Evolution Of Electrical Resistivity Research Articles

High Milling Time Influence on the Phase Stability and Electrical Properties of Fe50Mn35Sn15 Heusler Alloy Obtained by Mechanical Alloying.

Fe50Mn35Sn15 Heusler alloy, obtained by mechanical alloying, was subjected to larger milling times in the range of 30-50 h to study the phase stability and morphology. X-ray diffraction studies have shown that the milled samples crystallise in a disordered A2 structure. The A2 structure was found to be stable in the milling range studied, contrary to the computation studies performed on this composition. Using Rietveld refinements, the lattice parameter, mean crystallite size, and lattice strain were computed. The nature of the obtained phases by milling was found to be nanocrystalline with values below 50 nm. A linear increase rate of 0.00713 (h-1) was computed for lattice strain as the milling time increased. As the milling time increases, the lattice parameter of the cubic Heusler was found to have a decreasing behaviour, reaching 2.9517 Å at 50 h of milling. The morphological and elemental distribution-characterised by scanning electron microscopy and energy-dispersive X-ray spectroscopy-evidenced Mn and Sn phase clustering. As the milling time increased, the morphology of the sample was found to change. The Mn and Sn cluster size was quantified by elemental line profile. Electrical resistivity evolution with milling time was analysed, showing a peak for 40 h of milling time.

Electrical Resistivity and Phase Evolution of Fe–N Binary System at High Pressure and High Temperature

Partitioning experiments and the chemistry of iron meteorites indicate that the light element nitrogen could be sequestered into the metallic core of rocky planets during core–mantle differentiation. The thermal conductivity and the mineralogy of the Fe–N system under core conditions could therefore influence the planetary cooling, core crystallization, and evolution of the intrinsic magnetic field of rocky planets. Limited experiments have been conducted to study the thermal properties and phase relations of Fe–N components under planetary core conditions, such as those found in the Moon, Mercury, and Ganymede. In this study, we report results from high-pressure experiments involving electrical resistivity measurements of Fe–N phases at a pressure of 5 GPa and temperatures up to 1400 K. Four Fe–N compositions, including Fe–10%N, Fe–6.4%N, Fe–2%N, and Fe–1%N (by weight percent), were prepared and subjected to recovery experiments at 5 GPa and 1273 K. These experiments show that Fe–10%N and Fe–6.4%N form a single hexagonal close-packed phase (ɛ-nitrides), while Fe–2%N and Fe–1%N exhibit a face-centered cubic structure (γ-Fe). In separate experiments, the resistivity data were collected during the cooling after compressing the starting materials to 5 GPa and heating to ~1400 K. The resistivity of all compositions, similar to the pure γ-Fe, exhibits weak temperature dependence. We found that N has a strong effect on the resistivity of metallic Fe under rocky planetary core conditions compared to other potential light elements such as Si. The temperature-dependence of the resistivity also revealed high-pressure phase transition points in the Fe–N system. A congruent reaction, ε ⇌ γ’, occurs at ~673 K in Fe–6.4%N, which is ~280 K lower than that at ambient pressure. Furthermore, the resistivity data provided constraints on the high-pressure phase boundary of the polymorphic transition, γ ⇌ α, and an eutectoid equilibrium of γ’ ⇌ α + ε. The data, along with the recently reported phase equilibrium experiments at high pressures, enable construction of a phase diagram of the Fe–N binary system at 5 GPa.

Development of an Automated Experimental System for Thermomechanical and Electrical Characterization of NiTi Shape Memory Alloys

