GOALI: Ternary Metal Diboride Coatings with Enhanced Oxidation Resistance and Durability - Understanding Phase Formation from a Metastable Starting State

University Of Illinois At Urbana-Champaign, Urbana IL

Investigators

Abstract

NON-TECHNICAL DESCRIPTION: This project addresses the need to expand the performance of materials that resist wear at elevated temperatures in a wide range of applications from microelectronics to protective coatings for manufacturing. Such coatings are critical for ensuring component quality and reliability by reducing manufacturing flaws, reducing in-service damage and extending the lifetime of components in the field and in manufacturing processes - all of which will largely eliminate waste, inefficient operations and resource intensive redundancies. Improved coatings may also expand the design space, allowing engineers to make choices that are more sustainable or could improve performance but are otherwise impossible with existing technologies. Transition metal diborides have exceptional wear properties and are quite tolerant of high temperatures; however, the presence of oxygen in these service environments diminishes those properties. This research is coupling processing science with state of the art characterization tools to develop new coating chemistries in the diboride family that evolve to protect themselves in oxidizing environments. Moreover, the processing route uses chemically safe precursors and operates at lower temperatures, making it a sustainable alternative to many existing coating technologies. By engaging an industrial partner, UES Inc., though the GOALI program, this research is focused on industrially identified gaps in understanding and technology. Graduate student researchers are also benefiting from this close partnership, gaining invaluable training and professional skills by working directly with UES researchers. These graduate students will be well positioned to join companies across a wide spectrum of industries dependent on these protective coatings (e.g., automotive, microelectronics, aerospace, power generation, tooling, etc.) where they are very much in demand. Teaching, training and participation of underrepresented groups is being fostered through targeted recruitment of graduate students from the University of Illinois Support of Under-Represented Groups in Engineering (SURGE) program and undergraduate researchers from the Illinois Scholars Undergraduate Research (ISUR) program. TECHNICAL DETAILS: The overarching objective of this study is to establish the scientific underpinnings of a new sustainable kinetic route towards durable, oxidation resistant refractory diboride thin films of HfAlxBy and HfCrxBy. The initial metastable state is established through low temperature chemical vapor deposition and the use of chemically safe (halogen free) precursors. The PIs are committed to sustainable synthesis routes, specifically the co-PI is a co-founder and lead instructor in the 'Energy and Sustainability Engineering' graduate certificate and MEng degree programs at UI (http://EaSE.Illinois.edu). Once fabricated, film properties are evaluated in both as-deposited and annealed conditions using quantitative techniques, including transmission electron microscopy, electron energy loss spectroscopy, and energy dispersive X-ray spectroscopy. The results for film growth, microstructure and composition are then analyzed in terms of kinetic models for the component steps in the synthesis process. Additionally, in exploratory work, incorporation of Cr is examined using the Cr(B3H8)2 precursor developed by a collaborator. This precursor, which contains no heteroatoms other than hydrogen, has previously been demonstrated by the co-PI to deposit high quality CrB2 films, hence, it is expected to work well in combination with Hf(BH4)4. Film growth, including the pursuit and validation of chemically safe synthesis routes, analysis and testing actively involve the GOALI partner, UES Inc., facilitated by regular communication and extended visits of personnel between sites. Successful protocols are then transferred to industry. 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.