[go: up one dir, main page]
More Web Proxy on the site http://driver.im/
Next Article in Journal
Enhancement of Radar Detection Accuracy Using H-Beam Wave Polarization in Random Media
Next Article in Special Issue
Band Bending and Trap Distribution along the Channel of Organic Field-Effect Transistors from Frequency-Resolved Scanning Photocurrent Microscopy
Previous Article in Journal
The Influence of Design on Electrical Performance of AlGaN/GaN Lateral Schottky Barrier Diodes for Energy-Efficient Power Applications
Previous Article in Special Issue
Use of Different Metal Oxide Coatings in Stainless Steel Based ECDs for Smart Textiles
You seem to have javascript disabled. Please note that many of the page functionalities won't work as expected without javascript enabled.
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Electronics
Volume 10
Issue 22
10.3390/electronics10222803
electronics-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Epoxy-Based/BaMnO4 Nanodielectrics: Dielectric Response and Energy Storage Efficiency

by
Despoina I. Batsouli
1,2,
Anastasios C. Patsidis
1 and
Georgios C. Psarras
1,*
1
Smart Materials & Nanodielectrics Laboratory, Department of Materials Science, University of Patras, 26504 Patras, Greece
2
Adamant Composites Ltd., Platani-Patras, 26504 Patras, Greece
*
Author to whom correspondence should be addressed.
Electronics 2021, 10(22), 2803; https://doi.org/10.3390/electronics10222803
Submission received: 12 October 2021 / Revised: 4 November 2021 / Accepted: 13 November 2021 / Published: 16 November 2021
(This article belongs to the Special Issue Recent Advances in Nanoelectronics for Energy Conversion, Storage, and Saving)
Browse Figures
Graphical abstract
"> Figure 1
<p>Comparative spectra of the real part of dielectric permittivity as a function of frequency (<b>a</b>) at 30 °C and (<b>b</b>) at 160 °C for all the specimens under study. Insets depict the AC conductivity as a function of frequency at 30 °C and 160 °C, respectively.</p> "> Figure 2
<p>Dielectric spectra of the 3 phr BaMnO<sub>4</sub> nanocomposite as a function of temperature and frequency for (<b>a</b>) loss tangent—tan(δ) and (<b>b</b>) AC conductivity (σ<sub>AC</sub>).</p> "> Figure 3
<p>(<b>a</b>) Stored (charging procedure) and (<b>b</b>) retrieved (discharging procedure) energies (E<sub>stored</sub>, E<sub>retrieved</sub>) as a function of time for the 3 phr BaMnO<sub>4</sub> nanocomposite at different DC voltage levels.</p> "> Figure 4
<p>(<b>a</b>) Stored (charging procedure) and (<b>b</b>) retrieved (discharging procedure) energies (E<sub>stored</sub>, E<sub>retrieved</sub>) as a function of time for the 15 phr BaMnO<sub>4</sub> nanocomposite at different DC voltage levels.</p> "> Figure 5
<p>(<b>a</b>) Stored (charging procedure) and (<b>b</b>) retrieved (discharging procedure) energies (E<sub>stored</sub>, E<sub>retrieved</sub>) as a function of time for all the specimens under study at a DC voltage level of 200 V.</p> "> Figure 6
<p>Stored power (P<sub>in</sub>) of (<b>a</b>) 3 phr BaMnO<sub>4</sub> and (<b>b</b>) 5 phr BaMnO<sub>4</sub> specimens as a function of time. Insets depict the retrieved power (P<sub>out</sub>) as a function of time of 3 phr BaMnO<sub>4</sub> and 5 phr BaMnO<sub>4</sub> specimens, respectively.</p> ">
Versions Notes

Abstract

:
Compact capacitive energy storing/harvesting systems could play a key role in the urgent need for more energy-efficient technologies to address both energy and environmental issues. Therein, the purpose of the present work is to develop and investigate epoxy/BaMnO4 nanocomposites at various filler concentrations, which could be applicable as compact materials systems for energy storage and harvesting. Broadband dielectric spectroscopy was used for studying the dielectric properties and the relaxation processes of the examined nanodielectrics. The energy storing/retrieving ability of the nanocomposites was also evaluated via DC charge–discharge experiments. The coefficient of energy efficiency (neff) was found for all prepared nanocomposites to evaluate the energy performance of the systems. Dielectric data divulge the existence of two matrix-related relaxations, i.e., α-mode and β-mode, attributed to the glass-to-rubber transition of the polymer matrix and re-orientation of polar side groups, respectively. Interfacial polarization was also identified in the low-frequency and high-temperature region. The 7 phr BaMnO4 nanocomposite exhibits the best performance in terms of the stored and harvested energies compared to all systems. On the other hand, the 5 phr, 3 phr and 1 phr nanocomposites display optimum energy performance, reaching high values of neff.

