Dynamic Impedance Spectroscopy Research Articles

MALE AND FEMALE PERSPECTIVES: EXPLORING THE USE OF PASSIVE BRAIN HEALTH TECHNOLOGY TO MEASURE GLYMPHATIC FUNCTION

Abstract Older adults’ (OA) research participation is essential to gain insights into the causes, progression, and potential treatments of Alzheimer’s Disease (AD). Brain health technology, such as the Glymphatic Function (GF) Monitor, has the potential to measure the progression of AD. The GF Monitor is a multimodal in-ear dynamic impedance spectroscopy and electroencephalogram (EEG) system worn during sleep and records physiological signals: photoplethysmogram (PPG), bioimpedance (BioZ), and acceleration. This study aims to understand OA perceptions and perceived benefits of passive brain health technology such as the GF Monitor. Six focus groups (3 female, 3 male) were conducted with OA (N=48) between June-August 2022 in The Villages, Florida. Domains assessed included concerns for developing AD, health technology perceptions, and preferences for data/outcomes visualization. Focus groups were transcribed verbatim, and content analysis identified salient themes. Across genders, motivation to participate in brain health technology research was influenced by concerns of family history of AD. Females expressed that using the GF monitor “is a small sacrifice to pay” for data-driven interventions and “preventative measures.” Males value “receiving easily digestible results” that allow them to monitor their cognitive health. Overall participants desire passive brain health monitoring to “stay active” and “remain independent” while aging in place. Passive technology has the potential to engage OA in research. Participants value prevention, maintaining independence, and receiving comprehensive results. The GF monitor has the potential to harness these wishes to monitor and receive translational brain health findings.

Mechanistic Study of Lithium Electrodeposition Using Dynamic Electrochemical Impedance Spectroscopy

Lithium metal batteries have increased energy density over standard graphite-based Li-ion anodes. However, Li metal anodes have difficulty forming stable passivation layer (called solid electrolyte interphase, SEI) leading to poor use of Li inventory. That is, LI metals require larger cathode loading, which reduces the energy density gain. A holistic approach to Li anode incorporation includes electrolyte design, mechanism understanding, and battery engineering. A factor that has not been fully appreciated is the nature of the Lithium metal itself, namely its SEI before incorporation into the battery device may affect the subsequent SEI formation. Here, we present a mechanistic study on lithium SEI formation on various lithium sources, as well as the Li cycling.We utilized dynamic impedance spectroscopy (dEIS) to probe the formation and evolution of the SEI during Li cycling of various Li sources. dEIS superimposes a multisine waveform atop the dc stimulus signal. After applying a sliding window FFT protocol that takes the complex ratio of the measured potential and current signals time-resolved complex impedance can be obtained. We will discuss the differences between the Li cycling profiles using Lipon (a glassy solid electrolyte) and a liquid electrolyte. We will relate the differences in cycling performance, particularly the SEI evolution to the surface chemistry of the as-received Li metal source.The US Department of Energy's Energy Efficiency and Renewable Energy Vehicles Technologies Office provided funding for this work under the US-German Cooperation on Energy Storage: Lithium-Solid-Electrolyte Interfaces program.

Effect of Film Thickness on the Kinetics of Lithium Insertion in LiMn2O4 Films Made by Multilayer Pulsed Laser Deposition for Thin‐Film All‐Solid‐State Battery Cathode Materials**

AbstractMulti‐layer pulsed laser deposition is a promising technique for producing thin films for solid‐state batteries. In this work, thin films are deposited with different numbers of pulses, leading to different thicknesses and grain sizes. We investigated “in operando” the kinetics of the transfer into films by means of dynamic impedance spectroscopy. This technique allowed us to resolve the contributions of the reaction mechanism and of the transport phenomena, as well as to quantify their equivalent resistances. Surprisingly, with increasing film thickness, the charge transfer resistance increases while the apparent diffusion coefficient of lithium increases, leading to a decrease of the mass transport resistance. It appears that both these effects are related to the dimension of the crystals in the thin films. These results provide new insights for an optimal tuning of the materials’ preparation in view of maximizing their electrochemical performances.

