Electrical Conductivity Measurements Research Articles

Evaluation of Different Blending Methods to Obtain Copper Composites with Graphene Oxide

This study evaluated mixing methods for producing graphene oxide-reinforced copper matrix composites aiming for a better dispersion of graphene oxide in the composite, using powder metallurgy techniques. The compacted specimens were prepared by four different mixing processes that employed either a mechanical stirrer, rotary evaporator, tip ultrasound, or ultrasound process followed by mechanical stirring. Characterizations were performed using optical microscopy, scanning electron microscopy, X-ray diffraction, Raman spectroscopy, transmission electron microscopy, compression tests, Vickers microhardness, and electrical conductivity measurements. The results indicate that the combined method yields a more homogeneous microstructure and superior mechanical properties, while electrical conductivity was maintained at a level higher than that achieved by the other methods.

Recovery and Size-Tuning of Amorphous Silica from Geothermal Scales in Batangas, Philippines

Scale deposits in geothermal power plants are well-known potential sources of minerals. Extensive research in mineral recovery is crucial due to the considerable variability in scale composition and geochemistry based on location. Geothermal scales from Batangas, Philippines, were used to synthesize size-modified amorphous silica (SiO2) via sol-gel method. Initial analyses employing x-ray fluorescence spectroscopy (XRF), total dissolved solids (TDS), electrical conductivity (EC), and pH measurements confirmed that the scale is rich in silica and salts at neutral pH. Then, the effect of varying scale concentration, precipitation pH, and aging time on the particle size distribution of recovered amorphous silica were investigated. Dynamic light scattering (DLS) for particle size analysis (PSA) revealed that the sample with 2.5% (w/v) scale precursor in NaOH and precipitated until pH 10 had the lowest average cumulant diameter (1.66 μm). Moreover, the synergy of precipitation pH and aging time was found to significantly affect the polydispersity index and cumulative diameter of precipitated SiO2 based on 23 factorial ANOVA at 0.05 significance level. X-ray diffractometry (XRD), Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) confirmed that the precipitates were amorphous SiO2 with spherical morphology. This study proves the viability of utilizing geothermal scales from Batangas, Philippines for the synthesis of amorphous SiO2 with controlled particle size, which is a potential filler for composite materials.

DES/O microemulsion for solubilizing and delivering curcumin via the nasal administration to treat acute asthma

As a natural small molecule drug derived from turmeric, curcumin is known for its good biosafety and a range of beneficial effects, including anti-inflammatory, anti-spasmodic, antioxidant, antibacterial, anti-tumor, and neuroprotective effects. Even though, its insolubility in water and instability severely limit its bioavailability and clinical applications. The present study developed a deep eutectic solvent (DES) in oil microemulsion (DES/O-ME) system loaded with Cur for intranasal administration, aiming to enhance both the solubility and permeability of Cur to significantly increase its bioavailability. The project first constructed and screened the optimal choline chloride-based DES. Subsequently, the DES/O-ME system was prepared and optimized to achieve uniform particle size and stability using a pseudo-ternary phase diagram and electrical conductivity measurements. The resulting DES/O-ME system was thoroughly evaluated for its solubilization efficacy, permeability, mucosal cytotoxicity, and stability. Additionally, the therapeutic efficacy of the Cur-DES/O-ME was assessed in vivo using a murine model of allergic asthma. This comprehensive evaluation highlights the potential of the DES/O-ME system as a promising intranasal drug delivery platform to overcome the limitations of curcumin’s bioavailability and clinical application.

Comprehensive evaluation of TiO2 nanofluid stability: Insights from pH, EC measurements, and UV-Vis spectroscopy

This study delves into assessing the stability of different nanofluids containing TiO2 nanoparticles, employing either ethylene glycol (EG) or water as the base fluid. The results obtained will be applied to photovoltaic panels in future work, in particular to solve the cooling problems facing these systems, in order to improve their efficiency and durability. The nanoparticles, approximately 75 nm in size as determined by the Debye-Scherrer equation and X-ray diffraction (XRD), were utilized to formulate nanofluids at concentrations of 0.1 %, 0.3 %, and 0.5 % using a two-step method. To gauge the stability of these prepared nanofluids, practical investigations were conducted involving pH and electrical conductivity (EC) measurements, along with UV-Vis spectroscopy spanning the wavelength range of 200–800 nm. The findings reveal that nanofluids with 0.1 % and 0.5 % TiO2 in water demonstrated promising stability. Moreover, the absorbance levels of nanofluids containing 0.1 %, 0.3 %, and 0.5 % TiO2 in EG, as well as 0.3 % TiO2 in water, decreased with increasing settling time, as observed through UV-Vis spectroscopy analysis, consistent with prior research. Additionally, the study of pH and EC stability for 0.5 % TiO2 in water indicated satisfactory results.

