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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Synthesis of dense TiC-Ti based cerments via self-propagating high temperature synthesis and quasi-isostatic pressing /

Ma, JunKun. January 2004 (has links)
Thesis (Ph. D.)--University of California, San Diego, and San Diego State University, 2004. / Vita. Includes bibliographical references (leaves 189-200).

Chemical vapor deposition of dispersed phase ceramic composites

Lee, Woo Young 05 1900 (has links)
No description available.

I. High temperature oxidation of hydrocabons in the chemical shock tube ; II. Synthetic analogs of actinomycin D /

Wellman, William Edward January 1960 (has links)
No description available.

Liquid-phase synthesis of structure-controllable functional materials. / CUHK electronic theses & dissertations collection

January 2010 (has links)
Biocompatible anatase TiO2 single-crystals with 27 % -- 50 % chemically reactive facets were obtained in 90 minutes by using a microwave-assisted method. The preparation involved an aqueous solution of titanium tetrafluoride and an ionic liquid (1-methyl-imidazolium tetrafluoroborate). The as-obtained TiO2 single-crystals exhibited a truncated tetragonal bipyramidal shape. By simply changing the concentration of the ionic liquid, the level of reactive facets can be continuously tuned from 27 % to 50 %. The use of microwave heating is critical as it allows rapid and uniform heating of the reaction mixture. The TiO2 single-crystals were characterized by XRD, TEM, XPS and FESEM. The products exhibited excellent photocatalytic efficiency for both oxidation of nitric oxide in air and degradation of organic compounds in aqueous solution under UV light irradiation. The relationship between the physicochemical properties and the photocatalytic performance of the samples was discussed. The TiO2 single-crystals were found to be nontoxic using Zebrafish (D. rerio) as a model. / Bismuth oxyhalide semiconductors (BiOBr, BiOCl) with marigold-like open architectures were also prepared by a solvothermal method involving imidazolium-based ionic liquids and ethylene glycol. The 3D self-assembled marigold-like materials were effective photocatalysts for degrading organic pollutants and generating hydrogen. The main advantages of the new materials were large surface area, high surface-to-bulk ratio, facile species transportation, and ease of recovery and regeneration. / By using a microwave-assisted hydrothermal method involving titanium tetrafluoride and a tetrafluoroborate-based ionic liquid (1-butyl-3-methyl-imidazolium-tetrafluoroborate), a micro-sheet anatase TiO2 single crystal photocatalyst with remarkable 80 % reactive facets was synthesized. The as-obtained TiO2 single-crystal exhibited a truncated tetragonal bipyramidal shape. The high reactivity of facets made these single crystals highly photocatalytically active. They were easily recyclable and thermally stable up to 800 °C. / Furthermore, a simple and environmentally benign approach for the synthesis of photocatalytically active rutile TiO2 mesocrystals was developed. It was a microwave-assisted hydrothermal method involving titanium(III) chloride as the only reactant. The resulting 1D rutile nanowires could easily assemble into 3D hierarchical architectures without the help of surfactants or additives. The average aspect ratio for the nanowires was 267. The BET specific surface area of the mesocrystal was 16 m2/g. / Part I: Size-tunable monodispersed hierarchical metallic Ni nanocrystals (58-190 nm in diameter) were prepared by the reduction of Ni2+ with hexadecylamine under atmospheric pressure. The diameter of the particles could be tuned by simply changing the reaction time. A reaction mechanism was proposed and the relationships between the size, hierarchical surfaces and the magnetic properties were investigated. The as synthesized Ni crystals exhibited higher coercivities than the bulk metallic material owing to the reduced size and the hierarchical surface structure. The saturation magnetization (Ms) and the ratio of remanence to saturation (Mr/Ms) increased with increasing particle size. / Part II: A facile microwave-assisted solvothermal method was developed for the controlled synthesis of novel 3D CdS structures. Dendrite-, star-, popcorn- and hollow sphere-like CdS structures could be obtained by changing the reaction conditions including the reaction temperature and the amounts of reagents and solvents. The results revealed that the final structures were related to the solvent properties such as surface tension and viscosity. The degree of supersaturation was also responsible for the morphology variation and it could be adjusted by the reaction temperature. The CdS products with different morphologies exhibited interesting shape-dependent optical properties and photocatalytic activities. / The optical band energy of the product exhibited an obvious red-shift of 0.2 eV with aspect to that of pure rutile TiO2. This red-shift effect may be ascribed to the high aspect ratio of the rutile nanowires. The products showed excellent photocatalytic activity for NO removal in air and the activity was well maintained after three cycles. Gold modification on the rutile TiO2 resulted in a 50 % improvement in the photocatalytic performance. / This thesis focuses primarily on the preparation of various functional materials with controllable structures and properties. The first part describes the synthesis of materials by solvothermal methods. The second part describes the rapid fabrication of novel semiconductor materials by microwave-assisted methods. / Zhang, Dieqing. / Source: Dissertation Abstracts International, Volume: 72-04, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 189-190). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

