Publications

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A series of potassium aryloxides (KOAr) were isolated from the reaction of a potassium amide (KN(SiMe3)2) and the desired substituted phenoxide (oMP, 2-methyl; oPP, 2-iso-propyl; oBP, 2-tert-butyl; DMP, 2,6-di-methyl; DIP, 2,6-di-iso-propyl; DBP, 2,6-di-tert-butyl) in tetrahydrofuran (THF) or pyridine (py) as the following: {l_brace}([K(4-oMP)(THF)][K(3-oMP)])5{r_brace} (1), {l_brace}[K6(6,3-oMP)4(6,4-oMP)2(py)4] {center_dot} [K6(6,3-oMP)6(6-py)4]{r_brace} (2), [K(3-oPP)]4(THF)3 (3), {l_brace}K4(6,3-oPP)2(3-oPP)2(py)3{r_brace} (4), [K(3-oBP)(THF)]6 (5), {l_brace}K6(6,3-oBP)2(3-oBP)4(py)4{r_brace} (6), {l_brace}K3(6,3-DMP)2(-DMP)(THF){r_brace} (7), {l_brace}[K(6,-DMP)(py)]2{r_brace} (8), {l_brace}K(6,-DIP){r_brace} (9), {l_brace}K(6,-DBP){r_brace} (10). Further exploration of the aryl interactions led to the investigation of the diphenylethoxide (DPE) derivative which was isolated as [K(3-DPE)(THF)]4 (11) or [K(3-DPE)(py)]4 {center_dot} py2 (12) depending on the solvent used. In general, the less sterically demanding ligands (oMP, oPP, oBP, and DMP) were solvated polymeric species; however, increasing the steric bulk (DIP and DBP) led to unsolvated polymers and not discrete molecules. For most of this novel family of compounds, the K atoms were -bound to the aryl rings of the neighboring phenoxide derivatives to fill their coordination sites. The synthesis and characterization of these compounds are described in detail.

In this work, we investigated the controlled growth of nanocrystalline CdE (E = S, Se, and Te) via the pyrolysis of CdO and Cd(O2CCH3)2 precursors, at the specific Cd to E mole ratio of 0.67 to 1. The experimental results reveal that while the growth of CdS produces only a spherical morphology, CdSe and CdTe exhibit rod-like and tetrapod-like morphologies of temporally controllable aspect ratios. Over a 7200 s time period, CdS spheres grew from 4 nm (15 s aliquot) to 5 nm, CdSe nanorods grew from dimensions of 10.8 x 3.6 nm (15 s aliquot) to 25.7 x 11.2 nm, and CdTe tetrapods with arms 15 x 3.5 nm (15 s aliquot) grew into a polydisperse mixture of spheres, rods, and tetrapods on the order of 20 to 80 nm. Interestingly, long tracks of self-assembled CdSe nanorods (3.5 x 24 nm) of over one micron in length were observed. The temporal growth for each nanocrystalline material was monitored by UV-VIS spectroscopy, transmission electron spectroscopy, and further characterized by powder X-ray diffraction. This study has elucidated the vastly different morphologies available for CdS, CdSe, and CdTe during the first 7200 s after injection of the desired chalcogenide.

The polarization reversal process in a rhombohedral ferroelectric ceramic material was investigated using field-induced strain measurements and texture development. Special attention was focused on the difference in the field-induced strains between the first quarter cycle and subsequent loading conditions. Results show that the initial field-induced strain is about twelve times greater than the subsequent strain, which immediately suggests that mechanisms involved in these conditions during the polarization reversal process are different. The difference in the magnitude of field-induced strain is discussed in terms of 180 degree and non-180 degree domain reorientation processes.

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Developers of computer codes, analysts who use the codes, and decision makers who rely on the results of the analyses face a critical question: How should confidence in modeling and simulation be critically assessed? Verification and validation (V&V) of computational simulations are the primary methods for building and quantifying this confidence. Briefly, verification is the assessment of the accuracy of the solution to a computational model. Validation is the assessment of the accuracy of a computational simulation by comparison with experimental data. In verification, the relationship of the simulation to the real world is not an issue. In validation, the relationship between computation and the real world, i.e., experimental data, is the issue.

