Changes In Surface Resistance Research Articles

Textronic Sensors of Hazardous Gaseous Substances

Toxic materials are a threat in workplaces and the environment, as well as households. In them, gaseous substances are included, especially ones without any colour or fragrance, due to their non-detectability with the human senses. In this article, an attempt was made to find a solution for its detection in various conditions with the use of intelligent textiles. The approach was to perform modification on fifteen materials by screen printing using carbon nanotubes paste with expanded graphite and embroidery with stainless steel thread and then investigate their reaction with risky gases such as acetone, methanol and toluene. Four combinations of samples were tested: before tests, after the washing test and after the alkaline and acidic sweat contact test. Three materials can be highlighted. Para-aramid knitwear which reacted well to all tested gases. The biggest value of sensory percentage response was 144%. Screen-printed linen knitwear showed properly detecting skills after washing test for toluene. The biggest value of sensory percentage response was noted at 186%. The third most promising material was low surface mass cotton knitwear with embroidery which had a visible response at every stage of testing for acetone. The biggest value of sensory percentage response was 94% and the smallest one was 27%. For these three materials, repeated contact with harmful gases was tested. Simulations showed also repeated responses expressed in changes in surface resistance under changed conditions. After analysis, there is a possibility to create textile sensors for the detection of hazardous substances.

Study on the suppression of secondary electron emission characteristics based on TiN

Abstract With the continuous development of satellite communications, the problem of high-frequency high-power multipactor caused by the miniaturization of microwave passive components in the aerospace field has become more and more serious. In this paper, for the problem of multipactor suppression of load passive devices, we carried out research on the preparation of TiN thin films based on PEALD and put forward a new method for suppressing SEE with good suppression effect, high consistency, low surface resistance, and other aspects of the unity of the multipactor effect. The use of 20nm TiN coating can make the silver-plated surface secondary electron emission coefficient down to 1.59. The RF surface resistance change rate is less than 3%. In the field of communication, satellite and navigation and other fields have a wide range of application prospects.

Highly Conductive and Long-Term Stable Phosphorene-Based Nanocomposite for Radio-Frequency Antenna Application.

In this study, an omnidirectional and high-performance free-standing monopole patch radio-frequency antenna was fabricated using a urea-functionalized phosphorene/TiO2/polypyrrole (UTP) nanocomposite. The UTP nanocomposite antenna was fabricated via ball milling of urea-functionalized phosphorene, chemical oxidative polymerization of the UTP nanocomposite, and mechanical pelletizing of the composite. Based on experiments, the proposed UTP nanocomposite-based antenna exhibited long-term stability in terms of electrical conductivity. After 12 weeks, a slight change in surface resistance was observed. The proposed antenna exhibited high radiation efficiency (78.2%) and low return loss (-36.6 dB). The results of this study suggest the potential of UTP nanocomposite antennas for applications in 5G technology.

Polydopamine/SWCNT Ink Functionalization of Silk Fabric to Obtain Electroconductivity at a Low Percolation Threshold.

This study presents the functionalization of silk fabric with SWCNT ink. The first step was the formation of a polydopamine (PDA) thin coating on the silk fabric to allow for effective bonding of SWCNTs. PDA formation was carried out directly on the fabric by means of polymerization of dopamine in alkali conditions. The Silk/PDA fabric was functionalized with SWCNT ink of different SWCNT concentrations by using the dip-coating method. IR and Raman analyses show that the dominant β-sheet structure of silk fibroin after the functionalization process remains unchanged. The heat resistance is even slightly improved. The hydrophobic silk fabric becomes hydrophilic after functionalization due to the influence of PDA and the surfactant in SWCNT ink. The ink significantly changes the electrical properties of the silk fabric, from insulating to conductive. The volume resistance changes by nine orders of magnitude, from 2.4 × 1012 Ω to 2.3 × 103 Ω for 0.12 wt.% of SWCNTs. The surface resistance changes by seven orders of magnitude, from 2.1 × 1012 Ω to 2.4 × 105 Ω for 0.17 wt.% of SWCNTs. The volume and surface resistance thresholds are determined to be about 0.05 wt.% and 0.06 wt.%, respectively. The low value of the percolation threshold indicates efficient functionalization, with high-quality ink facilitating the formation of percolation paths through SWCNTs and the influence of the PDA linker.

