Depth-sensing Nanoindentation Technique Research Articles

Mechanical properties, bioactivity and cell behavior of barium-containing calcium-phospho-alumino-borosilicate glass

In this study, the effect of replacing CaO by BaO on mechanical properties, bioactivity, and cell adhesion of SiO2–B2O3–Al2O3–P2O5–CaO–Na2O based glass was investigated. Mechanical characterization, depth-sensing nano-indentation, and surface micro-indentation techniques were employed to determine the fracture toughness (KIC). The surface was photographed after micro-indentation effect using scanning electron microscopy. In vitro responses of the compounds of tris-buffered SBF solution were studied from different points of view: (i) morphology and elemental surface analysis using field emission electron microscopy equipped with energy dispersive spectroscopy; (ii) change in bonds using Raman spectroscopy; and (iii) ICP method for detecting the change in ion chemistry of SBF solution. The cell adhesion behavior was qualitatively evaluated by examining the morphology and attachment of mouse fibroblastic cells to the surface of the glasses. The results demonstrated that with the replacement of barium oxide, the hardness of the base glass increased, while the level of fracture toughness was maintained. In addition, in vitro bioactivity of barium oxide-containing glass was reduced compared to the base glass. However, structural dissolution and formation of calcium phosphate layers on their surfaces were also confirmed. The results showed that BaO-incorporated glasses had adequate cell propagation and proliferation, hence enjoying appropriate biocompatibility for use in coating applications.

Investigation on the combined effect of ZnO nanorods and Y2O3 nanoparticles on the microstructural and mechanical response of aluminium

In this work Al-ZnO-Y2O3 hybrid composites were fabricated utilizing powder metallurgy and hybrid microwave sintering approach from the powder blend of Al, ZnO and Y2O3. Depth sensing nano-indentation technique was adopted to assess the nano-hardness and elastic modulus of the composite material. Thermal analysis of the composite materials was done to gain an insight into surface decomposition and phase transformation behaviour. A strong interfacial bonding with clear interface between matrix and reinforcement was observed during the microstructural analysis of the composite material. The results of the current study exhibit ~89% improvement in the nano-hardness and ~11% improvement in the elastic modulus value. The improvement in the material response is attributed to the reasonably uniform distribution of ZnO and Y2O3 in the hybrid composite materials. The results of this study validate the capability of combined presence of ZnO and Y2O3 reinforcements to enhance the hardness and elastic modulus of aluminium.

High-dose ion irradiation damage in Fe28Ni28Mn26Cr18 characterised by TEM and depth-sensing nanoindentation

One of the key challenges for the development of high-performance fusion materials is to design materials capable of maintaining mechanical and structural integrity under the extreme levels of displacement damage, high temperature and transmutation rates. High-entropy alloys (HEAs) and other concentrated alloys have attracted attention with regards to their performance under fusion conditions. In recent years, a number of investigations of the irradiation responses of HEAs have peaked the community’s interest in them, such as the work of Kumar et al. (2016), who examined Fe27Ni28Mn27Cr18 at doses as high as 10 dpa. In this work, we study Fe28Ni28Mn26Cr18 concentrated multicomponent alloy with irradiation doses as high as 20 dpa. We find the presence of Cr rich bcc precipitates in both the un-irradiated and in the irradiated condition, and the presence of dislocation loops only in the irradiated state. We correlate the features found with irradiation hardening by the continuous stiffness method (CSM) depth-sensing nanoindentation technique and see that the change in the bulk hardness increases significantly at 20 dpa for temperatures 450 °C. These results indicate that the alloy is neither stable as a single phase after annealing at 900 °C, nor particularly resistant to irradiation hardening.

Frontiers in nanotribology: Magnetic storage, bio/nanotechnology, cosmetics, and bioinspiration

