Electrical Conductivity Of Metals Research Articles

Designing Bifunctional Oxygen Electrocatalysts Using Prussian Blue Analogue and Carbon Nanostructure Hybrids: Understanding the Role of Individual Components for Oxygen Reduction and Evolution Reactions

The incorporation and identification of active sites for OER and ORR is required for designing an efficient bifunctional oxygen electrocatalyst for low cost and high activity of electrochemical devices such as metal air batteries and regenerative fuel cells. In this work, we synthesized CoHCF/GO/f-CNT nanocomposite which showed excellent bi-functional activity with a low overvoltage of 0.8 V between the oxygen evolution reaction (E10 mA/cm 2) and the oxygen reduction reaction (E1/2). The specific functions of CoHCF and GO/f-CNT were described using hydrodynamic voltammetry measurements. For comparison, the pristine CoHCF and the composites with multiwalled carbon nanotubes (CoHCF/f-CNT) and graphene oxide (CoHCF/GO) were also synthesized and thoroughly characterised for physico-chemical and electrochemical properties. It was observed that CoHCF itself had poor ORR activity which increased on addition of GO/f-CNT. Electrochemical analysis suggested that CoHCF is primarily responsible for the OER activity in nanocomposites. The carbon nanostructure, due to strong metal support interactions (SMSI) and electrical conductivity helped in maximising the utilization of PBA active sites on the surface along with acting like a co-catalyst for ORR. The nanoscale geometries of the PBA and GO/CNT further enhanced the metal support and charge transfer interactions, thereby enhancing the activity. The findings of this study provide an insight for developing more effective PBA based nanocomposites for bifunctional OER/ORR electrocatalysis.

Microbial Community Composition and Diversity in Metal Sulfide Mine Water Systems

To understand the characteristics of heavy metal pollution and physicochemical properties caused by mining activities in mine water systems and the response of the microbial community to habitats with different contamination levels, this study selected different types of water (mining area wastewater, spoil heap area wastewater, dressing area wastewater, mine seepage water, and pond water) as the variables related to the mining activities in the water system of the Shizishan mining area in Tongling, Anhui Province. The pollution characteristics and physicochemical properties were compared, and the relationship between environmental factors and the microbial communities were analyzed. The results showed that the content of heavy metals, the physicochemical properties, and the structure and diversity of the microbial community of different types of water were significantly different in different mine areas, among which the most seriously polluted areas were the mining area, the spoil heap area, and the dressing area. There were significant differences in microbial community structure among different functional types of wastewaters, and the diversity and abundance of the microbial community in DW with the heaviest heavy metal pollution were weaker than those in the other four regions. PcoA analysis showed that samples of similar water types had similar clustering. Spearman correlation heat map analysis and canonical correlation analysis (CCA) indicated that heavy metal pollution, pH, electrical conductivity (EC), SO2-4, and chemical oxygen demand (COD) had the greatest effect on the microbial communities in the mine water systems. Moreover, this study found that Proteobacteria, Euryarchaeota, and Bacteroidetes dominated in mine water systems, and their potential use could be explored in the future. Our results provide a better understanding of the different types of water pollution characteristics in mine water systems and the key factors that determine the microbial community structure.

Exploring k5 students’ learning pathways regarding water’s electrical conductivity

ABSTRACT Background The educational research in the contemporary literature on the phenomenon of electrical conductivity of liquids is mainly linked to students in secondary and tertiary education and has shown that these students tend to ascribe liquids’ electrical conductivity to the presence of free electrons in them. Purpose The main purpose of this pilot study was to capture the learning pathways of k5 students, while teaching that the electrical conductivity of tap water is due to the presence of dissolved salts in it. Sample 24 students, from a k5 class in a Greek primary school, took part in the project. Design and methods A teaching intervention was designed and implemented to capture the students’ learning pathways during the teaching of the given phenomenon. The data was drawn from: a) an analysis of the video recordings of the conversations which took place during the implementation of the intervention, b) students’ written responses to pre- and post-tests. Results Initially, almost all the students considered tap water to be an insulator. The students’ prior knowledge about the electrical conductivity of metals, and their understanding of the nature of water as a material, were found to cause significant conceptual difficulties on their way to the intended conclusion. By the final step of the intervention, almost three quarters of students attributed the electrical conductivity of tap water to the solute salts it contains. Conclusion This study indicates that k5 students can attribute the electrical conductivity of tap water to the presence of dissolved salts in it. The conceptual obstacles the students seemed to encounter on their way to the desired conclusion were dealt with satisfactorily through the implementation of the teaching intervention. However, the teaching of elements of the microcosm seems to be prerequisites for the understanding the phenomenon in question, at this education level.

