Carbon nanotubes based engineering materials for thermal management applications (original) (raw)
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Advanced Materials Letters, 2013
Thermal grease is generally used as a thermal interface material for improved conduction between a heat source and heat sink. Here, we report the enhancement of thermal conductivity of commercially available off-the-shelf thermal grease (thermal compound LS6006) used in cooling of electronic devices, by the addition of multiwalled carbon nanotubes (MWCNTs). The thermal conductivity of the MWCNT mats and MWCNT modified thermal grease was measured relative to the thermal conductivity of the grease, which was taken as the benchmark. The thermal conductivity improves and the optimum thermal management is observed for aligned MWCNT arrays glued through the thermal grease.
Thermal transport of oil and polymer composites filled with carbon nanotubes
Applied Physics A, 2011
We studied the thermal transport properties of multi-walled carbon nanotubes (MWNTs) in polymer and oil matrices. The thermal conductivity of the oils and polymers increased linearly when adding tubes. We observe a particularly high increase in the thermal diffusivity of carbon-nanotube-loaded liquid crystal polymers (6×10 −5 cm 2 /s wt%), which is due to a spontaneous alignment of the MWNTs. Carbon nanotubes increased the thermal conductivity of oil by a factor of three for 20 wt% loading. We found little or no dependence of the thermal enhancement on the specific flavor of multiwall nanotubes used in the composites. Carbon nanotubes are excellent nanoscale fillers for composites in thermal management application.
Application of Carbon Nanotubes to Thermal Interface Materials
Journal of Electronic Packaging, 2011
Improvements in thermal interface materials (TIMs) can enhance heat transfer in electronics packages and reduce high temperatures. TIMs are generally composed of highly conductive particle fillers and a matrix that allows for good surface wetting and compliance of the material during application. Two types of TIMs are tested based on the addition of carbon nanotubes (CNTs): one mixed with a commercial TIM product and the other only CNTs and silicone oil. The materials are tested using an in-house apparatus that allows for the simultaneous measurement of temperature, pressure, heat flux, and TIM thickness. Results show that addition of large quantities of CNTs degrades the performance of the commercial TIM, while the CNT-silicone oil mixtures showed improved performance at high pressures. Thickness and pressure measurements indicate that the CNT-thermal grease mixtures are more compliant, with a small increase in bulk thermal conductivity over the range of tested pressures.
Advanced Materials, 2010
Among a broad range of carbonaceous materials, such as exfoliated graphite, graphene or diamond, carbon nanotubes (CNTs) are widely used as a thermal filler because of their exceptional intrinsic thermal conductivity (TC) and aspect ratios, which are larger than 1000. The TC of single-walled CNTs (SWNTs) has been reported as high as 6000 W m À1 K À1 , and that of multi-walled CNTs (MWNTs) was experimentally measured at 3075 W m À1 K À1 at room temperature, which remains above the performances of diamond (TC ¼ 2200 W m À1 K À1 ). Therefore the improvement of the TC of composites based on CNTs was extensively investigated over the past years. A recent work revealed that a TC of 0.28 W m À1 K À1 or a 40% increase had been reached in composites with a 10% weight fraction (wt%) of CNTs dispersed in polyvinylacetate matrix by using the classical sonication method. Another optimized configuration was proposed by Haddon and co-workers, who brought into play a hybrid filler based on the combination of SWNTs and graphite nanoplatelets. An improved TC of 1.7 W m À1 K À1 -about a fivefold increase-was obtained for epoxy composites. The hybrid loading mass fraction was as high as 10%, including 7 wt% graphite nanoplatelets and 3 wt% SWNTs.
2013
Uniform dispersion of carbon nanotubes (CNTs) in metal composites has been by far the most significant challenge in the field of CNT-reinforced metal matrices. This work presents a new dispersion and fabrication technique of Carbon nanotubes (CNTs) reinforced copper (Cu) matrix nanocomposites. A combination of nanoscale dispersion of functionalized CNTs in low viscose media of dissolved paraffin wax under ultrasonication treatment followed by powder injection molding (PIM) technique was adopted. CNTs contents were varied from 0 to 10 vol.%. TEM, EDX, FESEM and Raman spectroscopy analysis were used for materials characterization. Information about the degree of purification and functionalization processes, evidences on the existence of the functional groups, effects of ultrasonication time on the treated CNTs, and microstructural analysis of the fabricated Cu/CNTs nanocomposites were determined. The results showed that the impurities of the pristine CNTs such as Fe, Ni catalyst and the amorphous carbon have been significantly removed after purification process. Meanwhile, FESEM and TEM observations showed high stability of CNTs at elevated temperatures. It also showed an excellent homogeneous dispersion of CNTs in Cu matrix and led to a strong interfacial bonding between Cu particles and individual CNTs.
