Diamond cuboid-, rhombohedron- and hexagon-shaped nanocrystals as well as branched rods of the solid solution Co1-xMnxO have been synthesized via a solvothermal synthetic route from manganese formate and cobalt acetate at elevated temperature. Rhombohedra and hexagons have dimensions no larger than 50 nm on the longest axis, rods have branches up to 150 nm long and cuboids grow up to 250 nm on a side. X-ray and electron diffraction and transmission electron microscopy analyses show that these nanoparticles are single crystals of wurtzite-type and rock salt-type Co1-xMnxO. Varying the surfactant, water and precursor ratios allows control of particle size, morphology and stoichiometry. Extending growth time at high temperatures (>370°C) leads to the disappearance of the wurtzite phase due to Ostwald ripening. Longer reaction times at temperatures between 345-365°C lead to more crystalline wurtzite-lattice particles. These results show that nanoparticle morphologies and crystal lattices arise from crystal growth and Ostwald ripening at different rates selecting for either small, smooth-surfaced wurtzite lattice particles or large, dendritically-grown rock salt lattice particles.

Mesoporous materials attracted great interest due to their huge surface area and adjustable pore sizes. One of the important mesoporous materials is SBA-15 and has larger pore size, hydrothermal stability and thicker walls than other mesoporous materials. In this study, SBA-15 is synthesized by using sol-gel technique and cobalt oxide nanoparticles are incorporated in mesochannels by direct method. SBA-15 was produced from the self-assembly of non-ionic triblock co-polymer (Pluronic 123) and tetra ethyl ortho silicate (TEOS). Then cobalt chloride and cobalt nitrate were added at different loading ratios with two different addition sequences / after polymer and after TEOS. The loading ratios are in Si/Co mols and these ratios are / 15, 10, 5, 3, 1.5, 1 and 0.75 in increasing cobalt amount loaded. Characterization of the produced materials was performed by Powder X-Ray Diffraction (PXRD), Infrared (FTIR) analysis. Nitrogen Phisisorption measurements (BET and BJH Methods) were used to examine the textural properties of produced materials. By means of Transmission Electron Microscopy (TEM) the micro structures of materials were investigated. From the PXRD studies it is observed that the long range order of pores is preserved at even high loading amounts for cobalt chloride addition after TEOS. Co3O4 (JCPDS card no: 42-1467) crystallites are observed for Si/Co mol loading ratios 3, 1.5, 1 and 0.75. Above these loading ratios cobalt oxide is highly dispersed in SBA-15-type structure. FTIR studies revealed the formation of condensed silica network. From the Nitrogen Phisisorption measurements it is observed that addition of cobalt salt decreases the BET surface area of produced materials. All Nitrogen Adsorption-Desorption Isotherms are Type-IV, and has H-1 hysteresis which is a fulfillment of mesoporous structures according to IUPAC classification. BET surface area of samples loaded with cobalt chloride after TEOS possessed higher surface area than other samples. TEM images proved that at loading ratios above 3 there were not any cobalt oxide nanoparticles, cobalt oxide is highly dispersed on silica surface whereas at loading ratios 3 and below there were cobalt oxide nanoparticles embedded in the mesochannels for the samples prepared by addition of cobalt chloride after TEOS.

Nanoparticle and nanoparticulate films have been grown by a unique approach combining a microwave and nebulized droplets where the concentration and thus the resulting particle size can be controlled. The goal of such a scalable approach was to achieve it with the least number of steps, and without using expensive high purity chemicals or the precautions necessary to work with such chemicals. This approach was developed as a result of first using a laser unsuccessfully to achieve the desired films and particles. Some problems with the laser approach for growing desired films were solved by substituting the higher energy microwave for the laser. Additionally, several materials were first attempted to be grown with the laser and the microwave, and what was learned as result of failures was implemented to successfully demonstrate the technique. The microwave system was characterized by using direct temperature measurements and models. Where possible, the temperature of deposition was determined using thermocouples. In the region of the waveguide, the elemental spectral lines were measured, and the temperature was calculated from measured spectral peaks. From the determined temperature, a diffusion calculation modeled the rate of heat transfer to the nebulized droplets. The result of the diffusion calculations explained the reason for the failure of the laser technique, and success for the microwave technique for simple chemistries. The microwave assisted spray pyrolysis (MPAS) technique was used to grow ZnO nanoparticles of varying size. The properties of the different size particles was measured by optical spectroscopy and magnetic measurements and was correlated to the defects created. The MPAS technique was used to grow films of Ca3Co4O9 containing varying sizes of nanoparticulates. The resistivity, Seebeck coefficient, and the power factor (PF) measured in the temperature range of 300-700 K for films grown by MPAS process with varying concentrations of calcium and cobalt chlorides are presented. Films with larger nanoparticles showed a trend toward higher PFs than those with smaller nanoparticles. Films with PFs as high as 220 μW/mK 2 were observed in films containing larger nanoparticles.

