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  • 1.
    Allali, Naoual
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Urbanova, Veronika
    Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, UMR 7564, CNRS–University of Lorraine.
    Mamane, Victor
    Laboratoire de Structure et Réactivité des Systèmes Moléculaires Complexes, UMR 7565 CNRS–Université de Lorraine, 54506 Vandoeuvre-les-Nancy.
    Etienne, Mathieu
    Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, UMR 7564, CNRS–University of Lorraine.
    Mallet, Martine
    Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, UMR 7564, CNRS–University of Lorraine.
    Devaux, Xavier
    Institut Jean Lamour, Department P2M, UMR 7198 CNRS–Université de Lorraine, Ecole des Mines, 54042 Nancy.
    Vigolo, Brigitte
    Institut Jean Lamour, Department CP2S, UMR 7198 CNRS–Université de Lorraine, 54506 Vandoeuvre-les-Nancy.
    Fort, Yves
    Laboratoire de Structure et Réactivité des Systèmes Moléculaires Complexes, UMR 7565 CNRS–Université de Lorraine, 54506 Vandoeuvre-les-Nancy.
    Walcarius, Alain
    Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, UMR 7564, CNRS–University of Lorraine.
    Noël, Maxime
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Soldatov, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    McRae, Edward
    Institut Jean Lamour, Department CP2S, UMR 7198 CNRS–Université de Lorraine, 54506 Vandoeuvre-les-Nancy.
    Dossot, Manuel
    Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, UMR 7564, CNRS–University of Lorraine.
    Covalent functionalization of few-wall carbon nanotubes by ferrocene derivatives for bioelectrochemical devices2012In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 249, no 12, p. 2349-2352Article in journal (Refereed)
    Abstract [en]

    The present work reports the covalent functionalization of few-wall CNTs (FWCNTs) by ferrocene derivatives to (i) improve their dispersion efficiency in water and (ii) graft electroactive chemical groups on their side-walls in order to promote electron transfer to biomolecules. The functionalized CNTs (f-CNTs) are used to modify a glassy carbon electrode and this modified electrode is used for oxidizing the cofactor NADH (dihydronicotinamide adenine dinucleotide).

  • 2. Arvanitidis, J.
    et al.
    Meletov, K.P.
    Papagelis, K.
    Soldatov, Alexander
    Prassides, K.
    Kourouklis, G. A.
    Ves, S.
    Comparative Raman study of the 1D and 2D polymeric phases of C60 under pressure1999In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 215, no 1, p. 443-448Article in journal (Refereed)
    Abstract [en]

    The effect of symmetry lowering on the phonon spectra as well as the pressure effects on the vibrational spectrum of polymerized C60 were studied by Raman spectroscopy. Drastic changes related to the splitting of degenerate modes of the C60 molecule were observed together with selected softening of some of them. In spite of many similarities in the Raman spectra of the one- (1D) and two-dimensional (2D) polymeric forms of C60, some salient differences in the peak intensities and the appearance of complementary modes are evident. In the Raman spectrum of the 2D polymer under high pressure, new modes, which may be related to the deformations of molecular cages, appear. The observed pressure effects are reversible and the material remains stable for pressures up to 8.8 GPa.

  • 3.
    Benavides, Vicente
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Chernogorova, Olga
    A.A. Baikov Institute of Metallurgy and Materials Science (IMET), Moscow, Baikov Institute of Metallurgy and Materials Science (IMET), Russian Academy of Sciences.
    Drozdova, Ekaterina I.
    A.A. Baikov Institute of Metallurgy and Materials Science (IMET), Moscow.
    Ushakova, Iraida N.
    A.A. Baikov Institute of Metallurgy and Materials Science (IMET), Moscow.
    Soldatov, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Raman and electron microscopy study of C60 collapse/transformation to a nanoclustered graphene-based disordered carbon phase at high pressure/temperature2015In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 252, no 11, p. 2626-2629Article in journal (Refereed)
    Abstract [en]

    Transformation of C60 polymers to a superelastic hard carbon (nanoclustered graphene phase (NGP)) occurring in metal matrix at 5 GPa in a temperature interval of 1000–1100 K was studied by optical, scanning electron microscopy (SEM), and Raman spectroscopy. Raman spectral scan across the sample surface allowed us to identify different stages of the structural transformation. The SEM and Raman spectroscopy data testify for the NGP appearance at the defects concentration sites in the parent fullerite structure. We propose that the buckyballs collapse/formation of the NGP is governed by nucleation and growth (diffusive) mechanism unlike earlier discussed in the literature possibility of the martensitic-type (displacive) character of this transformation.

