Impedance Plots Research Articles

One-pot synthesis of 2D-Ni-MOF from waste PET plastic in aqueous medium for selective electrooxidation of glycerol, ethanol, and methanol

This study investigates the electrochemical performance and selectivity of a nickel-based metal-organic framework (Ni-MOF) catalyst synthesized from waste PET plastic using a one-pot approach in aqueous media. The Ni-MOF electrode was evaluated for glycerol electrooxidation reaction (GEOR), ethanol electrooxidation reaction (EEOR), and methanol electrooxidation reaction (MEOR). Linear sweep voltammetry (LSV) revealed current densities of 30mA/cm² at 0.5639V for GEOR, 50.07mA/cm² at 0.35V for EEOR, and 45.73mA/cm² at 0.39V for MEOR, indicating superior catalytic activity. Nyquist plots showed lower charge transfer resistance (Rct) values of 11.0 Ω for GEOR, 2.79 Ω for EEOR, and 2.69 Ω for MEOR, confirming efficient electron transfer. Bode impedance plots demonstrated lower impedance for alcohol electrooxidation compared to oxygen evolution reaction (OER). Chronoamperometry (CA) tests indicated excellent stability with 75.72% glycerol conversion for GEOR and selectivities of 94% for glyceric acid, 65.59% for acetic acid in EEOR, and 70.54% for formic acid in MEOR. These results highlight the potential of Ni-MOF derived from recycled PET plastic for sustainable and efficient electrooxidation of C1-C3 alcohols.

Short and Long Range Ordering on Dielectric Relaxation of AgI doped Glass-ceramic

The dielectric relaxation process of amorphous glassy system, AgI - CdO -V2O5 -P2O5 - ZnO has been reported here. Electric modulus formalism has been carried out to explore the dielectric behavior of the as-prepared samples and the experimental results have been analyzed in the light of some theoretical models. Study of the nature of peak separation between imaginary components electric modulus and the complex impedance plots reveals that the present system with lower AgI content should have a tendency to exhibit long range order for the relaxation of charge carriers. On the other hand, the present system with higher AgI content exhibits a relaxation process, dominated by short range order of charge carriers. This relaxation process is found to be Debye type for AgI doping up to x = 0.20 and it becomes non-Debye type beyond that composition range.

The structural, mechanical, optical and dielectric properties of aminated PMMA-Ag-GO nanocomposite for coatings

The present study reports the synthesis and characteristics of an aminated PMMA-Ag-GO polymer nanocomposite (PNGAg) for coatings. The XRD diffractogram data indicated the presence of crystallinity in samples. The lattice strain of (002) planes and crystallite size were computed to estimate the number of graphene oxide (GO) layers. The homogenous dispersion of GO with silver (Ag) nanoparticles over the surface of the samples was verified by the SEM and EDAX tests. The thermal stability and interaction of fillers with aminated PMMA is confirmed by of TGA–DTA and FTIR analysis. Moreover, the substantial shift of FTIR bands supports the bonding of functional groups with Ag decorated GO and the stability of nanocomposite. The estimated mechanical properties like flexural strength and composite modulus (> 90 MPa) supported the applicability of PNGAg as coatings. The UV–Vis spectroscopy evidenced the characteristic absorption peaks of GO in line with range of UVC radiation in aminated PMMA. Along with high values of relative permittivity, the shift of loss tangent maxima to higher end with increase in GO concentration is attributed to greater number of interfaces. Owing to the functionalisation by naproxen along with dispersion of GO, contributed to MWS polarisation and hence strengthen the dielectric properties. As the concentration of GO rises from 0.1 mol% to 0.7 mol%, substantial shift of AC conductivity (i.e. 2.49 × 10−6 Scm−1 to 37.9 × 10−6 Scm−1) is observed. The high conductivity of PNGAg5 at 0.9 mol% GO suggests the presence of numerous layers, leading to increased interfacial polarization and a higher dielectric constant. In addition to that, the semi-circle in impedance plot and bulk resistance also supported the optimal dielectric properties of samples. As a whole, the results have shown that PNGAg nanocomposites are good coating materials for wide variety of devices.

