Berkovich Diamond Indenter Research Articles

Evaluation of nanohardness, elastic modulus, and surface roughness of fluoride-releasing tooth colored restorative materials.

Recently, interest in tooth-colored fluoride-releasing dental materials has increased. Although physical and mechanical properties such as surface hardness, elastic modulus and surface roughness of the restorative materials have been investigated, the effect of different immersion media on these properties is still controversial. The aim of this study was to evaluate the nanohardness, elastic modulus and surface roughness of the fluoride release of tooth-colored restorative materials after immersion in acidic beverages. Prepared samples of three restorative materials (a highly viscous glass ionomer (EQUIA Forte; GC, Tokyo, Japan), a compomer (Dyract XP; Dentsply, Weybridge, UK), and a bioactive restorative material (Activa BioACTIVE; Pulpdent, MA, USA)) were randomly divided and immersed in distilled water, a cola and an orange juice for one week. The HYSITRON T1 950 TriboIndenter device (Hysitron, USA) with the Berkovich diamond indenter tip was used for all measurements. The nanohardness and elastic modulus of the samples were measured by applying a force of 6000 μN to five different points on the sample surface. Surface roughness measurements were evaluated on random samples by scanning five random 40 × 40 μm areas. The properties were measured at the initial and one week after immersion. The values of nanohardness, elastic modulus and surface roughness were tested for significant differences using a two-way analysis of variance (ANOVA) with repeated measures (p < 0.05). Tukey's honest significant difference (HSD) test was used for multiple comparisons. AB (Activa BioACTIVE) had the highest initial mean values for nanohardness. After post-immersion, the highest mean value for elastic modulus was the initial AB value. The lowest mean value for roughness of 100.36 nm was obtained for the initial DX (Dyract XP) measurement. Acidic beverages had a negative effect on the nanohardness, elastic modulus and surface roughness of the restorative materials.

A Comparative Evaluation of Surface Hardness and Nanomechanical Properties of Nickel-Titanium Orthodontic Wires: An In Vitro Study.

The study aimed to evaluate the influence of various surface coatings (epoxy, Teflon, and rhodium) on the surface roughness (SR) and nanomechanical characteristics of nickel-titanium (NiTi) archwires. The study compared these coated archwires to uncoated ones from a single manufacturer, which served as a control. There were 15 rectangular samples of four distinct archwires measuring 0.17 × 0.25. These were ultrasonically treated with an alkaline solution at 60°C for 15 minutes before being rinsed with distilled water to remove precipitates. With an orthodontic soft wire cutter, the straight buccal sections of coated and uncoated archwires were cut into 20 mm lengths. A three-dimensional optical noncontact surface profilometer evaluated the surface. Profilometers use contact scanning white light interferometry. Using the Vision64 software (Bruker Corporation, San Jose, CA), the profilometer's nanolens atomic force microscopy module has a completely automated turret with programmed X, Y, and Z motions. Images were taken in five random locations. Five average measurements matched specimen SR. A nanoindenter with a Berkovich diamond indenter measured nanohardness (NH) and elastic modulus (EM). The experimental results were analyzed using the Statistical Package for the Social Sciences software version 26.0 (SPSS Inc., Chicago, IL). To examine mean differences at 5% significance, analysis of variance and Tukey's post hoc test were applied for SR, NH, and EM. Wires coated with epoxy had the highest SR (1.499 ± 0.082), followed by Teflon (0.811 ± 0.023) and rhodium (0.308 ± 0.024). The SR of the control group was 0.289 ± 0.027. Significant differences in SR were found (p < 0.0001). Except for the comparison between rhodium and the control group (p = 0.684), all intergroup comparisons of SR showed significant differences (p < 0.0001). The rhodium-coated wires exhibited the highest NH (0.185 ± 0.014), and the epoxy group had the lowest (0.147 ± 0.017). Variations in NH were significant between the study groups (p < 0.0001). The epoxy, Teflon, and rhodium groups showed significant differences against the control group (p < 0.0001) in intergroup comparisons for NH. The Teflon group had the highest EM (5.367 ± 0.379), and the epoxy group had the lowest (5.012 ± 0.498). The EM of the control group was 56.946 ± 0.737. Results indicate considerable EM changes between the groups (p < 0.05). Comparisons between experimental and control groups showed significant differences (p < 0.0001). The study's findings indicate that the SR of rhodium-coated archwires is substantially comparable to that of uncoated archwires. However, Teflon-, rhodium-, and epoxy-coated archwires had significantly different NH and EM compared to uncoated ones. Further, uncoated archwires have higher NH and EM.

