Manufacturing and Processing of Advanced Ceramic Materials: New Advances in Ceramic Processing I: Sintering
Program Organizers: Bai Cui, University of Nebraska Lincoln; James Hemrick, Oak Ridge National Laboratory; Mike Alexander, Allied Mineral Products; Eric Faierson, Iowa State University; Keith DeCarlo, Blasch Precision Ceramics
Monday 2:00 PM
October 10, 2022
Room: 411
Location: David L. Lawrence Convention Center
Session Chair: Richard Todd, University of Oxford; Clive Randall, Pennsylvania State University
2:00 PM Invited
Flash Sintering of Ceramics: Towards Homogeneous Components with Improved Mechanical Properties: Richard Todd1; Y. Kubota1; Yinsheng Li1; Riccardo Torchio2; Simone Falco1; Piergiorgio Alotto2; 1University of Oxford; 2University of Padua
The fact that ceramics can be flash sintered in a few seconds using furnace temperatures significantly lower than those used conventionally is now well established. However, it is also evident that the production of ceramics with full density and uniform microstructure throughout the component is difficult. Perhaps because of this, there are very few reports of measurements of important mechanical properties such as strength in flash sintered ceramics. This presentation first explores the use of thermal management, novel electrode geometries and compositional modification to achieve fully dense and uniform microstructures. The experimental observations concerning specimen geometry and electrode design are investigated using a model incorporating densification and its effect on heat flow and electrical power dissipation. The optimised microstructures and properties of YSZ are reported. It is shown that microstructures not easily accessible by conventional sintering can be produced and that these lead to improved strength and hardness.
2:30 PM Invited
Ultrafast Sintering with and without Electric Fields and Electrochemically Controlled Microstructural Evolution: Jian Luo1; 1University of California, San Diego
This talk will first review our recent studies on understanding the scientific questions and technological opportunities of flash sintering [Scripta 146: 260 (2018); MRS Bulletin 46: 26 (2021)]. We originally proposed that flash sintering generally starts a thermal runaway [Acta 94:87 (2015)], but it can also be activated by bulk phase and grain boundary complexion transitions [Acta 181:544 (2019)]. We further proved that ultrafast densification is enabled by ultrahigh heating rates of ~100 K/s [Acta 125:465 (2017)]. Subsequently, a generic ultrafast high-temperature sintering was reported in a collaborative study [Science 368:521 (2020)]. Recent research discovered electrochemically induced grain boundary transitions [Nature Communications 12:2374 (2021)]. A series of on-going studies on electrochemically controlled microstructural evolution will be disused in detail [unpublished results].
3:00 PM
Doping Alumina with Carbon?: Li-or Cohen1; Priyadarshini Ghosh1; Rachel Marder1; Wayne Kaplan1; 1Technion - Israel Institute of Technology
Alumina (α-Al2O3) is commonly sintered in air, but several sintering techniques such as spark plasma sintering (SPS) use graphite dies. Alumina sintered in graphite furnaces often has a dark grey or even black color, and there is debate in the literature regarding the actual role of carbon on sintering and grain growth. The solubility limit of carbon in 99.99% pure alumina equilibrated at 1600°C under flowing He in a graphite furnace was measured using a wavelength dispersive spectrometer mounted on a scanning electron microscope. The solubility limit of carbon in alumina was found to be 3940 at. ppm, and it is believed that at low oxygen partial pressures carbon-hydrogen species substitutes oxygen which is charge-compensated by oxygen vacancies. Doping alumina with carbon at concentrations below the solubility limit does not impede densification and reduces grain growth. Doping above the solubility limit hinders densification during sintering.
