Optical Absorption Photospectrometry Research Articles

Radiation effects on ETFE polymer exposed to glow discharge

The polymer ethylenetetrafluoroethylene (ETFE) is composed of alternating ethylene and tetrafluoroethylene segments. Because it has applications in areas such as medical physics and industrial coatings, there is a great interest in surface modification studies of ETFE polymer. When this material is exposed to ionizing radiation it suffers damage that depends on the type, energy and intensity of the irradiation. In order to determine the radiation damage mechanism from exposure to low voltage plasma, ETFE films were exposed to residual gas plasma in glow discharge regime to a fluence of 2×1017ions/cm2. Irradiated films were analyzed with optical absorption photospectrometry, Fourier transform infrared (FTIR) and Raman spectroscopy to determine the chemical nature of the structural changes caused by low energy glow discharge.

Plasma ion induced Au nanocluster formation on silica

Inclusion of metal ions in photorefractive materials followed by thermal annealing leads to an increase in optical absorption. The glow discharge as well as thermal annealing have been used to change the optical properties of suprasil. We used the effects of the low-energy ions to induce the nucleation of nanocrystals on and near the surface of a silica nano-layer containing low concentrations of Au, produced by using the co-deposition of Au and silica thin film on a suprasil substrate. Au-nanoclusters were formed both by thermal annealing and glow discharge, then observed and studied by Rutherford backscattering spectrometry (RBS) and by optical absorption photospectrometry.

Damage effects of gamma and X-rays in polymer film electrets

Dosimeters produced with electret materials are able to detect X-rays, α, β, γ rays, electrons and other charged particles and, with appropriate converters, fast and slow neutrons. To produce and use an electret dosimeter, the polymer must be charged using a system that is able to inject an initial charge into the electret material. After charging, it can be exposed to ionizing radiation and the remaining electret charge density can be read with the help of an appropriate device, for radiation dosimetry estimation. In this work we have charged and exposed PFA (tetrafluoroethylene-per-fluoromethoxyethylene) and FEP (tetrafluoroethylene-hexa-fluoropropylene) polymeric films to various radiation absorbed doses using 60Co gamma rays (1.25 MeV) and X-rays (0.106 MeV). In order to identify damage that can compromise the use of these materials as dosimeters, the virgin, charged and exposed films were analysed with Optical Absorption Photospectrometry (OAP), Fourier Transform Infrared (FTIR) and Micro-Raman spectroscopy. The analysis results are shown to demonstrate the damage caused by these radiation sources in the polymers.

Effects of low and high energy ion bombardment on ETFE polymer

The polymer ethylenetetrafluoroethylene (ETFE) is used as anti-adherent coatings for food packages and radiation dosimeters. In this work, we compare the damage induced in ETFE bombarded with 100keV Si ions with that induced by 1MeV proton bombardment. The damage depends on the type, energy and intensity of the irradiation. Irradiated films were analyzed with optical absorption photospectrometry, Raman spectroscopy and Fourier transform infrared (FTIR) spectroscopy to determine the chemical nature of the structural changes caused by ion irradiation. Computer simulations were performed to evaluate the radiation damage.

Damage Effects of Ionizing Radiation in Polymer Film Electrets

ABSTRACTElectret sensors or dosimeters can be used to quantify the ionizing radiation dose from charged particles or waves beams (α, β, -e, p etc… γ, X), and with appropriate converters, from fast and slow neutrons. The electret state is reached, by some insulating materials (electrical conductivity lower than 10−8 (Ω m)−1), when once charged, the incorporated charge is quasi-permanent ≈ 109 s. The charge densities are read (before and after the irradiations) and the radiation dose inferred from the difference between them. PFA (Tetrafluoroethylene-per-fluoromethoxyethylene) and FEP (Tetrafluoroethylene-hexa-fluoropropylene) damage mechanisms were studied bombarding these fluoropolymers with: 1 MeV protons at constant current and fluences from 1×1011 tower 1×1016 ions/cm2, 60Co gamma and X-rays, respectively of 1.25 and 0.106 MeV for absorbed doses of 0.5, 1.0, 8,0 and 100 Gy. The emission of chemical species was monitored with a Residual Gas Analyzer (RGA), during proton bombardment and techniques of Optical Absorption Photospectrometry (OAP), Fourier Transform Infrared (FTIR) and Micro-Raman spectroscopy were used to analyze the virgin, exposed and irradiated films.

Study of the surface activation of ETFE by low energy (keV) Si and N bombardment

The ethylenetetrafluoroethylene (ETFE) is a polymer formed by alternating ethylene and tetrafluoroethylene segments. It can be applied in the field of medical physics as intra venous catheters and as radiation dosimeters. The increasing application of polymeric materials in technological and scientific fields has motivated the use of surface treatments to modify the physical and chemical properties of polymer surfaces. When a material is exposed to ionizing radiation, it suffers damage leading to surface activation depending on the type, energy and intensity of the applied radiation. In order to determine the radiation damage and the surface activation mechanism ETFE films were bombarded with keV Si and N at various fluences. The bombarded film was also analyzed with optical absorption photospectrometry (OAP), Raman and Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy showing quantitatively the chemical nature at the damage caused by the Si and N bombardment.