Dynamic Impedance Spectroscopy of Lithium Plating from Next Generation Electrolytes

The anode-free cells have emerged due to the need to maximize Li metal batteries' energy density. However, anode-free Li batteries suffer from short cycle life because of the lack of Li inventory at the anode. Freshly deposited Li metal anodes usually take hundreds of cycles to reach initial SEI stabilization optimum coulombic efficiency (CE) due to initial SEI stabilization and electrode activation. The anode-free cell design requires high Li metal CE over the whole cycling life, particularly during the initial activation cycles. A holistic approach to electrolyte design, mechanism understanding, and battery engineering is needed to fulfill these requirements. Here, we present a mechanistic study on lithium plating and stripping from next generation electrolytes.We conducted dynamic impedance spectroscopy (dEIS) to probe the formation and evolution of the SEI during Li plating and stripping on copper current collectors. dEIS superimposes a multisine waveform atop the dc stimulus signal, as shown by the lightly shaded curves in Fig 1 (top left). We applied a sliding window FFT protocol that takes the complex ratio of the measured potential and current signals obtained from Fig 1 (top right) and transforms it into complex impedance. We will discuss two Li platting systems, Lipon (an amorphous ceramic) and a liquid electrolyte with stabilizing additives. We observed drastic changes in the cells' impedance during plating and stripping, Figure 1 (bottom plots). We will show how the passivation layer's impedance continues to evolve during Li cycling and accounts for a significant amount of the overall cell resistance.The US Department of Energy’s Energy Efficiency and Renewable Energy Vehicles Technologies Office provided funding for this work under the US-German Cooperation on Energy Storage: Lithium-Solid-Electrolyte Interfaces program. Figure 1

Comprehensive studies of activity of Ni in inorganic sodium borosilicate glasses doped with nickel oxide

Sodium borosilicate (SBS) glasses containing nickel oxide were prepared by charge melting method, whereas their surface, structure and physical properties were investigated using a variety of complementary techniques. The chemical composition of the glasses was determined by standard analytical methods. Characterization of the glass structure was carried out by scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) and Raman spectroscopy before and after immersion of the glasses in HCl solution. SEM was utilized to observe the morphological changes of the samples surfaces upon immersion in HCl. The atomic ratio of the final result product was obtained by the X-ray photoelectron spectroscopy (XPS) analysis. The dynamic impedance spectroscopy (DIS) revealed the presence of various relaxation processes attributed to the addition of nickel oxide into the SBS glass structure, while the magnetic studies revealed antiferromagnetic properties related to the presence of the admixture. The experiments enable to study the effect of nickel oxide addition as well as changes caused by an increase of boron content and showed that the magnetic susceptibility of the glasses is correlated to the boron content, which is likely due to the increase of Ni2+ in octahedral coordination.

Research on water and heat management in the cold start process of proton exchange membrane fuel cell with expanded graphite bipolar plate

Water storage space and heat capacity are important factors affecting the cold start ability of fuel cell, and heat capacity is affected by materials. In the present study, the lumped static model and two-dimensional dynamic prediction model of the fuel cell with expanded graphite bipolar plates were established. The relationship between water storage space, heat production, heat capacity and the maximum temperature rise is analyzed based on the theoretical calculation model, and the cold start ability is also predicted. The calculation results show that the heat capacity of the bipolar plate is 1.3 J/K·cm2, which accounts for the largest proportion of 34% of all components. With the help of the heat generated by the air compressor, the reactor can be started in 100 s at −30 ℃ and 1.2A/cm2. The temperature difference in the reactor during cold start-up is about 2℃, which proves the reasonability of the isothermal assumption in the static model. The dynamic impedance spectroscopy experiment results show that the super cooled water icing during the cold start will cause the gas transmission impedance to increase rapidly, indicating that the icing mainly occurs at the pores or interfaces inside the catalyst layer and the gas diffusion layer during the cold start.

