A Novel 3D Network Architectured Hybrid Aerogel Comprising Epoxy

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Functional Nanostructured Materials (including low-D carbon)

A Novel 3D Network Architectured Hybrid Aerogel Comprising Epoxy, Graphene and Hydroxylated Boron Nitride Nanosheets Wei Yang, Ning-Ning Wang, Peng Ping, Anthony Chun-Yin Yuen, Ao Li, San-E Zhu, Li-Li Wang, Jian Wu, Timothy Bo-Yuan Chen, Jing-Yu Si, Bao-Dong Rao, Hong-Dian Lu, Qing Nian Chan, and Guan-Heng Yeoh ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.8b15301 • Publication Date (Web): 31 Oct 2018 Downloaded from http://pubs.acs.org on November 1, 2018

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ACS Applied Materials & Interfaces

A Novel 3D Network Architectured Hybrid Aerogel Comprising Epoxy, Graphene and Hydroxylated Boron Nitride Nanosheets

Wei Yang a, b, 1, Ning-Ning Wang a, 1, Peng Ping a, Anthony Chun-Yin Yuen b, Ao Li b, San-E Zhu a, Li-Li Wang a, Jian Wu c, Timothy Bo-Yuan Chen b, Jing-Yu Si a, Bao-Dong Rao a, Hong-Dian Lu a, *, Qing Nian Chan b, Guan-Heng Yeoh b

a

Department of Chemical and Materials Engineering, Hefei University, Hefei, Anhui

230601, People’s Republic of China b

School of Mechanical and Manufacturing Engineering, University of New South

Wales, Sydney, NSW 2052, Australia c

Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Materials

Technology and Engineering, Chinese Academy of Sciences, Ningbo, Zhejiang 315201, People’s Republic of China

*Correspondence 1

to: Hongdian Lu (E-mail: [email protected], Tel: 86-551-62158393)

These authors contributed equally to this work (co-first author).

KEYWORDS: aerogel, graphene, boron nitride, highly compressible, thermal properties

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ABSTRACT:

A

novel

three-dimensional

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(3D)

epoxy/graphene

nanosheet/hydroxylated boron nitride (EP/GNS/BNOH) hybrid aerogel was successfully fabricated in this study. This was uniquely achieved by constructing a well-defined and interconnected 3D network architecture. The manufacturing process of EP/GNS/BNOH involved a simple one-pot hydrothermal strategy followed by the treatment of freeze-drying and high temperature curing. In comparison with EP/GNS-3, EP/GNS/BNOH-3 demonstrated improvement of 97% for compressive strength at 70% strain. Through compression tests performed, fracture occurred for EP/GNS-3 at ninth compression cycles whilst EP/GNS/BNOH-3 retained its original form after twenty compression cycles with a residual height of 97% (i.e. only 3% reduction). By the addition of BNOH in the polymer matrix, the dynamic heat transfer and dissipation rates of EP/GNS/BNOH aerogels were also considerably reduced, indicating that the aerogel with BNOH additive possessed excellent thermal insulation properties. Thermogravimetric analysis results revealed that the thermal stabilities of EP/GNS and EP/GNS/BNOH aerogels were improved with increasing loading of EP, and EP/GNS/BNOH aerogels exhibited better thermal stability at high temperatures. Through the elevated levels attained in the compressive strength, super-elasticity and thermal resistance, EP/GNS/BNOH aerogels has the great potential of being a very effective thermal insulation material to be utilized across a board range of applications in building, automotive, spacecraft and mechanical systems.

1. INTRODUCTION 2 ACS Paragon Plus Environment

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Aerogels comprise of highly porous three-dimensional (3D) architectures with ultra-low density, high specific surface area, low thermal conductivity and strong adsorption. They can be potentially utilized for heat insulation,1-3 catalysis and photocatalysis supports,4,5 adsorbents,6-8 energy storage,9,10 pharmaceutical and biomedical applications.11,12 Recently, graphene aerogel (GA) and other 3D graphene macrostructures, including graphene foam (GF) and graphene hydrogel (GH), have attracted much interest within the material science community due to their superior physiochemical properties and increasing practical usages.13,14 Among the aforementioned graphene macrostructures, GA, a porous 3D graphene macrostructure assembled by individual reduced graphene oxide (rGO) nanosheets is one of the most extensively studied aerogel materials that have been used as adsorbents for water remediation, electrodes in electrochemical energy devices, supercapacitors, sensors, and fuel cells.13,15-19 GAs are commonly prepared through a sol-gel process where 3D interconnected structure is formed via gelation of GO dispersion by adding cross-linkers, reducing agent, or treating at an elevated temperature and pressure using a hydrothermal method.19-23 Although GAs display many outstanding properties such as electrical conductivity and adsorption, they generally suffer from low mechanical strength (see Table 1).24-26 Therefore, a viable method to improve the mechanical strength of GA is deemed essential if the material is intended to be targeted for applications in building, automotive, spacecraft and mechanical systems. In order to improve the mechanical properties of GA whilst maintaining its inherent porous structure, polymers are always added into the GA porous matrix 3 ACS Paragon Plus Environment


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structure to yield hybrid aerogels either by direct freeze-drying of the GO/polymer precursor or surface coating of polymers onto the GA walls.19,26-28 Reactive monomers are also utilized which will react with the functional groups of GO to form 3D crosslinking network aerogel via the covalent bonding. For example, Li et al. prepared tri-isocyanate reinforced GA (RGA) with a low bulk density (0.08 g/cm3) and high compressive failure strength (0.24 MPa) through self-assembly of graphene under

hydrothermal

condition,

tri-isocyanate

reinforcement

and

subsequent

supercritical CO2 drying process.29 Although the compressive strength is extremely high, one of the main issues is that the resultant aerogel has a compressible deformation of less than 25%. Ye et al. created EP/GO hybrid aerogels via solution blending, direct freeze drying and high temperature curing.30 The compressive strength of the hybrid aerogels increases with the concentration of GO. However, the elastic properties were measured via only 5 repeat compression tests at 50% strain, which can’t illustrate the reliability on super-elasticity. Introduction of other nanoparticles to GA, such as carbon nanotube (CNT),31 polypyrrole nanotube (PNT),32 MoS2 nanosheets,33 provides another effective avenue to improve GA’s mechanical properties, leading to the increase layer spacing between graphene and the enhancement in hydrogen bond and/or π-π interactions. However, the improvement on mechanical properties is limited especially when the CNT and MoS2 nanosheets are added into the graphene aerogels. Recently, hexagonal boron nitride (BN) nanosheets, denoted as “white graphene” due to its honeycomb atomic structure have attracted much interest for their excellence in mechanical strength and 4 ACS Paragon Plus Environment

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thermal conductivity (~2000 W m-1 K-1 by theoretical calculation and 380 W m-1 K-1 by experience).34,35 In spite of the reported mechanical, thermal and electrical properties of BN/graphene hybrids,36-40 very limited studies on BN/graphene aerogels exist, and the performance of the material in terms of mechanical and thermal properties are yet to be explored. The present study aims to fill the gap of knowledge via the creation of a novel hybrid GAs using BN as reinforcement for both mechanical and thermal properties. In this work, layered hexagonal BN was initially exfoliated in isopropanol. In order to increase the oxygen-containing functional groups, exfoliated BN was treated in NaOH solution under hydrothermal condition, and the hydroxylated boron nitride (BNOH) nanosheets were subsequently prepared. Hydrogels based on GO, epoxy (EP) and BNOH were then prepared via one-pot hydrothermal method. After the process of freeze drying and high temperature curing, the novel 3D network hybrid aerogels were fabricated (see Scheme 1). The mechanical and thermal properties of the hybrid aerogels were thoroughly investigated and discussed in upcoming sessions.