The word “nanotribology” was introduced for the first time in the title of a paper and a book in 1995. This field encompasses fundamental studies of surface characterization, adhesion, friction, scratching, wear, and lubrication at the atomic scale. At most solid-solid interfaces of technological relevance, contact occurs at numerous asperities. It is of importance to investigate a single asperity contact in the fundamental tribological studies. A nanoprobe sliding on a surface in probe-based microscopies, including atomic force microscopy (AFM) at ultralow loads, simulates one such contact. AFMs and depth-sensing nanoindentation techniques are also used for nanomechanical characterization. The field is referred to as nanomechanics. AFMs can also be used for nanoelectrical characterization which includes electrical resistance, surface potential, and capacitance mapping.Research in the field of nanotribology and nanomechanics was initiated by or for the magnetic storage industry in the late 1980s. Later in the mid-1990s, nanotribology and nanomechanics research became important in bio/nanotechnology devices which involve relative motion, as well as ultrathin films. Adhesion, friction and wear issues in bio/nanotechnology devices led to the development of the field of bio/nanotribology. Research in ultrathin films used in the cosmetic industry, including hair, hair conditioner, skin, and skin cream, led to development of the field of nanotribology in cosmetics. Biologically inspired design, adaptation, or derivation from nature, referred to as biomimetics or bioinspiration, can guide us to initiate and produce nanomaterials, nanodevices, and processes in a sustainable and environmentally friendly manner. So called, green nanotribology research is important in this field.This perspective article presents an overview of fundamental understanding of nanotribology and nanomechanics and their applications in various fields ranging from magnetic storage, bio/nanotechnology, hair and hair conditioner, skin and skin cream, and bioinspiration (green nanotribology).

Effect of annealing process on mechanical properties of n-type La1.9Ce0.1CuO4 superconducting films by depth sensing nanoindentation

The influence of annealing time on microstructure, morphological, electrical and mechanical properties of La1.9Ce0.1CuO4 (LCCO) superconducting films has been studied. Single-phase LCCO thin films were prepared by pulsed-laser deposition on SrTiO3 substrate with varying annealing time. Microstructure and morphology of the LCCO films were investigated using x-ray diffraction and atomic force microscopy. Temperature dependence of electrical resistance of the LCCO films was determined by four-point method. Hardness and elastic modulus of the LCCO films were characterized by depth sensing nanoindentation technique. Results show that annealing time mainly affects the hardness and elastic modulus of the LCCO films through Cu-rich particles and the crystallite size. However, the influence of Cu-rich particles is much less remarkable than that of the crystallite size.

Nano-scale elastic–plastic properties and indentation-induced deformation of amorphous silicon carbide thin film

Controllable low-temperature (500°C) deposition of amorphous a-SiC ceramic films on Si(100) was achieved using a pulsed dc-magnetron puttering system in a mixture of CH4/Ar. The nanoscale elastic-plastic response of the film upon contact loading was systematically characterized and analyzed by depth sensing nanoindentation technique using a Berkovich tip indenter. The mean values for elastic modulus and hardness were found to be 170±10 and 11.0±0.8GPa, respectively. The onset of elastic-plastic transition occurred with contact loading of 70µN at a depth of 10nm. By coupling the Hertzian contact theory and Johnson's cavity model, the critical shear stress (7.7GPa), yielding strength (14.4GPa), plastic zone size (30–300nm), and plastic work ratio (0.18–0.40) of a-SiC thin film under nanoindentation were determined. Based on the experimental results, the resolved shear stress analysis and deformation behavior were found to be consistent with the interpretation that the deformation behavior was associated with local readjustment of small clusters of atoms. The deformation mechanism was also explained on the basis of shear transformation zones (STZs) amorphous plasticity theory.

Determination of mechanical properties of Al2O3/Y-TZP ceramic composites: Influence of testing method and residual stresses

A series of Al2O3/Y2O3-stabilized zirconia (Y-TZP) ceramic composites with different zirconia contents (5 and 40vol% Y-TZP) and fabricated by different green processing techniques (a novel tape casting and conventional slip casting) were studied. The microstructure and mechanical properties of the composites were investigated systematically, by means of scanning electron microscopy, Vickers indentation, depth-sensing nanoindentation, and single-edge laser-notched beam (SELNB) techniques. The indentation fracture method was found to be unsuitable for fracture toughness determination in this work. Reliable values of fracture toughness were obtained by the SELNB method with an almost atomically sharp laser-machined initial notch. The microstructure and mechanical properties of the ceramic composites mainly depended on the Y-TZP content. No significant differences were induced by the choice of green processing technique. The contribution of residual stresses to fracture toughness in Al2O3/Y-TZP ceramic composites was investigated. To this end, a theoretical model was applied to estimate the increase in fracture toughness due to the measured residual stresses in the samples. It was found that in this case, residual stresses were not the main factor responsible for the toughening in Al2O3/Y-TZP composites.

