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Dissertations / Theses on the topic 'Yttrium'

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Published: 4 June 2021
Last updated: 26 July 2024

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1

Skaudžius, Ramūnas. "Synthesis and investigation of co-substituted yttrium aluminium and yttrium gallium garnets." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2014. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2014~D_20141209_112415-18733.

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Since 1926 when the preliminary structure of natural silicate minerals having cubic structure was determined, the family of garnets became one of the most extensively studied group of compounds. Garnets containing transition metals and rare-earths carry many important technological uses as magnetic materials, as phosphor materials employed in solid state lasers, television screens and light-emitting diodes, as computer memories, as near UV and near IR radiation up/down-converting compounds in Si solar cells and in other devices as microwave optical elements. The europium or chromium doped garnets also could be applied in the new field as optical imaging. The improvements in mechanical and optical properties, the new areas of applications provide a strong motivation for studying garnets in general. To synthesize and to characterize new mixed-metal garnets was the main aim of the present thesis. The investigation of the dependence of europium optical properties on the local environment in different garnets was also in the field of interest. Therefore, powders of the new mixed-metal garnets were synthesized by sol-gel route, while traveling solvent floating zone method was used for crystal growth. X-ray diffraction was used for phase identification. The neutrons diffractions and Rietveld refinement gave information of the crystal structure. Finally, reflection, excitation and emission spectra were recorded for the investigation of the optical properties.
Nuo 1926-ųjų metų, kai pirmą kartą buvo ištirta preliminari natūralių silikatinių mineralų, turinčių kubinę kristalinę gardelę, struktūra, granatų šeimai priskiriami junginiai tapo viena labiausiai tyrinėjamų medžiagų grupių. Granatai, kuriuose yra pereinamųjų metalų bei retųjų žemių metalų, pasižymi ypatingu technologiniu pritaikymu. Kaip šviečiančios medžiagos jie naudojami kietafaziuose lazeriuose, televizorių ekranuose ar dioduose. Europiu arba chromu legiruoti junginiai galėtų būti pritaikyti optiniam vaizdavimui medicinoje, kas iki šiol nebuvo daryta. Galimybė pagerinti granatų optines ir mechanines savybes bei naujos pritaikymo sritys suteikia stiprią motyvaciją tyrinėjimams. Pagrindinis disertacijos tikslas buvo naujų mišrių metalų granatų sintezė bei jų optinių savybių tyrimas. Taip pat siekta ištirti europį supančios aplinkos įtaką jo liuminescencinėms savybėms tiek milteliuose, tiek kristaluose. Milteliai buvo sintetinti zolių-gelių arba kietafazės reakcijos metodu. Kristalai auginti keliaujančio lydalo slankioje zonoje būdu. Medžiagų faziniai virsmai tirti Rentgeno spindulių difrakcijos metodu. Neutronų difrakcijos duomenys bei Rietveldo tikslinimas buvo panaudoti granatų struktūrinei analizei. Junginių optinės savybės įvertintos išmatavus atspindžio, sužadinimo ir emisijos spektrus.
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2

Norman, Timothy John. "Radioimmunotherapy with yttrium macrocycles." Thesis, Durham University, 1994. http://etheses.dur.ac.uk/5529/.

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Monoclonal antibody fragments (Fab') which recognise tumour-associated antigens provide an ingenious means of selectively targeting a therapeutic radionuclide to a tumour for radioimmunotherapy. The radionuclide yttrium-90, a long range β(^-) emitter, was chosen to deliver a sterilising dose of radiation to the tumour. A selection of novel functionalised macrocyclic ligands based on a 1,4,7,10-tetraazacyclododecane skeleton have been synthesised, and the stabilities of their yttrium (III) and gadolinium (III) complexes studied in vitro through association and dissociation measurements, and in vivo through animal biodistribution studies. The radiolabelled complexes do not dissociate in vivo. Maleimides are compounds which are capable of selectively reacting with a thiol of an antibody fragment. Selective functionalisation of one of the yttrium binding macrocyclic ligands with either one or three maleimides has been carried out, and the resulting compounds conjugated to tumour seeking humanised antibody fragments. Subsequent radiolabelling with (^90)Y, gave the desired tumour targeting drug for use in radioimmunotherapy. Acridines are a class of intercalating agents which are capable of reversibly binding to DNA. A maleimide functionalised ligand derivatised with acridine was formed. Conjugation of this compound to antibody fragments capable of entering a tumour cell, may permit drug binding to tumour cell DNA, and thus enhance the targeting efficacy of the radiolabelled conjugate.
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3

Azis, Rabaah Syahidah. "Structure development in sol-gel derived yttrium aluminium oxide, yttrium gallium oxide and their solid solutions." Thesis, University of Warwick, 2010. http://wrap.warwick.ac.uk/4483/.

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The structural study of the garnet system Y3Al5O12 (YAG) prepared by different sample preparations (solid-state sintering and sol-gel) is reported. Different sample preparations were investigated to find a suitable method for obtaining pure YAG. 27Al and 89Y MAS NMR were used to investigate the short range structure and results are compared to long-range order information from x-ray diffraction (XRD). These two techniques are comlementary in detecting phase composition and disorder in samples. There is a challenge in preparing pure Y3Al5O12 since intermediate phases easily grow when sintered at high temperature, i.e. YAlO3 (YAP), Y4Al2O9 (YAM), Y2O3 (Yttria) and Al2O3 (Corundum). Therefore structural information on these impurity phases was obtained to compare with samples under study. Different sample preparations were also used to try to obtain pure YAP and YAM. Since it is difficult to obtain pure YAG by high temperature solid-state sintering, the sol-gel technique was used to produce pure YAG at low temperature. In this work, pure YAG has been obtained at temperatures as low as 800oC using a sol-gel citrate-nitrate with combustion process (SGCNCT). Other sol-gel syntheses used are: sol-gel glycolate (SGG), citrate-nitrate (SGCN) and modification of the citrate-nitrate ratio with combustion process (SGCNCT). The modification of the citrate to nitrate ratio and controlling the mixing temperature as low as 50- 60oC is a novel route to produce pure YAG at low as 800oC. This technique was then used to prepare different garnet systems, i.e. Y3Ga5O12 (YGG) and also garnet solid solution system, Y3Al5-xGaxO12. Again, information from NMR was compared with results from XRD to determine different phase distribution and disorder. The 27Al chemical shift range for different structural units (e.g. AlO4, AlO5 and AlO6) in YAG allowed the aluminium distribution in these materials to be refined. This is important when dealing with low temperature amorphous phases. For example, the AlO5 site cannot be traced using XRD. The work was extended to study different nuclei, i.e. 89Y and 71Ga NMR. 27Al and 71Ga is a quadrupolar nuclei with spin, I=5/2 and 3/2, respectively. Extensive broadening of the NMR signal was observed at some sites due to the quadrupolar interaction and the effect of this on the quantitation of 27Al and 71Ga NMR is discussed. The substitution of Al and Ga in the garnet system was investigated. The different distribution of next nearest neighbour atom (nnn) produces a peak shift in 27Al, 71Ga NMR and also XRD.
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4

Nandor, Valerie Ann. "Nuclear magnetic resonance of Oxygen and Yttrium in the normal state of Yttrium Barium Copper Oxide /." The Ohio State University, 1999. http://rave.ohiolink.edu/etdc/view?acc_num=osu1488191667184518.

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5

Rajasekharan, Vishnu V. "New strategies for electrodepositing yttrium oxide." Laramie, Wyo. : University of Wyoming, 2005. http://proquest.umi.com/pqdweb?did=888860291&sid=1&Fmt=2&clientId=18949&RQT=309&VName=PQD.

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6

Morris, Susan. "Oxo species of zirconium and yttrium." Thesis, University of Reading, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240334.

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7

Clark, Howard C. S. "Amido derivatives of titanium and yttrium." Thesis, University of Sussex, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309437.

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8

ENGELS, JEAN-MARIE. "Interdiffusion reactive yttrium cuivre en films." Paris 11, 1996. http://www.theses.fr/1996PA112228.

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Des films d'alliages d'epaisseur variable sont fabriques a partir des metaux yttrium et cuivre. Dans une enceinte a ultra-vide, un depot d'yttrium est effectue par evaporation ou par pulverisation d'une cible sur un substrat de cuivre. La caracterisation de composition en profondeur et le dosage des impuretes est effectuee par analyse de masse par spectrometrie des ions secondaires et par thermo-ionisation de la matiere pulverisee (sims et stims), et par retrodiffusion rutherford (rbs). La caracterisation des etats de cristallinite utilise la diffraction des rayons x (rx), et la diffraction des electrons par transmission (met). Des conditions cinetiques appropriees permettent d'obtenir sequentiellement toutes les phases de l'equilibre majoritaires et texturees au sein du film. Le transport de matiere commence a basse temperature avec la germination heterogene de la phase ycu dont l'energie d'activation est pour la premiere fois evaluee. Elle se termine avec une phase type dycu7 de granulometrique millimetrique. Plusieurs alliages supplementaires inconnus dans le couple mais repertories dans d'autres binaires comparables apparaissent en grande quantite (deux cents plans atomiques). L'interdiffusion permet de former des alliages dotes d'une tres grande qualite cristalline. Elle se revele etre une technique puissante pour mettre en evidence la variete des phases existant dans le couple et l'influence des energies de surface sur la germination des phases. La forte sensibilite du binaire a la qualite des conditions experimentales a aussi ete observee. L'obtention de phases amorphes et d'un alliage cubique metastable au lieu des phases ycu et ycu2 en est l'illustration
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9

Chambers, James Joseph. "REACTIONS FOR YTTRIUM SILICATE HIGH-K DIELECTRICS." NCSU, 2000. http://www.lib.ncsu.edu/theses/available/etd-20000721-183205.

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CHAMBERS, JAMES JOSEPH. Reactions for Yttrium SilicateHigh-k Dielectrics. (Under the advisement of Dr. GregoryN. Parsons.)The continued scaling of metal-oxide-semiconductor-field-effect-transistors (MOSFETs) will require replacing the silicon dioxide gate dielectric with an alternate high dielectric constant (high-k) material. We have exploited the high reactivity of yttrium with both silicon and oxygen to form yttrium silicate high-k dielectrics. Yttrium silicate films with composition of (Y)1-x and x = 0.32 to 0.87 are formed by oxidizing yttrium on silicon where yttrium reacts concurrently with silicon and oxygen. The competition between silicon and oxygen for yttrium is studied using X-ray photoelectron spectroscopy (XPS) and medium energy ion scattering (MEIS). The initial yttrium thickness mediates the silicon consumption, and a critical thickness (~40-80 Å) exists below which silicon is consumed to form yttrium silicate and above which Y forms without silicon incorporation. Engineered interfaces modify the silicon consumption, and a nitrided silicon interface results in film with composition close to Y. The silicon consumption also depends on the oxidation temperature, and oxidation at higher temperature generally results in greater silicon incorporation with an activation energy of 0.3-0.5 eV. Yttrium silicate films (~40 Å) formed by oxidation of yttrium on silicon have an amorphous microstructure and an equivalent silicon dioxide thickness of ~12 Å with leakage current . Yttrium silicate formation on silicon is also demonstrated using plasma oxidation of yttrium on silicon, reactive sputtering of yttrium and annealing/oxidation of yttrium on thermal SiO. The interface reactions described here for yttrium are expected to be active during both physical and chemical vapor deposition of other high-k dielectrics containing Hf, Zr and La.

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10

Chael, Bradley. "Laser spectroscopy of cerium and yttrium isotopes." Thesis, University of Birmingham, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.422322.

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11

Jette, Bruce Donald. "Feasibility of electrodeposition of yttrium and barium." Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/79452.

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12

Su, Tingyu S. M. Massachusetts Institute of Technology. "Properties of off stoichiometric yttrium iron garnet." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/127115.

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Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, May, 2020
Cataloged from the official PDF of thesis.
Includes bibliographical references (pages 34-35).
YFO (YFeO3) target is used for deposition on GGG (Ga3Gd5O12) substrates with different directions: (001), (110) and (111) by PLD (Pulsed Laser Deposition). HRXRD characterization shows that high-quality epitaxial garnet phase is formed on GGG substrates. However, RSM results show that the off-stoichiometric YIG film on (111) GGG substrates can remain fully strained in plane with thickness from 23 nm to 74 nm; while the samples on (001) GGG substrates show different degrees of relaxation in-plane depending on film thickness. Magnetic characterization shows that the samples grown on (111) GGG substrates have saturation magnetization Ms~45 emu/cc, which is significantly smaller than standard YIG (~140 Ms~45/emu/cc). Furthermore, the Curie temperature of samples grown on (111) GGG is ~ 310K, in obvious contrast with standard YIG ~560K.
by Tingyu Su.
S.M.
S.M. Massachusetts Institute of Technology, Department of Mechanical Engineering
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13

Fung, Sing Chor. "Conductivity fluctuations in yttrium barium cooper oxides." HKBU Institutional Repository, 1994. http://repository.hkbu.edu.hk/etd_ra/34.

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14

Remhof, Arndt. "Hydrogen in yttrium films structure and phase formation /." [S.l. : s.n.], 1999. http://deposit.ddb.de/cgi-bin/dokserv?idn=959506136.

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15

Abdul-Al, Saleh. "Prédictions de la structure électronique de monohalogénures d'yttrium : YF, YBr, YI." Lyon 1, 2004. http://www.theses.fr/2004LYO10152.

