Resistance Technique Research Articles

Hydration monitoring of cement-based materials with resistivity and ultrasonic methods

Two test setups, the electrical resistivity and ultrasonic techniques, were used to monitor the hydration process of cement-based materials. In the electrical resistivity method, a non-contacting device was used. In the ultrasonic method, a wave was transmitted and measured by the embedded piezoelectric ultrasonic transducers, which had good coupling with the surrounding materials. The focus of the study was to detect the setting and hardening behaviors of cement paste during the first 7 days of hydration using the above techniques. Immediate after placing the cement paste into the mould, the measurement started and continued throughout the hydration process. The obtained resistivity and ultrasonic data were used to interpret the hydration process of the specimens. The correlation of two techniques was also studied. The results illustrated that both electrical resistivity and ultrasonic techniques were effective to accurately monitor the hydration of cement pastes. The resistivity method was able to study both the chemical reaction and physical change during hydration, while ultrasonic method was sensitive to physical change of cement only.

Highly absorbing Cu–In–O thin films for photovoltaic applications

We report in this paper on the preparation and characterization of improved quality Cu–In–O films for use as a high-efficiency solar cell absorber. Samples were prepared via sequential thermal vacuum deposition of Cu and In or In and Cu (at 10 −5mbar) on glass substrates heated at 150°C. After what, the obtained binary systems (Cu/In or In/Cu) were annealed in air at 400°C for 3h. These films were characterized for their structural, electrical and optical properties by using X-ray diffraction (XRD), electrical resistivity and optical (transmittance and reflectance) measurement techniques. The X-ray diffraction (XRD) patterns revealed the presence of CuO and In 2O 3 phases. The absorption coefficient of Cu–In–O thin films (4.10 5cm −1) is larger than 10 5cm −1 for the In/Cu case and in the range of 10 4–10 5cm −1 for the Cu/In case in the visible spectral range. Direct optical band gaps of 1.40 and 1.52eV were found for the In/Cu and Cu/In cases, respectively. The complex dielectric constants of the Cu–In–O films have been calculated. It was found that the refractive index dispersion data obeyed the Wemple–Di Domenico single oscillator model, from which the dispersion parameters and the high-frequency dielectric constant were determined. The electric free carrier susceptibility and the ratio of the carrier concentration to the effective mass were estimated according to the model of Spitzer and Fan. The electrical measurements show a conversion from a metallic phase to the semiconductor phase by a switching in the electrical resistivity values at an annealing temperature of 275°C. In both cases the samples were highly compensated.

Synthesis of nanocrystalline nickel ferrite (NiFe2O4) thin films using low temperature modified chemical method

Abstract A modified chemical method is depicted as a novel and powerful method for the synthesis of nanocrystalline nickel ferrite thin films onto glass substrates. This method is a suitable modification of chemical bath deposition. This method is relatively less expensive and convenient for large area deposition of metal oxide films. Nanocrystalline nickel ferrite films have been deposited onto the glass substrates at near room temperature using nickel(II) chloride and iron(II) chloride as cationic precursors. Double distilled water was used as an oxidizing agent. The structural, surface morphological, infrared, and electrical characterizations of the films were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), FT-IR spectra, and electrical resistivity techniques. The results show that modified chemical method allows the synthesis nanocrystalline NiFe 2 O 4 films with spinel phase. The films are free from pinholes and cracks.

