Nanoindentation Test Results Research Articles

PMMA-CNT-HAp nanocomposites optimized for 3D-printing applications

PMMA/CNT/HAp nanocomposites with various CNT and HAp ratios were prepared using melt mixing technique. Mechanical properties, rheological behavior, morphology and biocompatibility of the samples were reported. Results indicated that increasing the content of hydroxyapatite nanoparticles leads to lower mechanical properties which are pertaining to the low aspect ratio of hydroxyapatite particles and also lack of sufficient adhesion to the matrix. Nano-indentation test results revealed that upon addition of only 4 wt% HAp and 0.1 wt% CNT, modulus and hardness were improved 325 and 139%, respectively. This is favorable in implant applications. Rheological measurements and morphology depictions portrayed a better distribution for 2 wt% nanocomposite. Biocompatibility test results indicated that this nanocomposite accelerates cell attachment, growth, and proliferation. This observation propose this sample as a potential candidate for bone tissue applications. 3D-printing filaments were also successfully prepared using the optimized composition nanocomposite and specimens were printed.

Microstructure and corrosion characteristics of CrCuFeMoNi HEA coatings with different compositions in high-temperature and high-pressure water

Surface modification technology consists of a coating technique is one important method to improve the operational performance of nuclear fuel cladding. In this paper, different compositions of a CrCuFeMoNi high-entropy alloy (HEA) coating were deposited on a Zr-4 substrate by magnetron co-sputtering. The microstructures, mechanical properties and high-temperature corrosion behaviors of the CrCuFeMoNi HEA coatings were investigated. All as-deposited HEA coatings have an fcc structure and are well adhered to the Zr-4 substrate. The nanoindentation and autoclave test results showed that the as-deposited Cr0.26Cu0.3Fe0.1Mo0.15Ni0.19 HEA coating had superior hardness (12.5 GPa) and high-temperature corrosion resistance relative to others. The corrosion mechanisms of the CrCuFeMoNi HEA coatings with different compositions are also discussed.

Interfacial microstructure evolution and deformation mechanism in an explosively welded Al/Mg alloy plate

Interface plays a crucial role in the mechanical properties of composite materials. In this study, the interfacial morphology, microstructure and deformation mechanism of an explosively welded AA6061/AZ31B composite plate were both experimentally and numerically investigated. SEM analysis showed that the bonding interface has a periodic wavy shape with melted (vortex) zones. The vortex formation was found directly related with the deformation of the base plate. The compound composition found in the vortex was caused by the jetting at the interface. Owing to the different crystal structures and thermal/physical properties of the AA6061 and AZ31B, deformed grains were dominant at the Al matrix side near the bonding interface, while the Mg matrix side contained mainly recrystallized grains. Mg17Al12 intermetallic compounds were found in the melted zones through EDS and EBSD analyses. TEM analysis showed that a 2.5-μm-thick transitional layer of Mg17Al12 phase was formed at the bonding interface. Nanoindentation test results showed the melted zone had a high nano-hardness, owning to the formation of a hard and brittle Al–Mg intermetallic compound there.

Correlation Analysis of Surface Tilt Effect on Its Mechanical Properties by Nano-indentation

In this study, finite element analysis and nano-indentation experiments were carried out to investigate the effect of surface tilt on the nanoindentation test results. This paper revealed that standard Oliver–Pharr method underestimated the contact area due to the influence of the tilt condition. Consequently, it is necessary to compensate this difference to ensure that the result is reliable. The finding was verified by the nano-indentation experiments on a sinusoidal surface sample, which is used for the study of correlation between surface topography and its mechanical properties. A corrective action was implemented to compensate the errors by finite element analysis. By eliminating such errors, the study of the relationship between surface topography and mechanical properties was performed and discussed.

