Engineering Ceramics: Microstructures, Properties, and Applications: Microstructure and Properties of Engineering Ceramics
Sponsored by: ACerS Engineering Ceramics Division
Program Organizers: Young-Wook Kim, University of Seoul; Hua-Tay Lin, Guangdong University of Technology; Junichi Tatami, Yokohama National University

Monday 8:00 AM
November 2, 2020
Room: Virtual Meeting Room 17
Location: MS&T Virtual

Session Chair: Young-Wook Kim, University of Seoul; Junichi Tatami, Yokohama National University

8:00 AM
Introductory Comments: Engineering Ceramics: Microstructure-Property-Performance Relations and Applications: Young-Wook Kim¹; ¹University of Seoul
    Introductory Comments

8:05 AM
Influence of Three-dimensional Microstructure on the Impact Response of Advanced Ceramics: Jonathan Ligda¹; Brendan Koch²; Debjoy Mallick¹; David Hogan²; ¹Combat Capabilities Development Command Army Research Laboratory; ²University of Alberta
    Brittle materials fail due to pre-existing flaws serving as stress concentrators, causing cracks to grow and coalesce when loads are applied, leading to fragmentation. These flaws range from microscopic inclusions or grain boundaries to macroscopic cracks from prior loading. Before fragmentation these flaws also influence mechanical behavior such as apparent stiffness or Poisson’s ratio. Advanced ceramics manufacturing minimizes initial flaw populations, but extreme environments such as ballistic loading that can induce new flaws. Intentionally inducing damage produces complex internal structures that are characterized by computed x-ray tomography, scanning electron microscopy, energy-dispersive x-ray spectroscopy, and electron backscatter diffraction. Compressive loading to failure obtains the changes in material properties such as stiffness and Poisson’s ratio, and performance metrics such as failure strength. Impact experiments obtain physical performance, which can then be compared with performance metrics and characterization data to understand the relationships between physical damage and mechanical response of brittle material.

8:25 AM
Effect of Hot Forging on The Mechanical and Thermal Properties of Fine-grained SiC-TiC Composite: Rohit Malik¹; Young-Wook Kim¹; ¹University of Seoul, Dept. of Materials Science & Engineering, Republic of Korea
     We herein propose a novel technique of fabricating highly deformable SiC composites. The deformability of brittle SiC ceramics can be improved by reinforcing it with a second phase with low brittle to ductile transition temperature (BDTT), such as TiC (BDTT- 800 °C).Fine-grained monolithic SiC and SiC-20 vol% TiC composite were prepared by hot pressing via a two-step liquid phase sintering technique. The hot-pressed SiC-20 vol% TiC composite exhibited two times higher strain than the monolithic SiC after hot forging at 1900 °C. High deformation resulted in improved density, mechanical and thermal properties for the SiC-20 vol% TiC composite. The flexural strength, fracture toughness, and thermal conductivity of the hot-pressed SiC-20 vol% TiC composite were 608 MPa, 5.1 MPa·m^1/2, and 34.6 Wm^-1K^-1, respectively which increased to 777 MPa, 7.8 MPa·m^1/2, and 74.7 Wm^-1K^-1, respectively after hot forging. The hot-forged composite exhibited anisotropic properties attributed to the anisotropy in the microstructure.

8:45 AM
Characterizing the Flexural Strength of Nanocrystalline Ceramics and Associated Challenges: Heonjune Ryou¹; Kevin Anderson¹; John Drazin²; James Wollmershauser¹; Boris Feygelson¹; Edward Gorzkowski¹; ¹U.S. Naval Research Laboratory; ²Washington State University
    Emergence of advanced ceramic processing techniques in recent years have led to the development of nanocrystalline ceramics with extremely small grain sizes: below 100 nm. Various literature studies have reported the extent of the mechanical property improvement in nanocrystalline ceramics with extremely small grain sizes, albeit on produced on non-conventional processing equipment with small sample sizes and. In this presentation, various nanocrystalline ceramics with grain sizes below 100 nm were characterized with instrumented indentation, biaxial flexural, and beam flexural tests. The result from instrumented indentation result shows the Hall-Petch strengthening of nanocrystalline ceramics. Flexural strength measurement was influence by the sample processing, geometry, surface roughness, as well as test geometry, yet stilled showed Hall-Petch strengthening. The challenges of performing the tests for nanocrystalline ceramics arise from the nature of nanocrystalline ceramics and current manufacturing techniques.

9:05 AM  Invited
Control of Electrical Conductivity in Liquid-phase Sintered Silicon Carbide Ceramics: Young-Wook Kim¹; Gyoung-Deuk Kim¹; ¹University of Seoul
     Silicon carbide is one of the most important engineering ceramics because of its unique combination of properties including excellent mechanical properties, excellent oxidation and corrosion resistance at elevated temperatures, and high thermal conductivity. Recently, highly conductive liquid-phase sintered SiC (LPS-SiC) ceramics have been developed by the successful doping of N atoms into a SiC lattice. Fully dense N-doped SiC ceramics with electrical conductivity as high as 300 S·cm-1 at room temperature have been obtained. This presentation reviews the factors affecting the electrical conductivity of LPS-SiC ceramics, including the effects of grain boundary structure, soluble atoms, SiC polytype, porosity, and grain size.The results suggest that the electrical resistivity can be controlled over a wide range (10−3–1013 Ω·cm at RT) through (i) the donor-acceptor compensation mechanism, (ii) grain boundary engineering, and (iii) judicious selection of polytype of the starting SiC powder, sintering additive composition, sintering atmosphere, and bedding powder composition.

9:35 AM
New Insights into Deformation Mechanisms of Amorphous Silicon Nitride Nanoporous Membranes from Atomistic Simulations: Ali Shargh¹; James McGrath¹; Niaz Abdolrahim¹; ¹University of Rochester
    Ultrathin silicon nitride nanoporous membranes are extremely permeable silicon based ceramics that were first developed at University of Rochester in 2014. Despite their potential biomedical applications, the range of working pressure and the size of nanostructures in those applications are limited by mechanical properties. Here, our approach is to improve the mechanical properties of amorphous nanoporous membranes with the change of pore architecture parameters using molecular dynamics simulations. It is found that the arrangement, shape and aspect ratio of the pores are the main factors that control the mechanical properties of nanoporous membranes. Depending on the pore arrangement, three major deformation mechanisms are captured under uniaxial loading. Our results show that the pore arrangement governs the pattern of strain localization in the nanostructure which further control the ductility of structure. Moreover, it is find that the change of aspect ratio beyond a critical value maximize the strength of the nanostructures.