Papers by Keyword: Polarisation

Abstract: This research shows the successful functionalisation of bicomponent fibres, consisting of a conductive polypropylene (PP) core, doped with carbon nanotubes (CNT) and a piezoelectric sheath (polyvinylidene fluoride, PVDF) by draw winding and poling. These steps lead to the usability of the PVDF’s piezoelectric capabilities. The PP/CNT constitutes the fibre core that is conductive due to a percolation CNT network. The PVDF sheath’s piezoelectric effect is based on the formation of β phase crystals (all-trans conformation), caused by draw-winding of the fibres. This β phase eventually has to be poled for the uniform alignment of polymer chains. The material’s behaviour in high electric field is analysed recording the poling voltage during the poling process. The outcome is hysteresis curves for different β phase contents, which verify a successful material poling.

Abstract: The electrochemical behavior of welded joints with 308L stainless solid welding wire and low temperature transformation welding wire using different welding processes was investigated at ambient temperature in 3.5% NaCl solution using potentiodynamic polarisation technique. Welded joints exhibited different corrosion potential due to the dilutions of alloy elements such as Cr, Ni, Ti, Nb and Mo. To reveal the corrosion resistance of welded joints using different welding processes, some significant characterization parameters such as E_corr, E_b, △E and I_corr in polarisation curves were analyzed and compared. The result shows that the corrosion resistance of welded joints using low temperature transformation welding wire is better than that using 308L stainless solid welding wire.

Abstract: The electrochemical behavior of corrosion resistance alloys (316L SS, 2205 DSS and Inconel 625) was carried out at ambient temperature in 3.5% NaCl solution using potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS) techniques. Some significant characterization parameters such as E_corr, E_b, I_corr and △E in polarisation curves were analyzed and compared to reveal the corrosion resistance of corrosion resistance alloys. The ZsimpWin software was utilized to discuss the Nyquist plots of various corrosion resistance alloys. The result shows that the corrosion resistance of the corrosion resistance alloys in 3.5% NaCl solution at ambient temperature follows the sequence: Inconel 625> 2205 DSS > 316L SS.

Abstract: High-performance single crystals of ferroelectric Bi₄Ti₃O₁₂ (BiT) have been successfully obtained via the top-seeded solution growth under high oxygen pressure (Po₂) atmosphere. Crystals grown at 960°C at a Po₂ of 0.9 MPa exhibited a well-saturated hysteresis loop with a remanent polarization of 48 mC/cm² and a coercive field of 29 kV/cm. The results of piezoresponse force microscopy indicate that polarization switching is accomplished throughout the BiT crystals obtained. Electric-field-induced strain measurements along the a axis yield a piezoelectric constant d₁₁* of 37 pm/V for BiT.

Abstract: Plug-in specimens enable measurement of reliable Mg polarization curves. Cathodic polarization curves were measured for high purity Mg in 3.5% NaCl saturated with Mg(OH)₂ using (i) mounted specimens and (ii) plug-in specimens. Polarization curves yielded the corrosion current density i_corr and the corresponding corrosion rate P_i, which was compared with corrosion rates evaluated from hydrogen evolution, P_H, and weight loss, P_W. Mounted specimens produce P_i values three times larger than plug-in specimens, due to crevice corrosion in the mounted specimens. Plug-in specimens had no crevice and allow simultaneous measurement of P_H and P_i. P_i was less than P_H and indicated an apparent valence of 1.45 in support of the existence of the uni-positive Mg⁺ ion.

Abstract: Laminated fluoropolymer films with regular void structure, fabricated by using a process consisting of the patterning and fusion bonding steps, are polarized to be piezoelectric. The influence of the applied voltage on the piezoelectric d₃₃ coefficient is investigated. The measurements of ferroelectric-like polarization-voltage hysteresis loops are taken to further understand the capability of polarization in the laminated films. The compressive Young’s moduli of the films are determined from the dielectric resonance spectra. The results show that the laminated fluoropolymer films are piezoelectric after proper charging. The maximum d₃₃ coefficients of the five-layer laminated piezoelectrets are achieved at the applied voltage of 5 kV. The remnant charge density of 0.3 mC/m² is obtained from the polarization-voltage hysteresis loop at a bias voltage of 4 kV. The measured anti-resonance frequency and calculated compressive Young’s modulus for the five-layer laminated films are 112 kHz and 0.48 MPa, respectively.

