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  • 1451.
    Wei, Wei
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Oorganisk kemi.
    Berger, Steffen
    Shrestha, Nabeen
    Schmuki, Patrik
    Ideal Hexagonal Order: Formation of Self-Organized Anodic Oxide Nanotubes and Nanopores on a Ti–35Ta Alloy2010Inngår i: Journal of The Electrochemical Society, Vol. 157, nr 12Artikkel i tidsskrift (Fagfellevurdert)
  • 1452.
    Wei, Wei
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Oorganisk kemi.
    Macak, J M
    Schmuki, P
    High aspect ratio ordered nanoporous Ta< sub> 2 O< sub> 5 films by anodization of Ta2008Inngår i: Electrochemistry Communications, Vol. 10, nr 3, s. 428-432Artikkel i tidsskrift (Fagfellevurdert)
  • 1453. Wei, Wei
    et al.
    Macak, Jan M
    Shrestha, Nabeen K
    Schmuki, Patrik
    Thick Self-Ordered Nanoporous Ta2O5 Films with Long-Range Lateral Order2009Inngår i: Journal of The Electrochemical Society, Vol. 156, nr 6, s. K104-K109Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this work we report the anodic formation of highly ordered nanoporous Ta2O5 layers that exhibit a self-ordered alignment of pores uniformly over the anodized surface. These layers are grown by anodization of tantalum in a nonaqueous electrolyte consisting of an optimized glycerol/ethylene glycol mixture with the addition of NH4F . To reach an optimized nanoporous structure, several factors [fluoride concentration and content of supporting electrolyte (NH4)2SO4 ] need to be controlled. Once optimized, the nanopore diameter can be adjusted using the applied voltage in the range of 7–18 nm, and layers with a thickness of more than 10μm can be grown. As a result, a pore aspect ratio of 1000 can be reached.

  • 1454. Wei, Wei
    et al.
    Oltean, Gabriel
    Tai, Cheuk-Wai
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Edström, Kristina
    Björefors, Fredrik
    Nyholm, Leif
    High energy and power density TiO2 nanotube electrodes for 3D Li-ion microbatteries2013Inngår i: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 1, nr 28, s. 8160-8169Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Highly ordered anodic TiO2 nanotube arrays with a tube length of 9 mm are shown to provide areal capacities of 0.24 mA h cm(-2) (i.e. 96 mA h g(-1)) at a charge/discharge current density of 2.5 mA cm(-2) (corresponding to a rate of 5 C) and 0.46 mA h cm(-2) (i.e. 184 mA h g(-1)) at 0.05 mA cm(-2), when used as 3D free-standing anodes in Li-ion microbatteries. The present nanotube electrodes, which could be cycled for 500 cycles with only 6% loss of capacity, exhibited significantly higher energy and power densities, as well as an excellent cycling stability compared to previously reported TiO2-based Li-ion microbattery electrodes. The influence of parameters such as ordering, geometry and crystallinity of the nanotubes on the microbattery performance was investigated. A two-step anodization process followed by annealing of the nanotubes was found to yield the best microbattery performance. It is also demonstrated that the rate capability of the electrode depends mainly on the rate of the structural rearrangements associated with the lithiation/delithiation reaction and that the areal capacity at various charge/discharge rates can be increased by increasing the tube wall thickness or the length of the nanotubes, up to 0.6 mA h cm(-2) for 100 cycles.

  • 1455.
    Weissenrieder, Jonas
    et al.
    KTH, Tidigare Institutioner, Materialvetenskap.
    Leygraf, Christofer
    KTH, Tidigare Institutioner, Materialvetenskap.
    In-situ studies of the initial atmospheric corrosion of iron2002Inngår i: OUTDOOR ATMOSPHERIC CORROSION, 2002, Vol. 1421, s. 127-138Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    A unique experimental setup has been developed with the intent to provide molecular information during initial atmospheric corrosion of the iron surface. Infrared reflection absorption spectroscopy (IRAS) and quartz crystal microbalance (QCM) have been integrated into one surface analytical system. The results show that an aqueous adlayer of constant mass was physisorbed on the surface at a given relative humidity. The aqueous adlayer was found to be thicker when compared to previous studies performed on copper. A linear relationship between mass change and the intensity of the water absorption band at 3400 cm(-1) (IRAS) was found when altering the relative humidity. At high relative humidity a thick aqueous adlayer was formed, whereby an absorbance band at 1100 cm(-1) was observed that disappeared when dry air was introduced. When introducing SO2 and O-3 in the sub-ppm range, the formation of sulfate surface species could be monitored quantitatively with monolayer sensitivity and a significant increase in reaction kinetics could be discerned.

  • 1456.
    Wen, Rui-Tao
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Niklasson, Gunnar A.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Granqvist, Claes-Göran
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Electrochromic Iridium-Containing Nickel Oxide Films with Excellent Electrochemical Cycling Performance2016Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 163, nr 2, s. E7-E13Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Electrochromic Ni oxide thin films attract much interest because of their large potential for applications as optically active layers in energy-saving and comfort enhancing smart windows in buildings. However Ni oxide, typically being the anodic counter electrode in a W-oxide-based device, may suffer severe charge capacity degradation upon extended electrochemical cycling. It is therefore important to identify improved Ni-oxide-based thin films for electrochromics. Here we describe a new class of such films wherein an addition of a small amount of Ir to Ni oxide is found to provide strongly improved electrochemical cycling durability. Best properties were achieved with Ir/(Ir + Ni) = 7.6%, and such films displayed charge capacity and optical modulation that, remarkably, were still increasing after 10,000 cycles.

  • 1457.
    Wen, Xiaogang
    et al.
    Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China .
    Xie, Yu-Tao
    Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
    Mak, Wing Cheung
    Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
    Cheung, Kwan Yee
    Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
    Li, Xiao-Yuan
    Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
    Renneberg, Reinhard
    Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
    Shihe, Yang
    Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
    Dendritic nanostructures of silver: Facile synthesis, structural characterizations, and sensing applications2006Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 22, nr 10, s. 4836-4842Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Silver nanodendrites are synthesized by a simple surfactant-free method using a suspension of zinc microparticles as a heterogeneous reducing agent. Structural characterizations suggest the preferential growth along  <100>  and  <111>  directions by oriented attachment of silver nanocrystals in the diffusion limit, leading to the formation of silver nanodendrites 20−30 nm in stem and branch diameter and 5−50 μm in length. Surface-enhanced Raman scattering studies show that the silver nanodentrites give an intensive and enhanced Raman scattering when pyridine was used as a probing molecule. We have also demonstrated that the silver nanodendrites increase the sensitivity of an electrochemical glucose biosensor by as much as 1−2 orders of magnitude.

     

  • 1458. Westlund, Viktoria
    Effect of the filling and compaction process on insert weight and quality2014Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    In this thesis, the filling and compaction process in Sandvik Coromant’s production of

    inserts has been studied with the goal to determine which factors causes weight and

    shape variations. The study is based on previous research [1-4] in which the powder

    flow and the packing of the powder is studied with a model die shoe filling system.

    This study is more complex, taking also the compaction into account and a Fette

    MP120 press is used instead of a model.

    The factors which were confirmed to affect the final shape of the inserts were the

    fill-shoe velocity, the geometry of the die, the morphology of the powder and if a

    shaking motion was added to the fill-shoe or not. It was proven that to minimize the

    shape irregularities, really high fill-shoe velocities should be avoided. Since different

    powders have different flow rates, the fill-shoe velocity should be changed depending

    on which powder is being used. The fill-shoe velocity should also be lower for narrow

    die geometries since they are harder to fill. Finally, it is good to add a shaking motion

    to the fill-shoe because it increases the fill density.

    A different type of powder filling was tested called suction filling. This method turned

    out to take longer, give the same weight variations between the inserts as the regular

    filling method and is only able to be used for less than half of the inserts produced at

    Sandvik because it can only fill negative geometries.

  • 1459.
    Wetterskog, Erik
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Building crystals out of crystals: Synthesis, structure and magnetic properties of iron oxide nanoparticles and self-assembled mesocrystals2013Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This thesis is focused on the fabrication and characterization of self-assembled arrays of magnetic iron oxide (Fe3O4, γ-Fe2O3 and Fe1-xO) nanoparticles. The synthesis of spherical and cubic iron oxide nanocrystals, with sizes between 5 and 30 nm and narrow size distributions, is demonstrated, along with a rigorous morphological characterization of the cubic nanoparticles. The transformation of core|shell Fe1-xO|Fe3-δO4 particles into single-phase Fe3-δO4 particles is studied in detail. It is found that anti-phase boundaries in the particles result in the emergence of anomalous magnetic properties i.e. exchange bias, and a reduced saturation magnetization compared to that of bulk Fe3O4. Cubic nanocrystals are assembled into arrays possessing an exceptionally high degree of translational ordering and a high degree of crystallographic alignment. A combination of electron microscopy and small-angle X-ray scattering is used in the characterization of the 3D nanostructures. The directional (anisotropic) interactions in the 3D structures are modeled in an attempt to find a link between the nanocrystal morphology and the corresponding mesostructure. Here, the cohesive van der Waals energy is estimated for a system of nanocubes with a variable truncation. The assembly of nanocubes in magnetic fields of various strengths is systematically investigated. A perturbed mesocrystal growth habit is observed at intermediate fields, whereas at high field strengths, the assembly is dominated by ferrohydrodynamic instabilities. Last, magnetometry is used to study the collective magnetic properties of self-assembled nanocrystals. The magnetic susceptibility in a weak magnetic field is studied as a function of film thickness and particle size. An increase in the tendency to form ferromagnetic couplings  with decreasing film thickness can be established. This 2D to 3D crossover of the magnetic properties of the nanoparticle arrays can be related to a change in the magnetic vortex states.

