The challenge of ceramic/metal microcomposites and nanocomposites

Nonreciprocal surface waves

Characterization of Electronic Components by Acoustic Microscopy G. Pfannschmidt. Interaction of Acoustic Waves with Solid Surfaces Y. Tsukahara, et al. Scanning Acoustic Microscopy with Phase Contrast W. Grill, et al. Ultrasonic Focusing with Time Reversal Mirrors M. Fink, C. Prada.

Advances in acoustic microscopy

Lattice stability, elastic constants and macroscopic moduli of NiTi martensites from first principles

The authors have used Brillouin scattering to measure the thirteen independent elastic moduli of muscovite mica. The moduli reflect the monoclinic symmetry of the crystal, and demonstrate the anisotropy of the interlayer and intralayer bonding. The decrease in the acoustic velocity with increasing temperature is dominated by the decrease in the moduli that depend on interlayer bonding, giving an estimate of the temperature dependence of those moduli.

https://iopscience.iop.org/article/10.1088/0953-8984/5/11/008/pdf

Elastic moduli of muscovite mica

The effective elastic constants of a superlattice composed of layers of orthorhombic symmetry (with principal axes along the superlattice axis) are derived These results generalize previous determinations for elastically isotropic layers (Rytov, Akust Zh 2, 71 (1956) (Sov Phys: Acoust 2, 68 (1956))), but a completely different approach is used

Effective elastic constants of superlattices

An electronically driven lattice deformation which explains qualitatively the supermodulus effect in metallic superlattices is derived. It is shown in the Thomas-Fermi approximation that the total energy of a metallic superlattice is lowered by uniform deformations of the constituent materials. The theory gives the correct order of magnitude for changes in lattice constants, explains why the supermodulus effect is not observed in systems in which at least one constituent is nonmetallic, and predicts the absence of an effect when the bulk Fermi energies of the constituent metals are equal.

Lattice expansions and contractions in metallic superlattices.

The presence and origin of elastic anomalies in superlattices, interfaces, composites, and nanocrystalline materials has been a subject of much interest and controversy in recent years. In particular, superlattices are being used as model systems to study the effect of interfaces on the mechanical properties of novel materials. Early claims of anomalously large enhancements of the biaxial and flexural moduli of Au/Ni and Cu/Ni superlattices (“supermodulus effect”) created considerable controversy and contradictory reports in the experimental and theoretical literature. To understand the mechanical properties of superlattices and their implication for other types of nanofabricated materials, it is important to look critically at the field. Superlattices have been fabricated in different laboratories by a variety of preparation methods and have been characterized structurally and elastically to various degrees. Because of this, before addressing any sophisticated theoretical issues regarding elastic anomalies, it is important to understand in detail the experimental techniques and the possible pitfalls in the experimental determination of mechanical properties of thin films. Once the presence or absence of the effect is ascertained, the need arises to understand any possible experimental correlations with other structural and/or physical properties. These correlations can be used to address issues regarding the possible origins of the effect and their theoretical basis. It will be apparent from this article that slight changes in structural properties are correlated with relatively large elastic anomalies. Consequently, this points to the importance of precise, comprehensive, and detailed structural characterization. With our present understanding of the physics of superlattices, qualitative studies are no longer sufficient!

Elastic Anomalies in Superlattices

Surface waves in a layered material

In order to study the effect of fabrication technique on elastic properties of the superlattices, we have investigated a series of ion-beam-sputtered Cu/Ni superlattices and compared the results with those previously reported on evaporated samples. No systematic differences were observed in the relative intensities of the x-ray peaks from samples fabricated by the two techniques. The Brillouin-scattering results show no modulation-wavelength dependence.

M. Grimsditch

Papers

Effective elastic constants of superlattices

Lattice expansions and contractions in metallic superlattices.

Elastic Anomalies in Superlattices

Surface waves in a layered material

Brillouin scattering from ion-beam-sputtered Cu/Ni superlattices