Development and thermal properties of carbon nanotube-polymer composites
Composites Part B: Engineering, 2016
Illustration of of three different SWCNT structures (a) a zigzag type nanotube, (b) an armchair type nanotube, and (c) a helical (chiral) type nanotube. From Reference 11 .......8 2. Illustration from Reference 33 of (a) poor distribution and poor dispersion, (b) poor distribution but good dispersion, (c) good distribution but poor dispersion and (d) good distribution and good dispersion.
Advanced Materials, 2009
In the past twenty years, substances with low or negative thermal expansivities have attracted much interest because of their significance in electronic packaging, precision equipment, and intelligent materials. [1-3] In electronic packaging systems, mismatch in the coefficient of thermal expansion (CTE) between various materials has become a key issue for developing the next generation of electronic packaging with higher system reliability. CTE values of polymer portions are much higher than those of silicon, ceramic, and copper metallization. These large CTE mismatches lead to thermal-stress accumulation at contact interfaces during both packaging and device performance, which triggers component failure by, for example, warpage and rupture. [4] So far, the effective approach to reduce the CTE of the polymer portion has been to add fillers of low or negative CTEs into polymer matrices. [2,4] The low or negative CTEs of carbon nanotube (CNTs), together with their low mass density and outstanding mechanical and thermal properties, renders them the right filler for advanced polymer nanocomposites in microelectronic applications. [5] One of the most important applications for these materials is CNT-polymer nanocomposites for thermal interface materials (TIMs) with enhanced thermal conductivity and, equally importantly, reduced CTEs. Thermal properties of polymer composites filled with randomly dispersed CNTs have been extensively studied in the past decade. [6] Unfortunately, real-life applications of these materials were inhibited by their low thermal conductivity and relatively high CTEs, caused mainly by the weak CNT-polymer interface. [3,6] Alternatively, researchers turned to a simple infiltration process to prepare polymer composites filled with aligned carbon nanotubes (ACNT), because the CNT alignment ensures much higher thermal conductivities than a random dispersion. [7] However, a CTE study of ACNT-polymer composites has never been reported. The ACNT/polymer interface is still an issue, as such COMMUNICATION www.advmat.de
Flexographic printed carbon nanotubes on polycarbonate films yielding high heating rates
Journal of Applied Polymer Science, 2013
Carbon nanotube (CNT) formulations based on commercially available aqueous dispersions were printed using flexographic printing on a polycarbonate film which was provided with a polyethyleneimine-based primer layer to improve the wetting and adhesion properties. Depending on the formulation, the structured CNT layers (35 mm  50 mm) show heating rates of up to 14 K/s during resistive heating (applied voltage of 12 V) in the temperature range from room temperature to 70 C. The recording of temperature-time curves was carried out by means of an infrared camera system. The cooling largely depends on the substrate and its heat capacity as well as on environmental conditions, and could be actively supported and/or regulated. The formulations of different solid contents were described in terms of viscosity and surface tension while the printed layers were characterized regarding the mass load per area, sheet resistance, electrical power effective during resistive heating, and the layer morphology. V
ACS Nano, 2013
Carboxylic functionalization (ÀCOOH groups) of carbon nanotubes is known to improve their dispersion properties and increase the electrical conductivity of carbon-nanotubeÀpolymer nanocomposites. We have studied experimentally the effects of this type of functionalization on the thermal conductivity of the nanocomposites. It was found that while even small quantities of carbon nanotubes (∼1 wt %) can increase the electrical conductivity, a larger loading fraction (∼3 wt %) is required to enhance the thermal conductivity of nanocomposites. Functionalized multi-wall carbon nanotubes performed the best as filler material leading to a simultaneous improvement of the electrical and thermal properties of the composites. Functionalization of the single-wall carbon nanotubes reduced the thermal conductivity enhancement. The observed trends were explained by the fact that while surface functionalization increases the coupling between carbon nanotube and polymer matrix, it also leads to formation of defects, which impede the acoustic phonon transport in the single-wall carbon nanotubes. The obtained results are important for applications of carbon nanotubes and graphene flakes as fillers for improving thermal, electrical and mechanical properties of composites.