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Nous avons étudié YF, YBr et YI en utilisant une approche ab initio de type CASSCF suivi d'un calcul MRCI (simple et double excitations + correction de Davidson). L'yttrium étant un atome lourd il est indispensable de prendre en compte les effets spin-orbite dans ces études ce qui a été fait en introduisant un pseudopotentiel spin-orbite que nous avons construit. Nous avons fait une étude systématique pour chacune des molécules, en employant le progiciel international MOLPRO au travers de l'interface graphique GABEDIT créée au sein du LASIM. Pour YF et YBr nous avons étudié 20 états 2S+1 [Lambda] (+/-) et 41 états [Oméga] (+/-) tandis que pour YI nous avons étudié 15 états 2S+1 [lambda] (+/-) et 33 états [oméga] (+/-). La comparaison avec les résultats expérimentaux disponibles démontre la qualité satisfaisante de nos prédictions, nous autorisant à penser que nos nombreux résultats nouveaux pourront être utiles à de futures expériences sur ces molécules
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16

Webster, Scott Elliott. "Growth and structure of yttrium sesquioxide epitaxial films." Thesis, University of British Columbia, 2012. http://hdl.handle.net/2429/41417.

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The use of molecular beam epitaxy as a method for producing solid state host crystals for planar waveguide lasers has been investigated. Single crystal yttrium sesquioxide with a very high degree of structural order has been grown on R-plane sapphire substrates. The (01Ῑ2) Al₂O₃ substrates were annealed in air at 1150°C to generate atomically smooth surfaces with parallel atomic steps. This process was important for maximizing structural quality and minimizing surface roughness of the grown Y₂O₃ film. A critical-thickness-like phenomenon was discovered, where the Y₂O₃ would grow in regions with near structural perfection at the beginning of growth. In thicker films, the x-ray diffraction peaks became wider, indicating less crystalline uniformity. The maximum equivalent “critical thickness” achieved was 7 nm for a film grown at 800°C with a growth rate of 20 nm/hr. The highly ordered material may be present in one uniform layer or distributed in smaller regions throughout the thin film. Y₂O₃ films on Al₂O₃ were annealed in air at temperatures up to 1400°C to study interdiffusion. By analyzing x-ray diffraction measurements, we found that Al migrated from the substrate into the Y₂O₃ film with an approximate activation energy for bulk diffusion of 3.0 eV. Diffusion on the Y₂O₃ surface was estimated to have an activation energy of (0.5 ± 0.3) eV from atomic force microscopy images. After annealing, the presence of Y₄Al₂O₉, YAlO₃, and Y₃Al₅O₁₂ phases was confirmed using x-ray diffraction and photoluminescence measurements. Attempts were made to use molecular hydrogen gas and gallium as surfactants during growth to improve film properties. No conclusive benefit was observed. Y₂O₃ film surface roughness was observed to increase roughly proportionally to the square root of film thickness. A 600 nm thick waveguide layer grown under optimal conditions had a root-mean-square roughness of 5.8 nm. This level of roughness could cause scattering loss at the waveguide core-cladding interface that is problematic for practical applications.
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17

Cooper, C. S. "Computational modelling of yttrium stabilised zirconia in catalysis." Thesis, University College London (University of London), 2014. http://discovery.ucl.ac.uk/1431123/.

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This thesis employs a range of computational modelling techniques to explore the structure, properties and catalytic activity of yttrium stabilised zirconia (YSZ) with a focus on its functions as a catalyst in methane reforming by partial oxidation. The surface and bulk properties of the material are explored, including the use of an exhaustive search of all possible defect configurations at a low yttrium loading in a bulk and a surface system allowing conclusions to be drawn about the relationship between defect configurations and stability. One significant property of YSZ materials is their ability to become oxygen ionic conductors at high temperatures, which is crucial to their use in solid oxide fuel cells and may be significant in catalytic applications. This thesis presents results of calculations designed to explore the effects of surfaces and defects on the ionic conductivity of YSZ materials, presenting evidence that oxygen conduction may be significantly enhanced at the surfaces of the material. Calculations using electronic structure techniques are carried out to examine the catalytic properties of YSZ. Initially potential surface active sites are characterised. The surface model is then shown to strongly adsorb and activate molecular oxygen, carbon dioxide and water from the gas phase. The energetics and electron movements in these surface interactions are described. These results provide the basis for investigations of reforming reactions in subsequent chapters and will be of interest in investigations of other catalytic processes over YSZ materials. A novel mechanism of methane C-H bond activation is reported over YSZ, activated by the presence of an adsorbed partially reduced O2 species. The mechanism is investigated in detail, including the use of two electronic structure techniques to allow mechanistic details to be proposed and activation energy estimated. It may be that this mechanism is more generally applicable to oxidative C – H bond activation over many metal oxide materials.
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18

Soutar, Lyndsay. "Reactivity studies of phosphorus-stabilised yttrium carbene complexes." Thesis, University of Nottingham, 2016. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.754214.

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Reactivity studies of [Y(BIPM)(I)(THF)2] (73), [Y(BIPM)(CH2SiMe3)(THF)] (74) and [Y(BIPM)(CH2Ph)(THF)] (75) towards a range of unsaturated compounds have been performed. The isolation of single crystals suitable for X-ray diffraction studies for all the systems investigated has proven problematic. The low crystalline yields observed, where crystals of suitable quality for single crystal X-ray diffraction studies were obtainable, is a reflection of the high solubility of many of the products. The reactivity of 74 and 75 towards anthracene aldehyde and benzaldehyde revealed Wittig-type reactivity to yield the alkene products (Me3SiNPPh2)2C=C(H)R (65) (R = 9-anthracene) and (Me3SiNPPh2)2C=C(H)Ph (66), respectively. The respective reactions of 74 and 75 with four equivalents of acetophenone yielded the previously reported dypnopinacol 111 via a cyclotetramerization reaction.
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19

Dornheim, Martin. "Spannungen, Dehnungen und Lage der Phasengrenzen in dünnen Nb- und Y-Schichten bei Wasserstoffbe- und -entladung." [S.l.] : [s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=965265641.

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20

Picard, Vincent. "Etude du comportement thermique des oxalates hydrates d'yttrium." Dijon, 1993. http://www.theses.fr/1993DIJOS028.

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Les oxalates neutres Y#2(C#2O#4)#3, nH#2O (n=6 et 10) et l'oxalate acide YH(C#2O#4) 3H#2O sont les pr2curseurs de la synth7se de l'oxyde Y#2O#3. La d2shydratation sous pression de vapeur conduit à d'autres phases, dont la stœchiométrie en eau est égale a 3,5-3-2,5 et 2H#2O par mole de sel anhydre. Le dihydrate est egalement produit lors de la transformation du sel acide. Le trihydrate est la seule forme réellement stable dans les conditions ambiantes. La structure cristalline a été établie et comparée à celles du deca- et de l'hexahydrate. Cette comparaison révèle (I) la grande régularité de l'évolution de la compacité de ces structures lorsque la stœchiométrie en eau varie. (II) le rôle prédominant joué par l'eau dans la stabilité de ces structures. (III) l'origine des stœchiométries a 3,5-2,5 et 2H#2O. (IV) enfin, l'impossibilit2 pour l'oxalate anhydre d'être isolé autrement qu'à l'état amorphe. Les filiations structurales qui existent entre les oxalates et les produits de leur décomposition (l'oxycarbonate Y#2O#2CO#3 et l'oxyde Y#2O#3) permettent de comprendre le caractère limité des modifications morphologiques qui accompagnent la décomposition. C'est la fragmentation des cristaux précurseurs lors de l'étape de déshydratation qui détermine donc les formes et dimensions des grains d'oxyde produits
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21

Rayner, Timothy James. "Development and evaluation of yttrium modified aluminide diffusion coatings." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0008/MQ34151.pdf.

