Microstructure-Dependent Heat Transfer Modeling of Carbon Nanotube Arrays for Thermal Interface Applications

2013 ◽  
Author(s):  
Sridhar Sadasivam ◽  
Stephen L. Hodson ◽  
Timothy S. Fisher
Keyword(s):  
Heat Transfer ◽  
Carbon Nanotube ◽  
Effective Conductivity ◽  
Data Set ◽  
Thermal Interface ◽  
Heat Transfer Modeling ◽  
Strain Behavior ◽  
Thermal Network ◽  
Parametric Studies ◽  
Cnt Arrays

A growing interest has developed in the use of carbon nanotube (CNT) arrays as thermal interface materials (TIMs). However, theoretical modeling of CNT TIMs has largely been limited to semi-empirical methods without detailed consideration of array microstructure, primarily due to the inherent randomness of the microstructure and the computational complexity involved in full atomistic modeling of CNTs. In this work, we report combined thermo-mechanical simulation of CNT arrays with a coarse-grain approach for the mechanics modeling and a thermal network approach for the heat transfer modeling. Parametric studies on the effects of CNT height on the Young’s modulus and buckling load of CNT arrays are reported. The thermal network model is used to estimate the pressure dependence of diffusive and tip contact resistances of CNT arrays; the predictions are compared with thermal resistance measurements using the photoacoustic method. The resulting simulation framework enables a particularly rich and broad thermo-mechanical data set. Selected parametric variations are computed to assess the stress-strain behavior, effective conductivity within the CNT array, and aspects of the contact topologies of the CNT-substrate interface.

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.

Design, Synthesis, and Performance of a Carbon Nanotube/Metal Foil Thermal Interface Material

2007 ◽  
Author(s):  
Baratunde A. Cola ◽  
Xianfan Xu ◽  
Timothy S. Fisher
Keyword(s):  
Carbon Nanotube ◽  
Thermal Performance ◽  
Thermal Conduction ◽  
Thermal Interface Material ◽  
Metal Foil ◽  
Thermal Interface ◽  
Design Synthesis ◽  
Cnt Arrays ◽  
And Performance ◽  
Contact Spots

The thermal performance of an interface material comprised of a metal foil with dense, vertically oriented carbon nanotube (CNT) arrays synthesized on both of its surfaces is characterized for rough and smooth interfaces. The CNT/foil deforms in the interfaces by two mechanisms, CNT deformation and foil deformation, that may significantly increase the number of CNT contact spots on both sides of the foil. As a result, the thermal conduction at the CNT-array-free-tip interfaces is greatly increased from previous measurements.

Aluminum Foil/Carbon Nanotube Thermal Interface Materials

2007 ◽  
Author(s):  
Baratunde A. Cola ◽  
Xianfan Xu ◽  
Timothy S. Fisher
Keyword(s):  
Carbon Nanotube ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Aluminum Foil ◽  
Close Packing ◽  
Thermal Interface Materials ◽  
Thermal Interface ◽  
Small Height ◽  
Cnt Arrays ◽  
Interface Materials

Vertically oriented carbon nanotube (CNT) arrays have been simultaneously synthesized at relatively low growth temperatures (i.e., < 700°C) on both sides of aluminum foil via plasma enhanced chemical vapor deposition. The resulting CNT arrays were highly dense, and the average CNT diameter in the arrays was approximately 10 nm, much smaller than in previous work. Also, the CNT arrays were smaller in height than the arrays in previous work. At moderate pressures, the aluminum foil/CNT material achieves resistances as low as 10 mm2·K/W for relatively smooth and flat interfaces, similar to previous work. However, the aluminum foil/CNT material performs relatively poor for less ideal, rougher interfaces presumably due to the small height and very close packing of CNTs that decreases the materials ability to fill interfacial voids and conform to the geometry of the mating surfaces. It is also possible that the aluminum foil was slightly stiffened during CNT growth (through hydrogen embrittlement), which could further reduce the conformability of the aluminum foil/CNT material.

scholarly journals Effect of Contact Pressure on the Performance of Carbon Nanotube Arrays Thermal Interface Material

Nanomaterials ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 732 ◽  
Author(s):  
Yu Pei ◽  
Hongmei Zhong ◽  
Mengyu Wang ◽  
Peng Zhang ◽  
Yang Zhao
Keyword(s):  
Carbon Nanotube ◽  
Thermal Resistance ◽  
Contact Pressure ◽  
Surface Deformation ◽  
Strong Dependence ◽  
Thermal Conductance ◽  
Thermal Interface Material ◽  
Thermal Interface ◽  
Minimum Requirement ◽  
Cnt Arrays

Vertically aligned carbon nanotube (CNT) arrays are promising candidates for advanced thermal interface materials (TIMs) since they possess high mechanical compliance and high intrinsic thermal conductivity. Some of the previous works indicate that the CNT arrays in direct dry contact with the target surface possess low contact thermal conductance, which is the dominant thermal resistance. Using a phase sensitive transient thermo-reflectance (PSTTR) technique, we measure the thermal conductance between CNT arrays and copper (Cu) surfaces under different pressures. The experiments demonstrated that the contact force is one of the crucial factors for optimizing the thermal performance of CNT array-based TIMs. The experimental results suggest that the Cu-CNT arrays’ contact thermal conductance has a strong dependence on the surface deformation and has an order of magnitude rise as the contact pressure increases from 0.05 to 0.15 MPa. However, further increase of the contact pressure beyond 0.15 MPa has little effect on the contact thermal resistance. This work could provide guidelines to determine the minimum requirement of packaging pressure on CNT TIMs.

