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    Effect of Gd-doping in Ni/NiO core/shell magnetic nanoparticles (MNPs) on structural, magnetic, and hydrogen evolution reaction
    (Aip Publishing, 2022) Adanur, Idris; Karazehir, Tolga; Dogru Mert, Basak; Akyol, Mustafa; Ekicibil, Ahmet
    In this study, Gd-x-doped Ni/NiO MNPs (x: 0.0%, 2.5%, 5.0%, and 10.0%) with a protective polyvinylpyrrolidone (PVP) layer have been synthesized via a polyol reduction process. The x-ray diffraction patterns revealed that samples have a cubic structure with Fm3m space group and no change in the crystallite structure was observed with doping Gd3+ ions. The crystallite size (D-c) decreases from 2.70 to 1.27 nm when Gd is doped into Ni/NiO MNPs. Transmission electron microscopy analysis revealed that the Ni/NiO MNPs with Gd(5%) concentration are formed as spherical multicore-like shape core/shell MNPs with a protective PVP layer. The magnetic hysteresis measurements taken at 10 and 300 K show that the saturation magnetization (M-s) decreases with increasing Gd3+ ions in the structure. The highest effective magnetic moment (mu(eff)) was obtained as 10.34 mu(B) in the NG-2 sample. We ascribe that the high mu(eff) value in this sample is due to the increase in d-f exchange interaction between Ni(3d(7)) and Gd(4f(7)) and the contribution of the dipole moment of PVP molecules. The electrochemical measurements showed that the current density values were 0.294 and 0.319 mA/cm(2) at-1.3 V in the absence of Gd (NG-0) and Gd(5%) doped (NG-2) samples, respectively. beta c was 159 and 132 mV/dec for NG-0 and NG-2 samples, respectively. The diminishing of beta c and the charge resistance (Rct) proved that the Gd doped catalyst enhanced the hydrogen evolution activity and the Gd(5%) doped sample exhibited the highest catalyst performance.
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    Enhancing microstrip patch antenna performance through CNF-modified dielectric substrates and 3D printing techniques
    (Emerald Group Publishing Ltd, 2025) Avsar Aydin, Emine; Seyedzavvar, Mirsadegh; Boga, Cem; Mert, Mehmet Erman; Dogru Mert, Basak
    PurposeThis research investigates the impact of carbon nanofiber (CNF) incorporation on the dielectric properties, mechanical integrity and performance of microstrip patch antennas. This study examines how varying CNF concentrations affect key electromagnetic parameters like dielectric constant and loss tangent while assessing nanocomposite mechanical characteristics. Leveraging material modification and additive manufacturing, this study aims to enhance antenna performance, tunability and manufacturability.Design/methodology/approachAntenna substrates were fabricated using fused deposition modeling with acrylonitrile butadiene styrene (ABS) and polycarbonate (PC) containing 0.05%-2% CNFs. Dielectric properties were analyzed, while scanning electron microscopy assessed surface homogeneity and CNF dispersion. Mechanical tests evaluated yield strength and toughness. Antennas were tested over 1-15 GHz, focusing on reflection coefficient (S11) and voltage standing wave ratio (VSWR).FindingsCNF-modified substrates exhibited tunable dielectric properties (1.98-2.21 dielectric constant). Scanning electron microscopy confirmed improved dispersion. ABS-based antennas with 2 Wt.% CNFs showed optimal S11 and VSWR in the 2-4 GHz range. While CNFs slightly reduced ABS yield strength, they enhanced toughness, demonstrating the potential of customized dielectric materials for high-performance antennas.Originality/valueThis study introduces a novel microstrip patch antenna fabrication method using fused deposition modeling with customized dielectric materials. Unlike conventional approaches, it enables precise dielectric tuning via controlled CNF incorporation. ABS and PC were chosen for their dielectric stability, mechanical strength and three-dimensional printing compatibility. Investigating CNF concentrations (0.05%-2%) provides insights into dielectric behavior, mechanical properties and processing constraints. Enhanced antenna performance, especially in the 2-4 GHz range, underscores material composition's impact. This scalable approach supports next-generation communication systems, including IoT, 5G and aerospace applications.
