DMREF: Nitride Discovery – Creating the Knowledge Base for Hard Coating Design

D. Gall^a and S. V. Khare^b

Outcomes Report [Identical to connected award, NSF 1234872, report]

This research program has developed a systematic method to determine the intrinsic physical properties of transition metal nitrides. Such nitrides are of key importance for the rapid deployment of new coating materials for emerging applications including fuel-efficient jet engines and gas turbines, environmentally-friendly lubricant-free cutting tools, high-temperature concentrating solar power plants and wind turbines, and lubricant-free (maintenance free) moving parts in extreme environments including space, autonomous vehicles, and moving surveillance devices for exploration and defense. The key new knowledge that has been developed in this project is an understanding of the direct relationship between the atomistic properties including the calculated electronic structure and macroscopic mechanical properties such as the elasticity and hardness. The understanding of such a relationship facilities prediction of properties of new unknown nitrides, which is the key to an accelerated deployment of new materials. This understanding has been gained by combining state-of-the-art quantum mechanical computations with experimental measurements on new nitride materials. The new understanding was facilitated by a close collaboration between the computational researchers at the University of Toledo and the experimental researchers at the Rensselaer Polytechnic Institute.

Intellectual Merit: The technical achievements are grouped in three areas:

(1) Results from overview studies which systematically compare structural, energetic, elastic and mechanical properties with the electronic structure of transition metal nitrides. More than 200 material structures were investigated. One key finding is: The shear modulus is anti-correlated to the density of states at the Fermi energy, which provides a direct method to predict hardness.

(2) Results from detailed studies on specific promising nitrides where materials synthesis, characterization, and property predictions are combined to gain a new understanding of correlations between composition, structure, and mechanical properties. This includes work on nitrides of tungsten, niobium, and molybdenum, which are relatively unexplored but particularly promising as tough, wear resistant coatings. The experimental work was motivated by results from achievement (1) and this laboratory work, in turn, spurred new avenues for computational work. In this context multiple new material phases have been synthesized, predicted, or both (i.e. first predicted and then successfully synthesized).

(3) Results from exploratory studies that emerge from the developed synergistic theory-experiment collaboration that go beyond the core goals of the project, and catalyze new transformative research efforts. Examples include nitrides which also exhibit promising electronic and optical properties, in addition to the mechanical properties, and therefore may become interesting for multi-functional materials such as high-temperature thermo-electrics or wear-resistant optoelectronic materials, for uses in novel energy harvesting or optical communication applications.

Broader Impacts: The research team has disseminated the results in over 25 technical publications and over 20 presentations. They have also developed an interactive ceramics property database tool which is a web-based centralized platform for storage, search and analysis of single crystal data related to structure, composition, elastic and mechanical properties of ceramic materials. Computational tools for rapid calculations of mechanical properties of large number of materials were developed. This project has directly impacted a total of 7 graduate and 6 undergraduate students, who have been extensively trained in technologically relevant research and development of new materials.

Last Modified: 11/28/2016
Modified by: Sanjay V Khare