Nanoindentation Research Articles

Development and optimization of parameters for HVOF sprayed Al2O3 and ZrO2 blended aluminum coating on 316L SS

Abstract A significant number of gas turbines, aircraft engines, bearings, and automotive engines operating under a wide temperature range fail frequently due to fatigue and surface oxidation. Thus, a new coating formulation 40Al-35Al2O3-25ZrO2 was deposited on 316L SS substrate through the high velocity oxygen-fuel (HVOF) thermal spray coating method. The number of passes, spray distance and oxygen flow rate were varied by using Taguchi L9 array to achieve an optimized coating with higher hardness, less porosity, and roughness. The coating phase analysis, microstructure, elemental composition, microhardness and nano hardness were examined by x-ray diffraction (XRD), scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), energy dispersive x-ray spectroscopy (EDX), Vickers microhardness and nano indentation testing. The sample 5 prepared at spray distance of 20 cm and oxygen/acetylene ratio of 2 exhibited optimal hardness (1972 HV1), tensile strength (6.463 GPa), porosity (0.75%) and roughness (6.2 μm) due to α-Al2O3 and t-ZrO2 phases. Oxygen flowrate was the influential parameter contributing 48.71% to microhardness and 42.41% to roughness, while spray distance with contribution 51.62% was influential parameter for porosity.

Nanoindentation of nano-SiC/Si hybrid crystals and AlN, AlGaN, GaN, Ga<sup>2</sup>O<sup>3</sup> thin films on nano-SiC/Si

The review presents systematization and analysis of experimental data on nanoindentation (NI) of a whole class of new materials – wide-gap AlN, GaN, AlGaN and β-Ga2O3 heterostructures formed on a hybrid substrate of a new SiC/Si type, which were synthesized by the method of coordinated atom substitution. The deformational and mechanical properties of the investigated materials are described in detail. The methodology of the NI is described, and both advantages and disadvantages of the NI method were analyzed. The description of the apparatus to conduct the experiments on NI was given. The basic provisions of a new model for describing the deformation properties of a nanoscale rigid two-layer structure on a porous elastic base were proposed. The original method of visualization of residual (after mechanical interaction) deformation in transparent and translucent materials was described. Experimentally determined values of elastic moduli and hardness of SiC nanoscale layers on Si formed by the method of coordinated substitution on three main crystal planes of Si, namely (100), (110) and (111), and elastic moduli and characteristics (elastic modulus, hardness, strength) of surface layers of semiconductor heterostructures AlN/SiC/Si, AlGaN/SiC/Si, AlGaN/AlN/SiC/Si, GaN/SiC/Si and GaN/AlN/SiC/Si grown on SiC/Si hybrid substrates. The unique mechanical properties of a new material β-Ga2O3 formed on SiC layers grown on Si surfaces of orientations (100), (110) and (111) were described.

Impact of Paraben on Uterine Collagen: An Integrated and Targeted Correlative Approach Using Second Harmonic Generation Microscopy, Nanoindentation, and Atomic Force Microscopy.

This study investigates the structural and mechanical changes in uterine collagen following exposure to propylparaben (PP), using a combined methodology of Second Harmonic Generation (SHG) microscopy, Nanoindentation (NI), and Atomic Force Microscopy (AFM). SHG analysis identified significant disorganization in collagen fibril orientation in the circumferential layer and heterogeneous distribution of regions with elevated forward to backward ratios (F/B) across all uterine layers due to PP exposure. High F/B can indicate multiple potential fibril-level changes like thickened fibrils, higher crosslinking, fibril disorganization - changes not fully decipherable by SHG alone. Recognizing this limitation, the study employs NI and AFM to provide complementary mechanical and nanoscale insights. NI revealed increased indentation modulus in the exposed uteri, suggesting increased stiffness. Co-registration of the indentation response with SHG parameters uncovered that elevated F/B regions show enhanced mechanical stiffness, suggesting a fibrotic transformation following PP exposure. AFM was specifically performed on regions identified by SHG as having low or high F/B, providing the necessary nanoscale resolution to elucidate the structural changes in fibrils that are likely responsible for the observed alterations. This approach confirmed the presence of disordered and entangled collagen fibrils in the circumferential layer in all regions and an increase in fibril diameter in the high F/B regions in the exposed uteri. Together, these findings demonstrate significant alterations in collagen architecture due to PP exposure, revealing disruptions at both the fiber and fibril levels and highlighting the potential for broader applications of the multi-scale, multi-modal approach in collagenous tissue studies.

