Film Elastic Modulus Research Articles

Controlling strain localization in thin films with nanoindenter tip sharpness

Thin film nanoindentation has increased interest due to its usage in various applications. It is virtually impossible to measure thin film elastic modulus without the substrate influence. Several different methods exist to obtain the true thin film’s elastic modulus with no attention given to investigate what parameters can improve insight into thin film mechanical property measurement. A key parameter is the tip radius. This work is aimed at quantifying the influence of the tip radius on the strain field under the indenter. Three Berkovich indentation tips with different tip radii were used for thin multilayer nanoindentation with numerical modelling. The results confirm the existence of the large elastically deformed zone, with a strong localization under the tip. Comparison between the experiments and numerical model shows direct connection between the tip radius and strain localization affecting the experiment, emphasizing importance of knowing the tip radius.

Corrosion Resistance of Fe-Based Amorphous Films Prepared by the Radio Frequency Magnetron Sputter Method.

Amorphous thin films can be applied to increase the anti-corrosion ability of critical components. Atomized FeCrNiMoCSiB powders were hot-pressed into a disc target for R. F. magnetron sputtering on a 316L substrate to upgrade its corrosion resistance. The XRD spectrum confirmed that the film deposited by R. F. magnetron sputtering was amorphous. The corrosion resistance of the amorphous film was evaluated in a 1 M HCl solution with potentiodynamic polarization tests, and the results were contrasted with those of a high-velocity oxy-fuel (HVOF) coating and 316L, IN 600, and C 276 alloys. The results indicated that the film hardness and elastic modulus, as measured using a nanoindenter, were 11.1 and 182 GPa, respectively. The principal stresses in two normal directions of the amorphous film were about 60 MPa and in tension. The corrosion resistance of the amorphous film was much greater than that of the other samples, which showed a broad passivation region, even in a 1 M HCl solution. Although the amorphous film showed high corrosion resistance, the original pinholes in the film were weak sites to initiate corrosion pits. After polarization tests, large, deep trenches were seen in the corroded 316L substrate; numerous fine patches in the IN 600 alloy and grain boundary corrosion in the C276 alloy were observed.

Deposition of Ti[sbnd]Zr alloy films using Ti and Zr dual-cathode high-power impulse magnetron co-sputtering

In this study, titanium–zirconium binary alloy films were deposited using heterogeneous dual-cathode high-power impulse magnetron sputtering with a closed magnetron field. For both Ti and Zr cathodes, the discharge voltage pulses were synchronized with an equal pulse width. In addition, we investigated the effects of the average discharge power ratios of the two cathode materials, deposition pressure, and substrate bias voltage on the mechanical strength and microstructure of the deposited films. The results revealed that the film composition could be controlled by the average power ratio of the two cathodes at a constant deposition pressure; however, the deposition rate of each element varied with the deposition pressure. At a constant average power ratio at the two cathodes, the Zr content in the films decreased with decreasing the deposition pressure. Decreasing the deposition pressure can smoothen the film surface, but the dependence of the film composition on two cathode powers also changes. An adequate enhancement of the negative substrate bias can further increase the film hardness and reduce the film elastic modulus, yielding only a moderate loss in the film deposition rate and marginal variations in the film composition. However, the magnitudes of the increase in hardness and the decrease in elastic modulus brought by enhancing negative substrate bias varies with the film composition, and will be minimized when the atomic fractions of Ti and Zr are near equal. Notably, with adjusting the negative substrate bias, adding Zr can change the film hardness from 4.8 to 10.6 GPa, and the film elastic modulus from 100 to 162 GPa. Overall, the advantageous mechanical and structural properties of the TiZr alloy films deposited using HiPIMS might be useful in tools, biomedical devices, wearable equipment applications.

Magnetically recyclable polydopamine-polyquaternium modified Fe3O4 nanoparticles for demulsification of asphaltene-rich ASP flooding produced water

