Influence of Neodymium Doping on the Crystal and Electronic Properties of FeBO3 Oxide Materials

FeBO3 oksit bileşiğine neodyum katkısının elektronik ve kristal yapısı üzerine etkileri NdxFe1-x BO3 genel seri formülü ile çalışılmıştır. Ağır fermiyon seryum atomlarının örnekler içine katkılanmasıyla polikristal yapıların ortaya çıktığı görülmüştür. Bu duruma, bor merkezli BO3 ligand yapılarına metal Fe ve Nd atomlarının bağlanması sonucu ortaya çıktığı belirlenmiştir. Artan Nd katkısının, Fe düzlemlerinde bozulmaya neden olduğu, bununda polikristal yapıyı tetiklediği tespit edilmiştir. Kristal yapıların bünyesinde gerçekleşen elektronik etkileşme mekanizmalarını araştırmak üzere x-ışını soğurma ince yapısı tekniği (XAFS), x-ışını kırınım desenleri (XRD) ile koordineli olarak kullanılmıştır. Analizlerin sonucunda neodyum atomlarının f-seviyelerinin demir atomlarıyla olan zayıf etkileşmelerden sorumlu olduğu, bu nedenle güçlü elektron etkileşmelerinde en önemli etkileşme sahası olduğu tespit edilmiştir.Neodymium substitution in titanium coordinations of the FeBO3 materials were studied with their crystallographic and its related electronic structure properties according to the general formula NdxFe1- x BO3. With the doping of the heavy fermion “Neodymium”, samples were formed in polycrystalline structure due to boron centered ligands BO3. With the incressing Nd in the samples, disturbances on the Fe planes became more clear and it supports geometrically different crystal structures formations. Electronic structure properties were investigated by the X-ray Absorption Fine Structure Spectroscopy (XAFS) technique both to obtain the electronic mechanisms in the crystals and to support crystal structure study of the samples carried with the X-ray diffraction (XRD) patterns. As a result of the analysis, f-levels of the Neodymium atoms were determined not as the main playground of interplays and 5d-3d mixing were determined to emerge dominant interactions causing phase transitions

Uranium mobility in organic matter-rich sediments: A review of geological and geochemical processes

Uranium (U) is of enormous global importance because of its use in energy generation, albeit with potential environmental legacies. While naturally occurring U is widespread in the Earth's crust at concentrations of ~1 to 3 ppm, higher concentrations can be found, includingwithin organicmatter (OM)-rich sediments, leading to economic extraction opportunities. The primary determinants of U behaviour in ore systems are pH, Eh, U oxidation state (U(IV), U(VI)) and the abundance of CO3 2– ions. The concentration/availability and interrelationships among such determinants vary, and the solubility and mobility of ions (e.g. OH-, CO3 2–, PO4 3-, SiO4 4-, SO4 2-) that compete for U (primarily as U(VI)) will also influence the mobility of U. In addition, the presence of OM can influence U mobility and fate by the degree of OMsorption to mineral surfaces (e.g. Fe- and Si- oxides and hydroxides). Within solid-phase OM, microbes can influence U oxidation state and U stability through direct enzymatic reduction, biosorption, biomineralisation and bioaccumulation. The biogenic UO2 product is, however, reported to be readily susceptible to reoxidation and therefore more likely remobilised over longer time periods. Thus several areas of uncertainty remain with respect to factors contributing to U accumulation, stability and/or (re)mobilisation. To address these uncertainties, this paper reviews U dynamics at both geological and molecular scales. Here we identify U-OMbond values that are in agreement, relatively strong, independent from ionic strength and which may facilitate either U mobilisation or immobilisation, depending on environmental conditions. We also examine knowledge gaps in the literature, with U-OM solubility data generally lacking in comparison to data for U sorption and dissolution, and little information available on multi-component relationships, such as UOM-V (V as vanadate). Furthermore, the capability ofOMto influence the oxidation state of U at near surface conditions remains unclear, as it can be postulated that electron shuttling by OM may contribute to changes in U redox state otherwise mediated by bacteria. Geochemical modelling of the environmental mobility of U will require incorporation of data from multi-corporation studies, as well as from studies of U-OM microbial interactions, all of which are considered in this review

