Nanosilver Coated Coir Based Dielectric Materials with High K and

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Nanosilver coated coir based dielectric materials with high K and low Df for an embedded capacitor and insulating material applications – a greener approach Sanjay Rout, Shahid Anwar, and Bankim Tripathy ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.8b04465 • Publication Date (Web): 21 Jan 2019 Downloaded from http://pubs.acs.org on January 22, 2019

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ACS Sustainable Chemistry & Engineering

Nanosilver coated coir based dielectric materials with high K and low Df for an embedded capacitor and insulating material applications – a greener approach Sanjay K. Rout1, *, Shahid Anwar2, Bankim C. Tripathy2 1Department

of Chemistry, Konark Institute of Science & Technology, Bhubaneswar-752050, India of Minerals and Materials Technology, Bhubaneswar-751013, India

2CSIR-Institute

*Address correspondence to [email protected] ABSTRACT In this work, the dielectric properties of lignocellulosic coirs coated with silver nanoparticles were studied. Nanosilver coating increased the dielectric constant (K) value and decreased the dissipation factor (Df). The increase in dielectric constant of the nano composite could be assigned to the stacking of charges at the extended interface of the synthesized nanocomposites. In the present study, a significant decrease in Df was witnessed which could be due to the wellestablished quantum effect of metal nanoparticles, more precisely known as Coulomb blockade effect. It was found that the dielectric properties were influenced by the size and coating level of the metal nanoparticles in the nanocomposite and hydrophobicity of the fiber. Hydrophobicity of the fiber results in uniform silver coating throughout the coir resulting in a large number of interfaces, thus increasing the interfacial polarization and K. However, these newly formed interfaces restrain the motion of charges, which decreases the Df. It is interesting to note that all the fibers that are coated with silver nanoparticles show improved thermal stability when compared with parent coir. More importantly, the sintering temperature can go as high as 600℃ or more for the silver nanoparticle coated coir fibers which are usually not possible for the embedded capacitors made with low-cost organic polymers for printed circuit board (PCB) industries. Due to higher packing density and insulating properties of these silver nanoparticles (AgNPs) coated coir fibers, they are very important materials for embedded capacitors, optoelectronic devices, metal oxide semiconductor field effect transistors (MOSFET) and integrated circuits.

Key words: Dielectric constant, dissipation factor, hydrophobicity, nano silver coating, cellulose, hemicellulose, lignin 1 ACS Paragon Plus Environment

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INTRODUCTION Lignoellulosic fibers mainly contain cellulose, lignin, hemicellulose, pectin and water-soluble ingredients which are used for composite making,[1] production of lactic acid, active carbon, adhesives, ethanol, furfural and in automotive industries.[2] Many researchers have used plant extracts for the synthesis of silver nanoparticles (AgNPs).[3–5] There are also reports on the synthesis of nanoparticles from agricultural wastes.[6–8] Coir is a natural fiber containing 41-45% lignin, 0.15–0.25% hemicellulose, 36–43% cellulose, and pectin with some water-soluble constituents[9] which is broadly available in India mostly in the coastal region. Coir fibers have great potential for discrete applications due to their diverse physicochemical properties.[10–23] Since last few years natural fiber reinforced composite materials have received a substantial consideration in construction, packaging and automotive industries. However, their applications as dielectric materials has become most popular recently. The use of natural fiber reinforced composite materials as dielectric materials in microchips, transformers, terminals, connectors, switches, circuit boards, etc. have been reported.[24] Metal/polymer composites with metal fillers and polymer matrix, have prospective applications in electronic devices as potential dielectric materials.[25, 26] Recently, metal–polymer nanocomposite materials have become vital in view of their potential applications as electroactive materials in pH sensors and moreover in high chargestorage capacitors.[27–30] Silver has been one of the main metal fillers investigated in dielectric composites due to its chemical stability and better electrical and thermal conductivity. Silver nanoparticles have received considerable attention due to their attractive physical and chemical properties.[31] Recently it has been established that the presence of a large amount of boundaries in the composite between the polymer and the nanoparticles would endorse the exchange coupling effect through a dipolar interface layer, realizing higher polarization levels and promoting dielectric properties of the polymers.[32–36] Embedded capacitor is one of the evolving and imperative technologies for microelectronic system which reduces the dimension of many electronic systems and enhances their performances.[37, 38] Novel materials have very high demand for embedded passive applications, for which the important prerequisites are high K, low dielectric loss and process compatibility with the printed circuit boards (PCBs). Polymer composites are better alternatives for ceramics or metal fillers as 2 ACS Paragon Plus Environment

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they show the combined dielectric or electrical properties and at the same time can be processed at lower temperature without compromising with the mechanical properties of the polymer matrix.[25, 39-43] Materials made of nano sized metals by virtue of their novel properties such as plasmon absorption, super paramagnetism, Coulomb blockade etc.[44] are potential candidates for present and future high-tech demand. However, the nanocomposites require uniform dispersion of nanoparticles because the desired electrical or dielectric properties may not be achieved due to the formation of clusters of particles inside the polymer matrix. Further it is not easy to disperse the ultrafine particles in a polymer matrix as they can easily agglomerate, while the in-situ formation of metal nanoparticles in a polymer matrix could facilitate a more uniform dispersion of nanoparticles in polymers.[42, 44, 45] Besides, the nano sized particles attained by in-situ reduction can help achieve thinner dielectric films leading to better Coulomb blockade effects.[46] Khanna et al.[47] synthesise Ag-PVA nanocomposites by in-situ reduction of silver nitrate using two different reducing agents such as sodium formaldehyde sulfoxylate and hydrazine hydrate and reported the enhancements in optical and thermal properties of the Ag-PVA nanocomposites. Increased K value and decreased Df due to integration of ultra-fine sized Ag nanoparticles in the Ag/carbon black/epoxy nanocomposites has already been reported by Lu et al.[48] The dielectric properties of Ag/PbTiO3 composite films was affected by dispersed Ag nanoparticles where increase in K and decrease in Df was noticed[49] when Ag nanoparticles were added into PbTiO3 films at a certain loading level of Ag. Feng et al.[50] fabricated Ag/PVA nanocomposites with uniform dispersion of Ag accompanied by very low Ag content and reported that the composite with 20–30 nm Ag particles has a higher resistivity and breakdown voltage than PVA. Preferably, due to the Coulomb blockade effect, Ag nanoparticles in PVA matrix may decrease the electron tunneling and rise the resistivity of composites. Consequently, the conduction loss of the dielectric system would alleviate to some degree. However, Effect of chemical modification on coir fibers have been reported by many researchers,[9, 51–54] though no one has reported on coating of silver nanoparticles (AgNPs) except the present authors in their work on agro waste coir fiber.[55,

56]

In this work we have made an attempt to use an agrowaste (coir) fiber as a base material for producing an efficient dielectric material with diverse application in the advancement of modern 3 ACS Paragon Plus Environment


technology. The importance of silver nano particle coating for introducing dielectric properties onto the coir fiber and the versatility of the coated fiber showing excellent dielectric properties which is dependant in silver coating behaviour is the main objective of this work. This work has got lot of advantages over many due to the fact that these agrowaste coir fibers are plentily available with wide accessibility and have unique properties of reducing silver cations followed by their stabilization. Also the method applied was very simple and environment friendly. As this process does not involve any toxic discharge during coating it can be designated as a green process.[55] Usually the coir fiber behaves as an insulator. In the present work we have imparted dielectric properties to the fiber by efficiently coating silver nanoparticles on it. For the first time, in the present work parent and modified unused coir fibers that were coated with nanoparticles of silver have been investigated and their dielectric properties have been discussed to find out their suitability for use in integrated circuits, embedded capacitors and insulating materials. In this study, these coirs were then subjected to various characterization to determine their dielectric behavior by articulating dielectric constant (K), dissipation factor (Df), capacitance (C), resistance (R) and effect of frequency on their dielectric properties. EXPERIMENTAL

Materials and methods Raw coir fibers were purified by soxhelation with 1:1 benzene–ethanol mixture for 72 h at 50 oC followed by washing with acetone, ethanol in addition to air-drying, which are termed as parent coir (PC) hereafter. Butylacrylate (BA) was purified as reported earlier.[51] Silver nitrate was of analytical grade (Qualigens Fine Chemicals); other chemicals like acetic acid, acetone, methanol, benzoyl peroxide (BPO), and pyridine (Py), etc., were of analytical grade (BDH chemicals) and were used after purification. Silver nitrate was dissolved in deionized water to form an aqueous solution.

