Engineering Ceramics: Microstructure-Property-Performance Relations and Applications: On-Demand Processing-Property Relations
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
Friday 8:00 AM
October 22, 2021
Room: On-Demand Room 4
Location: MS&T On Demand
Session Chair: Tohru Suzuki, National Institute for Materials Science; Csaba Balazsi, Hungarian Academy of Sciences
Invited
Investigation and Fabrication of High Thermal Conductivity Silicon Nitride Ceramics: Hyun Min Lee1; Jung Hoon Kong2; Do-Kyung Kim2; 1Samsung Electromechanics; 2Korea Advanced Institute of Science & Tech
Increasing demands for electronic devices has revealed the importance of a structural material based on its high performance. The high power consumption results in large thermal stresses, which can be overcome by the ceramic substrates with high thermal conductivity and high mechanical strength. The Si3N4 ceramics are the most promising materials for ceramic substrate due to their outstanding properties such as high electrical resistivity, good resistance to corrosive environments, etc. The thermal conductivity of Si3N4 ceramics is highly dependent on the types and amount of sintering additives, morphology of secondary phases, and microstructure. In this talk, we will introduce powerful strategies for fabricating a high thermal conductivity Si3N4 ceramic. The effects of sintering additives, raw powders, and phase transformation on thermomechanical properties will be discussed. Various sintering methods; pressure-assisted and pressureless sintering were conducted to suggest added benefits of versatility.
Invited
Nanocarbon Added Silicon Nitrides: Csaba Balazsi1; Katalin Balazsi1; 1Centre for Energy Research, Eotvos Lorand Research Network, Hungary
Silicon nitride (Si3N4) based ceramics are well-known as low density materials with high strength and toughness. Silicon nitride, known as a typical dielectric material, is an ideal candidate for several structural applications, even at high temperatures. The addition of graphene or carbon nanotubes to silicon nitride to create ceramic nanocomposites gives rise to promising applications in a wide range of fields such as electronics, biomedical aids, membranes, flexible wearable sensors and actuators. The presentation shows how the use of different reinforcing phases and sintering methods affects microstructure and as a result, mechanical properties, electrical conductivity and friction coefficients of the final silicon nitride nanocomposites.
Invited
Fabrication of Transparent Polycrystalline Ceramics by Colloidal Processing and SPS: Tohru Suzuki1; 1National Institute for Materials Science
Transparent polycrystalline ceramics provides flexibility in size and shape design to apply for a wide field. Extremely low porosities are indispensable for high transparency. Colloidal processing is a very effective technique for controlling the pore size distribution in green compacts before densification by sintering. The green compacts having small residual pores with a narrow size distribution is expected to enhance the densification at low sintering temperature. Furthermore, spark plasma sintering (SPS) is also effective way for densification in low sintering temperature. In this presentation, this processing was applied to fabrication of transparent AlON. After slip casting of the mixture of alumina and AlN, transparent AlON was obtained by reactive sintering during SPS. In the case of alumina and AlN, the crystallographic orientation was controlled for improvement of transparency, because orientation prevent the birefringence due to anisotropic crystal structure.
Mechanical, Thermal, and Electrical Properties of Pressureless Sintered SiC Ceramics with BN and C Additives: Young-Wook Kim1; Rohit Malik1; 1University of Seoul
The full densification of SiC ceramics with 0.5–2.7 wt% BN and C addition has been achieved by pressureless sintering route. The electrical resistivity decreased by an order of magnitude (106 → 107 Ω·cm) as BN content increased from ~0.5 to ~0.9 wt% because of the increased BN-derived B doping in the SiC lattice. A further increase in BN content had no significant effect on the electrical resistivity, which is attributed to the limited solubility of B in the SiC lattice. The thermal conductivity decreased with increasing BN content owing to increased phonon scattering at B-doped sites and the thermally insulating BN phase located at the grain boundaries. The fracture toughness was found to increase with increasing BN content owing to crack bridging caused by the BN platelets. However, intrinsically weak BN grains with low hardness were responsible for reduced flexural strength and hardness with increasing BN content.
Relationship between the Microstructure and the Mechanical Properties of the MWCNTs Reinforced Potassium-based Metakaolin Alkali Activated Materials: Jiaxin Chen1; Ange-Therese Akono1; 1Northwestern University
This research studies the relation between the microstructure and the mechanical properties of high concentration levels of multi-walled carbon nanotubes (MWCNTs) on potassium-based metakaolin geopolymers including 0.3wt%, 0.6wt%, and 1.5wt% MWCNTs per mass of metakaolin. We investigated the rheology in the fresh state. The chemistry of MWCNTs geopolymers was assessed using XRD and statistical FTIR. We assessed the mechanical response using scratch tests and micro indentation tests. We investigated the microstructure using SEM. We observed an increase in Si-OH bonds, indicating that MWCNTs promote the hydroxylation of Si atoms. An inner strengthening effect was observed as MWCNTs reduced the microporosity, resulting in an increase in the indentation modulus and hardness for the dominant microphase. The microstructure results showed that MWCNTs acted as bridges for fracture surfaces and connections for pores. Thus, MWCNTs promote the geopolymerization reaction, strengthen the geopolymer skeleton, affect the pore structure, and improve mechanical characteristics.
Control of Thermal, Electrical, and Mechanical Properties of Porous SiC Ceramics via Doping: Shynar Kultayeva1; Young-Wook Kim1; In-Hyuck Song2; 1University of Seoul; 2Korea Institute of Materials Science
Aluminum-, boron-, nitrogen-, scandium-, and vanadium-doped porous SiC ceramics were fabricated to investigate the effects of dopants on thermal, electrical, and mechanical properties of porous SiC ceramics. A B-doped porous SiC ceramic exhibited the highest flexural strength (25.9 MPa) and thermal conductivity (16.6 W·m-1·K-1), whereas a Sc-doped porous SiC ceramic exhibited the lowest flexural strength (10.5 MPa) and thermal conductivity (7.7 W·m-1·K-1) among the doped porous SiC ceramics. The electrical conductivity of a nitrogen-doped porous SiC ceramic was 4.8 × 100 S/cm, four orders of magnitude higher than that of an undoped porous SiC ceramic (8.3 × 10-4 S/cm). The thermal and mechanical properties were dependent primarily on the necking area between SiC grains, whereas the electrical conductivity was strongly influenced by the doping. The results suggest that the electrical conductivities of porous SiC ceramics can be successfully tuned independently of the thermal conductivity by a suitable doping.