The asphaltene-rich alkaline-surfactant-polymer (ASP) flooding produced water has been identified with high interfacial stability and severe secondary emulsification, which poses great difficulties in its demulsification process. This leads to an urgent need to develop targeted and efficient demulsifiers. In this research, a novel polydopamine-polyquaternium modified Fe3O4 (PQA-PDA@Fe3O4) nanoparticle integrates the electrical neutralization, interfacial adsorption and magnetic aggregation functionalities was prepared to dispose this emulsion. Primarily, structural and surface properties of the PQA-PDA@Fe3O4 demulsifier were systemically characterized by a series of analytical techniques, which presents its core-shell, hydrophilic and positively charged characters. When employing PQA-PDA@Fe3O4 to treat the produced water that contained 500 mg/L emulsified oil, a demulsification efficiency of 90.5 % was achieved at 200 mg/L dosage. It was found that the PQA-PDA@Fe3O4 nanoparticles could coalesce the fine oil droplets into large and dense aggregates, as demonstrated by the raised fractal dimension values. By monitoring the interfacial properties (interfacial tension, zeta potential and interfacial film elastic modulus) variations, the demulsification mechanism was further explored. The PQA-PDA@Fe3O4 nanoparticle could spontaneously migrate to the oil/water interface and reassemble a loose interfacial film, thus leading the oil droplets destabilization and aggregation. Notably, the magnetic force between the PQA-PDA@Fe3O4 nanoparticles significantly accelerates the oil droplets aggregation and inhibits the secondary emulsification process, so as to achieve the outstanding demulsification efficiency. Moreover, this PQA-PDA@Fe3O4 nanoparticle exhibited acceptable magnetic recyclability. These results provided an effective and alternative protocol to demulsify the asphaltene-rich ASP flooding emulsions.

Carbon defect induced evolution of structural and mechanical properties in substoichiometric (HfMoNbZr)Cx films

Substoichiometric (HfMoNbZr)Cx films with varied carbon content were synthesized using non-reactive magnetron sputtering. Findings reveal that the (HfMoNbZr)Cx film predominantly exhibits a single-phase FCC structure, which transforms to a dual-phase structure consisting of FCC and Hex. phases at higher carbon content. This behavior arises from the segregation of group VB (Nb) and VIB (Mo) elements from the FCC lattice. The film hardness (H) and elastic modulus (E) increases with rising carbon content accompanied by a decrease of coefficient of friction (COF). However, the wear rate is not decreased despite the increased H and reduced COF of the as-deposited films. This phenomenon is explained by examining the differences in the wear mechanisms between (HfMoNbZr)Cx films with single- and dual- phase structures.

Effects of dielectric layer on ductility for dielectric/Au/dielectric multilayers on polycarbonate substrate

The ductility of transparent conductive films on polycarbonate (PC) substrate is of great concern as it significantly affects the stability and longevity of aeronautic equipment. Three types of dielectric/Au/dielectric multilayers, including ITO/Au/ITO (IAI), IZO/Au/IZO (ZAZ) and AZO/Au/AZO (AAA) were fabricated to obtain highly ductile films on thick rigid PC substrate. The ductility of multilayers was comparatively investigated using in situ scanning electron microscopy test and in situ electrical resistance test under uniaxial tension. The effect of dielectric layer on ductility was elucidated according to the results of film stress and elastic modulus, and analyzed using the energy release rate approach based on the mechanics model. The results of in situ tests revealed that the crack initiation strain by morphology and the conductive failure strain of AAA were found to be 1.04 ± 0.04% and 1.47 ± 0.07%, which were superior to those of IAI and ZAZ. This result can be attributed to differences in layer stress state and layer-substrate mechanical contrast induced by different dielectric layers. Although AAA has the lower fracture toughness, the higher compressive residual stress and the smaller elastic mismatch give AAA the smallest crack driving force under the same conditions, resulting in excellent ductility.

Axisymmetric Peeling of Thin Elastic Films: A Perturbation Solution

Abstract We study the mechanical behavior of a thin elastic film that is affixed to a rigid substrate and subjected to a transverse force using a shaft with a finite radius. This scenario, also referred to as axisymmetric peeling, is encountered frequently in conventional blister tests as well as in our daily lives when removing an adhesive film from a substrate. Our primary objective is to gain a quantitative understanding of how the shaft’s radius influences the relationships between force and displacement, as well as between force and delamination areas. These relationships can serve as a dependable method to determine both the film’s elastic modulus and the adhesion strength between the film and its substrate. In this work, we provide a simple perturbation solution to this geometrically nonlinear problem while avoiding any use of ad hoc assumptions that were previously required. As a result, our results are in excellent agreement with numerical simulations and offer improved accuracy compared to analytical solutions available in the literature.

