Controlled Synthesis, Processing, and Applications of Structural and Functional Nanomaterials: Nanoparticles & Nanocomposites I
Sponsored by: ACerS Basic Science Division, ACerS Electronics Division, ACerS Engineering Ceramics Division
Program Organizers: Haitao Zhang, University of North Carolina at Charlotte; Gurpreet Singh, Kansas State University; Kathy Lu, University of Alabama Birmingham; Edward Gorzkowski, Naval Research Laboratory; Jian Shi, Rensselear Polytechnich University; Michael Naguib, Tulane University; Sanjay Mathur, University of Cologne
Wednesday 8:00 AM
October 20, 2021
Room: B240/241
Location: Greater Columbus Convention Center
Session Chair: Edward Gorzkowski , Naval Research Laboratory; Kathy Lu, Virginia Tech
8:00 AM Invited
Controlling Grain Growth with Anisotropic Interfacial Energy and Heterogeneous Segregation: Amanda Krause1; 1University of Florida
Retaining nano-sized grains during processing is challenging with conventional sintering processes. Efforts to mitigate grain growth often rely on sintering aids to lower processing temperatures or dopants that segregate to the grain boundary to induce solute drag. However, anisotropic grain boundary energy often results in heterogeneous solute distribution and, thus, variation in grain boundary behavior. Here, we investigate how anisotropic grain boundary energy distributions lead to variations in irregular grain growth behavior in doped Al2O3, SrTiO3, and MgAl2O4. Grain boundary energy, measured with atomic force microscopy, is correlated with the boundary’s atomic structure and chemistry, which is characterized at the atomic scale with aberration-corrected scanning transmission electron microscopy. The advantages and challenges for using anisotropic grain boundary energy for controlling grain growth will be discussed.
8:30 AM
Low Temperature Synthesis of Metastable Tetragonal Yttria Doped Hafnia T-(Y-HfO2) Nanoparticles Through Mechanochemical Processing and Annealing: Zanlin Qiu1; Cheng-han Li1; Joerg Jinschek1; Pelagia-Irene (Perena) Gouma1; 1Ohio State Universsity
Tetragonal hafnia (T-HfO2) has shown great potential in MOSFET applications, because of its high dielectric constant and wide bandgap. However, a temperature of 1500-1800 ℃ and a critical particle size of 4-10 nm is required to stabilize metastable T-HfO2, preventing a stable T-phase at room temperature. Here, a viable route for stabilizing thermodynamically unfavored phases in the HfO2 system is described. Specifically, yttrium(Y)-doped T-HfO2 nanoparticles have been stabilized with a size of ~58nm using mechanochemical processing followed by subsequent annealing. Structural characterization using XRD, Raman spectroscopy and HRTEM imaging revealed the transformation pathway as M-HfO2 →amorphous phase + T-HfO2 seeds → T-HfO2. (Note: the first process occurs during milling and the second process occur during annealing) The stabilization of T-HfO2 is attributed to the grinding effect in the milling process, decreasing the grain size and simultaneously increasing the surface energy into the range stabilizing the tetragonal phase
8:50 AM Invited
Design of Nanoparticles from Environmentally Benign Precursors: Surojit Gupta1; 1University of North Dakota
Sustainability has become important and integral component of materials synthesis. Research and development of materials from agricultural biomass is critical from sustainability perspective. Lignin, cellulose, and hemicellulose are the important constituents of biomass. Among these compounds, lignin is the most difficult to valorize. In the presentation, I will present the research efforts of my research group to develop and design biomass-based nanomaterials with special emphasis on lignin. Detailed microstructural and particle size characterization of these novel materials will be presented.
9:20 AM
Surface Oxidation Behavior of FeNi-based Metal Amorphous Nanocomposite (MANC) for High Speed Motor Applications: James Egbu1; Paul Ohodnicki2; Ruishu Wright3; John Baltrus3; Michael McHenry1; 1Carnegie Mellon University; 2University of Pittsburgh; 3National Energy Technology Laboratory
New interest in high performance soft magnetic materials (SMMs) have been fueled by the need to lower losses at higher operating frequencies while maintaining high flux density and tunable permeability in electrical motors, transformer, and generator applications. Conventional SMMs like electrical steels and Fe-based metal amorphous nanocomposite (MANC) alloys are dominated by eddy current losses at high frequencies. Recent breakthrough in high-performance FeNi MANC have shown promise in reducing eddy current losses as compared to electrical steels. Their intrinsic adherent native surface oxide layer provides sufficient electrical insulation to reduce interlaminate eddy current losses. However, notwithstanding advances in MANCs, there exists a gap in literature on investigations of the surface oxide layer responsible for significant reduction of interlaminate eddy current losses in magnetic cores. This work presents a detailed characterization of the surface oxide, oxidation behavior, and relationship between oxide thickness and resistivity of a new FeNi MANC alloy (Fe70Ni30)80Nb4B14Si2.
9:40 AM
Mechanisms of Hillock Formation and Nanostructural Self-assembly during Vapor-deposition of Phase-separating Alloy Films: Rahul Raghavan1; Kumar Ankit1; 1Arizona State University
The formation of protruding grains, or hillocks, on the surface of nanostructured alloy films, is typically attributed to internal residual stresses arising due to a difference in thermal expansion coefficients of the film and the substrate. However, recent nanostructural characterization of phase-separated alloy films has indicated the role of disparate elemental mobilities which can contribute to the growth of hillocks. Given these findings, we report a 3D phase-field approach to numerically investigate the role of deposition rates, phase fraction, and separation kinetics, on the nanostructural self-assembly and growth of hillocks in immiscible alloy films. With the aid of n-point polytope analysis, we explore the processing conditions under which nano-sized hillocks evolve in arrays of distinguishable symmetries. Based on an extensive parametric study, we elucidate the influence of adatom mobility and surface contact angles on the hillock formation in vapor-deposited alloy films.