Reinforcement and shape stabilization of phase-change material via graphene oxide aerogel

doi:10.1016/j.carbon.2016.11.069

Carbon

Volume 114, April 2017, Pages 334-346

https://doi.org/10.1016/j.carbon.2016.11.069 Get rights and content

Abstract

Phase change materials (PCMs) are of interest in many applications which may require shape-stabilization. In this study, a graphene oxide aerogel (GOxA) reinforced paraffin PCM composite is developed, effectively reinforcing and shape-stabilizing the paraffin.

The molecular and diffraction characterizations suggest that the GOxA network potentially affects paraffin's crystallization. The mechanical characterizations using durometer and nanoindentation show that the composite is 3∼7× harder than pure paraffin and maintains significant strength even above paraffin's melting temperature. Moreover, the composite is much less strain-rate sensitive than paraffin. The reinforcement via GOxA is much beyond the prediction by the rule-of-mixture, implying a strong GOxA-paraffin interfacial bonding.

To our best knowledge, this is the first study on the mechanical behavior of paraffin and GOxA-PCM composite, providing critical insights into their behavior. Additionally, the relationship between the hardness and durometer index first-ever developed here will enable the quantitative durometer testing on materials for many other applications at different ambient conditions due to its versatility and simplicity.

Introduction

Phase change materials (PCMs) store and/or release thermal energy through the solid-liquid phase transition and exhibit the advantages of low cost and high energy density, making them a popular choice for energy storage materials [1], [2], [3], [4], [5], [6]. Paraffin is a high-performance PCM owing to its high latent heat, low super cooling, and chemical stability; however, its intrinsic low thermal conductivity can make it difficult to transfer energy effectively into larger masses, and the possibility of liquid phase leakage can lower the perceived reliability of the systems [1], [2], [7], [8], [9].

Aerogels are porous materials with extremely low bulk density, composed of nanoparticles, nanowires, nanotubes, or nanosheets of oxides [10], [11], [12], silicon [12], metals [12], [13], [14], [15], and carbon materials [16], [17], [18], [19]. Graphene-based three-dimensional (3D) aerogels have drawn attention due to their unique properties, including low density, high porosity, large specific surface area, excellent electrical conductivity and outstanding mechanical properties [9], [16], [20], [21], [22], [23], [24], [25], [26], [27], [28], [29]. This leads to many potential applications including energy storage [1], [9], [16], [30], [31], super-capacitors [20], [23], air and water purification [32], [33], and nanocomposites [34].

Recently, much research has focused on the integration of graphene-based nanomaterials with high thermal conductivities into PCMs to increase their overall thermal conductivity [35], [36], [37]. It is also known that graphene aerogel (GA) impregnated with PCM exhibited a rise in thermal conductivity [38].

While the use of nano-inclusions can mitigate the effects of low thermal conductivity, it is also necessary to address the issue of liquid leakage. Some methods are available to mitigate this potential leakage, such as encapsulation and shape stabilization [2], [39], [40]. Shape stabilization of PCMs occurs through the addition of supporting materials into the PCM which can hold the liquid phase in place with the matrix, usually by capillary action. Possible supporting materials include high density polyethylene (HDPE) [2], opal [8], graphite [41], carbon nanospheres [40], graphene oxide (GOx) [3], [4], [42], graphene aerogel [30], [38], exfoliated graphite nanoplatelets (xGnP) [43], graphite nanoplatelets [5], [44], and graphene nanoplatelets [45]. In some cases, large amounts of supporting materials are needed in order to shape stabilize PCMs. For example, a GO-paraffin composite showed no liquid leakage at 51.7 wt% of GO, but the latent heat dropped by 52% [4]. In the case of HDPE PCM [2], the shape-stabilization required at least 25–30 wt% of HDPE. In this paper instead, the use of graphene oxide aerogel (GOxA) is explored as both a shape stabilizer and a thermal conductivity enhancer, because its use has been shown to not decrease the latent heat [38].

