Loss Tangent Peak Research Articles

Structural, optical, and dielectric properties of aminated PMMA/GO polymer nanocomposite for storage device applications

A series of aminated PMMA/GO polymer nanocomposite (PNG) were synthesized by solution mixing in two step process. The synthesized PNG samples were analysed using X-ray diffraction (XRD), Fourier transform infrared (FTIR), Scanning Electron Microscope (SEM), energy dispersive X-ray analysis (EDAX), Thermo-gravimetric, differential thermal analysis (TG-DTA), UV–Visible spectroscopy (UV–Vis) and impedance spectroscopy. The X-ray diffraction (XRD) data indicated the existence of crystalline nature in PMMA and the reduction of graphene oxide (GO) which is also confirmed by TGA and DTA results. The interaction between graphene oxide nanoparticles and the functionalized polymer matrix has been validated using FTIR investigations. The SEM and EDAX measurements demonstrated the homogeneous dispersion of graphene oxide (GO) over the surface of the produced samples. The UV–Vis spectroscopy analysis revealed that the optical energy gap values of nano composites decrease as the amount of graphene oxide nanoparticles increases. All samples exhibited higher relative permittivity at low frequencies which is a key factor for high energy density. As the concentration of GO increases, the maximum peak of dielectric loss tangent also shifted to higher frequency due to increase in interfaces. The β relaxation is dominant in non-polar PMMA due to the functionalisation and dispersion of GO. The AC conductivity values increased with increase in concentration of GO. The single semicircle in plot from impedance spectroscopy and the drop in bulk resistance values of PNG samples made them as a good material for energy storage devices like supercapacitors.

The H+ ion transport study in polymer blends incorporated with ammonium nitrate: XRD, FTIR, and electrical characteristics

The present study gained insights into H+ ion transport through non-destructive techniques. The XRD outcome reveals that poly(2-ethyl-2-oxazoline) (POZ) reduced the crystalline phase of chitosan (CS) effectively. Films of ion-conducting polymer blend electrolytes were created from CS:POZ complexed with ammonium nitrate (NH4NO3) as an H+ supplier by using the solution casting method. X-ray diffraction was used to study the structural alterations that occurred. The degrees of crystallinity were estimated from the deconvoluted XRD pattern. Measurement of electrical impedance was carried out for the electrolytes. From FTIR measurement, free ion and ion pair values were calculated. Several ion transport parameters (ITP), such as number density (n), ionic mobility (μ), and diffusion coefficient (D), were determined. It was found that the maximum conductivity was 3.87 × 10−6 S cm−1 at 30 percent NH4NO3. The DC conductivity pattern changes linearly with temperature. Dielectric and electric modulus were studied in detail. It was discovered that the loss tangent peak transferred to a upper side of frequency when the salt concentration was increased. Long-range conductivity relaxation was seen in the Mi spectra. The lack of a full semicircle arc on the Argand figure suggested non-Debye ion dynamics. The observed AC conductivity (σac) spectra showed three different zones. In the high-frequency range, the σac value follows a power law (σac=Aωs).

Long-term hydrothermal aging of Carbon-Epoxy materials for rehabilitation of civil infrastructure

This paper presents results of long-term (upto 5 years) hydrothermal aging of wet layup carbon-epoxy composites and the unreinforced resin used for the rehabilitation of civil infrastructure. Accelerated aging as determined through moisture uptake and dynamic mechanical characterization is enabled through elevated temperatures of immersion. A two-stage model based on diffusion and relaxation/deteriorative mechanism dominated mechanisms was used to characterize moisture uptake which was correlated with effects of cure progression, moisture induced plasticization, water-molecular network interactions, fiber–matrix debonding and microcavitation type damage through changes in glass transition temperature, loss tangent peak heights and shape, and storage moduli. Effects are noted to be lower than those predicted through short-term exposures. The use of long-term exposure provides significant insight not possible previously with the traditionally used short periods and allows for the elucidation of competing mechanisms that need to be understood for the prediction of long-term response of such materials in the field.

