Bioinspired Nacre‐Like Alumina with a Metallic Nickel Compliant Phase Fabricated by Spark‐Plasma Sintering

Abstract

The remarkable damage-tolerance found in natural materials is developed through functional, multiscale architectures with structural gradients and graded interfaces. [1][2][3][4][5][6] One notable example is nacre, which comprises ceramic (mineral) platelets of polycrystalline aragonite (≈95% by volume) bonded by biopolymers in a "brick-and-mortar" structure. [1,3,7] The Many natural materials present an ideal "recipe" for the development of future damage-tolerant lightweight structural materials. One notable example is the brick-and-mortar structure of nacre, found in mollusk shells, which produces high-toughness, bioinspired ceramics using polymeric mortars as a compliant phase. Theoretical modeling has predicted that use of metallic mortars could lead to even higher damage-tolerance in these materials, although it is difficult to melt-infiltrate metals into ceramic scaffolds as they cannot readily wet ceramics. To avoid this problem, an alternative ("bottomup") approach to synthesize "nacre-like" ceramics containing a small fraction of nickel mortar is developed. These materials are fabricated using nickelcoated alumina platelets that are aligned using slip-casting and rapidly sintered using spark-plasma sintering. Dewetting of the nickel mortar during sintering is prevented by using NiO-coated as well as Ni-coated platelets. As a result, a "nacre-like" alumina ceramic displaying a resistance-curve toughness up to ≈16 MPa m ½ with a flexural strength of ≈300 MPa is produced. Ceramic-Metal Composites www.advancedsciencenews.com

Strong and tough nacre-like aluminas: Process–structure–performance relationships and position within the nacre-inspired composite landscape

“…10). NLA-TLP have a K IC equal or higher than all other nacre-like composites with both polymer [50,59] and metallic phases [53,54,56] while presenting strength 2 times higher than all the other nacrelike composites. The K J of MASC-TLP is only bested by two compositions, Ice T-glass and a composite made with a mixture of nickel metal and nickel oxide.…”

“…Because of Griffith scaling law, smaller reinforcement sizes usually mean stronger composites, so the next development was to use micron-sized bricks, with alumina platelets [45,46,47], glass flakes [33,48], or brushite platelets [49]. Several secondary phases have been used in these composites, from polymers [47,50,51] to metal [52,53,54,55,56] and even graphene [57] or metallic glasses [58]. The controlled dewetting of TiO 2 nanolayer allows in addition the careful study of the mineral bridges' effect on the mechanical properties [59,60].…”

“…Nacre-like composite with polymer secondary phase: MASC PUA-PHEMA[50], MASC TiO 2 -epoxy[59]. Nacre-like composite with metallic secondary phase: Ice T Ni[53], Ice T copper[54], MASC copper[52], pressing Ni/NiO[56].Invited Feature Paper -Review ª Materials Research Society 2020 cambridge.org/JMR 1087 j Journal of Materials Research j Volume Issue Apr 28, 2020 j www.mrs.org/jmr Downloaded from https://www.cambridge.org/core. /www.cambridge.org/core/terms.…”

Tough metal-ceramic composites with multifunctional nacre-like architecture

“…By combining design principles of nacre’s brick-and-mortar structure with the rich variety of chemistries available in synthetic systems, current nacre-like materials exhibit mechanical properties that even surpass those of the natural counterparts 4 – 9 . As opposed to conventional materials, such bio-inspired structures can be designed to showcase antagonistic properties, such as high stiffness and fracture toughness, that are not accessible through the optimization of chemical compositions alone 7 , 10 , 11 . Despite these promising prospects, a broader application of such bio-inspired materials requires the development of manufacturing technologies that ensure up-scalability and robust structural control.…”

“…In another example, nacre-inspired materials featuring a graphene percolating network as continuous phase have been developed to imbue brick-and-mortar structures with self-sensing capabilities 23 . In addition to these functionalities, studies have also been conducted to enhance the mechanical properties of nacreous materials by utilizing stiffer and tougher metals as the mortar phase between stiff ceramic bricks 7 , 20 , 24 – 30 . Because of the plastic deformation of the metallic phase during fracture, composites containing nickel, aluminum or amorphous metal alloys between alumina platelets have been shown to feature remarkable mechanical stiffness and enhanced resistance to crack growth 7 , 20 , 31 .…”