Advances in Powder and Ceramic Materials Science: Ceramic Nanoparticles and Powder
Sponsored by: TMS Extraction and Processing Division, TMS: Materials Characterization Committee
Program Organizers: Bowen Li, Michigan Technological University; Shefford Baker, Cornell; Huazhang Zhai, Beijing Institute of Technology; Sergio Monteiro, Instituto Militar de Engenharia; Rajiv Soman, Eurofins EAG Materials Science LLC; Faqin Dong, Southwest University of Science and Technology; Jinhong Li, China University of Geosciences; Ruigang Wang, Michigan State University
Tuesday 8:30 AM
February 25, 2020
Room: Theater A-6
Location: San Diego Convention Ctr
Session Chair: Ruigang Wang, University of Alabama ; Sergio Monteiro , Military Institute of Engineering
8:30 AM Introductory Comments
8:35 AM
High Densification Rates (10-3 s-1) in Nanocrystalline Oxides by CAPAD Processing: Effects of Water Absorption and Grain Size: Darren Dewitt1; Yasuhiro Kodera1; Javier Garay1; 1University of California, San Diego
The effects of grain size and water on the densification of oxide powders have long been recognized, but their effects on densification rates have not been adequately studied. Here, we measured the real-time densification rates of MgO using the current-activated, pressure-assisted densification (CAPAD) technique. The rates of samples densified from powders with grain sizes ~40nm are similar to those measured previously for other nanopowders, while those from 29nm powder are higher. Exposure to a humid environment increases the densification rates and allows densification at lower temperatures. The densification rate curves of samples with absorbed water display two peaks implying two controlling mechanisms, while the dry samples display one. We attribute lower temperature densification to Mg(OH)2-MgO conversion and the higher to diffusion-controlled densification. Recent work involving the densification of MgO+Al2O3 nanopowders in CAPAD will also be discussed - correlating densification rates with various mechanisms, including the phase evolution of MgAl2O4.
8:55 AM
Preparation of Rare Earth Stabilized Nanocrystalline Zirconia with Tunable Optical/mechanical Properties: Gottlieb Uahengo1; Javier Garay1; Yasuhiro Kodera1; 1University of California, San Diego
We present a systematic study investigating rare-earth dopant type and dopant concentrations effects on crystal phase compositions of zirconium dioxide (ZrO2) and the respective bulk mechanical and optical properties. Zirconium dioxide, a traditional structural ceramic possesses excellent mechanical properties, while simultaneously possessing a wide band gap (5-7eV). This combination of properties opens the door towards the design and fabrication of transparent (functionalized) structural ceramics. We use Current-Assisted Pressure Activated Densification (CAPAD), to achieve high heating rates, and comparatively short hold-times, which leads to ceramics with fine grain sizes. This affords the opportunity to investigate, the effects of dopant type and dopant concentration resultant microstructure (grain size, phases and phase ratios). We will discuss how the understanding of the interplay between bulk mechanical and optical properties can lead to a structural ceramic with tunable optical and mechanical properties.
9:15 AM
Pressure-less Processing of Ceramics with Deliberate Elongated Grain Orientation and Size: Hortense Le Ferrand1; 1Nanyang Technological University
Hard biomaterials reveal finely tailored complex assemblies of mineral crystals, often associated with impressive mechanical response. Here, we combine two methods to reproduce these complex assemblies in alumina ceramics. We combine magnetically assisted slip casting with templated grain growth in slurries containing particles of selected dimensions. After sintering, the obtained alumina parts exhibit high concentration and deliberate microstructures, but grain size and orientation varying as predicted by theories and models. Examples of periodic and multilayered microstructures are provided in aluminas of density from 65 to 95%. We investigate how the controlled microstructure only can be used to control the local mechanical properties and anticipate implications on the macroscopic response of the ceramics, in particular strength and toughness.
9:35 AM
Compressive Properties of Micro-spherical SiO2 Particles: Niko Hellsten1; Antti Karttunen1; Charlotta Engblom2; Alexander Reznichenko2; Erika Rantala2; 1Aalto University; 2Borealis Polymers Oy
Micron-sized, spherical SiO2 particles are important in many industrial applications, such as in the production of polyolefins, where they are used as solid catalyst supports. In polyolefin production, the quality of the final product, as well as the resource efficiency of the process, depends directly on the performance of the catalyst material. As the catalyst particles experience various stresses during the polymer particle growth, mechanical properties of catalyst play detrimental role in its performance in the polymerization process. However, there is currently a lack of experimental mechanical property measurements of micron-sized, spherical SiO2 particles.In this work, the compressive properties of commercial, porous, spherical micron-sized SiO2 powder was studied using a quasi-static micro-compression method. The method includes compressing single, micron-sized particles in controlled loading conditions. From the measurements, the compressive elastic-plastic properties of these particles can be determined.
9:55 AM
Development of Shape-Controlled Oxide Nanopowders as Support Materials in Emission Control Catalysts: Zhongqi Liu1; Ruigang Wang1; 1The University of Alabama
In heterogeneous catalysis, metal catalysts supported on different oxides have distinct catalytic properties, depending on the reducibility of oxides, surface acidity and basicity of oxides, and metal-oxide interaction/reaction. Charge transfer and/or redox reactions are essential steps for the catalytic reaction at elevated temperature, therefore the reducible oxide supports (CeO2, TiO2, and VOx) present a potential advantage compared to conventional non-reducible oxide supports, e.g. SiO2, ZrO2, and Al2O3. In addition, the morphology and surface structure of reducible oxides are critical in altering the metal-support interactions, hence determining the catalytic activity, selectivity and durability. In this presentation, we highlight three synthetic approaches towards shape-controlled synthesis and fine tuning of surface structure in various oxide support nanopowders, including hydrothermal method, electrospinning and electrochemical deposition. By regulating different reaction parameters, mono-dispersed and shape well-defined oxide nanopowders can be obtained for the application in emission control catalysts.