Most studies of PCMs have focused on their thermal characteristics, but their mechanical properties are also vitally important particularly as related to the shape stabilization behavior. The mechanical properties of graphene-based and GO-based polymer composites have been studied, showing improvements in their strength and modulus [8], [46], [47], [48], [49], [50] compared to the pure polymer counterparts. However, to our knowledge, the mechanical properties and shape stabilization behavior of GOxA-PCM composite have never been fundamentally studied. A comprehensive fundamental understanding of the mechanical behavior of GOxA-PCM composite is thus vitally important to understand the behavior of GOxA alone, pure paraffin, and the composite.

Typically, mechanical properties of porous 3D carbon aerogels/networks have been studied through either compression or nanoindentation tests. Table A1 in Appendix 1 summarizes some of the recent results, indicating a large discrepancy in the literature values. For example, for pristine graphene aerogel (GA) with density less than ∼30 mg/cm³, data on strength is in the wide range of 0.2–40 kPa, while the modulus data shows a range of 2–1200 kPa. In general, by increasing the bonding between carbon nanomaterials, e.g., by noble metal [51] or crosslinking [52], the overall strength and modulus should increase.

In this work, by infiltrating GOxA with paraffin, a PCM composite with ∼5 wt% of GOxA is formed. The mechanical behavior with respect to both shape stabilization and mechanical properties will be comprehensively characterized at different strain rates as well as at a range of temperatures, including above the melting point of the PCM. While the thermal analysis of this GOxA-PCM composite is also of interest, it will be left for a future paper in order to concentrate here on the mechanical characteristics.

To our best knowledge, this is the first study on the fundamental strain-rate-dependent and temperature-dependent mechanical behaviors of paraffin and GOxA-PCM composite, providing critical insights to understand the behavior of graphene-related PCM composites and their application into the design of high-performance energy storage PCM composites with high reliability.

Section snippets

Material and methods

The graphite powder was purchased from Spectrum Chemical Manufacturing Corp. The sodium nitrate (NaNO₃, high purity grade) and potassium permanganate (KMnO₄, ACS grade) were obtained from Amresco, Inc. The hydrogen peroxide (H₂O₂, 29–32% w/w ar. soln.) and Ethylenediamine (EDA, 99%) were purchased from Alfa Aesar. Paraffin wax (IGI 1230A) was purchased from International Group, Inc. All were used in as-purchased conditions.

In general, graphene-based aerogels are prepared by assembling 2D

Morphology and crystal structure characterization of graphene oxide aerogel

Images of the GOx suspension, GOxH and GOxA are shown in Fig. 1. The GOxH showed some volume shrinkage after self-assembly (Fig. 1a–b), although this shrinkage is minor compared to other chemical reduction methods [20]. Fig. 1b–c show that the GOxH shrank roughly by 1/3 after the supercritical CO₂ drying and kept the 3D structure nicely.

The GOxAs' density ρ ranges from 17 to 36 mg/cm³ based on 5 samples. The GOxAs' specific surface area (A_S) is determined as high as 476 m²/g. If we assume

Conclusions

A 5 wt% graphene oxide aerogel (GOxA) reinforced paraffin-PCM composite is developed. The composite maintains its original shape above melting temperature of the PCM and to hold the molten paraffin without any leakage, indicating superior shape stabilization.

The X-ray diffraction and Fourier transform infrared (FTIR) spectra imply a potentially new phase at the GOxA-paraffin interface in the composite. Durometer testing indicates that the composite is much harder than paraffin at both room

Acknowledgements

The authors appreciate the support of the National Science Foundation (CBET-1235769). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. We thank Nancy Peltier in Biology Department at Villanova for her help with the supercritical CO₂ drying. We also appreciate the comprehensive comments and constructive suggestions from the reviewers of this paper.

