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Öğe Comparison of NiM2O4 (M:Fe,Mn) nanofibers as anode for li-ion batteries(Elsevier, 2023) Sarf, Fatma; Eroglu, Omer; Kizil, HuseyinIn this study, NiM2O4 (M:Fe,Mn) nanofibers were produced by one-step electrospinning and then annealed at 500 degrees C. Their structural and morphological properties were investigated by XRD and TEM. Electrochemical properties of NiFe2O4 and NiMn2O4 nanofibers were investigated as an anode material in Li-ion batteries. From TEM images, the fiber formation of both samples is formed by the fusion of nanoparticles. However, the fiber length of the Fe-containing structure is longer and its dimension is smaller than that of the Mn-containing structure. NiFe2O4 electrodes have high specific capacity compared to NiMn2O4 electrodes during 100 cycles due to the stability of fiber structure in NiFe2O4 samples.Öğe Defect Emission Energy and Particle Size Efects in Fe:ZnO Nanospheres Used in Li?Ion Batteries as Anode(Springer, 2021) Sarf, Fatma; Kızıl, HüseyinPure and Fe-doped ZnO (FexZnyV1−x−yO2) nanostructures with varying iron mole percentages of 3%, 4.5%, and 6% were synthesized by co-precipitation without vacuum ambient. Structural, morphological, defect, and electrochemical properties, when serving as an anode in Li-ion batteries, were studied. All the samples have a wurtzite ZnO crystallinity, and a slight shift from the x-ray difraction patterns of Fe:ZnO samples shows that Fe3+ ions were substituted by Zn2+ ions. As the percentage of the Fe mole increases from 3% to 4.5%, the size of the particles decreases from 12 nm to 9 nm, but increases to 14 nm with 6% Fe doping. Although all the samples have a spherical type, and porous surfaces are exhibited in the 4.5% Fe:ZnO nanospheres. The emission bands originate due to energy levels generated by ZnO intrinsic defects in all the samples with changing emission peaks by Fe doping. The 4.5% Fe:ZnO results substantially enhance the specifc capacity of 400 mAh g−1 during 100 cycles.Öğe Effect of Cd dopant on structural, optical and CO2 gas sensing properties of ZnO thin film sensors fabricated by chemical bath deposition method(Springer Science and Business Media Deutschland GmbH, 2021) Altun, Büşra; Karaduman Er, Irmak; Çağırtekin, Ali Orkun; Ajjaq, Ahmad; Sarf, Fatma; Acar, SelimCadmium-doped zinc oxide (Cd-doped ZnO) films were produced by economic facile chemical bath deposition method. The Cd doping content was adjusted as 1%, 3%, 5% and 7%. The structural, morphological and optical properties of the films were characterized by XRD, Raman, SEM and UV–Vis. The response in a carbon dioxide atmosphere was measured by varying the concentration up to 100 ppm at different working temperatures (30–250 °C). XRD measurements demonstrated that all synthesized films have a good crystallite structure with hexagonal wurtzite dominant phase. A large variety of nanostructures are randomly distributed over the films’ surfaces depending on Cd doping content as was manifested by the corresponding SEM images. From the transmittance analysis, an ultraviolet absorption edge corresponding to pure ZnO film undergoes a redshift with the increase in Cd content. The results from Raman spectra are in good agreement with the XRD results. From the gas sensing measurements, a high response toward 100 ppm CO2 gas was detected by 3% Cd-doped ZnO sensor (88.24% at 125 °C) with an acceptable response of 8.36% at room temperature, which exhibited the lowest response/recovery times as well as highest selectivity, stability and reproducibility. Changes in the CO2 gas sensing response as a function of Cd doping content are explained based on particle size, optical bandgap and surface images.