Uma parcela considerável do consumo energético, e consequentemente, dos custos das operações de tratamento de minérios é atribuída a cominuição. O High Pressure Grinding Rolls (HPGR) surge com o apelo de eficiência energética, o que, potencialmente, reduziria os custos operacionais. Nesta pesquisa, esta tecnologia é analisada como uma alternativa à rota convencional de cominuição de óxido de alumínio eletrofundido de um empreendimento em particular, que compreende um complexo circuito de britadores de rolos. Duas amostras de óxido de alumínio eletrofundido, denominadas BT e TB, foram submetidas a ensaios de HPGR (circuito aberto) e de caracterização física (DWT, WI, AI, densidade). Adicionalmente, foram realizadas simulações no software JKSimMet® 6.0 com o objetivo de prever o desempenho do equipamento em circuito fechado e realizar o escalonamento da unidade industrial. As distribuições granulométricas dos produtos dos ensaios de HPGR em circuito aberto e as distribuições granulométricas dos produtos dos circuitos fechados de HPGR simulados foram comparadas às granulometrias do produto requeridas pelo circuito industrial. Avaliou-se, também, o atendimento da vazão mássica requerida. Os resultados demonstram que a rota alternativa baseada no HPGR oferece um expressivo potencial de simplificação do circuito, com uma redução considerável do número de equipamentos de cominuição de 13 para 1, o que, além de, possivelmente, impactar na redução de custos operacionais, facilita o controle da operação. / A considerable portion of energy consumption and, as a consequence, operational costs in mineral processing is associated with comminution. High Pressure Grinding Rolls (HPGR) are appealing for their energy efficiency, which would potentially reduce operating costs. This study evaluates this technology as an alternative to the conventional electrofused aluminum oxide comminution route of a specific plant comprising a complex roll crushing circuit. Two electrofused aluminum oxide samples, called BT and TB, were submitted to HPGR (open circuit) and physical characterization (DWT, WI, bulk density, specific gravity) tests. In addition, simulations were conducted using JKSimMet® 6.0 software, aiming to predict the performance of a closed-circuit equipment and scale-up of an industrial scale unit. Product size distributions of the open-circuit HPGR tests and closed circuit HPGR simulations were compared with the product size distribution required by industrial comminution circuit. The required throughput was also evaluated. Results show that the alternative HPGR route provides a remarkable potential for circuit simplification, while considerably reducing the number of comminution equipments from 13 to 1, which facilitates operational control and possibly reduces operating costs.

O objetivo principal deste trabalho foi preparar catalisadores suportados em γ-Al2O3, a partir da conformação do hidróxido de alumínio comercial Versal, utilizando como precursores das fases ativas sais comerciais dos metais Ni, Nb e Mo, resultando nos catalisadores: NbMo/γ-Al2O3, NiNb/γ-Al2O3 e NiMo/γ-Al2O3. Estes foram avaliados quanto ao seu desempenho catalítico na reação de Hidrodessulfurização (HDS), principal processo no refino do óleo diesel. O objetivo específico do trabalho foi avaliar a influência nas propriedades dos suportes e dos catalisadores, ao variar alguns parâmetros nas etapas de peptização e calcinação. As variáveis estudadas foram: o tipo de agente peptizante (ácido acético, ácido oxálico e hidróxido de amônio), a concentração do agente peptizante (2% e 3%) e a temperatura de calcinação (550°C e 650°C). Combinando-se esses diferentes parâmetros, foram produzidos nove suportes com características diferentes. Inicialmente, utilizando Difratometria de Raios X, foi avaliada a influência da peptização, da concentração do agente peptizante e da temperatura de calcinação na estrutura cristalina dos suportes. Os resultados demonstraram que as amostras que foram submetidas à peptização e com maior concentração de peptizante, apresentaram um maior grau de cristalinidade. Os suportes foram submetidos às análises de Volumetria de N2, que determina as propriedades texturais (área superficial específica, volume específico de poros e diâmetro médio de poros) e de Resistência Mecânica. Os resultados permitiram selecionar três suportes (ácido acético 3%/650°C, ácido oxálico 3%/650°C e hidróxido de amônio 3%/650°C) para a impregnação. Foi feita impregnação incipiente, em combinações de dois a dois (NbMo, NiNb e NiMo), e os catalisadores finais também foram avaliados com os