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Modified coir-1 (MC1): transesterification of parent coir with Butylacrylate or transesterified coir Transesterification of parent coir (1gm) was done by refluxing it with butylacrylate (20 mL) in acetone (20 mL) using pyridine (4 mL) as catalyst at 50 oC for 6 h in a reflux condenser. The reacted fibers were washed with dilute acetic acid and acetone, followed by methanol and distilled water, and then air-dried. These transesterification of parent coir with butylacrylate or transesterified coir was termed as modified coir-1 (MC1) hereafter. Modified coir-2 (MC2): curing of transesterified coir with benzoyl peroxide (BPO) or cured transesterified coir Curing of butylacrylate transesterified coir (0.5gm) was done under reflux with 10 mL of 0.1 M BPO in acetone (40 mL) at 50 oC for 2 h in a reflux condenser. The reacted fibers were washed with dilute acetic acid and acetone, followed by methanol and distilled water, and then air-dried. These cured transesterified coir with benzoyl peroxide (BPO) or cured transesterified coir were termed as modified coir-2 (MC2) hereafter. Silver nanoparticles-coated parent coir (PC-Ag) Silver nanoparticles-coated parent coir (PC-Ag) has been prepared by reaction of silver salt of AgNO3 (dissolved in deionized water) with parent coir. Parent coir (0.5gm) was taken in a 250mL beaker, and then, 100 mL of 0.1 M AgNO3 solution was added followed by continuous stirring at 400 rpm over a magnetic stirrer for 1/2 h under dark conditions at room temperature (28 oC). Subsequently, the reacted fibers were washed with distilled water and then dried at 50 oC in a hot electric oven; these fibers were termed as silver nanoparticles coated parent coir fiber in 0.1 M AgNO3 (PC-Ag0.1) hereafter. In the same way, silver nanoparticles-coated parent coir fiber in 0.2 M AgNO3 (PC-Ag0.2) has been prepared. Silver nanoparticles-coated modified coir-1 (MC1-Ag) and silver nanoparticles-coated modified coir-2 (MC2-Ag) Silver nanoparticles-coated modified coir-1 (MC1-Ag) has been prepared by reaction of silver salt of AgNO3 (dissolved in deionized water) with modified coir-1. MC1 (0.5gm) was taken in a 2505 ACS Paragon Plus Environment


mL beaker, and then, 100 mL of 0.1 M AgNO3 solution was added followed by continuous stirring at 400 rpm over a magnetic stirrer for 1/2 h under dark conditions at room temperature (28 oC). Subsequently, the reacted fibers were washed with distilled water and then dried at 50 oC in a hot electric oven, which was termed as silver nanoparticles coated modified coir-1 in 0.1 M AgNO3 (MC1-Ag0.1) hereafter. Similar process has been adopted for modified coir-2. A schematic representation of the coir, modified coir and the process of silver nanoparticles coating on them have been shown in Figure 1. Instrument and methodology The microstructure along with the morphology of the parent coir (PC), modified coir-1 (MC1), modified coir-2 (MC2), silver nanoparticles (AgNPs)-coated PC and MC fibers, and the size of the silver nanoparticles coated were examined using field emission scanning electron microscope (FESEM, ZEISS EM910) operated at 4–8 kV with sample working distance of 5 mm. The size of the particles were determined by grid method after evaluating the marker scales given on the micrographs. The measurements of dielectric properties for different specimens were carried out using a N4LNumetriQ frequency response analyzer (model PSM1735) with IAI interface connected to a computer. Measurements were carried out using a fabricated two probe dielectric test fixture. The specimens were analyzed using a contacting electrode method, which uses a rigid metal electrode. For dielectric measurement specimens were pressed in the form of circular disc with diameter of 14 mm and a thickness of about 1 mm using unaxial hydraulic press (Figure 2). The dielectric measurements were performed by sandwiching the sample between flat circular copper foil electrodes under spring loading arrangement at a frequency range of 100 Hz to 1 MHz and by using a programmable furnace in the temperature range of 50-400°C at a heating rate of 3°C/min with 2 min stabilizing time at each measured temperature.


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Fig.1 Schematic representation of the coir, modified coir and the process of silver nano particle coating on them.



The dielectric constant (K) was calculated from the capacitance using the following equation: K = Ct / 𝛆0A

(1)

Where K is the dielectric constant of the material, 𝛆0 is the permittivity of air (8.85 x 10-12 F/m), C is the capacitance, A is the area of cross section of the sample and t is the thickness of the sample.

RESULTS AND DISCUSSION Thermal Beahviour and Surface Charcterisation On modified coir fibers, AgNPs coating have been reported,[55, 56] to be better due to the improved hydrophobicity of the fibers. The modified and coated fibers display better thermal stability compared to parent coir fiber and the thermal stabilities has the order MC2 > MC1 > PC.[56] TG, DTG, and DSC studies show greater thermal stability of the coated fibers compared to PC and MCs.[56] Thermal stabilities of modified and silver nanoparticles-coated fibers follow the sequence as MC2-Ag0.2 > MC1-Ag0.2 > PC-Ag0.2 > MC2-Ag0.1 > MC2 > MC1-Ag0.1 > PC-Ag0.1 ~ MC1 > PC. It was seen that, when the fibers were coated with Ag nano particles the decomposition temperatures (endothermic peak) 393, 402.85 and 405.71 oC for PC, MC1, MC2 decreased to lower values of 390, 388, 399, 385, 358, 345 oC for PC-Ag0.1, PC-Ag0.2, MC1-Ag0.1, MC1-Ag0.2, MC2-Ag0.1 and MC2-Ag0.2, respectively. This decrease in decomposition temperature is more significant in MC2-Ag, which could be due to the size reduction and cubic shape of the coated silver nanoparticles on the coir fiber. In MC2-Ag0.1 and MC2-Ag0.2, broad exothermic peaks appeared at 750 and 800 oC, and endothermic peaks appeared at 823.52 and 870.58 oC respectively. These types of peaks above 800 oC occur due to the incombustible silver coating.[56, 57] No significant change was seen in the physical appearance of the fibers/discs after modification, however, they developed a change from light gray to deep gray color after the coating of AgNPs (Figure 2). Color arises due to the silver coating, as the oxygen atoms of cellulose, hemicellulose and lignin of the coir are polarized by Ag+ cations.[55]


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The FESEM micrographs of PC, MC1 and MC2 are shown in Figs. 3a, d and 4a, respectively and FESEMs of AgNPs-coated PC, MC1 and MC2 in 0.1 M and 0.2 M AgNO3 are shown in Figs. 3b, c, e, f and 4b, c, respectively. The inset of Fig. 4b, c shows higher magnification FESEM images (to clearly visualize differences in the fiber surface morphology) caused by curing of transesterified coir followed by coating of AgNPs. Due to surface plasmon resonance of metallic silver nanocrystals, characteristic optical absorption peak appeared at 3 keV,[55, 58] which confirms the coating of AgNPs on parent and modified coirs where the size of AgNPs was reported to be more than 30 nm. AgNPs coated on these fibers are predominately cubic, and in very few cases, these are in the form of nano bars or of truncated triangular and pyramidal shapes. The sizes of these AgNPs remain within the range of 40–210 nm. It was established that the fibers that were more hydrophobic had more numbers of silver particles coated on them. Dielectric properties When an external electric field is applied through parallel plates on a material that acts as a capacitor, it polarizes or stores charge based on the dielectric behavior of the material.[59] Polarizability of a material depends on it’s dielectric constant. Higher polarizability of the material indicates higher dielectric constant. Dipole or orientation polarization of a material arises due to the presence of polar groups in the material.[60] Thus polarizability of the material is governed by the dielectric constant of the material. Dielectric strength of an insulating material is determined from the dielectric constant of that material. This helps in selecting proper dielectric capacitor material to design and manufacture capacitor banks for improving electrical power factor of an electric system installation facilitating reduction in energy losses during transmission.[24] The amount of energy dissipated or the electrical loss by the insulating material when a voltage is applied to the circuit can be denoted by means of dissipation factor (Df). Which is defined as the ratio of the dissipated electrical power in a material to the total power circulating in the specified circuit. In an insulating material the measurement of Df is very important in the sense that the loss tangent is a measure of the electrical energy, which is converted to heat in an insulator. This increase in heat increases the insulator temperature and speeds up its deterioration.


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PC

PC-Ag0.1

PC-Ag0.2

MC1

MC1-Ag0.1 MC1-Ag0.2

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MC2

MC2-Ag0.1 MC2-Ag0.2

Fig.2. Variation in the colours of the fibres/discs from grey to deep grey depending on the concentration of silver ion after coating.


