Non-equilibrium Phase Discovery in Finite-sized Systems

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NON-TECHNICAL SUMMARYThe discovery of new materials with improved properties is a driver for technological advancement. An area potentially abundant with such improvements are systems that under normal conditions, cannot be formed stably. In this context, "normal conditions” and “stably” mean thermodynamic equilibrium, which is a scientific way of saying something will not change over time because it is in thermal, mechanical, chemical and radiative balance. By avoiding equilibrium, new configurations of materials can be accessed, and these new configurations may having new and better properties. In this project, equilibrium will be avoided by creating systems of material that are so small, they exist at a size invisible to the human eye. By condensing solid particles directly from a gas phase, with dimensions of a few nanometers, (1 x 10^-9 m) and maintaining isolation between the nanoparticles, elements which normally don’t go together, can be forced into mixing, thereby producing dramatic effects on the physical properties of these material systems. In this way, new magnetic materials can be discovered and developed, with potentially profound impacts on energy conversion to improve motors, generators, data storage, and even biomedical devices. Furthermore, a better understanding of materials behavior and structure formation in very, very small systems will result. This project is also focused on training the next generation of scientist. This project will support a graduate student who will learn advanced materials fabrication, characterization, and modeling techniques, while working with international partners. The project also provides support for an undergraduate community college student transferring to a four-year science or engineering (i.e., STEM) degree program, with the goal to ease the transition to the university environment. Finally, this project will partner with an existing Research Experience for Teachers Program, providing educational opportunities in nanotechnology for community college or high school science teachers as well as their students. TECHNICAL SUMMARYThis project will explore the field of non-equilibrium materials, by avoiding bulk equilibrium by creating isolated, finite-sized systems. This will be accomplished by using inert gas condensation to create nanoparticles on the order of nanometers, which will be isolated from one another. Focusing on normally immiscible systems, novel solid solution alloys and new ordered structures (i.e., intermetallic compounds) are expected to form. In addition, by controlling the size of the nanoparticles, the size-dependent phase formation can be explored, adding another axis to the temperature-composition phase diagram. Inert gas condensation is an ideal method of forming a wide variety of nanomaterials over large composition space, with excellent control over their size. In particular, at small nanoparticle sizes, complete or extended solid solution formation occurs, with strong effects on the magnetic behavior. Here, the focus will be on Fe and Co alloyed with 4d and 5d transition metals such as W and Mo, where extensive solid solution formation can have profound effects on the magnetic behavior, as well as Cu, Ag, and Au, with which they are immiscible but may have the propensity to form non-equilibrium intermetallic compounds. These investigations will be done in collaboration with computational studies by researchers at the University of Genoa, Italy. The knowledge gained from this project will expand the understanding of alloy and structure formation at the nanoscale, as well as develop new materials for energy conversion systems, data storage, and biomedical applications. Ultimately, this project provides a pathway to explore a world of undiscovered structures hidden by bulk equilibria. The project also provides support for a graduate student and an undergraduate community college student transferring to a four-year science or engineering (i.e., STEM) degree program, with the goal to ease the transition to the university. Finally, this project will partner with an existing Research Experience for Teacher program, providing nanotechnology educational opportunities for community college or high school science teachers and subsequently their students.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.