Multi-modal characterization of rodent tooth development.

Craniofacial tissues undergo hard tissue development through mineralization and changes in physicochemical properties. This study investigates the mechanical and chemical properties of developing enamel, dentin, and bone in the mouse mandible. We employ a multi-modal, multi-scale analysis of the developing incisor and first molar at postnatal day 12 by integrating micro-computed tomography (microCT), nanoindentation (NI), energy dispersive spectroscopy (EDS), and Raman spectroscopy. Our findings demonstrate distinct patterns of mechanical, elemental, and chemical changes across mineralized tissues. These results suggest that mineral composition drives mechanical properties across different craniofacial hard tissues. Integrating multi-modal characterization of mineralized tissues opens new opportunities for investigating structure-function relationships in craniofacial biology and genetics.

Nanomechanical properties of RENbO4 (RE = La, Gd, Dy, Y, Yb) ceramics: A comprehensive investigation by nano indentation

AbstractExcellent mechanical properties are indispensable for thermal barrier coatings (TBCs), including high hardness and low modulus, as well as excellent creep and wear resistance. This study focuses on nanomechanical properties of RENbO4 (RE = La, Gd, Dy, Y, Yb), and the effects of microstructures on their properties are analyzed. The evolutions of hardness and modulus of RENbO4 are studied based on the changes of RE3+ ionic radius, and the shorter bond lengths lead to the higher hardness and modulus due to the increasing bonding strength. The existence of ferroelastic domains causes the presence of pop out during nanoindentation, which affects the elastic and plastic work. Based on the load‐displacement curves, we further analysis the creep behavior and wear resistance of RENbO4 ceramics, and the results show that these two parameters show a negative correlation. Among the studied RENbO4 ceramics, YbNbO4 exhibits the best mechanical properties, and the used methods in current paper can be employed to screen materials with outstanding properties for various applications.

ZnO modified carbon fiber-matrix interfacial evaluation via nanoscale digital image correlation and nanoindentation

Improving the adherence of the fiber-matrix interface is an important step for enhancing the capabilities of polymer composites. In this study, carbon fibers were modified by growing zinc oxide (ZnO) nanorods on the fiber surface using a hydrothermal approach, with the aim of increasing the interfacial area and enhancing the friction between the fiber and the matrix. To fully understand the deformation mechanisms at the interface, a microscale evaluation combining nanoindentation with digital image correlation (DIC) for mapping the deformations by using nanoscale speckles is developed in this work. The main objective of this research was to develop a protocol for speckling the modified single fiber composite and show that DIC can be used in microscopic level and to evaluate the fiber-matrix interface by means of nano indentation. The speckle pattern was created using Ti nano powder and used to generate the strain maps in the fiber-matrix interface region. A comparative analysis of DIC results from ZnO modified carbon fibers has shown that shear strains around the interfacial boundary are 60 % reduced on average, as compared to neat carbon fibers, across all nano indentations from 8mN to 65mN of peak load. Results used direct strain measurements to confirm that modification by ZnO growth on the surface of individual fibers has a significant benefit to the interfacial mechanical properties of fiber-matrix composites.

Evaluation of nano indentation behavior of TIG, MIG and diffusion bonded Inconel 718 and austenitic Stainless Steel 316L joint interface

The nanomechanical characteristics of Metal Inert Gas (MIG), Tungsten Inert Gas (TIG), and diffusion-bonded Inconel (IN718) and Austenitic Stainless Steel (SS 316L) were investigated. The nano hardness and elastic modulus of different weldments were evaluated using nanoindentation and compared. The results showed that intermetallic compounds (IMCs) and carbides were reduced with diffusion bonding. Moreover, maximum nano hardness and elastic modulus occurred in the welded zone (WZ) of TIG and MIG welded joints while at the bonding interface in diffusion bonding (DB). Lastly, the nano hardness of the bonding interface in diffusion-bonded was 11 % and 7 % lower compared to MIG and TIG welded joints.

