Nanoindentation Results Research Articles

Quantification and characterization of C-S-H in silica nanoparticles incorporated cementitious system

This paper presents the quantification and nanomechanical properties of calcium silicate hydrate (C-S-H), formed at early stage hydration of tricalcium silicate (major cement phase) in presence of silica nanoparticles (SNPs). SNPs showed dominant nucleation effect at 8 h and pozzolanic effect at 24 h and accelerate the hydration rate (∼83% at 8 h and ∼51% at 24 h) due to the formation of additional C-S-H nuclei. Further, 29Si-NMR and FTIR techniques showed the acceleration in polymerization of silicate chain leading to the formation of tobermorite like structure. Formation of polymerized and crystalline C-S-H gel in presence of SNPs increases the percentage of high density C-S-H (∼40%) and lowers the low density C-S-H (∼52%) at 24 h of hydration, as observed in nanoindentation results.

Nanoindentation and in situ microcompression in different dose regimes of proton beam irradiated 304 SS

Recent developments in micromechanical testing have allowed for the efficient evaluation of radiation effects in micron-scale volumes of ion-irradiated materials. In this study, both nanoindentation and in situ SEM microcompression testing are carried out on 10 dpa proton beam irradiated 304 stainless steel to assess radiation hardening and radiation-induced deformation mechanisms in the material. Using a focused ion beam (FIB), arrays of 2 μm × 2 μm cross-section microcompression pillars are fabricated in multiple dose regimes within the same grain, providing dose-dependent behavior in a single crystal orientation. Analysis of the microcompression load-displacement data and real-time SEM imaging during testing indicates significant hardening, as well as increased localization of deformation in the irradiated material. Although nanoindentation results suggest that irradiation hardening saturates at low doses, microcompression results indicate that the pillar yield stress continues to rise with dose above 10 dpa in the tested orientation.

Synergetic Surface and Chemical Durability Study of the Aesthetically Enhanced Natural Quartz by Heat Treatment

The change in surface behavior of natural quartz stone before and after heat treatment with metal oxides such as: cobalt oxide (Co3O4) and copper oxide (Cu2O) under vacuum and open atmosphere has been investigated. The surface feature, bulk density and hardness value of quartz changed after heat treatment, converting to a high value product. Difference in crystallinity of quartz, pre- and post-heat treatment was obtained through X-ray diffraction (XRD) study. The electron probe microanalysis results clearly explicated the diffusion of metal ion in quartz matrix exposed under vacuum atmosphere but as coating on the surface under open atmosphere. The structural transformation of quartz after heat treatment has been observed from the XRD data and well corroborated with the nanoindentation results. Durability of such quartz to chemical hazardous environment was observed. Thus, this communication demonstrates the change in physical and chemical characteristics of natural quartz stone after heat treatment under different atmosphere.

Effects of Flotage on Immersion Indentation Results of Bone Tissue: An Investigation by Finite Element Analysis

In reality, nanoindentation test is an efficient technique for probing the mechanical properties of biological tissue that soaked in the liquid media to keep the bioactivity. However, the effects of flotage imposed on the indenter will lead to inaccuracy when calculating mechanical properties (for instance, elastic modulus and hardness) by using depth-sensing nanoindentation. In this paper, the effects of flotage on the nanoindentation results of cortical bone were investigated by finite element analysis (FEA) simulation. Comparisons of nanoindentation simulation results of bone samples with and without being soaked in the liquid media were carried out. Conclusions show that the difference of load-displacement curves in the case of soaking sample and without soaking sample conditions varies widely based on the change of indentation depth. In other words, the nanoindentation measurements in liquid media will cause significant error in the calculated Young’s modules and hardness due to the flotage. By taking into account the effect of flotage, these errors are particularly important to the accurate biomechanics characterization of biological samples.

