Advanced Materials Research Vols. 239-242

Abstract: Niobium doped Pb(Zr,Ti)O₃ fiber/epoxy resin 1-3 composites with different ceramic volume fraction of 10-85% were fabricated by filling-casting method. Effects of ceramic volume fraction on electric properties were investigated. For a typical 30% ceramic content composite, the thickness coupling coefficient k_t, mechanical quality factor Q_m, acoustic impedance Z_m and anisotropic property k_t/k_p were 0.67, 0.55, 11.03 MRayl and 2.23, respectively.

Abstract: The effect of cold rolling on thermal stability of bulk Zr₅₅Al₁₀Ni₅Cu₃₀ metallic glass at room temperature had been investigated by means of X-ray diffractometer, high-resolution transmission electron microscope and differential scanning calorimeter. A number of the cold rolling processes were carried out to obtain different thickness reduction in specimens with the same original size. The XRD patterns of cold rolled specimens with thickness reduction up to 95% showed no clear difference with that of completely amorphous specimens. The relationship of the deformation with the thermal parameters of cold rolled specimen indicates that with the increase of thickness reduction, the glass transition temperature decreases obviously and the crystallization onset temperature and peak temperature decreases slightly. At the same time, the enthalpy of crystallization peak keeps almost constant during rolling. These results have revealed that cold rolling deformation has an apparently effect on the glass transition process but slightly effect on the crystallization process of Zr₅₅Al₁₀Ni₅Cu₃₀ BMG.

Abstract: Schiff base of chitosan was obtained by the reaction of chitosan and aromatic aldehyde, and then Schiff base of chitosan reacted with methyl iodide to get soluble quaternary ammonium salts of chitosan which were N-metoxybenzenemethyl quaternary ammonium salt of chitosan (NM- Chitosan) and N-hydroxybenzenemethyl quaternary ammonium salt of chitosan(NH-Chitosan). The obtained chitosan derivatives were characterized by Infrared Spectra Analysis(FT-IR), Nuclear Magnetic Resonance Spectroscopy(¹H NMR) and elemental analysis. Quantitative analysis showed that there was small difference between degrees of quaternization(DQ) and degrees of substitution(DS), and the solubility of chitosan derivatives was demonstrated to be better in the organic solvents.

Abstract: Nanostructured ε-manganese dioxide films are deposited directly on three-dimensional nickel foam (NF) from 0.25 M Mn(CH₃COO)₂ by means of the potentiostatic method (PSM) and potentiodynamic method (PDM). The prepared MnO₂ films are characterized by X-ray diffraction and scanning electron microscopy. The electrochemical properties of MnO₂ films are investigated by cyclic voltammetry (CV), charge-discharge tests, and alternating current (AC) impedance spectroscopy. The results show that the PSM-MnO₂ films exhibit higher specific capacitance and better high-rate discharge ability, which are more promising for applications in supercapacitor than PDM-MnO₂ films. The specific capacitance of PSM-MnO₂ films is about 664 F g^-1 at 5.5 A g^-1, which is higher than many reported values.

Abstract: This paper has examined the hardening effect and mechanism of explosive working on high-manganese steel. According to the experiment result, the surface hardness of high-manganese steel is improved greatly after explosive working and the hardened depth exceeds 40mm. The surface hardness and hardened depth increase slightly, the tensile strength is improved and ductility is reduced after three times of explosion. Charpy impact test demonstrates that it has still high ductility, the fatigue performance isn’t inferior to that before the explosion, the abrasive resistance is higher than that before the explosion and macroscopic residual deformation is extremely small. Such changes are related with the internal stress and changes of metallographic structure after explosion. After explosion, the surface is at stress state and the metallographic structure still retains the single-phase austenite matrix; and it produces high-density dislocation, stacking fault, cross-slip, lattice torsion, twin-crystal and refinement of austenite crystal grains.

Abstract: Polythionphene (PTH)/polyaniline (PANI)/activated carbon (AC) composites as electrode materials for supercapacitors were synthesized by in-situ polymerization of thionphene on PANI/AC. The surface morphology and the molecular structure of the composites were examined by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The electrochemical performances were tested by cyclic voltammetry, Galvanostatic charge-discharge and electrochemical impedance spectrometry. Results show that the PTH/PANI/AC composites exhibit better large current charge-discharge performance and higher capacitance than those of PANI/AC. The capacitance value of the composites would reach 597.4 F/g. The PTH/PANI/AC composites also have better cycle stability than that of PANI/AC.

Abstract: In this paper reflow process is integrated into LIGA process in order to realize three dimensional fabrication. The melting and deformation process of photoresist, which has an initial cylindrical shape of D500μm and h66μm, and the influence of various processing parameters on the height of formed microlens, is simulated with Marc. The optimum processing parameters combination is obtained by orthogonal experiment method and the influence of different processing parameters on the height of micro-spherical structure is studied with single factor experiment method. The results showed that the optimum processing parameters combination was 1°C /s for heating rate, 110°C for heating temperature and 45min for holding time; the significance of processing parameters on the micro-spherical structure’s height can be ordered in holding time＞heating rate＞heating temperature.

Abstract: Microencapsulated phase change material (MEPCM) was successfully prepared by using paraffin as the core material and PMMA as shell material. Both raw materials are innocuous, cheap and rich in resource. The influences of the key factors (i.e. emulsifier, stabilizer, concentration of the oil phase) on synthesis reaction were systematically evaluated. Conditions of synthesis reaction were also optimized. The relevant research results indicate that the prepared microcapsules are regular spheres with smooth and compact surface. The diameter of these spheres ranges from 1 to 2 mm. No obvious overcooling or overheating phenomena can be observed even when the content of paraffin of MEPCM reaches approximately 50 wt%. TGA analyses indicate that the heat resistance of the microcapsule increases by 10 °C compared to the pure paraffin. Accelerated thermal cycling tests also verify that the MEPCM displays good thermal reliability. The MEPCMs synthesized in the current study have potentials for thermal energy storage purposes such as PCM slurries, textiles and building materials.

Abstract: Porous carbon film was prepared from polyimide (PI) containing nickel particles by heat-treatment at different temperature. The prepared samples were investigated by multipoint brunauer-Emmett-Teller surface area (BET), scanning electron microscopy (SEM) and X-ray diffraction. The mesopore structure was obtained by heat-treating at 1000°C and the macropore and layered-graphite structure was achieved by heat-treating at 1600°C. The electrochemical properties of the carbon films were studied by galvanostatic cycling. The results showed that the reversible capacity of the carbon film treated at 1600°C is a promising material to be used in the lithium battery.

Abstract: Lead-free potassium sodium niobate ceramic thin films were synthesized using rf magnetron sputtering technology for MFIS structures. The optimal sputtering parameters of the as-deposited KNN thin films for depositing times of 1h were obtained. Regarding the measured physical properties, the micro-structure and thickness of as-deposited KNN thin films for different oxygen concentration were obtained and compared by XRD patterns and SEM images. The surface roughness of KNN thin film was also observed by AFM morphology. The average grain size and root mean square roughness were 250 and 7.04 nm, respectively. For KNN thin films in the MFIS structure, the capacitance and leakage current density were 280 pF and 10^-8A/cm², respectively. We investigated that the leakage current density and the memory window increased, the capacitance critically increased as the oxygen concentration increased from 0 to 40%. However, the excess oxygen concentration process was decreased the electrical and physical of as-deposited KNN thin film. The effect of oxygen concentration on the physical and electrical characteristics of KNN thin films was investigated and determined.