Engineering Ceramics: Microstructure-Property-Performance Relations and Applications: Processing-Microstructure-Property Relations 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; Michael Halbig, NASA Glenn Research Center
Wednesday 8:00 AM
October 12, 2022
Room: 415
Location: David L. Lawrence Convention Center
Session Chair: Yiquan Wu, Alfred University; Soshu Kirihara, Osaka University
8:00 AM Invited
Investigation of Local Mechanical Responses in Ceramic Materials Based on In Situ TEM Observations: Eita Tochigi1; 1The University of Tokyo
Plastic deformation and fracture of ceramic materials typically initiate from a stress concentration region at a surface crack. Therefore, it is important to characterize the microscopic behavior of a surface crack under loading conditions. In situ transmission electron microscopy (TEM) mechanical experiments are known to be a powerful technique to visualize local structural changes upon loading. In recent years, microelectron mechanical system (MEMS) technology provides small and precise loading devices. In this study, we performed in situ loading experiments on ceramic materials with a MEMS loading device in an atomic-resolution scanning transmission electron microscope. Our experiments provided sequential atomic-resolution images. The local strain of the sample was examined based on atomic positions, and the results clearly show increasing of local strain with increasing load and following deformation/fracture behavior. In the presentation, we will discuss its strain distributions and structural changes in detail.
8:30 AM
The Effects of Microstructure on the Properties of Reticulated Porous Ceramics: Jang-Hoon Ha1; Jongman Lee1; In-Hyuck Song1; 1Korea Institute of Materials Science
There has been growing interest in porous ceramics in many research areas given their superior thermal and chemical resistance capabilities, unlike porous metals and porous polymers. Among the various types of porous ceramics, reticulated porous ceramics can offer significant industrial potential due to the low density and high permeability of these materials. However, industrial applications are somewhat rare owing to the rather low compressive strength of reticulated porous ceramics compared to other types of porous ceramics. Therefore, the aim of this study is to determine how to obtain high compressive strength in reticulated porous ceramics by optimizing the process conditions of the solid loading level and the particle size and by using additives in a ceramic slurry sample. The characteristics investigated include the pore characteristics (pore density, pore size and pore structure), the sintering behavior (linear shrinkage), the mechanical properties (compressive strength), and the dielectric properties (dielectric breakdown strength).
8:50 AM
Fabrication of Porous Silica with Controllable Porosity via Freeze Casting: Mert Arslanoglu1; Rahul Panat1; Burak Ozdoganlar1; 1Carnegie Mellon University
Porous ceramics offer advantageous properties that can bring advances to many application areas. The freeze casting (FC) process has a strong potential for fabricating porous ceramics; however, the effects of process parameters on part porosity must be well-understood for scalable manufacturing. This study presents an experimental analysis of this process that correlates the FC parameters with pore characteristics based on a unidirectional FC of silica and camphene slurry. Process parameters of solid loading, particle size, cooling temperature, and the distance from the cooling surface are evaluated. Scanning electron microscopy and computer tomography are used for imaging, and image processing is used for the analysis of the microstructures. Consequently, a quantitative understanding of the effects of FC process parameters on porosity characteristics is gained for the silica-camphene system. The solid loading is determined as the main process parameter that controls the final porosity and pore characteristics of freeze cast silica.
9:10 AM
Tin Oxide as a Model System for Sintering without Shrinkage – Monitoring Microstructure Evolution and Elastic Property Changes: Petra Simonova1; Willi Pabst1; Vojtech Necina1; 1University of Chemistry and Technology, Prague
Pure SnO2 ceramics exhibit unusual sintering behavior, because of the prevalence of non-densifying sintering mechanisms (surface diffusion, evaporation-condensation). Therefore, it is an exceptional model system for which property changes occur without changes in porosity. Thus, the influence of other microstructural parameters on the effective properties can be studied. We present experimental findings for pure SnO2 ceramics prepared by uniaxial pressing and sintered to temperatures in the range 500–1400 °C with different dwell times. Using scanning electron microscopy, mercury porosimetry and gas adsorption it is shown that during sintering the geometry and topology of the pore space changes, although the porosity remains constant. Despite the constant porosity, the elastic properties (Young’s modulus measured by temperature-dependent impulse excitation) undergo significant changes, when the original sintering temperature is exceeded. The results from stereology-based image analysis and other methods show that these changes are related primarily to changes in the pore surface curvature.