Liquid metal flexible electronics: Past, present, and future

Flexible electronics is one of the most overwhelming and promising technologies available today, receiving widespread attention from both academia and industry. As it continues to evolve, demands on flexible conductive materials are becoming increasingly prominent. Liquid metals (LMs), which combine the compliance of fluids with the electrical conductivity of metals, are excellent candidates among various material options for fabricating flexible electronics. Following more than a decade of development, LM flexible electronics has become a rather promising research field. This review aims to provide a comprehensive summary and interpretation of the typical progress in LM flexible electronics so as to promote further advancement in the area. First, modification strategies of LMs, such as oxidation and composite approaches (doped particles or mixed polymers), are systematically digested to improve their performances and increase the formability involved. Furthermore, we divide the LM flexible electronics into three major architectures (LM flexible electronics with channels, LM printed electronics, and LM/polymer flexible electronics) and introduce the core patterning methods for each type. In addition, we provide an overview of the representative applications of LM flexible electronics in the categories of soft sensors, biomedicine, flexible energy, electronic fabrics, etc. Finally, the current challenges and potential directions of LM flexible electronics are discussed. Overall, the past progress, current situation, and future outlook as outlined in full view in the present article is expected to inspire tremendous new opportunities for further fundamental research or practical explorations of LM flexible electronics in the coming time.

A concept of stretchable coaxial cable based on one-body Au nanonetworks

Recently, the demand for wearable electronics has sharply been increasing for diverse purposes. For the entire system to process enormous data simultaneously between the devices, the importance of stretchable interconnects with large bandwidth has been emphasized. However, achieving an appropriate attenuation level as well as stable transmission performance against elongation is still challenging. This report suggests the stretchable coaxial cable based on the one-body metal network, which is intrinsically stretchable and highly conductive. By multiple wrapping of the one-body metal network, excellent connectivity and electrical conductivity were realized. Its sheet resistance reached as low as that of the solid cylindrical metal. The low-loss cable was obtained through a simple fabrication procedure; its attenuation at 1 GHz remained under 0.011 and 0.033 dB/mm against 0% and 20% elongation, respectively. Also, it only experienced an insignificant change of the attenuation level (∼3.0%) during 100 stretching/releasing cycles, implying its feasibility of the dynamic connections in prospective applications.

2H-MoS 2 Modified Nitrogen-Doped Hollow Mesoporous Carbon Spheres as the Efficient Catalytic Cathode Catalyst for Aprotic Lithium-Oxygen Batteries

2H-MoS ₂ Modified Nitrogen-Doped Hollow Mesoporous Carbon Spheres as the Efficient Catalytic Cathode Catalyst for Aprotic Lithium-Oxygen Batteries

Prediction Models Based on Soil Characteristics for Evaluation of the Accumulation Capacity of Nine Metals by Forage Sorghum Grown in Agricultural Soils Treated with Varying Amounts of Poultry Manure.

Predictive models were generated to evaluate the degree to which nine metals (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) were absorbed by the leaves, stems and roots of forage sorghum in growing media comprising soil admixed with poultry manure concentrations of 0, 10, 20, 30 and 40g/kg. The data revealed that the greatest contents of the majority of the metals were evident in the roots rather than in the stems and leaves. A bioaccumulation factor (BAF) < 1 was calculated for Cr, Fe, Ni, Pb and Zn; BAF values for Co, Cu, Mn and Cd were 3.99, 2.33, 1.44 and 1.40, respectively, i.e., > 1. Translocation factor values were < 1 for all metals with the exception of Co, Cr and Ni, which displayed values of 1.20, 1.67 and 1.35 for the leaves, and 1.12, 1.23 and 1.24, respectively, for the stems. The soil pH had a negative association with metal tissues in plant parts. A positive relationship was observed with respect to plant metal contents, electrical conductivity and organic matter quantity. The designed models exhibited a high standard of data precision; any variations between the predicted and experimentally observed contents for the nine metals in the three plant tissue components were nonsignificant. Thus, it was concluded that the presented predictive models constitute a pragmatic tool to establish the safety from risk to human well-being with respect to growing forage sorghum when cultivating media fortified with poultry manure.

