c-BN has been in focus for several years due to its interesting properties. The possibility for large area CVD is a requirement for the realization of these different properties in various applications. Unfortunately, there are at present severe problems in the CVD growth of c-BN. The purpose with this research project has been to theoretically investigate, using DFT calculations, the possibility for a layer-by-layer CVD growth of c-BN. It could be established that, PEALD, using a BF3-H2-NH3-F2 pulse cycle and a diamond substrate, is a promising method for deposition of c-BN films. The gaseous species will decompose in the plasma and form BFx, H, NHx, and F species (x = 0, 1, 2, 3). The H and F radicals will uphold the cubic structure by completely hydrogenate, or fluorinate, the growing surface. However, surface radical sites will appear during the growth process as a result of atomic H, or F, abstraction reactions. The addition of NHx growth species (x = 0, 1, 2) to B radical sites, and BFx growth species (x = 0, 1, 2) to N radical sites, will then result in a continuous growth of c-BN.

Parametric performance analyses and comparison of a basic geothermal heat pump, a heat pump cycle with motor cooling/refrigerant preheating, and a heat pump cycle utilizing an economizer with respect to first law is conducted through simulation. Changing compressor, pump, and motor efficiency, along with condenser pressure, evaporator pressure, degree of subcooling at the condenser exit and degree of superheating at the evaporator exit is investigated. Economizer arrangements yield the highest coefficient of performance and resilience to change in COP with variation in evaporator pressure, and degree of superheating and subcooling. The basic vapor compression and motor cooling/refrigerant preheating systems have the lowest COP throughout and greatest resilience to variation in compressor efficiency, motor efficiency and condenser pressure. Motor cooling/refrigerant preheating and economizers have advantages over basic vapor compression cycles. Motor cooling reduces ground loop heat exchanger length with similar COP, and economizers allow for an increase in COP compared to the basic cycle. / UOIT

Piezoelectric actuators (PEA) hold the most promise for precision positioning applications due to their capability of producing extremely small displacements down to 10 pm (1 pm = 10-12 m) as well as their high stiffness and force output. The piezoelectric-driven stick-slip (PDSS) actuator, working on the friction-inertia concept, has the capacity of accomplishing an unlimited range of motion. It also holds the promises of simple configuration and low cost. On the other hand, the PDSS actuator has a relatively low efficiency and low loading capability, which greatly limits its applications. The purpose of this research is to improve the performance of the PDSS actuators by employing specially-designed working surfaces.<p> The working surfaces, referred as anisotropic friction (AF) surfaces in this study, can provide different friction forces depending on the direction of relative motion of the two surfaces, and are used in this research to accomplish the aforementioned purpose. To fabricate such surfaces, two nanostructure technologies are employed: hot filament chemical vapour deposition (HFCVD) and ion beam etching (IBE). The HFCVD is used to deposit diamond on silicon substrates; and the IBE is used to etch the diamond crystalloid with a certain angle with respect to the coating surface to obtain an unsymmetrical-triangle microstructure. <p> A PDSS actuator prototype containing the AF surfaces was developed in this study to verify the function of the AF surfaces and characterize the performance of PDSS actuators. The designed surfaces were mounted on the prototype; and the improvement in performance was characterized by conducting a set of experiments with both the normal isotropic friction (IF) surfaces and the AF surfaces, respectively. The results illustrate that the PDSS actuator with the AF surface has a higher efficiency and improved loading capability compared to the one with the IF surfaces.<p> A model was also developed to represent the displacement of the novel PDSS actuator. The dynamics of the PEA and the platform were approximated by using a second order dynamic system. The pre-sliding friction behaviour involved was investigated by modifying the LuGre friction model, in which six parameters (Note that three parameters are used in the LuGre model) were employed to represent the anisotropic friction. By combining the PEA mechanism model, the modified friction model, and the dynamics of end-effector, a model for the PDSS actuator with the AF surface was developed. The model with the identified parameters was simulated in MATLAB Simulink and the simulation results obtained were compared to the experimental results to verify the model. The comparison suggests that the model developed in this study is promising to represent the displacement of the novel PDSS actuators with AF surfaces.