Unveiling the potency of tetrahydropalmitine as a green anticorrosion material for 2024 aluminum alloy in acid-chloride environments

2024 aluminum alloy has garnered attention from researchers because of its numerous applications in the oil and gas, aerospace, and marine sectors. However, its constituent high Cu content (the primary alloying element) poses a significant challenge to its use, particularly in applications that demand high corrosion resistance. This is particularly troubling in oxygen-containing chloride systems. Herein, we developed a protection strategy for 2024 Al alloy in an acid-chloride environment (composed of 0.5 M NaCl and 0.25 M H2SO4) using natural tetrahydropalmitine (THP) isolated from Corydalis yanhusuo. THP was effectively characterized from its 1H NMR, 13C NMR, and FTIR spectra, and its anticorrosion potentials were methodically investigated by electrochemical, gravimetry and theoretical experiments. Upon the addition of THP to the test system, EIS measurements revealed a steady increase in the Nyquist semicircles, as well as the Bode impedance and phase angle plots, attaining an optimum inhibition efficiency of 91.5 % at 2.0 g/L THP. Tafel plots manifested mixed-type anticorrosion effects with dominant cathodic properties, ascribed to the ordered shielding effect of both the hydrogen evolution reaction and the oxidation of oxide-free ions. According to gravimetric corrosion assessment, the 2024 Al alloy mainly retained its protection over time in the presence of THP, exhibiting only minor decline in its protectability. This is attributed to the combined effect of stable oxide film formation and the adsorbed THP on the alloy surface. SEM afforded the proof of THP adsorption on 2024 Al while XPS offered clarity into its anticorrosion mechanism. Conceptual DFT parameters, molecular electrostatic potential and molecular dynamics simulation were used to comprehend the inhibition process of THP on Al surface. Generally, THP was proven to be a viable and sustainable bio-based anticorrosion material for the protection of 2024 Al alloy.

A Study of Acoustic Parameters of Transformer Oil Based on Its Water Content Utilizing a Single Ultrasonic Sensor

The health of a transformer is affected by several aspects, including water content in transformer oil. Researchers have introduced various techniques for measuring water content in transformer oil. In the case of acoustical measurement, researchers typically utilize two ultrasonic sensors to detect acoustical parameters. This study proposes a novel technique to characterize transformer oil based on its water content using a single ultrasonic sensor. This technique employs an indirect measurement approach, where a substrate separates the oil from the sensor. The echoes from measurements are observed and presented in terms of three acoustical parameters, i.e., the acoustic speed, acoustic impedance, and density. Based on measurement results, the acoustic speed of the samples is successfully calculated from the time of flight. and the thickness of the chamber. However, only four materials used as substrate 1, i.e., 3mm, 5mm, 8mm acrylic, and 3mm glass, successfully produce similar plots of acoustic impedance and density.

Insights into crystal structure, temperature-dependent magnetization and dielectric relaxation mechanism in Bi substituted samarium iron garnet

The single phase Sm3−xBixFe5O12 with x=0.0,0.2,0.4 and 0.6 samples are synthesized by solid-state reaction method. We have systematically studied the structural, morphological, temperature dependent magnetic and electric properties. All the samples crystallize in simple cubic crystal structure and belongs to Ia3‾d space group. The lattice constant and bond angle between Fe(a)−O−Fe(d) network is enhanced with Bi substitution. As a result, the ferrimagnetic transition temperature is also enhanced from 565K to 569K. We have examined the applicability of Bloch's and Cojocaru's laws to our temperature-dependent magnetization data and find that Bloch's T3/2 law is not suitable due to geometrical asymmetry, long wavelength excitation, and local atomic disorders. However, Cojocaru's law which accounts for the geometrical aspects, provides a better fit to our magnetization data. Further, the impedance plots at room temperature exhibit no relaxation which is attributed to the limited mobility of charge carriers. On the other hand, the high temperature impedance data represents dielectric relaxation at a particular frequency. This frequency is used to determine the relaxation time which is fitted to Arrhenius law and activation energy is evaluated. The activation energy lies in between 0.24−0.32eV which corresponds to the singly ionized oxygen vacancies. The conduction mechanism is analyzed with Variable range hopping model and the average hopping length and hopping energies are also determined for these garnet samples.