Microstructure evolution and mechanical properties of Al doped ta-C films prepared by filtered cathodic vacuum arc

Al-doped tetrahedral amorphous carbon (ta-C) films were prepared by filtered cathodic vacuum arc technique. Effect of Al content on the structure and properties of the ta-C film were systematically investigated. Results showed that Al content in films increased from 0 to 39.5 at. % as the Al target current altered from 0 to 2 A. Without Al doping, ta-C film mainly presented amorphous characteristic with disordered arrangement and compact structure. With a small amount of Al doping, the film maintained the amorphous phase structure, and Al atoms mainly existed in the carbon tetrahedral interstitial space in the form of solid solution. At high Al doping content, the formed Al nanoparticles embedded in the carbon matrix network. Meanwhile, the addition of Al could promote the graphitization of films. The residual stress of ta-C films decreased gradually with increase of Al content. Furthermore, the hardness and elastic modulus of films also decreased with increasing Al content. That's ascribed to the reduction of residual stress and graphitization of the carbon structure. In addition, the ta-C film with Al addition could effectively improve the friction and wear properties of films at both room and high temperature. The friction coefficient decreased with the increase of Al content at room temperature (RT). At 400 °C, the film containing 7.6 at. % Al obtained the lowest friction coefficient and wear rate, corresponding to the values of 0.29 and 12.3 × 10−8 mm3/N⋅m, respectively.

Effect of atomic oxygen erosion on mechanical and tribological properties of Cr and B doped hydrogen-containing diamond-like carbon films

To improve the mechanical and tribological properties of hydrogen-containing diamond-like (H-DLC) films under typical space environment—atomic oxygen (AO) erosion, H-DLC films with multilayer structure of Cr-doped and B-doped were prepared on the surface of GCr15 steel by non-equilibrium magnetron sputtering technique. The changes of mechanical properties such as hardness, elastic modulus and residual stresses of the three DLC films, H-DLC, Cr-H-DLC and B-H-DLC, before and after AO erosion were investigated contrastively. It was found that AO erosion reduced the sp3 hybrid bonds content in the three DLC films, leading to a decrease in film hardness and elastic modulus, and it was also found that the residual stresses in the films were all increased after AO erosion. Compared with the friction test carried out only in a vacuum condition without AO erosion, the coefficient of friction (COF) of the films after AO erosion changed slightly, but the wear life showed a notably decrease and a large number of pear grooves appeared in the wear scars. Although wear life of the three DLC films decreased after AO erosion, the decrease of Cr-H-DLC film was much smaller than the remaining two. According to the Raman spectra results, it was found that the ID/IG values at the wear scars of H-DLC film became larger after AO erosion, and the ID/IG values at the wear scars of Cr-H-DLC and B-H-DLC films did not change much, indicating that the AO erosion induced more sp2 CO bonds with high binding energy in the H-DLC films, which, together with the degradation of the films' mechanical properties, led to the decrease in the wear life of the H-DLC films. The doping of Cr element produced less CO bonds and thus the decrease of film's wear life was smaller. The effect of doping with B elements on film's wear life was not significantly, but achieving the lowest COF.

THE INFLUENCE OF SILICON ELEMENT-ADDED DLC FILM ON Ti-6Al-4V

Silicon added diamond-like carbon films fabricated from C2H2:TMS mixture were used to study the influence of silicon content on the deposition and tribological properties of films prepared on Ti-6Al-4V substrate by using plasma-based ion implantation (PBII). The structure of the film was analyzed by Raman spectroscopy. Hardness and elastic modulus of the film were measured by nano-indentation hardness tester. Tribological propertiesof the film were performed by using ball-on-disk friction tester. The results indicate that with the increasing silicon content in the pure DLC film, the friction coefficient increases. The hardness and elastic modulus of Si-DLC film can increase to a value of up to 31.1 GPa and 200.1 GPa with a silicon content of 13.1 at.%. This is because the greater C content. The Si-DLC films with Si content of 13.1 at.% (C:Si/1:2) and 14.3 at.% (C:Si/1:6) shows a low friction coefficient of 0.2, which is considerable improvement in the tribological properties. This is due to the high hardness and elastic modulus.

Interfacial Nanoblisters Formed in Water Serving as Freestanding Platforms for Measuring Elastic Moduli of Polymeric Nanofilms.

Polymeric nanofilms have been widely utilized in diverse cutting-edge technologies, yet accurately determining their elastic moduli remains challenging. Here we demonstrate that interfacial nanoblisters, which are produced by simply immersing substrate-supported nanofilms in water, represent natural platforms for assessing the mechanical properties of polymeric nanofilms using the sophisticated nanoindentation method. Nevertheless, high-resolution, quantitative force spectroscopy studies reveal that the indentation test must be performed on an effective freestanding region around the nanoblister apex and meanwhile under an appropriate loading force, to obtain load-independent, linear elastic deformations. The nanoblister stiffness increases with either decreasing its size or increasing its covering film thickness, and such size effects can be adequately rationalized by an energy-based theoretical model. The proposed model also enables an exceptional determination of the film elastic modulus. Given that interfacial blistering is a frequently occurring phenomenon for polymeric nanofilms, we envision that the presented methodology would stimulate broad applications in relevant fields.