Abstract: LiNbO₃ film (LNO)/AlGaN/GaN heterostructure was fabricated epitaxially. The preferable C⁺ oriented domains in LNO film lead to the formation of the spontaneous ferroelectric polarization. As a result, the sheet electron concentration of the 2DEG (n_s) decreased from 1.13×10¹³ cm^-2 to 1.04×10¹³ cm^-2 when a LNO film deposited on the AlGaN/GaN. The n_s decreased nonlinearly with decreasing the temperature. Additionally, the electron mobility for the LNO/AlGaN/GaN heterostructure decreased greatly compared with that for AlGaN/GaN heterostructure, which was caused by the non-uniform domain structure in the LNO film. By external bias switching the ferroelectric polarization, the relative enhancement of the 2DEG, about 7.68×10¹¹/cm², could be accessible from capacitance-voltage measurement. These results indicated that ferroelectric films combined with AlGaN/GaN would hold promise for next-generation GaN-based memory devices.

Abstract: In this paper the usability of using polarized filters for reading lamp to reduce disturbing reflected glare was tested based on a within-subject design ergonomic research. Results show that with the increasing polarization degree the subjective rating score decreases, which means that increasing polarization of the optical film reduces the reflected glare. Statistical analysis shows that there is high correlation (0.05 level, 2-tailed) between the subjective rating score on reflected glare and the degree of polarization. An univariate analysis of variance proves that the different evaluation caused by the optical films with different polarization degrees has statistically significant meaning (F=108.4, p<0.001). The results of this research is very useful for optical design of reading lamp, which occupies a big market in China, affecting the visual comfort of huge numbers of readers, such as students and office people.

Abstract: HRB400 reinforcing steel due to high strength and high ductibility is as the main reinforcing steel in “Code for design of concrete structures (GB50010-2002)” in China. Cyclic potentiodynamic polarization technique was used to investigate the electrochemical corrosion bebavior of HRB400 reinforcing steel in Simulated Concrete Pore solutions (SCP solutions) differently contaminated by bicarbonate ions and/or chloride ions. The evolution feature of the corrosion parameters was analyzed and was compared with that of HPB235 reinforcing steel. The results show that the corrosion characteristics of HRB400 and HPB235 were exceedingly similar before the destruction of the passivation film. However, HRB400 is remarkedly more susceptible to chloride ions and carbonation than HPB235 during the failure of the passivation films. The pH threshold for HRB400 is larger than that for HPB235, and the chlorides threshold for the former is smaller than that of the latter. When HRB400 and HPB235 were connected and exposed to an aggressive environment, the galvanic corrosion will occur where HRB400 is anode and HPB235 is cathode. To ensure the durability of the reinforcing concrete structures, it is necessary to make the connection points insulate.

Abstract: A kind of efficient, environment-friendly compound inhibitor was prepared with 2-mercaptobenzimidazole (2MBI), potassium iodide, triethanolamine, polyoxyethylene nonylphenyl ether and peregal by weight loss through orthogonal experiment. The effects of the compound on corrosion of A20 steel in citric acid have been investigated in relation to it’s concentration by weight loss measurements, polarization curve methods and electrochemical impedance spectroscopy (EIS). The result of weight loss reveals that the compound is a good inhibitor whose efficiency can reach 98.8%. Polarization curve results show that the compound restrain the process of cathode and anode, belonging to anode control-oriented and charge transfer-controlled. EIS results show that the changes in the impedance parameters (R_p and C_d) with concentrations of the compound are indicative of the adsorption of these molecules leading to the formation of a protective layer on steel surface.