  • 4.
    Botella, Pablo
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Devaux, Xavier
    Institut Jean Lamour, UMR 7198 CNRS–Université de Lorraine.
    Dossot, Manuel
    LCPME UMR 7564 CNRS-Université de Lorraine.
    Garashchenko, Viktor
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Beltzung, Jean Charles
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Soldatov, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Department of Physics Harvard University, Cambridge.
    Ananev, Sergey
    Joint Institute for High Temperatures of RAS.
    Single-Walled Carbon Nanotubes Shock-Compressed to 0.5 Mbar2017In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 254, no 11, article id 1700315Article in journal (Refereed)
    Abstract [en]

    Single-walled carbon nanotubes (SWCNTs) have been dynamically (shock) compressed to 0.5 Mbar, above the limit of their structural integrity. Two distinct types of material are identified by high-resolution transmission electron microscopy (HRTEM) and multi-wavelength Raman spectroscopy in the sample recovered after shock: multi-layer graphene (MLG) and a two-phase material composed of nano-clustered graphene and amorphous carbon whereas no diamond-like carbon or carbon nano-onions are found. Peak decomposition of the Raman spectra was used to estimate the coherent scatterers (clusters) size in MLG at 36 nm from the D- to G-band intensity ratio dependence on the photon excitation energy. Botella et al. (article no. 1700315) propose the peak fitting model for decomposition of the Raman spectra of highly disordered carbon material containing graphene nano-clusters and stress the importance of accounting for heptagonal- and pentagonal-ring defects in graphene layers for the analysis of such spectra. The cover image shows HRTEM images and the correspondent Raman spectra of the two types of material along with peak decomposition of the two-phase material with the peaks assigned to heptagons (a) and pentagons (b). Particulars of the SWCNTs transformation to other structural forms of carbon at high pressure/temperature are discussed

  • 5.
    Botella, Pablo
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Devaux, Xavier
    Institut Jean Lamour, UMR 7198 CNRS–Université de Lorraine.
    Dossot, Manuel
    LCPME UMR 7564 CNRS-Université de Lorraine.
    Garashchenko, Viktor
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Beltzung, Jean Charles
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Soldatov, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Department of Physics Harvard University, Cambridge.
    Ananev, Sergey
    Joint Institute for High Temperatures of RAS.
    Single-Walled Carbon Nanotubes Shock-Compressed to 0.5 Mbar2017In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 254, no 11, article id 1770259Article in journal (Refereed)
    Abstract [en]

    Single-walled carbon nanotubes (SWCNTs) have been dynamically (shock) compressed to 0.5 Mbar, above the limit of their structural integrity. Two distinct types of material are identified by high-resolution transmission electron microscopy (HRTEM) and multi-wavelength Raman spectroscopy in the sample recovered after shock: multi-layer graphene (MLG) and a two-phase material composed of nano-clustered graphene and amorphous carbon whereas no diamond-like carbon or carbon nano-onions are found. Peak decomposition of the Raman spectra was used to estimate the coherent scatterers (clusters) size in MLG at 36 nm from the D- to G-band intensity ratio dependence on the photon excitation energy. Botella et al. (article no. 1700315) propose the peak fitting model for decomposition of the Raman spectra of highly disordered carbon material containing graphene nano-clusters and stress the importance of accounting for heptagonal- and pentagonal-ring defects in graphene layers for the analysis of such spectra. The cover image shows HRTEM images and the correspondent Raman spectra of the two types of material along with peak decomposition of the two-phase material with the peaks assigned to heptagons (a) and pentagons (b). Particulars of the SWCNTs transformation to other structural forms of carbon at high pressure/temperature are discussed