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We have undertaken the synthesis of a thin film ''All Ceramic Battery'' (ACB) using solution route processes. Based on the literature and experimental results, we selected SnO{sub 2}, LiCoO{sub 2}, and LiLaTiO{sub 3} (LLT) as the anode, cathode, and electrolyte, respectively. Strain induced by lattice mismatch between the cathode and bottom electrode, as estimated by computational calculations, indicate that thin film orientations for batteries when thicknesses are as low as 500 {angstrom} are strongly controlled by surface energies. Therefore, we chose platinized silicon as the basal platform based on our previous experience with this material. The anode thin films were generated by standard spin-cast methods and processing using a solution of [Sn(ONep)]{sub 8} and HOAc which was found to form Sn{sub 6}(O){sub 4}(ONep){sub 4}. Electrochemical evaluation showed that the SnO{sub 2} was converted to Sn{sup o} during the first cycle. The cathode was also prepared by spin coating using the novel [Li(ONep)]{sub 8} and Co(OAc){sub 2}. The films could be electrochemically cycled (i.e., charged/discharged), with all of the associated structural changes being observable by XRD. Computational models indicated that the LLT electrolyte would be the best available ceramic material for use as the electrolyte. The LLT was synthesized from [Li(ONep)]{sub 8}, [Ti(ONep){sub 4}]{sub 2}, and La(DIP){sub 3}(py){sub 3} with RTP processing at 900 C being necessary to form the perovskite phase. Alternatively, a novel route to thin films of the block co-polymer ORMOLYTE was developed. The integration of these components was undertaken with each part of the assembly being identifiably by XRD analysis (this will allow us to follow the progress of the charge/discharge cycles of the battery during use). SEM investigations revealed the films were continuous with minimal mixing. All initial testing of the thin-film cathode/electrolyte/anode ACB devices revealed electrical shorting. Alternative approaches for preparing non-shorted devices (e.g. inverted and side-by-side) are under study.

This document summarizes research of reactively deposited metal hydride thin films and their properties. Reactive deposition processes are of interest, because desired stoichiometric phases are created in a one-step process. In general, this allows for better control of film stress compared with two-step processes that react hydrogen with pre-deposited metal films. Films grown by reactive methods potentially have improved mechanical integrity, performance and aging characteristics. The two reactive deposition techniques described in this report are reactive sputter deposition and reactive deposition involving electron-beam evaporation. Erbium hydride thin films are the main focus of this work. ErH{sub x} films are grown by ion beam sputtering erbium in the presence of hydrogen. Substrates include a Al{sub 2}O{sub 3} {l_brace}0001{r_brace}, a Al{sub 2}O{sub 3} {l_brace}1120{r_brace}, Si{l_brace}001{r_brace} having a native oxide, and polycrystalline molybdenum substrates. Scandium dideuteride films are also studied. ScD{sub x} is grown by evaporating scandium in the presence of molecular deuterium. Substrates used for scandium deuteride growth include single crystal sapphire and molybdenum-alumina cermet. Ultra-high vacuum methods are employed in all experiments to ensure the growth of high purity films, because both erbium and scandium have a strong affinity for oxygen. Film microstructure, phase, composition and stress are evaluated using a number of thin film and surface analytical techniques. In particular, we present evidence for a new erbium hydride phase, cubic erbium trihydride. This phase develops in films having a large in-plane compressive stress independent of substrate material. Erbium hydride thin films form with a strong <111> out-of-plane texture on all substrate materials. A moderate in-plane texture is also found; this crystallographic alignment forms as a result of the substrate/target geometry and not epitaxy. Multi-beam optical sensors (MOSS) are used for in-situ analysis of erbium hydride and scandium hydride film stress. These instruments probe the evolution of film stress during all stages of deposition and cooldown. Erbium hydride thin film stress is investigated for different growth conditions including temperature and sputter gas, and properties such as thermal expansion coefficient are measured. The in-situ stress measurement technique is further developed to make it suitable for manufacturing systems. New features added to this technique include the ability to monitor multiple substrates during a single deposition and a rapidly switched, tiltable mirror that accounts for small differences in sample alignment on a platen.

Palmierite (K2Pb(SO4)2) has been prepared via a chemical synthesis method. Intensity differences were observed when X-ray powder data from the newly synthesized compound were compared to the published powder diffraction card (PDF) 29-1015 for Palmierite. Investigation of these differences indicated the possibility of preferred orientation and/or chemical inhomogeneity affecting intensities, particularly those of the basal (00l) reflections. Annealing of the Palmierite was found to reduce the effects of preferred orientation. Electron microprobe analysis confirmed K:Pb:S as 2:1:2 for the for the annealed Palmierite powder. Subsequent least-squares refinement and Rietveld analysis of the annealed powder showed peak intensities very close to that of a calculated Palmierite pattern (based on single crystal data), yet substantially higher than many of the PDF 29-1015 published intensities. Further investigation of peak intensity variation via calculated patterns suggested that the intensity discrepancies between the annealed sample and those found in PDF 29-1015 were potentially due to chemical variation in the K2Pb(SO4)2 composition. X-ray powder diffraction and crystal data for Palmierite are reported for the annealed sample. Palmierite is trigonal/hexagonal with unit cell parameters a = 5.497(1) Å, c = 20.864(2) Å, space group R-3m(166), and Z=3. © 2007 International Centre for Diffraction Data.

