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Plasma electrolytic oxidation (PEO) is a widely applied surface treatment method which can improve the corrosion resistance of valve metals and their alloys. In this study, PEO treatment was conducted on pure Al using a power supply under a bipolar pulsed mode at fixed duty cycle and frequency. The effect of different concentrations of borax in the electrolyte on the corrosion resistance of PEO grown oxide coatings in 3.5 wt% NaCl solution was comprehensively studied by a potentiodynamic polarization test and electrochemical impedance spectroscopy method. We found that the average pore size and porosity on the PEO grown oxide coating decreased with increasing borax concentration. The dense microstructure of oxide coating can be seen when the borax concentration in the electrolyte was high. The corrosion resistance of PEO coating increased with increasing borax content. The corrosion resistance of pure Al was greatly improved up to 23,058 times higher by the formation of a PEO layer treated in the electrolyte containing 6 g L−1 borax due to its ability to grow a dense γ-Al2O3 phase with less defects.

High-performance room temperature based hydrogen gas sensor is fabricated using ultra-nanocrystalline diamond/molybdenum disulfide/zinc oxide nanorods (UNCD/MoS2/ZNRs) nanohybrids, through microwave plasma enhanced CVD (MPE-CVD) and hydrothermal techniques. The interfacial effect and structural analysis of UNCD/MoS2/ZNRs layers were comprehensively studied by several analyses. The systematic investigations were revealed that adding MoS2 layer between the ZNRs and UNCD, strongly influence the gas sensing device performance. In addition, the semi-grown UNCD films serve as an excellent substrate for the synthesis of MoS2/ZNRs. Thus the UNCD/MoS2/ZNRs hybrid sensors exhibits the superior sensitivity of 70.6%, which is overwhelmingly superior to that of ZNRs (7.2%). The outstanding improvement is observed due to the efficient material defects and formation of various heterojunction interfaces in the UNCD/MoS2/ZNRs hybrid. It was revealed that the exfoliated MoS2 layer under ZNRs induces more active sites for the adsorption of O2. Moreover, the chemisorbed O2 ions in the surface react with H2, and release a huge number of electrons to the conduction band. Also, the UNCD/MoS2/ZNRs nanohybrid exhibits excellent robustness along with ultra-high gas sensitivity and selectivity due to the addition of semi-continuous UNCD materials. The outstanding features of this UNCD/MoS2/ZNRs nanohybrid potentially extend to nanodiamond and TMD based hybrid materials for future gas sensor/storage applications.

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.

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.

In this study, high density (∼38 μm−2) ZnO nanotubes (NTs) were hydrothermally synthesized on a Cu47.2Zr42.1Al6.7Ti4.0 metallic glass quantum dot (MGQD)/glass substrate. The MGQD acts as a buffer and seed layer to improve the optical and crystalline properties of the ZnO nanotubes. The photocurrent-to-dark current ratio (∼2 × 104) of the ZnO NTs/MGQD is 28.1 times higher than that of ZnO NTs due to the Schottky junction and the localized surface plasmon resonance effect of the MGQD. The photocurrent-to-dark current ratio of the ZnO NTs/MGQD junction was enhanced an additional 10-fold to ∼2.0 × 105 upon annealing at 150 °C for 30 min under ambient atmosphere. The annealing treatment also decreased the photoresponse and relaxation times.

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.

Our objective in this study was to determine the biocompatibility and hemocompatibility of thin film metallic glass (TFMG) and its potential use in hypodermic needles for intramuscular or intravenous injection. Mouse and rabbit models were employed under approval from the Institutional Animal Care and Use Committee (n = 5/group, two groups in total for both animal models). Platelet-rich plasma (PRP) was collected from the whole blood of rabbits (ear vein) without anti-coagulant for use in in vitro coagulation tests. Histological analysis and optical microscopy were used to assess the endothelial structure of the inner lining of veins after being punctured with needles and detained for 3 days. Histological analysis of ear vein sections revealed that the extent of endothelial damage after puncturing with a TFMG-coated needle was 33% less than that produced by bare needles. Our results confirm that the deposition of a thin TFMG layer (e.g., Zr53Cu33Al9Ta5) on the surface of hypodermic needle can have remarkably clinical benefits, including anti-adhesion, reduced invasion, and minimal endothelial damage. Our results also confirm the good biocompatibility and hemocompatibility of the TFMG coatings.

