Nanoindentation Device Research Articles

Characterization of Changes to the Mechanical Properties of Arteries due to Cold Storage Using Nanoindentation Tests

Understanding the effect of cold storage on arterial tissues is essential in various clinical and experimental practices. Cold storage techniques could significantly affect the post-cryosurgical or post-cryopreservation mechanical behavior of arteries. Previously, arteries were considered homogenous and elastic and the changes in material properties due to cold storage were inconclusive. In this study, using a custom-made nanoindentation device, changes to the local viscoelastic properties of porcine thoracic aorta wall due to three common storage temperatures (+4, -20, and -80 °C) within 24 h, 48 h, 1 week, and 3 weeks were characterized. The changes to both elastic and relaxation behaviors were investigated considering the multilayer, heterogeneous nature of the aortic wall. The results showed that the average instantaneous Young's modulus (E) of +4 °C storage samples decreased while their permanent average relaxation amplitude (G (∞)) increased and after 48 h these changes became significant (10 and 13% for E and G (∞), respectively). Generally, in freezer storage, E increased and G (∞) showed no significant change. In prolonged preservation (>1 week), the results of -20 °C showed significant increase in E (20% after 3 weeks) while this increase for -80 °C was not significant, making it a better choice for tissue cold storage applications.

A novel and compact nanoindentation device for in situ nanoindentation tests inside the scanning electron microscope

In situ nanomechanical tests provide a unique insight into mechanical behaviors of materials, such as fracture onset and crack propagation, shear band formation and so on. This paper presents a novel in situ nanoindentation device with dimensions of 103mm×74mm×60mm. Integrating the stepper motor, the piezoelectric actuator and the flexure hinge, the device can realize coarse adjustment of the specimen and precision loading and unloading of the indenter automatically. A novel indenter holder was designed to guarantee that the indenter penetrates into and withdraws from the specimen surface vertically. Closed-loop control of the indentation process was established to solve the problem of nonlinearity of the piezoelectric actuator and to enrich the loading modes. The in situ indentation test of Indium Phosphide (InP) inside the scanning electron microscope (SEM) was carried out and the experimental result indicates the feasibility of the developed device.

Microstructure of Al4Sr Phase in Al-Sr Master Alloy and its Effect on Modification Properties

Al-Sr master alloys were prepared by “Direct reaction method” and “Direct reaction - hot extrusion method”, respectively, in the present study, and the microstructure including the morphology, size, structure, hardness, and elastic modulus of Al4Sr phase, as well as the fracture morphology of the Al-Sr master alloys have been analyzed and examined by means of the Metallurgical Microscope, X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM) and Nanoindentation device. And a new growth model of Al4Sr was proposed. The results showed that the Al4Sr intermetallic phase with small size of 10∼30μm in length and 5∼20μm in width were evenly distributed in the aluminium matrix in the Al-Sr master alloys prepared by “Direct reaction - hot extrusion method”. These microstructure characteristics guaranteed their excellent modification performance, good thermoforming properties and good machinability. By controlling the processing parameters of the Al-Sr master alloys, the morphology of Al4Sr can be controlled, and then the Al-Sr master alloys with better modification performance and higher Sr content can be obtained.

Experimental research on a modular miniaturization nanoindentation device

Nanoindentation technology is developing toward the in situ test which requires miniaturization of indentation instruments. This paper presents a miniaturization nanoindentation device based on the modular idea. It mainly consists of macro-adjusting mechanism, x-y precise positioning platform, z axis precise driving unit, and the load-depth measuring unit. The device can be assembled with different forms and has minimum dimensions of 200 mm × 135 mm × 200 mm. The load resolution is about 0.1 mN and the displacement resolution is about 10 nm. A new calibration method named the reference-mapping method is proposed to calibrate the developed device. Output performance tests and indentation experiments indicate the feasibility of the developed device and calibration method. This paper gives an example that combining piezoelectric actuators with flexure hinge to realize nanoindentation tests. Integrating a smaller displacement sensor, a more compact nanoindentation device can be designed in the future.

Design and Analysis of a Miniaturization Nanoindentation and Scratch Device

In this paper, a miniaturization nanoindentation and scratch device was developed. Finite element analysis was carried out to study static and modal characteristics of x/y flexure hinge and z axis driving hinge as well as effect of geometric parameters on output performances of z axis driving hinge. Results indicated that x/y flexure hinge and z axis driving hinge had enough strength and high natural frequencies. Geometric parameters of z axis driving hinge affected output performances significantly. The model of developed device was established. Indentation experiments of Si and amorphous alloy showed that the developed miniaturization nanoindentation and scratch device worked well and can carry out indentation experiments with certain accuracy.