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22

梁詠霞 and Wing-har Joanne Leung. "High resolution laser spectroscopy of yttrium and nickel monohalides." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2002. http://hub.hku.hk/bib/B31243320.

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23

Collingwood, Joanna Frances. "The magnetic properties of gadolinium-rich gadolinium-yttrium alloys." Thesis, University of Warwick, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.396855.

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24

Smith, R. G. "Neutral homoleptic alkyls of yttrium and the 4f elements." Thesis, University of Sussex, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384737.

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25

Gordon, Andrew Christian. "Tuning Your RADIOembolization| Imaging-guidance of Yttrium-90 Radioembolization." Thesis, Northwestern University, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10160495.

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Hepatocellular carcinoma (HCC) is the second leading cause of cancer death in the world and the liver is a common site of metastases from other primary neoplasms. Many patients are not surgical candidates. Radioembolization is an intra-arterial therapy delivering high doses of radiation emitted from microspheres infused selectively into the tumor feeding arteries. These microspheres land in the tumor microcirculation and deposit radiation to the tumor tissues. Over the past ten years, radioembolization has become part of the treatment guidelines for unresectable HCC, liver-dominant metastatic colorectal cancer, and neuroendocrine liver metastases, and it is often used in the salvage setting for patients with hepatic malignancy progressing on other therapies. The overarching goal of the thesis work was to advance the basic science of 90Y radioembolization based on existing clinical needs to ultimately improve patient outcomes. This included 1) setup of pre-clinical laboratory to study radioembolization, 2) optimization of radioembolization protocols in research animals, 3) validation of 90Y PET/CT imaging techniques to monitor microsphere delivery and dosing, 4) blood oxygen-level dependent (BOLD) imaging and evaluation of tumor biology and physiology after radioembolization in the VX2 rabbit model at a fixed dose of 50 Gy, 5) evaluation of normal tissue pathology (fibrosis, atrophy) and biology (hepatocyte proliferation, microvessel density, stellate cell activation) in rats after 90Y radiation lobectomy at clinically relevant dosing from 150 to >4,000 Gy, and 6) development of new yttrium microsphere compositions for combination therapy with electromagnetic hyperthermia.

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26

Leung, Wing-har Joanne. "High resolution laser spectroscopy of yttrium and nickel monohalides /." Hong Kong : University of Hong Kong, 2002. http://sunzi.lib.hku.hk/hkuto/record.jsp?B25211742.

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27

Duchateau, Robbert. "Ancillary ligand effects in organoyttrium chemistry." [S.l. : [Groningen] : s.n.] ; [University Library Groningen] [Host], 1995. http://irs.ub.rug.nl/ppn/142034959.

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28

Mouzon, Johanne. "Synthesis of ytterbium-doped yttrium oxide nanoparticles and transparent ceramics." Doctoral thesis, Luleå : Division of Engineering Materials, Luleå University of Technology, 2006. http://epubl.ltu.se/1402-1544/2006/64/.

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29

Braune, Wigand. "Aluminium- und Yttrium-Initiatoren für die koordinative Ringöffnungspolymerisation von Propylenoxid." [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=970659792.

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30

Hunt, Eden Meyer. "The implantation and annealing effects of yttrium implantation into alumina." Thesis, Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/19447.

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31

Pullan, Penelope Anne. "Flux pinning in yttrium barium copper oxide superconducting thin films." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320038.

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32

Elvidge, Benjamin Robert. "Yttrium chelating diamide complexes in olefin and polar monomer polymerisation." Thesis, University of Sussex, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.555266.

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33

Cox, Jonathan Paul Lawrence. "Yttrium macrocycles and their use in the treatment of cancer." Thesis, Durham University, 1989. http://etheses.dur.ac.uk/6509/.

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Six macrocyclic ligands have been synthesized for binding yttrium(III). Of the six, 1,4,7,10-tetraazacyclododecane-1,4,7,10- tetraacetic acid (DOTA) forms the most stable yttrium(III) complex in aqueous solution, log K(ML) = 24.9 and half life ~ 2 weeks at pH 1.0. In addition to an acid-dependent dissociative mechanism, release of Y(^3+) from Y(DOTA) may, it is tentatively suggested, be promoted by metal ions. DOTA also demonstrates rapid uptake of Y(^3+) (98% labelling efficiency at 310 K with [DOTA] = 10(^-5) M and [Y(^3+)1 ~ 10(^-9) M, pH 5.5 [0.1 M ammonium acetate]). Accordingly, an aminobutyl C-functionalised derivative of DOTA has been made and coupled to a monoclonal antibody. Once labelled with (^90)Y(^3+) a long range β- emitter, the conjugate can be used to selectively deliver a sterilising dose of radiation to a tumour. Preliminary experiments have indicated that the radiolabelled MoAb conjugate remains relatively inert in vivo. Tumour regression studies are in progress.
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34

Ramanujam, Prabhu. "Synthesis and processing of nanocrystalline YAG (Yttrium Aluminium Garnet) ceramics." Thesis, Loughborough University, 2014. https://dspace.lboro.ac.uk/2134/16651.

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Transparent ceramics are used in a variety of applications such as protective visors, thermo-graphic lens, night vision devices and windowpane of an armed vehicle, missile domes and in aircrafts. Yttrium Aluminium Garnet (YAG, Y3Al5O12) exhibits uniform index of refraction without birefringence owing to its cubic crystal structure and offers a range of optical and mechanical properties that makes it suitable for transparent applications.
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35

Chen, Jimmy Kuo-Wei. "The electrical and optical properties of doped yttrium aluminum garnets." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/32136.

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36

Scit, O., E. Garskaite, and A. Kareiva. "Samarium-Substitution Effects in Sol-Gel Derived Yttrium Aluminium Garnet." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/34830.

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In this study, yttrium aluminium garnet (YAG) powders substituted by samarium were prepared by simple an aqueous sol-gel method using aluminium nitrate nonahydrate, yttrium oxide, samarium oxide as the starting materials and etane-1,2-diol as complexing agent. The powders annealed at 1000 degrees Celsius in air were characterized by X-ray diffraction (XRD) analysis, infrared spectroscopy (IR) and scanning electron microscopy (SEM). It was demonstrated, however, that the total substitution of yttrium by samarium does not proceed in the YAG. Pure cubic garnet phase was formed only at low concentration of samarium. With further substitution, the main part of garnet phase transformed in to the perovskite samarium aluminate phase. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/34830
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37

Boston, Rebecca Helen. "Control of crystallisation in the yttrium barium copper oxide system." Thesis, University of Bristol, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.686173.

