Applied Mechanics and Materials Vol. 700

Abstract: This paper uses the method of S transformation to test the starting time, the end of the time, frequency and amplitude characteristics of common transient power quality signal disturbance. Through error analysis and simulation show that this method can accurately determine the disturbance occurred time and duration, and the identification and determination of disturbance can be simple and intuitive. It has the practical value and realistic significance to power quality signal interference analysis.

Abstract: With recent development of technology and management in power market and equipment, more and more distributed generation (DG) is embedded in the distribution network. However the approach of connecting DG in most cases is based on a so-called ‘fit and forget’ policy and the capacity of DG is limited rigidly by distribution system operator to avoid the negative effects of high level penetration. New management technologies have been proposed to handle the integration of DGs in the distribution networks. In this review, the micro grid (MG) was treated as the local control method to coordinate DGs within a small area of distribution network. And the active distribution network (AND) was treated as the global control mechanism to actively manage DGs, MGs and other equipment. The operation framework of ADN was firstly introduced. Then based on the static and dynamic models of DGs and MGs, impacts of DGs and MGs on the ADN are surveyed from power quality, stability to the operation. Finally, the conclusion and suggestion is given in this paper.

Abstract: Na₂BaMgP₂O₈ phosphors were synthesized by a standard solid state reaction and their luminescent properties were investigated. The phase structure was analyzed by X-ray powder diffraction measurement. Under the excitation of 365nm, Na₂BaMgP₂O₈:Tb³⁺, Eu³⁺ phosphors show two color bands of green and red color due to ⁵D₄−⁷F₅ transition of Tb³⁺ ions and ⁵D₀−⁷F₂ transition of Eu³⁺ ions, respectively. The emission intensity of Tb³⁺ deceased with the increasing concentration of Eu³⁺, which verified that an effective energy transfer occurred from Tb³⁺ to Eu³⁺ in Na₂BaMgP₂O₈ host. The present study indicated that the phosphors have a high potential application in solid state lighting.

Abstract: Polyaniline (PANI) polymer coating was electrochemically synthetised by cyclic voltammetry (CV) method on stainless steel bipolar plates of proton exchange membrane fuel cell (PEMFC). Structure and morphology of PANI polymer coating were characterized by means of fourier transform infrared reflection (FTIR) spectrum and scanning electron microscopy (SEM). The corrosion behavior of the coating was evaluated by polarization curve and electrochemical impedance spectroscopy (EIS) in the medium of 1M H₂SO₄ and 2ppM NaF at 70°C to simulate the corrosive condition of PEMFC. It was found that the optimal conditions for PANI polymer coating synthesis could be 10-15 circles when the voltage ranged from-1.2V to +1.2V(Vs.SCE) with a scan rate of 50 mV/s. SEM observation results indicated that the polymer coating presented with uniform and dense feature. FTIR results illustrated that the coating were composed of PANI. Corrosion current densities of 316L SS and PANI-coated steel were 10^-5 and 10^-6 A/cm² respectively. Corrosion potential of the coated SS shifted towards more positive values compared to the uncoated plate. EIS results indicated that the radius of the capacity impedance for PANI increased obviously.

Abstract: Lead zirconate titanate (PZT) materials are wildly used in aviation, industry and our daily life. Actually, it becomes more and more important to improve its electrical properties. In this paper, the influences of antimony (Sb)-doping and barium (Ba)-doping and sintering temperature upon properties of PZT ceramics have been investigated. The relationships between the microstructure and electrical properties have been analyzed by means of XRD, SEM and impedance analyzer, etc.The XRD patterns indicate that all samples exhibit the tetragonal perovskite structure.This research also suggests that the best sintering temperature is 1190°C if the doping amount of Sb₂O₃ and BaCO₃ are 0.6wt% and 0.2wt% respectively. In this case, the samples possess perfect electrical properties: tanδ=0.02, k_p=66.3%, d₃₃=438pC/N, ε=1740.

