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  • 1.
    Ahmed, Shibbir
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Micro-wave synthesis of co-doped transition metal oxides anchored on reduced graphene oxide and their implementation as catalysts for water oxidation2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Abstract: Artificial photosynthesis is a very attractive and a desirable way to solve the rising energy demand. In order to harvest energy directly from sunlight catalyst for oxygen reduction and evolution reaction are at the core of key renewable-energy technologies including fuel cells and water splitting. Herein, tungsten oxide-reduced graphene oxide (WO3-rGO), cobalt oxide-reduced graphene oxide (Co3O4-rGO) and tungsten oxide-cobalt oxide-reduced graphene oxide (WO3-Co3O4-rGO) nano-composites were synthesized via a facile, efficient, one-pot microwave assisted method as an efficient electro-catalyst for water oxidation. The structural and chemical compositions of the produced nano-structures were investigated by Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS), Raman Spectroscopy as well as thremogravimetric analysis. Catalytic performances of the engineered nano hybrids for the oxygen evolution reaction (OER) were evaluated using a standard three electrode system in 0.1 M KOH aqueous solution, with a coiled Pt wire as the counter electrode and an Ag/AgCl as the reference electrode. In the produced nano-composites, WO3 and Co3O4 nano-particles are uniformly decorated on the reduced graphene oxide sheets without any agglomeration. The WO3-Co3O4-rGO hybrids afforded current density 1 mA/cm2 at 1.693 V vs RHE and the Co3O4-rGO reached the current density 1 mA/cm2 at 1.769 V vs RHE regarding the catalytic performance for OER in alkaline solution. The over potential was significantly reduced by 76 mV after co-doping of WO3 with Co3O4-rGO nano hybrids. The WO3-Co3O4-rGO gives current density 1 mA/cm2 at 1.658 V vs RHE. We also show that the over potential for oxygen evolution of the WO3-Co3O4-rGO was further reduced by illuminating the catalyst to visible light thus manifesting the photo-catalytic properties of the hybrid catalyst.

  • 2.
    Barzegar, Hamid Reza
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics. Department of Physics, University of California, Berkeley, CA 94720, USA; Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA; Kavli Energy NanoSciences Institute at the University of California, Berkeley and the Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
    Yan, Aiming
    Coh, Sinisa
    Gracia-Espino, Eduardo
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Ojeda-Aristizabal, Claudia
    Dunn, Gabriel
    Cohen, Marvin L.
    Louie, Steven G.
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Zettl, Alex
    Spontaneous twisting of a collapsed carbon nanotube2017In: Nano Reseach, ISSN 1998-0124, E-ISSN 1998-0000, Vol. 10, no 6, 1942-1949 p.Article in journal (Refereed)
    Abstract [en]

    We study the collapsing and subsequent spontaneous twisting of a carbon nanotube by in situ transmission electron microscopy (TEM). A custom-sized nanotube is first created in the microscope by selectively extracting shells from a parent multi-walled tube. The few-walled, large-diameter daughter nanotube is driven to collapse via mechanical stimulation, after which the ribbon-like collapsed tube spontaneously twists along its long axis. In situ diffraction experiments fully characterize the uncollapsed and collapsed tubes. The experimental observations and associated theoretical analysis indicate that the origin of the twisting is compressive strain.

  • 3. Berge, John
    et al.
    Gevorgian, Spartak
    Tunable bulk acoustic wave resonators based on Ba0.25Sr0.75TiO3 thin films and a HfO2/SiO2 Bragg reflector2011In: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, ISSN 0885-3010, E-ISSN 1525-8955, Vol. 58, no 12, 2768-2771 p.Article in journal (Refereed)
    Abstract [en]

    A switchable and tunable bulk acoustic wave resonator based on a paraelectric phase Ba0.25Sr0.75TiO3 thin film and an all-dielectric HfO2/SiO2 Bragg reflector is presented. The achieved tuning range (3.8%) and effective electromechanical coupling coefficient (7.1%) are the highest reported for solidly mounted tunable bulk acoustic wave resonators. The non-conductive Bragg reflector stack provides excellent integration possibilities.

  • 4. Berge, John
    et al.
    Norling, Martin
    Vorobiev, Andrei
    Gevorgian, Spartak
    Field and temperature dependent parameters of the dc field induced resonances in BaxSr1-xTiO3-based tunable thin film bulk acoustic resonators2008In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 103, no 6Article in journal (Refereed)
  • 5. Berge, John
    et al.
    Norling, Martin
    Vorobiev, Andrei
    Gevorgian, Spartak
    The effect of Bragg reflectors on the electromechanical performance of parallel-plate ferroelectric capacitors2010In: IOP Conference Series: Materials Science and Engineering - Fundamentals and Technology of Multifunctional Oxide Thin Films, 2010Conference paper (Refereed)
    Abstract [en]

    Parallel-plate capacitors based on ferroelectric thin films are considered as high density capacitors and varactors. Due to the small thickness of the ferroelectric films, typically less than 1.0 mu m, high electric fields are generated even at relatively low voltages inducing piezoelectric effect associated with electrostriction. This induced piezoelectric effect has negative impact on ferroelectric capacitors since it causes extra loss (electroacoustic transformation of microwave energy). In this work the use of Bragg reflectors between the substrate and ferroelectric film is proposed as a possible way of suppression of the enhanced losses associated with the piezoelectric activity of the ferroelectric film.

  • 6. Berge, John
    et al.
    Vorobiev, Andrei
    Gevorgian, Spartak
    Design considerations for tunable bulk acoustic wave resonators based on paraelectric phase BaxSr1-xTiO3 thin films2010Conference paper (Refereed)
    Abstract [en]

    Paraelectric phase BaxSr1-xTiO3 (BSTO) is due to the pronounced field induced piezoelectric effect a promising candidate to realize hysteresis-free tunable thin film bulk acoustic wave resonators (TFBARs) at GHz frequencies. Compared to the conventional fixed-frequency TFBAR technology, mainly based on piezoelectric AlN films, the design of tunable BSTO based resonators require additional considerations due to the demanding conditions necessary for the growth of the BSTO active layer (high temperature, O2 ambient). In this work a number of problems and possible solutions are presented for the specific case of solidly mounted resonators based on an acoustic Bragg reflector structure. Simulation results for a proposed tunable resonator based on a BSTO film and a SiO2/HfO2 reflector stack co-optimized for both longitudinal and shear waves are presented and compared to simulations and existing experimental data from other structures.

  • 7. Berge, John
    et al.
    Vorobiev, Andrei
    Gevorgian, Spartak
    The effect of growth temperature on the nanostructure and dielectric response of BaTiO3 ferroelectric films2007In: Thin Solid Films, Vol. 515, no 16, 6302-6308 p.Article in journal (Refereed)
    Abstract [en]

    BaTiO3 ferroelectric films were grown on Si/SiO2/Ti/Pt/Au/Pt templates at different temperatures in the range 560-680 degrees C by pulsed laser deposition. Cross section scanning electron microscopy images and atomic force microscopy surface morphology analysis reveal films with columnar structure and in-plane grain size distribution, in the range 10-60 nm, depending on growth temperature. Low-field dielectric measurements were performed as functions of temperature in the range 40-500 K and extemal dc field up to 400 kV/cm. The apparent permittivity of ferroelectric films grown at 680 degrees C shows Curie-Weiss behavior above 400 K with Curie temperature and Curie-Weiss constant 240 K and 1 center dot 10(5) K, respectively. The films grown at lower temperatures reveal a decrease of Curie temperature down to - 80 K, reduced values of apparent permittivity and loss tangent, and broadening of maximum of temperature dependence of apparent permittivity. The film grown at 590 degrees C demonstrates state of the art combination of temperature stability (temperature coefficient of apparent permittivity 300 ppm/K in the range 50350 K), high tunability of apparent permittivity (up to 60% at room temperature), and relatively low loss tangent (less than 0.05 in the frequency range up to 10 GHz). The change in apparent permittivity and its temperature dependence, with variation of growth temperature are analyzed using two different composite models. The first model assumes the film to be a composite with vertical inclusions of low permittivity dielectric material associated with grain boundaries. This model may explain the observed decrease of permittivity with decreasing growth temperature, but not the shift of Curie temperature. The second model assumes a layered type of composite with low permittivity material associated with the film/ electrode interfaces, and allows explanation of the Curie temperature shift. (C) 2006 Elsevier B.V. All rights reserved.