Graphical Abstract">
Graphical Abstract

1. Introduction

Energy storage and retrieving has been identified as the key to mitigating the environmental problems resulting from the consumption of huge amounts of unsustainable energy sources such as fossil fuels. Since a small amount of power capacity is being globally stored and the energy consumption is rising, an exhaustion of fossil fuels will occur in the coming decades. In addition, global demand for energy is increasing as the developed countries continue to consume huge amounts of energy which has, as a consequence, caused the availability of reserves to constitute a major source of concern. Therefore, the urgent necessity for renewable energy sources, energy storing and energy retrieving leads to the development of novel functional materials and the fabrication of novel, environmentally friendly, low-cost and low-weight device structures [1,2,3,4,5].
Polymer matrix nanocomposites attract remarkable scientific attention because of their adaptable properties for potential applications, varying from energy storing, environmental remediation and electromagnetic (EM) shielding to novel catalysts. In particular, this type of materials can be employed in applications to address both energy and environmental issues, such as dielectric capacitors, electrochemical capacitors and batteries (energy storage), electrochromic devices and carbon dioxide capture (energy saving) [6,7,8]. Polymers, beyond their mechanical, lightweight, ease processing and insulating properties, exhibit high dielectric breakdown strength along with low energy density and are appropriate for insulating applications and possibly for capacitive energy storage. However, they have significantly low dielectric permittivity, and the enhancement of the polymer dielectric properties is required. To solve this issue, a plethora of high-permittivity nanofillers has been integrated in polymers. Ceramic particles with ferroelectric properties such as BaTiO3 [9,10,11], SrTiO3 [12] and BaSrTiO3 (BST) [13], 2D nanomaterials such as boron nitride [14,15] and various carbon allotropes [16,17] have been investigated to enhance dielectric permittivity, sometimes at the partial cost of voltage endurance and breakdown strength of polymers. This type of materials is also referred to as nanodielectric [18].
An epoxy resin and barium manganate (BaMnO4) nanoparticles were used as the polymer matrix and the reinforcing phase, respectively. Due to its primary advantages and the wide range of material characteristics, such as high chemical resistance, advanced thermomechanical behavior, efficient fatigue resistance, enhanced durability at low and high temperatures, better moisture resistance, easy processing, low shrinkage during cure and high adhesive properties (strong adhesion with filler), epoxy resin was selected as the polymer matrix [19,20,21]. On the other hand, BaMnO4 has a scheelite-like structure (ABO4) crystallizing in the orthorhombic (Pnma) structure with the average Mn-O distance calculated at 167.8 pm [22]. This material has potential applicability in energy storage because of the above characteristics. However, it has not been investigated so far as an additive in polymer nanocomposites for capacitive energy storage applications.
The preparation of barium manganate (VI) is considered as simple and easy in handling and thus its production appears to be more attractive on a medium to large scale. In addition, oxidations do not require any special activation, the isolation of the product is convenient and reduced oxidant is needed (1:1 to 1:10 compared to 1:5 to 1:50 for MnO2). Barium manganate finds various other applications in the synthesis and oxidizing of thiols to disulfides. It is worth mentioning that, in this oxidation, an aromatic amino group remains unaffected, since aromatic amines have been reported to yield azo compounds with barium manganate [23,24]. BaMnO4 is also used as an activator on the cathodic discharge of K2FeO4 for nonaqueous electrochemical energy storage applications. This synergistic improvement of a K2FeO4 cathode with BaMnO4 leads to an additional increase in high-power discharge storage capacity [25,26]. Stani et al. [27] have investigated the addition of barium compounds on manganese dioxide to enhance rechargeability of flat plate RAM™ (rechargeable alkaline manganese dioxide) cells. The mixing of barium manganate to the cathode yielded a more than 15% improvement of capacity after 25 cycles, compared to the barium sulfate additive.
In this study, BaMnO4/epoxy nanocomposites were effectually prepared and experimentally examined at various filler contents. The dielectric response and relaxation phenomena of the nanocomposites were investigated via broadband dielectric spectroscopy (BDS) with varying parameters—the filler content, the temperature and the frequency. However, the main goal was to study the energy efficiency of nanocomposite systems by examining their ability to store and harvest energy with parameters the applied DC voltage and the reinforcing phase concentration, targeted to develop an efficient, fast charge/discharge material/device.

2. Materials and Methods

BaMnO4/epoxy nanocomposites were fabricated in six different filler contents, that is 1, 3, 5, 7, 10 and 15 phr (parts per hundred resin per mass). A reference specimen of neat resin was prepared also. A bisphenol-A type epoxy resin (ER) with low viscosity, under the trade name Epoxol 2004A, and a cycloaliphatic amine curing agent, reacting at slow rate, under the trade name Epoxol 2004B, were combined for the fabrication of the polymer matrix phase. Both reactants were purchased by Neotex S.A., Athens, Greece. Barium manganate in the form of particles was provided by Sigma Aldrich with a purity of 90–95% according to the supplier.
For the preparation procedure, the following steps were performed. A pre-calculated amount of ceramic nanoparticles was added into epoxy monomers (Epoxol 2004A). The obtained mixture was slowly stirred in a sonicator at 50 °C for 10 min in order for omit clusters to be formed. After achieving a homogeneous mixture, a curing agent (Epoxol 2004B) was added in a weight ratio of 2:1 (w/w) of epoxy prepolymer to hardener. The resulted mixture was magnetically stirred for 15 min to improve particle dispersion.
The homogenized mixtures were subsequently poured into a cylindrical silicon mold and cured at ambient temperature for a week. Finally, the mold was moved into an oven and the post-curing was performed at 100 °C for 4 h. The curing and post-curing procedures have been investigated and established through various experimental tests in previous works [9,28]. The prepared specimens have a thickness ranging from 2.3 to 2.8 mm, with an average diameter in the range of 30 mm.
Broadband dielectric spectroscopy (BDS): BDS was used for the investigation of the dielectric properties of the prepared nanocomposites using an Alpha-N Frequency Response Analyzer supplied by Novocontrol Technologies GmbH & Co. KG (Montabaur, Germany). The frequency range was varied from 0.1 Hz to 10 MHz, while the applied voltage Vrms was 1 V in all cases. For the temperature control, a Novotherm system (Novocontrol Technologies) with ±0.1 °C accuracy was employed. The dielectric cell consisted of two gold-plated electrodes (BDS 1200, Novocontrol Technologies). Samples were put between the two gold-plated metal electrodes forming a parallel-plate capacitor configuration. In the case of BaMnO4 powder, the BD 1308 dielectric cell was employed. Frequency scans, at a constant temperature, were performed for all samples from 30 to 160 °C (200 °C for the BaMnO4 powder). The employed temperature step between successive scans was 5 °C. WinDETA software allowed the automatic, real-time, acquisition of data. AC dielectric measurements were conducted according to the ASTM D150 specifications.
DC electrical measurements: The DC tests were performed using a high-resistance meter (DC, Agilent 4339B) device. The experimental set-up included an automatic measurement process allowing continuous control of measurements for the charging/discharging sequence. For the automatic and real-time acquisition of data, a suitable software developed in the Smart Materials and Nanodielectrics Laboratory was used [29]. The testing cell was a two parallel-plate electrodes capacitor, and specimens were placed between the two electrodes. Four different voltages were applied in each specimen: 50, 100, 150 and 200 V at a charging time of 60 s and a discharging time of 300 s. Before every charging/discharging sequence, a discharging procedure via short-circuiting the electrodes was conducted for removing any remaining charges. The stored and retrieved energies were determined via the recorded charging and discharging currents as a function of time. Furthermore, the needed value of the material’s capacitance was selected from the dielectric measurements at the lowest measured frequency (0.1 Hz), where the dielectric permittivity attains the closer value to its static one (known also as the dielectric constant) [28]. DC measurements were performed according to the ASTM D257 specifications.
In all conducted experiments, errors were always less than 1% and were introduced via the measurements of geometrical characteristics of the specimens.