Öğe Impurity Defect Induced Ferromagnetism Investigation of SiO2-Supported NiO Particles(Soc Quimica Mexico, 2022) Sarf, FatmaThis study examines amorphous SiO2-supported NiO particles by nickel concentration and calcination temperature arrangement to determine photoluminescence emission peaks and magnetic properties. Conventional co-precipitation with thermal calcination was used to produce NiO nanoparticles. Cubic NiO crystallization with single phase was improved by doubling the nickel concentration by calcination at 500 degrees C and 600 degrees C. Average crystalline size of 72 nm was obtained in the samples where double nickel concentration with calcination temperature at 600 degrees C. Granular forms have been observed in all samples, and nickel clusters were shown in the samples where the nickel concentration is twice as high. Green band emission intensity increases with improved NiO crystallinity due to surface oxygen vacancies at 505 nm. It is interesting to observe ferrimagnetism for SiO2-supported NiO particles calcined at 500 degrees C. From these results, optimal synthesis procedure and reduction in nucleation growth of NiO nanoparticles was achieved by double nickel concentration with calcination temperature at 600 degrees C.Öğe Influence of isovalent Cd doping concentration and temperature on electric and dielectric properties of ZnO films(Elsevier Ltd, 2021) Altun, Büşra; Ajjaq, Ahmad; Çağırtekin, Ali Orkun; Karaduman Er, Irmak; Sarf, Fatma; Acar, SelimIn this study, pure zinc oxide and lightly cadmium doped zinc oxide (Zn1-xCdxO; x = 0.01, 0.03, 0.05 and 0.07) films were synthesized by chemical bath deposition to mainly investigate the possible impact of isovalent (in particular Cd) doping ratio and temperature on their electric and dielectric features. X-ray diffraction patterns revealed that all produced films have a dominance of ZnO hexagonal wurtzite structure with the emergence of a minor CdO cubic phase at x ≥ 0.03, and predicted the decrease in average crystallite sizes with Cd doping. Cd content in the films was verified by energy dispersive X-ray analysis. Images of scanning electron microscopy revealed the formation of nanorods and spheres on the surface of pure ZnO film which changed to porous/agglomerative spheres with Cd doping. Then a comprehensive electric and dielectric analysis was carried out as a function of frequency in a wide temperature range (300–700 K) using two separate experimental data sets, (Z, θ) and (C, G). The results demonstrated the critical effect of temperature and Cd doping ratio on the electrical and dielectric properties of ZnO films. Among the investigated films, Zn0·97Cd0·03O film recorded highest conductivity and enhanced dielectric properties which was attributed to the equal activation of grains and grain boundaries in the film structure verified by the estimation of activation energies from impedance spectrum. However, the effect of Cd doping on electric and dielectric properties was prominent only below 500 K, beyond which the doping effect became negligible which might be correlated with the effective dominance of grain boundaries at high temperatures as was witnessed by modulus spectrum.Öğe Investigation of Ferromagnetism and Growth Correlation ofTransition Metal Doped ZnO(2021) Sarf, Fatma; Aşıkuzun, Elif; Yakar, EminIn this study, a series of 3d transition metal (TM) (Co, Ni and Fe) doped ZnO particles synthesized by simple co-precipitation method. Structural, morphological and magnetic properties were investigated to determine correlation between growth process and ferromagnetism of metal doped ZnO samples. All samples had ZnO hexzagonal würtzite structure and slightly shift of ZnO indexed peaks was observed by TM incorporation in ZnO. Although ZnO samples had granular forms, agglomerative forms had emerged in TM:ZnO samples due to the fast growth process. The pure ZnO sample transformed paramagnetic to ferromagnetic by TM incorporation due to carrier mediated exchange interaction between TM ions. The results demonstatedthat doping with Fe3+ ions in ZnO structure had enhanced ferromagnetism although fast growth and high particle agglomeration.