Jamming Threshold of Dry Fine Powders

Abstract

We report a novel experimental study on the jamming transition of dry fine powders with controlled attractive energy and particle size. Like in attractive colloids dry fine particles experience diffusionlimited clustering in the fluidlike regime. At the jamming threshold fractal clusters crowd in a metastable state at volume fractions depending on attractive energy and close to the volume fraction of hard nonattractive spheres at jamming. Near the phase transition the stress-(volume fraction) relationship can be fitted to a critical-like functional form for a small range of applied stresses ÿ J as measured on foams, emulsions, and colloidal systems and predicted by numerical simulations on hard spheres. DOI: 10.1103/PhysRevLett.92.258303 PACS numbers: 83.80.Fg, 81.20.Ev, 47.55.Kf Supercooled liquids, granular systems, and colloidal suspensions are systems that display a nonequilibrium kinetic transition from a fluidlike to a solidlike jammed regime [1]. At jamming the constituent particles are suddenly arrested in a metastable static state forming a solid disordered network that spans the system. The jamming transition has been described by a phase diagram parametrized by interparticle attractive energy U, temperature T, particle volume fraction , and applied stress [2,3]. For example, granular systems jam when they are compressed or shear stress is lowered, a liquid jams when it is cooled, and colloid particles gelate with increasing U. Light scattering experiments suggest a link between the jamming transitions for suspensions of hard (nonattractive) spheres (U=K B T 0, where K B T is the thermal energy) and for suspensions of attractive particles (U=K B T > 0) [4]. While the kinetic arrest is driven by crowding of single particles in the absence of attractive forces, for attractive suspended particles jamming is driven by the crowding of fractal clusters. Suspensions of nonattractive hard spheres jam at J 0:56-0:59, which is comparable to the random loose packing (RLP) of nonattractive hard spheres at the limit of zero gravitational force ( RLP ' 0:56) but is well below the random close packing (RCP) limit ( RCP ' 0:64) [5]. On the other side, jamming of strongly attractive suspended particles takes place at J J U . In the limit U=k B T 1 fractal clusters crowd by a diffusion-limited cluster-cluster aggregation process (DLCA [6]). Since the density of this fractal structure decreases as it grows the system can form a gel at arbitrary small ( J

Physics of Compaction of Fine Cohesive Particles

“…4 in Ref. [14]), matching the reported value [16] for spheres of equivalent size to these clusters (kd p ' 50 m). The inset of Fig.…”

“…2 we have plotted near the jamming transition as a function of c for toner Canon CLC700 (100% SAC, in this commercial toner the additive is TiO 2 ) and for an experimental toner with similar particle size (7:8 m) but only 32% SAC. The jamming transition is discussed in detail in a previous work [14]. As seen in the data depicted in Fig.…”

Onset of Mechanical Stability in Random Packings of Frictional Spheres

“…Therefore, we extrapolate to determine 0 RLP : In the absence of theory we follow [5] and use the pressure dependence close to the jamming point known for frictionless static soft spheres [9][10][11]22] and frictionless thermal hard spheres [23]:…”

“…The value of RLP depends on the particle-particle interactions. Packings of cohesive particles like fine powders are stable under their own weight for values of RLP as low as 0.15 [5][6][7][8]. However, many granular materials do not exhibit cohesive forces.…”

“…However, after the excitation stops, dissipation quickly produces a static packing that is mechanically stable under its own weight. Experiments [1][2][3][4][5][6][7][8] and simulations [9][10][11][12][13] have shown that the volume fraction has a well-defined lower limit, RLP , called random loose packing (RLP). The value of RLP depends on the particle-particle interactions.…”