2. EXPERIMENTAL SECTION Materials. 1,4-butanediol diglycidyl ether (BDGE), triethylenetetramine (TETA), trisodium citrate (NaC), isopropanol and sodium hydroxyl (NaOH) were purchased from Sinopharm Chemical Reagent Co., Ltd. (China). Hexagonal boron nitride (h-BN, 99.9%, 1-2 μm) was supplied by Aladdin Reagent Co. Ltd., China. Graphene oxide 5 ACS Paragon Plus Environment


(GO) aqueous dispersion (5 mg/ml) was supplied by Suzhou Tanfeng Graphene Technology Co., Ltd. (China). All chemicals applied in the preparation procedures were used as received. Preparation of exfoliated BNOH nanosheets. 2.0 g of h-BN powder was added to a solution of 100 ml isopropanol and 100 ml deionized water. The mixture was mechanically stirred at 1500 rpm and simultaneously sonicated using ultrasonic baths at 50 W for 12 h (JK-5200B, Hefei Kinnic Machinery Manufacture Co., Ltd., China). The dispersions were centrifuged at 4000 rpm for 10 min to remove non-exfoliated h-BN powders. The exfoliated BN (E-BN) in the resultant supernatant was collected by centrifugation at 9000 rpm for 30 min then dried at 60 °C for 24 h (see Scheme 1 a). The mass of E-BN was approximately 0.2 g, indicating that the yield was about 10%. After 5 time repeated experiments, 1.0 g E-BN was collected. 0.6 g E-BN was then dispersed in 60 ml of 5 M NaOH aqueous solution with ultrasonic agitation for 30 min. The mixture was subsequently hydrothermally treated at 120 °C for 24 h. The products were washed using deionized water to ca. pH=7, collected by centrifugation and dried at 60 °C for 24 h. A stable aqueous dispersion of BNOH nanosheets (5 mg/ml) was obtained without any precipitation for 6 h after ultrasonic agitation treatment for 1 h (see Scheme 1 a and b). Preparation of epoxy/graphene nanosheet/BNOH (EP/GNS/BNOH) hybrid aerogels. The EP/GNS/BNOH hybrid aerogels were prepared by a facile one-pot hydrothermal strategy (see Scheme 1 b). Typically, the desired amounts of BDGE and TETA were firstly mixed in iced deionized water with magnetic stirring for 1 h to 6 ACS Paragon Plus Environment

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obtain a BDGE-TETA solution. Various amounts of GO and BNOH dispersions and NaC aqueous solution (10 wt%), as listed in Table S1, were sequentially added into the BDGE-TETA solution with gentle stirring for 1 h. The mixtures were transferred to a Teflon vessel and hydrothermally treated at 120 °C for 24 h. Subsequently, the as-prepared hydrogel was transferred into a lyophilizer and froze at -56 °C for 24 h. Finally, the cylinder samples were taken out and vacuum freeze-dried for 96 h. The aerogels were finally obtained after thermal curing at 110 °C for 12 h, followed by 135 °C for 2 h. Characterizations. X-ray diffraction (XRD) was studied via a D/max-TTR III X-ray diffractometer equipped with a Cu-Kα radiation (λ=1.5418 Å). Infrared spectra were

obtained

using

a

Fourier-transform

infrared

spectroscopy

(FTIR)

spectrophotometer (Nicolet 6700). The morphology of boron nitride was analyzed by JEM-2010F transmission electron microscope at an acceleration voltage of 200 kV. Microscopic images of the hybrid aerogels were examined using a SU8010 field-emission scanning electron microscopy (FESEM, Japan). The aerogel samples were fractured in liquid nitrogen and the fracture surfaces were later coated with gold before SEM observations. Compression tests were carried out on a Universal Testing Machine (China) with a speed of 1 mm/min. Three repeated tests for the hybrid aerogels were carried out to obtain the average value of compressive strength. To evaluate the elasticity of the hybrid aerogels, EP/GNS-3 and EP/GNS/BNOH-3 were selected to perform the compression cycle test up to 80% compression of the original portion height. The samples were submitted to several continuous compression cycles 7 ACS Paragon Plus Environment


with the same loading rate of 1 mm/min. To study the thermal dynamic transfer and thermal dissipation properties of aerogels, the variations of temperature with time for all aerogel samples were recorded by an infrared thermograph (Testo 865, Germany). Thermogravimetric analysis (TGA) was conducted with a Netzsch TG209 F1 thermoanalyzer instrument (Germany). The sample with 4~10 mg was heated from room temperature to 700 °C at a heating rate of 10 °C/min under nitrogen condition.

3. RESULTS AND DISCUSSION 3.1. Structure characterization. The structure and morphology of BNOH were characterized by XRD, FTIR and TEM as shown in Figure 1 (a-e). Figure 1 (a) shows that all the powders, h-BN, E-BN and BNOH, exhibit identical diffraction features, which correspond to the (002), (100), (101), (004) and (110) planes of the h-BN skeleton. It indicates that the hydrothermal treatment in NaOH solution did not affect the crystalline structure of the BNOH.41 In Figure 1 (b), two strong FTIR bands at 1395 and 805 cm-1 are observed for h-BN, E-BN and BNOH, which are attributed to the B-N stretching and deformation vibrations, respectively.41 The intensity of the peak centered at 3440 cm-1 corresponds to the O-H stretching mode. It can be clearly seen that the peak at 3440 cm-1 of BNOH is stronger than that of h-BN and E-BN. It indicates that the hydrothermal treatment can effectively increase the content of hydroxyl groups on the surface boron nitride, which is beneficial to the dispersion of boron nitride in aqueous solution and increase the surface activity of boron nitride. From the TEM images of E-BN shown in Figure 1 (c) and Figure S3 (a), it is 8 ACS Paragon Plus Environment

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observed that most of the BN sheets are thick with average lateral size of about 300 nm. It indicates that h-BN is not effectively exfoliated to the thinner layers. After the hydrothermal treatment in sodium hydroxide solution, thinner BN sheets are obtained, and the average lateral size of BNOH is reduced to 100-200 nm (see Figure 1d and S3b). The higher magnification TEM image of BNOH (Figure 1e) shows a well flaked structure and semi-transparent structure with smooth surface.41 It indicates that the hydrothermal treatment under alkaline condition is beneficial to the formation of ultrathin BN nanosheets with smaller lateral size. This can be attributed to the self-curling-assisted layer-by-layer exfoliation mechanism.42,43 In Figure 1 (d), the nanoscrolls and folded nanosheets can be found in the areas pointed by the red arrow. It confirms the self-curling behavior of the E-BN sheets at the edges, which is induced by the adsorption of cations (Na+) on the surface of E-BN sheets.42 After the initial self-curling, OH- can easily adsorb on the positively curved surface and trigger the following curling of the E-BN sheet. Meanwhile, Na+ starts to adsorb on the newly exposed surface and drive the next round of exfoliation. Therefore, the ultrathin BN nanosheets are achieved via the layer-by-layer exfoliation. Additionally, the reaction between BN and NaOH also leads to the reduction of lateral size of BN nanosheets. Figure 1 (c) shows the XRD patterns of GNS, GNS/BNOH, EP/GNS-2 and EP/GNS/BNOH-2 aerogels. The characteristic peak of GNS does not appear in the pattern of the EP/GNS-2 sample, because the GNS sheets are fully exfoliated in the epoxy resin and the coverage of numerous on GNS sheets. For EP/GNS/BNOH-2, the intensity of BNOH becomes weak, which further confirms the coverage of EP on 9 ACS Paragon Plus Environment


