Advanced Materials Research Vols. 60-61

Abstract: Pb1-xSrx (Zr0.53Ti0.47) O3 (PSZT) thin films have been fabricated on Pt/Ti/SiO2/Si substrate by a sol–gel method combined with a rapid thermal annealing process. The microstructure analysis of the thin films showed that the orientation ratio of (111) was 0.304，0.475 and 0.849 with x=0, 0.03, 0.08. The dielectric measurement suggested that the addition of Sr in Pb(Zr0.53Ti0.47) O3(PZT) thin films greatly improved the dielectric properties of PZT thin films. The dielectric constant for PZT thin films at a frequency of 2 kHz was 648，which was increased to 1239 when 3%at Sr was doped. Meanwhile, the dissipation factor was only increased from 0.02 to 0.03. Three kinds of piezoelectric micro-sensors have been prepared based on PSZT thin films and the sensing sensitivity of 0.017pc/uN, 0.033pc/uN, and 0.011pc/uN were realized as x increased, respectively. It indicated that micro-sensors with PSZT0.03 thin films showed better sensing property than other two.

Abstract: Chemical vapor deposition, Catalyst, Carbon nanocoils, High efficient growth Abstract: Carbon nanocoils (CNCs) were prepared by thermal chemical vapor deposition (CVD) using a Fe and Sn containing solution as the catalyst predecessor. The solutions of Fe2(SO4)3/SnCl2, FeCl3/SnCl2 and Fe(NO3)3/SnCl2 with the mol ratios of 3:0.1 to 3:1 were used as catalysts. Comparing the catalysts in different composition ratios with the grown deposits after CVD, we found that the optimum mol ratio between Fe and Sn is 6:0.1. It is noted that the catalyst combination of Fe2(SO4)3 /SnCl2 obviously increases the quantity of the grown carbon deposits indicating that it has the largest catalytic activity among the three kinds of combinations. Large surface area of catalyst films formed by release of SO3 from the decomposition of Fe2(SO4)3 over the temperature of 480 °C is very good for the carbon nanocoils growth and the introduction of sulfide impurities are the key factors leading to the high efficient growth for carbon nanocoils. It is known that Fe-additions lead to the growth of carbon nanotubes or nanofibers, while Sn induces their helical growth and a little sulfur impurities may induce the efficient growth of carbon nanocoils.

Abstract: Multifunctional BiFeO3 (BFO) thin films were deposited on Bi3.15Nd0.85Ti3O12 (BNdT)/Pt and Pb(Zr1−x,Tix)O3 (PZT)/Pt substrates respectively by sol-gel process. The ferroelectric properties were studied for Metal-Ferroelectric-Mental (MFM) capacitors. The MFM structure exhibited well clockwise capacitance-voltage hysteresis loops due to the ferroelectric polarization of multilayer thin films achieved. The remnant polarization (2Pr) of the BFO/PZT and BFO/PZT multilayer capacitors were 45.1μC/cm2 and 23.2μC/cm2, respectively at the applied voltage of 8V. The leakage current of Pt/BFO/BNdT/Pt is about 3×10-5A/㎝2 at applied voltage of 4V, one order smaller than Pt/BFO/PZT/Pt capacitor. For the BFO/BNdT/Pt, it exhibited a weak saturated ferromagnetic response at room temperature and the multilayer was anti-ferromagnetic. However, for the BFO/PZT/Pt, well-developed M-H loops together with remnant magnetizations can be observed in at room temperature. The highest saturation magnetizations (Ms) of both capacitors were measured to be 2.47emu/cm3.

Abstract: Based on the visualization technology, we investigated experimentally the effect of different flow patterns on anode fluid behaviors of the μDMFC (Micro Direct Methanol Fuel Cell) with a transparent material under the same condition. Stainless steel mesh was utilized as the current collector which was distinct from the carbon cloth or carbon paper. Four dissimilar flow patterns were developed and tested. The observation of the effect of different flow patterns revealed that movements of dilute methanol solutions and CO2 gas bubbles in the dot and parallel flow fields represented more difficult, which could result in a decline of the μDMFC performance. The study also showed that a channel blocking in the single-serpentine flow field would be extremely terrible which could lead to a fuels leaking of the μDMFC, meanwhile the liquid-gas flow was more fluent and stable in a double-serpentine flow field. Therefore, due to its advantages, a double-serpentine flow pattern is more suitable for the μDMFC application compared with the other flow patterns.

