No abstract

There is a need to find new paths for van der Waals 2D-systems detachment and transfer or to control their adhesion state in different environments. We have observed that supported multilayer graphene immersed in a fluid can be detached from a substrate through pressure application. The process is based on the development of wrinkles originated by the difference of in-plane-compressibility between the graphene stacks and the substrate. Graphene stacks comprised between 9 and 110 layers and immersed in various fluids allowed to investigate the growth and evolution of wrinkles with increasing pressure. The detachment from the substrate stops at the pressure-induced fluid solidification. Methanol, ethanol or their mixtures favor the pressure-induced wrinkle formation in SiO 2 /Si substrates. In these cases, the pressure evolution of the delamination process follows a universal behavior independently of the number of graphene layers with a complete delamination at /sim4GPa. The quantitative analysis of the wrinkle geometry evolution can be consistently interpreted as due to a pressure-induced increase of the bending stiffness of the graphene stacks, or a reduction of the adhesion forces between the sample and the substrate, or both. These results should also be of practical use in high-pressure experiments of van der Waals systems.

Technological advances in recent decades have made the growing demand for energy one of the main bottlenecks for the development of more complex equipment and processes, requiring a constant search to more efficient materials and techniques that increase the efficiency of energy storage devices.Making use of Raman, X-ray diffraction (XRD), and first-principles calculation techniques, applied in Na 3 MCO 3 PO 4 (M = Mn, Fe, Co, Ni) carbonophosphates in a wide range of pressure and temperature, several thermoelastic and structural parameters were determined. Grüneisen parameters, bulk modulus, and thermal expansion coefficient, as well as the anisotropy under pressure and temperature change, were satisfactorily quantified, characterizing the distinct molecular ambient from the carbonate and phosphate groups of these materials. The results indicate an increasing stiffness and a greater anharmonic contribution as we move towards a more compact structure, indicating an increase in its phonon-phonon interaction.