This dissertation describes a novel methodology to prepare, functionalize, and assemble polymer-coated ferromagnetic cobalt nanoparticles (PS-CoNPs) and cobalt oxide nanowires. This research demonstrated the ability to use dipolar nanoparticles as `colloidal monomers' to form electroactive 1-D mesostructures via self- and field-induced assembly. The central focus of this dissertation is in developing a novel methodology termed as `Colloidal Polymerization', in the synthesis of well-defined cobalt oxide nanowires as nanostructured electrode materials for potential applications in energy storage and conversion.Ferromagnetic nanoparticles are versatile building blocks due to their inherent spin dipole, which drive 1-D self-assembly of colloids. However, the preparation and utilization of ferromagnetic nanoparticles have not been extensively examined due to the synthetic challenges in preparing well-defined materials that can be easily handled. This dissertation has overcome these challenges through the hybridization of polymeric surfactants with an inorganic colloid to impart functionality, colloidal stability and improved processing characteristics. This modular synthetic approach was further simplified to prepare ferromagnetic nanoparticles in gram scale, which enabled further investigations to develop new chemistry and materials science with these materials. These polymer-coated magnetic nanoparticles self-assembled into extended linear chains due to strong dipolar attractions between colloids. Additionally, novel dipolar assemblies, such as, flux-closure nanorings and lamellae type mesostructures were demonstrated by controlling the interparticle of attractive forces (dipolar versus van der Waals).The research presented herein focused on utilizing polymer-coated ferromagnetic cobalt nanoparticles as `colloidal molecules' to form interconnected 1-D mesostructures via `Colloidal Polymerization'. This process exploited the magnetic organization of dipolar colloids into 1-D mesostructures followed by a facile oxidation reaction to form interconnected electroactive cobalt oxide nanowires. This facile and template free approach enabled the large scale synthesis of semiconductor cobalt oxide nanowires, in which the electronic and electrochemical properties were confirmed for potential applications for energy storage and conversion. This work served as a platform in fabricating a wide range of semiconductor heterostructures, which allowed for structure-property investigation of new nanostructured electrodes.

Lithium ion batteries (LIBs) play an essential role in modern life. Although relatively unknown throughout past decades, LIBs have supplanted several categories of chemically rechargeable batteries including lead-acid, nickel-cadmium and nickel-hydrogen batteries. Nowadays, LIBs dominate the market of portable electronic devices such as mobile phones, digital cameras and laptops. As the price of petroleum keeps increasing, electrically powered or assisted vehicles using LIBs are similarly gaining in the automotive market. However, current state-of-art LIBs using graphite as their electrical anode and Li metal oxides as the cathode are facing major challenges. For example, the current LIBs are approaching their capacity limit. Batteries that can maintain high charge and discharge rates are in great demand, which has not been adequately addressed by modern LIBs. Safety issues with these current batteries are being reported even from some market leaders such as Boeing and Tesla. Herein, several categories of novel anode materials have been investigated in a search for promising candidates to enable evolution of the next generation of lithium ion batteries. This research included silicon-carbon based materials, especially silicon-graphene (Si-G) materials and their derivatives, and transitional metal based materials, e.g., cobalt oxide (Co3O4). In this proposed work, Si-G composites were synthesized via a freeze-drying method; the conditions of the synthesis were controlled and adjusted to obtain a Si-G composite with the most promising morphology as well as battery performance. Based on preliminary results, graphene wrapped silicon electrodes showed significantly improved cycling performance than bare silicon electrodes. At high charge and discharge rates it was found that Si-G composites also showed superior stability and capacity retention over bare silicon electrodes. After 200 cycles, the optimized Si-G composite maintained a capacity retention close to 100%, with a capacity of 800 mAh g-1 at a 0.2 C rate and 600 mAh g-1 at a 1 C rate. This observation was a prominent increase from the performance of commercial graphite-based batteries at a theoretical capacity 372 mAh g-1. Considering the facile fabrication method and increasing use of commercial silicon nano-particles (Si-NPs) into account, Si-G composites could be a promising candidate for the anode material in LIBs. Extended work on the Si-G project also involved further decorations based on the Si-G composite synthesized from the method previously mentioned, as well as improvement on the synthesis method to make it more applicable for industrial purposes. Cobalt Oxide (Co3O4), a transitional metal oxide which has a theoretical capacity of 890 mAh g-1, draws attention as an anode material in LIBs due to its capacity compared to graphite and heavily reduced degradation compared to silicon. A novel electrode fabrication procedure was adopted in this research together with a simple material-synthesizing methodology. Similar to common silicon electrodes, Co3O4 suffers from poor electron conductivity volume change upon cycling. Herein the Co3O4 active material is directly deposited on stainless steel mesh, serving as both a current collector and a substrate for the active material. Through adapting the electrode fabrication process by directly depositing on the stainless steel electron conductor, the traditional conductive carbon material and binder requirements can be avoided. As a result, the process is reduced in both cost and complexity. The presented novel electrode design facilitates both ion diffusion and electron transportation, improving the overall performance of the material in LIBs. After 100 cycles of charge and discharge, Co3O4 on stainless steel mesh shows a capacity around 770 mAh g-1, which is more than twice that of graphite. The capacity retention was around 90% in this case.

