Zr-based Thin Film Metallic Glass Research Articles

Mechanical property evaluation of thin film metallic glasses via molecular dynamics and finite element analyses

This study presents a method for extracting free-volume model (FVM) parameters of Zr-based thin film metallic glasses (TFMG) using the molecular dynamics (MD) and finite element analyses (FEA). Nano-tension MD simulations are performed to obtain the first two elastic properties of thin film, i.e., Young's modulus and Poisson's ratio. The other two main FVM parameters (reference stress and pressure dependent coefficient) are determined by systematically matching FE stress-strain curves to those from MD analyses with the finite element model updating (FEMU) method. Nanoindentation FEA and experiments are performed with Zr-based TFMG specimens to validate the estimated FVM parameters. It demonstrates that the combined MD/FEA approach is not only simpler, but also more efficient than previous methods in obtaining all primary parameters.

Mechanical properties and thermal stability of thin film metallic glass compared to bulk metallic glass from ambient to elevated temperatures

Metallic glasses can exhibit a wide range of local atomic arrangements which are determined by their processing history, and which control their mechanical properties. While recent studies show that thermally stable thin film metallic glasses with high strength and plasticity can be synthesized using physical vapor deposition, they often differ in terms of their structure and mechanical performance from bulk metallic glasses. In that aspect, two different fabrication methods – physical vapor deposition and arc melting – were utilized to fabricate compositionally similar Zr-based glasses in thin-film and bulk form. The as-fabricated samples were characterized in terms of oxygen concentration, element composition, and atomic structure. The mechanical response of the thin film metallic glass (TFMG) and the bulk metallic glass (BMG) was examined using in situ micropillar compression in a scanning electron microscope over a temperature range of room temperature to 500 °C. While the two glasses show overall similar failure characteristics, the TFMG exhibits higher strength together than the BMG without sacrificing plasticity at all testing temperatures. At elevated temperatures, the deformation mechanism changes to homogenous deformation above glass transition temperature (Tg). The higher strength and thermal stability of the TFMG is associated with a much higher oxygen concentration in the thin film compared to the BMG. The enhanced mechanical performance of the TFMG compared to the BMG highlights the potential of oxygen in the thermal stability characteristics and deformation capacity of Zr-based thin film metallic glasses.

Probing the formation of ultrastable metallic glass from structural heterogeneity

• The structure underlying the unexpected stability of Zr-based TFMGs was tracked. • MGs with greater heterogeneity have a higher potential to form SMGs. • Slower deposition rates are required for ultrastability in more heterogeneous MGs. • The relaxation mechanism changes as the deposition rate decreases. • The geometry and distribution of loosely packed phases determines ultrastability. Ultrastable metallic glasses (SMGs) exhibit enhanced stability comparable to those of conventional glasses aged for thousands of years. The ability to understand why certain alloy compositions and processing conditions generate an SMG is an emerging challenge. Herein, amplitude-modulation dynamic atomic force microscopy was utilized for tracking the structure of Zr 50 Cu 50 , Zr 50 Cu 44.5 Al 5.5 and Zr 50 Cu 41.5 Al 5.5 Mo 3 thin film metallic glasses (TFMGs) that were produced by direct current magnetron sputtering at room temperature with the rate of deposition being the only variable. The transition in stability from bulk- to SMG-like behavior resides in the change of relaxation mechanism as the deposition rate is decreased. The formation of SMGs is directly linked with the degree of structural heterogeneity, whereby MGs with greater heterogeneity have a higher potential to form SMGs with more significant enhancement in stability. Slower deposition rates, however, are required to yield the more homogenous structure and lower energy state underlying the ultrastability. Ultrastability is closely linked with the geometric shape and distribution of loosely packed phases, whereby SMGs containing more slender loosely packed phases with a more skewed distribution achieve more significant improvements in stability. This work not only provides direct evidence of the structure of SMGs, but also opens new horizons for the design of SMGs. .

