Profile URL: https://hdl.handle.net/20.500.13091/11553
Job Title:Prof. Dr.
Email Address:oayildirim@ktun.edu.tr
Main Affiliation:02.11. Department of Metallurgical and Materials Engineering
Status: Current Staff
ORCID:
0000-0001-7867-7992
0000-0001-7867-7992Scopus ID:
56826023800
56826023800YÖK Akademik: B07255BDCD9B239D
Google Scholar:
y6ZruccAAAAJ
y6ZruccAAAAJWeb of Science ID:
HKN-3081-2023
HKN-3081-2023Name Variants:
Altintaş, Yıldırım, O. Yıldırım, Özlem Altıntaş
22 results
Scholarly Output Search Results
Now showing 1 - 10 of 22
Article Synthesis of Ag-Doped Zno Nanofibers Using Electrospinning Method and Their Photocatalytic Activities(2018) Yıldırım, Özlem AltıntaşSilver (Ag) doped zinc oxide (ZnO) nanofibers with 1 at.% and 3 at.% Ag content were prepared using the electrospinning technique and their structural, morphological and photocatalytic properties were investigated. Pure ZnO nanofibers were also prepared with the same procedure for structure and property related comparison purposes. The photocatalytic activity of the Ag doped ZnO nanofibers were determined as a function of Ag content by exploring the degradation behavior of methylene blue under UV light irradiation. It was found that photocatalytic ability of fibers was improved with Ag addition and higher Ag incorporation resulted higher methylene blue degradation rate. For pure ZnO fibers, the degraded amount of dye was 52% of its initial amount after 270 min of UV irradiation time. For the same irridation time, 60% and 67% decomposition ratios of the dye molecules were achieved with the fibers containing 1 at.% Ag and 3 at.% Ag, respectively. The origin of the improvement of photocatalytic activity in Ag doped ZnO nanofibers was attributed to the substitutional incorporation of Ag ions into Zn sites within the ZnO crystal. The substitutional incorporation has been proved with the positional shift of the XRD diffraction lines.Article Structural, Wear and Corrosion Properties of Nitrided, PVD and Electroless Ni-B Coated EN-GJS-700-2 Cast Iron(Springer, 2026) Yildirim, Mehmet; Ünalsan, Emre; Yildirim, Ozlem Altintas; Altintas Yildirim, Ozlem; Bayatlı, AleynaThe structural properties, surface hardness, wear and corrosion behaviors of plasma- and gas-nitrided, PVD TiN coated and electroless Ni-B coated EN-GJS-700-2 (GGG-70) grade ductile cast iron (DI) were investigated in detail. The structural properties were examined with an optical microscope, a scanning electron microscope and x-ray diffraction. The surface hardness was tested with Vickers microhardness tests; the wear behavior was investigated by ball-on-flat linear reciprocating abrasion/friction tests and the corrosion behavior was studied by electrochemical tests. The 1.95 & micro;m PVD TiN coating had the hardest surface hardness with 2782 HV0.001 value. All nitrided and coated specimens exhibited better wear and corrosion resistance than the DI-substrate. The PVD TiN coating demonstrated the best wear resistance with the lowest wear loss (0.231x10(-3) mm(3)) and the lowest friction coefficient value (0.16). Corrosion tests revealed that electroless Ni-B-coated specimens (0.002 mm/year corrosion rate) and nitrided specimens (0.002 mm/year for plasma- and 0.076 mm/year corrosion rate for gas-nitrided) showed excellent corrosion resistance, while the PVD TiN-coated specimen (0.673 mm/year corrosion rate) showed moderate corrosion protection0020.Article Citation - WoS: 7Citation - Scopus: 11Efficient Vapor-Liquid Synthesis of Copper Doped Zinc Oxide (cu:zno) Nanonails With Highly Homogeneous Dopant Distribution(ELSEVIER SCI LTD, 2019-10-01) Altıntaş Yıldırım, Özlem; Yildirim, Ozlem AltintasCopper doped zinc oxide (Cu:ZnO) nanonails with uniformly distributed Cu ions through the nail structure were synthesized via a vapor-liquid-solid technique using seed Cu:ZnO nanoparticles. The seed nanoparticles were prepared with a simple precipitation method. The structure and morphology of nanonails and the distribution