a temperature gradient of 90 °C. In addition, the turnover frequency reaches to 2.7 s–1 at 100 mV under this condition which was zero in the absence of temperature gradient. This result adds a new dimension to the properties of thermoelectric materials which has not been explored before and can be applied in the field of electrocatalysis and energy generation.

  • 17.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Physics.
    Low T hydrostatic limits of n-pentane/iso-pentane mixture measured by a self-supporting Manganin pressure gauge1987In: Journal of Physics. E, Scientific Instruments, ISSN 0022-3735, Vol. 20, no 8, p. 984-986Article in journal (Refereed)
    Abstract [en]

    A simple design for a self-supporting Manganin pressure gauge is described. The shear-strain sensitivity of the gauge has been used to determine the hydrostatic pressure limit below 150 K of the 50/50 mixture by volume of n- and isopentane that is commonly used as a pressure-transmitting medium in high-pressure experiments.

  • 18. Wang, Qian
    et al.
    Zhu, Linhe
    Ismail, Norafiqah
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Zhou, Qiuyueming
    He, Ting
    Zhou, Yue
    Wang, Zhaohui
    Cui, Zhaoliang
    Tavajohi Hassan Kiadeh, Naser
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Annealing of grain-like poly (vinylidene fluoride-trifluoroethylene) membranes with a single-crystalline electroactive phase and high anti-fouling activity2022In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 644, article id 120089Article in journal (Refereed)
    Abstract [en]

    Electroactive membranes are attracting attention due to their piezo-, pyro-, and ferro-electric properties. Here we report the fabrication of electroactive membranes from poly(vinylidene fluoride-trifluoroethylene) P(VDF-TrFE), i.e. co-polymers of vinylidene fluoride and trifluoroethylene. A new P(VDF-TrFE)/Polyvinylpyrrolidone (PVP)/Dimethylacetamide (DMAc)/water system was used to tailor the membranes’ structure. Since hot treatment in the air could induce defect on membrane structure (i.e., fracture, shrinkage, and rolling), the annealing was conducted in the glycerin. Thanks to the high boiling point and moderate surface tension of glycerin, the integrity of P(VDF-TrFE) membranes was preserved during the annealing process. X-ray diffraction, Fourier transform infrared spectroscopy, differential scanning calorimetry, and scanning electron microscopy experiments revealed that the relative abundance of the β–crystalline phase increased with the annealing temperature when the latter was above the Curie temperature. P(VDF-TrFE) membranes annealed at 130 °C exhibited high crystallinity with grain-like surface, which resulted from multiple stacks of edge-on lamellae, and possessed excellent physicochemical properties of filtration. The anti-fouling performance of pristine and annealed P(VDF-TrFE) membranes was tested by dead-end filtration with a 13.5 mg/L humic acid (HA) solution. Annealed P(VDF-TrFE) membranes achieved greater fluxes and had superior anti-fouling properties, which was attributed to the weaker hydrophobic attraction between HA and the aligned β–phase crystals. This work provides a facile method for designing highly crystalline P(VDF-TrFE) membranes with potential applications in filtration systems, smart wearable devices, and medicine.

  • 19. Wu, Zhongbin
    et al.
    Luo, Jiajia
    Sun, Ning
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Zhu, Liping
    Sun, Hengda
    Yu, Ling
    Yang, Dezhi
    Qiao, Xianfeng
    Chen, Jiangshan
    Yang, Chuluo
    Ma, Dongge
    High-Performance Hybrid White Organic Light-Emitting Diodes with Superior Efficiency/Color Rendering Index/Color Stability and Low Efficiency Roll-Off Based on a Blue Thermally Activated Delayed Fluorescent Emitter2016In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 26, no 19, p. 3306-3313Article in journal (Refereed)
    Abstract [en]

    Thermally activated delayed fluorescence (TADF)-based white organic light-emitting diodes (WOLEDs) are highly attractive because the TADF emitters provide a promising alternative route to harvest triplet excitons. One of the major challenges is to achieve superior efficiency/color rendering index/color stability and low efficiency roll-off simultaneously. In this paper, high-performance hybrid WOLEDs are demonstrated by employing an efficient blue TADF emitter combined with red and green phosphorescent emitters. The resulting WOLED shows the maximum external quantum efficiency, current efficiency, and power efficiency of 23.0%, 51.0 cd A(-1), and 51.7 lm W-1, respectively. Moreover, the device exhibits extremely stable electroluminescence spectra with a high color rendering index of 89 and Commission Internationale de L'Eclairage coordinates of (0.438, 0.438) at the practical brightness of 1000 cd m(-2). The achievement of these excellent performances is systematically investigated by versatile experimental and theoretical evidences, from which it is concluded that the utilization of a blue-green-red cascade energy transfer structure and the precise manipulation of charges and excitons are the key points. It can be anticipated that this work might be a starting point for further research towards high-performance hybrid WOLEDs.

  • 20. 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.

    Download full text (pdf)
    fulltext
1 - 20 of 20
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf