Change In Electrical Resistance Research Articles

Microstructure, Optical and Electrical Properties of Cu-Cu<sub>2</sub>O Core-Shell Nanostructures

Composites of nanometre-sized copper core–copper oxide (Cu-Cu2O) shell with different diameters were synthesized by a facile one step co-solvent technique. By the analysis of X-ray diffraction (XRD) and transmission electron microscope (TEM) data, the resultant particles were confirmed to be pure and nanocrystalline in nature. The perfect core-shell structure of nanocrystalline Cu-Cu2O was confirmed by using high resolution TEM. The presence of pure Cu and Cu2O was further confirmed from optical absorbance spectrum and Fourier transform infrared (FT-IR) spectroscopy. The tailoring of position of optical absorption peaks, originating from Cu or Cu2O nanoparticles, is possible by modulating the oil to water ratio, which controls the size of the composite particles and thickness of Cu2O. Drastic change of electrical resistivity with change in thickness of shell, has been observed. Variation of resistivity with temperature delineates a semiconducting nature with two distinct activation processes. Results demonstrate that the activation energies for the core-shell nanostructure composites were found to be smaller than the bulk Cu2O. Photoluminescence spectrum further confirms the semiconducting nature of the composite. In addition, the kinetic of core-shell morphology formation is also discussed briefly.

Self-Monitoring of Damage Evolution in Asphalt Concrete Based on Electrical Resistance Change Method

Abstract Asphalt pavements expose early damage during their service life. The early damage grows internally until it accumulates and transforms into macro-damage that leads to structural failure. To promote real-time monitoring of internal damage evolution in asphalt pavements, this study proposes an electrical resistance change (ERC) method that exploits the piezoresistive properties of conductive asphalt concrete as a nondestructive testing technique capable of detecting microstructural defects. For this purpose, the traditional asphalt mixtures were first made electrically conductive by adding carbon fibers and iron tailing aggregates as conductive aggregates to satisfy the piezoresistivity requirements. Secondly, piezoresistivity experiments were performed by applying cyclic tensile force in fatigue and progressively increasing mode. The self-monitoring ability of damage evolution was assessed based on the correlation between the fractional change in electrical resistance (FCR), displacement, and damage degree for each mode of the force application. It was observed that under fatigue mode, the FCR and displacement increase upon loading and decrease reversibly upon unloading in each cycle. Compared with the displacement, the FCR exhibits partial reversibility upon unloading, indicating damage initiation in each cycle. The damage grows with the number of loading cycles until it accumulates in the elastic regime and gradually affects the load-carrying capacity of the mixture. Under a progressively increasing mode, the mixture exhibits a good correlation between the FCR and force in the elastic regime, ensuring real-time monitoring of internal micro-damage. However, the FCR develops a nonlinear correlation with the force in the inelastic regime that reflects damage to the conductive network and eventually structural failure. In summary, the ERC method provides real-time monitoring of microstructural defects that manifest as early damage and gradually transform into macro-damage under repeated traffic loads.

Aging processes in the nanostructured temperature-sensitive ceramic materials

Aging processes in the two types of temperature-sensitive Cu0.1Ni0.8Co0.2Mn1.9O4 ceramics (two-phase and with different amount of NiO phase) as well as thick films base on Cu0.1Ni0.1Co1.6Mn1.2O4 ceramics were investigated. It is shown for Cu0.1Ni0.8Co0.2Mn1.9O4 ceramics prepared at 1170 °C with addition treatment at 850 °C that the post-separation process of the second phase continue under heat at temperatures of 125 and 170 °C. It has been found that higher thermal aging leads to more pronounced changes in electrical resistance. Addition temperature influences contribute to the stabilization of ceramic parameters. The aging test at 170 °C results in a 7.5% reduction in electrical resistance, while at 125 °C this value is only 6%. It is shown that NiO phase additives formed during sintering of Cu0.1Ni0.1Co1.6Mn1.2O4 ceramics and located near the grain boundaries of ceramics inhibit the aging process in these materials. This effect is characteristic of fine-grained ceramics obtained by thermal energy converted during sintering. It is established that the kinetics of aging in Cu0.1Ni0.1Co1.6Mn1.2O4 ceramics is described by the relaxation function of DeBast-Gillard or Williams-Watts, regardless of the composition of the ceramics. The aging kinetics in thick films based on Cu0.1Ni0.1Co1.6Mn1.2O4 ceramics at 170 °C is also adequately described by the compression-exponential relaxation function.

Structural Health Monitoring of the Carbon Fiber Reinforced Epoxy/MWCNTS Composites under Vibration Loading, Using Electrical Resistance Change Method

This work aims to investigate the structural deterioration of the Carbon Fiber Reinforced Epoxy (CFRE) composite under vibration loading by monitoring the variation of the electrical resistance of the composite. The vacuum assisted resin transfer moulding process is used to fabricate the CFRE composites. Multiwall Carbon Nanotubes (MWCNTs) (0.5% wt) are added to the non-conductive resin to increase its electrical conductivity before CFRE fabrication. The tests were carried out by monitoring the variation in electrical resistance of the CFRE composite at 90 Hz frequency vibration loading. The dispersion of MWCNTs into the matrix and the damage of CFRE composite are illustrated by the SEM images. The results show that the electrical resistance change can be considered as a good indication to detect damage in CFRE (modified with 0.5 wt % MWCNTs) under vibration loading.

Accelerated Solder Interconnect Testing Under Electromigratory and Mechanical Strain Conditions

Abstract Continuous power density increases and interconnect scaling in electronic packages raises risk of electromigration (EM) induced failures in high current interconnects. Concurrently, thermal cycling fatigue also places interconnects at risk of reliability failure during electronics' operating lifetime. These two differing failure mechanisms are historically treated separately, but in operation, the combination of EM effects and thermal cycling can act synchronously in accelerating failure. Presently, there is no model to predict the complexity of reliability estimation arising from these interacting failure modes but is certainly important for high current density applications. In this work, a novel testing system has been employed to facilitate the estimation of the reliability of solder interconnects under the combined influence of EM and mechanical strain. The system subjects solder interconnects to high current density, elevated ambient temperature, and a constant tensile stress while recording the change in electrical resistance and change in length of the solder over time. The solder samples were created using two copper wires connected by a eutectic Pb/Sn solder ball to imitate flip-chip or BGA packaging interconnects, allowing for controlled testing conditions in order to demonstrate the combined effects of a mechanical load and EM on the lifetime of a solder joint. A significant reduction in lifetime was observed for samples that endured the coupled accelerating factors. Comparing the experimental results of different current densities at different stress levels provided a new outlook on the nature of coupled failure acceleration in solders. This novel test methodology can inform model generation for better anticipating the failure rate of solder interconnects which naturally experience multiple stress inputs during their lifetime.

Efficacy of electrocoagulation hemostasis: a study on the optimal usage of the very-low-voltage mode.

The very-low-voltage (VLV) mode in electrosurgery can stably and deeply energize tissues even if the local electrical resistance changes with energization. Therefore, in electrosurgical hemostasis, the VLV mode is more reliable than other coagulation modes. In clinical practice, the appropriate use of combined saline drip and blood suction under the VLV mode can further enhance coagulation ability. However, the detailed mechanism is not known. The current study aimed to evaluate the association between electrosurgical activation time (ET) and hemostatic tissue effect (HTE) under the VLV mode. Further, the effect of saline drip and suction on power consumption and HTE was validated. Twelve female pigs weighing 35kg were included in the experiment. A liver hemorrhage model was established via an open abdominal procedure, and hemostasis in the hemorrhagic lesion was attempted using the VLV mode under different conditions (ET: 3, 6, 9, and 12s, with/without saline drip and/or continuous suction). Electrical data (such as voltage, current, and resistance) during coagulation were extracted. Then, the vertical/horizontal extent of HTE was assessed, and the hemostasis outcome (successful or failed) was recorded. The vertical/horizontal HTE, power consumption, and integrated current value were positively correlated with the ET. The coagulation depth deepened with saline drip (p < 0.01). However, it was not affected by continuous suction (p = 0.20). The HTE area increased with saline drip (p < 0.01) and decreased with suction (p < 0.01). The power consumption and integrated current increased with saline drip (p < 0.01) and decreased with suction (p < 0.01). The success rate of hemostasis decreased with saline drip alone (31of 48 trials [success rate = 64.5%] in the saline drip group and 44/48 trials (success rate = 91.7%) in the control group). However, it improved with continuous suction (46/48 trials [success rate = 95.8%]). The electrosurgical activation time was positively correlated with hemostatic tissue effect. Saline drip increased heat transfer efficiency but decreased the success rate of hemostasis. Therefore, the use of continuous suction in addition to saline drip increased hemostatic efficiency.

Four-parameter electromagnetic method for determining the parameters of brewery effluents

of the article is to study a four-parameter electromagnetic method for joint measurements of electrical resistivity k, relative permittivity εr, temperature t and density ρ of samples of acidic, alkaline and average effluents from a microbrewery based on a magnetic flux probe (MFP), which considers the influence of informative parameters of beer effluents on the components of the amplitude and phase signals of a multiparameter device. The implementation of the four-parameter method is carried out on the basis of the dependences G1 = f (A1) and G2 = f (A2) at two frequencies of the electromagnetic field f0 and f1 for acid, alkaline and average effluent and allows you to jointly determine the four parameters of effluent samples with the same converter in the same control area. The proposed method makes it possible to improve the accuracy of identifying effluent samples since the obtained multiparameter information makes it possible to determine the nature and properties of effluent samples using only one transducer with certain physical characteristics. The research results lead to the expansion of the technical capabilities of electromagnetic measurement methods, as well as to an increase in the metrological characteristics of electromagnetic transducers and an increase in the accuracy of measuring the parameters of effluent samples compared to reference methods and measuring instruments. Thus, the implementation of this approach contributes to the prediction and prevention of the reasons for the deviation of beer effluent samples from the specified indicators of environmental safety. The universal conversion functions MFP have been established, connecting the amplitude and phase components of the converter signals with the parameters k, εr, t and ρ of acidic, alkaline and average effluents. Based on the universal transformation functions G1 = f (A1) and G2 = f (A2), a four-parameter electromagnetic method for joint measurements of electrical resistivity k, relative permittivity εr, temperature t and density ρ of acidic, alkaline, and average effluents from breweries has been developed. When conducting research at two close frequencies of the electromagnetic field f0 = 20.3 MHz and f1 = 22 MHz, algorithms were obtained for measuring and calculating procedures for determining k, εr, t and ρ for samples of acidic, alkaline and average effluents from the brewing industry. Research perspectives consist in the creation of automated systems for multiparameter measuring control of the physicochemical characteristics of acidic and alkaline effluent from food and processing industries based on the immersed electromagnetic transducer. Based on the data obtained using informative methods to measure the parameters of effluent samples, an integrated method for treating beer effluents of various compositions will be proposed. At the same time, the scheme of the integrated treatment method should include a filter that provides the introduction of a magnetic fluid and a separation device that allows us to remove a fraction, including pollution in itself. Is that the proposed four-parameter electromagnetic method makes it possible to determine to what composition the controlled samples of wastewater should be attributed (acidic or alkaline). It, in turn, makes it possible to choose a rational method for treating beer effluents and to prevent the reasons for the deviation of effluent samples from the environmental safety indicators set by the standards. of the article is the research related to the expansion of the functional and technical capabilities of the electromagnetic two-frequency transducer MFP through the implementation of a four-parameter electromagnetic method of joint measurements of electrical resistivity k, relative permittivity εr, temperature t and density ρ of acidic, alkaline and average effluents from breweries. The universal transformation functions G1 = f (A1) and G2 = f (A2) found in the work at two close magnetic field frequencies, f0 = 20.3 MHz and f1 = 22 MHz, make it possible to control four physicochemical parameters of acidic, alkaline and average wastewater at the same time by the same MFP. An algorithm has been developed for determining the signal components of a two-frequency thermal MFP, the ranges of which correspond to the ranges of changes in electrical resistivity k, relative permittivity εr, temperature t and density ρ of acidic, alkaline, and average brewery effluents. The basic relations that describe the two-frequency four-parameter electromagnetic method of joint measurements of the physicochemical parameters of acidic, alkaline and averaged beer effluents have been obtained.

Unraveling the intestinal epithelial barrier in cyanotoxin microcystin-treated Caco-2 cell monolayers.

Microcystin is a widespread cyanobacterial toxin that affects the intestine to produce diarrheal symptoms after ingestion of freshwater blue-green algae. Our study aimed to characterize the mechanism by which the toxin leads to diarrhea via epithelial barrier dysfunction in a small intestine Caco-2 cell model. Microcystin-treated human Caco-2 epithelial monolayers were functionally and molecularly analyzed for barrier dysfunction. Tight junctions (TJs) and cell damage were analyzed in relation to transepithelial electrical resistance (TER) changes. TER of microcystin-treated Caco-2 cells was reduced by 65% of the initial value after 24 h; concomitantly, permeability for fluorescein increased 2.6-fold. Western blot analysis showed reduced claudin-1 expression, while expression of claudin-3 and -4 remained unchanged. Super-resolution stimulated emission depletion microscopy revealed that TJ integrity was compromised by fraying and splitting of the TJ domain of the epithelial cells. Epithelial apoptosis did not significantly contribute to epithelial barrier dysfunction, while cytoskeletal actomyosin constriction was associated with TJ disintegration and the barrier defect. Our results indicate that microcystin causes intestinal barrier leakiness, which helps to explain the leak flux type of diarrhea as the main pathomechanism after ingestion of cyanobacterial toxin.

Conducting Polymers for the Design of Tactile Sensors.

This paper provides an overview of the application of conducting polymers (CPs) used in the design of tactile sensors. While conducting polymers can be used as a base in a variety of forms, such as films, particles, matrices, and fillers, the CPs generally remain the same. This paper, first, discusses the chemical and physical properties of conducting polymers. Next, it discusses how these polymers might be involved in the conversion of mechanical effects (such as pressure, force, tension, mass, displacement, deformation, torque, crack, creep, and others) into a change in electrical resistance through a charge transfer mechanism for tactile sensing. Polypyrrole, polyaniline, poly(3,4-ethylenedioxythiophene), polydimethylsiloxane, and polyacetylene, as well as application examples of conducting polymers in tactile sensors, are overviewed. Attention is paid to the additives used in tactile sensor development, together with conducting polymers. There is a long list of additives and composites, used for different purposes, namely: cotton, polyurethane, PDMS, fabric, Ecoflex, Velostat, MXenes, and different forms of carbon such as graphene, MWCNT, etc. Some design aspects of the tactile sensor are highlighted. The charge transfer and operation principles of tactile sensors are discussed. Finally, some methods which have been applied for the design of sensors based on conductive polymers, are reviewed and discussed.

Electrophysical Properties of Monocrystalline n-Si+0.4at%Ge:P Alloy irradiated by 60Co Gamma Photons

In the monocrystal n-Si+0.4at.%Ge:P alloy irradiated with 60Co gamma photons non-monotonic changes in electrical resistance, current carrier concentration and mobility were detected by isochronal annealing at a temperature range of 20-400°C. The contribution of current transformations in the structure of radiation defects (PV, VO, VO2, CiCs, CiOi) to the temperature changes of electrical characteristics is analyzed. n-p conversion was detected at the critical temperature (~100°C) of isochronal annealing. Dissociation of PV centers and formation of electrically active VO centers were detected in the 120-150°C range. As a result, the concentration of current carriers increases. At elevated temperatures (&gt; 150°C) non-monotonic changes in electrical characteristics are observed.The paper analyzes the contribution of Ge to the anomalous temperature changes of the electrophysical characteristics of the n-SiGe alloy.