mesmos testes anteriormente feitos nos suportes, e como resultado, apenas os três catalisadores com suportes peptizados com ácido acético 3%/650°C, foram selecionados para a avaliação catalítica. As hidrodessulfurizações foram realizadas em uma unidade de alta pressão de H2 (30 bar) e alta temperatura (280°C), simulando as condições na refinaria industrial, utilizando como composto sulfurado de partida o Dibenzotiofeno (DBT). Os resultados indicaram que o catalisador NiMo/γ-Al2O3 foi o único que apresentou bom desempenho. / The more important purpose of this work was prepare supported γ-Al2O3 catalysts, by conformation of the aluminum hydroxide Versal, using as active phases precursors, commercial salts of the metals Ni, Nb e Mo, resulting in the catalysts NbMo/γ-Al2O3, NiNb/γ-Al2O3 e NiMo/γ-Al2O3. This were evaluated about the catalytic performance in the Hydrodessulfurization (HDS), principal process in the oil diesel refining. The work specific purpose was evaluated the influence in the properties of the supports and catalysts, diversified some parameters in peptizer and calcination. The studied variables were: the type of peptizer agente (acetic acid, oxalic acid and ammonium hydroxide), the peptizer agent concentration (2% e 3%) and the calcinations temperature (550°C e 650°C). Matching up this different parameters, were make nine supports with different characteristics. Initially, using X-Ray Diffraction, was evaluated the influence of the peptization, the concentration of peptizer agent and the calcination temperature in the supports crystalline structure. The results demonstrated that the peptizated samples with the superior peptizer concentration, show more crystalline. The supports were analyzed by Nitrogen Adsorption, that determine the textural properties (superficial specific area, specific volume of pore and medium diameter of pore) and Mechanical Resistance. The results allowed to select three supports (acetic acid 3%/650°C, oxalic acid 3%/650°C and ammonium hydroxide 3%/650°C) to impregnation. Was made incipient impregnation, in two to two combinations (NbMo, NiNb e NiMo) and the final catalysts were also evaluated with the supports tests, as result, just the three catalysts by supports peptizated with acetic acid 3%/650°C, were selected to catalytic tests. The Hydrodessulfuruzations were made in a high pressure unit of H2 (30 bar) and high temperature (280°C), simulating the industrial refining conditions, using as initial sufured compost the Dibenzothiophene (DBT). The results indicated that the catalysts NiMo/γ-Al2O3 was the only one to had a good performance.

Essa dissertação teve como objetivo desenvolver catalisadores suportados em gama alumina para o refino do óleo diesel. Avaliou-se o efeito do tipo de hidróxido de alumínio comercial utilizado, da quantidade do teor de nióbio adicionado ao suporte e do agente peptizante na conformação. Os pós comerciais de alumina e ácido nióbico foram peptizados, conformados por extrusão, secados e calcinados a 600°C para a obtenção de “pellets" cilíndricos com altura entre 4 e 6 mm e diâmetro entre 2 e 3 mm. O metal Mo, responsável pela fase ativa do catalisador, foi adicionado por impregnação incipiente ao suporte. Analisou-se as propriedades texturais, a resistência mecânica e a estrutura cristalina dos suportes. A partir dessas análises, o suporte que apresentou o melhor conjunto de resultados foi produzido a partir do hidróxido de alumínio Versal + 5% ácido nióbico peptizado com ácido acético 1%, e este foi impregnado com molibdênio. Foram também realizadas as mesmas análises nos catalisadores para avaliar a influência das fases ativas nas propriedades finais do material. / The purpose of this dissertation was develop supported gamma alumina catalysts for diesel oil refining. Were evaluated the effect of the type to commercial aluminum hydroxide used, the content of niobium added to the support and the peptizer agent, in the conformation. The commercial dust alumina and niobic acid were peptizated shaped by extrusion, dried and calcined in 600°C to obtain cylindrical pellets with height between 4 and 6mm and diameter between 2 and 3 mm. The Mo metal, responsable by the active phase of the catalysts, was added to the support by incipient impregnation. Were analyzed the textural properties, the mechanical resistance and the crystalline  structure of the supports. With this analysis the support with the better results was aluminum hydroxide Versal + 5% niobic acid with acetic acid 1%, and this was selected and impregnated with molibdenium. Were made the same analysis in the catalysts.