High temperature thermoelectric properties of BaxSr2−xFeCoO6 double perovskites

Abstract In this study, environmentally benign BaxSr2-xFeCoO6 (BSFC) double perovskites are synthesized via solid-state reaction route for high-temperature thermoelectric applications. The crystal structure and morphology of the ceramic samples are analyzed using XRD and SEM, respectively. Rietveld refinement of XRD data confirms a cubic structure with Pm3̅m space-group. High-temperature thermoelectric measurements exhibits that substituting Ba for Sr in Sr2FeCoO6 increases the Seebeck coefficient (S) but at the expense of the electrical conductivity (σ). The highest Seebeck coefficient of 117 μV/K has been observed in Ba0.5Sr1.5FeCoO6 at 910 K. Temperature-dependent electrical conductivity measurements indicates a semiconductor-to-metal like transition in all samples, with BSFC (x = 0.1) achieving the highest conductivity of 4 × 104 S m−1 at ∼623 K. The thermoelectric power factor has been enhanced by over 50% with Ba substitution in Sr2FeCoO6. Electron transport in these double perovskites is found to follow the small polaron hopping conduction mechanism.

Preparation and Electrical Properties of Nanocomposite Based on Epoxy Resin and Core-Shell Polyaniline/Multi-Walled Carbon Nanotubes

Nanocomposites of epoxy resin containing various concentrations of carboxylated multiwalled carbon nanotubes (C-MWCNTs) and surface modified C-MWCNTs various concentration of both C-MWCNTs and core-shell nanoparticles were prepared. The physical, mechanical and electrical properties of prepared epoxy nanocomposites were investigated using experimental evaluations such as dynamic mechanical thermal analysis (DMTA), differential scanning calorimeter (DSC), and tensile strength measurements. The results of DSC tests revealed that the introduction of nanoparticles into the epoxy resin did not have much effect on the curing system, and by adding these nanoparticles to the epoxy resin, there is no need to change the curing system. However, the released energy during of epoxy curing show a 24% increase with the introduction of nanofiller into the epoxy matrix. The results of electrical conductivity measurements indicated a higher elastic dielectric constant for nanocomposites up to 200% incomparison with neat epoxy resin. The use of these epoxy nanocomposites in modern electrical and electro-optical industries is of great practical importance.

Sustainable biomass derived natural surfactant of soybean seeds in fly ash industrial waste utilization for carbon storage: Evaluation of environmental impact

The rising carbon emissions challenge global environmental sustainability and climate stability. This study aims to advance climate change mitigation by integrating fly ash and natural surfactant into CO2 sequestration strategies. Fly ash, a by-product of industrial processes, presents an opportunity for innovative reuse. By combining fly ash with a natural surfactant extracted from soybean seeds, both industrial waste management and greenhouse gas reduction can be addressed. The surfactant was characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, surface tension, and electrical conductivity measurements, confirming saponin presence with a critical micelle concentration of 0.3 wt%. Pressure decay studies revealed that a (5 wt% fly ash + NS) demonstrated the highest CO2 absorption, supported by microscopic analysis. Further research on optimizing reaction conditions and kinetics of mineralization could enhance this method’s efficiency and scalability for broader application.

An increase of the oncogenesis frequency is associated with the DAMPs accumulation and the killer cell subpopulations ratio change in patients with long-term post-COVID-19 syndrome

In patients with malignant lesions of the lungs and pancreas, the development of which was facilitated by the long-term post-COVID-19 syndrome (PCS), presence a significant increase (on average by 80%) in the serum content of the cytotoxic oligonucleotide fraction DAMP was found. High antigenic load due to the increase of DAMP contributed to the absorptive function growth and insufficient digestive function of neutrophils; decrease in the NADPH-catalase activity reserve in oxygen-dependent phagocytosis. An increase of CD16+ NK cells of innate immunity and an overexpression of CD8+ killer/suppressor T lymphocyte receptors of adaptive immunity in response to the suppressor coreceptors competitive action were revealed. These changes in cellular immunity were more pronounced in patients with malignant lung lesions and correlated with low serum conductivity. To predict the individual course of the disease, it is advisable to carry out screening measurements of electrical conductivity of blood serum and to determine the control points of innate and adaptive immunity changes in patients with comorbid pathology: PCS and an oncological process. In further studies, attention should be paid to the algorithm development of immunological and screening tests for the oncological diseases course prognosis and the treatment tactics effectiveness.