Low cycle isothermal fatigue properties of lead‐free solders

PurposeThe purpose of this paper is to discuss a new method to measure the fatigue of single solder joints in shear, and hence calculate the joint strain energy density in each fatigue cycle.Design/methodology/approachThere has been a step change in the requirement to characterise solder joint reliability with the number of new alloys introduced as a result of the recent RoHS legislation. Experimental testing for every configuration is expensive and time consuming, and hence modelling has become more attractive. The accuracy of modelling predictions is limited by the accuracy of the materials data. The data for these new alloys must reflect the miniaturisation of electronics and that solder joints are loaded in shear, two aspects not well reflected in the existing SnPb data. The approach here has been to develop an instrument interconnect properties test machine, where the strain and stress can be measured directly for small solder volumes and in shear. A four‐point measurement system for resistance monitoring has also been evaluated and found to correlate well with load decreases recorded during fatigue testing of solders, and hence provide a method to calculate the crack area.FindingsThe experiments have recorded the stress strain behaviour during isothermal fatigue. The developing crack area has been measured using an electrical resistance technique and has been used to correct the stress values. Using the corrected stress the strain energy data can be calculated.Research limitations/implicationsThe work has been limited to a single alloy and a single joint configuration, with time these will be broadened and the experimental fatigue parameters extended.Practical implicationsThese measurements will provide a route for calibrating the finite element models. A databank of material properties could be built up for alloys used in a range of configurations. This would help support and widen the use of modelling to predict fatigue life.Originality/valueThere is an increasing awareness of the importance of measuring microelectronic solder joint fatigue properties. There are a number of approaches being pursued, but the work at NPL is important in allowing the experiment to be controlled by either stress, strain or temperature, and with the added ability to measure crack area. This uniquely enables the measurement directly of the strain energy density during a fatigue experiment.

Preparation and characterization of obliquely deposited copper oxide thin films

When a thin film is deposited by physical vapour deposition, with the vapour flux arriving at an oblique angle from the substrate normal, and under conditions of sufficiently limited adatom mobility to create a columnar microstructure, the resulting structure is somewhat porous and grows at an angle inclined toward the vapour source. This technique called glancing angle deposition was used in this work to grow nanocrystalline cuprous oxide thin films by annealing in air of copper films deposited firstly by this method onto glass substrates. The films were characterized for their structural, surface morphological, compositional; electrical and optical properties by using X-ray diffraction (XRD), scanning electron microscopy (SEM), electrical resistivity and optical (transmittance and reflectance) measurement techniques. It was found that the above properties were strongly dependent on the obliquely angle deposition. The nanocrystallite size in these films was varied by varying the obliquely angle deposition. Optical studies show a direct allowed transition around in the range 1.5–1.85 eV for the annealed films. An enhancement in the oxidation process was observed for high obliquely angles deposition.

Magnetic Properties of Polycrystalline PrCu2: A Quadrupolar Transition Material

Abstract Polycrystalline PrCu2, which has a quadrupolar transition at 7.7 K, has been investigated using electrical resistivity, magnetization and dilatometry techniques. To study dilution effects, two solid solutions of PrCu2, (Pr0.8La0.2)Cu2, and (Pr0.8Y0.2)Cu2, were also studied. The quadrupolar transition decreases in temperature with doping, while it increases slightly with the magnetic field. In resistivity and thermal expansion, the magnetic contributions show a clear evidence of crystal field excitations. The analysis of both properties provided benchmark values of the Debye temperature and Grüneisen parameters.

The interactions between brain microvascular endothelial cells and mesenchymal stem cells under hypoxic conditions

The purpose of the present study was to investigate the interactions between brain microvascular endothelial cells (BMEC) and mesenchymal stem cells (MSC) under hypoxic conditions. Primary cultured human bone marrow MSC and rat BMEC were isolated, cultured and identified. Vascular endothelial growth factor (VEGF) and matrix metalloproteinase-9 (MMP-9) were detected in the conditioned media of BMEC and MSC under normal and hypoxic conditions using ELISA. MSC differentiation was analyzed using flow cytometry and fluorescence immunocytochemistry. Transendothelial electrical resistance (TEER) techniques were employed to measure changes in permeability across the BMEC monolayer. Under hypoxic conditions, the concentration of VEGF and MMP-9 in the conditioned media increased significantly, with greater levels in the MSC than the BMEC media. Primary MSC did not express vWF and Flk-1. MSC were co-cultured with BMEC under hypoxic conditions 5 days later. MSC expressing Flk-1 accounted for 23.64 ± 2.50% ( n = 6, P < 0.001) of the total number of cells. Interestingly, some Flk-1 positive cells began to coexpress vWF simultaneously. Under hypoxic conditions, MSC conditioned media significantly enhanced the proliferation and migration of BMEC. In addition, MSC decreased the TEER of the BMEC monolayer (lowest values: 50.5 ± 2.6% of the original), which could partially be inhibited by both anti-VEGF antibody and MMP-9 inhibitor. These data indicate that under hypoxic conditions BMEC induce MSC to differentiate into endothelial cells, and MSC enhance the proliferation and migration of BMEC through paracrine functions, while simultaneously increasing the permeability of the BMEC monolayer.

