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Silver Nanowire/MnO2 Nanowire Hybrid Polymer Nanocomposites: Materials with High Dielectric Permittivity and Low Dielectric Loss Ali Shayesteh Zeraati, Mohammad Arjmand, and Uttandaraman Sundararaj ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.6b14948 • Publication Date (Web): 05 Apr 2017 Downloaded from http://pubs.acs.org on April 5, 2017

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ACS Applied Materials & Interfaces

Silver Nanowire/MnO2 Nanowire Hybrid Polymer Nanocomposites: Materials with High Dielectric Permittivity and Low Dielectric Loss Ali Shayesteh Zeraati, Mohammad Arjmand, Uttandaraman Sundararaj*

Department of Chemical and Petroleum Engineering, University of Calgary, 2500 University Dr NW, Calgary, Canada T2N 1N4 *Corresponding Author: Email: [email protected]

Abstract. This study reports the fabrication of hybrid nanocomposites based on silver nanowire/manganese dioxide nanowire/poly(methyl methacrylate) (AgNW/MnO2NW/PMMA), using solution casting technique, with outstanding dielectric permittivity and low dielectric loss. AgNW was synthesized using the hard-template technique, and MnO2NW was synthesized employing a hydrothermal method. The prepared AgNW:MnO2NW (2.0:1.0vol%) hybrid nanocomposite showed a high dielectric permittivity (64 at 8.2 GHz) and low dielectric loss (0.31 at 8.2 GHz), which are among the best reported values in the literature in the X-band frequency range (8.2-12.4 GHz). The superior dielectric properties of the hybrid nanocomposites were attributed to: (i) dimensionality match between the nanofillers, which increased their synergy, (ii) better dispersion state of AgNW in the presence of MnO2NW, (iii) positioning of ferroelectric MnO2NW in between AgNWs, which increased the dielectric permittivity of nanodielectrics, thereby increasing dielectric permittivity of the hybrid nanocomposites, (iv) barrier role of MnO2NW, i.e. cutting off the contact spots of AgNWs and leading to lower dielectric loss, and (v) AgNW aligned structure, which increased the effective surface area of AgNWs, as nanoelectrodes. Comparison of the dielectric properties of the developed hybrid nanocomposites with the literature highlights their great potential for flexible capacitors. Keywords: Dielectric permittivity, Dielectric loss, Nanocapacitors, Nanowire, Hybrid nanocomposite

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1. Introduction Polymeric nanocomposites with high dielectric permittivity (high-k), low dielectric loss and easy processability are excellent candidates for embedded dielectrics

1-5

. Essentially, high-k

polymer nanocomposites are developed by adding either ferroelectric or conductive filler to the polymer matrix. BaTiO3

6-9

, SiTiO3 10-11, and TiO2 9, 12 are among common ferroelectric ceramic

fillers incorporated into the polymer matrix to increase dielectric permittivity. High-k ceramic/polymer nanocomposites suffer high concentration of rigid ceramic particles in the flexible polymer matrix, which often deteriorates the mechanical properties of the nanocomposites. Incorporation of conductive fillers into the polymer matrix delivers high dielectric permittivity at low filler content while maintaining advantages of high flexibility, processability, and mechanical properties. Therefore, these materials have drawn a great deal of attention. Conductive filler/polymer nanocomposites (CPNs) have high dielectric permittivity, attributed to the formation of nanocapacitor structures, with conductive nanofillers acting as nanoelectrodes and polymer matrix as nanodielectric

13-14

. High-k CPNs have been reported for a broad variety

of conductive nanofillers, such as graphene

15-17

, carbon nanotube (CNT)

18-19

, and metallic

nanoparticles 20-23. It is well known that the shape of the conductive filler plays a crucial role in the dielectric properties of CPNs. Fillers with high aspect ratio have higher surface area and lower percolation threshold, and thus can improve the dielectric permittivity of the polymer medium more efficiently than spherical particles

14, 16-18

. Several research studies have also revealed that one-

dimensional (1D) nanostructures, such as nanotubes and nanowires, are very effective in enhancing the dielectric properties of the polymer matrix at low concentrations 2 ACS Paragon Plus Environment

7-10, 24

.

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Accordingly, in this study, we synthesized and employed silver nanowire (AgNW) as a 1D metallic nanofiller for charge storage application. To the best of our knowledge, there are a rare number of studies employing AgNW for dielectric applications 25-27. AgNW has higher electrical conductivity compared to other types of nanowires and carbonaceous fillers, portraying a promising future for charge storage applications

28-30

. In addition, AgNW has much larger

surface area compared to metallic nanoparticles, thereby could exhibit enhanced dielectric properties. Despite the significant progress that has been made on improving the dielectric permittivity of CPNs, considerable increase in dielectric loss due to the “insulator-conductor” transition at the percolation threshold is still a common drawback. So, if dielectric loss can be mitigated, the CPN approach can be promising to develop high-k nanocomposites. Hence, several strategies have been devised to hinder conductive network formation to alleviate the dielectric loss of CPNs. These techniques include, but are not limited to, fillers with core-shell structures

31-38

, filler alignment

39-40

, incorporation of secondary non-conductive filler

41-44

, and

surface oxidation of metallic nanowire 45. Among the aforementioned techniques, adding secondary non-conductive filler can be a promising approach as it does not need any further processing, making it simple and costeffective. Secondary non-conductive particles have been commonly employed to impede conductive network formation

41-44

. These particles usually do not provide good performance to

cut off the contact spots of 1D conductive nanofillers like CNTs or metallic nanowires. Bearing this in mind, to have an efficient impact of secondary filler, there should be a good dimensionality match between the primary conductive filler and secondary non-conductive filler. To the best of our knowledge, there is no report in the literature on employing secondary 3 ACS Paragon Plus Environment


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ferroelectric nanofiller with similar dimensionality to the primary 1D conductive nanofiller. Hence, in this study, we synthesized and used manganese dioxide nanowire (MnO2NW) as the secondary non-conductive filler to manipulate the conductive network of AgNWs. MnO2 has been the subject of intense attention for charge storage applications because of its high theoretical specific capacitance, low cost, natural abundance, and environmental friendly nature 46-49

. In

the

current

study,

we

have

fabricated

hybrid

AgNW/MnO2NW/polymer

nanocomposites. These materials are considered to be promising candidate materials for charge storage applications due to the following reasons: (1) AgNW is an ideal conductive filler to create high performance CPNs owing to its outstanding inherent conductivity coupled with large surface area 28-30; (2) high theoretical specific capacitance of MnO2NW and its large surface area give rise to dielectric permittivity of the AgNW/polymer assembly; (3) dimensionality match between AgNW and MnO2NW enhances their interaction, helping considerably to obstruct the conductive network of AgNW and thus reducing the dielectric loss. Additionally, it is well known that the dielectric properties not only rely on the filler type, but also on the filler dispersion state. On this basis and to fully exploit the potentials of AgNW as superior conductive nanofiller, a self-aligned structure of nanowire was fabricated to maximize the dielectric permittivity and to minimize the dielectric loss. The results of this study show that the fabricated nanocomposites are promising materials for high-performance flexible dielectrics at high frequency ranges, with highly superior dielectric properties to the materials reported in the literature. 2. Experimental 2.1. Materials Synthesis 4 ACS Paragon Plus Environment