Optimization of citron peel pectin and glycerol concentration in the production of edible film using response surface methodology

Pectin-based edible film plasticized with glycerol has been developed, and the effect of pectin and glycerol concentration was optimized using response surface methodology for better mechanical properties and transparency. The upper and lower concentration of pectin (3–5 g) and glycerol (15%–25%) concentration ranges were considered in this study based on the preliminary experiment. The responses of the edible film determined were tensile strength, elongation at break and elastic modulus and opacity. The interaction effects of glycerol and pectin concentrations on edible film properties significantly affected the film properties. Tensile strength and opacity were positively affected by pectin concentrations; however, elastic modulus and elongation at break were negatively affected. Glycerol concentration negatively affected the edible film's tensile strength and elastic modulus. The decrease in the opacity of the biofilm was observed as the pectin concentration increased; however, glycerol had not shown a significant influence on opacity. The numerical optimization provided 4 g of pectin, and 20% of glycerol showed a strong and transparent edible film. The TGA curve showed that the maximum weight loss occurred between the temperatures 250–400 °C due to the loss of polysaccharides. From FTIR analysis, observed peaks around 1037 cm−1 represented the C–O–C stretching vibrations of the saccharide found in pectin and glycerol.

Mechanical properties of tef starch based edible films: Development and process optimization

The non-biodegradable synthetic plastic is one of the greatest challenges facing the food packaging business since it seriously harms the environment. To solve this problem, non-biodegradable plastic may be disposed of more affordably and with less harm on the environment by using edible starch-based biodegradable film. Therefore, the present study was focused on the development and optimization of tef starch based edible films based on mechanical properties. In this study response surface methodology was employed by considering 3–5g of tef starch, 0.3–0.5% of agar and 0.3–0.5% of glycerol. The prepared film showed the tensile strength of 17.97–24.25 Mpa, elongation break of 1.21–2.03%, elastic modulus of 17.58–108.69 MPa, puncture force of 2.55–15.02 N, puncture formation of 9.59–14.95 mm. The findings showed that as glycerol concentrations in the film-forming solution increased, the prepared tef starch edible films' tensile strength, elastic modulus, and puncture force declined while their elongation at break and puncture deformation increased. Tef starch edible films' mechanical characteristics, including as tensile strength, elastic modulus, and puncture force, were increased by the increase of agar concentration. The optimized (from 5 gm tef starch, 0.4 g agar and 0.3% glycerol) tef starch edible film exhibited higher tensile strength, elastic modulus, and puncture force while lower elongation at break and puncture deformation. The composite edible film based tef starch with agar exhibited good mechanical properties and can be suggested for application in food industry as food packaging.

Determining the elastic modulus of film/substrate materials from instrumented indentation testing based on machine learning

<p indent="0mm">Instrumented indentation testing has been widely used to determine the mechanical properties of materials. However, due to the substrate effect, the mechanical properties of each layer of film/substrate material becomes complicated to determine using this method. Through the finite element simulation, combined with a classic neural network method of multi-output multilayer perceptron (MLP), the relationship between the film/substrate material parameters (elastic modulus of film and substrate), normalized indentation depth (indentation depth/film thickness), and composite modulus is established. This established relationship is used to develop an indentation method to determine the elastic modulus of film/substrate. Prediction results through deep learning and the finite element simulation results are compared. The comparison results indicate that the predicted values of hard film/soft and soft film/hard substrate materials obtained from MLP are in good agreement with the simulation results. Indentation tests of Ni/304 and Cu/304 stainless steel were conducted to verify the trained neural network. The results indicate that elastic modulus of each layer predicted using the MLP is close to those obtained in the test. The results of this study can provide alternative research methods for evaluating the properties of film/substrate materials.

Structural and mechanical behavior of Zr-W-Ti thin film metallic glasses prepared by multitarget co-magnetron sputtering

Zr-W-Ti thin films were deposited by magnetron co-sputtering technique with varied Ti-sputtering power between 25 and 150 W. The effect of Ti-sputtering power on their physical and mechanical properties was investigated. As a results of FE-SEM, XPS, AFM, XRD, and HR-TEM investigations, the Ti-sputtering power affected the Ti-containing structure of ZrW-based films, which exhibited an amorphous phase with a very low surface roughness layer. The mechanical properties, tested by nano-indentation, revealed the films strongest hardness and elastic modulus of 8.6 GPa and 121.3 GPa, respectively. In addition, the plastic responded, especially the serrated flow and shear banding showed that the prepared Zr-W-Ti thin films were excellent candidates for surface coating as the thin film metallic glasses (TFMGs).