Magnetic imaging and electrical resistivity tomography studies in a Roman military installation found in Satala archaeological site, northeastern Anatolia, Turkey

Satala is one of the last great military centers in the Roman East available for archaeological and historical investigations. This archaeological site is situated on the crossing of two singularly important routes in North-East Asia Minor. Only little archaeological fieldwork in and around Satala has so far been carried out, thus delimiting our knowledge of the site and its role within the Roman military structure of the East. In order to provide further data on the site, we carried out geophysical surveys including the application of magnetic and electrical resistivity techniques in an area north of the Sadak village. The geophysical surveys within this area (supposedly part of the Roman military camp) proceeded in two stages. The first stage saw magnetic gradiometer imaging studies being carried out on 2.1 ha, measured by a Geoscan FM-36 fluxgate gradiometer by using 0.5 × 1 m grid intervals. For the second stage a different geophysical technique was used—resistivity tomography. Resistivity data were collected using a number of combined 2D resistivity pseudosections in the eastern part of the area which contained very regular magnetic anomalies. The 3D data were obtained by the combination of all survey lines collected from 2D data sets, and thereafter the arranged data were processed by using the 3D robust inversion modified from the smoothness-constrained algorithm. Electrical resistivity tomography investigations revealed that the buried archaeological structures might be located near the surface, except for some structures found in the middle of the studied area. The archaeological structures were furthermore determined by realistic model sections and volumetric representations. Magnetic imaging and electrical resistivity tomography surveys show that the combined usage of these techniques advances the understanding of archaeological structures beneath the surface.

Explaining tunnel construction by joint mapping

Modern-day railway tunnels are a superb legacy from a bygone age, built by eminent Victorian tunnel engineers. The great skills and abilities of these engineers and their workmen, even in very poor working conditions and with very limited technology, have resulted in these tunnels being in constant use up to the present time and beyond. But how were they built to last so long? No plans or as-built drawings survive, and only very limited written accounts of their construction are available. Attempts at looking deeper through the linings with ground-probing radar and electrical resistance techniques have failed to reveal any of the secrets. Destructive testing such as coring has been used, but the overall picture is still missing. The only remaining signs of the construction works are the open shafts and the joints. The shafts indicate where some of the access and construction points were situated along the tunnel, and the joints mark the lengths of excavation used in building the tunnel. The joint lengths can be long in good ground, or shorter in poor ground; they can be shorter across an infilled or hidden shaft, or in a ‘break-up’ length, but longer in a ‘junction’ length. The length between joints can therefore reveal much about the conditions under which tunnelling took place, and can also point to the location of other working shafts that have been backfilled and hidden. The author believes that there is much to learn about tunnel construction from a careful study or ‘mapping’ of the joint lengths, particularly when now used in conjunction with a non-destructive testing technique such as ground-probing radar.

Comments on “Measurement and Modeling of the Solubility of Water in Supercritical Methane and Ethane from 310 to 477 K and Pressures from 3.4 to 110 MPa”

We describe a new flow cell apparatus for measuring the water content of gases up to 120 MPa at 490 K that uses a combination of gravimetric and electrical resistance techniques to determine the solubility of water in the gaseous phase. The new experimental data for the solubility of water in supercritical methane and ethane were obtained with our apparatus spanning pressures from 3.4 to 110 MPa covering a temperature range from 310 to 477 K. We model the experimental results by combining two equations of state; vapor-phase fugacities and fugacity coefficients are calculated with a modified Peng−Robinson equation of state, and aqueous-phase fugacities are calculated using an equation by Wagner and Pruss (J. Phys. Chem. Ref. Data 2002, 31, 387−535) or by a modification of a correlation developed by Saul and Wagner (J. Phys. Chem. Ref. Data 1987, 16, 893−901). We compare the model results with new and existing experimental data and with commercially available simulators. Our model reproduces the experimenta...