  • 1460. Wetterskog, Erik
    et al.
    Agthe, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Mayence, Arnaud
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Grins, Jekabs
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Wang, Dong
    Rana, Subhasis
    Ahniyaz, Anwar
    Salazar-Alvarez, German
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Bergström, Lennart
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Precise control over shape and size of iron oxide nanocrystals suitable for assembly into ordered particle arrays2014Inngår i: Science and Technology of Advanced Materials, ISSN 1468-6996, E-ISSN 1878-5514, Vol. 15, nr 5, artikkel-id 055010Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Here we demonstrate how monodisperse iron oxide nanocubes and nanospheres with average sizes between 5 and 27 nm can be synthesized by thermal decomposition. The relative importance of the purity of the reactants, the ratio of oleic acid and sodium oleate, the maximum temperature, and the rate of temperature increase, on robust and reproducible size and shape-selective iron oxide nanoparticle synthesis are identified and discussed. The synthesis conditions that generate highly monodisperse iron oxide nanocubes suitable for producing large ordered arrays, or mesocrystals are described in detail.

  • 1461.
    Wetterskog, Erik
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Jonasson, Christian
    RISE Acreo, S-40014 Gothenburg, Sweden..
    Smilgies, Detlef-M.
    Cornell Univ, Cornell High Energy Synchrotron Source, Ithaca, NY 14853 USA..
    Schaller, Vincent
    Chalmers Ind Tekn, S-41288 Gothenburg, Sweden..
    Johansson, Christer
    RISE Acreo, S-40014 Gothenburg, Sweden..
    Svedlindh, Peter
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Colossal Anisotropy of the Dynamic Magnetic Susceptibility in Low-Dimensional Nanocube Assemblies2018Inngår i: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 12, nr 2, s. 1403-1412Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    One of the ultimate goals of nanocrystal self-assembly is to transform nanoscale building blocks into a material that displays enhanced properties relative to the sum of its parts. Herein, we demonstrate that 1D needle shaped assemblies composed of Fe3-delta O4 nanocubes display a significant augmentation of the magnetic susceptibility and dissipation as compared to OD and 2D systems. The performance of the nanocube needles is highlighted by a colossal anisotropy factor defined as the ratio of the parallel to the perpendicular magnetization components. We show that the origin of this effect cannot be ascribed to shape anisotropy in its classical sense; as such, it has no analogy in bulk magnetic materials. The temperature-dependent anisotropy factors of the in- and out-of-phase components of the magnetization have an extremely strong particle size dependence and reach values of 80 and 2500, respectively, for the largest nanocubes in this study. Aided by simulations, we ascribe the anisotropy of the magnetic susceptibility, and its strong particle-size dependence to a synergistic coupling between the dipolar interaction field and a net anisotropy field resulting from a partial texture in the 1D nanocube needles.

  • 1462.
    Wetterskog, Erik
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Tai, Cheuk-Wai
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Grins, Jekabs
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Bergström, Lennart
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Salazar-Alvarez, German
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Anomalous Magnetic Properties of Nanoparticles Arising from Defect Structures: Topotaxial Oxidation of Fe1-xO|Fe3-δO4 Core|Shell Nanocubes to Single-Phase Particles2013Inngår i: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 7, nr 8, s. 7132-7144Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Here we demonstrate that the anomalous magnetic properties of iron oxide nanoparticles are correlated with defects in their interior. We studied the evolution of microstructure and magnetic properties of biphasic core|shell Fe1–xO|Fe3−δO4 nanoparticles synthesized by thermal decomposition during their topotaxial oxidation to single-phase nanoparticles. Geometric phase analysis of high-resolution electron microscopy images reveals a large interfacial strain at the core|shell interface and the development of antiphase boundaries. Dark-field transmission electron microscopy and powder X-ray diffraction concur that, as the oxidation proceeds, the interfacial strain is released as the Fe1–xO core is removed but that the antiphase boundaries remain. The antiphase boundaries result in anomalous magnetic behavior, that is, a reduced saturation magnetization and exchange bias effects in single-phase nanoparticles. Our results indicate that internal defects play an important role in dictating the magnetic properties of iron oxide nanoparticles.

  • 1463.
    Wetterskog, Erik
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Tai, Cheuk-Wai
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för oorganisk kemi och strukturkemi.
    Grins, Jekabs
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för oorganisk kemi och strukturkemi.
    Salazar-Alvarez, German
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Bergström, Lennart
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Strain relief during stepwise oxidation of monodisperse Fe1-xO/Fe3-xO4 nanocubes. Influence on their structure and magnetic properties.2011Konferansepaper (Annet vitenskapelig)
  • 1464. Whittle, Thomas A.
    et al.
    Brant, William
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Withers, Ray L.
    Liu, Yun
    Howard, Christopher J.
    Schmid, Siegbert
    Novel insight into the structure and properties of lead-free dielectric Sr3TiNb4O152018Inngår i: Journal of Materials Chemistry C, ISSN 2050-7526, E-ISSN 2050-7534, Vol. 6, nr 33, s. 8890-8896Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Sr3TiNb4O15 has been synthesised and its structure and dielectric properties characterised. In contrast to previously reported results the compound has been found to form with Pna21 symmetry and unit cell dimensions a = 12.3631(19), b = 12.4027(19) and c = 7.7601(12) Å. Variable temperature studies show a phase transition from orthorhombic to tetragonal symmetry at approximately 625 K, much higher than previously reported. Temperature-dependent dielectric measurements have also been performed and these correlate very well with the observed phase transition temperature.

  • 1465.
    Wicklein, Bernd
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi. KTH, Wallenberg Wood Sci Ctr, SE-10044 Stockholm.
    Salazar-Alvarez, German
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi. KTH, Wallenberg Wood Sci Ctr, SE-10044 Stockholm.
    Functional hybrids based on biogenic nanofibrils and inorganic nanomaterials2013Inngår i: JOURNAL OF MATERIALS CHEMISTRY A, ISSN 2050-7488, Vol. 1, nr 18, s. 5469-5478Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This feature article reviews some of the recent work on the fabrication of functional hybrids based on biogenic nanofibers and inorganic nanomaterials with an emphasis on their functional properties and suggested potential applications. We also discuss some of the work oriented towards the formation of ordered materials in the pursuit of achieving a hierarchical construction. Besides the academic interest in biogenic nanomaterials, it is anticipated that the use of natural, abundant nanomaterials, e.g., cellulose, chitin, collagen, and silk, could provide affordable functional nanomaterials in developing countries.

  • 1466. Wieland, D. C. F.
    et al.
    Garamus, V. M.
    Zander, T.
    Krywka, C.
    Wang, M.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. SP Tech Res Inst Sweden, Sweden.
    Dedinaite, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. SP Tech Res Inst Sweden, Sweden.
    Claesson, Per M.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. SP Tech Res Inst Sweden, Sweden.
    Willumeit-Roemer, R.
    Studying solutions at high shear rates: a dedicated microfluidics setup2016Inngår i: Journal of Synchrotron Radiation, ISSN 0909-0495, E-ISSN 1600-5775, Vol. 23, s. 480-486Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The development of a dedicated small-angle X-ray scattering setup for the investigation of complex fluids at different controlled shear conditions is reported. The setup utilizes a microfluidics chip with a narrowing channel. As a consequence, a shear gradient is generated within the channel and the effect of shear rate on structure and interactions is mapped spatially. In a first experiment small-angle X-ray scattering is utilized to investigate highly concentrated protein solutions up to a shear rate of 300000 s(-1). These data demonstrate that equilibrium clusters of lysozyme are destabilized at high shear rates.

  • 1467.
    Willhammar, Tom
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Yun, Yifeng
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Zou, Xiaodong
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Structural Determination of Ordered Porous Solids by Electron Crystallography2014Inngår i: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 24, nr 2 (SI), s. 182-199Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    Knowing the structure of porous materials is essential for understanding their properties and exploiting them for applications. Electron crystallography has two main advantages compared to X-ray diffraction for structure determination. Crystals too small or too complicated to be studied by X-ray diffraction can be studied by electron crystallography. The crystallographic structure factor phase information, which is lost in X-ray diffraction, can be obtained from high-resolution transmission electron microscopy (HRTEM) images. Here, different electron microscopic techniques and their applications for structure determination of porous materials are reviewed. The recently developed automated diffraction tomography (ADT), the rotation electron diffraction (RED), and the through-focus structure projection reconstruction (QFcous) methods make the structure determination by electron crystallography more feasible for non-TEM experts and as efficient as that by X-ray diffraction. How the various electron crystallographic methods are chosen are demonstrated and these methods used for solving different structural problems in porous materials. The benefits of combining electron crystallography and X-ray diffraction for studying complex zeolite structures are also shown. A large number of examples are given to demonstrate the use of various electron crystallographic techniques for structure determination of zeolites, metal-organic frameworks and ordered mesoporous materials. These electron crystallographic methods are general and can also be used for structural studies of other functional materials.

