Advanced Materials Research Vols. 557-559

Abstract: Pb(Zr_0.52Ti_0.48)O₃ was coated on the surface of CaCu₃Ti₄O₁₂ particles that prepared using sol-gel method. Then the composite particles were sintered into composite ceramics using cold press with the two different pressures and pressing time to achieve sufficient higher relative density after sintering. Afterward, the composite particles were sintered into composite ceramics with various sintering time at the same temperature to reach smaller grain size and higher relative density. The results show that the ceramics are composed of Pb(Zr_0.52Ti_0.48)O₃ and CaCu₃Ti₄O₁₂ phases, and Pb(Zr_0.52Ti_0.48)O₃ phase is mainly exist at the grain boundary even the composite particles sintered for 2h before pellet making. The results exhibit when density of CaCu₃Ti₄O₁₂/Pb(Zr_0.52Ti_0.48)O₃ composite ceramic is kept in higher level using this simple technology, not only The dissipation loss in these giant-dielectric constant materials was reduced to a considerable level of practical applications but also dielectric constant enhance to very high level in the large frequency range. The results show that the improvement of the dielectric loss and dielectric constant enhancing mainly comes from the increase in the density of the CaCu₃Ti₄O₁₂/Pb(Zr_0.52Ti_0.48)O₃ composite ceramics using suitable pressure in cold press, suitable short sintering time that lead to smaller grain size and sufficient grain boundary.

Abstract: Atmospheric pressure air glow plasma processing technology was used to treat the cotton fabric surface to improve its wettability. Based on the second-order regression general rotation design, influence of the plasma processing time, current intensity and the discharge distance on the capillary effect of cotton fabric was investigated with the capillary height as the index. The test results show that the optimal process is the processing time 20.2min, the current intensity of 1.84A, and the discharge distance 11.2mm. With the same total processing time, the cotton fabric with double-sided plasma treatment is better than that of single-sided processed.

Abstract: Chemical and electrochemical techniques were applied to evaluate the porosity of various electroless coatings (single-layer coating, multilayer coating and ternary coating). The electrochemical techniques include linear polarization resistance and Tafel extrapolation method. The effects of these techniques were compared. It’s evident that electrochemical methods performed better than chemical method when they were applied to assess the porosities of coatings with very fine through pores.

Abstract: Dielectric elastomer actuators with enhanced flexibility were prepared by thermosetting polyurethane (TSU) consisting of polypropylene glycol (PPG) as an active hydrogen component and toluene diisocyanate (TDI) as an isocyanate component. The improvement was achieved by less hard segment content, i.e. less isocyanate index, the synthesized film actuators were compared with the actuator softened using a plasticizer. It was found that the film actuators prepared by this method had significant advantages in actuation under a lower electric field as well as the increase of electrical breakdown strength and of strain. Furthermore, the mechanically-stretched effect of the films was also evaluated. It turned out that prestrain up to 200% was effective in the increase of electrical breakdown strength while maintaining the actuation under a lower electric field. However, prestrain over 200% caused a decrease in actuation under a lower electric field.

Abstract: To improve the corrosion resistance of Al alloy, diethylamine (DEA) was added into the sealing solutions. The electrochemical behavior of sealing coatings formed in different concentrations of diethylamine (DEA) was investigated by means of polarization curves and electrochemical impedance spectroscopy (EIS). Compared with the coatings with D. I. water and the bare aluminum alloy, the polarization curves show that the sealing coatings formed in 3.0 – 5.0 ml.L-1 diethylamine (DEA) solutions have more positive corrosion potential (Ecorr) and pitting corrosion potential (Epit), and lower corrosion current density (icorr). Electrochemical parameters of EIS indicate that the sealing coatings have higher corrosion resistance. The electrochemical tests present that the prepared sealing coatings have better corrosion resistance.

