WoS
Permanent URI for this collectionhttps://hdl.handle.net/20.500.14411/18
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Article Citation - WoS: 5Citation - Scopus: 54D Printing of Reusable Mechanical Metamaterial Energy Absorber, Experimental and Numerical Investigation(Iop Publishing Ltd, 2025-06-01) Fallah, Ali; Saleem, Qandeel; Scalet, Giulia; Koc, BahattinThis study investigates the compression behavior, energy absorption, shape memory properties, and reusability of 4D-printed smart mechanical metamaterials. Four structural configurations, i.e. honeycomb, re-entrant, and two modified re-entrant designs were developed to assess microstructure effects. Samples were fabricated using Polylactic Acid (PLA), a widely used shape memory polymer (SMP) in 4D printing, and polyethylene terephthalate glycol (PETG), an emerging SMP with demonstrated shape memory performance in recent studies. Cold-programming-induced shape recovery was evaluated at room temperature, simulating real-world conditions. Finite element simulations of compression and shape memory cycles matched experimental results well. Auxetic samples with negative Poisson's ratios showed superior energy absorption. However, only PETG demonstrated sufficient reusability, while PLA proved unsuitable for reusable designs. The PETG-3 modified re-entrant structure exhibited the best performance, with high energy absorption, delayed densification onset, and shape recovery and reusability factors of 0.95 and 0.96, respectively. Findings highlight the importance of considering both shape recovery and reusability when designing smart structures to address industrial challenges.Article Citation - WoS: 2Citation - Scopus: 1Integrating Theoretical and Experimental Approaches To Unveil the Mechanical Properties of Cusbse<sub>2</Sub> Thin Films(Iop Publishing Ltd, 2024-11-21) Surucu, Ozge; Gencer, Aysenur; Usanmaz, Demet; Parlak, Mehmet; Surucu, GokhanAn exhaustive investigation of the mechanical characteristics of CuSbSe2 thin films is conducted in this study by combining experimental nanoindentation methods with theoretical simulations. The Ab-initio Molecular Dynamics (AIMD) calculations are performed with the machine learning (ML) force fields. By employing the Vienna Ab-initio Simulation Package (VASP) based on Density Functional Theory (DFT), theoretical inquiries are carried out to identify crucial parameters, such as bonding characteristics, elastic constants, hardness, bulk modulus, shear modulus, Young's modulus, and Poisson's ratio. Experimental validation is conducted using nanoindentation to investigate load-dependent hardness and Young's modulus in a manner that closely matches the theorized predictions. The anomalies between experimental and theoretical outcomes are ascribed to anisotropic behavior and grain boundaries. Furthermore, an investigation is conducted into the directional dependence of sound wave velocities in the CuSbSe2 films, leading to the revelation of intricate elastic property details. By employing an integrated theoretical-experimental approach, the present attempt not only increases the knowledge concerning CuSbSe2 films but also fortifies the relationship between theory and experiment, thereby bolstering the dependability of our results. The insights provided as a result of this paper facilitate the development of CuSbSe2 film applications in a variety of technological fields in the future.Article Citation - WoS: 3Citation - Scopus: 3Performance Enhancement of Silicon Photodiodes Through the Integration of Green Synthesized Reduced Graphene Oxide Variants(Iop Publishing Ltd, 2024-08-06) Yildiz, D. E.; Sürücü, Özge; Surucu, O.; Balaban, H. Mert; Bilici, I; Yildirim, M.; Sürücü, Özge; Mert Balaban, H.; Electrical-Electronics Engineering; Electrical-Electronics EngineeringThis study examines the potential of enhancing the optoelectronic properties of silicon photodiodes by producing and analyzing heterostructures that incorporate reduced graphene oxide (rGO) synthesized with silicon using different reduction methods. Graphene oxide (GO) was manufactured utilizing an enhanced Hummers' method. Subsequently, reduced graphene oxides (rGOs) were made by chemical and thermal reduction processes, which are considered ecologically friendly. The use of ascorbic