BackgroundComprehensive datasets quantifying the coupled thermo-mechanical and electrical properties of shape memory alloys (SMAs) are lacking, as are standardized techniques for robust characterization. This hampers accurate modeling and design of SMA-based components. Objective: This work develops an automated experimental system to enable simultaneous measurement of stress-strain-temperature behavior and electrical resistivity evolution in NiTi SMA wires under controlled stress conditions. Methods: Customized test frames apply precise mechanical stresses while allowing for in situ electrical measurements and infrared imaging during complete thermal cycling protocols. Specialized instrumentation including a Keithley 2002 multimeter, Agilent E3631A programmable power supply, and FLIR A615 thermal camera are integrated with LabVIEW-based software routines for complete automation of the characterization process. Rigorous metrology principles are implemented throughout the measurement procedure to improve accuracy, repeatability, and consistency compared to prior manual techniques. Results: Extensive datasets are generated which reveal pronounced stress-dependencies in key SMA material parameters including transformation temperatures, recoverable strain, and electrical resistivity. A 3D regression model describes the comprehensive relationship between resistivity, temperature, and applied stress across the entire characterization domain. Conclusions: The automated measurement framework and methodology establishes a foundation for high-fidelity, reliable acquisition of coupled SMA property data. This will enable more accurate modeling and design of components and systems incorporating SMA actuation or sensing functions.

Volcanic monitoring of the 2021 La Palma eruption using long-period magnetotelluric data

Between September and December 2021, the first subaerial volcanic eruption in the Canary Islands in 50 years took place on the island of La Palma. Since November 2021, we have been conducting a long-period magnetotelluric (MT) monitoring experiment at a site located 2.4 km east of the volcanic cone. Having continuously recorded data since then, the obtained dataset shows significant changes in resistivity over the fourteen months following the eruption: more than ± 20% in apparent resistivity and ± 2 degrees in phase. These temporal variations in electrical resistivity, recorded continuously using long-period MT during both the syn- and post-eruptive stages, have not been reported to date, making this dataset unique. Four estimated impedances have been selected as representatives of the major temporal changes observed and inverted to generate new 3-D resistivity models. The results provide novel key information on the spatiotemporal evolution of the subsoil's electrical resistivity, enabling the characterization of a set of structures acting as preferred magmatic fluid pathways. Therefore, our study highlights the strong potential of MT as a volcanic monitoring tool and provides new insights about the evolution of the fluid pathways during the post-eruptive stage. These findings enhance our understanding of the magmatic system and may contribute to volcanic hazard mitigation in the future.

A study on the hydration of calcium aluminate cement pastes containing silica fume using non-contact electrical resistivity measurement

In this study, a non-contact electrical resistivity method is employed to investigate the hydration process of calcium aluminate cement (CAC) pastes incorporating silica fume (SF) at an early age. The CAC-SF pastes have a water-to-binder ratio (w/b) of 0.6 and a replacement of SF for CAC at 0, 5, 10, and 20% (by weight of the binder). The pastes are tested for electrical resistivity, thermal analysis (internal temperature), setting time, and compressive strength, and the hydration products of the pastes are also examined. The results indicate that the evolution of electrical resistivity is closely related to the hydration process of the CAC pastes, and the conversion stage is closely associated with the setting time of pastes. As the increase of SF replacement, the hydration process of CAC pastes was accelerated within 24 h, and the development of compressive strength was hampered at an early age but increased later. SF replacement inhibits the conversion of metastable CAC hydrates (CAH10 and C2AH8) to C3AH6 through filling, seeding, and reacting with CAC, thus reducing the heat of hydration.

Evolution of electrical resistivity and NMR during early-stage maturation of an organic-rich chalk

This paper studies the changes in the electrical resistivity of an organic-rich source rock chalk containing a Type-IIs kerogen during early-stage maturation of the kerogen. As bitumen is generated during maturation, the chalk changes from water wet to a complex mixed-wet pore system, with the micritic pore space remaining water wet while the bitumen expelled into the macro pores converts some pores to oil wet. This mixed-wet system results in non-Archie electrical behavior with pronounced curvature of the I-Sw curve. We find that this curvature is well fit by connectivity theory. The connectivity theory parameters are determined both on native state core and from artificial laboratory pyrolysis which generates bitumen. NMR is used to distinguish the brine in micritic, water-wet pore spaces from that in the intergranular, mixed-wet pore spaces, from which the observed connectivity parameters may be independently estimated. Comparison between electrical resistivity and dielectric logs show that the connectivity parameters match the laboratory results over a calcareous section more than 300 m thick.