of Cu ions were investigated using X-ray diffraction, electron energy loss spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and elemental mapping analysis. The defect states in the Cu:ZnO nanonails were characterized by room temperature photoluminescence (PL) spectra. The obtained Cu:ZnO nanonails have single phase wurtzite structure of ZnO and incorporated copper ions are in the Cu2+ oxidation state. SEM and TEM micrographs revealed that nanostructures with well-defined nail morphology composed of a hexagonal cap (similar to 350 nm in diameter) and a prismatic shaft (similar to 550 nm in diameter) connected with cylindrical neck (similar to 250 nm in diameter). Both SEM and TEM elemental mapping analysis proved that the usage of Cu:ZnO seed nanoparticles resulted in highly homogeneous distribution of Cu ions into ZnO nanonails. High crystallinity of the Cu:ZnO nanonails was revealed with PL spectra composed of predominant second order diffraction peak and near band edge of UV emission peak and also weak defect related deep level green and violent emission peaks.Review Citation - WoS: 23Detrimental Effects of Commonly Used Textile Dyes on the Aquatic Environment and Human Health - a Review(Parlar Scientific Publications (P S P), 2022) Yıldırım, Özlem Altıntaş; Bahadır, Mufit; Pehlivan, ErolProperties and hazards of various dye and pigment families used during textile manufacturing (like yarns, cloths, nonwovens, outerwear, cashmere and rugs) are already reported in the literature. Synthetic organic dyes are currently known as water pollutants. Such dyes are widely used in a variety of industries, including textiles, tanning, cosmetics, and food stuff, as well as in human and veterinary healthcare. They are classified as reactive, dispersed, indigo, azo, sulphur, and basic dyes. They are found in liquid wastes from textile washing and pose a serious risk to the receiving water environment's quality, if not purified. Because of their widespread use and large-scale production, various synthetic dyes have found their way into various parts of the water and soil ecosystems. In fact, because these dyes and pigments are not biodegradable, their presence can cause drastic changes in the ecological conditions of aquatic animals and plants. This will have a negative impact on the aquatic environment's stability, resulting in serious and significant damages (algal blooms, oxygen depletion, colour, turbidity and bad smells), long-term dangers (persistence, bioaccumulation of cancer-causing aromatic products, and emergence of chlorination side products), and carcinogenic and teratogenic effects. This overview picks up scientific information on possible application fields, toxic effects, sources, environmental presence and the eventual demise of synthetic organic dyes, as well as the ecological effects of synthetic natural dyes existence in the general environment.Article Citation - WoS: 49Citation - Scopus: 54Highly Efficient Photocatalytic Activity of Stable Manganese-Doped Zinc Oxide (mn:zno) Nanofibers Via Electrospinning Method(ELSEVIER SCI LTD, 2019-11-01) Baylan, Elif; Altıntaş Yıldırım, Özlem; Yildirim, Ozlem AltintasManganese-doped zinc oxide (Mn:ZnO) nanofibers were synthesized using the electrospinning process. Structural, chemical, morphological and optical properties of the nanofibers were characterized and compared with undoped ZnO nanofibers. To investigate photocatalytic activity of nanofibers under the both UV and visible light, methylene blue (MB) was used as a representative dye pollutant. It was found that substitutional incorporation of Mn2+ and Mn4+ ions in ZnO resulted in the generation of additional energy levels within the band gap of ZnO. Furthermore, higher manganese incorporation resulted in smaller-sized Mn:ZnO nanoparticles with highly concave-convex structures, and consequently, an increase in surface area. Substitutional incorporation of the dopant ions and the resulting morphological variations provide better photocatalytic efficiency due to formation of a greater number of charge carriers and the corresponding delay in the recombination process. Among the studied dopant content, 0.5 at.