Heat dissipation for the Intel Core i5 processor using multiwalled carbon nanotube based ethylene glycol

Journal of the Korean Physical Society, Vol 65, No 3, August 2014, pp 312∼316 Heat Dissipation for the Intel Core i5 Processor Using Multiwalled Carbon-nanotube-based Ethylene Glycol Bui Hung Thang,∗ Pham Van Trinh and Le Dinh Quang Institute of Materials Science (IMS), Vietnam Academy of Science and Technology (VAST), Vietnam Nguyen Thi Huong Hanoi University of Science (HUS), Vietnam National University (VNU), Vietnam Phan Hong Khoi and Phan Ngoc Minh† Center for High Technology Development (HTD), Vietnam Academy of Science and Technology (VAST), Vietnam (Received 14 January 2014) Carbon nanotubes (CNTs) are some of the most valuable materials with high thermal conductivity The thermal conductivity of individual multiwalled carbon nanotubes (MWCNTs) grown by using chemical vapor deposition is 600 ± 100 Wm−1 K−1 compared with the thermal conductivity 419 Wm−1 K−1 of Ag Carbon-nanotube-based liquids – a new class of nanomaterials, have shown many interesting properties and distinctive features offering potential in heat dissipation applications for electronic devices, such as computer microprocessor, high power LED, etc In this work, a multiwalled carbon-nanotube-based liquid was made of well-dispersed hydroxyl-functional multiwalled carbon nanotubes (MWCNT-OH) in ethylene glycol (EG)/distilled water (DW) solutions by using Tween-80 surfactant and an ultrasonication method The concentration of MWCNT-OH in EG/DW solutions ranged from 0.1 to 1.2 gram/liter The dispersion of the MWCNT-OH-based EG/DW solutions was evaluated by using a Zeta-Sizer analyzer The MWCNT-OH-based EG/DW solutions were used as coolants in the liquid cooling system for the Intel Core i5 processor The thermal dissipation efficiency and the thermal response of the system were evaluated by directly measuring the temperature of the micro-processor using the Core Temp software and the temperature sensors built inside the micro-processor The results confirmed the advantages of CNTs in thermal dissipation systems for computer processors and other high-power electronic devices PACS numbers: 81.05.Uw, 81.07.De, 65.80.+n, 73.63.Fg Keywords: Carbon nanotubes, Ethylene glycol, Coolant, Nanofluid, Heat dissipation, Intel Core i5 processor DOI: 10.3938/jkps.65.312 I INTRODUCTION through the working fluid without modifying the mechanical design or the key components Researchers have recently shown much interest on the issue of nanofluid thermal properties [2,3] Nanofluids are considered as a new class of fluids having enormous potential to improve the efficiency of heat-transfer fluids Many factors, such as the particle size, the effect of surfactant, the dispersion of particles, and the thermal properties of dispersed particle are expected to the influence thermal properties of nanofluids [4] The nanofluid concept is employed to designate a fluid in which nanometersized particles are suspended in conventional heat-transfer base fluids to improve their thermal physical properties The nanoparticles are made from various materials, such as metals (Cu, Ag, Au, Al, and Fe), oxide ceramics (Al2 O3 and TiO2 ), nitride ceramics (AlN, SiN), carbide ceramics (SiC, TiC), semi- Thermal management is widely recognized to be an important aspect of computer design, with device performance being significantly affected by temperature In addition, device lifetime can be decreased drastically because of large thermal stresses The challenge for thermal management is to develop high-conductivity structures that can accommodate the fixed temperature drop with the increasing power densities that characterize new generations of microprocessors [1] In recent years, many approaches have improved the cooling system performance; the most feasible one is to enhance the heat transfer (dissipation) performance ∗ E-mail: † E-mail: thangbh@ims.vast.ac.vn pnminh@vast.ac.vn -312- Heat Dissipation for the Intel Core i5 Processor· · · – Bui Hung Thang et al -313- conductors, carbon nanotubes, and composite materials such as alloyed nanoparticles or nanoparticle corepolymer shell