Study of Electrical and Mechanical Properties of Polypyrrole-Coated Three-Dimensional Spacer Fabric

In this study, the liquid phase oxidative polymerization method was utilized to prepare polypyrrole conductive three-dimensional spacer fabrics. By controlling pyrrole solution, oxidant FeCl3 solution, dopant p-toluene sulfonic acid concentration and reaction time, the optimal process for the preparation of conductive spacer fabrics was obtained. This led to the best preparation process of polypyrrole-coated three-dimensional spacer conductive fabric (polypyrrole/three-dimensional spacer fabrics) being obtained. The results showed that the conductive properties of polypyrrole/three-dimensional spacer fabrics were the best when 0.10 mol/L pyrrole, 0.40 mol/L oxidant FeCl3 solution, and 0.40 mol/L dopant p-toluene sulfonic acid were prepared within a 2-h reaction time. The properties of polypyrrole/three-dimensional spacer fabrics were analyzed using the results from surface resistance, Fourier transform-infrared spectroscopy, mechanical properties, and stability tests. The results showed that polypyrrole was well attached to the three-dimensional spacer fabric surface, and the concentration of polypyrrole in the fabric exhibited an inverse correlation with changes in surface resistance. The mechanical properties of polypyrrole/three-dimensional spacer fabrics after treatment exhibit superior performance, with consistent changes in the meridional and zonal electrical properties during tensile testing and can maintain excellent long-term electrical stability in atmospheric environments.

A Study on Process Diagnosis Technology to Improve the Reliability of the Etching Process

With the increasing demand for semifductors in various fields, productivity efficiency is emerging as an important issue in semiconductor device manufacturing. To maximize semi-conductor productivity, the semiconductor process must be monitored in real time to continuously reflect the results and utilize them for process stabilization. However, various unexpected variables that occur during the process and errors in their judgment may cause a significant loss in semiconductor productivity. In this study, basic research was conducted on the concept of a diagnostic sensor capable of monitoring the etch amount by changing the surface resistance of a thin film according to the process. In various etching processes, a change in the surface resistance was observed according to the change in the thickness of the thin film, and the correlation between the change in thickness and the change in the physical quantity was studied. The trend of the overall measured values showed linearity. Based on the linear change in the etch amount and surface resistance according to the cycle change, the change in surface resistance according to the etch amount was quantitatively calculated. For the reliability of measurement, the thickness was compared using SEM and an el-lipsometer, and both investigated a thickness of 304 nm.

Lung Cancer Cell-Derived Exosome Detection Using Electrochemical Approach towards Early Cancer Screening.

Lung cancer is one of the deadliest cancers worldwide due to the inability of existing methods for early diagnosis. Tumor-derived exosomes are nano-scale vesicles released from tumor cells to the extracellular environment, and their investigation can be very useful in both biomarkers for early cancer screening and treatment assessment. This research detected the exosomes via an ultrasensitive electrochemical biosensor containing gold nano-islands (Au-NIs) structures. This way, a high surface-area-to-volume ratio of nanostructures was embellished on the FTO electrodes to increase the chance of immobilizing the CD-151 antibody. In this way, a layer of gold was first deposited on the electrode by physical vapor deposition (PVD), followed by thermal annealing to construct primary gold seeds on the surface of the electrode. Then, gold seeds were grown by electrochemical deposition through gold salt. The cell-derived exosomes were successfully immobilized on the FTO electrode through the CD-151 antibody, and cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) methods were used in this research. In the CV method, the change in the current passing through the working electrode is measured so that the connection of exosomes causes the current to decrease. In the EIS method, surface resistance changes were investigated so that the binding of exosomes increased the surface resistance. Various concentrations of exosomes in both cell culture and blood serum samples were measured to test the sensitivity of the biosensor, which makes our biosensor capable of detecting 20 exosomes per milliliter.

