M.K. Wilkinson. / "May 7, 1952." / Bibliography: p. 18. / Army Signal Corps Contract DA36-039 sc-100, Project no. 8-102B-0. Dept. of the Army Project no. 3-99-10-022.

"December 11,1951." "This report is essentially the same as a doctoral thesis in the Department of Physics, Massachusetts Institute of Technology, 1950." / Bibliography: p. 25. / Army Signal Corps Contract No. DA36-039 sc-100. Project No. 8-102B-0. Dept. of the Army Project No. 3-99-10-022.

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The trapping behavior of deuterium and helium in polycrystalline tungsten (PCW) under D+-only, He+-only, sequential and simultaneous irradiation was studied as a function of incident ion fluences and irradiation temperature. Deuterium implanted at 300 and 500 K gets trapped at surface adsorption sites, vacancy-related traps, or extended defects. No deuterium was trapped for 700 K implantations. Results were affected by tungsten-carbide impurities in PCW specimens. It is suggested that He trapping occurs via the formation of He clusters, at impurity sites, or as part of He-vacancy complexes. For sequential implantations, D and He were found to de-trap each other, with He impeding the trapping of D when implanted first at 300 K. Under simultaneous irradiation a decrease in D inventories was observed for all cases, and a re-distribution of He to higher energy traps (associated with He-vacancy complex formation) was observed for higher fluences and temperatures.

The trapping behavior of deuterium and helium in polycrystalline tungsten (PCW) under D+-only, He+-only, sequential and simultaneous irradiation was studied as a function of incident ion fluences and irradiation temperature. Deuterium implanted at 300 and 500 K gets trapped at surface adsorption sites, vacancy-related traps, or extended defects. No deuterium was trapped for 700 K implantations. Results were affected by tungsten-carbide impurities in PCW specimens. It is suggested that He trapping occurs via the formation of He clusters, at impurity sites, or as part of He-vacancy complexes. For sequential implantations, D and He were found to de-trap each other, with He impeding the trapping of D when implanted first at 300 K. Under simultaneous irradiation a decrease in D inventories was observed for all cases, and a re-distribution of He to higher energy traps (associated with He-vacancy complex formation) was observed for higher fluences and temperatures.

Extensive research in recent years has failed to develop any essentially new method of large scale tungsten production. A new tungsten powder production technique from calcium tungstate (CaWO4) has recently been reported. In this thesis, this technique was further explored from the aspects of electrochemical reduction mechanism and kinetics, applicability to scheelite concentrates and industrial production. Cyclic voltammetry, constant potential and constant current electrochemical reduction tests were performed to determine the reversible cell potential. Analyses of the experimental results revealed that at least 2.2 V was required to compensate the potentials for the accompanying cell reaction and the electrode polarizations. A cell reaction was proposed by associating the experimental results and the Gibbs Energy changes of the possible reactions. An experiment (mixture) design was created to optimize the process parameters of the electrochemical reduction of CaWO4 to W in molten CaCl2-NaCl eutectic mixture. Temperature, applied voltage and the length of Kanthal wire winding of the CaWO4 pellets were selected as the process parameters and allowed to vary between the predetermined minimum and maximum values. The rates of the electrochemical reductions were interpreted from the variations of current and total charge vs. time graphs under different conditions. The analysis pointed out 640oC and 2.81 V from the created mixture design for the fastest reduction and it was seen that the effect of Kanthal wire winding on the output current was less pronounced when compared to the other two parameters. Another set of experiments was performed by full factorial design to investigate the cleaning procedure needed to remove calcium containing byproducts after electrochemical reduction experiments. Three levels were determined prior to the experiments for the selected three parameters / temperature, acid concentration and exposure time. Main effect and interaction graphs for calcium percent as a function of process parameters were plotted. Calcium contents of the samples were determined by XRF measurements. A 300 g/day capacity tungsten production line was manufactured to take the process one step closer to industrialization. Problems at larger scale were addressed as incomplete reduction, oxidation of graphite and corrosion of cathode materials. After careful research, AISI 316 Ti steel was found to impart sufficient resistance to highly corrosive environment. Oxidation of graphite anode inside the cell was lowered to acceptable levels by continuous nitrogen flow. Metallic tungsten powder was obtained from rich and flotation concentrates of Uludag Etibank Volfram Plant (closed in 1989) together with mainly iron. It was seen that tungsten and iron do not make compounds at the temperatures used for reduction (600-750oC). A basic diffusion model in the electrolyte was developed to better understand the decrease in current values and incomplete reduction encountered during large scale production. The model was used to simulate the recorded current vs. time graphs of selected experiments.

Reactions of Fullerene with Tris(diphenylacetylene)(carbonyl)Tungsten and structure identified of these compounds. Due to its have many special mechanism for Tris(diphenylacetylene)(carbonyl)Tungsten. They could form interested structure of new compounds. Synthesis in high temperature we could get metallofullerene compounds W(CO)(£b2-C60)(£b2-PhC¡ÝCPh)(£b4-C4Ph4) 1a and W(CO)(£b2-C60)(¡ÝCPh)(£b5-C5Ph5) 1b. We also through C-H activation to get compound W(CO)2(£b3,£b5-C5Ph4(o-C6H4)CHPh) 2. To separate and Purify these compounds. To make sure mechanism of compound 2, we use cross experiment to confirm it.