3. Results

3.1. Dielectric Characterization of BaMnO4 Nanocomposites

Since the free charge carriers’ concentration of polymer matrix nanocomposites is very low, the nanocomposites belong to the category of electrical insulators. Therefore, their electrical response is related to the dielectric relaxation effects that occur under the influence of an AC field. These relaxation processes mainly result from the orientation of both permanent and induced dipoles and, in many cases, are related to the space charge transport, glass-to-rubber transition, segment mobility of polar groups, interfacial effects and crystallization processes. The presence of nanofillers has an impact on these relaxations processes in various ways. Thus, it is vital to consider the effect of nanoinclusions upon these relaxations. Dielectric spectra of polymer-based composite systems are complex because of the interactions between polymer chains and particles and the coexistence of both permanent and induced electric dipoles [30].
The BaMnO4 nanocomposite systems were characterized electrically by means of BDS. The dielectric response, in the form of the real part of dielectric permittivity and AC conductivity as a function of frequency at 30 and 160 °C, is given for all the specimens under study in Figure 1a,b, respectively.
The complex dielectric permittivity, ε*, and tanδ are obtained via Equations (1) and (2), respectively:
ε *   = ε ′ −   i   ε ″
tan δ =   ε ″     ε ′
where ε′ and ε″ correspond to the real and imaginary parts of dielectric permittivity, respectively. AC conductivity was evaluated via Equation (3) and it includes all dissipative effects, from dipolar losses to ohmic contribution [31]:
σ AC = ε 0 ω   ε ″
where ε0 is the permittivity of vacuum (ε0 = 8.854 × 10−12 F/m) and ω the angular frequency.
Under isothermal conditions, AC conductivity can be expressed as:
σAC(ω) = σDC + A(ω)s
where σDC is the ω → 0 limiting value of σAC(ω), A and s are parameters depending on temperature and filler content. Equation (4) is usually referred to as the “the AC universality law” due to its general validity [32,33,34].
Three-dimensional dielectric spectra of the loss tangent (tanδ) and AC conductivity (σAC) as a function of frequency and temperature are shown for the 3 phr BaMnO4 nanocomposite in Figure 2a,b, respectively.

3.2. Energy Storage and Harvesting/Coefficient of Energy Efficiency

A capacitor is a device for storing and retrieving electrical energy. The development of materials with improved dielectric properties can be utilized in capacitor applications. To investigate the applicability of the prepared specimens for such technologies, the storage and harvesting processes were examined by measuring the charge/discharge currents at different voltage levels. Increasing the applied DC field leads to enhanced currents in both charging and discharging procedures. The discharging process is conducted without any applied voltage. The stored energy is a function of capacitance, related exclusively with the geometrical characteristics of the capacitor, and the permittivity of the dielectric substance, if the area between the electrodes is filled by a material. From Equation (5), it is evident that the dielectric permittivity is the only material property that affects the capacitance [35,36]:
C   = ε · ε 0 · A d
E   = ∫ 0 Q V   d q = 1 2 Q 2 C = 1 2 [ ∫ I ( t ) d t ] 2 C    
where C is the capacitance of each nanocomposite as evaluated via the BDS measurements at the lowest frequency [28], ε is the dielectric constant (permittivity) of the material, ε0 is the dielectric permittivity of vacuum, A the area of the capacitor’s electrodes, d the distance of the parallel plates (specimen’s thickness) and E and Q are the stored energy and charge at the capacitor, respectively.
The dispersed nanoinclusions in a polymer matrix can act as a dispersive network of nanocapacitors. So, this type of material’s systems is regarded as suitable for energy storing and retrieving and could perform a counterpart behavior as structural components and materials for energy storage. Stored and retrieved energies can be determined by integrating the I = f(t) curves; in all cases, the capacitance of the system is obtained by the dielectric data at the lowest measured frequency. In this work, the calculation of the stored and retrieved energy in the barium manganate nanocomposites was performed by integrating the time-dependent current functions under charging and discharging conditions by Equation (6).
The stored and retrieved energies under a DC electrical field are shown as a function of time at 50, 100, 150 and 200 V for the 3 phr BaMnO4 specimen in Figure 3a,b, respectively.
Figure 4a,b depict the stored and retrieved energies as a function of time at 50, 100, 150 and 200 V for the 15 phr BaMnO4 specimen.
Figure 5 depicts representative graphs of the stored and harvested energies for all studied nanocomposite systems at an applied voltage of 200 V.
Another crucial factor for the valuation of energy storage/harvesting performance is the coefficient of energy efficiency (neff), which is defined as the ratio of the retrieved to stored energy via Equation (7) [37]:
n eff = E retrieved E stored
The examined parameters are the applied DC voltage, the time and the content of the reinforcing phase. The coefficient of energy efficiency (neff) as a function of the filler content at applied voltages of 50, 100, 150 and 200 V for the time instant of 10 sec is presented in Table 1.
The study of power density in nanocomposite systems is vital to indicate their applicability as a material device. The stored energy density in supercapacitors is limited, while the traditional batteries rely on the chemical reactions and the motion of ions. Therefore, a combination of the advantages provided by nanostructured materials is needed in both battery and supercapacitor systems. For this reason, power is evaluated in this study. The power (P) of 3 phr and 5 phr BaMnO4 specimens (Figure 6) was calculated by Equation (8) [29]:
P   = d E d t
where E is the energy and t is the time.