composites Conventional heat transfer fluids, such as oil, water, and ethylene glycol, in general, are well known to have poor heat transfer properties compared to those of most solids Nanofluids have enhanced thermo- physical properties, such as thermal conductivity, thermal diffusivity, viscosity, and convective heat transfer coefficients compared with those of base fluids like oil or water [5] Carbon nanotubes (CNTs) are some of the most valuable materials with high thermal conductivity The thermal conductivity of individual MWCNTs grown by chemical vapor deposition is 600 ± 100 Wm−1 K−1 compared with thermal conductivity 419 Wm−1 K−1 of Ag [6–8] This suggests an approach in applying CNTs in grease or liquid for thermal dissipation systems for computer processors and other high-power electronic devices [9–17] In this paper, we present the results of hydroxyl-functional multiwalled carbon nanotubes (MWCNT-OH)-based ethylene glycol (EG)/distilled water (DW) solutions applied to thermal dissipation for a Intel Core i5 processor Fig (Color online) Scheme of the cooling system using MWCNT-based EG/DW solutions for the CPU II EXPERIMENTS AND DISCUSSION MWCNTs were produced at the Vietnam Academy of Science and Technology by using the thermal chemical vapor deposition (CVD) technique [18] The diameter and the length of the grown MWCNTs used in this experiment were 15 − 80 nm and several tens of μm, respectively The MWCNTs were functionalized with hydroxyl functional group (−OH) by using the following steps: - Step 1: MWCNTs were treated in a mixture of hot acid (HNO3 :H2 SO4 in a ratio of 1:3) at 60 ◦ C for h - Step 2: The suspension obtained in step was dried in an argon atmosphere at 80 ◦ C for 24 h - Step 3: The mixture obtained in step was treated in the SOCl2 to obtain MWCNTs-COCl - Step 4: The MWCNTs-COCl were filtered in H2 O2 and dried in an argon atmosphere at 80 ◦ C for 24 h to obtain MWCNTs-OH In order to disperse the MWCNT-OH in the EG/DW solutions, we used the Tween-80 surfactant and the Hielscher Ultrasonics Vibration instrument The volume percent of ethylene glycol in the EG/DW solution was 50% The MWCNT-OH were dispersed in the EG/DW solution in concentrations from 0.1 to 1.2 g/l Figure is a schematic view of the thermal dissipation system for computer processor using CNTs-based EG/DW solutions In this system, the copper heatsink was set in direct contact with the processor, and the tracks inside the copper substrate were fabricated to allow liquid to flows through the substrate and absorb heat from the processor The pump power consumption of the cooling system was 1.8 W The dimensions and the power consumptions of the two fans were 120 × 120 × 38 mm3 and 3.6 W, respectively The heat radiator was made of aluminum material, and the dimensions of heat radiator were 150 × 120 × 25 mm3 , respectively The environmental temperature was kept at 20 ◦ C for all measurements by using an air conditioner The thermal dissipation efficiency and the thermal response of the system were evaluated by using dedicated software and four built-in temperature sensors inside the micro-processor to measure the temperature of the micro-processor directly We chose a personal computer with the following configuration: Intel Core i5 – 3570 K Processor (6M Cache, 3.4 GHz), Corsair’s GB DDR3 SODIMM Memory, Toshiba’s TB Hard Disk Drive, Asrock H61M-VS3 Main-board, and Window Ultimate Service Pack Operating System for all experiments The temperature of the micro-processor was measured by using the Core Temp 1.0 RC5-32bit software The micro-processor was pushed to operate at full load (100% usage of the processor) by using Prime 95 v27.9 build software The existence of carboxyl (COOH) and hydroxyl (OH) functional groups bonded to the ends and the sidewalls was demonstrated by Raman and Fourier transform infrared (FTIR) spectra Raman scattering is a powerful technique to probe the changes in the surfaces and -314- Journal of the Korean Physical Society, Vol 65, No 3, August 2014 Fig FTIR transmission spectra of pristine MWCNTs, MWCNT-COOH, and MWCNT-OH Fig (Color online) Raman spectra of MWCNTs: pristine MWCNTs (black