Person: GÜLLÜOĞLU, ARİF NİHAT
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GÜLLÜOĞLU
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ARİF NİHAT
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Publication Metadata only Effect of irradiation by 140 Mev Ag11+ ions on the optical and electrical properties of polypropylene/TiO2 composite(ELSEVIER, 2009) GÜLLÜOĞLU, ARİF NİHAT; Qureshi, Anjum; Singh, Dolly; Singh, N. L.; Ataoglu, S.; Gulluoglu, Arif N.; Tripathi, Ambuj; Avasthi, D. K.Changes in the optical, structural, dielectric properties and surface morphology of a polypropylene/TiO2 composite due to swift heavy ion irradiation were studied by means of UV-visible spectroscopy, X-ray diffraction, impedance gain phase analyzer and atomic force microscopy. Samples were irradiated with 140 MeV Ag11+ ions at fluences of 1 x 10(11) and 5 x 10(12) ions/cm(2). UV-visible absorption analysis reveals a decrease in optical direct band gap from 2.62 to 2.42 eV after a fluence of 5 x 10(12) ions/cm(2). X-ray diffractograms show an increase in crystallinity of the composite due to irradiation. The dielectric constants obey the Universal law given by epsilon proportional to integral(n-1), where n varies from 0.38 to 0.91. The dielectric constant and loss are observed to change significantly due to irradiation. Cole-cole diagrams have shown the frequency dependence of the complex impedance at different fluences. The average surface roughness of the composite decreases upon irradiation. (C) 2009 Elsevier B.V. All rights reserved.Publication Metadata only Synthesis, characterization, thermal, and antibacterial activity studies on MgO powders(SPRINGER, 2021) GÜLLÜOĞLU, ARİF NİHAT; Demirci, Selim; Yildirim, Bercem Kiran; Tuncay, Mehmet Masum; Kaya, Nusret; Gulluoglu, Arif NihatIn this study, MgO particles were synthesized via sol-gel technique and calcined at 600 degrees C for 2 h with heating rates of 2, 5, 10, and 20 degrees C/min, respectively, for the first time. Comprehensive characterizations were performed by TGA-DTA, XRD, SEM, Raman spectroscopy, BET analysis, photoluminescence techniques. The kinetic parameters were determined by employing four popular model-free methods: Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sonuse (KAS), Starink, and Tang methods. MgO powders had a high crystalline structure regardless of different heating rates based on XRD results. Surface morphologies and surface areas of MgO powders did not change with heating rates. Surface morphologies of MgO powders were found to be nearly spherical with some rounded shape and exhibiting faceted edges in some regions. The specific surface area of MgO powders was found to be 5.9179, 5.6883, 3.6617, and 4.1942 m(2)/g with increasing heating rate, respectively. According to Raman analysis, MgO particles produced at 2 degrees C/min possessed higher surface defects like oxygen vacancies. The PL emission signals for MgO particles were observed at similar to 500 nm consisting of broad peaks, which might be attributed to oxygen defects on the surface of particles. The antibacterial performances of MgO particles were carried out against gram-negative E. coli and gram-positive B. subtilis by means of the agar disc diffusion method. MgO particles produced at a heating rate of 2 degrees C/min possessed the biggest inhibition zone against gram-positive B. subtilis. Having better antibacterial performances for MgO particles produced at 2 degrees C/min heating rate might be attributed to surface oxygen vacancies and surface area, which led to the generation of more reactive oxygen species (ROS). [GRAPHICS] .Publication Metadata only Effect of surface geometry on low-velocity impact behavior of laminated aramid-reinforced polyester composite(SAGE PUBLICATIONS LTD, 2016) GÜLLÜOĞLU, ARİF NİHAT; Ayten, Ali Imran; Ekici, Bulent; Gulluoglu, Arif NihatThe aim of this study is to investigate the effect of surface geometry for low-velocity impact applications. To achieve this purpose, aramid fiber-reinforced laminated polyester composite with various geometries such as cylindrical, elliptical, and spherical were prepared, and low-velocity impact properties were investigated numerically and experimentally. All properties such as orientation, fiber volume fraction, matrix material, and average thickness are the same in all samples. Experimental low-velocity impact behaviors of structure were determined by drop weight tester at low velocity 2.012 m/s. Simulations were carried out by LS-Prepost 4.2 and LS-Dyna v971 software. By this way, results of impact tests were verified and modeled with finite element method. Results of the impact tests showed that the elliptical samples have the highest energy absorption capability due to effective stress transfer capacity. According