Browsing by Author "Filleter, Tobin"

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    Damage-tolerant 3D-printed ceramics via conformal coating
    (AAAS, 2021) Sajadi, Seyed Mohammad; Vásárhelyi, Lívia; Mousavi, Reza; Rahmati, Amir Hossein; Kónya, Zoltán; Kukovecz, Ákos; Arif, Taib; Filleter, Tobin; Vajtai, Robert; Boul, Peter; Pang, Zhenqian; Li, Teng; Tiwary, Chandra Sekhar; Rahman, Muhammad M.; Ajayan, Pulickel M.
    Ceramic materials, despite their high strength and modulus, are limited in many structural applications due to inherent brittleness and low toughness. Nevertheless, ceramic-based structures, in nature, overcome this limitation using bottom-up complex hierarchical assembly of hard ceramic and soft polymer, where ceramics are packaged with tiny fraction of polymers in an internalized fashion. Here, we propose a far simpler approach of entirely externalizing the soft phase via conformal polymer coating over architected ceramic structures, leading to damage tolerance. Architected structures are printed using silica-filled preceramic polymer, pyrolyzed to stabilize the ceramic scaffolds, and then dip-coated conformally with a thin, flexible epoxy polymer. The polymer-coated architected structures show multifold improvement in compressive strength and toughness while resisting catastrophic failure through a considerable delay of the damage propagation. This surface modification approach allows a simple strategy to build complex ceramic parts that are far more damage-tolerant than their traditional counterparts. Conformal polymer coating leads to damage-tolerant architected ceramic structures with high strength and toughness. Conformal polymer coating leads to damage-tolerant architected ceramic structures with high strength and toughness.
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    Friction of magnetene, a non–van der Waals 2D material
    (AAAS, 2021) Serles, Peter; Arif, Taib; Puthirath, Anand B.; Yadav, Shwetank; Wang, Guorui; Cui, Teng; Balan, Aravind Puthirath; Yadav, Thakur Prasad; Thibeorchews, Prasankumar; Chakingal, Nithya; Costin, Gelu; Singh, Chandra Veer; Ajayan, Pulickel M.; Filleter, Tobin
    Two-dimensional (2D) materials are known to have low-friction interfaces by reducing the energy dissipated by sliding contacts. While this is often attributed to van der Waals (vdW) bonding of 2D materials, nanoscale and quantum confinement effects can also act to modify the atomic interactions of a 2D material, producing unique interfacial properties. Here, we demonstrate the low-friction behavior of magnetene, a non-vdW 2D material obtained via the exfoliation of magnetite, showing statistically similar friction to benchmark vdW 2D materials. We find that this low friction is due to 2D confinement effects of minimized potential energy surface corrugation, lowered valence states reducing surface adsorbates, and forbidden low-damping phonon modes, all of which contribute to producing a low-friction 2D material.