The aim of this work was to manufacture and test non noble metal catalysts for CO oxidation and soot combustion. The feeding gases consist in the products of the combustion diesel in a Reformtech heater. These gases contain CO, CO2, H2O as well as small amounts of NOx and hydrocarbons. Two different catalysts were prepared for CO oxidation, based on cobalt oxide supported on ceria. 12Co/CeO2 with 12% weight of cobalt and 15CoOx/CeO2 with 15%. The first one was prepared by impregnation of cobalt nitrates in cerium oxide support; the second one was prepared by co-precipitation of cobalt and cerium nitrates. Another catalyst called 12Co4.5K/CeO2, with 12% cobalt and 4.5% potassium, was made for the simultaneous combustion of soot and oxidation of CO. The base also consisted in cobalt oxide supported on ceria, but with the addition of potassium which could stabilize the cobalt oxide particles. Both co-precipitation and impregnation methods gave the desired catalyst structure in the CO oxidation catalysts and both catalysts (12Co/CeO2 and 15CoOx/CeO2) showed activity. Nevertheless, the activity was lower than desired due to low surface area and mass transfer limitations. The catalysts also deactivated in less than three hours on stream, probably due to poisoning. The co-precipitation method for the 12Co4.5K/CeO2 catalyst gave the desired cobalt and cerium oxides, but no conclusion can be drawn regarding potassium since it was not shown in the XRD tests. The catalyst for both CO oxidation and soot combustion (12Co4.5K/CeO2) showed no activity for any of the reactions. Nevertheless, the tests performed to test the soot combustion ability were not conclusive and should be improved in future studies.

abstract: Lithium titanium oxide (LTO), is a crystalline (spinel) anode material that has recently been considered as an alternative to carbon anodes in conventional lithium-ion batteries (LIB), mainly due to the inherent safety and durability of this material. In this paper commercial LTO anode 18650 cells with lithium cobalt oxide (LCO) cathodes have been cycled to simulate EV operating condition (temperature and drive profiles) in Arizona. The capacity fade of battery packs (pack #1 and pack#2), each consisting 6 such cells in parallel was studied. While capacity fades faster at the higher temperature (40°C), fading is significantly reduced at the lower temperature limit (0°C). Non-invasive techniques such as Electrochemical Impedance Spectroscopy (EIS) show a steady increase in the high-frequency resistance along with capacity fade indicating Loss of Active Material (LAM) and formation of co-intercalation products like Solid Electrolyte Interface (SEI). A two-stage capacity fade can be observed as previously reported and can be proved by differential voltage curves. The first stage is gradual and marks the slow degradation of the anode while the second stage is marked by a drastic capacity fade and can be attributed to the fading cathode. After an effective capacity fading of ~20%, the battery packs were disassembled, sorted and repackaged into smaller packs of 3 cells each for second-life testing. No major changes were seen in the crystal structure of LTO, establishing its electrochemical stability. However, the poor built of the 18650-cell appears to have resulted in failures like gradual electrolytic decomposition causing prominent swelling and failure in a few cells and LAM from the cathode along with cation dissolution. This result is important to understand how LTO batteries fail to better utilize the batteries for specific secondary-life applications. / Dissertation/Thesis / Masters Thesis Materials Science and Engineering 2019

No description available.

Mechanochemically synthesized cobalt oxide-based particles are employed for the catalytic reduction of 4-nitrophenol (4NP), a toxic water contaminant. This reduction produces 4‑aminophenol (4AP), a less toxic, pharmaceutical precursor for drugs such as paracetamol. The indicated reduction has been completed previously using noble metals and/or catalysts requiring extensive solvent use, and time as part of their preparation. The cost and synthesis of these noble metal catalysts hinders the sustainable broad scale application as an environmental remediation solution. The catalyst synthesis explored in this study utilizes the green chemistry technique of vibratory ball-milling and annealing cobalt oxide-based particles at different temperatures, producing unique agglomerates with differing surface structure and catalytic properties. Additional investigation into the mechanism through temperature, pH, and change in pressure over the reaction is completed. Further analysis shows that these catalysts are efficient for the reduction of 4-amino-3-nitrophenol and 2-amino-5-nitrophenol with unique catalytic rates. Finally, it is found that the application of this reduction in a flow process has potential for use on a broader scale.

No description available.