Estudo de traços de fissão em vidro utilizando-se microscopias de força atomica e eletronica de varredura : inferencia da estrutura de traços latentes a partir de traços atacados / Glass fission track analysis by AFM and SEM : inferring latent track structure trough etched tracks

AUTOR(ES)

Igor Alencar Vellame

DATA DE PUBLICAÇÃO

2008

RESUMO

A study on the geometric evolution of 235U induced fission tracks in a soda-lime glass was made. It was necessary to know about the geometric model for structure evolution of fission tracks in isotropic materials. This model is based on the competition of two chemical etching rates: one in the bulk material (VB) and another in each fragment trajectory (VT). This etching is generally used for track observation in an optical micro-scope. Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) were used because of the better resolution and for measurements at short etching times. Uranium films were produced and coupled to each glass trough an acrylic piece (collimator). Irradiated by thermal neutrons the film emits fragments. Energy loss calculations were simulated by SRIM software. Track diameters and wall angles were measured. The rate VB= (0,113 ± 0,003) µm/s were measured by recovering part of the glass surface with a non-etching material. Two values were obtained for the ratio between the etching rates: Vdiam= 1,66 ± 0,07 and Vdepth= 1,31 ± 0,09. The model was used to calculate the first value with the diameters measurements. The second one was obtained by indirect depth measurements with AFM. Thus, with all these constant values we can consider that the effect produced by fission fragments traversing a soda-lime glass is the production of a homogeneus cylinder of damage. This result is very important for annealing models

ASSUNTO(S)

microscopia eletronica de varredura microscopia de força atomica traços de fissão soda-lime glass scanning electron microscopy vidro base de emulsão atomic force microscopy fission track

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