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d b

a

b

e

c

f

Fig. 3 FESEM micrographs of (a) PC (b) PC-Ag0.1 (c) PC-Ag0.2 (d) MC1 (e) MC1-Ag0.1 (f) MC1-Ag0.2.



a

b

c

Fig. 4 FESEM micrographs of (a) MC2 (b) MC2-Ag0.1 (c) MC2-Ag0.2.


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The loss factor is usually used in the energy industry to define the losses in distribution and transmission.[61] However, the average power factor which is considered over a given period of time determines the loss factor. Effect of Chemical Modification The dielectric constants (K) and dissipation factors (Df) of parent coir (PC), modified coir-1 (MC1), modified coir-2 (MC2) at 10 kHz and at 1 MHz are shown in Figs. 5(a) and 5(aʼ) respectively. In Fig. 5(a) at 10 kHz both K and Df decrease in the same manner for MC1 in comparison to PC, but K decreases and Df increases for MC2 in comparison to MC1. In Fig. 5(aʼ) at 1 MHz, K decreases and Df increases for MC1in comparison to PC, but K and Df values decrease for MC2 in comparison to MC1. It was found that among PC, MC1, and MC2 dielectric properties enhanced in the order as: MC1 > MC2 > PC. In the present work the conductivity of fibers PC, MC1 and MC2 will be affected due to their moisture content, chemical composition, cellular structure, and moreover on their nature of arrangements. Hydroxyl groups of the fiber being responsible for moisture content, increase the conductivity of the fiber when present in higher quantity. Thus, PC being hydrophilic in nature has greater conductivity than MC1 and MC2. In general the dielectric constant of a fiber is affected by interfacial, dipole, electronic and atomic polarizations. Also the polarizability decreases with decreased number of polar groups.[62] The high dielectric constant of PC was attributed due to interfacial and orientation polarizations resulting from the presence of polar groups of cellulose, hemicellulose and lignin. Usually the interfacial polarization is more prominent in heterogeneous materials at lower frequencies. Further, interfacial relaxation occurs when charge carriers are trapped at the interfaces of heterogeneous systems.



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MC2

Fig. 5(a’) K and Df of PC, MC1 and MC2 at 1 MHz.


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It was observed that, in comparison to PC the dielectric constant values for MC1 and MC2 are lower. This happens due to the increased hydrophobicity of the modified coirs (MC1 and MC2) causing the decrease in orientation polarization. Modification of parent coir fiber like transesterification of PC with butylacrylate (MC1) and curing of transesterified coir with benzoyl peroxide (MC2) also decreased the moisture intake capacity owing to the decrease in the probability for the interaction between polar –OH groups of these coir fibers and moisture. In PC, the hydroxyl (–OH) groups of the crystalline cellulosic components were comparatively unreactive, as they form strong hydrogen bonds. The transesterified coir (MC1) and cured transesterified coir (MC2) destroyed some hydrogen bonding that made modified coirs more reactive. The reduction of hydrophilicity in the case of MC1 and MC2 fibers decrease the orientation polarization.[63] Thus, dielectric constant values of MC1 and MC2 reduced substantially in comparison to PC. Chemical modification of PC facilitated the interfacial linkage between PC and modifying agents leading to a reduction in empty spaces, which in turn triggered a decrease in water uptake properties. This modification also decreases the hydrophilic properties of PC. All the above informations indicates that MCs have lower dielectric constant values when compared to PC. The number of polar groups in PC is more due to its hydrophilicity, which is responsible for the increase in orientation polarization[61] that increased the dissipation factor. At lower frequencies there is a significant variation in the dissipation factor, which was higher for PC and lower for MC1 and MC2 respectively. MC1 and MC2 contain less number of polar groups and hence become more hydrophobic compared to PC, this caused a decrease in dissipation factor for MC1 and MC2 in compared to PC for almost all frequencies. Butylacrylate assisted transesterified coir introduced acrylate moiety (MC1) and benzoyl peroxide cured transesterified coir introduced phenyl and benzyl radical (MC2).[55] But due to incorporation of acrylate moiety (both polar and conductive group) in MC1, phenyl radical (conductive group) and benzyl radical (both polar and conductive group) in MC2, it is difficult to predict the exact dissipation factor relationship among PC, MC1 and MC2 at different frequencies.



Effect of silver nanoparticles (AgNPs) coating The dielectric constants (K) and dissipation factors (Df) of parent coir (PC), silver nanoparticles coated parent coir fiber in 0.1 M AgNO3 (PC-Ag0.1) and silver nanoparticles coated parent coir fiber in 0.2 M AgNO3 (PC-Ag0.2) at 10 kHz and at 1 MHz are shown in Figs. 5(b) and 5(bʼ) respectively. In Fig. 5(b) at 10 kHz both K and Df decreases in the same manner for PC-Ag0.1 in comparison to PC, but K decreases and Df increases for PC-Ag0.2 in comparison to PC-Ag0.1. In Fig. 5(bʼ) at 1 MHz, K decreases and Df increases for PC-Ag0.1 in comparison to PC, but K and Df value increases for PC-Ag0.2 in comparison to PC-Ag0.1. From Figs. 5(b) and 5(bʼ) it is found that among PC, PC-Ag0.1, and PC-Ag0.2 dielectric properties enhanced in the order as: PC-Ag0.1 > PCAg0.2 > PC. The dielectric parameters K and Df of MC1, MC1-Ag0.1 and MC1-Ag0.2 at 10 kHz and at 1 MHz are shown in Figs. 5(c) and 5(cʼ) respectively. In Fig. 5(c) at 10 kHz, when compared with MC1, Df decreases but K remains almost same for MC1-Ag0.1, however K and Df both increase for MC1Ag0.2. Similarly, in Fig. 5(cʼ) at 1 MHz, when compared with MC1, K increases and Df decreases for MC1-Ag0.1, but K and Df decrease for MC1-Ag0.2 in comparison to MC1-Ag0.1. From Figs. 5(c) and 5(cʼ) it is clear that among MC1, MC1-Ag0.1, and MC1-Ag0.2 the dielectric properties enhanced in the order as: MC1-Ag0.1> MC1-Ag0.2 > MC1. The dielectric parameters K and Df of MC2, MC2-Ag0.1 and MC2-Ag0.2 at 10 kHz and at 1 MHz are shown in Figs. 5(d) and 5(dʼ) respectively. In Fig. 5(d) at 10 kHz, when compared with MC2 both K and Df increases for MC2-Ag0.1, but K and Df decreases for MC2-Ag0.2 in comparison to MC2-Ag0.1. In Fig. 5(dʼ) at 1 MHz, both K and Df increases for MC2-Ag0.1 in comparison to MC2, but K decreases and Df increases for MC2-Ag0.2 in comparison to MC2-Ag0.1. From Figs. 5(d) and 5(dʼ) it is found that among MC2, MC2-Ag0.1, and MC2-Ag0.2 dielectric properties enhanced in the order as: MC2-Ag0.1 > MC2-Ag0.2> MC2. It was reported that oxygen atoms of parent and modified coirs were chemically bonded with silver cations, followed by reduction of silver cations to silver,[55] so the polarity of PC-Ag, MC1-Ag and MC2-Ag reduced in comparison to PC, MC1 and MC2 respectively due to the decreases in their 16 ACS Paragon Plus Environment

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orientation polarization.[63] But after silver coating, new interfaces are formed, which leads to increase in interfacial polarization. Thus, hydrophobicity, orientation and interfacial polarisations are the three important parameters which determine the value of dielectric constants (K) of these coated fiber. Due to weak interaction of silver cations with the hydrophilic PC, coating was poor, causing less interfacial polarisation owing to less number of interfaces. Thus, K of PC-Ag reduced when compared to PC. Coating was more in hydrophobic transesterified coir (MC1) compared to PC, causing more interfacial polarisation because of more number of interfaces, therefore, K of MC1-Ag increased compared to MC1 at some frequencies. Coating was adequate with better dispersion of AgNPs in hydrophobic cured transesterified coir (MC2) compared to PC and MC1 respectively, causing very high interfacial polarisation owing to large number of interfaces. Hence, K of MC2-Ag increased compared to MC2 in almost all frequencies. The number of polar groups is more in MC1 and MC2 compared to MC1-Ag and MC2-Ag respectively, which led to an increase in orientation polarization.[61] This resulted in an increase in Df for MC1 and MC2 compared to MC1-Ag and MC2-Ag respectively. At lower frequency region, dissipation factor is affected significantly. It was higher for MC1 and MC2 and lower for MC1Ag and MC2-Ag respectively. The interfaces formed by MC1-Ag and MC2-Ag are superior due to higher degree of hydrophobicity that can restrain the motion of charges and further, due to increase in crystallinity of these fibers dissipation factors of MC1-Ag and MC2-Ag deacrease when compared with MC, for almost all frequencies.



