Advances in Powder and Ceramic Materials Science: Structure Design and Processing
Sponsored by: TMS Extraction and Processing Division, TMS Materials Processing and Manufacturing Division, TMS: Materials Characterization Committee, TMS: Powder Materials Committee
Program Organizers: Bowen Li, Michigan Technological University; Shefford Baker, Cornell; Huazhang Zhai, Beijing Institute of Technology; Kathy Lu, University of Alabama Birmingham; Rajiv Soman, Eurofins EAG Materials Science LLC; Faqin Dong, Southwest University of Science and Technology; Jinhong Li, China University of Geosciences (Beijing); Ruigang Wang, Michigan State University; Eugene Olevsky, San Diego State University

Monday 8:30 AM
March 15, 2021
Room: RM 37
Location: TMS2021 Virtual

Session Chair: Ruigang Wang, The University of Alabama; Jinhong Li, China University of Geosciences (Beijing)


8:30 AM  Invited
Structural Integrity of Complex Oxide Scales for Improved Oxidation Resistance of Ultra-high Temperature Ceramics: Ambreen Nisar1; Cheng Zhang1; Benjamin Boesl1; Arvind Agarwal1; 1Florida International University
    Ultra-high temperature ceramics (UHTCs) such as Hafnium carbide (HfC) and Tantalum carbide (TaC) are potential candidates for hypersonic applications due to their extremely high melting temperature and oxidation resistance. Solid-solution formation in (Hf, Ta)C system has shown to improve the thermo-mechanical performance of these UHTCs. The formation of complex oxide Ta2H6O17 phase during the oxidation of (Hf, Ta)C improves its oxidation resistance by limiting the oxygen diffusion. Hence, it is imperative to study the chemical and structural integrity of the complex Ta2H6O17 oxide. In the present study, Hafnium oxide (HfO2) and Tantalum oxide (T2O5) powders in varying compositions were ball milled and spark plasma sintered (SPS) at 1300 °C to obtain Ta2H6O17 phase. Synthesis of the Ta2H6O17 phase and its effect on the thermal stability and mechanical integrity will be reported in this presentation.

8:50 AM  Invited
New Insights into Sintering Processing for Solid State Electrolytes – A Phase-Field Simulation Study : Rongpei Shi1; Marissa Wood1; Jose Espitia1; Xiaosi Gao2; Joshua Hammons1; LiWen Wan1; Shin Young Kang1; Dive Mukund1; Kwangnam Kim1; Tae Wook Heo1; Brandon Wood1; Jianchao Ye1; 1Lawrence Livermore National Laboratory; 2Cornell University
    For all-solid-state batteries, the key properties of solid electrolytes (e.g., ionic conductivity, mechanical properties, and critical current density) are governed by microstructural features, such as internal porosity, grain size and orientation, formed during sintering processing. By using 3D phase-field simulation, we investigated multiple concurrent microstructural processes and their interplay during sintering, including surface coarsening, grain growth, and pore shrinkage. We analyzed quantitatively the individual and coupled effect of various mass transport mechanisms on microstructural evolution and kinetics as a function of interfacial (i.e., free surfaces and grain boundaries) properties and powder particle size and distribution. Dominant mechanisms are found to vary over the course of the process. The predicted dependence between densification kinetics and particle size agrees well with experimental observations. The proposed modeling approach allows for rapid discovery of optimum processing conditions, leading to desired microstructures of solid electrolytes with improved kinetics.

9:10 AM  
Flash Sintering of Gadolinium-doped Ceria: Densification and Microstructure: Tarini Prasad Mishra1; Viviana Avila2; Rubens Roberto Ingraci Neto2; Rishi Raj2; Olivier Guillon1; Martin Bram1; 1Forschungszentrum Jülich GmbH; 2University of Colorado Boulder
    Ceria based materials have good chemical stability, ionic conductivity and catalytic properties in redox processes. These unique properties make them attractive for applications in various electro-chemical devices. Gadolinium Doped Ceria (GDC) is one of the promising representatives of this class of materials. However, Sintering of GDC is usually done in air at high temperatures, in the range of 1400° C-1600° C, and dwelling time of several hours to achieve almost theoretical density. A promising approach to achieve high densification rate at lowered temperatures is electric field assisted sintering. In this work, Ce0.9 Gd0.1 O1.95-δ (i.e. GDC10, gadolinium-doped ceria, with Gd 10 mol %) has been used for conducting a related flash sintering study. A novel mode of flash sintering known as current rate flash shown to be advantageous as the densification of the material can be better controlled than in conventional flash sintering and the microstructure can be tuned.

