Impedance Spectra Research Articles

Facile synthesis of Zn2V2O7/RGO nanocomposite for enhancing the electrochemical performance and evaluating the supercapacitor device

Pyrochlore-structured zinc vanadium oxide with RGO (Zn2V2O7/RGO) composite was synthesized using the simple hydrothermal process for energy storage device fabrication. The structural, vibration spectrum, surface morphology, and elemental of the Zn2V2O7/RGO composite were analyzed using different analytical methods. Then, the electrochemical performance was examined using Zn2V2O7/RGO composite modified electrode with 3-electrode and 2-electrode setup by cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectrum (EIS) techniques. Consequently, the Zn2V2O7/RGO composite revealed notable pseudo-capacitive behavior which has been confirmed through CV analysis. The nano size-based Zn2V2O7/RGO composite electrode material obtained notable specific capacitance (Csp) of 1400.51F/g owing to the synergistic promotion of Zinc and vanadium oxides. Furthermore, the ASC device of Zn2V2O7/RGO ||RGO displayed the efficient power density of 1371 kW/kg at the energy density of 8Wh/kg and the device has enhanced cycling performance with 72.8 % capacitance.

Realizing Outstanding Energy Storage Performance in KBT-Based Lead-Free Ceramics via Suppressing Space Charge Accumulation.

The great potential of K1/2Bi1/2TiO3 (KBT) for dielectric energy storage ceramics is impeded by its low dielectric breakdown strength, thereby limiting its utilization of high polarization. This study develops a novel composition, 0.83KBT-0.095Na1/2Bi1/2ZrO3-0.075 Bi0.85Nd0.15FeO3 (KNBNTF) ceramics, demonstrating outstanding energy storage performance under high electric fields up to 425kVcm-1: a remarkable recoverable energy density of 7.03Jcm-3, and a high efficiency of 86.0%. The analysis reveals that the superior dielectric breakdown resistance arises from effective mitigation of space charge accumulation at the interface, influenced by differential dielectric and conductance behaviors between grains and grain boundaries. Electric impedance spectra confirm the significant suppression of space charge accumulation in KNBNTF, attributable to the co-introduction of Na1/2Bi1/2ZrO3 and Bi0.85Nd0.15FeO3. Phase-field simulations reveal the emergence of a trans-granular breakdown mode in KNBNTF resulting from the mitigated interfacial polarization, impeding breakdown propagation and increasing dielectric breakdown resistance. Furthermore, KNBNTF exhibits a complex local polarization and enhances the relaxor features, facilitating high field-induced polarization and establishing favorable conditions for exceptional energy storage performance. Therefore, the proposed strategy is a promising design pathway for tailoring dielectric ceramics in energy storage applications.

Boosting the photocatalytic activity of bismuth vanadate (BiVO4) via optimization of the internal polarization

Photocatalytic performance can be improved by optimizing the morphology and surface texture of the photocatalyst or forming different p-n and/or n-n heterojunctions. Although the heterojunction system enhances photocatalytic property; however, an internal spontaneous polarization electric field may be much more effective due to the separation of electron-hole pairs when the polarization field forces them to move in different directions. The present study demonstrated this insight where the BiVO4 synthesis condition and polarization field forces were controlled via homogeneous precipitation in the presence of polyvinylpyrrolidone (PVP). The as-synthesized BiVO4 photocatalysts' structure and morphology were investigated using XRD, SEM, Raman, DRS, and PL. The result revealed that the increase of PVP concentration reformed the shaping to the truncated bipyramid-like shape and creates a spontaneous internal polarization that enhanced BiVO4 photocatalytic performance. The photocatalytic activity of BiVO4 was evaluated by monitoring the photocurrent enhancement using chronoamperometry, electrochemical impedance spectra and the photodegrading of methylene blue (MB) aqueous solution to harmless compounds in the presence of light. The spontaneous polarization between the different facets of BiVO4 crystal enhances the e−/h+ separation during internal facets homojunction and leads to four times photocurrent enhancement and the MB photocatalytic degradation rate increased from 0.43 to 1.92 min−1.