  • 8. Berge, John
    et al.
    Vorobiev, Andrei
    Steichen, William
    Gevorgian, Spartak
    Tunable Solidly Mounted Thin Film Bulk Acoustic Resonators Based on BaxSr1-xTiO3 Films2007In: IEEE Microwave and Wireless Components Letters, ISSN 1531-1309, E-ISSN 1558-1764, Vol. 17, no 9, 655-657 p.Article in journal (Refereed)
    Abstract [en]

    Electrically tunable solidly mounted thin film bulk acoustic resonators based on BaxSr1-xTiO3 films are reported for the first time. The films are acoustically isolated from the silicon substrate by a Bragg reflector stack. Applying DC bias induces piezoelectric effect and an acoustic resonance at approximately 4 GHz. Under 10 V applied DC bias the resonance frequency of the resonators based on Ba0.25Sr0.75TiO3 films is tuned 1.2% to lower frequencies. The Q-factor of these resonators is approximately 120, and the electromechanical coupling coefficient is 0.5%. The resonant frequency of the BaTiO3 based resonators shifts upwards 1.3% under 10 V DC bias, and the -factor is approximately 30, with an electromechanical coupling coefficient of 6.2%.

  • 9. Berglund, Linn
    et al.
    Anugwom, Ikenna
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Laboratory of Industrial Chemistry and Reaction Engineering, Johan Gadolin Process Chemistry Centre, Åbo Akademi University, Turku, Finland.
    Hedenström, Mattias
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Aitomäki, Yvonne
    Mikkola, Jyri-Pekka
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Laboratory of Industrial Chemistry and Reaction Engineering, Johan Gadolin Process Chemistry Centre, Åbo Akademi University, Turku, Finland.
    Oksman, Kristiina
    Switchable ionic liquids enable efficient nanofibrillation of wood pulp2017In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 24, no 8, 3265-3279 p.Article in journal (Refereed)
    Abstract [en]

    Use of switchable ionic liquid (SIL) pulp offers an efficient and greener technology to produce nanofibers via ultrafine grinding. In this study, we demonstrate that SIL pulp opens up a mechanically efficient route to the nanofibrillation of wood pulp, thus providing both a low cost and chemically benign route to the production of cellulose nanofibers. The degree of fibrillation during the process was evaluated by viscosity and optical microscopy of SIL treated, bleached SIL treated and a reference pulp. Furthermore, films were prepared from the fibrillated material for characterization and tensile testing. It was observed that substantially improved mechanical properties were attained as a result of the grinding process, thus signifying nanofibrillation. Both SIL treated and bleached SIL treated pulps were fibrillated into nanofibers with fiber diameters below 15 nm thus forming networks of hydrophilic nature with an intact crystalline structure. Notably, it was found that the SIL pulp could be fibrillated more efficiently than traditional pulp since nanofibers could be produced with more than 30% less energy when compared to the reference pulp. Additionally, bleaching reduced the energy demand by further 16%. The study demonstrated that this switchable ionic liquid treatment has considerable potential in the commercial production of nanofibers due to the increased efficiency in fibrillation.

  • 10.
    Bhatti, Tariq M.
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Bioleaching of organic carbon rich polymetallic black shale2015In: Hydrometallurgy, ISSN 0304-386X, E-ISSN 1879-1158, Vol. 157, 246-255 p.Article in journal (Refereed)
    Abstract [en]

    The present study describes the extraction of metals from organic-carbon rich Kyrk Tasjo (Sweden) polymetallic black shale using mixed cultures of acidophilic iron- and sulfur-oxidizing microorganisms. Quartz, Mite, micro-cline, calcite, dolomite and pyrite minerals were present in shale matrix. Black shale contained 10.77% organic carbon as kerogen and 1.16% inorganic carbon (graphite). The leaching experiments were performed in shake flasks and stirred tank reactors with and without acidophilic Fe- and S-oxidizing psychrotolerant, mesophile and moderate thermophile strains at 6,30 and 45 degrees C. Biological oxidation of pyrite generated sulfuric acid and ferric sulfate in leach solutions during leaching process. Microbial leaching solubilized 80-90% of the total metals (U, Cu, Ni, Mn, Mo, Y and Zn) after 15-20 days of bioleaching at 30 and 45 degrees C; whereas metal solubilization was slower with acidophilic psychrotolerant bacteria at 6 degrees C. The biodegradation of kerogen released tetradecane (CH3(CH2)(12)CH3), a long-chain aliphatic hydrocarbon compound and several other un-identified hydrocarbons in leach solutions during bioleaching of black shale. The addition of PO43- and NH4+ in the growth medium during bioleaching had no effect or decreased the metal solubilization, suggesting that the microorganisms obtained these nutrients from the minerals and kerogen (C100H112O9N2S5), a nitrogenous hydrocarbon compound present in the shale matrix. Metal dissolution from black shale was mainly attributed to the acid concentration in leach solution and temperature. The leaching data demonstrate the feasibility of extracting metals from the black shale without additional nutrient supply that constitute a cost saving for commercial scale application of bioleaching process. The bioleaching approach does not appear warranted to view of the low concentrations, albeit relatively high recoveries of valuable metals from the black shale. The leaching data indicate that exposed black shale occurrences, being subject to ambient weather conditions, constitute a long term environmental challenge.

  • 11.
    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).

  • 12. Challamel, Noel
    et al.
    Girhammar, Ulf Arne
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Boundary-Layer Effect in Composite Beams with Interlayer Slip2011In: Journal of Aerospace Engineering, ISSN 0893-1321, Vol. 24, no 2, 199-209 p.Article in journal (Refereed)
    Abstract [en]

    An apparent analytical peculiarity or paradox in the bending behavior of elastic-composite beams with interlayer slip, sandwich beams, or other similar problems subjected to boundary moments exists. For a fully composite beam subjected to such end moments, the partial composite model will render a nonvanishing uniform value for the normal force in the individual subelement. This is from a formal mathematical point of view in apparent contradiction with the boundary conditions, in which the normal force in the individual subelement usually is assumed to vanish at the extremity of the beam. This mathematical paradox can be explained with the concept of boundary layer. The bending of the partially composite beam expressed in dimensionless form depends only on one structural parameter related to the stiffness of the connection between the two subelements. An asymptotic method is used to characterize the normal force and the bending moment in the individual subelement to this dimensionless connection parameter. The outer expansion that is valid away from the boundary and the inner expansion valid within the layer adjacent to the boundary (beam extremity) are analytically given. The inner and outer expansions are matched by using Prandtl's matching condition over a region located at the edge of the boundary layer. The thickness of the boundary layer is the inverse of the dimensionless connection parameter. Finite-element results confirm the analytical results and the sensitivity of the bending solution to the mesh density, especially in the edge zone with stress gradient. Finally, composite beams with interlayer slip can be treated in the same manner as nonlocal elastic beams. The fundamental differential equation appearing in the constitutive law associated with the partial-composite action in a nonlocal elasticity framework is discussed. Such an integral formulation of the constitutive equation encompassing the behavior of the whole of the beam allows the investigation of the mechanical problem with the boundary-element method.