Estimation and correction of instrument artefacts in dynamic impedance spectra

Dynamic impedance spectroscopy is one of the most powerful techniques in the qualitative and quantitative mechanistic studies of electrochemical systems, as it allows for time-resolved investigation and dissection of various physicochemical processes occurring at different time scales. However, due to high-frequency artefacts connected to the non-ideal behaviour of the instrumental setup, dynamic impedance spectra can lead to wrong interpretation and/or extraction of wrong kinetic parameters. These artefacts arise from the non-ideal behaviour of the voltage and current amplifier (I/E converters) and stray capacitance. In this paper, a method for the estimation and correction of high-frequency artefacts arising from non-ideal behaviour of instrumental setup will be discussed. Using resistors, [hbox {Fe(CN)}_6]^{3-/4-} redox couple and nickel hexacyanoferrate nanoparticles, the effect of high-frequency artefacts will be investigated and the extraction of the impedance of the system from the measured dynamic impedance is proposed. It is shown that the correction allows acquiring proper dynamic impedance spectra at frequencies higher than the bandwidth of the potentiostat, and simultaneously acquire high precision cyclic voltammetry.

An insight into inorganic glasses and functional porous glass-based nanocomposites

Properties of dielectric and magnetic porous matrices and ferroelectrics porous glasses based nanocomposites were studied. Two types of modified and unmodified by iron oxides initial sodium borosilicate glasses and obtained from them porous matrices were investigated. The continuous pore structure was observed in porous glasses and additional in iron containing porous glasses inclusions of iron phase were stated. Depending on technological processes the pore diameters were estimated to be between 4 and 60 nm. The effect of structure and composition of investigated materials on electrical properties was discussed. Dynamic Impedance Spectroscopy measurements have revealed reversible. The dc conductivity and relaxation processes related to different types of transport of sodium and iron ions were discussed. The existence of ferroic KNO3 inside pores determines properties of nanocomposite based on porous matrices. The obtained porous dielectric and magnetic matrices can be applied as ferroics and multiferroeics elements.

Effect of the iron content on the structure and electrical properties of sodium borosilicate glasses: XRD, TEM, Mössbauer, FTIR and DIS spectroscopy study

The iron-bearing sodium borosilicate glasses with different contents of iron were prepared by the charge melting method and studied by XRD, TEM, FTIR, Mössbauer and Dynamic Impedance Spectroscopy techniques. An analysis and the transmittance spectra of two-phase sodium borosilicate glasses with different contents of iron oxide were carried out. A usage of the Mössbauer spectroscopy revealed differences between two-phase and porous glasses. In both cases Fe2+ and Fe3+ ions in octahedral and tetrahedral coordination were found, while in the two-phase glasses the significant contribution of magnetite was additionally detected. The activation energy associated with the relaxation processes determined from the electric modulus spectra was found to be in a range between 0.986 eV and 0.729 eV, which is close to the activation energy for dc conductivity. Two different conduction mechanisms were observed and their physical origin was explained. The hopping between two valence states of iron and the sodium ion conduction mechanism was additionally discussed.

Dynamic impedance spectroscopy of LiMn2O4 thin films made by multi-layer pulsed laser deposition

The kinetics of the reversible insertion of lithium ions assisted by aqueous environment into LiMn2O4 thin film fabricated by multi-layer pulsed laser deposition is studied using dynamic multi-frequency analysis (DMFA). This method allowed us to acquire time resolved impedance spectra in the range of 210 kHz to 11.5 Hz during cyclic voltammetry. The impedance spectra obtained comprises of two RC time constants (semi-circles) indicating that the reversible insertion process of lithium ions in LiMn2O4 thin films in aqueous media follows a two-stage intercalation process with the first stage as the (de)solvation step of the lithium ions and the second stage as a (de)insertion process with a concurrent change in the oxidation state of manganese. The temporal development of the kinetic parameters with the state of charge during the voltage sweep was investigated and reported in this work.