Preparation of a semi-conductive thermoplastic elastomer vulcanizate based on EVA and NBR blends with polyaniline

A thermoplastic elastomer vulcanizate (TPV), was blended with emulsion prepared polyaniline-doped with dodecylbenzenesulfonic acid (Pani.DBSA). Pani.DBSA was characterized by ultraviolet (UV)–visible (vis), wide-angle X-ray scattering (WAXS) and superficial electrical resistivity techniques. The semi-conductive thermoplastic elastomer vulcanizate (SCTPV) was submitted to mechanical and electrical tests and its reprocessing capability was tested. Even after three reprocessing cycles, the SCTPV showed practically unaffected mechanical and electrical properties, which indicates that the proposed SCTPV can be used successfully for preparation of pressure sensitive elements.

Study on copper precipitation during continuous heating and cooling of HSLA steels using electrical resistivity

Electrical resistivity technique was used to study the phase transformation and copper precipitation during continuous heating and cooling of three Cu bearing high strength low alloy (HSLA) steels. Dilatation measurements were performed to compare the results with the resistivity. During heating, the dilatation plot revealed Ac1 and Ac3 temperature, while resistivity measurements indicated precipitation of copper in the range of 370–550°C. A method was demonstrated to estimate the amount of copper precipitation during continuous heating. During continuous cooling, the austenite transformation temperatures could be derived from resistivity, which compare well with dilatometry. A hysteresis between heating and cooling curve was noted possibly owing to formation of bainite during cooling. Non-isothermal kinetic analysis of dilatation data during continuous cooling yields an activation energy of 62 kJ mol−1, which could be related to the formation of bainite, whereas higher activation energy of 237 kJ mol−1 obtained from resistivity data may correspond to the diffusion of Cu in iron, associated with the copper precipitation during austenite transformation.

Study of Liquid Distribution during Capillary Rise in Fabrics Using an Electrical Resistivity Technique: Influence of Structure and Composition

Study of Liquid Distribution during Capillary Rise in Fabrics Using an Electrical Resistivity Technique: Influence of Structure and Composition

Comparison of the Electrical Resistance and Potential Techniques for the Self-sensing of Damage in Carbon Fiber Polymer-Matrix Composites

The electric potential method, which involves measuring the potential at a distance from the line of current application, is effective for damage sensing of carbon fiber polymer-matrix composites when the distance is sufficiently small, such as 1.0 mm (8 laminae) in the through-thickness direction. It is ineffective when this distance is 2.1 mm (16 laminae). The electrical resistance method, which involves measuring the potential on the line of current application, has no thickness limitation. However, it suffers from current path distortion upon damage and the consequent reduced sensitivity for damage. A minor phenomenon of the measured resistance decreasing with increasing damage is observed for the regions of the composite not containing the point of impact. The major phenomenon of the resistance increasing with damage overshadows this minor phenomenon for the region containing the point of impact.

The effect of sintering temperature on the weak link behavior of Bi‐2223 superconductors

AbstractWe have studied the effect of sintering temperature on the weak link behavior of polycrystalline Bi2223 superconductors with different intergranular coupling using the XRD, electrical resistivity and AC susceptibility techniques. The XRD results show that by increasing sintering temperature up to 865 °C the Bi2212 phase fraction decrease. It was found that the Bi2212 phase on the grain boundaries is likely to play the role of weak links and consequently reduces the intergranular critical current densities. (© 2006 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Measurement and Modeling of the Solubility of Water in Supercritical Methane and Ethane from 310 to 477 K and Pressures from 3.4 to 110 MPa

We describe a new flow cell apparatus for measuring the water content of gases up to 120 MPa at 490 K that uses a combination of gravimetric and electrical resistance techniques to determine the solubility of water in the gaseous phase. The new experimental data for the solubility of water in supercritical methane and ethane were obtained with our apparatus spanning pressures from 3.4 to 110 MPa covering a temperature range from 310 to 477 K. We model the experimental results by combining two equations of state; vapor-phase fugacities and fugacity coefficients are calculated with a modified Peng−Robinson equation of state, and aqueous-phase fugacities are calculated using an equation by Wagner and Pruss (J. Phys. Chem. Ref. Data 2002, 31, 387−535) or by a modification of a correlation developed by Saul and Wagner (J. Phys. Chem. Ref. Data 1987, 16, 893−901). We compare the model results with new and existing experimental data and with commercially available simulators. Our model reproduces the experimental data within 2−6% using one adjustable parameter, indicating that the predictions of the model are equal to or superior to the commercially available simulators.

