Nanoindentation measurements

In AFM, the relative approach of sample and tip is nonnally stopped after contact is reached. Flowever, the instrument may also be used as a nanoindenter, measuring the penetration deptli of the tip as it is pressed into the surface of the material under test. Infomiation such as the elastic modulus at a given point on the surface may be obtained in tliis way [114], altliough producing enough points to synthesize an elastic modulus image is very time consuming. 

Fig. 4.22 Elastic moduli vs. temperature obtained by AFM nanoindentation measurements on various alkyd-based coatings (a) effect of oil number, (b) time evolution of modulus after application of the coating. (Reprinted with permission from [47].)...

Because the mechanical properties of amyloid fibrils are derived from AFM nanoindentation measurements on the basis of assumptions about the geometry of the fibrils, they cannot provide highly accurate information about deformation. Because of the vague information on structures, to determine how different loading conditions affect the amyloid fibrils structures and mechanical properties, we must resort to simulation. Thanks to the development of the molecular dynamics approach, one can obtain the Young s modulus of a biological system... 

As mentioned earlier, nanoindentation measurements of porous films deposited on substrates are much more complicated than that of bulk samples due to more factors affecting the indentation behaviour. Surface roughness was inherent to the processing method of our films and could be less problematic due to the use of spherical tips and diluted ink. Crack-free films with macroscopically flat surface were fabricated as shown in Figure 2. 

Huang, X. Pelegri, A. A. Nanoindentation Measurements on Low-k Porous Silica Thin Films Spin Coated on Silicon Substrates. Journal of Engineering Materials and Technology 125, 361-367 (2003). 

Mechanical and thermal characterization of ultra low k dielecteics is very similar to the characterization of dense low k dielectrics however the introduction of porosity requires the development of new characterization techniques in order to understand the pore structure. The dielectric constant, dielectric breakdown and coefficient of diermal expansion can be measured using the same techniques used for dense low k electrics. Modulus and hardness can also be measured by die same techniques, however, if using nanoindentation, measurements firom porous dielectrics may have larger substrate contributions at equivalent film thicknesses. Therefore, the modulus values... 

A Berkovich diamond tip with a total included angle of 142.3° and a radius of around 150 nm was used for the nanoindentation measurements [1-2]. Indentation load-displacement curves were obtained by applying loads ranging from 1 pN to 1 mN. The hardness and reduced elastic modulus of the tribofilms were determined with Oliver s method [35,36], where fused silica with a Young s modulus of 69.7 GPa was used as a standard sample for tip-shape calibration to determine the function of the contact area with respect to the contact depth in a range of 1.5-50 nm. Figure 9.5 shows indentation load-displacement curves obtained for the MoDTC/ZDDP and ZDDP tribofilms at a maximum load of 600 pN and in situ AFM images of the residual indent. A plastic pileup was clearly observed around the indent on both the MoDTC/ZDDP and ZDDP tribofilms. 

The addition of AC force modulation to the nanoindentation measurements increases sensitivity to elasto-plastic deformation and creep, as well as enables examination of damping or loss properties of materials, critical for determining mechanical properties of polymers (8). 

Monnet, TEM observations and nanoindentation measurements of Ti3SiC2 irradiated by charged particles, Proc. of the 2nd International Congress on Ceramics June 29 - July 4, Verona, Italy. 

Y.F. Cao, S. Allameh, D. Nankivil, S. Sethiaraj, T. Otiti, W. Soboyejo, Nanoindentation measurements of the mechanical properties of polycrystalline Au and Ag thin films on silicon substrates effects of grain size and film thickness. Mater. Sci. Eng. A-Struct. Mater. Prop. Microstruct Process. 427(1-2), 232-240 (2006)... 

Incorporating the nanoindentation measurement of the hardness (stress) for TiCrN [24] and Si [19] surfaces yield the relationships... 

However, nanoindentation measurement [51] revealed that the mechanical properties, such as the modulus and hardness, of anodic A1 oxide structures decrease monotonically as the pore size is increased from 30 to 80 nm, see Fig. 29.4b. Although the elastic modulus, hardness, and viscosity are different mechanical properties, a similar behavior was observed for all these properties, being the same to polymers [52]. The same trend of change in the seemingly different quantities indicates clearly their common origin and interdependence from the perspective of energy density, according to the BOLS correlation. 

Skin supersolidity slipperizes ice. The H-O contraction, core electron entrapment and dual polarization yield the high-elasticity, self-lubrication, and low-friction of ice and the hydrophobicity of water surface as well, of which the mechanism is the same to that of metal nitride [45, 46] and oxide [47] surfaces. Nanoindentation measurements revealed that the elastic recovery coefficient of TiCrN, GaAlN, and a-Al203 surfaces could reach 100 % under a critical indentation load of friction (<1.0 mN) at which the lone pair breaks with a friction coefficient being the same order to ice (0.1) [42], see Fig. 39.2. Albeit the pressure and the nature of loading pin materials, both show the comparatively low friction coefficients. The involvement of lone pairs makes the nitride and oxide surfaces more elastic and slippery under the critical load. This understanding supplements mechanism for the slippery of ice surface and the hydrophobicity of ultrathin water films as well. 

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