Advances in Powder and Ceramic Materials Science: High Entropy Ceramics III
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; Dipankar Ghosh, Old Dominion University; Eugene Olevsky, San Diego State University; Kathy Lu, University of Alabama Birmingham; Faqin Dong, Southwest University of Science and Technology; Jinhong Li, China University of Geosciences; Ruigang Wang, Michigan State University; Alexander Dupuy, University of Connecticut
Thursday 8:30 AM
March 23, 2023
Room: 30A
Location: SDCC
Session Chair: Alexander Dupuy , University of California Irvine
8:30 AM Introductory Comments
8:35 AM Invited
Interplay Between Structure, Charge, and Spin in Entropy-Stabilized Oxides for Widely Tunable Responses: John Heron1; 1University of Michigan
Entropy-stabilized oxides demonstrate a new and unprecedented degree of chemical control in materials. This broadens the compositional space of crystalline oxides and presents opportunities to understand and explore the local chemical and structural disorder. Here, I will discuss the control of stereochemically-driven structural disorder in single crystalline, rocksalt, (MgCoNiCuZn)O-type entropy-stabilized oxides through the incorporation of Co, Cu, and Mg cations. We harness the disorder to tune the degree of glassiness in the anisotropic antiferromagnetic magnetic structure. Electron transport measurements reveal a widely tunable conductivity via the Mg concentration that is mediated by hopping and correlated to the global disorder and defect density. Our findings demonstrate novel interplay between local and global structure, charge, and spin states in entropy-stabilized oxides for tunable magnetic and electronic responses.
8:55 AM
Rare-earth Doped Polycrystalline Alumina for High-energy Laser Applications: Ross Turner1; Xingzhong Wu1; Yasuhiro Kodera1; Javier Garay1; 1UC San Diego
This work explores processing of rare-earth doped aluminum oxide (or alumina) powders and the densification of bulk ceramic alumina as optical materials. Alumina has a much higher thermal conductivity when compared to traditional laser host materials such as Yttrium Aluminum Garnet (YAG) or other sesquioxides, and solid state laser power directly scales with the thermal conductivity of the laser host material. Doping alumina with rare-earths has historically been difficult but some new methods will be shared with respect to polycrystalline alumina. Processing techniques and conditions that significantly affect the ceramic microstructure will be presented. In addition we will explore the specific impact of the varying microstructure on the bulk ceramic optical properties. These bulk ceramics show high transmission at both the absorption and emission wavelengths, demonstrating their capability as new laser host materials for high-energy laser applications.
9:15 AM
The Role of Aliovalent Dopants in Multiphase Entropy Stabilized Oxides: Jacob Norman1; Alexander Dupuy1; Julie Schoenung1; 1UCI
Entropy stabilized oxides exhibit a reversible phase transformation between single-phase and multiphase states, giving rise to controllable phase heterogeneity. This presents an opportunity to produce oxide materials with highly controlled phase states, microstructures, and behavior. We hypothesize that doping with aliovalent oxides is an additional strategy to engineer the phase transformation behavior by changing the defect chemistry and promoting the formation of enthalpy driven phases. Here we test his hypothesis by synthesizing (CoCuMgNiZn)O (2+ valence) with single-valence and mixed-valence oxide dopants. Examples include oxides of Fe, Cr, Mn, and Ti. These doped powders are consolidated through conventional sintering and then heat-treated to examine the phase evolution as a function of temperature. The influence of dopant and heat-treatment on microstructure and phase state is characterized through X-ray diffraction and electron microscopy. The influence of the dopant and phase evolution on functional and mechanical behavior are also explored.
9:35 AM
Toughening Mechanisms of Nano-oxide Dispersion Strengthening (NDS) on CoCuNiFeMn High Entropy Alloys with Nano-twin Fabricated via Powder Metallurgy: Hansung Lee1; Ashutosh Sharma1; Byungmin Ahn1; 1Ajou University
High entropy alloys (HEAs) are multicomponent with five or more elements, exhibit simple solid solution due to a high configurational mixing entropy owing to constituent elements. Powder metallurgy is simple and scalable method fabricating HEAs that consists of mechanical alloying and densification. In this study, different weight fractions of WO3 nanoparticles were added to the CoCuNiFeMn HEAs. The fabrication of the NDS-HEAs was carried out by high energy milling (300rpm, 30h) and spark plasma sintering (900℃, 8min). The microstructural evolution in NDS-HEAs was observed by XRD, FE-SEM, and TEM. The strengthening mechanisms of the nano-dispersed phases was assessed by microhardness, nanoindentation, and tensile test. Formation of nano-twins in the FCC matrix was enhanced with increasing fraction of nanoparticles. The amount of the WO3 had an impact on the twin lamellae size, as well as 3wt.% of WO3 nanoparticles can be optimized for the microstructural and mechanical performance of NDS-HEAs.
