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  • 1. Delaunay, R.
    et al.
    Gatchell, Michael
    Stockholm University, Faculty of Science, Department of Physics.
    Mika, A.
    Domaracka, A.
    Adoui, L.
    Zettergren, Henning
    Stockholm University, Faculty of Science, Department of Physics.
    Cederquist, Henrik
    Stockholm University, Faculty of Science, Department of Physics.
    Rousseau, P.
    Huber, B. A.
    Shock-driven formation of covalently bound carbon nanoparticles from ion collisions with clusters of C-60 fullerenes2018In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 129, p. 766-774Article in journal (Refereed)
    Abstract [en]

    We show that the energetic processing of C-60 clusters by slow atomic projectiles leads to ultrafast (< ps) formation of large covalent carbon nanoparticles containing a few hundreds of atoms. The underlying mechanism is found to be due to impulse-driven collisions between the projectile and the nuclei of the molecules. Experimental findings are well reproduced by classical molecular dynamics simulations. The cross sections for molecular growth processes forming covalent systems which contain more than 60 carbon atoms are about 5.10(-14) cm(2) representing more than 70% of the geometrical cross sections. This demonstrates the high efficiency of the underlying processes. The formed carbon nanoparticles contain both aromatic and aliphatic structures which have also been considered as dust components in space.

  • 2.
    Hao, Wenming
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Keshavarzi, Neda
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Branger, Adrien
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Strong discs of activated carbons from hydrothermally carbonized beer waste2014In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 78, p. 521-531Article in journal (Refereed)
    Abstract [en]

    Strong and dense activated carbon discs (ACDs) were synthesized and studied. The discs were produced in a multistep manner from a precursor based on hydrothermally treated beer waste (HTC-BW). The precursor was processed by pulsed current processing (PCP) into ACDs. These discs were activated by physical activation in CO2 at an elevated temperature. The ACDs had surface areas of ∼500 m2/g and contained significant amounts of micro-, meso-, and macropores. The effect on the temperature during the PCP and the presence of tar in the precursor were studied with respect to the properties of the discs. The ACDs had strengths up to 7.2 MPa with densities up to 1.4 g/cm3. The density is the highest reported for discs of activated carbon.

  • 3. Huber, S. E.
    et al.
    Gatchell, Michael
    Stockholm University, Faculty of Science, Department of Physics.
    Zettergren, Henning
    Stockholm University, Faculty of Science, Department of Physics.
    Mauracher, A.
    A precedent of van-der-Waals interactions outmatching Coulomb explosion2016In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 109, p. 843-850Article in journal (Refereed)
    Abstract [en]

    Fullerenes (and clusters composed of them) yield a variety of promising structural, electronic, magnetic and chemical properties, governed by their specific electronic and geometric configuration. These systems have attracted many theoretical and experimental endeavors in order to describe, explain and predict their features. The conclusive description of some specific properties has remained a challenge though, such as a sound physicochemical description of the stability of multiply charged fullerene clusters, which we explore here. We show how simple models based on classical electrostatics allow one to understand the (fragmentation) dynamics of multiply ionized fullerene aggregates without the use of elaborate and time-consuming computational quantum chemical approaches. These models successfully explain why the fullerene pentamer is the smallest dicationic cluster experimentally observed, despite its thermodynamic instability. These predictions are of importance in various fields such as cluster physics, astrochemistry, electrochemistry and solid-state chemistry.

  • 4. Kim, Jong Min
    et al.
    Guccini, Valentina
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Seong, Kwang-dong
    Oh, Jiseop
    Salazar-Alvarez, Germán
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Piao, Yuanzhe
    Extensively interconnected silicon nanoparticles via carbon network derived from ultrathin cellulose nanofibers as high performance lithium ion battery anodes2017In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 118, p. 8-17Article in journal (Refereed)
    Abstract [en]

    Silicon is a good alternative to conventional graphite anode but it has bad cycling and rate performance. To overcome these severe problems, extensively interconnected silicon nanoparticles using carbon network derived from ultrathin cellulose nanofibers were synthesized. Ultrathin cellulose nanofibers, an abundant and sustainable material, entangle each silicon nanoparticle and become extensively interconnected carbon network after pyrolysis. This wide range interconnection provides an efficient electron path by decreasing the likelihood that electrons experience contact resistivity and also suppresses the volume expansion of silicon during lithiation. In addition, Ultrathin cellulose nanofibers are carboxylated and therefore adhesive to silicon nanoparticles through hydrogen bonding. This property makes ultrathin cellulose the perfect carbon source when making silicon composites. As a consequence, it exhibits 808 mAh g(-1) of the reversible capacity after 500 cycles at high current density of 2 A g(-1) with a coulombic efficiency of 99.8%. Even at high current density of 8 A g(-1), it shows a high reversible discharge capacity of 464 mAh g(-1). Moreover, extensively interconnected carbon network prevents the formation of a brittle electrode with a water-based binder. Therefore, this remarkable material has a huge potential for LIBs applications.

