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Using a new surface force apparatus, static and dynamic measurements have been conducted to investigate the squeeze of a liquid from the contact between a relatively smooth sphere and a plane. Simple liquids and polymer melts (polyisoprene) have been studied, with different solid surfaces (mica, cobalt, gold, platinum, and steel). It has been found that an ‘‘immobile’’ layer of fluid is present on each solid surface which does not participate in the hydrodynamic flow of the liquid. The thickness of this film is relatively independent of the roughness of the solid, corresponds to a small number of molecular layers (1 to 5), and is influenced by the structure of the molecule. These fluids shows two different behaviors: for small molecules the thickness of the ‘‘immobile’’ layer is proportional to the viscosity; for larger molecules the thickness is proportional to the one-tenth power of the viscosity. During the squeeze process, when the solid surfaces are close, a ‘‘confined’’ layer occurs due to molecule entanglement. This phenomenon is described for a semirigid hydrocarbon.

Studies of Vickers hardness of magnesium oxide are presented in the literature for three purposes. They give information about relations between hardness and brittleness, (plasticity and toughness behavior); they show the anisotropical effect of the structure of the material and they are a tool to study the chemomechanical effects (Rebinder effects). Generally, the Vickers hardness is evaluated by measurements of the diagonals of residual indentation. Equipment was built which gives a record of the applied depression depth (h) as a function of the carried load P (in the range 10−1 N to 10+1 N). Investigation of the curves P(h) during loading and unloading and microscopical observations of residual indentation show that phenomena are complex. The contact is elastoplastic. The roles played by the plasticity and elasticity are discussed. The physical meaning of Vickers hardness, determined by use of residual indentation measurements, is analyzed.

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