Advanced Materials Research Vols. 197-198

Abstract: A proton exchange membrane of blended poly (acrylamido-2- methylpropane sulfonic acid) (PAMPS) grafted onto modified poly (vinylidene fluoride) (PVDF) membrane (PVDF-g-PAMPS) was prepared. Fourier transform infrared spectroscopy is used to characterize changes of the membrane's microstructures after grafting. The morphology of the membrane's microstructures after grafting is studied by scanning electrolytic microscope.The results show that 2-acrylamido-2-methylpropane sulfonic acid is easily grafted into PVDF modified by Plain sodium silicate (Na₄SiO₄).

Abstract: Perovskite epitaxial multiferroic BiFeO₃ nanoislands were grown on SrTiO₃ (100) and Nb-doped SrTiO₃ (100) single crystal substrates by chemical self-assembled method. Their phase structure and morphology were characterized by X-ray diffraction, scanning electron microscopy, and atomic force microscopy, respectively. The results showed that epitaxial multiferroic BiFeO₃ nanoislands were obtained via post-annealing process in the temperature range of 650 - 800°C, and their lateral sizes were in the range of 50 - 160 nm and height of 6 -12 nm. With increasing the post-annealing temperature, the morphology of BiFeO₃ nanoisland in the (100) growth plane evolved from tri-angled to squared, and then to plated shapes. By using piezo-force microscopy, ferroelectric characteristics of a single epitaxial BiFeO₃ nanoisland (with lateral size of ~ 50 nm and height of 12 nm) grown on Nb-doped SrTiO₃ (100) single crystal substrate, was characterized. The results demonstrated that fractal ferroelectric domains existed in the single BiFeO₃ nanoisland, and self-biased polarization was also observed within this multiferroic nanoisland. This phenomenon can be ascribed to the interfacial stress caused by the lattice misfit between the BiFeO₃ nanoisland and the SrTiO₃ single crystal substrate.

Abstract: A series of novel liquid crystal polyurethanes containing biphenylnate and imide units were synthesized through the polyaddition reaction of 4,4′-Bis-(2-hydroxyhexoxy)biphenyl (BP2), 2,4-toluenediisocyanate (2,4-TDI) with N,N′-bis(2-hydroxyhexyl)-dicarboxyimide (BHDI) by altering the molar ratio of BP2 and BHDI. The effects of structure difference molar ratio between BP2 and BHDI on the liquid crystalline behavior and thermal stability were studied. Results showed that all of the polyurethane polymers exhibited thermotropic nematic liquid crystalline textures in the range of 160~190°C. The melting temperatures (Tm) and the thermal stability increased with increasing BHDI content.

Abstract: This study focuses on fabrication of a micro plastic part using custom made vertical injection molding machine. Electrical discharge machining (EDM) and micro mechanical machining was used to fabricate micro shape cavity on aluminum mold. The mold was embedded with Polymethyl Methacrylate (PMMA) window to observe the behavior of plastic melt flow during injection. The custom made vertical injection molding machine has capabilities to produce a micro plastic part. But, the filling behavior observation was contrast with MoldFlow analysis software. The flashing problem occurs at each molded micro part due to improper selection of injection molding parameter.

Abstract: Bis(2,6,7-trioxa-l-phosphabicyclo[2.2.2]octane-4-methanol) melaminium salt (Melabis) and microcapsules of Melabis with melamine resin shell as flame retardants (FR), respectively, were synthesized. Their structures were characterized by NMR, IR, SEM, TG and element analysis. 20% weight of microcapsules was doped into epoxy resins (EP) to get 28.5 % of LOI and UL 94 V-0. The heat and smoke release of EP containing microcapsules was valued by cone calorimeter.

Abstract: The conductive fibers have great potential as flexible sensors. In our previous study, based on the experimental studies on sensing behavior of PPy (polypyrrole)-coated Lycra fibers, the mechanism of the strain sensing behavior was identified as open-close mechanism of the cracks on the coating layer when experiencing large deformation. In order to modeling its strain sensing behavior and describe quantitively the development of the micro-cracks, statistical analysis is conducted by image processing technique in MATLAB software. It was concluded that the variation of resistance is related to the micro parameters of the surface cracks, suck as the number, width and length of micro-cracks. These will be used in our further modeling work.

Abstract: The electrical responses of Zn-Bi-Co-Mn-Ti system low-voltage varistor ceramics were prepared by solid-state reaction method and were analyzed by AC impedance spectroscopy over a wide range of temperature (100~270°C) in the frequency range of 40~13MHz. The equivalent circuit adopts R (RQ)(RC) model. Imaginary part of impedance and modulus with frequency plot exhibits the varistor ceramics including resistance and capacitance. Impedance analysis enables us to separate the contributions from grains and grain boundaries of our samples. It indicates that grain boundary impedance is the main contributor for ceramic resistance, and grain boundary relaxation effects are most obvious in Zn-Bi-Co-Mn-Ti system. The AC grain boundary conductivity activation energy is attributed to the motion of oxygen vacancies within the bulk, and calculated by Arrhenius equation.

Abstract: Pyrotechnical battery is successfully prepared, including an anode and cathode having pyrotechnic charges with an excess of fuel-anode and an excess of oxidation agent cathode (Zr, CuO and asbestos), the anode and cathode being separated by a separator formed from LiF, ZrO₂ and fibrous sponge. Main performance indexes system of pyrotechnical battery is put forward and tested under the premise of appropriate mass and corresponding size, such as discharge voltage, discharge time, activation time, excitation time, internal resistance, combustion temperature and storage life. The results show that pyrotechnical battery of Zr/CuO system can basically meet application requirements. Activation time is usually about 0.2 s. Discharge voltage is about 1.96 V and the discharge time is up to 13.8 s or more. The internal resistance keeps a low fixed value (0.47Ω , for example). Combustion temperature of pyrotechnic composition can reach 1500.6 °C (the case temperature of battery is lower) to ensure that electrode and separator is adequately melted, consequently, the internal resistance is reduced, and achieving satisfactory discharge effect.

Abstract: Based on the crystal plasticity theory, the slip-band traces on the specimen surface of polycrystalline copper tensioned uniaxially are investigated by using the finite deformation numerical algorithm, and the statistical distributions of the inhomogeneous strain and stress in the specimen are analyzed. The tension deformation of the polycrystalline specimen is simulated by the three dimensional FEM. Through the geometric analysis of intersect-lines between the active crystallographic slip-planes and the specimen surface, the different slip-band traces of the specimen surface are calculated and discussed. According to the results, it is confirmed that the crystal plasticity theory is feasible to study the deformation of the crystalline material.

Abstract: The objective of this paper is to use the specialty fracture software Crack3D FEA Code, well known Ansys software and Mushhelisvili’s torsion theorem to analyze the torsion problem of a crack rectangular cylinder. Several numerical results such as stress intensity factors K_III , torsion rigidity D, shearing stresses (τ_xy ,τ_yz ) and the contour nodal solution data are obtained. All the results are satisfactory.