References (104)

J.F. Li et al.
Simultaneous enhancement of latent heat and thermal conductivity of docosane-based phase change material in the presence of spongy graphene
Sol. Energy Mater. Sol. Cells
(2014)
R. Ehid et al.
Development and characterization of paraffin-based shape stabilized energy storage materials
Energy Convers. Manag.
(2012)
G.-Q. Qi et al.
Polyethylene glycol based shape-stabilized phase change material for thermal energy storage with ultra-low content of graphene oxide
Sol. Energy Mater. Sol. Cells
(2014)
M. Mehrali et al.
Shape-stabilized phase change materials with high thermal conductivity based on paraffin/graphene oxide composite
Energy Convers. Manag.
(2013)
J.-L. Zeng et al.
Preparation and thermal properties of palmitic acid/polyaniline/exfoliated graphite nanoplatelets form-stable phase change materials
Appl. Energy
(2014)
M.M. Farid et al.
A review on phase change energy storage: materials and applications
Energy Convers. Manag.
(2004)
M. Xiao et al.
Preparation and performance of shape stabilized phase change thermal storage materials with high thermal conductivity
Energy Convers. Manag.
(2002)
Y. Zhong et al.
Effect of graphene aerogel on thermal behavior of phase change materials for thermal management
Sol. Energy Mater. Sol. Cells
(2013)
A. Mikhalchan et al.
Continuous and scalable fabrication and multifunctional properties of carbon nanotube aerogels from the floating catalyst method
Carbon
(2016)
T. Horikawa et al.
Size control and characterization of spherical carbon aerogel particles from resorcinol–formaldehyde resin
Carbon
(2004)

G. Tang et al.

Three dimensional graphene aerogels and their electrically conductive composites

Carbon

(2014)

Y. Qian et al.

Ultralight, high-surface-area, multifunctional graphene-based aerogels from self-assembly of graphene oxide and resol

Carbon

(2014)

M.B. Lim et al.

Ultrafast sol–gel synthesis of graphene aerogel materials

Carbon

(2015)

S.T. Nguyen et al.

Morphology control and thermal stability of binderless-graphene aerogels from graphite for energy storage applications

Colloids Surfaces A Physicochem. Eng. Aspects

(2012)

R.J. Warzoha et al.

Temperature-dependent thermal properties of a paraffin phase change material embedded with herringbone style graphite nanofibers

Appl. Energy

(2015)

R.J. Warzoha et al.

Effect of carbon nanotube interfacial geometry on thermal transport in solid–liquid phase change materials

Appl. Energy

(2015)

J. Yang et al.

Cellulose/graphene aerogel supported phase change composites with high thermal conductivity and good shape stability for thermal energy storage

Carbon

(2016)

S. Tahan Latibari et al.

Synthesis, characterization and thermal properties of nanoencapsulated phase change materials via sol–gel method

Energy

(2013)

M. Mehrali et al.

Effect of carbon nanospheres on shape stabilization and thermal behavior of phase change materials for thermal energy storage

Energy Convers. Manag.

(2014)

Z. Zhang et al.

Study on paraffin/expanded graphite composite phase change thermal energy storage material

Energy Convers. Manag.

(2006)

Z. Sun et al.

Study on preparation and thermal energy storage properties of binary paraffin blends/opal shape-stabilized phase change materials

Sol. Energy Mater. Sol. Cells

(2013)

J.-N. Shi et al.

Improving the thermal conductivity and shape-stabilization of phase change materials using nanographite additives

Carbon

(2013)

S. Wi et al.

Thermal properties of shape-stabilized phase change materials using fatty acid ester and exfoliated graphite nanoplatelets for saving energy in buildings

Sol. Energy Mater. Sol. Cells

(2015)

M. Mehrali et al.

Preparation and characterization of palmitic acid/graphene nanoplatelets composite with remarkable thermal conductivity as a novel shape-stabilized phase change material

Appl. Therm. Eng.