A Tialita (- Al2TiO5) apresenta elevada resistência ao choque térmico, alto ponto de fusão, baixo coeficiente de expansão térmica linear reversível (25-1000C  1,0 x 10-6 C-1), baixa condutividade térmica, além de boa resistência ao ataque por banhos metálicos. Devido a estas características, ela apresenta um alto potencial no setor de refratários, para aplicações em indústrias de fundição e automotiva, tubos de proteção de termopares em banhos de metais não ferrosos, cadinhos, entre outros. Todavia, a tialita apresenta dois problemas críticos: a decomposição eutetóide em seus óxidos precursores na faixa de 750 a 1300ºC e a formação de trincas em sua matriz durante o resfriamento após a sinterização devido à sua elevada anisotropia, comprometendo a resistência mecânica do produto. De acordo com a literatura, a microestrutura final obtida em peças de tialita através de processamento cerâmico convencional (com tamanho de grãos maiores que 2 mícrons) não consegue impedir o problema do microtrincamento, com consequente fragilização do produto. Através da moagem de alta energia (MAE) é possível obter pós ultrafinos, com grãos de dimensões nanométricas, além de uma elevada homogeneidade na mistura e microestrutura refinada. Nesse trabalho foi investigada a obtenção de tialita variando-se a proporção de TiO2: Al2O3 em 45:45, 55:35 e 35:55 em peso, utilizando 10% em peso de óxido de magnésio como aditivo. Após moídos a úmido por quatro e oito horas via MAE (moagem de alta energia), os pós foram caracterizados por difração de Raios X, não sendo observada a formação de tialita. Pastilhas foram compactadas através de prensagem uniaxial e sinterizadas a 1500oC (2 e 4 horas); a difração de Raios X foi novamente utilizada, onde foi confirmada a formação de tialita em todas as composições e condições de queima avaliadas, sendo ainda identificado em todos os casos a presença de alumina e titânia. Medidas de densidade a verde comprovaram a influência do tempo de moagem na densidade dos corpos, tendo estas medidas variado de 2,25 g/cm3 para as amostras com equimolares em alumina e titânia moídas durante 4 horas até 2,41 g/cm3 para as amostras com excesso de titânia moídas durante 8 horas. Quanto maior o tempo de queima e de moagem, menor a porosidade encontrada, os maiores valores foram encontrados para a composição AT, que apresentaram porosidade entre 12 a 14%; já os melhores resultados foram obtidos para composição com excesso de titânia (5,54% de porosidade). Os valores de retração ficaram muito próximos, em torno de 10% para a maioria das amostras. Para a caracterização mecânica e microestrutural dos corpos queimados foram realizados ainda os ensaios de compressão diametral e microscopia eletrônica de varredura, respectivamente. No que concerne a resistência mecânica, os resultados mostraram o efeito positivo da moagem, onde foi observado que quanto maior o tempo de moagem, maior a resistência à compressão diametral, sendo que as amostras com excesso de titânia apresentaram os melhores resultados, chegando a 9,31 MPa, enquanto que as amostras AT não ultrapassaram 4,88 MPa. As amostras com maior teor de titânia foram as que apresentaram também microestrutura mais refinada, com tamanho de grãos de até 1 m. / The Tialite (- Al2TiO5) has an excellent thermal shock resistance, high melting point, very low coefficient of reversible linear thermal expansion (25-1000C1,0x10-6 C-1), low thermal conductivity, as well as good resistance to attack by molten metal. Due to these technical features, this material has good potential for application concerning refractory segments such as applications in the foundry and automotive industries, thermocouples for non-ferrous, metal baths, and crucibles, among others. However, the tialite presents two critical issues: 1). It decomposes, giving rise to Al2O3-α and titanium oxide (rutile) by a eutectoid reaction at temperatures between 750 a 1300ºC and 2). The expansion crystal structure anisotropy, that promotes the low thermal expansion coefficients, provokes micro cracking, affecting the product’s mechanical strength. These two issues impact, the final tialite microstructure obtained by the conventional ceramic processing (that has grain size larger than 2 micros) demonstrating that it cannot avoid a micro cracking problem, resulting in the consequential weakening of the product. Through the High Energy Milling or Mechanical Alloying (MA), it is possible to obtain ultrafine powders, grains with nanometric dimensions, as well as a high homogeneity in the mixture and refined microstructure. In this study, it was investigated different ways to obtain tialite by varying the ratio of TiO2: Al2O3 of 45:45, 55:35 and 35:55 molar weight, using 10% molar weight of magnesium oxide