Despite favorable properties of ceramic-metal composites, they have not been applied commercially to date, due in large part to processing cost and challenges. The conventional method for manufacturing lamellar ceramic-metal composites is melt-infiltration of the metal phase into the gaps of the ceramic scaffold. The smaller the gap, the more difficult the infiltration. Because of the poor wetting between most metals and ceramics, the process requires high pressure and temperature to squeeze the molten metal into the gaps in the ceramic phase. This project aims at developing manufacturing strategies inspired by nature to enable low-cost fabrication of ceramic-metal composites. Natural materials such as bone and the nacreous part of sea-shells have developed structural composites, using a set of rather ordinary constituents, which exhibit extraordinary mechanical properties. For example, seashells convert a brittle ceramic material to a super-tough material (nacre) by incorporation of around 5% polymer, in a layered ?brick-and-mortar? microstructure. The scientific community has been very successful in identifying the design principles of biological structural composites. However, manufacturing knowledge gaps persist. These include the challenge of infiltration of small gaps between ceramic bricks, the challenge of obtaining ductile (while strong) mortars; the challenge in design of proper (metal-ceramic) interfaces; and the high cost. Low-cost processes for fabrication of metal−ceramic composites can substantially increase their applications in various industries including automotive, aerospace, oil and defense, in products such as high performance wear-resistance parts, cutting tools, lightweight structural composites, and aero-engine components. For these reasons, the project directly impacts American economic welfare and national security. The educational objective of the project is focused on increasing the diversity in nanotechnology- STEM through ?NanoExplorer? summer program for high school students, with particular emphasis on female students, including Latinos.
The goal of this research is to investigate the mechanisms underlying processing and manufacturing of ceramic composites for damage-tolerant structural applications. The project is focused on understanding infiltration of nanotwinned metals into nano-gaps (<100 nm) of a 3-dimensional porous ceramic scaffold by pulsed electrodeposition. A conservative estimate shows that the energy consumption in this process is more than 200-fold smaller than the conventional molten metal infiltration process. The liquid electrolyte in electrodeposition has much less viscosity compared to molten metals, and hence can effectively penetrate into the small gaps between the ceramic bricks. A class of metals that defeat the trade-off between strength and toughness are ?nanotwinned? metals. Nanotwinned metals have high density of coherent twin boundaries, which has been shown to enhance both strength and ductility. Pulsed electrodeposition is one of the primary methods of synthesis of nanotwinned metals. To address the metal-ceramic interface challenge, electroless deposition of a thin metal layer on ceramic bricks is planned, which will result in uniform coating, as well as strong adhesion between ceramics and metals. This research, if successful, will result in new fundamental knowledge in following subjects: (i) Growth mechanism and microstructure of nanotwinned metals directly synthesized by pulsed electrodeposition into a laminated ceramic scaffold; (ii) Kinetics of pulsed electrodeposition process in nano-channels (<100 nm); and (iii) Infiltration of a nano-porous ceramic scaffold by electrodeposition.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