  • 5.
    Lee, Kian Keat
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Björkman, Eva
    Morin, Daniel
    Lilliestråle, Malte
    Björefors, Fredrik
    Andersson, Anna M.
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Effects of hydrothermal carbonization conditions on the textural and electrical properties of activated carbons2016In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 107, p. 619-621Article in journal (Refereed)
    Abstract [en]

    The influence of the hydrothermal conditions used for preparing precursors was studied with respect to the properties of the resulting KOH-activated carbons (KOH-ACs). The influence of the hydrothermal temperature (180 vs. 240 degrees C) was only minor on the textural properties of the KOH-ACs. However, the hydrothermal conditions did affect the electrical conductivity of the KOH-ACs. A higher conductivity was observed for the ACs prepared from precursors at the higher temperature and shorter reaction time. This study highlights an overlooked relationship in-between the degree of condensation in the precursors prepared from hydrothermal carbonization and the electrical conductivity of the corresponding ACs.

  • 6.
    Leis, J
    et al.
    Tartu Technologies Ltd., 185 Riia Str., 51014 Tartu, Estonia.
    Perkson, A
    Tartu Technologies Ltd., 185 Riia Str., 51014 Tartu, Estonia.
    Arulepp, M
    Tartu Technologies Ltd., 185 Riia Str., 51014 Tartu, Estonia.
    Kaarik, M
    Tartu Technologies Ltd., 185 Riia Str., 51014 Tartu, Estonia.
    Svensson, Gunnar
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Carbon nanostructures produced by chlorinating aluminium carbide2001In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 39, no 13, p. 2043-2048Article in journal (Refereed)
    Abstract [en]

    A number of carbon samples with different nanostructures such as: amorphous, nanoparticles and turbostratic, were synthesised through the reaction between aluminium carbide and gaseous chlorine at fixed temperatures between 300 and 900 degreesC. The synthesised carbon samples were characterised using high-resolution transmission electron microscopy and X-ray powder diffraction techniques, as well as low temperature nitrogen sorption measurements. The carbon produced at T=300 degreesC was amorphous with a surface area of similar to 1400 m(2) g(-1). At 700 degreesC, a large amount of carbon nanoparticles and with a lower surface area similar to 710 m(2) g(-1) was obtained. At 900 degreesC, mainly a turbostratic carbon with a surface area of similar to 680 m(2) g(-1) was produced.

  • 7.
    Leis, J
    et al.
    Tartu Technologies Ltd., 185 Riia Str., 51014 Tartu, Estonia.
    Perkson, A
    Tartu Technologies Ltd., 185 Riia Str., 51014 Tartu, Estonia.
    Arulepp, M
    Tartu Technologies Ltd., 185 Riia Str., 51014 Tartu, Estonia.
    Nigu, P
    Svensson, Gunnar
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Catalytic effects of metals of the iron subgroup on the chlorination of titanium carbide to form nanostructural carbon2002In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 40, no 9, p. 1559-1564Article in journal (Refereed)
    Abstract [en]

    The effect of the reaction temperature and the metals of an iron subgroup on the thermo-chemical treatment of titanium carbide with a chlorine gas and their influence on the carbon structure obtained thereby was studied. Different analytical methods such as porosity measure me tits, X-ray diffraction spectrometry and a high-resolution electron microscopy revealed the catalytic behaviour of the above-mentioned metals. which appeared to support the formation of graphitised carbon at much lower temperatures compared to those needed for the ordinary thermo-chemical chlorination of titanium carbide.

  • 8. Sharifi, Tiva
    et al.
    Nitze, Florian
    Barzegar, Hamid Reza
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Mazurkiewicz, Marta
    Malolepszy, Artur
    Stobinski, Leszek
    Wagberg, Thomas
    Nitrogen doped multi walled carbon nanotubes produced by CVD-correlating XPS and Raman spectroscopy for the study of nitrogen inclusion2012In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 50, no 10, p. 3535-3541Article in journal (Refereed)
    Abstract [en]

