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At an intermediate level between the atomic and the macroscopic scales, nano- and meso-structures crucially determine the properties of nanostructured materials. Such materials, either aggregations of nanoparticles, weakly or strongly interacting, or matrices containing nanoparticles, are of great interest for nanotechnologies. Inelastic light scattering, either coherent Brillouin scattering from traveling vibrational excitations or incoherent low frequency Raman scattering from non traveling excitations, is a powerful probe intrinsically tuned at a mesoscopic scale. Its potential is shown by several examples: tin particles embedded in a silica film, porous silicon, cluster assembled carbon films, sintered polytetrafluoroethilene particles, and single walled carbon nanotubes. Nanoparticle properties and inter-particle interactions are probed either directly or through the properties of the effective homogeneous medium in which acoustic wave propagation occurs.

Inelastic light scattering by acoustic phonons (Brillouin scattering) is a useful tool for probing material properties at the submicrometre scale. In media which are statistically homogeneous at this scale, it gives access to the acoustic properties and the elastic moduli. In nanostructures it probes the vibrational properties at the mesoscopic scale. Applications to carbonaceous materials are reviewed.

Infrared absorption spectra and Raman and Brillouin scattering were used as optical techniques for the characterization of intact, damaged and restored parchments. This study was aimed at understanding at both the molecular and mesoscopic levels the structural changes associated with damaged and restored materials. Copyright © 2000 John Wiley & Sons, Ltd.

Abstract: We present a method to measure the thermal diffusivity of metals. A homogeneous small heat source is fed into a cyclindrical sample of titanium by thermoelastic compression. This heating process is followed by a thermal relaxation controlled by the thermal diffusivity. The resulting temperature variation is detected by a miniature temperature sensor mounted on the lateral surface of the sample. The value so obtained for the thermal diffusivity of titanium is (6.6�0.2)�10−6 m2/s.

Grüneisen's parameter γ of polycrystalline α-titanium is experimentally found to be very sensitive to the amount of plastic deformation previously suffered by the sample. The observed behaviour may be explained in terms of sessile dislocation density within crystallites, leading to short-wavelength phonon-phonon coupling. Experimental values of γ, obtained by a new thermodynamic method, are fitted to a simple model based on dislocation attrition and multiplication and which is a modified version of a model due to Gilman (1965).

The statistical behaviour of classical massless excitations finds an increasing importance in the physics of low-dimensional condensed matter. Dislocation and disclination dipole-gases and plasmas play such a relevant role in the theory of 2D melting. Here the equilibrium statistical mechanics of a system of strongly interactingparticlesof this type is faced searching for the approximate stationary solution of the multivariate associated Fokker-Planck equation corresponding to zero eigenvalue. The problems, encountered in a preceding paper, involved by the nonhermiticity of Fokker-Planck operator, are evaded, following Risken, building anequivalentmany-body Schrödinger equation. This last is solved self-consistently in a Hartree-like way starting with a free-particleproduct wavefunctionin the case of a uniform background whosechargeis of sign opposite to that of theparticles. Unlike thetruequantum case, here the integral part of the equivalent Hamiltonian operator is not simply Coulomb-like and defines a more difficult novel integrodifferential problem which is solved using a convergence in mean procedure.

The mechanism of the thermomechanical instability of an elastically slowly strained solid is explored, by a normal mode analysis of temperature and strain fluctuations. The strain dependence of the Grüneisen parameter is found to play a major role, since it controls the rates of damping of the lowest wavevector acoustic excitations pumped by the imposed strain. For a-titanium the instability is found to occur at a critical strain comparable with that of the elastic limit. The instability can be envisaged in terms of a fast growing deformation, presumably associated with an acoustic emission.

Abstract: A homogeneous thermoelastic heat source is fed, in a cylindrical sample, by compression; the amount of generated heat is controlled by the Grneisen parameter. The heating process is followed by a thermal relaxation controlled by the thermal diffusivity. The temperature transient is detected by a miniature temperature sensor mounted on the lateral surface of the sample. The value obtained for the Grneisen parameter of a technological steel is 1.140.03, the thermal diffusivity turning out to be (6.10.1)10−6 m2 s−1.