Atomic force microscopy study of nanoindentation deformation and indentation size effect in MgO crystals

Abstract

The dependences of various nanoindentation parameters, such as depth of penetration d, indentation diameter a, deformation zone radius R, and height h of hills piled up around indents, on applied load were investigated for the initial (unrecovered) stage of indentation of the (100) cleavage faces of MgO crystals by square pyramidal Si tips for loads up to 10 N using atomic force microscopy. The experimental data are analyzed using theories of elastic and plastic deformation. The results revealed that (i) a, R, and h linearly increase with d; (ii) the development of indentation size and deformation zone and the formation of hills are two different processes; (iii) the load dependence of nanohardness shows the normal indentation size effect (i.e., the hardness increases with a decrease in load); and (iv) there is an absence of plastic deformation involving the formation of slip lines around the indentations. It is found that Johnson's cavity model of elastic-plastic boundary satisfactorily explains the experimental data. The formation of hills around indentations is also consistent with a new model (i.e., indentation crater model) based on the concept of piling up of material of indentation cavity as hills.

Measurement of Process-Dependent Material Properties of Pharmaceutical Solids by Nanoindentation

“…This has included spherical, cylindrical, and triangular and rectangular pyramid shapes. For surface preparation, several different methods are used, such as polishing,17 chemical etching,18 and cleaving a crystal surface 19. In the measurement, the surface is scanned using the indenter as the surface probe from which a microscopic, topographic image is obtained.…”

Study of Elastic Modulus and Yield Strength of Polymer Thin Films Using Atomic Force Microscopy

“…It must be noted that some "recovery" of the surface indent may take place during the 5-10 s elapse time between the act of indentation and the subsequent in situ imaging of the indent. 13 This time delay is much smaller compared to that needed in ex situ measurements, in cases where the relaxation time of the polymer is comparable to the elapse time of 5-10 s notably near the glass transition temperature of the polymer. AFM techniques that make use of the response of a sample to an indentation force have been employed for the study of various nanomechanical properties of polymer single crystals and amorphous polymer thin films, including elasticity, [14][15][16] and viscoelasticity.…”

“…Then the topography of the depression is measured almost immediately by using the same AFM cantilever/tip at a very light load. It must be noted that some “recovery” of the surface indent may take place during the 5−10 s elapse time between the act of indentation and the subsequent in situ imaging of the indent . This time delay is much smaller compared to that needed in ex situ measurements, in cases where the relaxation time of the polymer is comparable to the elapse time of 5−10 s notably near the glass transition temperature of the polymer.…”

Nanoindentation tests for TiO2, MgO, and YSZ single crystals

“…The techniques are expected to be useful for measurement of the mechanical properties of thin films or local structure of various materials. For example, the nanoindentation tests for MgO [8][9][10][11][12][13][14][15][16][17], TiO 2 [18,19], and YSZ [8,20,21] single crystals have been performed until now. However, there are few attempts to apply the nanoindentation to evaluate the mechanical properties of the nuclear fuels and materials.…”