Nanorheology and Fine Powder Flow

Publication Reference: 
Author Last Name: 
Steve Granick
Report Type: 
FRR - Final Report
Research Area: 
Powder Flow
United States


With the conclusion of this project, my students and I wish to thank the IFPRI member companies for their generous support and invaluable discussions during the past several years. The work summarized below, triggered by the invitation by IFPRI to submit a proposal for work in the nanorheology area, has been perhaps the most productive period during my research career.

Goals of this project: The objective of this project was systematic understanding of particle-particle nanorheology based on the single particle-particle contact of two atomically-smooth solid surfaces in molecularly-thin proximity. The main relevance was to understand the origins of suspension rheology, especially the origins of rheological anomalies that arise when interfacial films between two solid bodies are so thin that the intuition of what to expect based on bulk rheology no longer applies. Based on this understanding, we sought to develop new methods to control and manipulate the properties of their interfacial films. The premise for this work was the conviction that progress in understanding fine powder applications is impeded by difficulties in separating the overall rheology of a macroscopic-sized sample into various mechanistic subprocesses. Much is known about interparticle forces (van der Waals, electrostatic, hydrogen bonding, capillary, steric, etc.) and the information obtained in rheology experiments has often been interpreted in these terms. This project took the different approach of seeking to understand rate-dependent influences of nanorheological response. We were concerned with the rate-dependence of nanorheological responses not just in shear but also in adhesive mode.