GNS and BNOH nanosheets. The FTIR spectra of EP, EP/GNS-2 and EP/GNS/BNOH-2 are shown in Figure 1 (d). The peak at 1580 cm-1 in the spectra of EP/GNS-2 and EP/GNS/BNOH-2 corresponds to the stretching vibration of C=C in graphene. The peak at 1398 cm-1 in the spectrum of EP/GNS-2 is attributed to tertiary C-OH groups stretching.44,45 The absorption band at 3380 cm-1 in the spectrum of EP corresponds to the stretching vibration of O-H. When GNS is added into EP, the absorption bands of O-H stretching vibration shifts to lower wavenumbers (3332 cm-1), resulting from the hydrogen bonding interaction.30,46 For EP/GNS/BNOH-2, the absorption band of O-H stretching vibration becomes weaker and wider, indicating the further reinforcement of hydrogen bonding interaction between EP, GNS and BNOH. The peaks around 2864 and 2930 cm-1 are related to the C-H stretching vibration. The absorption band around 1108 cm-1 corresponds to the C-N band of amino hardener.47,48 The peak at 1452 cm-1 in the FTIR spectrum of epoxy is attributed to the amino (N-H) hardener group vibrations. The peaks at 1242 and 956 cm-1 are related to the epoxide bonds.49 There are almost no absorption bands at 1242 and 956 cm-1 in the FTIR spectrum of EP/GNS/BNOH-2, which indicates there is sufficient reaction between epoxide groups and amino (N-H) hardener or O-H in GNS and BNOH under hydrothermal condition (see Scheme 1). The absorption bands at 1350 and 768 cm-1 in the FTIR spectrum of EP/GNS/BNOH-2 should be attributed to the B-N stretching and deformation vibrations. In addition, both of the absorption bands are lower than those of BNOH (1395 and 805 cm-1), which is probably resulted from the reaction between BNOH and EP. 10 ACS Paragon Plus Environment

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Figure 2 shows the morphology of EP/GNS and EP/GNS/BNOH hybrid aerogels. From Figure 2 (a), it can be seen that EP/GNS-1, with the highest GNS content of 7.2% has a 3D “house of cards” microstructure. As shown in Figure 2 (b), the thickness of the internal slice increases significantly with the decrease in GNS content (EP/GNS-2). Owing to the increase of BDGE and TETA content, TETA can attach to the surface of GO via the reaction between the amines of TETA and the epoxy groups of GO. Through the cross-linking reaction between TETA and BDGE, GO nanosheets are encapsulated by the epoxy resins leading to the formation of thick hybrid layers (see Scheme 2a). After the hydrothermal treatment in sodium citrate solution, GO nanosheets are reduced to graphene nanosheets (GNS). With further decrease of GNS content, it can be clearly observed that the average pore size of EP/GNS-3 becomes smaller, and graphene nanosheets are covered by numerous epoxy resins, similar to the bulk structure of EP. As a result, there is a substantial increase on the density of EP/GNS-3 (see Table S1). The structural evolution of EP/GNS/BNOH aerogels is similar to EP/GNS aerogels. However, compared to EP/GNS-2, EP/GNS/BNOH-2 has a more perfect 3D network architecture (see Figure 2 e). Because the hydroxyl content of the BNOH surfaces is relatively low, BNOH nanosheets can be more uniformly dispersed in an aqueous solution, rather than aggregates like GO. When BNOH is dispersed into the GO layers, it can weaken the interaction of the GO layers, leading to a decrease of GO aggregates. In the hydrothermal environment, the hydroxyl groups on the surface of BNOH can react with epoxy groups of BDGE followed by a further cross-linking reaction with TETA (see Scheme 1). Compared to 11 ACS Paragon Plus Environment


GO, the lateral dimension of BNOH nanosheets is smaller, indicating that the unit mass of BNOH has a larger number of particles. Therefore, during the internal slices of GO, numerous BNOH nanosheets connect with GO via the epoxy resins generated by the cross-linking reaction of BDGE and TETA, resulting in the formation of a good 3D network architecture. It can be also seen from the SEM images of EP/GNS/BNOH-3 that there is a well-defined and interconnected 3D porous network with a large quantity of small pores while the porous structure of EP/GNS-3 is inhomogeneous and more similar to bulk structure (see Figure S4 e, f and S5). From the magnified SEM image and element mapping for EP/GNS/BNOH-3 (see Figure S6), it is clearly observed that the bigger GO nanosheets are connected by the EP chains, and B element, representing BNOH nanosheets, is detected. It shows that BNOH nanosheets are wrapped by lots of EP chains (represented by C element), and they are also homogeneously dispersed in EP/GNS. It indicates that the epoxy resin serves as a “glue” to bind the GO and BNOH nanosheets together to form 3D networks. The presence of BNOH promotes the formation of the unique hierarchical and more perfect 3D network architectures. 3.2. Compression properties. Figure 3 shows the compressive stress-strain curves of EP/GNS and EP/GNS/BNOH hybrid aerogels. All the graphene-based aerogels exhibit high compressibility and can bear a compression strain as high as 72%. The compressive strength of EP/GNS shows an obvious increasing trend when the GNS loading decreases in the aerogels (see Figure 3 a). As shown in Figure 3 (b), the compressive strengths at 70% strain are 0.0070, 0.0640 and 0.1590 MPa respectively, 12 ACS Paragon Plus Environment