Electrical transport and magnetic properties of the triangular-lattice compound Zr[formula omitted]NiP[formula omitted

We report the first investigation of the electrical and magnetic properties of the triangular-lattice compound Zr2NiP2 (space group P63/mmc). The temperature evolution of electrical resistivity follows the Bloch–Grüneisen–Mott law, and exhibits a typically metallic behavior. No transition is visible by both electrical and magnetic property measurements, and nearly no magnetization is detected (M0<0.002μB/Ni) down to 1.8 K up to 7 T. The metallic and nonmagnetic characters are well understood by the first-principles calculations for Zr2NiP2.

Experimental and numerical analyses of soil electrical resistivity under subfreezing conditions

The engineering behavior of frozen soils is critical to the serviceability of civil infrastructure in cold regions. Among various geophysical techniques, electrical resistivity imaging is a promising technique that is cost effective and provides spatially continuous subsurface information. In this study, under freeze–thaw conditions, we carry out lab–scale 1D electrical resistivity measurements on frost–susceptible soils with varying water content and bulk density properties. We use a portable electrical resistivity meter for temporal electrical resistivity measurements and thermocouples for temperature monitoring. Dynamic temperature-dependent soil properties, most notably unfrozen water content, exert significant influences on the observed electrical resistivity. Below 0 °C, soil resistivity increases with the decreasing temperature. We also observe a hysteresis effect on the evolution of electrical resistivity during the freeze–thaw cycle, which effect we characterize with a sigmoidal model. At the same temperature, electrical resistivity during freezing is consistently lower than that during thawing. We have implemented this sigmoidal model into a COMSOL finite element model at both laboratory and field scales which enables the simulation of soil electrical resistivity response under both short–term and long–term sub–freezing conditions. Atmospheric temperature variations induce soil temperature change, and thereby phase transition and electrical resistivity change, with the rate of change being a function of the depth of investigation and soil properties include initial water content and initial temperature. This study advances the fundamental understanding of the electrical behaviors of frozen soils and enhance the application of electrical geophysical investigations in cold regions.

Experimental and modeling investigations of the non-isothermal and isothermal precipitations in an Al-Cu-Mg-Zr alloy with various pre-precipitation microstructures

The complex precipitation evolutions of Al-Cu-Mg alloys during both non-isothermal and isothermal thermal processes have been found to work on their mechanical properties and electrical resistivity. Modeling of the precipitation kinetics, electrical resistivity and strength evolution is therefore essential for optimizing heat treatment and processing of these alloys. In this work, in situ electrical resistivity monitoring during both non-isothermal and isothermal thermal processes and microstructural characterizations were conducted on an Al-Cu-Mg-Zr alloy with different pre-precipitation microstructures to provide fundamental insights of precipitation behaviors. The results showed that precipitation behaviors of Al-Cu-Mg-Zr alloy, such as the dominant strengthening phase, were highly dependent on pre-precipitation microstructures and thermal history. A time–temperature-microstructure-properties map was established to unravel precipitation characteristics and their strengthening functions. The maximum hardness was indicated to be attributed to the combined presence of Guinier–Preston–Bagaryatsky (GPB) zones and fine S (Al2CuMg) phase. Further, in situ electrical resistivity was used as the main input data to develop an improved model based on the classical Kampmann and Wagner type numerical model (KWN model). This integrated model could not only reveal precipitation kinetics but also well predict hardness evolutions of the studied alloy during non-isothermal and isothermal processes.

