Changes In Specific Resistance Research Articles

Study on the Degradation of SOFC Anodes Induced by Chemical and Electrochemical Sintering Using EIS and µ-CT

The goal of the present study was to quantify degradation phenomena on anodes that can be attributed to chemical (thermal) and/or electrochemical sintering, to find out the underlying mechanisms, and to propose countermeasures. The samples were thermally aged for times from 0 to 1000 h, and additional samples of the same type were subjected to electrochemical loading over the same period. The cells were then examined for microstructural changes using FE-SEM/EDS and micro-computed tomography (µ-CT), and the results are correlated with electrochemical impedance spectroscopy (EIS) parameters of long-term electrochemical experiments under dry and humid conditions. It has been shown that it is possible to distinguish between the thermal (chemical) and the electrochemical part of the microstructure degradation. Humidity is an important factor that affects the microstructure in the long term. Tortuosity, porosity, and specific resistance change with time, depending on the humidity of the fuel. Tortuosity changes by one order of magnitude in the direction perpendicular to the electrode surface, while in the other two directions in the plane, the changes are only moderate. Porosity increases in all electrochemically treated samples by 1–5% depending on dry ore humidity conditions and time. As all other experimental parameters are the same in all experiments, the EIS results confirm through the increasing specific resistance, mainly the influence of the changes on the microstructure on the electrochemical properties of the cells.

Changes in Operating Characteristics of Transformer Oil under the Action of Ionizing Radiation

The changes in physicochemical parameters such as specific resistance, viscosity, density, and formation of gaseous products H2, CH4, C2H4, C2H6, C3H8, C4H10, C5H12, and C6H14 with respect to the adsorbed dose in the interval of 29.7–237.6 kGy are studied. It is established that the chemical composition of transformer oil changes under the action of γ irradiation, which is accompanied by the changes in specific resistance, viscosity, and density of oil. The degree of conversion depends on the adsorbed dose and grows when it increases. The IR spectra show =C–H stretching vibrations, –C=C in-plane deformation vibrations, and –CH out-of-plane deformation vibrations of aromatic compounds. In addition, there are –C–H stretching vibrations and antisymmetric and symmetric –C–CH3 deformation vibrations in alkanes. The IR absorption spectra are observed in the range of Δλ1 = 2800–3300 cm–1, Δλ2 = 2000 cm–1, Δλ3 = 1350–1450 cm–1, and Δλ4 = 600–1200 cm–1. The absorption band of Δλ4 = 600–1200 cm–1 is a smeared part of the spectrum with a number of weak absorption bands.

Estimation and analysis of various influential factors in the braking process of rail vehicles

Braking distances play an important role in the organization of rail traffic and exploitation of rail vehicles. The braking distances of rail vehicles affect several factors that cannot be defined and determined precisely. In this paper, a mathematical model, for train moving through braking, is presented by taking into account the relevant train braking resistance and a procedure is given for solving a differential equation of movement of the rail vehicle during braking. The procedure allows determining influential factors that have an effect on the length of braking distances. The influence and the changes of specific resistance during the movement of the train, braking force, and adhesion between wheel and rail during the braking process are presented. The results obtained with the presented mathematical model are accurate and match with the results obtained experimentally.

Evaluating the effects of the preoxidation of H2O2, NaClO, and KMnO4 and reflocculation on the dewaterability of sewage sludge

The preoxidation effects of H2O2, NaClO, and KMnO4 on the dewaterability of sewage sludge were compared by analyzing the changes in specific resistance to filtration (SRF), filter cake moisture content (FCMC), extracellular polymeric substance (EPS) fractions and components, and floc properties. The three oxidants varied in oxidation efficiency and exhibited distinctive mechanisms. NaClO not only destroyed sludge flocs and EPSs but also effectively caused cell lysis, resulting in release of a considerable amount of organic matters and subsequently significant deterioration of dewatering performance. The oxidation of H2O2 and KMnO4 was relatively mild and occurred mainly on the outer layers of the sludge flocs and cell-bound EPSs. By contrast, the SRF and FCMC of the sludge conditioned with a low dose of KMnO4 were slightly improved, and a fraction of soluble EPS was compressed because of the coagulation effect of the oxidation product MnO2. The pH of the sludge conditioned with H2O2 and KMnO4 showed no considerable change. Meanwhile, NaClO evidently increased the alkalinity of the sludge because of the hydrolysis effect. After the pH of the NaClO-treated sludge was readjusted to 7.0, the partial protonation efficiency slightly alleviated the deterioration of sludge dewatering performance. The preoxidized sludge was then subjected to reflocculation treatment using FeCl3, polyacrylamide, and a cationic starch-based flocculant, respectively. The combined treatment of preoxidation and reflocculation showed a high dewatering efficiency owing to their synergistic effect.

