Drops and bubbles wrapped in dense monolayers of hydrophobic particles are known to sustain a significant decrease of their internal pressure. Through dedicated experiments we investigate the collapse behavior of such armored water drops as a function of the particle-to-drop size ratio in the range 0.02-0.2. We show that this parameter controls the behavior of the armor during the deflation: at small size ratios the drop shrinkage proceeds through the soft crumpling of the monolayer, at intermediate ratios the drop becomes faceted, and for the largest studied ratios the armor behaves like a granular arch. The results show that each of the three morphological regimes is characterized by an increasing magnitude of the collapse pressure. This increase is qualitatively modeled thanks to a mechanism involving out-of-plane deformations and particle disentanglement in the armor.

We have studied the structural properties of tensile-strained Si layers grown on polished Si 0.6 Ge 0.4 and Si 0.5 Ge 0.5 virtual substrates as a function of their thickness. Two gaseous precursor chemistries have been assessed for the reduced pressure-chemical vapour deposition of the sSi layers: SiH 2 Cl 2 at 700 • C and SiH 4 at 600 • C. We have used specular x-ray reflectivity and spectroscopic ellipsometry to gain access to the sSi layer thickness (and the associated sSi growth rate). The surfaces of sSi layers grown at 600 • C using SiH 4 are characterized by a small spatial wavelength (a few hundred nm) roughness. Meanwhile, some lines along the 1 1 0 directions can be observed for thick sSi layers grown at 700 • C using SiH 2 Cl 2 , hinting at the presence of stacking faults. We obtained (for 10 µm × 10 µm atomic force microscopy images) surface root-mean-square roughness (Z ranges) between 0.19 and 0.36 nm (1.8 and 3.9 nm). By comparison, the rms roughnesses (the Z range) associated with 360 µm × 368 µm optical interferometry images are between 0.7 and 1.4 nm (7.1 and 12.1 nm), with some small amplitude but very long spatial wavelength (tens of µm) surface cross-hatch remaining on Si 0.6 Ge 0.4 VS. The interfaces between sSi and SiGe are very abrupt, as illustrated by high-resolution transmission electron microscopy and by the Ge decay profile in secondary ions mass spectrometry: 0.73 nm/decade for sSi on Si 0.5 Ge 0.5 VS and 1.06 nm/decade for sSi on Si 0.6 Ge 0.4 VS, more or less independently of the sSi growth chemistry. The larger value for sSi on Si 0.6 Ge 0.4 VS is most probably due to some instrumental broadening linked to the small remaining cross-hatch.

-Shape Memory Alloys present a large variety of behaviour in function of the thermomechanical loading pathes and the microstructural states of the material. These responses are due to different physical mechanisms of deformation which are associated to the thermoelastic martensitic transformation :-oriented growth of the martensitic plates by the applied stress in Superelasticity ; -mobility of the interfaces between the variants of martensite in the so-called Shape Memory Effect ; -capability of the internal stress field produced in the material by oriented defects left by some previous transformation sequences, to influence the growing of the martensite in the Two-Way Shape Memory Effect. The determination of the constitutive equations for the mechanical behaviour of these alloys must take into account these particular mechanisms of deformation. For each physical mechanism it is necessary, at first, to make a kinematical study of the strain associated to it. After this step, an energy balance between the driving and the resistive forces is established in each case from the analysis of the Gibb's free energy of the transformation or by using the Eshelby formalism of energy momentum. Phenomenological flow rules are then determined from the classical concept of normality rule. In this contribution, the micromechanical aspects of the phase transformation mechanisms me presented both from the statical and the kinematical point of view. Special attention is given to the internal stress state associated with variant and grain interactions. -Introduction.Complex stress-strain-temperature behaviour are observed in Shape Memory Alloys (SMA) leading to different effects : -pseudoelasticity, -one way shape memory effect, -two way shape memory effect after a paining sequence. A large number of experimental observations [I] [2] [3] [4] [5]have shown that the basic mechanisms for these effects are related to a reversible austenite-martensite phase transition and to the possibility of reorientation of the martensite by twinning. Basically, the displacive martensitic transformation is connected with a transformation strain (practically a pure shear) and an habit plane corresponding to the interface between the martensite and the austenite. Due to the symmetry of the parent phase, a complex microstructure, observed at the mesoscopic level, consists of several variants of martensite. For the pseudoelastic and the two way shape memory effects, the observed overall behaviour belongs to the class of non linear thermoelastic materials with hysteresis. The one way shape memory effect has some strong similarities with classical plasticity of metals but in addition a saturation strain is observed. During the last decade an important effort has been developed in order to describe this complex overall behaviour. Three class of models are proposed :Article published online by EDP Sciences and available at http://dx