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Conference Object Citation - Scopus: 1Enhancing Sustainable Machining of Inconel 718 Using Multi-Walled Carbon Nanotubes and TiO2based Nanofluid Minimum Quantity Lubrication(Elsevier B.V., 2025) Namlu, Ramazan Hakkı; Kaftanoĝlu, BılgınInconel 718 is extensively utilized especially in the aerospace sector due to its outstanding resistance to creep and corrosion, along with its capability to maintain strength at high temperatures. However, its high work hardening rate and low thermal conductivity present significant challenges in machining processes, including the need for extensive use of coolants, shortened tool life, and the necessity for post-processing operations for adequate surface quality, all of which hinder sustainable manufacturing. To address these issues, an innovative cooling/lubrication method, Nanofluid Minimum Quantity Lubrication (NMQL), aims to enhance the sustainable machining of Inconel 718 by minimizing these problems. NMQL involves the aerosolized delivery of nanoparticle-enriched nanofluid oil with compressed air to the cutting zone. In this way, NMQL utilizes the nanoparticles' cooling and lubrication abilities, resulting in lower cutting forces, reduced surface roughness, and decreased tool wear compared to other cooling/lubrication conditions, thereby improving machining performance. This study compares the performance of NMQL in terms of cutting forces, surface roughness and topography, and subsurface microhardness, using Multi-Walled Carbon Nanotubes (MWCNT) and TiO2nanoparticles, with Conventional Cutting Fluids (CCF), aiming to achieve more sustainable machining of Inconel 718. Also, a sustainability assessment was done using Pugh Matrix Approach in order to find the most sustainable cooling option. © 2025 Elsevier B.V., All rights reserved.Article Citation - WoS: 42Citation - Scopus: 53Preparation and Photocatalytic Activity of G-c3n4< Heterojunctions Under Solar Light Illumination(Elsevier Sci Ltd, 2020) Gundogmus, Pelin; Park, Jongee; Ozturk, AbdullahThe solar light sensitive g-C3N4/TiO2 heterojunction photocatalysts containing 20, 50, 80, and 90 wt% graphitic carbon nitride (g-C3N4) were prepared by growing Titania (TiO2) nanoparticles on the surfaces of g-C3N4 particles via one step hydrothermal process. The hydrothermal reactions were allowed to take place at 110 degrees C at autogenous pressure for 1 h. Raman spectroscopy analyses confirmed that an interface developed between the surfaces of TiO2 and g-C3N4 nanoparticles. The photocatalyst containing 80 wt% g-C3N4 was subsequently heat treated 1 h at temperatures between 350 and 500 degrees C to improve the photocatalytic efficiency. Structural and optical properties of the prepared g-C3N4/TiO2 heterojunction nanocomposites were compared with those of the pristine TiO2 and pristine g-C(3)N(4 )powders. Photocatalytic activity of all the nanocomposites and the pristine TiO2 andg-C3N4 powders were assessed by the Methylene Blue (MB) degradation test under solar light illumination. g-C3N4/TiO2 heterojunction photocatalysts exhibited better photocatalytic activity for the degradation of MB than both pristine TiO2 and g-C3N4. The photocatalytic efficiency of the g-C3N4/TiO2 heterojunction photocatalyst heat treated at 400 degrees C for 1 his 1.45 times better than that of the pristine TiO2 powder, 2.20 times better than that of the pristine g-C3N4 powder, and 1.24 times better than that of the commercially available TiO2 powder (Degussa P25). The improvement in photocatalytic efficiency was related to i) the generation of reactive oxidation species induced by photogenerated electrons, ii) the reduced recombination rate for electron-hole pairs, and iii) large specific surface area.Article Citation - WoS: 44Citation - Scopus: 43Silver-Loaded Tio2 Powders Prepared Through Mechanical Ball Milling(Elsevier Sci Ltd, 2013) Aysin, Basak; Ozturk, Abdullah; Park, JongeeSilver (Ag) was loaded on TiO2 powders through mechanical ball milling. Ag-loading was accomplished by adding 4.6, 9.2, and 13.8 ml of AgNO3 solution to the TiO2 powders during the milling process. The resulting powder was characterized by XRD, XPS, SEM, and EDS. The photocatalytic activity of the silver-loaded powder was evaluated in terms of the degradation of methyl orange (MO) solution under ultraviolet (UV) illumination. XRD patterns were refined using the Rietveld analysis to determine the lattice parameters. XRD analysis suggested that Ag was loaded