3R Composites: Knockdown Effect Assessment and Repair Efficiency via Mechanical and NDE Testing

In this study, the mechanical properties of purposefully synthesized vitrimer repairable epoxy composites were investigated and compared to conventional, commercial systems. The purpose was to assess the knockdown effect, or the relative property deterioration, from the use of the vitrimer in several testing configurations. Mechanical tests were performed using ILSS, low-velocity impact, and compression after impact configurations. At modeled structure level, the lap strap geometry that can simulate the stiffening of a composite panel was tested. Several non-destructive evaluation techniques were utilized simultaneously with the mechanical testing in order to evaluate (i) the production quality, (ii) the damage during or after mechanical testing, and (iii) the repair efficiency. Results indicated that the new repairable composites had the same mechanical properties as the conventional aerospace-grade RTM6 composites. The electrical resistance change method proved to be a valuable technique for monitoring deformations before the initiation of the debonding and the progress of the damage with consistency and high sensitivity in real time. In terms of repair efficiency, the values ranged from 70% to 100%.

4D electrical resistivity tomography for assessing the influence of vegetation and subsurface moisture on railway cutting condition

Instability of slopes, embankments, and cuttings on the railway network is increasingly prevalent globally. Monitoring vulnerable infrastructure aids in geotechnical asset management, and improvements to transport safety and efficiency. Here, we examine the use of a novel, near-real-time Electrical Resistivity Tomography (ERT) monitoring system for assessing the stability of a railway cutting in Leicestershire, United Kingdom. In 2015, an ERT monitoring system was installed across a relict landslide (grassed) and an area of more stable ground on either side (wooded), to monitor changes in electrical resistivity through time and space, and to assess the influence of different types of vegetation on the stability of transportation infrastructure. Two years of 4-Dimensional ERT monitoring results are presented here, and petrophysical relationships developed in the laboratory are applied to calibrate the resistivity models in order to provide an insight into hydrogeological pathways within a railway cutting. The influence of vegetation type on subsurface moisture pathways and on slope stability is also assessed – here we find that seasonal subsurface changes in moisture content and soil suction are exacerbated by the presence of trees (wooded area). This results in shrink-swell behaviour of the clays comprising the railway cutting, resulting in fissuring and a reduction in shear strength, leading to instability. As such, it is proposed that on slopes comprised of expansive soils, grassed slopes are beneficial for stability. Insights into the use of 4-D ERT for monitoring railway infrastructure gained from this study may be applied to the monitoring of critical geotechnical assets elsewhere.