Öğe Investigation of H2S gas sensing performance of Ni:WO3 films at room temperature: nickel precursor effect(Springer, 2022) Er, Irmak Karaduman; Sarf, Fatma; Yakar, EminIn this work, pure and nickel-doped WO3 films were produced by chemical bath deposition on In-doped SnO2 (ITO) substrates without annealing process. To synthesize the Ni:WO3 films, two different types of nickel precursors were used as NiSO4 and NiCl2. The influence of Ni doping using different Ni precursors on the structural, morphological, optical, and gas sensing properties of WO3 films toward H2S gas was investigated in detail. All samples have monoclinic WO3 polycrystallization where a substitution of Ni2+ ions with W6+ mi olmali ions is detected from the slight shift in x-ray diffraction patterns with the Ni doping process. With nickel chloride source, the synthesized Ni:WO3 samples exhibit nano-ball shapes with different dimensions on the film surfaces. Optical band gap energy severely decreases with nickel doping due to increasing oxygen vacancies, especially when nickel chloride is used as a precursor source in Ni:WO3 samples. Ni2+ ions introduction in WO3 host lattice has improved H2S gas detection capability; however, the biggest positive effect came from the NiSO4 precursor with increasing solubility and improved growth process. The response to 50 ppb H2S gas at room temperature was calculated as 7%, 11%, and 23% for pure WO3, NiCl2-based Ni:WO3, and NiSO4-based Ni:WO3 sensors, respectively. When the gas selectivity property was studied for NiSO4-based Ni:WO3 sensors, they showed more selectivity against H2S gas compared to H-2, benzene, methanol, etc. It is found that precursor type has an incredible impact on the H2S, reducing gas sensing properties in doped metal oxide gas sensor applications.Öğe Kompleks Etken Madde Oranına Bağlı Olarak ZnFe2O4 Filmlerin İncelenmesi(2018) Sarf, Fatma; Yakar, EminSon yıllarda spinel ferrit malzemeler (MFe2O4; M= Fe,Ni,Co,Mg vb.) oldukça farklıalanlarda, örneğin indüktörler, manyetik sensörler, magneto-optik depolama ve kayıt cihazlarıvb., kullanımı ile dikkat çekmektedir. Spinel ferrit malzeme grubu içerisinde yer alanZnFe2O4 (çinko-ferrit) yüksek direnci, mekanik stabilitesi ve düşük dielektrik kayıpları ileözellikle yüksek frekans uygulamalarında karşımıza çıkmaktadır. Basit sentezlenme sürecineve düşük üretim/güç maliyetine sahip ZnFe2O4 malzemelerine olan ihtiyaç bu yöndekiaraştırma ve geliştirme çalışmalarını arttırmaktadır.Bu çalışmada çinko-ferrit filmleri kimyasal banyo depolama ile ITO alttaşlar üstüne farklıoranlarda kompleks etken madde kullanılarak sentezlenmiştir. Kompleks etken madde olarakamonyak tercih edilmiştir. Filmlerin amonyak oranına ve dolayısıyla çözeltinin pH’ına bağlıolarak değişen yapısal, yüzeysel ve optik özellikleri sırasıyla XRD, SEM ve Uv-Vis/Ramanspektroskopisi ile incelenmiştir. XRD spektrumlarından elde edilen veriler ışığında, kristalleşmenin amonyak oranı artışı ile birlikte arttığı tespit edilmiştir. SEM-yüzey morfoloji görüntüleri ile amonyak oranı değişiminin farklı biçimlerde nanoparçacıklar oluşumuna sebepolduğu gözlenmiştir. Ayrıca filmlerin optik özelliklerinin amonyak oranı artışı ile iyileştiğitespit edilmiştir.Öğe Optical and Electrical Characterization of Crystallized M:$WO_3$ (Cu, Fe, Ni) Films in Acidic Medium(2024) Yakar, Emin; Er, Irmak Karaduman; Sarf, FatmaPure and metal (M) doped [copper (Cu), nickel (Ni) and iron (Fe)] $WO_3$ films have been produced on In:$SnO_2$ (ITO) slides by using facile chemical bath deposition and then annealed at 500 oC for 2 h. Structural, morphological, electrical and optical properties of the produced $WO_3$-based films were examined. Monoclinic $WO_3$ phase were observed in all the samples, and the peak intensities were decreased by metal inclusion with heterogeneous film growth on ITO substrate. Slight shifts from defect related emission peaks (blue and green) were observed in metal-substituted $WO_3$ samples from PL study. An optical band gap was observed to decrease in M:$WO_3$ samples. The surface resistance values were significantly reduced by metal additives compared to its pure counterpart, especially by the inclusion of nickel ions in $WO_3$. The results indicated that nucleus growth and thereby impurity/defect-related surfaces had a serious effect on the optical and electrical properties of M:$WO_3$ films.