In this work, we fabricated first-ever nanohybrid ZnO nanowires (ZnO-NWs)/Metallic Nanotube Arrays (MeNTA) structure for the large-scale fabrication of highly dense laterally and vertical aligned ZnO-NWs. To prepare heterogeneous surface MeNTA by using sputter-deposition of different metallic glass Zr55Cu30Al10Ni5), Cu47Zr42Al7Ti4, Pd72Cu12Si16, W50Ni25B25 and Ni54B0.3Si36Cr2.7Fe7) over on contact-hole arrays created by a photoresist template with 650 nm height and various diameter (2, 10 and 20 µm). A ZnO seed layer is deposited by sputtering method on MeNTA to provide the nucleation sites to grow the nanowires inside the MeNTA. To perform the material analysis like surface morphology, crystal structural, and optical properties were characterized by using scanning electron microscopy (SEM), X-ray diffraction (XRD), and photoluminescence (PL), respectively. Our results confirm that, the nanowires are single crystal with hexagonal wurtzite structure presenting strong UV emissions can be used in optoelectronics, sensors, piezoelectric-nanogenerator, solar cells and battery applications in near future.

The dissemination of tattooing into mainstream culture has raised concerns pertaining to the medical implications of these practices. This paper reports on the coating of tattoo needles with metallic-glass (MG) to reduce trauma to the skin. Extensive experimentation using pork samples and live pigs demonstrated the beneficial effects of non-stick MG coatings. Following 30 insertions into pork skin, significantly less tissue adhered to the MG-coated needles than to uncoated needles. MG-coated needles were also shown to reduce the spread of pigment to the surface of surrounding skin by up to 57%. This resulted in narrower tattoo lines of higher density, indicating that MG-coated needles could be useful in high-resolution tattooing. Histopathological analysis on live pigs revealed severe trauma induced by bare needles, as indicated by the secretion of fluids immediately after tattooing. The wounds formed by coated needles closed within 2 h after tattooing; however, those formed by bare needles remained open for at least 2 h and inflammation was still observed after 3 days. At 5 days after tattooing, skin punctured by the coated needle was entirely healed, whereas skin punctured by the bare needle was still covered with scabs. In addition to the medical benefits, it appears that MG-coated needles could improve the quality of tattoos, based on the fact that the amount of pigment retained in the skin is inversely proportional to the trauma caused by needles.

This is the first report on the coating of diamond dicing blades with metallic glass (MG) coating to reduce chipping when used to cut Si, SiC, sapphire, and patterned sapphire substrates (PSS). The low coefficient-of-friction (CoF) of Zr-based MG-coated dicing blades was shown to reduce the number and size of chips, regardless of the target substrate. Overall, SiC, sapphire and PSS were most affected by chipping, due to the fact that higher cutting forces were needed for the higher hardness of SiC, sapphire and PSS. Compared to the bare blade, the MG coating provided the following reductions in chipping area: Si (~ 23%), SiC (~ 36%), sapphire (~ 45%), and PSS (~ 33%). The proposed coating proved particularly effective in reducing chips of larger size (> 41 µm in chipping width), as indicated by an ~ 80% reduction when cutting sapphire. Small variations in kerf angle and depth demonstrate the durability of the coated blades, which would no doubt enhance consistency in dicing performance and extend the blade lifespan. Finite-element modeling revealed significant reductions in tensile stress and elastic–plastic deformation during dicing, thanks to a lower CoF.

The field emission properties of a novel ZnO-NWs/Cu-based metallic glass nanotube array (ZNWs/Cu-MeNTA) heterostructure are studied. A sample is annealed at 300 °C for 1 h at atmospheric pressure in a tube furnace as post-treatment. The turn-on electric field Eon (at a current density of 0.1 μA/cm2) and corresponding field enhancement factors β for the as deposited and 300 °C annealed ZNWs/Cu-MeNTA are respectively 1.47 V/μm, 13,042 and 1.77 V/μm, 10,954. The increase on the turn on field might be due to oxidation of the as-deposited ZNWs/Cu-MeNTA after the thermal post-treatment. Crystallization is enhanced after the field emission measurements, but parts of the ZnO-NWs break down. The Eon increases (1.29–1.47 V/μm) in the successive field emission measurements for the as-deposited ZNWs/Cu-MeNTA. In addition, the Eon decreases (2.26–1.77 V/μm) for the 300 °C annealed thermal post treatment ZNWs/Cu-MeNTA. This phenomenon might be due to the trade-off between the enhanced crystallization and the amounts of the ZnO-NWs break down, respectively causing a decrease and increase in the turn on field. This novel nanostructure for field emission studies might be useful for use in future mini-display device, optoelectronics, sensors, piezoelectric-nanogenerator, solar cells and battery applications.