Advanced Nuclear Magnetic Resonance, Fourier Transform–Infrared, Visible-NearInfrared and X-ray Diffraction Methods Used for Characterization of Organo-Mineral Fertilizers Based on Biosolids

Biosolids from stabilized sludge present a high fertilization potential, due to their rich content of nutrients and organic matter. The intrinsic and subtle properties of such fertilizers may greatly influence the fertilization efficiency. In this sense, the utility, advantages and limitations of advanced characterization methods, for the investigation of structural and dynamic properties at the microscopic scale of slightly different formulations of fertilizers were assessed. For that, three formulas of organo-mineral fertilizers based on biosolids (V1, V2 and V3), having at least 2% N, 2% P2O5, and 2% K2O, were characterized by advanced methods, such as 1H NMR relaxometry, 1H MAS and 13C CP-MAS NMR spectroscopy, 1H double-quantum NMR and FT-IR spectroscopy. Advanced structural characterization was performed using SEM, EDX and X-ray diffraction. Four dynamical components were identified in the NMR T2 distribution showing that the rigid component has a percentage larger than 90%, which explains the broad band of NMR spectra confirmed by the distributions of many components in residual dipolar coupling as were revealed by 1H DQ-NMR measurements. SEM and EDX measurements helped the identification of components from crystalline-like X-ray diffraction patterns. To evaluate the release properties of organo-mineral fertilizers, dynamic measurements of classical electric conductivity and pH were performed by placing 0.25 g of the formulas (V1, V2 and V3) in 200 mL of distilled water. The content of N and P were quantified using specific reactants, combined with VIS-nearIR spectroscopy. Two release mechanisms were observed and characterized. It was found that V3 presents the smallest release velocity but releases the largest number of fertilizers.

Electrical Conductivity Measurements in Ternary SiO2–PbO–CaO Slags

Electrical Conductivity Measurements in Ternary SiO2–PbO–CaO Slags

Aliovalent Doping of Niobium and Tantalum Pentoxide as Potential Alternative Support Material for Fuel Cell Catalysts

AbstractAs the usually used Carbon Blacks (CB) as support materials in fuel cell catalysts are thermodynamically unstable, alternative supports with high chemical stability and electrical conductivity are to be found. After the investigation of Nb and Ta‐doped SnO2 in an earlier publication, which revealed interesting conductivity properties, we expanded our portfolio of mutual doping of elements of stable oxides into the oxides of the others by reporting here on the Sn, Hf and W‐doping as guests into the base oxides Nb2O5 and Ta2O5. The changes in unit cell parameters as indicators for the doping success were investigated in the doping range of x=0–10 mol % guest fraction. From a complete solubility of the guest ions in case of Hf and W‐doping in the base oxides to a limited solubility in case of Sn‐doping, a whole spectrum of different results was obtained. Additional insight came from UV/vis spectroscopic investigations in diffuse reflectance as well as electrical conductivity measurements.

Effects of lattice instability on the thermoelectric behavior of kagome metal ScV6Sn6

Kagome metal ScV6Sn6 has been a subject of interest due to the emergence of a first-order structural phase transition with intriguing charge density wave behavior below the transition temperature Tc ∼ 92 K. To explore the thermoelectric properties and provide experimental insights into the nature of the phase transition, we have carried out a combined study by means of the electrical resistivity, Seebeck coefficient, and thermal conductivity measurements on single crystalline ScV6Sn6. Pronounced features near Tc have been characterized by all measured physical quantities. In particular, the Seebeck coefficient exhibits a marked reduction as lowering temperature across Tc, attributed to an imbalance of the contribution from different type of carriers induced by the structural phase transition. From the examination of the electronic and lattice thermal conductivities, we obtained a confirmation that the observed enhancement at Tc is essentially caused by the change of the lattice thermal conductivity, demonstrating the primary importance of lattice distortions for the heat transport of ScV6Sn6. In addition, the lattice thermal conductivity above Tc was found to increase monotonically with temperature. We associated the peculiar phenomenon with lattice fluctuations, highlighting the essence of structural instability in the kagome lattice ScV6Sn6. These results add to the knowledge about the thermal transport properties in kagome materials with a hexagonal HfFe6Ge6-type structure.

