Trend Of Electrical Conductivity Research Articles

The evaluation of microstructure of carbon/carbon composites generated by ultra-high temperature treatment towards excellent electromagnetic interference shielding property

Due to the need of electromagnetic shielding materials for satellites, carbon/carbon (C/C) composites have become a research focus due to their excellent properties. In this study, the ultrahigh treatment temperature was raised from 2500 °C to 2700 °C and 3000 °C, and the influence of micromorphology on the mechanical and electromagnetic shielding properties of materials was explored with an innovative image recognition method. The porosity of the C/C composites increased with increasing heat treatment temperature, from 6.95% to 8.65% after 3000 °C. The density decreased, and the graphitization degree increased gradually, indicating an improvement in the texture order degree. For the compression properties of the material, the Z direction after treatment at 3000 °C maintained a high compressive strength of 171 MPa. The electromagnetic interference (EMI) shielding efficiency (SE) of the C/C composites, which is completely consistent with the trend of electrical conductivity, increased with increasing heat treatment temperature, and the EMI SE of the C/C composites reached ∼80 dB after 3000 °C. It was found that reflection was the dominant EMI shielding mechanism of C/C composite materials. By comparing the comprehensive data indexes of C/C composites with other materials, the composites are expected to be a new generation of satellites with electromagnetic shielding material.

Investigation of mechanical properties, thermal and electrical conductivity of multi-walled carbon nanotubes reinforced with Al2024 nanocomposites

In the present research work, multi-walled carbon nanotubes (MWCNTs) were reinforced with Al2024 alloy has been developed via powder metallurgy technique. MWCNTs are taken in a weight percentage of 1%, 2%, and 3% were mixed in a planetary ball mill. Further, the mixture was compacted, sintered, and heat-treated for the evaluation of various properties. The density of the nanocomposite was found to be decreased by 4.8%, whereas porosity by 3.04% due to the incremental addition of MWCNTs. Hardness increases by 9.77% and tensile strength increase 17.39 % due to the reinforcement of MWCNT percentages. The thermal conductivity decreases by 30.53% in a sintered and 77.89% in a sintered-heat treated composite. The decreasing trend in electrical conductivity has been observed with an increase in the quantity of MWCNTs from 55.88% to 45.45% in sintered and sintered-heat treated composite respectively. The morphological, the elemental study, and uniform dispersion of the MWCNTs reinforced Al2024 were observed and analyzed using SEM, TEM, XRD, and EDS.

Disappearance Time of a Few Polycyclic Aromatic Hydrocarbons in Soil

The present study attempts to determine the order of reactions for degradation of four polycyclic aromatic hydrocarbons viz., anthracene, fluorene, naphthalene and phenanthrene in six selected soil samples by method of trials. The half-life period or the disappearance times in days for 50% (DT 50) of the hydrocarbons initially applied to the soil were determined after finding out the probable order of the reactions using the half-life equations. A few of the extracts are subjected to GC analysis. Nine of 21 samples studied in the experiment are degraded and zero-order while the remaining samples are of the first order. The increasing trend in electrical conductivity and decreasing trend of pH support the formation of polar substances from non-polar hydrocarbons. Average DT 50 values for a mixture of the cited PAHs are 6 and 16 days, respectively, in presence of Fenton’s Reagent and without it in the samples having 200 ppm concentration. In a semi-closed system, where there is no horizontal spread of solids and liquids, the DT 50 depends on initial pollutant concentration. Fenton’s Reagent has been found to enhance the rate of degradation by the rapid conversion of the hydrocarbons into derivatives or fragments.

Vermicomposting of distillery sludge waste with tea leaf residues

Abstract Studies on bioconversion of solid wastes have been performed for controlling pollution due to waste disposal. Vermicomposting has been identified as an efficient technology for this purpose. The present study aims at the management of distillery sludge waste (DSW) combined with tea leaf residues (TLR) using the eco-biological tool, vermicomposting. DSW and TLR were combined in different ratios and subject to vermicomposting for a period of 45 days using the earthworm, Eisenia fetida. The physico-chemical properties were analyzed in vermicompost samples taken on the 0, 15, 30 and 45th day. It was observed that the values of pH, total nitrogen, total phosphorus, total potassium, available nitrogen, available phosphorus, available potassium, total calcium and total magnesium were increased with a declining trend in electrical conductivity, total organic carbon and C/N ratio from its initial value. Finally, the solid wastes were successfully transformed into a nutrient-rich vermicompost.

Stability and electrical conductivity of BaCe0.85Tb0.05M0.1O3−δ (M=Co, Fe, Y, Zr, Mn) high temperature proton conductors

High temperature proton conductors (HTPCs) must possess both high electrical conductivity and good chemical and structural stability for practical applications. In this work, BaCe0.85Tb0.05M0.1O3−δ (BCTM) high temperature proton conductors doped with M=Co, Fe, Y, Zr, Mn were prepared by the sol-gel combustion method using EDTA and citric acid as the chelating agents. The structural and chemical stability, and electrical conductivity of the BCTM perovskites were measured in different atmospheres by the powder X-ray diffraction (XRD) and four-probe techniques. The results indicate that the perovskite phase formed in the BCTM oxides after calcination at 1000°C can be preserved well in H2 and water vapor-containing atmospheres, whereas the perovskites may be segregated into metal oxides and react with CO2 into carbonates in the CO2 environment due to the strong alkalinity of the BaCeO3 composites. The electrical conductivity of the BCTM oxides in hydrogen atmosphere is noticeably higher than in the air atmosphere, confirming the dominant protonic conductivity in the BCTM perovskites. Doping with Mn or Co ions in the BCTb perovskite favors improving the electrical conductivity with lower activation energy. The BCTMn perovskite demonstrates an N-shaped variation trend in electrical conductivity with temperature due to the multi-valence states for Mn ions presented at different temperatures.