Abstract: The growth of strontium doped barium titanate (BST) powder is performed by solid-state reaction. Microstructural characterization by SEM technique confirms the BST film is successfully formed on p-Si (100) substrate by spin coating technique. Dielectric properties of MFIS (Metal/ Ferroelectric/ Insulator/ Semiconductor) designs are measured by impedance analyzer (LCR meter, QuadTech :1730). P-E (polarization-electric field) hysteresis loops are also measured by applying the same triangular wave electric field in order to allow their application in NVFeRAM (Non-Volatile Ferroelectric Random Access Memory). The maximum remanent polarization density (P_r=38.6µC/cm²) is found at BST film 600°C. The film exhibits the potential to be a future promising memory. The results obtained from this research are quite interesting, acceptable, credible and applicable in use for NVFeRAM.

Abstract: Nano-SiO₂ which surface was modified by silane coupling agent was used to modify the epoxy coatings which was prepared by the method of chemical modification and physical dispersion using the modified nano-SiO₂ and epoxy. The molecular structure and dispersity of the modified nano-SiO₂ were studied by Fourier transform spectra(FT-IR) and scanning electron microcopy(SEM). The effect of nano-SiO₂ on corrosion resistance of epoxy coating was studied by electrochemical impedance spectroscopy(EIS). The results show that the modified nano-SiO₂ contained the Si-OH characteristic functional group which can promoted the nano-SiO₂ grafted with epoxy and had a good dispersion; Compared to epoxy coatings, wear rate of the modified epoxy coating reduced about 20% and the impedance value of the modified epoxy coating using the method of soak in 3.5% solution of NaCl for 240h, improved by 5 orders of magnitude.

Abstract: Dielectric elastomer actuators with high dielectric constant and flexibility were prepared. These actuators were fabricated by the composite of barium titanate (BaTiO₃) and polyester-type thermosetting polyurethane (TSU), which was molecularly-designed to become less hard segment content. In this study, the effects of particle size, volume fraction and manufacturing method of BaTiO₃ were investigated. In addition, the mechanically-stretched effect in composites was also evaluated. It turned out that the electrical breakdown strength increased with the increase of particle size of BaTiO₃ and in volume fraction as well as the use of BaTiO₃ synthesized by the oxalate method. In addition, prestrain of composites also raised the electrical breakdown strength. However, the addition of BaTiO₃ to polyurethane didn’t contribute to the actuation under a lower electric field.

Abstract: Commercially available magnesium alloy is extensively used in structural engineering components although, like many magnesium-based materials, it suffers from poor corrosion resistance, particularly in moist environments, which limit wider application. Previously, by reducing the contact area of metal substrate with surrounding water environment and decreasing the risk of corrosion is shown to improve the corrosion resistance of magnesium alloy in humid environments and in the presence of chloride-containing aqueous environments. The objective of this study, without the low-surface-energy materials modification, is to fabricate the superhydrophobic surfaces by wet-chemical methods and to understand how the microstructure influences the surface wettability of unstable materials such as magnesium alloy. The influence of the variety of experiment conditions on the wettability of the substrates was investigated by a contact angle goniometry with water as a probe liquid. Scanning electron microscopy and energy dispersive spectroscopy were used to study the surface chemistry and microstructure at various stages of the multi-wet-chemical process.

Abstract: Cu(In,Al)Se₂ (CIAS) thin films with different Al contents were prepared by dc magnetron sputtering method and selenization process. At first, CuInAl (CIA) precursor films were deposited by sputtering from copper target and indium-aluminum composite targets, then followed by selenization process. The morphology, microstructure, optical and electrical properties were investigated by scanning electron microscopy, energy dispersive analysis, X-ray diffraction, four probes method and optical transmission, respectively. Variation of structural, optical and electrical properties of CIAS films with different Al contents was studied. The results show that Al content has an effect on the morphology and grain distribution. All the CIAS films maintain chalcopyrite structure with preferred orientation along (112) direction. The electrical studies show that resistivity of the films increases when the Al content increases. The optical studies reveal that the films have high absorbance and the energy band gap calculated from transmission spectra are at the rang of 1.60-1.95 eV.