Arıburnu yalıtaşının (Gelibolu Yarımadası, Türkiye) kökeni ve yaşı üzerine

The beachrock formation on the Ariburnu coast situated in the Gelibolu Peninsula has been studied by field observation, thin-section interpretation, physicochemical analyses including ICP-AES and SEM/EDS, and OSL dating. These analyses reveal the presence of different amounts of major (Si, Ca, Mg, K, Fe, Al and Na) and trace elements within the beachrock cement with Si (36.2%) and Ca (32.68%) dominating the overall composition. Beachrocks composed of highly-fractured and friable beds reach a total thickness of 80 cm extending from + 60 cm at the uppermost level down to-1 m at their most seaward extent and grade from conglomerate to lithic arkose in vertical section. The total amount of CaCO(3) ranges between 59.08% and 36% and the cement consists of high-Mg calcite based on EDS analysis. From SEM examination, four main morphologies were identified in cement material: (1) micritic coatings, (2) cryptocrystalline pore-filling cement, (3) meniscus cement and (4) microbial cement and suggest the presence of marine phreatic conditions with the exception of meniscus bridges, which imply that cementation may have been dominated by carbonate-rich meteoric waters at any successive stage of cementation. Five buried beachrock samples under unconsolidated beach sand were sampled for Optically Stimulated Luminescence (OSL) dating and show that the minimum and maximum ages of beachrock are 1.42 +/- 0.20 ka and 2.28 +/- 0.28 ka BP, respectively.Bu çalışmada Gelibolu Yarımadası’nda, Arıburnu kıyılarındaki yalıtaşı oluşumu arazi verileri, ince kesit yorumlamaları, ICP-AES, EDS ve SEM analizleri ve OSL yaşlandırması ile ele alındı. Analizler yalıtaşı çimentosu içinde Si, Ca, Mg, K, Fe, Al ve Na gibi ana ve iz elementlerin nispeten farklı oranlarda bulunduğunu göstermektedir. Bileşimde Si (36.2%) ve Ca (32.68%) egemendir. Yalıtaşları bol kırıklı ve kırılgan, toplam 80 cm tabaka kalınlığına sahip olup, en yüksek seviyede +60 cm’den deniz içinde –1 m’ye kadar takip edilirler. Düşey kesitte çakıltaşlarından litik arkoza geçişlidirler. Toplam CaCO3 miktarı 59.08% ve 36% arasında değişir. EDS analizlerine gore çimento maddesi yüksek magnezyum kalsittir. SEM analizlerine göre çimento maddesinde 4 ana morfoloji tanımlanmıştır; (1) mikritik tabakalar, (2) kriptokristalin boşluk dolgusu çimento, (3) menisküs çimento ve (4) mikrobial çimento. Bu çimentolar, çimentolanmanın izleyen bir devresinde karbonat bakımından zengin meteorik sularca meydana getirildiğini gösteren menisküs çimento hariç, denizel freatik koşullarda geliştiğini göstermektedir. Kıyı çizgisi gerisindeki plaj kumları altından çıkarılan 5 örneğin ‘optik uyarımlı ışınım tekniği (OSL)’ yöntemi ile yaşlandırması yapıldı. Analizler yalıtaşının oluşum yaşı için minimum 1.42±0.20 bin yıl ve maksimum 2.28±0.28 bin yıl yaşlarını vermektedir.Publisher's Versio

Fe-%24.5Ni-%4.5Si alaşımında austenite-martensite faz dönüşümleri üzerinde çalışmalar

Tez (Doktora) -- Kırıkkale Üniversitesi78649

Studies on the austenite-martensite phase transformations in an Fe-%24.5i-%4.5 Si alloy