4. Discussion

The comparative plots of the real part of dielectric permittivity as a function of frequency for all studied specimens at 30 °C and 160 °C are depicted in Figure 1. It is evident from the comparative spectra that, in the low temperature range (Figure 1a), the addition of BaMnO4 nanoparticles augments, in general, the permittivity values compared to the neat epoxy matrix, apart from the 1, 3 and 5 phr BaMnO4 specimens. In the same figure, values of BaMnO4 are also presented. The filler’s permittivity values appear to be lower than the corresponding ones of the matrix at 30 °C and similar to epoxy at 160 °C. Interestingly, dielectric loss values for BaMnO4 are significantly low (ranging between 0.14 and 0.36 at 30 °C), indicating a low loss material. At low filler contents, nanocomposites exhibiting permittivity values lower than that of the neat matrix have been reported and discussed previously [11,38]. This effect has been attributed to local interactions between polymer chains and nanoparticles, resulting in molecular immobilization at interfacial regions. The presence of nanoparticles obstructs the synergetic polymeric motions/orientations and, consequently, the dipoles’ motion, causing the increase of free volume in the interface between the polymer and the nanoparticles [39]. The low ε′ values recorded for the 1, 3 and 5 phr BaMnO4 reinforced specimens could be attributed to these effects in addition with the low values of BaMnO4.
At higher temperatures (Figure 1b), the ε′ is enhanced for the neat epoxy specimen and remarkably augmented for the BaMnO4-reinforced specimens, with the systems containing 1, 3 and 5 phr BaMnO4 exhibiting now higher values of permittivity than the unfilled matrix. Τhis behavior is mainly ascribed to the contribution of the interfacial polarization effect related to the presence of the nanoinclusions. At higher concentrations, the contribution of BaMnO4 nanoparticles dominates the dielectric response with the 15 phr BaMnO4 specimen exhibiting dielectric permittivity (ε′) 500 times higher than that of the neat epoxy resin. It should be noted that the extremely high values of ε′ at the highest measured temperature and at the low-frequency edge is ascribed to: (i) interfacial polarization, (ii) increased conductivity and (iii) the unwanted effect of electrode polarization. Temperature increases the mobility of dipoles (permanent and induced) and space charges, augmenting thus all three processes [40]. ε′ values diminish with frequency since permanent and induced dipoles fail to be aligned with the alternating field as the alternation becomes higher, leading thus to the occurrence of relaxation phenomena.
Insets of Figure 1 depict comparative plots of the AC conductivity as a function of frequency at 30 and 160 °C. Temperature effect is pronounced in the low-frequency range, while, at high frequencies, σAC values grow exponentially with frequency and almost independently from the temperature.
Three-dimensional loss tangent spectra (Figure 2a) show three transitions, denoting the existence of dielectric relaxation processes.
Figure 2a depicts the formation of three peaks, indicating the presence of three relaxations. In the intermediate frequency and temperature range, a strong relaxation process arises. This mode is related to the glass-to-rubber transition of the amorphous polymer matrix, also known as α-relaxation. At low frequencies and high temperatures, another relaxation is recorded, which is assigned to interfacial polarization (IP). Interfacial polarization, known also as the Maxwell–Wagner–Sillars (MWS) effect, is observed mainly in electrically heterogeneous systems of two or more phases [29]. Unbounded charges accumulate at the constituents’ interface, forming large dipoles which exhibit time delay in their orientation in the direction of the field. The unbounded charges (also referred as space charge) are existing in the composites from the stage of their manufacture. After being accumulated at the interface of the constituents, they form induced dipoles having the dimensions of the inclusions. For this reason, they are characterized as large and they exhibit enhanced inertia in following the alternation of the applied field. Their orientation parallel to the field is facilitated by thermal agitation and low frequency alternation. Thus, maximum values of IP are recorded in the high-temperature and low-frequency region [21,32]. By increasing the field’s frequency, the IP effect vanishes significantly. Finally, a secondary relaxation is also recorded at high frequencies and low temperatures. It is weaker than α-relaxation and is attributed to the re-orientation of the polar side groups of the main polymer chain (β-relaxation).
Figure 2b presents the variation of σAC with frequency and temperature. At low frequencies, the effect of temperature is higher, implying a thermally activated conduction process. The influence of temperature diminishes with frequency and, at high frequencies, σAC appears temperature-unaffected. At constant temperature, σAC follows Equation (4), where, at low frequencies, σAC tends to acquire the constant σDC value, while in the high frequency range, σAC has an exponential dependence on frequency. The applied field, at low frequencies, forces the charges to transport over longer distances and their migration is bounded by the insulating matrix and the isolated inclusions. At high frequencies, charges move (hop) between adjusted sites in a localized motion, rising thus the values of conductivity. The exponential dependence commences at a characteristic frequency (ωc), the value of which is influenced by the filler content and temperature. With the increase of temperature, the exponential part of the σAC curve shifts to higher frequencies. Finally, the presence of a “shoulder-like” peak in the intermediate frequency range is the result of the observed dielectric relaxations in this frequency range. Figure 2 is representative of all studied systems. Figure 3 and Figure 4 depict the stored and harvested energies of the 3 phr BaMnO4 and the 15 phr BaMnO4 nanocomposites, respectively, as a function of time at different DC voltage levels. It is obvious that both stored and harvested energies increase significantly as the voltage increases since the applied field reduces the local potential barriers, facilitating the migration of the charges inside the nanocomposites. The harvested energy, in addition to DC charging, also depends on the filler content [35,41,42]. The values of charging curves are above the corresponding values of discharge curves for all diagrams. The systems can receive fast charge/discharge, as they acquire high charging and discharge values quickly. This phenomenon is characteristic of instantaneous power density capacitor systems. Storage technologies such as batteries do not have the ability to store and recover an amount of energy almost instantaneously. Thus, these systems have potential applications in numerous commercial and military devices, which require increased power density and fast charging/discharging current capabilities as well [17].
The comparative plots for the stored and retrieved energies as a function of time for all examined systems at 200 V are shown in Figure 5. The 7 phr BaMnO4 nanocomposite exhibits the optimum performance, since this system indicates the highest value of both stored and harvested energies compared to other nanocomposite systems. Additionally, it is noteworthy that the Eretrieved of the neat epoxy specimen acquires the highest values among all nanocomposite systems, while the Estored acquires low values. This behavior indicates that charge carriers trapped at the constituents’ interface are able to overcome potential barriers and to migrate. Increasing the applied field via the charging voltage results in lowering potential barriers, favoring the de-trapping of charges and their transport.
It is meaningful to employ the coefficient of energy efficiency to evaluate the energy performance of the systems. It is observed that the energy efficiency seems to acquire satisfactory values. Table 1 presents the coefficient of energy efficiency (neff) values of all specimens for four different applied voltages (50, 100, 150 and 200 V) at the time instant of 10 sec. The 5 phr BaMnO4 nanocomposite displays the optimum energy performance at 50 V reaching the value of neff = 99.1%. The energy efficiency for the 3 phr BaMnO4 system is also noteworthy with neff = 98.4% at 100 V. It is evident that the optimum energy performance does not correspond to the highest content of the filler. The coefficient of energy efficiency is a quantity that can be influenced by many factors in various ways. The content of the filler increases the heterogeneity of the nanocomposites and forms the extended interface. In addition, as the field intensity increases, the number of charge carriers augments and their migration within the nanocomposite is facilitated by reducing the local potential barriers. Thus, leakage currents occur, leading to lower values of the coefficient of energy efficiency at the highest applied voltage [12,43]. The energy storing/retrieving performance can also be examined regarding the influence of filler content. By these means, the relative coefficient of energy efficiency (neff (rel)) is introduced, according to Equation (9), as the ratio of the retrieved energy of a composite at a specific charging voltage and time instant upon the corresponding retrieved energy of the neat matrix:
n eff   ( rel ) = E retrieved ,   composite E retrieved ,   matrix
Indicative values of the relative energy efficiency index are listed in Table 1 at the time instant of 10 s. Its values are lower than unity because of the low values of barium manganate, Figure 1. In addition, BaMnO4 seems to be a low dielectric loss material; these materials are interesting for capacitive energy storage applications. A considerable drawback is its low permittivity values which indicate the possible need for a second reinforcing phase, characterized by a high (ε′) and the development of hybrid nanocomposites, where barium manganate could play the permittivity-adjusting role.
The variation of power as a function of time for the 3 phr and 5 phr BaMnO4 nanocomposites is shown in Figure 6. It is evident that the power Pin of both nanocomposites rises rapidly until the time instant of approximately 5 s and then continues to increase at a slower rate of up to 60 s. Additionally, the specimens deliver their stored power (Pout) promptly at a short period of time and then the remaining power is provided with a constant rate until the time instant of 300 s (insets). It is noticeable that the discharge time is much longer than that employed for charge. This may lead to the conclusion that, although the specimen can be fully charged quickly, it can provide power to its output for a relatively long period of time.