Investigating the Influence on the Electro-Conductive Properties of Leather as a Result of Natural Aging

Conductive leather and its use in smart products have found a lot of interest. Leather behaves as a good insulator, so it was treated with electrically conducting polypyrrole using a chemical polymerization technique to give it conductive characteristics. The electro-conductive properties are obtained by using the double in–situ oxidative polymerization of pyrrole. The electrical properties of conductive samples are studied using the Van Der Pauw method as a measuring method. The conductive leather transformation process was carried out during the 2018-2020 period, and the conductive leather samples were preserved in room conditions until the year 2023. The effect of natural ageing on the electro-conductive properties of conductive leather is the focus of this research. The results show that environmental factors influence polymer breakdown and stability, by causing an increase in electrical resistance. The changes in electrical surface resistance, as the effect of the ageing factor, vary from 39.8% to 129.9%. Those changes in electrical resistance indicate that ageing is one of the major concerns in the electrical properties and stability of conductive leather samples, so the performed measurements have importance in providing information for the researchers and designers regarding the conductivity changes over time as a result of natural ageing, which would like to work with conductive leather on smart products.

Investigating the Influence on the Electro-Conductive Properties of Leather as a Result of Natural Aging

Conductive leather and its use in smart products have found a lot of interest. Leather behaves as a good insulator, so it was treated with electrically conducting polypyrrole using a chemical polymerization technique to give it conductive characteristics. The electro-conductive properties are obtained by using the double in–situ oxidative polymerization of pyrrole. The electrical properties of conductive samples are studied using the Van Der Pauw method as a measuring method. The conductive leather transformation process was carried out during the 2018-2020 period, and the conductive leather samples were preserved in room conditions until the year 2023. The effect of natural ageing on the electro-conductive properties of conductive leather is the focus of this research. The results show that environmental factors influence polymer breakdown and stability, by causing an increase in electrical resistance. The changes in electrical surface resistance, as the effect of the ageing factor, vary from 39.8% to 129.9%. Those changes in electrical resistance indicate that ageing is one of the major concerns in the electrical properties and stability of conductive leather samples, so the performed measurements have importance in providing information for the researchers and designers regarding the conductivity changes over time as a result of natural ageing, which would like to work with conductive leather on smart products.

Investigating the Influence on the Electro-Conductive Properties of Leather as a Result of Natural Aging

Conductive leather and its use in smart products have found a lot of interest. Leather behaves as a good insulator, so it was treated with electrically conducting polypyrrole using a chemical polymerization technique to give it conductive characteristics. The electro-conductive properties are obtained by using the double in–situ oxidative polymerization of pyrrole. The electrical properties of conductive samples are studied using the Van Der Pauw method as a measuring method. The conductive leather transformation process was carried out during the 2018-2020 period, and the conductive leather samples were preserved in room conditions until the year 2023. The effect of natural ageing on the electro-conductive properties of conductive leather is the focus of this research. The results show that environmental factors influence polymer breakdown and stability, by causing an increase in electrical resistance. The changes in electrical surface resistance, as the effect of the ageing factor, vary from 39.8% to 129.9%. Those changes in electrical resistance indicate that ageing is one of the major concerns in the electrical properties and stability of conductive leather samples, so the performed measurements have importance in providing information for the researchers and designers regarding the conductivity changes over time as a result of natural ageing, which would like to work with conductive leather on smart products.

Tailoring mechanical and electrical properties of polydimethylsiloxane nanocomposites With graphene and carbon nanotubes for wearable electronics

We explored the use of soft and flexible graphene (Gr)-reinforced polydimethylsiloxane (PDMS; Gr-PDMS) and Gr-carbon nanotube (CNT)-reinforced PDMS (Gr-CNT-PDMS) as nanocomposites (NCPs) in wearable electronic applications and investigated their mechanical and electrical properties. Specifically, we evaluated the mechanical reinforcement of the NCPs by performing Shore scleroscope hardness and machine-washing tests and evaluated their electrical properties by using a four-point probe. The results revealed that as the Gr or CNT concentrations increased, the NCPs’ hardness and surface resistance increased and decreased, respectively. Scanning electron microscopy revealed the formation of layered polymeric structures in the Gr-PDMS NCPs, contributing to the increase in hardness and decrease in surface resistance. Furthermore, bending tests revealed that changes in resistance were positively correlated with the Gr concentration. PDMS with low Gr concentrations exhibited no substantial changes in surface resistance after bending tests. However, for PDMS, as the Gr concentration increased (>5 wt.%), the cross-sectional morphology observed after 500 bending cycles differed substantially from that before observed bending tests. Additionally, the influence of one-dimensional (CNT) and two-dimensional (Gr) nanomaterials on the mechanical and electrical properties of the flexible PDMS samples was investigated. The aim of this study is to highlight the importance of considering the properties of different nanomaterials in developing high-performance NCPs for wearable electronics.

