Electro-thermal Conversion Phase Change Composites: the Case of

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Materials and Interfaces

Electro-thermal Conversion Phase Change Composites: the Case of Polyethylene Glycol Infiltrated Graphene Oxide/Carbon Nanotube Networks Xinfeng Guo, Cui Liu, Nian Li, Shudong Zhang, and Zhenyang Wang Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.8b03093 • Publication Date (Web): 30 Oct 2018 Downloaded from http://pubs.acs.org on November 3, 2018

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Industrial & Engineering Chemistry Research

Electro-thermal

Conversion

Phase

Change

Composites: the Case of Polyethylene Glycol Infiltrated

Graphene

Oxide/Carbon

Nanotube

Networks Xinfeng Guo,†,§ Cui Liu,‡,§ Nian Li,‡ Shudong Zhang,*,‡ and Zhenyang Wang*,‡ † School of Electronic and Electrical Engineering, Nanyang Institute of Technology, Nanyang, Henan 473004, China. ‡ Institute of Intelligent Machines, Chinese Academy of Sciences, Hefei, Anhui 230031, China. *E-mail: [email protected]; [email protected].

Abstract: It is important for current practical electronics to run faultlessly in a good operating temperature because the electronic components (ECs) are not designed to work better at very low temperature, especially in cold climate and high-altitude zones. Herein, we designed and fabricated a conductive composite consisting of graphene oxide (GO)/carbon nanotube networks (CNTs) and polyethylene glycol (PEG) to fast supply heat through ECs even if at low temperature environment in future. The GO/CNTs/PEG composites afford a lot of conductive pathways by CNT networks with high conductivity and hold phase-change latent-heat material PEG for thermal energy storage and release, which permit self-heating of the composites through

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Joule heating generated by the low voltage across them. Therefore, the obtained composites may play an important role in thermal management applications for preheating effectively ECs to achieve desired performance and life cycle in the cold climate, etc.

KEYWORDS: electro-thermal conversion, phase change materials, Joule heating, thermal management, heat preservation For Table of Contents Only MCNTs GO

1. INTRODUCTION There is no doubt that the practical electronics have degrade performance or do not work well in cold climate, considering that some electronic components (ECs), such as resistors or capacitors, will fail at low temperature.1,2 Previous attempts to improve the low-temperature performance of ECs have focused on heating and insulating the units externally. In the prevalent methods, Joule heating is an effective, energy-efficient, and versatile method of heat preservation which is capable of real-time heating.3,4 Joule heating, also known as ohmic heating or resistive heating, is an electrothermal technique by the process in which the passage of an electric current through electrically conductive material release heat.5-8 Previously, the rigid, heavier metals or metal alloys are often used as Joule heating elements.3 Currently, lightweight, flexible, robust, and stable conductive composites and polymers have been developed and served as alternatives.9,10 It is worth mentioning that the main focus of these studies is how to fabricate appropriate conductive materials for producing Joule heat under an applied voltage. In this sense, developing


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di-functional nanocomposite materials process the performance of combining electro-thermal conversion with efficient thermal storage can help us avoid performance deterioration of ECs at both low and high temperature circumstance in practical applications. Therefore, it would be of great interest and useful to develop conductive materials if they can effectively collect, store and release heat energy, which will play an important role in thermal management applications for effectively preheating and heat preservation ECs. As a thermal storage material, it is well known that phase change materials (PCMs) exhibit a dramatic and reversible solid-liquid phase transition at a critical temperature (e.g. melting or solidification), accompanying with a large amount of latent heat storage or release, and have potential applications in many fields, such as solar energy storage, smart house construction, waste heat recovery, and so on.11-17 For instance, as a good example of solar thermal energy utilization, photodriven phase change composites with high sunlight-to-thermal storage efficiencies are taken as a kind of favorable thermal energy storage materials and show broad prospects is an effective solution to intermittent solar irradiation in time and space.