Er3+/ Yb3+ co-doped multi-functional silica phosphate glass films for integrated photonic applications

The multi-component silicate glasses co-doped with Er3+/Yb3+ were fabricated as thin films by the spin coating technique, which was analyzed for their optoelectronic response. Their monolith counterparts synthesized by the sol-gel route were used for the electrical studies. The films evidenced nanocristobalite phases at low levels of doping. The film micrographs explicated gas-trapped circular dimensions on the surface, due to the spreading of the sol on the substrate during the spin coating process. The glasses show a decrease in the number of polarizable non-bridging oxygen units with doping, reducing the polarizability and optical basicity. The films exhibit prominent green lasing in the downshifting process. The energy transfer from the Yb3+ ions endows the glasses with significant red lasing, suppressing the green emissions by the upconversion mechanism, which is also validated by the colorimetric chromaticity analysis. The gain cross-section of the glass doped with 1.5 mol% of Yb3+ is 23.3 × 10−20 cm2 in the S-band telecommunication domain. The glass film evidences its potential for NIR lasers, beyond a population inversion of 40 %, and a decreasing metastable lifetime of 6.6 μs. Beyond 1.5 mol% of the co-dopant Yb3+, energy transfer dominates, due to the dipole-quadrupole interactions, which has been corroborated by the Inokuti-Hirayama model. The conductivity in the glasses shows a decreasing trend with doping. The Randle's equivalent circuitry of the Nyquist impedance plots, predicts Warburg diffusion impedance that deters the space charge polarization. The consequential decrease in the dielectric constant and capacitance makes the glasses suggestive of multi-layer dielectric substrates in the integrated microelectronic technology for soldering of the printed circuit boards (PCB) that demand low signal losses.

Strong magnetoelectric coupling in novel Na0.5Bi0.5TiO3–BaFe12-2xCoxTixO19 multiferroic composite

Multiferroic composites of sol-gel synthesized Sodium Bismuth Titanate (Na0.5Bi0.5TiO3) and Co–Ti substituted Barium Hexaferrite (BaFe12-2xCoxTixO19; x = 0.0, 0.5, 1.0, 1.5 and 2.0) in the ratio 3:1 was synthesized through ceramic route. Successful formation of R3c rhombohedral and P63/mmc hexagonal phases corresponding to Na0.5Bi0.5TiO3 and BaFe12-2xCoxTixO19 respectively was confirmed from the XRD and Rietveld refinement pattern. The frequency and temperature dependence of dielectric constant and loss of the composite systems exhibited typical dispersion behaviour which could be understood using the Maxwell-Wagner model. Substituted samples showed enhanced dielectric behaviour where dielectric constant was observed to increase while loss tangent decreased. Using the Universal Jonscher's Power law (JPL), conductivition mechanisms of the composite systems were studied from the ac conductivity behaviour which revealed that the x = 0.0 sample followed Non-overlapping Small Polaron Tunnelling (NSPT) model while the remaining samples followed the Correlated Barrier Hopping (CBH) model. The complex impedance and Nyquist plot analysis showed the enhancement of resistive property in the x≠0 systems. Magnetic hysteresis loop measurements were conducted, and the associated parameters were determined with the assistance of the Law of Approach to Saturation (LAS). Favourable reduction in the magnetic anisotropy was observed indicating the disturbance of magnetic spin structure in the hexaferrite phase. The P-E loops established the novel room temperature multiferroic nature of the composite systems. Significant magnetoelectric coupling was detected at room temperature in all samples, with the x = 0.5 sample exhibiting the highest value of approximately 59.81 mV/cmOe. These desirable properties suggest that the composites may find future device applications as in magnetically tunable energy harvesting devices and self-powered magnetoelectric sensors in the future.