Evaluation of elastic modulus and hardness of highly inhomogeneous materials by nanoindentation

The experimental and numerical techniques for evaluation of mechanical properties of highly inhomogeneous materials are discussed. The techniques are applied to coal as an example of such a material. Characterization of coals is a very difficult task because they are composed of a number of distinct organic entities called macerals and some amount of inorganic substances along with internal pores and cracks. It is argued that to avoid the influence of the pores and cracks, the samples of the materials have to be prepared as very thin and very smooth sections, and the depth-sensing nanoindentation (DSNI) techniques has to be employed rather than the conventional microindentation. It is shown that the use of the modern nanoindentation techniques integrated with transmitted light microscopy is very effective for evaluation of elastic modulus and hardness of coal macerals. However, because the thin sections are glued to the substrate and the glue thickness is approximately equal to the thickness of the section, the conventional DSNI techniques show the effective properties of the section/substrate system rather than the properties of the material. As the first approximation, it is proposed to describe the sample/substrate system using the classic exponential weight function for the dependence of the equivalent elastic contact modulus on the depth of indentation. This simple approach allows us to extract the contact modulus of the material constitutes from the data measured on a region occupied by a specific component of the material. The proposed approach is demonstrated on application to the experimental data obtained by Berkovich nanoindentation with varying maximum depth of indentation.

Nanomechanical characterization of amorphous and nanocrystalline FeCuNbSiB thin films

Mechanical properties (hardness and Young's modulus) of amorphous and nanocrystalline Fe73.5Cu1Nb3Si15.5B7 thin films (thicknesses from 1.4μm to 2μm) have been investigated using the depth-sensing nanoindentation technique. The amorphous films, having uniform and smooth surfaces, were deposited on glass, aluminum, silicon, and sapphire substrates using the high power impulse magnetron sputtering technique. The nanocrystalline state was achieved after isothermal treatments performed at temperatures between 463°C and 475°C. The mean value for the effective Young's modulus of the amorphous Fe73.5Cu1Nb3Si15.5B7 thin films is about 146GPa, regardless of their thickness or the substrate's nature. Increasing the thickness of the films, the hardness value increases up to 1GPa. After the thermal treatments performed at 475°C (when the films’ structure consists of b.c.c. α-Fe(Si) grains with average size of 15nm embedded in a residual amorphous matrix) the effective Young's modulus value decreases by about 13%, while hardness value increases by about 13% with respect to the as-deposited state.

Mechanical properties of deposited carbon thin films on sapphire substrates using atomic force microscopy (AFM)

In this study, the mechanical properties of nano-layered carbon thin films deposited on Al2O3 single crystal substrates with varying orientations in A (1120), M (1010), R (1102) and C (0001) planes were investigated using depth-sensing nanoindentation techniques. All of the nano-layered films were deposited by a thermionic vacuum arc (TVA). In this experiment, a high purity amorphous carbon rod was used. Single crystal Al2O3 plates were used as the substrate material. All of the substrates were a commercial product that is readily available. For the surface topography, the roughness and depth-sensing nano-hardness of the deposited films were analyzed using an Ambios Q-scope atomic force microscope. An F20 thin film measurement system was used for the determination of thickness and reflection properties of the deposited thin films. Indention depths were determined as 5nm, 10nm and 15nm. In these indentation depths, hardness values were calculated in the range of 8–25GPa.

Evaluation of the nanostructure of cervical third cementum in health and chronic periodontitis: An in vitro study.

Background:During the progression of periodontal disease, the cementum undergoes alterations in its structure and composition. Understanding the nanostructure of cementum, in terms of its mechanical properties, will provide an insight into the milieu that periodontal ligament cells encounter in health and chronic periodontitis. This study aims to analyze the nanomechanical properties of the cervical third of the cementum (transverse section) in health and chronic periodontitis.Materials and Methods:Twenty teeth (10 healthy and 10 periodontally diseased) were collected and the nanomechanical properties of the transverse section of the cervical third cementum were evaluated with depth-sensing nanoindentation technique under dry conditions. A total of 100 nanoindentations were performed to analyze the modulus of elasticity and hardness of cervical third of the cementum.Results:The nanomechanical properties of the healthy cervical third cementum sections were significantly higher (P < 0.05) (hardness: 0.720 ± 0.305 GPa; modulus: 15.420 ± 3.902 GPa) than the diseased cementum section (hardness: 0.422 ± 0.157 GPa; modulus: 11.056 ± 3.434 GPa).Conclusion:The results of our study indicate that the hardness and modulus of elasticity of the cervical third cementum decreases significantly in chronic periodontitis.

Small‐Scale Deformation of Pulsed Electric Current Sintered Silicon Oxycarbide Polymer Derived Ceramics

The deformation behavior of pulsed electric current sintered silicon oxycarbide ceramics produced by the solid‐state thermolysis of polyhydridomethylsiloxane at small‐scale is investigated. The ceramics remained X‐ray amorphous after sintering at 1300 °C in vacuum and a high density of ≈2.35 g cm−3 is achieved. The elastic constants of these ceramics are determined using non‐destructive ultrasonic testing method. The elasto‐plastic deformation under contact loading is determined using depth sensing nanoindentation technique. An indentation hardness of ≈11 GPa and reduced elastic modulus of ≈105 GPa is observed. The load–displacement curves display significant elastic recovery with an elastic work ratio of ≈0.71. The evolution of Hertzian cone cracks upon microindentation indicates an anomalous deformation behavior.

