In this study, the pore structures and surface areas of activated carbons produced from hazelnut shell and hazelnut husk by chemical activation technique using phosphoric acid (H3PO4), at relatively low temperatures (300, 400 and 500oC), were investigated. Raw materials were impregnated with different H3PO4 solutions of 30%, 40%, 50% and 60% by weight. To produce activated carbon, acid impregnated samples were heated / at a heating rate of 20 oC/min to the final carbonization temperature and held at that temperature for 2 hours. The volume and surface areas of mesopores (2-50 nm) and BET surface areas of the samples were determined by N2 gas adsorption technique at -195.6oC. The pore volume and the area of the micropores with diameters less than 2 nm were determined by CO2 adsorption measurements at 0oC by the application of Dubinin Radushkevich equation. N2 (BET) surface areas of the hazelnut shell and hazelnut husk based activated carbons were in the range of 242-596 m2/g and 705-1565 m2/g, respectively. CO2 (D-R) surface areas of the hazelnut shell and hazelnut husk based activated carbons were in the range of 433-576 m2/g and 376-724 m2/g, respectively. The highest BET surface area was obtained as 596 m2/g among hazelnut shell based samples (HS 60.4 / shell impregnated with 60 wt.% H3PO4, carbonized at 400 &ordm / C) and as 1565 m2/g among hazelnut husk based samples (HH 40.4 / husk impregnated with 40 wt.% H3PO4, carbonized at 400 &ordm / C). Hazelnut shell based activated carbons were mainly microporous while hazelnut husk based ones were mesoporous.

As a novel high temperature fuel cell, the direct carbon fuel cell (DCFC) is drawing ever-increasing attention due to its significant high conversion efficiency, diversified fuel resources and low pollution compared with conventional coal-fired power plants. Despite the advantages of the DCFC technology, there are a number of fundamental and technological challenges which need to be overcome for its further development and commercialization. One of the major hurdles in current study of the DCFC is that the efficacy of carbon fuels is still unclear. Meanwhile, the effects of impurities in the carbon fuels on the performance and lifetime of the DCFC are still up for debate. Furthermore, the molecular-level study on the mechanism of electrochemical oxidation of carbon fuels in the DCFC is limited by the lack of techniques to detect the reaction intermediates at high temperature. Finally, how to scale up the DCFC system with suitable hardware materials and optimum structural designs needs further investigation. Based on successfully developing a DCFC system with a stirring molten carbonate electrolyte, various commercial and self-made carbon fuels including activated carbons, carbon blacks, graphitic carbons, coals and carbon nanofibers (CNFs) are systematically characterized and evaluated in this thesis. It is found that the nature of carbon fuels plays an important role in the anodic performance of the DCFC. A higher surface area and a smaller particle size of carbon fuel can effectively improve its electrochemical reactivity by increasing the interaction between the carbon particles and the molten carbonate electrolyte. On the contrary, a higher graphitic degree of carbon fuel results in a lower electrochemical reactivity in the DCFC due to the less reactive sites such as edges and defects on carbon surface. Furthermore, the order of the electrochemical reactivities for carbon fuels is in good agreement with the concentration of oxygen-containing functional groups on their surface, which is believed to play a key role in the electrochemical oxidation of carbons in the DCFC. In order to better understand the relationship between the surface chemistry of carbons and their electrochemical performance in the DCFC, various pre-treatment techniques including acid washing, air-plasma treatment, air oxidation, pyrolysis and the pre-electrochemical oxidation (in molten alkali carbonate electrolytes) have been conducted on the carbon fuels. It is shown that both the HNO3 washing and pre-electrochemical oxidation are much more effective to improve the electrochemical reactivities of carbon fuels compared to other pre-treatment techniques, which is attributed to the significant changes in the microstructure of carbon fuels and more surface oxygen functional groups produced during the pre-treatments. In contrast, the pyrolysis treatment results in a sharp decrease of electrochemical reactivity of carbon fuels due to the decreases in oxygen-containing surface groups and surface areas, and the increase of their graphitic degrees. For the sake of the optimum operational conditions for the DCFC system, the influences of stirring rates, the carbon fuel loadings and fuel cell temperatures on the anodic performance of the DCFC are investigated. It has been shown that the carbon discharge rates can be significantly boosted by effective stirring and high carbon fuel concentrations due to an improved mass transport. A higher operation temperature can also increase the current density and open circuit voltage of the DCFC. However, the complete electrochemical oxidation of carbon into CO2 can be only achieved at the low operation temperature of 600-700 ºC, while the partially electrochemical oxidation of carbon into CO occurs at 800 ºC, which will significantly decrease the carbon efficiency to less than 10% at 800 ºC. In the study of self-made CNFs as fuels for the DCFC, both microstructure and electrochemical reactivity of CNFs are highly dependent on their synthesis conditions. Compared with Ni-Al2O3 catalyst, the coprecipitated Ni-Cu-Al2O3 catalyst produced more CNFs with higher electrochemically reactivity. Over the same catalyst, the CNFs synthesized at lower temperature typically have higher surface areas, more surface oxygen functional groups and lower graphitic degrees, thereby leading to a higher electrochemical reactivity in the DCFC tests. In an effort to study the catalytic effects of mineral impurities on the electrochemical performance of the DCFC, Al2O3 and SiO2 present passivation effects in the anodic reaction. In contrast, the CaO, MgO and Fe2O3 show catalytic effects in the carbon electrochemical oxidation, which is demonstrated by the increases of current densities at low over-potentials in the polarization curves.