Investigating grain and grain boundary effects on charge transport and dielectrics in BaCoxAlxFe12-2xO19 nanoferrites

This investigation centres on the sol-gel preparation of M-type barium hexagonal ferrite (M-BaFe12O19) incorporating Co2+ and Al3+ as dopants. X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) were employed to assess the impact of dopants on the crystallographic structure and microstructure. The dielectric characteristics, electric modulus, impedance, and conductivity of the synthesized materials were evaluated at ambient temperature using an impedance analyzer. The structural analysis verified the presence of the hexagonal M-type crystal phase. Increasing dopant levels led to a reduction in lattice parameters, signifying unit cell shrinkage. FESEM imaging exposed the emergence of needle-shaped grains resulting from the doping process. Dielectric spectroscopy showed a decrease in both the dielectric constant (from 135.95 at x = 0.0 to 39.8) and the loss tangent (from 3.68 to 0.610) as dopant concentration increased. Conductivity exhibited relaxation at varying intervals, supported by the electric modulus spectra, which validated non-Debye relaxation behavior. Both relaxation time and AC conductivity diminished with higher dopant concentrations (from 0.000222 Ωm−1 to 0.000036 Ωm−1). The relaxation observed in conductivity and dielectric responses implies their contribution to the charge transport processes within BaCoxAlxFe12-2xO19. Electrochemical impedance spectroscopy (EIS) software was used to generate complex impedance plots, which aligned with the experimentally obtained impedance values for the synthesized compositions. Micrographs revealed a distribution of grains and grain boundaries that were consistent with calculated characteristics. This further substantiates the measured dielectric and electrical parameters.

Effect of surface roughness on corrosion behavior of AISI 4340 high-strength steel in sodium chloride solutions

In this work, an AISI 4340 high-strength steel alloy was surface machined to have four different grades of roughness (Ra). The impact of changing Ra on the corrosion of the steel alloy in 3.5% NaCl solutions after 40 min and 24 h was performed using various electrochemical techniques. The cyclic polarization experiments showed that an increase in Ra increases the steel corrosion via enhancing the corrosion current of the alloy. The electrochemical impedance plots also indicated that an increase in Ra reduces the corrosion resistance of the alloy by decreasing the diameter of the semicircle obtained by the Nyquist spectra. The change in potentiostatic current vs time measurements, which were obtained at −350 mV (Ag/AgCl), confirmed that pitting attack occurs and its intensity further increases with increasing Ra for all steel samples. An increase in immersion time also reduces the resistance to corrosion due to the iron dissolution from the surface of the steel alloy. After corrosion, the surface was analyzed using a scanning electron microscope and energy dispersive spectroscopy investigations.

Comprehensive analysis of Ni0.4Cu0.2Zn0.4Fe2-4xSn3xO4 nanospinel ferrites: Structural, electrical, and dielectric characterization through advanced techniques

This study extensively investigates Ni0.4Cu0.2Zn0.4Fe2-4xSn3xO4(x ≤ 0.10) nanospinel ferrites, denoted as NCZFe2-4xSn3xO4 NSFs, focusing on their structural, morphological, electrical, and dielectric characteristics. Utilizing various techniques such as SEM, EDX, TEM, XRD, and impedance analysis, the research confirms the cubic spinel structure and composition of the nanoferrites. The substitution of Sn4+ ions into Ni0.4Cu0.2Zn0.4Fe2O4 NSFs is explored, with a thorough examination of dielectric and electrical parameters up to 1.0 MHz and temperatures ranging from 20 to 180 °C. Complex impedance spectroscopy is employed to represent these parameters in a logarithmic 3D graph, revealing insights into ac/dc conductivity, activation energies, dissipation factor, dielectric constant, and loss. The study observes adherence to the power-law frequency rule in ac conductivity and highlights the impact of temperature and substitution ratios on grains, grain boundaries, and elemental composition. The investigation suggests a conduction mechanism involving electron and polaron hopping, and ionic contributions. Dielectric parameters show frequency-dependent changes that relate the dielectric constant to space charge polarization, inhomogeneous dielectric structure, impurities, and grains/grain boundaries. Cole-Cole impedance plots display semicircles dependent on substitution ratios and temperature, emphasizing contributions from grains, grain boundaries, and ionic mobilities. The Nyquist plots of Cole-Cole impedance functions further underscore substantial complexity in the conduction mechanism of the substituted NCZFe2-4xSn3xO4NSFs.