  • 1468.
    Wilson, Peter M.
    et al.
    University of Nebraska, USA.
    Zobel, Adam
    University of Nebraska, USA.
    Zaitouna, Anita J.
    University of Nebraska, USA.
    Lipatov, Alexey
    University of Nebraska, USA.
    Schubert, Eva
    University of Nebraska, USA.
    Hofmann, Tino
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten. University of Nebraska, USA.
    Schubert, Mathias
    University of Nebraska, USA.
    Lai, Rebecca
    University of Nebraska, USA.
    Sinitskii, Alexander
    University of Nebraska, USA; National University of Science and Technology MISIS, Russia.
    Solution-stable anisotropic carbon nanotube/graphene hybrids based on slanted columnar thin films for chemical sensing2016Inngår i: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 6, nr 68, s. 63235-63240Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Slanted columnar thin films (SCTFs) are promising anisotropic nano-structures for applications in optical sensing and chemical separation. However, the wide use of SCTFs is significantly limited by their poor mechanical properties and structural stability, especially in liquid media. In this work, we demonstrate the fabrication of solution-stable carbon nanotube (CNT)/graphene hybrid structures based on cobalt SCTFs. The CNT/graphene hybrid structures were synthesized through the use of a titanium underlayer for Co slanted nanopillars as a chemical vapor deposition catalyst, which allows simultaneous growth of CNTs at the Co/Ti interface and three-dimensional graphene over the surface of cobalt. Importantly, the CNT/graphene hybrid structures retain the anisotropy of the parent Co SCTFs and thus remain suitable for optical sensing. Graphene/CNT modification of Co SCTFs not only improves their stability in solutions but also enables their functionalization with pyrene-modified DNA probes, which can be monitored in real time by in situ ellipsometry measurements. In turn, the solution-stable DNA-modified SCTFs may find a wide range of applications in biosensing. The described synthetic approach that allows simultaneous growth of CNTs and graphene by engineering Co/Ti interfaces may also be applied to the fabrication of other kinds of complex CNT/graphene hybrid materials.

  • 1469.
    Wing Cheung, Mak
    et al.
    National University of Singapore.
    Cheung, Kwan Yee
    National University of Singapore.
    Trau, Dieter
    National University of Singapore.
    Influence of Different Polyelectrolytes on Layer-by-Layer Microcapsule Properties: Encapsulation Efficiency and Colloidal and Temperature Stability2008Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 20, nr 17, s. 5475-5484Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The fabrication of colloidal and temperature stable microcapsules for encapsulation of biomolecules based on matrix-assisted layer-by-layer (LbL) encapsulation by polyelectrolyte self-assembly has been demonstrated. In brief, the process is based on the emulsification of a hydrogel in warm oil for microdroplet formation. The hydrogel acts as a matrix for the later encapsulation process and can be loaded with biomolecules. After microdroplets of, for example, protein loaded hydrogel are formed by emulsification, cooling leads to solidification of the droplets to form microbeads, followed by encapsulation of the hydrogel microbeads with polyelectrolyte multilayers through an LbL self-assembly process to form polymeric capsules. Colloidal stability, encapsulation efficiency, and temperature stability of the LbL hydrogel microcapsules composed from different polyelectrolytes with various ionic strengths and charge densities have been studied. Microcapsules fabricated with strong polyelectrolytes showed better colloidal stability, while microcapsules fabricated with weak polyelectrolytes showed better encapsulation efficiency and temperature stability. After temperature treatment, microcapsules fabricated with different polyelectrolytes exhibited different morphological changes from complete rupturing over broken microcapsules with deformed hollow shells to intact microcapsules. Among all the studied polyelectrolyte pairs, the PAH/PSS polyelectrolyte system was found to be the best material to fabricate microcapsules with good colloidal and temperature stability and high encapsulation efficiency. Microcapsules with PSS as the outermost layer remained similar in size after temperature treatment, while microcapsules with PAH as the outermost layer shrunk by 76% in capsule volume. The present study provides a detailed overview on properties and design of LbL microcapsules as a function of polyelectrolyte materials and layer number. As a result of the versatility of loading LbL hydrogel microcapsules with various biomolecules or mixtures, potential applications are in the fields of diagnostics, drug delivery, and life sciences.

  • 1470.
    Wofford, Joseph M.
    et al.
    Paul Drude Institute Festkorperelektron, Germany.
    Nakhaie, Siamak
    Paul Drude Institute Festkorperelektron, Germany.
    Krause, Thilo
    Paul Drude Institute Festkorperelektron, Germany.
    Liu, Xianjie
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ytors Fysik och Kemi. Linköpings universitet, Tekniska fakulteten.
    Ramsteiner, Manfred
    Paul Drude Institute Festkorperelektron, Germany.
    Hanke, Michael
    Paul Drude Institute Festkorperelektron, Germany.
    Riechert, Henning
    Paul Drude Institute Festkorperelektron, Germany.
    Lopes, J. Marcelo J.
    Paul Drude Institute Festkorperelektron, Germany.
    A hybrid MBE-based growth method for large-area synthesis of stacked hexagonal boron nitride/graphene heterostructures2017Inngår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, artikkel-id 43644Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Van der Waals heterostructures combining hexagonal boron nitride (h-BN) and graphene offer many potential advantages, but remain difficult to produce as continuous films over large areas. In particular, the growth of h-BN on graphene has proven to be challenging due to the inertness of the graphene surface. Here we exploit a scalable molecular beam epitaxy based method to allow both the h-BN and graphene to form in a stacked heterostructure in the favorable growth environment provided by a Ni(111) substrate. This involves first saturating a Ni film on MgO(111) with C, growing h-BN on the exposed metal surface, and precipitating the C back to the h-BN/Ni interface to form graphene. The resulting laterally continuous heterostructure is composed of a top layer of few-layer thick h-BN on an intermediate few-layer thick graphene, lying on top of Ni/MgO(111). Examinations by synchrotronbased grazing incidence diffraction, X-ray photoemission spectroscopy, and UV-Raman spectroscopy reveal that while the h-BN is relaxed, the lattice constant of graphene is significantly reduced, likely due to nitrogen doping. These results illustrate a different pathway for the production of h-BN/graphene heterostructures, and open a new perspective for the large-area preparation of heterosystems combining graphene and other 2D or 3D materials.

  • 1471.
    Wolf, Matthew J.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Kullgren, Jolla
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Broqvist, Peter
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Hermansson, Kersti
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Interaction of Oxygen and Water Molecules with Flourine Impurities at CeO2(111) surface2016Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690Artikkel i tidsskrift (Fagfellevurdert)
  • 1472.
    Wolf, Matthew J.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Kullgren, Jolla
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Hermansson, Kersti
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Comment on "Clustering og Oxygen Vacancies at CeO2(111): Crytical Role of Hydroxyls"2016Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114Artikkel i tidsskrift (Fagfellevurdert)
  • 1473.
    Wolf, Thomas J. A.
    et al.
    Stanford PULSE Institute, SLAC National Accelerator Laboratory.
    Holzmeier, Fabian
    Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin; Institut für Physikalische & Theoretische Chemie, Universität Würzburg.
    Wagner, Isabella
    Institut für Physikalische & Theoretische Chemie, Universität Würzburg.
    Berrah, Nora
    Department of Physics, University of Connecticut.
    Bostedt, Christoph
    Linac Coherent Light Source, SLAC National Accelerator Laboratory; Argonne National Laboratory; Department of Physics and Astronomy, Northwestern University.
    Bozek, John
    Synchrotron SOLEIL, L’Orme des Merisiers; Linac Coherent Light Source, SLAC National Accelerator Laboratory.
    Bucksbaum, Phil
    Stanford PULSE Institute, SLAC National Accelerator Lab.oratory; Departments of Physics and Applied Physics, Stanford University.
    Coffee, Ryan
    Linac Coherent Light Source, SLAC National Accelerator Laboratory.
    Cryan, James
    Stanford PULSE Institute, SLAC National Accelerator Laboratory.
    Farrell, Joe
    Stanford PULSE Institute, SLAC National Accelerator Laboratory.
    Feifel, Raimund
    Department of Physics, University of Gothenburg.
    Martinez, Todd J.
    Stanford PULSE Institute, SLAC National Accelerator Laboratory; Departments of Physics and Applied Physics, Stanford University.
    McFarland, Brian
    Stanford PULSE Institute, SLAC National Accelerator Laboratory.
    Mucke, Melanie
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Molekyl- och kondenserade materiens fysik.
    Nandi, Saikat
    Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin; Department of Physics, Lund University.
    Tarantelli, Francesco
    Department of Chemistry, Biology and Biotechnology, University of Perugia.
    Fischer, Ingo
    Institut für Physikalische & Theoretische Chemie, Universität Würzburg.
    Guhr, Markus
    Stanford PULSE Institute, SLAC National Accelerator Laboratory; Institut für Physik und Astronomie, Universität Potsdam.
    Observing Femtosecond Fragmentation Using Ultrafast X-ray-Induced Auger Spectra2017Inngår i: Applied Sciences, E-ISSN 2076-3417, Vol. 7, nr 7, artikkel-id 681Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Molecules often fragment after photoionization in the gas phase. Usually, this process can only be investigated spectroscopically as long as there exists electron correlation between the photofragments. Important parameters, like their kinetic energy after separation, cannot be investigated. We are reporting on a femtosecond time-resolved Auger electron spectroscopy study concerning the photofragmentation dynamics of thymine. We observe the appearance of clearly distinguishable signatures from thymines neutral photofragment isocyanic acid. Furthermore, we observe a time-dependent shift of its spectrum, which we can attribute to the influence of the charged fragment on the Auger electron. This allows us to map our time-dependent dataset onto the fragmentation coordinate. The time dependence of the shift supports efficient transformation of the excess energy gained from photoionization into kinetic energy of the fragments. Our method is broadly applicable to the investigation of photofragmentation processes.