Influence of substrate type and film thickness on the failures of Zr-based thin-film metallic glass under nanoscratch

Nanoscratch experiments under constant and ramp loading conditions are performed to investigate the delamination, and spallation characteristics of Zr-based thin-film metallic glass (Zr-based TFMG, Zr65Cu15Al10Ni10). TFMGs with different film thickness = 200, 500, 1000 nm are deposited over hard and soft substrates via DC magnetron sputtering process. Coefficient of friction (COF) is measured to be less about 0.03 regardless of scratch mode and maximum normal load. The critical load for thin film delamination and spallation reveals that the deformation and failure mechanism of Zr-based TFMG significantly change with film thickness and substrate type. The failure mechanism is characterized by observing the scratch grooves via optical and scanning electron microscopes (SEM). The adhesion energy between thin film and soft substrate is calculated based on Burnett and Rickerby model, and an increase in adhesion energy with interfacial layer thickness is reported.

Improved Mechanical Properties and Corrosion Resistance of Mg-Based Bulk Metallic Glass Composite by Coating with Zr-Based Metallic Glass Thin Film

Mg-based bulk metallic glass (BMG) and its composite (BMGC) can be excellent candidates as lightweight structure materials, but lack of anti-corrosion ability may restrict their application. In order to enhance the natural weak point of Mg-based BMGC, a 200-nm thick Zr-based metallic glass thin film (MGTF) ((Zr53Cu30Ni9Al8)99.5Si0.5) was applied and its mechanical properties as well as its corrosion resistance were appraised. The results of a 3-point bending test revealed that the flexural strength of the Mg-based BMGC with 200-nm thick Zr-based MGTF coating can be greatly enhanced from 180 to 254 MPa. We propose that the Zr-based MGTF coating can help to cover any small defects of a substrate surface, provide a protecting layer to prevent stress concentration, and cease crack initiation from the specimen surface during bending tests. Moreover, the results of anti-corrosion behavior analysis revealed a similar trend between the Mg-based BMG, Mg-based BMGC, and Mg-based BMGC with Zr-based MGTF coating in 0.9 wt.% sodium chloride solution. The readings show a positive effect with the Zr-based MGTF coating. Therefore, the 200-nm thick Zr-based MGTF coating is a promising solution to provide protection for both mechanical and anti-corrosion behaviors of Mg-based BMGC and reinforce its capability as structure material in island environments.

Zirconium-based metallic glass and zirconia coatings to inhibit bone formation on titanium

Surface-modified commercially pure titanium (Cp-Ti) with zirconium (Zr)-based thin film metallic glasses (Zr-TFMGs) and ZrO2 thin films were surgically implanted into the tibiae of rats; the bone formation was analyzed to examine the performance of the coatings as a biomaterial. Zr-TFMGs and ZrO2 thin films were coated on Cp-Ti substrates to monitor the control of assimilation in vitro and in vivo. The microstructural and elemental analyses were carried out for the as deposited thin films by x-ray diffraction (XRD), transmission electron microscopy and x-ray photoelectron spectroscopy. TFMG- and ZrO2-coated Ti specimens were immersed in simulated body fluid (SBF) for a period of 21 days to evaluate the calcium phosphate precipitation in vitro. XRD, x-ray photoelectron spectroscopy and scanning electron microscopy/energy dispersive x-ray spectroscopy were used to quantify the mineralization on the coated Zr-TFMG and ZrO2. In vitro corrosion studies showed that the Zr-based TFMG and ZrO2 coatings sustained in the SBF, exhibited superior corrosion resistance to the bare crystalline Ti substrate. Wettability studies showed TFMG and ZrO2 coatings with a hydrophobic nature, and the TFMG-coated SBF-submerged specimens showed a hydrophilic nature. The in vitro cell viability of MC3T3-E1 cells showed good cell proliferation and low cytotoxicity. The calcification deposits were evaluated by staining with alizarin red S, which showed a lower calcium formation on Zr-TFMG compared to ZrO2. The present work also aims to assess the assimilation behavior of Cp-Ti, Zr-TFMG and ZrO2 in vivo by inserting the coated specimen in the femur of rats. After post-implantation of 8 weeks, specimens were examined by micro-CT evaluation. The bone contact ratios as calculated were 72.75%, 15.32% and 38.79%. Consequently, the bone affinity was Cp-Ti wire >ZrO2-coated Ti wire >Zr48Cu36Ag8Al8-coated Ti wire.

