Papers by Keyword: Transport Characteristics

Abstract: This study investigates the absence of superconductivity in bulk type nickelate and analyzes the structural and transport characteristics of the materials. Infinite layer bulk type Nd_1-xSr_xNiO₂ with Sr doping level x for 0.0, 0.1 and 0.2 are synthesized by conventional solid state synthesis method. The crystallographic structure Nd_1-xSr_xNiO₂ of is found to be stable for different doping levels using X-ray diffraction (XRD) analysis and confirms phase purity. Scanning electron microscopy (SEM) analysis reveals the grain morphology and indicates the absence of notable microstructural features that support superconductivity. The nature of grain size distribution of Nd_1-xSr_xNiO₂, with x = 0.0, 0.1 and 0.2 are analyzed. The transport measurement of prepared bulk type nickelate samples are performed by four probe technique with the help of closed cycle cryogenerator. The electrical transport characteristics based on 3D Variable Range Hopping (VRH) conduction models are examined. This study presents the alternative synthesis techniques to stabilize the superconducting phase and an overall insight into the causes for the failure of superconductivity.

Abstract: Transport phenomena in manganites (ABO₃), and indirectly the transition temperature from metallic to insulator state (T_MI), can be controlled by hole doping and the average ionic size at A positions (). In agreement with Zener theory, the strength of double exchange is determined by the Mn-O length (d_MnO) and Mn-O-Mn angles () of the Mn-O-Mn bonds. We will investigate the influence of substitution of Mn with V on the crystalline structure and transport characteristics in La_0.54Ho_0.11Sr_0.35Mn_1-xV_xO₃ manganites. The samples were prepared by sol-gel method to improve the purity and homogeneity of the samples. By XRD it was established that the samples contain only ABO₃ perovskite phases, except the samples with x0.1. The resistance of the samples vs temperature was determined by four probes method. The specific magnetization was obtained by using a Foner type magnetometer, working at 1.4 T, between 77 and 400 K.

Abstract: According to the service environment of light rail transit and subway structures, in this paper experiments on the corrosion characteristics of reinforced concrete under single corrosion environment of stray current, single corrosion environment of chloride ions and joint corrosion environment of stray current and chloride ions were respectively carried out. Loading direct current electric field was used to simulate the stray current. The experimental results showed that, the corrosion growth process of the rebar in reinforced concrete under single environment of chloride ions was slow and stable, while that under single environment of stray current being separated two stages, i.e., rapidly increasing stage and stably varying stage. In addition, the rebar of reinforced concrete in stray current alone environment was corroded faster than that in chloride ion alone environment did; when stray current and chloride ion coexist, the stray current speeded up the chloride ion transportation, which gave rise to the increase of the corrosion rate of the rebar of reinforced concrete; the corrosion degree of the rebar depended on the chloride ion concentration, stray current strength and test time. The stronger the stray current strength, the longer the stray current corrosion period and the heavier the chloride ion concentration, the more the corrosion products of the rebar and thus the more serious the reinforced concrete deterioration.

Abstract: The transport characteristics of cut tobacco as a typical biological wet slender particle were investigated in a pilot-scale rotary cylinder. Effect of solids and gas flow rate, moisture content of particles and rotating speed of cylinder was analyzed. The adaptability of the classical Friedman model for predicting average residence time of these type particles was also investigated. The result shows that the gas flow rate, moisture content of particles as well as rotating speed of cylinder have a significant influence on the axis transport velocity and forward step per cycle of cut tobacco in rotary cylinder. It’s difficult for Friedman model to accurately describe influence of gas flow rate and moisture content on transport of cut tobacco, which was associated with the particle characterize and influence of moisture content on the fluidity of particles.

Abstract: The porous metal fiber sintered felt (PMFSF), a new catalyst support, was successfully used to construct a methanol steam reforming microreactor for hydrogen production. To study the transport characteristics of PMFSFs, a three-dimensional model with the cubic pore cell structure for PMFSFs was established. Using computational fluid dynamics fluent software, the velocity and pressure distribution when the fluid through the PMFSFs was investigated by changing the porosity of PMFSFs and inlet velocity of the fluid. In addition, fluid temperature distribution was analyzed under different inlet velocities by setting the temperature of fluid and wall. The result shows that the PMFSFs greatly enhance the transport characteristics because of its three-dimensional network structure and microchannel structure, it will become an ideal candidate for catalyst support material.

Abstract: This paper reports on the defects created in a 6H-SiC p-type substrate by a process of ion implantation and a quite low temperature annealing (1300 °C), suitable for the realization of the source/drain regions of a MOSFET because it does not give rise to step bunching phenomena. Current voltage measurements showed the presence of a group of diodes featured by excess current. The effects of defects under the implanted layer on the transport properties of the diodes were investigated by DLTS: four hole traps were detected in all the measured diodes; besides, a broadened peak around 550 K was detected in the diodes that show excess current.