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Synthesis of AgNW: AgNWs were synthesized by AC electrodeposition of silver into the hard templates of porous aluminum oxide (PAO). Aluminum plates (10×25 cm2) of 1 mm thickness (+99.99%, Alfa Aesar) were cleaned with acetone, and then immersed into 1.0 M NaOH solution to remove the oxide layer. Ten of these aluminum plates were anodized in parallel by immersing in 0.3 M H2SO4 solution. Stainless steel plates with 1 cm spacing from the aluminum plates were used as the counter-electrode. The anodization was performed in two steps to improve the template structure. The first anodization was carried out for 2 h at 20 V DC at 0-4 °C. Then, the developed PAO templates were etched in 0.2 M H2CrO4 and 0.6 M H3PO4 solution at 60 °C for 30 min to make the already formed porous structure more uniform. The second anodization step was performed on the etched templates under identical conditions as the first anodization step but for 8 h. An agitator was used to enhance the heat transfer between the cooling system and the solution, making it possible to keep the temperature uniform between 0-4 °C. An important part of the anodization process was to thin the bottom of the PAO templates to make them electrically conductive for the electrodeposition process. Accordingly, at the end of the 8 h pore-growth step, the alumina barrier layer at the pore bottom was thinned by gradual reduction of the voltage. Further information about the anodization procedure is provided elsewhere 50. After preparing the PAO templates, the edges of the alumina plates were coated with nail polish to prevent preferential deposition of silver on the edges during the electrodeposition process. The electrodeposition solution was composed of 8.5 g/L of Ag2SO4, 200 g/L of diammonium hydrogen citrate ((NH4)2HC6H5O7), and 105 g/L of potassium thiocyanate (KSCN). The PAO templates were immersed in the electrodeposition solution for 5 min, and then a square wave voltage pulse at 100 Hz and ±8.0 V peaks (pulsed every 400 ms) for 2 h was applied to push the Ag ions towards the end of the pores. Two silver plates were used as the 5 ACS Paragon Plus Environment


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counter-electrode. The electrodeposited AgNWs were liberated by immersing the templates into 1 mol/L NaOH aqueous solution for 10 min at room temperature. Following the liberation, floating fragments were collected and dispersed in MeOH. AgNWs were filtered and rinsed with MeOH five times to remove the basic solution. Synthesis of MnO2NW: MnO2NW was synthesized according to a hydrothermal method 51. 0.608 g of KMnO4 (Sigma Aldrich, ACS reagent ≥99.0%) was dissolved in 70 ml distilled water for 30 min. Then, 1.27 ml HCl (EMD Chemicals, 37%) was added to the solution and stirred for an extra 10 min. The solution was transferred to a 100 mL Teflon-lined stainless steel autoclave (Hydrion Scientific Instruments) and kept for 12 h at 140 °C. It is worth noting that no surfactant was used in MnO2NW synthesis. Following cooling down of the autoclave to room temperature, the precipitates were collected, filtered and rinsed several times with distilled water to pH 7. The collected powder was dried for 4 h at 80 °C. Nanocomposites Preparation: Synthesized AgNWs and MnO2NWs were used to prepare the nanocomposites by the solution casting method. Poly(methyl methacrylate) (PMMA) (Arkema Group, Plexiglas® V920 Acrylic) was dissolved in acetone overnight. Acetone was chosen due to its high evaporation rate, mitigating the precipitation of the nanowires during the casting. Desired amounts of AgNW and MnO2NW were added to acetone separately, hand mixed and left stationary for 10 min to allow the acetone to wet the nanowires surface. Then, the AgNW and MnO2NW suspensions were stirred at 500 rpm for 30 min and 15 min, respectively. Further 60 min stirring at 1000 rpm was carried out for AgNWs, while this step was 45 min for the MnO2NWs suspension. Dispersing MnO2NW was performed at a lower time due to more brittle nature of MnO2NW. A uniform suspension was obtained at the end of this stage. For the binary nanocomposites (AgNW/PMMA and MnO2NW/PMMA nanocomposites), the nanowire


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dispersion was, then, added to the PMMA solution and mixed at 1500 rpm while heated at 60 °C to evaporate the solvent. Quickly reducing the amount of solvent hinders the nanowire precipitation and also could cause formation of a layered structure of nanowires at higher concentrations. For the hybrid nanocomposites (AgNW/MnO2NW/PMMA), both AgNW and MnO2NW suspensions were added to the PMMA solution simultaneously and stirred at 1500 rpm. After reducing the solvent amount, the suspension was cast in a petri dish and left overnight in a fume hood to produce nanocomposite films. The nanocomposite film was kept in an oven for 2 h at 80 °C to remove the residual solvent. Figure 1 depicts the preparation steps of the hybrid nanocomposite films.

Figure 1: Schematic of preparation steps of AgNW/MnO2NW/PMMA hybrid nanocomposite.

2.2. Materials Characterization



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Transmission Electron Microscopy: The microstructural features of the nanowires were studied by high-resolution transmission electron microscopy (HRTEM). The HRTEM was carried out on a Tecnai TF20 G2 FEG-TEM (FEI, Hillsboro, OR) at 200 kV acceleration voltage with a standard single tilt-holder. The images were captured by a Gatan UltraScan 4000 CCD Camera (Gatan, Pleasanton, CA). Typically, less than 1 mg of the nanopowders was suspended in 10 mL of acetone and the mixture was sonicated for 3 min. A drop of the suspension was placed on the carbon side of a standard TEM copper grid covered with a ∼ 40 nm thin holey carbon film (EMS, Hatfield, PA), and then placed on a filter paper to quickly dry. Size distribution of the nanowires was obtained for 400 individual ones. For the TEM analysis of the nanocomposites, samples were ultramicrotomed in the thickness direction to achieve 70 nm thick sections. Scanning Electron Microscopy: The microstructure of the nanocomposites was characterized by a scanning electron microscope (SEM, Phenom XPro, with EDS Model). The samples were prepared by fracturing the nanocomposites film in liquid nitrogen. Elemental analysis was also carried out on the fractured samples. X-ray Diffraction: The X-ray diffraction (XRD) analysis was performed using a Rigaku ULTIMA III X-ray diffractometer with Cu K-alpha radiation as the X-ray source. The scans were done in the range of 2θ = 0.92–90 degrees using a 0.02 degree step and a counting time of 1.0 degree per min at 40 kV and 44 mA to obtain the full diffractogram for the nanowires. Electrical Conductivity and Dielectric Properties: Two different types of electrical conductivity measurement setup were used to measure the electrical conductivity of the polymer nanocomposites. For the nanocomposites with conductivity less than 10-6 S·cm-1, the electrical conductivity measurements were performed using a Keithley 6517A electrometer. The Keithley 8 ACS Paragon Plus Environment