Electrical resistivity evolution in electrodeposited Ru and Ru-Co nanowires

• Propose a strategy to reduce electrical resistivity and complexity of current interconnect structure in ICs. • Emulate a semiconductor metallization environment employing porous nano-templates. • Design nanoscale Ru and Ru-Co structures by electrodeposition. • Uncover electrical properties of Ru-based nanowires and microstructural evolution. Nanoscale ruthenium (Ru)-based materials are promising replacements for existing multilayered Cu interconnects in integrated circuits. However, it is not easy to apply the results of previously reported studies directly to the electrochemical damascene process because the previous studies have mainly focused on thin films by dry deposition. Here, we report the electrical resistivity and microstructure of electrodeposited Ru nanowires. We estimate that the resistivity value of a 10 nm diameter Ru nanowire to be 71.6 μΩ cm after analyzing the resistivity values of individual nanowires with various diameters. Furthermore, we investigate the electrical properties of Ru x Co 1- x nanowires where x is 0.04–0.99 at.% as possible replacements of the current TaN barrier structures. Over the entire composition range, the resistivity values of alloys are much lower than that of the conventional TaN. Additionally, Ru and Ru-alloy nanowires surrounded by dielectric silica are thermally stable after 450 °C heat treatment. Therefore, the nanoscale Ru and Ru-Co alloys possessing low resistivity values can be candidates for the interconnect and barrier materials, respectively.

DNAPL flow and complex electrical resistivity evolution in saturated porous media: A coupled numerical simulation

Induced Polarization (IP) is a non-intrusive geophysical method to monitor Dense Non-Aqueous Phase Liquid (DNAPL) contamination and remediation processes underground. In this study, an advanced numerical code simulating DNAPL flow and complex electrical resistivity is presented. The model was validated against existing IP results and image measurements that were carried out previously in a series of 2D tank experiment. Multiphase flow modeling in porous media is coupled with electrical current modeling to simulate the process of DNAPL migration and the associated IP response. This brings a broader view of the contamination in space and time compared to surface and borehole measurements, especially when the results are supported by field measurements or laboratory experiments. The simulations are developed in 3D and are performed in COMSOL Multiphysics®. The simulations using petrophysical relationships for in-phase and quadrature resistivity and the results of the experiments are in complete accordance with each other in the parts of the tank where the saturation of DNAPL is relatively low (i.e. especially in the cone of depression in the pumping scenario). However, the parts associated with high saturation of DNAPL show high errors between the in-phase resistivity simulations and the results from experiments. The present work can be regarded as a preliminary study toward further applications of coupled IP-multiphase flow for more accurate detection and monitoring of DNAPLs. It is suggested that the choice of tool/approach in this study be extended to larger-scale studies for further investigation.

Electrical resistivity evolution of compacted silty clay under drying−wetting cycles sequentially coupled with dynamic loads

Electrical resistivity evolution of compacted silty clay under drying−wetting cycles sequentially coupled with dynamic loads

Influence of pumping on the resistivity evolution of high-strength concrete and its relation to the rheology

The pumping process exerts high pressure and strong shearing on fresh concrete, which may affect the hydration process and rheological behavior of concrete. In this paper, full-scale pumping circuits with lengths of 348-, 600-, and 924-m were established to evaluate the effect of pumping on hydration and rheology of concrete. Electrical resistivity measurement was employed to indirectly evaluate the hydration process of concrete. Ten high-strength concrete (HSC) mixtures with slump flow of 680 ± 50 mm and strength grades of C60-C100 were pumped, and HSC mixtures were sampled before and after pumping for rheological properties and electrical resistivity measurements. Findings indicated that the hydration process, determined by the electrical resistivity evolution, was accelerated after pumping. The end of the dormant period of fresh concrete was decreased by 10.3%-27.3%, and the end of the setting period was shortened by 15.6%-28.4% after pumping. The reduction in the dormant period can be well correlated with the drop in slump flow or increase in dynamic yield stress after pumping.