Influence of nanometer scale particulate fillers on some properties of microfilled composite resin

The aim of this study was to evaluate the effect of different weight fractions of nanometer sized particulate filler on properties of microfilled composite resin. Composite resin was prepared by mixing 33wt% of resin matrix to the 67wt% of silane treated microfine silica particulate fillers with various fractions of nanometer sized fillers (0, 10, 15, 20, 30wt%) using a high speed mixing machine. Test specimens made of the composites were tested with a three-point bending test with a speed of 1.0mm/min until fracture. Surface microhardess (Vicker's microhardness) was also determined. The volumetric shrinkage in percent was calculated as a buoyancy change in distilled water by means of the Archimedes principle. The degree of monomer conversion (DC%) of the experimental composites containing different nanofiller fractions was measured using FTIR spectroscopy. Surface roughness (Ra) was determined using a surface profilometer. Nanowear measurements were carried out using a nanoindentation device. The water uptake of specimens was also measured. Parameters were statistically analysed by ANOVA (P<0.05). The group without nanofillers showed the highest flexural strength and modulus, DC% and Ra value. The group with 30% nanofillers had the highest water uptake and volumetric shrinkage. No significant difference was found in Vicker's microhardness and the nanowear of the composites. The plain microfilled composite demonstrated superior properties compared to the composites loaded with nanofillers with the exception of surface roughness.

Correlation between PVD coating strength properties and impact resistance at ambient and elevated temperatures

The performance of PVD films depends on the operational mechanical and thermal loads of coated tools or components. To withstand these loads, sufficient film strength properties, at ambient and elevated temperatures are required. The present paper deals with the mechanical properties and the impact resistance of a TiAlN coating at temperatures up to 400 °C. Nanoindentations were conducted by a nanoindentation device, enabling measurements at room and elevated temperatures in an inert gas atmosphere. The obtained results were evaluated using appropriate FEM algorithms for determining the film's stress–strain curves, at the temperatures of the conducted nanoindentations. Moreover, perpendicular impact tests on the coated specimens were carried out up to 400 °C, for investigating the film's impact behaviour. The developed impressions were recorded by scanning electron microscopy and white light confocal measurements. The attained results demonstrate a non-linear dependence of the film fatigue properties versus the temperature, whereas a significant impact resistance improvement at approximately 150 °C develops. Finally, a convergence between the yield and the fatigue endurance stress versus the temperature was revealed.

Superglide at an Internal Incommensurate Boundary

The intriguing possibility of frictionless gliding of one solid surface on another has been predicted for certain incommensurate interfaces in crystals, based on Aubry's solution to the Frenkel-Kontorova model of a harmonic chain in a periodic potential field. Here we test this prediction for grain boundaries by comparing atomistic simulations with direct experimental observations on the structure and load-deformation behavior of gold nanopillars containing a root-two incommensurate grain boundary. The simulations show supergliding at this boundary limited by finite-size effects which cause edges to act as defects of the incommensurate structure. Structural relaxation at the edges generates stacking faults, dislocations, and asymmetric surface steps. These features as well as the related load-displacement behavior are replicated by experimental observations on the compression of nanopillars using a quantitative nanoindentation device inside a transmission electron microscope. The good agreement between the observed and predicted behavior suggests that incommensurate interfaces could play an important role in the deformation of polycrystalline materials.

Mechanical testing of single yeast cells in liquid environment: Effect of the extracellular osmotic conditions on the failure behavior

Abstract In industrial biotechnology microbial cells are utilized to produce diverse products (e. g., enzymes, food and animal feed additives, pharmaceutical agents). Whilst relationships on genetic and molecular levels are reasonably understood there are still numerous unsolved questions in matters of the mechanical properties of those cells. Recently, a compression test in liquid environment using a nanoindentation device was established to address the cell mechanical behavior of Saccharomyces cerevisiae (baker's yeast) cells. At higher deformations compressive stressing yielded failure of the cell wall. In the present work, the influence of the extracellular osmotic conditions on the failure characteristics (bursting force, bursting energy, and relative deformation at bursting) was studied. Moreover, a simple mechanical model was applied to characterize the mechanical properties of the cell wall.

