Characterization of Carbon Nanotube Forest Interfaces Using Time Domain Thermoreflectance

2015 ◽  
Author(s):  
Thomas L. Bougher ◽  
John H. Taphouse ◽  
Baratunde A. Cola
Keyword(s):  
Heat Transfer ◽  
Contact Resistance ◽  
Time Domain ◽  
Thermal Contact ◽  
Thermal Interface Materials ◽  
Length Scales ◽  
Aligned Carbon Nanotubes ◽  
Theoretical Predictions ◽  
Vertically Aligned

Forests comprised of nominally vertically aligned carbon nanotubes (CNTs) are excellent candidates for thermal interface materials (TIMs) due to their theoretically predicted outstanding thermal and mechanical properties. Unfortunately, due to challenges in the synthesis and characterization of these materials reports of the thermal conductivity and thermal contact resistance of CNT forests have varied widely and typically fallen far short of theoretical predictions. In particular, the micro- and nano-length scales characteristic of the heat transfer in CNT forests pose significant challenges and may lead to misreported results. Here we examine the ability of a popular and well-established thermal metrology technique, time-domain thermoreflectance (TDTR), to resolve the properties of CNT forest TIMs. The characteristic heating frequencies of TDTR (1–10 MHz) are used to probe heat transfer at length scales spanning ∼0.1–1 μm, applicable for measuring the contact resistance between the CNT forest free tips and an opposing substrate. We identify the range of CNT forest-opposing substrate interface resistances that can be resolved with TDTR, and simultaneously demonstrate the effectiveness of several processes developed to reduce the resistance of these interfaces. The limitations of characterizing CNT forests with TDTR are discussed in terms of uncertainty and sensitivity to parameters of interest.

Modeling and Experimental Characterization of Metal Microtextured Thermal Interface Materials

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
R. Kempers ◽  
A. M. Lyons ◽  
A. J. Robinson
Keyword(s):  
Thermal Resistance ◽  
Contact Resistance ◽  
Thermal Contact Resistance ◽  
Thermal Contact ◽  
Thermal Interface Material ◽  
Small Scale ◽  
Thermal Interface Materials ◽  
Thermal Interface ◽  
Main Challenge

A metal microtextured thermal interface material (MMT-TIM) has been proposed to address some of the shortcomings of conventional TIMs. These materials consist of arrays of small-scale metal features that plastically deform when compressed between mating surfaces, conforming to the surface asperities of the contacting bodies and resulting in a low-thermal resistance assembly. The present work details the development of an accurate thermal model to predict the thermal resistance and effective thermal conductivity of the assembly (including contact and bulk thermal properties) as the MMT-TIMs undergo large plastic deformations. The main challenge of characterizing the thermal contact resistance of these structures was addressed by employing a numerical model to characterize the bulk thermal resistance and estimate the contribution of thermal contact resistance. Furthermore, a correlation that relates electrical and thermal contact resistance for these MMT-TIMs was developed that adequately predicted MMT-TIM properties for several different geometries. A comparison to a commercially available graphite TIM is made as well as suggestions for optimizing future MMT-TIM designs.

A Model of the Contact Thermal Resistance of Vertical Carbon Nanotube Arrays

2016 ◽  
Author(s):  
Jin Zhang ◽  
Bo Shi
Keyword(s):  
Carbon Nanotube ◽  
Thermal Resistance ◽  
Contact Resistance ◽  
Thermal Contact Resistance ◽  
Thermal Contact ◽  
Interfacial Thermal Resistance ◽  
Elastic Rod ◽  
Aligned Carbon Nanotubes ◽  
Vertically Aligned ◽  
Thin Elastic Rod

This paper developes a model to predict the thermal contact resistance of the vertically aligned carbon nanotubes (VACNTs). The model includes the effects of CNT array properties and surface roughness, with the aim of providing useful information for optimizing CNT array thermal contact resistance. The contact resistance is consisted of two parts: interfacial thermal resistance and constriction thermal resistance. The carbon nanotube (CNT) is treated as a thin elastic rod and macroscopic mechanical is used to calculate the mechanical properties of CNT. Greenwood-Williamson (GW) model is used to describe the roughness. The interfacial thermal resistance is calculated by molecular dynamics. The calculated values are in good agreement with experimental data. The interfacial thermal resistance is the domain major factor.

scholarly journals Multifunctional Cantilevers as Working Elements in Solid-State Cooling Devices

Actuators ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 58
Author(s):  
Andraž Bradeško ◽  
Lovro Fulanović ◽  
Marko Vrabelj ◽  
Aleksander Matavž ◽  
Mojca Otoničar ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Ethylene Glycol ◽  
Contact Resistance ◽  
High Efficiency ◽  
Thermal Contact ◽  
Point Of View ◽  
Practical Implementation ◽  
Cooling Devices ◽  
Cascade Structure ◽  
Lead Magnesium