Defect-enriched hydroxyapatite induced by carboxylated chitosan as novel filler for pseudo solid-state supercapacitors

BackgroundThe severe crystalline region in pseudo solid-state polymer electrolyte needs to be addressed to improve the poor ionic conductivity performance. MethodsHydroxyapatite (HA) with rich defect, induced by carboxylated chitosan (CCS) via hydrothermal process is applied to serve as active filler for pseudo solid-state supercapacitor. Significant findingsCCS2 with high degree of carboxylation (DC) of 42.38% is introduced as defect inducing agents to generate CCS2-HA. CCS2-HA possesses small crystallinity index evaluated by FTIR and XRD. Moreover, the obvious structural defect of CCS2-HA in [301] orientation was observed from HRTEM. With CCS2-HA as defect-enriched filler, the crystallization temperature decreases from 75 to 65 °C. Meanwhile, the activation energy for the ionic conductivity decreases from 2.3 to 1.3 kJ/mol. Meanwhile, the loss tangent peak shifts to higher frequency with smaller intensity in the addition of CCS2-HA as active filler, showing the smaller relaxation time and less heat resistance than the pristine. CCS2-HA possessed rich defects to reduce crystalline region, increase amorphous region, enhance segmental motion, and assist short range ion migration for less internal resistance and heat dissipation as novel filler for superior solid-state energy storage devices.

An investigation of carboxylated chitosan hydrogel electrolytes for symmetric carbon-based supercapacitors at low temperatures

BackgroundChitosan (CS) is the most abundant cationic biopolymer on earth. However, the ionic conductivity performance of CS polymer electrolyte is relatively poor, restricting the application in energy storage devices. MethodsSubject to carboxylation at pH of 6. 8, and 10, CS turns into CCS6, CCS8, and CCS10 respectively with the DC of 100.9%, 20.0%, and 17.8%, respectively. Significant findingsFrom the Arrhenius plot, the activation energy of CS, CCS6, CCS8, and CCS10 electrolytes is estimated as 11.7, 2.5, 2.6, and 2.6 kJ/mol respectively. As for supercapacitor performance, CCS6 remains 57.2% capacitance but the others remain 0% with decreasing temperature from 25 °C to -7 °C. At -7 °C, only CCS6 supercapacitor shows relaxation peak in loss tangent versus frequency plot around 2 × 105 Hz according to dissociated ion pairs, being attributable to the existence of bound water. Three water states are examined by Differential Scanning Calorimetry (DSC) and Raman, verifying that CCS6 possesses high bound water proportion of 24.7%. With the highest DC, CCS6 possesses the almost equivalent amine and carboxyl groups in one glucosamine unit to play an important role to enhance dissociation, defer the breakpoints of ionic conductivity, and remain certain proportion of bound water for promising capacity at low temperature.

Influence of NaF salt doping on electrical and optical properties of PVA/PVP polymer blend electrolyte films for battery application

Solid polymer electrolyte films of poly(vinyl alcohol) (PVA)/polyvinylpyrrolidone (PVP) doped with sodium fluoride (NaF) of different weight ratios (2, 4, 6, 8, and 10 wt%) have been prepared by using solution casting method. These films are characterized by XRD, FTIR, and SEM analysis. The X-ray diffraction (XRD) spectra show a characteristic PVA peak signifying its semi-crystalline nature. As NaF salt is incorporated into the polymer blend, the peak intensity decreases gradually, implying a decrease in the degree of crystallinity of the samples. The FTIR study confirmed the complexation, functional group occurred, and interaction between the different components in the polymer blend electrolyte, which suggests the micro-structural variations, takes place in polymer blended films by addition of NaF salt. The a.c. conductivity was measured at room temperature as well as in the temperature between the range 300 and 343 K. The conductivity was found to depend on NaF concentration which increases with increase in frequency and rise in temperature. The dielectric constant was found to decrease with increase in frequency and increased with temperature increase. The dielectric loss tangent peak was observed to increase in lower frequency range and its intensity is found to decrease with increasing frequency. Optical constants such as absorption coefficient (α), bandgap (Eg), extinction coefficient (k), refractive index (n), and real & imaginary part of optical dielectric constant were calculated. It was found that these optical constants found to depend on the concentration of NaF in PVA/PVP blend system. Transference number measurement (TNM) was carried out in order to investigate the nature of charge transport mechanism which showed that charge transport in the as-prepared polymer blend films is predominantly due to ions. Electrochemical cells were fabricated for the as-prepared samples and various cell parameters were determined.