Thermodynamics of 3+ metal cation containing systems

Lukacs, Michael James, University of Lethbridge. Faculty of Arts and Science January 2003 (has links)
Measurements of relative densities and relative massic heat capacities have been made for several aqueous rare earth chloride and perchlorate systems. Densities and relative massic heat capacities of acidified aqueous perchlorates of yttrium, ytterbium, dysprosium, and samarium as well as the chlorides of yttrium, ytterbium, dysprosium, samarium and gadolinium have been measured at the temperatures 288.15, 298.15, 313.5 and 328.15 K. Using the density and massic heat capacity data, apparent molar volumes and apparent molar heat capacities have been calculated. These data have been modeled using the Pitzer ion interaction approach as well as the Helgeson, Kirkham and Flowers equations of state. Apparent molar volumes and apparent molar heat capacities previously presented in the literature have been compared to the data presented here. single ion apparent molar volume and apparent molar heat capacity contributions were calculated. Infinite dilution properties have been compared to existing models used to predict infinite dilution properties. Densities of aqueous perchloric acid and ytterbium perchlorate at the temperatures from 348.15 to 423.15 K and at pressured from 10.00 to 30.00 MPa were measured. Apparante molar volumes were calculated from the density measurements. The apparent molar volume data were modeled using Pitzer ion interaction theory as well as HKF equations of state. Models presented are compared to existing models. / xi, 149 leaves : ill. ; 29 cm.

Thermodynamics of aqueous solutions

Erickson, Kristy M., University of Lethbridge. Faculty of Arts and Science January 2007 (has links)
Relative densities and relative massic heat capacities have been measured for aqueous solutions of triflic acid (CF3SO3H), sodium triflate (NaCF3SO3), gadolinium triflate (Gd(CF3SO3)3), dysprosium triflate (Dy(CF3SO3)3), neodymium triflate (Nd(CF3SO3)3), erbium triflate (Er(CF3SO3)3), ytterbium triflate (Yb(CF3SO3)3), and yttrium triflate (Y(CF3SO3)3) at T = (288.15, 298.15, 313.15, and 328.15) K and p = 0.1 MPa. The resulting densities and massic heat capacities have been used to calculate out apparent molar volume and apparent molar heat capacity data for each of the investigated aqueous systems. The concentration dependencies of the apparent molar volumes and apparent molar heat capacities have been modeled using Pitzer-ion interaction equations. Single ion volumes and heat capacities have been calculated using estimates of the apparent molar properties at infinite dilution obtained from the Pitzer-ion interaction equations. These single ion values have, where possible, been compared with those previously reported in the literature. Also, relative densities have been measured for aqueous solutions of CF3SO3H, Gd(CF3SO3)3, Nd(CF3SO3)3, and Yb(CF3SO3)3 at T = (323.15, 348.15, 373.15, and 423.15) K and p = (5.00, 10.00, and 15.00) MPa. The resulting densities have been used to calculate apparent molar volumes. The concentration dependences of these properties have also been modeled using Pitzer-ion interaction equations. The apparent molar volumes have been used to calculate single ion volumes which, in turn, have been compared with those previously reported in the literature. This thesis also attempts to model the temperature, pressure, and concentration dependencies of the reported apparent molar properties of each system investigated using an equation of state commonly referred to as the density model. Where possible, the results of this model have been compared with those results from models previously reported in the literature. / xiv, 148 leaves ; 29 cm.