as additive. After wet milling for four and eight hours, using high energy milling, the powders were characterized by X-ray diffraction, tialite's formation was not being observed. Tablets were compacted by uniaxial pressing and sintered at 1500oC (2 and 4 hours); X-ray diffraction was used again, which confirmed tialita formation in all compositions. Evaluation of the firing conditions also been identified in all cases the presence of alumina and titanium oxide. Density measurements showed the influence of milling time on the density of the green samples, where density measurements varied from 2.25 g/cm3 for samples with equimolar alumina and titania milled for 4 hours until 2.41 g/cm3 for samples with greater titania content milled for 8 hours. For longer sintering and milling time, it results in lower porosity results, the higher porosity results were related the samples named AT, which showed porosity between 12 and 14%; on the other hand, good results were achieved for samples with greater titania content (5.54% of porosity). The diametrical shrinkage results were really similar for all samples, it were around 10% for the most samples. Mechanical and micro structural characterization of burned samples were also carried out, as well as, the diametrical compression tests and scanning electron microscopy, respectively. Concerning mechanical strength, the results showed the positive effects of milling time, where the, tests showed, the longer the milling time, the greater the resistance encountered in diametric compression, where samples with greater titania content demonstrated the highest resistance, achieved 9.31 MPA, while the samples AT didn’t achieve more than 4.88MPa. The samples with greater titania content also demonstrated more refined microstructure with grain size of 1m.

Made available in DSpace on 2014-06-12T17:37:34Z (GMT). No. of bitstreams: 2 arquivo2258_1.pdf: 3031473 bytes, checksum: f1fe6d2c49f4bca4b2d85eecc375a47f (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2010 / Fundação de Amparo à Ciência e Tecnologia do Estado de Pernambuco / A anodização de alumínio e processos de revestimento de superfície é técnica comumente usada para produzir uma película decorativa e protetiva de alta qualidade. Estes processos demandam um grande consumo de água, e como conseqüência, tem-se a geração de expressivo volume de Iodo industrial contendo quantidade significativa de hidróxido de alumínio coloidal, juntamente com o sódio, cálcio, sulfato de alumínio e água (entre 85-90%), resultando em uma problemática na eleiminação destes resíduos industriais e a devida proteção ao meio ambiente. O alto teor de hidróxido de alumínio em resíduos industriais da anodização constitui um amplo atrativo para fabricação de produtos industriais cerâmicos. No presente trabalho, foram coletados os resíduos numa indústria e anodização de alumínio no nordeste do Brasil. Estes foram secos a temperatura de 200ºC por um período de 24 horas para eliminação da água existente, que neste caso foi detectado uma umidade e 88% por peso com redução significativa do volume de massa. Na etapa seguinte, os resíduos secos foram calcinados a temperatura de 1000ºC por um período de 24 horas para dissociação de substâncias químicas, ou seja, eliminação de impurezas; e na etapa final, estes foram calcinados a temperatura de 1400ºC por um período de 48 horas com a finalidade de obtenção da maior porcentagem de alumina no material. Em todas as etapas de temperatura, os resíduos foram submetidos à apreciação estrutural e química através da análise de difratometria de raios x e flourescência de raios x, em que nos quais se evidenciava um grande potencial de alumina. Após avaliação do resultado destes ensaios, verificou-se um crescimento gradativo da porcetagem de alumina, principalmente na de 1400ºC que obtivemos aproximadamente 93% de alumina. Com a obtenção de uma massa cerâmica de alto teor de alumina, foram conformados corpos de prova de forma cilíndrica com 30 mm de diâmetro e 5 mm de espessura. Os mesmos foram submetidos aos ensaios cerâmicos, mecânicos e de medida elétrica. Após a obtenção de 93% de alumina no resíduo reciclado, o resultado da medida elétrica apresentou um resistência elétrica volumétrica de aproximadamente 1014 Ωm, o qual é suficiente para a fabricação de isoladores elétricos. Com base nas análises realizadas foi possível constatar que o resíduo quando tratado resulta em uma matéria prima para a produção de de isoladores elétricos de alta tensão