acid to produce ascorbic acid-reduced graphene oxide (ArGO) and thermal processing to produce thermally reduced graphene oxide (TrGO) have significantly contributed to the development of high-performance photodiode technology. The electrical properties were carefully assessed under different levels of light, revealing the substantial impact of integrating reduced graphene oxides (rGOs) on the performance of the diodes. Comparing ArGO/Si, TrGO/Si, and GO/Si heterostructures shows that customized rGO has the potential to greatly influence the responsivity and efficiency of Si-based optoelectronic devices, making a significant contribution to photodiode technology.Article Citation - WoS: 2Citation - Scopus: 2Post Annealing Effects on the Structural and Optical Properties of Moo<sub>3</Sub> Sandwiched With Indium Slabs(Iop Publishing Ltd, 2019-11-08) Qasrawi, A. F.; Qasrawı, Atef Fayez Hasan; Kmail, Haifaa K.; AbuSaa, M.; Khanfar, Hazem K.; Qasrawı, Atef Fayez Hasan; Department of Electrical & Electronics Engineering; Department of Electrical & Electronics EngineeringMolybdenum trioxide thin films are prepared by the thermal evaporation technique under vacuum pressure of 10(-5) mbar through insertion of indium slabs of thickness of 200 nm between layers of MoO3 and annealing the produced films in the air atmosphere at 250 degrees C for one hour. The films are studied by means of x-ray diffraction, scanning electron microscopy, energy dispersive x-ray spectroscopy, and optical spectrophotometry techniques. The structure of the films is found to be composed monoclinic MoO3, tetragonal indium and cubic In2O3. The phase percentage of In2O3 in the films increased to 26.3% upon annealing at 250 degrees C. The annealing process increased the microstrain, the defect density, the oxygen atomic content and lowered the crystallites and grains sizes in the films. Optically, two energy band gaps of values of 3.20 and 1.70 eV were detected for the MoO3/In/MoO3 system. In addition, nonlinear dielectric response associated with wide range of tunability in the dielectric constant value, in the optical conductivity and in the terahertz cutoff frequency was observed in the near IR spectral range. The annealing of the samples improved the nonlinearity in these parameters and make MoO3/In/MoO3 system more appropriates for optoelectronic technology applications as terahertz cavities and frequency convertors.Article Citation - WoS: 4Citation - Scopus: 5Znse/Al Nanosandwiched Structures as Dual Terahertz-Gigahertz Signal Receivers(Iop Publishing Ltd, 2019-03-20) Qasrawi, A. F.; Alsabe, Ansam M.In the current work, we focus on the enhancements in performance of the ZnSe terahertz/gigahertz signal receivers which are achieved by the insertion of nanosheets of Al layers of thickness of 30 nm between two 500 nm thick layers of ZnSe. The Al nanosandwiching which decreased the defect density, stacking faults and increased the grain size in the films increased the optical conductivity by more than 125%, increased the drift mobility to 313 cm(2) V-1 s(-1) and widens the plasmon frequency ranges to 0.49-4.92 GHz. In addition, the analysis of the terahertz cutoff (f(co)) frequency spectra have shown that the presence of Al nanosheets improves the cutoff frequency value by three orders of magnitude making the ZnSe receivers more suitable for visible light and IR communication technology. The value of f(co) is 49.6 THz when light signal of wavelengths of 408 nm that suits blue lasers is irradiated. Moreover, the impedance spectroscopy analysis in the gigahertz frequency domain has shown that the Al sandwiched ZnSe exhibits negative capacitance spectra in the frequency domain of 0.01-1.04 GHz. This property is useful for parasitic capacitance cancelling and noise reducing in circuits. Furthermore, the study of the microwave cutoff frequency spectra has shown that the value of f(co) is enhanced by three orders of magnitude above 1.5 GHz.Article Citation - WoS: 26Citation - Scopus: 27Preparation of Electrospun Pcl-Based Scaffolds by Mono/Multi-functionalized Go(Iop Publishing Ltd, 2019-05-28) Basar, Ahmet Ozan; Sadhu, Veera; Sasmazel, Hilal Turkoglu; Turkoglu Sasmazel, HilalIn the present study, sythetic biodegradable polymer poly(epsilon-caprolactone) (PCL) and graphene