High-strength MXene sheets through interlayer hydrogen bonding for self-healing flexible pressure sensor

MXenes have attracted widespread attention due to their excellent mechanical properties, metal electrical conductivity, and other excellent physical and chemical properties. However, its excellent mechanical properties are often manifested in nanoscale monolayer MXene sheets. Due to the poor van der Waals interactions among the MXene layers during the molding process, MXene films at the macroscopic scale tend to exhibit poor mechanical properties such as brittleness and even fracture. Therefore, when MXenes with excellent electronic properties are used in devices, their ability to resist external damage is often poor, which makes the device performance easily degraded or even failed. We constructed MXene sheet with high mechanical strength via the interlayer hydrogen bonding effect using one-dimensional aramid nanofibers. MXene sheet is used for self-healing flexible pressure sensor, which shows high sensitivity (208.7 kPa−1), fast response time (10 ms) and recovery time (33 ms), excellent cycle stability (45000 cycles), and outstanding self-healing properties. The high-strength MXene sheet with 30 % ANF of the champion sensor exhibits superior tensile strength (65.5 MPa) and toughness (210.9 MJ/m3), which are ∼712 % and ∼ 3347 % of those of pure MXene, respectively. The MXene/ANF based pressure sensor realizes good resistance to complex external damages due to the combined effect of self-healable shell and the robust MXene sensitive layer, thereby meeting the development requirements of future smart wearable electronic devices.

Preparation of an electrochemical immunosensor based on a Cu/Cu2O-rGO@Au signal synergistic amplification strategy and efficient and sensitive detection of alpha-fetoprotein.

The effective amplification of the signal is the prerequisite for the ultrasensitive detection of electrochemical immunosensors. To quantitatively detect alpha-fetoprotein (AFP), we prepared a sandwich-type electrochemical immunosensor. Using a gold nanoparticles (Au NPs) modified glassy carbon electrode (GCE) as the sensing platform and Cu/Cu2O-rGO@Au as the signal label, differential pulse voltammetry (DPV) was used to achieve sensitive detection of AFP. We found that the nanomaterials can undergo electro-oxidation and electro-reduction reactions between Cu(I) and Cu(II) in a buffer solution of pH = 6.0. It is worth mentioning that the incorporation of metals into metal oxide substrates is a new strategy to combine the catalytic activity of metal oxides with the electrical conductivity of metals. Reduced graphene oxide (rGO), which is rich in oxygen-containing groups, can load more Cu/Cu2O and Au NPs and increase the conductivity. The modification of Au NPs makes them have better biocompatibility and conductivity. Under the best detection conditions, the prepared immunosensor realizes the specific and ultrasensitive detection of AFP. The detection range is 0.01-50 ng mL-1 and the limit of detection (LOD) was as low as 0.589 pg mL-1 (S/N = 3); meanwhile it also has good practical application ability. Therefore, this immunosensor provides an important means for the early screening and detection of AFP.

Large violation of the Wiedemann–Franz law in Heusler, ferromagnetic, Weyl semimetal Co2MnAl

The Wiedemann–Franz (WF) law relates the electronic component of the thermal conductivity to the electrical conductivity in metals through the Lorenz number. The WF law has proven to be remarkably robust, however violations have been observed in many topological materials. In this work, we report thermoelectric measurements conducted on Heusler, ferromagnetic, Weyl semimetal Co2MnAl which shows a drastic, temperature dependent violation of the WF law below 300 K. We then discuss our result in the context of known physical explanations for WF law violation. Both the magnitude and temperature dependence of the violation in Co2MnAl are extreme, indicating that there may be more than one effect contributing to the violation in this system.

Are the soils and vegetation of a forest close to tailings ponds affected by metals and arsenic?

