Electrical Conductivity Measurements Research Articles

Electrolyte effect in electrochemical exfoliation of graphite

Exfoliated graphene has been successfully synthesized using electrochemical exfoliation method followed by sonication of the graphite rod. Ammonium sulfate, sodium sulfate, ammonium oxalate, hydrogen peroxide, and ammonium persulfate were used as electrolytes. The effect of sonication time was studied for several products. The exfoliated graphene (EG) was characterized using XRD, Raman, FTIR, SEM-EDS, TEM and electrical conductivity measurement. The exfoliation using ammonium sulfate-ammonium persulfate as the electrolyte gives the highest mass-product, with a yield of almost 70%. Adding peroxide to the electrolyte reduces the mass of the exfoliated product. In addition, different sonication times results in different phenomena of particle size changes. The XRD data show that the EG has 2θ = 26.4° which is lower than its origin graphite. Raman data confirm that the EG has been obtained with the FWHM (G) value of 45–70 cm−1, and the resulting EG is a multilayer (2D peak). The O–H and C–C aromatic group has been assigned from FTIR spectrum. From SEM and TEM images, it was understood that the morphology of material is wrinkled, crumpled, and has a transparent zone, while from EDS data, it is found that the O/C value is in the range of 0.15–0.35. The electrical conductivity of EG reaches 52 S/cm.

Characterization of a Graphene Oxide-Reinforced Whey Hydrogel as an Eco-Friendly Absorbent for Food Packaging.

This study presents a structural analysis of a whey and gelatin-based hydrogel reinforced with graphene oxide (GO) by ultraviolet and visible (UV-VIS) spectroscopy, Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD). The results revealed barrier properties in the UV range for the reference sample (containing no graphene oxide) and the samples with minimal GO content of 0.66×10-3% and 3.33×10-3%, respectively, in the UV-VIS and near-IR range; for the samples with higher GO content, this was 6.67×10-3% and 33.33×10-3% as an effect of the introduction of GO into the hydrogel composite. The changes in the position of diffraction angles 2θ from the X-ray diffraction patterns of GO-reinforced hydrogels indicated a decrease in the distances between the turns of the protein helix structure due to the GO cross-linking effect. Transmission electron spectroscopy (TEM) was used for GO, whilst scanning electron microscopy (SEM) was used for the composite characterization. A novel technique for investigating the swelling rate was presented by performing electrical conductivity measurements, the results of which led to the identification of a potential hydrogel with sensor properties.

Hydrodynamics of a high Alpine catchment characterized by four natural tracers

Abstract. Hydrological processes in high-elevation catchments are strongly influenced by alternating snow accumulation and melt in addition to summer rainfall. Although diverse water sources and flow paths that generate streamflow in the world's water towers emerge from these two driving inputs, a detailed process understanding remains poor. We measured a combination of natural tracers of water at a high frequency, including stable isotope compositions, electrical conductivity (EC), and water and soil temperature to characterize hydrological processes in a snow-dominated Alpine catchment and to understand the diversity of streamflow sources and flow paths. Stable isotope composition of the sampled water revealed the prominence of snowmelt year-round (even during winter baseflow), and a strong flushing of the entire system with snowmelt at the start of the main melt period, sometimes referred to as the freshet, led to a reset, or return to baseline, of the isotopic values in most sampled water. Soil temperature measurements help identify snow-free periods and indicate sub-snowpack local flow, for example, in the case of rain-on-snow events. Water temperature measurements in springs can indicate flow path depth. EC measurements reflect the magnitude of subsurface exchange and allow for the separation of subsurface snowmelt contribution to streamflow from the contribution of stored groundwater. These insights into the details of streamflow generation in such a dynamic environment were only made possible due to intense, year-round water sampling. The sampled tracers are revealed to complement each other in important ways particularly because they were sampled during winter and spring, both snow-covered periods, the importance of which is a key implication of this work.