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6517A electrometer was connected to a Keithley 8009 test fixture and equipped with Keithley 6524 high resistance measurement software. For conductivities higher than 10-6 S·cm-1, a Loresta GP resistivity meter (MCP-T610 model, Mitsubishi 48 Chemical Co., Japan) connected to an ESP four-pin probe (MCP-TP08P model, Mitsubishi Chemical Co., Japan) was used. Dielectric properties measurements in the X-band frequency range (8.2-12.4 GHz) were performed using an E5071C network analyzer (ENA series 300 kHz to 20 GHz). The samples were sandwiched between two waveguides of the network analyzer. The network analyzer sent a signal through the waveguide and incident to the samples, and then the S-parameters of each sample were recorded and converted to the dielectric properties using the Reflection/Transmission Mu and Epsilon method. 3. Results and Discussion 3.1. Characterization of Nanowires The XRD patterns of as-synthesized AgNWs and MnO2NWs are shown in Figure 2. For AgNWs, 2θ values at 38.1°, 44.3°, 64.4°, 73.4° and 81.5° can be assigned to the (111), (200), (220), (311) and (222) crystal planes, respectively, of face-centered cubic (FCC) silver

50

. No

evidence of the presence of crystalline silver oxide on AgNWs was found by XRD, implying that synthesized AgNWs had a high conductivity. The diffraction peaks of MnO2NW can be finely indexed to the pure tetragonal α-MnO2

51-52

. Since α-MnO2 has higher specific capacitance and

lower electrical conductivity than the other crystallographic forms of MnO2

53

, α-form of

MNO2NW was deliberately synthesized to not only increase the dielectric permittivity of the AgNW/PMMA nanocomposite, but also act as a non-conductive barrier between AgNWs to decrease the dielectric loss.



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Figure 2: XRD patterns of AgNW and MnO2NW.

TEM images of AgNW and MnO2NW are shown in Figure 3a-d. The image analysis indicated that AgNWs had an average length of 2.7 µm and average diameter of 15 nm. This gives an aspect ratio of 180 for AgNWs. In addition, the AgNWs made by the hard-template method have no impurity like PVP on the surface of nanowires, which is typical for other methods like polyol synthesis process 29-30. Furthermore, the low diameter of AgNWs (15 nm in this study) obtained via the hard-template method is an advantage compared to other techniques 54

. Statistical analysis of the TEM images of MnO2NW revealed that the average length and

diameter of α-MnO2NWs were 2.0 µm and 57 nm, respectively (aspect ratio of 35). Size distribution of the synthesized nanowires is depicted in Figure S1. Furthermore, the images show high purity of synthesized nanowires. Comparable length and geometry of synthesized AgNW and MnO2NW would contribute to the synergy between the synthesized nanowires to give enhanced dielectric properties.


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Figure 3: TEM images of (a) AgNW at low magnification, (b) AgNW at high magnification, (c) MnO2NW at low magnification and (d) MnO2NW at high magnification. The yellow box shows magnified area of Figure 3a, depicted as Figure 3b.

3.2. Microstructural Characterization of Nanocomposites The dispersion state and morphology of 2.0vol% AgNW/PMMA and 2.0vol% AgNW/1.0vol% MnO2NW/PMMA nanocomposites are demonstrated in Figure 4a-c. For the



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AgNW/PMMA nanocomposite, TEM images revealed significant orientation of AgNWs perpendicular to the gravity direction. This observation was more evident in the higher magnification TEM micrographs, where AgNWs were remarkably oriented along the planar surface (X-Y surface, Figure 4a). The aligned structure of AgNWs was achieved owing to the high evaporation rate of acetone, high nanowire density and aspect ratio, and the low viscosity of the dispersing medium

16, 55

. That is, the preferential orientation of high aspect ratio AgNWs in

the planar surface (X-Y surface, Figure 4) originates from gravitational forces experienced by AgNWs. Furthermore, low viscosity and high volatility of the medium contribute to nanowires orientation. Self-orientation of nanofillers in the polymer matrix has been reported for other high aspect ratio nanofillers, such as graphene

16

, BaTiO3 nanowires

56

, and BaTiO3 nanofibers

57

during film formation. As observed in the TEM images of AgNW/MnO2NW/PMMA nanocomposite, MnO2NW improved the dispersion state of AgNWs, thereby enhancing their effective surface area as nanoelectrodes. AgNW bundles in the AgNW/PMMA nanocomposites are vividly seen in Figure 4a, but addition of MnO2NW disintegrated the AgNW bundles into single or few nanowires assemblies (as shown in Figure 4c). Moreover, positioning of MnO2NW among AgNWs hinders the direct connection of AgNWs and thus does allow for conductive network formation. Because of the close proximity of the diameter of MnO2NW (ca. 60 nm) and thickness of microtomed layer (ca. 70 nm), TEM image cannot illustrate the whole microstructure of nanowires. Therefore, we performed SEM on fracture surface of the nanocomposites to obtain further insight about the nanocomposites microstructure. As an example, SEM image of 2.0vol% AgNW/1.0vol% MnO2NW/PMMA nanocomposite coupled with elemental analysis is shown in


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Figure S2. Figure S2 reveals that nanowires retained their rod-like structure in the nanocomposite, and elemental mapping shows the presence of MnO2NW in between AgNWs.

Thickness

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Y

X

Figure 4: TEM images of fabricated nanocomposites showing aligned nanostructures. (a) High magnification 2.0vol% AgNW/PMMA; (b) low magnification and (c) high magnification 2.0vol% AgNW/1.0vol% MnO2NW/PMMA nanocomposites.



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3.3. Dielectric properties In this section, we study the impact of MnO2NW addition on dielectric properties of AgNW/PMMA nanocomposites over the X-band frequency range. In order to develop a CPN appropriate for charge storage applications, the nanocomposites must be close to and below the percolation threshold

1, 3

. In this regard, investigating the percolation curves of the generated

nanocomposites is of prime significance (Figure 5). Employing the percolation theory, we obtained

an

electrical

percolation

threshold

equal to

0.8vol%

for

AgNW/PMMA

nanocomposites. The sharp upturn in electrical conductivity in the loading range of 0.5vol% 1.0vol% shows the beginning of conductive network formation. However, MnO2NW/PMMA nanocomposites presented a non-conductive behavior spanning the whole concentration range. This is attributed to the non-conductive nature of α-MnO2, with a bandgap width of 1.3 eV 46, 58. In this study, AgNW is considered as the primary conductive filler, whereas MnO2NW is the secondary non-conductive ferroelectric filler. Our objective is to incorporate MnO2NW in AgNW/PMMA nanocomposites at filler concentrations close to the percolation threshold, where the conductive network is formed but not well established (shaded area in Figure 5). This could push AgNW/PMMA nanocomposites into the insulative region, making the nanocomposites applicable for charge storage applications.