Enhanced mechanical properties of W1−yMoyO3 nanocomposite thin films

We report on the enhanced mechanical properties of ∼60 nm thick W-Mo-O nanocomposite films, which are of current interest as structural and electrode materials in photo-related energy technologies. W-Mo-O films were sputter-deposited onto Si(100) by varying the growth temperature (Ts) ranging from 25 to 500 °C. The molybdenum (Mo) content in the films was varied in the range of y = 0.05–0.15 by employing the W-Mo target with a variable Mo content. Structural and mechanical characterization was performed to understand the combined effect of the Mo content and Ts on the structure and mechanical behavior of W-Mo-O films. The results indicate that the effect of Ts is significant on the growth and microstructure of W-Mo-O films. The effect of the Mo-content is reflected in elevating the Ts needed for film crystallization coupled with the average grain-size reduction. Structural studies revealed that the W-Mo-O films were amorphous for Ts ≤ 300 °C, at which point amorphous-to-crystalline transformation occurs. Monoclinic (m) W-Mo-O nanocomposite films exhibit a combination of m-WO3 and m-MoO3 phases with m-WO3 being predominant in the matrix. The peak intensities of the m-MoO3 phase increases with increasing Mo-content. The nanoindentation results indicate a non-monotonic mechanical response in terms of hardness (H) and reduced elastic modulus (Er) of the deposited films with increasing Ts. The effect of microstructure evolution is remarkable on the mechanical properties. Structural transformation at Ts = 300 °C induces a significant change in H and Er values. The W-Mo-O with y = 0.05 exhibit maximum H (∼21 GPa) and Er (∼216 GPa), where Mo-incorporation induced enhancement in mechanical characteristics is pronounced. A strain rate dependence of the H value of W-Mo-O films has been observed. Based on the results, structure-composition-mechanical property correlation in W-Mo-O films is established.

Effect of hydrogen addition on the mechanical properties of a bulk metallic glass

The bending and nanomechanical behaviors of a Zr55Cu30Ni5Al10 bulk metallic glass were investigated in the present work via melt hydrogenation. The room temperature bending plasticity of samples after hydrogen addition is observed improving gradually with the increase of addition amount. A softening phenomenon is appeared in the results of nanoindentation, concomitantly with a decrease in the elastic modulus of the samples. A simple “spacer” model of hydrogen atoms can be used to describe for the softening behaviors of the Zr55Cu30Ni5Al10 samples prepared by melt hydrogenation in this work. The “spacer” can enhance the distance of the metal atoms and decrease the corresponding atomic cohesion which is represented as the elastic modulus. The local changes of the atomic configuration give rise to the emergence of large void structures which will facilitate the local atomic displacement. Consequently, the “spacer” effect promotes the shear band proliferation and weakens the local shear deformation, and this in turns, leads to the large plastic deformation in the amorphous alloy. The results may have some implications for improving the plasticity of bulk metallic glass and understanding its hydrogen-induced softening.

Mechanical properties of sol–gel prepared nanocomposite coatings in the presence of titania and alumina-derived nanoparticles

ABSTRACTHybrid nanocomposite coatings were prepared by sol–gel method using silica, titania and alumina nanoparticles derived from their alkoxides precursors; in the presence of 3-glycidoxypropyl-trimethoxysilane (GPTMS) and bisphenol A (BPA) on 1050 aluminium alloy substrate. The effect of type and ratio of nanoparticles on mechanical behaviour of the coatings were investigated by dynamic mechanical thermal analysis (DMA) and nanoindentation experiments. DMA results demonstrated that the values of the glass transition temperature (Tg) and the temperature at maximum tan (δ), (Tt) as well as the storage modulus of the hybrid samples depend mainly on the silane content and titania to alumina molar ratio of nanoparticles in the coating composition. In addition, nanoindentaion experiments were performed to study the mechanical properties such as hardness, elastic modulus and E/H ratio for the nanocomposite hybrid coatings. Nanoindentation results indicate that the homogenous reinforced structure was formed in the surface of nanocomposite coating with incorporation of titania and alumina-derived nanoparticles. The incorporation of TiO2 in comparison with AlOOH nanoparticles in the GPTMS-based coatings showed an improving effect on E/H ratio.

Copper thin films deposited under different power delivery modes and magnetron configurations: A comparative study

This study investigated the topological, structural, mechanical (hardness and Young's modulus) and tribological (critical loads and coefficient of friction) properties of copper (Cu) thin films with nanocrystalline structure, smooth and uniform surfaces and thickness of 800nm, deposited on silicon and graphite substrates by conventional dc magnetron sputtering (dcMS) and HiPIMS operated with single ultra-short pulses (3μs), in the absence and presence, respectively, of an additional magnetic field. Operating the HiPIMS discharge with such short pulses optimizes the deposition rate and provides a higher fraction of ionized metal flux, while the presence of the additional magnetic field facilitates the transport of charged particles towards the substrate, leading to a higher deposition rate. The density of the deposited thin films was obtained by measuring the areal atomic density using Rutherford backscattering spectrometry and the film thickness by cross-sectional scanning electron microscopy. The nanoindentation results were initially analyzed using the Oliver-Pharr method, and then, in order to correct de pile-up errors, other methods have been employed. Compared to the other samples, mainly due to the high energetic bombardment during the growing process and intense surface diffusion, the Cu thin films deposited using HiPIMS assisted by an additional magnetic field exhibit significantly smoother surfaces, higher crystallinity, denser microstructure, higher hardness and Young's modulus, and lower coefficient of friction.