  • 6.
    Briddon, Patrick
    et al.
    School of Electrical, Electronic and Computer Engineering, University of Newcastle upon Tyne.
    Rayson, Mark
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Accurate Kohn–Sham DFT with the speed of tight binding: Current techniques and future directions in materials modelling2011In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 248, no 6, p. 1309-1318Article in journal (Refereed)
    Abstract [en]

    We present a review of methodological and implementation details of the AIMPRO Kohn–Sham density functional code. It is demonstrated that full Kohn–Sham density functional theory calculations can be performed in a time only marginally greater than tight binding implementations and a route is opened to achieve full and demonstrable convergence with respect to basis size. Topics covered will include both the kernel and functionality of the current code, a discussion of recent developments as well as future research directions and perspectives. Also, a broad discussion regarding the application of these methods is made that, it is hoped, will serve as a useful guide to application specialists.

  • 7.
    Carvalho, Alexandra
    et al.
    Department of Physics, I3N, University of Aveiro, Campus Santiago.
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Barroso, Manuel
    Department of Physics, I3N, University of Aveiro, Campus Santiago.
    Rayson, Mark
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Briddon, Patrick
    Electrical, Electronic and Computer Engineering, University of Newcastle upon Tyne.
    Boron doped Si nanoparticles: the effect of oxidation2013In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 250, no 9, p. 1799-1803Article in journal (Refereed)
    Abstract [en]

    The preferred location of boron in oxidized free-standing Si nanoparticles was investigated using a first-principles density functional approach. The nanoparticles were modeled by a silicon core about 1.5 nm in diameter surrounded by an outer shell of SiO2 with a thickness of about 0.5 nm, and considered negatively charged. The calculated formation energies indicate that B is equally stable in the Si core and in the SiO2 shell, showing preference for interface sites. This indicates that, in contrast with phosphorus, the ratio of the boron concentration in the silicon core to that of the silicon shell will not be improved over one upon thermal annealing.

  • 8.
    Dixon, P.
    et al.
    School of Physics, University of Exeter.
    Richardson, D.
    School of Physics, University of Exeter.
    Jones, R.
    School of Physics, University of Exeter.
    Latham, Chris D.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Torres, V.J.B.
    Departamento de Fisica, Universidade de Aveiro.
    Brikddon, P.R.
    Department of Physics, University of Newcastle.
    Nitrogen-Hydrogen Defects in GaP1998In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 210, no 2, p. 321-326Article in journal (Refereed)
    Abstract [en]

    Models of the nitrogen-hydrogen defect in GaP, which contain one and two H atoms, are investigated using ab initio density functional cluster theory. We find that a single H atom binding to N possesses two infrared absorption frequencies close to those attributed to an NH2 defect. The modes shift with its charge state consistent with the photo-sensitivity found for the defect. A third mode observed for this centre is assumed to be an overtone of the bend mode. The isotope shifts of the calculated modes are in excellent agreement with experiment in contrast with the model which contains two H atoms

  • 9.
    Jones, R
    et al.
    University of Exeter.
    Coomer, B J
    University of Exeter.
    Goss, J P
    University of Exeter.
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Briddon, P R
    University of Newcastle Upon Tyne.
    Intrinsic defects and the D1 to D4 optical bands detected in plastically deformed Si2000In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 222, no 1, p. 133-140Article in journal (Refereed)
    Abstract [en]

    The properties of multi-vacancy and multi-interstitial defects that possess luminescent bands around 1 eV are reviewed. Prominent among these are the hexavacancy and tri- and tetra-self-interstitial defects. It is suggested that the formation of these defects on dislocation cores could lead to the D1 to D4 photoluminescent bands linked to dislocations in Si and SiGe.