Epitaksiyel grafen üzerinde kendiliğinden düzenlenen silikon oksit ağı

Thesis (Master)--Izmir Institute of Technology, Materials Science and Engineering, Izmir, 2017Includes bibliographical references (leaves: 59-69)Text in English; Abstract: Turkish and EnglishIn this thesis, I studied the formation and characterization of self-organized hexagonal-shaped SiO2 wrinkle structures on epitaxial graphene that was grown on SiC substrate. Monolayer graphene was grown by annealing the SiC substrate at high temperatures under ultra-high vacuum conditions. Following the growth process, SiO2 thin film was deposited on epitaxial graphene layer at different deposition temperatures by thermal evaporation method. We found that SiO2 film wrinkles on epitaxial graphene. The origin of the hexagonal shaped wrinkle structures were derived from the thermal expansion coefficient difference between epitaxial graphene and SiO2 thin film. The mesh density of these SiO2 hexagonal wrinkle structures was controlled by changing the cooling rate of the substrate after the thin film deposition. To make a comparison, SiO2 thin film was also deposited on CVD grown graphene and on bare SiC substrate. Unlike on the bare SiC surface, SiO2 thin film on epitaxial graphene exhibited a self-assembled network of hexagonally shaped wrinkles due to thermally induced compressive strain between the two materials. The observed network of wrinkles were found to be comprised of line shaped primary and secondary types of protrusions with distinct topographic characteristics as determined by optical microscopy, Scanning Electron Microscopy and Atomic Force Microscopy measurements. The wrinkle to wrinkle spacing and mesh density of the wrinkle network were modified simply by changing the SiO2 deposition temperature. Our experimental results imply that epitaxial graphene with its high chemical inertness on SiC offers a great potential to be used as a conventional substrate in the realm of thin film metrology.Bu çalışmada, silisyum karbür alttaş üzerinde büyütülmüş epitaksiyel grafen üzerinde kendiliğinden düzenlenen silikon oksit ağının oluşumu ve karakterizasyonu gerçekleştirildi. Tek katman grafen, silikon karbür alttaş üzerinde yüksek sıcaklıklarda tavlanarak ultra yüksek vakum koşullarında büyütüldü. Büyütme işlemi sonrası, silikon oksit ince film tabakası epitaksiyel olarak büyütülmüş grafen üzerine farklı kaplama sıcaklıklarında termal olarak buharlaştırıldı. Yüzeyde meydana gelen kırışıklık yapısının, epitaksiyel grafen ile SiO2 ince film arasındaki yüksek ısıl genleşme katsayısı farklılığından kaynaklandığı yapılan deneyler ile gösterildi. Bu kırışıklık yapılarının yoğunluğu ince film kaplandıktan sonraki soğutma hızı değiştirilerek kontrol edildi. Aynı zamanda epitaksiyel ve kimyasal buhar biriktirme (CVD) yöntemleri ile sentezlenmiş grafen üzerindeki kırışıklık yapısının oluşumu çalışıldı. Tek katman epitaksiyel grafen ve işlem uygulanmamış SiC alttaşın üzerinde kaplanan SiO2 ince filmin yüzey üzerindeki davranışı incelendi. İşlem uygulanmamış SiC alttaşının aksine, iki malzeme arasında termal olarak endüklenen basma gerinimden dolayı SiC üzerinde epitaksiyel olarak büyütülmüş tek katman grafenin üzerindeki SiO2 ince film, altıgen yapılı kendiliğinden oluşan kırışıklık ağını göstermiştir. Farklı topografik özellikler gösteren birincil ve ikincil tip yükseltilerden oluşan kırışık ağ yapısı; optik mikroskop, taramalı elektron mikroskopisi (SEM) ve atomik kuvvet mikroskopisi (AFM) ölçümleri ile karakterize edilmiştir. Kırışıklıklar arası mesafe ve yapıdaki ağ yoğunluğu SiO2 ince film kaplama sıcaklığı değiştirilerek modifiye edilmiştir. Elde edilen sonuçlar, yüksek oranda kimyasal olarak etkisiz olan silikon karbür üzerinde büyütülen epitaksiyel grafenin ince film metrolojisi alanında kullanılmak üzere yüksek bir potansiyele sahip olduğunu göstermiştir