Effects of nanoscale chemical heterogeneity on the wear, corrosion, and tribocorrosion resistance of Zr-based thin film metallic glasses

The effects of nanoscale chemical heterogeneity on the wear, corrosion, and tribocorrosion resistance of ZrCuNiAl thin film metallic glasses were investigated by examining samples of similar global composition but with either homogenous or heterogeneous local composition. Unlike the homogenous sample, the heterogeneous sample exhibited local compositional fluctuations of Zr-rich (~52.8 at.%) and Zr-lean (~51.7 at.%) regions separated by ~413.0 ± 64.7 nm. Dry scratch wear study showed that the homogenous samples exhibited lower wear rates and friction coefficients than their heterogenous counterparts due to their higher hardness and lower stiffness, as measured from nanoindentation tests. Corrosion resistance of both samples was studied through potentiodynamic polarization and Mott-Schottky analysis in 0.6 M NaCl aqueous solution under room temperature. It was found that the heterogeneous samples exhibited higher pitting resistance than their homogenous counterparts by forming a protective passive layer with lower defect density. Finally, the effects of chemical heterogeneity on the tribocorrosion rate and repassivation kinetics of both samples were discussed based on their differences in mechanical and electrochemical properties measured.

Study and fabrication of a flexible Zr-based metallic glass thin film strain gauge

Metallic glass is an amorphous structure and has excellent mechanical properties such as high strength, hardness and elastic strain limitation. In this study, a Zr-based metallic glass thin film was deposited on a polymer substrate using the sputter technique for strain gauge applications. A copper thin film strain gauge was fabricated to compare with the properties of the Zr-based strain gauge. Different thicknesses of the thin films were fabricated for comparison. The gauge factor of the Zr-based strain gauge is 2.4 times higher than that of the copper strain gauge. The temperature coefficient of resistance of the Zr-based metallic glass thin film is extremely low, 8 × 10−6 °C−1, which is essential to reduce thermal drift for strain gauge applications.

Zr基薄膜金属玻璃的制备及其光学常数测定

Zr基薄膜金属玻璃的制备及其光学常数测定

Fabrication and characterization of nitrogen selective thin-film metallic glass/polyacrylonitrile composite membrane for gas separation

Zr-based (Zr55Cu29Al11Ni5.0) thin-film metallic glass (TFMG) is a new material for gas separation membrane. In this study, we fabricated Zr-based TFMG/polyacrylonitrile (PAN) composite membranes via RF sputtering deposition. The surface morphology, crystallinity, and thermal stability of uncoated and TFMG-coated membranes were then characterized. Variable monoenergy slow positron beam analysis revealed a strong correlation between the pore size and thickness of the TFMG active layers. The resulting membranes were more permeable to N2 than to CO2 or O2 due to weaker interactions with the pore walls and faster diffusion. The best N2 performance was 4288 GPU with ideal selectivity of 1.81 for N2/O2 and 1.95 for N2/CO2. Overall, we demonstrated the considerable potential of TFMG/PAN composite as a membrane for nitrogen selective applications.