Crosslinking Dependence of Direct Current Breakdown Performance for XLPE-PS Composites at Different Temperatures

In this paper, crosslinked polyethylene-polystyrene (XLPE-PS) composites with different degrees of crosslinking were fabricated by using different crosslinking agent contents and their direct current (DC) breakdown performance at 30~90 °C was investigated. Results show that with the increase of the degree of crosslinking, the crystallinity of XLPE-PS composites decreases gradually, but their DC breakdown strength demonstrates an increasing trend at 30~90 °C and the enhancement also increases with the rise of temperature. And as the degree of crosslinking increases, the elastic modulus of XLPE-PS composites is reduced and the loss tangent peak temperature decreases but the peak shifts to a lower value, which reveals the suppression of the relaxation process for crystallites. It is believed that high DC breakdown strength with good temperature stability for XLPE-PS composites with a larger degree of crosslinking is attributable to the presence of PS and suppression in the formation of crystallites due to crosslinking.

Electrical Properties of lead free ceremics Na1−XKxNbO3, at x=0.305

By solid state reaction method, ceramic pellets of Na0.695K0.305NbO3 have been prepared. X-ray- diffraction, Piezo properties, scanning electron microscope, and temperature dependence of dielectric constant and loss tangent of the prepared samples have been studied. It has been observed that, at the transition temperature, dielectric constant peak shifts to lower temperature, and the dielectric constant and loss tangent peak heights decrease, with increasing frequency, and show three structural phase transitions.

Dielectric properties of soil mixed with urea fertilizer over 20 Hz to 2 MHz frequency range

The dielectric properties of sandy soil for various moisture contents of distilled water and Urea-fluid solutions in soil are estimated in the lower frequency range from 20 Hz to 2 MHz using precision LCR meter. The spectra of complex permittivity e*(ω), loss tangent tan δ(ω), electrical conductivity σ*(ω), and complex impedance Z*(ω) plane plots of these soil-fluid system have been investigated for various moisture contents of different concentrations of Urea solution in the soil samples. The dielectric constant and dielectric loss of the soil increase with increase in moisture content of different concentrations of Urea solution in the soil. The dielectric constant and dielectric loss of the soil increases significantly with the decrease in frequency over the given frequency range. The complex impedance plane (Zʹ versus Zʺ) plot separates electrode polarization and bulk material phenomena, which can also be observed in the dielectric loss tangent peaks.

Adjustable Graphene/Polyolefin Elastomer Epsilon-near-Zero Metamaterials at Radiofrequency Range.

While epsilon-near-zero (ENZ) metamaterials have marvelously shown various application prospects, the way to construct intrinsic ENZ metamaterials and adjust their ENZ properties precisely is still uncovered. The realization of stable and broadband ENZ properties at the radiofrequency range is of great significance. Herein graphene/polyolefin elastomer (POE) intrinsic ENZ metamaterials are initially constructed via the nanohybrid process. The metamaterials possess excellent adjustable ENZ properties by adjusting the content and reduction methods of graphene. The permittivities maintain between -1 and 1 steadily with increasing graphene content, which is attributed to the moderated carrier concentration of the conductive networks in the nanohybrids. Besides, different reduction methods also have significant impacts on ENZ properties. The hydrazine hydrate reduction method increases the maximum ENZ frequency region to 126 MHz. Lorentz type resonance is reasonable for the positive-negative transition in the ENZ frequency regions. As a significant indicator of the emergence of ENZ property, the sudden peak of dielectric loss tangent is observed. This work offers novel routes to construct intrinsic ENZ metamaterials with excellent adjustability in both values of permittivity and ENZ frequency regions.

Study on the Generalized Formulations with the Aim to Reproduce the Viscoelastic Dynamic Behavior of Polymers

Appropriate modelling of the real behavior of viscoelastic materials is of fundamental importance for correct studies and analyses of structures and components where such materials are employed. In this paper, the potential to employ a generalized Maxwell model and the relative fraction derivative model is studied with the aim to reproduce the experimental behavior of viscoelastic materials. For both models, the advantage of using the pole-zero formulation is demonstrated and a specifically constrained identification procedure to obtain the optimum parameters set is illustrated. Particular emphasis is given on the ability of the models to adequately fit the experimental data with a minimum number of parameters, addressing the possible computational issues. The question arises about the minimum number of experimental data necessary to estimate the material behavior in a wide frequency range, demonstrating that accurate results can be obtained by knowing only the data of the upper and low frequency plateaus plus the ones at the loss tangent peak.