Temperature dependency of impedance, dielectric, and conductivity properties for Si-p/beta-FeSi2-n heterostructures created through facing target sputtering

To connect thermal dependency with Si-p/beta-FeSi2-n heterostructure efficiency, this work explored the impedance characteristics accompanied by dielectric and conductivity properties under different temperatures of 160–400 K. The Nyquist impedance plots for the heterostructures showed a semicircular arc that shrank as the temperature increased. These can be equivalently interpreted as a loop of single resistance paralleled to single constant phase element representing the heterostucture which also paralleled to inductive elements representing the inductive effect, serially connected to electrode resistance. The dielectric properties implied a shift in behavior for the relaxation process since donor-acceptor deionization occurred when the temperatures reached 320 K or higher due to shorter relaxation time and higher thermal dissipation. The conductivity properties indicate that the transport mechanism at 180 K or lower involves a prolonged transitional movement before transitioning into localized hopping at higher temperatures, corresponding to faster carrier movement. The relaxation and activation energy of the heterostructure reveal drastic transition of the energy from a low temperature of 160–240 K to a higher temperature of 320–400 K, where the electrical mechanism of the heterostructures become highly dependent on the temperature likely due to the high carrier density based on unevenly high activation energy.

La3+ ion doped Cd0.5C0.5LaxFe2-xO4 nanomagnetic materials for high-frequency device applications

The sol-gel self-combustion technique was applied to form Cd–Co-based La-doped (Cd0.5Co0.5LaxFe2-xO4) spinel ferrite nanoparticles. A series of six samples was synthesized by varying lanthanum content from x = 0.00 to 0.20. The structural characteristics of the prepared nanoparticles were carried out using X-ray diffraction (XRD) analysis. The (311) plane verified that the prepared nanomaterials are in the spinel phase in all observed XRD patterns. The crystallite size for each sample was determined using the Scherrer formula found in the 8.7–17.8 nm range, which is well correlated with the SSP model. The crystallite size decreased while the lattice constant increased from 8.38 to 8.45 Å with increasing La-content. The increasing trend in the bulk density and X-ray density has been analyzed with the effects of La3+ contents. In Fourier-transform infrared spectroscopy (FTIR), the high-frequency absorption band (υ1) was found from 522.15 to 541.06 cm−1, whereas the low-frequency band (υ2) varied from 419.80 to 414.31 cm−1. The surface morphology was carried out by scanning electron microscope (SEM), which positively correlated with XRD analysis. Impedance analyzer (IA) assisted in observing the variations in complex dielectric properties of the compound in the frequency range from 1 MHz to 3 GHz. The dielectric constant and impedance plots depicted that the nano ferrites have good dielectric properties in low-frequency regions due contribution of polarization. While conduction can be made possible in the high-frequency areas as observed through AC conductivity. The electric modulus revealed the relaxation phenomenon at high frequency due to the hopping of electrons at the octa and tetrahedral sites. The magnetic properties were investigated to study the impact of La3+ ion under the applied magnetic field from −15 to 15 kOe. The saturation magnetization, and magnetic remanence were found from 40.6 to 27.7 emu/g and 19.6 to 2.7 emu/g, respectively. The synthesized nanoparticles can be utilized for microwave applications and magnetic storage devices.

Dielectric response of activated carbon decorated NiFe2O4 nanohybrids prepared via self-igniting route

The NiFe2O4 (NFO)/activated carbon (AC = 0 %, 1 %, 1.5 %, 2 %) nanohybrids were prepared via the novel one-step self-igniting method. The X-ray diffraction (XRD) indexed patterns confirmed the formation of spinel single-phase NFO/AC nanohybrids. It was found that the crystallite size was reduced from 21.78 nm to 20.41 nm with the incorporation of AC in the NFO lattice. Moreover, the strain and porosity percentage was also reduced from 5.59 × 10−c to 3.04 × 10−c and 34.79 % to 31.53 % respectively, with the addition of AC in the NFO lattice. The Nyquist plots of impedance revealed that the resistance was primarily restricted by the contribution of grain boundaries. The dielectric properties increased with higher concentrations of AC. Specifically, for a concentration of 2 % AC, the dielectric constant and loss reached maximum value compared to pure NFO. This enhancement in dielectric properties makes it suitable for applications at high frequencies.