  • 13.
    Chen, Genqiang
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry. College of Chemistry, Chemical Engineering and Biotechnology, Donghua University, Shanghai 201620, China.
    Wu, Guochao
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Alriksson, Björn
    Wang, Wei
    Hong, Feng F.
    Jönsson, Leif J.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Bioconversion of waste fiber sludge to bacterial nanocellulose and use for reinforcement of CTMP paper sheets2017In: Polymers, ISSN 2073-4360, E-ISSN 2073-4360, Vol. 9, no 9, 458Article in journal (Refereed)
    Abstract [en]

    Utilization of bacterial nanocellulose (BNC) for large-scale applications is restricted by low productivity in static cultures and by the high cost of the medium. Fiber sludge, a waste stream from pulp and paper mills, was enzymatically hydrolyzed to sugar, which was used for the production of BNC by the submerged cultivation of Komagataeibacter xylinus. Compared with a synthetic glucose-based medium, the productivity of purified BNC from the fiber sludge hydrolysate using shake-flasks was enhanced from 0.11 to 0.17 g/(L x d), although the average viscometric degree of polymerization (DPv) decreased from 6760 to 6050. The cultivation conditions used in stirred-tank reactors (STRs), including the stirring speed, the airflow, and the pH, were also investigated. Using STRs, the BNC productivity in fiber-sludge medium was increased to 0.32 g/(L x d) and the DPv was increased to 6650. BNC produced from the fiber sludge hydrolysate was used as an additive in papermaking based on the chemithermomechanical pulp (CTMP) of birch. The introduction of BNC resulted in a significant enhancement of the mechanical strength of the paper sheets. With 10% (w/w) BNC in the CTMP/BNC mixture, the tear resistance was enhanced by 140%. SEM images showed that the BNC cross-linked and covered the surface of the CTMP fibers, resulting in enhanced mechanical strength.

  • 14. Chen, Zhi-Qiang
    et al.
    Abramowicz, Konrad
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Raczkowski, Rafal
    Ganea, Stefana
    Wu, Harry X.
    Lundqvist, Sven-Olof
    Mörling, Tommy
    Sjöstedt de Luna, Sara
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Gil, Maria Rosario Garcia
    Mellerowicz, Ewa J.
    Method for accurate fiber length determination from increment cores for large-scale population analyses in Norway spruce2016In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 70, no 9, 829-838 p.Article in journal (Refereed)
    Abstract [en]

    Fiber (tracheid) length is an important trait targeted for genetic and silvicultural improvement. Such studies require large-scale non-destructive sampling, and accurate length determination. The standard procedure for non-destructive sampling is to collect increment cores, singularize their cells by maceration, measure them with optical analyzer and apply various corrections to suppress influence of non-fiber particles and cut fibers, as fibers are cut by the corer. The recently developed expectation-maximization method (EM) not only addresses the problem of non-fibers and cut fibers, but also corrects for the sampling bias. Here, the performance of the EM method has been evaluated by comparing it with length-weighing and squared length-weighing, both implemented in fiber analyzers, and with microscopy data for intact fibers, corrected for sampling bias, as the reference. This was done for 12-mm increment cores from 16 Norway spruce (Picea abies (L.) Karst) trees on fibers from rings 8-11 (counted from pith), representing juvenile wood of interest in breeding programs. The EM-estimates provided mean-fiber-lengths with bias of only +2.7% and low scatter. Length-weighing and length2-weighing gave biases of -7.3% and +9.3%, respectively, and larger scatter. The suggested EM approach constitutes a more accurate non-destructive method for fiber length (FL) determination, expected to be applicable also to other conifers.

  • 15.
    Dopson, Mark
    et al.
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Kupka, Daniel
    Halinen, Anna-Kaisa
    Rahunen, Nelli
    Özkaya, Bestamin
    Sahinkaya, Erkan
    Rzhepishevska, Olena I
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Kaksonen, Anna H
    Karnachuk, Olia V
    Tuovinen, IH
    Puhakka, Jaakko A
    Iron oxidation and bioleaching potential at low temperatures2007In: Biohydrometallurgy: from the single cell to the environment / [ed] Axel Schippers, Zurich: Trans Tech Publications Inc., 2007, 578-578 p.Conference paper (Refereed)
  • 16. Duan, Ran
    et al.
    Westerlind, Bo S.
    Norgren, Magnus
    Anugwom, Ikenna
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Laboratory of Industrial Chemistry and Reaction Engineering, Johan Gadolin Process Chemistry Centre, Åbo Akademi University, Finland.
    Virtanen, Pasi
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Mikkola, Jyri-Pekka
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Laboratory of Industrial Chemistry and Reaction Engineering, Johan Gadolin Process Chemistry Centre, Åbo Akademi University, Finland.
    Fibre Stress-Strain Response of High-Temperature Chemi-Thermomechanical Pulp Treated with Switchable Ionic Liquids2016In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 11, no 4, 8570-8588 p.Article in journal (Refereed)
    Abstract [en]

    The removal of lignin from a high-temperature chemi-thermomechanical pulp (HT-CTMP) using a switchable ionic liquid prepared from an organic superbase (1,8-diazabicyclo-[5.4.0]-undec-7-ene (DBU)), monoethanol amine (MEA), and SO2 was investigated. The objective was to measure the fibre properties before and after removal of the lignin to analyse the contributions from lignin in the HT-CTMP fibre to the tensile properties. It was found that the fibre displacement at break - measured in zero span, which is related to fibre strain at break - was not influenced by the lignin removal in this ionic liquid system when tested dry. There was a small increase in displacement at break and a reduction in tensile strength at zero span when tested after rewetting. At short span, the displacement at break decreased slightly when lignin was removed, while tensile strength was almost unaffected when tested dry. Under rewetted conditions, the displacement at break increased and tensile strength decreased after lignin removal. Nevertheless, no dramatic differences in the pulp properties could be observed. Under the experimental conditions, treatment with the ionic liquid reduced the lignin content from 37.4 to 15.5 wt%.

  • 17.
    Ekevad, Mats
    et al.
    Luleå Tekniska Universitet, Avdelning för Träteknik.
    Lundgren, Nils
    Luleå Tekniska Universitet, Avdelning för Träteknik.
    Flodin, Jens
    SP Technical Research Institute of Sweden, Wood Technology, Skeria 2, Skellefteå, Sweden.
    Drying shrinkage of sawn timber of Norway spruce (Picea abies): industrial measurements and finite element simulations2011In: Wood Material Science & Engineering, ISSN 1748-0272, Vol. 6, no 1, 41-48 p.Article in journal (Refereed)
    Abstract [en]

    Industrial measurements of green and dry cross-section dimensions were performed for 189 Norway spruce (Picea abies) centre-yield boards with dry dimensions 51x49 mm. Two, three or four boards were sawn from each log, depending on log size. Different approaches were used for simulations of cross-section shrinkage during drying. An analytical model, an elastic, an elastic mechanosorptive and an elastic plastic finite element simulation model were tested. Thickness and width shrinkage and deformation were simulated. Shrinkage results were compared with each other and with the experimental results. All simulation models gave roughly the same degree of agreement with experimental results except for the centre board from the three-board sawing pattern. For the other boards, the analytical model was not generally better or worse than the results from the finite element models. Shrinkage deformations in finite element models that included mechanosorption or plasticity were nearly the same as for the elastic finite element model except for the centre board of the three-board sawing pattern. The mechanosorptive model was the best model for the shrinkage of the centre board of this sawing pattern except for mid-thickness shrinkage. Comparison between the different finite element simulation models of stresses in the centre board revealed large differences.

  • 18. Gevorgian, Spartak
    et al.
    Lewin, T
    Vorobiev, Andrei
    Norling, Martin
    Berge, John
    A voltage controlled switching device2009Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    A capacitive device (100, 200) comprising first (110) and second (130) layers of electrically conductive material, each of which has a first and a second main surface. The device also comprises a third layer (120) of a paraelectric phase material between the first (110) and second (120) layers, so that one of said first or second surfaces of the first and second layers face the third layer. The device (100, 200) additionally comprises a non-conducting supporting structure (160) on which the device rests, and comprises means (DC) for applying a DC voltage across the third layer (160), so that the device by means of varying the applied DC voltage may be made to alter its electrical characteristics between that of a capacitor, a short circuit or an open circuit.