A study was conducted to investigate a novel route to low cost processing of alumina/calcium-hexaluminate (A/CA6) composites. The objectives of this study were to: (a) develop A/CA6 and ß-spodumene modified A/CA6 composites using an in-situ reaction sintering method and functionally-graded A/CA6 using an infiltration technique, and (b) evaluate the effects of CA6 platelets on the ensuing physical and mechanical properties. The study has revealed that the processing procedures played an important role in the microstructural development of A/CA6 composites. The microstructure-property relationships of these materials were found to be strongly influenced by the presence of CA6 phase.The A/CA6 composites were synthesised by in-situ reaction sintering of alumina powder and (0, 5, 15, 30, 50 and 100 wt%) CA6 precursor. The phase relations and development of this system were monitored using quantitative x-ray diffraction (XRD) and neutron diffraction (ND). Rietveld analysis which showed the CA6 content to increase in proportion with the increase of CA6 precursor added. The XRD study revealed that the CA and CA2 phases started to develop at approximately 1000 and 1100°C and transformed to CA6 phase at 1400T. Similarly, the dynamic high temperature ND study showed that the corresponding calcium aluminates phases commenced to develop at 1000°C and 1200°C and then eventually transformed to CA6 at 1400°C.The presence of the plate-like CA6 grains in the system was revealed by the back-scattered SEM imaging and confirmed by the Ca x-ray map. Although the presence of CA6 caused the reduction of hardness, the fracture toughness of A/CA6 composites were improved when compared with alumina. It was found that the presence of CA6 hindered the processes of sintering and densification in alumina matrix.The use of ß -spodumene had been investigated as a liquid-phase-sintering aid for ++ / the densification of A/CA6 composites. XRD, ND, differential thermal analysis (DTA), scanning electron microscopy (SEM) and Vickers indentation were used to characterise the effects of ß -spodumene on the phase relations, densification, microstructure and mechanical properties. The results showed that the presence of ß -spodumene had a profound influence on the phase relations, densification and microstructure of A/CA6 composites. Quantitative XRD and ND Rietveld analysis showed that the addition of > 2.5 wt% ß -spodumene caused the reduction of CA6 content due to the formation of ß -quartz solid solution. The reduction of porosity in the presence of ß -spodumene suggests that it may be used as an effective sintering aid for improving the densification of A/CA6 composites. However improvements in hardness and fracture toughness were not achieved probably due to the presence of large spherical pores as well as the formation of recrystallised ß -spodumene and ß -quartz solid solution.A functionally-graded alumina/calcium-hexaluminate (A/CA6) composite was successfully synthesised through infiltration of porous alumina preform with a solution containing calcium-acetate. The infiltration kinetics of liquid into porous alumina preform had also been investigated. It was found that the infiltration rate equation proposed by Washburn is most suitable for describing the effects of preform sintering temperature, viscosity and multiple infiltrations on the infiltration characteristics. The influence of applied pressure is consistent with the model proposed by Darcy, where the applied pressure enhances the infiltration rate behaviour. Key parameters for the optimum processing conditions of preforms for subsequent infiltration have also been identified.The graded composition character of the functionally-graded A/CA6 composites were characterised by XRD and synchrotron ++ / diffraction (SRD). Depth-profiling of compositions with XRD and SRD Rietveld refinement showed that the concentration of CA6 decreased with depth, while that of A1203 increased with depth. Both XRD and SRD results showed that CA and CA2 phases formed initially at 1000°C and 1300°C, respectively, but remained stable even at 1400°C, before eventually transformed to CA6 at 1650°C. These results are consistent with those of dynamic high temperature ND data.The graded microstructure was revealed by SEM back-scattered imaging whereby the content of CA6 platelets was most abundant near the surface and decreased with increasing depth towards the bulk. The presence of CA6 phase in the composite fire at 1400°C was also confirmed by the transmission electron microscopy (TEM) observation in conjunction with energy dispersive spectroscopy (EDS). The hardness results of the graded material showed that the graded-region was softer than the non-graded region as a result of the presence of softer CA6 phase in the former. However, the fracture toughness in the graded region was found to be higher than the non-graded region which might be attributed to the display of toughening processes such as crack deflection and grain bridging.