An Experimental Study on Electrical Properties of Self-Sensing Mortar

Self-sensing cementitious composites are a combination of conventional materials used in the construction industry along with any type of electrically conductive filler material. Research has already been carried out with various types of conductive fillers incorporated into cement mortars to develop a self-sensing material. Carbon fibres have been used as conductive fillers in the past, which is uneconomical. In order to overcome this drawback, brass fibres have been introduced. This study concentrates on the behaviour of self-sensing mortar under two different curing conditions, including air and water curing. The main aim of this paper is to determine the self-sensing ability of various types of smart mortars. For this purpose, an experimental study was carried out, with the addition of various brass fibres of 0.10%, 0.15%, 0.20%, 0.25%, and 0.30% by volume, to determine the electrical properties of cementitious mortar. In addition, different combinations of brass and carbon fibres were considered, such as 95% brass fibre with 5% carbon fibre, 90% brass fibre with 10% carbon fibre, and 85% brass fibre with 15% carbon fibre by volume, to determine the piezoresistive behaviour. A fractional change in electrical resistance was determined for all the mortar cubes. A fractional change in electrical resistance (fcr) is defined as the change in its electrical resistance with respect to its initial resistance (ΔR/R). Additionally, the temperature effects on self-sensing mortar under compressive loading were observed for various temperatures from room temperature to 800 °C (at room temperature, 200 °C, 400 °C, 600 °C, and 800 °C). It was observed that the addition of brass fibre to the cement mortar as an electrically conductive filler improved the self-sensing ability of the mortar. After 28 days of water curing, when compared to conventional mortar, the percentage increase in change in electrical resistance (fcr) was observed to be 26.00%, 26.87%, 27.87%, 38.55%, and 35.00% for 0.10%, 0.15%, 0.20%, 0.25%, and 0.30% addition of brass fibres, respectively. When the smart mortar was exposed to elevated temperatures, the compressive strength of the mortar was reduced. Additionally, the fractional change in electrical resistance values was also reduced with the increase in temperature. In addition to this, the self-sensing ability of smart mortars showed improved performance in water curing rather than in air-cured mortars. Compressive strengths, stress, strain, and change in electrical resistance (fcr) values were determined in this study. Finally, microstructural analysis was also performed to determine the surface topography and chemical composition of the mortar with different fibre combinations.

Polyethylene/carbon fiber composites reinforced by a non-covalent compatibilization approach for flexible electric heater and structural self-monitoring

The rational modulation for the interfaces of polymer/filler composites is the key to maximizing its mechanical property and functional performance. In this work, the interface of recycled carbon fiber (CF) enhanced linear low-density polyethylene (LLDPE) composites was modulated via graphene oxide (GO) bridging and alkyl group modification to increase the interface roughness and improve the compatibility. The optimized composite displays improved mechanical, thermal, and electrical properties due to the modulated interface synergistic effect, particularly as a flexible heater, the composites film displayed excellent electrical heating behavior at a fast speed of heating up in 50 s to a steady-state temperature of 40 °C under the low voltage of 5 V. In addition, the structural self-monitoring of this conductive composite could be reflected by the electrical resistance change based on the results of finite element analysis (FEA) and in-situ resistance-tensile measurements. This facile compatibilization approach and in-situ self-monitoring method provide a new route for expanding the application of functional polyethylene materials.

Carbon-Based Nanomaterials Thin Film Deposited on a Flexible Substrate for Strain Sensing Application.

Hybrid nanomaterial film consisting of multi-walled carbon nanotubes (MWCNT) and graphene nanoplatelet (GNP) were deposited on a highly flexible polyimide (PI) substrate using spray gun. The hybridization between 2-D GNP and 1-D MWCNT reduces stacking among the nanomaterials and produces a thin film with a porous structure. Carbon-based nanomaterials of MWCNT and GNP with high electrical conductivity can be employed to detect the deformation and damage for structural health monitoring. The strain sensing capability of carbon-based hybrid nanomaterial film was evaluated by its piezoresistive behavior, which correlates the change of electrical resistance with the applied strain through a tensile test. The effects of weight ratio between MWCNT and GNP and the total amount of hybrid nanomaterials on the strain sensitivity of the nanomaterial thin film were investigated. Experimental results showed that both the electrical conductivity and strain sensitivity of the hybrid nanomaterial film increased with the increase of the GNP contents. The gauge factor used to characterize the strain sensitivity of the nanomaterial film increased from 7.75 to 24 as the GNP weight ratio increased from 0 wt.% to 100 wt.%. In this work, a simple, low cost, and easy to implement deposition process was proposed to prepare a highly flexible nanomaterial film. A high strain sensitivity with gauge factor of 24 was achieved for the nanomaterial thin film.