Hydrogen intercalation of compounds with FeSe and MoS2 layered crystal structures

Two compounds with a layered structure of FeSe0.88 superconductor and MoS2 semiconductor are intercalated with molecular hydrogen (H2) and ionized hydrogen (H+) formed in a special ion source. In the case of FeSe0.88, intercalation with hydrogen ions causes a slight increase in the superconducting transition temperature of the compound. It is noteworthy that the temperature of the middle of superconducting transition Т cm of this system can be a little higher on account of magnetization of the FeSe ferromagnetic phase (in a field up to 0.1 T) being in the contact with it. Hydrogen intercalation of MoS2 is accompanied by an increase in the weight of the compound, and the lattice parameter c associated with the interlayer distance increases from 12.241(6) to 12.297(5) A. At the same time, along with the existing van der Waals forces, one observes the emergence of Н bonds, which leads to the formation of MoS2H0.38 hydride and to an abrupt change in specific resistance (by an order of magnitude) relative to its value before hydrogen intercalation.

열처리된 그래핀 산화물을 정공주입층으로 이용한 유기발광 다이오드

Article history: This paper reports on thermally adjusted graphene oxide (GO) as the hole transport layer (HTL) for organic light-emitting diodes (OLEDs). GO is generally not suitable for HTL of OLEDs because of intrinsic specific resistance. In this paper, the specific resistance of GO is adjusted by the thermal annealing process. The optimum specific resistance of HTL is found to be 10 2 Ω·m, and is defined by the maximum current efficiency of OLEDs, 2 cd/A. In addition, the reasons for specific resistance change are identified by x-ray photoelectron spectroscopy (XPS). First, the XPS results show that several functional groups of GO were detached by thermal energy, and the amount of epoxide changed substantially following the temperature. Second, the full width at half maximum (FWHM) of the C-C bond decreased during the process. That means the crystallinity of the graphene improved, which is the scientific basis for the change in specific resistance.

Transient variation of a cross-sectional area of inkjet-printed silver nanoparticle ink during furnace sintering

Abstract In this work, the transient variation of a cross-sectional area of inkjet-printed silver nanoparticle ink was monitored as a function of temperature. The ink was composed of 34 wt% silver nanoparticles with an average grain size of 50 nm. In order to determine the relationship between shrinkage and electrical properties, the cross-sectional area and specific resistance change were measured with various sintering temperatures and times. The samples were sintered at 150, 200, and 250 °C for 60, 120, 300, 600, 1200, and 3000 s. The cross-sectional profile was investigated in order to calculate the cross-sectional area of the ink using a surface profiler. To examine the mass transfer in a conductive line with various sintering temperatures and times, the surface morphology was investigated via field-emission scanning electron microscopy. As the temperature increased, the shrinkage ratio of the ink's cross-sectional area increased. By investigating the relationship between specific resistance and shrinkage, the sintering mechanisms can be determined.

Lung function and bronchial responsiveness after Mycoplasma pneumoniae infection in early childhood

Mycoplasma (M.) pneumoniae has been associated with exacerbation of symptoms in asthmatic school children and adults; and an etiological role in asthma has been suggested. The purpose of this study was to investigate whether infection with M. pneumoniae in early childhood has a long-term influence on lung function and bronchial responsiveness. In a retrospective, clinical cohort-study children younger than 5 years-of-age when PCR-tested for M. pneumoniae were enrolled. Sixty-five children with clinical symptoms suggesting infection with M. pneumoniae during an epidemic season completed a clinical follow-up examination including lung function testing (28 PCR-positive and 37 PCR-negative). In addition to the PCR-test for M. pneumoniae all respiratory tract specimens were additionally tested for other atypical bacteria and for viruses by PCR. Lung function was measured as specific airway resistance by whole-body plethysmography and bronchial hyperresponsiveness was assessed by cold, dry air hyperventilation. Neither baseline lung function nor bronchial response to cold dry air hyperventilation differed between M. pneumoniae-positive and -negative children: mean baseline lung function were 1.17 versus 1.21 (kPa sec), P = 0.45; and mean change in specific resistance was 13% versus 9%, P = 0.42. In conclusion, M. pneumoniae infection in early childhood was not associated with long-term effects on lung function and bronchial hyperresponsiveness 2 years after infection.