Research on the Relationship between Indenter Tip Radius and Hardness with a Self-Designed Nanohardness Test Device

Nanoindentation device has the ability to make the load-displacement measurement with sub-nanometer indentation depth sensitivity, and the nanohardness of the material can be achieved by the load-displacement curve. Aiming at the influence law of indenter tip radius to indentation hardness, testing on the hardness of single-crystal silicon were carried out with the new self-designed nanohardness test device based on nanoindentation technique. Two kinds of Berkovich indenter with radius 40nm and 60nm separately were used in this experiment. According to the load-depth curve, the hardness of single-crystal silicon was achieved by Oliver-Pharr method. Experimental results are presented which show that indenter tip radius do influence the hardness, the hardness value increases and the indentation size effect (ISE) becomes obvious with the increasing of tip radius under same indentation depth.

The viscoelastic behavior of dental adhesives: A nanoindentation study

Objectives In order to predict the long-term performance of dental adhesives, it is necessary to understand their mechanical properties. The objective of this study was to use a new nanoindentation technique to characterize the in-plane linear viscoelastic properties of dental adhesive layers. Methods The dental adhesives used were Clearfil SE Bond (CSE) and Clearfil Tri-S Bond (CTS) by Kuraray Medical and Single Bond (SIB) and Single Bond Plus (SBP) by 3M ESPE. A thin film of each adhesive was made on a micro-glass slide, and was then tested on a nanoindenter system (ENT 1100, Elionix) with a Berkovich indenter at a constant loading rate of 0.1 mN/s up to a maximum load of 1.8 mN. The load–displacement data of the loading segment were fitted to a curve to find best fit parameters for a generalized Kelvin viscoelastic model, from which creep compliance and Young's modulus were calculated. The modulus results were compared to the values calculated by the nanoindentation device. Results The experimental data fitted well to the viscoelastic model for all materials ( R > 0.9999). SIB and CTS showed higher creep compliance compared to SBP and CSE. The modulus values obtained using the model were 4.0, 2.6, 2.4 and 4.2 GPa for CSE, CTS, SIB and SBP, respectively. The nanoindentation default software designed for time-independent materials significantly overestimated the modulus values up to 2.5 times. Conclusion As generally expected for polymer materials, the adhesives tested showed time-dependent viscoelastic behavior. The mechanical evaluation techniques developed for time-independent materials ignore this behavior and may not be appropriate for dental adhesives.

Research on a New Nanohardness Test Device

Nanoindentation has become the main method to obtain the micro- characteristic of materials by now. Nanoindentation device has the ability to make the load-displacement measurement with sub-nanometer indentation depth sensitivity, and the nanohardness of the material can be achieved by the load-displacement curve. The article discusses a new convenient nanohardness testing device, and approves its practicability and reliability by taking the indentation experiment on single-crystal aluminum.

In situ observation of nano-abrasive wear

We have studied the nano-scale wear behavior using an in situ nanoindentation device in a transmission electron microscope. Nano-scale sliding experiments were conducted under TEM. In order to trigger localized changes, we used a gold-coated diamond indenter to slide against single crystal silicon (1 0 0). With the movement of the indenter, cracks along the elastic strain contours in the silicon were observed. Energy analysis was carried over possible mechanisms. It was observed that the onset of abrasive wear was due to cracks formation along the contour. Analysis of the possible mechanisms that lead to the abrasive wear is presented. Observations are presented as initial work into experimentally observing the fundamental mechanisms.

Surface modification of single crystal silicon by Ar + ion implantation and vacuum deposition of amorphous carbon coating

Single crystal silicon wafers (Si (100) ) were implanted with 110 keV Ar + ions at a fluence of 1 × 10 16 ions/cm 2. Then the unimplanted and ion-implanted Si surfaces were coated with an amorphous carbon coating of 50 ± 5 nm thick making use of vacuum vapor deposition. The microstructures of the unimplanted and Ar + ion implanted Si wafers were analysed by means of transmission electron microscopy (TEM). The hardness and elastic modulus of the unimplanted and Ar + ion implanted Si wafers were measured using a nano-indentation device. The adhesion strengths of the amorphous carbon coatings on the unimplanted and Ar + ion implanted Si surfaces were determined making use of scratch test. The friction and wear behaviors of the samples were evaluated using a ball-on-disk reciprocating friction and wear tester. The morphologies of the wear and scratch tracks of the Si samples were observed using a scanning electron microscope (SEM). It was found that Ar + ion implantation alone led to little effect on the friction and wear behavior of the Si sample. However, the amorphous carbon coating deposited on the Ar + ion implanted Si surface showed much better friction-reducing and antiwear ability than that on the unimplanted Si surface. The formation of a mixed nano-crystal and amorphous silicon structure during the Ar + ion implantation improves the ability of the amorphous carbon coating to resist plastic deformation, and hence increase the adhesion strength and antiwear-life of the amorphous carbon film.