A promising candidate for a top cell in a tandem solar cell setup is a superstate, high bandgap, CIGS (Copper Indium Gallium Diselenide) solar cell. To realize a tandem cell, both, front and back contact of the top cell must be transparent. In this work a molybdenum metal mesh electrode with four pattern derivatives is presented, which are designed towards this implementation in a tandem cell setup. The electrode consists of two-micron wide fingers arranged in an industry typical H-grid pattern and in a hexagonal shaped pattern, with each of these patterns being comprised of a derivative with and without tapered busbars. The electrode's micro structure, crystal orientation, surface roughness, electrical properties and optical properties are investigated. The manufacturing process as well as a comparison of this works electrodes with various competing electrode types is also presented. All electrode derivatives show excellent transmittance of up to 97% within and beyond the visible spectrum while retaining acceptable sheet resistances of about 30 Ω/□.

The adhesion of platelet cells is viewed as a first step in thrombus formation, and cancer cell attachment can lead to cancer seeding. In this study, we examined the feasibility of utilizing Zr53Cu33Al9Ta5 thin film metallic glass (TFMG) to minimize the adhesion of human cancer cells (breast cancer cell, colon cancer cell, and esophageal cancer cell), human and animal platelets. TFMG and pure titanium (Ti) were respectively grown on glass substrates to a thickness of 200 nm using magnetron sputtering. TFMG was shown to reduce surface roughness of approximately 27% than Ti coating did on glass samples. The concentrations of all major ions released from the TFMG were well below toxic levels. TFMG surfaces were more effective than Ti in increasing the contact angle of water, phosphate buffer saline (PBS) and blood from different animal species. The application of TFMG to bare surfaces was shown to reduce the attachment area of human platelets by 77% and that of pig platelets by 63%. TFMG also reduced the attachment of cancer cells by up to ~87%. These characteristics can be attributed to a low surface free energy of TFMG-coated surfaces (31.89 mN/m), which is far below that of Ti-coated (39.25 mN/m) and bare glass (47.80 mN/m). These findings demonstrate the considerable potential of TFMG coatings in the fabrication of medical instruments aimed at preventing the adhesion of platelet and cancer cells.

In this study, a photoresist template with well-defined contact hole array was fabricated, to which radio frequency magnetron sputtering process was then applied to deposit an alloyed Zr55Cu30Al10Ni5 target, and finally resulted in ordered metallic glass nanotube (MGNT) arrays after removal of the photoresist template. The thickness of the MGNT walls increased from 98 to 126nm upon increasing the deposition time from 225 to 675s. The wall thickness of the MGNT arrays also increased while the dimensions of MGNT reduced under the same deposition condition. The MGNT could be filled with biomacromolecules to change the effective refractive index. The air fraction of the medium layer were evaluated through static water contact angle measurements and, thereby, the effective refractive indices the transverse magnetic (TM) and transverse electric (TE) polarized modes were calculated. A standard biotin-streptavidin affinity model was tested using the MGNT arrays and the fundamental response of the system was investigated. Results show that filling the MGNT with streptavidin altered the effective refractive index of the layer, the angle of reflectance and color changes identified by an L*a*b* color space and color circle on an a*b* chromaticity diagram. The limit of detection (LOD) of the MGNT arrays for detection of streptavidin was estimated as 25nM, with a detection time of 10min. Thus, the MGNT arrays may be used as a versatile platform for high-sensitive label-free optical biosensing.