Attribution analysis of water use efficiency in tropical rubber plantations during drought-monsoon season transition

Understanding the water use efficiency (WUE) of rubber plantations to seasonal fluctuations is critical for understanding the water, energy, and carbon cycle in tropical regions. In this study, we examine the exchange of water and heat fluxes between land and atmosphere in rubber plantation ecosystems during monsoon and drought seasons, employing data collected from eddy covariance towers. Further attribution analysis demonstrates that drought-induced alterations in the water use efficiency are predominantly governed by changes in surface resistance (positive contribution). The contributions of incoming shortwave radiation are virtually counteracted by air temperature and longwave radiation. It is noteworthy that the light use efficiency presents the most conspicuous negative contribution; however, this effect is predominantly counterbalanced by vapor pressure deficit (VPD) and aerodynamic resistance. The elevated water use efficiency (WUE) observed in rubber plantation ecosystems during the drought season raises concerns regarding the potential implications of anthropogenic forests on food and water security in tropical regions.

High Performance Epoxy Composites Containing Nanofiller Modified by Plasma Bubbles.

The thermal conductivity of polymer materials is a fundamental parameter in the field of high-voltage electrical insulation. When the operating frequency and power for electrical equipment or electronic devices increase significantly, the internal heat will increase dramatically, and the accumulation of heat will further lead to insulation failure and serious damage of the whole system. The addition of filler with high thermal conductivity into polymer is a common solution. However, the interfacial thermal resistance between filler and bulk materials is the major obstacle to improve thermal conductivity. Herein, in order to reduce the interfacial thermal resistance, nanofillers are modified by plasma technology. The surface modification of nano-Al2O3 is carried out using plasma bubbles with three atmospheres (Ar, Ar+O2, air) as well as coupling agent. The situation of surface grafting before and after the modification is characterized using FTIR, XPS, and SEM. The effect of the mechanism of modification on the thermal conductivity and reaction pathway is investigated. The results showed that the thermal conductivity after plasma modification is increased significantly. Especially, the thermal conductivity is increased by 35% for the sample modified by Ar+O2 atmosphere. This results because more hydroxyl is introduced on the filler surface by the plasma bubbles, which enhance the interface compatibility between filler and epoxy. In addition, surface insulation performance for the modified samples also is enhanced by 14%. This is associated with the change of surface resistance and trap distribution. These results provide potential support for the development of fabrication for high performance epoxy composites.

Polyaniline/Reduced Graphene Oxide/Carbon Nanotube Composites for Actuation-Based Sensing for Energy Storage

Until now, many carbon-based soft actuators with excellent performance have been developed, and various indicators of actuators are close to the limit. However, compared with the intelligence and versatility of natural biological muscles, soft actuators still have the shortcomings of single function and insufficient intelligence. Herein, polyaniline/reduced graphene oxide/carbon nanotube (PANI/RGO/CNT) composites are fully used to design and fabricate a smart gripper with a self-powered temperature-sensing function. First of all, the PANI/RGO/CNT composites have the characteristics of low coefficient of thermal expansion (CTE) and negative temperature resistivity. By cooperating with polymers with high CTE, a multifunctional bilayer actuator with a temperature-sensing function can be constructed with a temperature coefficient of resistance of 2364 ppm K–1. With the light irradiation (power density of 300 mW cm–2), the surface temperature, bending curvature, and resistance change of the actuator are as high as 48.8 °C, 0.86 cm–1, and −6.1%, respectively. Second, the PANI/RGO/CNT composite also possesses the advantage of large-area capacitance (165.8 mF cm–2). Thus, an integrated bilayer actuator with energy storage modules can be constructed through clever structural design and used as deformable supercapacitors. Finally, based on the similarity in structure and actuation mechanism of the multifunctional bilayer actuator and the integrated bilayer actuator, a smart gripper with a self-powered temperature-sensing function is proposed to provide real-time feedback of the change in temperature of the smart gripper as it grasps the object. The versatility of the smart gripper is achieved without increasing the complexity of the structure, demonstrating the advantages of the design concept of integrating sensing and energy storage in the design of soft actuators. The proposed PANI/RGO/CNT composites have great potential to be used in the fields of intelligent actuators, deformable supercapacitors, and artificial muscles.