18-21

Nevertheless, inherent low thermal conductivity and sizeable volume fluctuation related to phase change resulting in leakage has bad influence on energy conversion and storage efficiency.22,23 Moreover, electrical insulator character of PCMs severely limits those applications in electricity as energy source.24 Therefore, the electrical conductivity of PCMs with improved and applicable encapsulation needs to be designed towards the catering for future energy conversion system, electronic components thermal control and safeguard.25-30 Herein, we explore a proposal of using conductive CNTs, graphene oxide (GO) with hydroxyl and carboxyl functional groups, and PEG with high thermal energy storage capacity to form an ideal stable composite material for thermal energy storage by Joule heating. First, the tunable


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conductivity of the obtained composites depends on interconnection of the CNTs to form electrical pathways because of their excellent electrical and thermal conductivities. Additionally, due to the presence of aromatic domains and functional groups (hydroxyl and carboxyl groups), GO becomes a very suitable material for direct imbedding PCMs into a layer-like matrix to effectively enhance stability of overall structures and preventing leakage and collapse.31-33 Last but not least, PEG1000 was chosen for appropriate melting/freezing temperatures in the prospective thermal energy storage application. The short-chain PEG can promote the colloidal dispersion of CNTs in water which is in favor of dispersing effectively the CNTs to form an electrical network in the obtained conductive composites due to a low hydrophilic-lipophilic balance.34,35 Therefore, due to their high conductive CNT networks, the newly fabricated GO/CNTs/PEG composites can achieve self-heating through Joule heating generated by a low voltage across them. Meanwhile, the composites can serve as a highly thermally conductive reservoir and hold phase-change material PEG for thermal energy storage and release without leakage. After a loss of power, the composites are able to continually output heat resulted from the heat storage capacity of the PEG units, ensuring effectively the ECs under a good operating temperature in cold climate, etc. The self-heated composites with energy storage and release are of vital importance to ensure desired performance of ECs and have wide potential for thermal management applications in future. 2. EXPERIMENTAL SECTION 2.1. Materials. MCNTs used were provided by Chengdu Organic Chemicals Co., Ltd., Chinese Academy of Sciences. Polyethylene glycol 1000 (PEG1000) with a melting temperature of 34-36 oC, potassium persulfate (K2S2O8), potassium permanganate (KMnO4), phosphorus pentoxide (P2O5), concentrated sulfuric acid (H2SO4), hydrochloric acid (HCl), and hydrogen


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peroxide 30% (H2O2) were provided by Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China). Natural graphite flake with an average particle size of 325 mesh and a purity of over 99.8% was purchased from Alfa Aesar Chemical Co., Ltd.. All chemicals were analytical-reagent grade. 2.2. Preparation of GO/CNTs/PEG composites. In a typical preparation process, firstly, GO was synthesized through acid oxidation of natural graphite flake by a classically Hummers method with minor modifications,36,37 as reported in our previous work.26 Secondly, different amount of PEG1000 (2.659g and 4.25g, respectively) was dissolved into ultrapure water (40 mL). CNTs (0.4g) were dispersed into above solution at room temperature subsequently. Then the acquired GO (0.3g) dispersed into ultrapure water (40 mL) was poured into the suspension under magnetic stirring to make the GO/CNT/PEG composites with PEG1000 weight percentages of 78% and 85%, respectively. In order to form a dispersed suspension, the above mentioned mixture was stirred over 24 hours at 60 oC. Last, the mixture was transferred to the wide-mouth containers over 24~36 hours at 70 oC, forming a gelatinous structure by evaporating excess water. Finally, the conductive netlike structure was fabricated into various shapes. 2.3. Characterization. The morphology of the GO/CNT/PEG composites was examined using a FEI Sirion-200 scanning electron microscope (SEM). X-ray diffraction (XRD) patterns of the samples were performed on a Philips X’Pert Pro Super diffractometer with Cu-Ka radiation (λ = 1.54178 Å). The thermal properties of the GO-CNT-PEG composites were investigated by differential scanning calorimetry (NETZSCH DSC 200 F3 instrument). The melting/freezing temperatures and latent heat of the composites were obtained at a heating/cooling rate of 10 oC min-1. The IR spectrums of PEG, GO, CNT and GO/CNT/PEG composites were measured using a Thermal-Fisher IS10 instrument, using pressed KBr tablets. Thermal gravimetric analysis (TGA) of the as-synthesized samples was carried out on a