% Mn:ZnO fibers was determined as the optimal composition and the degradation of MB can reach about similar to 100% after 90 min. UV light and similar to 35% after 100 min visible light illumination. The doped fibers displayed high stability and durability in the degradation tests, even after ten cycles. Mn:ZnO nanofibers are thus good candidate materials for photocatalytic applications with superior efficiencies and highly reusable properties.Other Effect of Lanthanum Doping on Structural, Optical, and Photocatalytic Properties of YVO4(2023) Yıldırım, Özlem Altıntaş; Öztürk, Teoman; Gül, Mert; Karacaoğlu, ErkulAbstract Yttrium vanadate (YVO 4 ) based undoped and La 3+ -doped powders were prepared through a solid-state reaction method. The structural characterization carried out with XRD indicating that the samples are crystalline tetragonal type crystal structure of YVO 4 . XRD of the YVO 4 : La 3+ powder contain same YVO 4 diffraction lines and no other lanthanum related impurity and/or secondary phases were detected. Both undoped and La 3+ -doped YVO 4 samples show combined white light emission peaks appeared at 478, 571 and 613 nm. The higher intensity of peaks located at 478 and 571 nm in YVO 4 : La 3+ sample can be attributed to O 2− -La 3+ and O 2− -V 5+ charge transfer mechanisms. Besides, photocatalytic activities of the undoped and La 3+ doped YVO 4 samples were investigated under the UV light irradiation monitoring the aqueous solution of methylene blue (MB) dye. Hence, the effects of La 3+ dopant ion on the photoluminescence properties are discussed in detail. While the degradation of MB reaches to 38.8% after 180 minutes of UV light exposure with undoped YVO 4 , the degradation efficiency of La 3+ doped YVO 4 reaches 76.7%. Pseudo-first-order reaction rate constant (k) of La 3+ -doped YVO 4 (0.00846 min − 1 ) is determined 66% greater than undoped one (0.00287 min − 1 ).Master Thesis Nitrasyon ve Fiziksel Buhar Depolama (pvd) Yöntemleri İlekaplanmış Küresel Grafitli Dökme Demirlerin Mekanik, Aşınma ve Korozyon Özelliklerinin İncelenmesi(Konya Teknik Üniversitesi, 2023) Ünalsan, Emre; Altıntaş Yıldırım, ÖzlemÇeşitli mühendislik uygulamaları ve makine parçalarındaki en büyük sorun malzemelerin aşınması ve korozyona uğramasıdır. Korozyon ve aşınma malzemenin yüzeyinde meydana gelmektedir. Fakat çeşitli yüzey modifikasyonları ile malzemelerin aşınma ve korozyon özelliklerinin iyileştirilebilmesi mümkündür. Bu çalışmada GGG50 (EN-GJS-500-7) ve GGG70 (EN-GJS-700-2) kalite küresel grafitli dökme demir malzemelere ayrı ayrı; akımsız Ni-B kaplama, TiN PVD kaplama, gaz nitrasyonu ve plazma nitrasyonu işlemleri uygulanmıştır. GGG50 numunelerin gaz nitrasyon ile kaplama işlemi sonucunda yüzeylerinde oluşan nitrür tabakanın kalınlığı ~8,9±0,5 μm iken plazma nitrasyon ile kaplama sonucunda yüzeylerinde ~6,6±0,4 μm kalınlıkta nitrür tabaka oluştuğu gözlemlenmiştir. GGG70 numunesinin gaz ve plazma nitrasyon ile kaplanmaları ile yüzeylerinde oluşan nitrür tabaka kalınlıkları ise sırası ile ~7,0±0,3 μm ve ~3,9±0,4 μm olarak belirlenmiştir. Bu sonuçlar GGG50 ve GGG70 küresel grafitli dökme demirlerin gaz ve plazma nitrasyon işlemleri ile başarılı bir şekilde kaplandıklarını göstermektedir. Her bir uygulama sonrası numunelerin; mikroyapısal, sertlik, aşınma ve korozyon özellikleri incelenmiştir. Kaplama sonucunda numune yüzeyinde oluşacak fazların belirlenmesi için yapılan XRD analizleri sonuçlarına göre nitrasyon yapılan numunelerde Fe3N ve Fe4N fazları, akımsız Ni-B kaplamada NiB3 fazı, PVD kaplamada ise TiN fazının oluştuğu tespit edilmiştir. Kaplanmamış GGG50 küresel grafitli dökme demir 178 HB sertliğe sahipken bu numunelerin gaz ve plazma nitrasyon ile kaplanmaları sonucunda ortalama sertlik değerlerinin sırası ile 838±23 HB ve 809±14 