Thermal Transport From Gold Nanorod to Solvent, an Investigation of Ligand Effects by Ultrafast Laser Spectroscopy

2008 ◽  
Author(s):  
Joshua Alper ◽  
Aaron Schmidt ◽  
Kimberly Hamad-Schifferli
Keyword(s):  
Heat Transfer ◽  
Thermal Properties ◽  
Gold Nanorods ◽  
Thermal Transport ◽  
Ultrafast Laser ◽  
Ultrafast Laser Spectroscopy ◽  
Optical Pump ◽  
Thermal Interface ◽  
Pump Probe ◽  
Ligand Effects

To facilitate analysis of nanoscale heat transfer in nanoparticle systems the thermal properties of ligand layers must be understood. To this end, we use an optical pump-probe technique to study the thermal transport across ligands on gold nanorods and into the solvent. We find that varying properties of the ligand can have large impacts on the thermal decay of a nanorod after exposure to a laser pulse. By raising the concentration of free CTAB from 1 mM and 10 mM in solutions, the CTAB layer’s effective thermal interface conductance increases three fold. The transition occurs near the CTAB critical micelle concentration. Similar results are found for other ligand layers.

scholarly journals Thermoreflectance of metal transducers for optical pump-probe studies of thermal properties

2012 ◽  
Vol 20 (27) ◽  
pp. 28829 ◽  
Author(s):  
R. B. Wilson ◽  
Brent A. Apgar ◽  
Lane W. Martin ◽  
David G. Cahill
Keyword(s):  
Thermal Properties ◽  
Optical Pump ◽  
Pump Probe

Pump-Probe Experimental Study of Phonon Reflectivity at an Interface and Phonon Relaxation Time

2005 ◽  
Author(s):  
Ronggui Yang ◽  
Xiaoyuan Chen ◽  
Aaron Schmidt ◽  
Gang Chen
Keyword(s):  
Heat Transfer ◽  
Thermal Management ◽  
Thermal Transport ◽  
Size Effects ◽  
Energy Transport ◽  
Quantum Size Effects ◽  
Pump Probe ◽  
Sensor Development ◽  
Quantum Size ◽  
Phonon Relaxation Time

Heat transfer in nanostructures differs significantly from that in macrostructures because of classical and quantum size effects on energy carriers, i.e., phonons, electrons, and photons [1–3]. Understanding thermal transport in nanostructures is of fundamental importance to a variety of technologies, including thermal management of nanoelectronics and optoelectronics, energy conversion, nanofabrication, and sensor development. A better understanding of the energy transport at nanoscale calls for both simulations and experimental techniques on thermal transport in nanostructures.

scholarly journals Modeling of Subcontinuum Thermal Transport Across Semiconductor-Gas Interfaces

2008 ◽  
Author(s):  
Dhruv Singh ◽  
Xiaohui Guo ◽  
Alina Alexeenko ◽  
Jayathi Y. Murthy ◽  
Timothy S. Fisher
Keyword(s):  
Heat Transfer ◽  
Boltzmann Equation ◽  
Thermal Transport ◽  
Phonon Transport ◽  
Interface Temperature ◽  
Molecular Flow ◽  
Parallel Plates ◽  
Thermal Interface ◽  
The Boltzmann Equation ◽  
Gas Molecules

A physically rigorous computational algorithm is developed and applied to calculate sub-continuum thermal transport in structures containing semiconductor-gas interfaces. The solution is based on a finite volume discretization of the Boltzmann equation for gas molecules (in the gas phase) and phonons (in the semiconductor). A partial equilibrium is assumed between gas molecules and phonons at the interface of the two media, and the degree of this equilibrium is determined by the accommodation coefficients of gas molecules and phonons on either side of the interface. Energy balance is imposed to obtain a value of the interface temperature. The problem of heat transfer between two parallel plates is investigated. A range of transport regimes is studied, varying from ballistic phonon transport and free molecular flow to continuum heat transfer in both gas and solid. In particular, the thermal interface resistance (or temperature slip) at a gas-solid interface is extracted in the mesoscopic regime where a solution of the Boltzmann equation is necessary. This modeling approach is expected to find applications in the study of heat conduction through microparticle beds, gas flows in microchannel heat sinks and in determining gas gap conductance in thermal interface materials.