Synthesis of PVDF-co-HFP-ZrO<sub>2</sub> Based Composite Polymer Electrolyte for Battery Applications

Composite polymer electrolytes based on poly (vinilydene fluoride-co-hexafluoro propylene) as polymer host, zinc triflate as dopant salt and ZrO2 as nanofiller were prepared by solution casting technique using N,N dimethylformamide (DMF) as solvent. The loading of the ZrO2 nanofiller carried out for the optimized composition shows an increasing trend of electrical conductivity from 10-11 to 10-5 Scm-1 at 298 K. The effective structural complexation of the polymer electrolyte system and influence of nanofiller were also analyzed by means of Fourier transform infrared spectral analysis. The detailed impacts on the degree of crystallinity were investigated by differential scanning calorimetric analysis. The electrochemical stability of the optimized composition with 7 wt% ZrO2 loading was found to exist up to 2.6 V.

Microstructure Characterization and Electrical Conductivity Measurement of La1−xCaxCrO3 (x = 0.25, 0.4, 0.5) Prepared by Aspartic Acid‐Assisted Solution Combustion

Nanocrystalline La1−xCaxCrO3 (x = 0.25, 0.40, 0.50) powders were synthesized by gel‐combustion process using aspartic acid as a fuel. Phase identification of the samples was carried out by powder X‐ray diffraction. Pore distribution and microstructure of sintered pellets were investigated by small angle neutron scattering (SANS) and scanning electron microscopy (SEM). SANS and relative density measurement results indicate better sinterability for products with lower Ca2+ concentration. Four‐probe direct current electrical conductivity of LaCrO3 with different Ca2+ concentrations was measured in the temperature range 350°C–1000°C in air as well as in hydrogen atmosphere. Linear behavior of Arrhenius plots of electrical conductivities in both air and hydrogen atmosphere indicates charge carrier transport is due to thermally activated hopping conduction of small hole‐polarons. It was observed that the electrical conductivity decreased with increasing substitution of Ca2+ concentration instead of increasing small polaron concentration as expected. This trend in electrical conductivity is attributed to the neutralization of some small polarons due to formation of oxygen vacancies with increase in Ca2+ concentration.

Transport properties of alumina nanofluids

Recent studies have showed that nanofluids have significantly greater thermal conductivitycompared to their base fluids. Large surface area to volume ratio and certain effects ofBrownian motion of nanoparticles are believed to be the main factors for the significantincrease in the thermal conductivity of nanofluids. In this paper all three transportproperties, namely thermal conductivity, electrical conductivity and viscosity, were studiedfor alumina nanofluid (aluminum oxide nanoparticles in water). Experiments wereperformed both as a function of volumetric concentration (3–8%) and temperature(2–50 °C). Alumina nanoparticles with a mean diameter of 36 nm were dispersed in water. Theeffect of particle size was not studied. The transient hot wire method as describedby Nagaska and Nagashima for electrically conducting fluids was used to testthe thermal conductivity. In this work, an insulated platinum wire of 0.003 inchdiameter was used. Initial calibration was performed using de-ionized water andthe resulting data was within 2.5% of standard thermal conductivity values forwater. The thermal conductivity of alumina nanofluid increased with bothincrease in temperature and concentration. A maximum thermal conductivity of0.7351 W m−1 K−1 was recorded for an 8.47% volume concentration of alumina nanoparticles at46.6 °C. The effective thermal conductivity at this concentration and temperature was observed tobe 1.1501, which translates to an increase in thermal conductivity by 22% when comparedto water at room temperature. Alumina being a good conductor of electricity, aluminananofluid displays an increasing trend in electrical conductivity as volumetric concentrationincreases. A microprocessor-based conductivity/TDS meter was used to perform theelectrical conductivity experiments. After carefully calibrating the conductivitymeter’s glass probe with platinum tip, using a standard potassium chloride solution,readings were taken at various volumetric concentrations. A 3457.1% increase in theelectrical conductivity was measured for a small 1.44% volumetric concentrationof alumina nanoparticles in water. The highest value of electrical conductivity,314 µS cm−1, was recorded for a volumetric concentration of 8.47%. In the determination of thekinematic viscosity of alumina nanofluid, a standard kinematic viscometer with constanttemperature bath was used. Calibrated capillary viscometers were used to measure flowunder gravity at precisely controlled temperatures. The capillary viscometers werecalibrated with de-ionized water at different temperatures, and the resulting kinematicviscosity values were found to be within 3% of the standard published values. An increaseof 35.5% in the kinematic viscosity was observed for an 8.47% volumetric concentration ofalumina nanoparticles in water. The maximum kinematic viscosity of alumina nanofluid,2.901 42 mm2 s−1, wasobtained at 0 °C for an 8.47% volumetric concentration of alumina nanoparticles. The experimentalresults of the present work will help researchers arrive at better theoretical models.

Optical and X-ray photoelectron spectro-scopic studies of electrically conducting benzimidazobenzophenanthroline type ladder polymers

X-ray photoelectron spectroscopic studies of two as-grown benzimidazobenzophenanthroline-type polymers (abbreviated BBL and BBB) are reported. The results demonstrate that intermolecular charge-transfer interactions between conjugated polymers and polyphosphoric acid solvent are involved with the trend of electrical conductivity. In addition, optical absorption spectroscopy has been used to characterize the as-grown polymers. The chemical and electronic structures of BBL and BBB polymers are discussed in light of the present results.