9:30 AM  
Processing of TiB2-TiC Based Materials with Fine Microstructure and Improved Mechanical Properties: Zhezhen Fu1; 1University of Wisconsin Platteville
    A group of TiB2-TiC based composite materials with fine microstructures and improved mechanical properties were developed for structural applications. First, a novel carbon coating precursor method was utilized to synthesis ultra-fine TiB2 and TiC powders with high purity. The synthesized powders were further used to process cermet materials with various metal additives such as Ni, Co, and high-entropy alloys. Due to the advantages of the fine particle size and high purity of the synthesized powders, the composite materials can be densified to high relative densities (>97%) at lower temperatures (lower up to 300°C). The materials also have very fine grain size (as fine as 1µm) and uniform microstructures (e.g. elongated grain structure due to the unique grain growth mechanism). Due to such microstructures, the materials have improved mechanical properties such as hardness, fracture toughness, and flexural strength. Hardening, toughening, and strengthening mechanisms were further discussed based on the microstructures.

9:50 AM  
Discovery of Novel High-entropy Ceramics via Machine Learning: Kevin Kaufmann1; William Mellor1; Tyler Harrington1; Chaoyi Zhu1; Alexander Rosengarten1; Daniel Maryanovsky1; Kenneth Vecchio1; 1University of California, San Diego
    Although high-entropy materials are attracting considerable interest due to a combination of useful properties and promising applications, predicting their formation remains a hindrance for rational discovery of new systems. Experimental approaches are based on intuition and/or expensive trial and error strategies. Most computational methods rely on the availability of sufficient experimental data and computational power. This work proposes a machine learning framework leveraging thermodynamic and compositional attributes of a given material for predicting the entropy-forming ability of disordered metal carbides. The approach’s suitability is demonstrated by comparing values calculated with density functional theory to ML predictions. Finally, the model is employed to predict the entropy-forming ability of new compositions; several of which are validated by additional density functional theory calculations and experimental synthesis. Compositions were specifically selected because they contain all three of the Group VI elements (Cr, Mo, and W), which do not form room temperature-stable rock-salt monocarbides.

10:10 AM  
Elucidating the Influence of the Thermodynamics, Kinetics, and Chemistries of Molten Salts to Synthesize Ceramics for Energy Applications: Benjamin Levitas1; Katsuyoshi Kakinuma2; Srikanth Gopalan1; 1Boston University; 2University of Yamanashi
    The molten salt synthesis (MSS) of ceramic materials drastically increases the reaction kinetics compared to the significant energy and time intensive high temperature calcination method. However, studies utilizing the MSS fail to address a critical aspect of this method: the chemistry inherent to each molten salt system. In this work, we investigate the synthesis of La0.8Sr0.2MnO3 (LSM) in LiCl-KCl eutectic and KNO3 molten salts. The high acidity of Li+ establishes a thermodynamic barrier that impedes Sr nucleation and thus does not favor LSM formation in LiCl-KCl eutectic. Bearing this result in mind, we performed a single-step KNO3 MSS of core-shell La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) – La0.8Sr0.2MnO3 (LSM) powders for solid oxide fuel cell cathodes in times as short as 10 minutes. The results presented further elucidate the influence of salt chemistry in the MSS, and demonstrate an expeditious method to synthesize highly relevant single phase and core-shell ceramic materials for energy applications.

10:30 AM  
Effects of Yttria Content and Atmosphere on Structural Evolution of Highly Porous Yttria-stabilized Zirconia Aerogels: Nathaniel Olson1; Frances Hurwitz2; Haiquan Guo3; Jessica Krogstad1; 1University of Illinois Urbana Champaign; 2NASA Glenn Research Center; 3Ohio Aerospace Institute
    Aerogels demonstrate extraordinarily low thermal conductivity and low density, presenting a promising form of lightweight insulation for aerospace applications. The primary challenge is stabilization of the highly porous structure at temperatures to 1200 °C. Upon collapse of the pore structure, the favorable thermal properties and low density are diminished. Yttria-stabilized zirconia (YSZ) aerogels are synthesized to investigate the effect of composition on morphology, phase behavior, and thermal stability (specific surface area, pore size distribution). This work demonstrates the improvement in thermal stability of zirconia aerogels with increased yttria content. Furthermore, changes in structure and surface chemistry of YSZ aerogels are studied in both oxidizing and inert atmospheres. With an improved understanding of aerogel structure and performance, metal oxide aerogels can be developed to withstand the extreme environments of space exploration.