A Comparative Investigation of Mechanical Properties of TiB2/Cr Multilayer Film by Indentation

Alternating TiB2-dcMS and Cr-HiPIMS layers are used to fabricate TiB2/Cr multilayer films. Introducing a 5-nm-thick Cr interlayer deposited under a substrate bias of −60 V produces slight increases in both film hardness and elastic modulus. The TEM observation indicates that the Cr grains favor epitaxial growth on the TiB2 interlayer, forming a coherent TiB2/Cr interface. This improves hardness. Mechanic measurement by using AFM illustrates that the coherent interface increases the elastic modulus of the Cr up to ~280 GPa, which is significantly higher than bulk material.

Interfacial Stress Analysis of PVD Thin Film Sensor Based on Finite Element

The ability to monitor fractures is based on the integration of PVD thin film sensors and substrates, and the interface stress distribution of the sensor under load which directly impacts the bonding performance. This research analyzes the impact of film elastic modulus and thickness on film-substrate interface stress using the Abaqus software to investigate the influence of PVD film sensor material properties on the film/substrate interface stress distribution. The higher the concentration of interfacial tension, the thicker the layer. The sensor's structural parameters were optimized and significantly enhanced crack detecting sensitivity. The results reveal that the PVD film sensor material can detect structural defects efficiently. The conclusions established in this work have some implications for the optimal design of PVD thin film sensors.

Elastic modulus of polyamide thin films formed by molecular layer deposition

Molecular layer deposition (MLD) is a gas-phase deposition technique that can create ultra-thin films with precisely controlled chemical composition and thickness by depositing one monolayer at a time. This makes MLD an attractive technology for desalination membranes among other applications. Given its relatively recent development, little information has been reported regarding the properties of MLD thin films. We present the results of an initial mechanical property study of MLD films with thicknesses ranging from ∼50 to 2000 nm. MLD was utilized to create crosslinked polyamide films grown using either m -phenylenediamine (MPD) and trimesoyl chloride (TMC) reactants or piperazine (PIP) and TMC reactants. The elastic modulus of the films was determined using atomic force microscopy (AFM). The results show that the modulus was independent of film thickness with values of 4.36 ± 1.19 GPa and 5.24 ± 1.06 GPa for the MLD films grown using the MPD-TMC and PIP-TMC chemistries, respectively. These values are of the same order of magnitude as those reported for much thicker polyamide films, but higher than the modulus of polyamide films fabricated using interfacial polymerization. • All-organic polyamide thin films were fabricated using molecular layer deposition. • The elastic modulus of the films was measured using atomic force microscopy. • Two film chemistries with thicknesses between ∼50 and 2000 nm were evaluated. • Modulus was independent of chemistry and film thickness. • Modulus values of ∼3–6 GPa were similar to those of bulk polyamides.

High-throughput characterization of mechanical parameters of thin-film array

The thin-film array is a typical multi-film structure in material genetic engineering. With the requirements for rapid and efficient characterization of new film materials, a high-throughput characterization method based on digital image correlation for mapping the film elastic modulus and Poisson’s ratio of thin-film arrays is developed. First, a high-throughput experimental structure and testing system for the film array are designed, from which we can load 10 × 10 circular film arrays in the range of 0–25 kPa and obtain the full-field bulging displacement. Then, the experimental results are combined with the surface wave velocity equation to decouple the elastic modulus and Poisson’s ratio of the film array. The results are consistent with the material manual parameters, which verifies the feasibility of the high-throughput test method proposed in this article. When the method in this paper is applied to gradient materials, high-throughput testing of the mechanical parameters of a variety of film materials can be achieved. The results show that this method is valuable for quick, reliable and high-throughput determination of the film elastic modulus and Poisson’s ratio in material genetic engineering.

Accurate measurement of thin film mechanical properties using nanoindentation

For decades, nanoindentation has been used for measuring mechanical properties of films with the widely used assumption that if the indentation depth does not exceed 10% of the film thickness, the substrate influence is negligible. The 10% rule was originally deduced for much thicker metallic films on steel substrates and involved only the hardness measurement. Thus, the boundaries of usability for measuring thin film elastic modulus may differ. Two known material systems of Mo and MoTa thin films on Si substrates are examined with nanoindentation and numerical modeling to show the limitations in measuring elastic moduli. An assessment of the hardness and elastic modulus as a function of contact depth and accurate modeling of the film/substrate deformation confirms the 10% rule for hardness measurements. For elastic modulus, the indentation depths should be much smaller. Results provide a recommended testing protocol for accurate assessment of thin film elastic modulus using nanoindentation.Graphical abstract