Effect of UV/ozone plasma treatment on sol–gel-derived HfO2 thin films

This study reports on the fabrication and characterization of sol–gel-derived HfO2 thin films on indium tin oxide (ITO) substrates. The films were dried in air and ultraviolet (UV)/ozone plasma environments and finally annealed at various temperatures ranging from 300 to 500°C. Crystallization of the films was observed to occur even at low annealing temperature of 300°C. Scanning electron microscopy results indicate that the films dried in the air environment were not uniform, and the grains were observed to be separated from each other. In contrast, the UV/ozone plasma-treated thin films exhibited smooth and uniform surfaces. The reduction of leakage current density of more than 3 orders of magnitude was observed with the UV/ozone plasma treated films. High transmittance of nearly 99% was observed for the films dried in both the air and UV/ozone plasma environments. Nanoindentation results of the air-dried films revealed pop-in events in the load–displacement curve at specific depths of 12.74 and 19.68nm; in contrast, smooth and regular curves without any discontinuities along either the loading or unloading sections were observed for the UV/ozone plasma-treated films. The obtained results demonstrated that UV/ozone plasma-treatment is proved to be a promising technique in improving the quality of HfO2 on ITO substrates.

Measurement of Temperature-Dependent Young’s Modulus at a Strain Rate for a Molding Compound by Nanoindentation

The mechanical properties of a molding compound on a packaged integrated circuit (IC) were measured by spherical nanoindentation using a 50 μm radius diamond tip. The molding compound is a heterogeneous material, consisting of assorted diameters of glass beads embedded in an epoxy. Statistical analysis was conducted to determine the representative volume element (RVE) size for a nanoindentation grid. Nanoindentation was made on the RVE to determine the effective viscoelastic properties. The relaxation functions were converted to temperature-dependent Young’s modulus at a given strain rate at several elevated temperatures. The Young’s modulus values at a given strain rate from nanoindentation were found to be in a good agreement with the corresponding data obtained from tensile samples at or below 90 °C. However, the values from nanoindentation were significantly lower than the data obtained from tensile samples when the temperature was near or higher than 110 °C, which is near the glass transition. The spatial distribution of the Young’s modulus at a given strain rate was determined using nanoindentation with a Berkovich tip. The spatial variation of the Young’s modulus at a given strain rate is due to the difference in nanoindentation sites (glass beads, epoxy or the interphase region). A graphical map made from an optical micrograph agrees reasonably well with the nanoindentation results.

Thermal and Nanoindentation Behaviours of Layered Silicate Reinforced Recycled GF-12 Nanocomposites

<p class="1Body">This work is an attempt to improve the thermal and nanoindentation behaviours of recycled Glass-Filled Polyamide-12 (GF-12) by adding layered Silicate (Nanoclay) as a reinforced filler. Differential Scanning Calorimetry (DSC) and Nanoindentation tests were conducted to study the effect of various loading levels (0-7 wt. %) of Nano-layered silicate on the thermal and nanohardness behaviours of GF-12 and its nanocomposites. Wide Angle X-ray Diffraction (WAXD) was employed to characterise the nanostructure of material and determine the intercalation/exfoliation for layered silicate in a GF-12 matrix. This study reveals that the layer silicate has a positive effect on the hardness results. Nanoindentation results showed remarkable improvement when layered silicate was added to recycled GF-12. The Glass transition (T<sub>g</sub>) and crystallization (T<sub>c</sub>) temperatures showed a slight improvement over the base polymer by the incorporation of layered silicate. Moreover, the enhancement of crystallization was obvious with the addition of clay loading, which functioned as a nucleating agent that could increase the rate of crystallization.</p>

Cyclic softening behavior of Ti–6Al–4V alloy at macro and micro-scale

The cyclic softening behavior of Ti–6Al–4V alloy with three typical microstructures at room temperature has been studied through cyclic deformation experiments at macro-scale and cyclic nanoindentation experiments at micro-scale. Strain control cyclic deformation tests were conducted on specimens with equiaxed, duplex and Widmannstatten microstructure, respectively. Displacement control nanoindentation tests were conducted on the specimen with duplex microstructure. Results show that equiaxed microstructure shows distinct softening since the first cycle, while, duplex and Widmannstatten microstructures exhibit hardening phenomenon at the initial several cycles and then exhibit cyclic softening in subsequent cycles. Cyclic nanoindentation results indicate that both primary and lamellar α phase exhibit cyclic softening phenomenon at micro-scale and the amplitudes of softening vary with grain orientations.

