| 1. |
- Makarova, Tatiana L, et al.
(författare)
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Conductivity of two-dimensional C60 polymers
- 2000
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Ingår i: Proceedings of the 4th International Workshop on Fullerenes and Atomic Clusters (IWFAC'99), St. Petersburg 1999. - : Overseas Publishers Association N.V.. ; , s. 151-156
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Konferensbidrag (refereegranskat)abstract
- The general trend in the shift of electronic properties as the result of polymerization has been studied with the aid of temperature dependences of conductivity. Samples representing the pure rhombohedral phase exhibit great anisotropy in their electrical properties. The main features of the behaviour of these samples are: (i) in the z-direction the resistivity is of the order of several kOhm cm and decreases with temperature; (ii) in the x-y direction resistivity is less than 1 Ohm cm and shows a minimum at a certain temperature.
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| 2. |
- Makarova, Tatiana L, et al.
(författare)
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Electrical properties of the rhombohedral C60 polymers
- 1999
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Ingår i: Fullerenes: Recent Advances in the Chemistry and Physics of Fullerenes and Related Materials, vol. 7. - Pennington, NJ : The Electrochemical Society. - 1566772346 ; , s. 628-639
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Konferensbidrag (refereegranskat)abstract
- Electrical properties of polymerized fullerenes C60 are governed by the type of polymerization which is in turn determined by the initial (P or H) orientation of molecules, the pressure and the temperature of polymerization. The mixed tetragonal - rhombohedral polymerized structure shows a semiconductor-like behavior. An increase in the polymerization temperature results in a decrease in the activation energy and an increase in conductivity. The conductivity prefactor and the activation energy are interconnected by the Meyer-Neldel rule. The pure rhombohedral phase shows highly anisotropic electrical properties. The conductivity in the polymerized (111) planes exhibits a metal-insulator transition and shows the features of 2D weak localization.
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| 3. |
- Malolepszy, A, et al.
(författare)
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Deactivation resistant Pd-ZrO2 supported on multiwall carbon nanotubes catalyst for direct formic acid fuel cells
- 2015
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Ingår i: International journal of hydrogen energy. - : Elsevier. - 0360-3199 .- 1879-3487. ; 40:46, s. 16724-16733
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Tidskriftsartikel (refereegranskat)abstract
- One of the main problems of palladium based catalysts for a direct formic acid fuel cell (DFAFC) is their low stability during a long-term operation. In these studies, the Pd–ZrO2 catalyst supported on the multiwall carbon nanotubes (MWCNTs) was prepared and thermo-chemically treated. These catalysts were tested in a fuel cell for formic acid electrooxidation, and their chemical composition and structure were characterised by the XPS, STEM, HR-TEM and XRD techniques.It was found that the Pd–ZrO2/MWCNTs catalyst after synthesis causes oscillations of the cell voltage during operation resulting in significantly higher deactivation resistance than that of Pd/MWCNTs. This may be attributed to the “self-cleaning” mechanism of poisoned Pd catalyst by carbon monoxide through the electrochemical oxidation of COads (adsorbed) to CO2 (gas).
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| 4. |
- Barzegar, Hamid Reza, et al.
(författare)
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Electrostatically Driven Nanoballoon Actuator
- 2016
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Ingår i: Nano letters (Print). - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 16:11, s. 6787-6791
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate an inflatable nanoballoon actuator based on geometrical transitions between the inflated (cylindrical) and collapsed (flattened) forms of a carbon nanotube. In situ transmission electron microscopy experiments employing a nanoelectromechanical manipulator show that a collapsed carbon nanotube can be reinflated by electrically charging the nanotube, thus realizing an electrostatically driven nanoballoon actuator. We find that the tube actuator can be reliably cycled with only modest control voltages (few volts) with no apparent wear or fatigue. A complementary theoretical analysis identifies critical parameters for nanotube nanoballoon actuation.
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| 5. |
- Barzegar, Hamid Reza, et al.