to experimental results, maximum energy absorption rate difference is 17% between elliptical 10mm and cylindrical 5mm geometries.Publication Metadata only Processing and mechanical properties of B4C reinforced Al matrix composites(ELSEVIER SCIENCE SA, 2009) GÜLLÜOĞLU, ARİF NİHAT; Topcu, I.; Gulsoy, H. O.; Kadioglu, N.; Gulluoglu, A. N.Aluminum matrix composites are emerging as advance engineering materials due to its high specific strength and stiffness, good wear resistance and high temperature properties. Properties of Al reinforced with Al2O3 and SiC are widely investigated. In the present study, mechanical properties of B4C reinforced Al matrix is investigated due to higher hardness and lower density properties than SiC and Al2O3. The high temperature deformation behavior of 5, 10, 15 and 20wt% B4C powder having an average particle diameter of about 10 mu m aluminum matrix composite sintered at 650 degrees C was investigated by creep tests at temperatures ranging from 400 to 450 degrees C and creep resistance of Al alloy is enhanced by the presence of B4C particles. Measurement of impact and hardness properties of composites showed that impact values decrease and hardness values increased with increase in weight fraction of reinforcement. (C) 2009 Elsevier B.V. All rights reserved.Publication Metadata only Dielectric properties of polymer composites filled with different metals(TAYLOR & FRANCIS INC, 2008) GÜLLÜOĞLU, ARİF NİHAT; Qureshi, Anjum; Mergen, Ayhan; Eroglu, Mehmet S.; Singh, N. L.; Gulluoglu, ArifElectrically conductive composite systems based on polyvinyl chloride (PVC) and polymethyl methacrylate (PMMA) filled with metal powders of Al and Cu have been studied. The composite preparation conditions allow the formation of a random distribution of metallic particles in the polymer matrix. Dependence of the dielectric and conductivity properties of the PVC and PMMA/fillers was studied over a broad range of frequency and volume fraction of metal fillers. The experimental results could be explained by means of the conductivity of fillers and the interface polarization between polymers and fillers. Percolation was also seen in this study when the volume fraction of conducting fillers was close to critical value, in which the composites undergo an insulator-conductor transition. The relation among the dielectric property and the fillers with different conductivity was proposed.Publication Metadata only Effect of surface modifications of additively manufactured Ti-6Al-4V alloys on apatite formation ability for biomedical applications(ELSEVIER SCIENCE SA, 2021) GÜLLÜOĞLU, ARİF NİHAT; Demirci, Selim; Dalmis, Ramazan; Dikici, Tuncay; Tuncay, Mehmet Masum; Kaya, Nusret; Gulluoglu, Arif NihatIn this study, Ti-6Al-4V alloys were additively manufactured (AM) with different laser powers. The goal was to investigate the effect of different surface modifications on apatite formation ability. Four types of surface modifications, namely, sandblasting (S), acid etching (E), anodic oxidation (AO) and anodic spark oxidation (ASO), were achieved on the Ti-6Al-4V samples. The microstructure, phase, morphology, roughness and wettability properties were examined by optical microscope (OM), scanning electron microscope (SEM), Xray diffraction (XRD), surface profilometer and contact angle techniques. The bioactivity analysis was performed in simulated body fluid (SBF) for 2 weeks. The results indicated that the microstructure, surface topography, roughness and wettability influenced the apatite formation were affected by the production laser power. Generally, the samples 3 showed higher Ca and P ion ratio value because of percentage of beta phase amount, the presence of bioactive phases on the surfaces. The E3 sample resulted in the best apatite formation theoretically. The etching procedure of AM Ti-6Al-4V in the acidic solution can be applied to improve the apatite formation ability of Ti-6Al-4V alloys. (c) 2021 Elsevier B.V. All rights reserved.Publication Metadata only Radiation induced modification of dielectric and structural properties of Cu/PMMA polymer composites(ELSEVIER SCIENCE BV, 2010) GÜLLÜOĞLU, ARİF NİHAT; Singh, Dolly; Singh, N. L.; Qureshi, Anjum; Kulriya, P.; Tripathi, Ambuj; Avasthi, D. K.; Gulluoglu, Arif N.In this study, composite films consisting of an insulating polymethyl methacrylate (PMMA) polymer matrix and metal powder (Cu) additive were prepared by solution costing method. These films were irradiated with 140 MeV silver ions at the fluences of 1 x 10(11) ions/cm(2) and 1 x 10(12) ions/cm2. The radiation induced changes in dielectric, structural and surface properties of PMMA/Cu composites were studied using impedance/gain phase-analyzer, X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). It