text

The rock and ice mechanics lab at Lamont-Doherty is led by PIs Heather Savage, Christine McCarthy and Ben Holtzman. We are in the process of growing our lab and building our experimental program. Along with a team of postdocs, undergrads, grads, and longtime staff engineer Ted, we are rehabilitating and revamping some of the old equipment and building new rigs for exciting new experiments on both rock and ice. You can follow along with our progress here.

Wednesday, 30 November 2011

"Triax this is Houston, do you read?"

Ted and Heather got a lot of work done on the Triaxial apparatus while I was away. For one thing, they got the pressure vessel all lined up and then set up these two blue mini-versions of the vessel, called intensifiers, that control the confining pressure and the pore fluid pressure (so, one controls the pressure outside the sample and the other, inside). We'll use kerosene for the confining liquid. There's also that row of seven things sitting atop the mini-vessels. I don't know what they do yet but I'm excited to find out.
In addition, there are now big hoses going to and from the vessel and intensifiers and a burly hydraulic fluid pump. The pump is so powerful and loud that it sits in its own insulated doghouse outside the lab, otherwise it would drive us all crazy.
And one very exciting development is that they rewired the old control panel that will be used to communicate with the Triax. Since the rig will get up to very high pressures during experiments, you really don't want to be standing next to it while it is running. Rather, you want to be safely around the corner at this groovy old school station, complete with analogue Heise pressure gauges (on the blue wall panel) and all the digital readings you require.

Thursday, 24 November 2011

Research Trip: Edinburgh

For the last 30 days I was in Edinburgh on a research exchange visit. It was an absolutely wonderful time to be visiting Scotland. The days were brisk, but not that cold and somehow I managed to avoid most of the rain. 

The visit was funded by a branch of the European Science Foundation, called MicroDICE. Their purpose is to promote the exchange of science and techniques between Universities and countries, especially if it is concerning the microstructures of Ice. 

I was visiting Jane Blackford, who is in the Materials Science department of the University of Edinburgh.  Here's Jane with the fields of outer Edinburgh below her. Whenever we weren't in the lab, we tried to sneak out to the surrounding hills for a hike or to the local climbing gym for a route or two.

Our research goal was to measure the "dihedral angle" of sulfuric acid and ice, that is, the wetting angle that a liquid acid solution makes in the corners of ice grains, which is determined by the surface energies. Sulfuric acid has been found in polar ice packs and is thought to exist on icy moons in the outer solar system. The reason for measuring the angle is because if the angle is very large (>60 degrees), sulfuric acid would be stuck and confined to the corners of grains, but if the angle is small (<60 degrees) it could travel through interconnected veins of liquid. Traveling liquid acid could really influence the physical properties of ice, so it is an important characteristic to measure. We sprayed a solution of ~5%acid into liquid nitrogen so that it would flash freeze into droplets that we collected and put into these little aluminum containers (right). Then we let the samples "cook" at various temperatures that were below the freezing temperature of ice yet above the freezing temperature for the liquid acid solution. We let them sit like that for about a week and then we quenched them in liquid nitrogen to capture that microstructure.  Then it was off to the Biology department to visit Chris Jeffree and his scanning electron microscope that is specially equipped to handle frozen samples (below).
Chris was an absolute wizard with the SEM and managed to take hundreds of images of dihedral angles. I am now in the process of measuring all those angles, first by hand and then electronically. Publication coming soon!