A new but relatively simple processing study was conducted to investigate the microstructure-property relationships of alumina/aluminium titanate (AAT) composites. The objectives of this study were: (a) to develop a process for fabricating AAT and β-spodumene modified AAT composites using a solid-state reaction method and functionally-graded AAT using an infiltration technique, and (b) to evaluate the effects of dispersed aluminium titanate (AT) on the phase relations, microstructure and mechanical properties of alumina-based composites. The study has revealed that the processing procedures played an important rule in the microstructural development of AAT composites. The microstructure and properties of AAT composites have been found to be strongly influenced by the presence of dispersed AT. The phase relations in the AAT system have been characterised by x-ray diffraction (XRD) and neutron diffraction (ND). Rietveld analysis showed that the AT content increased in proportion with the amount of rutile added. The dynamic ND study showed that AT commenced to form at ~1310°C The presence of AT caused a reduction of hardness but an improvement in fracture toughness. In addition, the presence of AT hindered the processes or kinetics of sintering and densification. The use of β-spodumene has been investigated as a liquid-phase-sintering aid for the densification of AAT composites. XRD, ND, differential thermal analysis (DTA), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Vickers indentation were used to characterise the effect of β-spodumene on the phase relations, densification, microstructure and mechanical properties of AAT composites. The presence of β-spodumene was found to have a profound influence on the phase relations, densification, microstructure and properties of AAT composites. / The addition of β-spodumene caused a small reduction of AT content and a commensurate increase of alumina phase. Functionally-graded AAT composites have been successfully synthesised through infiltration of porous alumina preform with a solution containing TiCl4. The infiltration kinetics of liquid into porous alumina preform has also been investigated and modelled. It was found that the infiltration rate equation proposed by Washburn was proven to be suitable for describing the kinetics of infiltration in terms of preform sintering temperature, viscosity, and multiple infiltrations. The influence of applied pressure was consistent with the model proposed by Travitzky and Shlayen, where the applied pressure enhanced the rate of infiltration. Pre-sintering of alumina preform at 900, 1000 and 1100°C for 2 h resulted in different rates of infiltration which may be attributed to a varying degree in tortuosity of the pore channels. The graded composition character of functionally-graded AAT composites has been determined by XRD and grazing incidence synchrotron diffraction (GISRD). Graded compositions from Rietveld refinement analysis showed that the concentration of AT decreased with depth. In contrast, the α-A12O3 content increased with depth. Microstructural examination by SEM showed that the content of AT grains was the most abundant near the surface and decreased gradually with an increase in depth. The hardness results showed that FGM had a soft graded-region (AT rich) but hard non-graded alumina region. / The lower hardness in the graded region can be attributed to the presence of intrinsically soft AT phase. The presence of graded AT caused a considerable improvement in damage tolerance. The isothermal decomposition of AT at 1100°C both in air and vacuum has been studied. Both ex-situ and in-situ studies have been conducted to examine the effect of environment on the decomposition behaviour of AT. The addition of MgO was effective in enhancing the thermal stability of AT against decomposition both in air and in vacuum.

Highly ordered nanoparticle arrays have been successfully fabricated by our group recently using ultra-thin porous alumina membranes as masks in the evaporation process. The sizes of the nanoparticles can be adjusted from 5-10 nm to 200 nm while the spacing between adjacent particles can also be adjusted from several nanometers to about twice the size of a nanoparticle. The configuration of the nanoparticles can be adjusted by changing the height of the alumina masks and the evaporation direction. Due to the high pore regularity and good controllability of the particle size and spacing, this method is useful for the ordered growth of nanocrystals. Different kinds of nanoparticle arrays have been prepared on silicon wafer including semiconductors (e.g., germanium) and metals (e.g., nickel). The germanium nanoparticle arrays have potential applications in memory devices while the nickel catalyst nanoparticle arrays can be used for the growth of ordered carbon nanotubes. / Singapore-MIT Alliance (SMA)

The present thesis focuses on characterisation of microstructure and the resulting mechanical and tribological properties of CVD and PVD coatings used in metal cutting applications. These thin and hard coatings are designed to improve the tribological performance of cutting tools which in metal cutting operations may result in improved cutting performance, lower energy consumption, lower production costs and lower impact on the environment.  In order to increase the understanding of the tribological behaviour of the coating systems a number of friction and wear tests have been performed and evaluated by post-test microscopy and surface analysis. Much of the work has focused on coating cohesive and adhesive strength, surface fatigue resistance, abrasive wear resistance and friction and wear behaviour under sliding contact and metal cutting conditions. The results show that the CVD deposition of accurate crystallographic phases, e.g. α-Al2O3 rather than κ-Al2O3, textures and multilayer structures can increase the wear resistance of Al2O3. However, the characteristics of the interfaces, e.g. topography as well as interfacial porosity, have a strong impact on coating adhesion and consequently on the resulting properties.  Through the deposition of well designed bonding and template layer structures the above problems may be eliminated. Also, the presence of macro-particles in PVD coatings may have a significant impact on the interfacial adhesive strength, increasing the tendency to coating spalling and lowering the surface fatigue resistance, as well as increasing the friction in sliding contacts. Finally, the CVD-Al2O3 coating topography influences the contact conditions in sliding as well as in metal cutting. In summary, the work illuminates the importance of understanding the relationships between deposition process parameters, composition and microstructure, resulting properties and tribological performance of CVD and PVD coatings and how this knowledge can be used to develop the coating materials of tomorrow.