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10+1

Conductivity (S·cm-1)

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AgNW/PMMA MnO2NW/PMMA

10-2 10-5 10-8 10-11 10-14

0

0.5

1.0

1.5

2.0

Nanofiller Concentration (vol%) Figure 5: Percolation curves of AgNW/PMMA and MnO2NW/PMMA nanocomposites. The error bars size is smaller than the marker point size.

Figure 6 depicts dielectric permittivity and imaginary permittivity of pristine PMMA, AgNW/PMMA and MnO2NW/PMMA nanocomposites with 1.0 and 2.0vol% loading over the X-band frequency range. Pristine PMMA showed an average dielectric permittivity around 2.0, and addition of AgNW gave a significant increase in dielectric permittivity, i.e. 13.9 and 44.8 for 1.0 and 2.0vol% AgNW at 8.2 GHz, respectively. On the other side, addition of 1.0 and 2.0vol% MnO2NW marginally increased dielectric permittivity to 4.9 and 10.0 at 8.2 GHz, respectively. The increase in the dielectric permittivity of AgNW/PMMA nanocomposites is due to the formation of nanocapacitors structure 13-14, 16. Namely, each of the two neighboring AgNWs can be considered as the electrode of nanocapacitor and the very thin PMMA layer in between as the nanodielectric. This gives rise to a substantial increase in the intensity of local electric field around AgNWs, which subsequently leads to the electronic polarization of the PMMA matrix as the nanodielectric layer. Initially, when a small amount of AgNWs is incorporated into the polymer matrix, the distance between AgNWs is large and there is a little possibility for the formation of nanocapacitors. With increase of AgNW content in the PMMA matrix, the distance



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between the neighboring fillers is continuously reduced (nanodielectric thickness decreases), resulting in a network of nanocapacitors building up throughout the nanocomposite. The self-alignment of AgNWs (especially at higher loadings of AgNW) could also play a governing role in high dielectric permittivity of AgNW/PMMA nanocomposites

16, 55

. In an

aligned structure, as shown in Figure 4a, parallel AgNWs provide the largest surface area of electrodes facing each other. Therefore, a typical well-aligned nanocomposite is comprised of a network of nanocapacitors. The huge network containing numerous nanocapacitors has extremely large capacity to store electric charges, enabling the nanocomposite to possess a high dielectric permittivity. Slight increase in the dielectric permittivity of MnO2NW/PMMA nanocomposites is due to high dielectric permittivity of MnO2NW, revealing that MnO2NW polarization is active over the X-band. Imaginary permittivity derives from Ohmic loss, signifying the dissipation of electrical energy by free charge carriers moving across a dielectric in phase with the applied electric field. Low imaginary permittivity is desired for charge storage applications 19-20, while high imaginary permittivity is important for electromagnetic interference shielding

52

. Figure 6 depicts that

incorporating MnO2NW into the PMMA matrix resulted in a slight increase in imaginary permittivity, in accord with the percolation curve and attributable to the non-conductive nature of α-MnO2. For AgNW, adding 1.0vol% nanofiller to the PMMA matrix slightly increased imaginary permittivity, confirming that conductive network is not well formed. However, 2.0vol% AgNW drastically increased imaginary permittivity, which can be ascribed to both high AgNW content and well-established conductive network.


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50

40

(a) Imaginary Permittivity

Real Permittivity

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40 PMMA 1.0vol% AgNW 1.0vol% MnO2NW

30

2.0vol% AgNW 2.0vol% MnO2NW

20 10

(b)

30

20

10

0

0 8.2

9.2

10.2

11.2

8.2

12.2

Frequency (GHz)

9.2

10.2

11.2

12.2

Frequency (GHz)

Figure 6: (a) Dielectric permittivity and (b) imaginary permittivity of pristine PMMA, AgNW/PMMA and MnO2NW/PMMA nanocomposites with 1.0 and 2.0vol% loading.

In order to investigate the impact of MnO2NW addition on AgNW/PMMA nanocomposites, the hybrid nanocomposites were generated at total filler contents of 2.0 and 3.0vol%, where AgNW contents around the percolation threshold were targeted (Figure 7). Dielectric permittivity data show that in the hybrid system, for a fixed total volume content of nanofillers, increasing the ratio of AgNW over MnO2NW is accompanied with an increase in the dielectric permittivity. For instance, at 8.2 GHz, dielectric permittivity for AgNW:MnO2NW (0.5:1.5vol%) nanocomposite was 12.3, but increased to 62.0 for AgNW:MnO2NW (1.5:0.5vol%) nanocomposites at the same frequency. This shows the superior role of AgNW on dielectric permittivity as primary conductive filler to MnO2NW as secondary ferroelectric filler. Imaginary permittivity also increased with increase in AgNW content in the hybrid systems, due to higher conductivity of AgNW compared with MnO2NW. The most interesting results belong to AgNW:MnO2NW (2.0:1.0vol%) nanocomposite, which showed higher dielectric permittivity (64.0 vs 44.8 at 8.2 GHz) and lower imaginary permittivity (20.2 vs 36.0 at 8.2 GHz) than 2.0vol% AgNW/PMMA nanocomposite. These results show that manipulating the ratio of 17 ACS Paragon Plus Environment


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ferroelectric filler versus conductive filler could lead to improvement in both components of permittivity, creating material ideal for charge storage applications. In this study, three parameters came into play to improve the dielectric permittivity of the hybrid system: namely, (i) better dispersion of AgNW in the presence of MnO2NW, (ii) positioning of MnO2NW among AgNWs, and (iii) AgNW alignment. It is well established that the dielectric properties of CPNs strongly rely on the dispersion state of the fillers in the nanocomposite

1, 4

. TEM analysis (Figure 4) vividly revealed that adding MnO2NW into the

nanocomposite films improved the dispersion state of AgNWs; hence, higher dielectric permittivity is expected. Moreover, based on the nanocapacitor model, by replacing the PMMA medium with MnO2NW/PMMA the dielectric permittivity of the nanodielectric layer increased, enhancing the dielectric permittivity of the hybrid nanocomposite (Figure 8). Among the aforementioned parameters, which are highly interrelated, the AgNWs alignment may play a more dominant role in increasing the dielectric permittivity 16, 56-57, as it increased the available surface area of AgNWs and also their effectiveness in nanocapacitors formation. Moreover, due to its ferroelectric nature, MnO2NW itself helps increase the dielectric permittivity of the nanocomposites. Figure 7 reveals that imaginary permittivity of the hybrid nanocomposites is lower than the non-hybrid systems. For instance, incorporating 1.0vol% MnO2NW to 2.0vol% AgNW/PMMA nanocomposites decreased imaginary permittivity from 36.0 to 20.2 at 8.2 GHz. In fact, MnO2NW not only serves as dielectric layer but also acts as non-conductive barrier layer, hindering the formation of conductive paths and thus efficiently decreasing the leakage current. It is worth noting that the comparative dimensionality of the employed nanofillers plays a significant role in their synergistic effect towards charge storage applications. Moreover, in a 18 ACS Paragon Plus Environment

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former study 38, it was shown that aligned CNTs have less probability of contacting each other, thereby presenting lower dielectric loss compared to random distribution; this might be the case for AgNWs.