  • 19. Gevorgian, Spartak
    et al.
    Vorobiev, Andrei
    Berge, John
    Electromechanical modelling and reduction of the electroacoustic losses in parallel-plate ferroelectric varactors2006In: Proc. European Microwave Conference 2006, 2006Conference paper (Refereed)
  • 20.
    Girhammar, Ulf Arne
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Kallsner, Bo
    Analysis of influence of imperfections on stiffness of fully anchored light-frame timber shear walls: elastic model2009In: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 42, no 3, 321-337 p.Article in journal (Refereed)
    Abstract [en]

    In order to stabilize light-frame timber buildings against horizontal loads, the diaphragm or in-plane action of roofs, floors and walls is often used. This paper deals with the influence of imperfections such as gaps and uplift on the horizontal displacement of fully anchored shear walls. The significance of analyzing the effects of imperfections is evident when evaluating the stiffness of shear walls; tests of walls show that the horizontal displacement is underestimated in calculations using the stiffness of sheathing-to-framing joints as obtained from experiments. Also, in real structures where hold-downs are used according to the elastic design method, the influence of gaps and uplift should be included in order to obtain realistic displacements in the serviceability limit state. A new elastic model for the analysis, based on linear elastic behaviour of the mechanical sheathing-to-framing joints, is presented and the equations for the stiffness and the deflection versus the number of segments in the wall are derived. The fully anchored condition for the shear walls are modelled by applying a diagonal load to the wall. Three types of imperfections are evaluated: gaps at all studs, a gap only at the trailing stud, and gaps at all studs, except at the trailing stud. It is shown that the effect of imperfections on the stiffness of the wall in the initial stage is considerable. Depending on the distribution of the gaps and the number of segments included in the shear wall, the displacement of the shear wall is increased several times compared to that of a fully anchored shear wall with no gaps; e.g. for a single segment wall more than three times. However, for walls with more than six to ten segments, the effect of imperfections can be neglected. Finally, the theoretical model is experimentally verified.

  • 21.
    Girhammar, Ulf Arne
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Pajari, Matti
    Tests and analysis on shear strength of composite slabs of hollow core units and concrete topping2008In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 22, no 8, 1708-1722 p.Article in journal (Refereed)
    Abstract [en]

    Prestressed concrete hollow core slabs are commonly used as load-bearing floors and roofs. The upper surface of the hollow core slabs is usually levelled with a cast-in situ screed or concrete topping. Reducing the thickness of the precast unit and increasing the thickness of the concrete topping, but maintaining the load-carrying capacity for the whole composite section is technically and economically an interesting alternative. The expensive screed could be replaced by a cheaper concrete and installations could be embedded in the topping layer. Proper shear and bond strength at the interface is required for composite action. An experimental and theoretical study on the effect of structural topping on the shear capacity of hollow core slabs and of the adequacy of the shear or bond strength of the non-treated interface is presented. It is concluded that concrete topping can be used to improve the shear capacity of hollow core units. For the test specimens, the theoretical increase was of the order of 35%, which was verified by the tests. The bond strength at the interface is adequate and the topping interacts with the slab in a proper manner.

  • 22. Grivel, J-C
    et al.
    Pitillas, A.
    Namazkar, S.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Department of Energy Conversion and Storage, Technical University of Denmark, 4000-Roskilde, Denmark.
    Alexiou, A.
    Holte, O. J.
    Preparation and characterization of MgB2 with Pd, Pt and Re doping2016In: Physica. C, Superconductivity, ISSN 0921-4534, E-ISSN 1873-2143, Vol. 520, 37-41 p.Article in journal (Refereed)
    Abstract [en]

    Samples with Mg1-xDxB2.04 (D = Pt, Pd or Re) nominal compositions have been synthesised by a solid-state route. None of these doping elements can be substituted for Mg in a detectable amount and their presence in the samples has no influence on the critical temperature and on the lattice parameters of the MgB2 superconductor. Impurity phases are formed by reaction mostly with Mg. The microstructure of the Pt, Pd and Re-based phases depends on the elements. Re-rich particles with large sizes up to 8 mu m form, whereas Pt- and Pd-containing impurities are finely dispersed with a particle size that does not exceed 1 mu m. The field dependence of the normalised critical current density is improved when Pt, Pd or Re are present in the samples. (C) 2015 Elsevier B.V. All rights reserved.

  • 23.
    Grundberg, Staffan
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Girhammar, Ulf Arne
    Luleå tekniska universitet.
    A Comparison of Exact and Approximate Analyses of Partially Interacting Composite Beam-Columns2015In: Proceedings of the Fifteenth International Conference on Civil, Structural and Environmental Engineering Computing / [ed] J. Kruis, Y. Tsompanakis and B.H.V. Topping, Stirlingshire, UK: Civil-Comp Press , 2015, 261Conference paper (Refereed)
    Abstract [en]

    Solutions of the static Euler-Bernoulli equations of composite beam-columns with interlayer slip have been compared with an approximate theory. The inter-layer force was taken to be proportional to the inter-layer slip. The general solutions were obtained for four different sets of boundary conditions corresponding to the four Euler cases: clamped-free, pinned-pinned, clamped-pinned and clamped-clamped. A transverse static point load was considered. The beam was axially loaded. The contribution of the axial force to the bending moment, or equivalently the work done by the axial force on the beam due to its deflection, was taken into account in the second order theory and neglected in the first order theory. In the approximate theory the second order effects were described by an approximate magnification factor obtained from critical loads calculated by approximating the buckling length coefficients of the composite beam with interlayer slip by the buckling length coefficients of a solid beam. The contribution of second order effects to deflections and internal actions were calculated in terms of exact magnification factors at different stiffness of the composite action and the results were compared with the approximate theory. Two composite beams were considered. The first was a combination of concrete and timber and the second was a combination of concrete and steel. The positions of the maximum internal shear forces were shown to occur at different positions in the two layers of the beam of concrete and steel when the exact first and second order calculations were compared. The approximate theory was fairly accurate for the deflection but showed higher deviations for other quantities. The approximate theory needs further evaluation. The exact results have been obtained by analytical calculations in combination with numerical evaluation.

  • 24. Guo, Li
    et al.
    Berglin, Lena
    Wiklund, Urban
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Mattila, Heikki
    Design of a garment-based sensing system for breathing monitoring2013In: Textile research journal, ISSN 0040-5175, E-ISSN 1746-7748, Vol. 83, no 5, 499-509 p.Article in journal (Refereed)
    Abstract [en]

    The long-term monitoring of biophysiological signals requires new types of sensor systems that are wearable and at the same time convenient for the users. This paper describes the design of a novel garment-based sensing system for the long-term monitoring of breathing rhythm. The system concept was realized in a prototype garment, integrated with coated piezoresistive sensors. The prototype garment was tested by five subjects, and compared with a standard piezoelectric respiratory belt. Each signal was quantitatively and qualitatively evaluated in the time and frequency domain to make sure that no medical and diagnostic information was lost. The results showed a good agreement between the garment-based sensors and the standard reference, where errors occurred only when the breathing rate was extremely high. The garment-based sensor system could also distinguish the predominance breathing compartment (chest versus abdominal breathing). The system could detect a 10 s pause in breathing, which could be of importance in studies of sleep apnea. A garment-based sensing system maintains the accuracy of the signal quality without reducing the comfort for the user. It makes possible long-term ambulatory monitoring and has home-based healthcare applications.