9:55 AM Break
10:15 AM
Tunable Self-assembled Metal and Metal-oxide Nanostructures Embedded in Complex Concentrated Oxide Thin Films: William Bowman1; Xin Wang1; Huiming Guo1; 1University of California, Irvine
Complex concentrated oxides (CCOs), such as the rock salt (Co,Cu,Mg,Ni,Zn)O, show entropy-enhanced stability and compositionally tunable properties desired for next-generation functional materials like cathodes, solid electrolytes, catalysts, and thermal insulators. However, metal and metal-oxide nanostructure design as an affordable and efficient route to tune properties is less investigated and more complicated in complex concentrated materials. Here, we use pulsed laser deposition (PLD) to fabricate rock salt and perovskite oxide CCO thin films with 1D, 2D, and 3D nanostructures. We tunable formation of metal- and metal oxide-CCO nanocomposite structures during PLD thin film growth. The mechanisms of nanostructure formation are under detailed investigation down to the atomic scale using a suite of physical and chemical characterization methods coupled with computational calculations of point defect complex formation energetics. The thin films’ functional and electrochemical properties are also under investigation and will be discussed.
10:35 AM
Tunable Grain Boundary Conductivity in Sodium Doped High Entropy Oxides: Justin Cortez1; Alexander Dupuy1; Hasti Vahidi1; Yiheng Xiao1; William Bowman1; Julie Schoenung1; 1University of California Irvine
Concerns with the safety and sourcing of lithium-ion batteries have prompted significant research into sodium-based systems. High entropy oxides (HEO), which contain five or more oxide components in equimolar quantities, are ideal for battery applications due to their ability to accommodate a substantial quantity of mobile charge carriers (such as Na), while also demonstrating promising stability, conductivity, and capacity retention. Here we investigate the influence of sodium doping and microstructure on charge transport in bulk sintered (Cu,Co,Mg,Ni,Zn)1-xNaxO. We find that the conductivity increases with increasing dopant amount, up to 1.4x10-5 S×cm-1 at x=0.33. Much of this increase is attributed to the high grain boundary conductivity, which originates from a NaCoO2 layered structure that forms in the grain boundaries during high temperature sintering. The relative contributions of the grain boundaries and the bulk to the charge transport are discussed, along with the ability to engineer grain boundaries in doped HEO materials.
10:55 AM
Compositionally Complex Perovskite for Solar Thermochemical Water Splitting: Dawei Zhang1; Héctor Santiago2; Boyuan Xu3; Cijie Liu2; Trindell Jamie4; Wei Li2; Jiyun Park3; Josh Sugar5; Anthony McDaniel4; Stephen Lany6; wenyuan Li2; Hanchen Tian2; Yue Qi3; Xingbo Liu2; Jian Luo1; 1University of California San Diego; 2West Virginia University; 3Brown University; 4Sandia National Laboratories; 5Sandia National laboratory; 6National Renewable Energy Laboratories
Solar thermochemical hydrogen generation (STCH) is emerging as a promising approach for eco-friendly production of solar fuels. However, STCH materials often suffer from thermodynamic and kinetics limitations and there is a limited compositional space to search and engineer existing STCH materials. Here, we introduce a new (medium- to high-entropy) compositionally complex design for STCH materials exemplified by {La,Sr}{Mn,Fe,Co,Al}O3. Co is the most redox active element. A parallel Monte Carlo and density functional theory calculation further elucidates that the favorable Co redox originates from local excess space due to Co bond stretching that outpaces the tendency to generate vacancies near Mn4+. The optimal STCH performance in is achieved due to a tradeoff of thermodynamic and kinetic properties, which outperforms the simpler benchmark (La,Sr)CoO3-δ. In a broader perspective, the vast compositional space in compositionally complex ceramics (CCCs) offers new possibilities to design and tailor STCH materials.