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NETZSCH TG 209 F3 thermal analyzer from room temperature to 800 °C at a heating rate of 10 °C min-1 in atmosphere. 2.4. Thermal energy conversion and storage by Joule heating. For the characterization of electrical to thermal energy storage, before the as-prepared composites were completely dried, copper wires were plugged into the composites at the side surfaces, making good electrical contact with the GO/CNT network in a spiral configuration. A temperature sensor (the K-type thermalcouple) was inserted into the GO/CNT/PEG composites to measure the temperature inside the sample during the heating and cooling processes. Temperature evolution of the sample was recorded by a data logger thermometer (CENTER 300/301) connected to temperature sensor (the K-type thermalcouple). The range accuracy of the temperature sensor is -200 oC ~200 oC ± (0.3% reading + 1 oC). A laboratory DC power supply was connected to the sample to provide the sample a certain voltage. 3. RESULTS AND DISCUSSION 3.1. Morphologies. The conductive GO/CNT/PEG composites of 3D interconnected netlike GO/CNTs assembled in the phase-change material (PEG1000) matrix were prepared by evaporation at high temperature and air-drying under ambient temperature, as reported by our group recently (more details are shown in Experimental Section 2.2).29 And the bulk composites could be fabricated facilely into arbitrary shapes, including Rectangle and L type, etc., displayed in Figure 1A, B of optical images. No GO and CNTs were observed in a cross-sectional SEM image of GO/CNT/PEG composite (Figure 1C), showing that the GO and CNT were wrapped completely and formed a close contact by PEG1000 without any gaps (inset of Figure 1C). In other words, the GO and CNT can anchor PEG1000 collectively and prevent its leakage during


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reversible phase change process. The interfacial interactions of the GO/CNT/PEG composites were analyzed by FT-IR spectroscopy method (Figure S1). The FT-IR spectra demonstrated the shifts to lower wavenumbers because of the stretching band of –OH groups (1454→1404cm-1) and hydroxyl stretching band (3447→3435cm-1) originated from intermolecular interactions, particularly from the intermolecular hydrogen bonds (Figure S1). Obviously, GO/CNT networks (schematic illustration in Figure 1D) are important for not only improving the electronic conductivity of PEG but also ensuring a lot of conductive pathways for energy transfer along the edge of CNT.

A

C 20 μm

1 cm 100 μm

B D

MCNTs MCNTs GO GO

1 cm

Figure 1. Digital photographs of GO/CNTs/PEG composites with different shapes, such as Rectangle (A) and L type (B), respectively, showing their high structural stability. (C) SEM image with content PEG of 78 wt %, showing architectures of 3D netlike GO/CNTs. The highmagnification SEM image (inset) show that the 3D netlike GO/CNTs are wrapped by polyethylene glycol. (D) a simple schematic illustration of architecture of interconnected netlike GO/CNTs assembled in polyethylene glycol matrix. 3.2. Thermal stability. After phase change, the fluidity of organic PCMs may result in leakage during cyclic use. Thermal stability of the GO/CNTs/PEG composites and the loading


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ratio of PEG in the composites have been measured by TGA as illustrated in Figure S2. Pure PEG1000 began to decompose early at ca. 170 oC and decompose completely after thoroughly absorption of the heat (Figure S2). However, the weight loss temperature of GO/CNTs/PEG composites was up to ca. 220 oC. The decomposition points of the GO/CNTs/PEG composites were obviously higher than the pure PEG, in that the CNTs with high thermal conductivity can transport heat homogenously to the entire samples. In addition, the GO/CNT networks can further restrict the mobility of PEG chains and improve the thermal stability of the GO/CNTs/PEG composites. Therefore, above two reasons could mainly and remarkably increase the thermal stability of the GO/CNTs/PEG composites. Meanwhile, to compare the form-stable performance of the as-prepared GO/CNTs/PEG composites (78 wt% of PEG molecules), the leakage tests above the melting temperature of PEG1000 have been carried out (Figure S3). The pure PEG1000 melt gradually when heated at 70 oC. After heated at 70 oC for 10 min, the PEG1000 melted into liquid completely. Hardly change of phase-change behavior of the GO/CNTs/PEG composites was observed, indicating that the confining states of the PEG in GO/CNTs matrix remain nearly unchanged after the leakage tests. 3.3. Conductivity performance. Conductive performance of the obtained conductive GO/CNT/PEG composites is remarkably adjusted by the weight ratio of CNT to conductive composites. Upon increasing the weight ratio of CNT to conductive composites from 5 to 20 wt%, the resistance of conductive GO/CNT/PEG composites decreased from 17.2 × 103 to 0.9 kΩ, showing that addition of CNT leads to good electric conductivity, which is appropriate for their further application. However, conductive GO/CNT/PEG composites lost their processing characteristics at 30 wt% of CNT, for the reason that the increase of CNT decreases the noncovalent interaction of PEGs via reduction in hydrogen bond formation of PEG chains.


