Browsing by Author "Ozturk, Abdullah"

Now showing 1 - 20 of 28

Citation - WoS: 10
Alkaline 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, Abdullah; Metallurgical and Materials Engineering; 06. School Of Engineering; 01. Atılım University
One-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.
Citation - WoS: 4
Citation - Scopus: 4
Bioactivity of Apatite-Wollastonite Glass-Ceramics Produced by Melting Casting
(World Scientific Publ Co Pte Ltd, 2013) Park, Jongee; Ozturk, Abdullah; Metallurgical and Materials Engineering; 06. School Of Engineering; 01. Atılım University
Glass-ceramics containing only apatite and wollastonite crystals were produced in the system MgO-CaO-SiO2-P2O5-F by the melt casting process. The bioactivity of the glass-ceramics was determined by immersing the glass-ceramics in a simulated body fluid (SBF) and by assessing the resulting apatite formation on the free surface after various immersion durations. A 12-mu m-thick apatite layer formed on the surface of the glass-ceramic containing only apatite crystals after 20 days immersion in SBF. However, the thickness of the apatite layer formed on the surface of the glass-ceramic containing apatite and wollastonite crystals was 1 mu m. Results have shown that the bioactivity of glass-ceramic depends strongly on the type of crystal(s) developed during the glass-ceramic process and their proportion in the glassy matrix.
Citation - WoS: 30
Citation - Scopus: 33
Boron and zirconium co-doped TiO₂ powders prepared through mechanical ball milling
(Elsevier Sci Ltd, 2013) Tokmakci, Tolga; Ozturk, Abdullah; Park, Jongee; Metallurgical and Materials Engineering; 06. School Of Engineering; 01. Atılım University
A titania photocatalyst co-doped with boron and zirconium was prepared by mechanical ball milling. The resulting powder was characterized by XRD, XPS, SEM, and EDS. The photocatalytic performance of the powder was evaluated by degradation of methylene blue (MB) solution under UV illumination. XRD patterns were refined by Rietveld analysis to obtain accurate lattice parameters and positions of the atoms in the crystal structure of the photocatalyst. XRD, XPS, and Rietveld analysis results indicated that mechanical ball milling successfully weaved the dopant elements into the crystal structure and distorted the lattice of TiO2. Also, SEM micrographs confirmed that mechanical ball milling led to a decrease in average particle size of the photocatalyst. Boron and zirconium co-doped TiO2 particles exhibited a better visible light response and photocatalytic activity than those of the mono-element doped TiO2 (i.e. B-TiO2 and Zr-TiO2) and undoped TiO2 particles. The enhanced photocatalytic activity is attributed to the synergistic effects of boron zirconium co-doping and particle size reduction. (C) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Citation - WoS: 13
Citation - Scopus: 14
Control of the Crystal Growth Shape in Ch₃nh_{3< Perovskite Materials}
(Amer Scientific Publishers, 2017) Le, Quyet Van; Shin, Jong Wook; Jung, Jin-Hee; Park, Jongee; Ozturk, Abdullah; Kim, Soo Young; Metallurgical and Materials Engineering; 06. School Of Engineering; 01. Atılım University
CH3NH3PbBr3 (MAPbBr(3)) materials with perovskite structure were grown by a two-step process using Pb(CH3COO)(2). 3H(2)O and methyl amine bromide (MABr). By changing the concentration of MABr in isopropyl alcohol (IPA) solvent and the annealing temperature, the shape of CH3NH3PbBr3 materials can be controlled to afford nanocubes, nanowires, nanorods, and wrinkled structures. MAPbBr3 with single cubic structure was obtained at a MABr concentration of 3 mg/mL in IPA, and a nanorod array of MAPbBr3 was realized at a MABr concentration of 9 mg/mL in IPA at room temperature. Uniformly wrinkled shapes were formed after the synthesis temperature was increased to 60 and 90 degrees C. The X-ray diffraction patterns, Fourier transform infrared spectra, and X-ray photoelectron spectra of CH3NH3PbBr3 nanorods confirmed that the pure perovskite phase was obtained by dipping Pb(CH3COO)(2). 3H(2)O in MABr/IPA solution. The optical bandgap of the CH3NH3PbBr3 nanorods was estimated from the Tauc plot as 2.2 eV. The evolution of perovskite shapes is expected to lead to improvements in the electrical properties and surface contact, which are important factors for realizing high-performance devices.
