ACerS Robert B. Sosman Award Symposium: Advancing the Science of Materials for Extreme Environments: Session I
Sponsored by: ACerS Basic Science Division
Program Organizers: Yiquan Wu, Alfred University; Greg Hilmas, Missouri University of Science and Technology; Eric Wuchina, NSWCCD
Wednesday 8:00 AM
October 12, 2022
Room: 407
Location: David L. Lawrence Convention Center
Session Chair: Laura Silvestroni, CNR - ISSMC (former ISTEC); Elizabeth Opila, University of Virginia
8:00 AM Invited
Ultra-High Temperature Ceramic Research at Missouri S&T: Greg Hilmas1; William Fahrenholtz1; 1Missouri University of Science and Technology
Ultra-high temperature ceramics (UHTCs) are a class of structural materials capable of withstanding extreme environments. UHTCs have the potential to be used in applications ranging from hypersonic flight and rocket propulsion to advanced nuclear reactors to electrodes, sensors, and sheathing materials for metal production. These applications involve temperatures, heat fluxes, radiation levels, strain rates, chemical reactivities, or other stresses that are beyond the capabilities of existing materials. The presentation will highlight past research from the UHTC research group at Missouri S&T, focusing on breakthroughs in our understanding of the processing and properties of UHTCs. The presentation will then discuss more recent research on UHTCs, focusing on thermal and mechanical properties at temperatures of 2000°C or higher. Examples from research related to improving the elevated temperature strength and thermal conductivity of boride and carbide UHTCs will be presented. The presentation will conclude with discussion of some emerging trends and future needs.
8:30 AM Invited
NSWC Research on UHTCs: A 40+ year Perspective: Eric Wuchina1; Mark Opeka2; Inna Talmy3; James Zaykoski1; Peter Kaczmarek1; 1NSWCCD; 2NSWCCD/Southern Research; 3NSWCCD/Retired
The Navy has a long history of research in ultra-high temperature materials, dating back to the early 1960s. Early investigations into boride materials studied the CrB2, NbB2, and CrB2-Al2O3 systems before moving to the Group IV borides and carbides. The chemical vapor codeposition of HfB2-SiB4 and HfB2-SiC was successfully accomplished, and UHTCMC processing studies were undertaken. Oxidation studies centered on ZrB2-SiC materials, and included work on the formation of immiscible glasses. A wide array of boride, carbide, nitride, mixed, and substoichiometric compositions were exposed in an arcjet in order to understand the response of materials at hypersonic flight temperatures, while furnace and rocket nozzle exposures helped to elucidate the role of system pressure and shear on the oxidation reactions. More recently, NSWCCD scientists have studied UHTC-based cermets, as well as the use of entropic stabilization techniques to investigate 2, 3, 4, 5, and 6 component diborides and silicides.
9:00 AM Invited
Regeneration, Co-generation and Generation via Ultra-High Temperature Ceramics: William Lee1; Michael Rushton2; Simon Middleburgh2; 1Bangor University and Imperial College London; 2Bangor University
Our research is aimed at regeneration of the region by supporting plans for its two nuclear licensed sites, which currently host reactors being decommissioned but have real potential for development of Advanced Modular Reactors (AMRs) based on fusion, lead cooled fast reactors and high temperature gas-cooled reactor which operate at temperatures high enough to support industrial processes via co-generation or even using dedicated reactors to provide process heat for production of hydrogen, chemicals and synthetic jet fuels. We are examining composite UN (Tm = 2847C), UB2 (Tm = 2430C), spray dried UO2/ZrB2 (Tm = 2865/3246C) fuels for AMRs including space reactors where UHTC moderators and neutron absorbers are also being considered. We work with local Further Education Colleges to support apprenticeships and training for students to fill nuclear jobs generated. Successful delivery of UHTC-driven advanced reactors has a crucial role in the economic future of the region.
9:30 AM Invited
Addressing Challenges to the Application of UHTCs in Extreme Environments: Michael Cinibulk1; 1AFRL
Uncertainty in the performance of high-temperature structural materials remains a challenge to their development and implementation in extreme environments. Materials in these applications are often exposed to high heat-fluxes resulting in very high temperatures, steep temperature gradients, oxidation, and erosion. Ultra-high temperature ceramics (UHTCs; e.g., refractory carbides and borides) are being considered for these applications due to their high temperature capability and high thermal conductivity. However, UHTCs are prone to oxidation under flight conditions and have low fracture toughness, which increases the risk of using them in demanding structural applications. This presentation will focus on our work in addressing these challenges via fiber reinforcement, and improving our understanding of oxidation behavior via an oxidation kinetics model and validating the model under relevant service conditions. The goal is to develop comprehensive modeling tools that overcome facility-dependent conditions and biases for improved the prediction of performance and life.