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Consequently, PEGs with ~9-12 wt% of CNT and ~6-8wt% of GO (weight ratio of CNT to GO is 3:2) were chosen on comprehensive consideration of thermal storage ability, electric conductivity, mechanical adaptability and further application in the field of preheating and heat preservation ECs.

A

GO/CNTs/PEG (78%)

Intensity Intensity (a.u.) (a.u.) Intensity Intensity a.u. a.u.

GO/CNTs/PEG (78%) GO/CNTs/PEG (85%) GO/CNTs/PEG (85%) MCNTs

MCNTs PEG

PEG GO GO

20 20

30 40 50 30 40 50 2 Theta 3 4 o 78% 2 Theta 16.14 C 10.11 oC B 32 C 43 78% 16.14 oC 10.11 oC 3 2 2 1 2 1 1 0 1 0 0 -1 0 -1 -1 -2 exo -1 37.24 oC -2 exo 33.85 oC -2 o -2 -3 exo -3 37.24 C 33.85 oC exo -3-60 -30 0 30 60 90 120 -3-60 -30 0 30 60 90 120 -60 -30 0 30 60 90 120 -60 -30 0 30 60 90 120 Heat Heat Flow Flow (W/g) (W/g)

10 10

Heat Heat Flow Flow (W/g) (W/g)

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Temperature (degree) Temperature (degree)

85 85

Temperature (degree) Temperature (degree)

Figure 2. (A) The XRD patterns of the as-prepared GO/CNTs/PEG composites containing the different amounts of PEG molecules (a) 78 wt%, (b) 85 wt%, (c) MCNTs, (d) PEG and (e) GO, respectively. DSC thermal spectra of GO/CNTs/PEG composites with different amounts of PEG molecules. (B) 78 wt% and (C) 85 wt%. Heat rate is 10 oC min-1. 3.4. Composition and thermal behavior. The obtained GO/CNTs/PEG composites were examined by X-ray diffraction patterns (XRD, Figure 2A) to analyze their structures and phase compositions. The XRD patterns (a and b in Figure 2A) of the GO/CNTs/PEG composites with


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high content of PEG (such as, 78 wt% and 85 wt%) didn’t exhibit a sharp peak at ~11° (e in Figure 2A), indicating that GO sheets hadn’t packed into an ordered layer structure,23 as suggested by the corresponding SEM image (Figure 1C). Meanwhile, the XRD patterns could be easily indexed to the structures of the CNTs and PEG (c and d in Figure 2A) and no other impurities peaks were obviously observed. Besides, heat storage capability was characterized by differential scanning calorimetry (DSC). Figure 2B and C shows the melting-freezing DSC curves of GO/CNTs/PEG composites with different PEG contents of 78 wt% and 85 wt%, respectively. The DSC curves for the GO/CNTs/PEG composites present endothermic peaks centered at 37.24 (78 wt% of PEG) and 33.85 °C (85 wt% of PEG) and exothermic peaks centered at 16.14 (78 wt% of PEG) and 10.11 oC (85 wt% of PEG), respectively, corresponding to the melting point (Tm) and freezing point (Tf) of PEG units. The melting point of GO/CNTs/PEG composites is very close to Tm of pristine PEG, presenting an endothermic peak centered at 35.7 oC (Figure S4). However, the freezing point of GO/CNTs/PEG composites show only a single sharp peak centered at 16.14 and 10.11 oC in the exothermal curve, respectively (Figure 2B and C), while multiple splitting peaks appear for pristine PEG (center temperature at 10.1 and 16.7 oC, as shown in Figure S4). That is to say, phase separation phenomena of pristine PEG are inhibited obviously. Considering PEG is uniformly embedded in GO/CNTs networks, the structure change of PEG with temperature change is delayed or in advance, resulted from the confinement effect of networks to change phase change temperature of the composites.22,38 The total latent heat of melting (ΔH) are 120.7 and 110.7 J/g for GO/CNTs/PEG composites with 85 wt% and 78 wt% PEG content, respectively. As compared with the ΔH for pure PEG of about 182.1 J/g, the thermal storage capability rate (η) is 66.3% and 60.6%, respectively. Those results