Monitoring corrosion rates and localised corrosion in low conductivity water

Monitoring of low corrosion rates and localised corrosion in a media with low conductivity is a challenge. In municipal district heating, quality control may be improved by implementing on-line corrosion monitoring if a suitable technique can be identified to measure both uniform and localised corrosion. Electrochemical techniques (LPR, EIS, crevice corrosion current) as well as direct measurement techniques (high-sensitive electrical resistance, weight loss) have been applied in operating plants. Changes in the corrosion processes are best monitored in non-aggressive, low conductivity media with sensitive electrical resistance technique and crevice corrosion current measurements.

Use of electrical resistivity technique for engineering site investigation: a case study from Ado-Ekiti, South-Western Nigeria

A geophysical investigation of part of the Federal Polytechnic Ado-Ekiti campus involved use of the electrical resistivity method for foundation studies. A combined geophysical technique of vertical electrical sounding and horizontal profiling was employed. The quantitative interpretation of the geophysical results allowed the layer parameters to be established, while the isoresistivity maps at varying electrode spacing provided information on the nature, type and competence of the underlying material. The qualitative interpretation of the horizontal profiling delineated the contact zone. Also analysis of transverse unit resistance showed the relevance of this parameter as an index in predicting engineering properties of the rock. The presence of moderately thick (1.5 – 16.5m) clay has been established in this area; therefore the use of raft foundation and/or any other foundation that is commensurate with civil engineering standard is suggested for high rise structures. Keywords : bedrock integrity, transverse unit resistance, foundation. Global Journal of Pure and Applied Sciences Vol. 11(4) 2005: 543-552

The effect of sintering temperature on the intergranular properties of Bi2223 superconductors

A systematic study of the intergranular properties of (Bi,Pb) 2Sr 2Ca 2Cu 3O y (Bi2223) polycrystalline samples has been done using the electrical resistivity and Ac susceptibility techniques. In this project, we have prepared a series of Bi2223 samples with different sintering temperature. The XRD results show that by increasing sintering temperature up to 865 °C the Bi2212 phase fraction decrease. It was found that the Bi2212 phase on the grain boundaries is likely to play the role of weak links and consequently reduces the intergranular critical current densities. Analysis of the temperature dependence of the Ac susceptibility near the transition temperature ( T c) has been done employing Bean's Critical State Model. The observed variation of intergranular critical current densities ( J c) with temperature indicates that the weak links are changed from superconductor–normal metal–superconductor (SNS) for well-coupled sample to superconductor–insulator–superconductor (SIS) type of junctions for the sample with high Bi2212 phase fraction.

Contribution of multiplexed electrical resistance and magnetic techniques to the archaeological investigations at Poros, Greece

AbstractThe Sanctuary of Poseidon at Kalaureia is located on the island of Poros in the Saronic Gulf in Greece. Two Swedish archaeologists first carried out excavations at the site in 1894; in 1997 investigations were resumed by the Swedish Institute at Athens. Although there are traces of occupancy in the area by the early Bronze Age, the results so far attest to some activity in the very late Bronze Age (ca. 1100 BC); with a considerable proportion of the remains dating from the eighth century BC and the visible remains dating to the sixth to second centuries BC.A geophysical investigation was conducted at the site using both electrical resistance techniques and magnetic methods. A small area of 20 × 15 m at the southeast section of the site was surveyed with high‐resolution multiplexed electrical resistance techniques in order to maximize the information content of the subsurface remains in both horizontal and vertical extent.The local vertical magnetic gradient of the Earth's magnetic field was measured using a fluxgate gradiometer, and multiplexed electrical resistance techniques were applied in order to map the subsoil resistance at different depths. In addition, the whole area was investigated with a double twin probe configuration.Emphasis was given to the use of the multiplex electrical resistance technique with different configurations. A small grid to the southeast of the survey area was investigated with a twin probe configuration, recording the subsurface resistance at four increasing depths. Additionally, 0.5 m dipole–dipole and 0.5 m Wenner mapping configurations were performed. The above data were processed using a specifically developed processing package (GPP). The resistance instrument was also programmed in such a way as to conduct parallel resistance tomographies along the x and y directions with a pole–pole array. Copyright © 2005 John Wiley &amp; Sons, Ltd.