Abstract: Porous carbon monoliths are prepared by carbonization of a simple polymer blend, in which phenolic resin (PF) as carbon precursor, polyvinyl butyral as pore former and activated carbon as conducting additive and contraction inhibitor are used to make polymer blend. The results show that the carbon monoliths, with a narrow pore size distribution with mean controlled diameters in the sub-micron/micron range, can be easily produced by controlling the stabilization temperature of the PF, the carbonization temperature, and particle diameters of the precursor powders. The pore size decrease as the stabilization temperature of the PF increases or the particle diameters of the precursor powders decreases. The electrical resistance of the carbon monoliths decreases as the carbonization temperature increases, but the average pore diameter and volume of the carbon monoliths are almost constant as the carbonization temperature increases.

Abstract: The experimental basis formula selected in this experiment is 0.1Pb (Ni_1/3Nb2_/3)O₃-0.9Pb (Zr_0.42Ti_0.58)O₃ (PNN-PZT). The traditional solid phase synthesis are applied piezoelectric ceramic samples. The relationship between the microstructure and electrical properties of the ceramic samples are analyzed by means of XRD, SEM, impedance analyzer etc. The XRD patterns show that all the ceramics exhibited a tetragonal perovskite structure. Through the analysis of the ceramic samples of piezoelectric and dielectric properties, PNN-PZT piezoelectric ceramics will possess best comprehensive properties when sintering temperature at 1190°C.

Abstract: An investigation into the suitability of carbon materials, metallic lead and its alloys as substrates for the zinc electrode in acid Zn-PbO₂ flow batteries was performed. No maximum current appears on the potentiostatic current transients recorded for the zinc deposition on the lead and its alloys. With increasing the overpotential, the progressive nucleation turns to be the 3D-instantaneous nucleation process employed for the resin-graphite composite. Hydrogen evolution on the graphite composite is effectively suppressed due to the doping of polymer resins. The rate of hydrogen evolution reaction on the lead is relatively weak, but on the lead alloys, the hydrogen evolution conversely becomes serious to a certain degree. Though the exchange current density of the zinc deposition and dissolution process on the graphite composite is relatively low, the zinc corrosion is weakened to a great extent. With the increase of deposition time, the zinc deposits tend to be more compact. Zinc galvanostatic charge-discharge cycling on the graphite composite reveals that the coulombic of over 90% can be found, exhibiting an excellent cycling stability.

Abstract: Well-defined Fe₃O₄ octahedrons have been readily realized in high yield via a simple and general hydrothermal synthesis technology free of any surfactant or template. Detailed investigations indicated that the octahedral Fe₃O₄ microcrystals are single crystal and were dominated by (110) surfaces. The influences of the amount of NaOH on the morphologies of the final products were investigated. The experimental results show that the high concentrations of NaOH play vital roles for the formation of octahdral Fe₃O₄ microcrystals. Besides, the magnetic property of the as-obtained Fe₃O₄ sample was evaluated as potential materials for electromagnetic device application on a vibrating sample magnetometer (VSM) at room temperature. The values of saturation magnetization and coercivity of octahedral Fe₃O₄ are approximately 95 emu g^-1 and 197 Oe, respectively.

Abstract: It is well known that piezoelectric ceramics are wildly used in many fields such as electrical sensors, actuators, alarm equipments etc. In this paper，the microstructure and the piezoelectric properties of Pb（Zr1/2Ti1/2）1-x（Nb2/3Mg1/3）xO3 (PMNZT) were studied. A novel B-site precursor method was adopted for preparing of Pb（Zr1/2Ti1/2）1-x（Nb2/3Mg1/3）xO3 samples. For investigating the crystallographic phase and microstructure of the samples, X-ray diffraction(XRD) and scanning electron microscopy(SEM) methods have been adopted respectively. The results show that a pure perovskite structure can be obtained after sintering at 1220°C for 2h. Through this experiment, it has been found that when sintering at 1220°C for 2h and the amounts of the Pbx（Nb2/3Mg1/3）xO3 (PMN) is 0.14, the Pb（Zr1/2Ti1/2）1-x（Nb2/3Mg1/3）xO3 samples are with the best electrical properties as follows: dielectric constant (ε) is 1858, dielectric loss(tanδ) is 0.017, electromechanical coupling coefficient (Kp) is 0.515, piezoelectric constant(d33) is 362PC/N