Nanoindentation and relaxation behavior of nitrogen doped zirconium based bulk metallic glass

In this paper, the effect of nitrogen doping on the mechanical properties of Zr-based bulk metallic glasses (BMGs) was studied by nano indentation experiment, and the correlation mechanism between microstructure evolution and mechanical properties was analyzed. The results show that the serrations events exhibited by metallic glasses during nanoindentation are related to the loading rates. With the decreasing loading rate, more obvious serrations events occur in the loading segment, which is attributed to the sufficient time for shear bands to multiply and propagate at low rates. The addition of nitrogen will induce the generation of more flow defects. Compared with BMGs without nitrogen, the nitrogen-doped Zr-based BMGs exhibit more serration events due to introducing more flow defects to form the shear transformation zones (STZs) and subsequently facilitating the shear bands to multiply. The possible relationships between the structural evolution, shear band initiation and propagation, and relaxation behavior of nitrogen doped and non doped metallic glasses were discussed.

Gluing parameters optimization and failure mechanism of cross-laminated timber prepared with Chinese fir

Cross-laminated timber (CLT) has become a popular engineered wood product, mainly prepared from imported wood in China. More extensive research is needed to improve the local production of cross-laminated timber with fast-growing coniferous wood species. Chinese fir (Cunninghamia lanceolata) and one component polyurethane (1C-PUR) adhesive were selected to prepare CLT under different process parameters. International standard methods, scanning electron microscopy (SEM), optical microscopy (LM), confocal laser scanning microscopy (CLSM), and nanoindentation (NI) were applied. The bonding performance and failure mechanism of Chinese fir CLT were investigated and clarified. The results showed that the optimal gluing parameters for preparing CLT from Chinese fir wood were 160 g/m2 of glue, 0.9 MPa of pressure, and 180 minutes of pressing time. Failure of CLT made from Chinese fir lumber was mainly due to the shear failure of the vertical layer board. Cracks often appeared in the earlywood cells near the boundary between earlywood and latewood. The impact of adhesive penetration on the mechanical properties of the wood cell wall showed that adhesive penetration increased the elastic modulus of the cell wall at earlywood and latewood cells.

Multi-scale investigation on mechanical properties of wood joints bonded with a polyurethane adhesive in successive cycles of accelerated aging treatments

To gain a deeper understanding of the bond durability in adhesively bonded wood products, a multiscale investigation of the mechanical properties of wood joints bonded with a one-component polyurethane (PU) adhesive in successive cycles of accelerated aging treatment was conducted by combining nanoindentation (NI) and conventional tensile-shear techniques. The delamination ratio, shear strength, and wood failure ratio of the wood joints, as well as the reduced elasticity modulus (Er) and hardness (H) of the PU resin, cell walls in the interphase region (CW–I), and control cell walls (CW) were evaluated. The correlations between the macro shear strength and micromechanical properties were further established. The results showed that the average delamination ratios of the wood joints were 10%–26 % after eight cycles of hydrothermal treatment. Macromechanical and most micromechanical properties substantially decreased with an increase in the number of treatment cycles, with maximum reductions of 37 %, 24 %, 60 %, 56 %, 48 %, and 57 % for the shear strength, wood failure ratio, Er of PU, H of PU, Er of CW-I, and Er of CW, respectively. The linear regression for the mechanical properties and the number of treatment cycles indicated that the Er of PU, CW-I, and CW, as well as the H of PU, showed linear downward trends (with R2 values of 0.765–0.921) during successive aging treatments. Significant and positive linear correlations were found between the shear strength and micromechanical properties of PU, with correlation coefficients of 0.970 (P < 0.01) and 0.941 (P < 0.05) for Er and H of PU, respectively. The wood failure ratio showed significant positive correlations with the Er values of CW-I (P < 0.01) and CW (P < 0.05), whereas the proportion of wood failure in the interphase was significantly (P < 0.05) negatively correlated with the Er value of CW. The shear strength was positively correlated with the Er of the cell walls, with correlation coefficients of 0.861 and 0.868 for CW-I and CW, respectively. In summary, both the micromechanical properties of the PU resin and the elasticity of the wood cell walls in the wood-adhesive interphase were demonstrated to be key factors affecting the bond durability of wood bond joints.

