PROJECT SUMMARY CTS-9731396 The development of smart materials in the form of multifunctional active coatings is proposed in this exploratory research program. To demonstrate the feasibility and potential of multifunctional active coatings in this six-month collaborative project between Massachusetts Institute of Technology and Naval Research Laboratory, research focus will be directed towards hybrid active coatings that will serve to protect against environmental hazards, such as toxic fumes associated with fire damage. The smart coatings will present a combination of superb thermal barrier and catalytic functions. To accomplish these goals simultaneously, novel materials processing will be explored to provide intrinsic capabilities for tailoring unique microstructures and compositional flexibility. The PI's propose the use of nanostructure processing to achieve coatings with enhanced performance and interfacial stability. Specifically, modified sol-gel processing will be examined for nanostructure tailoring and coating applications. The multifunctional coatings includes the design of a thermal barrier overcoat that protects the underlying structure from a high-temperature environment, and catalytically active layers that would neutralize the toxic gases released. Sol-gel processing will be used to achieve the ultrafine grain size, high volume fraction of grain boundaries and tailored pore structures of nanostructured yttria-stabilized zircona for controlled transport characteristics through the coatings. This advanced wet chemical approach is attractive for its intrinsic flexibility in tailoring compositional homegeneity grain size and pore structure, and will enable realization of a thermal barrier coating with superior thermal resistance than the conventional coarse-grained counterpart. The toxic fumes diffused past the thermal barrier overcoat will further be catalytically treated by the underlying nanocrystalline layers. The ultrahigh surface-to-volume ratio of nanostructured materials will be exploited to provide unique surface reactivity and ultrahigh dispersion of active species for effective catalytic remediation of toxic gases. Various processing parameters will be examined to control the relative nucleation and growth rates and minimize particle agglomeration to achieve high surface area nanoparticles. The PI's will further develop barium hexaaluminate as an effective catalyst for oxidation of hydrocarbons and carbon monoxide. This material is much less expensive and more thermally stable than conventional noble metal catalysts. The PI's propose an innovative controlled sol-gel hydrolysis synthesis in reverse nanoemulsion for the low-temperature derivation of ultrahigh surface area, nanocrystalline doped barium hexaaluminate for effective oxidation of hydrocarbons and CO. The proposed research will demonstrate that nanocrystals can be processed in the form of coatings with controlled microstructures that will retain their unique transport and catalytic characteristics displayed in the respective bulk ceramic form and particulate form. It is further sought to investigate the structural, thermal and chemical stability of the interface of these hybrid coatings. Nanocomposite processing has demonstrated the possibility to engineer the surface reactivity and grain boundary structure to mechanically reinforce and thermally stabilize desirable microstructures.