70

Dielectric Permittivity

40

PMMA 0.5 AgNW - 1.5 MnO2NW vol%

(a)

Imaginary Permittivity

80

1.0 AgNW - 1.0 MnO2NW vol% 1.5 AgNW - 0.5 MnO2NW vol%

60 50 40 30 20

(b)

30

20

10

10

0

0 8.2

9.2

10.2

11.2

8.2

12.2

9.2

PMMA 1.0 AgNW - 2.0 MnO2NW vol% 1.5 AgNW - 1.5 MnO2NW vol% 2.0 AgNW - 1.0 MnO2NW vol%

(c)

70 60

40

Imaginary Permittivity

80

10.2

11.2

12.2

Frequency (GHz)

Frequency (GHz)

Dielectric Permittivity

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


50 40 30 20 10

(d)

30

20

10

0

0 8.2

9.2

10.2

11.2

8.2

12.2

9.2

10.2

11.2

12.2

Frequency (GHz)

Frequency (GHz)

Figure 7: Dielectric permittivity and imaginary permittivity of AgNW/MnO2NW/PMMA hybrid nanocomposites with total volume contents of (a & b) 2.0vol% and (c & d) 3.0vol%.



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Figure 8: Schematic showing impact of MnO2NW addition on AgNW/PMMA nanocomposites.

Table 1 and Figure 9 present a comparison of the dielectric permittivity and dielectric loss

of the hybrid nanocomposites developed in this study with

various hybrid nanocomposites reported in the literature. Hybrid nanocomposites filled with carbonaceous materials, such as multi-walled CNT (MWCNT) and graphene, and high amount of ferroelectric particles showed moderate dielectric properties 59-61 in the X-band frequency, but high amount of ferroelectric materials leads to relatively low flexibility. Nanocomposites that contain metallic fillers and ferroelectric particles have been produced with limited success, where large amounts of conductive fillers had to be incorporated into the polymer to obtain sufficiently high dielectric permittivity

62

. The hybrid AgNW:MnO2NW (2.0:1.0vol%)

nanocomposite in the present study delivered exceptional dielectric permittivity in the X-band frequency (64 at 8.2 GHz or 53.5 at 12.4 GHz) and low dielectric loss (0.31 at 8.2 GHz or 0.35 at 12.4 GHz), which are among the best values for the hybrid nanocomposites reported in the literature. More importantly, the nanofiller content in the current work is an order of magnitude lower than those reported in the literature (Table 1 and Figure 9), which indicates that using hybrid fillers with the described properties is a promising and novel approach. Low amount of 20 ACS Paragon Plus Environment

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nanofiller used in the developed hybrid nanocomposites reduces the cost and sustains mechanical and adhesion properties of the generated CPNs as dielectric materials; this makes the developed nanocomposites applicable for advanced high frequency dielectric applications such as embedded capacitors.

Table 1: Dielectric properties of various hybrid polymer nanocomposites reported in the literature. Polymer Matrix

Nanofiller

Total Filler Conc.

Frequency (GHz)

PVDF

AgNP1:BT2NP (15:20vol%)

35.0vol%

10.0

Dielectric Permittivity Permittivity 31

PVDF

CB3:BTNP (20:10wt%)

30.0wt%

2.0

Epoxy

MWCNT4:Al2O3NP (0.4:40vol%)

40.4vol%

Epoxy

MWCNT:BTP5 (0.2:40vol%)

Epoxy

Dielectric loss

Fabrication Method

-

SC+CM

62

~35

1.10

SC+CM

61

12.4

24

0.70

Casting

60

40.2vol%

12.4

23

0.46

Casting

60

MWCNT:TiB2P (0.2:40vol%)

40.2vol%

12.4

17.5

0.68

Casting

60

Epoxy

MWCNT:MoSi2P (0.2:40vol%)

40.2vol%

12.4

32.5

0.46

Casting

60

Wax

Graphene:MoS2 (15wt%)

15wt%

2.0

14

0.55

Casting

63

PMMA

AgNW (2.0vol%)

2.0vol%

8.2

44.8

0.79

SC

PMMA

AgNW:MnO2NW

2.0vol%

8.2

62

0.50

SC

PMMA

AgNW:MnO2NW (2.0:1.0vol%)

3.0vol%

8.2

64

0.31

SC

(1.5:0.5vol%)

1

Nanoparticle Barium Titanate 3 Carbon Black 4 Multi-walled Carbon Nanotube 5 Microparticle PVDF: Polyvinylidene Fluoride SC: Solution Casting CM: Compression Molding 2


Ref.

This Work

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Figure 9: Comparison of dielectric properties of developed hybrid nanocomposites in this work with literature results 60-61, 63. Better results at lower filler content were obtained for AgNW/MnO2NW/PMMA hybrid nanocomposite compared to the literature.

4. Conclusions In summary, hybrid AgNW/MnO2NW/PMMA nanocomposites were developed by the solution casting method, which can be used for modern charge storage applications. A dielectric permittivity of 64 with a dielectric loss of 0.31 at 8.2 GHz for 2.0vol% AgNW/1.0vol% MnO2NW/PMMA nanocomposite were achieved, which are among the best dielectric properties data in the X-band reported in the literature. The unique dielectric properties of the hybrid nanocomposites were attributed to: (i) The dimensionality match of the synthesized nanowires, increasing the synergy between the primary conductive filler (AgNW) and the secondary non-conductive filler (MnO2NW); (ii) Better dispersion state of AgNW in the presence of MnO2NW, resulting in more effective nanocapacitors formation; 22 ACS Paragon Plus Environment

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(iii) Positioning of ferroelectric MnO2NWs in between AgNWs, increasing the dielectric permittivity of nanodielectrics and thus enhancing dielectric permittivity of the nanocomposites; (iv) Role of MnO2NW as non-conductive barrier layer, cutting off the contact spots of AgNWs and leading to lower dielectric loss; (v) AgNW aligned structure, increasing the effective surface area of AgNWs, as nanoelectrodes, and thus playing a dominant role in enhancing the dielectric permittivity of the nanocomposite. The outstanding dielectric properties of the developed hybrid nanocomposites at low nanofiller contents lead them to be promising materials for flexible capacitors, such as embedded capacitors in printed circuit boards. Acknowledgements Financial support from the Natural Sciences and Engineering Research Council of Canada (NSERC) is highly appreciated. We would like to acknowledge Ms. Samaneh Dordani Haghighi for designing and drawing the schematics. Supporting Information Size distribution of synthesized nanowires, SEM images and elemental analysis of 2.0vol% AgNW/1.0vol% MnO2NW/PMMA nanocomposite, and TEM image of 1.5vol% AgNW/0.5vol% MnO2NW/PMMA nanocomposite.