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for EP/GNS-1 (7.2 wt% GNS), EP/GNS-2 (4.9 wt% GNS) and EP/GNS-3 (2.3 wt% GNS) aerogels. This trend is determined by the structural evolution of EP/GNS. As noted in the above discussion, lower content of GNS leads to smaller pores and higher density on EP/GNS aerogels. The increase of stress is attributed to the smaller pore size of the aerogel providing higher stiffness and compressive strength.50 The compressive strengths of EP/GNS/BNOH aerogels have a similar trend to EP/GNS aerogels, but the compressive stress is significantly improved when GNS is substituted by BNOH. The compressive strengths at 70% strain for EP/GNS/BNOH-1, EP/GNS/BNOH-2 and EP/GNS/ BNOH-3 are 0.0121, 0.1126 and 0.3128 MPa, respectively. Compared to EP/GNS-3, The compressive strength of EP/GNS/BNOH-3 is increased by 97%, which is also much higher than most of the reported results (see Table 1). This significant increase on compressive strength can be attributed to the more compact 3D porous network caused by the introduction of BNOH, which leads to greater forces required to cause deformation. Elasticity is one of the most desired properties of aerogel materials.30,51 As a way of measuring the elastic properties, EP/GNS-3 and EP/GNS/BNOH-3 underwent several successive compression cycles to 80% strain until they were broken. Because of the high density, it was a relatively slow process for the compressed EP/GNS-3 to recover to the original shape, with a recovery time of around 13 minutes. Alternatively, the recovery process of EP/GNS/BNOH-3 was faster, which was around 1.5 minutes. EP/GNS-3 and EP/GNS/BNOH-3 show different performances during the first 5 compression cycles (see Figure 3 c, d and S7). For EP/GNS-3, after the first 13 ACS Paragon Plus Environment


compression, it only recovers back to 97% of the original height. From the second to the fifth compression, the stress-strain curves remain at the steady level, and the strength is higher than at the first compression cycle. The permanent deformation resulted from the first compression cycle creates a more compact internal structure that is more resistant to external force impacts, thus increasing the compressive strength. For EP/GNS/BNOH-3, it recovers to the original height during all five compression cycles, while the compressive strength reduces slightly at the fifth compression. After the eighth compression cycle, EP/GNS-3 and EP/GNS/BNOH-3 recover to 88% and 97% of the original height respectively. EP/GNS-3 is broken at the ninth compression cycle (see Figure S7 and S8). On the other hand, despite the decrease in stress, EP/GNS/BNOH-3 still recovered to 97% of the original height after 20 times compression cycles. The results indicate that EP/GNS/BNOH-3 has a better performance on compressibility and super elasticity. The improved compression properties are attributed to the unique hierarchical and interconnected 3D network architecture of EP/GNS/BNOH-3. Epoxy resins act as organic spacers and flexible links in the GNS and BNOH nanosheets, which impart rubber-like elasticity to the hybrid aerogels.30 When EP/GNS/BNOH-3 is subjected to external stress, the load can effectively transfer from the graphene nanosheets to disordered BNOH nanosheets, which can significantly improve the strength and elastic stiffness of the cell walls. After the seventh time of compression, partially disordered graphene and BNOH nanosheets become ordered under the influence of external force, leading to a weakened ability to resist external forces (see Scheme 2b). 14 ACS Paragon Plus Environment

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As a result, starting from the eighth compression, the maximum compressive strength decreases significantly, and permanent deformation (residual height of 97%) occurs. From the eighth to the twentieth compression, the average value of the maximum compressive strength is 0.6049 MPa, while the residual height remains at 97%, which indicate that the 3D network architecture remains undamaged. On the contrary, EP/GNS-3 is broken after the ninth compression. This can be attributed to the poor 3D network architecture of EP/GNS-3, which is more prone to permanent deformation. Additionally, the EP molecular chains between the GNS layers are easily broken when receiving a strong external force due to the lack of support from the inorganics with high stiffness (see Scheme 2a). 3.3. Dynamic thermal transfer and dissipation properties. The thermal dynamic transfer and dissipation properties of EP/GNS and EP/GNS/BNOH hybrid aerogels were investigated by monitoring the variations of temperature with time. Each aerogel sample was placed on the centre of one of the edges of a thermostatic heater (100 mm × 100 mm) with the temperature set at 170 °C, as measured in our previous work.52 The lateral-surface temperature of each aerogel sample was recorded by an infrared thermal imager. The optical photographs of EP/GNS-3 are illustrated in Figure 4, which provides a representation of the thermal dynamic transfer and dissipation properties. Point M was chosen as the reference point (center point approximately 5 mm from the bottom of the sample). Temperature of the sample at this point was recorded every 20 seconds and plotted in Figure 5 (a). Point N was chosen as the reference point (center point approximately 5 mm from the bottom of the sample). 15 ACS Paragon Plus Environment


Temperature of the sample at this point was recorded every 10 seconds and plotted in Figure 5 (c). As can be seen in Figure 5 (a) the temperature of the M point for all samples increases rapidly within 40 s, and the dynamic heat balance is reached at about 120 s. From Figure 5 (b), the temperature increasing rate of the sample during the initial 40 s decreases with the reduction of GNS and GNS/BNOH concentration in both EP/GNS and EP/GNS/BNOH systems. Moreover, at the same addition amount, the heating rate of EP/GNS/BNOH is lower than that of EP/GNS. Figure 5 (c) describes the heat dissipation curves of the N point temperature over time for all samples. Figure 5 (d) shows that the cooling rate of aerogels in the temperature range of 70-45 °C reduces with the decrease of GNS and GNS/BNOH content. The EP/GNS/BNOH has a lower cooling rate than the EP/GNS at the same loading. This indicates that the presence of BNOH leads to the better reduction in dynamic heat transfer rate and heat dissipation and improves the heat insulation capacity of EP/GNS/BNOH aerogel. These features highlight the great potential of BNOH in the field of thermal insulation materials. The changes in the thermal dynamic transfer and dissipation properties are attributed to the combination of aerogel components and structural changes. In the EP/GNS system, GNS is a better thermal conductor than EP. Thus by introducing GNS into EP, the thermal conductivity will be significantly enhanced. In addition, the higher the content of GNS, the closer the structure of the aerogel is to the layer structure thus the temperature rises faster. When the content of GNS is reduced, the microstructure of the aerogel becomes denser. Such a structure of the aerogel causes a 16 ACS Paragon Plus Environment

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relatively slow heat transfer process when the temperature is raised and lowered. When BNOH is introduced into EP/GNS, the internal 3D structure of the aerogel becomes more regular and compact. Therefore, heat transfer becomes more difficult inside the EP/GNS/BNOH aerogel. Additionally, it can be seen from Figure 5 (c) that the temperature at point N of EP/GNS/BNOH-2 is much higher than that of EP/GNS-2, and the temperature at point N of EP/GNS/BNOH-3 is higher than EP/GNS-3 in the range of 10-90 s. This result provides further evidence that this phenomenon is caused by the compact network architecture of the aerogel from the introduction of BNOH. 3.4. Thermal stability. The thermal decomposition behaviors of EP, GNS and BNOH are shown in Figure S9. EP undergoes a one-step thermal decomposition process, beginning from 251 °C (T-5%), reaching to the maximum weight loss rate at 321 °C (Tmax) and leaving 3.6 wt% residue at 700 °C. The thermal decomposition curve of BNOH shows almost no weight loss ranging from 50-700 °C, illustrating outstanding thermal stability. GNS has lower thermal stability (T-5%=103 °C) with a main decomposition step occurring between 150 and 400 °C, due to the removal of the oxygen-containing groups of un-reduced GO.30 Compared to neat EP, the presence of GNS reduces the onset thermal decomposition temperature of EP/GNS aerogels (see Table 2), because of the lower decomposition temperature of GNS compared to cured EP. With decreasing concentration of GNS, the thermal stability of EP/GNS aerogels is improved, as shown in Figure 6 (a). It indicates that the high loading of EP is beneficial to the 17 ACS Paragon Plus Environment


