Search results for "IRRADIATION"
showing 10 items of 1012 documents
Water diffusion and swelling stresses in ionizing radiation cured epoxy matrices
2017
Abstract In this work a DGEBF epoxy monomer was cured by electron beam radiation in the presence of an iodonium salt and the obtained system was hydrothermally aged as such and also after a thermal treatment, in order to obtain two systems having different uniformity in the cross-linking degree. On both systems, the transient stress field arising from swelling was measured and monitored by an optical Photoelastic technique and the results were commented with reference to a thermally cured epoxy system containing the same monomer and already discussed in a previous work. Beam samples with identical dimensions, obtained from the irradiated systems, have been aged at 80 °C in water, and charac…
Enhancement of pulsed laser removal of metal oxides by electrochemical control
1996
Pulsed laser irradiation of oxidized metallic surfaces in an electrolytic cell under proper voltage conditions is demonstrated to be a promising new approach for effective removal of oxide films. Systematic measurements on simulated corrosion-product films by optical reflectance profile and energy dispersive X-ray spectroscopy are used to study the physical mechanisms of this novel phenomenon, the physical conditions for its observation and its possible generality. It was observed that the utilization of a basic electrolyte solution and the imposition of a certain cathodic potential prior to laser irradiation is an essential requirement for a high removal efficiency. This new technique has …
Structure of amorphous SiO 2 nanoparticles probed through the E′ γ centers
2011
We report an experimental investigation by electron paramagnetic resonance (EPR) spectroscopy on the properties of the E′ γ centers induced by β-ray irradiation in nanoparticles of amorphous SiO 2 (fumed silica) with mean diameters from 7 up to 40 nm. We found that the E′ γ centers are induced in all the fumed silica types in the dose range 4-400 kGy. They are characterized by an EPR line shape similar to that observed in common bulk silica materials independently on the particle diameter. Moreover, the E′ γ center concentration decreases on decreasing of the particle size for each given dose. Our findings are interpreted in terms of a shell-like model of nanoparticles in which it is assume…
The effect of the composition on the properties of?-irradiated ethylenevinyl alcohol copolymers
1983
Two ethylene-vinyl alcohol copolymers (Eval E and Eval F with about 45% and 25% of ethylene respectively) have been irradiated in air in the dose range 0–200 Mrad. The irradiated samples show both crosslinking and degradation; the former effect is more relevant in the copolymer with a larger content of polyethylene. Calorimetric results show that both the crystalline and the amorphous phases are involved in the reactions initiated by the irradiation.
Femtosecond laser pulse shaping for enhanced ionization
2009
El pdf del artículo es la versión post-print: arXiv:0906.1938v1
Microfluidic synthesis of micrometer-sized photoresponsive actuators based on liquid crystalline elastomers
2016
The fabrication of photoresponsive micrometer-sized liquid crystalline elastomer (LCE) particles has been described in this article for the first time. The preparation of the LCE particles using a microfluidic device by a continuous “on the fly” technique allows their fast processing with an irradiation time of less than 2 seconds. In order to accelerate the polymerization and to make the preparation of samples with thicknesses of several hundred microns possible, we modified a NIR-photoinitiation system by adding a bleaching agent. In addition to the photoinitiator, a side-chain liquid crystalline monomer containing an azo-group and a LC-crosslinker were used in the polymerization mixture.…
Third-harmonic generation in the skin layer of a hot dense plasma
2003
The third-harmonic generation of a pump wave, resulting from the electron-ion collision frequency dependence on the electric field in the skin layer of a hot dense plasma is investigated. The relation of the current third harmonic with the high-frequency field in the skin layer is established for arbitrary ratios of the electron-ion collision frequency to the field frequency. For arbitrary ratios of these two frequencies, the field structure inside the skin layer is determined, and the field of the wave irradiated by the plasma at tripled frequency, too, is calculated. It has permitted us to find the explicit dependencies of the third-harmonic generation efficiency on the plasma and pump fi…
Vortex dynamics in Bi2Sr2CaCu2O8-thin films in the presence of columnar defects
1996
With heavy ion irradiation we create continous amorphous columnar defects in Bi2Sr2CaCu2O8-thin films. With regard to a reliable comparison of irradiation effects three of four identical striplines on the same samples were exposed to different irradiation procedures. We performed irradiations as well parallel as under different angles with respect to the film $$\vec c$$ -axis. Beside an enlarged normal state resistivity after irradiation the films suffer a Tc-reduction proportional to the volume of the damaged material. The activation energy ascertained from resistive transitions shows best enhancement for magnetic field values close to the matching field. Measurements of the transport crit…
Response charactterization of ammonium tartrate solid state pellets for ESR dosimetry with radiotherapeutic photon and electron beams.
2001
Solid state pellets (1 mm thick) for electron spin resonance (ESR) dosimetry were made using ammonium tartrate as the radiation-sensitive substance. Their behaviour was experimentally investigated as a function of dose with 60Co gamma rays. The calibration function obtained permits measurements of absorbed dose in the 2-50 Gy range, with a combined uncertainty of +/-4%. The lowest detectable dose was about 0.5 Gy. These properties are comparable with or even better than those of ESR dosimeters made from other materials. The time stability of the ESR signal of ammonium tartrate dosimeters at different storage conditions after irradiation was studied. A rather complex behaviour was observed, …
Thermally stimulated luminescence of undoped and Ce3+-doped Gd2SiO5 and (Lu,Gd)2SiO5 single crystals
2015
Abstract Thermally stimulated luminescence (TSL) characteristics (TSL glow curves and TSL spectra) are investigated in the 4–520 K temperature range for the single crystals of gadolinium and lutetium–gadolinium oxyorthosilicates X-ray irradiated at 4 K, 8 K, or 80 K. The nominally undoped Gd2SiO5 and (Lu,Gd)2SiO5 crystals, containing traces of Ce3+, Tb3+, and Eu3+ ions, and Ce3+-doped Gd2SiO5 and (Lu,Gd)2SiO5 crystals are studied. For the first time, the TSL glow curves of these materials are measured separately for the electron (intrinsic, Ce3+- or Tb3+-related) and hole (Eu3+-related) recombination luminescence, and the TSL glow curve peaks, arising from thermal decay of various electron …