Nanoindentaion and tensile testing of human hair fibres

Hair fiber comprises of cuticle, cortical cells made up of crystalline keratin molecules (α-helix keratin) embedded in amorphous sulfur rich crosslinked keratin matrix and innermost medulla. Since single fiber tensile test takes into account all the components of hair, nanoscale mechanical characterization is imperative in investigating the characteristics related exclusively to cortical cells. This paper lays out the method of specimens preparation for nanoindentation to obtain hardness and modulus of hair obtained from members of four families. Single fibre tensile tests were also performed and compared with nanoindentation data. DSC and TGA tests were performed on the hair samples to further corroborate mechanical analysis with thermal transitions and thermal stability. Nanoindentation modulus and hardness values in the range of 5–8 GPa and 222–400 MPa were obtained respectively. Single fibre tensile data revealed tensile modulus and yield strength in the range of 2–5 GPa and 50–180 MPa, respectively and this data correlated with the nanoindentation data satisfactorily well. From DSC studies it was found that the onset of endothermic melting peak of α-keratin in the range of 222–234 °C correlated well with the nanoindentation results.

Tensile strength of hydrated cement paste phases assessed by micro-bending tests and nanoindentation

The paper is focused on the experimental investigation of cement paste's tensile strength and related mechanical properties at the micrometer level. Small scale specimens with micrometer dimensions in the form of cantilever beams having a triangular cross section and ≈20 μm in length are fabricated by means of a focused ion beam and tested in bending with the aid of a nanoindenter. Elastic properties are evaluated from both bending and nanoindentation tests for all the phases with very close agreement. The phase separation is performed with SEM-based image analysis and the deconvolution of grid nanoindentation results. The load-deflection curves of bent beams are monitored up to the failure for distinct microlevel phases, namely for inner and outer products and Portlandite. The tensile strength of the phases is directly derived from the load-deflection curves in the range of 264 MPa (for the outer product) to 700 MPa (for the inner product and Portlandite). Moreover, the load-deflection curves are used for the supremum estimates of fracture energies for individual hydrated cement phases. Low values of the energies in the range of 4.4 − 20 J/m2 were found. The values obtained experimentally in this paper correspond well with those published in recent multiscale or molecular dynamics models.

Effect of Actual Indenter Shape on the Results of Spherical Nanoindentation

Actual shape of the diamond spherical indenter of nominal radius 20 μm was investigated in this study. 3D reconstruction was performed by atomic force microscope and by the method of stereopair using SEM images of the tip taken under several different angles. The results were compared with the shape obtained indirectly by the calibration performed on specimens with known Young’s modulus. It was found that lower effective values of tip radius for the small penetration depths are caused by the irregular geometry of contact between indenter and specimen surface. With increasing penetration depth the radius increased to the theoretical values and it decreased again for high penetration depths. The stress-strain curves were determined using corrected effective indenter radius.

Failure and deformation mechanisms at macro- and nano-scales of alkali activated clay

Here we report two qualitative models on failure and deformation mechanisms at macro- and nano-scales of alkali activated clay (AACL), a material of extraordinary importance as a low cost building material. The models were based on experimental data of compressive failure and nanoindentation response of the AACL materials. A 420% improvement in compressive strength (σc) of the AACL was achieved after 28 days (d) of curing at room temperature and it correlated well with the decrements in the residual alkali and pH concentrations with the increase in curing time. Based on extensive post-mortem FE-SEM examinations, a schematic model for the compressive failure mechanism of AACL was proposed. In addition, the nanoindentation results of AACL provided the first ever experimental evidence of the presence of nano-scale plasticity and a nano-scale contact deformation resistance that increased with the applied load. These results meant the development of a unique strain tolerant microstructure in the AACL of Indian origin. The implications of these new observations were discussed in terms of a qualitative model based on the deformation of layered clay structure.

Determining the curing parameters of furfuryl alcohol for wood modification by nanoindentation

Wood furfurylation is a very promising modification process, which can greatly improve several important properties of wood simultaneously. The polymerization degree of furfuryl alcohol (FA) in wood significantly influences the performances of modified wood. However, it is normally time-consuming and expensive to determine the curing parameters of a new FA solution formula for a target wood species, as the process requires lots of lab-scale experiments. To address this challenge, nanoindentation was used to determine the hardness and elastic modulus of FA resin which are cured with different catalyst content, curing time and curing temperature, assuming that these mechanical properties should closely relate to the polymerization degree of cured FA (resin). Single-factor experiments were designed to obtain preliminary curing parameters. Three key curing parameters were selected, namely the catalyst content of maleic anhydride (1.5, 3, 5 %), curing time (2, 3, 4, 5, 6 h) and curing temperature (95, 105, 115, 125 °C). The proposed set of curing parameters based on the nanoindentation results are 3 % maleic anhydride, 3 h curing time and 105 °C curing temperature. This set of parameters was slightly modified and then used as the starting process parameters for Masson pine modification, which resulted in greatly improved wood properties. Therefore, the method proposed in this study offers an effective and time-saving means of developing new processes of wood furfurylation.