The effect of annealing conditions on the microstructure evolution of CVD nickel was investigated systematically in the present study by differential scanning calorimetry, optical microscopy and transmission electron microscopy (TEM), upon both ex-situ and in-situ annealing. TEM observation revealed the as-deposited CVD nickel possessed a bi-modal grain structure, with large columnar grains embedded in nanocrystalline matrix. Ultrafine and nano growth twins were present as well as multiply twinned grains with five-fold symmetry. Microstructure observation upon annealing showed that grain growth did not occur until annealing at 400ºC. Detwinning was observed at 400ºC and higher temperatures. The ultrafine and nano twins tended to transform into dislocation cell structures and this phenomenon was driven by the excess free energy associated with the high density of grown-in twin boundaries. The five-fold twinned grains were found to be thermally stable up to 600ºC. The hardness was observed to decrease with increasing annealing temperature.

The effect of annealing conditions on the microstructure evolution of CVD nickel was investigated systematically in the present study by differential scanning calorimetry, optical microscopy and transmission electron microscopy (TEM), upon both ex-situ and in-situ annealing. TEM observation revealed the as-deposited CVD nickel possessed a bi-modal grain structure, with large columnar grains embedded in nanocrystalline matrix. Ultrafine and nano growth twins were present as well as multiply twinned grains with five-fold symmetry. Microstructure observation upon annealing showed that grain growth did not occur until annealing at 400ºC. Detwinning was observed at 400ºC and higher temperatures. The ultrafine and nano twins tended to transform into dislocation cell structures and this phenomenon was driven by the excess free energy associated with the high density of grown-in twin boundaries. The five-fold twinned grains were found to be thermally stable up to 600ºC. The hardness was observed to decrease with increasing annealing temperature.

Chemical vapor deposition (CVD) has been the main method for synthesizing diamond thin films on hetero substrate materials since 1980s. It has been well acknowledged that both nucleation and growth of diamond on non-diamond surfaces without pre-treatment are very difficult and slow. Furthermore, the weak adhesion between the diamond thin films and substrates has been a major problem for widespread application of diamond thin films. Up to now, Si has been the most frequently used substrate for the study of diamond thin films and various methods, including bias and diamond powder scratching, have been applied to enhance diamond nucleation density. In the present study, nucleation and growth of diamond thin films on Ti3SiC2, a newly developed ceramic-metallic material, using Microwave Plasma Enhanced (MPE) and Hot-Filament (HF) CVD reactors were carried out. In addition, synchrotron-based Near Edge Extended X-Ray Absorption Fine Structure Spectroscopy (NEXAFS) was used to identify the electronic and chemical structures of various NCD films. The results from MPECVD showed that a much higher diamond nucleation density and a much higher film growth rate can be obtained on Ti3SiC2 compared with on Si. Consequently, nanocrystalline diamond (NCD) thin films were feasibly synthesized on Ti3SiC2 under the typical conditions for microcrystalline diamond film synthesis. Furthermore, the diamond films on Ti3SiC2 exhibited better adhesion than on Si. The early stage growth of diamond thin films on Ti3SiC2 by HFCVD indicated that a nanowhisker-like diamond-graphite composite layer, different from diamond nucleation on Si, initially formed on the surface of Ti3SiC2, which resulted in high diamond nucleation density. These results indicate that Ti3SiC2 has great potentials to be used both as substrates and interlayers on metals for diamond thin film deposition and application. This research may greatly expand the tribological application of both Ti3SiC2 and diamond thin films. The results demonstrated that NEXAFS is a reliable and powerful tool to identify NCD films.

The isotopic composition of water in the atmosphere is influenced by how the water evaporated, how it was transported, and how it formed in the cloud before falling. Because these processes are temperature dependent, the isotopic ratios stored in glacial ice and other proxy sources have been used as an indicator of pre-instrumental climate. There is uncertainty, however, as to whether isotopic ratios should be interpreted as a proxy of local temperature, or as a broader indicator of changes in how the vapor was transported. To better understand these processes, the NASA GISS general circulation model (GCM) was used to examine two different types of controls on the isotopic composition of moisture. The first control was the large-scale circulation of the atmosphere. Over Europe, it was found that δ18O is strongly controlled by a Northern Annular Mode-like pattern, detected in both the GCM and for Europe’s high-quality precipitation δ18O data. Over the southwest Yukon, it was found that higher δ18O was associated with moisture transport from the south, which led to a re-interpretation of the large mid-19th century δ18O shift seen in the ice cores from Mt. Logan. The second type of control was microphysical, relating to the way precipitation interacts with vapor after it has formed. Using a GCM sensitivity experiment, the effects of ‘post-condensation exchange’ were found to depend primarily on the proportion between the amount of upstream precipitation that fell as rain and the amount that fell as snow, and at low latitudes, on the strength of atmospheric moisture recycling. This led to a partitioning of the well-observed correlation between temperature and precipitation δ18O into its initial and post-condensation components, and a GCM-based interpretation of satellite measurements of the isotopic composition of water vapor in the troposphere.