Efficient manufacture of high-performance electroplated diamond wires utilizing Cr-coated diamond micro-powder

The slicing of silicon ingots using electroplated diamond wires is a fundamental process in the creation of semiconductor devices such as chips and photovoltaic cells. Composite electroplating, a process that uses nickel (Ni) plating to fix diamond particles onto a steel wire, is a critical step in the manufacturing of these diamond wires. In this work, chromium (Cr)-coated diamond was used to achieve rapid and high-quality composite electroplating, thereby aiding the production of high-performance diamond wire saws. The Cr-coated diamond micro-powder was prepared utilizing vacuum slow evaporation technology at a temperature of 850 °C. This resulted in a uniform and firm Cr coating that was firmly bonded to the diamond surface via Cr3C2. Subsequent electrochemical tests were conducted in the composite electroplating bath. Linear scanning voltammetric curves revealed that the Cr-coated diamond was capable of inducing a more positive shift in the overpotential of Ni deposition, thus enhancing the reaction beyond that of uncoated diamond micro-powder. Additionally, the electrochemical impedance spectra indicated a decrease in charge transfer resistance during composite electroplating, attributable to the conductivity of the Cr-coated diamond. Electroplated diamond wires incorporating Cr-coated diamond demonstrated a greater abrasive density per unit length. SEM results showed that Ni was able to deposit on the Cr-coated diamond surface, resulting in the abrasives being completely covered by the Ni plating. The Cr-coated diamond wire exhibits a stronger resistance to abrasive detachment after cutting, which could increase the diamond-protrusion of the wire. The utilization of Cr-coated diamond micro-powder as an abrasive is anticipated to enhance the manufacturing efficiency of diamond wires and improve product quality, thereby promoting advancements in hard and brittle material processing technology.

Improved UV sensitivity in solution-processed PVDF/ZnO nanocomposites via piezo-phototronic effect

In this article, we report the enhanced UV photo-detection property of solution processed poly(vinyledene fluoride) (PVDF) membranes filled with zinc oxide (ZnO) nanoparticles at varying concentration. Microstructural analysis confirms β-crystalline phase formation. PVDF/ZnO membranes show increased photo-current compared to pristine PVDF, under UV (λ∼365 nm, 8.3 μW/cm2) irradiation, with PVDF/10% ZnO achieving 4.34 μA photo-current and 6 second response time at 10 V bias. Under mechanical stress in form of bending, UV photocurrent of the composite is enhanced significantly as a result of piezo-phototronic effect. Impedance spectra show significant variations under UV, revealing modifications in grain-boundary interfaces with ZnO and UV, and bending affecting electrical response, confirming the piezo-phototronic effect.

Humidity impact on polarization dynamics in polymer electrolyte membrane fuel cells through distribution of relaxation times analysis

The interaction among relative humidity, current density, and internal polarization plays a crucial role in optimizing the performance of polymer electrolyte membrane fuel cells (PEMFCs). However, achieving swift analysis and feedback on the internal humidity status of PEMFCs through on-vehicle impedance spectroscopy measurements remains a significant challenge. Conducting a series of impedance spectra under operating conditions of 30 %, 50 %, and 80 % relative humidity sheds light on the impact of humidity on performance. Correlations between specific distribution of relaxation times (DRT) peaks and internal polarization are established. Through DRT analysis, four polarization dynamics related to proton transfer at the proton exchange membrane interface, proton transport in the cathode catalyst layer, charge transfer, and the oxygen diffusion process are effectively identified based on characteristic frequencies and peaks. The rate-determining step of the polarization varies under idling, rated, and overload conditions, providing valuable insights. This study contributes analytical models and strategic guidance for tailoring relative humidity conditions to mitigate polarization, thereby enabling real-time control and enhancement of PEMFC performance.

