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Preparation and characterization of ceramic/polymer composite for ionizing and non-ionizing radiation detection


Pyroelectric sensors works as a thermal transducer, converting non-quantified heat flow into a measurable quantity of electric charge, or voltage or electrical current. After the proposal to use the pyroelectric sensor as thermal transducer, ferroelectric ceramics, polymers and ferroelectric crystals based on lithium, have been used to detect and measure radiant energy and non-ionizing radiation. The proposal is making a ceramic/polymer composite to be used as a detector of radiation from the infrared to gamma radiation. The composite films will be produced with 0-3 connectivity, i.e, the ceramic grains are dispersed in the polymer matrix. The index 0 indicates that the grains are not connected in any direction while the index 3 indicates that the polymer matrix is self-connected in 3 directions. The polymer PVDF is obtained commercially as a powder and thus will be used. The ferroelectric ceramics (PZT, PTCA and Pz34) also are in the form of powder. The composite will be obtained by hot pressing the mixture of the three materials (eg PZT / PVDF / PANI) in different proportions of PANI to evaluate the effect of the conductivity on the composite performance. When the polymer used is the polyurethane, the composite will be obtained by spin-coating as the pre-polymer and polyol, which form the PU, are in liquid form. In the beginning a fixed ratio of ceramics (40 or 50 vol.%) will be used for the preparation of the composite films. The choice of these percentages is due to earlier work with the manufacture of composite polymer / ceramic when was noted that the samples with these percentages are more flexible, and more homogeneous. In addition, over 50% in volume of ceramic begins to form a mixed structure of connectivity 0-3 and 1-3. An alternative way to obtain the composite is coating the ceramic grains with polyaniline. In this case, the polyaniline will be synthesized in the presence of ceramic. Initially the ceramic will be placed in a solution of hydrochloric acid 1.0 M, containing the monomer aniline. This solution will be kept under mechanical agitation for 24 hours at room temperature. Then, the solution will be filtered and ceramics will be placed in another solution of HCl 1.0 M, containing the oxidizing agent (NH4)2S2O8. This solution will be kept under constant agitation at low temperature for approximately 3 h. The presence of PANI (semiconducting phase) will modify the electrical conductivity of the material and consequently their dielectric permittivity. This change in dielectric constant influences the figure of merit, which is related with the sensitive property of the material. Also, making the material less insulator, the effective electric field of polarization of the ceramic grain will be greater, making more effective the process of polarization of the sample. (AU)

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