ETFE polymer bombarded with 1 MeV proton

The ethylenetetrafluoroethylene (ETFE) is a polymer formed by alternating ethylene and tetrafluoroethylene segments. It has high impact resistance and useful mechanical properties. ETFE can be used as components of pumps, valves, tie wraps, and electrical components. It can also be applied in the field of medical physics as intra venous catheters and as radiation dosimeter. When a material is exposed to the ionizing radiation, it suffers damage that depends on the type, energy and intensity of the radiation. In order to determine the radiation damage mechanism, ETFE films were bombarded with 1MeV protons to the fluence between 1×1011 and 1×1016protons/cm2 and the chemical species emitted during the bombardment were measured with residual gas analysis (RGA) and show that HF gas is the entity preferentially emitted. Optical absorption photospectrometry (OAP) and attenuated total reflectometry fourier transform infrared (ATR-FTIR) shows quantitative chemical evidence of the damage. Our results show that damage is detectable at low proton fluence, but damage that can compromise the application in dosimetry occurs only for fluence greater than 1014protons/cm2.

Low energy ion beam induced changes in ETFE polymer

Low energy ion beam bombardment of ethylenetetrafluoroethylene (ETFE) modifies the physical and chemical properties of the polymer surface in ways that enhance or compromise applications in the technological and medical physics fields. When a material is exposed to ionizing radiation, its changes depends on the type, energy and intensity of the applied radiation. In order to determine the nature of the induced radiation changes, ETFE films were bombarded with fluences from 1012 up to 1015ions/cm2 of keV N and protons. The emission of gaseous species during the bombardments was monitored with a residual gas analyser (RGA). The bombarded films were analysed with optical absorption photospectrometry (OAP), Fourier transform infrared (FTIR) and micro-Raman spectrometries that determine the chemical nature of the structural changes caused by ions bombardment.

Effects of MeV proton bombardment in thin film PFA and FEP polymers

The polymers tetrafluoroethylene-per-fluoromethoxyethylene (PFA) and tetrafluoroethylene-hexa-fluoropropylene (FEP) are widely used in aerospace engineering applications. In medical physics, they are used as substitutes for some human body tissues replacement and as radiation dosimeters. In the aerospace as in space field, they are used because they resist damage from the high of ionizing radiation met in space. When a polymer is exposed to ionizing radiation, it can suffer damage according to the type, energy and intensity of the radiation. In order to determine the damage mechanism of these polymers, they were bombarded with 1 MeV protons at constant current and fluence from 1×10 11 to 1×10 16 ions/cm 2. The emission of chemical species was monitored with a residual gas analyzer (RGA) during bombardment. Results from FEP and PFA show that the CF 3 is the specie preferentially emitted. The bombarded films were also analyzed with optical absorption photospectrometry (OAP), micro-Raman and Fourier transform infrared (FTIR) showing quantitatively the chemical specific evidence from the damage caused by the proton bombardment for each polymer. Our results show that damage to polymer surfaces is detectable at low fluence but damage that compromises applications in dosimetry occur only for fluence greater than 10 15 protons/cm 2.

Fluoropolymer studies for radiation dosymetry

The polymers Tetrafluoroethylene- hexa- fluoropropylene (FEP) and Tetrafluoroethylene- per- fluoromethoxyethelene (PFA) are normally used as anti-adherent coatings and can also be applied for several applications in research. For example, they can be used as radiation dosimeters for X-ray and gamma photons, electrons, protons and other ionazing particles. In order to determine radiation induced damage, that can compromise applications in dosimetry, FEP and PFA films were bombarded with protons of 1 MeV at fluences from 1 × 1011 protons/cm2 to 1 × 1016 protons/cm2. During the bombardment, the chemical species emission was monitored with a Residual Gas Analyzer (RGA), and results show that the CF3 radical is the specie preferentially emitted. The bombarded films were also analyzed with Optical Absorption Photospectrometry (OAP) which shows quantitative chemically specific evidence of the damage caused by the proton bombardment. Our results show that damage to polymers is detectable for all fluences used in this work, but damage that can compromise applications in dosimetry occurs only for fluences greater than 1 × 1014 protons/cm2.

Change in yhe Optical Properties of Sapphire Induced by Ion Implantation

ABSTRACTWe have studied the formation of nano-crystals, after implantation of 2.0 MeV gold, 1.5 MeV silver, 160 keV copper and 160 keV tin into single crystal of A12O3. We also studied the change in the linear optical properties of the implanted Al2O3 before and after subsequent annealing by measuring the increase in resonance optical absorption. Applying Doyle's theory and the results obtained from Rutherford backscattering spectrometry (RBS) as well as the full width half maximum of the absorption band from Optical Absorption Photospectrometry (OAP), we measured the average size of the metallic clusters for each sample after heat treatment. The formation and crystallinity of the nanoclusters were also confirmed using transmission electron microscopy (TEM) technique.