  • 10.
    Latham, Chris D.
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Jones, R.
    School of Physics, University of Exeter.
    Wagner, J.
    Fraunhofer-Institut für Angewandte Festkörperphysik, Tullastrasse 72, D-79108 Freiburg.
    Davidson, B.R.
    Interdisciplinary Research Centre for Semiconductor Materials, The Blackett Laboratory, Imperial College of Science, Technology and Medicine, London.
    Newman, R.C.
    Interdisciplinary Research Centre for Semiconductor Materials, The Blackett Laboratory, Imperial College of Science, Technology and Medicine, London.
    Button, C.C.
    Department of Electronic and Electrical Engineering, University of Surrey, Guildford.
    Briddon, P.R.
    Department of Physics, University of Newcastle.
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Di-carbon complexes in AlAs and GaAs1998In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 210, no 2, p. 869-872Article in journal (Refereed)
    Abstract [en]

    Heat treatment of heavily carbon doped AlAs and GaAs results in a loss of CAS shallow acceptors. In Raman scattering experiments on annealed CBE grown GaAs with 12C and 13C isotopes, and MOVPE grown AlAs it is found that the loss of carriers is accompanied by the appearance of two high frequency lines. These lie near to the stretch mode of an isolated C2 molecule (1855 cm-1). This is consistent with the formation of two types of di-carbon defects in these materials where the C atoms are bonded together and one or both of which act as a donor. Using a local density functional method to investigate the structure and dynamics of several di-carbon defects, we find that the dimer at an As site is bistable and aligned approximately in a [100] direction in the neutral charge state, and in a [110] direction when positively ionised. The calculated frequencies lie within 10% of the measured values in both materials. Other defects are investigated too with a view of determining the structures giving rise to the modes

  • 11. Marklund, Sune
    et al.
    Wang, Yong-Liang
    Electron-states of a vacancy in the core of the 90-degrees partial dislocation in silicon1995In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 189, no 2, p. 473-477Article in journal (Refereed)
    Abstract [en]

    An LCAO scheme (linear combination of atomic orbitals) taking into account ten atomic orbitals (s-, p-, and d-type) is used to calculate the electronic structure of a vacancy present in the core of the reconstructed 90 degrees partial dislocation in silicon. The levels in the band gap are extracted using Lanczos' algorithm and a continued fraction representation of the local density of states. The three-fold degenerate stale of the ideal vacancy is split into three levels with energies 0.26, 1.1, and 1.9 eV measured from the valence band edge.

  • 12.
    Mases, Mattias
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Milyavskiy, Vladimir V.
    Joint Institute for High Temperatures of RAS, Moscow.
    Waldbock, Jeremy
    Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, UMR 7564, CNRS–University of Lorraine.
    Dossot, Manuel
    Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, UMR 7564, CNRS–University of Lorraine.
    Devaux, Xavier
    Institut Jean Lamour, Department P2M, UMR 7198 CNRS–Université de Lorraine, Ecole des Mines, 54042 Nancy.
    MacRae, Edward
    Institut Jean Lamour, Department CP2S, UMR 7198, CNRS–Université de Lorraine.
    Soldatov, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    The effect of shock wave compression on double wall carbon nanotubes2012In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 249, no 12, p. 2378-2381Article in journal (Refereed)
    Abstract [en]

    Double wall carbon nanotubes (DWCNTs) have proven to have a very good structural stability when exposed to high static pressures. We report here on the study of DWCNTs after application of shock wave (dynamic) compression up to 36 GPa in a recovery assembly. TEM images of so-treated samples reveal a threshold between 19 and 26 GPa of shock wave compression above which significant structural damage is induced whereas only minor damage can be detected below. The threshold detected with TEM coincides well with the collapse pressure of DWCNTs previously reported [You et al., High Press. Res. 31, 186 (2011); Aguiar et al., Phys. Chem. C 115, 5378 (2011)]. Raman data demonstrate a gradual accumulation of structural defects via an increase in D-band to G-band intensity ratio (ID/IG-ratio) from ∼0.2 to ∼0.8 in going from the source CNT material to the nanotubes after compression to 36 GPa. Despite severe damage; the DWCNTs exposed to 36 GPa of shock wave compression survived which is evidenced by Raman spectra. The DWCNTs demonstrate a higher susceptibility to structural damage under dynamic than static pressure.

