Materials Science Forum Vols. 663-665

Abstract: Laminated thin films composed of V2O5 and Pd (or Pt-Pd) layers were deposited on glass substrates and the end faces of multimode optical fibers, and the sensitive behaviors of the thin films to hydrogen gas were studied using a UV-visible spectrophotometer and an optical fiber sensor’s experimental setup. Both the thickness of the V2O5 layer and that of the Pd layer have obvious influences on the sensitivity performance of the Pd/V2O5 films. The Pd (30 nm)/V2O5 (280 nm) film deposited on a glass substrate is sensitive to 0.1% hydrogen and the highest change in relative transmittance is about 25% when exposed to 4% hydrogen. Pd/V2O5 films were coated onto the end faces of multimode fibers to form optical fiber sensors. The response time of the Pd (20 nm)/V2O5 (280 nm) sensor is about 50 s and the change in relative reflected light intensity is about 18% upon exposure to 4% hydrogen. Deposition of Pt-Pd double layer instead of Pd signal layer over V2O5 can reduce the response time of the sensor. The response time of the Pd (20 nm)/V2O5 (280 nm) sensor is about 50 s, while that of the Pt (10 nm)-Pd (10 nm)/V2O5 (280 nm) sensor is about 25 s.

Abstract: On the basis of analysis of linear contour errors model, a new strategy of independent contour error control was presented for high precision contour machining. The proposed control scheme, in which the equations of the well-known cross-coupling controller were implemented, is shown to be able to diminish the linear contour error without using any cross-feeding signals between the driving axes. The simulation results show that the proposed control scheme is effective and that better effect of the contour tracking can be obtained. As a result, the contour machining precision is improved greatly.

Abstract: A simple and novel preparation method for Cu nanoparticles has been suggested in this work. Its main innovative thought lies in preparing nano-copper in liquid paraffin without addition of other reductant. The paraffin is cheap and nontoxic, and the copper nanoparticles prepared by this method are not oxidized when exposed to air at room temperature. The obtained nano-copper has been characterized by X-ray diffraction measurements (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), and energy dispersive analysis of X-ray (EDX), X-ray photoelectron spectra (XPS), and Fourier transform infrared spectroscopy (FTIR). The TEM results confirm that the optimal average size of nanoparticles is about 20 nm. The effects of time, temperature and surfactant on the size of nano-copper have been investigated. The results show that the optimized conditions are reaction temperature of 250 oC and reaction time of 3 h. By this method, the raw materials are cheap and the process is simple, so it can be applicable to large-scale production of copper nanoparticles.

Abstract: Ag2S thin films were fabricated on the ITO-coated glass substrates by cathodically electro-deposition from the mixture solution including 0.01mol·L-1 AgNO3 and 0.05 mol·L-1 Na2S2O3 with pH=2.5 at room temperature. The microstructure and surface morphology of the films were investigated with the deposition potential (E) varied from -0.23V to -0.28V. The X-ray diffractograms show that the deposited films are monoclinic Ag2S with the relative deviation of cell parameters within 1.5%. The estimated cell parameters of the Ag2S films deposited at E = -0.25V are closest to those of the standard sample. The SEM pictures show that films are uniform with better compactness at more negative deposition potential, but there are some aggregation when the potential up to -0.28V. According to the AFM images, the root mean square (RMS) roughness and grain size decrease with the decreasing of potential absolute value, but they will increase when the deposition potential is too small. The best potential is -0.25V for depositing Ag2S thin films.

Abstract: Multi-branched FeO(OH) nanorods are successfully prepared using a facile one-pot solution-phase synthesis method. Their morphology and structure were characterized using field emission scanning electron microscopy (FE-SEM), X-ray powder diffraction (XRD), and Fourier transform infrared (FTIR) absorption spectrum. The results show amount of surfactant (PEO)20(PPO)70(PEO)20 (P123) and precipitant hexamethylenetetramine (HMTA) have significant effect on the shape of the particles. When 20-25 g of the P123 alcohol solution (20 wt%) is added the reaction solution containing 5.0 mL HMTA (2 mol/L) or when 18 g of the P123 alcohol solution (20 wt%) is added the reaction solution containing 10.0 mL HMTA (2 mol/L), the multi-branched FeO(OH) nanorods can be obtained. While when 19-22 g of the P123 alcohol solution (20 wt%) is added the reaction solution containing 10.0 mL HMTA (2 mol/L), the products became the Fe3O4 nanosheets with irregular shape. A possible growth mechanism of the multi-branched FeO(OH) nanorods is suggested.

Abstract: The Shoushan Stone is one of the famous craft carving stones in China and transparency is one of the key indicators to evaluate the value of Shoushan Stone. The better the transparency is, the higher the value is. In this study, the mineral compositions and morphologies were investigated by XRD and SEM, respectively. Combining with the characterization of Shoushan Stone samples, the relationships between mineral composition, morphology and transparency were studied. The results show that the transparency of Shoushan Stone is determined by the mineral categories and microstructures. The sample with high transparency is fewer mineral composition numbers, similar mineral compositions and bigger crystal particles

Abstract: A novel material synthesis technique, microwave process was investigated for the production of phosphor powders. In this study, we have developed a new method to product phosphor powders, and applied this process into two materials fabrication. EuDL3 where L is cinnamic acid (C6H5CH = CHCOOH, HL), D = 2, 9-dimethyl-1, 10-phenantroline (dmp), or 2, 2'-bipyridine (bipy) phosphor powders were successfully synthesized by microwave process. The process takes only 24 min to obtain two phosphor powders. The process takes only 24 min to obtain two phosphor powders. The resultant phosphor powders were investigated by TG-DTA, IR, luminescence spectroscopy, and scanning electron microscope (SEM). The results revealed that the two materials is significant different, compared to micrographs of scanning electron microscope (SEM).

Abstract: A new kind of passive underwater acoustic sensor based on fiber Bragg grating is reported. The pressure sensitivity of the sensor is enhanced three orders of magnitude being packaged with polymer material, which is a foundation for underwater acoustic detection. An intensity modulation scheme is adopted to realize high-accuracy detection due to the extra-narrow line-width laser. The experimental results show that the sensor’s noise-limited pressure detection resolution is about 61dB (0dB＝1μPa/ Hz ) at 500 Hz, which satisfies the application of underwater target detection.

Abstract: Numerical calculation method is adopted to analyze to the influence of the polymer material on the sensitivity of coated FBG. The calculation results show that, the polymer material with high Young's modulus and high thermal expansion coefficient helps to improve the temperature sensitivity of the coated FBG; and the material with low Young's modulus and low Poisson's ratio helps to improve the pressure sensitivity. The polymer-coated FBG experiment is explored, in which the pressure and temperature sensitivities are enhanced 12-fold and 7-fold respectively.

Abstract: Grand Canonical Monte Carlo (GCMC) method was employed to simulate the adsorption properties of molecular hydrogen on crossing the critical temperature in all-silica ZSM-5 zeolite in this paper. The results indicated that the adsorbed amounts of hydrogen increased with decreasing temperatures and increasing pressures. The highest hydrogen uptake value is 2.24 wt% at 25 K and 10000 kPa. By comparing the variation of the hydrogen adsorption isotherms on crossing the critical temperature, it is shown that the micropore filling and capillary condensation were the main adsorption mechanism under the critical temperature of hydrogen, and the micropore filling was the adsorption mechanism above the critical temperature. The results and data of hydrogen adsorption properties obtained from the simulations are theoretically significant for understanding of the mechanism of hydrogen storage on microporous zeolites.