Palladium Thiolate Bonding of Carbon Nanotube Thermal Interfaces for High-Temperature Electronics

2009 ◽  
Author(s):  
Stephen L. Hodson ◽  
Thiruvelu Bhuvana ◽  
Baratunde A. Cola ◽  
Xianfan Xu ◽  
G. U. Kulkarni ◽  
...  
Keyword(s):  
Carbon Nanotube ◽  
Mechanical Stability ◽  
Interface Temperature ◽  
Thermal Interface Materials ◽  
Thermal Interface ◽  
High Temperature Electronics ◽  
Compliant Joint ◽  
Cnt Arrays ◽  
Interface Structures ◽  
Interface Materials

Carbon nanotube (CNT) arrays are attractive thermal interface materials with high compliance and conductance that can remain effective over a wide temperature range. Here we study CNT interface structures in which free CNT ends are bonded using palladium hexadecanethiolate Pd(SC16H35)2 to an opposing substrate (one-sided interface) or opposing CNT array (two-sided interface) to enhance contact conductance while maintaining a compliant joint. The palladium weld is particularly attractive for its mechanical stability at high temperatures. A transient photoacoustic (PA) method is used to measure the thermal resistance of the palladium bonded CNT interfaces. The interfaces were bonded at moderate pressures and then tested at 34 kPa using the PA technique. At an interface temperature of approximately 250°C, one-sided and two-sided palladium bonded interfaces achieved thermal resistances near 10 mm2K/W and 5 mm2K/W, respectively.

Transient Thermo-Reflectance Method for Characterization of Thermal Interface Material Based on Carbon Nanotube Array

2009 ◽  
Author(s):  
Yang Zhao ◽  
Rong-Shiuan Chu ◽  
Arun Majumdar
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotube ◽  
Thermal Resistance ◽  
Thermal Interface Material ◽  
Measuring System ◽  
Bonding Layer ◽  
Thermal Interface ◽  
Interface Resistance ◽  
Interface Thermal Resistance ◽  
Cnt Arrays

Vertically aligned carbon nanotube (CNT) arrays have been explored as advanced thermal interface materials because of their compliance and high cross-plane thermal conductivity. Our previous work showed that a CNT array directly bridging two surfaces by dry contact had a surface-surface interface resistance of order of 10 m2-K/MW. With an indium bonding layer, the interface thermal resistance was reduced by a factor of ten. Therefore, a more sensitive measuring system is needed to accurately determine the thermal resistance. In this paper, we achieved a higher sensitivity measurement by applying the phase sensitive transient thermo-reflectance technique to a front side heating and detecting system. A detailed analysis is presented. We used this technique to characterize a 71-μm long CNT array with packing density of 9.4 ± 1.4%. The CNT array was sequentially wetted with chromium/gold films and was bonded to a glass surface with an indium bonding layer. We found that the CNT array-surface interface resistance is 0.35 ± 0.11 m2-K/MW and the cross-plane thermal conductivity of CNT array is 94 ± 40 W/m-K.

Palladium Thiolate Bonding of Carbon Nanotube Thermal Interfaces

2011 ◽  
Vol 133 (2) ◽  
Author(s):  
Stephen L. Hodson ◽  
Thiruvelu Bhuvana ◽  
Baratunde A. Cola ◽  
Xianfan Xu ◽  
G. U. Kulkarni ◽  
...  
Keyword(s):  
Carbon Nanotube ◽  
Mechanical Stability ◽  
Interface Temperature ◽  
Thermal Interface Materials ◽  
Thermal Interface ◽  
High Compliance ◽  
Compliant Joint ◽  
Cnt Arrays ◽  
Interface Structures ◽  
Interface Materials

Carbon nanotube (CNT) arrays can be effective thermal interface materials with high compliance and conductance over a wide temperature range. Here, we study CNT interface structures in which free CNT ends are bonded using Pd hexadecanethiolate, Pd(SC16H35)2, to an opposing substrate (one-sided interface) or opposing CNT array (two-sided interface) to enhance contact conductance while maintaining a compliant joint. The Pd weld is particularly attractive for its mechanical stability at high temperatures. A transient photoacoustic (PA) method is used to measure the thermal resistance of the palladium-bonded CNT interfaces. The interfaces were bonded at moderate pressures and then tested at 34 kPa using the PA technique. At an interface temperature of approximately 250°C, one-sided and two-sided palladium-bonded interfaces achieved thermal resistances near 10 mm2 K/W and 5 mm2 K/W, respectively.

Heat transfer modeling and identification using fractional order state space models

2008 ◽  
Vol 42 (6-8) ◽  
pp. 939-951 ◽  
Author(s):  
Tounsia Jamah ◽  
Rachid Mansouri ◽  
Saïd Djennoune ◽  
Maâmar Bettayeb
Keyword(s):  
Heat Transfer ◽  
State Space ◽  
Fractional Order ◽  
State Space Models ◽  
Heat Transfer Modeling ◽  
Order State
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