Citation - WoS: 8
Effect of H₂o Ratio on Photocatalytic Activity of Sol-Gel Tio₂ Powder
(Ice Publishing, 2013) Agartan, Lutfi; Kapusuz, Derya; Park, Jongee; Ozturk, Abdullah; Metallurgical and Materials Engineering; 06. School Of Engineering; 01. Atılım University
Effect of water/tetraethyl orthotitanate molar ratio (R) on the formation and morphology of sol-gel-derived titania powder has been studied. Solutions for R of 3 and 5 have been prepared. Initial viscosity of the solutions and viscosity of the gels prepared by aging the solutions for some time were measured. Results revealed that lower gel viscosities lead to better crystallization of the aerogel. Aerogels were dried at 80 degrees C for 24 h and then calcined at 300 degrees C for 1 h to obtain titania powders. The structural and morphological analyses of the powders were performed using X-ray diffraction and scanning electron microscopic characterization techniques. Titania particles obtained after calcination composed of only anatase phase and were in the size range of 9-50 nm. The photocatalytic activity of the powders was evaluated in terms of the degradation of methylene blue (MB) solution under UV (ultraviolet) illumination. A diffuse reflectance spectroscopy was used for the band gap energy measurements. Results revealed that R had a profound effect on the particle morphology and photocatalytic activity of sol-gel-derived titania powders. The titania powders prepared from the solution for R of 5 degraded 99.47% of MB solution under UV illumination in 90 min.
Citation - WoS: 30
Citation - Scopus: 36
Effect 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, Abdullah; Metallurgical and Materials Engineering; 06. School Of Engineering; 01. Atılım University
The 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.
Citation - WoS: 16
Citation - Scopus: 16
Effects of Fluorination and Thermal Shock on the Photocatalytic Activity of Bi₂o_{3< Nanopowders}
(Elsevier, 2021) Bouziani, Asmae; Park, Jongee; Ozturk, Abdullah; Metallurgical and Materials Engineering; 06. School Of Engineering; 01. Atılım University
Fluorinated Bi2O3 (F-Bi2O3) nanopowder was prepared via fluorination followed by thermal shock of alpha-Bi2O3 nanopowder. The XRD, FTIR, SEM, and DRS characterization techniques were employed to investigate the effects of fluorine (F) insertion into the alpha-Bi2O3 host and the thermal shock from different temperatures. The crystal structure, optical and photocatalytic properties of the F-Bi2O3 nanopowders prepared were researched. The XRD results confirmed the substitution of O2- with F-. The FTIR results revealed that the coordination of Bi atoms changed upon F- substitution. The incorporation of F into the alpha-Bi2O3 host and thermal shock did not influence the morphology but modified the band structure of alpha-Bi2O3, leading to a red-shift in the optical absorption edge. Also, the bandgap narrowed from 2.8 eV to 2.6 eV. The density functional theory calculation proved that the F 2p orbitals were positioned in the valence band (VB), resulting in broader and more spread bands for F-Bi2O3. The results suggested that the photoexcited charge carrier mobility in the valence band (VB) and conduction band (CB) are enhanced upon F insertion into alpha-Bi2O3. The photocatalytic efficiency of the synthesized nanopowders was assessed by the degradation of Bromocresol Green (BG) under visible light illumination. Photocatalytic activity improved upon fluorination. The F-Bi2O3 nanopowders thermally shocked from higher temperatures showed negligible photocatalytic performance. The best photocatalytic performance of 70% BG degradation was realized after 180 min visible irradiation for the F-Bi2O3 nanopowder thermal shocked from 500 degrees C.