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The control of crystallisation of complex oxides on the nano- and macro-scale is vital for the progression of technology and the fundamental understanding of the processes which govern functional oxide synthesis. The use of biotemplates has been shown to be a highly effective means of controlling both the phase and morphology of complex oxides, with macro- and nano-structures being formed which would otherwise be impossible using standard synthetic techniques. One complex functional material, yttrium barium copper oxide (YBCO), has generated huge amounts of interest for its superconducting properties, in particular its relatively high transition temperature (93 K), however given the complex nature of its crystal structure, it has proved to be very difficult to illicit control over the crystallite growth on the nano- or larger scales. Standard synthetic techniques, whilst very effective in producing a pure phase, are either slow or prohibitively expensive, and, due to the processes involved, offer no control over the final morphology. Herein are presented several new methods for the production of superconducting YBCO, including macro-scale control of polycrystalline samples in the formation of hollow microspheres through the use of the polysaccharide dextran, monolithic foams and highly layered tapes using a graphene oxide template, and nano-scale control to produce nanowires, through which a type of nanowire growth, the microcrucible mechanism, which has been directly observed and characterised for the first time. In addition, two sulphur-containing templates, K-carrageenan and a barnacle cement protein, which were thought to be unsuitable for use with YBCO (and any other phases containing precursors which would form stable sulphates during synthesis) were also investigated and found, after careful optimisation of the synthesis protocol, to be useable under certain experimental constraints. This is significant as it means that sulphur-rich proteins can now be successfully used for the production of YBCO, with the possibility of creating designer morphologies, giving even higher control over crystallisation. Each templating protocol was fully investigated using the standard chemical and physical characterisation techniques such as powder X-ray diffraction and transmission electron microscopy, in order to examine the phases and morphologies produced, and the superconducting properties investigated using a superconducting quantum interference device magnetometer. Where appropriate a number of other techniques such as in situ measurements using heating stages or X-ray micro computer-aided tomography were employed to give a deeper understanding of each templated system. The templating systems detailed here for YBCO should be applicable for other complex oxides, with the insights gained into the mechanisms which govern the phases and morphologies formed allowing optimised systems to be more quickly developed. This may lead to further advances in the production of complex functional oxide materials
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38

Ranta, Päivi. "Retinal detachment after neodymium : yttrium-aluminum-garnet laser posterior capsulotomy." Helsinki : University of Helsinki, 2002. http://ethesis.helsinki.fi/julkaisut/laa/kliin/vk/ranta2/.

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39

Paprottka, Karolin [Verfasser]. "Radioembolisation mit Yttrium 90 Harzmikrosphären : Weiterentwicklung und Outcome / Karolin Paprottka." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2017. http://d-nb.info/114278763X/34.

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40

Chapurina, Yulia. "Nouveaux complexes chiraux d'yttrium pour l'hydroamination intramoléculaire asymétrique des aminoalcènes." Thesis, Paris 11, 2011. http://www.theses.fr/2011PA112219.

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Les hétérocycles azotés chiraux représentent une classe importante de composés biologiquement actifs. L’hydroamination asymétrique intramoléculaire correspond parfaitement au concept d’économie d’atomes et permet l’accès direct à la formation de nouvelles liaisons carbone-azote. Le développement de catalyseurs pour la formation de pyrrolidines et piperidines reste cependant une tâche importante. Le thème de cette thèse est l’étude de nouveaux complexes chiraux binaphthylamide d’yttrium facilement accessibles et leur application pour promouvoir la réaction d’hydroamination/cyclisation des amines primaires liées à des alcènes stériquement encombrés.Des complexes chiraux binaphthylamidure alkyl ate d’yttrium ont été développés. Ces systèmes catalytiques ont été préparés in situ par une réaction simple stœchiométrique en présence d’un précurseur d’yttrium [Li(THF)4][Y(CH2SiMe3)4] connu et d’une variété de ligands chiraux binaphthyldiamine substitués. Les complexes chiraux hétéroleptiques obtenus se sont révélés actifs et énantiosélectifs pour la réaction d’hydroamination asymétrique intramoléculaire des aminoalcènes 1,2-disubstitués conduisant à la formation d’hétérocycles azotés avec cinq et six châinons. Les catalyseurs d’yttrium préparés à partir du ligand (R)-N-anthrylmethyl-binaphthylamine H2L13 et des ligands (R)-benzyl N-para-substitués H2L4 or H2L6 se sont révélés les plus énantiosélectifs à 70-110°C pour la réaction d’hydroamination/cyclisation des aminoalcènes encombrés. Un excès énantiomérique de 77% a été obtenu comme valeur la plus élevée décrite jusqu’à présent pour l’hydroamination asymétrique intramoléculaire des amines comportant des alcènes 1,2-disubstitués. Les premiers exemples de la réaction d’hydroamination intramoléculaire asymétrique des aminoalcènes 1,1,2-trisubstitués ont été rapportés. Les complexes ate alkyl d’yttrium ont fourni les produits hétérocycliques avec des centres quaternaires énantiomériquement enrichis dans des conditions réactionelles plus sévères que la cyclisation des aminoalcènes 1,2-disubstitués et avec des énantiosélectivités prometteuses atteignant 55%. Les complexes alkyl d’yttrium contenant une molécule de chlorure de lithium [{(R)-C20H12(NSiMe3)2}Y{CH2SiMe3}{LiCl(THF)2}] and [{(R)-C20H12(NC5H9)2}Y{CH2SiMe3}{LiCl(THF)2}] ont été préparés et comparés aux mêmes complexes sans LiCl. Ils se sont révélés être des catalyseurs efficaces pour la réaction d’hydroamination intramoléculaire des aminoalcènes terminaux
Chiral nitrogen-containing heterocycles represent an important class of biologically active compounds. The asymmetric intramolecular hydroamination perfectly matches the concept of sustainable chemistry and allows the formation of new nitrogen-carbon bonds in an ideal atom efficiency and economy, starting from non activated substrates. The development of catalysts for formation of enantioenriched pyrrolidines and piperidines derivatives remains however a challenging task. The topic of this dissertation is the study of new easily accessible chiral yttrium binaphthylamide complexes and their application for promoting the hydroamination/cyclisation of primary amines tethered to sterically demanding alkenes. Chiral binaphthylamido alkyl ate yttrium complexes have been investigated. These catalytic systems have been prepared by a facile in situ stoichiometric reaction of a well-known yttrium precursor [Li(THF)4][Y(CH2SiMe3)4] with a variety of chiral substituted (R)-binaphthylamine ligands. These chiral heteroleptic complexes are shown to be efficient catalysts for the enantioselective intramolecular hydroamination of 1,2-disubstituted aminoalkenes leading to the formation of five and six-membered N-heterocycles. Yttrium catalysts prepared from (R)-N-anthrylmethyl-binaphthylamine ligand H2L13 and (R)-N-para-substituted benzyl ligands H2L4 or H2L6 proved to be the most enantioselective catalysts at 70-110°C for the hydroamination/cyclisation of challenging aminoalkenes. An enantiomeric excess value of 77 % was indeed disclosed as the highest value reported so far for the asymmetric intramolecular hydroamination of amines tethered to 1,2-disubstituted alkenes. The first examples of asymmetric intramolecular hydroamination of 1,1,2-tri-substituted aminoalkenes have been reported. The alkyl ate yttrium complexes produced the heterocyclic compounds with enantioenriched quaternary centres under harsher reaction conditions than the cyclisation of the corresponding 1,2-disubstituted alkenes, and with promising enantioselectivities of up to 55 %.The neutral alkyl yttrium complexes containing one molecule of lithium chloride [{(R)-C20H12(NSiMe3)2}Y{CH2SiMe3}{LiCl(THF)2}] and [{(R)-C20H12(NC5H9)2}Y{CH2SiMe3}{LiCl(THF)2}] have been prepared and compared with the same complexes lacking LiCl. They have been revealed as efficient catalysts for intramolecular hydroamination of terminal aminoalkenes
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41

Pu, Song. "Heat transport in the high-temperature superconductor yttrium barium copper oxide." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ29767.pdf.