The impact of H2 partial pressure (H2 pp) during the hydrotreating of heavy gas oil, derived from Athabasca bitumen, over commercial NiMo/¥ã-Al2O3 catalyst was studied in a micro-trickle bed reactor. The experimental conditions were varied as follows: temperature: 360 to 400¨¬C, pressure: 7 to 11 MPa, gas/oil ratio: 400 to 1270 mL/mL, H2 purity range of 0 to 100 vol. % (with the rest either CH4 or He), and LHSV range of 0.65 to 2 h-1. The two main objectives of the project were to study the nature of the dependence of H2 pp on temperature, pressure, gas/oil ratio, LHSV (Liquid Hourly Space Velocity), and H2 purity. The project was divided into three phases: in phase one the effect of H2 purity on hydrotreating of heavy gas oil (HGO) was studied, in phase two the nature of H2 pp dependency and the effect of H2 pp on hydrotreating of HGO was investigated, and in phase three kinetic studies were carried out using different kinetic models.<p> The objective of phase one was to study the effect of hydrogen purity on hydrotreating of HGO was studied in a trickle bed reactor over a commercial Ni−Mo/¥ã-alumina catalyst. Methane was used as a diluent for the hydrogen stream, and its effect on the catalyst performance was compared to that of helium, which is inert toward the catalyst. Furthermore, a deactivation study was conducted over a period of 66 days, during which the catalyst was subjected to H2 purities ranging from 75 to 95% (with the rest methane); no significant deterioration in the hydroprocessing activities of the catalyst was observed. Therefore, it was concluded that methane was inert toward a commercial Ni−Mo/¥ã-alumina catalyst. However, its presence resulted in hydrogen partial pressure reduction, which in turn led to a decrease in hydrodesulphurization (HDS), hydrodenitrogenation (HDN), hydrodearomatization (HDA) conversions. This reduction can be offset by increasing the total pressure of the system. HDS, HDN, HDA, and mild hydrocracking (MHC) conversions were studied. Also determined were cetane index, density, aniline point, diesel index, and fractional distribution of the products.<p> The main objective of phase two was to study the effects of H2 pp on hydrotreating conversions, feed vaporization, H2 dissolution, and H2 consumption were studied. The results show that HDN and HDA are significantly more affected by H2 partial pressure than HDS; with the HDN being the most affected. For instance as the inlet H2 partial pressure was increased from 4.6 to 8.9 MPa HDS, HDN, and HDA conversions increased for 94.9%, 55.1%, and 46.0% to 96.7%, 83.9%, and 58.0% , respectively. Moreover, it was observed that H2 dissolution and H2 consumption increased with increasing H2 pp. No clear trend was observed for the effect of H2 pp on feed vaporization.<p> In phase three the kinetics of HDS, HDN, and HDA were studied. The power law, multi-parameter, and Langmuir - Hinshelwood type models were used to fit the data. The prediction capacities of the resulting models were tested. It was determined that, while multi-parameter model yielded better prediction, L-H had an advantage in that it took a lesser number of experimental data to determine its parameters. Kinetic fitting of the data to a pseudo-first-order power law model suggested that conclusions on the effect of H2 pp on hydrotreating activities could be equally drawn from either inlet or outlet hydrogen partial pressure. However, from the catalyst deactivation standpoint, it is recommended that such conclusions are drawn from the outlet H2 partial pressure, since it is the reactor point with the lowest hydrogen partial pressure.