  • 25. Hägglund, Håkan
    et al.
    Norberg, Ole
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Edström, Per
    Prediction of optical variations in paper from high resolution measurements of paper properties2013In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, Vol. 28, no 4, 596-601 p.Article in journal (Refereed)
    Abstract [en]

    A method to predict optical variations from high resolution measurements of paper properties is evaluated in this work. The method combines the point-wise values of high resolution maps of filler content and grammage with an empirical model derived in an earlier study to predict the spatial optical variations in paper. The method has been applied on two paper samples, a laboratory paper and a commercial 80 g/m(2) copy paper. The optical variations have been predicted at a scale of 1 mm(2). Validation has been made by using a high resolution spectrophotometric setup to measure the spatial reflectance variations in the paper. The results show that for the samples used, the influence of filler content variations and density variations on the optical variations is small compared to influence of the grammage variations.

  • 26.
    Hållberg, Richard
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Produktion BM/FS. Produktionsavsnitt Färdigställning: Interna Reklamationer*Process*Kostnader2014Independent thesis Basic level (university diploma), 5 credits / 7,5 HE creditsStudent thesis
    Abstract [en]

    This report describes the project work on the clarification of the nature and the amound of resources required in relation to internal complaints of copy products and the creation of a culculation template that clarifies the costs of these complaints. The goal is to estmate the model is to clarify what cost it will be for internal clains and thereby increase understanding of how important it is to always produce products with the right at all process stages throughout production.

    To illustrate what and how much resources it takes to take care of internal complaints of copy products have been affected positions were interviewed by a single interviewer template. Interview template highlights issuses such as what each position has the primary task in the context of internal complaints, how many hours required for each position and which costs are incurred.

    The results of the compilation of internal complaints of copy products are described, calculating the costs of internal complaints of copy products is clarified through three tables costs of internal/external staff and loss of production per machine culculated in a developed culation template.

    Costs of consumable materials are described. Then all costs in a Pivottable. Suggestions are given for the improvement of the quality of copy products can be done to avoid the problems that internal complaints.

  • 27. Johansson, Kristin
    et al.
    Jönsson, Leif J
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Järnström, Lars
    Oxygen scavenging enzymes in coatings: effect of coating procedures on enzyme activity2011In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, Vol. 26, no 2, 197-204 p.Article in journal (Refereed)
    Abstract [en]

    The oxygen content in food packaging may be reduced by attaching oxygen scavengers to the packaging material. The critical parameters that determine the oxygen-scavenging ability of an enzyme-based coating i.e. pH, heat and coating color formulation were evaluated. Glucose oxidase, catalase and glucose were added to latex dispersions in the preparation of the coating colors. The enzymes were entrapped in the coating layers after coating and drying. The clay concentration and drying conditions were varied and the enzymatic activity of the coated layer was evaluated. The need for a pH-buffered system was also studied and the results indicated that, when using a carboxylated latex of a standard coating grade, a buffered system was not needed. A rapid drying at a high temperature was preferred over a slow drying at a low temperature in order to prevent pre-oxidation of the substrate in the wet coating color. The scavenging capacity of the coating was dependent on the amount of substrate for the enzyme reaction left after complete drying. The concentration of clay in the coating formulation was shown to have a marked impact on the oxygen-scavenging ability of the coated layer. The enzyme activity was increased by the addition of clay up to a pigment volume concentration (PVC) of ca. 10%. At higher concentrations of clay, the enzyme activity decreased until the critical pigment volume concentration (CPVC) was reached, probably due to the prevention of diffusion of oxygen and consumption of glucose in the coating process before the layer was completely dried. Further additions of clay above the CPVC resulted in an increased enzyme activity, probably due to the creation of a porous structure.

  • 28.
    Järvinen, Kristiina
    et al.
    Department of Pharmacy, University of Eastern Finland, Kuopio, Finland.
    Jokiniemi, Jorma
    Deaprtment of Environmental Science.
    Lammi, Mikko
    Institute of Biomedicine, University of Eastern Finland, Kuopio, Finland.
    Lappalainen, Reijo
    Department of Applied Physics, University of Eastern Finland, Kuopio, Finland.
    Närvänen, Ale
    Department of Pharmacy, University of Eastern Finland.
    Pakkanen, Tapani
    Department of Chemistry, University of Eastern Finland, Kuopio,Finland.
    Lehto, Vesa-Pekka
    Department ofApplied Physics, University of Eastern Finalnd, Kuopio, Finland.
    Nanoteknologia biomateriaalien ja lääkkeiden kantaja-aineiden pintojen räätälöinnissä [Nanoscale tailoring of the surface properties of biomaterials and drug carriers]2012In: Duodecim, ISSN 0012-7183, Vol. 128, no 20, 2085-2092 p., 23167167Article, review/survey (Refereed)
    Abstract [en]

    Functionalities of biomaterials and drug delivery systems are improved by tailoring their surface properties using modern nanotechnology. Orthopedic implants and invasive electrodes are examples of implantable biomaterials. Biological interactions of orthopedic implants can be optimized by the synergetic effect of surface micro- and nanotexturing with a chemical composition of coating. Further, mechanical flexibility and electrochemical characteristics of invasive electrodes are improved by using micro- and nanotechnology. In nano-size drug delivery systems, surface properties of nanocarriers strongly affect their safety and efficacy. Mesoporous silicon nanoparticles are example of nanocarriers those properties can be tailored for drug delivery applications.

  • 29.
    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, 025009- p., 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.

  • 30. Kvyatkovskii, Oleg E
    et al.
    Zacharova, Irina B
    Shelankov, Andrei
    Umeå University, Faculty of Science and Technology, Department of Physics. A.F. Ioffe Physico‐Technical Institute of the RAS , St. Petersburg, Russia .
    Makarova, Tatiana
    Umeå University, Faculty of Science and Technology, Department of Physics. A.F. Ioffe Physico‐Technical Institute of the RAS , St. Petersburg, Russia .
    Magnetic transition in the polymerized fullerene matrix2006In: Fullerenes, Nanotubes and Carbon Nanostructures vol. 14, issue 2&3: Proceedings of the International Workshop on Fullerenes and Atomic Clusters 2005 (IWFAC2005), St. Petersburg, Taylor & Francis, 2006, Vol. 2-3, 373-380 p.Conference paper (Refereed)
    Abstract [en]

    A mechanism of the ferromagnetism in the polymerized fullerene phase is proposed. We show that non‐magnetic defects and impurities give rise to a magnetic transition in the polymerized fullerene matrix. In our model, C60 molecules acquire spin and charge and become magnetically active due to the spin and charge transfer from non‐magnetic dopants. The interaction between magnetic moments of the arising paramagnetic species (C60 ± ions or C60 R radical adducts) dispersed in the polymeric network is inspected by using ab initio Hartree‐Fock and B3LYP hybrid density functional methods. It is revealed that the interaction is ferromagnetic and large enough for creating the high‐T c magnetism.

  • 31. Källsner, Bo
    et al.
    Girhammar, Ulf Arne
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Analysis of fully anchored light-frame timber shear walls: elastic model2009In: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 42, no 3, 301-320 p.Article in journal (Refereed)
    Abstract [en]

    In order to stabilize light-framed timber buildings against lateral loads, the diaphragm action of roofs, floors and walls is often used. This paper deals with an elastic analysis model for fully anchored sheathed wood frame shear walls. The model is based on the assumption of a linear elastic load-slip relation for the sheathing-to-framing joints. Only static loads are considered. The basic structural behaviour and assumptions for the elastic model are elucidated. Formulas for the load-bearing capacity and the deformation of the shear walls in the ultimate and serviceability limit states, respectively, are derived. Both a discrete point description and a continuous flow per unit length modelling of the fasteners are discussed. Also, the forces and displacements of the fasteners and sheathing are derived. The effect of different patterns and spacing of the fasteners on the capacity and displacement of the wall is illustrated. The influence of flexible framing members and shear deformations in the sheets, and also the effect of vertical loads on the shear wall, both with respect to tilting and second order effects, on the horizontal load-bearing capacity and displacement are evaluated. The stress distribution and the reaction forces at the ends of the different framing members are derived. The elastic model is experimentally verified and an illustrative example is given.