The impact of intermetallic compound on microstructure, mechanical characteristics, and thermal behavior of the melt-spun Bi-Ag high-temperature lead-free solder

PurposeThis study aims to study the impact of intermetallic compound on microstructure, mechanical characteristics and thermal behavior of the melt-spun Bi-Ag high-temperature lead-free solder.Design/methodology/approachIn this paper, a new group of lead-free high-temperature Pb-free solder bearing alloys with five weight percentages of different silver additions, Bi-Agx (x = 3.0, 3.5, 4.0, 4.5 and 5.0 Wt.%) have been developed by rapidly solidification processing (RSP) using melt-spun technique as a promising candidate for the replacement of conventional Sn-37Pb common solder. The effect of the addition of a small amount of Ag on the structure, microstructure, thermal and properties of Bi-Ag solder was analyzed by means of X-ray diffractometer, scanning electron microscopy, differential scanning calorimetry and Vickers hardness technique. Applying the RSP commonly results in departures from conventional microstructures, giving an improvement of grain refinement. Furthermore, the grain size of rhombohedral hexagonal phase Bi solid solution and cubic IMC Bi0.97Ag0.03 phase is refined by Ag addition. Microstructure analysis of the as soldered revealed that relatively uniform distribution, equiaxed refined grains of secondary IMC Bi0.97Ag0.03 particles about 10 µm for Bi-Ag4.5 dispersed in a Bi matrix. The addition of trace Ag led to a decrease in the solidus and liquidus temperatures of solder, meanwhile, the mushy zone is about 11.4°C and the melting of Sn-Ag4.5 solder was found to be 261.42°C which is lower compared with the Sn-Ag3 solder 263.60°C. This means that the silver additions into Bi enhance the melting point. The results indicate that an obvious change in electrical resistivity (?) at room temperature was noticed by the Ag addition. It was also observed that the Vickers microhardness (Hv) was increased with Ag increasing from 118 to 152 MPa. This study recommended the use of the Bi-Ag lead-free solder alloys for higher temperature applications.FindingsSilver content is very important for the soldering process and solder joint reliability. Based on the present investigations described in this study, several conclusions were found regarding an evaluation of microstructural and mechanical deformation behavior of various Bi-Ag solders. The effect of Ag and rapid solidification on the melting characteristics, and microstructure of Bi-Ag alloys were studied. In addition, the mechanical properties of Bi with different low silver were investigated. From the present experimental study, the following conclusions can be drawn. The addition of Ag had a marked effect on the melting temperature of the lead-free solder alloys, it decreases the melting temperature of the alloy from 263.6 to 261.42°C. Bi-Ag solders are comprised of rhombohedral Hex. Bi solid solution and cubic Ag0.97Bi0.03 IMC is formed in the Bi matrix. The alloying of Ag could refine the primary Bi phase and the Bi0.97Ag0.03 IMC. With increasing Ag content, the microstructure of the Bi-Ag gradually changes from large dimples into tiny dimple-like structures. The refinement of IMC grains was restrained after silver particles were added into the matrix. The inhibition effect on the growth of IMC grains was most conspicuous when solder was doped with Ag particles. As a result, the Vickers microhardness of the Bi-Ag lead-free solder alloys was enhanced by more than 100% ranging from 118.34 to 252.95 MPa. Bi-Ag high-temperature lead-free solders are a potential candidate for replacing the tin-lead solder (Sn-37Pb) materials which are toxic to human and the environment and has already been banned.Originality/valueThis study recommended the use of the Bi-Ag lead-free solder alloys for high-temperature applications.

Broadband Dielectric Spectroscopic Detection of Ethanol: A Side-by-Side Comparison of ZnO and HKUST-1 MOFs as Sensing Media

The most common gas sensors are based on chemically induced changes in electrical resistivity and necessarily involve making imperfect electrical contacts to the sensing materials, which introduce errors into the measurements. We leverage thermal- and chemical-induced changes in microwave propagation characteristics (i.e., S-parameters) to compare ZnO and surface-anchored metal–organic-framework (HKUST-1 MOF) thin films as sensing materials for detecting ethanol vapor, a typical volatile organic compound (VOC), at low temperatures. We show that the microwave propagation technique can detect ethanol at relatively low temperatures (&lt;100 °C), and afford new mechanistic insights that are inaccessible with the traditional dc-resistance-based measurements. In addition, the metrological technique avoids the inimical measurand distortions due to parasitic electrical effects inherent in the conductometric volatile organic compound detection.

