LENS History 2014

Go To year:   2014  •  2013  •  2012  •  2011  •  2010  •  2009  •  2008  •  2007  •  2006  •  2005  •  2004

AOT membrane phase miscibility gap - April 2014

AOT membrane phase miscibility gap The LENS SANS instrument has recently been used to track the behavior of coexisting membrane phases of the surfactant AOT in heavy brine. The figure at left shows scattering curves as a 25% volume fraction AOT sample was heated: a low Q peak indicative of the convoluted L3 sponge phase disappearing while a higher Q peak indicative of an Lα lamellar phase appears. The figure at right shows, for several concentrations, how these coexisting phase peak positions move together at a roughly constant ratio (~1.7) which is rather higher than the bulk single phase peak ratio (~1.25). These trends reflect the equality of Gibbs free energy of the phases as a positive membrane curvature modulus favoring the L3 becomes smaller while more thermal energy can be taken up by extra bending modes in Lα, balanced against the entropy difference between the phase topologies.
W.A. Hamilton (ORNL) & S.R. Parnell (LENS-IU)

D2O scattering cross-section measurements at LENS - July 2014

D2O scattering- Dr. Ignacio Marquez Damian
The LENS SANS instrument has recently been used in collaboration with colleagues from the CNEA, Bariloche Argentina. Shown here is Dr Ignacio Marquez Damian preparing the setup for measurements. The measurements were performed to test predictions of current scattering models as a function of temperature.