This study aimed to determine the transfer of metals (Cd, Pb and Zn) and As to a Mediterranean forest close to five tailings ponds in Cartagena-La Union mining district (SE Spain). In addition, the effect of the rhizosphere of two native plant species, Olea europaea (OE) and Pistacia lentiscus (PL), on soil properties and chemical speciation of metal(oid)s was evaluated. Results showed there was no influence of the rhizosphere in the total concentration of metal(loid)s in soil, decreasing as Pb > Zn > As > Cd. Chemical partitioning revealed that only Cd and As can be considered hazardous, with a high percentage of these elements in the soil-labile fractions (20-40%). The accumulation in vegetal tissues was only high for Pb in PL roots, which makes it a suitable species for phytostabilization. Additionally, translocation factors showed transfer of Pb and Zn in OE, and Zn in PL to aerial parts, although no toxicity evidences for plants or animals were found. Finally, soil properties affected metal(loid)s accumulation in plants. The OE species was related to soil-labile metal(loid) fractions and pH, total N, organic carbon and silt content. The PL species were associated with immobilized metal(loid) fractions, sand content, electrical conductivity and total concentrations of As, Cd and Pb. Hence, mining activity has affected native adjacent soils, with accumulation of metals in plant species, although translocation was low, likely due to physiological strategies of the studied species to protect themselves against hazardous elements, and to the high soil pH, which limits metals' mobility.

Exploration of D022-Type Al3TM(TM = Sc, Ti, V, Zr, Nb, Hf, Ta): Elastic Anisotropy, Electronic Structures, Work Function and Experimental Design.

The structural properties, elastic anisotropy, electronic structures and work function of D022-type Al3TM (TM = Sc, Ti, V, Y, Zr, Nb, La, Hf, Ta) are studied using the first-principles calculations. The results indicate that the obtained formation enthalpy and cohesive energy of these compounds are in accordance with the other calculated values. It is found that the Al3Zr is the most thermodynamic stable compound. The mechanical property indexes, such as elastic constants, bulk modulus, shear modulus, Young’s modulus, Poisson’s ratio, and Vickers hardness are systematically explored. Moreover, the calculated universal anisotropic index, percent anisotropy and shear anisotropic factors of D022-type Al3TM are analyzed carefully. It demonstrates that the shear modulus anisotropy of Al3La is the strongest, while that of Al3Ta is the weakest. In particular, the density of states at Fermi level is not zero, suggesting that these phases have metal properties and electrical conductivity. More importantly, the mechanisms of correlation between hardness and Young’s modulus are further explained by the work function. Finally, the experimental design proves that D022-Al3Ta has an excellent strengthening effect.

Electron Transfer through a Natural Oxide Layer on Real Metal Surfaces Occurring during Sliding with Polytetrafluoroethylene: Dependence on Heat of Formation of Metal Oxides

Electron emission (EE) from real metal surfaces occurring during sliding contact with a polytetrafluoroethylene (PTFE) rider has been investigated using the thermodynamic data of metal oxides and the X-ray photoelectron spectroscopy (XPS) intensity ratio of oxygen/metal on the surfaces. EE was termed triboelectron emission (TriboEE). Rolled metal sheets of 18 types were used. The metal‒oxygen bond energy calculated from the heat of the formation of metal oxide, (D(M–O)), was shown to be a key factor in dividing the EE into two routes, the so-called Schottky effect and the tunnel effect, due to the surface oxide layer. The metals in periodic groups 4 (Ti and Zr), 5 (V, Nb, and Ta), and 6 (Mo and W) maintained higher values of D(M–O), while, moving down the groups, the TriboEE intensity increased, being ascribed to the former route. In groups 10 (Ni, Pd, and Pt) and 11 (Cu, Ag, and Au), the D(M–O) values decreased moving down the groups, but the TriboEE intensity increased significantly, which can be attributed to the latter route. Furthermore, with the increase in the electrical conductivity of metals, the TriboEE intensity became remarkably high, while the D(M–O) value fell rapidly and became almost constant. The XPS results showed that the dependence of the D(M–O) and XPS metal core intensity on the O1s intensity and the XPS intensity ratio of the O1s/metal core was different between groups 10 and 11 and groups 4, 5, and 6. It was concluded that, under the electric field caused on the real metal surface by the friction with PTFE, the electron from metals with small D(M–O) values predominantly tunnels the surface oxide layer as a surface barrier, while with large D(M–O) values, the electron passes over the top of the barrier.