Optical Study of Few‐Layer Graphene Treated by Oxygen Plasma

Oxygen plasma treatment is often used to clean the surface or etch graphene for functional structures. Some unique properties such as photoluminescence (PL), energy bandgap engineering, and so on are presented in single‐layer graphene (SLG). Compared with SLG, few‐layer graphene (FLG) has higher luminescence intensity, slower decay rate, and better controllability. It is more universal in the application of new optoelectronic devices and transparent electrodes. So, a systematic study is provided to analyze the mechanism between chemical vapor deposition of few‐layer graphene and oxygen plasma process based on the optical characterization method. Surface morphology, structural defects, resistance change, chemical state, and PL are traced and investigated under different oxygen plasma treatment times. The CO and CO bonds on the surface of the FLG appear to increase and then decrease with oxygen plasma etching based on X‐ray photoelectron spectroscopy (XPS) characterization. A linear square resistance change is presented from 1.4 to 4.8 kΩ sq−1. Besides that, an obvious redshift–blueshift change is produced in fluorescence characteristic spectra. Herein, comprehensive research on the influencing mechanism of graphene and oxygen treatment is exhibited, which provides the potential to construct optoelectronic devices.

Graphene Functionalized Cotton Nonwoven for Thermotherapy

ABSTRACT Graphene-based electroconductive textile materials are advantageous over metal/gel-based heating pads for thermotherapy because of their flexibility, processability, and ability to maintain a constant temperature for an extended period. The electro-thermal properties of graphene-based nonwoven depend on its surface resistivity which in turn depends on the amount of graphene oxide (GO) deposition. In this work, highly conductive, flexible, lightweight, and antibacterial graphene functionalized cotton nonwoven with excellent electro-thermal performance is reported. For this, needle punched nonwoven structure is designed and its construction variables (Fabric GSM, punch density, and depth of penetration) are optimized with the Box-Behnken response surface design to achieve maximum GO adsorption and minimum surface resistivity. The lowest surface resistivity of 727.57 Ω sq−1 is achieved at 22.18% GO add-on. The functionalized fabric shows excellent electro-thermal properties and a maximum surface temperature of 118°C is achieved at 30V DC supply. The change in surface resistivity of rGO-cotton (reduced graphene oxide coated cotton) is insignificant even after atmospheric aging for 10 weeks, 4 washings and 10 rubbings. Antibacterial activity of 97.10% is achieved toward Staphylococcus aureus bacterium.

Effect of Graphite Content on the Conductivity, Wear Behavior, and Corrosion Resistance of the Organic Layer on Magnesium Alloy MAO Coatings

To impart electrical conductivity on magnesium alloy micro-arc oxidation coatings, a graphite/epoxy conductive layer was prepared on the surface of a ceramic layer in this work, focusing on wear behavior and corrosion resistance of the coating. At a graphite weight of 80 wt%, the square resistance of the coating decreased to 217.6 kΩ/□, and it exhibited good resistance. Combined with the distribution of graphite particles in the coating and the change in surface resistance, we determined that the conductive mechanism of the coating occurred through quantum tunneling when the graphite content was 60 wt%. When the graphite content increased from 60 to 80 and 100 wt%, the formation of conductive paths on the surface of the coating further improved the conductivity. The hardness of the organic coatings was positively related to the graphite content. Analysis of the wear scars and wear debris after dry friction and wear testing showed that the wear forms of the coating consisted of abrasive wear when the graphite content was in the range of 20–40 wt%. When the graphite content was in the range of 60–100 wt%, the wear forms of the coating consisted of abrasive wear and peeling wear.