YÖK Tez ID: 196777ÖZETFe-%24.5Ni-%4.5Si ALAŞIMINDAAUSTENİTE-MARTENSİTE FAZ DÖNÜŞÜMLERİÜZERİNDE ÇALIŞMALARGÜNGÜNEŞ, HakanKırıkkale ÜniversitesiFen Bilimleri EnstitüsüFizik Anabilim Dalı, Doktora TeziDanışman : Prof. Dr. Tahsin Nuri DurluTemmuz 2005, 97 sayfaFe-%24.5Ni-%4.5Si alaşımında ısıl işlem sıcaklığı, ısıl işlem süresi vesoğutma hızı gibi farklı işlemler sonucu oluşan martensitik fazdönüşümlerinin morfolojik, kristalografik, manyetik ve termal özellikleri çeşitlifiziksel yöntemler kullanılarak araştırılmıştır. Isıl işlem sıcaklığı, ısıl işlemsüresi ve soğuma hızının değişmesi ile martensite morfolojisinin değiştiğigözlemlendi. Austenite yapı içerisinde oluşan αâ?² (b.c.c) martensite'ninKurdjumov-Sachs tipi dönme bağıntısı sergilediği bulundu. Bu sonuçlarikizlenmiş kelebek tipi martensite plakaların termal etki ile de oluştuğunugöstermiştir.iFe-%24.5Ni-%4.5Si alaşımında austenite yapı içerisinde oluşanmartensite fazın antiferromanyetik düzenlemeye sahip olduğu ve ısıl işlemsıcaklığının artması ile manyetik alınganlık değerinin arttığı AC manyetikalınganlık ölçümlerinden belirlenmiştir.Fe-%24.5Ni-%4.5Si alaşımında ısıl işlem sıcaklığı, ısıl işlem süresi vesoğuma hızının artması ile oluşan martensite miktarının ve izomer kaymadeğerinin arttığı buna karşın iç manyetik alanın azaldığı Mössbauerspektroskopisi yöntemiyle belirlenmiştir.Fe-%24.5Ni-%4.5Si alaşımında ısıl işlem sıcaklığı ve ısıl işlemsüresinin artması ile martensite başlama sıcaklığı (Ms)' in düştüğü termalanaliz sistemi (DSC) ölçümleriyle belirlenmiştir.Anahtar Kelimeler: Austenite, Martensite, Fe-Ni-Si Alaşımı, MartensitikDönüşümler, αâ?² martensite, Manyetik Alınganlık, Mössbauer Spektroskopisi,İzomer Kayma, İç Manyetik Alan, DSC, TEM, SEMiiABSTRACTSTUDIES ON THE AUSTENITE-MARTENSITEPHASE TRANSFORMATIONSIN AN Fe%24.5Ni-%4.5Si ALLOYGÜNGÜNEŞ, HakanKırıkkale ÜniverstyGraduate School of Natural and Applied SciencesDepartment of Physics, Ph. D ThesisSupervisor : Prof. Dr. Tahsin Nuri DurluJuly 2005, 97 pagesMorpholigical, crystallographic, magnetic and thermal properties ofmartensitic phase transformations in an Fe%24.5Ni-%4.5Si alloy, underdifferent heat treatments such as heat treatment temperature, heat treatmenttime and cooling rate were investigated by using various physical systems. Itwas observed that the morphology of the martensite was changed due toheat treatment temperature, heat treatment time and cooling rate. It was alsofound that the αâ?² (b.c.c) martensite which was formed in the austenite matrixexhibited a Kurdjumuv-Sachs type orientation relationship. The presentresults indicate the twinned substructure of butterfly-like plate martensitesalso in thermally induced conditions.iiiAC magnetic susceptibility studies of the alloy revealed that themartensitic phase which was formed in the austenite matrix of Fe%24,5Ni-%4,5Si alloy showed an antiferromagnetic ordering and the magneticsusceptibility was increased with increasing of heat treatment temperature.Mössbauer spectroscopy method was employed to determine theamount of martensite and the value of isomer shift were increased with theincreasing of heat treatment temperature. Heat treatment time and coolingrate where hyperfine magnetic fields of martensitic phase were decreased.Differential scanning calorimetry (DSC) measurements revealed that,martensite start temperature (Ms) was decreased as the increase of heattreatment temperature and heat treatment time.Key Words: Austenite, Martensite, Fe-Ni-Si Alloy, Martensiticαâ?²Transformations, martensite, Magnetic Susceptibility, MössbauerSpektroscopy, Isomer Shift, Hyperfine Magnetic Fields, DSC, TEM, SEMi

Fe-22.3%Ni-2.7%Mn Alaşımında Martensite Oluşumunun Mössbauer Spektrometresi İle İncelenmesi

Tez (Yüksek Lisans) -- Kırıkkale Üniversitesi47897

Fe-22.3% Ni-2.7 % mn alaşımında martensite oluşumunun mösbaver spektrometresi ile incelenmesi

YÖK Tez ID: 105850ÖZET Yüksek Lisans Tezi Fe-22.3%Nİ-2.7%Mn ALAŞIMINDA MARTENSİTE OLUŞUMUNUN MÖSSBAUER SPEKTROMETRESİ İLE İNCELENMESİ Hakan GÜNGÜNEŞ Kırıkkale Üniversitesi Fen Bilimleri Enstitüsü Fizik Anabilim Dalı Danışman: Prof. Dr. D. Mehmet ZENGİN 2001,Sayfa:59 Jüri: Prof. Dr. D. Mehmet ZENGİN Prof. Dr. İhsan ULUER Prof. Dr. Hüseyin AKTAŞ Fe-22.3%Ni-2.7%Mn alaşımında soğutma etkisi ile ortaya çıkan martensitik faz geçişleri Mössbauer Spektrometresi kullanılarak incelenmiştir. Bu amaçla 25 (im kalınlığında hazırlanıp austenite fazda kristalleştirilen örneğin oda sıcaklığında Mössbauer Spektrumu alınmıştır. Daha sonra sıvı azot içerisinde bir hafta bekletilen örneğin oda sıcaklığında yeniden Mössbauer Spektrumu alındı. Sonuçta austenite fazdaki örneğin oda sıcaklığında hala austenite fazda bulunduğunu, ama sıvı azot'ta bir hafta bekletilmesi sonucu örnekte austenite miktarının 75.982%' lik kısmının martensite dönüştüğü gözlendi dolayısıyla martensite fazın oluştuğu sonucuna varıldı. Anahtar Kelimeler: Austenite-Martensite faz geçişi, Mössbauer Spektrumu, Düşük SıcaklıkABSTRACT Masters Thesis THE INVESTIGATION OF THE MARTENSITE TRANSFORMATIONS IN Fe-22.3%Ni-2.7Mn ALLOYS USING BY MÖSSBAUER SPECTROMETER Hakan GÜNGÜNEŞ Kırıkkale Üniversitesi Graduate School of Natural and Applied Sciences Department of Physics Supervisor: Prof. Dr. D. Mehmet ZENGİN 2001,Page:59 Jüri: Prof. Dr. D. Mehmet ZENGİN Prof. Dr. İhsan ULUER Prof. Dr. Hüseyin AKTAŞ Martensite phase tansformations obtained from cooling effect in Fe-22.3%Ni- 2.7%Mn alloy have been investigated using by Mössbauer Spectrometer. In this study, a Mössbauer spectrum of a sample with 25 um thickness crystallized in austenite phase has been taken at room temperature. After that measurement the same sample has been waited for a week at liquid nitrogen temperature and then the Mössbauer spectrum of the sample has been taken again. As a result, the sample in austenite phase was still in austenite phase at room temperature. But the part of 75.982% of the sample that was kept for a week at liquid nitrogen temperature has been transformed to the martensite phase. So it has concluded that martensite phase has been obtained. Key Words: Austenite-martensite phase transformation, Mössbauer spectrum, Low temperatur