Understanding the origin of high corrosion inhibition efficiency of bee products towards aluminium alloys in alkaline environments

Various bee products were found to be efficient corrosion inhibitors of aluminium in different environments. In particular, bee pollen was found to be highly effective in alkaline electrolytes, yet its highly complex composition and possible synergistic interactions hinder determination of the compounds acting as active corrosion inhibitors. The main purpose of the following work is to investigate the effect of solvents used for pollen extraction process on the corrosion inhibition of AA5754 alloy in alkaline environment. Both infrared and mass spectroscopies as well as chromatographic analysis were used to determine differences in the composition of each obtained extract.The inhibition efficiency (IE%) of each extract was determined by using the potentiodynamic polarization and impedance studies. The highest IE%, exceeding 90% at 10 gL-1, was recorded for the water/ethanol extract. Most importantly, it has been found that the dichloromethane extract containing less polar compounds enhanced the corrosion rate at low bee pollen concentrations, and offered lower inhibition efficiency at the concentrations above 10 gL-1. The adsorption isotherms were drawn based on dynamic impedance spectroscopy in galvanostatic mode (g-DEIS), while the measurements carried out at elevated temperatures allowed the construction of Arrhenius plots and, consequently, the confirmation of the physical mechanism of adsorption.

Dynamic impedance spectroscopy using dynamic multi-frequency analysis: A theoretical and experimental investigation

Dynamic impedance spectroscopy is a powerful tool to investigate the temporal development of reaction kinetics in electrochemical systems, where the reactive species may undergo irreversible changes during the measurement. In this work we redefined dynamic impedance based on quadrature filters and underwent an analysis of multisine waveforms for the measurement of the dynamic impedance spectra during cyclic voltammetry. We proposed a quasi-triangular wave in order to minimize the interactions between the dc and ac signals. We showed on both simulated and experimental data that a proper design of the multisine wave allows accessing spectra with large number of frequencies and quasi-triangular waves with high values of scan rate. The key point is the frequency distribution of the multisine, optimized according to the implicit time variation of the system. Moreover, we quantify the non-linear artifacts as a function of both multisine amplitude and number of frequencies. Backed up by numerical simulation, we show how to recover simultaneously high quality impedance spectra and pristine voltammograms.

Clean electrochemical deposition of calcium carbonate to prevent scale formation in cooling water systems

Calcium carbonate (CaCO3) deposited in water systems leads to scale formation, decreases flow rate, reduces heat transfer and favors microbial proliferation of toxic bacteria such as Legionella. This issue may be solved by electrochemical deposition, without adding toxic chemicals. Therefore, we studied here the deposition of CaCO3 by electrochemical reduction of oxygen into hydroxide ions with stainless steel and titanium (Ti) working electrodes. Analysis was done using cyclic voltammetry, chronoamperometry, dynamic impedance spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy (EDX) coupled with X-ray diffraction (XRD). Results show that optimal formation of CaCO3 is done at −1.2 V with the stainless steel electrode and at −1.4 V for the Ti electrode. More negative potentials induce the formation of calcite. Using the Ti electrode, we found that aragonite is the major form (82 %), with only one capacitive loop. Using the stainless steel electrode at 1.2 V, we found 47 % of aragonite and 38 % of calcite. Overall, our findings demonstrate the feasibility of the electrochemical deposition of CaCO3 in cooling water systems, without the addition of any chemical.