Magnesium vanadates are potentially important catalytic materials for the conversion of alkanes to alkenes via oxidative dehydrogenation. However, little is known about the active sites at which the catalytic reactions take place. It may be possible to obtain a significant increase in the catalytic efficiency if the effects of certain material properties on the surface reactions could be quantified and optimized through the use of appropriate preparation techniques. Given that surface reactivity is often dependent upon surface structure and that the atomic level structure of the active sites in these catalysts is virtually unknown, we desire thin film samples consisting of a single magnesium vanadate phase and a well defined crystallographic orientation in order to reduce complexity and simplify the study of active sites. This report describes the use of reactive RF sputter deposition to fabricate very highly oriented, stoichiometric Mg{sub 3}(VO{sub 4}){sub 2} thin films, and subsequent studies of the reactivity of these films under reaction conditions typically found during oxidative dehydrogenation. We demonstrate that the synthesis methods employed do in fact result in stoichiometric films with the desired crystallographic orientation, and that the chemical behavior of the films closely approximates that of bulk, high surface area Mg{sub 3}(VO{sub 4}){sub 2} powders. We further use these films to demonstrate the effects of oxygen vacancies on chemical behavior, demonstrate that surface composition can vary significantly under reaction conditions, and obtain the first evidence for structure sensitivity in Mg{sub 3}(VO{sub 4}){sub 2} catalysts.

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Magnesium aryloxides were prepared in a variety of solvents through the reaction of dibutyl magnesium with sterically varied aryl alcohols: 2,6-dimethylphenol (H-DMP), 2,6-diisopropylphenol (H-DIP), and 2,4,6-trichlorophenol (H-TCP). Upon using a sufficiently strong Lewis-basic solvent, the monomeric species Mg(DMP){sub 2}(py){sub 3} (1, py = pyridine), Mg(DIP){sub 2}(THF){sub 3}, (2a, THF = tetrahydrofuran) Mg(TCP){sub 2}(THF){sub 3} (3) were isolated. Each of these complexes possesses a five-coordinate magnesium that adopts a trigonal bipyramidal geometry. In the absence of a Lewis base, the reaction with H-DIP yields a soluble trinuclear complex, [Mg(DIP){sub 2}]{sub 3} (2b). The Mg metal centers in 2b adopt a linear arrangement with a four-coordinate central metal while the outer metal centers are reduced to just three-coordinate. Solution spectroscopic methods suggest that while 2b remains intact, the monomeric species (1, 2a, and 3) are involved in equilibria, which facilitate intermolecular ligand transfer.

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A series of arylalcohols [H-OAr where OAr = OC{sub 6}H{sub 5} (OPh), OC{sub 6}H{sub 4}(2-Me) (oMP), OC{sub 6}H{sub 3}(2,6-Me){sub 2} (DMP), OC{sub 6}H{sub 4}(2-Pr{prime}) (oPP), OC{sub 6}H{sub 3}(2,6-Pr{prime}){sub 2} (DIP), OC{sub 6}H{sub 4}(2-Bu{prime}) (oBP), OC{sub 6}H{sub 3}(2,6-Bu{prime}){sub 2} (DBP) where Me = CH{sub 3}, Pr{prime} = CHMe{sub 2}, and Bu{prime} = CMe{sub 3}] were reacted with LiN(SiMe{sub 3}){sub 2} in pyridine (py) to generate the appropriate ``Li(OAr)(py){sub x}'' complex. The resultant products were characterized by single crystal X-ray diffraction as: [Li(OPh)(py){sub 2}]{sub 2} (1), [Li(oMP)(py){sub 2}]{sub 2} (2), [Li(DMP)(py){sub 2}]{sub 2} (3), [Li(oPP)(py){sub 2}]{sub 2} (4), [Li(DIP)(py){sub 2}]{sub 2} (5), [Li(oBP)(py){sub 2}]{sub 2} (6), and [Li(DBP)(py)]{sub 2} (7). Compounds 1--6 adopt a dinuclear, edge-shared tetrahedral complex. For 7, due to the steric crowding of the DBP ligand, only one py is coordinated yielding a dinuclear fused trigonal planar arrangement. Two additional structure types were also characterized for the DIP ligand as [Li(DIP)(H-DIP)(py)]{sub 2} (5b) and [Li{sub 2}(DIP){sub 2}(py){sub 3}] (5c). {sup 6,7}Li and {sup 13}C NMR solid state MAS spectroscopy indicated that the bulk powder was consistent with the crystalline material. Solution state NMR spectroscopy revealed a symmetric molecule existed in solution for 1--7.

Erbium hydride thin films are grown onto polished, a-axis {alpha} Al{sub 2}O{sub 3} (sapphire) substrates by reactive ion beam sputtering and analyzed to determine composition, phase and microstructure. Erbium is sputtered while maintaining a H{sub 2} partial pressure of 1.4 x 10{sup {minus}4} Torr. Growth is conducted at several substrate temperatures between 30 and 500 C. Rutherford backscattering spectrometry (RBS) and elastic recoil detection analyses after deposition show that the H/Er areal density ratio is approximately 3:1 for growth temperatures of 30, 150 and 275 C, while for growth above {approximately}430 C, the ratio of hydrogen to metal is closer to 2:1. However, x-ray diffraction shows that all films have a cubic metal sublattice structure corresponding to that of ErH{sub 2}. RBS and Auger electron that sputtered erbium hydride thin films are relatively free of impurities.