Öğe Potasyum Katkılamanın Ag:ZnO Filmlerinin Yapısal Özellikleri Üzerine Etkisinin İncelenmesi(2022) Sarf, Fatma; Yakar, EminBu çalışmada, Ag:ZnO ve Ag-K:ZnO filmleri basit ve efektif bir üretim tekniği olan kimyasal banyolama tekniği ile ZnO gövde tabakalar üzerine sentezlenmiştir.Filmlerin yapısal özelliklerinin detaylı şekilde incelenmesinin yanı sıra yüzey pürüzlülük değerleri hesaplanmış ve örneklerin Raman spektrumu incelenmiştir. Tüm filmler hekzagonal würtzite ZnO kristal yapısına sahiptir. Ag katkılaması ile tane büyüklüğü µm mertebesinden 36 nm’ye azalmış ve ZnO kristalleşmesi iyileşmiştir. Buna karşın, K+ iyonlarının yapıya girmesiyle tane büyüklüğü nispeten azalmasına karşın (32 nm) ZnO kristalleşmesi ciddi biçimde bozunmuştur. Yüzeyde nanoparçacıkların oluşumuna ve yüzey pürüzlülük değerlerinde azalmaya potasyum katkılamanın etkisi olduğu gözlenmiştir. Numunelerde gözlenen farklı şiddette tüm zirveler, ZnO würtzite yapısının Raman modlarından bazıları ile eşleşme göstermiştir. Elde edilen sonuçlardan, gerek tekil (Ag) gerek ise ikili (Ag-K) katkılamayla beraber, ZnO yapısındaki kusur yoğunluklarının artması ve değişmesi nedeniyle, kristal yapı ve yüzey dağılımında bozulma meydana geldiği düşünülmektedir. Ancak potasyum atomlarının Ag:ZnO yapısına girmesi ile fiziksel ve kimyasal özellikler üzerinde iyileştirici etkisi saptanmıştır.Öğe Substrate critical effect on the structural and H-2 Gas sensing characteristics of solution-processed Zn0.075Cu0.025O films(IOP Publishing, 2021) Sarf, Fatma; Er, Irmak Karaduman; Yakar, Emin; Acar, Selim; Yakar, EminIn this study, we report the synthesis of Zn0.075Cu0.025O films by chemical bath deposition to determine the effect of substrate (glass slide or ZnO seed layer) on the structural and H2 gas sensing properties of the produced films. The crystal phase, structural topography, surface morphology, and functional groups of the as-synthesized films as well as H2 gas sensing properties were investigated. Although both films have a hexagonal wurtzite structure, ZnO seed layer-based Zn0.075Cu0.025O film is more crystalline than glass slide-based Zn0.075Cu0.025O films. ZnO seed layer-based Zn0.075Cu0.025O films exhibited much more nanorod and fewer nanosphere forms compared to glass slide-based Zn0.075Cu0.025O films. EDX analysis and Raman spectra of both samples confirmed the presence of defects in Cu: ZnO samples. ZnO seed layer-based sensors showed higher response (140%) and lower operating temperature (80 °C) compared to glass slide-based sensors(87% response and 140 °C operating temperature). The most important thing to note here is that the fabricated sensors exhibited a high response at room temperature. The responses at room temperature were found as 46% and 23% for the ZnO seed layer-based and glass slide-based sensors, respectively. Sensors operating at room temperature are especially important for commercial applications.Öğe Surface dynamics and electrochemical examination of Co3O4 films by iron doping(Iop Publishing Ltd, 2024) Yakar, Emin; Sarf, Fatma; Bayirli, Mehmet; Ilgaz, AykutThis study focused on Co3O4 films, which were prepared by cost-effective chemical bath deposition on In:SnO2 (ITO) substrates with iron doping concentrations ranging from 2 to 6 mol %. Structural properties were investigated by XRD as well as nanotexture of Fe: Co3O4 films was captured via SEM and detailed fractal analysis was analyzed in each prepared film. Effective using of prepared Fe: Co3O4 electrodes for electrochemical charge storage applications has been examined by using CV and EIS. From x-ray patterns, spinel cubic structure of Co3O4 was observed in all samples, while peaks with Co(2)O(3 )and substrate indexed peaks were also shown. Pure and iron doped Co3O4 surfaces have spherical agglomerative forms while porous structures were observed in 4% Co3O4 samples. Redox peaks induced by Faradaic reactions in the CV plots present pseudo- capacitive nature for all electrodes and improves charge transfer process in 4% Co3O4 and 6% Co3O4 from EIS measurements. Additionally, using scaling theory, the coverage ratio, fractal dimensions, cluster sizes and interface critical exponent values of the superficial hetero morphology of the samples are calculated. While the coating rate decreases according to the iron concentration, fractal dimensions increase. However, as the number of clusters increases, the average cluster size decreases. The interface critical exponent value shows an irregular change.