  • 32.
    Lammi, Mikko
    et al.
    Institute of Biomedicine, University of Eastern Finland.
    Qu, Chengjuan
    Institute of Biomedicine, University of Eastern Finland.
    Prittinen, Juha
    Institute of Biomedicine, University of Eastern Finland.
    Kröger, Heikki
    Department of Orthopaedics and Traumatology, Kuopio University Hospital, Kuopio, Finland.
    Koistinen, Arto
    SIB-Labs, University of Eastern Finland, Kuopio, Finland.
    Myllymaa, Sami
    SIB-Labs, University of Eastern Finland, Kuopio, Finland.
    Lappalainen, Reijo
    Department of Applied Physics, University of Eastern Finland, Kuopio, Finland.
    Adhesion and spreading of different skeletal celltypes on variable surface coatings2012In: 5th International Conference on Biomedical Engineering and Informatics, IEEE Conference Publications , 2012, 582-587 p.Conference paper (Refereed)
    Abstract [en]

    The adhesion and spreading of human bone marrow-derived mesenchymal stem cells (hMSCs), bovine primary chondrocytes and human osteoblastic osteosarcoma cell line (Saos-2) cultured on various coated surfaces were examined to determine whether different materials coated on the silicon wafer could affect the growth of the different cell types. The amorphous diamond (AD), titania (TiO2), alumina (Al2O3) or carbon nitride (C3N4) coating on the silicon wafer was obtained by using ultra short pulsed laser deposition. The differences in surface characteristics were characterized with atomic force microscope and contact angles and zeta potential measurements. Human MSCs, bovine primary chondrocytes and Saos-2 osteoblasts were cultured for 48 h in direct contact with AD-, TiO2-, Al2O3- and C3N4-coated surfaces. Cell proliferation was assayed with MTT assay. The morphology, adhesion and spreading of the cultured cells were examined with scanning electron microscope. Human MSCs had the highest cell number after 48-h-culture on all of the different coated surfaces, followed by Saos-2 osteoblasts, and then bovine primary chondrocytes. The morphological appearance of MSCs, chondrocytes and Saos-2 osteoblasts remained as original. No statistically significant differences on cell proliferation were found among the different coated surfaces. Ultra short pulsed laser deposited high quality AD-, TiO2-, Al2O3- and C3N4-coated surfaces, and provided a good environment for the adhesion and spreading of the hMSCs, primary chondrocytes and Saos-2 osteoblasts

  • 33.
    Lanz, Thomas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sandström, Andreas
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB, Tvistevägen 47, PO Box 7970, SE-90719 Umeå, Sweden.
    Tang, Shi
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB, Tvistevägen 47, PO Box 7970, SE-90719 Umeå, Sweden.
    Chabrecek, Peter
    Sefar AG.
    Sonderegger, Uriel
    Sefar AG.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB, Tvistevägen 47, PO Box 7970, SE-90719 Umeå, Sweden.
    A light–emission textile device: conformal spray-sintering of a woven fabric electrode2016In: Flexible and Printed Electronics, ISSN 2058-8585, Vol. 1, no 2, 025004Article in journal (Refereed)
    Abstract [en]

    We report on the realization of an ultra-flexible, light-weight and large-area emissive textile device. The anode and active material of a light-emitting electrochemical cell (LEC) were deposited by conformal spray-coating of a transparent fabric-based electrode, comprising a weave of fine Ag-coated Cu wires and poly(ethylene naphthalene) monofilament fibers embedded in a polyurethane matrix. The yellow-emitting textile featured low turn-on voltage (5 V), high maximum brightness (>4000 cd m−2), good efficiency (3.4 cd A−1), and reasonable lifetime (180 h at >100 cd m−2). Uniform emission to the eye was attained from thin and highly flexible textiles featuring a large emission area of 42 cm2, without resorting to planarization of the partially wavy-shaped (valley-to-peak height = 2.7 μm) fabric electrode. The key enabling factors for the functional emissive textile are the characteristic in situ electrochemical doping of LEC devices, the 'dry' spray-sintering deposition of the active material, and the attractive mechanical, electronic and optical properties of the fabric-based electrode.

  • 34.
    Leander, D
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Östberg, A
    Potentiostatic methods in sample preparation and etching2004In: Praktische metallographie, ISSN 0032-678X, E-ISSN 2195-8599, Vol. 41, no 11, 561-576 p.Article in journal (Refereed)
    Abstract [en]

    A potentiostat was used in order to optimise etching and phase extraction. Polarisation curves for different grades of steel and different electrolytes were collected and the results were used for optimisation of the voltage and time with multivariate methods. In electrolytic etching a potential is set to control the etching reaction. With the help of a potentiostat the potential is maintained at the set value and the process is well defined and reproducible. Etching procedures were tried out to differentiate between various intermetallic phases that were indistinguishable using other etching methods and the results were evaluated with light and X-ray diffraction methods. Settings for rapid phase extraction of duplex stainless steels in 10% HCl in ethanol were found from the Potentio dynamic scan (PDS), without dissolving the desired phase. An investigation of the influence of the illumination of the sample in image processing was also performed.

  • 35. Lindberg, D
    et al.
    Perander, L
    Backman, Rainer
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Hupa, M
    Kochesfahani, S
    Rickards, H
    Borate autocausticizing equilibria in recovery boiler smelt2005In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 20, no 2, 232-236 p.Article in journal (Refereed)
    Abstract [en]

    The effect of the potassium and boron concentration in an alkali carbonate/borate mixture and the effect of CO, concentration in the gas were studied with thermogravimetry and thermal analysis up to 900 degrees C. Results show that the auto-causticizing reaction is readily reversible with 1 % CO2 or higher in the gas if the mixtures contain only sodium compounds. Both a higher CO, concentration and a higher potassium concentration lead to lower autocausticizing. In systems that contain only potassium compounds, the autocausticizing is low and no recarbonation is observed. In potassium-rich systems, volatilization of alkali- and/or boron-components becomes more prominent than in sodium systems.

  • 36. Lindberg, Daniel
    et al.
    Backman, Rainer
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Hupa, Mikko
    Thermodynamic modeling of the stability and melting properties of sodium borates relevant to black liquor combustion and gasification2007In: International Journal of Materials Research - Zeitschrift für Metallkunde, ISSN 1862-5282, E-ISSN 2195-8556, Vol. 98, no 10, 1012-1018 p.Article in journal (Refereed)
    Abstract [en]

    The use of borates as an autocausticizing agent in kraft recovery boilers of pulp mills is an interesting concept for decreasing the lime consumption at pulp mills. The main autocausticizing reaction is between NaBO2 and Na2CO3 forming Na3BO3 and CO2 at high temperatures in a liquid phase in the recovery boiler. The thermodynamic and phase equilibrium data of the Na2CO3-NaBO2-Na3BO3 system were evaluated and optimized. The liquid phase was modeled with the modified quasichemical model. The thermodynamic database obtained can be used to calculate the phase equilibrium and thermodynamic properties of multicomponent sodium salt mixtures of importance for the borate autocausticizing concept. The thermodynamic database is a part of an extensive thermodynamic database for alkali salt mixtures of importance for black liquor combustion in the pulp and paper industry.

  • 37.
    Makarova, Tatiana
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Ricco, Mauro
    Pontiroli, Daniele
    Mazzani, Marcello
    Belli, Matteo
    Goffredi, Angelo
    Ageing effects in nanographite monitored by Raman spectroscopy2008In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 245, no 10, 2082-2085 p.Article in journal (Refereed)
    Abstract [en]

    The structural relaxation of nanographite ball-milled in argon atmosphere and stored in evacuated ampoules, has been studied by monitoring the evolution of the Raman spectra. Reduction of some Raman bands associated with “in-plane” structural defects, such as vacancies, dislocations or grain boundaries, and those associated with “out-of-plane” defects, such as stacking faults, is accompanied by the rise of new bands around 1180 and 2000 cm–1. The development of these bands is suppressed in nanographite samples exposed to a flux of pure anhydrous hydrogen.