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demonstrate that the heat energy storage capacity of the obtained GO/CNTs/PEG composites is promising to utilize thermal energy. The presence of CNT networks could have an important role to increase the thermal behavior of GO/CNT/PEG composites, considering that single CNT has very high thermal conductivity. We have measured thermal conductivity of the obtained GO/CNT/PEG composites by the hotwire method at room temperature (Figure S5). As a parallel sample, pure PEG exhibits a very low thermal conductivity of 0.23 W m-1 K-1. For example, the high thermal conductivity of GO/CNTs/PEG composites was as high as 0.46 and 0.45 W m-1 K-1, with PEG content of 70 and 78 wt%, respectively, which represents a 2-fold enhancement. By increasing the content of PEG, the thermal conductivity of GO/CNTs/PEG composite with PEG content of 85 wt% drops by 17%

A Joule’s law Q=I2Rt

U 60 50

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7.0 V 6.6 V 6.2 V 5.8 V 5.4 V

40 30 20 10

Temperature (degree)


(0.37 W m-1 K-1). This is because CNT netwoks was disturbed by high PEG content.


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Figure 3. (A) Schematic illustration of thermal energy conversion and storage by Joule heating. Heating profile of the GO/CNTs/PEG composites with different shapes, including Rectangle (B)


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and L type (D), respectively, at different applied voltages. (C) Collection of temperature-time curves of the rectangle composite (78 wt% of PEG) were tested for 50 cycles by periodic Joule heating, showing a small shift of the temperature plateaus and the positions of PEG melting and freezing in all the cycles. 3.5. Electro-thermal conversion behavior. The obtained GO/CNTs/PEG composites afford a lot of conductive pathways by CNT networks with high conductivity, which permits self-heating of the composites through Joule heating generated during the voltage across them (more details are shown in Experimental Section 2.4). Besides, our composites can also absorb and store a large amount of heat in a short time. Accordingly, we can directly apply an electric voltage across the two ends of the bulk composites to initiate the energy conversion and storage from electro to heat via Joule’s law (Figure 3A). The temperature of the different samples is measured to evaluate the temperature evolution across the composite during Joule heating. The heating profiles of the composites with different shapes are shown in the time-dependent temperature profiles in Figure 3B-D. Such as for a piece of rectangle/L-type sample placed in an environmental temperature of 15 oC, the temperatures increase with applied voltage rising for all samples and reach an equilibrium state due to heat dissipation from the Joule-heating composites to environment. Based on the power P=U2/R, higher temperatures were generated when the voltage increased through the composites. And the sample temperature reach higher under higher applied voltage. For example, for the rectangle composite at 5.4 V, the temperature plateau is at 32 oC (Figure 3B). When the voltage is increased to 7 V, the temperature rises to 56 oC (Figure 3B). Meanwhile, the slopes of temperature-time profiles decrease gradually and follow to rise fast for applied voltage in the range of 5.8-7.0 V, showing that PEG1000 melting starts and ends in the scope of approaching a minimum slope. When the input voltage is terminated, all