Development and characterization of fly ash enriched epoxy coatings for corrosion protection in deep sea water

Fly ash (FA) has recently received increasing attention as inexpensive and readily abundant filler for development of epoxy-based anticorrosive coatings. In the present investigation a series of FA enriched epoxy coatings (FECs) has been developed and investigated for their anticorrosive behaviour under immersion in DSW (pH 8.2) over 48 h. The development of FECs was conducted through enrichment of FA ranging 0 to 80 phr (parts of FA per 100 g of epoxy) into epoxy matrix. The formation of FECs was ascertained through spectral, thermal, electrical and microscopic methods. Electrochemical impedance spectra in coherence with DC polarization measurements reveal enhanced corrosion protection efficiency (83 %) of FECs derived at 40 phr enrichment of FA. Enrichment of FA (phr) ranging 40 to 60 has rendered fair (0.01) to moderate (0.05) resistance (mm/year) to FECs against pitting corrosion in DSW. Whereas, FECs derived at 60 phr of FA has shown promising electrical behaviour, moderate heat resistance (TG onset 200 °C with 94.70 % weight residue) with enhanced limiting oxygen index (38.50 %). FECs developed in the present investigation may find their possible applications as anticorrosive coatings sustainable in DSW over 48 h.

Magnetic exchange interactions and non-Debye relaxation in spin-3/2 frustrated Kagomé magnet Co3V2O8

We report the experimental determination of the magnetic exchange parameter ( J/kB = 2.88 ± 0.02 K) for the Spin-3/2 ferromagnetic (FM) Kagomé lattice system: Co3V2O8 using the temperature dependence of dc-magnetic susceptibility χ(T) data by employing the fundamental Heisenberg linear chain model. Our results are quite consistent with the theoretically reported nearest neighbor dominant FM exchange coupling strength Jex−NN∼ 2.45 K. Five different magnetic phase transitions (6.2–11.2 K) and spin-flip transitions (9.6–7.7 kOe) have been probed using the ∂ ( χT )/ ∂T vs. T, heat capacity (CP -T) and differential isothermal magnetization curves. Among such sequence of transitions, the prominent ones being incommensurate antiferromagnetic (AFM) state at 11.2 K, commensurate AFM state at 8.8 K, and commensurate FM state across 6.2 K. All the successive magnetic phase transitions have been mapped onto a single H-T plane through which one can easily distinguish the above-mentioned different phases. The magnetic contribution of the CP -T near TN (11.2 K) has been analyzed using the power-law expression CM = A|T — TN|−α resulting in the critical exponent α = 0.18 ± 0.01 (0.15 ± 0.003) for T < TN (T > TN ), respectively for the Co3V2O8. It is interesting to note that non-Debye type dipole relaxation is quite prominent in Co3V2O8 and was evident from the Kohlrausch–Williams–Watts analysis of complex modulus and impedance spectra (0 ⩽β⩽ 1). Mott’s variable-range hopping of charge carriers process is evident through the resistivity analysis ( ρac -T −1/4 ) in the temperature range 275 ∘C–350 ∘C. Moreover, the frequency-dependent analysis of σac (ω) follows Jonscher’s power law yielding two distinct activation energies ( Ea∼ 0.37 and 2.29 eV) between the temperature range 39 ∘C–99 ∘C and 240 ∘C–321 ∘C.

Effect of Li2O composition and temperature on the ionic conductivity of lithium-borate-silicate glasses containing gold nanoparticles using electrochemical impedance spectroscopy

This research systematically investigates the conductivity properties of a lithium-borate-silicate glass containing varying amounts of Li2O (30 to 50 mol %) in the presence and absence of a fixed concentration of gold nanoparticles (0.05 M). Three techniques were used to characterize the glass material: Electrochemical Impedance Spectroscopy, X-ray diffraction, and Differential Scanning Calorimetry. Impedance spectra were recorded at temperatures of 100 °C, 140 °C, and 200 °C, and the results were analyzed qualitatively and quantitatively using models based on the equivalent circuit approach. It was observed that below a critical concentration of Li2O, namely 35 mol %, the conductivity behavior exhibits a single relaxation process. However, above the critical concentration, the materials present two relaxation processes associated with changes in morphology. Impedance measurements also evaluate the DC and AC conductivity properties of the glasses. Interestingly, regardless of the morphology, conduction in the glasses appears to be thermally activated, with the conduction mechanism being controlled by polaron hopping in a correlated barrier. There is no evidence suggesting that the gold nanoparticles play a significant role in determining the conduction properties of the glasses, at least within the concentration range studied here.