  • 38. Mikhlin, Yuri
    et al.
    Karacharov, Anton
    Tomashevich, Yevgeny
    Shchukarev, Andrey
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Interaction of sphalerite with potassium n-butyl xanthate and copper sulfate solutions studied by XPS of fast-frozen samples and zeta-potential measurement2016In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 125, 98-105 p.Article in journal (Refereed)
    Abstract [en]

    We acquired low-temperature X-ray photoelectron spectra of fast-frozen wet pastes prepared by centrifugation of the natural sphalerite slurries containing potassium n-butyl xanthate (KBX), without washing or any additional treatment, before and after the mineral activation in 0.1 mM CuSO4 solution. Zeta potentials of the slurry particles were also measured. The method allowed characterizing the mineral surfaces and adsorbates, volatile substances and hydrated species within the interfacial layers under more realistic flotation-related conditions. The uptake of xanthate by unactivated mineral was low even in 10 mM KBX, while the surface became metal-deficient (enriched in sulfur), more hydrophobic and contaminated with carbonaceous matter. Dibutyl dixanthogen was the major interfacial product of the interaction of Cu-activated sphalerite having the surface atomic Zn/Cu ratio of 3 and excess of sulfur with the KBX solutions. The spectra revealed only minor quantities of Zn and Cu xanthates and oxyhydroxides at all the samples; some hydrated K+ counter-ions were detected at the negatively charged surfaces after the xanthate treatment. The dixanthogen was concluded to form via oxidation of xanthate at the interface, probably catalyzed by surface cuprous species but not direct interaction with cupric ions.

  • 39.
    Mwaba, Misheck G
    et al.
    Carleton University, Ottawa, Canada.
    Gu, Junjie
    Carleton University, Ottawa, Canada.
    Golriz, Mohammad R
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Effect of magnetic field on calcium sulfate crystal morphology2007In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 303, no 2, 381-386 p.Article in journal (Refereed)
    Abstract [en]

    The shape of crystal morphology from magnetically treated calcium sulfate (CaSO4) solutions were investigated using microscopic methods. The motivation was to gain knowledge that may assist in unraveling the possible mechanisms involved in the reduction and/or elimination of scales from heat transfer surfaces exposed to magnetically treated fluids. Solutions of CaSO4 at different concentrations were prepared and subjected to magnetic fields of up to 0.1 T, under static and dynamic conditions. The resulting crystals were examined with a scanning electron microscope (SEM). The SEM micrographs obtained show changes in the structure of the crystals. Crystals from magnetically treated solutions appear to have a larger surface in one plane relative to the other planes. It is concluded that subjecting a magnetic field to a supersaturated solution affects the direction of crystal growth, possibly increasing the growth rate in one direction and suppressing it in the other directions.

  • 40.
    Müller, Malin
    Umeå University, Faculty of Science and Technology, Umeå Institute of Design.
    Functional workwear for miners working in the worlds largest underground mine: In what way can the future workwear for an extreme mine environment improve safety, facilitate the work flow as well as increase the comfort for workers situated more than 1045 meter below ground?2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    PROBLEM

    This is my graduating thesis from the bachelor program in Industrial Design from Umeå Institute of design.

    In this project I have looked at in what way the future work wear for an extreme mine environment could improve safety, facilitate the workflow as well as increase the comfort for workers situated more than 1045 meters below ground. I have collaborated with LKAB in Kiruna, Sweden.

    LKAB is a mining company, exporting iron ore from the worlds largest underground iron ore mine. In the Kiruna mine, a new main level was recently opened at the level of 1365 meters. The extreme conditions down at this depth have created new challenges when it comes to work wear for the employees.

    METHODS AND FINDING RESULT

    During the project I have used several methods, all following a typical Industrial Design methodology. I started with visiting the mine, having a look at the entire process and talking to workes. After this I wrote a brief for the project, containing information on what the problem is today. I made an other trip to the mine to host a Pin-Point meeting and a workshop together with workers from different positions and work places within the mine. This to gain a further and more specific understanding in the problem -s. The workshop I hosted was to see what they themselves thought would be good solutions. Other methods I've used is survey, sketch ideation, evaluations with users, interviews, observations, visits to manufacturers, visit to the industrial wash / warehouse and mock-ups.

    I divided the problems in to categories:

    The fit of the clothes

    Ability to carry tools

    Material

    Functions / Adjustments

    The project has resulted in a concept of a new trouser and a new jacket for the workers at the LKAB iron or mine in Kiruna. The garments are of a lighter more durable material than the garments used today. The jacket and the trouser have now more specific pockets and are placed in better positions than earlier. I also tried to place seams better, this to avoid any discomfort and work related injuries. One of the problems today was that the jacket for some, created a pressure over the neck. I've added adjustment possibilities to the garments and inserted "softed" materials in some places to increase level of comfort. The result is portrayed as a full size model, in a women’s fit.

    RESULT

    The project has resulted in a concept of a new trouser and a new jacket for the workers at the LKAB iron or mine in Kiruna. The garments are of a lighter more durable material than the garments used today. The jacket and the trouser have now more specific pockets and are placed in better positions than earlier. I also tried to place seams better, this to avoid any discomfort and work related injuries. One of the problems today was that the jacket for some, created a pressure over the neck. I've added adjustment possibilities to the garments and inserted "softed" materials in some places to increase level of comfort. The result is portrayed as a full size model, in a women’s fit.

  • 41. Niska, John
    et al.
    Andersson, Britt M.
    Umeå University, Faculty of Science and Technology, Physics.
    Easterling, Kenneth
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Physics.
    Loberg, Bengt
    Formation of the 124 phase superconductor (YBa2Cu4O8) by retaining oxygen in a reaction HIP sintering process1990In: Journal of materials science letters, ISSN 0261-8028, Vol. 9, no 7, 770-771 p.Article in journal (Refereed)
    Abstract [en]

    The ceramic superconductor YBa2Cu4O8 has been produced by high temperature sintering of a mixture of CuO and YBa2Cu3O7 in a glass capsule under high hydrostatic argon pressure. The resulting highly dense material is investigated by X-ray diffraction, optical and electron microscopy, resistance measurements and hardness measurements, and shown to be a homogeneous High transition temperature superconductor.

  • 42.
    Nordbo, Kalle J
    Umeå University, Faculty of Science and Technology, Umeå Institute of Design.
    City bus interior: Intergrity, experience and individual needs2002Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Big cities of the future will be challenged with pressing traffic problems as the ever increasing traffic in the city centers causes queuing, delays and increasing air pollution. Subsequently, city dwellers become inflicted by stress and deteriorating health.

    Modern society demands mobility, and we are all dependent on being able to travel around smoothly and efficiently. The private car leaves room for individualism and flexibility, yet it is rather space demanding and thus a root cause for the prevailing chaos of many big cities. In contrary, the bus gathers a large number of persons in a relatively small area, thus saving space and being environmentally friendly. Regrettably, however, with bus designs human aspects such as the mental and physical comfort often are given low priority in endeavors to run an economically viably visible business.