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    Experimental and theoretical study on hydrogen production by using Ag nanoparticle-decorated graphite/Ni cathode
    (Wiley, 2021) Yildiz, Resit; Dogru Mert, Basak; Karazehir, Tolga; Gurdal, Yeliz; Toprak Doslu, Serap
    In this study, graphite (G) electrode was coated with nickel and decorated with silver nanoparticles (G/Ni/Ag) with the help of galvanostatic method, and electrodes were used as a cathode in alkaline water electrolysis system. The characterization was achieved using X-ray diffraction and field emission scanning electron microscopy. Hydrogen evolution performance of electrodes was investigated via cyclic voltammetry, chronoamperometry, cathodic polarization curves, and electrochemical impedance measurements. Electrochemical results showed that hydrogen production efficiency significantly increased and charge transfer resistance decreased via G/Ni/Ag. The electrochemical water splitting performance of G/Ni/Ag, was established in a joint experimental and computational effort. Water and proton adsorption on Ag-decorated Ni surface were investigated using density functional theory. Electronic structure calculations identified the role of Ag adatom and Ni surface on water and proton adsorptions. From the computational studies, O in water was more reliable to adsorb at the bridge position of the Ag and Ni atoms, leading improved orbital overlap between H and Ni atoms and maximized chemical and physical interactions between the H2O molecules. Therefore, the Ag-decorated Ni(111) surface provides preferable adsorption site for the O atom in water and direct interactions between water Hs and available surface Ni atoms promote water dissociation.
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    Hydropower-Assisted Alkaline Electrolysis with NiCo-Modified Electrodes Produced by Additive Manufacturing for Enhanced Hydrogen Evolution Reaction
    (Springer Heidelberg, 2025) Ekinci, Firat; Durhasan, Tahir; Mert, Mehmet Erman; Dogru Mert, Basak; Esenboga, Burak
    In this study, micro hydropower assisted alkaline electrolysis system was investigated to meet small-scale energy needs in rural areas. One of the noteworthy aspects of the study is the modification of metal electrodes produced by additive manufacturing with high HER activity metals such as Ni and Co. Additive manufacturing offers benefits in terms of creating complex geometries, reducing material waste, and enabling rapid prototyping. The NiCo modification created through the galvanostatic method provides advantages in enhancing the electrochemical activity and stability of the electrodes, particularly regarding HER activity. The electrochemical activity of the hydrogen evolution reaction (HER) in 1 M KOH was investigated using linear sweep voltammetry, cyclic voltammetry and bulk electrolysis. Surface characterization was achieved through scanning electron microscopy, energy-dispersive X-ray analysis and X-Ray diffraction analysis. The water wettability characteristics of electrode surfaces were examined using contact angle measurements. The 3Dm NiCo electrode demonstrated higher catalytic performance, with a contact angle of 61 degrees compared to 92 degrees for 3Db, indicating improved wettability. XRD investigation revealed NiCo crystalline phases. At 3 V, compared to the unmodified 3Db electrode, the 3Dm NiCo electrode demonstrated a similar to 64% increase in hydrogen production (46.8 mL vs. 28.5 mL), confirming its enhanced HER performance. Long-term catalyst stability was determined over 180,000 s.
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    Lignocellulosic biomass based catalysis for hydrogen generation effect of pistachio shells and Raney nickel in NaBH4 hydrolysis
    (Nature Portfolio, 2025) Sismanoglu, Sedef; Abed, Luay Duraid Abed; Mert, Mehmet Erman; Dogru Mert, Basak
    Pistachio shell, which has a layered, porous structure, is a natural polymer composed of lignin, hemicellulose and cellulose. This study investigates the catalytic performance of a composite catalyst made from pistachio shell (PS) and Raney Ni (Ra-Ni) in sodium borohydride (NaBH4) hydrolysis for hydrogen production. Characterization techniques, ATR-FTIR, XRD, TGA, and FESEM-EDX, were utilized to analyze the morphology and structure of the catalyst. To assess catalytic performance, the rate of H2 generation was measured using a water displacement method at 298 K. A 0.15 g sample of catalyst, composed of 1:1 weight ratio of Ra-Ni and ball milled PS, was mixed with 100 mL of water and 1 wt% NaBH4. H2 production rate was monitored, providing insights into the catalyst's efficiency and effectiveness. Results demonstrated that the Ra-Ni and PS composite exhibited high catalytic activity, with H2 generation rates of 409 mL g- 1 catalyst after 450 s and 430 mL g- 1 catalyst after 900 s, respectively. Activation energy of Ra-Ni-PS was 23.30 kJ mol- 1. The produced composite has promising potential for H2 production applications via NaBH4 hydrolysis.