Archive for year: 2011
Quasi 2D granular dynamics
4000 spheres of steel (diameter 2mm) are deposited on a horizontal rough plate (200mm diameter, only a square 100mm X 100mm is shown) and are put in motion by vertical vibration of the plate (sinusoidal shaking, amplitude 0.7mm, frequency 200Hz). The resulting motion, on the plane, is a composition of random sliding on the plate and inelastic collisions among particles. This is a “non-equilibrium” Brownian motion.… Read the rest
Empty Liquids and Equilibrium Gels in a Colloidal Clay
CNR researchers (CNR-ISC and CNR-IPCF) in collaboration with University La Sapienza and ESRF (Grenoble) have observed a new kind of extremely light and stable gel in a suspension of colloidal clay. The so-called equilibrium gel, predicted 4 years ago by theoretical calculations by members of the same research team for a simplified model[1], could lead to improved drug-delivery systems and other novel microscopic devices.… Read the rest
Soft matter
The term “soft matter” refers to a very large class of materials, whose common characteristic is that they are composed of mesoscopic particles, i.e. particles with typical sizes ranging from 1 nm to a few microns. These particles are normally dispersed in a solvent, whose molecules are much smaller in size (typically of atomic dimensions). In addition, the solution may contain other small objects, such as polymeric chains, salt ions, etc.… Read the rest
Volume collapse transition in Ce
Crystalline Ce has a remarkable phase diagram in that is the solid state analogue of a Van der Walls system with a line of discontinuous transitions ending at a critical point.
The two phases alpha and gamma have the same cubic symmetry and differ only on density just like water and vapor but in the solid state!.
However unlike water and vapor the critical exponents close to the critical point are not three dimensional Ising critical exponents, as one would naively guess from symmetries, but classical (Gaussian) exponents.… Read the rest
Granular Dynamics Laboratory
Since July 2010, the Granular Dynamics Laboratory is operative – originally in room “010” and (from november 2012) – in room “012” (ground floor of Fermi Building of the Physics Department) at the Sapienza unit of ISC. The laboratory includes two main experimental setups:
- Vertical vibration (2d and 3d granular experiments): an electrodynamic shaker LDS V455, which can reach a maximum acceleration of 105g, powered by a PA1000L power amplifier.