Polymer/carbon nanotube nanocomposites as temperature sensing materials

Multi-walled carbon nanotubes and high-density polyethylene (MWCNTs/HDPE) nanocomposite sheets with (1.0, 0.5, and 0.1) wt.% MWCNT were successfully prepared by coating the MWCNTs on the surface of the matrix particles (HDPE). The sample resistivities of the nanocomposites were investigated in relation to the temperature influence. Several findings could be drawn from these experiments: For instance, among all of the prepared MWCNT/HDPE nanocomposite sheets with (0.1, 0.5, and 1.0) wt. % MWCNT, the electrical resistivity of the 1.0 wt. % MWCNT/HDPE nanocomposite was 33.18 kΩ.m, demonstrating the best electrical conductivity. The resistivities of 0.1 wt. % and 0.5 wt. % samples were found to be 2594 and 372.23 kΩ.m respectively. Also, the measurements of temperature versus electrical conductivity revealed that the rise in temperature causes the electrical resistivity for the MWCNT/HDPE nanocomposites to increase due to the expansion of the distances between the conductive nanofillers (CNT), i.e., the sample resistivity increased under heating due to the thermal expansion of the polymer matrix. For example, the initial electrical resistivity for the 1.0 wt. % MWCNT/HDPE nanocomposite sheet decreased from 36.25 kΩ.m to 33.18 kΩ.m after the heat treatment. Besides, heat treatment could effectively improve the reproducibility of the MWCNT/HDPE nanocomposites. The reproducibility of the 1.0 wt. % MWCNT/HDPE nanocomposite was better than that of the 0.5 wt. % MWCNT/HDPE nanocomposite.

Preparation of some Complexes of Nickel(II) and Copper (II) Metals with Macrocyclic Ligand, 1,7,9,15 tetra-aza-3,5,11,13 difurano-cyclo-1,6,9,14-hexa-deca tetra ene

The complexes of Nickel(II) and Copper(II) metals have been prepared with the macrocyclic ligand-1,7,9, 15-tetra-aza-3, 5,11,13- - difurano-cyclo-1,6,9,14-hexa deca tetra-ene. The complexes of both the metals have been characterised by usual physico-chemical methods such as elemental analysis, measurement of electrical conductance, magnetic moment and electronic transition spectra of the complexes and I.R. spectral behaviour of both ligands and the complexes. All the complexes of both the metals have been found to be non-electrolyte, mono-meric, paramagnetic with octahedral geometryy . T he general molecular formula of the complexes have been found to be [M(L) (X)2] Where M= Nickel(II) and Copper(II) Cations, L= ligand and X= monodentate anions.

Potential application of electrical conductivity measurement for freshness assessment of tofu

Potential application of electrical conductivity measurement for freshness assessment of tofu

Pressure-independent through-plane electrical conductivity measurements of highly filled conductive polymer composites

Highly filled conductive polymer composites (CPCs) are widely used in applications such as bipolar plate materials for polymer electrolyte membrane fuel cells and redox flow batteries, electromagnetic interference shielding and sensors due to their useful electrical properties. A common method for determining through-plane electrical conductivities $\left(\sigma_{\rm tp} \right)$ of such highly filled CPCs applies a conductive carbon paper between electrodes and sample with application of external pressure to improve electrical contact. We show the pressure-dependence of the measured $\sigma_{\rm tp}$ can be eliminated by using a liquid metal such as the gallium-indium eutectic alloy (EGaIn) as contact material. Results indicate that EGaIn reduces contact resistances and cause three to five times larger $\sigma_{\rm tp}$ compared to measurements with carbon paper contacts and pressures up to 20 bar.

Constituent- and Composition-Dependent Surfactant Aggregation in (Lanthanide Salt + Urea) Deep Eutectic Solvents