    High purity aligned nitrogen doped multi walled carbon nanotubes were synthesized by the catalytic chemical vapor deposition method using pyridine and Fe/Co (2:1 volume ratio) as the single C/N precursor and catalyst material. The average diameter of the synthesized tubes ranges between 29 nm and 57 nm and the nitrogen content of the tubes reaches a maximum of 9.2 (at.)% nitrogen. The effect of nitrogen doping on the Raman scattering of doped tubes and its correlation with X-ray photoelectron spectra (XPS) was investigated. The analysis is based on the investigation of the I-D/I-G (integrated area ratio), other nitrogen characteristic Raman modes and the type of nitrogen inclusion interpreted from the N 1s electron bonding energies in XPS. At doping levels higher than 5% the nitrogen inclusion takes place through another mechanism than at low nitrogen doping levels. Most significant is that pyridinic defects are relatively readily incorporated at low nitrogen doping levels while at nitrogen content higher than 5% the major incorporation mechanism is dominated by pyridinic and pyrrolic defects on an equal basis. Our study gives further insight into nitrogen doping effects and the relation between type of nitrogen inclusion and nitrogen doping levels.

  • 9.
    Urbonaite, Sigita
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Wachtmeister, Staffan
    Stockholm University, Faculty of Science, Department of Physics.
    Mirguet, Claude
    Coronel, Ernesto
    Zou, W.Y.
    Csillag, Stefan
    Stockholm University, Faculty of Science, Department of Physics.
    Svensson, Gunnar
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    EELS studies of carbide derived carbons2007In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 45, no 10, p. 2047-2053Article in journal (Refereed)
    Abstract [en]

    Carbide derived carbons (CDCs) have been synthesized from VC, WC, TaC, NbC, HfC and ZrC at T = 1000 °C, and from TiC at T = 700–1200 °C via a chlorination reaction. The CDCs have been studied by means of high resolution transmission electron microscopy and electron energy-loss spectroscopy (EELS). These studies show that the structures of CDCs are strongly dependent upon the nature of the starting carbide and the synthesis temperature. The structures range from very disordered nanoporous carbon, consisting of randomly curved graphene layers, to compact spherical entities of compactly packed graphitic layers. EELS studies of carbon core-loss spectra show that the relative sp2 content in these carbons varies between 83% and 98%. The low-loss part of the EEL spectra shows that the positions of the π-plasmons and the bulk plasmons are more dependent on the carbide precursor, than the synthesis temperature. The densities of the CDC particles have been estimated using the bulk plasmon positions as well as the sp3 content determined from the C-K edge spectra. The densities calculated from sp3 are close to the pycnometric ones, while the densities calculated from bulk plasmon positions are lower and reflects the nanostructure of CDCs.

  • 10.
    Wachtmeister, Staffan
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Csillag, Stefan
    Stockholm University, Faculty of Science, Department of Physics.
    Nanostructured CNx (0 < x < 0.2) films grown by supersonic cluster beam deposition2005In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 43, p. 1460-1469Article in journal (Refereed)
    Abstract [en]

    Nanostructured CNx thin films were prepared by supersonic cluster beam deposition (SCBD) and systematically characterized by transmission electron microscopy (TEM), electron energy-loss spectroscopy (EELS), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The incorporation of nitrogen in the films (0 < x < 0.2) and the nanostructure were controlled by using different synthesis routes. Films containing bundles of well-ordered graphene multilayers, onions and nanotubes embedded in an amorphous matrix were grown alongside purely amorphous films by changing the deposition parameters. Graphitic nanostructures were synthesized without using metallic catalysts. The structural and electronic properties of the films have been studied by EELS. The role played by N in the carbon nanostructures has been deduced from XPS line-shape analysis.

  • 11.
    Zakharchenko, Konstantin V.
    et al.
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Balatsky, Alexander V.
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Institute for Materials Science, USA.
    Controlled healing of graphene nanopores2014In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 80, p. 12-18Article in journal (Refereed)
    Abstract [en]

    Nanopores - nanometer-size channels hold significant promise for numerous applications: DNA sequencing, sensing, biosensing and molecular detectors, and catalysis and water desalination. However, these applications require accurate control over the size of the nanopores. Since graphene is often mentioned as a promising material to host nanopores, we have performed realistic computer simulation studies of regrowth and healing of graphene nanopores of different sizes ranging from 30 to 5 angstrom. Our simulations clearly point to at least two distinct healing mechanisms for graphene sheets: edge attachment (where carbons are attached to the edges of the graphene sheet/pore) and direct insertion (where individual atoms insert directly into a sheet of graphene, even in the absence of the edges). The insertion mechanism is a surprising prediction that points to the growth process that would be operational in pristine graphene. We have uncovered an unusual dependence in the speed of nanopore regrowth and the structure of healed areas as a function of its size in a wide range of temperatures. Our findings point to significantly more complicated pathways for graphene annealing. They also provide an important enabling step in the development of graphene-based devices for numerous applications in nanotechnology. Our results suggest the possibility to control the final size of healed nanopore by terminating the annealing at a prescribed time dependent on the temperature.

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