We studied a colloidal suspension of polystyrene beads deposited on a glass substrate. The glass substrate contained either straight rough areas on the borders of an open channel or only straight rough areas. The drying of the suspension was observed with an optical microscope which light bulb acted as an energy source to evaporate the suspension. Moreover, the light bulb of the microscope provided optical pressure due to light. We observed that the colloidal particles where trapped on the rough areas of the substrate and not in the open channel, at the end of the drying process. In order to understand the experimental results, we modelled numerically the drying of the suspension by a Molecular Dynamics program. The forces acting on the substrate by the particles are their weight, the optical pressure due to the light bulb of the optical microscope, the attractive Van der Waals force and the repulsive diffuse layer force. The forces acting between two particles are the attractive Van der Waals forces, the repulsive diffuse layer force, the capillary force. The Gaussian random force (linked to the Brownian motion), the particle liquid viscous drag force (also linked to the Brownian motion) are horizontal and applied on one particle. The relation between the normal forces N (forces acting by the particles on the substrate) and the horizontal forces F is Amontons' third law for friction F ≤ µ k N ; in rough areas of the substrate µ k is larger than in smooth areas. This explains that particles are trapped in the large roughness areas.

Recently, filling zeolites with gaseous hydrocarbons at high pressures in diamond anvil cells has been carried out to synthesize novel polymer-guest/zeolite-host nanocomposites with potential, intriguing applications, although the small amount of materials, 10–7 cm3, severely limited true technological exploitation. Here, liquid phenylacetylene, a much more practical reactant, was polymerized in the 12 Å channels of the aluminophosphate Virginia Polytechnic Institute—Five (VFI) at about 0.8 GPa and 140 °C, with large volumes in the order of 0.6 cm3. The resulting polymer/VFI composite was investigated by synchrotron X-ray diffraction and optical and 1H, 13C, and 27Al nuclear magnetic resonance spectroscopy. The materials, consisting of disordered π-conjugated polyphenylacetylene chains in the pores of VFI, were deposited on quartz crystal microbalances and tested as gas sensors. We obtained promising sensing performances to water and butanol vapors, attributed to the finely tuned nanostructure of the composites. High-pressure synthesis is used here to obtain an otherwise unattainable true technological material.

We report a study of polymorphic boron nitride samples. We interpret the photoluminescence line at 6.032±0.005 eV, that can be recorded at 8K in sp2-bonded boron nitride, as being the signature of the excitonic fundamental bandgap of the Bernal (or graphitic) boron nitride polymorph (bBN). This is determined by advanced photoluminescence measurements combined with x-ray characterizations on pure hexagonal boron nitride (hBN) and on polymorphic crystal samples, later compared with the theoretical predictions of Lorenzo Sponza, et al., Physical Review B 98, 125206 (2018). The overall picture is consistent with a direct excitonic fundamental bandgap of the Bernal (or graphitic) polymorph of boron nitride. This value dXb = 6.032±0.005 eV is higher than the indirect bandgap of hBN (iXh =5.955±0.005 eV).

The Miles theory of wave amplification by wind is extended to the case of finite depth h and a shear flow with (constant) vorticity {\Omega}. Vorticity is characterised through the non-dimensional parameter {\nu} = {\Omega} U_1 /g, where g the gravitational acceleration, U_1 a characteristic wind velocity and k the wavenumber. The notion of 'wave age' is generalised to account for the effect of vorticity. Several widely used growth rates are derived analytically from the dispersion relation of the wind/water interface, and their dependence on both water depth and vorticity is derived and discussed. Vorticity is seen to shift the maximum wave age, similar to what was previously known to be the effect of water depth. At the same time, a novel effect arises and the growth coefficients, at identical wave age and depth, are shown to experience a net increase or decrease according to the shear gradient in the water flow.

In order to analyze why the CIGS (CuInGaSe2) - based solar cells efficiency decrease for wide band gap (high Ga content), we have performed a series of samples by PVD using the three stage process. The average compositions of our solar cells range from x = 0 to x = 0.88, as measured by X-ray diffraction. An important feature of this process is to create a double Ga gradient into the absorber, which contributes to improve efficiencies, and this has a major impact on the determination of the sample composition from x-ray diffraction data. We have developed a model in order to assess this impact and question the validity of the compositions extracted from x-ray data. This model allows to get some information about gradient shapes. Using our model, we have obtained some insights on the evolution of the gallium gradient in samples with increasing Ga content, and we determine that this gradient is less pronounced when increasing the amount of gallium. It is a well known fact that this gradient assists the extraction of photocreated carriers, and the modifications of the gallium profile that we have determined may explain, for some part, the degradation of solar cells efficiency for high gallium compositions.