Interfacial Thermal Transport in Carbon Nanotubes

2009 ◽  
Author(s):  
Satish Kumar ◽  
Jayathi Y. Murthy
Keyword(s):  
Carbon Nanotubes ◽  
Energy Transport ◽  
Pulse Propagation ◽  
High Energy ◽  
Dynamics Simulation ◽  
Phonon Modes ◽  
Thermal Pulse ◽  
Slow Moving ◽  
Wavelet Methods ◽  
Wavelet Transformations

There is significant amount of research to analyze the thermal, electrical and other physical properties of carbon nanotubes (CNTs). However, the energy transport mechanism at the contact of two tubes is still not well understood. This study investigates the interfacial thermal interaction between two carbon nanotubes using molecular dynamics simulation and wavelet methods. We place the tubes in a crossed configuration and pass a high temperature pulse along one of the CNTs while keeping other ends fixed, and analyze the interaction of this pulse with other nanotube. We apply this technique for nanotubes of chirality in the range of (5,0) to (10,0) to observe the response of tubes with changing diameter. This thermal pulse analysis shows that the coupling between the two tubes is very weak and may be dominated by the slow moving phonon modes with high energy. We perform a wavelet analysis of thermal pulse propagation along a CNT and its impact on another CNT in cross contact. Wavelet transformations of the heat pulse show how different phonon modes are excited and how they evolve and propagate along the tube axis depending on its chirality.

scholarly journals Modelling Dispersion Compensation in a Cascaded-Fiber-Feedback Optical Parametric Oscillator

Optics ◽  
2021 ◽  
Vol 2 (2) ◽  
pp. 96-102
Author(s):  
Ewan Allan ◽  
Craig Ballantine ◽  
Sebastian C. Robarts ◽  
David Bajek ◽  
Richard A. McCracken
Keyword(s):  
Pulse Propagation ◽  
Dispersion Compensation ◽  
Numerical Aperture ◽  
Tunable Laser ◽  
High Energy ◽  
Order Effects ◽  
Optical Parametric Oscillators ◽  
Fiber System ◽  
Parametric Oscillators ◽  
Optical Parametric

Fiber-feedback optical parametric oscillators (OPOs) incorporate intracavity fibers to provide a compact high-energy wavelength-tunable laser platform; however, dispersive effects can limit operation to the sub-picosecond regime. In this research article, we modeled pulse propagation through systems of cascaded fibers, incorporating SMF-28 and ultra-high numerical aperture (UHNA) fibers with complementary second-order dispersion coefficients. We found that the pulse duration upon exiting the fiber system is dominated by uncompensated third-order effects, with UHNA7 presenting the best opportunity to realise a cascaded-fiber-feedback OPO.

scholarly journals Confine sulfur in double-hollow carbon sphere integrated with carbon nanotubes for advanced lithium–sulfur batteries

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Maru Dessie Walle ◽  
You-Nian Liu
Keyword(s):  
Carbon Nanotubes ◽  
Coulombic Efficiency ◽  
Specific Capacity ◽  
High Energy ◽  
High Energy Density ◽  
Carbon Sphere ◽  
Hollow Carbon Sphere ◽  
Lithium Sulfur Batteries ◽  
Hollow Carbon ◽  
Lithium Sulfur

AbstractThe lithium–sulfur (Li–S) batteries are promising because of the high energy density, low cost, and natural abundance of sulfur material. Li–S batteries have suffered from severe capacity fading and poor cyclability, resulting in low sulfur utilization. Herein, S-DHCS/CNTs are synthesized by integration of a double-hollow carbon sphere (DHCS) with carbon nanotubes (CNTs), and the addition of sulfur in DHCS by melt impregnations. The proposed S-DHCS/CNTs can effectively confine sulfur and physically suppress the diffusion of polysulfides within the double-hollow structures. CNTs act as a conductive agent. S-DHCS/CNTs maintain the volume variations and accommodate high sulfur content 73 wt%. The designed S-DHCS/CNTs electrode with high sulfur loading (3.3 mg cm−2) and high areal capacity (5.6 mAh mg cm−2) shows a high initial specific capacity of 1709 mAh g−1 and maintains a reversible capacity of 730 mAh g−1 after 48 cycles at 0.2 C with high coulombic efficiency (100%). This work offers a fascinating strategy to design carbon-based material for high-performance lithium–sulfur batteries.

Cohesive Zone Model for the Interface of Multiwalled Carbon Nanotubes and Copper: Molecular Dynamics Simulation

2014 ◽  
Vol 5 (3) ◽  
Author(s):  
Ibrahim Awad ◽  
Leila Ladani
Keyword(s):  
Carbon Nanotubes ◽  
Normal Stress ◽  
Multiwalled Carbon Nanotubes ◽  
Cohesive Zone ◽  
Large Scale ◽  
Cohesive Zone Model ◽  
Dynamics Simulation ◽  
Zone Model ◽  
Multiwalled Carbon ◽  
Significant Difference

Due to their superior mechanical and electrical properties, multiwalled carbon nanotubes (MWCNTs) have the potential to be used in many nano-/micro-electronic applications, e.g., through silicon vias (TSVs), interconnects, transistors, etc. In particular, use of MWCNT bundles inside annular cylinders of copper (Cu) as TSV is proposed in this study. However, the significant difference in scale makes it difficult to evaluate the interfacial mechanical integrity. Cohesive zone models (CZM) are typically used at large scale to determine the mechanical adherence at the interface. However, at molecular level, no routine technique is available. Molecular dynamic (MD) simulations is used to determine the stresses that are required to separate MWCNTs from a copper slab and generate normal stress–displacement curves for CZM. Only van der Waals (vdW) interaction is considered for MWCNT/Cu interface. A displacement controlled loading was applied in a direction perpendicular to MWCNT's axis in different cases with different number of walls and at different temperatures and CZM is obtained for each case. Furthermore, their effect on the CZM key parameters (normal cohesive strength (σmax) and the corresponding displacement (δn) has been studied. By increasing the number of the walls of the MWCNT, σmax was found to nonlinearly decrease. Displacement at maximum stress, δn, showed a nonlinear decrease as well with increasing the number of walls. Temperature effect on the stress–displacement curves was studied. When temperature was increased beyond 1 K, no relationship was found between the maximum normal stress and temperature. Likewise, the displacement at maximum load did not show any dependency to temperature.

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