Implementação do sistema de cristalização superficial induzida por laser em vidro de composição eutética
Resumo
The radiation from lasers has been successfully applied to materials
processing such as drilling, cutting and welding, sintering of ceramic oxides,
surface heat treatment, directional solidification of single crystal fibers and
texturing of crystalline compounds. The characteristics that make the laser
radiation attractive to surface heat treatment processing are its coherence and
collimation, which allowed the spatial control of the thermal energy. The
modification of the material´s surface is dependent on the composition of the
sample, the power of the laser and the radiation exposure time. Thus, the
efficiency of crystallization, scalability and the possibility of local heating are
some of the main attributes of laser crystallization. In addition, the laser can be
used to induce crystallization on an amorphous substrate. Low cost of
production is the main feature offered by laser crystallization to become an ideal
solution for many industrial applications. A laser writing system can lead to the
development of devices that can operate in aggressive environment like an acid
or at high temperatures. Thus, the present work has the objective of developing
versatile, low cost and programmable laser writing system, which allows the
superficial heat treatment in glasses. In this work a CO2 laser source was used,
which allowed the production of superficial crystallization. For the study of the
developed system, it was chosen an eutectic composition glass (system
LiO2.SiO2-CaO.SiO2), as the material model, in order to verify the control of the
microstructure. After the crystallization the identified crystalline phases were
calcium and lithium metassilicate, independent of the laser scanning speed. The
microstructure formed and the depth of the heat affected zone shows a
dependency with the laser scanning speed. Finally, it was found that the
average interphase spacing obeys a similar relationship described by Jackson
and Hunt for the solidification of eutectic systems, that is, by controlling the
laser scanning speed it is possible to control the formed microstructure and
thereby obtain the control of the final properties of the material.