This work uses a modification of the chemical vapor deposition (CVD) technique to study the effects of source gas flow geometry (and the corresponding parameters) on carbon nanotube growth. Our approach is to flow the carbon-containing source gas through a nozzle, projecting the gas stream onto targeted regions of the substrate. This technique not only allows the potential for localized nanotube growth, but also offers an interesting opportunity to provide an experimental test of theoretical nanotube growth models.

The isotopic composition of water in the atmosphere is influenced by how the water evaporated, how it was transported, and how it formed in the cloud before falling. Because these processes are temperature dependent, the isotopic ratios stored in glacial ice and other proxy sources have been used as an indicator of pre-instrumental climate. There is uncertainty, however, as to whether isotopic ratios should be interpreted as a proxy of local temperature, or as a broader indicator of changes in how the vapor was transported. To better understand these processes, the NASA GISS general circulation model (GCM) was used to examine two different types of controls on the isotopic composition of moisture. The first control was the large-scale circulation of the atmosphere. Over Europe, it was found that δ18O is strongly controlled by a Northern Annular Mode-like pattern, detected in both the GCM and for Europe’s high-quality precipitation δ18O data. Over the southwest Yukon, it was found that higher δ18O was associated with moisture transport from the south, which led to a re-interpretation of the large mid-19th century δ18O shift seen in the ice cores from Mt. Logan. The second type of control was microphysical, relating to the way precipitation interacts with vapor after it has formed. Using a GCM sensitivity experiment, the effects of ‘post-condensation exchange’ were found to depend primarily on the proportion between the amount of upstream precipitation that fell as rain and the amount that fell as snow, and at low latitudes, on the strength of atmospheric moisture recycling. This led to a partitioning of the well-observed correlation between temperature and precipitation δ18O into its initial and post-condensation components, and a GCM-based interpretation of satellite measurements of the isotopic composition of water vapor in the troposphere.

