The research objective of this EArly-concept Grant for Exploratory Research (EAGER) project is to study the processing-structure-property relationship of functionally gradient nanolayered ceramic nanocomposite coating fabricated through a new paper making - laser sintering process, and test the hypothesis that the addition of carbon nanotubes can yield significant enhancement in mechanical properties of the ceramic coatings. It is a high-risk but high-payoff project because the new process is radically different from traditional approaches to make ceramic nanocomposite coating. This project's approach involves: 1) paper making process to manufacture nanolayered carbon nanotube paper consisting of both ceramic nanoparticles and carbon nanotubes, 2) laser sintering of the paper layer by layer to fabricate the functionally gradient coating, and 3) characterization of microstructures and mechanical properties of the fabricated nanocomposite coating. In the paper making - laser sintering process, good dispersion and controlled alignment of carbon nanotubes will be achieved in a suspension under an electric field. A suitable functionally gradient multilayered coating can be realized by laser sintering of the paper layer by layer, with varied and controlled compositions in each layer. The developed functionally gradient coating can potentially decrease the possibility of cracks and delamination at the coating-substrate interface significantly. Specifically, the grant will be used to demonstrate whether the addition of the carbon nanotubes will result in improved fracture toughness of the coating. This research will have a major impact on ceramic nanocomposite coating through advancing manufacturing science of ceramic nanocomposite coating and better understanding its structure-property relationship. The project will have broad potential impacts on aerospace, automotive, biomedical, and many other areas, where ceramic coatings play a key role. Some examples include the thermal barrier coatings in gas turbine engines, and the wear or corrosion resistance coatings needed in numerous medical implants and mechanical components.
The method to fabricate of carbon nanotube (CNT) reinforced ceramic nanocomposites through laser sintering has been rarely studied. Laser sintering is a flexible, localized and high-precision process, which can also potentially produce coatings or parts with complicated shapes and/or spatially controlled compositions. This EArly-concept Grant for Exploratory Research (EAGER) project has studied the feasibility of fabricating CNT-reinforced ceramic nanocomposites through laser sintering of ceramic nanoparticles and CNTs. The uniform dispersion of CNTs and ceramic particles can be realized in a thin sheet using the vacuum-assisted spray-infiltration process. This study shows that laser sintering can induce the agglomeration of ceramic nanoparticles and create a relatively more continuous ceramic phase in the composites. During the sintering process, CNTs are well preserved without obvious thermal degradation. In addition, they are bonded with the ceramic phase after the laser sintering process. The experimental results show that the hardness of the laser-sintered ceramic composite is higher than thermal spraying. The addition of CNTs has increased the fracture toughness of ceramics. This project has a major impact on ceramic nanocomposite coating through advancing manufacturing science and technologies of ceramic nanocomposite coating and better understanding the processing-structure-property inter-relationship. The potential commercial use of this technology includes advanced ceramics for aerospace and defense, cutting tools and wear components, brake pad, and thermal protective coating. Some real life applications include the thermal barrier coatings in gas turbine engines, and the wear or corrosion resistance coatings needed in numerous medical implants and mechanical components.