Effects of Graphene Transfer and Thermal Annealing on Anticorrosive Properties of Stainless Steel
(Amer Scientific Publishers, 2017) Oh, Jeong Hyeon; Han, Sangmok; Kim, Tae-Yoon; Park, Jongee; Ozturk, Abdullah; Kim, Soo Young; Metallurgical and Materials Engineering; 06. School Of Engineering; 01. Atılım University
Stainless steel (STS) films were annealed in a thermal quartz tube and covered with graphene to improve their anticorrosive properties. Graphene was synthesized via the chemical vapor deposition method and transferred onto the surface of the STS film by the layer-by-layer approach. The structure of the STS film changed from alpha-Fe to gamma-Fe after annealing at 700 C for 1 h, resulting in an increase of 82.72% in the inhibition efficiency. However, one-layer graphene acted as a conductive pathway and therefore deteriorated the anticorrosive properties of the STS film. To overcome this problem, graphene was transferred layer by layer onto the STS film. It was found that transfer of three layers of graphene onto the STS film resulted in a 91.57% increase in the inhibition efficiency. Therefore, thermal annealing and transfer of multilayer graphene are considered to be effective in enhancing the anticorrosive properties of STS films.
Citation - WoS: 11
Citation - Scopus: 9
Enhanced Bioactivity and Low Temperature Degradation Resistance of Yttria Stabilized Zirconia/Clay Composites for Dental Applications
(Elsevier Sci Ltd, 2022) Tufan, Yigithan; Park, Jongee; Ozturk, Abdullah; Ercan, Batur; Metallurgical and Materials Engineering; 06. School Of Engineering; 01. Atılım University
Yttria stabilized zirconia (YSZ)/clay composites were produced to improve osseointegration and undesired tetragonal-to-monoclinic phase transformation (low temperature degradation, LTD) of YSZ ceramics so that long-term clinical success of YSZ implants is achieved. Various amounts (0.5,1,2, and 4 wt%) of clay was incorporated to YSZ. Predetermined amounts of clay and YSZ were mixed and pressed uniaxially at 15 MPa into compacts that were subsequently pressureless sintered at 1450 degrees C. Density, compressive strength, hardness and indentation crack resistance of 4 wt% clay incorporated YSZ/clay composite were 5.77 +/- 0.01 g/cm3, 1188 +/- 121 MPa, 1223 +/- 9 HV, and 4.4 +/- 0.1 MPa root m, respectively. Additionally, biological properties of YSZ/clay composites were assessed in vitro using bone cells. Incorporation of 4 wt% clay significantly enhanced bone cell prolifer-ation, spreading, and functions. Moreover, a significant increase in the LTD resistance of YSZ was achieved upon 4 wt% clay incorporation. The findings collectively suggest that YSZ/clay composites have a potential to be used as an alternative material for dental applications.
Citation - WoS: 21
Citation - Scopus: 24
Facile synthesis of CsPbBr₃/PbSe composite clusters
(Taylor & Francis Ltd, 2018) Thang Phan Nguyen; Ozturk, Abdullah; Park, Jongee; Sohn, Woonbae; Tae Hyung Lee; Jang, Ho Won; Kim, Soo Young; Metallurgical and Materials Engineering; 06. School Of Engineering; 01. Atılım University
In this work, CsPbBr3 and PbSe nanocomposites were synthesized to protect perovskite material from self-enlargement during reaction. UV absorption and photoluminescence (PL) spectra indicate that the addition of Se into CsPbBr3 quantum dots modified the electronic structure of CsPbBr3, increasing the band gap from 2.38 to 2.48 eV as the Cs:Se ratio increased to 1:3. Thus, the emission color of CsPbBr3 perovskite quantum dots was modified from green to blue by increasing the Se ratio in composites. According to X-ray diffraction patterns, the structure of CsPbBr3 quantum dots changed from cubic to orthorhombic due to the introduction of PbSe at the surface. Transmission electron microscopy and X-ray photoemission spectroscopy confirmed that the atomic distribution in CsPbBr3/PbSe composite clusters is uniform and the composite materials were well formed. The PL intensity of a CsPbBr3/PbSe sample with a 1:1 Cs: Se ratio maintained 50% of its initial intensity after keeping the sample for 81 h in air, while the PL intensity of CsPbBr3 reduced to 20% of its initial intensity. Therefore, it is considered that low amounts of Se could improve the stability of CsPbBr3 quantum dots.
