Home About us Contact
|
Home About us Contact | ||
|
|
||
Electron-beam Irradiation (electron-beam + irradiation)
Selected AbstractsTuning and Enhancing Photoluminescence of Light-Emitting Polymer Nanotubes through Electron-Beam IrradiationADVANCED FUNCTIONAL MATERIALS, Issue 4 2009Young Ki Hong A new method for the tuning and enhancing photoluminescence (PL) characteristics of light emitting poly (3-methylthiopnehe) (P3MT) nanotubes through E-beam irradiation under atmospheric environments is reported. An E-beam generated from a linear electron accelerator (1 MeV, 1.6,×,1013,8.0,×,1016 electrons cm,2) is irradiated onto P3MT nanotubes including an Al2O3 template. From laser confocal microscope (LCM) PL experiments, significant enhancements in the PL intensity,up to about 90 times of an isolated single strand of the E-beam irradiated P3MT nanotubes,are observed. The luminescent color of the P3MT nanotubes changes from green to red color depending on the variation of E-beam dosage. These results might originate from the de-doping effect and the conformational modification through E-beam irradiations. Conformational changes of the E-beam irradiated P3MT nanotubes are confirmed by LCM single Raman and ultraviolet-visible (UV/Vis) absorption spectra. From UV/Vis absorption spectra, it is observed that the ,,,* transition peak and the doping induced bipolaron peaks of the P3MT nanotubes dramatically vary with E-beam irradiating conditions. [source] Synthesis of Core,Shell Inorganic NanotubesADVANCED FUNCTIONAL MATERIALS, Issue 15 2010Ronen Kreizman Abstract New materials and techniques pertaining to the synthesis of inorganic nanotubes have been ever increasing since the initiation of the field in 1992. Recently, WS2 nanotubes, which are produced now in large amounts, were filled with molten lead iodide salt by a capillary wetting process, resulting in PbI2@WS2 core,shell nanotubes. This work features progress in the synthesis of new core,shell nanotubes, including BiI3@WS2 nanotubes produced in a similar same manner. In addition, two new techniques for obtaining core,shell nanotubes are presented. The first is via electron-beam irradiation, i.e., in situ synthesis within a transmission electron microscope. This synthesis results in SbI3 nanotubes, observed either in a hollow core of WS2 ones (SbI3@WS2 nanotubes), or atop of them (WS2@SbI3 nanotubes). The second technique involves a gaseous phase reaction, where the layered product employs WS2 nanotubes as nucleation sites. In this case, the MoS2 layers most often cover the WS2 nanotube, resulting in WS2@MoS2 core,shell nanotubes. Notably, superstructures of the form MoS2@WS2@MoS2 are occasionally obtained. Using a semi-empirical model, it is shown that the PbI2 nanotubes become stable within the core of MoS2 nanotubes only above a critical core diameter of the host (>12,nm); below this diameter the PbI2 crystallizes as nanowires. These model calculations are in agreement with the current experimental observations, providing further support to the growth mechanism of such core,shell nanotubes. [source] Multiscale approach to investigate the radiochemical degradation of epoxy resins under high-energy electron-beam irradiationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 2 2006N. Longiéras Abstract A multiscale investigation of the degradation mechanism of two epoxy systems exposed to electron-beam irradiation under a helium atmosphere was carried out with a variety of analytical methods, including high-resolution solution- and solid-state NMR spectroscopy, NMR relaxometry, infrared spectroscopy, sterical exclusion chromatography, and differential scanning calorimetry. As a first step, we studied a linear phenoxy polymer, poly(2-hydroxyether of bisphenol A), which provided a basis for the investigation of the degradation of a more complex, insoluble epoxy,amine network, diglycidyl ether of bisphenol A/triethylene tetramine. Among different structural modifications, the main degradation process was shown to produce in both cases a chain scission. For the phenoxy resin, the hydroxypropylidene moiety was identified as the fragile site leading to the formation of two phenolic chain ends and acetone and isopropyl alcohol as low-molecular-weight products. All methods, ranging from molecular to supramolecular scales, were shown to correlate both qualitatively and quantitatively. Experimental results obtained with diglycidyl ether of bisphenol A/triethylene tetramine evidenced a different degradation scheme occurring at the ethylene amine part and producing a dangling vinyl amine as the major degradation product. A selective increase in the molecular mobility at this site was confirmed by a two-dimensional, local-field wide-line separation experiment. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 865,887, 2006 [source] Thermo-Responsive Nanogels Based on Poly[NIPAAm -graft- (2-alkyl-2-oxazoline)]s Crosslinked in the Micellar StateMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 9 2010Stefan Zschoche Abstract Graft copolymers with thermo-sensitive PNIPAAm backbone and hydrophilic PEtOxa graft chains demonstrated typical amphiphilic behavior. For specific compositions stable micelle-like aggregates were formed depending on the temperature. Applying long polyoxazoline side chains (,>,120), stable reversible micelle-like aggregates with hydrodynamic radii of 30,40,nm could be obtained between 33 and 55,°C. These graft copolymers have been successfully crosslinked by electron-beam irradiation in the micellar state yielding core/shell type nanogels with thermo-reversible swelling behavior. The temperature dependent volume change of the new thermo-responsive nanogels due to the phase transition of the PNIPAAm core has been verified by DLS. [source] host-defect luminescence of stishovitePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2005A. Trukhin Abstract a detailed study of the 4.75 eV luminescence band of stishovite single crystal (SiO2 with rutile structure) is reported. Kinetics of luminescence intensity is studied at durable (tens of minutes) X-ray excitation. The observed behaviour of the band intensity is explained by creation and destruction of luminescence centres depending on temperature both being determined by radiation stimulated diffusion of atomic particles. The luminescence decay is observed to last for minutes after X-ray irradiation while only for ns and hundreds of µs under pulsed e-beam irradiation suggesting a complicated recombination of the created defects. The UV band of stishovite is compared with the 4.9 eV luminescence band in ,-quartz, which could not be created by X-ray. the latter being associated with transient centres created by destructive electron-beam irradiation or with permanent centres at neutron or ,-irradiation, and with oxygen-deficient luminescence of silica glass. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Effect of electron-beam irradiation on poly(vinyl chloride)/epoxidized natural rubber blend: dynamic mechanical analysisPOLYMER INTERNATIONAL, Issue 5 2001Chantara Thevy Ratnam Abstract The irradiation-induced crosslinking in 50/50 poly(vinyl chloride)/epoxidized natural rubber (PVC/ENR) blend was investigated by means of dynamic mechanical analysis. The influence of trimethylolpropane triacrylate on the irradiation-induced crosslinking of PVC/ENR blends was also studied. The enhancement in storage modulus and Tg with irradiation dose indicated the formation of irradiation-induced crosslinks. This is further supported by the decrease in tan ,max and loss modulus peak. The compatibility of the blend was found to be improved upon irradiation. The Fox model was used to provide a further insight into the irradiation-induced compatibility in the blend. Scanning electron microscopy studies on the cryofracture surface morphology of the blends as well as the homopolymer have been undertaken in order to gain more evidence on the irradiation-induced crosslinking. © 2001 Society of Chemical Industry [source] | ||||||||||