Fibrinogen and albumin adsorption profiles on Ni-free Zr-based thin film metallic glass

In this study, we assessed the fibrinogen and albumin adsorption performance of Ni-free Zr-based (Zr53Cu33Al9Ta5) thin-film metallic glass (TFMG). Quartz crystal microbalance (QCM) system and fluorescence spectrophotometer were used to obtain protein adsorption measurements, using two different substrates (QCM and glass). Test samples were fabricated by coating both of the substrates with TFMG and Ti (widely used in implants) for comparison. In dynamic QCM as well as static fluorescence spectrophotometer tests, the TFMG achieved a lower fibrinogen to albumin adsorption ratio. The TFMG coating also exhibited high hydrophobicity (water contact angle of 96°) with low surface roughness of 1.06 nm and surface free energy of 35.3 mN/m. This is a clear demonstration of the excellent hemocompatibility of Ni-free Zr-based TFMG.

Property optimization of Zr-Ti-X (X = Ag, Al) metallic glass via combinatorial development aimed at prospective biomedical application

Exceptional materials with enhanced bio-compatibility are a quest among the researchers in the medical community. Conventional crystalline materials, including 316L stainless steel, titanium and titanium-based alloys, are most commonly used for medical equipment or devices. However, materials with greater compatibility with biological systems should be studied. An amorphous solid, such as Zirconium (Zr)-based metallic glass, is a possible alternative to the conventional crystalline materials. The prospect of achieving multi-property requirements (i.e., high corrosion and wear resistance, lower elastic modulus and enhanced antibacterial capacity) with Zr-based thin film metallic glass (TFMG) were studied in this work. To form a ternary system with the optimized composition of Zr46Ti40Ag14 and Zr46Ti43Al11, TFMGs were fabricated by magnetron co-sputtering or combinatorial development of a binary Zr-Ti alloy with silver (Ag) or aluminum (Al). The structural characterization via grazing incidence x-ray diffraction (GI-XRD) and high-resolution transmission electron microscopy (HR-TEM) manifested an amorphous structure for the ternary TFMGs. The electrochemical analyses of the ternary systems revealed lower corrosion- and passive-current density when compared to 316L stainless steel and commercially pure titanium (cp-Ti). These data demonstrated that TFMGs have better corrosion resistant characteristics. Moreover, the systems exhibited appreciable hardness and elastic modulus lower than 316L stainless steel and cp-Ti. Both of the ternary TFMGs exhibited hydrophobicity, whereas only the Zr46Ti40Ag14 exhibited significant antibacterial properties and reduced the growth of methicillin-resistant Staphylococcus aureus. The combination of such desirable properties makes these TFMGs an excellent candidate material for a wide range of biomedical applications.

Thin film metallic glass as an effective coating for enhancing oil/water separation of electrospun polyacrylonitrile membrane

Thin film metallic glass (TFMG) is next-generation materials that are gaining importance in surface modification. In this work, we used magnetron sputtering to coat electrospun polyacrylonitrile (PAN) membrane with Zr-based TFMG (Zr53Cu26Al16Ni5) to enable the separation of oil and water. The proposed coating also provides protection from chemical and thermal degradation as well as irreversible internal fouling. The smooth TFMG coating also provides a strongly hydrophobic surface (water contact angle of 136°). We also investigated the effects of sodium dodecyl sulfate (SDS) surfactant on oil/water separation performance. The resulting combination of the hydrophobic TFMG-coated membrane with the surfactant enabled oil rejection performance ranging from 95% to 100%, depending on the concentration of SDS. This work confirms that membrane-related problems such as fouling, chemical, and thermal stability can be resolved through the application of metallic glass coatings.

