| 1. |
- Mases, Mattias, et al.
(författare)
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Comparative study of double walled carbon nanotubes exposed to shock wave (dynamic) vs static compression
- 2013
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Ingår i: Book of Abstracts, 7th EEIGM International Conference on Advanced Materials Research. ; , s. 3-
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Konferensbidrag (refereegranskat)abstract
- We present the study of double walled carbon nanotubes (DWNTs) after application of shock wave (dynamic) compression in a recovery assembly. In the different shock wave experiments the pressure was ramped to a certain level (14, 19, 26 and 36 GPa) with a new CNT sample but always from the same source batch. The recovered samples were characterized by Raman, XPS and HRTEM revealing outer wall disruption along with unzipping and shortening of the CNTs. The carbon nanotube destruction due to temperature increase is minor compared to the effect of the shock wave for the short exposure times in the experiment. Structural damage of the CNTs increases with the shock pressure. Simultaneously, the Raman data exhibit a gradual increase of D/G-band intensity ratio. On the contrary, recent experiments in a diamond anvil cell (DAC) demonstrate high structural stability of DWCNTs exposed to a static pressure of 35 GPa. The ID/IG-ratio after exposure to static pressure starts to increase only after a clear threshold corresponding to the tubes collapse pressure. Remarkably, there are indications that the largest diameter CNTs were destroyed (RBM signal disappeared) by application of the highest shock contrary to the behavior of DWNTs at comparable static pressures. Along with the nature of the applied pressure, we discuss other possible reasons which may have caused such an effect.
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| 2. |
- Mases, Mattias, et al.
(författare)
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Effects on Raman spectra of functionalisation of single walled carbon nanotubes by nitric acid
- 2011
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Ingår i: Physica status solidi. B, Basic research. - : Wiley. - 0370-1972 .- 1521-3951. ; 248:11, s. 2552-2555
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Tidskriftsartikel (refereegranskat)abstract
- 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
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| 3. |
- Mases, Mattias, et al.
(författare)
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In situ electrical conductivity and Raman study of C60 tetragonal polymerat high pressures up to 30 GPa
- 2010
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Ingår i: Physica status solidi. B, Basic research. - : Wiley. - 0370-1972 .- 1521-3951. ; 274:11/12, s. 3068-3071
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 4. |
- Mases, Mattias, et al.
(författare)
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Laser-induced damage and destruction of HiPCO nanotubes in different gas environments
- 2011
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Ingår i: Physica status solidi. B, Basic research. - : Wiley. - 0370-1972 .- 1521-3951. ; 248:11, s. 2540-2543
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 5. |
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| 6. |
- Mases, Mattias
(författare)
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Nanostructured carbon materials under extreme conditions
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The discovery of the Buckminsterfullerene in 1985 by Richard Smalley, Robert Curl and Harold Kroto opened an era of great interest to the exploration of nanostructured carbon materials. These materials come in many forms and are often categorized by their dimensionality. Graphene is an ideal 2-dimensional (2D) sheet of sp2-bonded carbon atoms. A carbon nanotube (CNT) is a graphene sheet rolled up into a 1D structure and the Buckminsterfullerene is a 0D truncated icosahedron comprised of 60 carbon atoms. Graphene can be stacked in two, three or more layers on top of each other forming graphite as the number of layers approaches infinity. CNTs can consist of a single roll of graphene or one or more rolls inside another and are hence referred to as single, double or multi walled (SW/DW/MW) CNTs. Fullerenes are distinguished by their size and are referred to as Cn where n is the number of carbon atoms in the molecule. The Buckminsterfullerene, comprising 60 carbon atoms, is consequently denoted C60. Nanostructured carbon materials exhibit outstanding physical properties like extreme strength and hardness, high electrical and thermal conductivity, efficient optical emission to name just a few. Though these systems have been extensively studied during recent years many outstanding questions, in particular, their behaviour at extreme conditions like high temperature and high pressure still remain to be answered. Aim of this work is to probe nanocarbon materials at the limit of their structural stability using pressure and temperature as variables. High temperature can be reached in different ways but laser heating, being of practical importance during characterization of nanostructured carbon materials, is in focus here. High static pressures are generated in diamond anvil cells (DACs) while high dynamic pressure can be achieved in a shock wave assembly where the material is simultaneously exposed to high pressure and high temperature during microsecond time spans. The primary characterization technique is Raman spectroscopy and transmission electron microscopy (TEM) although complementary methods such as energy dispersive X-ray spectroscopy, thermo-gravimetric analysis, mass spectrometry and X-ray photoelectron spectroscopy have also been employed. We have studied the thermal and chemical stability of SWCNT bundles to high laser power in air and argon. The samples were exposed to 110 kWcm−2 of laser irradiation bringing the sample temperature up to 870º C and 550º C under argon and air respectively. The experiments in air show the importance of oxidation during laser heating. Our results demonstrate different temperature thresholds for the CNT destruction due to oxidation and pure overheating. Importantly, the small diameter CNTs are more easily destroyed than large diameter ones. The metallic nanotubes also tend to have lower thermal stability in comparison to semiconducting species. SWCNTs exposed to 35GPa of static compression were compared to material from the same batch exposed to 35GPa of dynamic compression. Raman studies indicate differences in the CNT destruction process between the two methods of pressurization. The SWCNTs exposed to high static compression were albeit highly defective partially retrieved whereas the SWCNTs exposed to high dynamic compression were essentially destroyed as further supported by transmission electron microscopy analysis. On the contrary, no significant differences were revealed between SWCNTs and DWCNTs recovered after exposure to dynamic compression in spite of the expected higher structural stability of the DWCNTs. A series of experiments was dedicated to an in-situ monitoring of DWCNTs response to a static pressure of up to 35GPa in a DAC via recording their Raman spectra. An onset of the CNTs cross section change was observed at 14GPa followed by their collapse at 24GPa. Strong hysteresis in the nanotubes’ cross-section recovery was revealed on pressure release and a complete reopening of the tubes occurred at 3.5GPa. Characterization of the material recovered after the high pressure experiments testifies for complete restoration of the DWCNT structure after the nanotubes’ collapse though the density of structural defects on the CNT surface increased. CNT polymerization at moderate pressures recently predicted theoretically was not confirmed in our experiments at both dynamic and static pressure. The resistance of polymerized tetragonal C60 (T-C60) was measured in situ at high pressure up to 33GPa in a DAC. The measurements reveal a sharp drop in sample resistance near 15GPa which may be an indication of and onset of a theoretically predicted phase transition into a metallic 3D polymer. T-C60 polymers retained their structural integrity after recovery from the high-pressure experiment thus demonstrating much higher resilience to high pressure/stress than monomeric C60 that, on the contrary, collapses already at about 22GPa.