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PC-Ag0.1

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Fig. 5(b’) K and Df of PC, PC-Ag0.1 and PC-Ag0.2 at 1 MHz.


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MC1-Ag0.2

Fig. 5(c) K and Df of MC1, MC1-Ag0.1 and MC1-Ag0.2 at 10 kHz.

0.030

50

0.028

48

@1MHz

46

0.024

44

0.022

42

Df

0.026

K

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


0.020

MC1

MC1-Ag0.1

40

MC1-Ag0.2

Fig. 5(c’) K and Df of MC1, MC1-Ag0.1 and MC1-Ag0.2 at 1 MHz.



0.20

60

@ 10 kHz 58

0.16

56

0.14

54

0.12

52

Df

0.18

K

0.10

MC2

50

MC2-Ag0.1

MC2-Ag0.2

Fig. 5(d) K and Df of MC2, MC2-Ag0.1 and MC2-Ag0.2 at 10 kHz.

0.030

50

@1 MHz 48

0.026

46

0.024

44

0.022

42

Df

0.028

K

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

Page 20 of 47

0.020

MC2

MC2-Ag0.1

MC2-Ag0.2

40

Fig. 5(d’) K and Df of MC2, MC2-Ag0.1 and MC2-Ag0.2 at 1 MHz.


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The average and minimum size of coated silver nanoparticles found for different fibers are 110, 55 nm (PC-Ag0.1), 122, 40 nm (PC-Ag0.2), 188, 42 nm (MC1-Ag0.1), 205, 40 nm (MC1-Ag0.2), 95, 42 nm (MC2-Ag0.1) and 84, 40 nm (MC2-Ag0.2) respectively. At 100Hz both dielectric constants (K) and dissipation factors (Df) decreases for PC-Ag and MC1-Ag in comparison to PC and MC1 respectively. At 100Hz both K and Df decreases for MC2-Ag0.1, but K decreases and Df increases for MC2-Ag0.2 in comparisons to MC2. From EDS elemental composition analysis[55] it is found that among PC, PC-Ag0.1 and PC-Ag0.2, the fiber PC-Ag0.1 containing 8.55 weight % Ag (61.41 weight % O) showed K of 727.230 while Df was maintained at around 1.9071, and the fiber PCAg0.2 containing 14.65 weight % Ag (61.95 weight % O) showed K of 338.529 and Df at 0.9589, that are lower than PC (61.33 weight % O) without Ag nanoparticles (K: 852.428, Df: 1.9364). Among MC1, MC1-Ag0.1 and MC1-Ag0.2, the fiber MC1-Ag0.1 containing 11.20 weight % Ag (58.42 weight % O) showed K of 403.28 while Df was maintained at around 0.78526, and the fiber MC1Ag0.2 containing 38.76 weight % Ag (43.68 weight % O) showed K of 400.567 while the Df was maintained at around 1.0101, which are lower than MC1 (70.62 weight % O) without Ag nanoparticles (K: 411.817, Df: 1.28820) and PC. Similarly among MC2, MC2-Ag0.1 and MC2Ag0.2, the fiber MC2-Ag0.1 containing 10.49 weight % Ag (53.38 weight % O) showed K of 347.770 and Df at 0.9693, that are lower than MC2 (59.23 weight % O) without Ag nanoparticles (K: 556.781, Df: 1.09340) and PC. But the fiber MC2-Ag0.2 containing 15.23 weight % Ag (54.14 weight % O) showed K of 307.799 while Df was maintained at around 1.2243. Since PC has more polar groups it can stabilize and hence can reduce higher concentration of AgNO3 solution easily, this supports the weak coordinative chemical bonding between oxygen atoms of PC and Ag+ cations of 0.2 M AgNO3, which facilitates easy coating of Ag nanoparticles and in turn produces new interfaces in PC-Ag0.2. But MC1 and MC2 have less number of polar groups, thus they can stabilize and hence can reduce lower concentration AgNO3 solution easily, this supports the weak coordinative chemical bonding between oxygen atoms of MC1 and MC2 with Ag+ cations of 0.1M AgNO3, which facilitates easy coating of Ag nanoparticles and in turn produces more number of interfaces in MC1-Ag0.1 and MC2-Ag0.1 respectively. Due to the above reasons among PC-Ag, MC1-Ag and MC2-Ag lower Df was maintained by PC-Ag0.2, MC1-Ag0.1 and MC2-Ag0.1 respectively. It was observed that K decreases for MC1 and MC2 in comparison to PC from 100 Hz to 1 MHz, Df also follows the same trend except at frequency 1 MHz for which 21 ACS Paragon Plus Environment


it increases. K decreases for PC-Ag in comparison to PC from 100 Hz to 1 MHz and Df behaves in the same manner except at frequency 1 MHz where PC-Ag has got higher value. Similarly K increases at 1 kHz, 100 kHz, 1 MHz and Df decreases at 10 kHz, 1 MHz for MC1-Ag0.1 in comparison to MC1. But K increases at 1 kHz, 10 kHz and Df decreases at 100 Hz, 100 kHz, 1 MHz for MC1-Ag0.2 in comparison to MC1. K increases at 1 kHz, 10 kHz, 100 kHz, 1 MHz for both MC2-Ag0.1 and MC2-Ag0.2 respectively in comparison to MC2. Df decreases at 100 Hz, 1 kHz for MC2-Ag0.1 in comparison to MC2, and Df decreases at 100 kHz for MC2-Ag0.2 in comparison to MC2. In these studies 0.1 M AgNO3 and 0.2 M AgNO3 solution was used in the coating of PC, MC1 and MC2, respectively. It is well understood that, surface area of these coated silver nanoparticles are very high due to its nano structure. These coated silver nanoparticles produce a large number of interfaces and these result in high interfacial polarization. In these cases, when the number of interfaces increases the values of K increases and vice versa. Further, due to hydrophobicity, existence of a large number of interfaces and polymer chain entanglements in silver nanoparticle coated fibers the motion of charges are hindered, which in turn causes a reduction in the electrical conductivity, hence a lower Df value. Thus, it clearly shows that both K and Df are influenced by hydrophobicity of the fiber. But at this stage it is difficult to predict the exact number, quality and quantity of interfaces in PC-Ag, MC1-Ag and MC2-Ag. Further from EDS analysis,[55] it is found that PC-Ag, MC1-Ag and MC2-Ag contain different weight % of Ag with different weight % of O. Here, the lone pair electrons of oxygen atoms are responsible for the reduction of Ag+ cations, followed by their stabilization during coating. At this stage it is difficult to predict the exact correlationship of weight % of Ag, O and fiber during the coating processes and hence the exact relationship of K and Df for PC-Ag, MC1-Ag and MC2-Ag respectively. Coating is preferred in hydrophobic modified coir which promotes controlled reduction of silver cations and hence size reduction followed by their stabilization. Smaller the size of silver nanoparticles, higher is the adhesive force between silver nanoparticles and the coir fibers. Higher the hydrophobicity better the silver coating as the coating is uniform throughout and does not show any agglomeration of silver particles, which affects the interfacial polarization due to large


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number of interfaces in these fibres. This indicates that AgNPs coating on hydrophobic coir increases interfacial polarization and decreases dissipation factor. The dielectric property depends on the synergistic effect of (i) interfacial area, (ii) interparticle distance and (iii) interfacial adhesion all of which are highly dependent on silver nanoparticle size. Because K is directly proportional to interfacial area, adhesive force, and inversely proportional to interparticle distance among the nanoparticle. Considering this small sizes silver nanoparticles coated in more hydrophobic fiber MC2, but the sizes of coated silver nanoparticle in MC1-Ag are larger than MC2-Ag. The newly formed interfaces due to coated silver nanoparticles restrain the motion of charges, which decreases Df. There is increase in K and decrease in Df values according to sizes of coated silver nanoparticles. The bulk metal has a specific electrical conductivity depending on its temperature, which is associated with electron mobility. This behavior is not effective when the size of metal is reduced to nanometer scale. Electrical conductivity of metal nanoparticles fluctuates as it depends on the size of the particles. Usually, it is observed that electrical conductivity decreases as the size of particles decreases especially in nano-dimensions. Similarly, it is expected in our case also: the overall dielectric properties of the fiber may vary with coating concentrations which result in different particle sizes. It has been reported[64] that Df depends on the mobility of the charge carrier and on the applied excitation frequency as it is a function of electrical conductivity. They have also stated that the behavior of Df is influenced by two different interacting processes such as the number of interfaces and polymer chain entanglements in the bulk. Fig. 5 shows that with increasing frequencies there is a continuous decrease in Df values for all the samples. Decrease in electrical conductivity in this material with increasing frequency is the main reason of this observation which, could be due to the inability of the charge carriers to traverse the thickness of the hydrophobic AgNPs coated coir material at higher frequencies. This blockade to the charge transport in polymers can occur due to defects, charge transport through inter-chain and interfaces. At high frequencies, the motion of charge carriers contributing to the conductivity primarily occurs along polymer chains.[65] This phenomenon is important due to the heterogeneity of the metal polymer nano-composites.



