Abstract The nanostructured hydroxyapatite (HAp) was synthesized by precipitation from aqueous phase, using hen’s eggshells and different sucrose concentrations. The XRD results confirmed the formation of HAp, with crystallite size of about 15-22 nm. The SEM and TEM characterization showed morphological changes when increasing the amount of sucrose used, with the tendency to form spheroidal particles. The specific surface area increases from 36 to 93 m2.g-1 as the amount of sucrose used increases. Our results indicated that sucrose can be used as a promising additive/template, easy to obtain at low cost. In addition to contributing to the recycling of this biowaste (eggshells), the synthesized HAp has the potential to be used in bone tissue engineering applications, since the samples were no cytotoxicity to dental pulp stem cells in the in vitro assessment by resazurin assay.

Welding is widely used in the manufacture of steel products. Metallurgical processes during welding produce residual stresses in different zones of the welded parts. Welding residual stresses, particularly tensile stresses, can significantly impact the reliability and the integrity of the welded components. Our recent works report the effect of residual stress redistribution in a relatively short, up to two weeks, period after the welding procedure. The hypothesis that the observed stress relaxation phenomenon is associated to the microstructure evolution that occur in the material after the end of the welding procedure was proposed. To prove this hypothesis a physical simulation of the influence of the welding thermal cycles on the base metal with GLEEBLE equipment was performed. Using SEM EBSD, technique the variation of grain boundary misorientation accompanied by the residual stresses redistribution in the first days after welding thermal cycles simulation were observed.