Abstract: In this paper, a MEMS surface resonant magnetometer based on Lorentz force is presented. This magnetometer has three current carriers to sense the magnetic field and changes into deflection of beams which will be detected by the comb-capacitance. The alternating current carried by oscillate beams has the same frequency as resonant frequency of the magnetometer structure to make the deflection magnified Q (Quality-factor) times, therefore, it becomes more easily to measure. In this paper, the mechanical model of the sensitive element is established. The equations of stiffness of the system, deflection, first-order resonance frequency and sensitivity are setup and simulated in ANSYS, as well as second-order to fourth-order modal, and harmonic excitation response simulation. It can be seen that the simulation results are in good accordance with the theoretical calculations, which proves the feasibility and the rationality of the theoretical model. The dimensions of the structure are designed, as well as the processing sequence Anodic Silicon-Glass Bonding and Silicon DRIE Multi-user Bulk Micromachining Process which will be used to manufacture the magnetometer. The MEMS surface resonant magnetometer has a high sensitivity, simple structure and easy to manufacture. The prototype sensors are being manufactured in NEDI now.

Abstract: In order to analyze the effect of proceeding on the mechanical and tribological properties of DLC films. Three DLC films samples on single silicon wafers were prepared by CVD method. The changed bias voltages were 300V, 350V, 450V separately. The structure and topography of prepared films were studied by Raman spectroscopy and atomic force microscopy (AFM), respectively. The hardness and elastic modulus together with friction coefficient of DLC films were measured by Tribolab system. According to the Raman spectra, the G and D peak shift to left with the increasing of bias voltage. Nano indent showed that the hardness (H) of the DLC films decreases from 19.63GPa to 18.12GPa with the increasing of bias voltages, and the value of elastic modulus (E) is also behaving the same trend as H from 157.95GPa to 146.95GPa. Friction coefficients of the three samples were measured by nano-scratch method under the constant normal load of 1000uN and the slide velocity of 3 um/sec, the corresponding friction coefficient is 0.0804 for DLC300, 0.0508for DLC350 and 0.0594 for DLC450 separately, which indicates that high hardness materials may not necessarily the perfect frictional material, but compound properties of hardness and elastic modulus

Abstract: . Error autocompensation using a non-MEMS micromotor is used to reduce the drift of micromachned gyroscopes. Theoretic deviation, numerical simulation and experiments are carried out. Test results show that the bias instability of micromachined gyroscopes is reduced from 542°/h to 39°/h, which makes their high end applications possible

Abstract: High density ZnO nanostructures were fabricated on Au coated Si and quartz substrates through once and the same oxidative evaporation of pure zinc powder. The coated side of the substrate was intentionally positioned in two directions of face and back to the zinc sources. Structure, morphology and optical properties of the samples were investigated by scanning electron microscopy, X-ray diffraction, Raman spectra and room temperature photoluminescence measurements. The results showed that the samples on the different substrates with different directions have three different morphologies, including film-, rod- and comb-like nanostructures. Photoluminescence spectra of the samples showed the various bands centered in UV (380-390 nm), blue (470-490 nm), green (500-550 nm) and orange (610-620 nm) region. It demonstrates that the substrate material and the direction of substrate significantly affect the growth of ZnO nanostructures.

Abstract: CuO/SiO2 nanocomposite films were prepared by sol-gel process combined with the dip-coating technique. The mean diameter of CuO nanoparticles formed during the heat treatment process and mainly lay in the pores of mesoporous SiO2 matrix increased by increasing the heat treatment temperature. Consequently, compared with mesoporous SiO2 matrix, the pore volume and specific surface area of prepared samples descend. The diffraction peaks of Cu and CuO and the crystalline diffraction ring of CuO with body centered cubic structure can be clearly observed after heat-treated in air and H2 at 800 oC for 1h. By increasing the heat treatment temperature and concentration of CuO, a slightly red-shift could be observed.

Abstract: PMMA, Capillary Electrophoresis, Thermal bonding, Factor, Deformation. Abstract. In this paper, using the powder hot embossing machine, the effects of the bonding temperature, pressure and time on the deformation of microchannel dimensions is studied systematically. The bonding temperature is mainly influence factor on the deformation of microchannel determined by the method of orthogonal experiment. Some mathematical models are described to optimize the thermal bonding process parameters. According theory and experimental curve, the optimal experimental model (83°C, 0.4Mpa and 7 min) is suggested. Under the process parameters the deformation of crossing section dimension before and after thermal bonding is 37.8%. The channel is successfully sealed underneath with a thin foil 30μm thickness PMMA for contactless conductivity detection. The entire fabrication methodology may also be useful for preparation of other polymer microfluidic systems. Finally, the performance of the PMMA chip is demonstrated to separate continuously K+ ions using the contactless conductivity detection.