The reactivity of Ca-based sorbents with acid gases (specifically SO2, HCl and NO2) at low temperature has been a subject of interest in the last decades, since it constitutes the fundamental reactive system in a number of technologies aimed at the reduction of acid gas emission from industrial combustors or incinerator plants. However, a complete understanding of the chemistry involved still presents unsolved challenges. This thesis has been devoted to provide new insight on the kinetic modeling and reaction mechanism of the system Ca(OH)2-SO2 (+NO2) and direct evidence of the role of water on them. The mechanistic pathways of the Ca(OH)2-NO2 (+SO2) and Ca(OH)2-HCl systems are also discussed.The experimental breakthrough curves of SO2 obtained from a Ca(OH)2 bed reactor are successfully simulated by a semi-empirical kinetic model (DM-ISCM). This model takes into account (1) the deactivation of the reagent surface as the reaction product deposits on the surface and (2) an outward solid-state diffusion of hydrated Ca2+ and HO- ions from the inner Ca(OH)2/CaSO3·(1/2)H2O interface to the outer CaSO3(1/2)·H2O/gas one. The examination of Ca(OH)2 single crystals reacted with SO2 by atomic force microscopy (AFM) reveals that the reaction product crystallizes forming "needle-like" features irrespective of the RH at which reaction takes place. Furthermore, the AFM explorations provide evidence of product crystal (CaSO3·(1/2)H2O) mobility on the surface of the reactant crystal and further product crystal aggregation, as long as the crystal is in contact with water vapor. This finding suggests that once a product crystal is formed during the reaction, it is removed from its position, and consequently, new surface of Ca(OH)2 is opened up for further reaction. A reaction mechanism that might be consistent with the DM-ISCM and AFM results would consist of the following steps: (1) formation of an adsorbed water layer on the reagent surface; (2) hydration of SO2 with adsorbed water molecules to form SO2·zH2O complexes; (3) reaction of the complexes with Ca(OH)2 to form the reaction product CaSO3·(1/2)H2O by a solid-state mechanism; (4) diffusion of product crystallites and rearrangement of the reacted surface to form needle-like features; (5) ionic solid-state diffusion or reaction with residual active surface. Although in all the steps the adsorbed water could play a role, the most relevant one that might account for the outstanding effect of the RH on the reactivity of the system could be step (4). It could be proposed that product crystallites diffusion is promoted by the formation of H-bonds.On the other hand, the mechanistic pathway proposed for the system Ca(OH)2-NO2 is based on redefining the reactions that take place in aqueous solution, but considering their solid state character. It consists of two consecutive reactions: (1) NO2 reacts with Ca(OH)2 to give Ca(NO3)2 and Ca(NO2)2; (2) the product Ca(NO2)2 further reacts with adsorbed water to form NO and Ca(NO3)2. Furthermore, when SO2 is also present in the gas phase, a redox reaction between CaSO3 and NO2 could also occur. These reactions are consistent with the results from solid analyses and they seem to be promoted by adsorbed water. Moreover, the formation of Ca(NO3)2 and Ca(NO2)2 hygroscopic salts might account for the strong enhancement of the ability of Ca(OH)2 to capture SO2 under the presence of NO2. The SO2 experimental breakthrough curves obtained in these conditions are also reasonably well described by the DM-ISCM. Regarding the Ca(OH)2-HCl system, a possible mechanistic pathway consistent with our experimental results and the those seemingly diverse from literature concerns two consecutive reactions: (1) formation of Ca(OH)Cl, and (2) final formation of CaCl2 from the reaction between Ca(OH)Cl and HCl. A kinetic control of these reactions might be suggested, that is, depending on the experimental conditions, the second reaction does not take place. This second reaction is only expected to be promoted at high HCl concentrations and temperatures and/or at high reaction times. / En les últimes dècades, la contínua i creixent demanda de qualitat de vida, juntament amb un progressiu i sostingut increment de la població mundial, ha generat un fort creixement de l'activitat industrial i del transport. Aquesta situació ha originat una emissió massiva de contaminants a l'atmosfera, alterant-ne la seva composició i causant així efectes nocius en el medi ambient i en la salut humana. Tradicionalment, tant la legislació nord-americana com l'europea s'han centrat en la contaminació causada per la pluja àcida i per l'anomenat smog fotoquímic. La pluja àcida pot originar-se a partir de l'emissió directa de gasos àcids forts, com el HCl, però la major part és produïda indirectament per l'emissió d'altres gasos com el SO2 i el NO2 El SO2 i el HCl atmosfèrics s'originen bàsicament a partir de la combustió de materials sòlids que contenen sofre o clor, respectivament. En aquest sentit, la principal font d'emissió del SO2 són les centrals tèrmiques de combustió de carbó -el petroli també pot contenir sofre-, però també se'n pot generar a partir d'altres processos com el refinat del petroli i les plantes incineradores. Una de les alternatives més utilitzades per a reduir les emissions de gasos àcids generats en fonts estacionàries són les tecnologies de control post-combustió, que consisteixen en l'addició de sòlids alcalins en el corrent gasós per a neutralitzar els seus components gasosos àcids. Aquest procés genera productes sòlids amb un potencial contaminant molt menor que l'associada als seus precursors gasosos. En moltes d'aquestes tecnologies s'afegeix aigua de diferents formes en el procés, ja que la reacció de neutralització dels gasos àcids s'afavoreix en la seva presència. Depenent de la quantitat d'aigua i forma que s'introdueixi en el procés i del punt d'inserció del sòlid adsorbent en les centrals tèrmiques, les tecnologies es poden classificar en mètodes humits i mètodes secs, que al mateix temps es poden que es poden dividir en tres grups: injecció al forn, "Spray dry scrubbing" i injecció d'adsorbent sec . En els darrers anys s'ha dut a terme una recerca intensiva a escala de laboratori i de planta pilot per a la determinació de l'efecte de les diferents variables de procés en els processos "in-duct" -temperatura, humitat relativa, àrea superficial del sòlid adsorbent i relació calci/sofre- sobre la capacitat dels sòlids per a retenir SO2. En canvi, s'han publicat pocs estudis centrats en la cinètica i mecanismes de reacció que intervenen en aquests processos. La manca d'estudis de les reaccions implicades és més acusada en aquelles parts dels processos on l'aigua intervé en forma vapor, com és en els col·lectors de partícules de les centrals tèrmiques -normalment filtres de mànigues- i en els conductes on les temperatures són suficientment elevades per a què l'aigua es trobi en forma vapor.