Epitaksiyel grafen üzerinde kendiliğinden düzenlenen silikon oksit ağı

Thesis (Master)--Izmir Institute of Technology, Materials Science and Engineering, Izmir, 2017Includes bibliographical references (leaves: 59-69)Text in English; Abstract: Turkish and EnglishIn this thesis, I studied the formation and characterization of self-organized hexagonal-shaped SiO2 wrinkle structures on epitaxial graphene that was grown on SiC substrate. Monolayer graphene was grown by annealing the SiC substrate at high temperatures under ultra-high vacuum conditions. Following the growth process, SiO2 thin film was deposited on epitaxial graphene layer at different deposition temperatures by thermal evaporation method. We found that SiO2 film wrinkles on epitaxial graphene. The origin of the hexagonal shaped wrinkle structures were derived from the thermal expansion coefficient difference between epitaxial graphene and SiO2 thin film. The mesh density of these SiO2 hexagonal wrinkle structures was controlled by changing the cooling rate of the substrate after the thin film deposition. To make a comparison, SiO2 thin film was also deposited on CVD grown graphene and on bare SiC substrate. Unlike on the bare SiC surface, SiO2 thin film on epitaxial graphene exhibited a self-assembled network of hexagonally shaped wrinkles due to thermally induced compressive strain between the two materials. The observed network of wrinkles were found to be comprised of line shaped primary and secondary types of protrusions with distinct topographic characteristics as determined by optical microscopy, Scanning Electron Microscopy and Atomic Force Microscopy measurements. The wrinkle to wrinkle spacing and mesh density of the wrinkle network were modified simply by changing the SiO2 deposition temperature. Our experimental results imply that epitaxial graphene with its high chemical inertness on SiC offers a great potential to be used as a conventional substrate in the realm of thin film metrology.Bu çalışmada, silisyum karbür alttaş üzerinde büyütülmüş epitaksiyel grafen üzerinde kendiliğinden düzenlenen silikon oksit ağının oluşumu ve karakterizasyonu gerçekleştirildi. Tek katman grafen, silikon karbür alttaş üzerinde yüksek sıcaklıklarda tavlanarak ultra yüksek vakum koşullarında büyütüldü. Büyütme işlemi sonrası, silikon oksit ince film tabakası epitaksiyel olarak büyütülmüş grafen üzerine farklı kaplama sıcaklıklarında termal olarak buharlaştırıldı. Yüzeyde meydana gelen kırışıklık yapısının, epitaksiyel grafen ile SiO2 ince film arasındaki yüksek ısıl genleşme katsayısı farklılığından kaynaklandığı yapılan deneyler ile gösterildi. Bu kırışıklık yapılarının yoğunluğu ince film kaplandıktan sonraki soğutma hızı değiştirilerek kontrol edildi. Aynı zamanda epitaksiyel ve kimyasal buhar biriktirme (CVD) yöntemleri ile sentezlenmiş grafen üzerindeki kırışıklık yapısının oluşumu çalışıldı. Tek katman epitaksiyel grafen ve işlem uygulanmamış SiC alttaşın üzerinde kaplanan SiO2 ince filmin yüzey üzerindeki davranışı incelendi. İşlem uygulanmamış SiC alttaşının aksine, iki malzeme arasında termal olarak endüklenen basma gerinimden dolayı SiC üzerinde epitaksiyel olarak büyütülmüş tek katman grafenin üzerindeki SiO2 ince film, altıgen yapılı kendiliğinden oluşan kırışıklık ağını göstermiştir. Farklı topografik özellikler gösteren birincil ve ikincil tip yükseltilerden oluşan kırışık ağ yapısı; optik mikroskop, taramalı elektron mikroskopisi (SEM) ve atomik kuvvet mikroskopisi (AFM) ölçümleri ile karakterize edilmiştir. Kırışıklıklar arası mesafe ve yapıdaki ağ yoğunluğu SiO2 ince film kaplama sıcaklığı değiştirilerek modifiye edilmiştir. Elde edilen sonuçlar, yüksek oranda kimyasal olarak etkisiz olan silikon karbür üzerinde büyütülen epitaksiyel grafenin ince film metrolojisi alanında kullanılmak üzere yüksek bir potansiyele sahip olduğunu göstermiştir

MnS, ZnO ve SnO2 ince filmlerin elektronik yapısının X-ısını soğurma spektroskopisi ile incelenmesi

TEZ5699Tez (Doktora) -- Çukurova Üniversitesi, Adana, 2006.Kaynakça (s. 101-104) var.viii, 123 s. : res. ; 29 cm.Bu çalismanin amaci, çesitli metalik ince filmlerin yapisal ve elektronik özelliklerinin spektroskopik yöntemlerle incelenmesidir. Bazi 3d metallerinin farkli özelliklerdeki bilesikleri ile ilgili hesaplar FEFF 8.0 programiyla hesaplandi ve deneysel sonuçlarla kiyaslandi. X-isinlari sogurma temelindeki hesaplamalar çoklu elektron saçilmasi ile yapildi. Çesitli yöntemlerle elde edilen MnS, ZnO, SnO2 v.b. metalik ince filmlerin elektronik yapisi XAFS (X-ray Absorption Fine Structure Spectroscopy) yöntemiyle belirlendi. Hesaplamalardan elde edilen sonuçlar deneysel verilerle uyumludur.The aim of this study is to investigate the structural and electronic properties of metallic thin films by XAFS (X-ray Absorption Fine Structure) spectroscopy. Some of different types of 3d metallic compounds are calculated with using the XAFS computer code FEFF 8.0 and compared with the experimental results. Calculations are based on multiple scattering process of photoelectrons. Electronic structure investigations of the thin films of 3d metallic compounds are calculated with XANES method and structural investigations are calculated with EXAFS method of XAFS spectroscopy. Calculations are agree with the experimental results.Bu çalışma Ç.Ü. Bilimsel Araştırma Projeleri Birimi Tarafından Desteklenmiştir. Proje No: FEF2003D2