(2013)

C.-C. Ji et al.

Self-assembly of three-dimensional interconnected graphene-based aerogels and its application in supercapacitors

J. Colloid Interface Sci.

(2013)

N. Shukla et al.

FTIR study of surfactant bonding to FePt nanoparticles

J. Magnetism Magnetic Mater.

(2003)

R. Yogamalar et al.

X-ray peak broadening analysis in ZnO nanoparticles

Solid State Commun.

(2009)

Y.H. Zhao et al.

Microstructures and mechanical properties of ultrafine grained 7075 Al alloy processed by ECAP and their evolutions during annealing

Acta Mater.

(2004)

G. Feng et al.

An analytical expression for the stress field around an elastoplastic indentation/contact

Acta Mater.

(2007)

D. Jauffrès et al.

Mechanical properties of hierarchical porous silica thin films: experimental characterization by nanoindentation and Finite Element modeling

Microporous Mesoporous Mater.

(2011)

R. Crawford et al.

Experimental study on the lift generation inside a random synthetic porous layer under rapid compaction

Exp. Therm. Fluid Sci.

(2012)

X. Li et al.

A review of nanoindentation continuous stiffness measurement technique and its applications

Mater. Charact.

(2002)

J.M. Wheeler et al.

Activation parameters for deformation of ultrafine-grained aluminium as determined by indentation strain rate jumps at elevated temperature

Mater. Sci. Eng. A

(2013)

G. Feng et al.

Indentation size effect in MgO

Scr. Mater.

(2004)

K.O. Kese et al.

Method to account for true contact area in soda-lime glass during nanoindentation with the Berkovich tip

Mater. Sci. Eng. A

(2005)

G. Feng et al.

Creep and strain burst in indium and aluminium during nanoindentation

Scr. Mater.

(2001)

P. Zhang et al.

General relationship between strength and hardness

Mater. Sci. Eng. A

(2011)

W.D. Nix et al.

Indentation size effects in crystalline materials: a law for strain gradient plasticity

J. Mech. Phys. Solids

(1998)

M.-Y. Shen et al.

Mechanical properties and tensile fatigue of graphene nanoplatelets reinforced polymer nanocomposites

J. Nanomater.

(2013)

T.F. Baumann et al.

Synthesis of high-surface-area alumina aerogels without the use of alkoxide precursors

Chem. Mater.

(2005)

M. Moner-Girona et al.

Sol-gel route to direct formation of silica aerogel microparticles using supercritical solvents

J. Sol-Gel Sci. Technol.

(2003)

S.M. Jung et al.

A facile route for 3D aerogels from nanostructured 1D and 2D materials

Sci. Rep.

(2012)

Y. Tang et al.

Ultralow-density copper nanowire aerogel monoliths with tunable mechanical and electrical properties

J. Mater. Chem. A

(2013)

S.M. Jung et al.

Porous Cu nanowire aerosponges from one-step assembly and their applications in heat dissipation

Adv. Mater.

(2016)

W. He et al.

Polypyrrole/silver coaxial nanowire aero-sponges for temperature-independent stress sensing and stress-triggered joule heating

ACS Nano

(2015)

M.A. Worsley et al.

Synthesis and characterization of monolithic carbon aerogel nanocomposites containing double-walled carbon nanotubes

Langmuir

(2008)

T.Q. Tran et al.

Advanced morphology-controlled manufacturing of carbon nanotube fibers, thin films and aerogels from aerogel technique

H. Hu et al.

Ultralight and highly compressible graphene aerogels

Adv. Mater.

(2013)

L. Qiu et al.

Mechanically robust, electrically conductive and stimuli-responsive binary network hydrogels enabled by superelastic graphene aerogels

Adv. Mater.

(2014)

Y. Xu et al.

Self-assembled graphene hydrogel via a one-step hydrothermal process

ACS Nano

(2010)

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