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temperature curves drop promptly to the initial solidification temperature point of PEG1000 (~ 30 oC, see Figure 3B), consistent with the phase change temperature of the fabricated composites (Figure 2B), and the appearance of another tilt platform in the curve is related to PEG freezing and subsequent to phase change done. Similar behavior is demonstrated in the L-type sample (Figure 3D). In addition, the obtained composite shows a very stable performance during repeated Joule heating process. As shown in Figure 3C, the temperature-time curves of the rectangle composite were tested for 50 cycles under the same conditions, in which the temperature plateaus and the positions of PEG melting and freezing have a small shift from all the cycles. Such high reversibility is of importance for recycle application of the conductive and heat storage composites without degradation caused by Joule heating. Therefore, the obtained composites not only can be utilized to fast supply heat, electrical energy also can be stored as heat to cater for use in low temperature environments. The Joule heat (electro-to-heat) storage efficiency (the calculated method in the Figure S6) is about 70% under 6.6 V, but 63% under higher voltage (7.0 V) (Table S1 of the Supporting Information), which is attributed to convection heat loss from the Joule-heating composites to air.22,23 The corresponding Joule heat storage efficiency could be further improved to prevent heat loss to environment by some appropriate thermal isolation means. Additionally, the phase change temperature, melting enthalpy, and PCM content are more competitive than those of the former reports. More comparison with former research studies is shown in Table S2. 4. CONCLUSIONS In conclusion, a conductive GO/CNTs/PEG composite with 3D interconnected netlike GO/CNTs assembled in the phase-change material (PEG1000) matrix was successfully fabricated. It is successfully demonstrated that the heat generation and storage effect of the GO/CNTs/PEG


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composites can be produced by Joule-heating effect. The composites with enormous conductive pathways for electronic and heat transportation show a good response to electro-to-heat conversion and storage. Phase change material PEG matrix can collect, store thermal energy and supply heat for use to the required place later effectively. Therefore, the obtained composites may play an important role in thermal management applications for effectively preheating ECs to achieve desired performance and life cycle in the cold climate, etc. ASSOCIATED CONTENT Supporting Information. The Supporting Information is available free of charge. Supporting Information includes the contents of FT-IR, TGA, leakage test, DSC thermal spectra of PEG and Joule heat storage efficiency (PDF). AUTHOR INFORMATION Corresponding Author * Email: [email protected], [email protected]. Tel: (+86)-551-65591156. ORCID Zhenyang Wang 0000-0002-0194-3786 Shudong Zhang 0000-0002-0215-1641 Cui Liu 0000-0003-0496-9735 Nian Li 0000-0002-1267-629X Author Contributions The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. §These authors contributed equally.


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Notes The authors declare no competing financial interest. ACKNOWLEDGMENT This work was financially supported by the National Natural Science Foundation of China (No. 61605222, U1432132 and 51202253), the Innovative Program of Development Foundation of Hefei Center for Physical Science and Technology (2017FXCX006), and the Youth “spark” of Chinese Academy of China (YZJJ2018QN25). REFERENCES (1) Wang, C. Y.; Zhang, G. S.; Ge, S. H.; Xu, T.; Ji, Y.; Yang, X. G.; Leng, Y. J. Lithium-ion battery structure that self-heats at low temperatures. Nature 2016, 529, 515-518. (2) Armand, M.; Tarascon, J. M. Building better batteries. Nature 2008, 451, 652-657. (3) Raji, A. R. O.; Varadhachary, T.; Nan, K.; Wang, T.; Lin, J.; Ji, Y. S.; Genorio, B.; Zhu, Y.; Kittrell, C.; Tour, J. M. Composites of Graphene Nanoribbon Stacks and Epoxy for Joule Heating and Deicing of Surfaces. ACS Appl. Mater. Interfaces 2016, 8, 3551-3556. (4) Volman, V.; Zhu, Y.; Raji, A. R. O.; Genorio, B.; Lu, W.; Xiang, C.; Kittrell, C.; Tour, J. M. Radio-Frequency-Transparent, Electrically Conductive Graphene Nanoribbon Thin Films as Deicing Heating Layers. ACS Appl. Mater. Interfaces 2014, 6, 298-304. (5) Chen, C. C.; Lin, Y. S.; Sang, C. H.; Sheu, J.-T. Localized Joule Heating As a Mask-Free Technique for the Local Synthesis of ZnO Nanowires on Silicon Nanodevices. Nano Lett. 2011, 11, 4736-4741. (6) Song, T. B.; Chen, Y.; Chung, C. H.; Yang, Y.; Bob, B.; Duan, H. S. S.; Li, G.; Tu, K. N.; Huang, Y.; Yang, Y. Nanoscale Joule Heating and Electromigration Enhanced Ripening of Silver Nanowire Contacts. ACS Nano 2014, 8, 2804-2811.