Effect of anodization and annealing on corrosion and biocompatibility of NiTi alloy

Anodization of NiTi alloy was carried out on a biomedical grade NiTi alloy in phosphoric acid based electrolyte and subjected to post treatment by annealing. The morphology of anodized surface was porous with irregularly distributed pores and annealing resulted in the formation of nodules of titanium oxides on the porous structure. Studies showed that the corrosion potential shifted to more noble direction after annealing and there was one order decrease in corrosion current density compared to as-anodized surface. Cyclic potentiodynamic polarization behavior of mechanically polished and anodized surfaces was almost similar and both the surfaces exhibited positive hysteresis loop on reversing the scan direction. The formation of negative hysteresis loop in the case of annealed anodized alloy showed that the surface was capable of retaining its passive behavior even at higher potentials. Dynamic impedance spectroscopy studies carried out on annealed anodized surfaces showed that on increasing the potential from open circuit potential (ocp) to higher potentials (0.8 V), the thickness of the oxide layer also increased, but behaved as a leaky capacitor. In terms of bioactivity, the entire surface of the annealed sample was covered with hydroxyapatite after 12 days of immersion in Hanks' solution and the nickel released (370 ppb) was comparatively less than bare NiTi surface (633 ppb).

Electrical and mechanical characterization of two-phase alloys by means of scanning probe microscopy in dynamic impedance spectroscopy mode

Dynamic impedance spectroscopy, evaluated for measuring non-stationary systems, was used in combination with scanning probe microscope. Using this approach, localized impedance measurements in the AFM contact mode could be carried out. Additionally, impedance–force curves were made at each phase of investigated materials to illustrate the relation between impedance and the force applied to a probe. Therefore, correlation of electrical and mechanical properties with particular phases of investigated two-phase alloys was made possible. The materials used in this study were spheroidal graphite cast iron and 2205 duplex stainless steel, both materials with clearly defined phases having significantly different properties.

Dynamic Nanoimpedance Characterization of the Atomic Force Microscope Tip-Surface Contact

Nanoimpedance measurements, using the dynamic impedance spectroscopy technique, were carried out during loading and unloading force of a probe on three kinds of materials of different resistivity. These materials were: gold, boron-doped diamond, and AISI 304 stainless steel. Changes of impedance spectra versus applied force were registered and differences in the tip-to-sample contact character on each material were revealed. To enable comparison between materials and phases, a new standardization method is proposed, which simulates conditions of initial contact.

Carbon Nanotube-Epoxy Nanocomposites: Correlation and Integration of Dynamic Impedance, Dielectric, and Mechanical Analyses

This study focuses on the characterization of MWNT-epoxy composites for different MWNT concentrations of 0–7 wt% by correlating different dynamic analysis techniques, including DMA, impedance, and DEA. An optimum composition was established at 0.1 wt% MWNTs corresponding to the best MWNT dispersion which resulted in the formation of an optimum MWNT network. The addition of this low fraction of MWNTs in epoxy resulted in stiffening the molecular structure and suppressing certain molecular transitions, raising the dielectric constant especially in the low-to-medium frequency range, raising the electrical conductivity especially at the high frequencies, and increasing the electromagnetic shielding effectiveness. The 0.1% MWNT-epoxy nanocomposite switched the electromagnetic shielding behaviour from being a very effective absorber at low frequencies to being an effective reflector at high frequencies. Finally, the Nyquist plot derived from the dynamic impedance spectroscopy proved most useful at providing evidence of multiple size distribution of MWNT agglomerates.

Evaluation of cavitation erosion–corrosion degradation of mild steel by means of dynamic impedance spectroscopy in galvanostatic mode

Cavitation erosion and corrosion of mild steel was studied by means of a vibratory facility in 3% w/w NaCl solution. Dynamic Electrochemical Impedance Spectroscopy (DEIS) measurements were carried out in the galvanostatic mode to allow on-line monitoring of impedance parameters in cavitation failure. The results, based on an analysis of instantaneous impedance spectra, correspond to degradation under the influence of cavitation erosion–corrosion. It has been shown that a change of pseudo-capacitance corresponds to an increase in sample roughness, while the charge-transfer resistance determines changes in the corrosion rate under the combined mechanical and electrochemical factors.

Study of Formaldehyde and Carbon Monoxide Oxidation on Palladium in Sulfuric Acid by Dynamic Impedance Spectroscopy

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Dynamic Impedance Spectroscopy of Peroxide Reduction at a Pt(poly) Rotating Disk Electrode in 0.5 M H2SO4

not Available.