Study of the oxidation behavior of CrN coating on Zr alloy in air

With the aim of improving the oxidation resistance of fuel cladding in a light water reactor, CrN coating, which has good uniformity and compactness with an average thickness of about 13 μm, was deposited by multi-arc ion plating on a Zr alloy substrate heated to 400 °C. A series of comparative experiments of the oxidation resistances of the original (i.e., uncoated) and CrN-coated Zr alloys were performed in air atmosphere at high temperatures. The oxidation tests revealed that the CrN coating did not show any sign of cracking or shedding even after oxidation at 1160 °C. The weight gain of the Zr alloy decreased by 97.7% as a result of deposition of the CrN coating. The oxidation activation energy, calculated using Arrhenius plots, was obviously higher for the CrN-coated Zr alloy than for the uncoated Zr alloy. The results of transmission electron microscopy and X-ray diffraction analyses before and after the oxidation tests revealed that the oxidation product of CrN at high temperature was Cr2O3 and that the thickness of the oxide layer increased with an increase in oxidation temperature. Nanoindentation test results showed that the CrN coating also enhanced the mechanical properties of the Zr alloy. Even after oxidation at high temperature, the hardness and Young's modulus of the coating were significantly higher than those of the original Zr alloy. The CrN coating deposited by multi-arc ion plating exhibited excellent oxidation resistance and mechanical properties, which demonstrates its potential as a candidate material for accident-tolerant fuel cladding.

Micro-mechanical properties and corrosion resistance of Zr55Cu30Al10Ni5 bulk metallic glass fabricated by spark plasma sintering

Bulk Zr55Cu30Al10Ni5 metallic glasses were fabricated by spark plasma sintering (SPS) of gas-atomized alloy powders and their micro-mechanical and electrochemical characteristics were investigated. The XRD and DSC results showed the sintered samples were nearly fully amorphous when sintering temperature was below material's glass transition temperature (Tg). However, partial crystallization occurred when the sintering temperature was increased above Tg. Nanoindentation test results showed that micro-mechanical characteristics of the sintered samples improved with increasing sintering temperature. The sample sintered above Tg (at 703 K) exhibited the highest hardness, elastic modulus, and fracture toughness among all the ones sintered at various temperatures, owning to the formation of thermodynamically stable intermetallic phases and annihilation of free volumes during the sintering process. Electrochemical performance of the sintered sample was also found enhanced with increasing sintering temperature. However, when the sintering temperature was above Tg, the electrochemical performance of the sintered sample was significantly weakened due to the formation of crystalline phases. The sample sintered just below Tg (at 683 K) was found to have the best thermal, micro-mechanical, and electrochemical characteristics among all the ones sintered.

Improved laser induced damage thresholds of Ar ion implanted fused silica at different ion fluences

In this work, effects of 10 keV argon ion implantation on laser-induced damage threshold (LIDT) of fused silica were systematically investigated with ion fluences ranged from 1 × 1016 ions/cm2 to 1 × 1018 ions/cm2. Results show that only when the ion fluence increases above 1 × 1017 ions/cm2, the surface roughness apparently increases due to the formation of argon bubbles in the surface of fused silica. The concentration of defects decreases with the increased fluences up to 1 × 1017 ions/cm2 but then increases further, especially for the oxygen deficient center (ODC) defect. Based on the nanoindentation test results, Ar ion implantation generates large compressive stress and strengthens the surface of fused silica by surface densification. With the increase of the Ar ion fluences, the LIDTs of the samples increase due to the increases in both surface compressive stress and defects annihilation. However, at higher ion fluences, the increase of the densities of defects and argon bubbles are identified as the key reasons for the decrease of the LIDTs. Therefore, Ar ion implantation can improve the LIDTs of fused silica at moderate fluences.

Spark plasma sintered Al-0.5 wt% MWCNT nanocomposite: Effect of sintering pressure on the densification behavior and multi-scale mechanical properties

The current study aims to understand the effect of sintering pressure on densification behaviour and mechanical properties of multi walled carbon nanotube (MWCNT) reinforced aluminum (Al) based nanocomposite synthesized via spark plasma sintering (SPS). Physio-chemical functionalization, a novel dispersion technique, was followed which led to homogenous dispersion of MWCNTs in Al matrix. The crystallite size and density of the synthesized Al-0.5 wt% MWCNT nanocomposites increased with increase in sintering pressure. The relative density increased from 90.4% to 95.1% upon increasing the sintering pressure from 30 MPa to 80 MPa. To understand the densification behaviour, the movement of graphite punch within the die filled with Al-MWCNT powder mixture during sintering was monitored. Higher sintering pressure led to early onset of sintering and the total punch displacement during sintering increased from 0.38 mm to 1.48 mm upon increasing the applied pressure from 30 MPa to 50 MPa. The impact of high sintering pressure, leading to enhanced densification, was also translated in the improvement in mechanical properties. Compressive strength and microhardness increased by ~30% and ~13%, respectively as sintering pressure was increased from 30 MPa to 80 MPa. Higher sintering pressure leading to significantly enhanced mechanical properties at micro and macro scale was also replicated at nano-scale as confirmed by the results of nanoindentation and nanoscratch tests.

