Preparation and Ferroelectric Properties of YMnO3 Thin Films with c-Axis Preferred Orientation by the Sol-Gel Method

Hexagonal YMnO₃ has a ferroelectric property with an optimal remanent polarization along the c-axis. The c-axis oriented YMnO₃ thin films with a small leakage current were prepared by the sol-gel dipping method. The c-axis orientation of the films was promoted by the addition of diethanolamine to the Mn precursor solution. A heat treatment with multiple steps led to a dense film structure with fine grains. The dense structure resulted in the decrease of the leakage current. Furthermore, when the films were heat-treated in a vacuum, the leakage current became considerably small and the ferroelectricity of the YMnO₃ thin films was observed even at room temperature.     

Magnetic properties of Terfenol-D film on a compliant substrate

Substrate thickness effects on the magnetization and magnetostriction of Terfenol-D films was studied by using a nonlinear constitutive model combined with the Timosheko elastic theory. Results show that characteristics of Terfenol-D films on compliant substrates are different from those of their bulk counterpart. Tunable properties can be obtained by adjusting the film/substrate thickness ratio.     

Free surface Stokes flows obstructed by multiple obstacles

Gravity‐driven Stokes flow down an inclined plane over and around multiple obstacles is considered. The flow problem is formulated in terms of a boundary integral equation and solved using the boundary element method. A Hermitian radial basis function (RBF) is used for the interpolation of the free surface, generation of the unit normal and curvature, and to prescribe the far‐field conditions. For flow over an obstacle, hemispheres are taken. For flow around an obstacle, circular cylinders are modelled and the contact angle condition on the obstacle/free surface intersection specified using the RBF formulation. Explicit profiles are produced for flow over and around two obstacles placed in various locations relative to one another. Interaction due to two obstacles is given by comparisons made with the profiles for flow over and around individual obstacles. In general, when the obstacles are separated by a sufficiently large distance the flow profiles are identical to a single obstacle analysis. For flow over and around two obstacles in‐line with the incident flow, effects of the governing parameters are examined, with variations in plane inclination angle, Bond number, obstacle size, and in the case of obstacles intersecting the free surface, static contact angle is considered. Finally flows over and around three obstacles are modelled. Copyright © 2009 John Wiley & Sons, Ltd.     

柔性基底红外波段左手材料制备及光学特性

采用平板电极化学电沉积的方法,通过调节实验参量,在柔性ITO导电薄膜基底上制备了尺度与红外波长匹配、结构单元大小不等、排列无序的银树枝状结构.通过调节聚乙二醇-20000浓度可以很好地调控银树枝状结构单元的形貌和尺寸,研究发现,在一定范围内增加电解液中的聚乙二醇-20000浓度,可在基底上形成分布较密、分枝较细、分枝级数较高的银树枝状结构单元.通过在银树枝状结构表面涂覆一定厚度的聚乙烯醇作为绝缘层,组装成了柔性"三明治"结构复合材料,测试得到样品在红外波段的多通带透射谱,平板聚焦实验进一步验证了样品的左手效应.     

Hall effects on hydromagnetic falling liquid film

An investigation is made of flow of an electrically conducting falling liquid film over a smooth vertical surface taking Hall effects into account, the liquid being permeated by a transverse magnetic field. Consideration of Hall current into the flow indicates a similarity between the flow of a rotating liquid and that due to the non-rotating system in presence of Hall currents. Discussion has been made for electrically conducting falling film in presence of cross-flow due to hall effect in non-rotating system.     

Novel Protonic Conductive Silicates Produced by the Sol-Gel Method

ABSTRACT

Materials which display ionic conductivity were produced by the sol-gel and microemulsion-gel methods. The charging and discharging characteristics were investigated and it was found that a single ionic species was responsible for the conduction, the ionic species being residual protons from the initial component mixture. The complex impedence of various samples was measured and the ionic conductivities ranged in value from 9 × 10^?8 to 1 × 10^?5 ohm^?1 cm^?1. An Arrhemius plot for a microemulsion-gel revealed that the energy of activation was 0.15 eV.     

Synthesis and properties of phenothiazylene vinylene‐based polymers: New organic semiconductors for field‐effect transistors and solar cells

