Non-stick syringe needles : Beneficial effects of thin film metallic glass coating

This paper reports on the use of Zr-based (Zr53Cu33Al9Ta5) thin film metallic glass (TFMG) for the coating of syringe needles and compares the results with those obtained using titanium nitride and pure titanium coatings. TFMG coatings were shown to reduce insertion forces by ∼66% and retraction forces by ∼72%, when tested using polyurethane rubber block. The benefits of TFMG-coated needles were also observed when tested using muscle tissue from pigs. In nano-scratch tests, the TFMG coatings achieved a coefficient of friction (COF) of just ∼0.05, which is about one order of magnitude lower than those of other coatings. Finite-element modeling also indicates a significant reduction in injection and retraction forces. The COF can be attributed to the absence of grain boundaries in the TFMG coating as well as a smooth surface morphology and low surface free energy

Microstructure and mechanical properties of laser shocked iron-based alloys

The effects of laser shock processing (LSP) on the microstructure and mechanical properties of the low carbon (0.04 wt.%C) and Hadfield manganese (1%C and 14%Mn) steels have been studied. LSP was performed with a 1.054 $\mu$m wavelength Nd:phosphate laser operating in a pulse mode (600 ps pulse length and up to 200 J energy) with power densities above 10\sp{11} W/cm\sp2. Shock waves were generated by volume expansion of the plasma formed when the material was laser irradiated. Maximum shock wave intensities were obtained using an energy-absorbing black paint coating without a plasma-confining overlay. Maximum modification of the material surface properties and favorable compressive residual stresses were achieved when LSP-induced deformation occurred without melting.Mechanical properties of materials such as surface hardness were greatly improved through modifying the microstructure by LSP. High density arrays of dislocations ($>$10\sp{11}/cm\sp2) were generated in low carbon steel by high strain-rate deformation of LSP, resulting in surface hardness increases of 30 to 80%. In austenitic Hadfield steel, LSP caused extensive formation of $\epsilon$-hcp martensite (35 vol.%), producing increases of 50 to 130% in surface hardness. The LSP strengthening effect in Hadfield steel was attributed to the combined effects of the partial dislocation/stacking fault arrays and the grain refinement due to presence of the $\epsilon$-hcp martensite. Surface and near surface compressive residual stresses due to plastic deformation by LSP were measured in both steels. Comparisons of LSP microstructure and properties were made with the lower strain rate processes of shot peening and cold rolling for both steels.U of I OnlyETDs are only available to UIUC Users without author permissio

Fracture-resistant thin-film metallic glass: Ultra-high plasticity at room temperature

We report the first example of room-temperature rubber-like deformation in thin-film metallic glasses (TFMGs), 260-nm-thick Zr60Cu24Al11Ni5 layers, under ultra-high shear strain. The TFMGs were deposited, with no external heating, on Zr-based bulk metallic glass (BMG) and Si(001) substrates by rf magnetron sputtering in a 3 mTorr Ar plasma. Cross-sectional transmission electron microscopy (XTEM) analyses and nanoindentation results reveal that the TFMGs undergo an incredibly large shear strain, estimated to be ∼4000%, during fatigue tests, and thickness reductions of up to 61.5%, with no shear-banding or cracking, during extreme nanoindentation experiments extending through the film and into the substrate. TFMG/BMG samples also exhibit film/substrate diffusion bonding during deformation as shown by high-resolution XTEM

Negative Effects of Annealed Seed Layer on the Performance of ZnO-Nanorods Based Nitric Oxide Gas Sensor

Nitric oxide (NO) is a toxic gas, which is dangerous for human health and causes many respiratory infections, poisoning, and lung damage. In this work, we have successfully grown ZnO nanorod film on annealed ZnO seed layer in different ambient temperatures, and the morphology of the nanorods sensing layer that affects the gas sensing response to nitric oxide (NO) gas were investigated. To acknowledge the effect of annealing treatment, the devices were fabricated with annealed seed layers in air and argon ambient at 300 °C and 500 °C for 1 h. To simulate a vertical device structure, a silver nanowire electrode covered in ZnO nanorod film was placed onto the hydrothermal grown ZnO nanorod film. We found that annealing treatment changes the seed layer’s grain size and defect concentration and is responsible for this phenomenon. The I–V and gas sensing characteristics were dependent on the oxygen defects concentration and porosity of nanorods to react with the target gas. The resulting as-deposited ZnO seed layer shows better sensing response than that annealed in an air and argon environment due to the nanorod morphology and variation in oxygen defect concentration. At room temperature, the devices show good sensing response to NO concentration of 10 ppb and up to 100 ppb. Shortly, these results can be beneficial in the NO breath detection for patients with chronic inflammatory airway disease, such as asthma

Zinc gallate (ZnGa2O4) epitaxial thin films : determination of optical properties and bandgap estimation using spectroscopic ellipsometry

Electronic grade ZnGa2O4 epitaxial thin films were grown on c-plane sapphire substrates by metal-organic chemical vapor deposition and investigated using spectroscopic ellipsometry. Their thickness, roughness and optical properties were determined using a Multiple Sample Analysis based approach by the regression analysis of optical model and measured data. These samples were then compared to samples which had undergone ion etching, and it was observed that etching time up to four minutes had no discernible impact on its optical properties. Line shape analysis of resulting absorption coefficient dispersion revealed that ZnGa(2)O(4 )exhibited both direct and indirect interband transitions. The modified Cody formalism was employed to determine their optical bandgaps. These values were found to be in good agreement with values obtained using other popular bandgap extrapolation procedures. Published by Optica Publishing Group under the terms of the Creative Commons Attribution 4.0 License. Further distribution of this work must maintain attribution to the author(s) and the published articles title, journal citation, and DOI.Funding Agencies|Vetenskapsradet [2018-04198]; Stiftelsen foer Strategisk Forskning [2009-00971]; STINT foundation [MG2019-8485]; Wafer Works Corporation; Ministry of Science and Technology [109-2221-E-009-143-MY3, 109-2622-E-009-033, 109-2634-F-009-028, 109-2224-E-009-002, 110-2218-E-A49-020-MBK, 110-2622-8-009-018-SB, 110-2224-E-A49-003, 111-2923-E-A49-003-MY3]; MAtek [2021-T-006]</p

Titanium-based thin film metallic glass as diffusion barrier layer for PbTe-based thermoelectric modules

The thin film metallic glass (TFMG) is an effective diffusion barrier layer for PbTe-based thermoelectric (TE) modules. Reaction couples structured with Cu/TFMG/PbTe are prepared via sputter-deposition and are annealed at 673 K for 8-96 h. The transmission line method is adopted for the assessment of electrical contact resistivity upon the PbTe/TFMG, and the value remains in the range of 3.3-2.5 × 10−9 (Ω m2). The titanium-based TFMG remains amorphous upon annealing at 673 K for 48 h and effectively blocks the inter-diffusion by not having grain-boundaries, which only allows the bulk diffusion between the metal electrode and the TE substrate