Estudo da formação de rastos nucleares em polímeros / Study of the Nuclear Tracks Formation in Polymers
Adriana de Oliveira Delgado
DATA DE PUBLICAÇÃO
The research in the field of material modification with ion implantation has greately improved, stimulated by technological applications in biology, medicine, electronics and other related areas. One of the correlated aspects in understanding these new materials is the identification and characterization of the damage produced by ion beam irradiation. In this work, we propose to identify the microscopic modification in polymers, after their irradiation with a high energy beam. Three polymers have been used: polycarbonate foils (Makrofol KG), 8 µm thick; polyalyl diglycol carbonate PADC (CR39) 900 µm thick and cellulose nitrate(LR115) 12 µm thick. The samples were irradiated with 350 MeV Au beam from the Cyclotron accelerator at Hahn-Meitner Institut (HMI) in Berlin. The Makrofol samples were placed in a 6-foil stack positioned in normal direction relative to the incident beam, in order to stop the projectiles. The irradiations were performed with ion fluences of 10^8, 10^9 e 10^11 ions/cm^2. The CR39 and LR115 samples, thicker than the range, were irradiated with the fluency of 10^9 ions/cm^2. The investigation of structural damage in the samples, after irradiation, was performed through analytical techniques such as: Fourier Transform Infrared Absorption Spectroscopy (FTIR), X Ray Difraction (XRD), Elastic Recoil Detection Analysis (ERDA), and Etching, followed by pore characterization using an optical and a scanning electron microscopes. The FTIR analysis of the samples showed a decrease in the number of simple bonds and an increase in the number of double and triple bonds, after irradiation. Moreover, it was observed that the damage intensity increases with the mean stopping power of Au. The XRD analysis allowed the observation of crystallinity decrease in Makrofol, and gave indications about a possible deviation in CR39 density, after sample irradiation, and no variation in LR115 samples. The methodology proposed using ERDA technique was not eficient to determine the H atoms teor in the polymers after irradiation, so, it was not possible to get conclusive results from the data. In the pore analysis, after etching, different behaviors were observed. The CR39 samples showed an evolution from a porous surface to a sharply peaked surface and a pore opening rate Va = 1,213 (17) µm/h was obtained. On the contrary, different Makrofol KG foils preserved the porous topography for different etching times. The pore opening rate showed dependence with ion stopping power in the irradiation. Comparing samples with similar values of stopping power, the result is that Makrofol Va is three times greater than the obtained to CR39.
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