Experimental investigation during nano powder added µ-ED milling on nickel-titanium shape memory alloy

Nickel-titanium (NiTi) shape memory alloy (SMA) is one of the smart materials which has a vast application in the aerospace and biomedical industry due to its shape memory effect (SME), strong corrosion and wear resistance. Thus, the present study investigates the influence of process variables like gap voltage (V), powder concentration (PC) and pulse on time (ton) towards the material removal rate (MRR), surface roughness (SR) and micro-hardness (MH) amid graphene nano powder added micro-electrical discharge milling (µ-ED milling) of NiTi SMA. ANOVA analysis has been carried out to determine the % distribution of individual machining parameters towards all responses. The addition of graphene nano particles to the dielectric oil considerably enhanced the MRR, MH, and decreased the SR of the milled micro-channel. Taguchi’s grey relational analysis (GRA) and grey-desirability approach have been applied for multi-response optimisation to find the maximum MRR, MH, and minimum SR. It is discovered that the grey-desirability method improves all the responses. The Field emission scanning electron microscopy (FESEM) micro-graphs confirm defect-free mirror-like surface finish at the optimal grey-desirability setting. The X-ray diffraction (XRD) analysis discovered the formation of oxides and hardened phases in the machined surface. The application of graphene enhanced the recast layer thickness and reduced the indentation depth at subsurface region. The nano indentation test validates the rise in nano hardness and elastic modulus at the grey desirability optimal setting compared to the initial machining condition.

Investigation on the influence of gradation design on the road performance of cold mixed epoxy asphalt mixture based on microstructure evaluation

Cold mixed epoxy asphalt mixture (CMEAM) has excellent anti-deformation and fatigue performance which shows remarkable superiority on bridge pavements. Previous studies have done comprehensive researches on its properties through macroscopic experiments. However, few studies revealed the impact of gradation design on the road property of CMEAM through microscopic method. Thus, in this paper, X-Ray computed tomography (X-ray CT), nanoindentation (NI), field emission scanning electron microscopy (FESEM) and mercury intrusion porosimetry (MIP) are introduced to investigate the coarse aggregates contact degree, the thickness and elastic modulus of interfacial transition zone (ITZ) and the pore diameter distribution of CMEAM. Results showed that the contact points of coarse aggregates in EA-05 mixture are around 40 while those in EA-10 mixture are around 20. (40°, 50°) is the key inclination angle interval for EA-10 mixture type while (70°, 80°) and (10°, 20°) are of significance for EA-05 mixture type. The contact points and inclination angles are positively and inversely proportional to Marshall stability, respectively. In addition, the ITZ thickness of EA-05 and EA-10 mixture is below 10 μm and above 40 μm, respectively. The ITZ elastic modulus of EA-10 mixture is approximately 1.5 times than that of EA-05. The thickness and elastic modulus of ITZ are inversely proportional to low-temperature indirect tensile strain (εT). Meanwhile, EA-05 mixture has higher proportion in gel micropores and middle capillary pores while EA-10 mixture has higher proportion in mesopores and large capillary pores. Mesopores has the highest correlation coefficients with tensile strength ratio (TSR), followed by large capillary pores. The suggested proportion for above two type pores is around 21.5% and 51.0%, respectively.

Mechanical Tester Driven by Surface Tension.

The measurement of in-plane mechanical properties, such as Young's modulus and strength, of thin and stretchable materials has long been a challenge. Existing measurements, including wrinkle instability and nano indentation, are either indirect or destructive, and are inapplicable to meshes or porous materials, while the conventional tension test fails to measure the mechanical properties of nanoscale films. Here, we report a technique to test thin and stretchable films by loading a thin film afloat via differential surface tension and recording its deformation. We have demonstrated the method by measuring the Young's moduli of homogeneous films of soft materials including polydimethylsiloxane and Ecoflex and verified the results with known values. We further measured the strain distributions of meshes, both isotropic and anisotropic, which were otherwise nearly impossible to measure. The method proposed herein is expected to be generally applicable to many material systems that are thin, stretchable, and water-insoluble.