Effects of Fe2+ on dielectric and magnetic properties in rare earth garnet type high entropy oxides

Given the important role played by the valence state of the transition metal in determining material this paper investigates the effect of Fe2+ content on the structure and dielectric properties of garnet-structured high entropy oxides (Y0.2Eu0.2Er0.2Dy0.2Lu0.2)3(Al0·5Fe0.5)5O12 through Fe2+ doping. The results of XPS and Mӧssbauer spectra showed that the Fe2+ content in the tetrahedron increased with Fe2+ doping. With increasing Fe2+ content, the dielectric constants gradually increased, and the maximum dielectric constant reached 2.78 × 104 at 100 Hz under 30 °C. The analysis of the AC impedance spectrum and electrical conductivity revealed that the difference between the activation energy of grain boundary and grain conductivity resulted in increased dielectric constants of the samples. In addition, the doping of Fe2+ increased the maximum magnetization of the samples. This work provides a new idea for designing giant dielectric materials and magnetic materials with a high entropy strategy.

Extracting and Interpreting Electrochemical Impedance Spectra (EIS) from Physics-Based Models of Lithium-Ion Batteries

This paper implements a highly efficient algorithm to extract electrochemical impedance spectra (EIS) from physics-based battery models (e.g., a P2D model). The mathematical approach is different from how EIS is practiced experimentally. Experimentally, the voltage (current) is harmonically perturbed over a wide range of frequencies and the amplitude and phase shift of the corresponding current (voltage) is measured. The experimental approach can be implemented in simulation software, but is computationally expensive. The approach here is to determine locally linear state-space models from the full physical model. The four Jacobian matrices that are the basis of the state-space models can be derived by numerical differentiation of the physical model. The EIS is then extracted from the state-space model using computationally efficient matrix-manipulation techniques. The algorithm can evaluate the full EIS at an instant in time during a transient, independent of whether the battery is in a stationary state. The approach is also able to separate the full-cell impedance to evaluate partial EIS, such as for a battery anode alone. Although such partial EIS is difficult to measure experimentally, the partial EIS provides valuable insights in interpreting the full-cell EIS.

Characteristics of hydride electrodes using Mg-Ti-Ni-Co-Al-based alloys synthesized by mechanical milling

For Ni-MH batteries, crystalline Mg-based alloys such as MgNi, Mg2Ni, REMg12, and La2Mg17 are regarded as hopeful negative electrode materials. Even though these alloys are inexpensive and have promising discharge capacity, they hardly ever electrochemically absorb or desorb hydrogen at room temperature. In this paper, the MgNi-based Mg50-xTixNi45Al3Co2 (x = 0, 1, 2, 3, 4) alloy electrodes were fabricated. The surface of the as-cast alloys was modified by mechanical Ni coating. The nanocrystalline and amorphous Mg50-xTixNi45Al3Co2 (x = 0, 1, 2, 3, 4) + 50 wt%Ni alloys for Ni-MH batteries were prepared using mechanical ball milling. The effects of Ti content and ball milling time on the structure and electrochemical hydrogen storage properties of the alloys were investigated. The electrochemical testing reveals that the as-milled alloys can electrochemically absorb and desorb hydrogen well at room temperature. Without any activation, the milled alloys can achieve maximum discharge capacity in the first cycle. With the extension of ball milling time and the increase of Ti content, the cycle stability and discharge capacity of the alloys are significantly enhanced. The electrochemical impedance spectrum, high rate discharge ability, potentiodynamic polarization curve, and potential-step measurement all indicate that the electrochemical kinetics of the prepared alloys initially increase and subsequently decrease with the increase of Ti content, while significantly improve with the prolongation of milling time.