  • 1474. Wu, Ming-Chung
    et al.
    Liao, Hseuh-Chung
    Cho, Yu-Cheng
    Toth, Geza
    Chen, Yang-Fang
    Su, Wei-Fang
    Kordás, Krisztián
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Photo-Kelvin probe force microscopy for photocatalytic performance characterization of single filament of TiO2 nanofiber photocatalysts2013Inngår i: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 1, nr 18, s. 5715-5720Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This is an in-depth study on the photocatalytic performance characterization for single filament of TiO2 nanofiber photocatalysts by the novel photo-Kelvin probe force microscopy technique (photo-KPFM) and first principles calculations. Three kinds of TiO2 nanofibers: anatase TiO2 nanofibers (anatase TiO2 NFs), nitrogen doped TiO2 nanofibers (N-TiO2 NFs), and nitrogen doped TiO2 nanofibers decorated with platinum nanoparticles (N-TiO2-Pt NFs) were investigated. The N-TiO2-Pt NFs exhibit the largest negative photo surface potential shift (-182 mV) as compared to anatase TiO2 NFs (-29 mV). The first-principles calculations based on density functional theory (CASTEP simulation software) indicate that the significant photo surface potential shift obtained by adding nitrogen and platinum into TiO2 NFs is induced by two mechanisms: (1) enhancement in absorbance to increase exciton generation and (2) decreased charge recombination to increase surface charge. These changes in the photo surface potential of various TiO2 nanofibers are closely correlated with their photocatalytic activity. Thus, this novel photo-KPFM provides a useful technique to easily monitor the photocatalytic capability of materials in the development of high performance photocatalysts.

  • 1475.
    Wu, Xujun
    et al.
    Med Univ Innsbruck, Dept Craniomaxillofacial & Oral Surg, Maximilianstr 10, A-6020 Innsbruck, Austria..
    Bruschi, Michela
    Med Univ Innsbruck, Dept Craniomaxillofacial & Oral Surg, Maximilianstr 10, A-6020 Innsbruck, Austria..
    Waag, Thilo
    Univ Wurzburg, Inst Organ Chem, D-97074 Wurzburg, Germany..
    Schweeberg, Sarah
    Univ Wurzburg, Inst Organ Chem, D-97074 Wurzburg, Germany..
    Tian, Yuan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi.
    Meinhardt, Thomas
    Univ Wurzburg, Inst Organ Chem, D-97074 Wurzburg, Germany..
    Stigler, Robert
    Med Univ Innsbruck, Dept Craniomaxillofacial & Oral Surg, Maximilianstr 10, A-6020 Innsbruck, Austria..
    Larsson, Karin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi.
    Funk, Martin
    DiaCoating GmbH, Weisstr 9, A-6112 Wattens, Austria..
    Steinmueller-Nethl, Doris
    DiaCoating GmbH, Weisstr 9, A-6112 Wattens, Austria..
    Rasse, Michael
    Med Univ Innsbruck, Dept Craniomaxillofacial & Oral Surg, Maximilianstr 10, A-6020 Innsbruck, Austria..
    Krueger, Anke
    Univ Wurzburg, Inst Organ Chem, D-97074 Wurzburg, Germany.;Univ Wurzburg, Wilhelm Conrad Rontgen Res Ctr Complex Mat Syst, D-97074 Wurzburg, Germany..
    Functionalization of bone implants with nanodiamond particles and angiopoietin-1 to improve vascularization and bone regeneration2017Inngår i: Journal of materials chemistry. B, ISSN 2050-750X, E-ISSN 2050-7518, Vol. 5, nr 32, s. 6629-6636Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    One of the major challenges in bone tissue engineering is adequate vascularization within bone substituents for nutrients and oxygen supply. In this study, the production and results of a new, highly functional bone construct consisting of a commercial three-dimensional beta-tricalcium phosphate scaffold (beta-TCP, ChronOS (R)) and hydrophilic, functionalized nanodiamond (ND) particles are reported. A 30-fold increase in the active surface area of the ChronOS + ND scaffold was achieved after modification with ND. In addition, immobilization of angiopoietin-1 (Ang-1) via physisorption within the beta-TCP + ND scaffold retained the bioactivity of the growth factor. Homogeneous distribution of the ND and Ang-1 within the core of the three-dimensional scaffold was confirmed using ND covalently labelled with Oregon Green. The biological responses of the beta-TCP + ND scaffold with and without Ang-1 were studied in a sheep calvaria critical size defect model showing that the beta-TCP + ND scaffold improved the blood vessel ingrowth and the beta-TCP + ND + ND + Ang-1 scaffold further promoted vascularization and new bone formation. The results demonstrate that the modification of scaffolds with tailored diamond nanoparticles is a valuable method for improving the characteristics of bone implants and enables new approaches in bone tissue engineering.

  • 1476.
    Wu, Yuan
    et al.
    Shanghai Univ, Res Ctr Nanosci & Nanotechnol, Shanghai 200444, Peoples R China.
    Chen, Guorong
    Shanghai Univ, Res Ctr Nanosci & Nanotechnol, Shanghai 200444, Peoples R China.
    Wang, Zhuyi
    Shanghai Univ, Res Ctr Nanosci & Nanotechnol, Shanghai 200444, Peoples R China.
    Zhao, Yin
    Shanghai Univ, Res Ctr Nanosci & Nanotechnol, Shanghai 200444, Peoples R China.
    Shi, Liyi
    Shanghai Univ, Res Ctr Nanosci & Nanotechnol, Shanghai 200444, Peoples R China.
    Zhu, Jie-Fang
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Zhang, Meihong
    Shanghai Univ, Res Ctr Nanosci & Nanotechnol, Shanghai 200444, Peoples R China.
    Jia, Rongrong
    Shanghai Univ, Res Ctr Nanosci & Nanotechnol, Shanghai 200444, Peoples R China.
    Yuan, Shuai
    Shanghai Univ, Res Ctr Nanosci & Nanotechnol, Shanghai 200444, Peoples R China.
    In situ constructed Ag/C conductive network enhancing the C-rate performance of Si based anode2018Inngår i: Journal of Energy Storage, E-ISSN 2352-152X, Vol. 17, s. 102-108Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Poor intrinsic electrical conductivity as well as considerable volume change during lithium alloying/dealloying process has been a critical defect for high theoretical capacity silicon-based anodes. In our work, we demonstrate the synthesis design of multiscale recombined dendritic Si/Ag/C anode for high energy density LIBs via compositing bulky silicon with uniformly distributed Ag NPs, followed by a carbon source PDA (polydopamine) coating step. Here Ag NPs are generated by an in situ redox reaction between Ag+ and PDA, no need for additional reducing agents. According to the characterization analysis, the robust porous Si/Ag/C structure can provide channels for fast Li+ diffusion and electron conduction, promoting the formation of a thinner and more stable SEI film. As a result, the Si/Ag/C composite anode still yields a relatively high residual capacity of 1422.1 mAh g (1) after 100 cycles at 0.2 A g (1). In addition, it remains 633.1 mAh g (1) after 500 cycles at a high current density of 8 A g (1).

  • 1477. Wu, Zhifang
    et al.
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Ågren, Hans
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Hua, Jianli
    Tian, He
    Pyrimidine-2-carboxylic Acid as an Electron-Accepting and Anchoring Group for Dye-Sensitized Solar Cells2015Inngår i: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 7, nr 48, s. 26355-26359Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report a new dye (INPA) adopting pyrimidine-2-carboxylic acid as an electron-accepting and anchoring group to be used in dye-sensitized solar cells. IR spectral analysis indicates that the anchoring group may form two coordination bonds with TiO2 and so facilitate the interaction between the anchoring group and TiO2. The INPA-based cell exhibits an overall conversion efficiency of 5.45%, which is considerably higher than that obtained with cyanoacrylic acid commonly used as the electron acceptor.