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(7) Li, I. Park. Z. Y.; Pisano, A. P.; Williams, R. S. Selective Surface Functionalization of Silicon Nanowires via Nanoscale Joule Heating. Nano Lett. 2007, 7, 3106-3111. (8) Yun, J.; Jin, C. Y.; Ahn, J. H.; Jeon, S.; Park, I. A self-heated silicon nanowire array: selective surface modification with catalytic nanoparticles by nanoscale Joule heating and its gas sensing applications. Nanoscale 2013, 5, 6851-6856. (9) Zheng, Z. L.; Jin, J. D.; Xu, G. K.; Zou, J. L.; Wais, U.; Beckett, A.; Heil, T.; Higgins, S.; Guan, L. H.; Wang, Y.; Shchukin, D. Highly Stable and Conductive Microcapsules for Enhancement of Joule Heating Performance. ACS Nano 2016, 10, 4695-4703. (10) He, W. N.; Li, G. Y.; Zhang, S. Q.; Wei, Y.; Wang, J.; Li, Q. W.; Zhang, X. T. Polypyrrole/Silver Coaxial Nanowire Aero-Sponges for Temperature-Independent Stress Sensing and Stress-Triggered Joule Heating. ACS Nano 2015, 9, 4244-4251. (11) Zhang, S.; Wang, Z. Thermodynamics behavior of phase change latent heat materials in micro-/nanoconfined spaces for thermal storage and applications. Renew. Sustain. Energy Rev. 2018, 82, 2319-2331. (12) Wang, X.; Li, C.; Zhao, T. Fabrication and characterization of poly(melamineformaldehyde)/silicon carbide hybrid microencapsulated phase change materials with enhanced thermal conductivity and light-heat performance. Sol. Energy Mater. Sol. Cells 2018, 183, 82-91. (13) Wang, W.; Tang, B.; Ju, B.; Gao, Z.; Xiu, J.; Zhang, S. Fe3O4-functionalized graphene nanosheet embedded phase change material composites: efficient magnetic- and sunlight-driven energy conversion and storage. J. Mater. Chem. A 2017, 5, 958-968. (14) Liu, J.; Chen, L.; Fang, X.; Zhang, Z. Preparation of graphite nanoparticles-modified phase change microcapsules and their dispersed slurry for direct absorption solar collectors. Sol. Energy Mater. Sol. Cells 2017, 159, 159-166.


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(15) Huang, X.; Alva, G.; Jia, Y.; Fang, G. Morphological characterization and applications of phase change materials in thermal energy storage: a review. Renew. Sustain. Energy Rev. 2017, 72, 128-145. (16)Aftab, W.; Huang, X.; Wu, W.; Liang, Z.; Mahmood, A.; Zou, R. Nanoconfined phase change materials for thermal energy applications. Energy Environ. Sci. 2018, 11, 1392. (17) Li, B.; Liu, T.; Hu, L.; Wang, Y.; Nie, S. Facile preparation and adjustable thermal property of stearic acid-graphene oxide composite as shape-stabilized phase change material. Chem. Eng. J. 2013, 215-216, 819-826. (18) Li, B.; Nie, S.; Hao, Y.; Liu, T.; Zhu, J.; Yan, S. Stearic-acid/carbon-nanotube composites with tailored shape-stabilized phase transitions and light-heat conversion for thermal energy storage. Energy Convers. Manage. 2015, 98, 314-321. (19) Wu, W.; Huang, X.; Li, K.; Yao, R.; Chen, R.; Zou, R. A functional form-stable phase change composite with high efficiency electro-to-thermal energy conversion. Appl. Energy 2017, 3, 474-480. (20) Hassina, T.; Huang, X.; Chen, R.; Zou, R. Tailoring Thermal Properties via Synergistic Effect in a Multifunctional Phase Change Composite Based on Methyl Stearate. J. Materiomics 2015, 1, 229-235. (21) Huang, X.; Xia, W.; Zou, R. Nanoconfinement of phase change materials within carbon aerogels: phase transition behaviours and photo-to-thermal energy storage. J. Mater. Chem. A 2014, 2, 19963-19968.


