Dislocation Loop Formation and Growth under In Situ Laser and/or Electron Irradiation

Vacancies and interstitial atoms are primary lattice (point) defects that cause observable microstructural changes, such as the formation of dislocation loops and voids in crystalline solids. These defects' diffusion properties determine the phase stability and environmental resistibility of macroscopic materials under ambient conditions. Although in situ methods have been proposed for measuring the diffusion energy of point defects, direct measurement has been limited. In this study, we propose an alternative in situ method to measure the activation energy for vacancy migration under laser irradiation using a pulsed laser beam from a laser-equipped high-voltage electron microscope (laser-HVEM). We made in situ observations that revealed the formation and growth of vacancy dislocation loops in an austenitic stainless steel during laser irradiation. These loops continued to grow when thermal annealing was performed after laser irradiation at the same temperature. We anticipate that laser-HVEM will provide a new method for investigating lattice defects

Is buffalo enamel a suitable substrate for bond strength tests?

Juliana Costa Pereira Baia,1 Mara Eliane Soares Ribeiro,1 Bárbara Catarina Lima Nogueira,1 Rafael Rodrigues Lima,2 Mário Honorato da Silva e Souza Júnior,1 Sandro Cordeiro Loretto1 1Department of Restorative Dentistry, UFPA – Federal University of Pará, Belém, PA, Brazil; 2Laboratory of Structural and Functional Biology, UFPA – Federal University of Pará, Belém, PA, Brazil Aim: The aim of this study was to compare the bonding strength of dental materials in buffalo (Bubalus bubalis var. kerebau), bovine, and human enamel and the susceptibility of these substrates in acid etching.Materials and methods: A total of 20 human third molars, 20 bovine incisors, and 20 buffalo incisors were used in a mechanical assay of microshear. The substrates were demineralized via conditioning with 37% phosphoric acid, and the ultra-morphological pattern of each substrate was analyzed by scanning electron microscopy.Results: The results showed that there was no significant difference in adhesive bonding strength values between buffalo and human enamel (P≥0.05), with a fracture pattern of mixed type for all experimental groups.Conclusion: The results indicate that buffalo enamel is similar to human dental substrate in tests of adhesive bonding strength and also show a similar behavior in the acid conditioning of the enamel. Keywords: dental enamel, shear strength, dental acid etching, scanning electron microscopy &nbsp