10:00 AM Break
10:20 AM Invited
Exploring Why Ultra-high Temperature Ceramic Ceramics Work in Extreme Environments: Laura Silvestroni1; Nicola Gilli1; Jeremy Watts2; William Fahrenholtz2; 1CNR - ISTEC; 2Missouri University of Science and Technology
The latest generation UHTCs, based on a borides and sintered in the presence of transition metal (TM) compounds, has demonstrated strengths beyond current benchmark ranges. Peaks of ~1 GPa were achieved at 1800°C and strength remained above 400-600 MPa up to 2100°C. Upon exploration of the microstructural features by TEM, a unique multi-scale microstructural arrangement was discovered. The TM, partially dissolved into the boride matrix during sintering, led to the formation of a core-shell grain structure characterized by dislocation networks and polygonised dislocation walls. Particularly, the shell was found to be a super-saturated solid solution in which nano-particles precipitated. These were rounded metallic W droplets or elongated and oriented TaC needles, when WC or TaSi2 additives were introduced, respectively.This complex hierarchical microstructure, featured by several levels of spatial variations and resulting in an improved combination of strength and ductility is thought to be responsible for the elevated temperature strengthening.
10:50 AM Invited
The Peculiarities of Deformation in Transition Metal Carbides: Gregory Thompson1; Christopher Weinberger2; 1University of Alabama; 2Colorado State University
Transition metal carbides comprise a class of high and ultrahigh melting temperature materials and depending upon temperature and phase type, brittle to significant plasticity responses is observed. This presentation will address the underlying deformation mechanisms as a function of the microstructure and crystallography found in group IVB and VB metal carbides. Specifically, how stacking fault energy differences in the metal-carbon bonding environment governs the energy hierarchy for slip. This information is applied to explain slip changes reported in the B1 group IVB and VB carbides, the anomalous hardening in sub-stoichiometric B1 group IVB and VB metal carbides, and the high fracture toughness found in tantalum-rich carbides but absent in other carbides. Finally, thermo-mechanical testing at temperatures in excess of 2500 deg. C, with the slip systems experimentally identified, will be described by the use of a non-contact loading method.
11:20 AM Invited
Vacancy Ordering in Zirconium Carbide: Theresa Davey1; Ying Chen1; 1Tohoku University
Zirconium carbide (ZrCx, 0.5≤x≤1) has wide range of substoichiometry facilitated by varying numbers of carbon vacancies. At high temperatures, these vacancies form a continuous solution phase, but at lower temperatures, long- and short-range ordering is predicted and occasionally observed, where vacancies self-assemble into a homologous series of superstructural ordered phases. The thermophysical properties are affected by the number of vacancies and their arrangement, allowing potential application as a tuneable ceramic. The mechanism of vacancy ordering in zirconium carbide is described using insights from first-principles calculations, and possible reasons for the infrequent experimental fabrication of ordered phases are discussed, including fabrication temperatures, vacancy diffusion, and the effects of impurities.
11:50 AM Invited
Effects of Liquid and Gas Phase Formation on Mechanisms of Ultra-high Temperature Ceramic Oxidation: Lavina Backman1; Connor Stephens2; Elizabeth Opila2; 1U.S. Naval Research Laboratory; 2University of Virginia
Ultra-high temperature ceramics (UHTCs) such as group IV, V, and VI transition metal carbides and borides are proposed for use as hypersonic vehicle leading edges due to their high melting temperatures. Unfortunately, their oxidation rates are rapid. The recent “high entropy” (HE) materials design approach has been applied to UHTCs and found to yield improved mechanical properties, but increased degradation by oxidation due to formation of low melting oxide eutectics. The HE carbides performed worse than the borides. The poor performance of carbides is often attributed to the generation of CO(g) during oxidation that promotes the formation of porous oxide scales. However, there are no known studies that compare the oxidation of transition metal carbides to the oxidation of corresponding transition metals. In this presentation, the complexities of oxidation mechanisms in cases where liquid and gaseous products form are discussed with recommendations for design of UHTCs with improved oxidation resistance.