Effects of surface morphology, size effect and wettability on interfacial adhesion of carbon nanotube arrays

Vertically-aligned multi-walled carbon nanotube (MWCNT) arrays with various diameters and surface morphologies are fabricated to mimic gecko foot-hairs. The peeling behavior and interfacial adhesion characteristics of the MWCNT arrays are examined by means of depth-sensing nanoindentation technique. The results show that the adhesive force increases with an increasing surface roughness. However, the adhesive force significantly reduces with an increasing cap size due to a reduction in the number of contact sites between the MWCNT array and the indenter. Furthermore, the pull-off force of the MWCNT arrays is also found to increase with an increasing preload due to the corresponding deformation-induced increase in the contact area. Finally, it is shown that the contact angle of a water droplet on the MWCNT surface reduces with an increasing surface roughness. Thus, it is inferred that the enhanced adhesion of the MWCNT arrays with a greater surface roughness is due in part to an increased humidity and wettability of the MWCNT surface.

Experimental investigation on the indentation hardness of precursor derived Si–B–C–N ceramics

The elasto-plastic response of the precursor derived Si–B–C–N ceramics upon contact loading was determined by depth sensing nanoindentation technique. The indentation response of as-thermolyzed Si–B–C–N ceramic was compared with the heat-treated counterpart. The as-thermolyzed ceramic was X-ray amorphous and the heat-treated ceramic was phase separated and crystallized. The hardness and reduced elastic modulus values of the as-thermolyzed ceramic were ∼16 GPa and ∼172 GPa, respectively. The reduction in hardness to ∼9 GPa in the heat-treated ceramic was attributed to phase separation and crystallization of SiC and Si 3 N 4 . Furthermore, high elastic recovery with a plastic work ratio of ∼0.3 was observed and ascribed to volume controlled deformation mechanism .

Anticorrosion and nanomechanical performance of hybrid organo-silicate coatings integrating corrosion inhibitors

Corrosion protective sol–gel silica coatings were developed on AA2024-T3 alloy by in situ cross-linking with hyperbranched poly(ethylene imine). Coatings with or without corrosion inhibitors (2-mercaptobenzothiazole or 2-mercaptobenzimidazole) and of two different thicknesses (1–1.5 and 3–3.5μm, respectively) were obtained. Potentiodynamic scans and electrochemical impedance spectroscopy (after immersion in Harrison's solution for up to 4weeks) were employed to evaluate the anticorrosion performance of coatings, whereas their thickness, morphology and integrity were assessed by scanning electron microscopy and atomic force microscopy. Further the depth sensing nanoindentation technique was employed to measure the hardness and reduced modulus of coatings and the obtained data were analyzed to indicate their wear resistance, plastic deformation and mechanical integrity. In all cases, coatings of high quality with good barrier properties (impedance modulus reaching up to 106Ωcm2 at the very low frequency regime) and self-healing abilities (in case of the inclusion of an inhibitor) were obtained. The coating thickness was found to affect the anticorrosion performance, however, even thinner coatings demonstrate satisfactory protection and self-healing effect. Nanoindentation analysis revealed the flexible nature and viscous behavior of the coatings (with the theoretical transition of the elastic to plastic behavior appearing at 1000μN applied load) demonstrating also an optimal integration of the organic inhibitors into the film. It also revealed an effect of thickness with thinner coatings exhibiting slightly superior behavior in terms of elasticity and wear resistance.

Indentation response of pulsed electric current sintered polymer derived HfO2/Si–C–N(O) nanocomposites

Abstract The influence of pulsed electric current sintering on the structural evolution and indentation response of hafnia incorporated silicon carbonitride polymer derived ceramics was studied. Despite the absence of any sintering additives, appreciable sintering at 1400 °C with a density of ∼2.7 g/cc was observed. Sintering beyond 1300 °C resulted in the phase separation and nano-crystallization of amorphous Si–Hf–C–N–O ceramic. The crystallite coarsening was insignificant and thereby the tetragonal phase of hafnia was retained in the ceramic nanocomposite. A relatively high indentation hardness and elastic modulus of ∼18 GPa and ∼313 GPa were determined by depth sensing nanoindentation technique.