Coating thickness effect of metallic glass thin film on the fatigue-properties improvement of 7075 aluminum alloy

The outstanding strength-to-weight performance of 7075 aluminum alloy (AA 7075) has prompted its wide-scale application to light-weight sport equipment, automobile bodies, and airframe design. However, the fatigue performance of AA 7075 cannot match that of steel. In this study, we used direct current sputtering to coat AA 7075 substrates with (Zr53Cu30Ni9Al8)99.5Si0.5 (Zr-based) metallic glass thin film (MGTF) coupled to a 50-nm titanium thin-film buffer layer. The Zr-based MGTF coating was applied at thicknesses of 200, 300, 400, and 500 nm. The fatigue characteristics of as-polished and coated AA 7075 samples were then tested in accordance with ASTM-C1161-02c specifications. The 200-nm-thick Zr-based MGTF coating was shown to extend the fatigue life of the AA 7075 by 26 times at a stress level of 250 MPa. The application of 200-nm-thick Zr-based MGTF coating also extended the fatigue limit from 150 MPa (as-polished sample) to 235 MPa, which represents an improvement of 56.7%.Transmission electron microscopy analysis revealed that the Zr-based MGTF coating restricted the formation of offsets and cracks beneath the surface of specimen. This can be attributed to the high strength, good flexibility, and strong adhesion of the Zr-based MGTF coating, which provided sufficient compressive stress to suppress slip band protrusions. The increases in fatigue life and fatigue limit were proportional to the thickness of the MGTF coating, due to changes in surface roughness and adhesion capability. A coating thickness of 200 nm was found to provide the best resistance to fatigue, due to its superior flexibility. These results demonstrate the outstanding potential of Zr-based MGTF coatings to improve the fatigue resistance of AA 7075.

Enhanced Thermochromic Properties of Vanadium Dioxide (VO2)/Glass Heterostructure by Inserting a Zr-Based Thin Film Metallic Glasses (Cu50Zr50) Buffer Layer

Vanadium dioxide (VO2) with reversible metal–insulator transition (MIT) is one of the most promising energy-efficient materials. Especially for VO2-based smart windows, the visible transmittance and solar modulation ability are the most critical parameters. However, VO2 thin films that are directly deposited onto glass substrates are of poor crystallinity and MIT performance, limiting the practical applications of VO2/glass heterostructures. In this paper, a buffer layer of Cu50Zr50 was introduced to build a novel Zr-based thin film metallic glass (VO2/Cu50Zr50/glass) with multilayer structures for thermochromic applications. It is observed that the insertion of a Cu50Zr50 buffer layer with appropriate thickness results in a clear enhancement of crystalline quality and MIT performance in the VO2/Cu50Zr50/glass thin films, compared with the single-layer VO2/glass thin films. Moreover, the VO2/Cu50Zr50/glass bi-layer films exhibit better optical performance with enhanced solar modulation ability (ΔTsol = 14.3%) and a high visible transmittance (Tvis = 52.3%), which represents a good balance between ΔTsol and Tvis for smart window applications.

Excellent near-infrared transmission of Zr-based thin film metallic glasses

Abstract Zr50Cu50, Zr47Cu44Al9, Zr46.3Cu43.4Al8.3Nb2 and Zr41.2Ti13.8Cu17.5Ni5Be22.5 thin film metallic glasses (TFMGs) were prepared by pulsed laser deposition (PLD) on glass substrates at room temperature. The effect of thickness on the electrical and optical properties of the Zr-based TFMGs was investigated. It was found that the resistivity of the Zr-based TFMGs basically decreased as the thickness varied from 10 nm to 40 nm. Interestingly, while the transmittance in the visible region decreased significantly with the increase of thickness, the transmittance in the near-infrared range still remained at a high level of larger than 80%. Through the characterization of electrical properties, the high transmittance of the Zr-based TFMGs in the near-infrared range was attributed to their rather low carrier concentration. Our findings provided the possibility for TFMGs to be used as transparent electrodes in the field of near infrared sensors and solar cells.