Due to the ease of tailoring the physicochemical properties by simply changing a constituent or composition, deep eutectic solvents (DESs) possess widely varying capabilities for surfactant self-assembly that could depend on the surfactant headgroup charge. The self-aggregation process of three surfactants, sodium dodecylsulfate (SDS), cetyltrimethylammonium bromide (CTAB), and Triton X-100 (TX-100), dissolved in DESs composed of a lanthanide salt (Ln) and urea (U) is investigated. The role of the identity of the metal salt is assessed by using [La(NO3)3·6H2O] (La) and [Ce(NO3)3·6H2O] (Ce) and that of the composition is deciphered by systematically changing the mole ratio of the metal salt and urea in (La/U) DESs. The response to a fluorescence probe pyrene-1-carboxaldehyde along with electrical conductance and surface tension measurements is used to obtain the critical aggregation concentration (CAC). While the CACs in 1:3.5 (Ln/U) for SDS are significantly lower than that in water, the values are marginally higher for CTAB and TX-100. The CACs for all three surfactants are similar in 1:3.5 (La/U) and (Ce/U) DESs, implying that the identity of the metal in the salt is not so important. Increasing the urea composition in (La/U) DESs results in increased CAC for SDS and CTAB; however, a minimal decrease in CAC is observed for TX-100. From the temperature dependence of CAC, thermodynamic parameters, ΔGagg0, ΔHagg0, and ΔSagg0, of the surfactant self-aggregation process are estimated. These parameters reveal that while at a lower urea content, the SDS/CTAB self-assembly process is enthalpically driven, it becomes entropically favored at higher urea concentrations. The TX-100 self-aggregation in these DESs is found to be strongly enthalpically favored and entropically un-favored. These parameters are explained as a combination of passage of the solvophobic surfactant chain from the bulk DES to the aggregate pseudo-phase and differential orientation/organization of DES constituents around surfactant monomers and/or aggregates.

Studies on Electrochemical Properties of Polycarbazole Prepared Via Self-Support Polymerization and Self-Doping

Mixed glassy zirconium-tin phosphate, g-Zr0.64.Sn.0.36(HPO4)2.3H2O(g-ZrSnP), nano fibrous cerium phosphate, Ce(HPO4)2 2,9H2O(nCePf), and mixed glassy zirconium-tin phosphate / fibrous cerium phosphate nanocomposite membrane, [g-Zr0.64 Sn0.36 (HPO4)2]0.25 [Ce(HPO4)2]0.75 ..4.43H2O, were prepared and characterized. By chemical , x-ray diffraction (XRD), thermogravimetric analysis (TGA), and Fourier transform spectroscopy (FTIR), Zirconium tin mole ratio were estimated using (EDAX). Novel [g-Zr0.64 Sn0.36 (HPO4)2]0.25 [Ce(HPO4)2]0.75 / polycarbazole nanocomposite membrane was prepared via self-support polymerization of carbazole, which was promoted by the reduction of Ce(iv) phosphate present in the inorganic matrix. Possible explanation is nCePf present on the surface of the nanocomposite is attacked by carbazole, converted to cerium (III) orthophosphate(CePO4). The resultant polycarbazole was characterized by C,H,N analysis, SEM ,FT-IR. UV-Vis and electrical conductance measurements. From elemental (C,H,N) analysis, the amount of polycarbazole present in the composite found to be (2.15 % in wt.). Polycarbazole is considered as one of modern material used in solar cells, furthermore it has become an important material for optoelectronic applications in recent years. The dc conductivity of polycarbazole nanocomposite membrane at 280C (using RC-Circuit) found to be equal to 3x10-5 Scm-1, range of semi-conductors. We suggest self-doping occurred on polymerization, which is due to H+ present in (O3POH)2 groups of [g-Zr0.64 Sn0.36 (HPO4)2]0.25. The electrochemistry of resultant polycarbazole in acetonitrile solution for a range of concentrations from 1.06 x10-4 to 2.19 x 10–3 mol dm-3 was carried out using CV techniques. Investigation of its electrochemical properties affords insight into the mechanisms for their oxidation and reduction, therefore provides the basis for evaluating the stabilities of the material and for designing novel polycarbazole-derived materials with desired properties as well as new devices. That will be discussed.

Physical properties and dielectric response of (Gd, Pr)-dual doped samarium iron garnet