Investigation of structural, electrical, and magnetic variations of Ni-Zn-Co ferrites by substituting rare earth Ho3+ for high-frequency applications

The investigation of structural, magnetic, and electrical properties of Ni0.6Zn0.3Co0.1HoxFe2−xO4 (NZCHF, 0 ≤ x ≤ 0.2) ferrites, synthesized through the sol–gel autocombustion method, has been undertaken. The refined x-ray diffraction (XRD) analysis was performed for XRD data analysis using Fullprof Suite software and it confirmed a single-phase cubic spinel structure, with the determination of crystallite size, refinement parameters and lattice constants. The bulk density of the samples consistently remained lower than the x-ray density, with densities increasing proportionally to the enhancement of Ho concentration. FTIR analysis corroborated the presence of metal-oxygen bonds within the ferrite possessing a spinel cubic structure. 57Fe Mossbauer spectroscopy showed that the hyperfine magnetic field of tetrahedral (A) and octahedral (B) sites decreased with the substitution of Ho3+ ions that preferentially occupy the B site. The impedance analyzer and vibrating sample magnetometer (VSM) were utilized to measure the real and imaginary parts of the complex permeability and magnetic properties of the samples, respectively. Complex impedance plots were scrutinized to discern the contributions of grain and grain boundary resistances, providing insights into the electrical behavior of the ferrite samples. Furthermore, the introduction of Ho concentration led to alterations in other key properties of the ferrites, including coercivity (H c ), retentivity (M r ), anisotropy constant (K), and magnetic moment (μ B ).The impact of the rare-earth content on the magnetic features of the prepared NiZnCo ferrite microspheres was investigated by analyzing magnetic-hysteresis (M-H) loops, which showed soft ferrimagnetism. Concurrently, the dielectric constant and dielectric loss tangent of the studied samples exhibited a decrease with the rise in Ho3+ concentration. The expected reduction in tan loss in the prepared samples is attributed to the increase in ac resistivity associated with the higher Ho3+ content.

A Comprehensive Study of Cu/W Double Substitution in Strontium Manganate Ceramics for Some Device Applications

AbstractIn this communication, the synthesis and characterizations of modified strontium manganate (SrCu1/3Mn1/3W1/3O3) (SCMWO) by high‐temperature solid‐state method are reported. The structural analysis predicts a monoclinic structure with a crystallite size of 36.8 nm. The analysis of the Raman active modes reveals the presence of all the constituent atomic vibrations. The study of the ultraviolet–visible spectrum provides a bandgap energy of 1.71 eV, which may be suitable for photovoltaic applications. A Maxwell‐Wanger type of polarization effect is observed at low frequency while low dielectric loss makes the material suitable for energy storage devices. The study of the impedance plots reveals the negative temperature coefficient of resistance (NTCR) character. The activation energy increases with both frequency and temperature in the modified perovskite suggesting that conductivity of the sample increases and material characters are changing from dielectric to semiconducting. The symmetrical curves in the electrical modulus plots and shift toward higher frequency region agree with the results of the non‐Debye‐type of relaxation mechanism. The semicircular curves in the Cole–Cole plots confirm the semiconducting nature and are also well supported by the results of Nyquist plots. The studied material exhibits a semiconductor nature, which may be found suitable for energy storage device applications.

An electromechanical impedance measurement-based solution for monitoring fresh concrete maturity

This paper proposes an electromechanical impedance measurement (EIM)-based solution for monitoring concrete maturity that refers to concrete strength development at the early stage. A smart aggregate (SMA) that consists of a waterproofed piezoelectric patch is developed. The working principle is explained based on the impedance theory of an electromechanically coupled system. A finite element (FE) model of the EIM-SMA unit is established. The stiffness of the applied spring foundation is varied to emulate the concrete hardening process. The simulation results reveal that a peak located between 60 and 70 kHz in the impedance plot could be used as an indication to reflect the stiffness variation of the spring foundation. A 3D-printed mold is designed for rapid production of the EIM-SMA units. In the experiment, two sample EIM-SMA units are used to monitor fresh concrete maturity in the first 6 h after casting. The results of the two sample EIM-SMA units agreed well. The experimental results matched the simulation prediction. Compared to a bar-dropping test that is widely adopted at construction sites, the impedance evolution of an EIM-SMA unit is much smoother and has better monotonicity. In general, the proposed method has been proven to be a reliable solution to monitor the maturity development of concrete.

