Journal of the American Ceramic Society Awards Symposium: Journal of the American Ceramic Society Awards Symposium
Sponsored by: ACerS
Program Organizers: William Fahrenholtz, Missouri University of Science and Technology

Tuesday 8:00 AM
October 11, 2022
Room: 408
Location: David L. Lawrence Convention Center

Session Chair: William Fahrenholtz, Missouri University of Science and Technology


8:00 AM Introductory Comments

8:10 AM  Invited
Historical and Basic Introduction to Antiferroelectrics: Clive Randall1; Ian Reaney2; Zhongming Fan1; Long-Qing Chen1; Susan Trolier-McKinstry1; 1Pennsylvania State University; 2University of Sheffield
    Antiferroelectric materials are far less frequently discovered than their ferroelectric and ferroelastic counterparts. In this presentation, we will give some insight into the reasons for this and the peculiarity of antiferroelectrics in relation to the ferroelectric transitions. This will also be extended to consider them from a perspective of the soft mode condensation, and also the basic crystal chemistry within the perovskite family, where they are mostly found. There are also other basic characteristics of antiferroelectrics in relation to their prototypic to antiferroelectric phase transition. These empirically identified characteristics are important, as antiferroelectric behavior can often be mistaken and inferred from a misinterpretation of the various characteristics. In particular, double hysteresis loops are not necessarily demonstrating an antiferroelectric material. In addition to the fascinating science that underpins ferroelectricity, we will also discuss some important application areas, of which the most notable is the high energy density electrostatic capacitor.

8:30 AM  Invited
Flash Sintering: A Paradigm Shift for Processing of Ceramics: Tarini Prasad Mishra1; Rishi Raj2; Olivier Guillon1; Martin Bram1; 1Forschungszentrum Julich Gmbh; 2University of Colorado Boulder
    Flash-sintering is a promising approach for the ultra-rapid densification of ceramics at low furnace temperatures under an applied electric field and current. In the present work, the influence of the electrical parameters on the onset temperature, densification behavior, and microstructure of the flash sintered samples will be discussed on the example of Gadolinium doped-ceria (GDC). In particular, we focus on the development of a processing map that delineates the safe and failed regions for flash sintering over a wide range of applied current densities and electric fields for GDC. Hot spot and crack formation due to current localization are identified as two distinct failure modes in flash sintering. Furthermore, controlling the densification and tailoring of the microstructure for GDC by an innovative flash sintering mode known as the “Current-rate Flash sintering” was achieved. The electrical conductivity of the flash sintered and conventional sintered samples were found to be identical.

8:50 AM  Invited
Synthesis of β-MoO3 Whiskers by Thermal Evaporation Method and Its Application in Production of 99Mo/99mTc: Chu Ngo1; Tatsuya Suzuki1; Dung Do1; Tadachika Nakayama1; Koichi Niihara1; Hieu Nguyen2; Hisayuki Suematsu1; 1Nagaoka University of Technology; 2National Institute for Materials Science (NIMS)
    In developing the 99Mo/99mTc extraction process using water utilizing the hot atom effect in the neutron capture method, the β-MoO3 1D structure (whiskers) with a good filtering property was considered as a more suitable target than used α-MoO3 powder. Therefore, β-MoO3 whiskers were attempted to synthesize using the thermal evaporation method. By heating α-MoO3 powder from 750 to 1000 ℃ and cooling its vapor, the β-MoO3 whiskers with an average width of 10 nm and length above 1 mm were synthesized and confirmed by XRD and lattice image analyses. These β-MoO3 whiskers were irradiated in an experimental nuclear reactor to produce 99Mo/99mTc. After irradiating, from the γ-ray spectrum measurement, 66.8% of 99Mo formed in the β-MoO3 whiskers was extracted in water. From this result, the β-MoO3 whiskers were considered to be a promising irradiation target in production of 99Mo/99mTc, from which water can be used to extract the radioisotopes.

9:10 AM  Invited
Observation of the Electromechanical Responses of (Na,K)NbO3 under Combined External Mechanical and Thermal Fields: Neamul Khansur1; Alexander Martin2; Keiichi Hatano3; Kenichi Kakimoto2; Dominique De Ligny1; Kyle Webber1; 1Friedrich-Alexander-Universität Erlangen-Nürnberg; 2Nagoya Institute of Technology; 3Taiyo Yuden Co., Ltd.
    For (Na,K)NbO3 based systems, the monoclinic (or orthorhombic) to tetragonal phase boundary plays an important role on the overall electromechanical response. This phase boundary can be shifted via external thermal, electrical, and mechanical fields, which in return has an effect on the ferroelectric and piezoelectric response. As such, it is important to understand the processes behind these changes, as in applications for ferroelectric materials, large thermal electrical, and mechanical fields are typically applied to the electro-active material. At first, the influence of thermal and compressive mechanical fields on the small-signal relative permittivity and direct piezoelectric coefficient of polycrystalline Li-modified (Na0.5K0.5)NbO3 will be discussed. Interestingly, anomalies occurred in both the dielectric and piezoelectric properties in the vicinity of the monoclinic-tetragonal (M-T) phase boundary. To reveal changes to the crystallographic phase of Li-modified (Na0.5K0.5)NbO3 under the same fields, in situ combined temperature- and uniaxial compressive stress-dependent Raman spectroscopy was used.

