Metalurji ve Malzeme Mühendisliği
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ÖgeElectrocatalytic performance of interconnected self-standing tin nanowire network produced by AAO template method for electrochemical CO2 reduction(Wiley, 2023)In this study, we used a specially designed aluminum anodic oxide (AAO) template technique to produce interconnected self-standing tin nanowire electrocatalysts having a high surface-to-volume ratio for CO2 reduction toward formate. These electrodes consisted of interconnected tin nanowires with 150 nm diameter and 7 μm length supported on 70–100 μm thick tin film. As prepared electrodes produced 6 times higher formate than the flat tin sheets, yet Faradaic efficiencies (FE%) were unsatisfactory. The main reason for low FE% is determined as the etching of native oxide on tin nanowires during hot alkali treatment to remove AAO and remnant aluminum. Porous anodic oxidation in 1 M NaOH solution was realized to recover tin oxides on the surface. Anodized tin nanowire electrocatalysts produced higher formate than anodized tin sheets, reaching FEformate% of ~87 at −1 V vs. RHE cathodic reduction potential. Moreover, while anodic oxide on flat tin flaked off the surface in 1 h, these electrodes preserved their integrity and formate production ability even after 12 h.
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ÖgeA study on tailoring silver release from micro-arc oxidation coating fabricated on titanium(Wiley, 2024)This study is initiated with the aim of regulating the release of silver (Ag) as an antibacterial agent from the micro-arc oxidation (MAO) coating. Herein, an external 5 wt% Tin(II) chloride (SnCl2) containing biodegradable polycaprolactone (PCL) layer is formed on the 0.8 wt% Ag-incorporated MAO coating by the dip coating method. 5 wt% SnCl2 addition into PCL provides a steady release of Ag into concentrated simulated body fluid (1.5X SBF) from the underlying MAO coating at 37 °C. When the Ag release rate is taken into consideration, it is quantified as 0.0089 and 0.0586 ppm day−1 for PCL-covered MAO and PCL-free MAO coatings, respectively. It is finally concluded that the preliminary result of this study can be promising for minimizing the in vivo adverse effects of Ag+ ions arising from rapid release as well as maintaining antibacterial efficacy for prolonged periods, which is ideal for preventing the risk of postimplantation infections.
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ÖgeMechanochemical synthesis and characterization of nanostructured ErB4 and NdB4 rare-earth tetraborides(Wiley, 2024)Rare-earth borides have become very popular in recent decades with high mechanical strength, melting point, good corrosion, wear, and magnetic behavior. However, the production of these borides is very challenging and unique. The production of ErB4 and NdB4 nanopowders via mechanochemical synthesis (MCS) is reported in this study first time in the literature. Er2O3 or Nd2O3, B2O3, and Mg initial powders are mechanically alloyed for different milling times to optimize the process. Rare-earth borides with MgO phases are synthesized, then MgO is removed with HCl acid. The nanostructured rare-earth tetraboride powders are analyzed using X-ray diffraction (XRD). Based on the XRD, ErB4 powders are produced successfully at the end of the 5 h milling. However, the NdB4 phase does not occur as the stoichiometric ratio, so the B2O3 amount is decreased to nearly 35 wt%. When the amount of B2O3 is decreased to 20 wt%, NdB4 and NdB6 phases are 50:50 according to the Rietveld analysis. However, a homogenous NdB4 phase is obtained with 30 wt% loss of B2O3. The average particle sizes of ErB4 and NdB4 powders are nearly 100.4 and 85.6 nm, respectively. The rare-earth tetraborides exhibit antiferromagnetic-to-paramagnetic-like phase transitions at 18 and 8.53 K, respectively.
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ÖgeMelt rheological and bead foaming behavior of recycled polyethylene terephthalate/polybutylene terephthalate blends modified with a joncryl chain extender(American Chemical Society, 2024)This study investigates the melt rheological properties and foamability of recycled polyethylene terephthalate (rPET) and its blends with polybutylene terephthalate (PBT) modified through an epoxy-based Joncryl ADR 4468 chain extender. A twin-screw extruder was used to prepare rPET/PBT blends at various weight ratios (i.e., 100/0, 75/25, 50/50, 25/75, and 0/100) and with varying Joncryl chain extender contents (i.e., 0.25, 0.5, 0.75, and 1.0 wt %). The small-amplitude oscillatory shear rheological experiments were conducted to analyze the melt viscoelastic behavior of the samples. The melt strength and strain-hardening behavior of the compounds were examined by measuring the extensional rheology and Rheotens tests. Crystallization analysis was conducted on the processed samples by using differential scanning calorimetry. The bead foaming behavior of the samples was investigated using a batch-based foaming reactor with supercritical CO2. Both compounding with PBT and Joncryl chain modification increased the complex viscosity, melt strength, and strain-hardening behavior of the blends, while their synergistic effect revealed a more noticeable enhancement. Although direct modification of rPET with Joncryl and its direct compounding with PBT could not generate a meaningful foam structure, a homogeneous microcellular foam structure could successfully be induced when 25 wt % rPET was incorporated in blends with PBT modified with 1.0 wt % Joncryl.
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ÖgeCryo-assisted nitrogen treatment for the fabrication of nanoengineered, mixed transition metal oxide anode from inorganic domestic waste, for lithium-ion batteries(Springer, 2024)A novel method for the fabrication of nanoengineered, mixed transition metal oxide anode active material is proposed based on implementing liquid nitrogen treatment during the chemical precipitation process, for the first time in open literature. Such interference in the precipitation is believed to change the surface energy of the nuclei leading to differentiation in the growth process. To exemplify this hypothesis with an environmentally friendly approach, kitchen scourer pads, an existing waste, are used as a starting material instead of using a mixture of primary quality metals’ salts. Therefore, in this study, firstly, an optimization is realized to leach the scouring pad with 100% efficiency. Then, by applying a conventional chemical precipitation to this leachate at pH 5.5, Sample 1-P is produced. Herein, innovatively liquid nitrogen treatment is carried out during the chemical precipitation to produce Sample 2-P. Lastly, these precipitates (Samples 1-P, 2-P) are calcinated in the air to form mixed transition metal oxide powders: Samples 1 and 2, respectively. Structural, chemical, and morphological characterizations are carried out to examine the effect of liquid nitrogen treatment on the powders’ properties. To discuss the effect of nitrogen treatment on the electrochemical performances of the anode active materials (Sample 1 and Sample 2), galvanostatic tests are realized. The results show that Sample 2 demonstrates a higher 1st discharge capacity (1352 mAh/g) and retains 62% of its performance after 200 cycles when 50 mA/g current load is applied. Moreover, this electrode delivers around 500 mAh/g at 1 A/g current load. The remarkable cycle performance of Sample 2 is believed to be related to the superior chemical, structural, and physical properties of the electrode active material.