Dissipation factor of a dielectric material originates from dipolar, distortional, interfacial, and conduction loss. Distortional loss arises due to ionic and electronic polarization and similarly the interfacial loss due to excessive polarized interface is prompted by modification, and possibly due to the movement or revolution of the atoms or molecules in an alternating electric field. Flow of real charge through a dielectric material signify the conduction loss. Further conduction loss ascribed to the dc electrical conductivity of the material. It is supposed that owing to the higher conducting properties of silver, the conduction loss contributes substantially to the high Df of silver composites particularly at low frequency. The decreased Df with the incorporation of metal nano particles can be explained as the coulomb blockade effect. This effect is known as quantum effects of metal nanoparticles. When the dimension of the nanoparticles sometimes called as “Coulomb island” is small, an additional barrier is created by the tunneling electrons due to the charging energy e2/2C (Here C denotes capacitance of the metal island and e represents the electron charge unit). Coulomb blockade will occour, when the charging energy surpasses the thermal fluctuation energy kBT (kB is boltzman constant and T is the absolute temperature), which will in turn inhibit the charge transfer through the small island below a definite threshold voltage and will lead to a rise in resistance.[46, 50, 66] In the present study the Ag nanoparticles may cause high charging energy for the tunneling electrons that could hinder the charge transfer through the small metal island which reduces the conduction loss representing the flow of charge through the dielectric materials. Effect of Frequency Figures 6(a) to 6(d) show that all the fibers exhibit higher values of dielectric constants owing to the reduction in the orientation polarization at lower frequencies. At lower frequencies, the complete orientation of the molecules is feasible. Further, compared to electronic and atomic polarizations the orientation polarization needs more time to attain the equilibrium static field value. Subsequently, the decreased dielectric constant is attributable to the delay in the orientation polarization at high frequencies. In the lower frequency region the values of dielectric constant were maximum due to the interfacial polarization. Figures 7(a) to 7(d) show that all the fibers exhibit lower values of Df at higher frequencies except that the Df curves came more closer to each other in the higher frequency range. In PC the flow of current enhanced through the amorphous component of lignin and hemicellulose due to their 24 ACS Paragon Plus Environment

Page 24 of 47

Page 25 of 47

capability for moisture absorption. Orientation polarization of polar groups was limited in the high frequency region and hence there was a significant decrease in the dissipation factor. At the low frequency region, the dissipation factor varies significantly, as for example, it was higher for PC and lower for MC1 and MC2 in almost all frequencies. Yet, the precise description for the above behavior is somewhat difficult as Df also depends upon chemical composition, its constituent distribution, water absorbing capacity, orientation and uniformity of coir fiber. Coir is a tripolymer composite material consisting of cellulose, hemicellulose and lignin mostly. Since they were inserted in these composite materials in a statistical random orientation manner, there may be significant variations in Df and K from section to section of the material under investigation. In modified coirs, the fibers are arranged in an order when treated with BA and BPO through transesterification followed by curing in the moiety of hydroxyl and vinyl groups respectively.[67]

100 Hz 1 kHz 10 kHz 100 kHz 1MHz

900 800 700 600 500 400

K

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


100

0

PC

MC1

MC2

Fig. 6(a) K of PC, MC1 and MC2 at 100 Hz, 1 kHz, 10 kHz, 100 kHz and 1 MHz.



900 800 700 600

100 Hz 1 kHz 10 kHz 100 kHz 1 MHz

500

K

400

100

0

PC

PC-Ag0.1

PC-Ag0.2

Fig. 6(b) K of PC, PC-Ag0.1 and PC-Ag0.2 at 100 Hz, 1 kHz, 10 kHz, 100 kHz and 1 MHz.

420 400


380

100

K

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

Page 26 of 47

50

MC1

MC1-Ag0.1

MC1-Ag0.2

Fig. 6(c) K of MC1, MC1-Ag0.1 and MC1-Ag0.2 at 100 Hz, 1 kHz, 10 kHz, 100 kHz and 1 MHz.


Page 27 of 47

600

500

400


300

K

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


100

50

MC2

MC2-Ag0.1

MC2-Ag0.2

Fig. 6(d) K of MC2, MC2-Ag0.1 and MC2-Ag0.2 at 100 Hz, 1 kHz, 10 kHz, 100 kHz and 1 MHz.

During silver nanoparticles (AgNPs)-coating, oxygen atoms of parent and modified coirs were chemically bonded with silver cations, followed by reduction of silver cations to silver.[55] These changes chemical composition and its constituent distribution, orientation and uniformity of modified and silver nanoparticles coated fiber respectively. Due to these disparities in the fibers significant variations in dielectric properties and dissipation factors were observed. It is also found that the values of K and Df for all types of coir fibers were decreased with increasing frequency, which indicate that the major contribution to the polarization may come from interfacial polarization and orientation polarization.[68] Effect of Capacitance and Resistance The profile of capacitance (C) and resistance (R) for four set of fibers (PC, MC1, MC2), (PC, PCAg0.1, PC-Ag0.2), (MC1, MC1-Ag0.1, MC1-Ag0.2) and (MC2, MC2-Ag0.1, MC2-Ag0.2) at 10 kHz and



at 1 MHz are shown in Figs. 8(a), (aʼ), (b), (bʼ), (c), (cʼ), (d) and (dʼ) respectively. The impedance (Z) was calculated from the following equation: 2

( )

1 |Z| = R + 2πfC 2

(2)

Where R is the resistance, C is the capacitance and f is the frequency of the sample. According to the value of C and R from Figs. 8(a) and 8(aʼ) at 10 kHz and 1 MHz respectively, impedance increases for MC1 in comparison to PC, but impedance for MC2 decreases against MC1 and increases against PC. Since MC1 and MC2 have less number of electrons on oxygen atoms than PC, their impedances are more than PC at 10 kHz and 1 MHz. From Fig. 8(aʼ) it is found that at high frequency (1 MHz) insulating properties follow the order as MC1 > MC2 > PC. Similarly, from Figs. 8(b) and 8(bʼ) at 10 kHz and 1 MHz respectively, impedance increases for PC-Ag0.2 in comparison to PC, but for PC-Ag0.1 it decreases against PC-Ag0.2 and increases against PC. Since number of electrons on oxygen atoms decreases progressively in PC, PC-Ag0.1 and PC-Ag0.2, the impedance increases for both PC-Ag0.2 and PC-Ag0.1 in comparison to PC at 10 kHz and 1 MHz. From Fig. 8(bʼ) it is found that at high frequency (1 MHz) insulating properties follow the order as PC-Ag0.2 > PC-Ag0.1 > PC. From figs. 8(c) and 8(cʼ) at 10 kHz and 1 MHz respectively, impedance increases for MC1-Ag0.2 in comparison to MC1, but impedance decreases for MC1Ag0.1 against MC1-Ag0.2 and increases against MC1. Since number of electrons on oxygen atoms decreases progressively in MC1, MC1-Ag0.1 and MC1-Ag0.2, the impedance increases for both MC1-Ag0.2 and MC1-Ag0.1 in comparison to MC1 at 10 kHz and 1 MHz. From Fig. 8(cʼ) it is found that at high frequency (1 MHz) insulating properties follow the order as MC1-Ag0.2 > MC1-Ag0.1 > MC1. Similarly from figs. 8(d) and 8(dʼ) at 10 kHz and 1 MHz respectively, impedance increases for MC2-Ag0.2 in comparison to MC2, but impedance for MC2-Ag0.1 decreases against MC2-Ag0.2 and increases against MC2. Since number of electrons on oxygen atoms decreases progressively in MC2, MC2-Ag0.1 and MC2-Ag0.2 the impedance increases for MC2-Ag0.2 and MC2-Ag0.1 in comparison to MC2 at 10 kHz and 1 MHz. From Fig. 8(dʼ) it is found that at high frequency (1 MHz) the insulating properties follow the order as MC2-Ag0.2 > MC2-Ag0.1 > MC2. Effect of Frequency on Capacitance (C) and Resistance (R) for the above four sets of fibers are shown in Figs.9(a), (aʼ), (b), (bʼ), (c), (cʼ), (d), and (dʼ) respectively. It is found that at higher 28 ACS Paragon Plus Environment