on TiO2 powders in the form of AgO. X-ray photoelectron spectroscopy and Rietveld analysis revealed that silver did not dope into the crystal structure of TiO2. SEM investigations confirmed that ball milling caused a decrease in the average particle size of the powders. Silver-loading improved the photocatalytic activity of the TiO2 powders. The TiO2 powder ball milled without Ag-loading degraded 46% of the MO solution whereas the ball milled with 13.8 ml AgNO3 solution degraded 96% of the MO solution under 1 h UV irradiation. Moreover, TiO2 powders gained antibacterial property after Ag-loading. (c) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved.Article Citation - WoS: 10Alkaline Hydrothermal Synthesis, Characterization, and Photocatalytic Activity of Tio2 Nanostructures: the Effect of Initial Tio2 Phase(Amer Scientific Publishers, 2019) Erdogan, Nursev; Park, Jongee; Choi, Woohyuk; Kim, Soo Young; Ozturk, AbdullahOne-dimensional (1D) titanate nanostructures were synthesized by hydrothermal route, using commercially available TiO2 (P25) and anatase powders as precursor materials and strong NaOH solution as catalyzer. The prepared titanates were calcined, followed by protonation to produce TiO2 nanostructures having enhanced photocatalytic and photovoltaic properties. The synthesized TiO2 1D nanostructures were characterized using field-emission scanning electron microscope, high-resolution electron microscope, X-ray diffraction analysis, and UV-Vis photospectroscopy to understand the effect of initial TiO2 phase on morphological and crystallographic features, and bandgap. Methylene blue degradation test was applied to evaluate the photoactivity of the products obtained after different stages of the process. The findings indicate that 1D TiO2 nanostructures form by different mechanisms from dissolved aggregates during hydrothermal process, depending on the crystal structure of the initial precursor used. Photocatalytic test results reveal that protonated titanates have considerable adsorption capability, while photocatalytic degradation depends on TiO2 transformation.Article Citation - WoS: 31Citation - Scopus: 37Effect of Initial Water Content and Calcination Temperature on Photocatalytic Properties of Tio2 Nanopowders Synthesized by the Sol-Gel Process(Elsevier Sci Ltd, 2015) Agartan, Lutfi; Kapusuz, Derya; Park, Jongee; Ozturk, AbdullahThe effects of initial water content and calcination temperature on sol gel synthesized TiO2 powders were studied. Mother solutions had water/Ti-precursor mole ratios (R ratio) of 1, 5, 10, and 50. Dried aerogels were calcined for 3 h at temperatures of 300, 400, and 500 degrees C to obtain crystallized TiO2 nanopowders in the range of 15-30 nm. PE-scanning electron microscopy and X-ray diffraction techniques were employed to investigate the morphological and structural properties of the nanopowders synthesized. Profound effect of gel viscosity was observed on the formation mechanism and extent of crystallinity in the powders. Methylene blue degradation test results suggest, photocatalytic performance is enhanced as initial water content and calcination temperature increased. Band-gap energy of the powders ranged from 3.09 to 3.27 eV. Overall, this study shows that initial water content and calcination regime have a profound effect on the phase assembly, crystallite size, band-gap energy, and photocatalytic performance of sol gel synthesized TiO2 nanopowders. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.Article Citation - WoS: 10Citation - Scopus: 7Fabrication and Characterization of Tio2 Thin Film for Device Applications(World Scientific Publ Co Pte Ltd, 2019) Hosseini, A.; Gullu, H. H.; Coskun, E.; Parlak, M.; Ercelebi, C.Titanium oxide (TiO2) film was deposited by rectification factor (RF) magnetron sputtering technique on glass substrates and p-Si (111) wafers to fabricate n-TiO2/p-Si heterojunction devices for the investigation of material and device properties, respectively. The structural, surface morphology, optical and electrical properties of TiO(2 )film were characterized by means of scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), UV-visual (UV-Vis) spectral and dark current-voltage (I-V) measurement analyses. The deposited film layer was found to be homogeneous structure with crack-free surface. The bandgap value of TiO2 film was determined as 3.6 eV and transmission was around 65-85% in the spectral range of 320-1100 nm. The conductivity type of the deposited film