Citation - WoS: 3
Citation - Scopus: 4
Friction and Wear Behavior of Selected Dental Ceramics
(World Scientific Publ Co Pte Ltd, 2009) Park, Jongee; Pekkan, Gurel; Ozturk, Abdullah; Metallurgical and Materials Engineering; 06. School Of Engineering; 01. Atılım University
The purpose of this study was to determine the friction coefficients and wear rates of six commercially available dental ceramics including IPS Empress 2 (E2), Cergo Pressable Ceramic (CPC), Cercon Ceram (CCS) and Super porcelain EX-3 (SPE). Bovine enamel (BE) was also tested as a reference material for comparison purposes. Samples of the dental ceramics were prepared according to the instructions described by the manufacturers in disk-shape with nominal dimensions of 12 mm x 2 mm. The wear tests were performed by means of a pin-on-disk type tribometer. The friction coefficients and specific wear rates of the materials were determined at a load of 10 N and rotating speed of 0.25 cm/s without lubrication. Surface morphology of the wear tracks was examined using a scanning electron microscope. Statistical analyses were made using one-way ANOVA and Turkey's HSD (P < 0.05).
Citation - WoS: 28
Citation - Scopus: 27
Hydrothermal Synthesis of 3d Tio₂ Nanostructures Using Nitric Acid: Characterization and Evolution Mechanism
(Elsevier Sci Ltd, 2016) Erdogan, Nursev; Ozturk, Abdullah; Park, Jongee; Metallurgical and Materials Engineering; 06. School Of Engineering; 01. Atılım University
Various 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.
Citation - WoS: 4
Citation - Scopus: 4
In Vitro Evaluation of Tooth-Colored Yttria Stabilized Zirconia Ceramics
(Taylor & Francis Ltd, 2021) Akarsu, Melis Kaplan; Basar, Ahmet Ozan; Sasmazel, Hilal Turkoglu; Park, Jongee; Ozturk, Abdullah; Metallurgical and Materials Engineering; 06. School Of Engineering; 01. Atılım University
Effects of MoCl3 and NiCl2, originally incorporated as coloring agent, on the cellular response of 3 mol% yttria stabilized zirconia (3Y-TZP) ceramics was investigated. MoCl3 and NiCl2-MoCl3 incorporated, tooth-colored 3Y-TZP ceramics were produced through cold isostatic pressing at 100 MPa followed by pressureless sintering at 1450 degrees C for 2 h. Aging was performed on the sintered ceramics using distilled water in a reactor at 134 degrees C at 2.3 bar pressure for 2 h. The phases developed during different stages of processing were identified by X-ray diffraction (XRD) analysis. In vitro cell culture studies were carried out using L929 fibroblast cell line. The cell viability and proliferation studies revealed that none of the specimens showed cytotoxicity with respect to coloring. Confocal laser scanning microscope (CLSM) analyses suggested that all of the specimens exhibited good in vitro cytocompatibility. Enhancement in cell attachment, adhesion, and proliferation was observed in all specimens via scanning electron microscope (SEM) analysis. Although the coloring process did not improve the proliferation performance of the aged specimens, the incorporation of transition metals enhanced the in vitro performance of 3Y-TZP ceramics.