enhancement of thermal stability for EP/GNS aerogels. EP/GNS/BNOH aerogels show a similar trend of initial decomposition temperature (see Figure 6 c and Table 2). However, the T-5% values of EP/GNS/BNOH-2 and EP/GNS/BNOH-3 are lower than those of EP/GNS-2 and EP/GNS-3, respectively. This can be attributed to the difference in structures. In EP/GNS-2 and EP/GNS-3 aerogel samples, the graphene nanosheets are wrapped by large amounts of epoxy resins (see Figure 2 b and c). As a result, the pyrolysis of GNS are influenced by the thermally stable EP. In contrast, there is more perfect 3D network architecture in EP/GNS/BNOH-2 and EP/GNS/BNOH-3 aerogel samples. The epoxy resins are homogeneously distributed in the aerogels, which binds the GO and BNOH nanosheets. Therefore, the improvement of T-5% value for EP/GNS/BNOH aerogels is not as remarkable as EP/GNS aerogels when the EP concentration increases. In the temperature region between 250-350 °C, EP decomposes very rapidly with a T-50% value of 322 °C. Owing to the porous structure, the thermal transfer in EP-based aerogels is more difficult than that of EP bulk. Additionally, there is a barrier effect in the aerogels caused by GNS and BNOH. As a result, the T-50% values of EP/GNS and EP/GNS/BNOH aerogels are much higher than that of EP (see Table 2). The results indicate that compared to neat EP, the presence of GNS and BNOH delay the decomposition of EP-based aerogels in high temperature region. However, the onset thermal decomposition temperatures of EP/GNS and EP/GNS/BNOH aerogels are lower. Figure 6 (b) and (d) show the DTG curves of EP/GNS and EP/GNS/BNOH hybrid 18 ACS Paragon Plus Environment

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aerogels. All the curves exhibit two decomposition steps. The first decomposition step is attributed to the weight loss of GNS (Tmax1), and the other one corresponds to the decomposition of EP (Tmax2). Neglecting EP/GNS-1, the Tmax1 values of EP/GNS and EP/GNS/BNOH aerogels improves with increasing EP concentration. Furthermore, the Tmax1 values of EP/GNS-2 and EP/GNS-3 are higher than those of EP/GNS/BNOH-2 and EP/GNS/BNOH-3, respectively. It is consistent with the T-5% value, indicating that the presence of EP can improve the thermal stability of the hybrid aerogels and the effect improves with better coverage of EP around the GNS surfaces. In the second decomposition step, the maximum weight loss rate of EP is much higher than that of EP-based aerogels, as shown in Figure 6 (b and d) and Figure S8 (b). In addition, all the Tmax1 values of EP/GNS and EP/GNS/BNOH aerogels are larger than that of neat EP. This result can be attributed to the porous structure of aerogels and the barrier effect of GNS and BNOH. With the exception of EP/GNS-3 and EP/GNS/BNOH-3, the Tmax2 values of EP/GNS/BNOH-1 and EP/GNS/BNOH-2 are higher than those of EP/GNS-1 and EP/GNS-2, respectively. Furthermore, the addition of BNOH into EP/GNS can improve residue contents due to the barrier effect of the thermally stable BNOH.

4. CONCLUSIONS In this article, EP/GNS/BNOH hybrid aerogels have been prepared for the first time through a simple one-pot hydrothermal strategy followed by the process of freeze-drying and high temperature curing. The surface hydroxyl groups of BNOH 19 ACS Paragon Plus Environment


reacts with BDGE, and further cross-linking reactions with TETA will take place in the hydrothermal environment. During the internal slicing of GO, cross-linking action occurs among numerous BNOH nanosheets with BDGE, TETA and connect slices of GO, leading to the successful fabrication of EP/GNS/BNOH aerogel with a well-organized and defined 3D network architecture. Through mechanical testing, the compressive strength of EP/GNS/BNOH-3 aerogel was significantly higher than EP/GNS-3 (~1.97 times) and EP/GNS/BNOH-3 managed to recover 97% of its original height after 20 times compression cycles. In contrast, fracture occurred during the ninth compression cycle for EP/GNS-3. The results clearly demonstrated that the highly ordered and compact 3D porous aerogel network of the EP/GNS/BNOH-3 significantly increased the compressibility and super elasticity of the aerogel. EP/GNS/BNOH has also lower heating and cooling rates in comparison to EP/GNS aerogel with the same loading. The addition of BNOH not only increased the heat insulation capacity of EP/GNS/BNOH aerogel, but also reduced its heat dissipation capacity. With increasing loading of EP, the thermal stability of EP/GNS/ BNOH aerogels was significantly improved. Since the presence of GNS and BNOH can complimentarily create an effective barrier in the porous structure, the amount of residue remained for EP/GNS/BNOH aerogels was considerably enhanced. These uniquely fabricated EP/GNS/BNOH aerogels satisfy a number of key performance factors: low cost, super elasticity, elevated compressive strength and exceptionally high thermal resistance, which they can be potentially applied in numerous building, automotive, spacecraft and mechanical systems. 20 ACS Paragon Plus Environment

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ASSOCIATED CONTENT Supporting Information The Supporting Information is available free of charge on the ACS Publications website. Table S1. Formulation and density of EP/GNS and EP/GNS/BNOH hybrid aerogels; Figure S1. The chemical structure of BDGE and TETA; Figure S2. Digital photos of the as-prepared EP/GNS and EP/GNS/BNOH hybrid aerogels; Figure S3. The TEM images of E-BN (a) and BNOH (b); Figure S4. SEM images of EP/GNS and EP/GNS/BNOH hybrid aerogels; Figure S5. SEM images of EP/GNS-3 (a) and EP/GNS/BNOH-3 (b) hybrid aerogels; Figure S6. SEM images of EP/GNS-3 (a) and EP/GNS/BNOH-3 (b) hybrid aerogels; (c) magnified SEM image and element mapping for EP/GNS/BNOH-3; Figure S7. Stress-strain curves for repeat compression tests on EP/GNS-3 (a) and EP/GNS/BNOH-3 (b-d) at 80% strain; Figure S8. The digital photographs for EP/GNS-3 (a) after the 9th compression and EP/GNS/BNOH-3 (b) after the 20th compression; Figure S9. TG (a) and DTG (b) curves of EP, GNS and BNOH; Figure S10. The diced aerogel sample for EP/GNS/BNOH-2.

AUTHOR INFORMATION Corresponding Author *E-mail: [email protected]. 21 ACS Paragon Plus Environment


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ORCID Wei Yang: 0000-0003-4759-4996 Hong-Dian Lu: 0000-0002-8630-9740 Notes The authors declare no competing financial interest.

ACKNOWLEDGEMENTS The work was financially supported by National Natural Science Foundation of China (51276054, 51403048, and 21702042), Anhui Provincial Key Technologies R&D Program (1804a09020070), Program of Anhui Province for Outstanding Talents in University (gxbjZD39), Natural Science Foundation in University of Anhui Province (KJ2016A606 and KJ2018A0550), Talent Scientific Research Foundation of Hefei University (16-17RC07 and 16-17RC15), Program for Excellent Young Talents in University of Anhui Province (gxfx2017098), Natural Science Foundation of Shanxi Province (201701D221055). It is also sponsored by the Australian Research Council Industrial Training Transformation Centre (ARC IC170100032). All financial and technical supports are deeply appreciated by the authors.

REFERENCES (1)

Maleki,

H.;

Whitmore,

L.;

Hüsing,

N.

