Search results for "Nanoindentation"
showing 10 items of 54 documents
Nanoindentation and photoluminescence characterization of ZnO thin films and single crystals
2010
In this work an optical and micromechanical properties of ZnO films deposited on glass by simple method based on the mechanoactivated oxidation have been investigated and compared with those of bulk ZnO single crystal and commercial ZnO films. Results showed that investigated ZnO films have stable high adhesion with glass and can form grained structure with hardness 8–10 GPa or whiskers nanostructure with high hardness 18–20 GPa. Young’s modulus is in range from 80 to 120 GPa. Optical properties of obtained ZnO films with whiskers structure are typical for transparent high quality ZnO single crystal. These coatings also exhibit a photo-electric response which reflects on the change in resis…
Color centers and nanodefects in LiF crystals irradiated with 150MeV Kr ions
2012
Abstract The modifications of structure, optical and nano-mechanical properties of LiF crystals after irradiation with 150-MeV Kr +14 ions at a fluence of 6 × 10 12 ions cm −2 have been studied using optical absorption spectroscopy, scanning electron and atomic force microscopy, and nanoindentation. Optical spectroscopy shows the saturation of F centers and a comparatively high number of F n centers. AFM and SEM imaging reveals a nanostructured region with columnar nanocrystallites (size 30–90 nm). Nanostructuring occurs in depths up to 10 μm, where the ion energy loss surpasses a critical threshold of about 10 keV/nm. At a lower energy loss a zone enriched with dislocations is observed. S…
Nanostructuring and strengthening of LiF crystals by swift heavy ions: AFM, XRD and nanoindentation study
2012
Abstract Modifications of the structure and micromechanical properties of LiF crystals under high-fluence irradiation (10 11 –10 13 ions cm −2 ) with swift C, Ti, Au and U ions of the specific energy of 11.1 MeV/u have been studied. In the case of heavy ions (U, Au), the AFM and SEM results reveal the bulk nanostructure consisting of columnar grains with nano-scale dimensions (50–100 nm). For lighter C ions the structure enriched with prismatic dislocation loops has been observed. High-resolution XRD reciprocal space maps for nano-structured LiF expose a mosaic-type structure with low-angle boundaries between grains.
Formation of dislocations in LiF irradiated with 3He and 4He ions
2018
Influence of the irradiation with 13.5 MeV 3He and 5 MeV 4He ions on the micro-structure and mechanical properties of LiF single crystals was studied. The depth profiles of nanoindentation, dislocation mobility, selective chemical etching and photoluminescence served for the characterization of damage. Strong ion-induced increase of hardness and decrease in dislocation mobility at the stage of track overlapping due to accumulation of dislocations and other extended defects was observed. At high fluences (1015 ions/cm2) the hardness saturates at about 3.5 GPa (twofold increase in comparison to a virgin crystal) thus confirming high efficiency of light projectiles in modifications of structur…
Improving surface detection on nanoindentation of compliant materials
2010
Nanoindentation is a versatile tool for monitoring mechanical properties on a local scale. Accurate knowledge of a contact area, and therefore an initial contact, is however necessary for translating the force curve into sample mechanical properties. It is shown that methods for sensing an initial contact by depth sensing instruments (DSI) may be severely in error for compliant materials. With the hardware adopted in this work, the threshold is determined by the elastic modulus; hence the error potentially increases if the material becomes more compliant. A simple method is therefore suggested to determine with accuracy the initial contact on compliant materials whereby the surface contact …
Accurately evaluating Young’s modulus of polymers through nanoindentations: a phenomenological correction factor to the Oliver and Pharr procedure
2006
The Oliver and Pharr [J. Mater. Res. 7, 1564 (1992)] procedure is a widely used tool to analyze nanoindentation force curves obtained on metals or ceramics. Its application to polymers is, however, difficult, as Young’s moduli are commonly overestimated mainly because of viscoelastic effects and pileup. However, polymers spanning a large range of morphologies have been used in this work to introduce a phenomenological correction factor. It depends on indenter geometry: sets of calibration indentations have to be performed on some polymers with known elastic moduli to characterize each indenter.
Nanoscale mechanical characterization of polymers by AFM nanoindentations: Critical approach to the elastic characterization
2006
AFM nanoindentations show a dependence of penetration, i.e., the relative motion between the sample and the tip (indenter), on material elastic properties when using the same load. This elationship becomes visible by using of samples being homogeneous down to the scale of nanoindentation. They were prepared from materials covering a broad range of mechanical behavior: from rubbery networks to glassy and semicrystalline polymers. The elastic modulus can be obtained applying Sneddon’s elastic contact mechanics approach. To do this, some calibrations and instrumental features have to be measured accurately. All the polymers tested show that the contact between the tip and the sample is dominat…
Magneto-Transport Results in SAM Based MTJs
2015
This chapter is dedicated to the description of the magneto-transport results obtained in LSMO/SAM/Co magnetic tunnel nanojunctions fabricated by nanoindentation lithography technique. We started by focusing on the study of LSMO/C12P/Co MTJs. This because C12P is a medium size alkyl chain: long enough to avoid short-circuits in the junction but short enough to give a device resistance in the order of few tens of MO and thus easier to measure. Next, we started to tune the molecule thickness from C10P to C18P (from 10 carbon atoms in the alkyl chain to 18). This allowed on one hand to validate our system by comparing the exponential increase of the junction resistance to the one reported in t…
On the Use of the Nanoindentation Unloading Curve to Measure the Young's Modulus of Polymers on a Nanometer Scale
2005
Summary: The nanoindentation test is a fundamental tool to assess the link between morphology and mechanical properties. The preliminary results of a more exhaustive study about the applicability to polymers of the most used procedure to determine elastic modulus by indentation are reported in this short communication. A departure of the experimental conditions from the theoretical assumptions and results that give rise to the Oliver and Pharr analysis is shown to occur under a wide range of experimental conditions, with applied loads and penetration depths covering several orders of magnitude and using different indenter geometries. Unloading curves with exponents significantly larger than…
Swift heavy ion induced modifications of luminescence and mechanical properties of polypropylene/ZnO nanocomposites
2014
Abstract The effect of irradiation with 150 MeV Kr ions at fluencies 10 11 and 10 12 ions/cm 2 on luminescence of PP/ZnO nanocomposites and PP matrix has been studied. In unirradiated composite the luminescence is comparatively weak and is contributed mainly by the excitonic luminescence of ZnO. Irradiation of nanocomposite and PP matrix leads to a strong increase of luminescence intensity in a wide spectral range of 360–600 nm. It follows from the obtained results that the enhancement of luminescence originates mainly from the broken bonds in PP matrix. Ion-induced scission of polymer bonds and fragmentation of polymer chains is deduced also from the nanoindentation tests which show a rem…