A series of new phenothiazylene vinylene‐based semiconducting polymers, poly[3,7‐(4′‐dodecyloxyphenyl)phenothiazylene vinylene] ( P1 ), poly[3,7‐(4′‐dodecyloxyphenyl)phenothiazylene vinylene‐alt‐1,4‐phenylene vinylene] ( P2 ), and poly[3,7‐(4′‐dodecyloxyphenyl)phenothiazylene vinylene‐alt‐2,5‐thienylene vinylene] ( P3 ), have been synthesized via a Horner‐Emmons reaction. FTIR and ¹H NMR spectroscopies confirmed that the configurations of the vinylene groups in the polymers were all‐trans (E). The weight‐averaged molecular weights (M_w) of P1 , P2 , and P3 were found to be 27,000, 22,000, and 29,000, with polydispersity indices of 1.91, 2.05, and 2.25, respectively. The thermograms for P1 , P2 , and P3 each contained only a broad glass transition, at 129, 167, and 155 °C, respectively, without the observation of melting features. UV–visible absorption spectra of the polymers showed two strong absorption bands in the ranges 315–370 nm and 450–500 nm, which arose from absorptions of the phenothiazine segments and the conjugated main chains. Solution‐processed field‐effect transistors fabricated from these polymers showed p‐type organic thin‐film transistor characteristics. The field‐effect mobilities of P1 , P2 , and P3 were measured to be 1.0 × 10^?4, 3.6 × 10^?5, and 1.0 × 10^?3 cm² V^?1 s^?1, respectively, and the on/off ratios were in the order of 10² for P1 and P2 , and 10³ for P3 . Atomic force microscopy and X‐ray diffraction analysis of thin films of the polymers show that they have amorphous structures. A photovoltaic device in which a P3 /PC₇₁BM (1/5) blend film was used as the active layer exhibited an open‐circuit voltage (V_OC) of 0.42 V, a short circuit current (J_SC) of 5.17 mA cm^?2, a fill factor of 0.35, and a power conversion efficiency of 0.76% under AM 1.5 G (100 mW cm^?2) illumination. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 635–646, 2010     

Effect of low-temperature processing on dry film photoresist properties for flexible electronics

This study presents the mechanical characterization of the dry film photoresist PerMX and its adhesion properties when laminated onto Kapton® E (PI) and Melinex® ST506 (PET). Additionally, the processing temperature, the adhesion strength, and the neutral plane position are investigated and optimized. A relatively low-temperature (85 °C) process is developed to protect the integrity of the polymers with low glass transition temperature and reduce the thermal mismatch stress. Reduction in processing temperature led to a decrement in the adhesion strength. To counteract this unwanted effect, surface treatments (oxygen plasma) are performed on the polymer surface before lamination. Using the latter techniques, adhesion of PerMX to PET (hard bake: 1 h at 85 °C) is increased from 0.07 to 0.26 N mm⁻¹ (variation of 270%). Finally, the mechanical robustness is investigated and increased by tuning the position of the neutral plane, after 50,000 bending cycles and a radius of curvature of 2.5 mm. © 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013     

Film-thickness Error Analysis of Optical Disk Systems

1　Ｉｎｔｒｏｄｕｃｔｉｏｎ　　Ｒｅｃｅｎｔｌｙｏｐｔｉｃａｌｄｉｓｋｓａｂｌｅｔｏｓｔｏｒｅａｌａｒｇｅｑｕａｎｔｉｔｙｏｆｉｎｆｏｒｍａｔｉｏｎｈａｖｅｂｅｅｎｕｓｅｄａｓｃｏｍｐａｃｔｄｉｓｋ (ＣＤ ) ,ｄｉｇｉｔａｌｖｅｒｓａｔｉｌｅｄｉｓｋ(ＤＶＤ) ,ａｎｄｔｈｅｉｒｒｅｃｏｒｄａｂｌｅｏｒｒｅｗｒｉｔａｂｌｅｔｙｐｅｓ(ｓｕｃｈａｓＣＤ Ｒ ,ＣＤ ＲＷ ,ＤＶＤ Ｒ ,ａｎｄＤＶＤ ＲＡＭ ) [1 ] .Ａｎｏｐｔｉｃａｌｄｉｓｋｉｓａｋｉｎｄｏｆｍｕｌｔｉｌａｙｅｒｓｙｓｔｅｍｄｅｐｏｓｉｔｅｄｏｎａ…     

Theory of Microbial Carbonate Precipitation and Its Application in Restoration of Cement-based Materials Defects

Bacterial induced carbonate mineralization has been demonstrated as a new potential method for restoration of limestones in historic buildings and monuments. We claim here the formation of calcium carbonate was controlled by extracellular polymeric substances (EPS) isolated from Bacillus pasteurii. The process of crystallization nucleation was accelerated in the presence of cells and inhibited in the presence of EPS. The CaCO₃ film deposited on cement paste surface was about 100 µm after 7 d treatment. The results of various restoring methods showed that higher decrease of water absorption of cement paste was gained in brushing application in the presence of agar, which could maintain urease with high activity in long term compared to spraying method. The coefficient of capillary suction of cement paste treated with brushing method was reduced by 90%. Mixed media consisted of sands, urea, Ca²⁺ and concentrated biomass, was injected into artificial cracks of cement paste followed by continual nutrient supplement, and CaCO₃ particles were precipitated gradually between sands particles which were combined with cement matrix. The results showed that the compressive strength of recovered specimens was restored to 84%, which demonstrated that this kind of bio‐restoration method is effective in repairing surface defects of cement‐based materials.