Four-dimensional electrochemical impedance spectroscopy: Role of microstructure on corrosion behaviour of Al-Si alloys additive-manufactured by laser powder bed fusion

Four-dimensional (4D) electrochemical impedance spectroscopy was applied to clarify the role of microstructures on the corrosion behaviour of Al-Si alloys additively manufactured by laser powder bed fusion in the immersion of NaCl solution. 3D complex impedance plots, comprising real, imaginary, and time axes, indicate that the impedance increases gradually at initial stage and then does not show apparent time variation. These behaviours, following surface morphology analysis, are strongly related to the remaining fine silicon particles on the surface due to the preferential Al dissolution, which suppress the further dissolution from underlying along with the protective oxide film formation.

Evaluation of Corrosive Properties of Hafnium Nitride Coating Over Titanium Screws: An In Vitro Study.

Background Varied surface coatings have been studied time and again in medical sciences. Whether general or dental, studying the performance of coatings aims to assess their potential to improve the durability and longevity of titanium implants, thereby advancing implant technology for enhanced patient outcomes. Various analytical techniques are utilized to assess the performance of the coating, providing insights into its effectiveness in preventing corrosion. The findings of this evaluation will contribute to our understanding of corrosion mitigation strategies for titanium implants and pave the way for the development of more durable implant materials. This article aims to evaluate the corrosion resistance of an innovative metal compound coating applied over titanium implants. Materials and methods In this study, a total of 20 medical-grade, commercially pure titanium screws were collected. The dimensions of the titanium screws were 2mm x 7mm. Around 10 of these commercially pure titanium screw samples were used as the control group. Hafnium nitride (HfN) (0.1 M) was mixed with 100% ethanol and stirred using a glass rod for about 48 hours. Then 10 of the implant screw samples were immersed in the prepared sol and sintered at 400o C for two hours. The HfN-coated samples were then used as the test group. The corrosion resistance of both groups was tested using electrochemical impedance spectroscopy and potentiodynamic polarization studies. The Nyquist, Bode impedance, and Bode phase angle plots were obtained and studied. Results Using the Stern-Geary equation, the corrosion current density was calculated. On analysis, these values indicated that the higher impedance in HfN-coated titanium screws showed higher mean corrosion potential (Ecorr = -0.452 V) andcorrosion current density ( icorr = 0.0354 μA/cm2) than the uncoated titanium screws. Conclusion It was concluded that the corrosion properties of HfN-coated titanium screws had higher impedance and consequently the highest corrosion resistance. This thereby provides a promising scope for further research of this novel metal coating for use in the biomedical sectors, specifically for dental implants.

Detailed investigation of the structural and electrical properties of ZnO/Fe3O4 nanocomposites

The nanocomposites with the formula (1-x)ZnO+xFe3O4 (x = 0, 0.01, 0.03, 0.05, 0.7 and 0.09) were prepared using the sonomechanical method, while the pristine ZnO and Fe3O4 were prepared using the co-precipitation technique. X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), and a high-resolution broadband impedance analyzer were used to examine the structural, microstructure, and dielectric properties of the investigated samples. XRD analysis assures the wurtzite hexagonal structure of ZnO for all nanocomposite samples. The FTIR showed the existence of a functional group of ZnO and Fe3O4. The ac conductivity, dielectric constant (ε′), dielectric loss (ε′), electric modulus, impedance, and Nyquist plot were studied as a function of frequency and at different temperatures. The results show that the small concentration of Fe3O4 affects the ac conductivity and dielectric properties. The Koops phenomenological theory and the Maxwell-Wagner interfacial model were used to analyze the observed dielectric dispersion. The analysis of modulus and impedance results indicated the existence of non-Debye relaxation and the involvement of both grains and grain borders in polarization. The impedance study reveals that just one semicircle is observed in all samples, indicating that the influence of grain boundaries is more significant than the contribution of grains.