Nickel ferrite nanoparticles for simultaneous use in magnetic resonance imaging and magnetic fluid hyperthermia

We demonstrate magnetic resonance imaging (MRI) contrast enhancement and ac-field induced heating abilities of tetramethylammoniumhydroxide (TMAH) coated nickel ferrite (NiFe2O4) nanoparticles and discuss the underlying physical mechanisms. The structural characterization revealed that the NiFe2O4 particles synthesized with a modified co-precipitation method have a very narrow size distribution with a 4.4 nm magnetic core and 15 nm hydrodynamic diameters, with relatively small fraction of agglomerates. The as-prepared particles presented superparamagnetic behavior at room temperature. The in vitro hyperthermia experiments, performed in ac-field conditions under human tolerable limits, showed that the suspensions of the synthesized nanoparticles exhibit a maximum specific absorption rate (SAR) value of 11 W/g. The 1H nuclear magnetic resonance (NMR) relaxometry measurements indicated the suspensions of NiFe2O4 have a transverse-to-longitudinal relaxivity ratio r2/r1 greater than two, as required for superparamagnetic MRI contrast agents. On the basis of the parameters obtained from the magnetic measurements, by comparing the relevant theoretical models with the experimental results, we found that the presence of agglomerates, and particularly the interactions within the agglomerated nanoparticles, caused a significant increase in the hyperthermia and MRI efficiencies. On the other hand, from an applicative point of view, both the MRI contrast enhancement and the heating capabilities allow the simultaneous use of nickelferrites in diagnostic and therapeutic applications as theranostic agents

Spin Canting in Silica-Coated Nickel Ferrite (NiFe2O4@SiO2) Nanoparticles: a Mossbauer Spectroscopy Study

We present a comparative study on superparamagnetic uncoated and silica-coated NiFe2O4@SiO2 nanoparticles with identical NiFe2O4 cores and two different silica coating thicknesses, focusing on the surface spin arrangement on NiFe2O4. For the investigation of surface spin dynamics, in addition to the SQUID magnetometry experiments which probe the macroscopic behaviour of particle magnetization, Mossbauer spectroscopy was utilized as being a local technique with superior characteristic measurement time. It was revealed that two common aspects observed in nanoscaled magnetic particles, namely the surface spin canting and interparticle dipolar interactions, are intertwined with respect to their contributions to the total magnetic anisotropy, where the latter is significantly decreased with silica coating thickness and allowed surface effects to manifest itself in Mossbauer spectra. The reduced saturation magnetization of uncoated NiFe2O4 nanoparticles with respect to their bulk counterparts indicated the existence of a "magnetically dead" layer on NiFe2O4 surface. In opposite to some assumptions in the literature, the Mossbauer spectra confirmed that such reduced magnetization arises from spin disorder, rather than a change in coordination from inverse spinel to the mixed spinel structure. On the other side, emergence of broad sextet peaks at room temperature Mossbauer spectra showed that for NiFe2O4@SiO2 samples, silica coating further enhanced the spin canting on NiFe2O4 surface. Similarly, for NiFe2O4@SiO2 sample, an unusual asymmetric hysteresis loop at spin freezing temperature was observed as a signature of the existence of disordered spins in the SiO2/NiFe2O4 interface. It was shown that the sextet components in Mossbauer spectra can be reproduced with a continuous hyperfine field distribution due to the frustrated local spin arrangement at the surface. The thickness of the "magnetically dead" disordered surface spin layer was estimated for uncoated NiFe2O4, and average spin canting angle was calculated for NiFe2O4@SiO2 nanoparticles