On the electrical conductivity of metals with a rough surface

ABSTRACT We discuss surface roughness effects on the conduction of electrons in metals using both the quantal Kubo–Greenwood formalism and the semi-classical Fuchs–Sondheimer method. The main purpose here is to compare these methods and clarify a few subtle and widely misunderstood conceptual issues. One of such issues is concerned with the conditions under which the broken translation symmetry along a rough surface may be restored. This symmetry has often been presumed in existing work but not always with proper justifications. Another one relates to the physical meaning of a phenomenological parameter (denoted by p) intuitively introduced in the semi-classical theory. This parameter, called the specularity parameter or sometimes the Fuchs parameter, plays an important role in the experimental studies of surface roughness but has so far lacked a rigorous microscopic definition. The third issue arises as to the domain of validity for the electrical conductivity obtained in those methods. A misplacement of the domain may have resulted in erroneous analysis of surface effects in a variety of electrodynamic phenomena including surface plasma waves.

Linker Defects Triggering Boosted Oxygen Reduction Activity of Co/Zn-ZIF Nanosheet Arrays for Rechargeable Zn-Air batteries.

The poor electronic conductivity and low intrinsically electrocatalytic activity of most metal-organic frameworks (MOFs) greatly limit their direct applications as oxygen reduction reaction (ORR) electrocatalysts. In this work, it is reported that introduction of linker defects can effectively trigger the ORR activity of leaf-shaped zeolitic imidazolate framework (ZIF) by increasing the intrinsic activity of metal sites and electrical conductivity. Experimental results show that part of imidazole molecules is successfully removed from ZIF after a low-temperature thermal treatment without destroying its structure integrity, resulting in the formation of unsaturated metal sites and faster electron transport rate. Consequently, the ZIF with imidazole molecules defects (D-ZIF) exhibits a superior ORR activity than the pristine ZIF, possessing an onset potential of 0.86V and higher half-wave potential of 0.60V. Furthermore, the home-made Zn-air batteries with D-ZIF as air cathode exhibit high open-circuit voltage and well cycling stability. The developed linker-deficient modulation strategy can provide a new prospect to enable MOF-based electrocatalysts with efficient catalytic activity.

Quality of the groundwater of the Serra Geral Aquifer System of Santa Catarina west region, Brazil

Abstract: The objective of this study was to evaluate the quality of groundwater located in the west of Santa Catarina state, at Serra Geral Aquifer System (SGAS). It was selected 100 deep tubular wells distributed in urban and rural areas. 300 wells samples were collected at three different periods (march, september and november of 2014), which were submitted to heavy metal analysis (Cd, Cu, Fe, Mg, Mn, Pb and Zn), nitrogen compounds (NO2−, NO3− e NH4+), pH, electrical conductivity, and turbidity. The results showed high levels of Fe and Mn, 31% and 85%, respectively, with not agreement with Brazil Ministry of Health Decree 2.914 of 2011 for human consumption. For the Cd, Cu, Mg, Pb, Zn analysis and nitrogen compound the results obtained agreed with the levels established in the current Brazilian legislation. On the other hand, for Cu, NO2− e NO3− analysis, it was observed the relation between sample and soil occupation, where high metal presence was observed in the urban perimeter, showing the relation with human occupation (population density in urban and rural areas). The influence of the geological formation in the presence of metals (Fe, Mg and Mn) in the groundwater of the study region was also observed.

Conductivity of Metal–Dielectric–Semiconductor Structures Based on Ferroelectric Films

In this paper, we present the results of experimental studies of the frequency and temperature dependences of the electrical conductivity of metal–dielectric–semiconductor structures based on ferroelectric films of the Ba0.8Sr0.2TiO3 composition. In the temperature range of 290–400 K and the frequency range of 25–106 Hz, the conductivity was found to obey the σ ∝ f 0.76 law, which is characteristic of the hopping mechanism of charge transfer over states localized near the Fermi level. The density of these states, average distance and time of jumps are estimated.