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frequency (MHz) range, the resistance remains constant, so the material shows better insulating properties. Similarly capacitance remains almost constant at higher frequency therefore the insulation resistance in AC transmission line will be quite dependent on the resistance of the insulator. Due to the increase in resistances at higher frequencies, the material offers good insulating properties. As the PC-Ag, MC1-Ag and MC2-Ag contains less number of electrons on oxygen atoms compared to PC, MC1and MC2 respectively, this caused an increase in resistance and decrease in dissipation factor or dielectric loss of PC-Ag, MC1-Ag and MC2-Ag. Incorporation of metal nanoparticles decreased the Df, this effect could be explained as due to Coulomb blockade effect. Due to very fine sizes, the Ag nanoparticles might cause high charging energy for the tunneling electrons, reducing the conduction loss and increasing the resistance, which represents the flow of charge through the dielectric materials. Although till date there is no such evidence on the use of this type of material, use of natural cellulose fibers as substrate for super capacitors,[69] metal-coated coconut fibers with tin and palladium for water purification and electromagnetic shielding have been reported elsewhere.[70] Further, electrodes have also been made out of gold coated coir fibers.[71] Based on the above reports, the authors believe that the materials prepared in the present work particularly with high K and low Df would have better performance over other existing materials however need further investigation.



2.0 1.8 1.6


1.4

Df

1.2 1.0 0.8 0.6 0.4 0.2 0.0

MC1

PC

MC2

Fig. 7(a) Df of PC, MC1 and MC2 at 100 Hz, 1 kHz, 10 kHz, 100 kHz and 1 MHz.

2.0 1.8 1.6


1.4 1.2

Df

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

Page 30 of 47

1.0 0.8 0.6 0.4 0.2 0.0

PC

PC-Ag0.1

PC-Ag0.2

Fig. 7(b) Df of PC, PC-Ag0.1 and PC-Ag0.2 at 100 Hz, 1 kHz, 10 kHz, 100 kHz and 1 MHz.


Page 31 of 47

1.3 1.2 1.1 1.0 0.9 0.8

Df

0.7 0.6


0.5 0.4 0.3 0.2 0.1 0.0

MC1-Ag0.1

MC1

MC1-Ag0.2

Fig. 7(c) Df of MC1, MC1-Ag0.1 and MC1-Ag0.2 at 100 Hz, 1 kHz, 10 kHz, 100 kHz and 1 MHz.

1.2

1.0


0.8

Df

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


0.6

0.4

0.2

0.0

MC2

MC2-Ag0.1

MC2-Ag0.2

Fig. 7(d) Df of MC2, MC2-Ag0.1 and MC2-Ag0.2 at 100 Hz, 1 kHz, 10 kHz, 100 kHz and 1MHz.



0.040

80 78

@10 kHz

0.038

76 0.036

C (pF)

74 72

0.034 70

R (MOhm)

0.032

68 66

0.030

PC

MC1

MC2

Fig. 8(a) Capacitance (C) and Resistance (R) of PC, MC1 and MC2 at 10 kHz.

70

5.75 68

@ 1MHz

C (pF)

5.5 66

5.25

64

-5

R (MOhm) X [10 ]

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

Page 32 of 47

62

5

60

4.75

PC

MC1

MC2

Fig. 8(a’) Capacitance (C) and Resistance (R) of PC, MC1 and MC2 at 1 MHz.


Page 33 of 47

80

0.040

0.038

@ 10 kHz

76

0.036

74

0.034

72

0.032

70

R (MOhm)

C (pF)

78

0.030

PC

PC-Ag0.1

PC-Ag0.2

Fig. 8(b) Capacitance (C) and Resistance (R) of PC, PC-Ag0.1 and PC-Ag0.2 at 10 kHz. 68

6

5.8

@ 1 MHz 66

C (pF)

5.6

64

5.4

-5

R (MOhm) x [10 ]

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


5.2 62

5

60

PC

4.8

PC-Ag0.1

PC-Ag0.2

Fig. 8(b’) Capacitance (C) and Resistance (R) of PC, PC-Ag0.1 and PC-Ag0.2 at 1 MHz.



76

0.038

75 0.036

@ 10kHz

0.034

73

72

R (MOhm)

C (pF)

74

0.032 71

70

MC1

MC1-Ag0.1

0.030

MC1-Ag0.2

Fig. 8(c) Capacitance (C) and Resistance (R) of MC1, MC1-Ag0.1and MC1-Ag0.2 at 10 kHz. 65

5.8

@ 1 MHz

C (pF)

64

5.7

5.6 63

5.5

-5

R (MOhm)x [10 ]

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

Page 34 of 47

62

5.4 61

5.3

60

MC1

MC1-Ag0.1

MC1-Ag0.2

5.2

Fig. 8(c’) Capacitance (C) and Resistance (R) of MC1, MC1-Ag0.1 and MC1-Ag0.2 at 1 MHz.


Page 35 of 47

80

0.038 0.037

@ 10 kHz

78

0.036 0.035

C (pF)

0.034 74

0.033

R (MOhm)

76

0.032 72 0.031 70

0.030

MC2-Ag0.1

MC2

MC2-Ag0.2

Fig. 8(d) Capacitance (C) and Resistance (R) of MC2, MC2-Ag0.1 and MC2-Ag0.2 at 10 kHz. 5.6

65

C (pF)

@ 1MHz 5.5

63

5.4

62

5.3

61

5.2

-5

64

R (MOhm) x [10 ]

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


5.1

60

MC2

MC2-Ag0.1

MC2-Ag0.2

Fig. 8(d’) Capacitance (C) and Resistance (R) of MC2, MC2-Ag0.1 and MC2-Ag0.2 at 1MHz.




120 110 100 90 80 70 60

C (pF)

50

10

PC

MC1

MC2

Fig. 9(a) Capacitance (C) of PC, MC1 and MC2 at 100 Hz, 1 kHz, 10 kHz, 100 kHz and 1 MHz.

8


6

R (MOhm)

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

Page 36 of 47

4

2

0

PC

MC1

MC2

Fig. 9(a’) Resistance (R) of PC, MC1 and MC2 at 100 Hz, 1 kHz, 10 kHz, 100 kHz and 1 MHz.


120 110 100 90 80 70 60 50 40


10

PC

PC-Ag0.1

PC-Ag0.2

Fig. 9(b) Capacitance (C) of PC, PC-Ag0.1 and PC-Ag0.2 at 100 Hz, 1 kHz, 10 kHz, 100 kHz and 1 MHz.

8 7


6 5

R (MOhm)

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


C (pF)

Page 37 of 47

4 3 2 1 0 -1

PC

PC-Ag0.1

PC-Ag0.2

Fig. 9(b’) Resistance (R) of PC, PC-Ag0.1 and PC-Ag0.2 at 100 Hz, 1 kHz, 10 kHz, 100 kHz and 1 MHz.



C (pF)

55


50

10

5

MC1

MC1-Ag0.1

MC1-Ag0.2

Fig. 9(c) Capacitance (C) of MC1, MC1-Ag0.1 and MC1-Ag0.2 at 100 Hz, 1 kHz, 10 kHz, 100 kHz and 1MHz. 8 7


6 5

R (MOhm)

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

Page 38 of 47

4 3 2 1 0 -1

MC1

MC1-Ag0.1

MC1-Ag0.2

Fig. 9(c’) Resistance (R) of MC1, MC1-Ag0.1 and MC1-Ag0.2 at 100 Hz, 1 kHz, 10 kHz, 100 kHz and 1 MHz.


Page 39 of 47

80 75 70 65 60


55 50 45

C (pF)

40

10

5

MC2

MC2-Ag0.1

MC2-Ag0.2

Fig. 9(d) Capacitance (C) of MC2, MC2-Ag0.1 and MC2-Ag0.2 at 100 Hz, 1 kHz, 10 kHz, 100 kHz and 1 MHz.

