Papers by Keyword: Electrical Conductivity

Abstract: Ba_0.2Sr_0.8Co_0.9Nb_0.1O_3-δ (BSCN0.2)-xGd_0.1Ce_0.9O_1.95 (GDC) (x = 10, 20, 30 and 40 wt.%) composite cathodes were investigated for the potential application in the IT-SOFCs. The results of chemical compatibility measurement show that a small number of Gd and/or Ce ions may melt into the lattice of BSCN0.2 to form BSCN0.2-GDC solid solution. Thermal expansion coefficients effectively reduced by the incorporation of GDC. The electrochemical performance of BSCN0.2-xGDC composite cathodes increased with increasing x from 10 to 30 wt.%. When x = 30 wt.%, the area specific resistances were only 0.040 and 0.017 Ω cm² at 750 and 800^oC, respectively. This improved electrochemical performance is attributed to the good thermal expansion match between BSCN0.2-xGDC composite cathode and GDC electrolyte, and the increased oxygen vacancy concentration. With further increasing x, the electrochemical performance of the composite cathode decreased. This result may be due to the ambipolar resistance model of porous composite cathode and the poor electrical conductivity of BSCN-40GDC. The maximum power densities of a BSCN0.2-30GDC/La_0.9Sr_0.1Ga_0.8Mg_0.2O_3-δ/NiO-Sm_0.2Ce_0.8O_1.9 single-cell achieve 537 and 722 mW cm^-2 at 750 ^oC and 800^oC, respectively. These results indicate that the BSCN0.2-30GDC composite cathode is a promising candidate for IT-SOFC.

Abstract: Infrared detection based on polymeric materials is continuously developed in order to be cheap and easy to processing and also having high pyroelectric coefficient to convert heat to electrical signal. PANI/DBSA was blended with polyvinylidene fluoride (PVDF) with different weight ratios to improve pyroelectric coefficient and electrical conductivity of PVDF. The temperature dependence of the electrical conductivity is measured in the range of 20-100 °C It was found that the pyroelectric coefficient increased from 1.5×10^-8 C/m² °C for pristine PVDF to 2.61×10^-5 C/m² °C at 25 wt.% PANI at 30 °C. The infrared detector circuit connected to the gate of a voltage follower JFET with high input impedance was designed to convert the high output impedance of the sensor into the output resistance. The output from the sensor and JFET is amplified in two stages of operational amplifier with high voltage gain with low noise.

Abstract: Olivine structured LiNi_1-xZn_xPO₄ (x=0, 0.05, 0.10, 0.15, 0.20) have been prepared by a polyol method using 1, 2 propanediol as a polyol medium. The XRD results of pure and Zn doped LiNiPO₄ sample authenticate the orthorhombic crystal structure with high crystalline nature. The crystallite size is calculated from the Debye Scherer formula and it is found in the range of 55-65nm and 49-55nm for undoped and doped samples respectively. The thermal properties of LiNi_1-xZn_xPO₄ were investigated by thermo gravimetric analysis (TG) and differential thermal analysis. Laser Raman studies confirm that the dopant is entered in to the LiNiPO₄ lattice. Morphology of the samples is analyzed through SEM analysis. The higher electrical conductivity is calculated for LiNi_0.85Zn_0.15PO₄ sample compared with other concentrations of dopant and it is found to be 1.08×10^-7 S cm^-1 at ambient temperature. Dielectric and Modulus studies are also discussed through impedance spectroscopy.

Abstract: Carbon nanofillers/polymer nanocomposites foam with electrical conductivity was a novel functional material. In this study, the CNTs/PMMA nanocomposites were prepared by the combination of ultrasonic dispersion and anti-solvent precipitation method. Then supercritical foaming method was untilized applied to prepare the foams. The morphology and the electrical conductivity of the foams were investigated. The conductivity of the nanocomposites showed a conductor behavior which was increased t from 1×10^-6 S/cm to 1×10^-5S/cm with the CNTs content range from 1 wt.% to 2.5 wt.%. After foaming, the cell size of the foams was below 10 μm while the cell density increased 2~3 orders of magnitude compared with PMMA foams. The produced CNTs/PMMA nanocomposites foams exhibited a wide range electricity conductivity of the nanofiller contents. Key words: structure, electrical conductivity, CNTs, nanocomposites foams

Abstract: Temperature dependence of the femtosecond laser modified region on silicon carbide was measured. The current-voltage characteristics showed the ohmic properties and thus we could evaluate the specific resistance for each irradiation conditions and the measured temperatures. The specific resistance was increased with decreasing temperature. From the double exponential fit to the temperature dependence of the specific resistance, the trapping energy of the impurity levels formed by the femtosecond laser modification was found to be 4.5 meV and 51.4 meV.