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42

Stanlake, Louisa Janet Easton. "Yttrium amidate complexes : fundamental reactivity and applications in catalysis and polymerization." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/7589.

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Rare-earth complexes are attractive catalyst systems due to their low cost, low toxicity and high reactivity. Modular ligand sets are ideal for complex formation since the steric and electronic properties of the resultant metal complexes can be easily varied. This thesis explores the structure and reactivity of new yttrium amidate complexes, which combine the highly reactive metal with the modular amidate ligand set. A library of tris, bis and mono(amidate) yttrium complexes have been directly synthesized from yttrium tris(trimethylsilyl)amidate and simple amide proligands. The tris(amidate) yttrium complexes are highly active initiators of ring-opening polymerization of Ɛ-caprolactone, yielding some of the largest molecular weight values for poly(Ɛ-caprolactone) reported. The initiation of this polymerization is proposed to be ligand initiated; however, a side-reaction is postulated where formation of a Ɛ-caprolactone-enolate yttrium complex results in broad polydispersity values of the resultant polymers. The bis(amidate) yttrium complexes are also excellent precatalysts for the hydroamination of aminoalkenes. Simple modification to the amidate backbone to include electron-withdrawing groups was found to significantly enhance reaction efficiency. These catalysts can mediate cyclohydroamination with both primary and secondary amine containing substrates. The mono(amidate) yttrium complexes were also investigated as novel precursors for the synthesis of the elusive terminal yttrium imido complex. Mixed anilido/amidate yttrium complexes were synthesized in high yield and a-H abstraction and deprotonation reactions were attempted in the hopes of isolating a crystalline compound. The addition of monodentate and neutral donors was required for isolation and characterization of the key reactive intermediates. This new family of yttrium complexes has proven to be very successful in preliminary catalytic studies. The ease with which the complexes can be synthesized and their steric and electronic properties make these complexes ideal for further catalytic investigations.
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43

Pu, Song 1968. "Heat transport in the high-temperature superconductor Yttrium Barium copper oxide." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=27392.

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The thermal conductivity $ kappa$ of the high-temperature superconductor $ rm YBa sb2Cu sb3O sb{7- delta}$ has been the subject of numerous investigations in recent years. Previous measurements show that $ kappa$: (1) exhibits a large peak in the superconducting state; (2) is anisotropic in the basal plane of the orthorhombic crystal structure. The main two subjects of this thesis are: (1) the origin of the peak and (2) a detailed investigation of the anisotropy.
In order to investigate the relative contribution of electrons and phonons to the heat conduction in YBCO, we have measured the thermal and electrical conductivities of high-quality twinned and detwinned crystals, with different levels of Zn-doping (from 0% to 3%). We found that the peak was rapidly suppressed by the impurities. Two scenarios are used to explain our results, attributing the effect to decrease in the carrier mean free path of either the electrons or the phonons.
As for the anisotropy between the a-axis and the b-axis, only two previous studies had previously been done. We find some new striking features: (1) a peak appears in $ kappa sb{chain}$ below 50 K, revealed as a result of our using of higher purity samples. (2) this peak is similar to that of $ kappa sb{a}$ below $T sb{c} (i.e., kappa sb{plane}),$ which we take as the evidence for the growth of superfluid density in the chains below 60 K. We discuss these results in terms of a model of single-electron tunneling between chains and planes.
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44

Farzadfar, Seyed-Amir. "Effect of yttrium on the microstructure and texture of deformed magnesium." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=110625.