The AI-Pt-Ru ternary phase diagram

Prins, Sara Natalia. January 2003 (has links)
Thesis (M.Sc.(Metallurgical Engineering))--University of Pretoria, 2003. / Includes bibliographical references (leaves 127-128).

Preparation and characterization of ceramic sensors for use at elevated temperatures /

You, Tao. January 2005 (has links)
Thesis (Ph. D.)--University of Rhode Island, 2005. / Typescript. Includes bibliographical references (leaves 255-258).

The AI-Pt-Ru ternary phase diagram

Prins, Sara Natalia 19 September 2005 (has links)
No abstract available. / Dissertation (MSc (Metallurgy))--University of Pretoria, 2006. / Materials Science and Metallurgical Engineering / unrestricted

Solvothermal chemistry of luminescent lanthanide fluorides

Jayasundera, Anil January 2009 (has links)
Exploration of novel lanthanide fluoride framework materials in inorganic-organic hybrid systems under solvothermal conditions towards development of new luminescent materials is discussed. X-ray single crystal and powder diffraction methods have been used as crystallographic characterisation techniques. Determination and study of luminescence properties for selected hybrid materials has also been carried out. The first organically templated luminescent lanthanide fluoride framework, [C₂N₂H₁₀]₀.₅ [Ln₂F₇] (Ln= Nd, Tb, Dy, Ho, Er, Yb and Lu), has been synthesised and characterised. This structure type consists of a three-dimensional yttrium fluoride framework incorporating two similar, but crystallographically distinct, yttrium sites. Photoluminescence studies of [C₂N₂H₁₀]₀.₅ [Y₂F₇]: Ln³⁺ (Ln³⁺ = Gd³⁺, Eu³⁺ and Tb³⁺) have been explored and characteristic luminescence emissions are reported. An inorganic-organic hybrid indium fluoride and its scandium fluoride analogue, [C₄H₁₄N₂][MF₅](M=In and Sc) is reported. The structure consists of infinite trans vertex sharing (InF₅)[subscript(∞)] chains, which are linked via H-bonded organic moieties. The scandium and fluorine local environments of [C₄H₁₄N₂][ScF₅] are characterised by ¹⁹F, and ⁴⁵Sc solid-state MAS NMR spectroscopies. A single scandium site has been confirmed by ⁴⁵Sc MAS NMR. ¹⁹F MAS NMR clearly differentiates between bridging and terminal fluorine. The photoluminescence properties of these complexes, [C₄H₁₄N₂][In[subscript(1-x)] Ln[subscript(x)]F₅] (Ln=Tb and/or Eu), have been explored. The optimum composition for Eu³⁺ doped samples occurs at x = 0.05 Eu³⁺ and the “asymmetry ratio” of R = I₅₉₀/I₆₁₅ ( ⁵D₀ → ⁷F₂ and ⁵D₀ → ⁷F₁) gives a clear picture of the sensitivity for crystal field of the compound. For x = 0.08 Tb³⁺, a strong down-conversion fluorescence corresponding to ⁵D₄ → ⁷F₅ (green at 543.5 nm) occurs. In addition, a Tb³⁺/Eu³⁺ co-doped sample exhibits a combination of green (Tb³⁺) and orange (Eu³⁺) luminescence, with Tb³⁺ enhancing the emission of Eu³⁺ in this host. Exploration of novel indium, aluminium, and zirconium fluoride crystal structures with potential luminescent properties has also been undertaken. A chiolite-like phase K₅In₃F₁₄ (space group P4/mnc) has been synthesised. No phase transition occurs over the temperature range 113K< T< 293 K, as has been seen in other chiolite-like structures. An organically templated indium fluoride, [NH₄]₃[C₆H₂₁N₄]₂[In₄F₂₁] has been prepared; this features the trimeric unit [In₃F₁₅]³⁻ which appears to be the first of its type in a metal fluoride. A new hybrid fluoride, Sr[N₂C₂H₁₀]₂[Al₂F₁₂].H₂O has been synthesised. Because the ionic radius of Eu²⁺ is similar to that of Sr ²⁺ this may be a potential host for blue luminescent Eu²⁺. The new material KZrF₅.H₂O shows pentagonal-bipyramidal geometry of Zr⁴⁺ with a polar space group, Pb2₁m, which may potentially have ferroelectric properties.

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