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| 7. |
- Mases, Mattias, et al.
(författare)
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The effect of shock wave compression on double wall carbon nanotubes
- 2012
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Ingår i: Physica status solidi. B, Basic research. - : Wiley. - 0370-1972 .- 1521-3951. ; 249:12, s. 2378-2381
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 8. |
- Noël, Maxime, et al.
(författare)
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Effects of non-hydrostatic pressure on electrical resistance of bundled single-wall carbon nanotubes
- 2013
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Ingår i: 7th EEIGM International Conference on Advanced Materials Research. - : IOP Publishing Ltd.
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Konferensbidrag (refereegranskat)abstract
- Recent studies have shown that single wall carbon nanotubes (SWCNT) exhibit a sequence of phase transitions and demonstrate a high structural stability up to 35 GPa of quasi-hydrostatic pressure [1] beyond which an irreversible structural transformation occurs. Here we report on the study of electrical resistance of SWCNTs at pressures up to 34 GPa in the temperature range of 293 – 395 K. In the pressure range 10–25 GPathe rate of resistance change decreases considerably. We associate such behavior of the resistance with a structural modification of the SWCNTs or/and change of the conductivity character at high pressure. Raman spectra of the samples recovered after 30 GPa exhibit a large increase of defect concentration in the CNTs. Isobaric temperature dependences of the CNT resistance R(T) measured in the temperature range 300–400 K reveal some changes with pressure whereas the semiconducting character of the R(T) remains unaltered.
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| 9. |
- Noël, Maxime, et al.
(författare)
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Electrical transport in bundled single-wall carbon nanotubes under high pressure
- 2013
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Konferensbidrag (refereegranskat)abstract
- According to recent experimental data single wall carbon nanotubes (SWCNT) exhibit a sequence of phase transitions and demonstrate a high structural stability up to 35 GPa of non-hydrostatic pressure beyond which an irreversible transformation occurs. Here we report a study of electrical transport in SWCNTs at pressures up to 45 GPa in the temperature range of 300 - 400K. High pressure was generated in diamond anvil cell. The anvils are made of electrically conducting "carbonado"-type synthetic diamond. In the pressure range 10-25 GPa the CNT electrical resistance decreases considerably, whereas above 25 GPa it remains essentially unchanged. Such behaviour of the resistance can be connected to a structural modification of the SWCNTs accompanied by change of the conductivity character at high pressure. Raman spectra of the samples recovered after 30 GPa exhibit a large increase of D/G band intensity ratio. The Radial Breathing Mode part of the spectra remains essentially unaltered which testifies for structural integrity of the nanotubes after exposure to high non-hydrostatic pressure and lack of covalent interlinking between the tubes. Pressure dependences of resistance, activation energy for conductivity and charge carriers mobility were determined and discussed.
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| 10. |
- Noël, Maxime, et al.
(författare)
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Probing structural integrity of single walled carbon nanotubes by dynamic and static compression
- 2014
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Ingår i: Physica Status Solidi. Rapid Research Letters. - : Wiley. - 1862-6254 .- 1862-6270. ; 8:11, s. 935-938
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Tidskriftsartikel (refereegranskat)abstract
- We report on a first study of single walled carbon nanotubes (SWCNTs) after application of dynamic (shock) compression. The experiments were conducted at 19 GPa and 36 GPa in a recovery assembly. For comparison, an experiment at a static pressure of 36 GPa was performed on the material from the same batch in a diamond anvil cell (DAC). After the high pressure treatment the samples were characterized by Raman spectroscopy and transmission electron microscopy (TEM). After exposure to 19 GPa of shock compression the CNT material exhibited substantial structural damage such as CNT wall disruption, opening of the tube along its axis (“unzipping”) and tube shortening (“cutting”). Dynamic compression to 36 GPa resulted in essentially complete CNT destruction whereas at least a fraction of the nanotubes was recovered after 36 GPa of static compression though severely damaged. The results of these shock wave experiments underline the prospect of using SWCNTs as reinforcing units in material
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