HB'ye yükseldiği gözlemlenmiştir. Benzer şekilde kaplanmamış halde 222 HB sertliğe sahip GGG70 numunesinin sertlik değerinin gaz nitrasyon ile kaplama sonucunda 817±19 HB ve plazma nitrasyonla kaplama ile 832±27 HB değerine arttığı belirlenmiştir. Bu sonuçlara göre her iki kaplama türünün de küresel grafitli dökme demirlerin sertlik değerlerinde önemli artışa sebep oldukları görülmüştür. Ayrıca nitrürlenmiş numuneler işlem öncesi ve sonrası çekme testine tabi tutulmuştur. Çekme testleri ile gaz nitrürleme işleminden sonra numunelerin yüzeyinde oluşan sert nitrür tabakasının akma dayanımını arttırdığı, çekme dayanımı ve uzama değerlerini önemli ölçüde düşürdüğü gözlenmiştir. Numunelerin aşınma dirençleri kıyasladığında ise TiN PVD kaplanmış numunelerin aşınma direncinin iyileştiği gözlemlenirken Ni-B kaplama sonrasında numunelerin aşınma direncinde önemli bir iyileştirme görülmemiştir. Yapılan çekme testleri ile gaz nitrasyon işlemi sonrası numunelerin yüzeyinde oluşan sert nitrür tabakanın akma dayanımını arttırdığı, çekme dayanımı ve uzama değerlerini ise belirgin oranda azalttığı gözlemlenmiştir. Kısacası numuneler bir miktar kırılganlaşmıştır. Yapılan korozyon testleri neticesinde GGG50 ve GGG70 kalite Sfero malzemelerin kaplama sonrası farklı korozyon dirençleri gösterdiği tespit edilmiştir. Bu çalışmada yapılan uygulamalar içerisinde GGG50 kalite numunelerde akımsız Ni-B kaplama en düşük korozyon direncine sahip iken, GGG70 kalite numunelerde akımsız Ni-B kaplama yapılmış numune yüksek korozyon direncine sahip olduğu tespit edilmiştir.Article Citation - WoS: 7Citation - Scopus: 7Effect of Lanthanum Doping on Structural, Optical, and Photocatalytic Properties of Yvo4(Springer Heidelberg, 2023-06-20) Karacaoglu, Erkul; Altıntaş Yıldırım, Özlem; Öztürk, Teoman; Gül, Mert; Yildirim, Ozlem AltintasIn this study, we report the solid-state reaction synthesis of yttrium vanadate (YVO4)-based undoped and lanthanum (La)-doped powders. The photocatalytic performances, structural, morphological, and optical analyzes are presented. The X-ray diffraction analysis of samples indicates the crystalline tetragonal type crystal structure of YVO4 and no other lanthanum related impurity and/or secondary phases were detected. Photoluminescence analysis of samples show combined white light emission peaks that appeared at 478, 571 and 613 nm. To examine the photocatalytic activities, the degradation of methylene blue (MB) dye was monitored in the presence of these photocatalysts under the ultraviolet light irradiation. Pseudo-first-order reaction rate constant (k) of YVO4:La3+ (0.00846 min(-1)) is determined 66% greater than undoped one (0.00287 min(-1)). These results are compatible with the absorption spectra, as the energy band gap of the undoped photocatalyst was 3.8 eV while that of the doped one decreased to 3.54 eV.Article Citation - WoS: 7Citation - Scopus: 8Synthesis and Performance Evaluation of Biochar-Supported Zto Nanocatalyst for Photodegradation of Rhodamine B in Water(Springer Nature, 2023-12-12) Altintaş, Yıldırım, O.; Hasan, M.M.; Pehlivan, E.; Altintas Yildirim, Ozlem; Yildirim, Ozlem AltintasIn this study, rosehip seeds were activated as biochar (BC) in a tube furnace. Then, BC powder was mixed with hydrothermally synthesized zinc stannate (Zn2SnO4, ZTO) nanoparticles and the resulting mixture was activated by a co-calcination method to fabricate a mesoporous ZTO/BC nanocomposite. The dye removal performance samples were evaluated by measuring the photodegradation of Rhodamine B (RhB) under UV light irradiation. The effects of the catalyst type, dosage of the catalyst, and pH of the aqueous solution were examined to show the nanocomposite’s compatibility. It was found that ZTO/BC nanocomposite containing 15wt% of ZTO showed the strongest photocatalytic activity and could almost entirely degrade RhB (99.4%) after 45 min of UV light irradiation. Both photocatalytic and sorption methods have the ability to effectively remove RhB with ZTO/BC nanocomposite from an aqueous solution. The results of this study exhibit that the proposed nanocomposite system can be effectively used for low dye-concentrated aqueous solutions. Graphical abstract: [Figure not available: see fulltext.]