  • 1478.
    Wåhlander, Martin
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Ytbehandlingsteknik.
    Nilsson, Fritjof
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Andersson, Richard L.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Cobo Sanchez, Carmen
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Ytbehandlingsteknik.
    Taylor, Nathaniel
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Carlmark, Anna
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Ytbehandlingsteknik.
    Hillborg, Henrik
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material. ABB AB.
    Malmström, Eva
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Ytbehandlingsteknik.
    Tailoring Dielectric Properties using Designed Polymer-Grafted ZnO Nanoparticles in Silicone Rubber2017Inngår i: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 5, s. 14241-14258, artikkel-id C6TA11237DArtikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Polymer grafts were used to tailor the interphases between ZnO nanoparticles (NPs) and silicone matrices. The final electrical properties of the nanocomposites were tuned by the grafted interphases, by controlling the inter-particle distance and the NP-morphology. The nanocomposites can be used in electrical applications where control of the resistivity is desired. Hansen's solubility parameters were used to select a semi-compatible polymer for grafting to obtain anisotropic NP morphologies in silicone, and the grafted NPs self-assembled into various morphologies inside the silicone matrices. The morphologies in the semi-compatible nanocomposites could be tuned by steering the graft length of poly(n-butyl methacrylate) via entropic matrix-graft wetting using surface-initiated atom-transfer radical polymerization. Image analysis models were developed to calculate the radius of primary NPs, the fraction of aggregates, the dispersion, and the face-to-face distance of NPs. The dielectric properties of the nanocomposites were related to the morphology and the face-to-face distance of the NPs. The dielectric losses, above 100 Hz, for nanocomposites with grafted NPs were approximately one decade lower than those of pristine NPs. The isotropic nanocomposites increased the resistivity up to 100 times compared to that of neat silicone rubber, due to the trapping of charge carriers by the interphase of dispersed NPs and nanoclusters. On the other hand, the resistivity of anisotropic nanocomposites decreased 10–100 times when the inter-particle distance in continuous agglomerates was close to the hopping distance of charge carriers. The electrical breakdown strength increased for compatible isotropic nanocomposites, and the temperature dependence of the resistivity and the activation energy were ∼50% lower in the nanocomposites with grafted NPs. These flexible dielectric nanocomposites are promising candidates for low-loss high-voltage transmission cable accessories, mobile electronic devices, wearables and sensors.

  • 1479.
    Xia, Chen
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi. Hubei Collaborative Innovation Center for Advanced Materials, Faculty of Physics and Electronic Technology, Hubei University, Wuhan, Hubei, China.
    Wang, Baoyuan
    Hubei Collaborative Innovation Center for Advanced Materials, Faculty of Physics and Electronic Technology, Hubei University, Wuhan, Hubei, China.
    Ma, Y.
    Cai, Y.
    Afzal, Muhammad
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik.
    Liu, Y.
    He, Y.
    Zhang, W.
    Dong, W.
    Li, J.
    Zhu, Bin
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi. Hubei Collaborative Innovation Center for Advanced Materials, Faculty of Physics and Electronic Technology, Hubei University, Wuhan, Hubei, China.
    Industrial-grade rare-earth and perovskite oxide for high-performance electrolyte layer-free fuel cell2016Inngår i: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 307, s. 270-279Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the present work, we report a composite of industrial-grade material LaCePr-oxide (LCP) and perovskite La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) for advanced electrolyte layer-free fuel cells (EFFCs). The microstructure, morphology, and electrical properties of the LCP, LSCF, and LCP-LSCF composite were investigated and characterized by XRD, SEM, EDS, TEM, and EIS. Various ratios of LCP to LSCF in the composite were modulated to achieve balanced ionic and electronic conductivities. Fuel cell with an optimum ratio of 60 wt% LCP to 40 wt% LSCF reached the highest open circuit voltage (OCV) at 1.01 V and a maximum power density of 745 mW cm-2 at 575°C, also displaying a good performance stability. The high performance is attributed to the interfacial mechanisms and electrode catalytic effects. The findings from the present study promote industrial-grade rare-earth oxide as a promising new material for innovative low temperature solid oxide fuel cell (LTSOFC) technology.

  • 1480.
    Xia, Senlin
    et al.
    Tech Univ Munich, Lehrstuhl Funkt Mat, Phys Dept, James Franck Str 1, D-85748 Garching, Germany..
    Song, Lin
    Tech Univ Munich, Lehrstuhl Funkt Mat, Phys Dept, James Franck Str 1, D-85748 Garching, Germany..
    Koerstgens, Volker
    Tech Univ Munich, Lehrstuhl Funkt Mat, Phys Dept, James Franck Str 1, D-85748 Garching, Germany..
    Opel, Matthias
    Bayerische Akad Wissensch, Walther Meissner Inst, Walther Meissner Str 8, D-85748 Garching, Germany..
    Schwartzkopf, Matthias
    Deutsch Elekt Synchrotron DESY, Notkestr 85, D-22603 Hamburg, Germany..
    Roth, Stephan V.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. Deutsch Elekt Synchrotron DESY, Notkestr 85, D-22603 Hamburg, Germany.
    Mueller-Buschbaum, Peter
    Tech Univ Munich, Lehrstuhl Funkt Mat, Phys Dept, James Franck Str 1, D-85748 Garching, Germany..
    Magnetic nanoparticle-containing soft-hard diblock copolymer films with high order2018Inngår i: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 10, nr 25, s. 11930-11941Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    For sensor applications, superparamagnetic anisotropy is an indispensable property, which is typically achieved by employing an external field to guide the arrangement of magnetic nanoparticles (NPs). In the present investigation, the diblock copolymer polystyrene-block-poly(N-isopropylacrylamide) (PS-b-PNIPAM) is printed as a template to localize magnetic iron oxide NPs without any external field. Via microphase separation, cylindrical nanostructures of PS in a PNIPAM matrix are obtained, aligned perpendicular to the substrate. Since the magnetite NPs (Fe3O4) are functionalized with hydrophobic organic chains showing affinity to the PS blocks, they can selectively aggregate inside the PS cylinders. Moreover, solvent vapor annealing allows the achievement of nanostructures inside the hybrid system with a very high order, even at a high NP loading. Therefore, NPs can accumulate within PS domains to form perpendicularly aligned aggregates with high periodicity. The magnetic properties of the hybrid films are determined at various temperatures in two orthogonal directions (with PS cylinders vertical and parallel to the applied magnetic field). All hybrid films show superparamagnetism and a remarkable magnetic anisotropy is achieved at certain NP concentrations. This investigation shows a facile route to prepare superparamagnetic films with magnetic anisotropy and offers a novel possibility to future magnetic sensor fabrication.

  • 1481.
    Xia, Wei
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    Grandfield, Kathryn
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    Schwenke, Almut
    Institute of Materials Science and Technology, Jena, Tyskland.
    Engqvist, Håkan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    Synthesis and release of trace elements from hollow and porous hydroxyapatite spheres2011Inngår i: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 22, nr 30, s. 305610-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    It is known that organic species regulate fabrication of hierarchical biological forms via solution methods. However, in this study, we observed that the presence of inorganic ions plays an important role in the formation and regulation of biological spherical hydroxyapatite formation. We present a mineralization method to prepare ion-doped hydroxyapatite spheres with a hierarchical structure that is free of organic surfactants and biological additives. Porous and hollow strontium-doped hydroxyapatite spheres were synthesized via controlling the concentration of strontium ions in a calcium and phosphate buffer solution. Similarly, fluoride and silicon-doped hydroxyapatite spheres were synthesized. While spherical particle formation was attainable at low and high temperature for Sr-doped hydroxyapatite, it was only possible at high temperature in the F/Si-doped system. The presence of inorganic ions not only plays an important role in the formation and regulation of biological spherical hydroxyapatite, but also could introduce pharmaceutical effects as a result of trace element release. Such ion release results showed a sustained release with pH responsive behavior, and significantly influenced the hydroxyapatite re-precipitation. These ion-doped hydroxyapatite spheres with hollow and porous structure could have promising applications as bone/tooth materials, drug delivery systems, and chromatography supports.