In this study, we fabricated first-ever metallic glass nanotubes (MGNTs) in a distinct pattern on a Si substrate, by sputter-depositing a coating of metallic glass (Zr55Cu30Al10Ni5) over a contact-hole array template created in photoresist. The resulting nanotubes were 500 or 750 nm in height with a diameter of 500 or 750 nm and wall thickness ranging from 44 nm to 103 nm. The structure of the nanotubes was preserved by the high strength and ductility of the metallic glass during the removal of the photoresist template under ultrasonic vibration. We observed an increase in the hydrophobicity of the MGNT with an increase in the thickness of the walls, with the thickest walls presenting an apparent contact angle of 139°. The hydrophobicity is due to air trapped within the tubes, which prevents the intrusion of water into the nanostructures. We also observed thermal-response behavior on the surface of the MGNT array. Surface cooling produced negative pressure within the nanochambers, which created a sucking force against the water droplets. Surface heating produced positive pressure within the nanochambers, which actually lifted the droplets. This thermal-response behavior was shown to be reversible for at least five cycles between 25 and 55 °C. The MGNT created adhesion forces reaching 14.2 N cm−2, which was sufficient to secure the water droplets even when the surface was tilted or completely inverted. The MGNT array in this study represents a biomimetic analog with switchable contact interface, the behavior of which can be controlled simply by altering the surface temperature.

The amorphous thin film metallic glasses (TFMGs) have been studied widely due to their unique properties and ease of fabrication as compared with the bulk metallic glasses (BMGs). Among the many TFMG systems, the W-based TFMG remains unstudied. In this work, a series of ternary W-Zr-Si TFMGs containing various W content ranging from 49.3 to 66.5 at.% were fabricated using a magnetron co-sputtering system. Increasing the W content of W-Zr-Si TFMG rendered an increase of Young's modulus up to 182 ± 4 GPa with the highest W content of 66.5 at.%. The film hardness was 13 GPa, independent of the W concentration in the as-deposited W-Zr-Si TFMGs. The influence of post-annealing on the microstructure and mechanical properties of TFMGs was studied by a vacuum thermal treatment ranging from 450 to 750 °C under various holding times. The surface roughness increased with increasing annealing temperature, with the sample annealed at the supercooled liquid region exhibited the lowest surface roughness of 1.14 nm. The hardness of TFMGs increased with increasing annealing temperature and longer holding time due to annealing-induced crystallization with a highest hardness of 16.8 ± 0.5 GPa. However, the indentation toughness decreased upon annealing and the lowest value was achieved for the hardest film due to the increasing amount of short range ordered (SRO) clusters.

The concurrent attachment and detachment movements of geckos on virtually any type of surface via their foot pads have inspired us to develop a thermal device with numerous arrangements of a multi-layer thin film together with electrodes that can help modify the temperature of the surface via application of a voltage. A sequential fabrication process was employed on a large-scale integration to generate well-defined contact hole arrays of photoresist for use as templates on the electrode-based device. The photoresist templates were then subjected to sputter deposition of the metallic glass Zr55Cu30Al10Ni5. Consequently, a metallic glass nanotube (MGNT) array having a nominal wall thickness of 100 nm was obtained after removal of the photoresist template. When a water droplet was placed on the MGNT array, close nanochambers of metallic glass were formed. By applying voltage, the surface was heated to increase the pressure inside the nanochambers; this generated an expanding force that raised the droplet; thus, the static water contact angle (SWCA) was increased. In contrast, a sucking force was generated during surface cooling, which decreased the SWCA. Our fabrication strategy exploits the MGNT array surface as nanosuckers, which can mimic the climbing aptitude of geckos as they attach to (>10 N m−2) and detach from (0.26 N m−2) surfaces at 0.5 and 3 V of applied voltage, respectively. Thus, the climbing aptitude of geckos can be mimicked by employing the processing strategy presented herein for the development of artificial foot pads.

Currently, wound dressing is often used to accelerate wound healing, avoid contaminations from the external environment and protect wound from infections, control moisture around the wound, meanwhile being biocompatible and non-toxic. Thin film metallic glass (TFMG) possess amorphous structure that driven to several unique properties such as excellent strength and high surface smoothness. Zr-based (Zr63.5Cu19.9Al11.5Ni5.1 (at%)) and W-based (W65.4Ni30.5B4.1) metallic glasses were selected as the candidate of nanotube array in this study. A layered structure Zr/W/Zr-based TFMGs were deposited on a nanotube array template and then fabricated into MeNTA and applied as a substrate of wound dressing. Hyaluronic acid (HA) and hyaluronic acid/ gold nanoparticles (HA/AuNPs) composite were loaded into the MeNTA under vacuum ambient. Animal test was conducted on live pigs in order to observe the improvement in wound healing and wound biopsy by attaching drug-loaded MeNTA. After loading the drugs into nanotubes array, significant change in diameter and surface appearance of nanotube is observed. In the animal test, both HA and HA/AuNPs loaded MeNTA accelerated wound healing process up to 96.4% and 90.5%, respectively.

