Page 23 - PR 2014 2016 02 Lasers Technology

Lasers Technology | Progress Report 37

Figure 19 - High Resolution Electron Diffraction of the (a) diamond-like phase and (b), its graphite precursor; (c) shows a HRTEM micrography
of the laser created structure with the characteristic 0.205 nm d-spacing of the diamond phase; (d) exhibits the corresponding electron diffrac-
tion peaks as a function of the inverse of the d-spacing for the precursor graphite (gray spectrum) and diamond-like phase (blue spectrum).

of a small area shown in the bottom inset. structures. Figure 20 shows fs-LIBS spectra of
Fig. 19d exhibits the corresponding electron (a) the amalgam, evidencing the presence of
diffraction peaks as a function of the inverse of the metallic components, (b) the amalgam/
the d-spacing for the polycrystalline graphite dentin interface, and (c) the dentin. The metals
(PG, gray spectrum) and diamond-like phase can be observed in the interface, but they are
(blue spectrum). absent of the dentin 400 μm away from the
interface. Our results showed that the metals
The ultrashort pulses ablation creates an abla- diffuse on the dentin of both deciduous and
tion plume that leaves the substrate in a highly
energetic state, atomizing their molecules
and ionizing these atoms, which return to
their ground state emitting its characteristic
atomic lines. This, the emission spectrum can
be used to analyze the elemental composition
of the substrate. This technique is known as fs-
LIBS (femtosecond-Laser Induced Breakdown
Spectroscopy), and can be used in dissimilar
materials with similar efficiencies due to the
nonselective characteristic of the ultrashort Figure 20. High Resolution Electron Diffraction of the (a) di-
pulses ablation. Taking advantage of this fact, amond-like phase and (b), its graphite precursor; (c) shows a
HRTEM micrography of the laser created structure with the
we used the fs-LIBS technique to determine characteristic 0.205 nm d-spacing of the diamond phase; (d)
the diffusion of dental amalgam elements exhibits the corresponding electron diffraction peaks as a
function of the inverse of the d-spacing for the precursor graph-
(Hg, Ag, Cu and Sn) into the surrounding tooth ite (gray spectrum) and diamond-like phase (blue spectrum).