Colossal permittivity with ultra-wide temperature stability in Bi + Ca co-doped BaTiO3

The poor temperature stability of the BaTiO3 ceramic has always been the main problem limiting their application. This situation has been improved but sacrifices the intrinsic polarization, which significantly reduces the dielectric constant. In this work, the mechanism of multiple polarization was creatively introduced, and the temperature stability and dielectric properties of BaTiO3-based ceramics are simultaneously enhanced. In particular, the Ba0.9925Bi0.005Ti0.995Ca0.005O2.995 (BBTC0.5) ceramic sample achieved excellent temperature stability (−14.8% to 8.85%) over an ultra-wide temperature range (−47 to 400 °C) and exhibited colossal permittivity (27,125, 25 °C, 1 kHz) and low dielectric loss (0.07, 25 °C, 1 kHz). The dielectric properties, complex impedance spectra combined with XPS results indicate that the defective dipole clusters (Ti3+-VO..-Ti3+, BiBa. and CaTi″-VO..) along with surface effects lead to colossal permittivity effect. More importantly, SEM images show the presence of the second phase at grain boundaries, which prevent the carriers within the grains from accumulating at the grain boundaries. As a result, the dielectric loss was reduced and the temperature stability was further extended. This strategy breaks the traditional limitation of single/noncomprehensive enhancement by single-polarization mechanism, and is of great theoretical and practical significance to promote the research and application of high-performance BaTiO3-based ceramic materials.

Fabrication of g-C3N4 films with enhanced mechanical and charge transfer properties by electrophoretic deposition and subsequent citric acid modification

A low-cost 2D metal-free material based on a graphitic carbon nitride (g-C3N4) film functionalized with a citric acid molecule has been successfully fabricated by Electrophoretic Deposition (EPD) and thermal techniques, aiming to evaluate its suitability for optoelectronic devices. The thickness-controlled g-C3N4 film having a good mechanical property was successfully performed. The chemical stability and photostability of the citric-modified g-C3N4 films deposited on indium tin oxide (ITO) glass were investigated. New chemical links were clarified such that it could possibly become a bridge for enhancing charge transport. The modified samples exhibited a significant increase in their photocurrent response, reaching 25 μA/cm2 at a thickness of about 20 μm. Electrochemical impedance spectra (EIS) verified the enhanced conductivity, efficient charge transfer, and reduced electron-hole recombination rate. This research revealed a facile synthetic route and environmentally benign materials, thereby suggesting promising prospects for their application in the optoelectronic field.

Metal-free g-C3N5 photocatalysts with defect sites as efficient peroxymonosulfate activators for antibiotic removal in aqueous media

Nitrogen-rich graphitic carbon nitride (g-C3N5) has emerged as a promising and fascinating photocatalyst for tackling problems related to antibiotic pollution. Herein, porous O-doped g-C3N5 with N vacancy (g-C3N5-x-O) was fabricated via a facile two-step pyrolysis technique using 3-amino-1,2,4-triazole and oxalic acid as precursors. The sample modified with 2.0 mol.% oxalic acid (CN-2.0) exhibits a porous structure with a specific surface area of 249.78 m2. g−1, 2.77 times greater than that of pristine g-C3N5 (CN-0). In addition, the existence of O-doping and N vacancies in g-C3N5 framework not only promotes charge transfer properties but also suppresses photogenerated electron-hole recombination according to the results of transient photocurrent responses, photoluminescence and electrochemical impedance spectra. The CN-2.0 sample displays the highest photocatalytic activity, which eliminates 77.3% sulfamethoxazole (SMX, 20 mg. L−1) after 60 min irradiation under UV 365 nm light source. The addition of peroxymonosulfate (PMS, HSO5-) significantly accelerates SMX photodegradation rate as well as reduces the influence of pH solution during treatment process. The reactive oxygen species including •O2−, 1O2, SO4•−, •OH, h+ contribute to SMX removal. The efficient degradation of numerous antibiotic classes highlights the possible applicability of g-C3N5-x-O. Interestingly, the catalyst retains its high activity and stability even after four consecutive reuse cycles. The intermediates of SMX degradation were determined and plausible SMX degradation pathways were proposed. Toxicity assessments demonstrated that the overall toxicity of the solution decreased after treatment. This work provides a feasible strategy to design and modulate g-C3N5 photocatalyst activated by PMS for antibiotic removal in wastewater.