(författare)
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Spontaneous twisting of a collapsed carbon nanotube
- 2017
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Ingår i: Nano Reseach. - : Tsinghua University Press. - 1998-0124 .- 1998-0000. ; 10:6, s. 1942-1949
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Tidskriftsartikel (refereegranskat)abstract
- We study the collapsing and subsequent spontaneous twisting of a carbon nanotube by in situ transmission electron microscopy (TEM). A custom-sized nanotube is first created in the microscope by selectively extracting shells from a parent multi-walled tube. The few-walled, large-diameter daughter nanotube is driven to collapse via mechanical stimulation, after which the ribbon-like collapsed tube spontaneously twists along its long axis. In situ diffraction experiments fully characterize the uncollapsed and collapsed tubes. The experimental observations and associated theoretical analysis indicate that the origin of the twisting is compressive strain.
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| 6. |
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| 7. |
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| 8. |
- Gernandt, Renate, et al.
(författare)
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Polyelectrolyte complexes for surface modification of wood fibres - I. Preparation and characterisation of complexes for dry and wet strength improvement of paper
- 2003
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Ingår i: Colloids and Surfaces A. - 0927-7757 .- 1873-4359. ; 213:1, s. 15-25
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Tidskriftsartikel (refereegranskat)abstract
- Polyelectrolyte complexes (PEC) were formed between a cationic polyamideamine epichlorohydrine condensate (PAE) and an anionic carboxymethylcellulose (CMC) at different ratios between the polymers, orders of mixing, salt concentrations and polymer concentrations. Initially the polymers were characterised by polyelectrolyte titration (charge), static light scattering (molecular weight, radius of gyration) and measurements with a scanning interferometric refractometer (refractive index). The complexes were characterised by ocular inspection and static light scattering in combination with a special evaluation algorithm allowing an estimation of the geometric form of the complexes. The results show that the initial complexes have a spherical form and that the size is fairly constant over a large range of charge ratios between the polymers, provided the complexes are formed in deionised water. When the charge mixing ratio exceeded neutrality a secondary agglomeration of the initially formed complexes occurred. The presence of salt during PEC formation caused a dependence of the level of aggregation on the mixing ratio, whereby small amounts of NaCl drastically lowered the particle mass at lower mixing ratios. Subsequent addition of salt to PECs formed in water led to a strong swelling of the complex particles and at a critical salt concentration to dissolution.
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| 9. |
- Görür, Yunus Can, et al.
(författare)
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Rapidly Prepared Nanocellulose Hybrids as Gas Barrier, Flame Retardant, and Energy Storage Materials
- 2022
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Ingår i: ACS Applied Nano Materials. - : American Chemical Society (ACS). - 2574-0970. ; 5:7, s. 9188-9200
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Tidskriftsartikel (refereegranskat)abstract
- Cellulose nanofibril (CNF) hybrid materials show great promise as sustainable alternatives to oil-based plastics owing to their abundance and renewability. Nonetheless, despite the enormous success achieved in preparing CNF hybrids at the laboratory scale, feasible implementation of these materials remains a major challenge due to the time-consuming and energy-intensive extraction and processing of CNFs. Here, we describe a scalable materials processing platform for rapid preparation (<10 min) of homogeneously distributed functional CNF-gibbsite and CNF-graphite hybrids through a pH-responsive self-assembly mechanism, followed by their application in gas barrier, flame retardancy, and energy storage materials. Incorporation of 5 wt % gibbsite results in strong, transparent, and oxygen barrier CNF-gibbsite hybrid films in 9 min. Increasing the gibbsite content to 20 wt % affords them self-extinguishing properties, while further lowering their dewatering time to 5 min. The strategy described herein also allows for the preparation of freestanding CNF-graphite hybrids (90 wt % graphite) that match the energy storage performance (330 mA h/g at low cycling rates) and processing speed (3 min dewatering) of commercial graphite anodes. Furthermore, these ecofriendly electrodes can be fully recycled, reformed, and reused while maintaining their initial performance. Overall, this versatile concept combines a green outlook with high processing speed and material performance, paving the way toward scalable processing of advanced ecofriendly hybrid materials.
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| 10. |
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