Spin-memory loss and current-perpendicular-to-plane-magnetoresistance in sputtered multilayers with Au

We derive a spin-diffusion length at 4.2 K in sputtered Au, lsfAu=35−5+65 nm, spin-memory-loss at Au/Cu interfaces, δAu/Cu=0.13−0.02+0.08, and Au/Cu interface specific resistance, 2ARAu/Cu=0.35−0.05+0.10 fΩ m2. We also show that exchange biased spin valves with Au sandwiched between Co layers produce changes in specific resistance, AΔR, comparable to those for Cu and Ag.

Enhancing current-perpendicular-to-plane magnetoresistance by adding interfaces within ferromagnetic layers

We show that adding “internal interfaces” within each Co layer can enhance both the total current-perpendicular-to-plane specific resistance, AR, and the change in specific resistance with magnetic field, AΔR, of [Py/Cu/Co/Cu]3 hybrid multilayers, AΔR by over 100%, with only a small increase in the total sample thickness. However, the growth of both AR and AΔR with the number of inserted interfaces is slower than predicted by a simple two-current series-resistor model. We provide evidence that this less rapid growth is due to spin-flipping at the Co/Cu interfaces, plus the formation of “incomplete interfaces” when the Cu layers are very thin.

Water-in-oil microemulsion : influence of co-surfactant chain- length and nature of emulsifier

Two types of water-in-oil (w/o) microemulsions : anionic sodium dodecyl sulfate (SDS) and cationic cetyltrimethylammonium bromide (CTAB) have been studied at various temperatures (25-35°) as a function of alkyl chain-length of co-surfactant (n-alkanols, C 4 OH-C 8 OH) and oil (n-alkanes, C 5 H-C 7 H). The free energy of transfer of co-surfactant from the continuous oil phase to the interfacial region (ΔG 0 5 ) has been reported and the adsorption free energy per methylene group of the alkanols (ΔG 0 s , a l k a n o l /CH 2 ) has been computed. With increase in the water content the appearance of mieroemulsion systems changed from a clear solution to bluish which finally became turbid. The transitions were identified on the basis of specific resistance measurements. A significant change in specific resistance was observed at the transitions. The critical n w a t e r /n o i l ratio (V c ) where the microemulsion is about to breakdown, was calculated with the help of viscosity measurements.

Stabilization of shielding effectiveness of electromagnetic interference of aluminium fibre and polyamide composites

Recent rapid development of electronic devices such as TV, OA instruments, computers, etc., has given rise to electromagnetic interference (EMI) because almost all housings of these devices are made of plastics which are transparent to electromagnetic interference. In order to shield EMI, technical approaches have been considered extensively to provide electrically conductive housing, i.e., coating, metallizing and compounding of conductive materials. Thus, a number of workers have endeavoured to prepare electrical conductive composites, namely electromagnetic interference shielding composites and a comprehensive review appeared recently [1]. It is believed that fibrous fillers are superior to other conductive fillers such as powdery particles or flakes, except in economical feasibility [1-4]. However, a new manufacturing process for short-length metal fibre (Chatter machining) developed by Nakagawa et al., overcame the problem [2-4]. When the development of functional materials such as in this case is desired, electrically conductive composites, durability or life-time of the function of the materials should be taken into consideration. From this point of view we have been studying thermal stability of shielding effectiveness of EMI of composites, and in our previous paper [8] we reported thermal stability of shielding effectiveness of EMI of composites prepared with various metal fibrous fillers and high-density polyethylene. Subsequently, we have examined thermal stability of the shielding effectiveness of EMI of composites prepared with various conductive fillers and polyamide, Nylon 12, and we found that in the case of aluminium fibre composites their functional stability was improved remarkably by the surface treatment of the fillers with commercial polymers and oligomers. Chatter-machined aluminium fibres, (10.9 g, Kobe Chutetsu Co. Ltd, Japan, diameter 60#m, length 3mm) were thoroughly blended with commercial powdery polyamide, Nylon 12 (23.4 g, Daiamid, Daicel, Japan) in a polyethylene envelope, and placed between steel plates with a spacer 0.2cm thick. The blended materials were heated at 130°C for 10 min in air, and then pressed at 130°C under 200kgcm -2 pressure for 5rain to give a 15cm x 15cm x 0.2cm sized composite containing 15 vol % aluminium. Aluminium fibres (10.9g) were dipped in 200ml dilute solution of commercial polymers or oligomers (0.1 wt%) for 10min under stirring, taken out and dried under reduced pressure for a day. Measurements of electrical conductivity and shielding effectiveness of EMI were similar to those described in a previous paper [5]. Thermal treatment was carried out up to 2500 h at 80°C in an electric oven equipped with a fan. It is well known that the aspect ratio of fillers is important for the generation of the electrical conductivity of the composites and fibrous fillers, especially chatter-machined short-lenght metal fibres which are superior to other conductive fillers such as powdery particles or flakes [1]. In addition, in a previous paper [5], we observed that 15 vol % metal fibrous fillers was quite sufficient to generate the electrical conductivity of the composites. Therefore, a series of composites were prepared using 15 vol % chatter-machined aluminium fibres which had been treated with various commercial polymers and oligomers. Shielding effectiveness of EMI of the composites is closely related to the electrical conductivity of the samples, therefore, changes in specific resistance of the samples during thermal treatment at 80 ° C were initially measured up to 2500h. As shown in Fig. 1, before heating the specific resistance of the sample prepared with untreated aluminium fibre was of the order of 10 .2 f~cm. The electrical conductivity of the composites prepared with aluminium fillers treated with