9:30 AM  Invited
Synthesis, Densification, Microstructure, and Mechanical Properties of High-entropy Carbide Ceramics: Lun Feng1; William Fahrenholtz1; Gregory E. Hilmas1; Wei-Ting Chen1; 1Missouri University of Science and Technology
    High-entropy carbide powders were synthesized by a two-step process consisting of carbothermal reduction followed by solid solution formation. Nominally pure (Hf,Zr,Ti,Ta,Nb)C in a single-phase rock salt structure had an average particle size of about 550 nm and an oxygen content of 0.2 wt%. Nominally pure and dense (Hf,Zr,Ti,Ta,Nb)C ceramics with an average grain size of 1.2 µm were produced at 1900°C by hot pressing. Dense ceramics had a Young’s modulus of 452 GPa, Vickers hardness of 24.8±0.8 GPa, fracture toughness of 3.5±0.3 MPa·m1/2, and flexural strength of 421±27 MPa at room temperature. With increasing the temperature, flexural strength was maintained until 1800°C, then decreased from 318±21 MPa at 2000°C to 93±10 MPa at 2300°C.The degradation of flexural strength above 1800°C was attributed to a decrease in dislocation density that was accompanied by an increase in dislocation motion. These are the first reported flexural strengths of HEC ceramics at elevated temperatures.

9:50 AM Break

10:20 AM  Invited
Unique Performance of Thermal Barrier Coatings Made of Yttria Stabilized Zirconia at Extreme Temperatures (> 1500°C): Robert Vassen1; Daniel Emil Mack1; Martin Tandler1; Yoo Jung Sohn1; Doris Sebold1; Olivier Guillon1; 1Forschungszentrum Jülich GmbH
    Yttria stabilized zirconia (YSZ) as state of the art material for thermal barrier coatings has unique properties, further efficiency improvement is limited due to its maximum temperature capability of about 1200°C. Above this temperature the deposited metastable t´ phase undergoes a detrimental phase transformation as well as enhanced sintering. We show here for the first time experimentally, that under typical cycling conditions not the dwell time at elevated temperatures plays the major role for the reduced lifetime but the transient cooling rates. If cooling rates were reduced, TBC systems could be operated in a burner rig at a surface temperature well above 1500°C without lifetime reduction. These astonishing findings can be explained by the evaluation of energy release rate peaks during fast transient cooling in combination with the phase evolution. Furthermore, also recent experiments with dwell times included during the cooling phase will be presented and discussed.

10:40 AM  Invited
Micromechanics of Machining and Wear in Hard and Brittle Materials: Brian Lawn1; Oscar Borrero-Lopez2; Han Huang3; Yu Zhang4; 1National Institute of Standards and Technology; 2Universidad de Extremadura; 3The University of Queensland; 4University of Pennsylvania
    Hard and brittle solids with covalent/ionic bonding are used in a wide range of modern-day manufacturing technologies. Optimization of a shaping process can shorten manufacturing time and cost of component production, while extending component longevity. The same process can contribute to wear and fatigue degradation in service. Educated development of advanced finishing protocols for this class of solids requires a comprehensive understanding of damage mechanisms at small-scale contacts from a materials perspective. Here, we present basic science of deformation and removal modes pertinent to contact events in the context of brittle and ductile machining as well as severe and mild wear. Essentials of brittle–ductile transitions in micro- and nano-indentation fields are outlined, with distinctions between blunt and sharp contacts, axial and sliding loading, and brittle and quasiplastic materials. The central role of microstructure in damage modes and material removal mechanisms is highlighted. Pathways to future research—experimental, analytical, and computational—are indicated.

11:00 AM  Invited
Initial Fragmentation and Granular Transition of Ceramics: Lori Graham-Brady1; Amartya Bhattacharjee1; Ryan Hurley1; 1Johns Hopkins University
    As armor ceramics are impacted, crack growth and coalescence lead to an initial state of fragmentation, causing a granular medium that resists penetration through various energy dissipation mechanisms, such as granular friction and re-fragmentation. The fragmented material also abrades the penetrator itself. Hence, initial fragmentation and granular transition of ceramics play a vital role in the penetration resistance of ceramics. Instantaneous crack statistics predicted from a previously developed crack growth model, modified to account for flaw orientation distribution, are used as inputs to a fragmentation and crack coalescence model to predict fragment statistics. Cracks are modelled discretely in a voxellized simulation region with periodic boundary conditions. Neighboring cracks are allowed to coalesce. Fragments are delineated using a connected region approach, with morphological dilation to compensate for resolution effects. Fragment size and shape distribution, are used to conduct parametric studies and propose a microstructure dependent granular transition criterion.

11:20 AM  Invited
Models for the Behavior of Boron Carbide in Extreme Dynamic Environments: Kaliat Ramesh1; Lori Graham-Brady1; William Goddard2; Ryan Hurley1; Andrew Tonge3; Amartya Bhattacharjee1; Joel Clemmer4; Qinglei Zeng1; Weixin Li1; Yidi Shen5; Qi An5; Nilanjan Mitra1; 1Johns Hopkins University; 2California Institute of Technology; 3DEVCOM Army Research Laboratory; 4Sandia National Laboratory; 5University of Nevada, Reno
    We describe models for the behavior of hot-pressed boron carbide that is subjected to extreme dynamic environments such as ballistic impact. We first identify the deformation and failure mechanisms that are observed in boron carbide under such conditions, and then review physics-based models for each of these mechanisms and the integration of these models into a single physics-based continuum model for the material. Atomistic modeling relates the composition and stoichiometry to the amorphization threshold, while mesoscale modeling relates the processing-induced defect distribution to the fracture threshold. The models demonstrate that the relative importance of amorphization and fracture are strongly dependent on the geometry and impact conditions, with the volume fraction of amorphized material unlikely to be significant until very high velocities are reached for geometries such as ball impact on plates. These connections to the physics provide guidelines for the design of improved boron carbide materials for impact applications.

11:40 AM Concluding Comments