Abstract In this study, EAVD(Electrostatic Assisted Vapor Deposition) technique was used to fabricate NiO/CGO (Cerium Gadolinum Oxide) films for the anode of IT-SOFCs (Intermediate Temperature-Solid Oxide Fuel Cells). The objective of this work is to establish the relationship between the morphology of NiO/CGO films and deposition parameters. The effects of different deposition parameters on film morphology were studied. The systematically changed deposition parameters were : deposition temperature, deposition time, flow rate and concentration of precursor solution and substrate types. According to experiment results, deposition temperature and deposition time are most important deposition parameters of controlling the morphology of films. The deposited NiO/CGO films with a highly porous structure were obtained above 400 oC and 5mins. On the other hand, when deposition temperature and time were decreased below 400 oC and 5mns, dense films were obtained. In this study, the flow rate and concentration of precursor solution and substrate types also influence the morphology of films, although to a lesser degree. The most suitable range of the flow rate is 0.7 cc/hr to 1.4 cc/hr. The XRD results show that the crystalline NiO/CGO film were obtained by EAVD technique.

No description available.

Albertan coal has been used to produce extracts as precursor for production of anode coke. Coal extractability was studied using digestion with Tetralin in a 500 ml reactor. Different operating conditions were tried and optimum conditions were chosen for runs with coal-derived solvents. Extracts from runs with coal-derived solvents and their hydrotreated versions were distilled and heat treated to produce pitches as coke precursors. Coking experiments were performed using a molten salt bath furnace. Coal, solvents, pitches and cokes were characterized to study the effects of process chemistry on coke anisotropy. Coke anisotropy was studied using image analysis of polarized light optical micrographs and x-ray diffraction. Aromaticity of the pitch was found to be the key parameter controlling coke anisotropy. Solvent was found to be the most important factor contributing to pitch aromaticity. Heat treated products of high aromaticity yield the highest coke conversion and anisotropy. / Chemical Engineering

Techn. Universiẗat, Diss., 2002--Dresden.

University, Diss., 2003--Köln.

An electrochemical technique has been developed for the production of precursors to ceramic films on hydrogen sorbing metal substrates. It involves the electrolysis of aqueous metal salt solutions which yields hydrogen at the cathode, resulting in local generation of base (hydroxide ions) around this electrode. Such conditions promote the precipitation of metallic hydroxides from a suitable electrolyte. If the local alkaline environment is not disrupted by convective or other forces, then a solid phase accumulates near the cathode, and forms an adherent gel-like structure on its surface. In order to maintain deposition, it is essential that gaseous hydrogen evolution is minimised, and preferably eliminated. This can be achieved by use of a hydrogen sorbing cathode material, such as palladium. The electrode, and adherent film (or, in appropriate circumstances, the deposit alone) can then undergo a subsequent calcination treatment to yield the ceramic layer. It is possible to generate both porous and compact structures by this method, depending on the potential programme employed during deposition. Research has been conducted into the understanding of mechanisms involved in porosity control of films deposited during different potential regimes, with view to establishing routes to layers of predetermined physical structure. In-situ optical methods were employed to complement the electrochemical techniques, providing valuable insight into the initial mechanisms of film formation and the subsequent thickening processes. The utility of the precipitation process was illustrated by the fabrication of films which demonstrated a variable conductivity over a range of humidities appropriate to sensing application. Investigation into the use of a bipolar palladium electrode as an aid to generating thick film deposits was carried out. The device comprised a palladium plate, operated as a bipolar electrode in aqueous electrolyte. Under suitable conditions, the negative face of this electrode can be made to generate and absorb hydrogen, whilst simultaneously, the positive face oxidises hydrogen transported across the bipolar substrate by diffusion. Thus the cathode face is a non-gassing electrode on which thick deposits of metal hydroxide can be grown. This line of research lead to the realisation of a self-feeding hydrogen anode at the electrode's positive face. Further research was undertaken to assess the electrochemical properties of this anode. The effective operating window for hydrogen oxidation was investigated, and the effect of prolonged potential cycling, elevated temperature and bipolar plate thickness on this region was also considered.