Despite the challenges of practical implementation, electrocaloric (EC) cooling remains a promising technology because of its good scalability and high efficiency. Here, we investigate the feasibility of an EC cooling device that couples the EC and electromechanical (EM) responses of a highly functionally, efficient, lead magnesium niobate ceramic material. We fabricated multifunctional cantilevers from this material and characterized their electrical, EM and EC properties. Two active cantilevers were stacked in a cascade structure, forming a proof-of-concept device, which was then analyzed in detail. The cooling effect was lower than the EC effect of the material itself, mainly due to the poor solid-to-solid heat transfer. However, we show that the use of ethylene glycol in the thermal contact area can significantly reduce the contact resistance, thereby improving the heat transfer. Although this solution is most likely impractical from the design point of view, the results clearly show that in this and similar cooling devices, a non-destructive, surface-modification method, with the same effectiveness as that of ethylene glycol, will have to be developed to reduce the thermal contact resistance. We hope this study will motivate the further development of multifunctional cooling devices.

scholarly journals Noncured Graphene Thermal Interface Materials for High-Power Electronics: Minimizing the Thermal Contact Resistance

Nanomaterials ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1699
Author(s):  
Sriharsha Sudhindra ◽  
Fariborz Kargar ◽  
Alexander A. Balandin
Keyword(s):  
Contact Resistance ◽  
High Power ◽  
Thermal Contact Resistance ◽  
Thermal Contact ◽  
Wide Band ◽  
Thermal Interface Material ◽  
Thermal Interface Materials ◽  
Total Thermal Resistance ◽  
Thermal Interface ◽  
Interface Materials

We report on experimental investigation of thermal contact resistance, RC, of the noncuring graphene thermal interface materials with the surfaces characterized by different degree of roughness, Sq. It is found that the thermal contact resistance depends on the graphene loading, ξ, non-monotonically, achieving its minimum at the loading fraction of ξ ~15 wt %. Decreasing the surface roughness by Sq~1 μm results in approximately the factor of ×2 decrease in the thermal contact resistance for this graphene loading. The obtained dependences of the thermal conductivity, KTIM, thermal contact resistance, RC, and the total thermal resistance of the thermal interface material layer on ξ and Sq can be utilized for optimization of the loading fraction of graphene for specific materials and roughness of the connecting surfaces. Our results are important for the thermal management of high-power-density electronics implemented with diamond and other wide-band-gap semiconductors.

Characterization of an Air-PCM Energy Storage Design for Air Handling Unit Applications

2017 ◽  
Author(s):  
Sarah Wert ◽  
Cynthia A. Cruickshank ◽  
Dominic Groulx
Keyword(s):  
Heat Transfer ◽  
Energy Storage ◽  
Testing Temperature ◽  
Storage Device ◽  
Flow Rates ◽  
Transfer Rates ◽  
Melting Temperatures ◽  
Air Handling Unit ◽  
Vertically Aligned

This paper will discuss the characterization of an air-PCM storage design for commercial air handling unit (AHU) applications during winter. The air-PCM storage design consists of two rows of 29 aluminum flat plate containers (0.45 m × 0.35 m × 0.01 m) filled with PCM, vertically aligned leaving an air channel between each plate of 0.011 m wide. The storage device was placed within a closed air loop which conditions the air to the desired testing temperature and velocity. The PCM selected for testing was RT44HC with a melting temperature of 44 °C. This PCM was chosen for its similar properties to other PCMs having lower melting temperatures (in the range of 5 to 18°C) that could be used in actual HVAC application implementation. The system was instrumented and calibrated with Type T thermocouples and a velocity sensor. The system was tested at various inlet temperatures (55°C to 63°C for charging and 12°C to 25°C for discharging) and flow rates. The instantaneous heat transfer rates and total energy storage were calculated for each test from the data collected. The results provide a baseline value for heat transfer rates in a simple air-PCM design, to be used for model validation.

scholarly journals Study of an inclined interface of contact using lattice Boltzmann method

2019 ◽  
Vol 23 (3 Part B) ◽  
pp. 1837-1846
Author(s):  
Mhamdi El ◽  
Elalami Semma
Keyword(s):  
Heat Transfer ◽  
Contact Resistance ◽  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Thermal Contact Resistance ◽  
Transfer Problem ◽  
Thermal Contact ◽  
Image Model ◽  
Steady Regime ◽  
Boltzmann Method

The lattice Boltzmann method and the particle image model are adopted to study a heat transfer problem with thermal contact resistance. In this paper, a new study involving an inclined interface of contact between two media is introduced in order to evaluate a 2-D heat transfer in the steady regime. A case of study and numerical results are provided to support this configuration. The obtained results show the effect of the thermal contact resistance on the heat transfer, as well as the temperature distribution on the two contacting media.

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