  • 13.
    Mases, Mattias
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Noël, Maxime
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Dossot, Manuel
    Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, Nancy Université.
    McRae, Edward
    Institut Jean Lamour, CNRS – Nancy Université.
    Soldatov, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Laser-induced damage and destruction of HiPCO nanotubes in different gas environments2011In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 248, no 11, p. 2540-2543Article in journal (Refereed)
    Abstract [en]

    We have studied the thermal and chemical stability of HiPCO-produced single-walled carbon nanotube bundles to high laser power in air and argon. The samples were exposed to 110 kW/cm2 during 8 h with a 1.96 eV laser and the temperature was monitored via downshift of G+-Raman peak. The structural changes in the carbon nanotubes (CNTs) caused by laser heating were monitored by recording their Raman spectra at ambient T (reference conditions) to ensure unaltered resonance conditions. The initial temperature was estimated to be 550 °C and 870 °C in air and argon, respectively. The Raman signal intensity from the CNTs radial breathing mode (RBM) increased rapidly at the beginning of the laser heating both under air and argon due to desorption of impurities for all but the smallest diameter CNTs. The temperature dropped by 30% under argon and 60% under air due to destruction of the absorbers – CNTs in resonance with incident radiation. The final RBM spectra exhibited intensity loss only for the smallest diameter CNTs in argon atmosphere and for all but the largest diameter CNTs in air. Our results demonstrate the importance of (i) impurity desorption from exterior and interior of CNTs; (ii) different temperature thresholds for the CNT destruction due to oxidation and overheating; (iii) the role of photon absorbers on the thermal stability of the sample. The small diameter CNTs are more easily destroyed than large diameter ones. The metallic nanotubes also tend to have lower thermal stability.

  • 14.
    Mases, Mattias
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Noël, Maxime
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mercier, G.
    Institut Jean Lamour, CNRS – Nancy Université.
    Dossot, M.
    Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, Nancy Université.
    Vigolo, B.
    Institut Jean Lamour, CNRS – Nancy Université.
    Mamane, V.
    Laboratoire de Structure et Réactivité des Systèmes Moléculaires Complexes, Nancy Université.
    Fort, Y.
    Laboratoire de Structure et Réactivité des Systèmes Moléculaires Complexes, Nancy Université.
    Soldatov, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    McRae, Edward
    Institut Jean Lamour, CNRS – Nancy Université.
    Effects on Raman spectra of functionalisation of single walled carbon nanotubes by nitric acid2011In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 248, no 11, p. 2552-2555Article in journal (Refereed)
    Abstract [en]

    In the ultimate aim of grafting a fluorescent group on carbon nanotubes (CNTs) using COOH functions as anchoring groups, it was realised that optimisation of the carboxylation step of the CNTs was essential in the overall process. To reach this goal, three different treatment times with refluxed nitric acid have been tested: 2, 5 and 10 h. Electron microscopy has allowed evaluating the microstructure changes and the chemical composition on a local level. Raman spectroscopy has revealed a number of interesting evolutions especially in the D and G bands spectral region. It seems that residual nitric acid molecules may partially transfer charge to CNTs, giving rise to a doping effect, as is well known in graphite intercalation compounds

  • 15. Mases, Mattias
    et al.
    You, Shujie
    Weir, Samuel T.
    Lawrence Livermore National Laboratory.
    Evans, William J.
    Lawrence Livermore National Laboratory.
    Volkova, Yana
    Ural State University.
    Tebenkov, Alexander
    Ural State University.
    Babushkin, Alexey N.
    Ural State University.
    Vohra, Yogesh K.
    University of Alabama at Birmingham.
    Samudrala, G.
    University of Alabama at Birmingham.
    Soldatov, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    In situ electrical conductivity and Raman study of C60 tetragonal polymerat high pressures up to 30 GPa2010In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 274, no 11/12, p. 3068-3071Article in journal (Refereed)
    Abstract [en]

    Theory predicts that tetragonal polymeric C60 will undergo a phase transition into a metallic phase at pressures around 20 GPa. Raman and structural experiments at high pressures confirmed formation of a new phase above 20 GPa although the question about its electrical properties was still open. We report on the first simultaneous in situ study of vibrational and electrical properties of two-dimensional (2D) tetragonal C60 polymer at pressures up to 30 GPa in a diamond anvil cell (DAC) specially designed for this purpose. Our results reveal an anomaly in Raman spectra and a drop in electrical resistance of the sample at 20-25 GPa. We tentatively associate this anomalous behaviour with a phase transition into the conductive phase although its metallic character is yet to be proven.At high pressures the Raman spectra exhibit a high degree of disorder. Upon pressure release the order was partially restored and, more importantly, a significant amount of the initial 2D polymeric phase was recovered.

