Key Engineering Materials Vols. 334-335

Abstract: Ni-Zn ferrite is a kind of important magnetically soft material that has been used widely in medical signal deal and medical apparatus. So, many people are interested in both the prepare process of Zn ferrite (especially the prepare process of nanometer ferrite) and the study of its structure and properties. In this paper the condition in which Ni-Zn ferrite powders was prepared by sol-gel methods was studied. The pH value, calcined temperature, calcined time were investigated. With the designing experiment, the best condition was confirmed. The microstructures and particles size were characterized by means of TEM、IR、XRD and so on.

Abstract: Nanometer level α-Fe2O3 is a sort of important nanometer material, which can be used comprehensive in the field of catalysis, ultraviolet radiation absorption material, functional ceramics and so on. This article uses the method of microwave radiation combined with high temperature sintering to prepare dispersive and symmetrical α-Fe2O3 nanometer grains for the first time, and this method not only may reduce the reactive cycle, but also may enhance the concentration of reactive initial solution of FeCl3. At the same time, in the process of experiment we found that if we put different crystal promotion agents in reaction solution at different calcining heat and calcining time, we can obtain round, cubic or rod-like α-Fe2O3 nanometer grains separately.

Abstract: A new attempt is made for application of the NafionTM nanofiber mat prepared by the electrospinning process to solve the main disadvantage of slow response speed of ionomer-ionic liquid transducers. The measured conductivities of water hydrated Nafion electro-spun fibers are 16.8 mS/cm, which are lower than the nominal 110 mS/cm that of H+ Nafion membranes. The uptake is measured to be around 250 wt % compared to 58 wt % obtained in Nafion films. The ionic conductivity of 110 wt % swollen ionic liquids-Nafion mat composite is computed to be 0.9 mS/cm compared to 0.3 mS/cm in ionic liquid-Nafion membrane composite. The speed of response in actuators with an ionic liquid- NafionTM mat is 1.34 %/s compared to 0.88 %/s for that in ionic liquid NafionTM film transducers.

Abstract: The ionic-polymer-metal-composite actuators can easily actualize the bio-mimetic fish-like locomotion owing to their best merit for large deformation. And novel fabrication methods of IPMC patterned with multiple electrodes were developed to apply the different driving waves to the multiple electrodes. Generally, the IPMC actuator has been fabricated in electroless plating technique, while it is high time-consuming process, showing poor repeatability in the actuation performance due to the variables in the process of fabrication. Therefore the several fabricating methods was newly investigated by combining electroless plating, photolithography, physical sputtering and electroplating techniques capable of precisely patterning and actuating of the multiple electrodes. On the whole, four different methods were compared and analyzed in similar thickness level of Platinum electrodes. Consequently, the mixing the electroless chemical reduction and electroplating can be a promising candidate for the low time-consuming method and the better bending performance.

Abstract: In this study, the stabilization of thermoelastic unstable postbuckling in cylindrical piezolaminated panels was investigated by applying piezoelectric actuation. In order to derive the finite element equations of motion of the active piezolaminated cylindrical panels, the total Lagrangian formulation was derived using the Hamilton’s virtual work principles for largely deformed structures with small strain. For the purpose of finding the load-displacement tracking, a cylindrical arc-length method was applied to the iterative Newton-Raphson scheme. Present results show that the eccentric piezoelectric patch can passively remove the unstable postbuckling and the snap-through without piezoelectric actuation. Also, the thermoelastic snap-through can be successfully suppressed by using a piezoelectric actuation.

Abstract: Although demand for composite structures rapidly increase due to the advantages in weight, there are few effective assessment techniques to enable the quality control and guarantee the durability. In particular, an invisible microscopic damage detection technology is highly required because damages such as transverse cracks, debondings, or delaminations can lead to the critical failure of the structures. Among many non-destructive evaluation (NDE) methods for composite structures, fiber optic sensors are especially attractive due to the high sensitivity, the lightweight, and the small size. In the current trend of the structural health monitoring technology, fiber Bragg gratings (FBG) sensors are frequently used as strain or temperature sensors, and Brillouin scattering sensors are also often used for a long distance distributed measurement. The Brillouin distributed sensors can measure strain over a distance of 10km while a spatial resolution was limited to 1m. Some novel sensing method is proposed to improve the spatial resolution. The pulse-prepump Brillouin optical time domain analysis (PPP-BOTDA) is one of the latest distributed sensing applications with a cm-order high spatial resolution. The PPP-BOTDA commercial product has the spatial resolution of 10cm, and can measure the strain with a precision of ±25og. This precision, however, can be achieved by using conventional single-mode optical fibers. In our research, small-diameter optical fibers with a cladding diameter of 40om were embedded in the CFRP laminate to avoid the deterioration of the CFRP mechanical properties. Thus, in order to verify the performance of PPP-BOTDA, the distributed strain measurement was conducted with the small-diameter optical fibers embedded in the CFRP laminate.

Abstract: A description is given of a possible solution of an important practical problem in microelectronics, namely producing a material of thermal expansion coeffiecient to equal that of silicon.

Abstract: In this work, we report the magnetoelectric HoMnO3-BaTiO3 composites prepared by the solid-state reaction method. X-ray diffraction and scanning electron microscopy were used to characterize the phase composition and structures of the composites. The material/impedance analyzer was used to investigate the dielectric properties of the composites. It is shown that the composite consists of both ferroelectric ordering and magnetic ordering. The addition of BaTiO3 decreases the antiferromagnetic phase transformation temperature of the HoMnO3, indicating that there exists the coupling interaction between BaTiO3 and HoMnO3 phases.

Abstract: In this study, TiO2 was successfully coated on Stober silica beads followed by depositing Au nanoparticles on this core-shell structure. The size of the Au nanoparticles was well controlled in the range of 2 – 7 nm. This composite exhibited high thermal stability. When used as a model catalyst for oxidation of CO at low temperatures, the Au/TiO2/SiO2 showed a much higher catalytic activity than the Au/SiO2 and Au/TiO2(P25) catalysts.