Developments of Insturments for Groundwater Flow Velocity and Direction Measured its Specific Resistance Change in a Boring Hole.

Developments of Insturments for Groundwater Flow Velocity and Direction Measured its Specific Resistance Change in a Boring Hole.

Effect of Chain Length of Alkanes on Water-in-Oil Microemulsions

In the present study, observations and data on the formation and characterization of water-in-oil (W/o) microemulsion systems composed of a cationic surfactant (Cetyltrimethylammoniumbromide)-water-alkanes (C 6 -C 7 ) 2-ethyl-1-hexanol have been reported. The influence of the alkane chain length on the formation of microemulsion systems has been investigated. When the amount of oil or water was increased, the appearance of microemulsion changed from clear to bluish to turbid. These transitions were indentified on the basis of both resistance measurement and visual appearance. Changes in specific resistance with water composition were interpreted in terms of water inforced-micellar structural changes. The critical moles of water/mole of oil ratio, Vc values, at which the microemulsion remains stable, was calculated from viscosity measurements. The linear dependence of Vc values on the number of carbon atoms in the alkyl chain of oil has been reported for predicting the size of the chain length of oil for the formation of a wide range of stable W/o microemulsions. The standard free energy change for transfer of cosurfactant from oil phase to the interfacial phase is also reported.

Parameters of alloy p-n junctions in Cu2O

The p-n junctions are made by melting copper on single-crystal Cu2O plates. A change in specific resistance of the Cu2O from 2.8 × 102 to 1.15 × 105 ohm-cm causes the reverse voltage at a reverse-current density of 2 m A/cm2 to increase from 15 to 500 V, while the forward current density at 2 V decreases from 250 to 2 mA/cm2.

Electrical Properties of Polyethylene Single Crystals

The currents through polyethylene single crystals have been measured as functions of voltage and temperature between 200°K and 400°K. The negative resistance phenomena were sometimes observed when thin wire electrodes were used for measuring the current through polyethylene single crystals of 70–300 Å thickness, but their behaviors were different from those described by Roggen. In the case of vacuum evaporated electrodes, however, such phenomenon was not observed. Similar measurements have been done with polyethylene thin films formed by vacuum evaporation. In this case, the negative resistance similar to that described by Hickmott was sometimes observed. Changes of specific resistance were closely related with the change of crystal thickness in thinner crystals, and the electron transport mechanism was discussed quantitatively with simple theoretical expressions of tunneling effect and Schottky emission.

Preparation of Ceramic Semiconductors from High‐Vanadium Glasses

A number of phosphate glasses with unusually high vanadium content were studied with respect to some of their electrical properties. It was found that 75 to 85 wt% V2O5 could be reacted with various metaphosphates (Ba, Pb, Li, Na, Cd, V, and K) resulting in good‐quality reproducible glasses in 500‐g melts. The electrical resistance of these glasses appeared to be particularly dependent on their thermal history below the liquidus but above the transformation range. A large change in specific resistance resulted when vitreous specimens were heat‐treated to produce varying amounts of devitrification. For a specimen containing potassium metaphosphate, resistivity was reduced from about 103 to 10 ohm‐cm.

XIII.—The Effect of Permanent Elongation on the Specific Resistance of Metallic Wires

The object of this investigation was to obtain information as to the change of specific resistance produced in wires of various metals by different amounts of elongation. The present paper refers to experiments on copper, iron, and German silver wires.