&lt;em&gt;In situ&lt;/em&gt; study of mechanical properties and structural transformations during heating of WC–TaC–Co cemented carbides in a transmission electron microscope column

This study investigated the hardness of lamella with varying thickness, obtained from a massive, fine-grained cemented carbide comprising WC–6 %Co–0.2 %TaC, characterized by an average grain size of approximately 5 μm. The picoindentation method was employed for this analysis. Picoindentation was carried out using a Berkovich diamond indenter with a radius of curvature around 50 nm, and the experimental data were analyzed using the Oliver–Pharr model. The results revealed a significant correlation between hardness and lamella thickness. The hardness of the electron transparent section (thickness less than 100 nm) of the lamella measured 11.3±2.8 GPa, while the electron nontransparent section (thickness more than 200 nm) exhibited a hardness of 20.8±1.2 GPa. The lower hardness in electron transparent objects (thickness ~100 nm) is likely attributed to a combination of factors, including the potential bending of thin cobalt layers, the presence of edge effect, and closely spaced structural defect dislocations on the lamella surface. In situ TEM studies were conducted to examine structural transformations during the heating of WC–6 %Co–0.2 %TaC lamella, including in the presence of oxide phases (WOx ). Oxide phases on the lamella’s surface were generated by oxidizing the lamella at 200 °C in an air atmosphere. The results indicated that heating up to 500 °C did not bring about significant changes in the structure. However, at 600 °C, there was a notable thinning of cobalt layers due to intense surface diffusion of cobalt. Simultaneously, the formation of nanosized particles of the Co3W3C phase, ranging in size from 5 to 20 nm, was observed in the binder. These particles resulted from a shift in the equilibrium phase composition of the carbide, changing from a two phase region (WC + γ) to a three phase region (WC + γ + Co3W3C) as a consequence of the lamella’s oxidation.

Anisotropic Deformation Behavior and Indentation Size Effect of Monocrystalline BaF2 Using Nanoindentation.

In this study, our objective is to investigate the anisotropic deformation behavior and the indentation size effect (ISE) of monocrystalline barium fluoride (BaF2) using nanoindentation experiments with a diamond Berkovich indenter. BaF2 is known for its anisotropy, which results in significant variations in its mechanical properties. This anisotropy poses challenges in achieving high processing quality in ultra-precision machining. Through our experiments, we observed numerous pop-in events in the load-displacement curves, indicating the occurrence of plastic deformation in BaF2 crystals, specifically in the (100), (110), and (111) orientations; these pop-in events were observed as the indentation depth increased to 56.9 nm, 58.2 nm, and 57.8 nm, respectively. The hardness-displacement and elastic modulus-displacement curves were obtained from the tests exhibiting the ISE. The nanoindentation hardness of BaF2 is found to be highly dependent on its crystallographic orientation. Similarly, for BaF2 in the (100) orientation, the range is from 2.43 ± 0.74 and 1.24 ± 0.12 GPa. For BaF2 in the (110) orientation, the values range from 2.15 ± 0.66 to 1.18 ± 0.15 GPa. For BaF2 in the (111) orientation, the values range from 2.12 ± 0.53 GPa to 1.19 ± 0.12 GPa. These results highlight the significant influence of crystallographic orientation on the mechanical properties of BaF2. To better understand the ISE, we employed several models including Meyer's law, the Nix-Gao model, the proportional specimen resistance (PSR) model, and the modified PSR (mPSR) model, and compared them with our experimental results. Among these models, the mPSR model demonstrated the best level of correlation (R2>0.9999) with the experimental measurements, providing a reliable description of the ISE observed in BaF2. Our reports provide valuable insights into the anisotropic mechanical characteristics of BaF2 materials and serve as a theoretical guide for the ultra-precision machining of BaF2.

Measurement of Creep Stress Exponent of TC17 Titanium Alloy by Nanoindentation Method at Room Temperature.