This study demonstrated highly-ordered metallic nanotube arrays (MeNTAs) with a precisely controlled geometric shape to promote surface-enhanced Raman scattering (SERS). Using both simulation and experimental methods, we designed and fabricated MeNTAs with nanotube geometries that possess a large surface area to absorb probe molecules as well as geometric features capable of inducing hot spots for SERS enhancement. The proposed top-down wafer-scale lithographic and sputter-deposition process is a simple and cost-effective approach to the fabrication of 1 mm × 1 mm MeNTA at room temperature. Simulation results of nanotubes with various materials (Au, Ag, and Cu), diameters (100 nm to 1500 nm), geometric shapes (circle, equilateral triangle and square) and triangle corner curvatures (ranging from 0 nm to 300 nm) identified Ag triangles with sharp tips as the geometry best suited to SERS enhancement. The SERS spectra of crystal violet (CV) molecules generated from the Ag MeNTAs verified the patterns observed in computational simulations, wherein the effects of MeNTA on SERS decreased with an increase in the size of the nanotubes. Enhancement factor of 1.06 × 109was obtained from our triangular Ag MeNTA, confirming its efficacy as an ultrahigh sensitivity SERS-active substrate.

In this article a series of Stainless steel thin films are fabricated by DC power magnetron sputtering of a SUS316 stainless steel target at various argon working pressure. The sample film compositions retain that of an austenitic stainless steel, while XRD spectra reveal that all films possess a single phase, body-centered cubic ferrite crystal structure. At working pressure 6 mTorr and above, the film exhibits a textured surface morphology made up of nano-sized pyramids. Cross-sectional images show that increasing argon pressure cause a microstructural evolution from dense, fibrous grain to coarse tapered grains. This observation agrees with the prediction by Thornton's structural zone model and causes a drastic reduction in static water contact angle (WCA) from ~65° to ~17°. With further increase of argon pressure, a minimum WCA of 11° at 8 mTorr can be achieved. In addition, our textured film deposited at 12 mTorr exhibits both excellent hydrophilicity and low contact angle hysteresis (CAH) at the same time. In summary, this work reports a convenient way of depositing a stainless steel-like hydrophilic coating, in which the wetting properties are tunable via working pressure control.

The few layers Cu-based (Cu47Zr42Al7Ti4) thin-film metallic glasses (TFMGs) was sputtered on hydrothermally synthesized ZnO nanowires/glass and ZnO nanotubes/glass to fabricate UV photodetectors. The few layers of Cu-based TFMG are ultra-thin at approximately 0.98 nm and have a non-crystalline metal structure according to XRD, Raman, PL and HT-TEM verification. The photoresponse performance of the coated few layers Cu-TFMG samples was enhanced 1680~7700% compared with the non-coated sample. The few layers Cu-TFMG has high transmittance ~90% in the visible band and creates a large capacitor to absorb UV photocurrent and release dark current.

The viscous flow typically plays an important role for the deformation of metallic glasses in the supercooled liquid region. This deformation behavior has been widely investigated for bulk metallic glasses. However, studies on the viscous flow and viscosity measurement of thin film metallic glasses (TFMGs) were sparse. In this work, we synthesized four compositions of fully amorphous AuCuSi TFMGs by magnetron sputtering. The glass transition temperature, which is also the temperature of the critical transition point from elastic/plastic deformation to time-dependent viscous flow, was determined using nanoindentation. The nanoindentation creep tests performed with hemispherical and Berkovich indenter tips in the temperature range of 50 to 170 °C were proven to be suitable for the viscosity measurements of AuCuSi TFMGs. The activation energy of the flow process was also evaluated from the indentation results and good agreement was obtained between the results evaluated from hemispherical and Berkovich tips. Finally, a nano-scaled imprinted AuCuSi TFMG showed great topological resolution. Keywords: Metallic glass, Thin film, Nanoindentation, Rheology, Thermal imprint

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 5.13 MPa m for Zr- and W-based TFMGs, respectively, than TiN (2.15 MPa m ) and Ti (0.74 MPa m ) 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.