3:20 PM Break
3:40 PM Invited
Utilizing Cold Sintering in the Design and Integration of New Functional Composite Materials: Clive Randall1; 1Pennsylvania State University
Typical ceramic sintering temperatures occurs at 0.5 to 0.95 of the melting temperatures (Tm), in oxides; we conventionally sinter around 800 to 1800 oC. This lecture reviews various chemical pathways, and variables such as pressure, temperature, and time that enable the cold sintering processes to occur at low temperatures. Using model systems, it is possible to contrast the energetics and mechanisms with conventional sintering processes regarding densification and grain growth kinetics. With the introduction of a cold sintering strategy, a common processing platform ~ 200 oC enables the integration of multiple materials that permits new types of composites and devices to be designed. The power of such design versatility will be demonstrated with number of functional ceramics and multilayer devices impacting a broad number of applications. Beyond the successful examples, the many challenges and opportunities of cold sintering will also be discussed, including the vision of a sustainable cyclic economy.
4:10 PM Invited
High Throughput, Ultra-fast Laser Sintering of Alumina Sample Array for Establishing the Machine-learning-based Mapping Between Microstructure and Hardness: Fei Peng1; Hai Xiao1; Dongsheng Li1; Rajendra Bordia1; Jianhua Tong1; Jianan Tang1; Xiao Geng1; Siddhartha Sarkar1; Bridget Sheridan1; 1Clemson University
We report ultra-fast laser sintering of alumina that achieves the desired density and microstructure for alumina within ~10 seconds. Compared to furnace sintering, ultra-fast laser sintering can either suppress or enlarge the grain size for the same sintering density. A sample array of ~80 sample units (~500 μm × 500 μm × 100 μm each) can be sintered simultaneously under one laser scan, which results in various microstructures for each sample unit due to the laser power distribution. The hardness of each sample unit and corresponding microstructure were characterized to establish the datasets for machine learning (ML) training. The hardness vs. relative density data obtained from this high throughput method, well match the literature data. We developed ML algorithms that can precisely predict the laser-sintered alumina microstructure from the hardness values and also precisely predict the hardness of the laser-sintered alumina from the SEM micrographs with less than 5% error.
4:40 PM
Cold and Flash Sintering of Metal-doped LLZO for Solid-State Battery Applications: Gareth Jones1; Christopher Green2; Dinesha Dabera1; Parinaz Tabrizian1; Scott Gorman3; Sherry Ghanizadeh2; Sandra Fisher John2; David Pearmain2; Geoff West1; Emma Kendrick3; Claire Dancer1; 1University of Warwick; 2Lucideon Ltd; 3University of Birmingham
Solid-state ceramic electrolytes are a crucial component of solid-state batteries, however the processing conditions for these ceramic materials is challenging requiring elevated temperatures during sintering to produce suitably dense layers. As solid-state electrolytes (SSEs) start to reach market there is an increasing drive for faster and more energy efficient sintering methods, especially methods that can reduce the volatilisation of lithium during typical sintering. In this talk we present the result of two different advanced sintering methods, cold-sintering, and flash-sintering, on the oxide SSE aluminium doped lithium lanthanum zirconium oxide. The contrast between these two methods is compared through examination of the sintered ceramics microstructural features by scanning electron microscopy, X-ray diffraction, and Raman spectroscopy. The optimisation of both methods is discussed in detail such as the effect of pressure, temperature, solvent quantity and time during cold-sintering, and the effect of furnace temperature, current profile, and various electrode configurations during flash-sintering.
5:00 PM
Processing of High Entropy Garnet Optical Ceramics: Jiao Li1; Yiquan Wu1; 1Alfred University
Inspired by the unique chemical and optical properties of some high entropy ceramics, we demonstrate preparation of the high-entropy garnet optical ceramics by using co-precipitation method combined with spark plasma sintering (SPS) technique. The synthesized powder is characterized by XRD, SEM to study its phase structure and morphology. The FTIR and TGA are used to characterize the synthesis of powders. The synthesized garnet powders are sintered at different temperatures by SPS. The grain size, morphology, phase structure of garnet high-entropy optical ceramics are characterized by SEM and XRD. The in-line transmittance and photoluminescence of the ceramics are characterized by the UV-Vis spectrophotometer and spectrofluorometer to understand the optical properties of the optical ceramics.