Lazer-plazma etkileşme mekanizmalarının incelenmesi

TEZ3549Tez (Yüksek Lisans) -- Çukurova Üniversitesi, Adana, 2000.Kaynakça (s. 87-90) var.vii, 91 s. ; 30 cm.…Bu çalışma Ç.Ü. Bilimsel Araştırma Projeleri Birimi Tarafından Desteklenmiştir. Proje No: FBE. 98. YL. 99

Temperature dependent change of the MnS K-edge

The x-ray absorption near-edge structure (XANES) of Mn K-edge in MnS have been investigated. The full multiple scattering approach has been applied to the calculation of Mn K edge XANES spectra of MnS. The calculations are based on different choices of one electron potentials according to Manganese coordinations by using the real space multiple scattering method FEFF 8 code. The crystallographic and electronic structure of the MnS are tested at various temperature ranges from 300 to 573 K. We have found prominent changes in the XANES spectra of MnS by the change of the temperature. Such observed changes are explained by considering the structural, electronic and spectroscopic properties. The results are consistent with experimental spectra

Electronic and structural properties of SnO and SnO2 thin films studied by X-ray-absorption spectroscopy

Tin oxide thin films have been investigated by X-ray Absorption Fine Structure spectroscopy (XAFS). XAFS provides a description of the structure of the films. The paper also presents a structural characterisation of the SnO 2 thin films and their crystallisation behaviour by annealing at increasing temperatures. The x-ray absorption fine structure (XAFS) of Sn L III - edge in SnO and SnO2 have been investigated. The full multiple scattering approach has been applied to the calculation of Sn LIII edge XANES spectra of SnO. The calculations are based on different choices of one electron potentials according to Tin coordinations by using the real space multiple scattering method FEFF 8.2 code. The crystallographic and electronic structure of the SnO and SnO2 are tested at various temperature ranges from 300 to 873 K. We have found prominent changes in the XANES spectra of Tin oxide thin films by the change of the temperature. Such observed changes are explained by considering the structural, electronic and spectroscopic properties. The results are consistent with experimental spectra

The electronic structure of wurtzite MnS

National Nuclear Energy Agency of Indonesia (BATAN);Directorate Higher Edu. Ministry Natl. Edu. Indonesia (DIKTI);International Atomic Energy Agency (IAEA);International Union of Crystallography (IUCr);Abdus Salam International Centre for Theoretical Physics (ICTP);Deutsche Forschungsgemeinschaft (DFG)International Conference on Neutron and X-ray Scattering 2007, ICNX 2007 --23 July 2007 through 31 July 2007 -- Serpong and Bandung --Manganese sulfide thin films have been investigated by X-ray Absorption Fine Structure spectroscopy (XAFS). XAFS provides a description of the structure of the films. The paper also presents a structural characterisation of the wurtzite MnS thin films and their crystallisation behaviour by annealing at increasing temperatures. The x-ray absorption fine structure (XAFS) of Mn K-edge and S K-edge in wurtzite MnS have been investigated. The full multiple scattering approach has been applied to the calculation of Mn K edge XANES spectra of MnS. The calculations are based on different choices of one electron potentials according to Mn coordinations by using the real space multiple scattering method FEFF 8.0 code. The crystallographic and electronic structure of the MnS are tested at various temperature ranges from 300 to 573 K. We have found prominent changes in the XANES spectra of Mangeanese sulfide thin films by the change of the temperature. Such observed changes are explained by considering the structural, electronic and spectroscopic properties. The results are consistent with experimental spectra. © 2008 American Institute of Physics

Preparation and characterization of crystalline MnS thin films by chemical bath deposition

Crystalline ?-MnS thin films were deposited by chemical bath deposition method at 27 °C. The MnS thin films were characterized by X-ray diffraction (XRD), scanning electron microscopy, energy dispersive X-ray analysis (EDAX) and optical absorption spectroscopy. XRD measurements show that the films are crystallized in the wurtzite phase and present a preferential orientation along the c-axis. Only one peak, corresponding to the (002) phase (2? = 28.26°), appears on the diffractograms. The X-ray absorption fine structure spectroscopy calculation of Mn K-edge in MnS is in agreement with the measured result. The deposited MnS thin films on glass substrates consist of nanocrystalline grains. EDAX analysis shows that average ratio of atomic percentage of Mn : S is 1 : 0.82 so one can conclude that the films are in good stoichiometric ratio. The optical band gap of thin film was estimated to be 3.88 eV. © 2005 Elsevier B.V. All rights reserved.FEF2004BAP3This work was supported by Cukurova University under FEF2004BAP3 project number