Novel

Multifunctional

Polymethylsilsesquioxane–Silk Fibroin Aerogel Hybrids for Environmental and Thermal Insulation Applications. J. Mater. Chem. A 2018, 6, 12598-12612. 22 ACS Paragon Plus Environment

Page 23 of 43 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(2) Seantier, B.; Bendahou, D.; Bendahou, A.; Grohens, Y.; Kaddami, H. Multi-Scale

Cellulose

based

New

Bio-Aerogel

Composites

with

Thermal

Super-Insulating and Tunable Mechanical Properties. Carbohyd. Polym. 2016, 138, 335-348. (3) Zu, G.; Kanamori, K.; Shimizu, T.; Zhu, Y.; Maeno, A.; Kaji, H.; Nakanishi, K.; Shen, J. Versatile Double-Cross-Linking Approach to Transparent, Machinable, Supercompressible, Highly Bendable Aerogel Thermal Superinsulators. Chem. Mater. 2018, 30, 2759-2770. (4) Maleki, H.; Hüsing, N. Current Status, Opportunities and Challenges in Catalytic and Photocatalytic Applications of Aerogels: Environmental Protection Aspects. Appl. Catal., B 2018, 221, 530-555. (5) Hees, T.; Zhong, F.; Rudolph, T.; Walther, A.; Mulhaupt, R. Nanocellulose Aerogels for Supporting Iron Catalysts and In Situ Formation of Polyethylene Nanocomposites. Adv. Funct. Mater. 2017, 27, 1605586-1605593. (6) Si, Y.; Fu, Q.; Wang, X.; Zhu, J.; Yu, J.; Sun, G.; Ding, B. Superelastic and Superhydrophobic Nanofiber-Assembled Cellular Aerogels for Effective Separation of Oil/Water Emulsions. ACS Nano 2015, 9, 3791-3799. (7) Sun, F.; Liu, W.; Dong, Z.; Deng, Y. Underwater Superoleophobicity Cellulose Nanofibril Aerogel through Regioselective Sulfonation for Oil/Water Separation. Chem. Eng. J. 2017, 330, 774-782.



Page 24 of 43

(8) Ma, C. -B.; Du, B.; Wang, E. Self-Crosslink Method for A Straightforward Synthesis of Poly(Vinyl Alcohol)-based Aerogel Assisted by Carbon Nanotube. Adv. Funct. Mater. 2017, 27, 1604423-1604431. (9) Sha, C.; Lu, B.; Mao, H.; Cheng, J.; Pan, X.; Lu, J.; Ye, Z. 3D Ternary Nanocomposites of Molybdenum Disulfide/Polyaniline/Reduced Graphene Oxide Aerogel for High Performance Supercapacitors. Carbon 2016, 99, 26-34. (10) Cheng, L.; Du, X.; Jiang, Y.; Vlad, A. Mechanochemical Assembly of 3D Mesoporous

Conducting-Polymer

Aerogels

for

High

Performance

Hybrid

Electrochemical Energy Storage. Nano Energy 2017, 41, 193-200. (11) Stergar, J.; Maver, U. Review of Aerogel-based Materials in Biomedical Applications. J. Sol-Gel Sci. Technol. 2016, 77, 738-752. (12) Ulker, Z.; Erkey, C. An Emerging Platform for Drug Delivery: Aerogel based Systems. J. Control Release 2014, 177, 51-63. (13) Fang, Q.; Shen, Y.; Chen, B. Synthesis, Decoration and Properties of Three-Dimensional Graphene-based Macrostructures: A Review. Chem. Eng. J. 2015, 264, 753-771. (14) Gao, Y.; Tang, Z. Design and Application of Inorganic Nanoparticle Superstructures: Current Status and Future Challenges. Small 2011, 7, 2133-2146. (15) Xiao, J.; Tan, Y.; Song, Y.; Zheng, Q. A Flyweight and Superelastic Graphene Aerogel as A High-Capacity Adsorbent and Highly Sensitive Pressure Sensor. J. Mater. Chem. A 2018, 6, 9074-9080. (16) Wu, S.; Ladani, R.; Zhang, J.; Ghorbani, K.; Zhang, X.; Mouritz, A. P.; 24 ACS Paragon Plus Environment

Page 25 of 43 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Kinloch, A. J.; Wang, C. H. Strain Sensors with Adjustable Sensitivity by Tailoring the Microstructure of Graphene Aerogel/PDMS Nanocomposites. ACS Appl. Mater. Interfaces 2016, 8, 24853-24861. (17) Cao, X.; Yin, Z.; Zhang, H. Three-Dimensional Graphene Materials: Preparation, Structures and Application in Supercapacitors. Energy Environ. Sci. 2014, 7, 1850-1865. (18) Nardecchia, S.; Carriazo, D.; Ferrer, M. L.; Gutiérrez, M. C.; Del Monte F. Three dimensional macroporous architectures and aerogels built of carbon nanotubes and/or graphene: Synthesis and applications. Chem. Soc. Rev. 2013, 42, 794-830. (19) Wang, Z.; Shen, X.; Garakani, M. A.; Lin, X.; Wu, Y.; Liu, X.; Sun, X.; Kim, J. -K. Graphene Aerogel/Epoxy Composites with Exceptional Anisotropic Structure and Properties. ACS Appl. Mater. Interfaces 2015, 7, 5538-5549. (20) Zhang, X.; Sui, Z.; Xu, B.; Yue, S.; Luo, Y.; Zhan, W.; Liu, B. Mechanically Strong and Highly Conductive Graphene Aerogel and Its Use as Electrodes for Electrochemical Power Sources. J. Mater. Chem. 2011, 21, 6494-6497. (21) Bai, H.; Li, C.; Wang, X.; Shi, G. On the Gelation of Graphene Oxide. J. Phys. Chem. C 2011, 115, 5545-5551. (22) Worsley, M. A.; Pauzauskie, P. J.; Olson, T. Y.; Biener, J.; Satcher, J. H.; Baumann, T. F. Synthesis of Graphene Aerogel with High Electrical Conductivity. J. Am. Chem. Soc. 2010, 132, 14067-14069. (23) Xu, Y.; Sheng, K.; Li, C.; Shi, G. Self-Assembled Graphene Hydrogel via A One-Step Hydrothermal Process. ACS Nano 2010, 4, 4324-4330. 25 ACS Paragon Plus Environment


