The goal of this research was to understand the role of the glass substrate and molybdenum (Mo) back contact on the performance of Copper Indium Gallium diselenide (CIGS) / Cadmium Sulphide (CdS) based photovoltaic devices, and to improve the performance of these devices. The CIGS absorber layer was fabricated in a 2 stage process. In this process the metal precursors were deposited at 275oC followed by a high temperature selenization step. The advantage of the 2 stage process is that it is manufacturing friendly. The first step in fabrication of solar cells is to clean the substrate which is necessary to obtain good device performance. A variety of environmentally friendly solvents were evaluated, to determine the optimal cleaning agent. At elevated temperatures of processing sodium tends to diffuse out of Soda lime glass (SLG) and enter the semiconductor. The presence of this sodium during CIGS fabrication is necessary to obtain high efficiency CIGS based solar cells. A silicon nitride barrier layer was sputtered onto the SLG substrates, and this substrate was used to make complete devices. The CIGS absorber layer was deposited by the Type I recipe in two different vacuum systems.These devices were compared with standard devices the Si3N4 barrier layer, to understand the role of sodium on the devices fabricated from both of the systems. Furthermore, the influence of molybdenum processing parameters, such as thickness and rate of sputtering, on device performance were studied. The Voc of devices fabricated using the Type I process was limited to 460mV. In order to improve the Voc's a new absorber recipe (Type IV) was developed. Voc's of upto 490mV, Jsc's of upto 37.4mA/cm² and FF of 64%, were obtained. This improvement in performance was due to incorporation of gallium in the space charge region. Techniques such as I-V measurements, spectral response, SEM and EDS measurements were used to characterize the devices.

No description available.

Iron-based alloys containing 15% chromium, 2-3% molybdenum and 0.02-1.7% carbon, consisting of M23C6 and M6C carbides in an austenitic matrix were oxidised at 8500C to study their oxidation resistance and a precipitate-free zone formation. Alloy design was carried out using a thermodynamic software Thermo-Calc. Carbides in these alloys were expected to dissolve during oxidation, releasing chromium required for the protective oxide formation. Decarburisation of the matrix was expected to trigger the carbide dissolution, and form a precipitate-free zone. Transformation of the austenitic into ferritic matrix in the precipitate-free zone was expected be essential for providing a fast chromium supply to the oxide/alloy interface. Upon exposure to pure oxygen, most of the alloys oxidised non-protectively due to the fast oxidation attack and low chromium content in the matrix, while carbide dissolution was too slow. The alloys were then pre-oxidised in H2+10%H2O to grow a purely chromia scale. In this low oxygen partial pressure environment, carbides in the alloy's sub-surface dissolved and formed a ferritic precipitate-free zone. The precipitate dissolution model developed by previous investigators was then tested and proven to be valid in this iron-based alloy system. The endurance of the pre-formed chromia scale with its underlying precipitate-free zone was then tested in pure oxygen environment. All of the alloys that had successfully developed a ferritic precipitate-free zone in the pre-oxidation stage, survived the subsequent oxidation in pure oxygen up until 3 weeks observation. Although x-ray diffraction found some minor iron oxides, the oxide consisted of mainly Cr2O3. Since iron activity had increased and iron oxides had become stable after the pure oxygen gas was introduced, the growth of the precipitate-free zone had to compete with the rate at which it was consumed by oxidation. It was concluded that the transformation from austenite to ferrite at the subsurface region of the alloy could be achieved provided that the volume fraction of the carbides did not exceed 0.2. Evidence indicated that the chromia scale grew by chromium provided by the dissolving carbides. Pre-oxidation led to a promising use of the alloys at atmospheric oxygen pressure.

"January 1967." / Includes bibliographical references. / v, 238 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physical and Inorganic Chemistry, 1967

The interactions of a model synthetic liquid fuel reactant (furan) with a model hydrodeoxygenation catalyst (clean and sulfided single crystal molybdenum) were investigated using the following UHV tools: Auger electron spectroscopy (AES), low energy electron diffraction (LEED), and temperature programed reaction spectroscopy (TPRS). In addition to furan, the reactions of hydrogen, carbon monoxide, ethylene, and propene on clean and sulfided Mo(110) were also examined. All adsorbates exposed to the extremely reactive clean or sulfided Mo(110) surface decomposed, yielding gaseous H��� and surface C. In addition, furan TPRS caused the production of gaseous CO. The presence of background hydrogen caused no major changes in the TPRS of furan or the other adsorbates. Sulfur pre-adsorption caused the chemical shifting of H��� TPRS peaks. Both sulfur and carbon pre-adsorption resulted in the Van der Waal's radius blocking of adsorption sites for all adsorbates studied. / Graduation date: 1997

The reactivities of several electron rich, low-valent group 6 complexes with a series of N-donor ligands were explored in order to gain information about the nature of M-N binding. Reactions of trimethylsilyl diazomethane (N=N=CHSiMe3) and 1-adamntyl azide (N=N=N-Ad) with the organometallic complexes [Cr(CO)3(C5R5)]2 (R = H, Me) and HMo(CO)3(C5R5) (R = H, CH3) were studied from both a kinetic and thermodynamic aspect. Ultimately, this information was used to propose plausible mechanisms by which the reactions take place. Furthermore, reactions of M(PiPr3)2(CO)3 (M = Mo, W; iPr = isopropyl) with N2, trimethylsilyl diazomethane, 1-adamantyl azide, a series of nitriles, and a choice group of N-heterocyclic compounds were studied. The use of the coordinatively unsaturated but sterically hindered M(PiPr3)2(CO)3 complex was used to evaluate the importance of sigma and pi bonding in these complexes.

