Key Engineering Materials Vols. 562-565

Abstract: Hot-dip galvanized steels are widely used in modern industry. The corrosion resistance and formability of them are closely related to the thickness and cross section microstructure of the hot-dip coating. In this paper, the effects of Si and RE on the thickness of Zn-6Al-3Mg alloy coating (ZAM) were investigated. Steel sheets were coated by using an experimental hot-dip galvanizing simulator. The thickness and cross section microstructure of ZAM coating alloyed with different content of Si and RE were characterized by using optical microscope and SEM, and element distribution was study by EDS. The results demonstrated that the reaction between Al from the bath and Fe form the steel sheets was suppressed by the addition of 0.1 wt. % Si to the Zn-6Al-3Mg bath, and the addition of RE effectively decreased the thickness of coating by means of improving the flowing property of the zinc alloy bath. Under the combined effects of Si and RE, the thickness of Zn-6Al-3Mg alloy coating went down from 33 μm to 10.1 μm.

Abstract: This paper describes the fabrication and measurement results of piezoelectric energy harvester arrays based on aluminum nitride (AlN) as a piezoelectric material. The AlN piezoelectric thin film with crystal orientation (002) and crystal orientation (101) is deposited respectively by pulsed_DC sputtering on the different bottom electrode materials. Based on the AlN thin film, the piezoelectric vibration energy harvester arrays with 5 cantilever beams were developed. Then the load characteristics, frequency characteristics, harvester connected in series and parallel properties of harvester were investigated. In addition, we compare the properties of piezoelectric vibration energy harvester arrays with crystal orientation (101) and (002), where a record max power output of 0.23 μW and 0.38μW are obtained respectively when the value of acceleration was 1 g, while for the latter, the maximum power is 9.13 μW at the acceleration of 5.0g with the optimized resistance of 15 kΩ.

Abstract: To obtain a large surface area, the aluminum electrode foils (AEF) were etched by direct current (DC) in hot chloride solution to get lots of vertical [001] tunnels. Whereas, because of the defects as rolling trace, distorted oxidation film, non-uniform organization, pollution layer on the surface of the aluminum foil, and the easy corrosion in hot Cl- acid solution, the etch pits are disorder and merged. These merged pits cause laterally directed dissolution and excessive dissolution on the aluminum surface, which limited the surface enlarging and decreased the strength of the aluminum foils. In this paper, we adopted anodic oxidation to fabricate the porous anodic alumina (PAA) on the high-purity electronic aluminum foils with 99.99% purity, and polarized by a negative voltage in the KCl solution. The result showed that several nanopores combined together to form a large open holes without barrier layers. With this membrane on, the foils were etched in 70°C HCl+H2SO4 solution, and the etch pits were just generated in the combining-nanopores. The etch pits grew into tunnels respectively without merged, and the surface was also smooth.

Abstract: As a key MEMS transducer materials, PbZr_0.52Ti_0.48O₃(PZT) piezoelectric thick film should have good piezoelectric properties as well as lower stress. But now few studies on PZT film stress were carried out. The PZT thick films are deposited by a modified sol-gel method, and the influences of crystallization temperature and slurry concentration on stress are investigated in this paper. The result shows that the PZT thick film stress is tensile stress about 100-1000Mpa. With crystallization temperature increasing, thermal stress increases gradually. The stress increases about 3.5 times as the crystallization temperature rises from 600°C to 700°C. With powder concentration of slurry increasing, the stress of PZT thick film becomes smaller. The stress decreases about 7 times as powder concentration of slurry increasing from 1:4.5 to 1:3.5. The relationship between stress of PZT thick films and crystallization temperature is simulated by using the finite element method, and the results of simulation agree well with the experimental results.

Abstract: Aimed at the lack of the cladding materials such as micro or nanopowder, the micro/nanocomposite powders prepared for experiment are feed directly, the key process parameters on the quality of the surface quality and microstructure analysis of the single-layer of laser cladding are studied in detail. Compared to the ordinary laser micro-cladding layer feeding by the micro powder, the cladding layer is more refined, which has more good mechanical properties. The results showed that: using reasonable parameters, the microstructure and macro-morphology of cladding layer with micro-nanocomposite powders feed directly are better than of micron powders.