The creep stress exponent is commonly employed to characterize the deformation mechanism during the steady-state creep stage, serving as an indicator of creep behavior. The creep phenomenon of high melting point metallic materials is not obvious at room temperature. However, the nanoindentation method proves suitable for investigating the creep properties of metallic materials under such conditions. Consequently, this paper places emphasis on measuring the creep stress exponent of TC17 titanium alloy at room temperature using the load preservation stage of the nanoindentation method with a constant loading rate. In order to investigate the effects of loading rate and maximum load on the experimental results, different loading rates were applied to the diamond Berkovich indenter to reach different maximum loads. The indenter was held under the maximum load for a duration of 360 s, and the relationship between the indentation strain rate and indentation stress during the holding process was used to obtain the creep stress exponent of the material at room temperature. The findings indicate that within the loading rate range of 1.25 to 15 mN/s and maximum load range of 50 to 300 mN, the influence on the experimental results is insignificant. Ultimately, the distribution range of the creep stress exponent for TC17 titanium alloy at room temperature was measured to be 8.524-8.687.

Elastic-plastic properties of Li2B4O7 determined by nanoindentation

Relevance. Crystalline and amorphous lithium tetraborate (Li2B4O7) has a wide range of practical applications due to its physical properties. The knowledge of the mechanical characteristics of the surface layers of these materials, which are studied by nanoindentation, is necessary for optimising the technological processes for obtaining “optically perfect” samples. Aim. A comparative study of the mechanical properties and deformation mechanisms of glassy and crystalline Li2B4O7 samples in a wide range of applied loads. Methodology. The elastic-plastic properties of crystalline and glassy lithium tetraborate were investigated using the multiple-loading cyclic nanoindentation method. The samples were measured at maximum loading forces of 50, 100, 150, 200, 250, 300, 350, 400, 450, and 500 mN. Four measurements (in the form of a 2x2 matrix) were made at a distance of 50 µm from each other on each sample and at each load. Young’s modulus, hardness, and Poisson’s ratio of Li2B4O7 glass were also calculated using the Makishima-Mackenzie theory. Results. The load-displacement curves and graphs of the dependence of the average contact pressure on the displacement of the diamond Berkovich indenter were obtained, which have a “smooth” shape and no anomalies associated with “pop-in” or “pop-out” effects. The indentation modulus (Young’s modulus E) and hardness H of the studied samples were obtained from the experimental P-h load-displacement diagrams. The measured values mainly depend on the applied load or the contact depth of the indenter penetration into the crystalline and vitreous lithium tetraborate. Conclusions. Both the hardness and Young’s modulus of Li2B4O7 glass are lower than those of the single crystal, indicating a lower resistance of amorphous lithium tetraborate to elastic and plastic deformations. The obtained experimental values of hardness and Young’s modulus of Li2B4O7 glass correlate well with the results of the calculation within the framework of the Makishima-Mackenzie theory. Multiple-loading cyclic nanoindentation leads to deformation densification of glassy Li2B4O7 due to changes in the angles and lengths of chemical bonds, which leads to a decrease in the free volume in the medium-order structure of glass, as well as a change in the coordination of Boron atoms relative to Oxygen, i.e., the transformation of three-coordinated Boron into four-coordinated Boron

Giant Increase of Hardness in Silicon Carbide by Metastable Single Layer Diamond-Like Coating.

Silicon carbide (SiC) is one of the hardest known materials. Its exceptional mechanical properties combined with its high thermal conductivity make it a very attractive material for a variety of technological applications. Recently, it is discovered that two-layer epitaxial graphene films on SiC can undergo a pressure activated phase transition into a sp3 diamene structure at room temperature. Here, it is shown that epitaxial graphene films grown on SiC can increase the hardness of SiC up to 100% at low loads (up to 900µN), and up to 30% at high loads (10mN). By using a Berkovich diamond indenter and nanoindentation experiments, it is demonstrated that the 30% increase in hardness is present even for indentations depths of 175nm, almost three hundred times larger than the graphene film thickness. The experiments also show that the yield point of SiC increases up to 77% when the SiC surface is coated with epitaxial graphene. These improved mechanical properties are explained with the formation of diamene under the indenter's pressure.