was determined as n-type by hot probe method. These values make TiO2 film a suitable candidate as the n-type window layer in possible diode applications. TiO2 film was also deposited on p-Si (111) wafer to obtain Al/n-TiO2/p-Si/Al heterojunction device structure. The dark I-V characteristic was studied to determine the possible conduction mechanisms and diode parameters.Article Citation - WoS: 8Citation - Scopus: 9Temperature-Dependent Optical Properties of Tio2 Nanoparticles: a Study of Band Gap Evolution(Springer, 2023) Isik, Mehmet; Delice, Serdar; Gasanly, NizamiIn this study, we present the first comprehensive investigation of the temperature-dependent band gap energy of anatase TiO2 nanoparticles, utilizing transmission measurements in the range of 10-300 K. X-ray diffraction pattern exhibited nine peaks related to tetragonal crystal structure. Scanning electron microscope image showed that the nanoparticles with the dimensions of 25-50 nm were found as micrometer sized agglomerated. When the spectrum obtained as a result of the transmission measurements was analyzed, it was seen that the band gap energy decreased from 3.29(5) to 3.26(6) eV as the temperature was increased from 10 to 300 K. Temperature-band gap dependence was analyzed using Varshni and O'Donnell-Chen optical models and optical parameters of the TiO2 nanoparticles like absolute zero band gap energy, rate of change of band gap with temperature and average phonon energy were reported.Article Citation - WoS: 28Citation - Scopus: 27Hydrothermal Synthesis of 3d Tio2 Nanostructures Using Nitric Acid: Characterization and Evolution Mechanism(Elsevier Sci Ltd, 2016) Erdogan, Nursev; Ozturk, Abdullah; Park, JongeeVarious morphologies of TiO2 nanostructures were synthesized by HNO3 assisted hydrothermal treatment with respect to the acid molarity (1 M, 3 M, and 8 M), temperature (110, 140, and 180 degrees C), and time (1, 3, and 6 h). An additional sample was synthesized inside the protonated titanate nanoribbon coated vessel with the acid molarity of 8M at 140 degrees C for 3 h. The crystal structure and morphology of the nanostructures synthesized were investigated using X-Ray diffractometer, scanning electron microscope, and transmission electron microscope. The results revealed that lower acid concentrations, longer synthesis durations and higher temperatures favored anatase phase formation. Meanwhile, a phase pure 3D lotus structure ruffle TiO2 could be obtained by hydrothermal synthesis at 8M HNO3 concentration at 140 degrees C for 3 h using protonated Htitanate nanoribbons. A probable mechanism for the evolution of 3D ruffle lotus structure was highlighted. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.Article Citation - WoS: 18Citation - Scopus: 19Synthesis and Enhanced Photocatalytic Activity of Molybdenum, Iron, and Nitrogen Triple-Doped Titania Nanopowders(Elsevier Sci Ltd, 2016) Erdogan, Nursev; Park, Jongee; Ozturk, AbdullahA novel Mo, Fe, and N triple-doped rutile TiO2 nanopowder was synthesized with simple HNO3 assisted hydrothermal treatment. Powders synthesized were characterized by using x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), inductively coupled plasma mass spectrometry (ICP-MS), scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), and Brunauer-Emmett-Teller (BET) surface area analysis techniques. Mo doping initiated the formation of a structure composed of a mixture of anatase and rutile with some modifications in morphology; but Mo, Fe, and N triple-doped titania powders are composed of entirely rutile structures. XPS analysis confirmed that Mo dissolved in the structure, replacing Ti atoms and forming some MoO3 partially crystallized nano regions on the surface. Existence of Fe in the TiO2 crystal lattice was confirmed by ICP analysis. Fe doping had an influence on the crystal structure and morphology. N was found to be dissolved in the co-doped structure by HNO3 catalyzer autogenously. Methylene blue degradation testing and band gap measurements were performed by using UV-vis photospectroscopy and diffuse reflector apparatus in order to evaluate the photocatalytic performance of the powders. Dopant elements decreased band gap energy steadily. An enhanced photoactivity was reached by Mo, Fe, and N triple-doping as compared with that of undoped, and mono doped TiO2 powders under UV-light irradiation. Possible reasons for the enhancement in photocatalytic activity are outlined. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
