ABSTRACT
Several analytical techniques that are currently available can be used to determine the spatial distribution and amount of austenite, ferrite and precipitate phases in steels. The application of magnetic force microscopy, in particular, to study the local microstructure of stainless steels is beneficial due to the selectivity of this technique for detection of ferromagnetic phases. In the comparison of Magnetic Force Microscopy and Electron Back-Scatter Diffraction for the morphological mapping and quantification of ferrite, the degree of sub-surface measurement has been found to be critical. Through the use of surface shielding, it has been possible to show that Magnetic Force Microscopy has a measurement depth of 105-140 nm. A comparison of the two techniques together with the depth of measurement capabilities are discussed.
ABSTRACT
Shear force microscopy is not normally associated with the imaging of biomolecules in a liquid environment. Here we show that the recently developed scattered evanescent wave (SEW) detection system, combined with custom-designed vertically oriented cantilevers (VOCs), can reliably produce true non-contact images in liquid of DNA molecules. The range of cantilever spring constants for successful shear force imaging was experimentally identified between 0.05 and 0.09 N m(-1). Images of λ-DNA adsorbed on mica in distilled water were obtained at scan rates of 8000 pixels s(-1). A new constant-height force mapping mode for VOCs is also presented. This method is shown to control the vertical position of the tip in the sample plane with better than 1 nm accuracy. The force mode is demonstrated by mapping the shear force above λ-DNA molecules adsorbed on mica in a liquid environment at different tip-sample separations.