Evaluation of the Fracture Toughness KIc for Selected Magnetron Sputtering Coatings by Using the Laugier Model.

Nanoindentation is one of the methods that allows for determining the fracture properties of brittle materials. In this article, the authors present the possibility of the fracture toughness coefficient calculation of ceramic-based coatings doped by metal (W, Cr) by using the nanoindentation method with the Berkovich diamond indenter. The mechanical properties of selected coatings, such as hardness and Young's modulus, were investigated from nanohardness experiments. We analyzed the brittle fracture, which includes changes in hardness (H), Young's modulus (E), plasticity index H/E and resistance to plastic deformation H3/E2, enabled the concentration of tungsten and chromium. Due to the size of the indentation and the size of the initial cracks, it is necessary to use Scanning Electron Microscopy (SEM) to observe and measure the indentations made and the generated cracks. For evaluation of the fracture toughness in mode I, the Laugier model was chosen experimentally. The fracture toughness analysis showed that doping with concentrations of 10% W and 10% Cr causes an increase in the fracture toughness for KIc = 4.98 for TiBW (10%) and KIc = 6.23 for TiBCr (10%).

Crmnv and Crmntiv Heas Elastic Properties for Use in Beam Exit Windows for MW Irradiation Facilities

The choice of a material and the engineering design that is intended to lead to a beam exit window capable of sustaining mechanical and thermal loads in a high-radiation environment, while minimizing the beam loss and maximizing the window lifetime is discussed. Thin titanium windows have been typically used in industrial accelerators in the tens of kW beam power [1].The focus of this research is to conduct fundamental studies related to the choice of a material, from a material science point of view, for MW-class beam exit windows and an engineering design, including parameters such as the window size, thickness, and cooling scheme, suitable for industrial accelerators. CrMnV and CrMnTiV HEAs were selected for this study. According to Yang et al., [2], 1.1 and 6.6% should be expected as the criteria for forming high entropy stabilized solid solution phases. The two parameters of the CrMnV and CrMnTiV alloys are and respectively. Therefore, the two alloys are expected to be solid solution.The mechanical properties of CrMnV and CrMnTiV solid solution HEAs exit window prior to E-beam irradiation were measured using nanoindentation. The nanoindentation testing was carried out using XP Nanoindenter tester equipped with a three-sided diamond Berkovich indenter tip with maximum displacement of 2000 nm. The hardness is measured as 5.2 and 6.1 GPa for the bulk CrMnV and CrMnTiV solid solution HEAs at a depth of indentation of 900 nm respectively, Fig. 1. We also observe that both solid solution CrMnV and CrMnTiV HEAs depict indentation size effect. References Chmielewski A.G., Zimek, Z., Panta P., Drabik W., Radiat. Phys. Chem. 45 1029 (1995). Yang, X. and Y. Zhang, Prediction of high-entropy stabilized solid-solution in multi-component alloys. Materials Chemistry and Physics, 2012. 132(2-3): p. 233-238. Figure 1

Nanoindentation Response of Ion-Irradiated Fe, Fe-Cr Alloys and Ferritic-Martensitic Steel Eurofer 97: The Effect of Ion Energy

Nanoindentation of ion-irradiated nuclear structural materials and model alloys has received considerable interest in the published literature. In the reported studies, the materials were typically exposed to irradiations using a single ion energy varying from study to study from below 1 MeV to above 10 MeV. However, systematic investigations into the effect of self-ion energy are still insufficient, meaning that the possibilities to gain insight from systematic energy variations are not yet exhausted. We have exposed pure Fe, ferritic Fe-9Cr, martensitic Fe-9Cr and the ferritic-martensitic reduced-activation steel Eurofer 97 to ion irradiations at 300°C using 1, 2 and 5 MeV Fe2+ ions as well as 8 MeV Fe3+ ions and applied nanoindentation, using a Berkovich diamond indenter, to characterize as-irradiated samples and unirradiated references. The effect of the ion energy on the measured nanoindentation response is discussed for each material. Two versions of a primary-damage-informed model are applied to fit the measured irradiation-induced hardening. The models are critically compared with the experimental results also taking into account reported microstructural evidence. Related ion-neutron transferability issues are addressed.