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Single-phase solid solution alloys, Mg-2.9Y and Mg-2.9Zn (in wt%), and two-phase (α-Mg solid solution + intermetallic) Mg-Zn-Y alloys were selected using the CALPHAD (Calculation of Phase Diagram) method to investigate texture weakening mechanisms in the presence of Y. Microstructure and texture evolution during deformation and subsequent isothermal annealing were studied using optical and electron microscopy, X-ray texture measurements and EBSD (electron backscatter diffraction) techniques.It was found that at large strain levels (i.e. the steady state region of hot compression flow curves), a strong basal texture with similar maximum intensity of basal pole figures developed in all the alloys, indicating that the hot deformation texture at large strains is independent of alloy composition, initial microstructure and the volume fraction of dynamic recrystallization (DRX). The progress of DRX during deformation did not lead to texture weakening, regardless of the presence of Y. Although recrystallization of new grains at intermetallics was observed in the ternary alloys, the bulk texture remained strongly basal during and after hot deformation.Y in solid solution, unlike Zn, suppressed DRX; however, a strong basal texture with the same maximum intensity of basal pole figures developed in the Mg-2.9Y and Mg-2.9Zn alloys after hot deformation (compression and rolling at 350 °C). When the two hot-rolled binary alloys were isothermally annealed (at 400 °C between 15 min and 30 min), static recrystallization (SRX) occurred in Mg-2.9Y and grain coarsening took place in Mg-2.9Zn. The texture was weakened only in the Mg-2.9Y alloy during annealing, which resulted in higher ductility and lower in plane anisotropy in the tensile flow curve and r value when compared to Mg-2.9Zn.It was shown that, even in the absence of Y, texture weakening can be attained in Mg when there is no DRX, and SRX occurs during annealing. When DRX was absent in the Mg-2.9Y and Mg-2.9Zn alloys, i.e. by rolling of the latter alloy at room temperature, deformation was partly accommodated by compression and double twinning in basal parent grains, leading to the formation of bands. In the two binary alloys, compression and double twinning during deformation generated orientations that mostly lay within the orientation spread of basal parent grains, and did not therefore participate in the weakening of the basal texture, but rather to basal texture formation. The orientation of statically recrystallized grains at bands/twins (TSRX grains) was close to that of double and compression twins. However, the orientation of such recrystallized grains was much more evenly distributed and slightly wider than that of the basal parent grains and twins, which resulted in a weaker basal texture. In both Mg-2.9Zn and Mg-2.9Y alloys, a continuous texture weakening occurred during SRX, which resulted in a bimodal microstructure consisting of small TSRX grains and larger ones which mainly formed by recrystallization of basal parent grains. During grain coarsening following the completion of SRX in the two binary alloys, the value of maximum intensity vs. grain size rose linearly, with the slope of the lines being nearly identical. This texture strengthening was ascribed to the consumption of small TSRX grains by larger ones.
Les alliages binaires et monophasés de solution solide, Mg-2.9Y et Mg-2.9Zn (en pourcentage massique) et les alliages ternaires (Mg-Zn-Y) et biphasés (solution solide α-Mg + intermétallique) ont été sélectionnés par la méthode CALPHAD (Calculation of Phase Diagram) afin d'étudier les mécanismes d'affaiblissement de la texture en présence de l'yttrium (Y). L'effet de la déformation et des traitements thermiques sur la microstructure et la texture de ces alliages a été étudié par microscopie optique et électronique ainsi que par la méthode de diffraction des rayons-X (XRD) et des électrons rétrodiffusés (EBSD).À des niveaux élevés de contrainte (à l'état d'équilibre des courbes de déformation à chaud), une texture fortement basale avec une intensité similaire a été développée dans tous les alliages, indiquant que la texture de déformation à chaud est indépendante de la composition chimique, la microstructure initiale et la fraction volumique de la recristallisation dynamique (RXD).L'augmentation de la fraction volumique de la RXD lors de la déformation n'a pas conduit à l'affaiblissement de la texture, indépendamment de la présence de l'yttrium. Même si la recristallisation des nouveaux grains aux composés intermétalliques a été observée dans les alliages ternaires, dans l'ensemble, leur texture est demeurée fortement basale pendant et après la déformation à chaud.L'yttrium en solution solide, contrairement au Zn, a empêché la RXD de se produire; cependant, une forte texture basale avec la même intensité maximale des figures de pôles basales s'est développée dans les alliages Mg-2.9Y et Mg-2.9Zn après la déformation (compression et laminage à 350 °C). Lorsque les deux alliages binaires laminés à chaud ont été recuits (400 °C durant 15-30 min), la recristallisation statique (RXS) s'est produite dans Mg-2.9Y et le grossissement des grains a eu lieu dans Mg-2.9Zn. La texture a été uniquement affaiblie dans Mg-2.9Y pendant le recuit, ce qui a permis d'obtenir une meilleure ductilité et une faible anisotropie planaire par rapport au Mg-2.9Zn.Les résultats de cette étude démontrent que même en l'absence de l'yttrium l'affaiblissement de la texture peut être atteint dans le Mg lorsque la RXD est empêchée de se produire, et la RXS se développe au cours du recuit. L'absence de RXD durant la déformation des alliages Mg-2.9Y et Mg-2.9Zn, par laminage de l'alliage Mg-2.9Zn à la température ambiante, a mené à la formation de macles de contractions et secondaires dans les grains parents basals, conduisant à la formation des bandes. Dans les deux alliages binaires, le maclage a généré des orientations proches de celle de texture basale, et n'a donc pas participé à l'affaiblissement de la texture basale, mais plutôt à sa formation. L'orientation des grains statiquement recristallisés dans les bandes/macles (nommés MRXS) a été proche de celle des macles. Toutefois, l'orientation de ces grains recristallisés est beaucoup mieux répartie et légèrement plus large que celle des grains parents basals et des macles, donnant naissance ainsi à une plus faible texture basale. Dans le Mg-2.9Y et Mg-2.9Zn, un affaiblissement de la texture dans le temps s'est produit lors de la RXS, produisant une microstructure bimodale constituée de petits grains MRXS et de gros grains qui ont été formés par la recristallisation des grains déformés. Pendant la croissance des grains (après la fin de la RXS) dans les deux alliages binaires, l'intensité de la texture en fonction de la taille des grains a augmenté de façon linéaire avec une pente similaire. L'intensification de la texture a été attribuée à la croissance des gros grains de forte texture aux dépends des grains MRXS.
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45

Vormawah, L. J. "Collinear laser spectroscopy of scandium and yttrium isotopes at IGISOL IV." Thesis, University of Liverpool, 2017. http://livrepository.liverpool.ac.uk/3009054/.

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This thesis presents the results of two separate collinear laser spectroscopy investigations; one of proton-neutron pairing correlations in the odd-odd self-conjugate nucleus 42Sc, and the other investigating the charge radii of neutron-rich Y isotopes and the sudden onset of nuclear deformation in the Z~40, N~60 region of the nuclear chart. For the first time, the 42g,42mSc isomer shift, and corresponding change in mean-square charge radius, has been studied via collinear laser spectroscopy at IGISOL IV. The result for the change in mean-square charge radius supports the qualitative prediction given by the intuitive picture of proton-neutron pairing, in which the nuclear charge radius should be greater for an I=0, T=1 nuclear state than an I≠0, T=0 state. This result is also, qualitatively speaking at least, in agreement with the results of previous proton-neutron pairing studies, namely studies of the charge radii of 38g,38mK and 50g,50mMn. In addition to this, new values of the atomic factors for the mass and field shift, F and M, have allowed for a recalibration of the Sc charge radii measured previously on the same atomic transition as used here. Spectroscopy has been performed on radioactive Y2+ ions for the first time. The motivation for this was to recalibrate previously measured charge radii for 86-90,92-102Y and isomeric states in 87-90,93,96,98Y, which were measured on the 363.3nm 5s2 S0 → 4d5p 1P1 transition occurring in the Y+ ion. The complexity of this transition hindered the ability to reliably calculate the atomic mass and field shift factors, which are necessary for extraction of nuclear charge radii.
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46

Vanhoutte, Michiel. "Erbium-ytterbium-yttrium compounds for light emission at 1.54[mu]m." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/80259.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2013.
In title on title page, "[mu]" appear as lower case Greek letter. Cataloged from PDF version of thesis.
Includes bibliographical references (p. 181-193).
Silicon microphotonics has emerged as the leading technology to overcome the interconnect bottleneck that limits a further increase of computation power following Moore's law. Optical interconnects between different electronic microprocessors in an electronic-photonic integrated circuit (EPIC) can provide a fast, low-loss and high-bandwidth alternative to electrical interconnects, which suffer from issues such as resistive heating, RC delays and channel crosstalk at an increasing device density. A crucial device in such an electronic-photonic integrated circuit is a compact, high-gain and low power optical amplifier to compensate for signal attenuation due to propagation losses and to recover signal strength after subsequent 3dB splits during fanout of the optical signal to different microprocessors. Erbium ions (Er3+) are an excellent candidate to provide amplification around [lambda] = 1.54[mu]m for optical telecommunications. Erbium-doped fiber amplifiers (EDFAs) have already enabled long-haul optical data transmission through silica optical fibers, but scaling down a fiber amplifier to an on-chip erbium-doped waveguide amplifier (EDWA) brings along significant materials and device design challenges. In this thesis, erbium-ytterbium oxide (Er.Yb2.0 3) and erbium-ytterbium-yttrium silicate (ErxYbYY 2 ,ySi 2O7 ) compounds are investigated as novel materials systems for the development of EDWAs. The high erbium and ytterbium solubility (>1022 cm-3) and refractive index (1.71 < n < 1.92) make these materials excellent candidates for compact, low-power optical amplifiers. ErxYb2.xo 3 and ErxYb2 -. Si2O7 thin films were deposited on Si0 2 and analyzed structurally and optically. The role of ytterbium in these compounds is twofold. First, ytterbium can be used as an alternative to yttrium for dilution of the erbium concentration in order to mitigate parasitic concentration quenching effects. Second, ytterbium acts as a sensitizer for erbium during optical pumping at [lambda] = 980nm. Comparison of the different oxide and silicate thin films reveals that the a-disilicate phase is the best candidate for an EDWA gain medium pumped at [lambda] = 980nm. By means of rate and propagation equations, the composition of an ErxYbY 2 -x-ySi 2 07 gain medium was optimized for application as a 3dB EDWA. The optimal composition was found to be Ero.02 5Ybo.2 00 Y1 .7 75 Si2 07, which provides a 1.5dB/cm gain at only 3mW of pump power. In terms of the figure of merit 3dB gain/(device area - pump power), this material outperforms other EDWA materials reported in literature.
by Michiel Vanhoutte.
Ph.D.
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47