A coating of the Zr-based thin-film metallic glass (TFMG) was deposited on the Zr 50 Cu 30 Al 10 Ni 10 bulk metallic glass (BMG) to investigate shear-band evolution under four-point-bend fatigue testing. The fatigue endurance-limit of the TFMG-coated samples is ~ 33% higher than that of the BMG. The results of finite-element modeling (FEM) revealed a delay in the shear-band nucleation and propagation in TFMG-coated samples under applied cyclic-loading. The FEM study of spherical indentation showed that the redistribution of stress by the TFMG coating prevents localized shear-banding in the BMG substrate. The enhanced fatigue characteristics of the BMG substrates can be attributed to the TFMG coatings retarding shear-band initiation at defects on the surface of the BMG.

In this study, 10-nm rare-earth metal-oxide (REMO) films, namely, pure HoScO x (HSO) and HoScO x doped with Nb (HSO-Nb) and Zn (HSO-Zn), were deposited to build resistive random access memory (RRAM) devices with a Pt/REMO/Pt structure using radio frequency magnetron sputtering. The results of x-ray diffraction and transmission electron microscopy showed that all as-deposited REMO films are featureless microstructures lacking long-range order. In all RRAM devices, layer structures were well adhered to each other with relatively smooth interfaces and no cracks or holes were observed. Hall measurements demonstrated n-type conduction in the as-deposited films. The addition of Nb and Zn increased carrier concentration and mobility of the HSO films and reduced electrical resistivity. The former was possibly caused by the electronic compensation of NbSc ··, thereby triggering the formation of polarons, and the latter was probably due to the increase in concentration of oxygen vacancies associated with acceptor doping. The RRAM devices revealed unipolar switching behavior characterized by a resistance ratio of more than three orders of magnitude, good endurance, and a long retention time. The switching behavior of the RRAM with amorphous HSO films was altered by the doping species. Doping with Nb and Zn decreased the forming voltage, facilitated the use of a smaller switching voltage, and increased the resistance ratio of high- and low-resistance states. The conduction mechanisms for the low resistive state and high resistive state were dominated by Ohmic conduction and trap-controlled space-charge-limited current mechanisms, respectively.

In this study, we sought to enhance the cutting properties of the various blades by coating them with Zr- and Fe-based thin film metallic glasses (TFMGs) to a thickness of 234–255 nm via sputter deposition. In oil-repellency/sliding tests on kitchen blades, the sliding angle and friction forces were as follows: bare blades (31.6°) and (35 µN), Ti-coated blades (20.3°) and (23.7 µN), and Z-TFMG coated blades (16.2°) and (19.2 µN). Comparisons were conducted with bare blades and those with a Teflon coating (a low-friction material commonly used for the coating of microtome blades). We also found that the Teflon coating reduced the cutting forces of an uncoated microtome blade by ~80%, whereas the proposed Z-TFMG achieved a ~51% reduction. The Z-TFMG presented no indications of delamination after being used 30 times for cutting; however, the Teflon coating proved highly susceptible to peeling and the bare blade was affected by surface staining. These results demonstrate the efficacy of the TFMG coating in terms of low friction, non-stick performance, and substrate adhesion. The performance of Z-TFMG and F-TFMG was also evaluated in split-thickness skin graft surgery using dermatome blades aimed at elucidating the influence of TFMG coatings on the healing of surgical incisions. When tested repeatedly on hairless skin, the surface roughness of uncoated blades increased by approximately 70%, whereas the surface roughness of TFMG-coated blades increases by only 8.6%. In the presence of hair, the surface roughness of uncoated blades increased by approximately ~108%, whereas the surface roughness of TFMG-coated blades increases by only ~23%. By Day 7, the wounds produced using TFMG-coated blades were noticeably smaller than those produced using uncoated blades, and these effects were particularly evident in hairy samples. This is a clear demonstration of the efficacy of TFMG surface coatings in preserving the cutting quality of surgical instruments.