Pump-Probe Measurements Using Silicon Nanocrystal Waveguides

2003 ◽  
Vol 770 ◽  
Author(s):  
Nathanael Smith ◽  
Max J. Lederer ◽  
Marek Samoc ◽  
Barry Luther-Davies ◽  
Robert G. Elliman
Keyword(s):  
Probe Beam ◽  
Time Resolution ◽  
Pump Beam ◽  
Silicon Nanocrystals ◽  
Continuous Wave ◽  
Optical Gain ◽  
Optical Pump ◽  
Time Resolved ◽  
Pump Probe ◽  
Probe Measurements

AbstractOptical pump-probe measurements were performed on planar slab waveguides containing silicon nanocrystals in an attempt to measure optical gain from photo-excited silicon nanocrystals. Two experiments were performed, one with a continuous-wave probe beam and a pulsed pump beam, giving a time resolution of approximately 25 ns, and the other with a pulsed pump and probe beam, giving a time resolution of approximately 10 ps. In both cases the intensity of the probe beam was found to be attenuated by the pump beam, with the attenuation increasing monotonically with increasing pump power. Time-resolved measurements using the first experimental arrangement showed that the probe signal recovered its initial intensity on a time scale of 45-70 μs, a value comparable to the exciton lifetime in Si nanocrystals. These data are shown to be consistent with an induced absorption process such as confined carrier absorption. No evidence for optical gain was observed.

Temperature Rise Times in Pneumatic Tires

1976 ◽  
Vol 4 (3) ◽  
pp. 181-189 ◽  
Author(s):  
S. K. Clark
Keyword(s):  
Heat Transfer ◽  
Thermal Properties ◽  
Temperature Rise ◽  
Thermal Equilibrium ◽  
Transfer Coefficients ◽  
Pneumatic Tire ◽  
Heat Transfer Coefficients ◽  
Idealized Model ◽  
Pneumatic Tires

Abstract An idealized model is proposed for heating of a pneumatic tire. A solution is obtained for the temperature rise of such a model. Using known thermal properties of rubber and known heat transfer coefficients, the time to reach thermal equilibrium is estimated.

scholarly journals A Thermal Transport Study of Branched Carbon Nanotubes with Cross and T-Junctions

2021 ◽  
Vol 11 (13) ◽  
pp. 5933
Author(s):  
Wei-Jen Chen ◽  
I-Ling Chang
Keyword(s):  
Heat Transfer ◽  
Carbon Nanotubes ◽  
Thermal Management ◽  
Thermal Transport ◽  
Topological Defects ◽  
Branch Length ◽  
Phonon Transport ◽  
Heat Current ◽  
Transport Mechanisms ◽  
Non Equilibrium Molecular Dynamics

This study investigated the thermal transport behaviors of branched carbon nanotubes (CNTs) with cross and T-junctions through non-equilibrium molecular dynamics (NEMD) simulations. A hot region was created at the end of one branch, whereas cold regions were created at the ends of all other branches. The effects on thermal flow due to branch length, topological defects at junctions, and temperature were studied. The NEMD simulations at room temperature indicated that heat transfer tended to move sideways rather than straight in branched CNTs with cross-junctions, despite all branches being identical in chirality and length. However, straight heat transfer was preferred in branched CNTs with T-junctions, irrespective of the atomic configuration of the junction. As branches became longer, the heat current inside approached the values obtained through conventional prediction based on diffusive thermal transport. Moreover, directional thermal transport behaviors became prominent at a low temperature (50 K), which implied that ballistic phonon transport contributed greatly to directional thermal transport. Finally, the collective atomic velocity cross-correlation spectra between branches were used to analyze phonon transport mechanisms for different junctions. Our findings deeply elucidate the thermal transport mechanisms of branched CNTs, which aid in thermal management applications.

Combined Microstructure and Heat Transfer Modeling of Carbon Nanotube Thermal Interface Materials1

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
Sridhar Sadasivam ◽  
Stephen L. Hodson ◽  
Matthew R. Maschmann ◽  
Timothy S. Fisher
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Finite Volume ◽  
Pressure Dependence ◽  
Matrix Material ◽  
Three Dimensional ◽  
Coarse Grain ◽  
Total Thermal Resistance ◽  
Thermal Interface ◽  
Cnt Arrays

A microstructure-sensitive thermomechanical simulation framework is developed to predict the mechanical and heat transfer properties of vertically aligned CNT (VACNT) arrays used as thermal interface materials (TIMs). The model addresses the gap between atomistic thermal transport simulations of individual CNTs (carbon nanotubes) and experimental measurements of thermal resistance of CNT arrays at mesoscopic length scales. Energy minimization is performed using a bead–spring coarse-grain model to obtain the microstructure of the CNT array as a function of the applied load. The microstructures obtained from the coarse-grain simulations are used as inputs to a finite volume solver that solves one-dimensional and three-dimensional Fourier heat conduction in the CNTs and filler matrix, respectively. Predictions from the finite volume solver are fitted to experimental data on the total thermal resistance of CNT arrays to obtain an individual CNT thermal conductivity of 12 W m−1 K−1 and CNT–substrate contact conductance of 7 × 107 W m−2 K−1. The results also indicate that the thermal resistance of the CNT array shows a weak dependence on the CNT–CNT contact resistance. Embedding the CNT array in wax is found to reduce the total thermal resistance of the array by almost 50%, and the pressure dependence of thermal resistance nearly vanishes when a matrix material is introduced. Detailed microstructural information such as the topology of CNT–substrate contacts and the pressure dependence of CNT–opposing substrate contact area are also reported.

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