Microstructural interpretations on thermo-mechanical relaxation and electrical conductivity of polyamide-12/polypropylene-MWCNT nanocomposites

Ternary-nanocomposites of polyamide 12 (PA-12) and multi-walled carbon nanotubes-embedded-polypropylene (MWCNT-embedded-PP) were fabricated by direct-melt-mixing-route and characterized for their dispersion-nanomorphology and phase-selective micromorphology. The crystallite sizes remained in the range of 8–9 nm and a broadening in loss-tangent peaks shifting towards higher temperatures with MWCNT was observed. The DC electrical conductivity remained dependent on the change in morphology from domain-dispersed (MWCNT-embedded-PP dispersed in PA-12 matrix) in PA-12/PP-MWCNT (70:30) to quasi-co-continuous (MWCNT-embedded-PP forming elongated domains of PP-MWCNT dispersed in PA-12 matrix tending to be near-continuous) in PA-12/PP-MWCNT (60:40). The conceptual feasibility of designing nanocomposites wherein the switch-over in solid-state relaxation behaviour vis-a-vis electrical conductivity is thus found to be controlled by morphology that ensures phase-selective conductive response for functional applications, as in flexible electronics, unlike the ones with rigid and high melting (thermally stiff) polyamides such as polyamide 6 or polyamide 66.

Ultratoughening of Biobased Polyamide 410.

The microstructural, thermomechanical, and quasistatic mechanical properties of biobased polyamide 410 (PA410)/poly(octane-co-ethylene)-g-maleic anhydride (POE-g-MA) blends with the impact toughener in the composition range of 0–20 wt % have been investigated, with an aim to overcome the poor notch and strain sensitivity of PA410. The crystallinity of the blends obtained from enthalpic measurements and initial degradation temperature indicating thermal stability remained mostly unaffected. A remarkably substantial increase, i.e., ∼15-fold enhancement, in the impact strength of the PA410/POE-g-MA blends leading to ultratoughening of PA410 accompanied by a significant increase in tensile strain at breaking is achieved though the elastic modulus (E) and yield strength (σ) decreased with impact modifier content. Thermomechanical analysis revealed a broadening in the loss tangent peak in the temperature range of ∼−50 to −30 °C corresponding to the POE phase, whereas the loss tangent peak corresponding to the PA410 phase stayed unaffected. Conventional theoretical models such as the rule of mixture and foam model were used to analyze the micromechanics of low-strain (<1%) mechanical response (E), and Nikolais–Narkis model and Isahi–Cohen models, for high-strain (>2%) mechanical response (σ). The interdependence of impact toughness, ductility ratio, and domain size of the dispersed rubber phase in the PA410/POE-g-MA blends could successfully be established vis-à-vis the mechanistic role of interparticle distance. Scanning electron microscopy showing domain coalescence of the soft elastomeric POE phase thus reiterated the pivotal role of interdomain distance and domain size in influencing the toughening mechanism of PA410/POE-g-MA blends. The qualitative phase distribution attributes based on atomic force microscopy remained in sync with quantitative parameters, such as domain size, hence reaffirming the mechanism behind ultratoughening of PA410 by POE.

Effect of Aromatic Petroleum Resin on Damping Properties of Polybutyl Methacrylate.

The damping properties of polybutyl methacrylate (PBMA)/aromatic petroleum resin (C9) composite were investigated in this work. In particular, a trace of styrene (St) was introduced to copolymerize with PBMA to improve the compatibility between C9 and matrix. The structure of the copolymer, P(BMA-co-St), was characterized by FTIR and 1HNMR. The P(BMA-co-St)/C9 composites were tested by differencial scanning calorimetry (DSC), scanning electron microscopy (SEM) and dynamical mechanical analysis (DMA). DSC curves of all P(BMA-co-1wt%St)/C9 composites expressed only one glass transition temperature (Tg). SEM images showed that C9 had good compatibility with the matrix after St was introduced. DMA curves indicated that the addition of C9 had a positive effect on the damping properties of PBMA. The loss tangent (tanδ) peak moved to a higher temperature with the increment content of C9, and the effective damping temperature range increased significantly. The influence of aromatic resin C9 and aliphatic resin (C5) on PBMA damping performance was compared. It was further shown that C9 with benzene ring effectively improved the damping performance of PBMA.