Resistivity anisotropy of tilted columnar W and W[sbnd]Cu thin films

Electrical resistivity of tilted columnar thin films is theoretically and experimentally investigated considering the anisotropic structure of the columns. To this end, W and WCu thin films were deposited by the GLAD co-sputtering technique. These films were prepared using two different sputtering pressures: 2.5 × 10−3 and 15 × 10−3 mbar. Their morphological and crystallographic properties were studied in order to understand the correlations between some structural characteristics and electrical behaviors of these structured films. The influence of the sputtering pressure on the film's morphology was demonstrated and related to the electronic transport properties in these columnar films. For WCu films, the copper was chemically etched in order to tune even more the electrical properties. By rotating the sample along its azimuthal axis, it was shown that the measured resistivity in the axis perpendicular to the particle flux is maximum, but decreases significantly along the axis parallel to the flux, leading to an anisotropic resistivity coefficient higher than 1.9 for some films. Similarly, an analytical model based-on effective medium approximations was successfully applied to determine the evolution of electrical resistivity versus azimuthal axis for W, WCu and etched WCu thin films.

Geo-electrical characterization of physical and mechanical properties of zinc tailing

In the present study, an attempt is made to characterize the tailing material using the electrical resistivity method through a series of laboratory experiments. Tailing materials are a by-product of the metal extraction industry, which are usually disposed off in the form of slurry to the disposal area surrounded by tailing impoundment. Nowadays, a large amount of water is removed through the filtration process, and dry stacking of tailing is followed. Effect of various basic (physical) geotechnical properties on the electrical resistivity of compacted tailing material is investigated using fabricated soil resistivity box based on four-electrode method (ASTM G57–20). To establish the correlation between electrical resistivity and permeability, measurements were made using modified rigid wall falling head permeameter at different densities. Triaxial shear tests, i.e., consolidated undrained (CU) test and consolidated drained (CD) tests were conducted on zinc tailings specimens to study the evolution of electrical resistivity with stress-strain and effective shear strength parameters (c’ and ϕ’) using customized triaxial cell. The present study can be useful for the estimation of in-situ soil properties using electrical resistivity measurement, which will help to understand the engineering properties of the compacted tailings and thus prevent failure of tailing dams.

Electrical resistivity and microstructural evolution of electrodeposited Co and Co-W nanowires

As the design rule of the integrated circuits is decreasing to a 10 nm scale, the total electrical resistance of conventional Cu metallization increases rapidly. New conducting materials such as Co with shorter electron mean free paths, have gained significant attention and may replace Cu. Further, CoW alloys are being considered as alternatives to replace the TaN/Ta barrier layers. However, limited studies have been carried out to elucidate electrical resistivity changes in nanoscale Co and its alloys depending on the size and composition. In this study, we report the variations in electrical resistivity and the microstructural evolution of a series of single Co nanowires (NWs) prepared using template-assisted electrochemical deposition, with diameters ranging from 16 to 130 nm. Besides, we investigate CoW alloy NWs with W content ranging from 0 to 25.1 at.%. The Co NWs, in all diameter ranges, show substantially lower resistivity values compared to that in previous reports, where the value of an NW with a diameter of 16 nm is approximately 40 μΩ∙cm. The grain size also decreases as NW diameter decreases. Alloying W with Co NWs increases electrical resistivity. The 30 nm diameter CoW alloy NW with 25.1 at.% W shows the highest electrical resistivity value at 170 μΩ∙cm. This value decreases as post-deposition annealing temperature increases.

Electrical resistivity and capillary absorption in mortar with styrene-acrylic emulsion and air-entrained agent: improvement and correlation with pore structure

In realistic situation, the uptake of water through capillary absorption process substantially decrease the bulk electrical resistivity. Pore structure is vital to both the bulk electrical resistivity and the capillary absorption process. In this study, to improve the bulk electrical resistivity and mitigate the capillary absorption, styrene-acrylic emulsion (SAE) and air-entrained agent (AE) were incorporated into the mortar sample to modify the pore structure. The evolution of bulk electrical resistivity during the capillary absorption process was investigated. Results showed that the evolution of bulk electrical resistivity exhibits a periodic change along with the water absorption process. The addition of 6% SAE executes a significant improvement on both bulk electrical resistivity and sorptivity coefficient. To reveal the underlying mechanism, the evolution of electrical resistivity of pore solution and porosity was estimated and measured by a theoretical method and mercury intrusion porosimetry (MIP). Characteristic values of pore structure including tortuosity and connectivity were deduced from models. These obtained values indicated that the tortuosity or connectivity exerts a greater influence on the bulk electrical resistivity compared to porosity. No evident relationship between pore structure and sorptivity coefficient was observed via the conventional Lucas-Washburn model. To integrate the effect of the characteristic parameters of pore structure on the capillary absorption, a fractal model was established. The alternations of SAE and AE on the pore structure were manifested into the change of tortuosity fractal dimension and pore fractal dimension. The sorptivity coefficient calculated from this proposed model is in good agreement with the experimental value.