oxide (GO) were combined together to prepare 3D, composite tissue scaffolds (PCL/GO scaffolds) by using electrospinning technique. Also, the influence of Gly-Arg-Gly-Asp-Ser-Pro (GRGDSP) and/or thiophene (Th) modified GO on the composite PCL/GO mats (PCL/GO, PCL/GO-GRGDSP, PCL/ GO-Th, PCL/GO-GRGDSP-Th) was further investigated. Characteristic examinations of the scaffolds were carried out by scanning electron microscope (SEM), contact angle (CA) measurements, x-ray photoelectron spectroscopy, TGA, electrical conductivity tests, phosphate buffer saline absorption and shrinkage tests and mechanical tests. All of the scaffolds were exhibited suitable bead free and uniform morphology according to SEM images. With the addition of GO, better hydrophilicity and a slight CA decrease (similar to 5 degrees) for the PCL/GO scaffolds were observed. Mechanical properties were reinforced drastically with the addition and well-dispersion of GO into PCL matrix. The incorporation of PCL and GO exhibited enhanced electrical conductivity and the highest value was found for PCL/GO-GRGDSP-Th (2%) as 15.06 mu S cm(-1). The MG-63 osteoblast cell culture studies (MTT assay, ALP activity, Alizarin-Red staining, fluorescence and SEM analyses) showed that PCL/GO-GRGDSP-Th (1%) scaffolds exhibited the highest biocompatibility performance (1.87 fold MTT absorbance value comparing with neat PCL) due to the advanced properties of GO and the biological interfaces.Article Citation - WoS: 11Citation - Scopus: 11<i>in Situ</I> Monitoring of Heat Assisted Oxidation and Its Effects on the Structural, Dielectric and Optical Conductivity Parameters of Pb Thin Films as Promising Terahertz Transmitters(Iop Publishing Ltd, 2019-09-27) Qasrawi, A. F.; Abu Ghannam, Arwa N.In this work, thermal vacuum deposited lead thin films are subjected to an in situ monitoring of the oxidation process during heating in the temperature range of 300-480 K by the x-ray diffraction technique. The heating effects on the crystallinity, phase formation and structural parameters are additionally investigated with the help of computer simulation to explore the possible formed oxides. In addition, the heating effects of the optical transmission, reflection and absorption, optical conduction and terahertz signal transmission spectra are also investigated. It is found that, the cubic crystalline Pb films comprises tetragonal Pb3O4 in it's as grown form. When heated, while the Pb3O4 content increases from 18.5% to 21.3%, tetragonal PbO phase with weight of 30.9% is formed. Even though more than half of the film content relates to the oxides after the samples were left to cool, the microstrain and defect density in the films decreased and the grain size increased. Optically, the oxidation process enhanced, the light transitivity, reflectivity and decreased the absorption coefficient. Two energy band gaps one is assigned to Pb3O4 with value of 2.12 eV before heating and the other is assigned to PbO with value of 2.60 eV after cooling are detected. Dielectrically, the oxidation increased the real part and the quality factor in the infrared region of light. On the other hand, the optical conductivity analyses which are treated via Drude-Lorentz approach has shown that Pb films exhibit plasmon frequency and mobility values of 3.2 GHz and 0.62 cm(2) V-1 s(-1), respectively. The oxidation slightly lowered the optical conductivity parameters. Application directed analysis of the terahertz cutoff frequency has shown that the oxidized Pb films behaves as promising layers for use as terahertz wave transmitters suitable for visible light communications.Article Citation - WoS: 25Citation - Scopus: 25First Principles Study on the Structural, Electronic, Mechanical and Lattice Dynamical Properties of Xrhsb (x = Ti and Zr) Paramagnet Half-Heusler Antimonides(Iop Publishing Ltd, 2019-09-13) Surucu, Gokhan; Candan, Abdullah; Erkisi, Aytac; Gencer, Aysenur; Gullu, Hasan HuseyinThe half-Heusler TiRhSb and ZrRhSb alloys in the formation of face-centered cubic MgAgAs-type structure, which conforms to the F (4) over bar 3m space group with 216 as the space number, have been investigated using Generalized Gradient Approximation (GGA) implemented in Density Functional Theory (DFT). The calculated formation enthalpies and the