Journal of the American Ceramic Society Awards Symposium: Journal of the American Ceramic Society Awards Symposium I
Sponsored by: ACerS
Program Organizers: William Fahrenholtz, Missouri University of Science and Technology
Wednesday 8:00 AM
October 20, 2021
Room: B233
Location: Greater Columbus Convention Center
Session Chair: William Fahrenholtz, Missouri University of Science and Technology; Jonathon Foreman, American Ceramic Society
8:00 AM Introductory Comments
8:10 AM Invited
A Novel Strategy to Strengthen Alumina-carbon Refractories for Flow Control of Molten Steel: Zhe Chen1; Wen Yan1; Stefan Schafföner2; Yajie Dai1; Qiang Wang1; Guangqiang Li1; 1Wuhan University of Science and Technology; 2University of Bayreuth
Al2O3-C refractories are essential to control the flow of molten steel during continuous casting due to their excellent thermal shock resistance. Ordinary Al2O3-C refractories are produced from dense corundum aggregates. According to traditional concept, the denser the refractories, the higher the strength of refractories. However, we proposed a novel strategy to enhance the strength of Al2O3-C refractories by using microporous corundum aggregates instead of dense ones. The lightweight Al2O3-C refractories combining the approach of using microporous aggregates and formation of SiC whiskers inside of microporous aggregates demonstrated an optimized bonding at the aggregate/matrix interface, which significantly enhanced their strength. On this basis, we found that using the carbon source with a higher reactivity resulted in more SiC whiskers in the microporous aggregates. The higher amount of SiC whiskers led to a more intertwined and compacter microporous aggregate/matrix interface structure. Thus, a higher strength was achieved for the lightweight Al2O3-C refractories.
8:40 AM Invited
A Thermodynamics-guided Framework to Design Spherical Lightweight Aggregate from Waste Coal Combustion Ash: Mohammad Balapour1; Thiha Thway1; Rathin Rao1; Newell Moser2; Edward Garboczi2; Yick Hsuan1; Sabrina Spatari1; Yaghoob Farnam1; 1Drexel University; 2National Institute of Standards and Technology
Using a thermodynamics-based framework, the process to successfully manufacture synthetic lightweight aggregate (LWA) from waste coal combustion ash through sintering was investigated in which a delicate balance among three phenomena was required: (i) sufficient liquid phase formation during sintering, (ii) appropriate viscosity for the liquid-solid phase, and (iii) sufficient gas emission amount to form pores in the LWA. Using thermodynamics modeling, the liquid phase formation during sintering was quantified, where its correlation to X-ray computed tomography observations indicated that a minimum of 35 % by mass liquid phase content is necessary for gas-filled pores formation in LWA. The Browning and Krieger-Dougherty models were used to quantify the liquid and liquid-solid phases viscosity, respectively. A lower bound of 100 Pa·S for the viscosity was found to ensure the spherical shape of the LWA. Thermogravimetric analysis showed a considerable gas release potential for the LWA, creating gas-filled pores in the LWA.
9:10 AM Invited
Direct Ink Writing (DIW) of Hierarchical Porous Alumina Stabilized Emulsions: Rheology and Printability: George Franks1; Shareen Chan1; Mitchell Sesso2; 1University of Melbourne; 2La Trobe University
Multiscale porous ceramics are produced by Direct Ink Writing (DIW) (3D printing) alumina pastes. Millimeter scale porosity is created by the 3D printed filaments. 20 micron scale porosity is introduced within the scaffold filaments by adding oil to the aqueous suspension to create pores via particle stabilized emulsions or capillary suspensions. Micron scale porosity is developed by partial sintering. The printed and sintered alumina lattices possess high overall porosity (78.7%) and open porosity (64.7%). The effects of formulation (surfactant and oil concentrations, particle size, and mixing) on rheology and pore size and morphology are presented. The rheological properties (storage modulus, yield stress) of the emulsions have been found to delineate samples with good shape retention from those that slump. The internal features of the sintered structures have been analyzed via X-ray tomography and SEM. Additional more recent work on the ultra-high temperature ceramic, zirconium diboride will be presented as well.
9:40 AM Invited
Effect of Moisture on the Oxidation Behaviour of ZrB2.: Ravisankar Naraparaju1; 1German Aerospace Center
Oxidation studies of ZrB2 were performed under wet air and dry air conditions at 1200, 1400 and 1500°C for 1, 4 and 10h. Compared to dry air, the presence of water vapor was found to enhance the oxidation kinetics by a factor of 7 to 30, depending on the temperature. Thermodynamic calculations suggested that water vapor promoted the formation of additional volatile species such as boric acid (HBO2), in addition to boria (B2O3) produced in dry air, which increased the evaporation rate of B2O3. Compared to dry air, the presence of water vapor leads to more rapid evaporation of boria and the transition from parabolic oxidation kinetic behavior (i.e., rate controlled by diffusion through boria) to linear (i.e., underlying ZrB2 is directly exposed to the oxidizing environment) at shorter times and lower temperatures.
10:10 AM Break
10:30 AM Invited
Processing of MAX Phases: From Synthesis to Applications: Jesus Gonzalez-Julian1; 1Forschungszentrum Jülich
MAX phases have been extensively investigated during the last 25 years due to their unique combination of properties, bridging the gap between ceramics and metals. However, despite the potential to operate under aggressive environments of compositions such as Ti2AlC and Cr2AlC, their transfer to applications is limited by three main factors: i) complexity of this large family of materials, ii) unavailability of highly pure commercial powders, and iii) extensive time to license products in strategic fields. In this work, reasons and potential solutions of these three points are discussed and correlated to the main properties of MAX phases and their synthesis routes. Emphasis is given to processing routes for developing different structures such as dense bulk samples, ceramic matrix composites, foams with controlled porosity, coatings, and near-net shaping. Well-known and novel potential applications are described as well as future challenges to facilitate the transfer to the market.