Micro/Nano-Rheology of Thin and Thick Coatings of Functional Sol-Gel Hybrids

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A research project on the micro/nano-indentation contact rheology had been intensively as well as extensively conducted for (a)developing theoretical frameworks of elastoplastic/viscoelastic contact mechanics, and its application to coating/substrate composites systems, (b)examining the chemical/physical conditions of sol-gel-derived coating films on a solid substrate that are appropriate for studying the elastoplastic and viscoelastic contact deformations and flows, and (c)applying the present novel techniques/analyses of nano-indentation rheology to in situ probing the siloxane clusters and networks that are evolved during the condensation chemical reaction in sol-gel processing. The major research results of the present project are summarized in what follows :(1)Theoretical considerations were made for the constitutive equations of indentation contact deformations and flows in the time-independent elastoplastic and the time-dependent viscoelastic regimes, and then they are extended … More to coating/substrate composite systems. Analytical/numerical studies were also conducted on the basis of finite element analyses to scrutinize the theoretical frameworks proposed in this research project.(2)A novel instrumented nano-indentation test system was designed and constructed. It is efficient for researches in micro/nano-regimes not only for the time-independent elastic, plastic, and elastoplastic responses, but also for the time-dependent viscoelastic and viscous responses.(3)Sol-gel-derived thin and thick organic-inorganic hybrid films (MeSiO_<3/2> and PhSiO_<3/2>) coated on a soda-lime glass plate were prescribed for nano-rheological testing. The molecular structures of siloxane chain networks that are evolved in sol-gel processing were examined in terms of the time and the temperature of the condensation reaction, through the elastoplastic analysis for the former hybrid and the viscoelastic for the latter. It was confirmed that the micro/nano-indentation rheology is very efficient for characterizing coating/substrate systems having not only time-independent, but time-dependent behaviors, as well. Less