37 research outputs found
Micro-Brillouin spectroscopy mapping of the residual density field induced by Vickers indentation in a soda-lime silicate glass
High-resolution Brillouin scattering is used to achieve 3-dimensional maps of
the longitudinal acoustic mode frequency shift in soda-lime silicate glasses
subject to Vickers indentations. Assuming that residual stress-induced effects
are simply proportional to density changes, residual densification fields are
obtained. The density gradient is nearly isotropic, confirming earlier optical
observations made on a similar glass. The results show that Brillouin
micro-spectroscopy opens the way to a fully quantitative comparison of
experimental data with predictions of mechanical models for the identification
of a constitutive law.Comment: 4 pages, 3 figures, revised version, to appear in Appl. Phys. Let
Glass-specific behavior in the damping of acoustic-like vibrations
High frequency sound is observed in lithium diborate glass,
LiO--2BO, using Brillouin scattering of light and x-rays. The sound
attenuation exhibits a non-trivial dependence on the wavevector, with a
remarkably rapid increase towards a Ioffe-Regel crossover as the frequency
approaches the boson peak from below. An analysis of literature results reveals
the near coincidence of the boson-peak frequency with a Ioffe-Regel limit for
sound in {\em all} sufficiently strong glasses. We conjecture that this
behavior, specific to glassy materials, must be quite universal among them.Comment: 4 pages, 4 figures, revised versio
High Frequency dynamics in metallic glasses
Using Inelastic X-ray Scattering we studied the collective dynamics of the
glassy alloy NiZr in the first pseudo Brillouin zone, an
energy-momentum region still unexplored in metallic glasses. We determine key
properties such as the momentum transfer dependence of the sound velocity and
of the acoustic damping, discussing the results in the general context of
recently proposed pictures for acoustic dynamics in glasses. Specifically, we
demonstrate the existence in this strong glass of well defined (in the Ioffe
Regel sense) acoustic-like excitations well above the Boson Peak energy.Comment: 4 pages, 4 .eps figures, accepted in Phys. Rev. Let
Eliminating the broadening by finite aperture in Brillouin spectroscopy
We present a new optical arrangement which allows to avoid the broadening by
finite aperture in Brillouin spectroscopy. In this system, all the rays
scattered at the same angle by the whole scattering volume are collected on a
single pixel of the area detector. This allows to use large collection angles,
increasing the luminosity without lowering the accuracy of the frequency-shift
and linewidth measurements. Several results of experimental checks are
provided, showing the efficiency of the device.Comment: 14 pages, 8 figure
Scaling the Temperature-dependent Boson Peak of Vitreous Silica with the high-frequency Bulk Modulus derived from Brillouin Scattering Data
The position and strength of the boson peak in silica glass vary considerably
with temperature . Such variations cannot be explained solely with changes
in the Debye energy. New Brillouin scattering measurements are presented which
allow determining the -dependence of unrelaxed acoustic velocities. Using a
velocity based on the bulk modulus, scaling exponents are found which agree
with the soft-potential model. The unrelaxed bulk modulus thus appears to be a
good measure for the structural evolution of silica with and to set the
energy scale for the soft potentials.Comment: Accepted for publication in Physical Review Letter
Plastic flow and structural heterogeneities in silicate glasses - A high throughput investigation
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Observation of the onset of strong scattering on high frequency acoustic phonons in densified silica glass
The linewidth of longitudinal acoustic waves in densified silica glass is
obtained by inelastic x-ray scattering. It increases with a high power alpha of
the frequency up to a crossover where the waves experience strong scattering.
We find that \alpha is at least 4, and probably larger. Resonance and
hybridization of acoustic waves with the boson-peak modes seems to be a more
likely explanation for these findings than Rayleigh scattering from disorder.Comment: 4 pages, 4 figures, to appear in Phys. Rev. Letter
The Boson Peak and its Relation with Acoustic Attenuation in Glasses
Experimental results on the density of states and on the acoustic modes of
glasses in the THz region are compared to the predictions of two categories of
models. A recent one, solely based on an elastic instability, does not account
for most observations. Good agreement without adjustable parameters is obtained
with models including the existence of non-acoustic vibrational modes at THz
frequency, providing in many cases a comprehensive picture for a range of glass
anomalies.Comment: 4 pages, 3 figures, Physical Review Letters in pres