Key Engineering Materials Vols. 562-565

Abstract: Multiwalled carbon nanotubes (MWNTs) grafted by Poly(methyl methacrylate) (PMMA) can well disperse in organic solutions like toluene，which were synthesized via a microemulsion polymerization of methyl methacrylate (MMA) in the presence of acid-modified multiwalled carbon nanotubes (c-MWNTs). The polyamide thin-film nanocomposite (TFN) membranes with embedded PMMA-MWNTs were prepared using piperazine (PIP) and trimesoyl chloride (TMC) on a polyacrylonitrile (PAN) porous substrate via interfacial polymerization for selective permeability. PMMA-MWNTs’ structure was analyzed by Fourier transform infrared spectrophotometry (FTIR), Raman spectrophotmetry (RAM), Scanning electron microscope (SEM) and thermo gravimetric analysis (TGA). Orthogonal experiment was used to study the effect of PIP concentration, TMC concentration and concentration of PMMA-MWNTs in organic phase. The results showed that the membrane performances is good, Na2SO4 rejection is above 98% and water flux is up to 150% improvement over the TFC membrane as PIP in aqueous phase was 2g/L, TMC and PMMA-MWNTs in organic phase were 4g/L and 0.67g/L, respectively . Demonstrated PMMA-MWNTs in the nanofiltration membrane can improve selective permeability.

Abstract: A composite membrane of konjac/gelatin was prepared by electrospinning process. Gelatin and konjac were dissolved in acetic acid with different concentration and the resulting blend sol was electrospun into the composite nanofibrous membranes. The influence of technical parameters on morphology and diameter of nanofibers was investigated by Scanning Electron Microscope (SEM). The results show that the concentration of gelatin/konjac blend sol affects significantly on the fiber diameter and the morphology of composite membranes, and the increase of the voltage results in the decrease of the fiber diameter. The composite nanofibrous membranes with the average fiber diameter ranging from 356nm to 463nm were fabricated by electrospinning at the following conditions: 25% (w/v) of the concentration of gelatin/konjac blend sol (weight ratio of gelatin to konjac=125/1), 20KV of electric voltage, 0.0025mm s-1 of the feeding rate, 42°C of the electrospinning temperature and 15cm of receiving distance.

Abstract: _{Subscript textSubscript text}Er₂O₃、Tm₂O₃ and Yb₂O₃ films were deposited on Si (100) and quartz substrates by radio frequency magnetron technique. The energy gaps of the films were measured by X-ray photoelectron spectroscopy (XPS) and optical methods. The energy gaps of Er₂O₃、Tm₂O₃ and Yb₂O₃ are found to be 6.3±0.1、5.8±0.1 and 7.1±0.1 eV by optical measurements. For XPS measurements, the energy gaps of the films are 6.2±0.2、6.0±0.2 and 6.9±0.2 eV, respectively. The results show that using XPS to measure the energy gap of rare earth metal oxide film is feasible in an allowable deviation.

Abstract: SPR phase detection method is adopted in this paper to measure the thickness of nanometer scale metal film. It provided a novel means to calculate the value of thickness through figuring up the relative offset of interference fringes with the TM-polarized and TE-polarized wave reflected from the prism which is covered by a film-substrate step. Simulation results are presented out to illustrate the relations between phase variation and metal film thickness. This method is succeeded in measuring the target metal film with nominal thickness 50 nm and the average measurement value is 50.02 nm. The standard deviation is 0.41 nm and the maximum repeatability error is 0.90 nm.

Abstract: Most of research on formation mechanism of black silicon stays in the stage of experimental analysis. Consequently, it is quite difficult to perceive the mechanism of its formation process theoretically. In this paper, Quantum Mechanics is involved in our research on mechanism of how black silicon is formed in the fabrication process based on DRIE. Satisfying result is obtained through our simulation: Pillar structures with spacing raging from 500nm to 550nm can be formed when there exist particles with single momentum size in emulated experiment environment; With further efforts, more complicated pillar structures are obtained assuming that there exist particles with two sizes of momentum. By comparing with SEM image of black silicon, the simulated pillar structures are quite similar with real black silicon in both spacing and height distribution.