Nanoindentation and nanoscratch behavior of electroless deposited nickel-phosphorous coating

Electroless nickel-phosphorous (NiP) coating was deposited on steel substrate followed by annealing at 600 °C in an argon atmosphere. Nanoindentations and nanoscratch experiments were performed on the as-deposited and annealed coating. Improvement of 32% in hardness was found on annealing the coating, which might be due to the two major phenomena. Firstly, presence of Ni3P precipitates which accelerated the bowing of dislocations and observed to be the dominant mechanism in increased hardness. Secondly, diffusion of iron (Fe) and chromium (Cr) atoms from the substrate to the coating. Scherrer technique and TEM analysis showed the increase in Ni grain size on annealing. Annealed coating showed an enhancement of 31% in elastic modulus compared to as-deposited coating. Increased elastic modulus could be due to the reduction in triple junction and grain boundary as a result of increased grain size. Strain hardening exponent was found higher for annealed coating (0.33) compared to as-deposited coating (0.25) indicating lower pile-up formation in annealed coating during indentation. Higher scratch hardness resulted lower scratch width and depth for the annealed coating. Coefficient of friction decreased from 0.30 for as-deposited coating to 0.23 for annealed coating, resulting 58% reduction in calculated wear rate of the scratch of annealed coating. Direct correlation was observed between nanoindentation and nanoscratch results of as-deposited and annealed NiP coatings.

EFFECTS OF Mo CONTENT ON THE MICRO-STRUCTURE AND TRIBOLOGICAL PROPERTIES OF CrMoAlN FILMS

In recent decades, CrAlN coatings have been widely used for cutting tools due to their high hardness, good wear resistance, especially excellent thermal stability and oxidation resistance. However, the rapid development in high speeds and dry cutting applications demands further improvement in hardness and wear properties of CrAlN coatings. Mo nitrides coatings are commonly used as protective surface layers against wear and corrosion. The combination of CrAlN and Mo may lead to the development of new composite coatings with superior wear properties. In this study, the CrMoAlN multilayer coatings with different Mo contents were deposited on M2 tool steel and silicon wafers substrates by closedfield unbalanced magnetron sputtering ion plating (CFUMSIP) technique in a gas mixture of Ar+N2. The chemical composition, surface and cross sectional morphologies, microstructure, mechanical and tribological properties of coatings were studied by EDS, SEM, XRD, XPS, nano-indentation and pin-on-disk tribometer, respectively. The results indicate that the CrMoAlN coatings exhibit fcc structure. Mo atoms substitute Cr and/or Al atoms in CrAlN lattice forming the solid solution CrMoAlN coatings. The surface and cross-sectional morphologies of the CrMoAlN coatings show that the grain size and the column width decrease with the increasing of Mo content. Nano-indentation result reveals a promoted hardness and elastic modulus *浙江省自然科学基金资助项目Y15E050060 收到初稿日期: 2015-09-21,收到修改稿日期: 2016-03-09 作者简介:楼白杨,女, 1958年生,教授,博士 DOI: 10.11900/0412.1961.2015.00493 第727-733页 pp.727-733

Study of modifications in the mechanical properties of sodium aluminoborosilicate glass induced by heavy ions and electrons

Radiation effects on the mechanical properties of sodium aluminoborosilicate glass induced by 4MeV Kr, 5MeV Xe ions and 1.2MeV electrons have been investigated by nano-indentation measurements. Raman and electron paramagnetic resonance (EPR) spectroscopies were used to characterize the microstructure evolution of electron irradiated samples. The nano-indentation results indicated that the mean hardness was reduced by 12.8%, and the mean reduced Young modulus was increased by 3.5% after heavy ion irradiation. Both the hardness and reduced Young modulus variations reached stabilization when the nuclear deposited energy was around 3×1021keVnucl/cm3. Although decreases of hardness (about 6.6%) and reduced Young modulus (about 3.1%) were also observed when the deposited electronic energy reached approximately 1.5×1022keVelec/cm3 after electron irradiation, the results still emphasized that the nuclear energy deposition is the major factor for the evolution in the hardness and modulus of the sodium aluminoborosilicate glass under ion irradiation, rather than a synergy process of the electronic and nuclear energy depositions.