. © 2023, The Author(s), under exclusive licence to The Materials Research Society.Article Citation - WoS: 41Citation - Scopus: 44Hydrothermally Synthesized Uv Light Active Zinc Stannate:tin Oxide (zto: Sno2) Nanocomposite Photocatalysts for Photocatalytic Applications(ELSEVIER SCI LTD, 2020-05-01) Keles, Elif; Yıldırım, Mehmet; Öztürk, Teoman; Altıntaş Yıldırım, Özlem; Yildirim, Ozlem AltintasThis study was carried out for the simple synthesis of zinc stannate (Zn2SnO4, ZTO): tin oxide (SnO2) nanocomposite photocatalyst in order to investigate the photodegradation of Rhodamine B (RhB) dye molecules under the UV light irradiation. For this purpose, nanocomposite photocatalysts were prepared via a low temperature hydrothermal method. Pure ZTO nanoparticles were also synthesized for the comparison purpose of the photocatalytic activity. Formation of the ZTO:SnO2 nanocomposites could be easily controlled by tuning of the hydrothermal reaction temperature. The structural properties of ZTO:SnO2 nanocomposites and ZTO nano-particles were schematically characterized by XRD, XPS and FTIR. Morphological investigation was performed via SEM and TEM. Band structure and optical properties were investigated with UV-Vis spectroscopy and PL analyses. It was found that ZTO:SnO2 nanocomposites keep hexagonal ZTO nanoparticles and SnO2 nanorods together and have more surface defects than that of the ZTO nanoparticles. The degradation of RhB dye molecules in the presence of ZTO:SnO2 nanocomposites reached to 62.0% degradation after first 60 min and 94.5% after 240 min. The photocatalytic rate constant of the ZTO:SnO2 nanocomposites (k = 0.0111 min(-1)) was two times higher than that of the pure ZTO nanoparticles (k = 0.00527 min(-1)). In addition, ZTO:SnO2 nanocomposites exhibited very high stability in the cycling degradation test with 90.1% RhB degradation even after ten times cycling run.
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Research Topics
Domains
Physical Sciences
Fields
EnergyMaterials ScienceEngineering
Subfields
Renewable Energy, Sustainability and the EnvironmentMaterials ChemistryElectrical and Electronic Engineering
Specific Research Areas
Advanced Photocatalysis Techniques
ZnO doping and properties
Gas Sensing Nanomaterials and Sensors
Copper-based nanomaterials and applications
TiO2 Photocatalysis and Solar Cells
Sustainable Development Goals
6CLEAN WATER AND SANITATION
7
Research Products
9INDUSTRY, INNOVATION AND INFRASTRUCTURE
4
Research Products
14LIFE BELOW WATER
3
Research Products
11SUSTAINABLE CITIES AND COMMUNITIES
2
Research Products
3GOOD HEALTH AND WELL-BEING
2
Research Products
12RESPONSIBLE CONSUMPTION AND PRODUCTION
1
Research Products
Documents
17
Citations
755
h-index
11
Documents
22
Citations
812
Publication Collaboration
| Affiliation Name | Count |
|---|---|
| Konya Technical University | 16 |
| Selçuk University | 8 |
| Middle East Technical University | 6 |
| Karamanoğlu Mehmetbey University | 4 |
| Eskisehir Technical University | 2 |
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Data obtained from OpenAlex
| Journal | Count |
|---|---|
| MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING | 3 |
| Journal of Materials Research | 2 |
| Konya mühendislik bilimleri dergisi (Online) | 2 |
| Journal Of Dispersion Science And Technology | 1 |
| Journal of Materials and Manufacturing | 1 |
Current Page: 1 / 3
Scholarly Output
22
Articles
17
Views / Downloads
70/157
Supervised MSc Theses
3
Supervised PhD Theses
0
WoS Citation Count
196
Scopus Citation Count
185
Patents
0
Projects
2
WoS Citations per Publication
8.91
Scopus Citations per Publication
8.41
Open Access Source
9
Supervised Theses
3
Scopus Quartile Distribution
Competency Cloud