plotted energy-volume curves of different types of structural phases (alpha, beta, and gamma) in these alloys indicate that the gamma-phase structure is the best energetically suitable structure. In addition, TiRhSb and ZrRhSb alloys have been found as paramagnetic (PM) with the investigation of antiferromagnetic (AFM), ferromagnetic (FM), and paramagnetic (PM) orders in the most stable gamma-phase structure. Therefore, their electronic, mechanical, and dynamical properties have been examined in the gamma structural phase and paramagnetic order. These alloys have semiconducting nature due to the observed same band gaps in both the majority and minority spin channels of the calculated spin-polarised electronic band structure. These calculated band gaps are 0.75 eV for gamma-TiRhSb and 1.18 eV for gamma-ZrRhSb. The predicted elastic constants indicate that the alloys in this study are mechanically stable and show nearly isotropic behavior in the gamma structural phase. Also, the minimum and the diffuson thermal conductivites have been determined for these alloys. Finally, the calculated phonon dispersion spectras for the gamma-TiRhSb and gamma-ZrRhSb half-Heusler antimonide alloys show the dynamic stability of these systems.Article Citation - WoS: 14Citation - Scopus: 15Formation, Negative Capacitance and Negative Conductance Effects in Selenium Stacked Layers Sandwiched With Ag Nanosheets(Iop Publishing Ltd, 2019-05-21) Qasrawi, A. F.; Aloushi, Hadil D.In this work, we report the nature of formation in the presence and absence of Ag nanosheets being inserted between of two stacked layers of Se thin films which are grown onto Au substrates. The Se/Se and Se/Ag/Se films which are prepared by the thermal evaporation technique under vacuum pressure of 10(-5) mbar are studied by means of x-ray diffraction, conductance and capacitance spectroscopy techniques in the frequency domain of 0.01-1.80 GHz. Metal inducted crystallization processes from amorphous to hexagonal phases are achieved by using the Au substrate. The presence of Ag nanosheets of thicknesses of 50 nm between two 500 nm thick stacked layers of Se strongly affects the structural parameters through increasing the lattice constants, the microstrain and the defect density and decreasing the crystallite size. While the two stacked layers of Se sandwiched between Au and In metals displayed negative conductance effect associated with resonance in the capacitance and maximum microwave cutoff frequency (f(co)) of 0.68 GHz near 1.31 GHz, the insertion of Ag nanosheets forced the two stacked layers to exhibit higher positive conductance values and increased the f(co) values to 17.4 GHz. Ag nanosheets also caused negative capacitance (NC) effect in all the studied frequency domain. NC effect is associated with resonance-anti-resonance phenomena in the region of 1.33-1.37 GHz. The features of the selenium stacked layers make them attractive for use in microwave circuits as cavities, noise reducers, parasitic capacitance cancellers and bandpass filters.Article Citation - WoS: 5Citation - Scopus: 5Structural and Dielectric Performance of the Ba(zn<sub>1/3< Perovskite Ceramics(Iop Publishing Ltd, 2019-07-26) Qasrawi, A. F.; Sahin, Ethem Ilhan; Emek, Mehriban; Kartal, Mesut; Kargin, SerdarIn this work, we have explored the antimony doping effects on the structural and dielectric properties of Ba(Zn1/3Nb2/3)O-3 ceramics (BZN). The ceramics displayed perovskite structures with a lattice constant that decreases with increasing Sb content. The antimony solubility limit of the BZN ceramics is x < 0.50. Belowthis limit and in the range of 0.30 <= x <= 0.40, the microstrain, the dislocation density and the stacking faults decreased and the crystallite size increases with increasing Sb content in the composition of BZN. When the limit is exceeded minor phases are predicted by software analysis and confirmed by the experimental techniques. The presence of these phases is also verified by the scanning electron microscopy and energy dispersive x-ray spectroscopy techniques. Increasing the Sb content is observed to decrease the value of the dielectric constant. The Sb doped BZN ceramics exhibits high dielectric quality factors that nominate it for applications in electronics as radio waves resonators.