Abstract: Ferrocene is a well-known electron donor due to its chemical stability and redox behaviour. By introducing azo dye as an acceptor in the system, the characteristics of azo-ferrocene (AF) compound as a semiconductor material have been investigated. A single layer film of AF compound was deposited on an indium tin oxide (ITO) glass substrate by electrochemical method in the potential range of 0.4 V to 0.8 V. Electrical conductivity of the thin film was investigated using a four-point probe and I-V characteristic of the diode was determined via a two-point probe method. AF material showed an average electrical conductivity of 0.246 ± 0.003 Scm^-1. The forward current-voltage measurement demonstrated a bias voltage in the range of 0.87 V to 10.0 V, and the backward current-voltage measurement indicated a bias voltage in the range of-0.87 V to-7.0 V. In both forward and backward voltages, the current showed a slow increase beyond the readings of 10.0 V to-7.0 V.

Abstract: The microstructure and properties of Cu-7.5Ni-5Sn alloy after homogenization treatment was investigated. The research results show that homogenization treatment can obviously eliminate dendritic segregation in Cu-7.5Ni-5Sn alloy. The temperature of homogenization annealing has a great influence than the effect of holding time. The ingots of Cu-7.5Ni-5Sn alloy which were homogenization treated at 780°C for 24 hours can be rolled up to 30% deformation by cold-rolling. Some tiny white matter is still remaining in dendrite boundary, but atom fraction of Ni and Sn of the dendritic segregation is decreased by 12.04% and 4.73% respectively compare with casting state. The electrical conductivity and Brinell hardness of Cu-7.5Ni-5Sn alloy homogenization treated at 800°C for 24 hours is 12.8%IACS and 132Hv, and increases 18.5% and 29.9% respectively.

Abstract: Liquidus temperature, electrical conductivity and phase composition of Al₂O₃-CaO-SiO₂-CaF₂-MgO slag system were studied. The results showed that the liquidus temperature of the slag decreased with increasing MgO content, and its electrical conductivity increased with increasing MgO content and temperature. When the content of MgO is 5 %, the main phase compositions of the slag are composed of MgAl₂O₄, Ca₂SiO₂F₂, CaAl₄O₇ and Ca₅Al₆O₁₄. When the content of MgO is 7 %, the main phase compositions of Al₂O₃-CaO-SiO₂-CaF₂-MgO are composed of MgAl₂O₄, Ca₄Si₂O₇F₂, CaAl₄O₇ and Ca₅Al₆O₁₄.And the content of MgAl₂O₄ and Mg₂SiO₄ increased with increasing MgO.

Abstract: As we know that ceria (CeO₂), alumina (Al₂O₃), aluminum (Al) and iron oxide (Fe₂O₃) can improve the anti-aging properties of the rubber, mixed these materials with carbon black and filling conductive silicone rubber, some samples have been prepared. Have described the anti-aging method of the silicone rubber and discussed the test method of the changes in properties after aging. Have tested the changes of mechanical properties and electrical conductivity before and after the air aging test of the conductive silicone rubber which with or without addition of modified material. Have discussed the reasons why modified materials can improve the anti-aging performance of the conductive silicon rubber. The results show that with the addition of these types of nanomaterials the stability of mechanical and electrical properties of the conductive silicone rubber can be improved before or after aging treatment.

Abstract: The polymer composites consist of phenolic resin, natural graphite, carbon fiber and copper powder, are fabricated by hot compression moulding or compression moulding followed by post-curing. The density, electrical conductivity and flexural strength of composites are analyzed to determine the influences of post-curing temperature and preparing method on the physical, electrical and mechanical properties of composites. It is found that the density, electrical conductivity and flexural strength of composites increase with increasing post-curing temperature for composites prepared by compression moulding followed by post-curing. The flexural strength is more strongly dependent on post-curing temperature. At 170 °C, the density, electrical conductivity and flexural strength of composites were 1.85 g/cm³, 2.94 × 10³ S/m and 40 MPa respectively. The cross-linking skeleton structure well established in the composites could be the main reason for the largely increasing of flexural strength as post-curing temperature increases. The results also show that the properties of composites prepared by hot compression moulding are higher than those of composites prepared by compression moulding followed by post-curing.