  • 1482.
    Xie, Zhen
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi. Shandong Normal Univ, Sch Phys & Elect, Shandong Prov Key Lab Med Phys & Image Proc Techo, Jinan 250014, Shandong, Peoples R China.
    Duan, Sai
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Tian, Guangjun
    Yanshan Univ, Coll Sci, Qinhuangdao 066004, Peoples R China..
    Wang, Chuan-Kui
    Shandong Normal Univ, Sch Phys & Elect, Shandong Prov Key Lab Med Phys & Image Proc Techo, Jinan 250014, Shandong, Peoples R China..
    Luo, Yi
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi. Univ Sci & Technol China, Hefei Natl Lab Phys Sci Microscale, Hefei 230026, Anhui, Peoples R China..
    Theoretical modeling of tip-enhanced resonance Raman images of switchable azobenzene molecules on Au(111)2018Inngår i: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 10, nr 25, s. 11850-11860Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    With a highly localized plasmonic field, tip-enhanced Raman spectroscopy (TERS) images have reached atomic-scale resolution, providing an optical means to explore the structure of a single molecule. We have applied the recently developed theoretical method to simulate the TERS images of trans and cis azobenzene as well as its derivatives on Au(111). Our theoretical results reveal that when the first excited state is resonantly excited, TERS images from a highly confined plasmonic field can effectively distinguish the isomer configurations of the adsorbates. The decay of the plasmonic field along the surface normal can be further used to distinguish different nonplanar cis configurations. Moreover, subtle characteristics of different molecular configurations can also be identified from the TERS images of other resonant excited states with a super-high confined plasmonic field. These findings serve as good references for future TERS experiments on molecular isomers.

  • 1483.
    Xing, Xing
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Wang, Chuan Fei
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ytors Fysik och Kemi. Linköpings universitet, Tekniska fakulteten.
    Liu, Xianjie
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ytors Fysik och Kemi. Linköpings universitet, Tekniska fakulteten.
    Leiqiang, Qin
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Wang, Ergang
    Chalmers University of Technology, Sweden.
    Zhang, Fengling
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    The trade-off between electrochromic stability and contrast of a thiophene-Quinoxaline copolymer2017Inngår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 253, s. 530-535Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The stability of organic electrochromic devices is a crucial issue for their applications. However, until now the degradation mechanism of electrochromic materials are still not fully understood especially for electrochromic conjugated polymers (ECPs). To improve device stability, intensive investigation on the degradation mechanism of ECPs is urgently needed. Here we report our study on the electrochromic degradation in a thiophene-quinoxaline copolymer: poly [2,3-bis-(3-octyloxyphenyl) quinoxaline-5,8diyl- alt-thiophene-2,5-diyl] (TQ1). The results of X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectra (UPS) and UV-vis transmission spectra reveal that there are three main factors during the electrochromic degradation of TQ1. The first one is anion (ClO4-) irreversibly deep trapped, while the second is peroxidation of the thiophene group in TQ1. Both factors reduce the conductivity and electrochromism of TQ1. The third is structural relaxation resulting lager conjugated system of TQ1 molecules in film, which is gradually developed during 400 cycling of CV at a narrow potential range (01 V). When a potential range 0-0.7 V is applied, all three factors are prohibited, no electrochromism degradation is observed anymore, although the contrast becomes smaller. Our investigation systematically discloses the degradation mechanism during the electrochemistry processing of a ECP (TQ1), demonstrating the significance of trade-off between the electrochromic stability and contrast of the ECP. (C) 2017 Elsevier Ltd. All rights reserved.

  • 1484.
    Xing, Xing
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Zeng, Qi
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ytors Fysik och Kemi. Linköpings universitet, Tekniska fakulteten.
    Vagin, Mikhail
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Fahlman, Mats
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ytors Fysik och Kemi. Linköpings universitet, Tekniska fakulteten.
    Zhang, Fengling
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Fast switching polymeric electrochromics with facile processed water dispersed nanoparticles2018Inngår i: Nano Energy, ISSN 2211-2855, E-ISSN 2211-3282, Vol. 47, s. 123-129Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this work, water dispersed electrochromic polymer nanoparticles (WDENs) prepared with miniemulsion process are introduced into electrochromic polymer (ECP) electrode for the first time. The poly [2, 3-bis-(3-octyloxyphenyl) quinoxaline-5,8-diyl-alt-thiophene-2,5-diyl]) nanoparticle (NP) electrode shows much faster switching speed than the compacted electrode (e.g. 2.10 s vs. 24.15 s for coloring, 8.65 s vs. 25.95 s for bleaching @ 0.4 V; 1.30 s vs. 9.20 s coloring and 1.7 s vs. 2.90 s for bleaching @ 1.0 V). Moreover, the potentiality of WDENs for universal ECPs is demonstrated. The microelectrochemical measurement indicates much more efficient counter-ion diffusion between the electrolyte and the NP films than the compacted films, which results in much faster electrochromic switching. Besides the facile and eco-friendly processing of the WDENs, all solution and low cost fabrication of ECP NP films suggest their broad applications in commercial production of polymer electrochromic display and great potential for other polymer electrochemical electronics.

  • 1485.
    Xiong, Yan
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). Hubei University of Technology, China.
    Fu, Zhengyi
    Pouchly, Vaclav
    Maca, Karel
    Shen, Zhijian
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Preparation of Transparent 3Y-TZP Nanoceramics with No Low-Temperature Degradation2014Inngår i: Journal of The American Ceramic Society, ISSN 0002-7820, E-ISSN 1551-2916, Vol. 97, nr 5, s. 1402-1406Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The progresses of the relative density, average grain size (GS), and maximum pore size entering into the final sintering stage are investigated in 3mol% yttria-stabilized tetragonal zirconia polycrystals (3Y-TZP) compacts in the range of 87%similar to 99% theoretical density. It is found that during conventional pressureless sintering, the pores in the compact enlarged dramatically, which appears to be the major obstacle for preparing fully dense nanoceramics. Transparent 3Y-TZP nanoceramics with an average GS of 87nm were prepared by exploiting microstructural refinement on nanoscale. The yields a maximal optical transmittance of 67% and shows no noticeable low-temperature degradation after 100h aging at 134 degrees C under a hydrothermal pressure of two bars.

  • 1486.
    Xiong, Yan
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Hu, Jianfeng
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för oorganisk kemi och strukturkemi.
    Shen, Zhijian
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Pouchly, Vaclav
    Maca, Karel
    Preparation of Transparent Nanoceramics by Suppressing Pore Coalescence2011Inngår i: Journal of The American Ceramic Society, ISSN 0002-7820, E-ISSN 1551-2916, Vol. 94, nr 12, s. 4269-4273Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Microstructural developments in nanoceramics were investigated in 3Y-TZP compacts with relative density (RD) exceeding 93%. Special attentions were paid to the evolutions of pore structures. It was found that the densification process of nanoceramic compacts with apparently close porosity was greatly jeopardized by pore coalescence. This observation was interpreted by the coalescence of locally interconnected pores originated from inhomogeneous packing of particles. The pore coalescence can be suppressed by application of an external pressure. The processing principle was demonstrated by spark plasma sintering (SPS) with extended holding at a minimized sintering temperature. The highly dense 3Y-TZP nanoceramics containing no large pores became optically transparent.

  • 1487.
    Xu, Bo
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi. KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    Tian, Haining
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi. KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    Bi, Dongqin
    Gabrielsson, Erik
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi. KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    Johansson, Erik M. J.
    Boschloo, Gerrit
    Hagfeldt, Anders
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi. KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    Efficient solid state dye-sensitized solar cells based on an oligomer hole transport material and an organic dye2013Inngår i: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 1, nr 46, s. 14467-14470Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A low-cost and easily-synthesized organic hole transport material (HTM) X3 bearing triphenylamine units and an organic dye was utilized for solid state dye sensitized solar cells (ssDSCs), which have achieved the power conversion efficiencies of 5.8% and 7.1% under 1 sun and 0.46 sun, respectively, outperforming the ssDSC based on Spiro-OMeTAD 5.4% (1 sun) and 6.4% (0.46 sun).

  • 1488.
    Xu, Changming
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Flodström, Katarina
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Esmaeilzadeh, Saeid
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Low temperature densification of B4C ceramics with CaF2/Y2O3 additives2012Inngår i: International journal of refractory metals & hard materials, ISSN 0958-0611, E-ISSN 2213-3917, Vol. 35, s. 311-314Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study deals with low temperature densification of boron carbide (B4C) ceramics with combined employment of CaF2/Y2O3 sintering additive and Spark Plasma Sintering (SPS) technique. It demonstrates that a small amount addition of CaF2/Y2O3 has strong effect on the densification of B4C ceramics. With 0.5-1 wt.% CaF2/Y2O3 addition, nearly full-densification up to 99.1% of B4C ceramics can be attained at a temperature as low as 1700-1750 degrees C.