This dissertation focuses on the synthetic exploratory synthesis of molybdenum chalcogenides and rare earth metal-rich ternary tellurides as a part of an effort to produce molecular building blocks of molybdenum chalcogenide clusters and to explore their structural relationships with solid state cluster networks. The tightly cross-linked Mo3nSe3n+2(n = 2, 3, ...∞) clusters and chain compounds react with alkali metal cyanide or cyanide salt mixtures at temperatures of 450-675 °C to yield reduced, cyanide-terminated molybdenum chalcogenide clusters that are thermodynamically stable. At temperatures of 650-675 °C, linear chain compounds I6[Mo6Se8(CN)4(CN)2/2] (MI = K, Cs) were prepared from reactions of Mo6Se8 or elemental starting materials, Mo and Se with excess molten cyanide (KCN, CsCN). These are the first known compounds to feature linking of Mo6Se8 clusters via cyanide bridges. Magnetic susceptibility and EPR measurements indicate that there is one unpaired electron per cluster. A new reduced molecular octahedral complex, Na8[Mo6Se8(CN)6]•20H2O was prepared by the reduction of [Mo6Se8(CN)6]7-with Zn in an aqueous NaCN solution. Single crystal structure was determined. Cyclic voltammetric measurements in basic aqueous media show multiple reversible redox waves corresponding to [Mo6Se8(CN)6]6-/7-, [Mo6Se8(CN)6]7-/8-, [Mo6Se8(CN)6]8-/9-redox couples with half-wave potentials of E1/2 = -0.442 V, -0.876 V, and 11.369 V respectively versus the standard hydrogen electrode (SHE). UV-Vis studies support the presence of the reduced cluster compound. New reduced molecular tetrahedral complexes, K7Na[Mo4Se4(CN)12]•5H2O•MeOH, Na4Cs7[Mo4Se4(CN)12]Cl3, Na8[Mo4Se4(CN)12], and Na4K4[Mo4Se4(CN)12]•12H2O were prepared. Preparation of Na8[Mo4Se4(CN)12] is an improved method for the synthesis of the Mo4Se4 core. Half-wave potentials of E1/2 for the [Mo4Se4(CN)12]6-/7-and [Mo4Se4(CN)12]7-/8-couples are 0.233 V, and -0.422 V respectively versus SHE. The molecular cubane clusters [Mo4Se4(CN)12]7-/8-play an essential role in the process by which the discrete [Mo6Se8(CN)6]6-and [Mo6Se8(CN)6]are excised from the CN-linked chain compound, K6Mo6Se8(CN)5. A new rare-earth telluride compound with the empirical composition of Gd4NiTe2 was synthesized from a high-temperature solid-state reaction. Gd4MTe2 (M = Ni) crystallizes in the orthorhombic space group Pnma. This unprecedented structure consists of a cluster condensation of Ni-centered gadolinium tricapped trigonal prisms along the rectangular faces of the trigonal prism such that the Ni atoms act as two of the caps to the trigonal prisms.

Uranium-Molybdenum (U-Mo) alloys are of interest to the nuclear engineering community for their potential use as reactor fuel. The addition of molybdenum serves to stabilize the gamma phase of uranium, as well as increasing the melting point of the fuel. Thermal properties of U-Mo alloys have not been fully characterized, especially within the area of partial phase decomposition of the gamma phase of the alloy. Additional data was acquired through this research to expand the characterization data set for U-Mo alloys. The U-Mo alloys used for this research were acquired from the Idaho National Laboratory and consisted of three alloys of nominal 7, 10, and 13 percent molybdenum by weight. The sample pins were formed by vacuum induction melt casting. Once the three sample pins were fabricated and sent to the Fuel Cycle and Materials Laboratory at Texas A&M University, the pins were homogenized and sectioned for heat treatment. Several heat treatments were performed on the samples to induce varying degrees of phase decomposition, and the samples were subsequently sectioned for phase verification and thermal analysis. An Electron Probe Microanalyzer with wavelength dispersive spectroscopy was used to observe the phases in the samples as well as to characterize each phase. The density of each sample was determined using Archimedes method. Finally, a light flash analyzer was used to determine thermal diffusivity of the samples up to 300 degrees C as well as to estimate the thermal conductivity. For U-10Mo, thermal diffusivity increased with increasing phase decomposition from gamma to alpha +U2Mo while U-7Mo saw a flattening of the thermal diffusivity curve with increased phase decomposition.

Thesis (Ph. D.)--University of Missouri-Columbia, 2003. / Typescript. Vita. Includes bibliographical references (leaves 110-113). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2003. / Typescript. Vita. Includes bibliographical references (leaves 110-113). Also available on the Internet.