Effect of Mo and Cr additions on the microstructure, mechanical properties and pitting corrosion resistance of austenitic Fe-30Mn-10.5Al-1.1C lightweight steels

Five Fe-30 wt%Mn-10.5 wt%Al-1.1 wt%C steels containing different Mo and Cr contents were prepared to investigate the effect of Mo and Cr addition on the microstructure, mechanical properties and pitting corrosion resistance of austenitic lightweight steels. The microstructures of all samples after solution treatment at 1050 °C consisted of austenite and κ-carbide, while DO3 ordered phases were additionally formed in samples containing 3 wt%Mo-3wt%Cr or 5 wt%Cr. The results of Nanoindentation tests indicated that the intrinsic strength of the austenite matrix decreased with the addition of Mo and Cr due to the suppression of κ-carbide precipitation and then the strength of the DO3 phase is equal or higher as compared to the austenite matrix. The tensile tests also showed that the yield strength decreased when 3 wt%Mo or 3 wt%Cr was added due to the suppression of κ-carbide precipitation, whereas it increased with further additions of Mo and Cr in both cases due to the formation of a DO3 ordered phases and grain refinement. Electrochemical tests showed that the resistance to pitting corrosion was improved by the addition of Mo and Cr due to the formation of a protective passive film; however, the excessive additions of Mo or Cr adversely deteriorated the resistance to pitting corrosion as the DO3 ordered phase which acted as pit initiation sites.

Effect of Ti Transition Layer Thickness on the Structure, Mechanical and Adhesion Properties of Ti-DLC Coatings on Aluminum Alloys.

Multilayers of Ti doped diamond-like carbon (Ti-DLC) coatings were deposited on aluminum alloys by filtered cathodic vacuum arc (FCVA) technology using C2H2 as a reactive gas. The effect of different Ti transition layer thicknesses on the structure, mechanical and adhesion properties of the coatings, was investigated by scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), nanoindentation and a scratch tester. The results showed that the Ti transition layer could improve interfacial transition between the coating and the substrate, which was beneficial in obtaining excellent adhesion of the coatings. The Ti transition layer thickness had no significant influence on the composition and structure of the coatings, whereas it affected the distortion of the sp2-C bond angle and length. Nanoindentation and scratch test results indicated that the mechanical and adhesion properties of the Ti-DLC coatings depended on the Ti transition layer thickness. The Ti transition layer proved favorable in decreasing the residual compressive stress of the coating. As the Ti transition layer thickness increased, the hardness value of the coating gradually decreased. However, its elastic modulus and adhesion exhibited an initial decrease followed by an increasing fluctuation. Among them, the Ti-DLC coating with a Ti transition layer thickness of 1.1 μm exhibited superior mechanical properties.

Mechanical properties of top neck mollusks shell nano composite in different environmental conditions

The mechanism of biological materials structure is very complex and has optimal properties compared to engineering materials. Top Neck mollusks shells, as an example of biological materials, have hierarchical structure, which 95 percent of its structure is Aragonite and 5 percent organic materials. This article detected mechanical properties of the Top Neck mollusks shell as a Nano composite using Nano-indentation method in different situations. Research findings indicate that mechanical properties of the Top Neck mollusks shell including elastic modulus and hardness are higher than a fresh one preserved in -50 centigrade and also a Top Neck mollusks shell preserved in environmental conditions. Nano-indentation test results are so close in range, overall, that hardness degree is 3900 to 5200 MPa and elastic modulus is 70 to 85 GPa.

Enhancing the adhesion of diamond-like carbon films to steel substrates using silicon-containing interlayers

Diamond-like carbon (DLC) films were deposited on AISI 316L stainless steel by using a unipolar pulsed-DC plasma assisted chemical vapor deposition (PACVD) system. In order to improve the adhesion of the DLC films to the substrate, three different silicon-containing interlayers (a-Si:H, a-SiCx:H, and a-SiNx:H) were deposited at two temperatures of 150 and 350 °C using silicon tetrachloride, methane, nitrogen, and hydrogen precursors. The DLC films with silicon-containing interlayers, deposited at 150 °C, did not show appropriate adhesion to the substrate due to the presence of a high amount of chlorine and hydrogen in the structure of the interlayers. By increasing the temperature of the interlayer deposition, the adhesion of DLC films improved significantly. The results of Raman spectroscopy, Nano indentation and adhesion tests showed that the DLC film with a-SiNx:H interlayer exhibited the lowest ID/IG ratio, highest hardness, and highest adhesion to the substrate.