  • 1489.
    Xu, Chao
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    All silicon lithium-ion batteries2015Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Lithium-ion batteries have been widely used as power supplies for portable electronic devices due to their higher gravimetric and volumetric energy densities compared to other electrochemical energy storage technologies, such as lead-acid, Ni-Cd and Ni-MH batteries. Developing a novel battery chemistry, ‘‘all silicon lithium-ion batteries’’, using lithium iron silicate as the cathode and silicon as the anode, is the primary aim of this Ph.D project. This licentiate thesis is focused on improving the performance of the silicon anode via optimization of electrolyte composition and electrode formulation. Fluoroethylene carbonate (FEC) was investigated as an electrolyte additive for silicon composite electrodes, and both the capacity retention as well as coulombic efficiency were significantly improved by introducing 10 wt% FEC into the LP40 electrolyte. This is due to the formation of a stable SEI, which mainly consisted of FEC decomposition products of LiF, -CHFOCO2-, etc. The chemical composition of the SEI was identified by synchrotron radiation based photoelectron spectroscopy. This conformal SEI prevented formation of large amounts of cracks and continues electrolyte decomposition on the silicon electrode. An alternative lithium salt, lithium 4,5-dicyano-2-trifluoromethanoimidazole (LiTDI), was studied with the silicon electrode in this thesis. The SEI formation led to a rather low 1st cycle coulombic efficiency of 44.4%, and the SEI layer was found to contain hydrocarbon, ether-type and carbonate-type species. Different to conventional composite silicon electrodes, which require heavy and expensive copper current collector, a flexible silicon electrode, consisted of only silicon nanopowder, Cladophora nanocellulose and carbon nanotube, was facilely prepared via vacuum filtration. The electrode showed good mechanical, long-term cycling as well as rate capability performance.

  • 1490.
    Xu, Chao
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Imine/azo-linked microporous organic polymers: Design, synthesis and applications2015Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Microporous organic polymers (MOPs) are porous materials. Owing to their high surface area, tunable pore sizes and high physicochemical stability, they are studied for applications including gas capture and separation and heterogeneous catalysis. In this thesis, a series of imine/azo-linked MOPs were synthesized. The MOPs were examined as potential CO2 sorbents and as supports for heterogeneous catalysis.

    The MOPs were synthesized by Schiff base polycondensations and oxidative couplings. The porosities of the imine-linked MOPs were tunable and affected by a range of factors, such as the synthesis conditions, monomer lengths, monomer ratios. All the MOPs had ultramicropores and displayed relatively high CO2 uptakes and CO2-over-N2 selectivities at the CO2 concentrations relevant for post-combustion capture of CO2. Moreover, the ketimine-linked MOPs were moderately hydrophobic, which might increase their efficiency for CO2 capture and separation.

    The diverse synthesis routes and rich functionalities of MOPs allowed further post-modification to improve their performance in CO2 capture. A micro-/mesoporous polymer PP1-2, rich in aldehyde end groups, was post-synthetically modified by the alkyl amine tris(2-aminoethyl)amine (tren). The tethered amine moieties induced chemisorption of CO2 on the polymer, which was confirmed by the study of in situ infrared (IR) and solid-state 13C nuclear magnetic resonance (NMR) spectroscopy. As a result, the modified polymer PP1-2-tren had a large CO2 capacity and very high CO2-over-N2 selectivity at low partial pressures of CO2.

    Pd(II) species were incorporated in the selected MOPs by means of complexation or chemical bonding with the imine or azo groups. The Pd(II)-rich MOPs were tested as heterogeneous catalysts for various organic reactions. The porous Pd(II)-polyimine (Pd2+/PP-1) was an excellent co-catalyst in combination with chiral amine for cooperatively catalyzed and enantioselective cascade reactions. In addition, the cyclopalladated azo-linked MOP (Pd(II)/PP-2) catalyzed Suzuki and Heck coupling reactions highly efficiently.

  • 1491.
    Xu, Chao
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Non-aqueous Electrolytes and Interfacial Chemistry in Lithium-ion Batteries2017Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Lithium-ion battery (LIB) technology is currently the most promising candidate for power sources in applications such as portable electronics and electric vehicles. In today's state-of-the-art LIBs, non-aqueous electrolytes are the most widely used family of electrolytes. In the present thesis work, efforts are devoted to improve the conventional LiPF6-based electrolytes with additives, as well as to develop alternative lithium 2-trifluoromethyl-4,5-dicyanoimidazole (LiTDI)-based electrolytes for silicon anodes. In addition, electrode/electrolyte interfacial chemistries in such battery systems are extensively investigated.

    Two additives, LiTDI and fluoroethylene carbonate (FEC), are evaluated individually for conventional LiPF6-based electrolytes combined with various electrode materials. Introduction of each of the two additives leads to improved battery performance, although the underlying mechanisms are rather different. The LiTDI additive is able to scavenge moisture in the electrolyte, and as a result, enhance the chemical stability of LiPF6-based electrolytes even at extreme conditions such as storage under high moisture content and at elevated temperatures. In addition, it is demonstrated that LiTDI significantly influences the electrode/electrolyte interfaces in NMC/Li and NMC/graphite cells. On the other hand, FEC promotes electrode/electrolyte interfacial stability via formation of a stable solid electrolyte interphase (SEI) layer, which consists of FEC-derivatives such as LiF and polycarbonates in particular.

    Moreover, LiTDI-based electrolytes are developed as an alternative to LiPF6 electrolytes for silicon anodes. Due to severe salt and solvent degradation, silicon anodes with the LiTDI-baseline electrolyte showed rather poor electrochemical performance. However, with the SEI-forming additives of FEC and VC, the cycling performance of such battery system is greatly improved, owing to a stabilized electrode/electrolyte interface.

    This thesis work highlights that cooperation of appropriate electrolyte additives is an effective yet simple approach to enhance battery performance, and in addition, that the interfacial chemistries are of particular importance to deeply understand battery behavior.

  • 1492.
    Xu, Chao
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Afewerki, Samson
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Córdova, Armando
    Hedin, Niklas
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    A Cyclopalladated Microporous Azo-linked Polymer as a Heterogeneous Catalyst for Eco-friendly Suzuki and Heck Coupling ReactionsManuskript (preprint) (Annet vitenskapelig)
  • 1493.
    Xu, Chao
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Dinka, Ermiase
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Hedin, Niklas
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Hydrophobic Porous Polyketimines for the Capture of CO22016Inngår i: ChemPlusChem, ISSN 2192-6506, Vol. 81, nr 1, s. 58-63Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new type of porous polymers is presented. Polyketimines (PPKs) were synthesized by condensing 1,3,5-tris(4-aminophenyl)benzene with aromatic diketones usingp-toluenesulfonic acid catalyst. They were characterized by infrared spectroscopy and solid-state 13C{1H} nuclear magnetic resonance spectroscopy, and their porosities were probed through the adsorption of N2 and CO2. The PPKs had low uptakes of N2 (at −196 °C), which was attributed to diffusion limitations and/or a shrinking of the polymer. They had relatively high uptakes of CO2 (at 0 °C; up to 1.26 mmol g−1 at 0.15 bar and 2.99 mmol g−1 at 1 bar), which was related to ultramicropores (6–9 Å). The PPKs had high estimated CO2-over-N2 selectivities (30–40 at 0 °C). Studies on the vapor adsorption of water and ethanol showed the PPKs to be moderately hydrophobic and had a high uptake of ethanol at low partial pressures.

  • 1494.
    Xu, Chao
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Hedin, Niklas
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Microporous adsorbents for CO2 capture - a case for microporous polymers?2014Inngår i: Materials Today, ISSN 1369-7021, E-ISSN 1873-4103, Vol. 17, nr 8, s. 397-403Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    Microporous polymers (MOPs) belong to a relatively new class of polymers that could find applications in gas separation processes, both as adsorbents and as polymer membranes. These polymers are constructed from purely organic building blocks by covalent bonds. It is possible to synthesize them by a range of different reactions that are either catalyzed with or without metal centers. Recently, these polymers have been researched in detail as potential sorbents, or membrane materials for a separation of CO2 from flue gas. Both adsorption driven and membrane driven separation of CO2 from flue gas could offer more cost effective alternatives to the methods currently in use. Here, we review recent papers and present our view on the opportunities and challenges when it comes to the use of MOPs in carbon capture and storage (CCS).

  • 1495.
    Xu, Chao
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Hedin, Niklas
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Synthesis of microporous organic polymers with high CO2-over-N-2 selectivity and CO2 adsorption2013Inngår i: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 1, nr 10, s. 3406-3414Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A series of microporous organic polymers (MOPs) were synthesized by Schiff base condensation of 1,3,5-tris(4-aminophenyl)benzene and a number of dialdehyde monomers. The polymers were structurally characterized by in situ infrared and ex situ solid state C-13{H-1} nuclear magnetic resonance (NMR) spectroscopy. Synthesis conditions were optimized to enhance CO2 uptake by the MOPs. Synthesis at low temperatures results in the MOPs being linked by imine groups. Heating of the MOPs reduces the number of imine groups and after heating to >300 degrees C nitrile groups were found to be present in the MOPs. The MOPs have specific surface areas up to 614 m(2) g(-1) and narrow pore size distributions of similar to 4 to 8 angstrom. The selectivity of CO2-over-N-2 at 273 K and 1 bar was 56-77, which requires either an influence of chemisorption on CO2 or a molecular sieving (or kinetic selection) of CO2-over-N-2. The materials had also heats of adsorption typical for physisorption of CO2.

