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Non-crystalline, transparent methylsilsesquioxane-titania hybrid films for application in micropatterning were prepared from methyltriethoxysilane and titanium tetrabutoxide by the sol-gel method. The hybrid films were heat-treated at 100 °C for 1 h and then irradiated with UV light using an ultrahigh-pressure mercury lamp. The refractive index of the film increased as the amount of incorporated TiO2 increased. No changes in hardness were observed for the films lacking TiO2 during UV irradiation, whereas adding a small amount of TiO2 caused the hardness to increase significantly following UV irradiation. These changes in the physical properties of the films with UV irradiation were caused by the cleavage of Si-C bonds in the films induced by the photocatalytic effect of TiO2. On the basis of the changes in surface profiles, and optical, chemical, and mechanical properties induced by UV irradiation, it is concluded that the methylsilsesquioxane-titania films are promising for micropatterning by photolithography. [ABSTRACT FROM AUTHOR]

In instrumented indentation tests for a thin film coated on a substrate (film/substrate composite), it is well known that the substrate-affected contact area estimated through conventional approximations includes significant uncertainties, leading to a crucial difficulty in determining the elastic modulus and the contact hardness. To overcome this difficulty, an instrumented indentation microscope that enables researchers to make an in situ determination of the contact area is applied to an elastoplastic film on substrates having various values of their elastic moduli. Using the indentation microscope, the substrate-affected indentation contact parameters including contact hardness of the film/ substrate composites are determined directly as well as quantitatively without any undesirable assumptions and approximations associated with the contact area estimate. The effect of a stiffer substrate on the contact profile of impression is significant, switching the profile from sinking in to piling up during penetration, and resulting in the substrate-affected contact hardness being highly enhanced at deeper penetrations. Through the present experimental study, it is demonstrated that the instrumented indentation microscopy is highly efficient in determining the substrate-affected elastoplastic contact parameters of film/substrate composite systems. [ABSTRACT FROM AUTHOR]

This paper describes the development of the contact area during indentation of polycarbonate. The contact area was measured in situ using an instrumented indentation microscope and compared with numerical simulations using an elasto-plastic constitutive model. The parameters in the model were obtained using macroscopic tests. Indentations were performed on samples with different thermal histories and at different speeds. For all cases, the numerical model correctly predicted the development of the contact area during indentation. For increasing strain rates, the contact area decreased at equal indentation depths. Annealing the samples resulted in a smaller contact area at equal indentation depth. Using only numerical simulation, it was also shown that pile-up around the indenter resulted from localization effects and was, thus, promoted by strain-softening properties of the indented material. Strain hardening, on the other hand, will tend to promote sink-in. Finally, we performed simulations of load relaxation during indentation. The results indicate that about 40% of the total observed relaxation may be assigned to plastic effects. [ABSTRACT FROM AUTHOR]

An instrumented indentation microscope was constructed and applied to the measurements of the Meyer hardness and the elastic modulus of several engineering materials ranging from ductile metals to brittle ceramics. Because of the in situ optical observation and determination of the indentation contact area that is synchronized to the indentation load versus depth relation, the mechanical properties determined on the indentation microscope are precise and reliable without any undesirable approximations and assumptions required for estimating the contact area. It is also demonstrated that the instrumented indentation microscope is capable of determining in a quantitative manner the in situ contact profiles of impression (sinking-in/piling-up profiles). The present work suggests that the instrumented indentation microscope will be a powerful tool in the science and engineering of indentation contact mechanics. [ABSTRACT FROM AUTHOR]

The article discusses a study on the application of instrumented indentation microscopy to estimate the contact area of thin film/substrate composites. Indentation microscopy was applied to an elastoplastic film on substrates with various elastic moduli. The contact hardness of the composites was one of the substrate-affected indentation contact parameters identified under the study. The study found that a stiffer substrate significantly affect the contact profile of impression.