was observed that the dielectric properties and ac electrical conductivity increased significantly with the concentration of dispersed metal powder (Cu) and also with the fluence. This reveals that ion beam irradiation creates free radicals, unsaturation etc. due to emission of hydrogen and/or other volatile gases, which makes the polymer more conductive. XRD analysis of the pristine and irradiated samples shows that the crystallinity improved upon irradiation at low fluence and deteriorated on further increase of the fluence, which could be attributed to cross linking of polymer chains at low fluence and degradation at higher fluence. High energy ion beam irradiation of semicrystalline polymer composite films changes its Tg behavior as observed from DSC analysis. This result is also corroborated with the results of XRD. The average surface roughness and topography of surfaces changed with the concentration of filler and also with the ion fluence as revealed from AFM/SEM analysis. (C) 2010 Elsevier B.V. All rights reserved.Publication Metadata only IN THE JEWELRY, BRAZING AND LASER WELDING WITH PARAMETER OPTIMIZATION(POLSKA AKAD NAUK, POLISH ACAD SCIENCES, INST METALL & MATER SCI PAS, 2012) GÜLLÜOĞLU, ARİF NİHAT; Kallek, M.; Ataoglu, S.; Yagci, Y.; Bozkurt, H. N.; Gulluoglu, A. N.In this study, brazing and laser welding were experimentally compared for 9, 14 and 18 carat gold alloys in different color. The gold alloys were joined by laser welding and brazing and the microstructure, hardness, chemical composition, color of the weld joints were investigated. According to study, in laser welding, voltage, pulse duration, pulse diameter and frequency are the most important welding parameters that influence the quality of joints. Welded joints are characterized using three geometric parameters: penetration depth, width of heat affected zone and underfill defects. Finally, optimum laser welding parameters of different color of 9, 14 and 18 carat gold alloys were determined. It is observed that laser welding has numerous advantages compared to the other joining techniques used in the jewelry industry.Publication Metadata only Temperature Dependent Mechanical Characterisation of Styrene-Acrylonitrile(RAPRA TECHNOLOGY LTD, 2009) GÜLLÜOĞLU, ARİF NİHAT; Solakoglu, Ilker; Ataoglu, Senol; Gulluoglu, Arif N.; Kadioglu, NeclaPoly(styrene-co-acrylonitrile) (SAN) which is a random, amorphous, linear copolymer produced by copolymerising styrene and acrylonitrile was investigated experimentally. Specimens were supplied from a private company and they were analysed using a differential scanning calorimetry machine (DSC). The behaviour of the material in creep, tension and hardness experiments was investigated experimentally at several temperatures. The creep response of SAN was also evaluated.Publication Metadata only Electrical and Thermal Studies on the Polyvinylchloride/Carbon Black Composites Induced by High Energy Ion Beam(TAYLOR & FRANCIS LTD, 2010) GÜLLÜOĞLU, ARİF NİHAT; Singh, Dolly; Singh, N. L.; Qureshi, Anjum; Gavade, Chaitali; Avasthi, D. K.; Gulluoglu, Arif N.; Phase, D. M.Modification induced by energetic ion in polyvinylchloride (PVC)/carbon black (CB) composites was studied using impedance gain-phase analyzer, differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Different concentrations of CB were dispersed in PVC films. These films were irradiated with 140 MeV Ag11+ ions at the fluences of 1 x 10(11) and 1 x 10(12)ions/cm(2). The ac electrical conductivity and dielectric response were studied as a function of filler, frequency and ion fluence. It was found that ac electrical conductivity increases with increasing the percentage of CB, frequency and ion fluence. The observed enhancement in ac electrical conductivity is attributed to the increase in the number of conduction paths created by the carbon black contents in the composites to give a higher electrical conductivity. An increase in dielectric constant was observed with the ion fluence and also with the carbon black content, which is attributed to the interfacial polarization of heterogeneous systems. Differential scanning calorimetry (DSC) analysis showed that the glass transition temperature (Tg) shifted towards lower temperature with increasing the ion fluence. It may be attributed to the scissioning of polymer chains and as a result increase of free radicals, unsaturation etc., which lead to the transformation of polymer into amorphous phase. Atomic force microscopy (AFM) studies revealed that the surface average roughness of the composites increases as filler concentration increases and decreases upon irradiation. SEM micrographs showed that carbon black particles organized into aggregates of micro spherical voids and decreased its size upon irradiation.