Samarium iron garnet, Sm3Fe5O12, co-doped with Gd3+ and Pr3+ ions, having the chemical formula Sm3-2xGdxPrxFe5O12 (0.0 ≤ x ≤ 0.8), were synthesized by the co-precipitation method. The structural study confirmed the cubic crystallization of the Sm3Fe5O12 phase in the addition of two secondary phases, α-Fe2O3 and SmFeO3. The variation of the lattice parameters and crystalline size indicated that both Gd3+ and Pr3+ ions were incorporated into the lattice. The elemental analysis confirmed the stoichiometry proposed for Sm3-2xGdxPrxFe5O12. The co-doping process of SmIG affected the absorbance of photo-radiations, making them possible candidates for transparent electrodes and optoelectronic devices. Energy band gap values were in the range of 2.921–3.004eV. DC electrical conductivity measurements studied the transport properties through which two activation energies were determined. The co-doping process affected the dielectric constants (ε′, ε″, tan δ), which reached a maximum value for x = 0.2. Dielectric relaxation was observed in the measurements, which could be due to the presence of oxygen vacancies as detected in XPS results. The Nyquist plots revealed that all the samples exhibited a negative temperature coefficient of impedance, where the arc of the semicircles decreased as the temperature increased from 413 to 743K. Also, the contribution of the resistance at high-frequency was related to the grains and grain boundaries. The ac conductivity mechanism followed the small polaron and the correlated barrier hopping models. In the temperature range between 333 and 583K, the prepared samples are promising for ion-conducting glasses and ionic crystals.

The study of ionic interactions of potassium iodide in the vegetable oil-N,N-dimethylformamide solvent by electrical conductivity measurements

The study of ionic interactions of potassium iodide in the vegetable oil-N,N-dimethylformamide solvent by electrical conductivity measurements

Maintaining Colloidal Stability of Polymer/Reduced Graphene Oxide Nanocomposite Aqueous Dispersions Produced via In Situ Reduction of Graphene Oxide for the Preparation of Electrically Conductive Coatings

Chemical reduction of graphene oxide (GO) in an aqueous polymer/GO dispersion invariably causes restacking and precipitation of reduced GO (rGO) sheets leading to spontaneous phase separation. This has been a significant challenge limiting the commercial production of aqueous polymer/rGO paints and coatings. In this study, we developed in situ reduction strategies to chemically reduce GO while maintaining the colloidal stability of an aqueous polymer/rGO dispersion. An aqueous polymer/GO latex was prepared using miniemulsion polymerization, which was subsequently reduced in situ using four different chemical reducing agents (hydroiodic acid, sodium borohydride, ascorbic acid, and hydrazine hydrate) to obtain colloidally stable polymer/rGO dispersions. The reduction of GO was confirmed using X-ray photoelectron spectroscopy (XPS), Raman, and X-ray diffraction (XRD). The colloidal stability of the reduced dispersions was maintained for over 6 months under ambient storage conditions. Stable polymer/rGO dispersions were drop cast to form nanocomposite films at ambient temperature. Finally, the electrical conductivity measurement of polymer/rGO films revealed the highest conductivity for hydrazine hydrate-reduced films (∼6.6 S m–1), which was marginally higher than for hydroiodic acid-reduced films (∼3.4 S m–1). The electrical conductivity of sodium borohydride- and ascorbic acid-reduced films was two orders of magnitude lower than for hydrazine hydrate- and hydroiodic acid-reduced films. Overall, the present results pave a path for the commercial production of colloidally stable aqueous polymer/rGO composite paints and coatings.

Revealing conductance variation of molecular junctions based on an unsupervised data analysis approach

For single-molecule electrical junction conductance measurements the data analysis can be a key challenge because of the large datasets and large stochastic variation in junction conformation from one junction formation cycle to the next. Here, a data sorting algorithm was used to analyze the most dominant conductance groups for four molecular systems. The algorithm was applied to data sorting of molecular junctions repetitively formed during STM current-distance (I-s) retraction traces. The data was recorded using the STM I(s) technique to form molecular junctions, which avoids direct contact between the gold STM tip and gold substrate. The algorithm has been employed to identify different dominant conductance features for two saturated molecular bridges and two conjugated molecular bridges. The former molecular targets featured thiolmethyl and isothiocyanate anchoring groups on each respective end of the polymethylene molecular bridge, while the conjugated molecular wires featured thiol anchoring groups. In each case the sorting algorithm is able to identify two main junction conductance groups related to differing molecular junction configurations. This algorithm is demonstrated to effectively sort and rationalize complex molecular junction formation datasets, where junction formation probably can be relatively low, and thereby shows potential to quantify hidden features in single-molecule charge transport data.

