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632 records · Page 36

Investigation of P(VDF-TrFE)/ZrO{sub 2}-MMA polymer composites applied to radiation shielding

Exposure to high radiation dose in medical diagnostic imaging procedures can lead patients to suffer tissue damaging. However, there are several studies that identify significant dose reduction with the use of radiation protective attenuators, minimizing the delivered dose in the region that covers the main beam, while preserving the diagnostic quality of the generated image. Most radiation attenuator materials are produced from shielding metal containing composites, whose efficiency is the goal of investigations around the world. In this context, polymeric materials were chosen for this investigation in order to provide light-weighted and flexible protective composites, a must in personal protective shielding. Therefore, this work is concerned to the investigation of poly(vinylidene fluoride - try-fluor-ethylene) [P(VDF-TrFE)] copolymers mixed with zirconia nanoparticles. The resulting polymer composites, prepared with 1, 2, 3, 5 and 10 at.% of ZrO{sub 2} nanoparticles, were investigated for application as protective shielding in some interventional radiology procedures. Two variety of composites were produced, one using pure ZrO{sub 2} nanoparticles and the other using sol-gel route with zirconium butoxide as the precursor for zirconium oxide nano-clusters. The P(VDFTrFE)/ ZrO2-MMA polymer composites produced by sol-gel route have provided a much better dispersion of the pure ZrO{sub 2} material into the P(VDF-TrFE) host matrix. UV-Vis and FTIR spectrometry and differential scanning calorimetry (DSC) were used to characterize the composite samples. FTIR data reveal a possible link between the MMA monomers with the P(VDF-TrFE) chain through shared C=O bonds. The radiation shielding characterization was conducted by using a 70 kV x-rays beam which is applicable, for instances, in catheter angiography. The results demonstrate that composites with 10% of ZrO{sub 2}, and only 1.0 mm thick, can attenuate 60% of the x-rays beam. The composite density was evaluated to be 2.20 g/cm{sup 3}. The results indicate that P(VDF-TrFE)/ZrO{sub 2}-MMA polymer composites have potential to be investigated as light-weighted and flexible protective shielding for application in some radiological procedures that uses low kilovoltage x-ray beams. (authors)

36 MATERIALS SCIENCE↗

Response of Ferroelectric Polyvinylidene Fluoride under Pulsed Fast Neutron Irradiation

Because the spontaneous polarization of a ferroelectric material is a function of temperature, heating or cooling it slightly will cause bound charge to accumulate on faces normal to the polarization, and the phenomenon is called pyroelectric effect. The pyroelectric detectors can uses pulsed gamma rays or neutrons as the heat source, and they do not require external power supply units and have a high radiation stability. Pb(Zr, Ti)O{sub 3}-based ceramics are widely used ferroelectrics and have a relatively high density of about 7.8 g/cm{sup 3}, which is promising for gamma-ray detection. To develop a pyroelectric thermal neutron detector, E.A. de Souza and L.P. Geraldo et al. prepared a layer of neutron converter on the surface of Pb(Zr, Ti)O{sub 3} ceramic pellet, and the neutron converter can be uranium (with 20% enrichment in {sup 235}U) or boron (with natural isotopic abundance or with 92.41% enrichment in {sup 10}B). The proposed pyroelectric neutron detector is interesting, but not suitable for fast neutron detection accompanied with gamma rays. As the polyvinylidene fluoride (PVDF) is also a kind of ferroelectric material, but with a low density about 1.78 g/cm{sup 3}, indicating a low sensitivity to gamma radiation. This material contains about 3.35 x 10{sup 22}/cm{sup 3} of H, which has a relatively large cross section with fast neutrons. The PVDF possibly has the potential for fast neutron detection, and the response of ferroelectric polyvinylidene fluoride under pulsed fast neutron irradiation was reported. (authors)

36 MATERIALS SCIENCE↗