Science and Technology of Nanomaterials

Volume 23

doi: 10.4028/

Paper Title Page

Authors: Zheng Peng, Ling Xue Kong
Abstract: A novel micro-spray-assembly process and an automatic device to fabricate multilayer ultra-thin film are introduced. Employing self-assembly monolayer (SAM) technique, ultra-thin film can be assembled by utilizing the micro-spray-assembly device. The thickness and roughness of each monolayer can be controlled by varying various materials attributes, i.e., deposition time, ionic strength, pH value, molecular concentration and by selecting different manufacturing parameters of the automatic device such as spraying rate, size of micro-drop, N2 flow rate, temperature of N2 flow.
Authors: N. Gupta, H. Mallik, A. Sarkar
Abstract: A nanocomplex of Chromium oxide nanoparticles with biopolymer matrix of gum Arabica is synthesized by natural self-assembly in chemical sol-gel route. Gum Arabica is chosen as base matrix due to its inherent biodegradable property. Experimental specimen of the said complex is prepared to satisfy near quantum size effect criterion. Due to near quantum size effect and spatial localization of nanoclusters, the developed specimen becomes an ideal 2D quantum well system. The longitudinal electrical conduction of the developed system is studied experimentally. Some of its structural aspects are also investigated to make the study conclusive. The dispersed cluster size is estimated by Transmission Electron Microscope (TEM) and X-ray diffraction (XRD). The results of I-V characteristics at temperatures 253 K show the distinctive features of localized energy levels. The spacing between energy levels near ground state to be comparable to the thermal energy at temperature 253 K for a cluster dimension below 10 nm. In this present study the developed specimens with the mentioned nanoclusters estimated from TEM and XRD as below 10 nm. The overall results are found to be encouraging.
Authors: Rengaswamy Jayaganthan, Rohitkumar H. Vora
Abstract: The glass transition temperature (Tg) of Fluoro-Poly(ether-imide) and Fluoro-Poly(either-Imide)/MMY clay Nanocomposites has been investigated by both experiments and Monte Carlo Simulation. It was observed that the (Tg) values of the nanocomposites increases with increase in clay contents.
Authors: Challa S.S.R. Kumar, Mher Aghasyan, Hartwig Modrow, Josef Hormes, Rolland Tittsworth
Abstract: Cetyl trimethyl ammonium bromide (CTAB) stabilized gold(III) salt in chloroform was reduced using NaBH4 in the presence of commercially available methanethiol-polyphoResinTM to obtain polystyrene micro beads with gold nanoparticles on their surface. X-ray Absorption Near Edge Spectra (XANES) of Au and S revealed S-Au bonding state. TEM studies coupled with Selected Area Electron Diffraction(SAED) patterns revealed the morphology of the Au nanoparticles on the surface of the micro beads.
Authors: R. Sarathi, S. Deepa, A. Mishra, Rohitkumar H. Vora
Abstract: In the present work, the fluoro polyimide films were aged in the transformer oil and the characteristic changes in the film and the transformer oil are analyzed through physico-chemical diagnostic studies. The WAXD and FTIR studies showed that no characteristic change in the material due to thermal aging of the material. The FTIR spectra of the corona aged specimen indicate the formation of new functional groups. The fluorescence spectra of the aged transformer oil suggest dissolvement of heavy ions in the clay material.
Authors: P. Zhang, W.M. Tan, B.K. Tay
Abstract: Amorphous silicon-carbon films have been successfully deposited by the filtered cathodic vacuum arc techniques. One set of films was deposited from varying silicon-carbon composition in the targets and another set of films was deposited at different various substrate bias voltages from 5 at.% silicon target. The properties of the film were investigated by using atomic force microscopy (AFM), Raman spectroscopy, x-ray photoelectron spectroscopy (XPS) and contact angle measurement. The first set of the samples exhibit atomic smooth surface morphology with RMS roughness below 0.26 nm. The silicon composition in the films determined by XPS varies from 0 to 61 at.%. The Raman results show that at low silicon composition, the G peak position of C-C bond shifts to a low wavenumber, that demonstrates the silicon atom predominantly substitutes for the carbon atom. As the silicon composition increase, the G peak disappeared and a strong broad peak corresponding to the amorphous silicon carbide cluster appears around 800 cm-1. For the second set, the Raman results show the ID/IG ratio increased from 0.24 to 0.67 with using the high bias voltages during the deposition. That indicates the disorder of C-C bond within the films increased. While, both the silicon concentration in the films and contact angles remain relatively constant with the change of bias voltage.
Authors: H. Srikanth, P. Poddar
Abstract: Nanocomposites hold tremendous potential as ‘designer’ materials with multifunctional, tunable physical properties. We have synthesized and studied two classes of nanocomposite systems –(a) Magnetorhelogical (MR) fluids with uniformly dispersed Fe nanoparticles and (b) Polypyrrole doped with soft ferrite nanoparticles. Static and dynamic magnetic measurements show a variety of phenomena ranging from superparamagnetism to collective spin-flip transitions. A resonant RF method has been used to map the switching and anisotropy fields. Our studies indicate that the rich cooperative magnetism in these systems is governed not only by the particle size distribution but also by the matrix-mediated interactions.
Authors: S. Swaddiwudhipong, K.K. Tho, Z.S. Liu, K.Y. Zeng
Authors: M.H. Nai, Chwee Teck Lim, K.Y. Zeng, Vincent B.C. Tan
Abstract: Nanoindentation is a useful technique to measure hardness as well as elastic and timedependent plastic properties of materials with nanometer resolution. The measurement of elastic modulus of polymeric materials remains challenging due to their viscoelastic behavior. Clay reinforced nylon6 nanocomposites are found to have great improvement in the elastic modulus and tensile strength due to exfoliated hybrid structure. However, its mechanical properties have not been well investigated. In the present study, hardness and elastic modulus of nylon6-5wt%clay nanocomposites were investigated using nanoindentation. Creep effects of the nanocomposites on the unloading stiffness, which directly relates to the elastic modulus, were studied under various unloading rates and holding periods. It was found that the elastic modulus and hardness of nylon6-5wt%clay nanocomposites increased by 58% and 80%, respectively, as compared to pure nylon6. Experimental results for both polycarbonate and nylon6-5wt%clay nanocomposites showed that loading rate had no significant effects on the unloading stiffness. However, stiffness decreased to more consistent values after longer holding periods (more than 30 sec) and at faster unloading rates. The results indicated that creep behavior of the polymers affects the measurement of the unloading stiffness and may possibly overestimate the elastic modulus. Errors in the stiffness measurements from nanoindentation could be minimized with appropriate loading, unloading and holding conditions.
Authors: A.H. Yuwono, J.M. Xue, J. Wang, H.I. Elim, Wei Ji, Yuan Yuan Li, T.J. White
Abstract: Nanohybrid thin films consisting of nanocrystalline TiO2 particles in poly(methyl methacrylate)(PMMA) were successfully synthesized by in-situ sol-gel and polymerization assisted by spin coating. Using titanium isoproproxide (Ti-iP), methyl methacrylate (MMA) and 3-(trimethoxysily)propyl methacrylate (MSMA) as the starting materials, nanohybrids containing up to 60% Ti-iP in PMMA were realized. The resulting nanohybrid thin films coated on quartz substrates are optically transparent and demonstrate nonlinear optical behaviour, where their nonlinear absorption increases with the loading of Ti-iP in PMMA, as confirmed by Z-scan measurements. Using pump-probe technique, these thin films are shown to exhibit an ultrafast relaxation time of ~1.5 picosecond.

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