Influence of trace silicon addition on the strengthening precipitates, mechanical properties and stress relaxation resistance of Cu-Cr alloy

First-principles calculations and experimental studies, including transmission electron microscopy (TEM), electrical conductivity measurements, and yield strength and stress relaxation resistance tests, were carried out to determine the influence mechanism of trace Si on the precipitates and stress relaxation resistance of a Cu-Cr alloy. TEM observation and aging precipitation kinetic analysis showed that the addition of trace Si significantly refined the Cr-rich precipitates of the Cu-Cr alloy but did not appreciably promote the nucleation of the precipitated phase. The influence of trace Si on the Cr-rich precipitates was assessed in terms of the Si-Cr and Si-vacancy interactions. The first-principles calculations reveal that there exists a strong attraction between Si and Cr with an interaction energy of − 0.27 eV for the nearest neighbor, which could promote the formation of Si-Cr clusters in the early aging stage that serve as heterogeneous nucleation particles for precipitates and induce the refinement of body-centered cubic (bcc) Cr-rich precipitates, resulting in an increase in the yield strength of the Cu-Cr alloy. The strengthening precipitates of the Cu-Cr-Si alloy mainly consisted of fcc Cr-rich precipitates and bcc Cr-rich precipitates, the strengthening mechanisms of which were the dislocation shear mechanism and dislocation bypass mechanism, respectively. In terms of performance, the conductivity of the Cu-Cr alloy decreased with the addition of trace Si from 94.5% IACS to 92.5% IACS, the yield strength increased from 178 MPa to 193 MPa, and the stress relaxation rate decreased from 18.93% to 15.27%. The improvement in the stress relaxation resistance of the Cu-Cr alloy with the addition of trace Si was mainly attributed to the drag effect of the element on dislocation movement and the refinement effect of the element on Cr-rich precipitates.

Ba-doped Pr2NiO4+δ electrodes for proton-conducting electrochemical cells. Part 2: Transport and electrochemical properties

Materials based on barium-containing Pr2NiO4+δ are considered as promising air electrodes for protonic ceramic electrochemical cells owing to a wide range of attractive properties. In the present work, we thoroughly analyze the transport properties of Pr2NiO4+δ upon its chemical modification by Ba-doping. In detail, electrical conductivity and thermo-EMF measurements of Pr2–xBaxNiO4+δ (where x = 0, 0.1, 0.2, and 0.3) allow the effects of charge carrier concentration and mobility on overall transport to be determined depending on the chemical composition and defect structure. Lower polarization resistances of the Ba-containing electrodes when used in symmetrical cells with a BaCe0.5Zr0.3Y0.1Yb0.1O3–δ proton-conducting electrolyte confirm the functional benefits of barium as a dopant. However, the obtained experimental results can be explained not only by the better transport properties of barium-containing Pr2NiO4+δ (shown in the second part of our research), but also by the improved chemical and thermal compatibilities resulting in a good interface quality in an electrolyte/electrode couple (shown in the first part).

In-situ electrical conductivity monitoring of slag solidification during continuous cooling for slag recycling

Large volumes of steel slag are produced annually, leading to significant environmental protection and sustainable development issues. An online technology to monitor the solidification process of steel slag can assist in obtaining the right mineralogy to valorize these slags or render them harmless. For this purpose, we investigated the electrical properties and microstructural relationships of a CaO-Al2O3-SiO2-MgO (CASM) slag during cooling using an innovative setup. The electrical impedance was determined over the frequency range of 20 Hz to 300 kHz at two cooling rates, and the solidification behaviour was observed simultaneously by confocal scanning laser microscopy (CSLM). Four zones can be distinguished in the conductivity-temperature curves for the slag cooled at 10 °C/min, whereas only two distinct zones are visible at 100 °C/min. The liquid fraction of the slag has a significant impact on the slag conductivity during cooling. The electrical conductivity is, therefore, an accurate indicator of the solidification degree. Different theoretical and empirical models were evaluated on their ability to relate the bulk conductivity of the slag to the liquid fraction. The empirical Archie’s model proved to be the most suitable model for relating the bulk conductivity of the slag to the liquid fraction. In-situ electrical conductivity measurements during cooling can provide an online assessment of the slag solidification process, including indicating the appearance of solid precipitates, monitoring the growth of crystals, indicating complete solidification when no liquid phase remains, and indicating the cooling rate.