8 7


6 5

R (MOhm)

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


4 3 2 1 0 -1

MC2

MC2-Ag0.1

MC2-Ag0.2

Fig. 9(d’) Resistance (R) of MC2, MC2-Ag0.1 and MC2-Ag0.2 at 100 Hz, 1 kHz, 10 kHz, 100 kHz and 1 MHz.

CONCLUSIONS 39 ACS Paragon Plus Environment


From the present study the following conclusions may be drawn; 

Hydrophobicity of the fiber results in uniform silver coating throughout the coir increasing the interfacial polarization causing high K and low Df.



Dielectric constants (K) increases at 1 kHz, 100 kHz, 1 MHz and Df decreases at 10 kHz, 1 MHz for MC1-Ag0.1 in comparison to MC1, however, K increases at 1 kHz, 10 kHz and Df decreases at 100 Hz, 100 kHz, 1 MHz for MC1-Ag0.2 in comparison to MC1.



K increases at 1 kHz, 10 kHz, 100 kHz, 1 MHz for both MC2-Ag0.1 and MC2-Ag0.2 respectively in comparison to MC2. Df decreases for MC2-Ag0.1 at 100 Hz, 1 kHz and for MC2-Ag0.2 at 100 kHz in comparison to MC2.



The sintering temperature can go as high as 600o C or more for the silver nanoparticle coated coir fibers which is usually not possible for the embedded capacitors made with low cost organic polymers for PCB industries.



Composite materials containg silver nano particles with high K show reduced Df due to Coulomb blockade effect that reduces the electron tunneling.



These AgNPs coated coir fibers are very important materials for embedded capacitors, optoelectronic devices, metal oxide semiconductor field effect transistors (MOSFET), integrated circuits due to higher packing density and insulating properties.

REFERENCES 1. John, M. J.; Thomas, S., Biofibres and biocomposites. Carbohydr. Polym. 2008, 71 (3), 343– 364. DOI: 10.1016/j.carbpol.2007.05.040 2.

Reddy, N.; Yang, Y., Biofibers from agricultural by products for industrial applications. Trends Biotechnol. 2005, 23 (1), 22–27. DOI: 10.1016/ j.tib tech. 2004.11.002

3.

Bar, H.; Bhui, D. K.; Sahoo, G. P.; Sarkar, P.; Pyne, S.; Misra, A., Green synthesis of silver nanoparticles using seed extract of Jatropha curcas. Colloids Surf. A Physicochem. Eng. Asp. 2009, 348 (1-3), 212–216. DOI: 10.1016/ j.colsurfa. 2009.07.021

4.

Lukman, A. I.; Gong, B.; Marjo, C. E.; Roessner, U.; Harris, A. T., Facile synthesis, stabilization, and anti-bacterial performance of discrete Ag nanoparticles using Medicago sativa seed exudates. J. Colloid. Interface. Sci. 2011, 353 (2), 433–444. DOI: 10.1016/ j.jcis. 20 10.09.088

5.

Vijayaraghavan, K.; Nalini, S. P.; Prakash, N. U.; Madhankumar, D., One step green synthesis of silver nano/microparticles using extracts of Trachyspermum ammi and Papaver 40 ACS Paragon Plus Environment

Page 40 of 47

Page 41 of 47 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


somniferum. Colloids Surf. B Biointerfaces. 2012, 94, 114-117. DOI: 10.1016/ j.colsurfb. 2012.01.026 6.

Kumar, R.; Roopan, S. M.; Prabhakarn, A.; Khanna, V. G.; Chakroborty, S., Agricultural waste Annona squamosa peel extract: biosynthesis of silver nanoparticles. Spectrochim. Acta Part A. 2012, 90, 173–176. DOI: 10.1016/ j. saa.2012.01.029

7.

Roopan, S. M.; Bharathi, A.; Kumar, R.; Khanna, V. G.; Prabhakarn, A., Acaricidal, insecticidal, and larvicidal efficacy of aqueous extract of Annona squamosa L peel as biomaterial for the reduction of palladium salts into nanoparticles. Colloids Surf. B Biointerfaces. 2012, 92, 209–212. DOI: 10.1016/j.colsurfb.2011.11.044

8.

Bankar, A.; Joshi, B.; Kumar, A. R.; Zinjarde, S., Banana peel extract mediated novel route for the synthesis of silver nanoparticles. Colloids Surf. A Physicochem. Eng. Asp. 2010, 368 (1-3), 58–63. DOI: 10.1016/ j.colsurfa. 2010. 07.024

9.

Samal, R. K.; Panda, B. B.; Rout, S. K.; Mohanty, M., Effect of chemical modification on FTIR spectra. I. Physical and chemical behavior of coir. J. Appl. Polym. Sci. 1995, 58 (4), 745–752. DOI: 10.1002/app.1995.070580407

10. Silva, G. C.; Souza, G. C.; Machado, J. C.; Hourston, D. J., Mechanical and thermal characterization of native Brazilian coir fiber. J. Appl. Polym. Sci. 2000, 76 (7), 1197–1206. DOI: 10.1002/(SICI)1097-4628(20000516)76:73.0.CO;2-G 11. Tomczak, F.; Sydenstricker, T. H. D.; Satyanarayana, K. G., Studies on lignocellulosic fibers of Brazil. Part II – Morphology and properties of Brazilian coconut fibers. Compos. A. 2007, 38 (7), 1710–1721. DOI: 10.1016/ j. compositesa.2007.02.004 12. Satyanarayana, K. G.; Guimaraes, J. L.; Wypych, F., Studies on lignocellulosic fibers of Brazil. Part I – Source, production, morphology, properties and applications. Compos. A. 2007, 38 (7), 1694–1709. DOI: 10.1016/ j. compositesa.2007.02.006 13. Dey, G.; Chakraborty, M.; Mitra, A., Profiling C6–C3 and C6–C1 phenolic metabolites in Cocos nucifera. J. Plant. Physiol. 2005, 162 (4), 375–381. DOI: 10.1016/j.jplph.2004.08.006 14. Carrijo, O. A.; Liz, R. S.; Makishima, N., Fibra da casca de coco verde como substrato agrícola. Horticultura Brasileira. 2002, 20 (4), 533–535. DOI: 10.1590/s0102-053620020004 00003 15. Brígida, A. I. S.; Rosa, M. F., Determinacao do teor de taninos na casca de coco verde (Cocos nucifera L.). Proceedings of the Inter american Society For Tropical Horticulture. 2003, 47, 25–27 16. Kalia, S.; Kaith, B. S.; Kaur, I., Pretreatments of natural fibers and their application as reinforcing material in polymer composites—A review. Polym. Eng. Sci. 2009, 49 (7), 1253– 1272. DOI: 10.1002/pen.21328 17. Dey, G.; Nagpal, V.; Banerjee, R., Immobilization of a-amylase from Bacillus circulans GRS 313 on coconut fiber. Appl. Biochem. Biotech. 2002, 102-103 (1-6), 303–313. DOI: 10.1385/ abab:102-103:1-6:303



