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| 2. |
- Ding, Feng, 1970, et al.
(författare)
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Graphitic encapsulation of catalyst particles in carbon nanotube production
- 2006
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-5207 .- 1520-6106. ; 110:15, s. 7666-7670
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Tidskriftsartikel (refereegranskat)abstract
- A new model is proposed for the encapsulation of catalyst metal particles by graphite layers that are obtained, for example, in low-temperature chemical vapor deposition production of carbon nanotubes (CNTs). In this model graphite layers are primarily formed from the dissolved carbon atoms in the metal-carbide particle when the particle cools. This mechanism is in good agreement with molecular dynamics simulations (which show that precipitated carbon atoms preferentially form graphite sheets instead of CNTs at low temperatures) and experimental results (e.g., encapsulated metal particles are found in low-temperature zones and CNTs in high-temperature regions of production apparatus, very small catalyst particles are generally not encapsulated, and the ratio of the number of graphitic layers to the diameter of the catalyst particle is typically 0.25 nm(-1)).
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| 3. |
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| 4. |
- Harutyunyan, Avetik, et al.
(författare)
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Hidden features of the catalyst nanoparticles favorable for single-walled carbon nanotube growth
- 2007
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Ingår i: APPLIED PHYSICS LETTERS. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 90:16
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Tidskriftsartikel (refereegranskat)abstract
- Combining in situ studies of the catalyst activity during single-walled carbon nanotube (SWCNT) growth by mass spectrometry with differential scanning calorimetry and Raman spectroscopy results, the authors expose the favorable features of small catalyst for SWCNT growth and their relationship with synthesis parameters. The sequential introduction of C-12 and C-13 labeled hydrocarbon reveals the influence of catalyst composition on its lifetime and the growth termination path. Ab initio and molecular dynamics simulations corroborate "V"-shape liquidus line of metal-carbon nanoparticle binary phase diagram, which explains observed carbon-induced solid-liquid-solid phase transitions during nanotube growth.
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| 5. |
- Larsson, Andreas, et al.
(författare)
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Modelling of Carbon Nanotube Catalytic Growth
- 2008
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Konferensbidrag (refereegranskat)abstract
- Carbon nanotubes (CNTs) have; due to their remarkable mechanical; electronic and thermal properties; many suggested uses; and have even been demonstrated as interconnects and nano-transistors in laboratory built devices [1-4]. The reason CNTs are not yet incorporated into electronics is due to growth control and placement issues. With present day state-of-the-art techniques it is not possible to grow CNTs with only one property (i.e. either all metallic or all semiconducting); which presents the first and principal hurdle for the utilisation of CNTs in semiconductor industry. It is; however; possible to grow CNTs of a certain type (multi-walled; double-walled; or single walled); within a rather narrow diameter distribution. It is also well understood how the orientation of the honey-comb structure relative to the CNT axis determines the property of the CNT itself. The problem lies in realizing growth of CNTs with control over this internal graphene structuring. We have performed first-principles calculations of how single-walled carbon nanotubes (SWNTs) bond with different metal nanoparticles explaining why the traditional catalysts (Fe; Co; Ni) are more successful than other metals (Cu; Pd; Au) [5]; and how this realization relates to new nanocomposite catalyst particles (Cu/Mo) [6]. We will present our contribution to understanding the mechanism of catalytic CNT growth; since it is only through better knowledge that property-controlled growth of CNTs can be achieved
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| 7. |
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| 8. |
- Romero, H E, et al.
(författare)
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Atom collision-induced resistivity of carbon nanotubes
- 2005
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Ingår i: SCIENCE. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 307:5706, s. 89-93
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Tidskriftsartikel (refereegranskat)abstract
- We report the observation of unusually strong and systematic changes in the electron transport in metallic single-walled carbon nanotubes that are undergoing collisions with inert gas atoms or small molecules. At fixed gas temperature and pressure, changes in the resistance and thermopower of thin films are observed that scale as roughly M-1/3, where M is the mass of the colliding gas species (He, Ar, Ne, Kr, Xe, CH4, and N-2). Results of molecular dynamics simulations are also presented that show that the maximum deformation of the tube wall upon collision and the total energy transfer between the colliding atom and the nanotube also exhibit a roughly M-1/3 dependence. it appears that the transient deformation (or dent) in the tube wait may provide a previously unknown scattering mechanism needed to explain the atom collision-induced changes in the electrical transport.
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| 9. |
- Sizov, Andrey, 1989, et al.
(författare)
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Thermal conductivity versus depth profiling of inhomogeneous materials using the hot disc technique
- 2016
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 87:7, s. 074901-
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Tidskriftsartikel (refereegranskat)abstract
- Transient measurements of thermal conductivity are performed with hot disc sensors on samples having a thermal conductivity variation adjacent to the sample surface. A modified computational approach is introduced, which provides a method of connecting the time-variable to a corresponding depth-position. This allows highly approximate—yet reproducible—estimations of the thermal conductivity vs. depth. Tests are made on samples incorporating different degrees of sharp structural defects at a certain depth position inside a sample. The proposed methodology opens up new possibilities to perform non-destructive testing; for instance, verifying thermal conductivity homogeneity in a sample, or estimating the thickness of a deviating zone near the sample surface (such as a skin tumor), or testing for presence of other defects
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