Enhancing LSCF-based air electrode durability: Insights into sulfur poisoning and air purification

The electrochemical performance of perovskite-type air electrodes in solid oxide cells is strongly affected by a trace amount of SO2 as the air impurity. The present work aims to study air purification efficiency in suppressing the degradation rate for the LSCF-GDC air electrode while operating under different SO2 concentrations. For this purpose, the electrochemical performance of symmetrical cells was evaluated using impedance spectra measured over 320 h and compared with intrinsic electrode degradation in synthetic air. Accordingly, the intrinsic degradation rate was measured at 0.05 mΩ cm2 h−1 while exposing the cell to synthetic air containing 10 and 100 ppb SO2, causing a severe increase to 0.17 and 0.30 mΩ cm2 h−1, respectively. Nevertheless, the calculated degradation rate under purified air containing 100 ppb SO2 was similar to the LSCF-GDC intrinsic degradation rate, representing the high practicality of filter material to adsorb SO2 species. Interpreting the impedance spectra using a distribution of relaxation times (DRT) and a complex nonlinear least squares fit (CNLS) revealed that the intrinsic degradation mechanisms were the limitation of dissociative surface adsorption of oxygen and charge transfer to the adsorbed oxygen. At the same time, inhibition of the O2 adsorption caused by the deposition of SrO, SO32−, and SrSO4 phases and increasing surface diffusion resistance for the adsorbed oxygen atoms were the rate-determining steps in SO2-containing synthetic air. Lastly, the effective suppression of degradation rate by gas purification indicates an extensive use of filter material to extend the lifespan of SOCs.

Impedance of nanocapacitors from molecular simulations to understand the dynamics of confined electrolytes

Nanoelectrochemical devices have become a promising candidate technology across various applications, including sensing and energy storage, and provide new platforms for studying fundamental properties of electrode/electrolyte interfaces. In this work, we employ constant-potential molecular dynamics simulations to investigate the impedance of gold-aqueous electrolyte nanocapacitors, exploiting a recently introduced fluctuation-dissipation relation. In particular, we relate the frequency-dependent impedance of these nanocapacitors to the complex conductivity of the bulk electrolyte in different regimes, and use this connection to design simple but accurate equivalent circuit models. We show that the electrode/electrolyte interfacial contribution is essentially capacitive and that the electrolyte response is bulk-like even when the interelectrode distance is only a few nanometers, provided that the latter is sufficiently large compared to the Debye screening length. We extensively compare our simulation results with spectroscopy experiments and predictions from analytical theories. In contrast to experiments, direct access in simulations to the ionic and solvent contributions to the polarization allows us to highlight their significant and persistent anticorrelation and to investigate the microscopic origin of the timescales observed in the impedance spectrum. This work opens avenues for the molecular interpretation of impedance measurements, and offers valuable contributions for future developments of accurate coarse-grained representations of confined electrolytes.

Experimental study on impedance dispersion characteristics and electrical resistivity of high temperature granite

Electromagnetic methods are widely used in geothermal exploration. The electrical resistivity and impedance dispersion characteristics of high temperature rocks are the basis for the inversion interpretation of electromagnetic responses from geothermal reservoirs. Alternating current impedance spectroscopy experiments on granite at different temperatures and water contents were carried out. The impedance spectrum from these tests show that the resistivity of both dry and wet granite is mainly caused by grain boundaries or microfractures, rather than the mineral grains. The resistivity of granite decreases dramatically with the appearance of water, and decreases with increasing temperature. When temperature increases from 25 °C to 150 °C, the resistivity of dry granite decreases from 5690–5812 Ω·m to 5519–5638 Ω·m, while that of wet granite decreases from 3123–3278 Ω·m to 2618–2736 Ω·m. The relationship between temperature and resistivity can be described by an empirical equation, in which the temperature coefficient of dry granite is about 2.8 × 10−4, and that of wet granite is about 1.7 × 10−3. It shows the resistivity of wet granite is more significantly affected by temperature than that of dry granite. A mixing model describing resistivity of wet granite was established based on the resistivity of dry granite and water. This mixing model can also take temperature into consideration. Even though the equivalent porosity of granite is quite small, the resistivity of granite can still be described by Archie's equation, which was initially developed for high porosity sandstone. The coefficients in Archie's equation for granite were calculated from experimental results, with a tortuosity factor a = 0.005 and a cementation exponent m ranging from 1.50 to 1.75.