Innovative conductive polymer composite coating for aircrafts lightning strike protection

ABSTRACTA new kind of high electrical conductive epoxy coating with low filler rate was investigated for lightning strike protection (LSP) of carbon fiber reinforced polymer (CFRP). The coating without CFRP substrate was firstly studied. The influence of silver submicronic wires (AgSWs) with a high aspect ratio on the electrical behavior is observed; that is, the electrical resistivity evolution, the current density value, and the electrical conduction mechanisms as function of temperature. The preponderant electrical conduction mechanism is an Ohmic behavior. The higher level of conductivity obtained is 5.5 × 105 S m−1 for 9% vol of AgSWs. Lightning strike tests were carried out on an epoxy/AgSWs coating filled with 8% in volume (74 gsm) and deposited on a CFRP. The ultrasonic testing after lightning strike on coated CFRP shows no structural delamination and demonstrates the interest of this new route for an efficient LSP. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 137, 48700.

Neutron irradiation response of a Co-free high entropy alloy

Low dose neutron irradiation has been conducted on a NiFeMnCr (Co-free) high entropy alloy (HEA) near room temperature. Post-irradiation examination (PIE) at room temperature revealed that this HEA exhibited qualitatively similar change in mechanical properties (hardness, strength and ductility) as conventional austenitic stainless steels. Isochronal annealing was performed to determine the hardness, electrical resistivity and defect property evolution with respect to annealing temperature. Different annealing behavior was observed. Irradiation hardening nearly completely anneals by 650 °C, although the annealing trend is different following exposure to 0.1 and 1 displacements per atom (dpa). Positron Annihilation Spectroscopy (PAS) measurements indicate that the temperature to initialize vacancy cluster (stage V) recovery is ∼400 °C, and that the density of vacancy-type defects is reduced to that of the unirradiated control specimen at 500 °C. No significant change in the chemical ordering near defects was measured by PAS after neutron irradiation or after isochronal annealing up to 700 °C. Electrical resistivity measurements revealed a large increase in resistivity following irradiation, and this resistivity increase does not significantly recover even after the 700 °C anneal. Overall, these annealing results indicate the HEA vacancy cluster annealing behavior is similar to conventional face centered cubic (FCC) alloys whereas solute diffusion is limited up to 700 °C (significantly more sluggish than conventional FCC alloys). X-ray diffraction (XRD) and transmission electron microscopy (TEM) results indicated that this HEA exhibit good phase stability upon neutron irradiation up to 1 dpa and post-irradiation annealing up to 700 °C.

Electro-mechanical Degradation Model of Flexible Metal Films Due to Fatigue Damage Accumulation

An electro-mechanical degradation model is developed to evaluate the electronic and mechanical reliability performance of metal films due to fatigue accumulation. The model establishes the relationship between electrical resistivity and damage, which can be used to predict the change in electrical resistivity and damage evolution of metal films under fatigue loading. Based on the developed model, fatigue damage evolution and change in electrical resistivity simulation of metal films can be implemented to evaluate the electronic and mechanical reliability performance of metal films for the condition where the stress/strain level is heterogeneous. As a case study, fatigue damage evolution and change in electrical resistivity of a copper film on flexible substrate under cyclic loading is numerical analyzed and compared with experiment. It shows that the electro-mechanical degradation model and implemented simulation are effective, and can be used to evaluate the electronic and mechanical reliability performance of metal films due to fatigue accumulation reasonably.