  • 43. Norling, Martin
    et al.
    Berge, John
    Gevorgian, Spartak
    Parameter extraction for tunable TFBARs based on BaxSr1-xTiO32009In: IEEE MTT-S International Microwave Symposium Digest 2009, 2009Conference paper (Refereed)
  • 44.
    Näsström, Gunilla
    Umeå University, Faculty of Social Sciences, Department of Educational Measurement.
    Measurement of alignment between standards and assessment2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Many educational systems of today are standards-based and aim at for alignment, i.e. consistency, among the components of the educational system: standards, teaching and assessment. To conclude whether the alignment is sufficiently high, analyses with a useful model are needed. This thesis investigates the usefulness of models for analyzing alignment between standards and assessments, with emphasis on one method: Bloom’s revised taxonomy. The thesis comprises an introduction and five articles that empirically investigate the usefulness of methods for alignment analyses.

    In the first article, the usefulness of different models for analyzing alignment between standards and assessment is theoretically and empirically compared based on a number of criteria. The results show that Bloom’s revised taxonomy is the most useful model. The second article investigates the usefulness of Bloom’s revised taxonomy for interpretation of standards in mathematics with two differently composed panels of judges. One panel consisted of teachers and the other panel of assessment experts. The results show that Bloom’s revised taxonomy is useful for interpretation of standards, but that many standards are multi-categorized (placed in more than one category). The results also show higher levels of intra- and inter-judge consistency for assessment experts than for teachers. The third article further investigates the usefulness of Bloom’s revised taxonomy for analyses of alignment between standards and assessment. The results show that Bloom’s revised taxonomy is useful for analyses of both standards and assessments. The fourth article studies whether vague and general standards can explain the large proportion of multi-categorized standards in mathematics. The strategy was to divide a set of standards into smaller substandards and then compare the usefulness and inter-judge consistency for categorization with Bloom’s revised taxonomy for undivided and divided standards. The results show that vague and general standards do not explain the large proportion of multi-categorized standards. Another explanation is related to the nature of mathematics that often intertwines conceptual and procedural knowledge. This was also studied in the article and the results indicate that this is a probable explanation. The fifth article focuses on another aspect of alignment between standards and assessment, namely the alignment between performance standards and cut-scores for a specific assessment. The validity of two standard-setting methods, the Angoff method and the borderline-group method, was investigated. The results show that both methods derived reasonable and trustworthy cut-scores, but also that there are potential problems with these methods.

    In the introductory part of the thesis, the empirical studies are summarized, contextualized and discussed. The discussion relates alignment to validity issues for assessments and relates the obtained empirical results to theoretical assumptions and applied implications. One conclusion of the thesis is that Bloom’s revised taxonomy is useful for analyses of alignment between standards and assessments. Another conclusion is that the two standard setting methods derive reasonable and trustworthy results. It is preferable if an alignment model can be used both for alignment analyses and in ongoing practice for increasing alignment. Bloom’s revised taxonomy has the potential for being such an alignment model. This thesis has found this taxonomy useful for alignment analyses, but its’ usefulness for increasing alignment in ongoing practice has to be investigated.

  • 45.
    Pesquet, Edouard
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Arrhenius Laboratories, Department of Ecology, Environment and Plant Sciences (DEEP), Stockholm University, Sweden.
    The COST action FP1105: a research network to understand wood cell wall structure, biopolymer interaction and composition2016In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 70, no 12, 1103-1104 p.Article in journal (Other academic)
  • 46. Rezania, B.
    et al.
    Severin, Nikolai
    Talyzin, Alexandr V.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Rabe, Juergen P.
    Hydration of bilayered graphene oxide2014In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 14, no 7, 3993-3998 p.Article in journal (Refereed)
    Abstract [en]

    The hydration of graphene oxide (GO) membranes is the key to understand their remarkable selectivity in permeation of water molecules and humidity-dependent gas separation. We investigated the hydration of single GO layers as a function of humidity using scanning force microscopy, and we determined the single interlayer distance from the step height of a single GO layer on top of one or two GO layers. This interlayer distance grows gradually by approximately 1 A upon a relative humidity (RH) increase in the range of 2 to similar to 80% and the immersion into liquid water increases the interlayer distance further by another 3 A. The gradual expansion of the single interlayer distance is in good agreement with the averaged distance measured by X-ray diffraction on multilayered graphite oxides, which is commonly explained with an interstratification model. However, our experimental design excludes effects connected to interstratification. Instead we determine directly if insertion of water into GO occurs strictly by monolayers or the thickness of GO layers changes gradually. We find that hydration with up to 80% RH is a continuous process of incorporation of water molecules into single GO layers, while liquid water inserts as monolayers. The similarity of hydration for our bilayer and previously reported multilayered materials implies GO few and even bilayers to be suitable for selective water transport.

  • 47.
    Salh, Roushdey
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Defect related luminescence in silicon dioxide network: a review2011In: Crystalline Silicon: Properties and Uses / [ed] Sukumar Basu, Rijeka: InTech , 2011, 135-172 p.Chapter in book (Refereed)
  • 48. Sand, K. K.
    et al.
    Pedersen, C. S.
    Sjöberg, Staffan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Nielsen, J. W.
    Makovicky, E.
    Stipp, S. L. S.
    Biomineralization: long-term effectiveness of polysaccharides on the growth and dissolution of calcite2014In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 14, no 11, 5486-5494 p.Article in journal (Refereed)
    Abstract [en]

    Our results demonstrate that in addition to being used for controlling morphology during calcite growth, polysaccharide (PS) that has been designed for biomineralization is also extremely robust, influencing calcite reactions even after millions of years. We investigated calcite (CaCO3) behavior in solutions with very small concentrations of PS that was produced similar to 70 Ma ago by coccolithophorids. We used atomic force microscopy (AFM) and the constant composition method to monitor calcite growth in the presence of this ancient PS. The ancient PS is still very active and has a high affinity for calcite step edges. Adsorption, even at extremely low concentrations (0.5 mu g/mL), results in decreased growth rate and dramatic morphology changes during growth and dissolution. The experimental results are complemented with surface complexation modeling for adsorption of components of polysaccharide from a modern coccolithophorid, Emiliania huxleyi. We generated surface complexation constants for the branch components: malonate: 14.25 +/- 0.17, succinate: 11.91 +/- 0.06, tricarballylate: 14.86 +/- 0.04, and citrate: 15.25 +/- 0.04. The implication is that complex PS could hold promise for smart material engineering and for preventing scaling.

  • 49.
    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.

  • 50.
    Skrypnychuk, Vasyl
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Vertical charge transport in conjugated polymers2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Conjugated polymers are novel organic electronic materials highly important for organic photovoltaic applications. Charge transport is one of the key properties which defines the performance of conjugated polymers in electronic devices.

    This work aims to explore the charge transport anisotropy in thin films of P3HT, one of the most common conjugated polymers. Using X-ray diffraction techniques and charge transport measurements, the relation between vertical charge transport through thin P3HT films and structure of the films was established.

    It was shown that particular orientations of crystalline domains of P3HT, namely face-on and chain-on, are beneficial for vertical charge transport. These orientations provide the efficient pathways for the charges to be transported vertically, either via π-π stacking interaction between the adjacent conjugated chains, or via the conjugated chain backbones. It was also demonstrated that particular orientations of crystallites are favourable for the formation of interconnected percolated pathways providing enhanced vertical charge transport across the film.

    Deposition of P3HT on most commonly used silicon substrates typically results in the formation of mostly edge-on orientation of crystallites which is unfavourable for vertical charge transport. Nanoimprint lithography was demonstrated as a powerful processing method for reorienting the edge-on crystalline domains of P3HT into chain-on (vertical) orientation. It is also shown that thin P3HT films with preferentially face-on orientations of crystallites can be deposited on graphene surface by spin coating.

    Using patterning of thin P3HT films by nanoimprint lithography, unprecedentedly high average vertical mobilities in the range of 3.1-10.6 cm2 V-1 s-1 were achieved in undoped P3HT.

    These results demonstrate that charge transport in thin films of a relatively simple and well-known conjugated polymer P3HT can be significantly improved using optimization of crystallinity,orientation of crystallites, polymer chain orientation and alignment in the films.

12 1 - 50 of 72
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