New nuclear magnetic resonance spectrometer allows researchers to better understand how materials age

A new nuclear magnetic resonance (NMR) spectrometer is allowing researchers in Organic Materials Dept. 1811 to better characterize the molecular structure of materials and to gain a greater understanding about how they age and what gives them their properties.

Since the instrument was purchased and installed in a specially designed room in the Processing and Environmental Technology Laboratory (PETL) last year, Dept. 1811 has been characterizing materials from throughout the Labs, including polymers, glasses, and ceramics — almost anything but metals. They’ve also done some characterization work for industrial partners.

The NMR spectrometer at PETL is the third spectrometer at Sandia. New, with state-of-the-art technology, it is more powerful than its predecessors.

"Because of the power and capabilities of this new spectrometer, we can characterize materials with greater resolution and can determine chemical and physical properties of some materials not readily accessible before, like thin films for MEMS [microelectromechanical systems]," Roger Assink (1811) says.

Todd Alam (1811), who works closely with the instrument, cites some examples:

• Using the NMR technique, the group has employed selective isotopic labeling to gain a better idea of how materials age and degrade. For example, the stable oxygen isotope, 17O, has been used to study the chemistry of oxidation, hydrolysis, and other environmental agents in organic and inorganic polymers important to the stockpile.
• NMR has helped researchers better understand the chemistry involved in a wide variety of ceramic materials. In collaboration with May Nyman (6118), NMR is being used to understand the structural and chemical changes that occur in oxide sorbents following the adsorption of cesium, including what structural changes can improve these uptake capabilities. These studies are geared toward nuclear waste legacy issues.
• NMR can help in predicting the aging of materials used for electrical cables in nuclear power reactors. Roger is working with Ken Gillen (1811) and the nuclear power industry to employ a smaller, less expensive NMR spectrometer that can be installed at nuclear power plants to test cables on site.
• In addition to determining the molecular structure of materials, their larger scale morphology, such as crystallinity and phase separation, can also be characterized. These properties often affect the way in which a material degrades.
• Recent NMR studies on thin films of amorphous carbon, done in collaboration with Tom Friedmann (1112), have allowed the evolution of the bonding structure within the film due to processing at elevated temperatures to be studied. These studies pushed the sensitivity limits of the device but clearly demonstrated that NMR investigations of thin films are feasible.
• NMR is also being used to monitor the condition of elastomeric binders in solid rocket propellants. In this instance the dynamics of the material, rather than its chemistry, tells if the binder is degraded. This program is conducted jointly with Leanna Minier (9116), the Department of Defense, and Thiokol.

In the future, Todd sees even more uses for the NMR spectrometer at Sandia. "I hope we will soon be able to do three-dimensional mapping inside an intact sample of rubber or plastic, possibly at a resolution of 100 microns," he says. " In addition to mapping the chemistry, we will also be able to map processes such as reaction kinetics and water diffusion."

Making up the Nuclear Magnetic Resonance (NMR) spectrometer team are Todd Alam, Roger Assink, post doc Brian Cherry, and contractor Sean Winters (all 1811). Roger Clough is the department manager.