UC Researcher Awarded $400K NSF Grant for Fabricating and Characterizing Hollow Metallic Scaffolds

By:      Ashley Duvelius
Date:   August 29, 2017

Dr. Ashley Paz y Puente, University of Cincinnati materials science researcher and assistant professor, is revolutionizing materials for a wide range of applications ranging from batteries to commercial jets to tissue regeneration with her advances in the production of Nickel (Ni)-based metallic scaffolds.  

Dr. Ashley Paz y Puente

Dr. Ashley Paz y Puente

Ashley Paz y Puente, assistant professor of mechanical and materials engineering at the University of Cincinnati (UC) College of Engineering and Applied Science (CEAS), has been awarded a three-year, $400,741 grant from the National Science Foundation (NSF). Beginning September 1, 2017 through August 31, 2020 (estimated), Paz y Puente will lead as the Principal Investigator of her project, “Gas-Phase Alloying and Sintering Kinetics of 3D Printed Ni Scaffolds.”

Garnering the increasing attention of several industries is the fabrication of metallic scaffolds, or lattice structures, with progressively complex geometries. Thanks to their open porosity, these structures possess a rare coupling of low density and high surface area, making them the ideal candidates for a wide array of applications ranging from batteries to commercial airplanes to biomedical implants.

Yet, the challenge remains in fabricating these technologically important alloys that house such useful geometries. The ever-beneficial increase in porosity often compromises the mechanical properties that are important in maintaining the structural stability of the scaffold. Thus, traditional manufacturing and newer additive manufacturing techniques (commonly referred to as 3D printing) often fall short in successfully creating these open-structure materials.

Paz y Puente explains, “While the ability to create near-net-shape metallic parts with high geometric complexity has made powder-bed additive manufacturing techniques attractive, many engineering relevant alloys are difficult to fabricate with high quality due to poor sintering, internal porosity, and cracking.”

Paz y Puente and her team of UC CEAS graduate students—Safa Khodabakhsh, Arun Bhattacharjee, Haozhi Zhang, Ajith Achuthankutty, and Aditya Patibandla—have been awarded the prestigious NSF grant to conduct further research aimed at providing fundamental knowledge required for the development of an alternative process for successfully making these metal scaffolds.

The main material system of interest in this research is the basis for Nickel (Ni)-based superalloys, which are most well-known for their use in jet engines. By creating this material in an open structure, the weight can be significantly reduced. Additionally, the increased surface area and permeability of a scaffold allow for highly efficient active cooling of the material resulting in the ability to operate at higher temperatures.

Paz y Puente and her group theorize a new process for producing these metal scaffolds using a two-step approach controlled by thermodynamics and kinetics.

She describes, “One alternative approach is to decouple the printing and alloying by using particle-based ink printing to create the desired geometry from a pure metal or simple alloy that is known to print successfully, and then further alloy the part in a separate step using a deposition process and homogenization to reach the target composition. This process will enable an assortment of different materials to be produced from the same precursor printed metal part."

To accomplish this, Paz y Puente’s team will work with different characterization techniques to investigate the relationships between the processing, structure, and properties of these materials. They will focus on developing ways to combine additive manufacturing and coating deposition processes to fabricate metallic scaffolds while studying the governing diffusion and phase transformation kinetics.

Paz y Puente addresses their hypothesis, “Our new two-step approach is ideal for creating metallic scaffolds, taking advantage of the open porosity and small diffusion distances. The overall aim of this project is to study the fundamental sintering and alloying kinetics of such scaffolds using a combination of conventional metallography and in situ X-ray tomographic microscopy. The phase and pore evolution will be systematically studied as a function of geometry, composition, powder and strut size, and anneal time and temperature and the mechanical behavior will be computationally predicted and experimentally determined.”

Tomographic reconstruction showing Kirkendall porosity (eyes and mouth of the smiley) in a metallic wire

Tomographic reconstruction showing Kirkendall porosity (eyes and mouth of the smiley) in a metallic wire


If successful, this work could be extended to other alloying additions, beyond Chromium and Aluminum as Paz y Puente has proposed for this project, by using the same or similar techniques to fabricate more complex alloys closer to those of commercial Ni-based superalloys. The research team expects their results to promote technological innovations that will benefit a number of manufacturing sectors including energy, automotive and biomedical industries. The commercial airlines industry invests billions of dollars in the safe transportation of both people and cargo, and therefore, even a slight reduction in weight and/or engine efficiency would positively result in significantly lower costs, better fuel efficiencies, and overall, a greatly reduced carbon footprint.

In addition to the technological and innovation impacts of the work, Paz y Puente is enthusiastic about and has added an outreach and engagement component into her proposal. She has been actively recruiting undergraduate students to work on the project itself. Also, she plans to teach an Honors Seminar through the University Honors program in which she will teach fundamental materials science concepts to undergraduate students who will in turn be asked to develop their own hands-on workshop activity, which they will conduct at an outreach event with local high school students.

Paz y Puente explains, “In particular, I am working to partner with Saint Ursula Academy, which is a local all-girl Catholic high school, and also Hughes-STEM to engage with traditionally underrepresented groups in STEM and get them involved in this research effort. Additionally, I would like to help organize and launch an Expanding Your Horizons Conference here in Cincinnati. Expanding Your Horizons is a program in which middle-school and high-school girls participate in STEM workshops led primarily by adult women in STEM careers. I would also like to create more outreach activities aimed at engaging high school and undergraduate students, particularly young women, and increasing their participation in this research as well as the materials science field and STEM fields, in general.”

Paz y Puente joined UC CEAS in August 2016 as part of the College’s 50-in-5 hiring initiative and has been conducting diffusion-related research for the past ten years and has extended that fundamental diffusion background and experience to this research. She stresses that the importance of this research stretches far beyond technological applications into the reaches of our everyday lives, “Remember, everything around us is made out of something, and therefore, you can’t make it without materials!”

Paz y Puente received her BS in Mechanical Engineering from the University of Central Florida in 2011. Paz y Puente earned her MS and PhD in Materials Science and Engineering from the University of Central Florida and the Northwestern University in 2012 and 2016, respectively. Her research interests include physical metallurgy, phase transformations; diffusion reactions and kinetics; diffusion coatings; Kirkendall effect; metallic microtubes; intermetallics; high temperature alloys; shape memory alloys; additive manufacturing; metallic scaffolds; and X-ray tomography.

 

About the UC College of Engineering and Applied Science
The UC College of Engineering and Applied Science unleashes education by immersing students in a rigorous and innovative curriculum and culture of real-world, experience-based learning. The value of a CEAS degree is unparalleled, providing elevated placement, greater earning potential and unlimited post-graduate options. Because here, 
WE ENGINEER BETTER™.

About the University of Cincinnati
The University of Cincinnati offers students a balance of educational excellence and real-world experience. UC is a public research university with an enrollment of more than 44,000 students and has been named "Among the top tier of the Best National Universities," according to U.S. News & World Report.