(24) Li, J.; Li, J.; Meng, H.; Xie, S.; Zhang, B.; Li, L.; Ma, H.; Zhang, J.; Yu, M. Ultra-Light, Compressible and Fire-Resistant Graphene Aerogel as A Highly Efficient and Recyclable Absorbent for Organic Liquids. J. Mater. Chem. A 2014, 2, 2934-2941. (25) Hu, H.; Zhao, Z.; Wan, W.; Gogotsi, Y.; Qiu, J. Ultralight and Highly Compressible Graphene Aerogels. Adv. Mater. 2013, 25, 2219-2223. (26) Ha, H.; Shanmuganathan, K.; Ellison, C. J. Mechanically Stable Thermally Crosslinked Poly(Acrylic Acid)/Reduced Graphene Oxide Aerogels. ACS Appl. Mater. Interfaces 2015, 7, 6220-6229. (27) Qiu, L.; Liu, D.; Wang, Y.; Cheng, C.; Zhou, K.; Ding, J.; Truong, V. -T.; Li, D. Mechanically Robust, Electrically Conductive and Stimuli-Responsive Binary Network Hydrogels Enabled By Superelastic Graphene Aerogels. Adv. Mater. 2014, 26, 3333-3337. (28) Hu, H.; Zhao, Z.; Wan, W.; Gogotsi, Y.; Qiu, J. Polymer/Graphene Hybrid Aerogel with High Compressibility, Conductivity, and “Sticky” Superhydrophobicity. ACS Appl. Mater. Interfaces 2014, 6, 3242-3249. (29) Li, J.; Wang, F.; Liu, C. Tri-isocyanate Reinforced Graphene Aerogel and Its Use for Crude Oil Adsorption. J. Colloid Interf. Sci. 2012, 382, 13-16. (30) Ye, S.; Feng, J.; Wu, P. Highly Elastic Graphene Oxide-Epoxy Composite Aerogels via Simple Freeze-Drying and Subsequent Routine Curing. J. Mater. Chem. A 2013, 1, 3495-3502. (31) Hu, H.; Zhao, Z.; Gogotsi, Y.; Qiu, J. Compressible Carbon 26 ACS Paragon Plus Environment

Page 26 of 43

Page 27 of 43 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Nanotube-Graphene

Hybrid

Aerogels

with

Superhydrophobicity

and

Superoleophilicity for Oil Sorption. Environ. Sci. Technol. Lett. 2014, 1, 214-220. (32)

Ye,

S.;

Feng,

Graphene/Polypyrrole

J.

Self-Assembled

Nanotube

Hybrid

Three-Dimensional

Aerogel

and

Its

Hierarchical

Application

For

Supercapacitors. ACS Appl. Mater. Interfaces 2014, 6, 9671-9679. (33) He, P.; Zhao, K.; Huang, B.; Zhang, B.; Huang, Q.; Chen, T.; Zhang, Q. Mechanically Robust and Size-Controlled MoS2/Graphene Hybrid Aerogels as High-Performance Anodes for Lithium-Ion Batteries. J. Mater. Sci. 2018, 53, 4482-4493. (34) Jo, I.; Pettes, M. T.; Kim, J.; Watanabe, K.; Taniguchi, T.; Yao, Z.; Shi, L. Thermal Conductivity and Phonon Transport in Suspended Few-Layer Hexagonal Boron Nitride. Nano Lett. 2013, 13, 550-554. (35) Fang, H.; Bai, S.; Wong, C. P. “White Graphene”-Hexagonal Boron Nitride based Polymeric Composites and Their Application in Thermal Management. Compos. Commun. 2016, 2, 19-24. (36) Barrios-Vargas, J. E.; Mortazavi, B.; Cummings, A. W.; Martinez-Gordillo, R.; Pruneda, M.; Colombo, L.; Rabczuk, T.; Roche, S. Electrical and Thermal Transport in Coplanar Polycrystalline Graphene-hBN Heterostructures. Nano Lett. 2017, 17, 1660-1664. (37) Eshkalak, K. E.; Sadeghzadeh S.; Jalaly M. The Mechanical Design of Hybrid Graphene/Boron Nitride Nanotransistors: Geometry and Interface Effects. Solid State Commun. 2018, 270, 82-86. 27 ACS Paragon Plus Environment


(38) Zhang, D.; Zhang, D. B.; Yang, F.; Lin, H. Q.; Xu, H.; Chang, K. Interface engineering of electronic properties of graphene/boron nitride lateral heterostructures, 2D Mater. 2015, 2, 041001. (39) Eshkalak, K. E.; Sadeghzadeh, S.; Jalaly, M. Studying the effects of longitudinal and transverse defects on the failure of hybrid graphene-boron nitride sheets: A molecular dynamics simulation. Physica E 2018, 104, 71-81. (40) Eshkalak, K. E.; Sadeghzadeh, S.; Jalaly, M. Mechanical properties of defective hybrid graphene-boron nitride nanosheets: A molecular dynamics study. Comp. Mater. Sci. 2018, 149, 170-181. (41) Wang, J.; Zhao, D.; Zou, X.; Mao, L.; Shi, L. The Exfoliation and Functionalization of Boron Nitride Nanosheets and Their Utilization in Silicone Composites with Improved Thermal Conductivity. J. Mater. Sci.: Mater. Electron. 2017, 28, 12984-12994. (42) Li, X.; Hao, X.; Zhao, M.; Wu, Y.; Yang, J.; Tian, Y.; Qian, G. Exfoliation of Hexagonal Boron Nitride by Molten Hydroxides. Adv. Mater. 2013, 25, 2200-2204. (43) Zhang, S.; Peng, L. M.; Chen, Q.; Du, G. H.; Dawson, G.; Zhou, W. Z. Formation Mechanism of H2Ti3O7 Nanotubes. Phys. Rev. Lett. 2003, 91, 256103. (44) Cao, A.; Liu, Z.; Chu, S.; Wu, M.; Ye, Z.; Cai, Z.; Chang, Y. ; Wang, S.; Gong, Q.; Liu, Y. A Facile One-step Method to Produce Graphene-CdS Quantum Dot Nanocomposites as Promising Optoelectronic Materials. Adv. Mater. 2010, 22, 103-106. (45) Zhou, K.; Zhu, Y.; Yang, X.; Jiang, X.; Li, C. Preparation of Graphene-TiO2 28 ACS Paragon Plus Environment

Page 28 of 43

Page 29 of 43 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Composites with Enhanced Photocatalytic Activity. New J. Chem. 2011, 35, 353-359. (46) Bao, C.; Guo, Y.; Song, L.; Hu, Y. Poly (Vinyl Alcohol) Nanocomposites based on Graphene and Graphite Oxide: A Comparative Investigation of Property and Mechanism. J. Mater. Chem. 2011, 21, 13942-13950. (47) Qiao, Y.; Li, W.; Wang, G.; Zhang, X.; Cao, N. Application of Ordered Mesoporous Silica Nanocontainers in An Anticorrosive Epoxy Coating on A Magnesium Alloy Surface. RSC Adv. 2015, 5, 47778-47787. (48) Kartsonakis, I. A.; Balaskas, A. C.; Kordas, G. C. Influence of Cerium Molybdate Containers on The Corrosion Performance of Epoxy Coated Aluminium Alloys 2024-T3. Corros. Sci. 2011, 53, 3771-3779. (49) Jahan, M. S.; Saeed, A.; He, Z.; Ni, Y. Jute as Raw Material for The Preparation of Microcrystalline Cellulose. Cellulose 2011, 18, 451-459. (50) Lv, P.; Tan, X. -W.; Yu, K. -H.; Zheng, R. -L.; Zheng, J. -J.; Wei, W. Super-Elastic Graphene/Carbon Nanotube Aerogel: A Novel Thermal Interface Material with Highly Thermal Transport Properties. Carbon 2016, 99, 222-228. (51) Mi, H. -Y.; Jing, X.; Politowicz, A. L.; Chen, E.; Huang, H. -X.; Turng, L. -S. Highly Compressible Ultra-Light Anisotropic Cellulose/Graphene Aerogel Fabricated by Bidirectional Freeze Drying for Selective Oil Absorption. Carbon 2018, 132, 199-209. (52) Yang, W.; Ping, P.; Wang, L. -L.; Chen, T. B. -Y.; Yuen, A. C. -Y.; Zhu, S. -E.; Wang, N. -N.; Hu, Y. -L.; Yang, P. -P.; Sun, C.; Zhang, C. -Y.; Lu, H. -D.; Chan, Q. N. Yeoh, G. -H. Fabrication of Fully Bio-based Aerogels via Microcrystalline 29 ACS Paragon Plus Environment


Cellulose and Hydroxyapatite Nanorods with Highly Effective Flame-Retardant Properties. ACS Appl. Nano Mater. 2018, 1,1921-1931.