Influences of hybrid fiber-reinforcement using wollastonite and cellulose nanofibers on strength and microstructure characterization of ultra-high-performance mortar

This paper presents the effect of incorporating wollastonite microfibers and cellulose nanofibers on mechanical properties and microstructure of ultra-high-performance mortar (UHPM). Cellulose nanofibers of 0.005%, 0.015%, and 0.030% are combined with 4.8% wollastonite microfiber by weight of binder, which consists of 10% silica fume and 90% cement. Compressive and flexural strengths of the UHPM specimens are measured at 7 days. The microstructure is characterized in terms of SEM/EDX, XRD, FTIR, and nanoindentation. The results show the effectiveness of the fiber hybridization in enhancing the compressive and flexural strength of ultra-high-performance mortar with the improvement in flexural toughness and fracture energy by as much as 10% than control mortar. Moreover, hybrid fiber-reinforcement based on the microstructural analysis provided more synergic effect and uniform distribution of the fibers, thus developing an efficient micro crack bridging mechanism as well as resulting in enhanced toughening properties and an increased load carrying capacity. Additionally, the combination of wollastonite microfibers and cellulose nanofibers promoted the hydration reaction products and contributed a denser matrix between the fibers and cement matrix, resulting in an increase of the microstructure and interface area between the fibers and cement matrix. Nano indentation analysis also confirmed the increase of UHD C-S-H from 65% to 84% and lower percentage of anhydrous phase in ultra-high-performance matrix after combining wollastonite microfibers and cellulose nanofibers.

Investigating the structural and mechanical behavioral properties of semi-organic nonlinear optical single crystal: L-arginine tetrafluoroborate

A semi-organic nonlinear optical material L-Arginine tetrafluoroborate (LAFB) was synthesized as single crystal using Slow Evaporation Technique. Various properties of this material were analyzed to make it suitable for NLO applications. The structural behavior of the material was determined by single crystal XRD and found that the crystal has orthorhombic structure and was synthesized with P212121 space group. The High-Resolution X-Ray Diffraction (HRXRD) study was conducted to determine the change in the lattice parameters resulting from strain, defects or by other means in LAFB material. The diffraction curve analysis show that the grown crystal consisted of interstitial type point defect. The Shock Damage Threshold (SDT) measures the stability of the compound against shock, the analysis exhibits that under Mach number 2.2 up to 10th shock no significant cracks were observed in the crystal but damage area of the crystal was increased. The mechanical behavior of the sample against highly intense laser was analyzed through Laser Damage Threshold (LDT). The calculated value of LDT was to be 0.75[Formula: see text]GW/cm2 for 1 pulse per second whereas it decreased to 0.57[Formula: see text]GW/cm2 for 10 pulse per second. To explore the mechanical properties of the material, Nano indentation was carried out, by which the values of H[Formula: see text][Formula: see text]MPa and E[Formula: see text][Formula: see text]GPa were obtained.

Molecular dynamics study on the dislocation evolution mechanism of temperature effect in nano indentation of FeCoCrCuNi high-entropy alloy

ABSTRACT In this paper, the atomic model of high-entropy alloy is established by molecular dynamics simulation. By applying nano-indentation, the influence of Cu atomic ratio and temperature on the deformation of FeCoCrCuNi high-entropy alloy was studied, and the micro-scale dislocation movement evolution mechanism was obtained. The results show that, with the increase of temperature, the load of FeCoCrCuNi high-entropy alloy under nano indentation decreases. The total length of dislocations in each stage of nanoindentation decreases monotonically, and the types of dislocation reactions decrease. Under the action of high temperature, the number of perfect dislocations decomposed into Shockley partial dislocations decreases, resulting in more Frank dislocations and Stair-rod dislocations, which makes the extended dislocations recombine into perfect dislocations, and the length of dislocations decreases sharply. The dislocation defect is replaced by a cavity at high temperature, which makes the high-entropy alloy lose elastoplastic mechanical properties.