>Magister Scientiae - MSc / The objective of the thesis is to develop highly efficient catalysts for solid polymer electrolyte (SPE) electrolyser anodes.The anode is the primary cause of the large overpotential of SPE electrolysers and also adds significantly to the cost of the electrolysers. Currently, unsupported IrO2 is a widely used anode catalyst as it exhibits the best stability during the oxygen evolution reaction. The activity of IrO2 needs to be improved significantly to address the high cost and efficiency issues of the SPE electrolyser. Developments aimed at improving the activity of unsupported IrO2 are however limited due to the limitations of the wellknown supports under the operating conditions of electrolysers, leading to their oxidation.In this study binary metal oxides based on IrO2 were developed and optimized as anode catalysts for the SPE electrolyser and compared to the ‘state-of-art’ commercial IrO2 catalyst. The Adams fusion method was adapted and used to synthesize the catalysts.The activities of the catalysts were determined using half-cell studies. Optimum conditions for the preparation of unsupported IrO2 catalysts were found to be 350 oC and 2 hours. The resulting catalysts had twice the activity of the ‘state-of-art’ commercial IrO2 catalyst. Secondary metals were carefully selected, after carrying out both a literature study and an experimental study. Binary metal oxides were then developed using the optimum synthesis conditions. Four binary metal oxides were studied to identify the best/most efficient catalyst for electrolysis. The catalysts were characterized using XRD, TEM, SEM and EDS analyses, in efforts to understand and correlate the activity of the catalysts to its physical properties and obtain information that could be useful for the further development of efficient catalysts.Although all the binary metal oxides studied showed improved activity compared to IrO2, the catalytic activity of Ir0.7Ru0.3O2 was found to be significantly better than the commercial catalyst: it was over 5 times more active than the ‘state-of-art’ commercial IrO2 catalyst. Ir-Pd mixed oxides also proved to be highly efficient as anode catalysts for SPE electrolysers.

Solid Oxide Fuel Cells (SOFCs) are a promising technology in the power-generation sector because of their ability to use either hydrocarbons or pure hydrogen. However, introducing hydrocarbons to SOFCs has the negative effect of poisoning the anode of the SOFC with carbon molecules. These carbon deposits in the anode place mechanical stress on the anode and crack the anode interrupting the nickel-based electron percolation network. Gradual interruption of this network increases anode electrical resistance and can eventually lead to complete SOFC functional failure. However, one technology that may reduce premature anode failure due to carbon deposition is the use of a getter anode. A getter anode intercepts the carbon prior to deposition on the functional anode. In this work, A CFD model was modified to incorporate a getter anode, and the functional anode in the study saw a roughly 60% drop in carbon deposition with the addition of a 0.1mm getter anode, compared to the baseline. Also a trend was found that total carbon deposited on the functional anode decreased as the porosity of the getter anode decreased. However, lengthening the getter anode and decreasing its porosity can potentially starve the functional anode of hydrogen fuel, so a tradeoff exists removing carbon and maintaining fuel cell performance.

No description available.

The production of halloysite-derived silicon (HDS) is investigated as a potential anode material in lithium-ion batteries (LIBs). Other researchers have found HDS to be electrochemically active in small test cells. To test larger electrochemical cells, the production process needs to be scaled up and optimized. HDS is produced through magnesiothermic reduction of acid-etched halloysite. The reduction process is very exothermic and requires special consideration while being scaled up. A reactor and pressure release system were designed and fabricated to perform the reduction process in a safe manner. Various steps of the process were tested to determine their influence on the purity of the HDS and the stability of the reaction. The concentration of aluminum chloride was determined to be critical in preventing excessive thermal spikes during the reaction. We also found that there was no benefit to increasing the amount of the reducing agent, as it can lead to undesired side reactions. We also determined that proper mixing and sufficient temperature are some of the most important influences on the purity of HDS product. The HDS produced in our process performed well electrochemically. Si electrodes had up to 2284 mAh/g of discharge capacity after initial formation cycle. The Coulombic efficiency was as high as 95% for a given Si-G electrode. Detailed analyses using differential scanning calorimetry (DSC) revealed multiple side reactions involving magnesium, aluminum chloride, and silica. Magnesium reacts with aluminum chloride to produce magnesium chloride. This would mean that aluminum metal would react with silica, instead of magnesium. The combination of those two reactions releases 90% more heat than would magnesiothermic reduction of silica, increasing the possibility of unwanted thermal events. The newly formed magnesium chloride then reacts with the remaining aluminum chloride to form a hybrid salt, MgAl2Cl8.