Morphological evaluation of heterogeneous oolitic limestone under pressure and fluid flow using X-ray microtomography

Pore-scale analysis of carbonate rock is of great relevance to the oil and gas industry owing to their vast application potentials. Although, efficient fluid flow at pore scale is often disrupted owing to the tight rock matrix and complex heterogeneity of limestone microstructures, factors such as porosity, permeability and effective stress greatly impact the rock microstructures; as such an understanding of the effect of these variables is vital for various natural and engineered processes. In this study, the Savonnières limestone as a carbonate mineral was evaluated at micro scales using X-ray micro-computed tomography at high resolutions (3.43 μm and 1.25 μm voxel size) under different effective stress (0 MPa, 20 MPa) to ascertain limestone microstructure and gas permeability and porosity effect. The waterflooding (5 wt% NaCl) test was conducted using microCT in-situ scanning and nanoindentation test was also performed to evaluate microscale geomechanical heterogeneity of the rock. The nanoindentation test results showed that the nano/micro scale geomechanical properties are quite heterogeneous where the indentation modulus for the weak consolidated area was as low as 1 GPa. We observed that the fluid flow easily broke some less-consolidated areas (low indentation modulus) area, coupled with increase in porosity; and consistent with fines/particles migration and re-sedimentation were identified, although the effective stress showed only a minor effect on the rock microstructure.

Nanoindentation tests of Sulcata Tortoise’s carapace

This paper illustrates the dependence of tortoise carapace’s hardness and elastic modulus on peak-load of nanoindentation tests. Sulcata Tortoise carapace is a sandwich-like structure consisting of four submicron layers: keratin scutes, dorsal cortex, cancellous interior (porous layer) and ventral cortex. Nanoindentation test is a viable option for measuring their mechanical properties due to the size of the layers. However, preliminary results of nanoindentation tests on a carapace sample vary according to the indentation peak load. As the indentation peak load increases, both measured hardness and elastic modulus decrease. A systematic approach to determine an optimal peak load for nanoindentation test is presented.

Multilayered vacuum-arc nanocomposite TiN/ZrN coatings before and after annealing: Structure, properties, first-principles calculations

Nanoscale multilayered TiN/ZrN films were deposited using sequential vacuum-arc deposition of Ti and Zr targets in a nitrogen atmosphere. Studies of film's properties were carried out using various modern methods of analysis, such as XRD, STEM, HRTEM, SIMS combined with results of nanoindentation and tribological tests. To interpret the mechanical properties of the deposited multilayer films first-principles calculations of TiN(111), ZrN(111) structures and TiN(111)/ZrN(111) multilayer were carried out. To study the influence of thermal annealing, several samples were annealed in air at the temperature 700°C. All deposited samples were highly polycrystalline with quite large 20–25nm crystals. The crystalline planes were very ordinated and demonstrated an excellent coordinated growth. The nanohardness and elastic modulus of non-annealed coatings reached 42GPa and 348GPa, respectively. Annealing in air at the temperature 700°C led to partial oxidation of the multilayered coatings, however hardness of the non-oxidized part of the coatings remained as high, as for initial coatings. All deposited coatings demonstrate good wear resistance.

Laser Indirect Shock Welding of Fine Wire to Metal Sheet.

The purpose of this paper is to present an advanced method for welding fine wire to metal sheet, namely laser indirect shock welding (LISW). This process uses silica gel as driver sheet to accelerate the metal sheet toward the wire to obtain metallurgical bonding. A series of experiments were implemented to validate the welding ability of Al sheet/Cu wire and Al sheet/Ag wire. It was found that the use of a driver sheet can maintain high surface quality of the metal sheet. With the increase of laser pulse energy, the bonding area of the sheet/wire increased and the welding interfaces were nearly flat. Energy dispersive spectroscopy (EDS) results show that the intermetallic phases were absent and a short element diffusion layer which would limit the formation of the intermetallic phases emerging at the welding interface. A tensile shear test was used to measure the mechanical strength of the welding joints. The influence of laser pulse energy on the tensile failure modes was investigated, and two failure modes, including interfacial failure and failure through the wire, were observed. The nanoindentation test results indicate that as the distance to the welding interface decreased, the microhardness increased due to the plastic deformation becoming more violent.