Silver influence on the antibacterial activity of multi-functional Zr-Cu based thin film metallic glasses

Influence of the silver content of magnetron-sputtered Zr-Cu-based thin film metallic glasses (TFMGs) on their antibacterial activity is investigated to enlarge their multifunctional character. These TFMGs are also characterized from microstructural, mechanical and electrochemical points of view. Ternary Zr-Cu-Ag thin films are amorphous (DRX) for silver contents higher than 11at.%. TEM analysis shows the formation of nanoparticles embedded in amorphous matrix for 25Agat.%. These thin films appear uniformly thick and smooth. Mechanical properties were determined by nanoindentation and an effect of silver on Young's modulus and hardness was observed for ternary Zr-Cu-Ag. The silver content favors the corrosion protectiveness of Zr-based TFMG in moderately aggressive medium. The presence of nanoparticles however induces pitting corrosion for Ag-rich thin film in chloride medium. Finally, the antibacterial activity of these TFMGs against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) is evaluated and correlated to the electrochemical behavior. Besides, a beneficial influence of silver addition on the antibacterial activity of Zr-Cu-based TFMGs is clearly established and a critical silver content of 11at.% leading to a biocide effect is determined.

Tuning colors in Zr-based thin film metallic glasses

In this work, a novel approach for the preparation of a variety of colored thin film metallic glasses (TFMGs) is proposed. Based on magnetron sputtering technique using a mixture of nitrogen and argon as the sputtering gas, ZrCuFeAlAg TFMGs with a high hardness of 8.9 GPa and a variety of colors ranging from yellow to aqua to pink to purple were achieved by adjusting the nitrogen-doping content and the thickness of the thin films. It was revealed that the change of colors of the TFMGs is governed by a two-step mechanism: i) the TFMGs first became partially transparent by nitrogen doping owing to the formation of amorphous ZrxNy nitrides, which led to expansion of the energy band gap of the films, and ii) the color was varied by changing the thickness of the film due to the interference effect. The present work presents the possibility of making functional TFMGs for optical and electrical device applications.

Measuring notch toughness of thin film metallic glasses using focused ion beam-based microcantilever method: Comparison with Ti and TiN crystalline films

This study measured the notch toughness of Zr- and W-based thin film metallic glasses (TFMGs), and compared the results with those data obtained from crystalline Ti and TiN thin films as well as bulk metallic glass (BMG). Deflection testing was conducted using microcantilevers fabricated by focused ion beam machining. The resulting load vs. deflection curves revealed that Zr-based TFMG, BMG, and Ti films exhibited non-linear curves after yielding, which represented the ductile deformation characteristics. Higher notch toughness values of 3.84 and 5.13MPam for Zr- and W-based TFMGs, respectively, than TiN (2.15MPam) and Ti (0.74MPam) films were obtained. Thus, at micro-scales, metallic glasses present relatively better fracture behavior than do crystalline materials. This paper presents a direct comparison of works related to the notch toughness of amorphous and crystalline materials.

ZrCuFeAlAg thin film metallic glass for potential dental applications

In this study, the application of a Ni-free Zr60.14Cu22.31Fe4.85Al9.7Ag3 thin film metallic glass (TFMG) was examined as an approach to retard the poor tribological properties of Ti-alloys for dental applications. The TFMGs were coated on biomedical Ti6Al4V substrate by single-target magnetron sputtering. The fretting resistance was assessed using a reciprocating tribo-tester against Si3N4 counterpart in air and in artificial saliva. Bio-corrosion resistance of TFMG-coated Ti6Al4V samples was tested via electrochemical polarizations and electrochemical impedance spectroscopy in artificial saliva. Biocompatibility of the TFMG was tested in vitro, in comparison with that of the Ti6Al4V alloy. The results showed that this TFMG not only possessed 1.8–2.8 times higher fretting resistance than the Ti6Al4V alloy under various tribological conditions, but also lower bio-corrosion rate and superior passive film. In-vitro assessments of cytotoxicity and cell adhesion indicated that the TFMG has no any cytotoxicity and well-flattened cell adhesion morphology, as good as the Ti6Al4V alloy. The present Ni-free Zr-based TFMG is expected to improve the lifetime and quality of biomedical implants or devices for dental applications.