5. Conclusions

In this study, epoxy-based nanocomposites at various barium manganate concentrations were fabricated and examined. The investigation of electrical properties was performed for all studied nanocomposites by means of BDS. Dielectric permittivity is enhanced by increasing the BaMnO4 concentration, compared to the epoxy matrix, at high temperature. However, at low temperatures, the 1, 3 and 5 phr BaMnO4 specimens exhibit lower values of ε′ than the unfilled epoxy system. This effect is attributed to local interactions that lead to molecular immobilization at interfacial regions. Three peaks occurred in the 3D loss tangent spectra, indicating the existence of dielectric relaxation processes. The detected relaxations are: (a) glass-to-rubber transition of the polymer matrix (α-relaxation), (b) rearrangement of the polar side groups of the main polymer chain (β-relaxation) and (c) the interfacial polarization (IP) effect. To investigate the applicability of the prepared specimens as bulk capacitive energy storage/harvesting systems, the stored and harvested energies were determined by measuring the charge/discharge currents at different voltage levels. It was found that both stored and harvested energies increase significantly as the voltage increases. In comparison with all nanocomposite systems, the 7 phr BaMnO4 specimen exhibits the optimum performance. Finally, the coefficient of energy efficiency (neff) was calculated for all systems, reaching the best values of 99.1% at 50 V, 98.4% at 100 V and 72.4% at 150 V for the 5 phr, 3 phr and 1 phr BaMnO4 nanocomposites, respectively.