Citation - WoS: 2
Citation - Scopus: 4
Influence of Boron And/Or Zirconium Doping on Morphology and Optical Properties of Titania
(Tanger Ltd, 2011) Kapusuz, Derya; Park, Jongee; Ozturk, Abdullah; Metallurgical and Materials Engineering; Metallurgical and Materials Engineering; 06. School Of Engineering; 01. Atılım University
Sol-gel derived B (boron) and Zr (zirconium) doped TiO2 (Titania) nanoparticles were synthesized. Microstructural, photocatalytic and crystallographic properties of the doped particles were investigated. Highest photocatalytic activity was achieved by 10 wt% Zr doping. 5 wt% doping was the optimum value for effective B doping. B ions were found to form oxygen vacancies behaving as interstitial defects whereas Zr ions substituted Ti4+ ions in the lattice.
Citation - WoS: 20
Citation - Scopus: 23
Mechanical and Biological Properties of Al₂o_{3< and Tio₂ Co-Doped Zirconia Ceramics}
(Elsevier Sci Ltd, 2017) Agac, Ozlem; Gozutok, Melike; Sasmazel, Hilal Turkoglu; Ozturk, Abdullah; Park, Jongee; Metallurgical and Materials Engineering; 06. School Of Engineering; 01. Atılım University
Various amounts (ranging from 0 to 2 wt%) of TiO2 and Al2O3 were mono and co-doped to tetragonal zirconia ceramic containing 3 mol% yttria (3Y-TZP) by mechanical ball milling. Powders were compacted by uniaxial pressing at a pressure of 23 MPa. The compacts were pressureless sintered at 1450 degrees C for 2 h. Density, hardness, fracture toughness, and cell attachment of the co-doped 3Y-TZP ceramics were measured with respect to dopant addition to determine the effects of the kind and amount of dopants on the properties. The results show that density decreased gradually as the amount of dopant was increased. The mechanical properties showed the maximum value when 0.5 wt% TiO2 and 1.0 wt% Al2O3 were co-doped to 3Y-TZP. Crystalline phase formation and microstructural morphology were investigated by XRD and SEM analyses to explain the variations in the properties. Co-doping of TiO2 and Al2O3 to 3Y-TZP did not have an influence on the phases present, but decreased the grain size. The co-doping also affected the cell attachment and the growth on the surface of the zirconia ceramics.
Citation - WoS: 39
Citation - Scopus: 37
MoS₂-nanosheet/graphene-oxide composite hole injection layer in organic light-emitting diodes
(Korean inst Metals Materials, 2017) Park, Minjoon; Thang Phan Nguyen; Choi, Kyoung Soon; Park, Jongee; Ozturk, Abdullah; Kim, Soo Young; Metallurgical and Materials Engineering; 06. School Of Engineering; 01. Atılım University
In this work, composite layers comprising two-dimensional MoS2 and graphene oxide (GO) were employed as hole injection layers (HILs) in organic light-emitting diodes (OLEDs). MoS2 was fabricated by the butyllithium (BuLi) intercalation method, while GO was synthesized by a modified Hummers method. The X-ray diffraction patterns showed that the intensity of the MoS2 (002) peak at 14.15A degrees decreased with increase in GO content; the GO (001) peak was observed at 10.07A degrees. In the C 1s synchrotron radiation photoemission spectra, the contributions of the C-O, C=O, and O-C=O components increased with increase in GO content. These results indicated that GO was well mixed with MoS2. The lateral size of MoS2 spanned from a few hundreds of nanometers to 1 mu m, while the size of GO was between 400 nm and a few micrometers. Thus, the coverage of the MoS2-GO composite on the ITO surface improved as the GO content increased, owing to the large particle size of GO. Notably, GO with large size could fully cover the indium tin oxide film surface, thus, lowering the roughness. The highest maximum power efficiency (PEmax) was exhibited by the OLED with MoS2-GO 6:4 composite HIL, indicating that similar contents of MoS2 and GO in MoS2-GO composites provide the best results. The OLED with GO HIL showed very high PEmax (4.94 lm W-1) because of very high surface coverage and high work function of GO. These results indicate that the MoS2-GO composites can be used to fabricate HILs in OLEDs.