Room-temperature plasticity and size-dependent mechanical responses in small-scale B1-NbC(001) single-crystals

We report on the mechanical responses of NbC(001) single-crystals subjected to nanoindentation and in situ scanning electron microscopy based uniaxial microcompression tests at room-temperature. Using X-ray diffraction and X-ray photoelectron spectroscopy, we determine that the as-purchased bulk NbC is a 001-oriented, B1-structured, single-crystal with lattice parameter of 0.4446 ± 0.0002 nm and C/Nb ratio of ∼0.99. From nanoindentation experiments performed on the bulk crystal using a Berkovich diamond indenter, we measure an elastic modulus of 495 ± 14 GPa and an indentation-depth (h) dependent hardness decreasing from 31.0 ± 1.2 GPa at h = 0.2 µm to 26.4 ± 0.4 GPa at h = 0.9 µm. During uniaxial compression of cylindrical pillars with top diameters D between ∼0.25 µm and ∼0.75 µm, we observe strain hardening, increasing yield strengths with decreasing D, and surprisingly extensive plastic deformation with strains exceeding 2% and up to 30% in larger-size pillars. Electron microscopy characterization of the compressed pillars reveal slip traces characteristic of {110}〈11¯0〉 and {111}〈11¯0〉 slip systems. We suggest that the unexpected activation of {111}〈11¯0〉 facilitates plasticity in NbC(001).

Temperature-dependent deformation behavior of γ and γ′ single-phase nickel-based superalloys

High-temperature nanoindentation measurements were employed to reveal the fundamental deformation behavior of γ and γ′ single-phase in nickel-based superalloy at various temperatures. The single-crystal samples of each phase with the equilibrium chemical compositions as in the conventionally utilized alloy were used to elucidate the temperature-dependent behavior of the individual phase leading to a further interpretation of each phase effect in the intensively used dual-phase alloy. Nanoindentation tests were conducted at room and elevated temperatures on the γ and γ′ single-phase using the Berkovich diamond indenter probe, and the Hysitron's xSol800 high-temperature stage. The noiseless load-displacement curves were obtained owing to thermal stability up to 1073 K and 873 K on the γ and γ′ sample, respectively. Furthermore, load-displacement curve shows a clear plasticity initiation in a strain burst as “pop-in” on a loading segment. The number of pop-in events in load-displacement curves of both, the γ and γ′ samples, increases with temperature. The elastic modulus and hardness of the γ phase decrease as the temperature increases, while the γ′ phase demonstrates thermal stability up to 573 K, indicating the γ′ phase domination for the high-temperature property in the dual-phase alloy. At small-scale mechanical property measurements no inverse temperature dependence of hardness was detected for the γ′ phase as a consequence of the multi-axial stress state with high hydrostatic pressure. Further, real-time topographical observations of the surface with increasing temperature reflect the behaviors of slip deformation and oxidation evolution.

Microstructural responses of Zirconia materials to in-situ SEM nanoindentation

Development of optimal shaping processes for pre-sintered and sintered zirconia materials requires a fundamental understanding of damage and deformation mechanisms at small-scale contacts with diamond tools. This paper reports on responses of zirconia materials with distinct microstructures to nanoindentation associated with diamond machining using a Berkovich diamond indenter. In-situ nanoindentation was performed in a scanning electron microscope (SEM) and in-process filmed to record small contact events. Indentation morphology was SEM-mapped at high-magnifications. Although both pre-sintered porous and sintered dense zirconia materials mechanically revealed the quasi-plastic behavior in indentation, there were distinct responses of the two materials to quasi-plasticity at the microstructural level. For pre-sintered porous zirconia, the quasi-plasticity was attributed to shear faults resulting from breaking pore networks as microstructurally discrete interfaces, to lead to compression, fragmentation, pulverization and microcracking of zirconia crystals in indentation imprints. In contrast, sintered dense zirconia had shear band-induced quasi-plastic deformation, accompanied with localized tensile microfracture. A material index associated with the mechanical properties ranked the lower quasi-plasticity for pre-sintered porous zirconia than its sintered dense state, predicting more machining-induced damage in the former than the latter. Significantly higher indentation imprint volumes induced in indented pre-sintered porous zirconia than sintered dense state previses higher machining efficiency for the former than the latter. The microstructure-dependent indentation mechanisms provide the fundamental knowledge into micromechanics of abrasive machining of zirconia materials and may lead to a new microstructural design for zirconia materials to achieve a balanced machining efficiency and damage control.