Author Contributions

Conceptualization, D.I.B. and G.C.P.; methodology, D.I.B., A.C.P. and G.C.P.; validation, D.I.B. and G.C.P.; formal analysis, D.I.B.; investigation, D.I.B. and A.C.P.; resources, G.C.P.; data curation, D.I.B. and A.C.P.; writing—original draft preparation, D.I.B. and G.C.P.; writing—review and editing, D.I.B. and G.C.P.; visualization, D.I.B.; supervision, G.C.P.; project administration, G.C.P. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Data Availability Statement

The data presented in this study are available on request from the corresponding author.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Chen, S.; Skordos, A.; Thakur, V. Functional nanocomposites for energy storage: Chemistry and new horizons. Mater. Today Chem. 2020, 17, 100304. [Google Scholar] [CrossRef]
  2. Simon, P.; Gogotsi, Y. Materials for electrochemical capacitors. Nanosci. Technol. 2009, 7, 320–329. [Google Scholar] [CrossRef] [Green Version]
  3. Cook, T.R.; Dogutan, D.K.; Reece, S.Y.; Surendranath, Y.; Teets, T.S.; Nocera, D.G. Solar Energy Supply and Storage for the Legacy and Nonlegacy Worlds. Chem. Rev. 2010, 110, 6474–6502. [Google Scholar] [CrossRef]
  4. Wang, G.; Zhang, L.; Zhang, J. A review of electrode materials for electrochemical supercapacitors. Chem. Soc. Rev. 2012, 41, 797–828. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  5. Das, T.; Krishnan, V.K.; McCalley, J.D. Assessing the benefits and economics of bulk energy storage technologies in the power grid. Appl. Energy 2015, 139, 104–118. [Google Scholar] [CrossRef]
  6. Yang, C.; Wei, H.; Guan, L.; Guo, J.; Wang, Y.; Yan, X.; Zhang, X.; Wei, S.; Guo, Z. Polymer nanocomposites for energy storage, energy saving, and anticorrosion. J. Mater. Chem. A 2015, 3, 14929–14941. [Google Scholar] [CrossRef]
  7. Wang, Q.; Zhu, L. Polymer nanocomposites for electrical energy storage. J. Polym. Sci. Part B Polym. Phys. 2011, 49, 1421–1429. [Google Scholar] [CrossRef]
  8. Riggs, B.; Adireddy, S.; Rehm, C.H.; Puli, V.S.; Elupula, R.; Chrisey, D.B. Polymer Nanocomposites for Energy Storage Applications. Mater. Today Proc. 2015, 2, 3853–3863. [Google Scholar] [CrossRef]
  9. Manika, G.C.; Psarras, G. Barium titanate/epoxy resin composite nanodielectrics as compact capacitive energy storing systems. Express Polym. Lett. 2019, 13, 749–758. [Google Scholar] [CrossRef]
  10. Drakopoulos, S.X.; Patsidis, A.C.; Psarras, G.C. Epoxy-based/BaTiO3 nanodielectrics: Relaxation dynamics, charge transport and energy storage. Mater. Res. Bull. 2022, 145, 111537. [Google Scholar] [CrossRef]
  11. Patsidis, A.C. Barium titanate/polydimethylsiloxane nano/microcomposites fabrication, morphology, dielectric response and functionality. IET Nanodielectr. 2020, 3, 14–19. [Google Scholar] [CrossRef]
  12. Manika, G.C.; Psarras, G.C. SrTiO3/Epoxy Nanodielectrics as Bulk Energy Storage and Harvesting Systems: The Role of Conductivity. ACS Appl. Energy Mater. 2020, 3, 831–842. [Google Scholar] [CrossRef] [Green Version]
  13. Xie, Y.; Jiang, W.; Fu, T.; Liu, J.; Zhang, Z.; Wang, S. Achieving High Energy Density and Low Loss in PVDF/BST Nanodielectrics with Enhanced Structural Homogeneity. ACS Appl. Mater. Interfaces 2018, 10, 29038–29047. [Google Scholar] [CrossRef] [PubMed]
  14. Li, Q.; Chen, L.; Gadinski, M.R.; Zhang, S.; Zhang, G.; Li, H.U.; Iagodkine, E.; Haque, A.; Chen, L.-Q.; Jackson, T.N.; et al. Flexible high-temperature dielectric materials from polymer nanocomposites. Nat. Cell Biol. 2015, 523, 576–579. [Google Scholar] [CrossRef] [PubMed]
  15. Li, Q.; Zhang, G.; Liu, F.; Han, K.; Gadinski, M.R.; Xiong, C.; Wang, Q. Solution-processed ferroelectric terpolymer nanocomposites with high breakdown strength and energy density utilizing boron nitride nanosheets. Energy Environ. Sci. 2015, 8, 922–931. [Google Scholar] [CrossRef]
  16. Georgakilas, V.; Tiwari, J.N.; Kemp, K.; Perrnan, J.A.; Bourlinos, A.B.; Kim, K.S.; Zboril, R. Noncovalent Functionalization of Graphene and Graphene Oxide for Energy Materials, Biosensing, Catalytic, and Biomedical Applications. Chem. Rev. 2016, 116, 5464–5519. [Google Scholar] [CrossRef] [Green Version]
  17. Stavropoulos, S.; Sanida, A.; Psarras, G. Carbon Allotropes/Epoxy Nanocomposites as Capacitive Energy Storage/Harvesting Systems. Appl. Sci. 2021, 11, 7059. [Google Scholar] [CrossRef]
  18. Psarras, G.C. Nanodielectrics: An emerging sector of polymer nanocomposites. Express Polym. Lett. 2008, 2, 460–467. [Google Scholar] [CrossRef]
  19. Gibson, G. Epoxy Resins, Brydson’s Plastics Materials; Elsevier: Amsterdam, The Netherlands, 2017; pp. 773–797. [Google Scholar]
  20. Kavouras, P.; Dragatogiannis, D.A.; Batsouli, D.I.; Charitidis, C.A. Effect of local microstructure on the indentation induced damage of a fiber reinforced composite. Polym. Test. 2017, 61, 197–204. [Google Scholar] [CrossRef]