Citation - WoS: 38
Citation - Scopus: 49
Preparation and Photocatalytic Activity of G-c₃n_{4< Heterojunctions Under Solar Light Illumination}
(Elsevier Sci Ltd, 2020) Gundogmus, Pelin; Park, Jongee; Ozturk, Abdullah; Metallurgical and Materials Engineering; 06. School Of Engineering; 01. Atılım University
The 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.
Citation - WoS: 24
Citation - Scopus: 26
Production and Properties of Tooth-Colored Yttria Stabilized Zirconia Ceramics for Dental Applications
(Elsevier Sci Ltd, 2018) Kaplan, Melis; Park, Jongee; Kim, Soo Young; Ozturk, Abdullah; Metallurgical and Materials Engineering; 06. School Of Engineering; 01. Atılım University
Dense zirconia stabilized with 3 mol% yttria ceramics were produced in disc shape by first cold isostatically pressing at 100 MPa and then sintering at 1450 degrees C at ambient laboratory conditions. Coloring was accomplished by immersion the discs in NiCl2, MoCl3, and NiCl2 + MoCl3 solutions for 5, 30, and 60 s. Different concentrations (0.1, 0.25, and 0.5 wt%) were applied to get the color of natural tooth. The density, color, microhardness, fracture toughness, compressive strength, and wear rate of the discs were measured to evaluate the suitability of the colored discs for dental applications. Color assessments were made by measuring CIE Lab L*, a*, b, and Delta E* values. Low temperature degradation of the samples was evaluated by aging sensitivity tests in autoclave for 2, 4, and 6 h. Results have shown that color produced depends on the kind and concentration of the colorant solution while time of immersion has no significant effect on coloring process. Coloring solutions containing 0.1 and 0.25 wt% MoCl3 provided clinically acceptable color with the Delta E* value ranging from 5.16 to 6.42 for dental applications.
Citation - WoS: 1
PRODUCTION OF SILVER LOADED PHOTOCATALYTIC TIO₂ POWDERS BY BALL MILLING
(Tanger Ltd, 2011) Aysin, Basak; Park, Jongee; Ozturk, Abdullah; Metallurgical and Materials Engineering; 06. School Of Engineering; 01. Atılım University
The present study was undertaken to improve photocatalytic efficiency of TiO2 powder by silver doping and/or particle size reduction through mechanical ball milling. A planetary ball mill was employed to reduce the particle size of TiO2 powders to nanoscale and silver loading to TiO2 powders. Silver nitrate was used as silver source to obtain about 1% Ag load. Slurry taken from ball mill was separated by centrifugal separator into nano and micro sols. Separated nanosol was taken into the furnace to be dried at 103 degrees C and calcined at 400 degrees C for 1 hour to assist silver loading. X-Ray powder diffraction (XRD) was employed to identify the crystalline phases present in the powders produced. XRD results revealed that doped TiO2 powders were consisted of only anatase phase of TiO2. Changes in lattice parameters of TiO2 structure after doping were determined also by XRD. Scanning Electron Microscope (SEM) and particle size analyzer were used for examining the size reduction effect of ball milling process. Photocatalytic performance of the powders was evaluated by Methylene Orange (MO) test under UV light illumination using UV-Spectrophotometer.
Citation - WoS: 44
Citation - Scopus: 43
Silver-Loaded Tio₂ Powders Prepared Through Mechanical Ball Milling
(Elsevier Sci Ltd, 2013) Aysin, Basak; Ozturk, Abdullah; Park, Jongee; Metallurgical and Materials Engineering; 06. School Of Engineering; 01. Atılım University
Silver (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.