Design of Polymer Blends Based on Chitosan:POZ with Improved Dielectric Constant for Application in Polymer Electrolytes and Flexible Electronics

There is a considerable demand for the development and application of polymer materials in the flexible electronic- and polymer-based electrolyte technologies. Chitosan (CS) and poly(2-ethyl-2-oxazoline) (POZ) materials were blended with different ratios to obtain CS:POZ blend films using a straightforward solution cast technique. The work was involved a range of characteristic techniques, such as impedance spectroscopy, X-ray diffraction (XRD), and optical microscopy. From the XRD spectra, an enhancement in the amorphous nature in CS:POZ blend films was revealed when compared to the pure state of CS. The enhancement was verified from the peak broadening in CS:POZ blend films in relative to the one in crystalline peaks of the CS polymer. The optical micrograph study was used to designate the amorphous and crystalline regions by assigning dark and brilliant phases, respectively. Upon increasing POZ concentration, the dielectric constant was found to increase up toɛ′ = 6.48 (at 1 MHz) at 15 wt.% of POZ, and then a drop was observed beyond this amount. The relatively high dielectric constant and dielectric loss were found at elevated temperatures. The increase of POZ concentration up to 45 wt.% made the loss tangent to shift to the lower frequency side, which is related to increasing resistivity. The increases of dielectric constant and dielectric loss with temperature were attributed to the increase of polarisation. The loss tangent peaks were found to shift to the higher frequency side as temperature elevated. Obvious relaxation peaks were observed in the imaginary part of electric modulus, and no peaks were found in the dielectric loss spectra. The concentration dependent ofM″ peaks was found to follow the same trend of loss tangent peaks versus POZ content. The relaxation process was studied in terms of electric modulus parameters.

Metal-Filled Epoxy Composites: Mechanical Properties and Electrical/Thermal Conductivity

The mechanical properties and the electrical and thermal conductivity of composites based on an epoxy polymer (EP) filled with dispersed copper (Cu) and nickel (Ni) were studied. It was shown that the electrical conductivity of the composites demonstrated percolation behavior with the values of the percolation threshold being 9.9 and 4.0 vol.% for the EP-Cu and EP-Ni composites, respectively. Using the Lichtenecker model, the thermal conductivity of the dispersed metal phase in the composites, λf, was estimated as being 35 W/mK for Cu powder and 13 W/mK for Ni powder. It was shown that introduction of the filler in EP led to a decrease in the intensity of the mechanical loss tangent (tan δ) peak that was caused by the existence of an immobilized polymer layer around the filler particles which did not contribute to mechanical losses. Using several models the thickness of this layer, ΔR, was estimated. The concept of an “excluded volume” of the polymer, Vex, i.e. the volume of the immobilized polymer layer, which does not depend on the particle size and is determined solely by the value of the interaction parameter, B, was proposed.

Selection of best composition of Na+ ion conducting PEO-PEI blend solid polymer electrolyte based on structural, electrical, and dielectric spectroscopic analysis

In this paper, we report the investigation on structural, electrical, dielectric properties, and ion dynamics of novel blend polymer electrolyte matrix (PEO-PEI) complexed with sodium hexafluorophosphate salt. All the solid polymer electrolyte films have been synthesized via solution cast method. The SPE films were characterized by the X-ray diffraction, field emission scanning electron microscope, impedance-dielectric spectroscopy, and thermogravimetric analysis. The morphology of the SPE alters with salt addition and confirms the blend polymer complex formation. The FTIR analysis evidenced the complex formation, and increase in the fraction of free ions is achieved. The ionic conductivity exhibits a maximum at the stoichiometric ratio O/Na = 10 and follows the Arrhenius behavior. The fraction of free ions is maximum for the SPE film with the highest ionic conductivity. The optimum electrolyte possesses a voltage stability window of about 4 V, excellent thermal stability up to 380 °C, and high ionic transference number (~ 1). The complex permittivity and conductivity have been simulated in whole frequency window to extract relaxation time and dielectric strength. The dielectric constant and relaxation time exhibited sequentially a maximum and minimum for the SPE film with the highest ionic conductivity. The loss tangent peak shifts toward high frequency with addition of salt, and it infers the faster ion dynamics in the polymer matrix. Then the ion transport parameters number density of charge carriers (n), ion mobility (μ), and diffusion coefficient (D) have been obtained by three methods (FTIR, impedance spectroscopy, and loss tangent method) and are in absolute correlation with the impedance results. An ion transport mechanism has been proposed based on experimental findings.