Abstract: By sol-gel processing and electrospinning technique, ultrathin fibers of PVP/ ZnTiO3:Pb2+ composites were synthesized. After calcined of the fibers at 600°C, the spinel ZnTiO3:Pb2+ nanofibers, with a diameter of 100-200nm, were successfully obtained. The scanning electron microscopy (SEM), fourier transform infrared (FT-IR), X-ray diffraction (XRD) and photoluminescence (PL) were employed in the study. The results displayed that the morphology and crystalline phase of the fibers were greatly affecteded by the calcination temperature. The PL spectra of the samples measured at different excitation wavelength reveal a novel luminescent phenomenon in blue and green region, which can be attributed to the Pb2+-related charge-transfer transitions in ZnTiO3 nanofibers.

Abstract: Avian feather is the outstanding protein fiber structure that still lacks an interpretation generally acceptable in any detail. In this paper, asio otus feathers were morphological represented and their barbs were mechanical characterized by a developed micro-tensile tester with a load resolution of 0.25 mN and a displacement resolution of 10 nm. With a tensile loading speed at 0.02 μm/s, Young’s modulus of the flight feather barbs with length of 1450-1900 μm was calculated to be 3.13-3.66 GPa, higher than 1.47-2.04 GPa for the down feather barbs with length of 520-710 μm. It is concluded that the asio otus’s flight feathers on its wing and tail are more rigid than the down feathers on its body.

Abstract: The integration of molecular imprinting technique and solid-phase extraction (SPE) implements an effective alternative for sample pre-concentration in the determination and analysis of veterinary drug/pesticide residues. Herein, we reports a preliminary study on the preparation of streptomycin imprinted polymers on the surface of silica micro-spheres (with an average size of 50μm) and nano-spheres (with an average size of 500nm) via sol gel method. A mixed solution of tetrahydrofuran, ethanol and water (volume ratio is 7:1:1) was choose as dispersion agent, 3-aminopropyltriethoxysilane and phenyltriethoxysilane as functional monomers, and tetraethyl orthosilicate as cross-linker, while ammonia solution served as catalyst in the polymerization process. Scanning electron microscopic characterization was employed, suggesting that activating time exerts important influences on the morphology of activated silica micro-spheres, and also resultant molecular imprinted polymers (MIPs). The absorption capacity and selectivity of the obtained two MIPs were also evaluated for streptomycin and its analogue compounds in water samples. The results illustrate that the streptomycin-imprinted silica micro-spheres (MMIP) exhibited both larger absorption capacity and higher selectivity than those of silica nano-spheres (NMIP). The variant analytical performance might result from inadequate polymerization on the surface of silica nano-spheres.

Abstract: Antiwetting BNNT films have been achieved by milling-ink method. Superhydrophobic (CA <5°) are demonstrated on films with stainless steel as substrate. The high density and purity are confirmed by EDX and NEXAFS. There are only a few oxygen point defects in the form of nitrogen vacancies due to ink and annealing process in air.

Abstract: Two kind of on-chip integrated fatigue bending test structures are designed through system-level simulation method based on macromodels to measure the fracture strength and fatigue mechanical properties of polysilicon thin films. The first on-chip fatigue test structure is actuated by V-beam thermal actuator, and the other test structure actuated by electrostatic comb. The static and dynamic analysis was performed by Coventorware Architect module using self-bulid reduced order model described with the MAST hardware language and some other commercial parts from Coventorware parts library. The structural dimension parameters are determined and optimized according to system-level simulation and the computing result has shown that the self-build macromodels and the on-chip integrated test system are efficient and reliable. Two kinds of polysilicon on-chip fatigue bending test structure were fabricated with two-layer polysilicon surface micromachining process in Institute of Microelectronics, Peking University.