Wittorff, Vaughan William. "Thermal conductivity of single crystals of yttrium-based high temperature superconductors." Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612054.

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48

Zhang, Jianyuan. "Yttrium, Gadolinium, and Lutetium Based Endohedral Metallofullerenes: From Synthesis to Application." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/25290.

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Endohedral metalofullerenes (EMFs) have emerged as an important class of nanomaterials with vast promise in applications of molecular devices and nanomedicines. This dissertation addresses the EMF research span from synthesis to application, with an emphasis of work on trimetallic nitride template (TNT) EMF and carbide clusterfullerenes (CCFs). As a general introduction, chapter 1 reviews the main literature in TNT EMF studies. Also key works in CCF area are highlighted to show the common feature and uniqueness of this class of EMF in comparison with other EMFs. In the last part of the chapter a list of milestone progress in EMF area has been summarized. Chapter 2 is devoted to the synthetic work on EMFs. Especially, for isotopic modification, the trial and actual EMF syntheses in efforts to introduce 13C, 89Y and 177Lu are described. The next three chapters address the structural characterization of EMFs. Chapter 3 focuses on structural studies of CCFs. With detailed interpretation of 13C NMR and DFT computational results for selected members of the Y2C2@C2n family, the influence of fullerene cage on the size and shape of the yttrium carbide cluster (Y2C2)4+ is investigated. It has also been established that the carbide cluster prefers a linear shape in sufficiently large fullerene cages but adopts a compressed butterfly shape in smaller cages where space is constrained. Chapter 4 presents a systemic examination of dipole moments in TNT EMFs. The first 13C NMR study of M3N@C2(22010)-C78 is achieved on Y3N@C2(22010)-C78. In addition, dipole moments of the M3N@C2n (n=39-44) family are probed by interpretation of chromatographic retention behavior, DFT computational results and single-crystal data. It has been found that TNT EMFs with pentalene motifs exhibit enhanced dipole moments due to the cluster-cage interplay. Chapter 5 provides full characterization of the M2C2@C1(51383)-C84 (M=Y, Gd) molecule, which contains the first example of an asymmetric fullerene cage with fused pentagons. Furthermore, it is suggested that the C1(51383)-C84 cage is capable of a cascade of rearrangements into high symmetry and stable fullerene cages via well-established mechanistic steps, namely, extrusion of C2 units from pentalene or indene motifs and Stone-Wales transformations. As an important intermediate in the formation of high symmetry fullerene cages, the C1(51383)-C84 represents a missing link that implies the "top-down" fullerene formation mechanism. Chapter 6 describes the endeavor to functionalize two exotic EMFs, the room-temperature radical heterometallofullerene Gd2@C79N, and the egg-shaped TNT EMF Gd3N@C84. The reactivity of Gd2@C79N is directly compared to Y2@C79N, Gd3N@C80 and Sc3N@C80 in two reactions and the paramagnetic Gd2@C79N is proven to be very inert toward many known common fullerene cage reactions. Eventually both EMFs have been successfully functionalized via the Bingel reaction, and the derivatives are characterized with HPLC and mass-spectrometry. Chapter 7 compares the effective magnetic moment of Gd3N@C80 and Gd3N@C84, together with the previously reported Gd@C82. The magnetic moment has a second-order contribution to the T1 relaxivity and thereby is an important factor to evaluate an EMF's value in application as MRI contrast agents. Furthermore the influence of cluster motion to magnetic behavior in TNT EMF is discussed.
Ph. D.
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49

McMichael, Robert Dugald. "Nonlinear dynamics of the magnetoexchange modes of yttrium iron garnet films." The Ohio State University, 1990. http://rave.ohiolink.edu/etdc/view?acc_num=osu1329153437.

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50

Cheng, Xu. "Synthesis of Nanometer-sized Yttrium Oxide Particles in Diisooctyl Sodium Sulphosuccinate/Isooctane Reverse Micelle Solution." Thesis, Virginia Tech, 1999. http://hdl.handle.net/10919/31610.

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This thesis describes the synthesis of yttrium oxide nanoparticles in an AOT/isooctane reverse micelle solution. Two synthetic methods are compared. First is the precipitation reaction between yttrium nitrate and ammonia, second is the hydrolysis of yttrium isopropoxide. The effects of annealing of the resulting the yttrium oxide nanoparticles are also described. The nitrate method produced network-like aggregates of yttrium oxide nanoparticles ranging from 10 nm to 40 nm in diameter. Reaction conditions, including the water/AOT ratio (1 to 15), the nitrate concentration (0.02 M to 1.0 M), the ammonia concentration (2 M to 14.8 M), the AOT concentration (0.1 M and 0.5 M), the aging time (1 h to 5 d), and the washing method, were varied to investigate their influence on nanoparticle formation. The optimized synthetic conditions were: a water/AOT ratio of 7.5, [NO3-] = 0.5 M, [NH3] = 2 M, and [AOT] = 0.1 M. The as-prepared yttrium oxide nanoparticles had highly distorted structures related to the cubic Y2O3 phase. Annealing improved the crystallinity of the as-prepared nanoparticle products and led to larger particles. As annealing temperatures increased, the yttrium oxide nanoparticles gradually evolved into the cubic Y2O3 phase. However, an unknown intermediate phase was also observed during the annealing process, which disappeared when the annealing temperature was sufficiently high and the annealing time was long enough (>1000 °C and 4 h). As-prepared products from the isopropoxide hydrolysis also contained network-like nanoparticle aggregates. Particle sizes ranged from 10 nm to 20 nm. Some experimental conditions were varied; they were the water/AOT ratio (10 to 40), the isopropoxide concentration (0.0001 M to 0.003 M), the aqueous phase pH (7.0 and 12.0), the aging temperature (room temperature, approximately 25 °C, and refluxing temperature, approximately, 100 °C), and the aging time (1 h to 5 d). Transmission Electronic Micrographs showed that products of desirable morphology could be produced in a much wider range of experimental conditions by this method compared to those produced by nitrate hydrolysis.
Master of Science
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