In this work Fe39Co39Si8B14 thin film metallic glasses (TFMGs) of thickness ranged between 122– 475 nm were deposited by magnetron sputtering on a commercial filter paper to act as a peroxymonosulfate (PMS) activator for degradation of Orange G (OG) azo dye. Degradation of 98.6% was achieved in 16 min. The influence of parameters such as catalyst dosage, light irradiation intensity, dye and PMS concentration to the efficiency of degradation were also investigated. SEM and XPS results revealed that the outstanding performance was attributed to the abundance of amorphous zero valent metals given by the amorphous atomic packing structure of TFMG. Zero valent metals readily activated PMS and favored the generation of SO4• and •OH radicals, which were the responsible species in degrading OG dye molecules. Another contribution was from the fibrous and porous texture of the filter paper substrate which provides specific surface area as high as 1.152 m2/g. TFMG-coated filter paper also showed good reusability that repeated degradation was possible. Results suggests that applying TFMG on a textured substrate could drastically reduce the dosage of Fe-based metallic glass needed compared to its powder or foil counterparts, which is significantly more cost effective.

High-power impulse magnetron sputtering (HiPIMS) is a thin film deposition technique that combines the advantages of energetic deposition methods with magnetron sputtering. HiPIMS has so far mostly been utilized for the growth of crystalline coatings. Here we offer a study devoted to metallic glasses, in which we compare Zr60Cu25Al10Ni5 (target composition) thin films deposited by conventional direct current magnetron sputtering (DC) and HiPIMS. Film microstructure is strongly dependent on the choice of the sputtering method. The DC layers show a columnar structure with intra-columnar porosity, which provides a pathway for oxygen diffusion into the film. In contrast, HiPIMS films are column-free and possess about 4% higher density, as revealed by X-ray reflectivity. Electron diffraction reveals a decrease in average atomic spacing for the latter film of about 12%. These differences in film properties and morphology can be attributed to an increase in ad-atom mobility during HiPIMS caused by an increase in ion energy and flux of the film-forming species enabling a more efficient energy and momentum transfer to the growing film surface. The relative contribution of metallic and hence film forming ions to the overall ion flux of the DC plasma compared to the HiPIMS plasma is 13% and 96%, respectively. Additionally, a substrate bias causes the ionized film forming species during HiPIMS to arrive close to the substrate normal reducing shadowing effects. Different microstructures have a direct effect on the average roughness values, which for DC and HiPIMS films are 1.4 nm and 0.2 nm, respectively. The indentation hardness H and Young's modulus E are higher for the HiPIMS sample, at 9.2 ± 0.3 GPa and 131.6 ± 3.6 GPa, respectively. The increase in hardness for the HiPIMS sample as compared to the DC sample (~35%) can be attributed to higher film density, compressive (HiPIMS) as opposed to tensile (DC) stress and the lack of a columnar structure.

In this study, ZnAl 2 O 4 (ZAO) films having a thickness of 20.1 nm, which serve as the resistive switching layer in random access memory (RRAM) devices based on a Pt/ZAO/Pt structure, were prepared using radio frequency magnetron sputtering. The as-deposited film appeared to be amorphous with distributed nano-crystalline ZnAl 2 O 4 particles, while the ZAO film annealed at 450 °C was composed of cubic ZnAl 2 O 4 spinel crystallites. The chemical formula of the former was (Zn 0.340 Al 0.66 )O 0.69 □ 0.64 while that of the latter was (Zn 0.91 Al 0.09 )Al 2 O 3.73 □ 0.27 , as calculated from energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) results, indicating that both these films consisted of oxygen vacancies. Pt/ZAO/Pt devices containing the as-deposited ZAO film exhibited excellent unipolar switching behavior marked with a resistance ratio larger than an order of magnitude, good endurance, and a long retention time. The conduction mechanisms for the low resistive state and high resistive state were dominated by the Ohmic conduction and trap-controlled space charge limited current mechanisms, respectively. The resistive switching behavior in the Pt/ZAO/Pt device was attributed to the formation and rupture of the conduction filaments formed by the oxygen vacancies.

The cutting sharpness and durability of commercial blades without and with 200–500 nm thicknesses of Zr-Cu-Al-Ag-Si and Zr-Cu-Ni-Al-Si metallic glass thin film (MGTF) coating were systematically characterized and evaluated. The amorphous states of all MGTF coatings were examined by grazing incident X-ray diffraction analysis. The observation of scanning electron microscopy reveals that MGTF coated blades own much smoother surface than the commercial one which indicates smaller friction force during cutting process. Results of sharpness test in the beginning reveal that all MGTF-coated blades possess smaller value of blade sharpness index (BSI) than the commercial one. The cutting durability of the MGTF-coated and commercial blades was evaluated by the variation of BSI values by 25 cm cutting test. The commercial blade was blunted (BSI = 0.49) after 20 cm cutting path. Conversely, the 300 nm-thick MGTF-coated blades present the smallest BSI value after 20 cm cutting path in comparison with other thicknesses MGTF-coated blades and commercial blade. As a result, the cutting durability of surgical blade can be significant improved by Zr-based MGTF-coating, can keep the BSI value less than 0.45 after 20 cm cutting test.