  • 1496.
    Xu, Chao
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Jeschull, Fabian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Brant, William R.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Brandell, Daniel
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Edström, Kristina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Gustafsson, Torbjörn
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    The Role of LiTDI Additive in LiNi1/3Mn1/3Co1/3O2/ Graphite Lithium-Ion Batteries at Elevated Temperatures2018Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 165, nr 2, s. A40-A46Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The poor thermal stability of conventional LiPF6-based electrolytes is one of the major obstacles for today's lithium-ion batteries. Recently, lithium 4,5-dicyano-2-( trifluoromethyl) imidazolide (LiTDI) has demonstrated to be highly efficient in scavenging moisture from the electrolyte and thereby improving electrolyte stability. In this context, effects of the LiTDI additive on LiNi1/3Mn1/3Co1/3O2 (NMC)/graphite cells are evaluated at a temperature of 55 degrees C. With the incorporation of LiTDI, an improved cycling performance of NMC/graphite cells was achieved, and the impedance increase at the NMC/electrolyte interface was significantly mitigated. Furthermore, LiTDI exhibited a profound influence on the interfacial chemistries in the full cell, and LiTDI-derived species were found on the surfaces of both the cathode and the anode. The SEI layer formed on graphite anodes was more homogenous in morphology and consisted of larger amounts of LiF and fewer oxygen-containing species, as compared to graphite in additive-free cells. This study shows that LiTDI is a promising electrolyte additive for NMC/graphite cells operated at elevated temperatures, highlighting that the influence of the LiTDI additive is worth exploring also in other battery chemistries.

  • 1497.
    Xu, Chao
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Jeschull, Fabian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Brant, William R.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Brandell, Daniel
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Edström, Kristina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Gustafsson, Torbjörn
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    The Role of LiTDI Additive in LiNi1/3Mn1/3Co1/3O2/Graphite Lithium-Ion Batteries at Elevated Temperatures2018Inngår i: Journal of The Electrochemical Society, Vol. 165, nr 2, s. A40-A46Artikkel i tidsskrift (Fagfellevurdert)
  • 1498.
    Xu, Haiping
    et al.
    Shanghai Univ, Res Ctr Nanosci & Nanotechnol, Shanghai 200444, Peoples R China..
    Shi, Liyi
    Shanghai Univ, Res Ctr Nanosci & Nanotechnol, Shanghai 200444, Peoples R China..
    Wang, Zhuyi
    Shanghai Univ, Res Ctr Nanosci & Nanotechnol, Shanghai 200444, Peoples R China..
    Liu, Jia
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Zhu, Jiefang
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Zhao, Yin
    Shanghai Univ, Res Ctr Nanosci & Nanotechnol, Shanghai 200444, Peoples R China..
    Zhang, Meihong
    Shanghai Univ, Res Ctr Nanosci & Nanotechnol, Shanghai 200444, Peoples R China..
    Yuan, Shuai
    Shanghai Univ, Res Ctr Nanosci & Nanotechnol, Shanghai 200444, Peoples R China..
    Fluorine-Doped Tin Oxide Nanocrystal/Reduced Graphene Oxide Composites as Lithium Ion Battery Anode Material with High Capacity and Cycling Stability2015Inngår i: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 7, nr 49, s. 27486-27493Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Tin oxide (SnO2) is a kind of anode material with high theoretical capacity. However, the volume expansion and fast capability fading during cycling have prevented its practical application in lithium ion batteries. Herein, we report that the nanocomposite of fluorine-doped tin oxide (FTO) and reduced graphene oxide (RGO) is an ideal anode material with high capacity, high rate capability, and high stability. The FTO conductive nanocrystals were successfully anchored on RGO nanosheets from an FTO nanocrystals colloid and RGO suspension by hydrothermal treatment. As the anode material, the FTO/RGO composite showed high structural stability during the lithiation and delithiation processes. The conductive FTO nanocrystals favor the formation of stable and thin solid electrolyte interface films. Significantly, the FTO/RGO composite retains a discharge capacity as high as 1439 mAhg(-1) after 200 cycles at a current density of 100 mAg(-1). Moreover, its rate capacity displays 1148 mAhg(-1) at a current density of 1000 mAg(-1).

  • 1499.
    Xu, Lu
    et al.
    Xian Univ Architecture & Technol, Sch Environm & Municipal Engn, Minist Educ, Key Lab Northwest Water Resources Environm & Ecol, Xian 710055, Shaanxi, Peoples R China.
    Yang, Lei
    Xian Univ Architecture & Technol, Sch Environm & Municipal Engn, Minist Educ, Key Lab Northwest Water Resources Environm & Ecol, Xian 710055, Shaanxi, Peoples R China.
    Johansson, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Wang, Yuanhao
    Chinese Acad Sci, Xinjiang Tech Inst Phys & Chem, Urumqi 830011, Peoples R China.
    Jin, Pengkang
    Xian Univ Architecture & Technol, Sch Environm & Municipal Engn, Minist Educ, Key Lab Northwest Water Resources Environm & Ecol, Xian 710055, Shaanxi, Peoples R China.
    Photocatalytic activity and mechanism of bisphenol a removal over TiO2-x/rGO nanocomposite driven by visible light2018Inngår i: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 350, s. 1043-1055Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the present study, Ti3+ and oxygen vacancies (Ti3+/O-v) self-doped TiO2 and coupled with a reduced graphene oxide (rGO) nanocomposite (TiO2-x/rGO) was successfully synthesized via a facile hydrothermal-calcination method for the efficient degradation of bisphenol A (BPA) under visible light. The results of XPS, ERP and TEM analyses revealed that the presence of Ti3+/O-v in the lattice of TiO2-x/rGO leads to the narrowed band gap and enhanced visible light harvesting. The chemical bonds (TieOeC) between TiO2-x and rGO act as the channel for electron transfer, consequently resulting in the efficient charge separation, which was investigated and confirmed by such methods as PL spectra and time-resolved PL spectra. In addition, the coupling of TiO2-x and rGO could strongly suppress the aggregation of TiO2-x particles and therefore improve the adsorption of organic pollutants. For the synergistic effect of the three preeminent features mentioned above, TiO2-x/rGO exhibited a 6.16-, 2.92-and 2.55-fold faster reaction rate for BPA degradation than that of pristine TiO2, TiO2/rGO and TiO2-x, respectively. Moreover, the effects of the initial substrate concentration, initial solution pH, catalyst dosage and inorganic anions on BPA removal were also investigated in depth. EPR measurements indicated that center dot O-2(-) as the major oxidizing species, is responsible for the degradation of BPA. Next, the feasible pathway of BPA degradation by TiO2-x/rGO was proposed based on the analysis of intermediate products. Finally, the mechanism of the enhanced photocatalytic performance by TiO2-x/rGO under visible light was discussed. Based on these results, the TiO2-x/rGO nanocomposite could be an efficient and promising photocatalyst for the degradation of organic pollutants in water.

  • 1500.
    Xu, Peng
    et al.
    Yunnan Univ, Sch Mat Sci & Engn, Yunnan Key Lab Micro Nano Mat & Technol, Kunming 650091, Yunnan, Peoples R China.
    Liu, Peng
    KTH Royal Inst Technol, Appl Phys Chem, Dept Chem, Teknikringen 30, SE-10044 Stockholm, Sweden.
    Li, Yuanyuan
    KTH Royal Inst Technol, Wallenberg Wood Sci Ctr, Dept Fiber & Polymer Technol, Chem Sci & Engn, SE-10044 Stockholm, Sweden.
    Xu, Bo
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Kloo, Lars
    KTH Royal Inst Technol, Appl Phys Chem, Dept Chem, Teknikringen 30, SE-10044 Stockholm, Sweden.
    Sun, Licheng
    KTH Royal Inst Technol, Organ Chem, Dept Chem, SE-10044 Stockholm, Sweden.
    Hua, Yong
    Yunnan Univ, Sch Mat Sci & Engn, Yunnan Key Lab Micro Nano Mat & Technol, Kunming 650091, Yunnan, Peoples R China.
    D-A-D-Typed Hole Transport Materials for Efficient Perovskite Solar Cells: Tuning Photovoltaic Properties via the Acceptor Group2018Inngår i: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 10, nr 23, s. 19697-19703Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Two D-A-D-structured hole-transport materials (YN1 and YN2) have been synthesized and used in perovskite solar cells. The two HTMs have low-lying HOMO levels and impressive mobility. Perovskite-based solar cells (PSCs) fabricated with YN2 showed a power conversion efficiency (PCE) value of 19.27% in ambient air, which is significantly higher than that of Spiro-OMeTAD (17.80%). PSCs based on YN1 showed an inferior PCE of 16.03%. We found that the incorporation of the stronger electron-withdrawing group in the HTM YN2 improves the PCE of PSCs. Furthermore, the YN2-based PSCs exhibit good long-term stability retaining 91.3% of its initial efficiency, whereas PSCs based on Spiro-OMeTAD retained only 42.2% after 1000 h lifetime (dark conditions). These promising results can provide a new strategy for the design of D-A-D HTMs for PSC applications in future.

27282930313233 1451 - 1500 of 1624
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