Biocompatibility screening of Mo–Si–Ta glassy alloy films sputtered on additive manufactured Ti–6Al–4V implant prototypes and PCL scaffolds

A ternary system of amorphous alloy with the components Mo, Ti, and Si with the composition Mo54Si33Ta13 has been chosen as the surface coating for the implantable materials to improve Ti6Al4V bioactivity. Ti6Al4V alloy metal powders were used to create the implant prototypes with the 3D metal printer. With the aid of a DC magnetron, the films are sputtered onto the implant prototypes. Elemental composition, amorphous nature, surface chemistry and topography of the as-fabricated microstructure films were comprehensively analysed using X-ray diffraction analysis, X-ray photoelectron spectroscopy and electron/atomic force microscopic techniques. The mechanical properties were studied from Nano indentation method. The coatings were confirmed to be cytocompatible determined from the in-vitro biocompatibility investigations using human osteosarcoma cells. The electrochemical corrosion studies carried out in SBF showed the higher corrosion resistance for the thin film metallic glass (TFMG)-coated customized 3D printed Ti-alloy implants than the pristine specimen.

Effects of B4C on the formation of LPSO phase and mechanical properties of Mg–Zn–Y–Mn alloy

Effects of B4C on the microstructure and properties of Mg94Zn2.5Y2.5Mn1 alloy were investigated by means of optical microscope, scanning electron microscope, X-ray diffraction, transmission electron microscope, nano indentation tester and electronic universal testing machine. The results indicated that the as-cast Mg94Zn2.5Y2.5Mn1 alloy was mainly composed of α-Mg, fishbone-like W phase, and block 18 R long period stacking ordered (LPSO) phase. The addition of an appropriate amount of B4C could effectively refine grains, promote the formation of the LPSO phase and inhibit the generation of the W phase. The microstructure and mechanical properties of the alloy were both optimal at the addition of 0.5 at.% B4C. The microstructure exhibited a refined grain size from 41.2 μm to 20.7 μm, and the volume fraction of the LPSO phase increased from 8.1 % to 22.5 %. The yield strength increases from 112 MPa to 145 MPa, the tensile strength of the alloy was enhanced from 192 MPa to 256 MPa, and the elongation increased from 4.8 % to 8.6 %.

Nanoindentation analysis of corrosion products and induced expansion stress in reinforced concrete exposed to marine environments

Reinforced concretes are widely used in construction owing to their ultrahigh mechanical properties and long-term durability. However, the corrosion of steel bar within concrete poses a substantial threat to the structural integrity of buildings, impeding advancements in ocean engineering and necessitating expensive maintenance measures. In this study, the corrosion mechanisms of reinforced concrete under marine environments were investigated. The elastic modulus of corrosion products and the identification of rust compositions in different corrosive environments were comprehensively investigated using nano indentation technique and microscopic characterizations. The average young's modulus of rust products in chloride, sulfate, and chloride-sulfate composite solutions were measured to be 47.6 GPa, 37.59 GPa, and 61.52 GPa, respectively. And the analysis identified the presence of two distinct layers of rust product, providing valuable insights into the corrosion process. In addition, the real-time and in-situ monitor of corrosion expansion stress shows that the rust expansion stress generated in chloride solution was almost twice as high as that under sulfate solution and 1.3 times higher than that in the composite solution. The advanced wire beam electrode technique was employed to compare and analyze the different stages of depassivation, pitting corrosion and corrosion rate during the whole process. The corrosion process under chloride solution showed larger and more serious corrosion than under sulfate solution, with the anodic peak current spreading and reaching 4.00 μA cm-2 after 300 days. This work reveals valuable insights into the corrosion behaviour of reinforced concrete in three corrosive conditions and can be used to inform the development of strategies for corrosion prevention and mitigation.

Microstructure and activation volume of a Cu-6 wt %Zn brass processed by equal channel angular pressing

The generation of a high density of twins few tens nanometers in size can enhance both strength and ductility. The present work aims to produce highly twinned microstructure in Cu-6 wt % Zn alloy of a moderate stacking fault energy (SFE) by equal channel angular pressing (ECAP) using a die with angles ϕ= 110° and Ψ = 0. X ray diffraction (XRD) shows that a high density of defects is stored up to 2 passes then a recovery takes place. EBSD imaging reveals a high density of twins and a fibrous microstructure. Grains close to 100 nm in size are formed. Strain rate sensitivity (SRS) was investigated in compression and nanoindentation (NI). Compression curves show that deformation occurs by slipping with a contribution of twins to hardening. A high contribution of shear bands was revealed during ECAP and compression tests. The activation volume V* in compression and NI is in the range 70b3 - 100b3, consistent with the emission of dislocations from grain boundaries and twin boundaries The experimental values of V* were compared to those expected from defect densities.