Carbon nanotubes for optimizing response stability and speed of acrylate hybrid copolymers humidity sensor

AbstractCarbon nanotubes (CNTs) are one‐dimensional nanomaterials with a hollow structure, high specific surface area and excellent chemical conductivity, which show great potential for application in the field of humidity‐sensitive responsive materials and humidity sensors. In this paper, CNTs were composited with a hybrid copolymer (HAC) of octavinyl POSS/acrylate to prepare the hybrid copolymer composites HAC/CNTs and their humidity sensors, which demonstrated exceptional thermal stability and fast response speed. Among them, acrylic resin serves as a humidity‐sensitive material; POSS introduce a stable three‐dimensional cage skeleton structure to the material; and CNTs are used as conductive fillers, which further enhance the stability of the material, as well as improve the sensitivity and humidity‐sensitive response speed of the material. The experimental findings indicate that the HAC/8.0% CNTs composite material exhibits a remarkable sensitivity of 119.94 KΩ/%RH within the humidity range of 11%–95%RH. Compared with HAC, HAC/8.0% CNTs demonstrate a significant reduction in response/recovery time from 16.0 s/70.0 s to 0.8 s/80.0 s, representing a considerable improvement in response speed; the wet hysteresis is reduced from 0.88 %RH to 0.77 %RH; and the temperature change coefficient is reduced from 0.035 %RH/°C to 0.008 %RH/°C over the temperature range of 20–60°C, indicating superior stability against temperature variation. Meanwhile, the humidity response mechanism of HAC/CNTs was discussed by using complex impedance spectrum. The hybrid copolymer composites, HAC/CNTs, that were prepared in this study have tremendous potential in the development of advanced, high‐performance, and miniaturizable humidity sensing technologies.Highlights A hybrid copolymer composite humidity‐sensitive material HAC/CNTs is prepared. HAC/CNTs are compounds consisting of CNTs and POSS/acrylate hybrid copolymer. POSS improve the skeleton structural stability of acrylic resins. CNTs enhance the sensitivity and response speed of humidity sensor. The HAC/8.0% CNTs have higher response stability and faster response speed.

Disk flower-like structure of PANI Modulated electronic transport dynamics of Sr[formula omitted] ferrite

This study conducted a comprehensive analysis of the low frequency-based electrical characteristics of ferrite composites, exploring the influence of morphology on tunning and optimizing dielectric and conductivity relaxation. Specifically, composites of PANI: Sr CoxZnxFe12−2xO19 in 1:4 ratio by weight, with varying levels of substitution x = 0.0, 0.4, 0.8, 1.2, 1.6, and 2.0 were synthesized using the physical blending method. X-ray diffraction analysis of composites shows the existence of M-type hexagonal and PANI particles, along with some secondary phases in all synthesized samples. The morphology of composites revealed disk flower-like and hexagonal platelet-type structures of PANI and hexagonal ferrite, respectively. Substituting Co–Zn ions induced a non-linear increase in grain size from 0.781 to 1.566 μm, calculated using ImageJ software. The dielectric and electrical properties of composites were examined over the frequency range of 20 Hz to 2 MHz. The replacement of Fe ions with Co–Zn ions resulted in a non-linear variation in conductivity and is maximum for FP3 (1.33 × 10−2 Ω−1m−1) at 2 MHz. The complex impedance spectra deviated from an ideal Debye type and were modeled using an equivalent circuit encompassing resistances of grain boundaries and grains, grain capacitance, and a constant phase element. Modulus and impedance spectra analysis illustrated the contribution of both grain and grain boundaries in their respective relaxations. The simulation of impedance parameters in EIS software elucidated a substantial value of Cg = 290 μF for FP1, which aligned with the large-sized grain observed in FESEM micrographs.