Evapotranspiration in Semi-Arid Climate: Remote Sensing vs. Soil Water Simulation

Estimating crop evapotranspiration (ETa) is an important requirement for a rational assessment and management of water resources. The various remote sensing products allow the determination of crops' biophysical variables integrated in the evaluation of ETa by using surface energy balance (SEB) models. This study compares ETa estimated by the simplified surface energy balance index (S-SEBI) using Landsat 8 optical and thermal infra-red spectral bands and transit model HYDRUS-1D. In semi-arid Tunisia, real time measurements of soil water content (θ) and pore electrical conductivity (ECp) were made in the crop root zone using capacitive sensors (5TE) for rainfed and drip irrigated crops (barley and potato). Results show that HYDRUS model is a fast and cost-effective assessment tool for water flow and salt movement in the crop root layer. ETa estimated by S-SEBI varies according to the available energy resulting from the difference between the net radiation and soil flux G0, and more specifically according to the assessed G0 from remote sensing. Compared to HYDRUS, the ETa from S-SEBI was estimated to have an R2 of 0.86 and 0.70 for barley and potato, respectively. The S-SEBI performed better for rainfed barley (RMSE between 0.35 and 0.46 mm·d-1) than for drip irrigated potato (RMSE between 1.5 and 1.9 mm·d-1).

Determination of carbon nanotubes penetration level into epoxy-woven glass fibre composite laminates manufactured with vacuum infusion process via electrical conductivity measurement

ABSTRACT This study investigates the carbon nanotube (CNT) penetration phenomenon in vacuum infusion (VI) process by means of electrical conductivity measurement. Effects of resin temperature, CNT content, and the processing technique on the overall composite laminate quality were investigated by monitoring electrical properties of composite sheets. Epoxy/woven glass fibre composites loaded with various CNT contents were also manufactured using compression moulding and vacuum bagging techniques for comparison purposes. VI was achieved at two different temperatures (25°C and 50°C) to study the effect of variation in viscosity on CNT penetration during infusion. The results showed that electrical conductivity measurement was a very effective tool to assess the CNT penetration state of composite laminates in VI method. Both the resistive and capacitive behaviour in composite laminates due to filtration of CNTs at higher CNT contents was observed. However, the CNT penetration was improved by increasing the temperature of epoxy/CNT mixture before the infusion.

Electrical conductivity measurement using a microfluidic chip and evaluation of vsiscosity by Walden's rule

AbstractIn this study, the electrical conductivity of low‐volume samples was measured using a prototype microfluidic chip with electrodes. We were able to show the difference of electrical conductivity in the samples of saline solution (0.9w/v% NaCl solution) with sucrose. The correlation between the electrical conductivity and the viscosity evaluated by the capillary method was shown. This correlation was shown that it is possible to evaluate viscosity based on the Walden's rule with our chip.

Biochar from Agro-Forest Residue: Application Perspective Based on Decision Support Analysis

The present work aims at (a) carbonizing agriculture biomass residue; (b) characterizing the obtained biochar; and (c) exploring its potential use for energy/resource recovery purposes. Six types of biomass were carbonized. The biochar was investigated through scanning electron microscopy with energy dispersive X-ray spectroscopy detector, thermogravimetric (TGA), proximate, ultimate, and Brunauer–Emmett–Teller analyses, along with bulk density, pH, electrical conductivity, and salt content measurements. The results served as input data for multi-criteria, multi-objective decision analysis of biochar, aiming to evaluate its best application prospective. The TGA identified two general stages: devolatilization (stage 2: 180–560 °C), and combustion (stage 3: 560–720 °C). The activation energy of stage 2 decreased with an increasing heating rate, but the opposite trend was observed for stage 3. The biochar CO2 adsorption suggested possible applications beyond energy conversion technologies. The decision support analysis revealed that peach stones, cherry stones, and grape pomace biochar achieved the most promising results for all evaluated applications (biofuel; catalyst; CO2 sequestration and soil amendment; supercapacitor) in contrast to colza, softwood, or sunflower husks char.