Mechanical Properties of Poly(methyl methacrylate-co-3-sulfopropyl methacrylate) Ionomers Acting as a Filled System

The dynamic mechanical properties of newly-made poly(methyl methacrylate-co-3-sulfopropyl sodium methacrylate) (M-SPMA) ionomers were measured and compared with those of methyl methacrylate ionomers having sodium methacrylate units (M-MA) and styrene ionomers having SPMA or MA units (S-SPMA or SMA). It was observed that the position of the matrix loss tangent peak of M-SPMA ionomers was not changed by the ion content, but the size of the peak was decreased. At high ion contents, however, the ionomers showed a cluster loss tangent peak and a very weak SAXS peak. These results were quite different from those obtained from the styrene ionomers. Thus, it was concluded that this dissimilarity was due to the differences in the polarity and persistence length of PS and PMMA. When the mechanical data of M-SPMA ionomers were compared with those of M-MA ionomers, M-SPMA and M-MA ionomers were found to behave like a filled system and a cross-linked system, respectively. This was due to the fact that M-SPMA ionomers had propyl groups and sodium sulfonate ion pairs, and thus the ionic groups formed fewer and larger ionic aggregates than M-MA ionomers.

Influence of adding carbon black on electrical conductivity in dynamically vulcanized of poly (vinylidene fluoride)/fluoroelastomer composites

The present work was focused on studying the effects of different CB loadings on the rheological, thermal, tensile, dynamic mechanical, and electrical properties of polyvinylidene fluoride and FKM composites. To these ends, dynamic mechanical thermal analysis (DMTA) was conducted, and the CB grade and method chosen for compound preparation were CB (N330) by melt mixing with different shear effects were examined, respectively. The composites were melt-blended with CB at 190 °C in an internal mixer, after which the properties of filled and unfilled composites were compared. The DMTA analysis revealed that the area under the loss tangent (tanδ) peak decreased and that the tanδ temperature of the rubber phase increased with CB loading. The presence of CB improved the mechanical properties, such as the Young’s modulus and tensile strength, of the composites and increased thermal stability given the high thermal stability of CB and the interaction between the CB particles and the polymer matrices. The increase in the electrical conductivities of the composites under different CB loadings was also examined with different shear effects because of the different dispersion states of CB. The percolation threshold of conductive thermoplastic vulcanizate composite based on conductive CB was observed and the experimental data could be well fitted to the general equation model.

Structure dependent dielectric response of spray coated nanostructured zirconia thin films

In this work the structural dependent dielectric property of ZrO2 nanoparticles and films prepared using these nanoparticles is studied. The tetragonal and monoclinic dominant zirconia nanoparticles were obtained through thermal treatment of PVP/CTAB capped hydrous amorphous zirconia (HAZ) at 500 °C. The grain (Rg) and grain boundary (Rgb) resistances of both types of nanoparticles along with films are estimated by fitting the respective complex impedance (Nyquist) plots with an equivalent electrical circuit. The nanostructured tetragonal dominant zirconia films are highly conductive as compared to monoclinic films due to large amount of Zr3+ ions present at tetragonal sites. Consequently the film exhibits a high dielectric constant at lower frequency range due to Maxwell-Wagner polarization. Moreover the EPR signals observed at 1.946 (g∣∣) and 1.967 (g⊥) reveals the presence of greater Zr3+ ions tetragonal films. The Rgb of monoclinic dominant film is increased by an order of 103 and consequently results in significant reduction of dielectric constant. Further the shift of loss tangent peak to higher frequency side of tetragonal dominant films endorses the higher mobility of charge carriers as that of monoclinic films. The enhancement of dielectric properties shows the potential application of tetragonal dominant ZrO2 films for future electronic devices.