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Page 18 of 19

(22) Chen, L. J.; Zou, R. Q.; Xia, W.; Liu, Z. P.; Shang, Y. Y.; Zhu, J. L.; Wang, Y. X.; Lin, J. H.; Xia, D. G.; Cao, A. Y. Electro- and Photodriven Phase Change Composites Based on WaxInfiltrated Carbon Nanotube Sponges. ACS Nano 2012, 6, 10884-10892. (23) Chen, R. J.; Yao, R. M.; Xia, W.; Zou, R. Q. Electro/Photo to Heat Conversion System Based on Polyurethane Embedded Graphite Foam. Appl. Energ. 2015, 152, 183-188. (24) Kürklü, A. Energy storage applications in greenhouses by means of phase change materials (PCMs): a review. Renew. Energ. 1998, 13, 89-103. (25) Xin, F.; Li, L.; Chan, S. H.; Zhao, J. Influences of carbon fillers on electrical conductivity and crystallinity of polyethylene terephthalate. J. Compos. Mater. 2012, 46, 10911099. (26) Moniruzzaman, M.; Winey, K. I. Polymer nanocomposites containing carbon nanotubes. Macromolecules 2006, 39, 5194-5205. (27) Potts, J. R.; Dreyer, D. R.; Bielawski, C. W.; Ruoff, R. S. Graphene based polymer nanocomposites. Polymer 2011, 52, 5-25. (28) Luan, V. H.; Tien, H. N.; Cuong, T. V.; Kong, B. S.; Chung, J. S.; Kim, E. J.; Sur, S. H. Novel conductive epoxy composites composed of 2-D chemically reduced graphene and 1-D silver nanowire hybrid fillers. J. Mater. Chem. 2012, 22, 8649-8653. (29) Jiang, Y. C.; Wang, Z. Y.; Shang, M. Y.; Zhang, Z. P.; Zhang, S. D. Heat collection and supply of interconnected netlike graphene/polyethyleneglycol composites for thermoelectric devices. Nanoscale 2015, 7, 10950-10953. (30) Liu, Z.; Zou, R.; Lin, Z.; Gui, X.; Chen, R.; Lin, J. Tailoring Carbon Nanotube Density for Modulating Electro-to-Heat Conversion in Phase Change Composites. Nano Lett. 2013, 13, 4028-4035.


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(31) Zhang, S. D.; Tao, Q. H.; Wang, Z. Y.; Zhang, Z. P. Controlled heat release of new thermal storage materials: the case of polyethylene glycol intercalated into graphene oxide paper. J. Mater. Chem. 2012, 22, 20166-20169. (32) Ramakrishnan, S.; Wang, X. M.; Sanjayan, J. Thermal performance of buildings integrated with phase change materials to reduce heat stress risks during extreme heatwave events. Appl. Energ. 2017, 194, 410-421. (33) Wang, T.; Jiang,Y.; Huang,J.; Wang,S. High thermal conductive paraffin/calcium carbonate phase change microcapsules based composites with different carbon network. Appl. Energ. 2018, 218, 184-191. (34) Wickramaratne, C.; Dhau, J. S.; Kamal, R.; Myers, P.; Goswami, D.Y.; Stefanakos, E. Macro-encapsulation and characterization of chloride based inorganic Phase change materials for high temperature thermal energy storage systems. Appl. Energ. 2018, 221, 587-596. (35) Jin, Z.; Mcnicholas, T. P.; Shih, C. J. Click Chemistry on Solution-Dispersed Graphene and Monolayer CVD Graphene. Chem. Mater. 2011, 23, 3362-3370. (36) Hummers, W. S.; Offeman, R. E. Preparation of graphitic oxide. J. Am. Chem. Soc. 1958, 80, 1339-1339. (37) Tung, V. C.; Allen, M. J.; Yang, Y.; Kaner, R. B. Graphene oxide as a transparent and flexible electronic material. Nat. Nanotech. 2009, 4, 25. (38) Siligin, S. S.; Derya, K.; Cemil, A.; Isa, G. Biodegradable PEG/cellulose, PEG/agarose and PEG/chitosan blends as shape stabilized phase change materials for latent heat energy storage. Carbohyd. Polym. 2011, 84, 141-144.


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