  Investigating microstructure of suspensions with particles having anisotropic
shape that share complex interactions is a challenging task leading to
competing claims. This work investigates phase behavior of one such system:
aqueous Laponite suspension, which is highly contested in the literature, using
rheological and microscopic tools. Remarkably, we observe that over a broad
range of Laponite (1.4 to 4 weight %) and salt concentrations (0 to 7 mM), the
system overwhelmingly demonstrates all the rheological characteristics of the
sol-gel transition leading to a percolated network. Analysis of the rheological
response leads to fractal dimension that primarily depends on the Laponite
concentration. We also obtain the activation energy for gelation, which is
observed to decrease with increase in Laponite as well as salt concentration.
Significantly, the cryo-TEM images of the post-gel state clearly show presence
of a percolated network formed by inter-particle bonds. The present work
therefore conclusively establishes the system to be in an attractive gel state
resolving a long-standing debate in the literature.