Nanoindentation time-dependent deformation/recovery suggestive of methylglyoxal induced glycation in calcified nodules

Although empirical findings have indicated increase in bone fracture risk in type 2 diabetes patients, that has yet to be proven by results obtained at the material level. Here, we report evidence showing nanoscale time-dependent deformation/recovery of in vitro calcified nodules mimicking bone turnover in type 2 diabetes in respect to methylglyoxal (MG)-induced glycation. Nanoindentation test results revealed that calcified nodules cultured with MG did not show adequate dimensional recovery, despite a large creep rate during constant load indentation testing. This lesser recovery is likely based on the linear matrix polymerization network formed by advanced glycation end products (AGEs) as a secondary product of MG. Since elevated serum MG and abnormal bone turnover related to the amount of AGEs are observed in cases of type 2 diabetes, this time-dependent behavior may be one of the factors of the bone fracture mechanism at the material level in affected patients.

Characterization and corrosion behavior of graphene oxide-hydroxyapatite composite coating applied by ultrasound-assisted pulse electrodeposition

Abstract Hydroxyapatite (HA) coating reinforced with graphene oxide (GO) had been developed for getting rid of restrictions associated with its brittleness. This study introduced a promising method of ultrasound-assisted pulse electrodeposition to fabricate the GO-HA coating on the anodized heat-treated surface of titanium. The SEM images indicated that the combined effect of employing ultrasonic waves and GO as a second mechanically resistant phase resulted in the formation of a fine and compact microstructure for the HA-based coating. The EDS elemental maps and micro-Raman spectra showed that the ultrasonic power of 60 W was more effective to incorporate the GO sheets into the coating. However, aggressive agitation of electrolyte with increasing the power to 100 W limited the electrocrystallization of HA crystals in some regions of the surface. The results of nanoindentation test demonstrated the highest nano-hardness (3.08 Gpa) and elastic modulus (41.26 Gpa) for the GO-HA coating prepared by the ultrasound-assisted method. The EDS and FTIR analyses revealed that both the GO sheets and highly reactive OH · radicals produced during the water sonolysis had a positive influence on the mineralization of HA phase. In addition, the pore size distribution diagrams calculated from the N 2 adsorption-desorption isotherms indicated a decrease in the pore size of HA crystals for the electro-co-deposited GO-HA sample. Finally, anodizing/heat-treatment process and the incorporation of GO sheets into the coating led to a significant improvement in the corrosion protection of titanium.

Amino Group Bearing Organic–Inorganic Hybrid Materials for Joining Aluminum Alloys and Thermoplastic Fiber‐Reinforced Parts

The production of metal‐based hybrid laminates, such as aluminum combined with thermoplastics like polyamide 6, requires a precise and purposeful design of the interface between the two components. The utilization of twin polymerization has been successfully examined and an improved adhesion behavior is shown. By utilizing the monomers 2,2′‐spirobi[4H‐1,3,2‐benzodioxasiline] and 2‐(3‐amino‐n‐propyl)‐2‐methyl‐4H‐1,3,2‐benzodioxasiline in a molar ratio of 15:85, medial tensile shear strength values of 12.9 ± 3.9 MPa are achieved in tests according to DIN EN 1465. Electron microscopic and atomic force microscopic investigations give further structural details of the hybrid material. Additionally, the results of nanoindentation and microscratch tests clearly demonstrate that the choice of an adhesion promoter depends on its chemical as well as its mechanical characteristics.

Study on the crack resistance of CrBN composite coatings via nano-indentation and scratch tests

Abstract Crack resistance of CrBN coatings in relation to B concentration was investigated via nano-indentation and scratch tests. A nano-composite structure consisting of CrN nano-grains embedded in amorphous BN (a-BN) matrix was observed by transmission electron microscope (TEM). XRD and XPS analyses revealed a decrease of crystallinity in coatings as B content increased from 16.4 to 27.2 at.%, which led to a hardness decrease from 28.9 GPa to 23.6 GPa. All CrBN coatings, regardless of composition, prevented radial cracks due to superior mechanical properties (H/E ≥ 0.077). However, owing to high compressive stress (3.27–4.74 GPa), circumferential cracks were found along indent edge, and the number of circumferential cracks was proportional to B concentration. Meanwhile, the critical load of initiating crack dropped from 17.9 to 13.4 N when B concentration raised from 12.8 to 22.2 at.%. The results of nano-indentation and scratch tests indicated that the crack resistance of CrBN coatings became poor when the B doping content increased. In here, the CrBN coating with 12.8 at.% B exhibited the best crack resistance.