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Captions Table 1. Comparison of the compressive properties of different graphene-based aerogels (GA: graphene aerogel). Table 2. TGA data of EP, GNS, BNOH, EP/GNS and EP/GNS/BNOH hybrid aerogels. Scheme 1. The preparation routes of BNOH (a) and EP/GNS/BNOH hybrid aerogels (b). Scheme 2. Schematic 3D network structures of EP/GNS-3 (a) and EP/GNS/BNOH-3 (b), including the structural evolution with the added force. The gray layers with large size represent the GNS, and the yellow parts are epoxy resins. The green ones, located in the middle of GNS, are BNOH nanosheets. Figure 1. XRD patterns (a) and FTIR spectra (b) of h-BN, BNNSs, and BNOH powders; TEM images of BNNSs (c) and BNOH (d and e); XRD patterns (f) of GNS, GNS/BNOH, EP/GNS-2 and EP/GNS/BNOH-2; FTIR spectra (g) of EP, EP/GNS-2 and EP/GNS/BNOH-2. Figure 2. SEM images of EP/GNS and EP/GNS/BNOH hybrid aerogels: (a) EP/GNS-1;

(b)

EP/GNS-2;

(c)

EP/GNS-3;

(d)

EP/GNS/BNOH-1;

(e)

EP/GNS/BNOH-2; (f) EP/GNS/BNOH-3. Figure 3. (a) The compressive stress-strain curves of EP/GNS and EP/GNS/BNOH hybrid aerogels; (b) The average compressive strength for each sample at 70% strain; (c) and (d) Typical stress-strain curves for repeat compression tests on EP/GNS-3 and EP/GNS/BNOH-3 at 80% strain. 31 ACS Paragon Plus Environment


Figure 4. (a) Real-time variations of lateral-surface temperature with time for EP/GNS-3 aerogel. (b) Thermal dissipation properties of EP/GNS-3. The selected temperature points, M and N, are the center point approximately 5 mm from the bottom of the sample. Figure 5. Temperature vs time curves at M point during heating process (a) and at N point during dissipation process (c), thermal transfer rate (b), and thermal dissipation rate (d), for EP/GNS and EP/GNS/BNOH hybrid aerogels. Figure 6. TG and DTG curves of the hybrid aerogels: (a) and (b) EP/GNS; (c) and (d) EP/GNS/BNOH.


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Table 1. Comparison of the compressive properties of different graphene-based aerogels (GA: graphene aerogel). Compressive

Density

Strain

(mg/cm3)

(%)

GA

/

70

2.4

94% after 10th compression to 90% strain

[19]

GA

6.9

48

3.5


[24]

GA

3.0-5.4

70

1.4


[25]

XPAA/rGO

6.7

48

20.8

Not compressible

[26]

PDMS/CGA

/

70

6.0

/

[28]

RGA

80.0

11

240.0

Not compressible

[29]

EP/GA

92.9

70

163.5


[30]

CNT/GA

/

70

2.0

/

[31]

PNT/GA

84.0

70

350.0

/

[32]

MoS2/GA

/

70

3.0

/

[33]

284.7

70

312.8


Aerogel sample

EP/GNS/BNOH-3

strength

Residual height after cyclical compression tests

(kPa)


Ref.

This work


Page 34 of 43

Table 2. TGA data of EP, GNS, BNOH, EP/GNS and EP/GNS/BNOH hybrid aerogels. Residues at Sample

T-5% (°C)

T-50% (°C)

Tmax1 (°C)

Tmax2 (°C) 700 °C (wt%)

EP

251

322

/

321

3.6

GNS

103

/

275

/

68.9

/

/

/

/

97.5

EP/GNS-1

226

359

/

363

18.6

EP/GNS-2

237

351

302

352

15.2

EP/GNS-3

244

354

316

378

12.1

EP/GNS/BNOH-1

228

358

279

370

20.1

EP/GNS/BNOH-2

228

357

281

379

17.4

EP/GNS/BNOH-3

236

356

284

376

13.8

BNOH


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Graphical Abstract 480x199mm (150 x 150 DPI)

ACS Paragon Plus Environment


Scheme 1. The preparation routes of BNOH (a) and EP/GNS/BNOH hybrid aerogels (b). 556x299mm (149 x 149 DPI)


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Figure 1. XRD patterns (a) and FTIR spectra (b) of h-BN, BNNSs, and BNOH powders; TEM images of BNNSs (c) and BNOH (d and e); XRD patterns (f) of GNS, GNS/BNOH, EP/GNS-2 and EP/GNS/BNOH-2; FTIR spectra (g) of EP, EP/GNS-2 and EP/GNS/BNOH-2. 290x328mm (150 x 150 DPI)



Figure 2. SEM images of EP/GNS and EP/GNS/BNOH hybrid aerogels: (a) EP/GNS-1; (b) EP/GNS-2; (c) EP/GNS-3; (d) EP/GNS/BNOH-1; (e) EP/GNS/BNOH-2; (f) EP/GNS/BNOH-3. 266x300mm (150 x 150 DPI)


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Figure 3. (a) The compressive stress-strain curves of EP/GNS and EP/GNS/BNOH hybrid aerogels; (b) The average compressive strength for each sample at 70% strain; (c) and (d) Typical stress-strain curves for repeat compression tests on EP/GNS-3 and EP/GNS/BNOH-3 at 80% strain. 479x350mm (150 x 150 DPI)



Scheme 2. Schematic 3D network structures of EP/GNS-3 (a) and EP/GNS/BNOH-3 (b), including the structural evolution with the added force. The gray layers with large size represent the GNS, and the yellow parts are epoxy resins. The green ones, located in the middle of GNS, are BNOH nanosheets. 495x299mm (150 x 150 DPI)


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Figure 4. (a) Real-time variations of lateral-surface temperature with time for EP/GNS-3 aerogel. (b) Thermal dissipation properties of EP/GNS-3. The selected temperature points, M and N, are the center point approximately 5 mm from the bottom of the sample. 411x350mm (150 x 150 DPI)



Figure 5. Temperature vs time curves at M point during heating process (a) and at N point during dissipation process (c), thermal transfer rate (b), and thermal dissipation rate (d), for EP/GNS and EP/GNS/BNOH hybrid aerogels. 475x350mm (150 x 150 DPI)


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Figure 6. TG (a) and DTG (b) curves of EP/GNS and EP/GNS/BNOH aerogels. 475x350mm (150 x 150 DPI)


A Novel 3D Network Architectured Hybrid Aerogel Comprising Epoxy

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