| 1. |
- Asanou, I. P., et al.
(författare)
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Graphene nanochains and nanoislands in the layers of room-temperature fluorinated graphite
- 2013
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Ingår i: Carbon. - : Elsevier. - 0008-6223 .- 1873-3891. ; 59, s. 518-529
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Tidskriftsartikel (refereegranskat)abstract
- Intercalated compound of graphite fluoride with n-heptane has been synthesized at room temperature using a multi-stage process including fluorination by a gaseous BrF3 and a set of intercalant exchange reactions. It was found that composition of the compound is CF0.40(C7H16)(0.04) and the guest molecules interact with the graphite fluoride layers through the van der Waals forces. Since the distance between the filled layers is 1.04 nm and the unfilled layers are separated by similar to 0.60 nm, the obtained compound can be considered as a stack of the fluorinated graphenes. These fluorinated graphenes are large in area making it possible to study local destruction of the a conjugated system on the basal plane. It was shown that fluorine atoms form short chains, while non-fluorinated sp(2) carbon atoms are organized in very narrow ribbons and aromatic areas with a size smaller than 3 nm. These pi electron nanochains and nanoislands preserved after the fluorination process are likely responsible for the value of the energy gap of the compound of similar to 2.5 eV. Variation in the size and the shape of pi electron regions within the fluorinated graphene layers could be a way for tuning the electronic and optical characteristics of the graphene-based materials.
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| 2. |
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| 3. |
- Biryulin, YF, et al.
(författare)
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Strongly non-linear carbon nanofibre influence on electrical properties of polymer composites
- 2008
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Ingår i: Fullerenes, nanotubes, and carbon nanostructures. - : Informa UK Limited. - 1536-383X .- 1536-4046. ; 16:5-6, s. 629-633
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Tidskriftsartikel (refereegranskat)abstract
- Composites of carbon nanofibres (CNF) (30-50 nm diam., length up to 1 mu m) in two polymer matrices (polybutadiene-styrene and polypyrrhol) show strong non-linearities of conductivity vs. CNF concentration. We have studied their voltage-current dependencies, and observed correlation of their extrema and layer morphology. Multistability of conductivity is discovered, with apparent effect of magnetic field effect on it in polypyrrhol-based composites. In addition CNF spatial configuration influence on layers' conductivity is discussed.
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| 4. |
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| 5. |
- Buga, Sergei G., et al.
(författare)
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Electrical properties of 3D-polymeric crystalline and disordered C60 and C70 fullerites.
- 2005
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Ingår i: Diamond and Related Materials vol. 14, special Issue (3-7). - : Elsevier B.V.. ; , s. 896-901
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Konferensbidrag (refereegranskat)abstract
- Crystalline and disordered 3D-polymeric C60 and C70 with different lattice parameters and with densities in the range of 2.2÷3.25 g cm−1 were obtained by high-pressure-high-temperature treatment at P=11.5÷15 GPa, T=670÷1800 K. Their d.c. electrical conductivity was investigated at temperatures 30÷350 K. The variable range hopping mechanism dominates in all samples up to room temperature. A temperature activated conductivity via delocalized states was observed at T>160÷260 K in crystalline C60 samples and in some samples with disordered structure. The evaluated band gap value is Eg=0.28÷0.54 eV for different crystalline structures and 0.06÷0.25 eV for disordered ones
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| 6. |
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Carbon based magnetism : an overview of the magnetism of metal free carbon-based compounds and materials
- 2006
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Samlingsverk (redaktörskap) (övrigt vetenskapligt/konstnärligt)abstract
- Carbon Based Magnetism is the most complete, detailed, and accurate guide on the magnetism of carbon, the main element of living creatures. Written by the leading experts in the field, the book provides a comprehensive review of relevant experimental data and theoretical concepts related to the magnetism of metal-free carbon systems. These systems include carbon based compounds, namely organic radical magnetic systems, and magnetic materials based on carbon structures. The aim is to advance the understanding of the fundamental properties of carbon. This volume discusses all major modern hypotheses on the physical nature of magnetic ordering in carbon systems. The first chapters deal with magnetic ordering mechanisms in p-electron systems as well as molecular magnets with spins residing only in p-orbitals. The following chapters explore the magnetic properties of pure carbon, with particular emphasis on nanosized carbon systems with closed boundary (fullerenes and nanotubes) and with open boundary (structures with edge-localized magnetic states). The remaining chapters focus on newer topics: experimental observation and theoretical models for magnetic ordering above room temperature in pure carbon. The book also includes twenty three review articles that summarize the most significant recent and ongoing exciting scientific developments and provide the explanation. It also highlights some problems that have yet to be solved and points out new avenues for research. This book will appeal to physicists, chemists and biologists.
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| 7. |
- Danishevskii, AM, et al.
(författare)
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Characteristics of magnetism in nanoporous carbon with palladium clusters
- 2011
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Ingår i: Physics of the solid state. - 1063-7834 .- 1090-6460. ; 53:5, s. 1017-1024
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Tidskriftsartikel (refereegranskat)abstract
- The magnetic properties of samples of nanoporous carbon with palladium clusters prepared from polycrystalline SiC have been studied over a wide range of temperatures. The specific magnetic moment rapidly decreases with increasing temperature. The obtained experimental magnetization curves have a nonlinear character but do not reach saturation even in a field of 10 kOe. Being constructed as functions of H/T, they lie on a universal curve, which suggests superparamagnetism of the system. The experimental curves have a hysteresis. The coercive force, first, decreases with increasing temperature and, then (in the range of 5–20 K), increases, thus forming a notch singularity. On the contrary, the residual magnetization rapidly decreases with increasing temperature. A conclusion on the prevailing contribution of superparamagnetic clusters to the magnetic subsystem is made.
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| 8. |
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| 9. |
- Han, Kyoo-Hyun, et al.
(författare)
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Proton bombardment of Hard Carbon
- 2006
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Ingår i: Fullerenes, Nanotubes and Carbon Nanostructures vol. 14 issue 2&3. - : Informa UK Limited. ; , s. 381-384
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Konferensbidrag (refereegranskat)
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| 10. |
- Iwasiewicz-Wabnig, Agnieszka, et al.
(författare)
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Absence of an insulator-metal transition in Rb4C60 up to 2 GPa
- 2008
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Ingår i: Physical Review B. - 0163-1829. ; 77:8, s. 085434-
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Tidskriftsartikel (refereegranskat)abstract
- We present the results of direct resistance measurements on Rb4C60 under pressures up to 2 GPa. At all pressures covered by this study and over the temperature range of 90–450 K Rb4C60 is a semiconductor with a weakly pressure dependent band gap near 0.7 eV. We do not observe the insulator-to-metal transition previously reported to occur below 1.2 GPa, although we cannot rule out the possibility that such a transition might occur at some significantly higher pressure. The measured resistivity is surprisingly low and is dominated by carriers excited over a 0.1 eV gap. Because the corresponding conductivity increases with deformation of the sample, we assign these states to structural or orientational defects. The known structural transformation below 0.5 GPa leads to a decrease in resistivity under high pressure, but the material remains semiconducting. A Rb6C60 control sample showed a similar behavior, also being a semiconductor under all conditions studied. At temperatures above 460 K, Rb was partially lost from our samples, resulting in metallization by a transformation into Rb3C60.
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