Advanced Materials Research Vol. 528

Abstract: Atomic/molecular adsorption on a microcantilever surface can cause the cantilever to deflect as a result of the adsorption-induced surface stress. In this paper, based on atomic/molecular interactions, an energy-based model is proposed to calculate the chemisorption-induced surface stress. The connection between the chemisorption-induced surface stress and the covalent bond interactions is established. The results are consistent with relevant experimental observations. This study is helpful for characterizing and optimizing the mechanical response of cantilever-based sensors.

Abstract: Fatty acids have been used as additive for modifying chitosan-based system particularly in hydrophobic manner. Generally, techniques for preparing chitosan-fatty acid conjugate system are take time, involved with high temperature and high shear force and need some surfactants. In this study, alternative technique for simply blending chitosan with fatty acid was performed by taking advantage of ionization of metal stearate and chitosan in acidic condition. Metal stearate used in this study, aluminum monostearate (Alst), was dispersed in chitosan dissolved in lactate buffer solution pH 4.5 with various concentrations of chitosan. Physicochemical properties such as pH value, viscosity and rheology, morphology and particle size of the dispersions were characterized. The pH value and viscosity of the chitosan solutions was higher as the chitosan concentration was increased. For the dispersions, their pH value was not changed by mixing time but their viscosity was decreased by mixing time. All dispersions exhibited Newtonian flow behavior. Larger mean particle size of the dispersions was observed when the mixing time was longer. At higher chitosan concentration, mean particle size of the aggregated chitosan-stearate particles was smaller than the lower chiotsan concentration systems

Abstract: Microsystems, both in space and ground level, will use systems with III-V semiconductors and devices of nanoscale. Vulnerability of this system towards the radiations warrants extra care to be taken. Therefore, appropriate test and analysis to assure the hardness (radiation resistance) of components to be used in various radiation environments is necessary. In this paper, the defect generated in the interaction of alpha (α) particles and silicon (Si) semiconductor material is simulated using SRIM (Stopping and Range of Ions in Matter). The induced defects are in the form of vacancies, defect clusters and dislocations. Besides, the defect is found influencing the kinetic processes that occur both inside and outside the cascade volume. The radiation tolerance between the conventional scale and nanoscale thickness of silicon layer is also being compared. From the findings, it is observed that when the thickness of silicon layer is scaled down, defect that induced by the energy deposition of -particles is significantly lesser. This means that nanoscale silicon layer features improved radiation robustness towards the deposition of energetic ions.

Abstract: This paper focused on the differences of nano-structure between waxy wheat starch (WWS), normal wheat starch (NWS), waxy maize starch (WMS), and normal maize starch (NMS). Observed by Atomic Force Microscope (AFM), it found that the nano-structure of waxy starch was composed by nano-particles and nano-chains. The nano-particles, which should be the remained crystalline region after the collapse of granules, were wrapped by nano-chains, which should be the dissociated amylose/amylopectin chains in amorphous region. But the nano-structure of normal starch was a little difference, namely only nano-particles could be observed. These distinctions changed the viscosity of starch pasting. That is to way, the viscosity of waxy starch pasting was higher than those of normal starch. The reasons for this should come from the interaction between nano-structure. Specifically, the interaction between particles was weaker than it between particles and chains. Therefore, the viscosity of waxy starch was higher than it of normal starch

Abstract: Rhodamine 6G (R6G) and Poly(methyl methacrylate) (PMMA) light-guided films accompanied with titanium dioxide thin layer were prepared by spin-coating process onto on glass substrate. Dichloromethane was used as disperser for blending R6G and PMMA. The TiO2 layer thickness was varied by controlling spinning speed. The effects of TiO2 layer with different thickness on optical absorption and florescence performance of the films were investigated and the results exhibited strong absorption of TiO2 in UV region and the enhancement in florescence efficiency with increasing TiO2 film thickness.

Abstract: The paper describes the results obtained on the enhanced electrochromic performance of Tungsten oxide (WO3) thin films assisted by electrospun PVA nanofibers. WO3 was fabricated by spin coating technique with tungsten powder as starting precursor. The effect of electrospun-PVA nanofibers layer on structural, chemical composition, surface morphology and electrochromic properties of the films were characterized by X-ray diffractometer (XRD), X-ray photo-emission spectroscopy (XPS), scanning electron microscope (SEM) and UV-VIS spectrophotometer. The XRD analysis suggested that the crystalline of WO3 can be identified as a monoclinic WO3 structure. XPS investigations also confirmed the existence of characteristic peaks of W. The significant enhancement of electrochromic properties of the films is achieved by additive electrospun-PVA nanofiber layer.

Abstract: To obtain textured surface with low friction and high fluid load support capacity, in this work, based on the basic tenet of fluid film lubrication theory that converging gap is the first necessary condition to generate a hydrodynamic pressure in a confined fluid film, a fabrication method via through-mask electrochemical micromachining (EMM) for microstructure array on metal substrate with topographical gradient in a single micromachining step is investigated. After analyzing the factors that influence the current density distribution on the anode surface in EMM process, three potentially feasible schemes are presented and their fabrication results are predicted through numerical simulation. Combining the simulation results with practical application requirements, the scheme with machining gap gradient is adopted. With the selected fabrication scheme, the experiments are performed and the microstructure array with a feature size of 25μm and a height variance from 12μm to 24μm within 2mm distance has been produced successfully, which is in good agreement with the numerical calculation prediction.

Abstract: The short multi-walled carbon nanotube-TiO2 (SMWNT-TiO2) hybrid was synthesized via direct growth of TiO2 nanoparticles on the surface of the functionalized SMWNTs by the hydrothermal treatment and utilized as the photocatalyst in the sulfonamides degradation under UV light irradiation. The photodegradation efficiency of sulfonamides was examined by HPLC technique, which demonstrates that sulfonamides can be readily degraded under UV light irradiation. However, the four sulfonamides have different degradation rates, which is in the order of sulfadimidine > sulfanilamide > sulfamethoxazole > sulfathiazole. These experimental results can be attributed to the point charge of the atoms in the sulfonamide molecule and its adsorption on the surface of the SMWNT-TiO2 hybrid.

Abstract: Silane coupling agent KH550 was used to modify the surface of nano-alumina. Ultrasonic dispersion was employed to take the place of traditional mechanical stir. Absorbency of the aqueous solution of nano-Al2O3, which had been modified, was determined to confirm that under this process condition the optimum amount of KH550 was 2.5% while the optimum time was 50 minutes. The infrared spectra indicated that the surface of nano-Al2O3 had been modified and the absorption of KH550 really existed there.

Abstract: A set of ZSM-5/MCM-41 composite zeolite were synthesized hydrothermally with CTAB as a template and ZSM-5 zeolite as a silica source. XRD patterns of ZSM-5/MCM-41 zeolites contain the characteristic peaks both of ZSM-5 and MCM-41. TEM images show that ZSM-5 zeolite surface was covered with a MCM-41 thin layer varying the thickness with the crystallization time. The BET specific surface area of the composite zeolite increased with increasing the NaOH concentration up to a maximum at 1.5 M, followed by decreased as the NaOH concentration was increased. Catalytic tests were carried out in a tubular reactor coated with the zeolite on its inner wall at 550°C and 4 MPa. The ZSM-5/MCM-41 zeolite with a core-shell structure exhibited a higher conversion of supercritical n-dodecane cracking compared to ZSM-5.