line), MWCNT-COOH (red line) and MWCNT-OH (blue line) the structures of MWCNTs Figure clearly shown that the two bands around 1583.10 cm−1 and 1333.69 cm−1 in the spectra were assigned to the tangential mode (G-band) and the disorder mode (D-band), respectively The D-band intensity was increased in the functinalized MWCNTs compared to the pristine MWCNTs The peak intensity ratios (ID /IG ) of the D-band to the Gband of 0.99 and 1.87 corresponding to MWCNT-COOH and MWCNT-OH exceeded those of pristine MWCNTs (ID /IG = 0.79) The intensity ratio of D lines to G lines were different, suggesting some changes in the surfaces and the structures of the MWCNTs This result indicates that some of the sp2 carbon atoms (C=C) were converted to sp3 carbon atoms (C−C) at the surfaces of the MWCNTs after the acid treatment in HNO3 /H2 SO4 The intensity ratio of MWCNT-OH was higher than that of MWCNT-COOH indicating that the two chemical treatment processes had formed new defects on the surfaces of the MWNCTs Figure presents typical FTIR spectra of the pristine MWCNTs, MWCNT-COOH and MWCNT-OH Some important peaks are seen after the MWCNTs have been treated with a mixture of H2 SO4 and HNO3 The vibration of O-H bonding in the carboxyl group is shown as a peak at 3431.81 cm−1 It was expanded more than that of the O-H bonding of H2 O The peak at 1707.31 cm−1 showed the existence of vibrations of the C=O bond in the carboxyl group This shows the importane of proving the existence of carboxyl (COOH) functional groups due to the oxidation resulting from the nitric and the sulfuric acids This clearly shows that the acids functionalized the surfaces of the MWCNTs The FTIR transmittance spectra of MWCNT-OH show that the peak of the conjugated O-H stretching vibration mode appears at 3431.81 cm−1 and that the central position of the O-H peak is shifted to a lower frequency as well; the expansion of Fig (Color online) MWCNT-OH size distribution in the EG/DW solutions by number with 10 minutes of ultrasonication: (a) immediately after the sonication and (b) 72 hours after the sonication the vibration peak and the disappearance of the vibration peak of the C=O bond at 1707.31 cm−1 indicate the generation of hydroxyl groups on the surfaces of the MWCNTs In order to evaluate the dispersion of the MWCNTOH in the EG/DW solutions, we used the Malvern Zetasizer Nano ZS Instrument Figure presents spectra of the MWCNT-OH size distribution in EG/DW solutions by number for 10 minutes of ultrasonication Figure 4(a) shows that immediately after the ultrasonication, the MWCNT-OH were still gathering into large bundles, with peaks at 437 nm and 93.5 nm The 437-nm peak corresponds to the large bundles of MWCNT-OH whereas the 93.5-nm peak corresponds to the individual MWCNT-OH in the EG/DW solutions In order Heat Dissipation for the Intel Core i5 Processor· · · – Bui Hung Thang et al -315- Fig (Color online) Measured temperature of the microprocessor as a function of the operation time in the case of using the cooling fan method Fig (Color online) MWCNT-OH size distribution in the EG/DW solutions by number at 72 hours after from the sonication: (a) 20 minutes of sonication, (b) 30 minutes of sonication, and (c) 40 minutes of sonication to remove large bundles from the EG/DW solutions, we settled the solutions for 72 hours Figure 4(b) showed that after 72 hours from ultrasonication, the 437-nm peak didn’t exist, which means there were no longer large bundles of MWCNT-OH in the EG/DW solutions However, the MWCNTs were still gathering into small bundles with a size distribution from 70 to 270 nm Figure presents spectra of the MWCNT-OH size distributions in the EG/ DW solution by number for sonication times from 20 to 40 minutes In the case of 20minute ultrasonic vibration time (shown as Fig 5(a)), the spectrum of the MWCNT-OH size distribution by number was from 18 nm to 95 nm This result showed that MWCNT-OH were better dispersed in the EG/DW solutions with a 20-minute ultrasonic vibration time However, the range didn’t match with the 15- to 80-nm diameter of the MWCNT-OH In the case of 30-minute or a 40-minute ultrasonic vibration time, the MWCNT-OH were