This dissertation employs the density functional theory (DFT) to investigate the oxidation of carbon monoxide (CO) on the W(111) surface and on the surface of Wn (n=10¡V15) nanoparticles. Since the properties of materials are significantly dependent on material size, we look into the influence of both the size and surface structure of tungsten catalysts on the CO oxidation process. The work contains two parts. Part 1: The adsorption and dissociation of O2 and CO on W(111) surface and Wn (n=10¡V15) nanoparticles. The chemical adsorption of O2 and CO on solid catalysts plays a very important role in heterogeneous catalysis for the CO oxidation reaction. The configurations, adsorption energies, vibration frequencies and electronic structures of adsorbates on W(111) and Wn (n=10¡V15) nanoparticles have been calculated to investigate their surface activity. The results indicate that adsorption of O2 and CO on Wn (n=10¡V15) nanoparticles are more stable compared to on the W(111) surface. The minimum energy pathways and transition states of chemical reaction processes on metal surfaces were also studied by the nudged elastic band (NEB) method. The dissociation barriers of O2 chemisorbed on Wn (n=10¡V15) nanoparticles are smaller those for the W(111) surface. Our results demonstrate that both the surface structure and size of metal significantly influence the adsorption and dissociation properties of adsorbates. Density functional theory-molecular dynamics (DFT-MD) simulation was also adapted to clarify the mechanism of O2 deposition on the W(111) surface. Observations of the variations of energy and bond lengths as a function of time show that the interaction between O2 and W atoms weakens the O¡VO bond, giving rise to the dissociation process. We conclude that the dissociation probability of an O2 molecule is affected by chemisorbed O2 coverage in the vicinity. Part 2: The mechanism of CO oxidation on W(111) and Wn nanoparticles. The oxidation of the CO molecule on transition metals usually follows two reaction pathways, either the Eley-Rideal (ER) mechanism or the Langmuir-Hinshelwood (LH) mechanism. In the ER mechanism, the CO molecule in the gas phase reacts directly with activated O2. The LH mechanism generally involves a few elementary steps, namely the co-adsorption of the O2 and CO molecules, O2 dissociation to form atomic oxygen, diffusion of atomic oxygen, and desorption of CO2. The oxidation of CO on a W10 nanoparticle surface and the W(111) surface are investigated by DFT calculations. Three pathways were studied in this dissertation: (i) CO + O2¡÷CO2 + O, (ii) CO + O2¡÷CO + O + O¡÷CO2 + O and (iii) CO + O¡÷CO2 via both LH and ER mechanisms. The calculated results show that CO oxidation on both the W10 nanoparticle and W(111) surfaces follow the ER rather than the LH mechanism. The CO oxidation on the W10 nanoparticle and W(111) surfaces occurs most easily via pathway (i) as compared to other two.

In this study, the carbon electrode of supercapacitor was fabricated by using mesocarbon microbeads. For finding the optimal processing parameters of carbon electrode, the effects of specific surface area of activated carbon, the amount of carbon black and binder, and various electrolytes on the capacitative properties of supercapacitor are investigated. To fabricate the composite electrode of supercapacitor, NiO and WO3 thin films were deposited respectively on the carbon electrode by electron beam evaporation. The influences of various scan rates of cyclic voltammograms (CV) on the characteristic of capacitance are studied. The charge-discharge efficiency and life time of the composite electrode are also discussed. Experimental results reveal that the optimum carbon electrode can be obtained using mesocarbon microbeads with high specific surface area (2685 m2/g) and larger pore volume (0.6 cm3/g) and adding 10 wt.% carbon black and 2wt.% binder. The specific capacitances of carbon electrodes in 1 M KOH and 1 M Et4NBF4 are 230.8 F/g and 221.5 F/g, respectively. Besides, the XRD and SEM results showed that NiO and WO3 thin films on composite electrode are sheet-liked crystal structure and stone-liked amorphous structure, respectively. The composite electrode exhibits better capacitance properties than those of carbon electrode at high scan rate by CV analysis. It reveals the promotion of the capacitative property of supercapacitor at higher power density and the improving of the decay property in capacitance at high scan rate. Finally, in the test of charge-discharge efficiency and life time, the charge-discharge efficiency is near 100% after 5000 cycles and it still retains good adhesion between electrode material and substrate.

The microstructural, electrochemical and optical properties of sol-gel derived tungsten oxide electrochromic coatings have been investigated. Coatings were formed by spinning of tungsten metal based aqueous sol on glass with native ITO layer. Three sol formulations / acetylated peroxotungstic acid (APTA), peroxotungstic acid (PTA) and titanium-doped peroxotungstic acid (Ti-PTA) were employed to obtain 200-300 nm thick multi-layered coatings. Material and electrochromic characterization of the coatings have been performed by DSC, XRD, SEM, cyclic voltammetry and UV-Vis spectroscopy. The electrochromic performance of the WO3 coatings was influenced by calcination temperature, by sol chemistry and by the adsorbed water content. For all sol formulations the coatings calcined at 250 &deg / C were amorphous and have shown better performance compared to crystalline counterparts calcined at 400 &deg / C. High calcination temperature also leads to formation of WO3 nanocrystals for APTA and PTA derived coatings, titanium doping retards crystallization. Presence of acetic acid as in APTA sol improved the electrochromic and electrochemical performance. This was related to removal of organics- acetic acid and peroxo ligands- during calcination, which results in an open W-O network providing more ion insertion sites. The water adsorption affected the electrochromic performance in different ways for the coatings calcined at 250 &deg / C and 400 &ordm / C. The amorphous coatings with limited structural water removal and excessive hydroxyl groups tend to crystallize by condensation of W-OH groups upon storage in open atmosphere, therefore exhibiting degrading electrochromic activity with aging. Conversely, hydroxyl groups enhanced Li+ ion insertion for the stable crystalline coatings calcined at 400 &deg / C.