Abstract: This work presents a novel thermal assisted ultra-violet (UV) photocatalysis oxidation method for total phosphorus (TP) detection. A 365nm wavelength UV light was used as the UV light source, and the TiO₂ particles, immobilized on silicon wafer, were used as the catalyst. The sodium glycerophosphate was digested as the typical compound of TP. The digested samples were determined by spectrophotometry after the phosphomolybdenum blue reaction. The catalyst can be used repetitively with long-term stability in this work. For the photocatalysis digestion process under room-temperature, when the reaction time reached 120min, the conversion rates were 92.31% and 93.66% for 1mg/L and 4mg/L of C₃H₇Na₂O₆P solutions, respectively. And conversion rates were 95.48% and 99.37% respectively for thermal assisted ultra-violet (UV) photocatalysis digestion process at the condition of 30min and 60°C. Compared with the conventional thermal digestion method and photocatalysis digestion method for TP detection, this thermal assisted UV digestion method can greatly decrease the digestion time and enhance the efficiency.

Abstract: Spatial modulation Fourier transform spectrometer(FTS) based on micro step mirror arrays with high optical path difference sampling precision was a new high-tech measuring instrument. To depress the interferogram aliasing resulted from the chromatic dispersion of beam splitter, considering interferogram contrast reversal as the criterion of image degradation, the thickness difference between beam splitter and compensating plate was determined smaller than 0.2μm. So as to restrain the ghost images induced by secondary reflection on the surface of beam splitter, the transmittance of anti-reflection film should be more than 98% and the transmittance of beam splitter film should be controlled within (50±5) %. Since the restriction of processing method and machining accuracy to micro step mirrors, the thickness deviation and angle deviation existed between various sub-mirrors. After the error synthesis to sub-mirror errors using Monte Carlo method, the tolerance of the thickness deviation and angle deviation was controlled in 1μm and 2×10-5rad. Meanwhile, the step height deviation of micro step mirrors may induce non uniform sampling to interference signal. Thus a spectrum method by least-squares cosines progression arithmetic was advanced and the validity of which was demonstrated well.

Abstract: Length and support mode are the key to restrict the ultrasonic motor miniaturization. This paper presents a miniature langevin-type ultrasonic motor stator, it has both short length and simple support mode. With fixed-free ends, the stator adopts a square base and is fixed at its four corners. A new excitation mode is utilized to solve the problem of insistence of excitation position in the conventional excitation mode. Since the stator is unsymmetrical along the circumferential direction, there should be an optimal excitation angle. By using finite element method, axial displacement and radial displacement of nodes are achieved along the outer edge of the upper end of the stator when excitation angle is changed , then the results are analyzed and the conclusion can be reached that 45^o is the optimal excitation angle. Finally, a photo of the stator prototype is presented.

Abstract: In order to analyze the influence of scattering particles on the optical properties of light scatter of polymer diffusion plate, we establish the microspheres of scattering particles in mathematical physics model. According to Mie scattering theory, we study the relationship between the scattering intensity distribution and the particle radius, the refractive index and the wavelength of the incident light. The results show that the particle radius is larger and incident wavelength is smaller, scattering intensity distribution is concentrated; the particle refractive index and scattering intensity distribution are not a simple corresponding relationship. At the same time according to the Monte Carlo method, the simulation is also used to analysis the effect that scattering particle concentration, the scattering particle radius and refractive index influence the diffusion plate light transmission rate and uniformity. The result shows that as the particle concentration is greater and transmittance is smaller, uniformity increases first and then decreases. As the particle radius is small, light transmission rate is higher and the particle refractive index is larger, light transmittance increases first and then decreases. But the relationship of the uniformity, the particle radius and the particle refractive index are all not simple corresponding law.

Abstract: In the paper, it demonstrates highly integrated tenth-order filters in silicon-on-insulator (SOI). The micro-ring resonators have a small radius of 5μm and a very large free spectral range ~ 18nm at 1.55μm communication band. For through port responses, the grating and the high-order optic filters with ten coupled micro-ring resonators are designed and demonstrated, and grating responding well matches with the experiment resonators. Devices are patterned with electron-beam lithography (EBL). And 2μm SiO2 layer is covered on the silicon waveguide, thus reducing the propagation loss in micro-ring resonators.