The application of thin film metallic glass (TFMG) has been shown to improve the fatigue characteristics of ZK60 magnesium alloys. This paper reports on the deposition of Zr 51 Cu 32 Al 10 Ni 7 ( Z -TFMG) and W 70 Ni 20 B 10 (W-TFMG) on ZK60 Mg alloy to a thickness of 200 nm and its effect on fatigue characteristics. In four-point-bending fatigue studies at room temperature, the fatigue limits of the bare, W-, and Z-TFMG-coated Mg alloys were 225, 270, and 280 MPa, respectively. These values indicate that the TFMG coatings improved fatigue resistance by as much as 24% through 10 7 cycles. The hardness of TFMGs, their excellent adhesion to the substrate, and the resulting reduction in surface roughness are believed to account for the enhanced fatigue characteristics.

We have used nanoindentation to investigate mechanical properties of 200-nm-thick amorphous multilayer consisting of alternating layers of Zr-based thin film metallic glass (TFMG) and holmium scandium oxide (HSO). Nanoindentation results show that TFMG/HSO multilayer exhibits the high hardness and Young's modulus. Owing to its high hardness, smooth surface, and good adhesion properties, TFMG/HSO multilayer is then employed as a protective coating to improve the four-point bending fatigue properties of 316L stainless steel. With coating, the fatigue life is increased from 2.4×10 5 to 4.9×10 6 cycles, at the stress of 700 MPa. A crack retardation mechanism has been proposed to explain the role of TFMG/HSO multilayer in improving fatigue properties of 316L stainless steel substrate.

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.

Anatase titanium dioxide (TiO2) nanoparticles (NPs) embedded in poly(vinyl alcohol) (PVA) nanofibers were fabricated for the photodegradation of methylene blue (MB) as the test analyte. 1 wt% TiO2 NPs were dispersed in 12 wt% PVA solution prior to electrospinning to form the nanofibers. Raman spectroscopy implied the incorporation of the NPs into the nanofibers without significant change in the chemical structure of either TiO2 or PVA. Scanning electron microscopy, energy dispersive x-ray spectroscopy, and transmission electron microscopy revealed smooth, bead-free, and continuous nanofibers, uniform NP distribution, and negligible NP agglomeration, respectively. The effect of oxygen plasma treatment on the photodegradation efficiency of the PVA/TiO2 was also investigated. Photodegradation of MB exhibited up to 30% increase in degradation efficiency using the plasma-treated PVA/TiO2 nanofiber mats. The partially exposed immobilized TiO2 NPs became more photocatalytically active while being supported by PVA nanofibers. Immobilization of TiO2 NPs would allow reusability thereby extending its service life ideal for environmental applications.

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.

The plasma electrolyte oxidation (PEO) process has been considered an environmentally friendly surface engineering method for improving the corrosion resistance of light weight metals. In this work, the corrosion resistance of commercially pure Al and PEO treated Al substrates were studied. The PEO layers were grown on commercially pure aluminum substrates using two different alkaline electrolytes with different addition concentrations of Si3N4 nanoparticles (0, 0.5 and 1.5 gL&minus, 1) and different duty cycles (25%, 50%, and 80%) at a fixed frequency. The corrosion properties of PEO coatings were investigated by the potentiodynamic polarization and electrochemical impedance spectroscopy test in 3.5 wt.% NaCl solutions. It showed that the weight gains, layer thickness and surface roughness of the PEO grown oxide layer increased with increasing concentrations of Si3N4 nanoparticles. The layer thickness, surface roughness, pore size, and porosity of the PEO oxide layer decreased with decreasing duty cycle. The layer thickness and weight gain of PEO coating followed a linear relationship. The PEO layer grown using the Na2B4O7∙10H2O contained electrolyte showed an excellent corrosion resistance and low surface roughness than other PEO coatings with Si3N4 nanoparticle additives. It is noticed that the corrosion performance of PEO coatings were not improved by the addition of Si3N4 nanoparticle in the electrolytic solutions, possibly due to its detrimental effect to the formation of a dense microstructure.