Complex Permittivity Spectra of Granular Polymer Composites with Dispersed Ag-Coated Cu Flakes

AbstractConductive particle-containing granular composites with tuneable negative permittivity are being studied to improve the performance of electromagnetic devices, such as shielding materials. In this study, we investigated the relative complex permittivity and electrical conductivity of granular composites of polyphenylene sulfide (PPS) resin and Ag-coated Cu flakes in the radio- to microwave-frequency range and compared them with those of PPS/bare Cu flake composites. Electrical conductivity measurements revealed that the PPS/Ag-coated Cu flake composites have a lower percolation threshold (φc) than the PPS/bare Cu flake composites, whereas the electrical conductivity of the PPS/Ag-coated Cu flake composites in the percolated particle state was higher at the same particle volume fraction. At particle contents above φc, a low-frequency plasmonic state of conduction electrons was achieved in the percolated particle chains in both composites, and negative permittivity spectra were obtained. The percolated PPS/Ag-coated Cu flake composites had a negative permittivity up to a higher frequency than the percolated PPS/bare Cu flake composites. Furthermore, the Drude model was used to analyze the negative permittivity spectra of the composites in the percolated particle state. The plasma frequency of the composites with percolated Ag-coated Cu flakes was higher than that of the composites with percolated bare Cu flakes. Thus, coating Ag on Cu particles improved the conductivity of the composite, leading to negative permittivity up to higher frequencies. This study contributes to the enhancement of the negative permittivity achieved by granular composites, which is useful for microwave technology applications. Graphical Abstract

3D printing carbon from aqueous all aromatic polyimides

All-aromatic polyimides serve as versatile precursors for carbon formation due to their high aromatic content and repeating unit planarity, which synergistically enables pyrolysis to ordered carbon. Recent publications disclosed facile synthetic methods for additive manufacturing (3D printing) of all-aromatic polyimides using a pendant salt approach for ultraviolet-assisted direct ink write (DIW) additive manufacturing. This manuscript describes the introduction of pendant sodium sulfonate functionality to the poly(amic acids), and water-soluble all-aromatic polyimide precursors displayed suitable rheological properties for DIW at room temperature and vat photopolymerization (VP) at 50 °C. These aqueous solutions enabled the formation of microporous polyimide structures with a direct freeze-casting method and dense structures with gradual heating under inert atmosphere to 200 °C and subsequent thermal post-processing to 400 °C. Furthermore, polyimide 3D structures function as efficient carbon precursors when pyrolyzed at 2000 °C under inert atmosphere. Raman spectroscopy revealed carbonized 3D structures with characteristic graphitic and disordered carbon bands, which was indicative of polycrystalline, disordered glassy carbon. Furthermore, electrical conductivity measurements suggest opportunities for the formation of 3D conductive structures.

Fundamental study on measurement of soil pH and electrical conductivity in batch tests for the determination of soil-soil solution distribution coefficient

Soil-soil solution distribution coefficient, Kd, is used to understand the mobility of radionuclides in the soil environment. Soil pH and electrical conductivity (EC) are the important factors affecting soil Kd, but existing methods for Kd employed different conditions, as well, standard soil pH and EC methods varied in the test conditions. It would be desirable to measure both pH and EC using the same soil solution for Kd with portable meters (non-glass electrode type) that need only a small liquid volume. In this study, at first, we utilized portable pH and EC meters to examine effects of different conditions on measurements, i.e., the water/soil ratios, contact time and standing time. The results showed that portable meter measurements of soil supernatant after 1 h shaking and 1 h standing could provide comparable pH and EC values with other standard soil tests. Then measurements of pH, and EC up to 168 h were carried out, considering the Kd methods for radiocesium (Cs); only slight differences in these values were observed compared to the standard test method. Considering these results, further analysis was carried out on the correlation between soil Kd-Cs and pH and found a clear decrease of Kd-Cs at pH<5.

Assessment on the Effect of Rapid Urbanization on Groundwater Quality of Mirpur Area, Dhaka City, Bangladesh

Dhaka’s population is increasing day by day as more people are migrating towards Dhaka city for improving their level of living and for availing the cities amenities. Hence, this is creating pressure on the overall water quality of Dhaka city. The work intended to assess the groundwater standard in Mirpur area of Dhaka City, Bangladesh by analyzing eight (08) different physicochemical water quality parameters. In December 2023, six (06) separate water samples were taken throughout the dry season from six (06) sites across the area. The results showed that all sites had pH levels between 7.18 to 7.50, which is within acceptable ranges for drinking water quality and indicates neutral to slightly alkaline conditions. Total dissolved solids (TDS) continued to be far below safety limits (210–250 ppm), indicating that the water's mineral content was quite low. Electrical conductivity (EC) measurements fell within acceptable ranges (290-350 μS/cm), indicating suitable groundwater quality. Dissolved oxygen (DO) levels varied (3.7-9.3 mg/L), with some sites exhibiting satisfactory oxygenation while others raised concerns about potential water quality issues. Total hardness (TH) levels (330-900 mg/L) exceeded recommended limits (200-500 mg/L) at all sites, suggesting potential issues with water quality. However, chemical oxygen demand (COD) levels were minimal or zero (0-3 mg/L), indicating minimal organic pollution. Iron concentrations were generally low (0-0.05 mg/L). Total chlorine (TC) concentrations varied (0- 0.03 mg/L) across sites. In summary, the study emphasizes how crucial it is to continuously monitor and regulate the quality of groundwater in order to guarantee the sustainability and safety of water resources in the Mirpur region.