Influence of eccentric nanoindentation on top surface of silicon micropillar arrays

In this paper we present an investigation of the influence of nanoindentation location on the top surface of silicon micro-pillar. This silicon micro-pillar array which will be employed as a micro force sensor array based on three-dimension silicon (3D Si) structures, is fabricated by near UV nanoimprint lithography (NIL) technique and etched by Cryogenic Inductively Coupled Plasma (ICP) sequentially. To determine its mechanical properties, those micropillars are measured by instrument indentation testing (IIT) to obtain its hardness and reduced modulus. For the measurement, a Berkovich diamond indenter is utilized to penetrate a single and also multiple point indentations on a micro-pillar surface. Afterwards, these results are compared to the indentation at the central point of the tested pillar and Si bulk as its reference to examine the influence of different probing locations on the measured reduced modulus and hardness.

Room-Temperature Plasticity and Size-Dependent Mechanical Responses in Small-Scale B1-NbC(001) Single-Crystals

We report on the mechanical responses of NbC(001) single-crystals subjected to nanoindentation and in situ scanning electron microscopy based uniaxial microcompression tests at room-temperature. Using X-ray diffraction and X-ray photoelectron spectroscopy, we determine that the as-purchased bulk NbC is a 001-oriented B1-structured single-crystal with lattice parameter of 0.4446 ± 0.0002 nm and C/Nb ratio of ~0.99. From nanoindentation experiments performed on the bulk crystal using a Berkovich diamond indenter, we measure an elastic modulus of 495 ± 14 GPa and an indentation-depth (h) dependent hardness decreasing from 31.0 ± 1.2 GPa at h = 0.2 µm to 26.4 ± 0.4 GPa at h = 0.9 µm. During uniaxial compression of cylindrical pillars with top diameters D between ~0.25 µm and ~0.75 µm, we observe strain hardening, increasing yield strengths with decreasing D, and surprisingly extensive plastic deformation with strains exceeding 2% and up to 30% in larger-size pillars. Electron microscopy characterization of the compressed pillars reveal slip traces characteristic of {110}〈1‾10〉 and {111}〈1‾10〉 slip systems. We suggest that the unexpected activation of {111}〈1‾10〉 facilitates plasticity in NbC(001).

Hardness behaviour of carbon nanotube-aluminium nano-composite using nanoindentation technique

The aim of the current paper is to study the hardness behaviour of carbon nanotube reinforced aluminium (CNT-Al) nano composite material under nanoindentation and Vickers micro hardness techniques. The four different types of nano-composites with 1, 1.5, 2.0 and 2.5 wt% CNT indented by diamond Berkovich indenter in sub microns. The Vickers micro hardness test was performed using a Wilson Wolpert Vickers micro hardness tester. The results showed that the value of hardness increases with the increasing of CNT percentage in Al matrix up to 2 wt%. The highest hardness was obtained from 1.5 wt% CNT-Al nano-composite with the value of 1.90 GPa. From the CNT-Al load-displacement curve a good bonding property was observed between the reinforcement and the matrix material due to the same trend followed with other strong materials such as steel and silicon. However, there is a significant enhancement in the Vickers micro hardness of the 1.5 wt% CNT-Al nano-composite compared to other CNT reinforcement nano-composites. The highest hardness with the value of 102 VH was obtained from 1.5 wt% CNT-Al nano-composite which is three times higher than pure Al.

Effect of Laser Shock Peening on the Microstructure and Properties of the Inconel 625 Surface Layer

The aim of this work was to investigate the influence of laser shock peening on the topography, microstructure, surface roughness and the mechanical properties of the Inconel 625 nickel alloy. Examination of the topography and microstructure of the nickel alloy after laser treatment was carried out by means of scanning electron microscopy as well as atomic force microscopy. The roughness of the surface was measured by WYKO NT9300 equipment. Nanohardness test was carried out using a nanoindenter NHT 50-183 of CSM Instruments equipped with a Berkovich diamond indenter. Additionally, transmission electron microscopy was used to examine the microstructural changes on the surface layer after laser treatment. The investigations showed that the laser process produced an ablation and melting of the surface layer and, hence, increased the surface roughness of the Inconel 625. On the other hand, the presence of the slip bands on the surface and on the cross section of the treated material, a high density of dislocations and a higher hardness of the treated region indicated that the laser shock processing caused severe plastic deformation of the surface layer. Additionally, due to the high plastic deformation, cracking of the carbide precipitates was observed.