Thermal spray is a well established technology that is commonly used in the aerospace and automotive industries. This thesis reports on the effect that substrate surface chemistry, morphology and temperature has on the morphology of PEEK single splats on aluminium substrates. PEEK single splats were deposited by HVAF and plasma spraying on aluminium substrates with 6 different pretreatments. Substrates were either sprayed at room temperature, or 323°C, and a subset of substrates was held at incremental temperatures up to 363°C. HVAF deposited splats on room temperature substrates showed sensitivity to surface chemistry, with increased circularity and area associated with low levels of hydroxide and chemisorbed water on the aluminium surface. Substrates held at 323°C were more sensitive to substrate morphology, where rough surfaces resulted in decreased circularity and area apparently independent of surface chemistry. Substrate temperature trials revealed a significant step in the results, equating to greater circularity, and lower splat area, perimeter and Feret diameter. This step occurred between 123°C and 163°C, the two points bracketing the glass transition temperature of PEEK (143°C). This result was due to the relaxation of splats deposited on surfaces above 143°C, whilst splats on cooler substrates quench through the glass transition and do not relax. PEEK splats deposited by plasma spray on room temperature and 323°C substrates showed sensitivity to the amount of hydroxide and chemisorbed water present on the aluminium substrates, with low levels resulting in more circular and larger area splats. Plasma splats did not show the same temperature effects as HVAF splats, thought to be due to the more molten state of plasma splats upon impact compared to the HVAF splats. The primary conclusions reached were that plasma sprayed polymers were sensitive to surface chemistry, and that as such the surface chemistry of a substrate should be considered when forming plasma spray polymer coatings. It was also concluded that the kinetic energy of particles in HVAF thermal spray contributed significantly to the thermal energy of a particle on impact, allowing for improved splat properties without overheating the particles in flight. Finally it was concluded that substrate temperature is far more important for HVAF thermal spray of polymers than plasma spray of polymers, but that it improves splat properties for both techniques.

Thermal spray is a well established technology that is commonly used in the aerospace and automotive industries. This thesis reports on the effect that substrate surface chemistry, morphology and temperature has on the morphology of PEEK single splats on aluminium substrates. PEEK single splats were deposited by HVAF and plasma spraying on aluminium substrates with 6 different pretreatments. Substrates were either sprayed at room temperature, or 323°C, and a subset of substrates was held at incremental temperatures up to 363°C. HVAF deposited splats on room temperature substrates showed sensitivity to surface chemistry, with increased circularity and area associated with low levels of hydroxide and chemisorbed water on the aluminium surface. Substrates held at 323°C were more sensitive to substrate morphology, where rough surfaces resulted in decreased circularity and area apparently independent of surface chemistry. Substrate temperature trials revealed a significant step in the results, equating to greater circularity, and lower splat area, perimeter and Feret diameter. This step occurred between 123°C and 163°C, the two points bracketing the glass transition temperature of PEEK (143°C). This result was due to the relaxation of splats deposited on surfaces above 143°C, whilst splats on cooler substrates quench through the glass transition and do not relax. PEEK splats deposited by plasma spray on room temperature and 323°C substrates showed sensitivity to the amount of hydroxide and chemisorbed water present on the aluminium substrates, with low levels resulting in more circular and larger area splats. Plasma splats did not show the same temperature effects as HVAF splats, thought to be due to the more molten state of plasma splats upon impact compared to the HVAF splats. The primary conclusions reached were that plasma sprayed polymers were sensitive to surface chemistry, and that as such the surface chemistry of a substrate should be considered when forming plasma spray polymer coatings. It was also concluded that the kinetic energy of particles in HVAF thermal spray contributed significantly to the thermal energy of a particle on impact, allowing for improved splat properties without overheating the particles in flight. Finally it was concluded that substrate temperature is far more important for HVAF thermal spray of polymers than plasma spray of polymers, but that it improves splat properties for both techniques.