18. Coelho, M. A. Z.; Leite, S. G. F.; Rosa, M. D. F.; Furtado, A. A. L., Aproveitamento de resíduos agroindustriais: Produçao de enzimas a partir da casca de coco verde. Boletim CEPPA. 2001, 19 (1), 33–42. DOI: 10.5380/cep.v19i1.1220 19. Brígida, A. I. S.; Pinheiro, A. D. T.; Ferreira, A. L. O.; Gonçalves, L. R. B., Immobilization of Candida antarctica lipase B by adsorption to green coconut fiber. Appl. Biochem. Biotech. 2008, 146 (1-3), 173–187. DOI: 10.1007/s12010-007-8072-4 20. Brígida, A. I. S.; Pinheiro, A. D. T.; Ferreira, A. L. O.; Gonçalves, L. R. B., Immobilization of Candida antarctica lipase B by covalent attachment to green coconut fiber. Appl. Biochem. Biotech. 2007, 137 (1-12), 67–80. DOI: 10.1007/s12010-007-9040-8 21. Roopan, S. M.; Rohit.; Madhumitha, G.; Rahuman, A. A.; Kamaraj, C.; Bharathi, A.; Surendra, T. V., Low-cost and eco-friendly phyto-synthesis of silver nanoparticles using Cocos nucifera coir extract and its larvicidal activity. Ind. Crops Prod. 2013, 43 (1), 631–635. DOI: 10.1016/j.Indcrop.2012.08.013 22. Rosa, M. F.; Chiou, B. S.; Medeiros, E. S.; Wood, D. F.; Williams, T. G.; Mattoso, L. H. C.; Orts, W. J.; Imam, S. H., Effect of fiber treatments on tensile and thermal properties of starch/ethylene vinyl alcohol copolymers/coir biocomposites. Bioresour. Technol. 2009, 100 (21), 5196–5202. DOI: 10. 1016/ j.biortech. 2009. 03.085 23. Rout, J.; Tripathy, S. S.; Nayak, S. K.; Misra, M.; Mohanty, A. K., Scanning electron microscopy study of chemically modified coir fibers. J. Appl. Polym. Sci. 2001, 79 (7), 1169– 1177. DOI: 10.1002/1097-4628(20010214)79:73.0.CO;2-Y 47. Khanna, P. K.; Singh, N.; Charan, S.; Subbarao, V. V. V. S.; Gokhale, R.; Mulik, U. P., Synthesis and characterization of Ag/PVA nanocomposite by chemical reduction method. Mater. Chem. Phys. 2005, 93 (1), 117–121. DOI: 10.1016/j.matchemphys.2005. 02.029 48. Lu, J.; Moon, K.S.; Xu, J.; Wong, C.P., Synthesis and Dielectric Properties of Novel HighK Polymer Composites Containing In-Situ Formed Silver Nanoparticles for Embedded Capacitor Applications. J. Mater. Chem. 2006, 16, 1543–1548. DOI: 10.1039/B514182F 49. Tang, L.; Du, P.; Han, G.; Weng, W.; Zhao, G.; Shen, G., Effect of dispersed Ag on the dielectric properties of sol-gel derived PbTiO3 thin films on ITO/glass substrate. Surf. Coat. Technol. 2003, 167 (2-3), 177–180. DOI: 10.1016/S0257-8972(02)00892-7 50. Feng, Q.; Dang, Z.; Li, N.; Cao, X., Preparation and dielectric property of Ag–PVA nanocomposite. Mater. Sci. and Eng. B. 2003, 99 (1-3), 325–328. DOI: 10.1016/S0921-5107(02) 00564-0 51. Samal, R. K.; Rout, S. K.; Panda, B. B.; Senapati, B. K., Vinyl-ester-participated transesterification and curing on the physicochemical behavior of Coir- IV. J. Appl. Polym. Sci. 1997, 64 (12), 2283–2291. DOI: 10.1002/(SICI)1097-4628(19970620)64:123.0.CO;2-H 52. Rosa, M. F.; Medeiros, E. S.; Malmonge, J. A.; Gregorski, K. S.; Wood, D. F.; Mattoso, G. Glenn, L. H. C.; Orts, W. J.; Imam, S. H., Cellulose nanowhiskers from coconut husk fibers: effect of preparation conditions on their thermal and morphological behavior. Carbohydr. Polym. 2010, 81 (1), 83–92. DOI: 10.1016/j.carbpol.2010.01.059 53. Varma, D. S.; Varma, M.; Varma. I. K., Part I: Effect of Physical and Chemical Treatments on Properties. Text. Res. J. 1984, 54 (12), 827–832. DOI: 10.1177/004051758405401206 54. Jayavani, S.; Deka, H.; Varghese, T. O.; Nayak, S. K., Recent development and future trends in coir fiber‐reinforced green polymer composites: Review and evaluation. Polym. Compos. 2016, 37 (11), 3296-3309. DOI: 10.1002/pc.23529 55. Rout, S. K.; Tripathy, B. C.; Padhi, P.; Kar, B. R.; Mishra, K. G., A green approach to produce silver nano particles coated agro waste fibers for special applications. Surf. Interfaces. 2017, 7, 87–98. DOI: 10.1016/j.surfin.2017.03.004 56. Rout, S. K.; Tripathy, B. C.; Ray, P. K., Significance of nano-silver coating on the thermal behavior of parent and modified agro-waste coir fibers. J. Therm. Anal. Calorim. 2018, 131(2), 1423-1436. DOI: 10.1007/s10973-017-6555-2


Page 44 of 47

Page 45 of 47 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


57. Abraham, E.; Deepa, B.; Pothan, L. A.; Jacob, M.; Thomas, S.; Cvelbar, U.; Anandjiwala, R., Extraction of nanocellulose fibrils from lignocellulosic fibres: A novel approach. Carbohydr. Polym. 2011, 86(4), 1468–1475. DOI: 10.1016/j.carbpol.2011.06.034 58. Pollini, M.; Russo, M.; Licciulli, A.; Sannino, A.; Maffezzoli, A., Characterization of antibacterial silver coated yarns. J. Mater. Sci. Mater. Med. 2009, 20, 2361–2366. DOI: 10.1007/s10856-009-3796-z 59. Mehta, N. M.; Parsania, P. H., Fabrication and evaluation of some mechanical and electrical properties of jute‐biomass based hybrid composites. J. Appl. Polym. Sci. 2006, 100 (3), 17541758. DOI: 10.1002/app.23014 60. Joseph, S.; Thomas, S., Electrical properties of banana fiber‐reinforced phenol formaldehyde composites. J. Appl. Polym. Sci. 2008, 109 (1), 256-263. DOI: 10.1002/app.27452 61. Sreekumar, P. A.; Saiter, J. M.; Joseph, K; Unnikrishnan, G.; and Thomas, S., Electrical properties of short sisal fiber reinforced polyester composites fabricated by resin transfer molding. Composites Part A: Appl. Sci. Manufact. 2012, 43 (3), 507-511. DOI: 10.1016/j. compositesa.2011.11.018 62. Pathania, D.; Singh, D., A review on electrical properties of fibre reinforced polymer composites. Int. J. Theor. Appl. Sci. 2009, 1(2), 34–37. ISSN: 0975-1718 63. George, G.; Joseph, K.; Nagarajan, E. R.; Jose, E. T.; George, K. C., Dielectric behaviour of PP/jute yarn commingled composites: Effect of fibre content, chemical treatments, temperature and moisture. Composites Part A: Appl. Sci. Manufact. 2013, 47, 12-21. DOI: 10.1016/j.compositesa.2012.11.009 64. Singha, S.; Thomas, M. J., Permittivity and tan delta characteristics of epoxy nanocomposites in the frequency range of 1 MHz-1 GHz. IEEE Trans. Dielectr. Electr. Insul. 2008, 15 (1), 2– 11. DOI: 10.1109/T-DEI.2008.4446731 65. Prins, P.; Grozema, F. C.; Schins, J. M.; Siebbeles, L. D. A., Frequency dependent mobility of charge carriers along polymer chains with finite length. Phys. Status. Solidi. (b). 2006, 243(2), 382–386. DOI: 10.1002/pssb.200562719 66. Ferry, D. K.; Goodnick, S. M., Transport in nanostructures. 1997, Cambridge University Press, London. 67. Rout, S. K.; Tripathy, B. C.; Ray, P. K., Thermal Properties of Butylacrylate (BA) Transesterified and Benzoyl Peroxide (BPO) Cured Coir Fibers. Res. Rev. J. Mater. Sci. 2017, 5 (3), 82-91. DOI: 10.4172/2321-6212.1000186 68. Patra, A.; Bisoyi, D. K., Dielectric and impedance spectroscopy studies on sisal fibrereinforced polyester composite. J. Mater. Sci. 2010, 45 (21), 5742–5748. DOI: 10.1007/ s10853-010-4644-8 69. Gui, Z.; Zhu, H.; Gillette, E.; Han, X.; Rubloff, G. W.; Hu, L.; Lee, S. B. Natural cellulose fiber as substrate for supercapacitor. ACS Nano 2013, 7, 6037-6046.DOI: 10.1021/nn401818t 70. Minoru, H.; Minoru, H.; Hideyuki, Y.; Kanako, H.; Hitoshi, K.; Satoshi, H. Metal-Coated Coconut Fibers and Their Manufacture by Electroplating. Patent JP 2004277847A, 2004, October 7. 45 ACS Paragon Plus Environment


71. Mondal, D.; Perween, M.; Srivastava, D. N.; Ghosh P. K. Unconventional Electrode Material Prepared from Coir Fiber through Sputter Coating of Gold: A Study toward Value Addition of Natural Biopolymer. ACS Sustainable Chem. Eng. 2014, 2, 348-352. DOI: 10.1021/ sc400389u


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FOR TABLE OF CONTENTS USE ONLY

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Synopsis Silver nano-particle coated agro waste coir fibers as sustainable dielectric materials with high K and low Df for their use in embedded capacitors.


Nanosilver Coated Coir Based Dielectric Materials with High K and

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