Impact of Spartina alterniflora invasion on evapotranspiration water loss in Phragmites australis dominated coastal wetlands of east China

A comparative analysis of co-existing invasive and native wetland plants is a practical approach to exploring exotic plant invasiveness. Spartina alterniflora is an invasive C4 grass, prevalent in China's coastal wetlands and other parts of the world, posing a risk to the hydrological cycle. While the crop coefficient Kc and evaporative water loss of the invasive S. alterniflora are still considerably unexplored, we utilized field measurements and a modeling technique to evaluate water loss to Evapotranspiration ET in marshes with S. alterniflora and P. australis. Changes in surface resistance, canopy height, and the technique used to calculate net radiation from incoming solar radiation have all been shown to influence the Penman–Monteith methodology for estimating ET. Overall, S. alterniflora surpassed P. australis in leaf area index LAI, ET, crop coefficient Kc, peak net photosynthetic rate, and growing season. Daily ET values in both plants ranged from 0.98 to 6.35 mm/day and 1.91 to 8.16 mm/day during the monitoring period. According to regression analysis, the key driving factors of ET from both plant communities throughout the growing season are net radiation, soil moisture, relative humidity, air temperature, and surface temperature. These findings highlight the necessity of precisely determining these parameters based on site-specific data instead of depending on empirical models developed mainly for crops and forests. Given the mean ET rates found in this study, S. alterniflora invasion in China currently accounts for ~4.3 × 106 m3 day−1 of water loss to ET, posing a severe threat to the availability of water resources in China's wetlands. Our findings contribute to a better understanding of the link between plant invasiveness and water loss in wetlands, offering stakeholders a benchmark for achieving future goals and plans related to the utilization of wetland water resources worldwide.

Asymmetry of Western U.S. River Basin Sensitivity to Seasonally Varying Climate Warming

AbstractFuture climate warming over the Western U.S. (WUS) is projected to be greater in summer than winter. Previous model‐based studies of large river basins in the WUS showed much different annual streamflow responses to warming in warm versus cool seasons. However, it remains unclear how the annual streamflow relative responses to seasonal warming (asymmetry) and drivers of the response asymmetry vary across the entire WUS at the catchment‐scale, and how the simulated results compare with observations. Here, we investigate the asymmetry of annual streamflow responses to warm versus cool season warming at the HUC‐8 level across the entire WUS using model simulations and observations. We also examine the asymmetries' relationship with land surface and hydroclimate characteristics, and the primary contributor to the response asymmetry for each HUC‐8 basin. The HUC‐8 level results reveal more complexity than do earlier analyses of much larger river basins. Over 25% of WUS area has annual streamflow increases in response to warming in at least one season (mostly cool season). Annual streamflow is most sensitive to warm season warming in cool, inland basins, especially the northern Columbia River basin and most of the Upper Colorado River Basin, and most sensitive to cool season warming in warm, coastal basins. This bi‐directional pattern is enhanced by vegetation coverage but weakened by long‐term snowpack decline. In coldest basins with short snow‐free seasons, net radiation changes dominate the streamflow response asymmetry. For basins with cold‐to‐intermediate temperatures, vapor pressure deficit changes dominate. For warmest basins, surface resistance changes dominate.

Electrochemical Polishing of 7075 Al Alloy in Phosphoric Acid

7075 aluminum (Al) alloy has been widely used in aircraft structures and other high-end electronic products owing to its excellent mechanical and chemical properties, while its damage-free and highly efficient surface finishing remains a challenge. Herein, we demonstrate a systematic study of the anodic behaviors of 7075 Al alloy during the electrochemical polishing (ECP) process in phosphoric acid under different applied potentials, and the changes of surface morphology, roughness, electric current, and resistance are studied intensively. According to the surface morphology and current density, the ECP of 7075 Al alloy can be divided into 4 stages including the negative leveling stage, leveling and corrosion stage, leveling and brightening stage, and pitting and corrosion stage. Different factors influencing each stage and the effects of impurity phases in the ECP process are experimentally validated. Under optimized conditions, a mirror surface with a roughness (Ra) of 46.7 nm (decreased from an initial value of 153.2 nm) can be obtained by ECP for 10 min. The presented findings are of great value for the further development of ECP process of multiphase alloys.