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References (1)

Dang, Z.-M.; Yuan, J.-K.; Zha, J.-W.; Zhou, T.; Li, S.-T.; Hu, G.-H. Fundamentals,

Processes and Applications of High-Permittivity Polymer–Matrix Composites. Prog. Mater. Sci. 2012, 57 (4), 660-723. (2)

Thakur, V. K.; Gupta, R. K. Recent Progress on Ferroelectric Polymer-Based

Nanocomposites for High Energy Density Capacitors: Synthesis, Dielectric Properties, and Future Aspects. Chem. Rev. 2016, 116 (7), 4260-4317. (3)

Dang, Z. M.; Zheng, M. S.; Zha, J. W. 1D/2D Carbon Nanomaterial‐Polymer Dielectric

Composites with High Permittivity for Power Energy Storage Applications. Small 2016, 12 (13), 1688-1701. (4)

Zhu, L. Exploring Strategies for High Dielectric Constant and Low Loss Polymer

Dielectrics. J. Phys. Chem. Lett. 2014, 5 (21), 3677-3687. (5)

Dang, Z. M.; Yuan, J. K.; Yao, S. H.; Liao, R. J. Flexible Nanodielectric Materials with

High Permittivity for Power Energy Storage. Adv. Mater. 2013, 25 (44), 6334-6365. (6)

Zhang, G.; Brannum, D.; Dong, D.; Tang, L.; Allahyarov, E.; Tang, S.; Kodweis, K.;

Lee, J.-K.; Zhu, L. Interfacial Polarization-Induced Loss Mechanisms in Polypropylene/BaTiO3 Nanocomposite Dielectrics. Chem. Mater. 2016, 28 (13), 4646-4660. (7)

Lin, X.; Hu, P.; Jia, Z.; Gao, S. Enhanced Electric Displacement Induces Large Energy

Density in Polymer Nanocomposites Containing Core–Shell Structured BaTiO3@TiO2 Nanofibers. J. Mater. Chem. A 2016, 4 (6), 2314-2320.


Page 25 of 34

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


(8)

Feng, Y.; Li, W.; Hou, Y.; Yu, Y.; Cao, W.; Zhang, T.; Fei, W. Enhanced Dielectric

Properties of PVDF-HFP/BaTiO3-Nanowire Composites Induced by Interfacial Polarization and Wire-Shape. J. Mater. Chem. C 2015, 3 (6), 1250-1260. (9)

Wang, G.; Huang, X.; Jiang, P. Tailoring Dielectric Properties and Energy Density of

Ferroelectric Polymer Nanocomposites by High-K Nanowires. ACS Appl. Mater. Interfaces 2015, 7 (32), 18017-18027. (10)

Liu, S.; Zhai, J. Improving the Dielectric Constant and Energy Density of Poly

(Vinylidene Fluoride) Composites Induced by Surface-Modified SrTiO3 Nanofibers by Polyvinylpyrrolidone. J. Mater. Chem. A 2015, 3 (4), 1511-1517. (11)

Yu, D.; Xu, N.-X.; Hu, L.; Zhang, Q.-l.; Yang, H. Nanocomposites with BaTiO3–SrTiO3

Hybrid Fillers Exhibiting Enhanced Dielectric Behaviours and Energy-Storage Densities. J. Mater. Chem. C 2015, 3 (16), 4016-4022. (12)

Xu, N.; Hu, L.; Zhang, Q.; Xiao, X.; Yang, H.; Yu, E. Significantly Enhanced Dielectric

Performance of Poly (Vinylidene Fluoride-Co-Hexafluoropylene)-Based Composites Filled with Hierarchical Flower-Like TiO2 Particles. ACS Appl. Mater. Interfaces 2015, 7 (49), 2737327381. (13)

Kim, J. Y.; Lee, W. H.; Suk, J. W.; Potts, J. R.; Chou, H.; Kholmanov, I. N.; Piner, R. D.;

Lee, J.; Akinwande, D.; Ruoff, R. S. Chlorination of Reduced Graphene Oxide Enhances the Dielectric Constant of Reduced Graphene Oxide/Polymer Composites. Adv. Mater. 2013, 25 (16), 2308-2313.



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

(14)

Page 26 of 34

Hashemi, R.; Weng, G. J. A Theoretical Treatment of Graphene Nanocomposites with

Percolation Threshold, Tunneling-Assisted Conductivity and Microcapacitor Effect in AC and DC Electrical Settings. Carbon 2016, 96, 474-490. (15)

Wang, D.; Bao, Y.; Zha, J.-W.; Zhao, J.; Dang, Z.-M.; Hu, G.-H. Improved Dielectric

Properties of Nanocomposites Based on Poly (Vinylidene Fluoride) and Poly (Vinyl Alcohol)Functionalized Graphene. ACS Appl. Mater. Interfaces 2012, 4 (11), 6273-6279. (16)

Yousefi, N.; Sun, X.; Lin, X.; Shen, X.; Jia, J.; Zhang, B.; Tang, B.; Chan, M.; Kim, J. K.

Highly Aligned Graphene/Polymer Nanocomposites with Excellent Dielectric Properties for High‐Performance Electromagnetic Interference Shielding. Adv. Mater. 2014, 26 (31), 54805487. (17)

Wu, C.; Huang, X.; Wang, G.; Wu, X.; Yang, K.; Li, S.; Jiang, P. Hyperbranched-

Polymer Functionalization of Graphene Sheets for Enhanced Mechanical and Dielectric Properties of Polyurethane Composites. J. Mater. Chem. 2012, 22 (14), 7010-7019. (18)

Arjmand, M.; Sundararaj, U. Effects of Nitrogen Doping on X-Band Dielectric Properties

of Carbon Nanotube/Polymer Nanocomposites. ACS Appl. Mater. Interfaces 2015, 7 (32), 17844-17850. (19)

Dang, Z. M.; Wang, L.; Yin, Y.; Zhang, Q.; Lei, Q. Q. Giant Dielectric Permittivities in

Functionalized Carbon‐Nanotube/Electroactive‐Polymer Nanocomposites. Adv. Mater. 2007, 19 (6), 852-857.


Page 27 of 34

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


(20)

Quinsaat, J. E. Q.; Alexandru, M.; Nüesch, F. A.; Hofmann, H.; Borgschulte, A.; Opris,

D. M. Highly Stretchable Dielectric Elastomer Composites Containing High Volume Fractions of Silver Nanoparticles. J. Mater. Chem. A 2015, 3 (28), 14675-14685. (21)

Lu, J.; Moon, K.-S.; Wong, C. Silver/Polymer Nanocomposite as a High-K Polymer

Matrix for Dielectric Composites with Improved Dielectric Performance. J. Mater. Chem. 2008, 18 (40), 4821-4826. (22)

Lu, J.; Moon, K.-S.; Xu, J.; Wong, C. Synthesis and Dielectric Properties of Novel High-

K Polymer Composites Containing in-Situ Formed Silver Nanoparticles for Embedded Capacitor Applications. J. Mater. Chem. 2006, 16 (16), 1543-1548. (23)

Kofod, G.; Risse, S.; Stoyanov, H.; McCarthy, D. N.; Sokolov, S.; Kraehnert, R. Broad-

Spectrum Enhancement of Polymer Composite Dielectric Constant at Ultralow Volume Fractions of Silica-Supported Copper Nanoparticles. ACS Nano 2011, 5 (3), 1623-1629. (24)

Tang, H.; Zhou, Z.; Sodano, H. A. Relationship between BaTiO3 Nanowire Aspect Ratio

and the Dielectric Permittivity of Nanocomposites. ACS Appl. Mater. Interfaces 2014, 6 (8), 5450-5455. (25)

Mi, H.-Y.; Li, Z.; Turng, L.-S.; Sun, Y.; Gong, S. Silver Nanowire/Thermoplastic

Polyurethane Elastomer Nanocomposites: Thermal, Mechanical, and Dielectric Properties. Mater. Design 2014, 56, 398-404. (26)

Liang, X.; Zhao, T.; Hu, Y.; Sun, R. Dielectric Properties of Silver Nanowires-Filled

Polyvinylidene Fluoride Composite with Low Percolation Threshold. J. Nanopart. Res. 2014, 16 (9), 1-10. 27 ACS Paragon Plus Environment


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

(27)

Mukherjee, P. K.; Dutta, D.; Bhattacharyya, S.; Ghosh, A.; Chakravorty, D. Giant

Dielectric Permittivity in Aligned Silver Nanowires Grown within (AgI)(AgPO3) Glasses. J. Phys. Chem. C 2007, 111 (10), 3914-3919. (28)

Huang, G.-W.; Xiao, H.-M.; Fu, S.-Y. Electrical Switch for Smart pH Self-Adjusting

System Based on Silver Nanowire/Polyaniline Nanocomposite Film. ACS Nano 2015, 9 (3), 3234-3242. (29)

Yao, S.; Zhu, Y. Nanomaterial‐Enabled Stretchable Conductors: Strategies, Materials and

Devices. Adv. Mater. 2015, 27 (9), 1480-1511. (30)

Yang, C.; Gu, H.; Lin, W.; Yuen, M. M.; Wong, C. P.; Xiong, M.; Gao, B. Silver

Nanowires: From Scalable Synthesis to Recyclable Foldable Electronics. Adv. Mater. 2011, 23 (27), 3052-3056. (31)

Yang, C.; Lin, Y. H.; Nan, C. W. Modified Carbon Nanotube Composites with High

Dielectric Constant, Low Dielectric Loss and Large Energy Density. Carbon 2009, 47 (4), 10961101. (32)

Shen, Y.; Lin, Y.; Nan, C. W. Interfacial Effect on Dielectric Properties of Polymer

Nanocomposites Filled with Core/Shell‐Structured Particles. Adv. Funct. Mater. 2007, 17 (14), 2405-2410. (33)

Shen, Y.; Lin, Y.; Li, M.; Nan, C. W. High Dielectric Performance of Polymer

Composite Films Induced by a Percolating Interparticle Barrier Layer. Adv. Mater. 2007, 19 (10), 1418-1422.


Page 28 of 34

Page 29 of 34

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


(34)

Zhang, L.; Yuan, S.; Chen, S.; Wang, D.; Han, B.-Z.; Dang, Z.-M. Preparation and

Dielectric Properties of Core–Shell Structured Ag@Polydopamine/Poly(Vinylidene Fluoride) Composites. Compos. Sci. Technol. 2015, 110, 126-131. (35)

Zhang, Y.; Wang, Y.; Deng, Y.; Li, M.; Bai, J. Enhanced Dielectric Properties of

Ferroelectric Polymer Composites Induced by Metal-Semiconductor Zn-ZnO Core–Shell Structure. ACS Appl. Mater. Interfaces 2012, 4 (1), 65-68. (36)

Wu, C.; Huang, X.; Wu, X.; Xie, L.; Yang, K.; Jiang, P. Graphene Oxide-Encapsulated

Carbon Nanotube Hybrids for High Dielectric Performance Nanocomposites with Enhanced Energy Storage Density. Nanoscale 2013, 5 (9), 3847-3855. (37)

Guo, Q.; Xue, Q.; Sun, J.; Dong, M.; Xia, F.; Zhang, Z. Gigantic Enhancement in the

Dielectric Properties of Polymer-Based Composites Using Core/Shell MWCNT/Amorphous Carbon Nanohybrids. Nanoscale 2015, 7 (8), 3660-3667. (38)

Zhao, D.-L.; Li, X.; Shen, Z.-M. Electromagnetic and Microwave Absorbing Properties

of Multi-Walled Carbon Nanotubes Filled with Ag Nanowires. Mater. Sci. Eng: B 2008, 150 (2), 105-110. (39)

Liu, H. Y.; Shen, Y.; Song, Y.; Nan, C. W.; Lin, Y. H.; Yang, X. P. Carbon Nanotube

Array/Polymer Core/Shell Structured Composites with High Dielectric Permittivity, Low Dielectric Loss, and Large Energy Density. Adv. Mater. 2011, 23 (43), 5104-5108. (40)

Arjmand, M.; Mahmoodi, M.; Park, S.; Sundararaj, U. An Innovative Method to Reduce

the Energy Loss of Conductive Filler/Polymer Composites for Charge Storage Applications. Compos. Sci. Technol. 2013, 78, 24-29. 29 ACS Paragon Plus Environment


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

(41)

Page 30 of 34

Wang, D.; Zhou, T.; Zha, J.-W.; Zhao, J.; Shi, C.-Y.; Dang, Z.-M. Functionalized

Graphene-BaTiO3/Ferroelectric Polymer Nanodielectric Composites with High Permittivity, Low Dielectric Loss, and Low Percolation Threshold. J. Mater. Chem. A 2013, 1 (20), 61626168. (42)

George, S.; Sebastian, M. T. Three-Phase Polymer–Ceramic–Metal Composite for

Embedded Capacitor Applications. Compos. Sci. Technol. 2009, 69 (7), 1298-1302. (43)

Dang, Z.-M.; Yao, S.-H.; Yuan, J.-K.; Bai, J. Tailored Dielectric Properties Based on

Microstructure Change in BaTiO3-Carbon Nanotube/Polyvinylidene Fluoride Three-Phase Nanocomposites. J. Phys. Chem. C 2010, 114 (31), 13204-13209. (44)

Wang, J.; Shi, Z.; Mao, F.; Wang, X.; Zhang, K.; Shi, J. Ni/Al2O3/Epoxy High-K

Composites with Ultralow Nickel Content Towards High-Performance Dielectric Applications. RSC Adv. 2016, 6 (49), 43429-43435. (45)

da Silva, A. B.; Arjmand, M.; Sundararaj, U.; Suman Bretas, R. E. Novel Composites of

Copper Nanowire/PVDF with Superior Dielectric Properties. Polymer 2014, 55 (1), 226-234. (46)

Yu, G.; Hu, L.; Liu, N.; Wang, H.; Vosgueritchian, M.; Yang, Y.; Cui, Y.; Bao, Z.

Enhancing the Supercapacitor Performance of Graphene/MnO2 Nanostructured Electrodes by Conductive Wrapping. Nano Lett. 2011, 11 (10), 4438-4442. (47)

Li, Q.; Wang, Z.-L.; Li, G.-R.; Guo, R.; Ding, L.-X.; Tong, Y.-X. Design and Synthesis

of MnO2/Mn/MnO2 Sandwich-Structured Nanotube Arrays with High Supercapacitive Performance for Electrochemical Energy Storage. Nano Lett. 2012, 12 (7), 3803-3807.


Page 31 of 34

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


(48)

Dai, Y. M.; Tang, S. C.; Ba, Z. X.; Zhu, S. S.; Wang, Q.; Wang, C.; Meng, X. K. Coating

MnO2 Nanowires by Silver Nanoparticles for an Improvement of Capacitance Performance. Mat. Lett. 2014, 117, 104-107. (49)

Liang, W. F.; Yang, R. B.; Choi, S. T. Microwave Complex Permittivity and Absorption

of MnO2 Nanorods and Nanoparticles. Ferroelectrics 2012, 434 (1), 100-106. (50)

Gelves, G. A.; Lin, B.; Sundararaj, U.; Haber, J. A. Low Electrical Percolation Threshold

of Silver and Copper Nanowires in Polystyrene Composites. Adv. Funct. Mater. 2006, 16 (18), 2423-2430. (51)

Xiao, W.; Xia, H.; Fuh, J. Y.; Lu, L. Growth of Single-Crystal Α-MnO2 Nanotubes

Prepared by a Hydrothermal Route and Their Electrochemical Properties. J. Power Sources 2009, 193 (2), 935-938. (52)

Weir, W. B. Automatic Measurement of Complex Dielectric Constant and Permeability

at Microwave Frequencies. Proc. IEEE 1974, 62 (1), 33-36, (53)

Devaraj, S.; Munichandraiah, N. Effect of Crystallographic Structure of MnO2 on Its

Electrochemical Capacitance Properties. J. Phys. Chem. C 2008, 112 (11), 4406-4417. (54)

da Silva, R. R.; Yang, M.; Choi, S.-I.; Chi, M.; Luo, M.; Zhang, C.; Li, Z.-Y.; Camargo,

P. H.; Ribeiro, S. J. L.; Xia, Y. Facile Synthesis of Sub-20 nm Silver Nanowires through a Bromide-Mediated Polyol Method. ACS Nano 2016, 10 (8), 7892-7900. (55)

Yousefi, N.; Gudarzi, M. M.; Zheng, Q.; Aboutalebi, S. H.; Sharif, F.; Kim, J.-K. Self-

Alignment and High Electrical Conductivity of Ultralarge Graphene Oxide-Polyurethane Nanocomposites. J. Mater. Chem. 2012, 22 (25), 12709-12717. 31 ACS Paragon Plus Environment


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

(56)

Page 32 of 34

Song, Y.; Shen, Y.; Liu, H.; Lin, Y.; Li, M.; Nan, C.-W. Improving the Dielectric

Constants and Breakdown Strength of Polymer Composites: Effects of the Shape of the BaTiO3 Nanoinclusions, Surface Modification and Polymer Matrix. J. Mater. Chem. 2012, 22 (32), 16491-16498. (57)

Hu, P.; Shen, Y.; Guan, Y.; Zhang, X.; Lin, Y.; Zhang, Q.; Nan, C. W. Topological‐

Structure Modulated Polymer Nanocomposites Exhibiting Highly Enhanced Dielectric Strength and Energy Density. Adv. Funct. Mater. 2014, 24 (21), 3172-3178. (58)

Song, W.-L.; Cao, M.-S.; Hou, Z.-L.; Lu, M.-M.; Wang, C.-Y.; Yuan, J.; Fan, L.-Z. Beta-

Manganese Dioxide Nanorods for Sufficient High-Temperature Electromagnetic Interference Shielding in X-Band. Appl. Phys. A 2014, 116 (4), 1779-1783. (59)

Yu, C.-R.; Wu, D.-M.; Liu, Y.; Qiao, H.; Yu, Z.-Z.; Dasari, A.; Du, X.-S.; Mai, Y.-W.

Electrical and Dielectric Properties of Polypropylene Nanocomposites Based on Carbon Nanotubes and Barium Titanate Nanoparticles. Compos. Sci. Technol. 2011, 71 (15), 1706-1712. (60)

Qing, Y.; Wang, X.; Zhou, Y.; Huang, Z.; Luo, F.; Zhou, W. Enhanced Microwave

Absorption of Multi-Walled Carbon Nanotubes/Epoxy Composites Incorporated with Ceramic Particles. Compos. Sci. Technol. 2014, 102, 161-168. (61)

Meng, X.-M.; Zhang, X.-J.; Lu, C.; Pan, Y.-F.; Wang, G.-S. Enhanced Absorbing

Properties of Three-Phase Composites Based on a Thermoplastic-Ceramic Matrix (BaTiO3+ PVDF) and Carbon Black Nanoparticles. J. Mater. Chem. A 2014, 2 (44), 18725-18730.


Page 33 of 34

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(62)

Joseph, N.; Singh, S. K.; Sirugudu, R. K.; Murthy, V. R. K.; Ananthakumar, S.;

Sebastian, M. T. Effect of Silver Incorporation into PVDF-Barium Titanate Composites for EMI Shielding Applications. Mater. Res. Bull. 2013, 48 (4), 1681-1687. (63)

Wang, Y.; Chen, D.; Yin, X.; Xu, P.; Wu, F.; He, M. Hybrid of MoS2 and Reduced

Graphene Oxide: A Lightweight and Broadband Electromagnetic Wave Absorber. ACS Appl. Mater. Interfaces 2015, 7 (47), 26226-26234.



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Materials with High Dielectric Permittivity and Low ... - ACS Publications

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