Coatings to Protect Materials from Extreme Environments: On-Demand Poster Presentations
Sponsored by: ACerS Engineering Ceramics Division
Program Organizers: Kang Lee, NASA Glenn Research Center; Yutaka Kagawa, The University of Tokyo; Daniel Mumm, University of California, Irvine; Rodney Trice, Purdue University; Emmanuel Boakye, UES Inc.; Valerie Wiesner, NASA Langley Research Center; Edward Gorzkowski, Naval Research Laboratory; Scooter Johnson, Naval Research Laboratory
Friday 8:00 AM
October 22, 2021
Room: On-Demand Poster Hall
Location: MS&T On Demand
Poster
Thermal and Mechanical Properties of Y3(Nb1-xTax)O7 as a Material for Thermal Barrier Coating: Janghyeok Pyeon1; Dowon Song2; Gualin Lyu3; Junseong Kim3; Seungcheol Yang3; Yeongil Jung3; 1Materials Convergence and System Engineering of Changwon National University; 2Hangyang University; 3Changwon National University
The glass-like thermal conductivity behavior has been observed in the fluorite-type Y3NbO7, which has a great potential as a high-temperature thermal barrier coating material. Therefore, in this study, the heavier Ta5+ with same ionic radius was selected to substitute Nb5+ in the Y3NbO7 in order to distort the lattice structure, forming various compositions of Y3(Nb1-xTax)O7 (x=0.1~0.5). The crystal structure was characterized by an X-ray diffraction and Raman spectroscopy. The highest coefficient of thermal expansion and lowest thermal conductivity at 1273K were 10.2-6/K at Y3(Nb0.9Ta0.1)O7 and 1.2 W/mK at Y3(Nb0.5Ta0.5)O7, respectively, resulting from the long-range disordered atomic arrangement and highly distorted crystal structure. Mechanical properties of Y3(Nb1-xTax)O7, such as elastic modulus and hardness, decreased as increasing the addition amount of Ta5+. The thermo-physical properties of Y3NbO7 can be optimized via the substitution of Ta5+, indicating that the Y3(Nb1-xTax)O7 system has a potential for application as a new thermal insulating material.
Self-generated Tribo-coatings on Glass from Nano-dispersions in Aqueous Medium: Sourav Sahoo1; Om Khatri2; N. M. Anoop Krishnan1; Nitya Gosvami1; 1Indian Institute of Technology (IIT) Delhi; 2CSIR-Indian Institute of Petroleum
Glasses are constantly subjected to scratch-induced damage, which significantly reduces the surface integrity leading to failure. Here, we show that the interfacial friction on glasses during sliding in an aqueous medium can be significantly reduced using nano-dispersions. To this extent, the tribological generation of protective coatings during sliding of a spherical alumina probe over fused silica glass surface in an aqueous environment containing various nano-dispersions at ambient temperatures is investigated in this study. Such tribo-coatings are observed to reduce the shear-induced tensile stresses determining the initiation of partial Hertzian cone cracks. Micro-Raman spectroscopy analysis confirms the deposition of dense films derived from the dispersions within the wear track. The optical and SEM micrographs display clear differences in the crack density and severity of sliding with and without the presence of the tribo-coatings. The results provide new insights into the scratch-induced surface damage mechanisms of glasses in the presence of nano-dispersions.