Thermal spray is a well established technology that is commonly used in the aerospace and automotive industries. This thesis reports on the effect that substrate surface chemistry, morphology and temperature has on the morphology of PEEK single splats on aluminium substrates. PEEK single splats were deposited by HVAF and plasma spraying on aluminium substrates with 6 different pretreatments. Substrates were either sprayed at room temperature, or 323°C, and a subset of substrates was held at incremental temperatures up to 363°C. HVAF deposited splats on room temperature substrates showed sensitivity to surface chemistry, with increased circularity and area associated with low levels of hydroxide and chemisorbed water on the aluminium surface. Substrates held at 323°C were more sensitive to substrate morphology, where rough surfaces resulted in decreased circularity and area apparently independent of surface chemistry. Substrate temperature trials revealed a significant step in the results, equating to greater circularity, and lower splat area, perimeter and Feret diameter. This step occurred between 123°C and 163°C, the two points bracketing the glass transition temperature of PEEK (143°C). This result was due to the relaxation of splats deposited on surfaces above 143°C, whilst splats on cooler substrates quench through the glass transition and do not relax. PEEK splats deposited by plasma spray on room temperature and 323°C substrates showed sensitivity to the amount of hydroxide and chemisorbed water present on the aluminium substrates, with low levels resulting in more circular and larger area splats. Plasma splats did not show the same temperature effects as HVAF splats, thought to be due to the more molten state of plasma splats upon impact compared to the HVAF splats. The primary conclusions reached were that plasma sprayed polymers were sensitive to surface chemistry, and that as such the surface chemistry of a substrate should be considered when forming plasma spray polymer coatings. It was also concluded that the kinetic energy of particles in HVAF thermal spray contributed significantly to the thermal energy of a particle on impact, allowing for improved splat properties without overheating the particles in flight. Finally it was concluded that substrate temperature is far more important for HVAF thermal spray of polymers than plasma spray of polymers, but that it improves splat properties for both techniques.

The dissolution of quantum sized CdS and MnO2 particles in water was conducted using 20 kHz ultrasound. CdS particles were found to dissolve chemically via an oxidation process while MnO2 particles dissolved via a reductive process. It was found that the dissolution of the colloids could be controlled via the addition of surface active chemicals to solution and by varying the saturation gas type. In the presence of Na2S or propan-2-ol and argon gas, the dissolution of CdS was inhibited, whereas the addition of alcohols (methanol, ethanol, propan-2-ol, butan-1-ol and pentan-1-ol) to the MnO2 system led to an increase in the amount of dissolution for a given time of sonication. This increase in dissolution was found to be dependent on the ability of the surface active radical scavenger to accumulate around the bubble interface during the cavitation process. Eventually, at higher alcohol concentration there was a plateau or a limiting value reached for the efficiency of colloid dissolution which was common for each alcohol. (For complete abstract open document)

Thermal spray is a well established technology that is commonly used in the aerospace and automotive industries. This thesis reports on the effect that substrate surface chemistry, morphology and temperature has on the morphology of PEEK single splats on aluminium substrates. PEEK single splats were deposited by HVAF and plasma spraying on aluminium substrates with 6 different pretreatments. Substrates were either sprayed at room temperature, or 323°C, and a subset of substrates was held at incremental temperatures up to 363°C. HVAF deposited splats on room temperature substrates showed sensitivity to surface chemistry, with increased circularity and area associated with low levels of hydroxide and chemisorbed water on the aluminium surface. Substrates held at 323°C were more sensitive to substrate morphology, where rough surfaces resulted in decreased circularity and area apparently independent of surface chemistry. Substrate temperature trials revealed a significant step in the results, equating to greater circularity, and lower splat area, perimeter and Feret diameter. This step occurred between 123°C and 163°C, the two points bracketing the glass transition temperature of PEEK (143°C). This result was due to the relaxation of splats deposited on surfaces above 143°C, whilst splats on cooler substrates quench through the glass transition and do not relax. PEEK splats deposited by plasma spray on room temperature and 323°C substrates showed sensitivity to the amount of hydroxide and chemisorbed water present on the aluminium substrates, with low levels resulting in more circular and larger area splats. Plasma splats did not show the same temperature effects as HVAF splats, thought to be due to the more molten state of plasma splats upon impact compared to the HVAF splats. The primary conclusions reached were that plasma sprayed polymers were sensitive to surface chemistry, and that as such the surface chemistry of a substrate should be considered when forming plasma spray polymer coatings. It was also concluded that the kinetic energy of particles in HVAF thermal spray contributed significantly to the thermal energy of a particle on impact, allowing for improved splat properties without overheating the particles in flight. Finally it was concluded that substrate temperature is far more important for HVAF thermal spray of polymers than plasma spray of polymers, but that it improves splat properties for both techniques.

Thesis (Ph. D.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on February 29, 2008) Vita. Includes bibliographical references.

Thesis (Ph. D.)--State University of New York at Binghamton, Mechanical Engineering Department, 2005. / Includes bibliographical references (leaves 149-155).

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.