Nanoindentation Creep Behavior of Nanocomposite Sn-Ag-Cu Solders

High-density, ultrasmall-pitch electronic applications require miniaturized solder bumps with improved thermomechanical performance. In addition, novel techniques which are able to precisely characterize these solder bumps are needed. One approach to meeting both of these requirements is to make use of recently developed nanocomposite solders with enhanced creep resistance, and to characterize these solders using a nanoindentation technique. In the present study, the creep behavior of ceria-reinforced nanocomposite solder foils fabricated by the accumulative roll-bonding process was characterized using a depth-sensing nanoindentation technique. It was found that the creep resistance of the composites increased with increasing volume fraction of CeO2 reinforcement, and it was deduced that the creep deformation of this nanocomposite proceeded by deformation of the matrix, with the role of the reinforcement being to increase the creep resistance by reducing the effective stress acting on the matrix. The values of the creep exponent suggested that the dominant creep deformation mechanisms involved were diffusion creep and grain boundary sliding.

Nanomechanical properties of thick porous silicon layers grown on p- and p+-type bulk crystalline Si

Abstract The nanomechanical properties and the nanoscale deformation of thick porous Si (PSi) layers of two different morphologies, grown electrochemically on p-type and p+-type Si wafers were investigated by the depth-sensing nanoindentation technique over a small range of loads using a Berkovich indenter and were compared with those of bulk crystalline Si. The microstructure of the thick PSi layers was characterized by field emission scanning electron microscopy. PSi layers on p+-type Si show an anisotropic mesoporous structure with straight vertical pores of diameter in the range of 30–50 nm, while those on p-type Si show a sponge like mesoporous structure. The effect of the microstructure on the mechanical properties of the layers is discussed. It is shown that the hardness and Young's modulus of the PSi layers exhibit a strong dependence on their microstructure. In particular, PSi layers with the anisotropic straight vertical pores show higher hardness and elastic modulus values than sponge-like layers. However, sponge-like PSi layers reveal less plastic deformation and higher wear resistance compared with layers with straight vertical pores.

A new approach to evaluate irradiation hardening of ion-irradiated ferritic alloys by nano-indentation techniques

The present work investigates the irradiation hardening of Fe-based model ferritic alloys after Fe-ion irradiation experiments in order to deduce mechanistically based nominal hardness from the nano-indentation tests on the ion-irradiated surface. Ion-irradiation experiments were carried out at 290 °C with 6.4 MeV Fe 3+ ions. The constant stiffness measurement (CSM) was used to obtain the depth-profile of hardness. The results has been analyzed and discussed based on the Nix–Gao model and an extended film/substrate system hardness model. The depth-sensing nano-indentation techniques with CSM revealed that the hardness gradient of the unirradiated Fe-based model alloy can be explained through the indentation size effect (ISE). On the other hand, the gradient of ion-irradiated surface of these samples includes not only the ISE but also softer substrate effect (SSE). We propose a new approach to evaluate a nominal hardness, which may connect to the bulk hardness, from experimentally obtained nano-hardness depth profile data.

Effects of precursor evaporation temperature on the properties of the yttrium oxide thin films deposited by microwave electron cyclotron resonance plasma assisted metal organic chemical vapor deposition

Yttrium oxide thin films are deposited using indigenously developed metal organic precursor (2,2,6,6-tetra methyl-3,5-hepitane dionate) yttrium, commonly known as Y(thd) 3 (synthesized by ultrasound method). Microwave electron cyclotron resonance plasma assisted metal organic chemical vapor deposition process was used for these depositions. Depositions were carried out at a substrate temperature of 350 °C with argon to oxygen gas flow rates fixed to 1 sccm and 10 sccm respectively throughout the experiments. The precursor evaporation temperature (precursor temperature) was varied over a range of 170–275 °C keeping all other parameters constant. The deposited coatings are characterized by X-ray photoelectron spectroscopy, glancing angle X-ray diffraction and infrared spectroscopy. Thickness and refractive index of the coatings are measured by the spectroscopic ellipsometry. Hardness and elastic modulus of the films are measured by load depth sensing nanoindentation technique. C-Y 2O 3 phase is deposited at lower precursor temperature (170 °C). At higher temperature (220 °C) cubic yttrium oxide is deposited with yttrium hydroxide carbonate as a minor phase. When the temperature of the precursor increased (275 °C) further, hexagonal Y 2O 3 with some multiphase structure including body centered cubic yttria and yttrium silicate is observed in the deposited film. The properties of the films drastically change with these structural transitions. These changes in the film properties are correlated here with the precursor evaporation characteristics obtained at low pressures.