Determination of the melting and freezing temperatures of Pb nanoparticles embedded in a PbO–B₂O₃–SnO₂glass by using only the SAXS method

Abstract

Melting and freezing of metallic nanoparticles embedded in glass matrices usually occur at temperatures lower than for the same metal in the bulk state. In situ small-angle X-ray scattering (SAXS) measurements using a synchrotron beamline and a specially designed high-temperature chamber allowed the determination of the temperature dependence of the SAXS intensity produced by a dilute and nearly monodisperse set of spherical Pb nanoparticles, with an average radius hRi = 16.1 nm, embedded in a homogeneous lead-borate oxide glass. The temperature dependences of the nanoparticle volume V(T) and nanoparticle radius of gyration R g (T) derived from SAXS results exhibit clear discontinuities during the cooling and during the heating processes, thus allowing for precise determinations of the melting and freezing temperatures of the studied Pb nanoparticles. Additional features observed in both V(T) and R g (T) curves showed that during the heating cycle the frozen Pb nanoparticles suffer a transition to a more compact phase at 433 K before melting at 580 K. The results of this work demonstrate that the melting and freezing temperatures of nanoparticles in a very diluted state -for which the X-ray diffraction technique is not sensitive enough -can be precisely determined by applying only the SAXS method.

Melting and freezing temperatures of confined Bi nanoparticles over a wide size range

“…As established in a previous study of a set of spherical Pb nanoparticles with a narrow radius distribution embedded in glass (Kellermann et al, 2015), precise determination of transition temperatures was achieved by only analysing Q(T) functions derived from experimental SAXS patterns. For the previously studied Pb-glass composites (Kellermann et al, 2015) the Q(T) functions actually exhibit sharp jumps at the transitions, this behaviour being expected for systems of nanoparticles with narrow size distributions. On the other hand, for the glass samples containing Bi nanoparticles studied here, smooth variations in Q(T) at the transition temperatures are observed in the different hysteresis loops displayed in Figs.…”

“…A number of nanostructured materials with interesting optical properties are composed of a homogeneous glass matrix in which dilute sets of metallic (Uchida et al, 1994;Itoigawa et al, 1997;, 2003, 2008Kellermann et al, 2015) or semiconductor (Borelli et al, 1987;Liu & Risbud, 1990;Medeiros Neto et al, 1991;Craievich et al, 1997Craievich et al, , 2002 nanoparticles are embedded. These doped glasses exhibit interesting optical properties with potential applications in photonics (Barbosa et al, 1995;Olivares et al, 2001).…”

“…Recently, the melting and freezing temperatures of a dilute set of metallic (Pb) spherical nanoparticles having nearly identical radii embedded in a lead borate glass have been determined using small-angle X-ray scattering (SAXS) alone, without using thermal analysis (Kellermann et al, 2015). On the other hand, the melting and freezing temperatures of a dilute system composed of a polydisperse set of spherical Bi nanoparticles with some radius dispersion were determined by applying another method based on the combined use of SAXS and wide-angle X-ray scattering (WAXS) , 2008.…”

In situ study of the kinetics of growth of Pb nanoparticles embedded in a PbO–B2O3 glass

“…A determination of the melting and freezing temperatures of Pb nanoparticles embedded in a lead borate glass was previously performed by combined use of SAXS, TEM and electron diffraction (Kellermann et al, 2015). The TEM and electron diffraction analyses of that material at room temperature demonstrated that the observed nanoparticles are Pb nanocrystals with face-centered cubic crystallographic lattice and nearly the same lattice parameter as bulk Pb.…”

“…The TEM and electron diffraction analyses of that material at room temperature demonstrated that the observed nanoparticles are Pb nanocrystals with face-centered cubic crystallographic lattice and nearly the same lattice parameter as bulk Pb. In the present study, quenched (initially nearly homogeneous) samples of the same material as another studied before (Kellermann et al, 2015) were annealed for 120 min at 649 K and then observed by TEM at room temperature in order to establish the nature, shape and size of the precipitated Pb nanoparticles embedded in the glass matrix. The TEM images displayed in Figs.…”