well dispersed in the EG/DW solutions are shown as Figs 5(b) and (c) The spectra of the MWCNT-OH size distribution by number in Figs 5(b) and (c) matched with the 15- to 80-nm diameter of the MWCNT-OH The results show that the ultrasonic vibration time required is more than 30 minutes for good dispersion of the MWCNT-OH in EG/DW solutions, so we chose 30 Fig (Color online) Measured temperature of the microprocessor as a function of the operation time in the case of using a MWCNT-OH-based EG/DW solution minutes of ultrasonic vibration time for all subsequent experiments We measured directly the temperature of the microprocessor during the operation of the computer at fullload mode (100% usage micro-processor mode) To estimate the role of the MWCNT-OH-based EG/DW solutions, we investigated the temperature of the microprocessor when using a cooling fan Figure shows the micro-processor’s temperature as a function of working time when using a cooling fan As seen in Fig 6, at the initial time, the temperature of the micro-processor was 35 ◦ C, and then the temperature of the micro-processor became saturated at approximately 71 ◦ C after 200 seconds of working time In order to reduce the saturation temperature and slow down the temperature increase of the processor, we used MWCNT-OH-based EG/DW solutions as coolants in a -316- Journal of the Korean Physical Society, Vol 65, No 3, August 2014 liquid cooling system for the micro-processor Figure shows the micro-processor’s experimental temperature as a function of working time when using MWCNT-OHbased EG/DW solutions for thermal dissipation At the initial time, the temperature of the micro-processor was about 30 − 32 ◦ C The saturation temperature of the microprocessor reached 57, 54 and 51 ◦ C when using an EG/DW solution without CNTs, an EG/DW solution with 0.5 g of MWCNT-OH/liter of concentration, and an EG/DW solution with 1g of MWCNT-OH/liter of concentration after 350 seconds of working time, respectively These results indicated that, in comparison to the cooling fan, the saturation temperature of the processor decreased about 14 − 20 ◦ C, and the time for the temperature to increase was prolonged from 200 seconds to 350 seconds By mixing MWCNT-OH (1 g/l of concentration) in the EG/DW solution, we could decrease the saturation temperature of CPU ◦ C compared to using EG/DW solutions without MWCNT-OH III CONCLUSION The successful hydroxyl functionalization of nanotubes with a mixture of acid solution was proven by Raman and FTIR spectral measurements to have opened new applications for thermal-dissipation-based liquids in electronic devices We have successfully dispersed MWCNTOH into EG/DW solutions by using Tween-80 surfactant and an ultrasonication method The thermal dissipation efficiency of the PC’s micro-processor using the cooling fan and liquid cooling was examined and evaluated Compared to the cooling fan, the saturation temperature of the processor using the EG/DW solutions decreased about 14 ◦ C By mixing MWCNT-OH (1 g/l of concentration) into the EG/DW solutions, the saturation temperature of the CPU decreased ◦ C compare to using the EG/DW solution without MWWCNTs-OH The experimental results confirmed the advantage of using a MWCNT-based liquid in thermal dissipation for microprocessors and other high-power electronic devices ACKNOWLEDGMENTS The authors acknowledge the financial support from the Vietnam National Foundation for Science and Tech- nology Development (Project No NAFOSTED 103.992012.35) The 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(MWCNT-OH) -based ethylene glycol (EG)/distilled water (DW) solutions applied to thermal dissipation for a Intel Core i5 processor Fig (Color online) Scheme of the cooling system using MWCNT -based. .. schematic view of the thermal dissipation system for computer processor using CNTs -based EG/DW solutions In this system, the copper heatsink was set in direct contact with the processor, and the tracks... corresponds to the large bundles of MWCNT-OH whereas the 93.5-nm peak corresponds to the individual MWCNT-OH in the EG/DW solutions In order Heat Dissipation for the Intel Core i5 Processor ·