On the sign of the chemical potential in the statistical mechanics of ideal boson and fermion gases

The chemical potential is one of those concepts in thermodynamics that physics students still find difficult to grasp. An indication of this is the steady stream of papers dealing with different aspects of the phenomenon that appear at regular intervals, particularly in those journals dedicated to the teaching of physics. At undergraduate level, the chemical potential is encountered primarily in (i) the area of statistical thermodynamics where it plays an important role in Bose–Einstein condensation and in the quantum theory of electrical conduction in metals, and (ii) the study of phase equilibria involving the transfer of particles. In the present communication we address an issue that can still present difficulties, namely the sign of the value of the potential as it appears in the statistical thermodynamics of boson and Fermi gases. Our aim is to show the physical reasoning underlying this sign as it varies with changing conditions.

Electrodeposition of Sn/SnO2 Composite Materials As Anode Material for Lithium Ion Batteries and the Micro-Mechanical Property

Sn/SnO2 composite materials are promising anode materials in lithium ion battery. Electrodeposition with supercritical CO2(sc-CO2) emulsified electrolyte (EP-SCE) is an effective method in controlling morphology (Ni [1], Cu[2], and Co[3]) and crystallinity (ZnO [4]and TiO2 [5]) of electrodeposited materials. Sc-CO2 is CO2 at temperature and pressure above its critical point, which is 304.1 K and 7.38 MPa. CO2 is non-polar, therefore, the solubility of metal salts and electrical conductivity are both very low in sc-CO2. In order to conduct electrochemical reactions, surfactants are used to form emulsified electrolyte. Co-deposition of SnO2 along with electrodeposition of metallic Sn can occur at the same time in a SnCl2 based electrolyte containing NO3 - ions [6]. The EP-SCE is expected to be effective in controlling concentration and properties of the SnO2 in metallic Sn film. In this study, Sn/SnO2 composite films are prepared by electrodeposition with supercritical CO2 (sc-CO2) emulsified electrolyte, and the mechanical properties in micro-scale are evaluated by compression test of micro-pilliars fabricated from the Sn/SnO2 composite film for practical applications. Details of the high pressure electrochemical apparatus can be found in a previous study [1]. The electrolyte is composed of 0.22 M SnCl2, 0.015 M HCl and 0.31 M (NH4)3C6H5O7. The current density applied is varied from 2.8 to 17.3 mA/cm2. For the EP-SCE, the surfactant is C12H25(OCH2CH2)15OH. 0.2 vol.% of the surfactant is used to form the sc-CO2 emulsions. 20 vol.% of CO2 at 343 K and 15 MPa under agitation are used to ensure the formation of a stable emulsion. Electrodeposition without the sc-CO2 emulsions at ambient condition (CONV) was also conducted to be used as a comparison. Surface morphology of the films prepared by EP-SCE were very smooth and compact, and the CONV films were porous. On the other hand, there is not much different in the average grain size between the EP-SCE and CONV films, which was about 50 μm for both the EP-SCE and CONV films. The oxygen content in the EP-SCE films can be up to 28.3 at.% by adjusting the electrodeposition parameters. Micro-pillars with a 20×20 μm2 cross-section and a height at 40 μm were fabricated by focus ion beam from the deposited films. The yield stresses were ranged from 10 to 40 MPa when the current density changed. Acknowledgment: This work was supported by JST CREST Grant Number JPMJCR1433. Reference: [1] Electrochim. Acta 55 (2010) 6469-6475 [2] Thin Solid Films 529 (2013) 25-28 [3] J. Electrochem. Soc. 162 (2015) D423-D426 [4] J. Phys. Chem. C 117 (2013) 25596-25603 [5] Electrochem. Commun. 33 (2013) 68-71 [6] J. Alloys Compd. 403 (2005) 335-340

Investigations of laser produced x-rays effect on the structural, morphological and electrical properties of Pb and Cu

X-rays produced by LASER have many applications in research and electronic industries. Current work is based on effects of x-rays on the structural, morphological and electrical properties of lead (Pb) and copper (Cu). In vacuum, KrF Excimer laser is irradiated on Cu and Pb targets. After that, Cu and Pb targets are exposed by these x-rays which are obtained from laser induced plasma. XRD showed that grain size of exposed samples is decreased as compared to unexposed samples. SEM analysis showed that the lead surface is more damaged as compared to Cu. Electrical conductivity of metals is decreased after exposure of x-rays, according to four-point probe technique. The present study will facilitate the effect of x-rays of Cu and Pb on different properties of material. The results thus obtained will be applicable in many industries including optoelectronics, biomedical etc.