The Potential of a Nanostructured Titanium Oxide Layer with Self-Assembled Monolayers for Biomedical Applications: Surface Properties and Biomechanical Behaviors

This study investigated the surface properties and biomechanical behaviors of a nanostructured titanium oxide (TiO) layer with different self-assembled monolayers (SAMs) of phosphonate on the surface of microscope slides. The surface properties of SAMs were analyzed using scanning electron microscopy, X-ray photoemission spectroscopy, and contact angle goniometry. Biomechanical behaviors were evaluated using nanoindentation with a diamond Berkovich indenter. Analytical results indicated that the homogenous nanostructured TiO surface was formed on the substrate surface after the plasma oxidation treatment. As the TiO surface was immersed with 11-phosphonoundecanoic acid solution (PUA-SAM/TiO), the formation of a uniform SAM can be observed on the sample surface. Moreover, the binding energy of O 1s demonstrated the presence of the bisphosphonate monolayer on the SAMs-coated samples. It was also found that the PUA-SAM/TiO sample not only possessed a higher wettability performance, but also exhibited low surface contact stiffness. A SAM surface with a high wettability and low contact stiffness could potentially promote biocompatibility and prevent the formation of a stress shielding effect. Therefore, the self-assembled technology is a promising approach that can be applied to the surface modification of biomedical implants for facilitating bone healing and osseointegration.

Nanomechanical properties of spark plasma sintered multiwall carbon nanotubes reinforced Ti6Al4V nanocomposites via nanoindentation technique

In this study, nanoindentation tests were carried out to investigate the nanomechanical behaviours of Ti6Al4V and its nanocomposites comprising of multiwall carbon nanotubes (MWCNTs) fabricated via spark plasma sintering. Prior to the nanoindentation tests, the fabricated alloy and the nanocomposites comprising of 0.5 and 1.0 wt% of MWCNTs were observed under a scanning electron microscope (SEM) to reveal the morphology and the presence of the MWCNTs in the nanocomposites. The nanoindentation study was conducted using a Berkovich diamond indenter with a load of 75 mN to ascertain the nanohardness, reduced elastic modulus, plasticity index and elastic recovery index of the sintered materials. The SEM results revealed the dispersibility of the nanotubes in the titanium-based matrix and the presence of lamellar structures in the fabricated alloy. Furthermore, it was observed that the nanohardness and elastic modulus of the sintered materials ranges from 3.4–5.7 GPa and 27.6–38.9 GPa, which improved with the MWCNTs content. Also, the elastic recovery index increased with MWCNTs content in the nanocomposites. While the sintered Ti6Al4V displayed the maximum plasticity during the nanoindentation study.

The Indentation-Induced Pop-in Phenomenon and Fracture Behaviors of GaP(100) Single-Crystal

The deformation behaviors and fracture features of GaP(100) single-crystal are investigated by using nano- and micro-scale indentation techniques. The hardness and Young’s modulus were measured by nanoindentation using a Berkovich diamond indenter with continuous contact stiffness measurements (CSM) mode and the values obtained were 12.5 ± 1.2 GPa and 152.6 ± 12.8 GPa, respectively. In addition, the characteristic “pop-in” was observed in the loading portion of load-displacement curve, which was caused by the nucleation and/or propagation of dislocations. An energetic estimation methodology on the associated nanoindentation-induced dislocation numbers resulting from the pop-in events was discussed. Furthermore, the Vickers indentation induced fracture patterns of GaP(100) single-crystal were observed and analyzed using optical microscopy. The obtained fracture toughness KC of GaP(100) single-crystal was ~1.7 ± 0.1 MPa·m1/2, which is substantially higher than the KIC values of 0.8 MPa·m1/2 and 1.0 MPa·m1/2 previously reported for of single-crystal and polycrystalline GaP, respectively.