Öğe The role of rare-earth metal (Y, Ru and Cs)-doped ZnO thin films in NH3 gas sensing performances at room temperature(Springer, 2020) Sarf, Fatma; Er, Irmak Karaduman; Yakar, Emin; Acar, SelimPure and rare-earth metal [Yttrium (Y), Ruthenium (Ru) and Caesium (Cs)]-doped ZnO thin films were deposited onto In-doped SnO2 substrates by chemical bath deposition. The present study detailed investigated the effect of rare-earth metal-doped ZnO on NH3 gas sensing. X-ray diffraction analysis indicated that the incorporated rare-earth metal ions substitute Zn sites in the ZnO lattice. Dimension of ZnO films decreased with rare-earth metal doping which detected from surface morphology images. The response of 100 ppb NH3 gas was calculated to be 0.80 (200 degrees C), 14.00 (90 degrees C), 17.00 (50 degrees C), and 10.00 (120 degrees C) for the pure, Y-, Ru-, and Cs-doped ZnO films, respectively. In addition, the response of 15 ppm NH3 gas at room temperature was calculated to be 0.20, 27.00, 57.00, and 18.00 for undoped Y-, Ru-, and Cs-doped ZnO films, respectively.Öğe Varying electrical and dielectric properties of Ni:SnO2 films by MWCNTs and GNPs coating(Iop Publishing Ltd, 2022) Sarf, Fatma; Er, Irmak Karaduman; Ajjaq, Ahmad; Cagirtekin, Ali Orkun; Yakar, Emin; Acar, SelimIn this research, pure SnO2 and Ni-doped SnO2 (Ni:SnO2) nanocomposite films were produced by chemical bath deposition method and the latter were coated with multi-walled carbon nanotubes (Ni:SnO2/MWCNTs) or graphene nanoplatelets (Ni:SnO2/GNPs) by spin coating. All samples have tetragonal rutile SnO2 structure with the presence of carbon (002) peak in MWCNTs- or GNPs-coated films. Crystallite size of SnO2 films decreased remarkably with Ni doping followed by a slight decrease with MWCNTs coating and slight increase with GNPs coating. Scanning electron microscope images manifested a dispersed agglomerative nature of SnO2 nanoparticles which reduced especially with MWCNTs coating due to the porous surface provided by carbon nanotubes. From the photoluminescence measurements, oxygen defects-related peaks were spotted in the SnO2-based structures with different luminescence intensities. The most significant decrease in resistance was observed with the addition of GNPs into Ni-doped SnO2 nanocomposites compared to the other produced films mainly due to the synergetic effect that promotes excellent charge transfer between surfaces of Ni:SnO2 and graphene nanosheet. The huge increase in conductivity of GNPs-coated films led to a huge increase in dielectric losses and this followed by a drop down of dielectric constant of the GNPs-coated films.Öğe WO3 filmlerin mikroyapısal kusur ve optik özelliklerinin incelenmesi(Çanakkale Onsekiz Mart Üniversitesi, Lisansüstü Eğitim Enstitüsü, 2022) Gülen, Orhan Emre; Sarf, Fatma; Yakar, EminBu çalışmada, WO3 filmleri, asidik ortamda kimyasal banyo yöntemiyle In:SnO2 (ITO) substratları üzerinde biriktirildi. Sentezlenen WO3 filminin yapısal, morfolojik ve optik özellikleri x-ışını kırınımı (XRD), taramalı elektron mikroskobu (SEM), atomik kuvvet mikroskobu (AFM), fotolüminesans (PL), Uv-Vis ve Raman spektrofotometresi kullanılarak incelenmiştir. X-ışını desenlerinden, tungsten oksit kaplama monoklinik faz yapısı sergilemektedir. Nanoçubuk/nano-diĢ karışık formlarının göreceli homojen partikül dağılımı yüzeyde gözlemlenmiştir ve ayrıca yüzey pürüzlülüğü literatürdeki benzer çalışmalara göre daha azdır. Yüzey kusuru emisyon zirveleri, özellikle oksijen boşlukları PL spektrumundan belirlenir. Yeşil emisyon, heterojen film büyüme sürecine atfedilir. Filmlerin Raman spektrumları WO3 oluşumunun kanıtıdır. Bu sonuçlardan, toplama-biriktirme mekanizması WO3 film büyüme sürecinden sorumludur.