Effect of solvent and temperature on the micellization and thermophysical properties of cetyltrimethylammonium bromide

The Micellization is the fundamental phenomenon in colloid and surface chemistry which plays a pivotal role in a multitude of industrial processes, biological systems, and everyday applications. In this study, we investigate the micellization behavior of the cationic surfactant, cetyltrimethylammonium bromide (CTAB) within aqueous and ethanol–water mixtures across a temperature range. The electrical conductivity measurements unveil insights into the critical micelle concentration (CMC) and the degree of counterion dissociation (β) at each temperature. Notably, as ethanol content increases in the solvent, both CMC and β values exhibit a corresponding uptick. These findings enable the assessment of standard Gibbs free energy (ΔGmic0). Furthermore, our investigation extends to find out the thermophysical properties (viz., density, dynamic viscosity, and kinematic viscosity) assessments across varying ethanol compositions and temperatures. These metrics facilitate the calculation of activation energy for mixed systems. The implications of these results (data) could be useful for both the fundamental as well applied research, and promise valuable insights for future endeavors.

Simulation of Quench Rate by Jominy End Quench Test for 6082 Aluminium Alloys

In the present study, it is aimed to investigate the influence of quench rate on the hardness and electrical conductivity that obtained after artificial aging by using Jominy End Quench test method. The Jominy End Quench test bars were solution heat treated at 560°C for 3 hours. After solution heat treatment, water, spray, and air quenching medias were used in order to obtain different quench rates. After the quench, quench rate determination, hardness and electrical conductivity measurements were performed for three different quenching medias. Then, artificial aging heat treatment were applied to all samples at 180°C for 8 hours to understand the effect of quench rate on aging process. The relationship between quench rate, hardness and electrical conductivity have presented.

Enhanced gas sensing performance of ZnO and Pt-doped ZnO nanostructured films by chemical spray pyrolysis

This study focuses on the preparation and characterization of zinc oxide (ZO) and platinum-doped zinc oxide (Pt-ZO) nanostructured thin films using the chemical spray pyrolysis technique. Structural and morphological properties of the films were investigated via X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). To understand the semiconducting nature and carrier dynamics, UV-Vis spectroscopy, electrical conductivity measurements, and a static gas sensing system were employed. The films exhibited crystallization in the hexagonal wurtzite structure with a preferred orientation along the (002) plane. FESEM images revealed the presence of small bright particles, particularly abundant in the 5 wt% Pt-doped ZO thin film, indicating the presence of platinum catalysts. Electrical conductivity measurements confirmed the semiconducting nature of the films. Optical parameters such as band gap and absorption index were obtained from UV-Vis spectroscopy. Gas sensing performance towards liquefied petroleum gas (LPG) showed that the 5 wt% Pt-doped ZO thin film exhibited a high response (69.9) to a 50 ppm concentration of LPG at 350 °C. The gas response and recovery times were observed to be 8 s and 12 s, respectively. These results are attributed to interactions between LPG molecules and adsorbed oxygen species on the sensor surface. Platinum atoms on the oxide surface facilitate the formation of oxygen vacancies and the dissociation of oxygen molecules at low temperatures, leading to increased adsorption and reaction with LPG molecules. This results in significant changes in the sensor's resistance, thereby amplifying the sensor response. The findings demonstrate the potential of Pt-doped ZO thin films for practical gas sensing applications.

Measurement of electrical conductivity of human tissue: A feasibility study of a novel time-domain approach

A straightforward, non-invasive experimental approach to the extraction of electrical conductivity of human tissue using the transient electromagnetic field coupling between two loop antennas is presented. The main objective of this initial study is to demonstrate the feasibility of the new time-domain (TD) methodology. The designed loop antennas and the experimental setup with its instrumentation are described. The presented results show that the proposed method is capable of obtaining accurate values of the electrical conductivity of human tissue.