CO2 gas sensing properties of Na3BiO4-Bi2O3 mixed oxide nanostructures.

In this paper, we report Na3BiO4-Bi2O3 mixed oxide nanoplates for carbon dioxide gas sensing applications. These nanoplates have been synthesized using electrochemical deposition with potentiostatic mode on ITO substrate and characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD) to analyze their surface morphology and structure. SEM study shows the presence of horizontally aligned nanoplates stacked on top of one another (thickness ≈ 40 to 75nm). XRD pattern shows the presence of monoclinic Na3BiO4 and Bi2O3. The gas percentage response is evaluated by measuring the change in electrical resistance of the nanoplates in the presence of carbon dioxide for different pressures at 50°C, 75°C, and 100°C. Percentage response of more than 100% is seen at 30 psi gas pressure which increases to ≈ 277% at 90 psi at 100◦C.

Textile-Based 3D Truss Reinforcement for Cement-Based Composites Subjected to Impact Loading - Part II: &lt;i&gt;In Situ&lt;/i&gt; Stress Analysis under Quasistatic and Dynamic Tensile Loading

This research focuses on the electromechanical strain-sensing behaviour of steel wires on the fiber and composites scale. The electromechanical properties are investigated by using a uniaxial fiber tensile test with a simultaneous electrical resistance measurement. Further, this work conducts a comprehensive stress analysis of textile reinforced concrete (TRC) specimen in quasistatic and dynamic tensile tests by using integrated steel wires in a textile 3D-weaving reinforcement as piezoresistive in-situ-sensors. The results are compared to optical strain measurements using digital image correlation (DIC). The acquisition and analysis of the electrical resistance changes of the steel wire sensors enable an in-situ stress analysis as well as a better understanding of the mechanical response of the TRC specimen under different loading scenarios.

Arbitrarily shapeable and conductive hydrogel with “Magic Cube” like structure for real-time monitoring and promoting wound healing

Developing hydrogel dressings for chronic non-healing wounds in irregular-shaped or moveable sites has great practical applications. In this work, a novel polyelectrolyte composite hydrogel (HSa) was fabricated from chitosan quaternary ammonium salt (HACC) and sodium alginate (SA) through blending and acid-treated process. The positive charges of HACC and negative charges of SA self-assembled and intertwined to form a “Magic Cube”-like structure. The amino groups of HACC were protonized and the Na + of SA was replaced by proton after acid treatment, further strengthening the interactions between the two chips of “Magic Cube”. HSa hydrogel was proven to be arbitrarily shapeable with high flexibility (tensile strain is around 280%). Due to free Cl − , HSa hydrogel presented good conductivity (1.14 × 10 −3 S/cm) and positive linear relationship between its electrical resistance change and area change, which denoted its ability to monitor joint movement or subtle shrinkage. HSa hydrogel exhibited good biocompatibility and was further applied as dressing in an irregular-shaped wound model. HSa hydrogel could significantly accelerate the wound healing by elevating collagen deposition and vessel formation. Simultaneously, HSa hydrogel could monitor the wound closure in real-time. Therefore, HSa hydrogel had multifunctional potential for wound healing and monitoring, especially for irregular-shaped or movable sites. • A simple strategy for fabricating arbitrarily shapeable and conductive hydrogel. • HSa hydrogel has a “Magic Cube” like structure. • HSa hydrogel has good hemostasis effects and biocompatibility. • HSa hydrogel combines wound pro-healing and real-time monitoring functions. • HSa hydrogel could be beneficial for chronic non-healing wounds.