A methodology to investigate size scale effects in crystalline plasticity using uniaxial compression testing

A methodology for performing uniaxial compression tests on samples having micron-size dimensions is presented. Sample fabrication is accomplished using focused ion beam milling to create cylindrical samples of uniform cross-section that remain attached to the bulk substrate at one end. Once fabricated, samples are tested in uniaxial compression using a nanoindentation device outfitted with a flat tip, and a stress–strain curve is obtained. The methodology can be used to examine the plastic response of samples of different sizes that are from the same bulk material. In this manner, dimensional size effects at the micron scale can be explored for single crystals, using a readily interpretable test that minimizes imposed stretch and bending gradients. The methodology was applied to a single-crystal Ni superalloy and a transition from bulk-like to size-affected behavior was observed for samples 5 μm in diameter and smaller.

Measurements of mechanical properties in Ni-base superalloys using nanoindentation and atomic force microscopy

The morphology and the nanomechanical properties of two Ni-base superalloys at length scales of <1μm were measured, using an atomic force microscope in combination with an add-on nanoindentation device, varying both the γ′-precipitate volume fraction and the annealing time. The γ′-precipitate phase was found to be harder up to 45% than the matrix phase. In both phases the hardness decreased with increasing indentation depth, well known as indentation size effect. For the precipitates this decrease appeared uniformly and independent of alloy composition and annealing time, whereas for the matrix the hardness decrease was less pronounced, moreover it did not appear in a uniform manner. The latter observation is explained by an influence of neighbouring precipitates as well as by a high supersaturation of γ′ and γ (matrix) in the early stages of phase separation. The elastic moduli showed no significant difference between the two phases, no dependence on the annealing time and no depth dependence as long as the indentation size was clearly below the size of the particular phase domain but increased by up to 20%, if the size of the indented area approached the size of the measured phase domain.

Study of the mechanical properties of ceramic materials by the nanoindentation technique

A nanoindentation device has been developed allowing the application of forces ranging between a few micronewtons and 100 milinewtons with nanoindentation capabilities. The apparatus offers also very accurate positioning in three directions through the use of a high resolution tridirectional piezoelectric actuator. One of the main interests of the device is to allow fast and precise measurements in normal laboratory environment, making nanoindentation testing as simple to use as conventional hardness ones. After a short presentation of the device and its working principle and of some of the methods used to derive the mechanical properties of materials, some results concerning the nanoscale plasticity in some ceramic materials are presented. Special features as unloading pop-out in silicon, associated to a reversible densification process, and pop-in or yield points during loading, in GaAs and MgO, are pointed out.

A new technology for nanohardness measurements: principle and applications

A nanoindentation device has been developed allowing the application of forces ranging between a few micronewtons and 100 mN with nanoindentation capabilities. The apparatus offers also very accurate positioning in the directions through the use of a high resolution tridirectional piezoelectric actuator. One of the main interests of this device is its capabability to allow fast and precise measurements in normal laboratory environment, making nanoindentation testing as simple to use as conventional hardness testing. After a short presentation of the device and its working principle, some of the methods used to derive the mechanical properties of the materials are presented and illustrated by experimental curves. Interesting features, such as the micro yielding of different materials under low applied forces, are also presented.

Nanoindentation characterization of SiC coatings prepared by dynamic ion mixing

Silicon carbide coatings have been synthesized at 750 °C and at room temperature by ion beam-sputtering of a SiC-target with simultaneous bombardment with a 160-keV Ar + ion beam (dynamic ion mixing). These coatings are studied using a recently developed nanoindentation device in order to determine their hardness and their reduced Young modulus as a function of penetration depth. High hardness values (22–24 GPa) are obtained for the more crystallized coatings deposited at 750 °C, whereas the amorphous ones deposited at room temperature are softer. We discuss the mechanical properties-structure relationship.

Nanoscale Indentation of Polymer Systems Using the Atomic Force Microscope

The use of the atomic force microscope (AFM) to measure surface forces has been developed to optimize its operation as a surface imaging tool. This capability can potentially be extended to evaluate nanoscale material response to indentation and would be ideal for the evaluation of multi-component polymer systems, such as adhesives and composites. In this paper, previous work related to the development of the AFM as a nanoindentation device is reviewed, and a technique is proposed which allows the AFM to be used to probe local stiffness changes in polymer systems. Cantilever probes with spring constants ranging from 0.4–150 N m were used to investigate a number of polymer systems, including an elastomer, several polyurethane systems, thermally cured epoxies, a thermoplastic polymer-thermosetting polymer adhesive system, and a thermoplastic matrix composite.