  • 16.
    Müller, Andreas
    et al.
    Luleå tekniska universitet.
    Vigolo, Brigitte
    Institut Jean Lamour, CNRS – Nancy Université.
    McRae, Edward
    Institut Jean Lamour, CNRS – Nancy Université.
    Soldatov, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Raman study of inhomogeneities in carbon nanotube distribution in CNT-PMMA composites2010In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 247, no 11-12, p. 2810-2813Article in journal (Refereed)
    Abstract [en]

    This work is aimed at characterization of the carbon nanotube (CNT) distribution in polymethyl methacrylate (PMMA)-CNT composites by high-resolution Raman spectroscopy. In particular, we focus on study of the boundary regions between the CNT aggregates and the surrounding areas where the CNTs are well dispersed in the PMMA matrix. Different laser excitation energies (1.96 and 2.33 eV) were used to preferentially probe metallic and semiconducting SWCNTs, respectively. At both photon energies, spectral line scans across the boundary regions were performed revealing a substantial drop in intensity of G+ CNT Raman mode and an increase of the D/G+-intensity ratio. The latter testifies to a preferential dispersion of functionalized CNTs in the PMMA matrix. Certain inhomogeneities were observed by Raman spectral imaging even in the areas with well-dispersed CNTs.

  • 17. Olevik, David
    et al.
    Soldatov, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Dossot, M.
    Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, Nancy Université.
    Vigolo, B.
    Laboratoire de Chimie du Solide Minéral, Nancy Université.
    Humbert, B.
    Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, Nancy Université.
    McRae, E,
    Laboratoire de Chimie du Solide Minéral, Nancy Université.
    Stability of carbon nanotubes to laser irradiation probed by Raman spectroscopy2008In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 245, no 10, p. 2212-2215Article in journal (Refereed)
    Abstract [en]

    We report on a systematic study of the influence of laser irradiation on the Raman spectra of HiPco-produced single-wall CNTs. Specifically, we have examined the Raman response of bundled CNTs to: i) laser power density; ii) exposure time and iii) photon energy (1.96 and 2.33 eV). Our results show that irreversible destruction of CNTs in the bundles can occur at even low laser power density (0.15 kW/cm2). The tubes with smaller diameters are influenced first and the rate of CNT destruction increases with photon energy. Finally, we determined that when investigating destruction of CNT bundles, the use of a low laser power density is required because changes in the structure of the bundles can lead to sample temperature changes for otherwise identical measurement parameters. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

  • 18.
    Silvera, Isaac F.
    et al.
    Harvard University.
    Chijioke, Akobuije D.
    Harvard University.
    Nellis, W.J.
    Harvard University.
    Soldatov, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Tempere, J.
    Universiteit Antwerpen.
    Calibration of the ruby pressure scale to 150 GPa2007In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 244, no 1, p. 460-467Article in journal (Refereed)
    Abstract [en]

    For many years the ruby pressure standard has been the so-called quasi-hydrostatic scale of Mao, Xu, and Bell published in 1986. The calibration was determined by X-ray diffraction of metal markers in an argon pressurization medium to 80 GPa, along with simultaneous measurement of the shift of the ruby R lines. We have used data in the literature, as well as our own, mostly for ruby in quasi-hydrostatic helium, to produce a new ruby scale with calibration data that extends to 150 GPa. The new scale shows that at the highest shifts of the ruby R lines the pressures are substantially higher than on the old scale. To understand small systematic shifts of the pressures as determined from the X-ray diffraction of metal "markers" used in the calibration, a finite element analysis of quasi-hydrostatic conditions in a diamond anvil cell has been carried out.

1 - 18 of 18
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