  21. Patsidis, A.C.; Psarras, G.C. Dielectric and Conductivity Studies of Epoxy Composites. In Epoxy Composites: Fabrication, Characterization and Applications, 1st ed.; Parameswaranpillai, J., Pulikkalparambil, H., Rangappa, S.M., Siengchin, S., Eds.; WILEY-VCH GmbH: Weinheim, Germany, 2021; pp. 299–348. ISBN 9783527824083. [Google Scholar]
  22. Fiedler, D.A.; Albering, J.H.; Besenhard, J.O. Characterization of strontium and barium manganates by abrasive stripping voltammetry. J. Solid State Electrochem. 1998, 2, 413–419. [Google Scholar] [CrossRef]
  23. Fatiadi, A.J. The classical permanganate ion: Still a novel oxidant in organic chemistry. Synthesis 1987, 2, 85–127. [Google Scholar] [CrossRef]
  24. Firouzabadi, H.; Mostafavi-Pour, Z. Barium Manganate. A Versatile Oxidant in Organic Synthesis. Bull. Chem. Soc. Jpn. 1983, 56, 914–917. [Google Scholar] [CrossRef] [Green Version]
  25. Licht, S.; Naschitz, V.; Ghosh, S. Silver Mediation of Fe(VI) Charge Transfer: Activation of the K2FeO4 Super-Iron Cathode. J. Phys. Chem. B 2002, 106, 5947–5955. [Google Scholar] [CrossRef]
  26. Licht, S. Chemistry of the Fe6+/B2− Super-Iron Boride Battery: An Overview of Primary Alkaline Fe6+ Cathodic Charge Storage Including the New B2− Anode. ECS Trans. 2007, 11, 187–214. [Google Scholar] [CrossRef]
  27. Stani, A.; Taucher-Mautner, W.; Kordesch, K.; Daniel-Ivad, J. Development of flat plate rechargeable alkaline manganese dioxide–zinc cells. J. Power Source 2006, 153, 405–412. [Google Scholar] [CrossRef]
  28. Manika, G.C.; Psarras, G.C. Energy storage and harvesting in BaTiO3/epoxy nanodielectrics. High Volt. 2016, 1, 151–157. [Google Scholar] [CrossRef]
  29. Manika, G.C. Polymer Matrix Composite Nanodielectrics as Compact Capacitive Energy Storage Systems. Ph.D. Thesis, University of Patras, Patras, Greece, 2019. [Google Scholar]
  30. Psarras, G.C.; Siengchin, S.; Karahaliou, P.K.; Georga, S.N.; Krontiras, C.A.; Karger-Kocsis, J. Dielectric relaxation phenomena and dynamics in polyoxymethylene/polyurethane/alumina hybrid nanocomposites. Polym. Int. 2011, 60, 1715–1721. [Google Scholar] [CrossRef]
  31. Von Hippel, A.R. Dielectrics and Waves; Artech House: Boston, MA, USA, 1995; p. 5. [Google Scholar]
  32. Psarras, G.C. Conductivity and Dielectric Characterization of Polymer Nanocomposites. In Polymer Nanocomposites: Physical Properties and Applications, 1st ed.; Tjong, S.C., Mai, Y.W., Eds.; Woodhead Publishing Limited: Cambridge, UK, 2010; pp. 31–69. ISBN 978-184569-672-6. [Google Scholar]
  33. Jonscher, A.K. Universal Relaxation Law, 1st ed.; Chelsea Dielectric Press: London, UK, 1992; pp. 254–257. [Google Scholar]
  34. Psarras, G.C. Dielectric polymer materials for high-density energy storage. In Fundamentals of Dielectric Theories, 1st ed.; Dang, Z.M., Ed.; Elsevier Inc.: Cambridge, UK, 2018; p. 11. ISBN 978-0-12-813215-9. [Google Scholar]
  35. Hao, X. A review on the dielectric materials for high energy-storage application. J. Adv. Dielectr. 2013, 3, 1330001. [Google Scholar] [CrossRef]
  36. Imanaka, Y.; Amada, H.; Kumasaka, F. Microstructure and Dielectric Properties of Composite Films for Embedded Capacitor Applications. Int. J. Appl. Ceram. Technol. 2011, 8, 653–657. [Google Scholar] [CrossRef]
  37. Sanida, A.; Stavropoulos, S.; Speliotis, T.; Psarras, G. Probing the magnetoelectric response and energy efficiency in Fe3O4/epoxy nanocomposites. Polym. Test. 2020, 88, 106560. [Google Scholar] [CrossRef]
  38. Vryonis, O.; Virtanen, S.T.H.; Andritsch, T.; Vaughan, A.S.; Lewin, P.L. Understanding the cross-linking reactions in highly oxidized graphene/epoxy nanocomposite systems. J. Mater. Sci. 2018, 54, 3035–3051. [Google Scholar] [CrossRef] [Green Version]
  39. Li, S.; Yin, G.; Bai, S.; Li, J. A new potential barrier model in epoxy resin nanodielectrics. IEEE Trans. Dielectr. Electr. Insul. 2011, 18, 1535–1543. [Google Scholar] [CrossRef]
  40. Drakopoulos, S.X.; Manika, G.C.; Nogales, A.; Kim, T.; Robbins, A.B.; Claudio, G.; Minnich, A.J.; Ezquerra, T.A.; Psarras, G.C.; Martin-Fabiani, I.; et al. Gold/ultra-high molecular weight polyethylene nanocomposites for electrical energy storage: Enhanced recovery efficiency upon uniaxial deformation. J. Appl. Polym. Sci. 2021, 138, 51232. [Google Scholar] [CrossRef]
  41. 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, 6334–6365. [Google Scholar] [CrossRef]
  42. Song, H.J.; Choi, Y.T.; Wereley, N.M. Energy harvesting devices using macro-fiber composite materials. J. Intell. Mater. Syst. Struct. 2010, 21, 647–658. [Google Scholar] [CrossRef]
  43. Dennison, J.; Brunson, J. Temperature and Electric Field Dependence of Conduction in Low-Density Polyethylene. IEEE Trans. Plasma Sci. 2008, 36, 2246–2252. [Google Scholar] [CrossRef] [Green Version]
Electronics 10 02803 g001 550
Figure 1. Comparative spectra of the real part of dielectric permittivity as a function of frequency (a) at 30 °C and (b) at 160 °C for all the specimens under study. Insets depict the AC conductivity as a function of frequency at 30 °C and 160 °C, respectively.
Figure 1. Comparative spectra of the real part of dielectric permittivity as a function of frequency (a) at 30 °C and (b) at 160 °C for all the specimens under study. Insets depict the AC conductivity as a function of frequency at 30 °C and 160 °C, respectively.
Electronics 10 02803 g001
Electronics 10 02803 g002 550
Figure 2. Dielectric spectra of the 3 phr BaMnO4 nanocomposite as a function of temperature and frequency for (a) loss tangent—tan(δ) and (b) AC conductivity (σAC).
Figure 2. Dielectric spectra of the 3 phr BaMnO4 nanocomposite as a function of temperature and frequency for (a) loss tangent—tan(δ) and (b) AC conductivity (σAC).
Electronics 10 02803 g002
Electronics 10 02803 g003 550
Figure 3. (a) Stored (charging procedure) and (b) retrieved (discharging procedure) energies (Estored, Eretrieved) as a function of time for the 3 phr BaMnO4 nanocomposite at different DC voltage levels.
Figure 3. (a) Stored (charging procedure) and (b) retrieved (discharging procedure) energies (Estored, Eretrieved) as a function of time for the 3 phr BaMnO4 nanocomposite at different DC voltage levels.
Electronics 10 02803 g003
Electronics 10 02803 g004 550
Figure 4. (a) Stored (charging procedure) and (b) retrieved (discharging procedure) energies (Estored, Eretrieved) as a function of time for the 15 phr BaMnO4 nanocomposite at different DC voltage levels.
Figure 4. (a) Stored (charging procedure) and (b) retrieved (discharging procedure) energies (Estored, Eretrieved) as a function of time for the 15 phr BaMnO4 nanocomposite at different DC voltage levels.
Electronics 10 02803 g004
Electronics 10 02803 g005 550
Figure 5. (a) Stored (charging procedure) and (b) retrieved (discharging procedure) energies (Estored, Eretrieved) as a function of time for all the specimens under study at a DC voltage level of 200 V.
Figure 5. (a) Stored (charging procedure) and (b) retrieved (discharging procedure) energies (Estored, Eretrieved) as a function of time for all the specimens under study at a DC voltage level of 200 V.
Electronics 10 02803 g005
Electronics 10 02803 g006 550
Figure 6. Stored power (Pin) of (a) 3 phr BaMnO4 and (b) 5 phr BaMnO4 specimens as a function of time. Insets depict the retrieved power (Pout) as a function of time of 3 phr BaMnO4 and 5 phr BaMnO4 specimens, respectively.
Figure 6. Stored power (Pin) of (a) 3 phr BaMnO4 and (b) 5 phr BaMnO4 specimens as a function of time. Insets depict the retrieved power (Pout) as a function of time of 3 phr BaMnO4 and 5 phr BaMnO4 specimens, respectively.
Electronics 10 02803 g006
Table
Table 1. Coefficient of energy efficiency (neff) and relative coefficient of energy efficiency (neff (rel)) of the BaMnO4 nanocomposites at applied voltages of 50, 100, 150 and 200 V.
Table 1. Coefficient of energy efficiency (neff) and relative coefficient of energy efficiency (neff (rel)) of the BaMnO4 nanocomposites at applied voltages of 50, 100, 150 and 200 V.
BaMnO4
Nanocomposites		Applied Voltage
50 V100 V150 V (neff (rel))200 V (neff (rel))
Neat0.5120.2410.206 (1.000)0.303 (1.000)
1 phr0.4340.3800.724 (1.1100.390 (0.613)
3 phr0.4800.9840.238 (0.612)0.238 (0.650)
5 phr0.9910.3970.640 (0.519)0.323 (0.566)
7 phr0.3380.2770.325 (0.507)0.253 (0.839)
10 phr0.3750.3620.319 (0.827)0.317 (0.884)
15 phr0.4170.4290.347 (0.865)0.340 (0.921)
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Share and Cite

MDPI and ACS Style

Batsouli, D.I.; Patsidis, A.C.; Psarras, G.C. Epoxy-Based/BaMnO4 Nanodielectrics: Dielectric Response and Energy Storage Efficiency. Electronics 2021, 10, 2803. https://doi.org/10.3390/electronics10222803

AMA Style

Batsouli DI, Patsidis AC, Psarras GC. Epoxy-Based/BaMnO4 Nanodielectrics: Dielectric Response and Energy Storage Efficiency. Electronics. 2021; 10(22):2803. https://doi.org/10.3390/electronics10222803

Chicago/Turabian Style

Batsouli, Despoina I., Anastasios C. Patsidis, and Georgios C. Psarras. 2021. "Epoxy-Based/BaMnO4 Nanodielectrics: Dielectric Response and Energy Storage Efficiency" Electronics 10, no. 22: 2803. https://doi.org/10.3390/electronics10222803

APA Style

Batsouli, D. I., Patsidis, A. C., & Psarras, G. C. (2021). Epoxy-Based/BaMnO4 Nanodielectrics: Dielectric Response and Energy Storage Efficiency. Electronics, 10(22), 2803. https://doi.org/10.3390/electronics10222803

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop