Wear resistant surfaces with high toughness and impact resistant properties are to be created to improve the life cycle cost of brake discs for trains. A potential solution to this industrial problem is to use an arc cladding process. This work describes the application of gas tungsten arc welding (GTAW) for a structural ceramic Metal Matrix Composite (MMC) on steel. The structure of the two ceramics examined indicates the possibility of development of a wear resistant surface, which would extend the life of the brake disc. Silicon Carbide (SiC) and Tungsten Carbide (WC) ceramics were studied to embed them in a steel matrix by an advanced GTAW method. WC particles penetrated the liquid weld pool and also partially dissolved in the steel matrix, whereas, SiC because of the physical properties never penetrated deeper into the weld pool but segregated on the surface. Successful embedding and bonding of WC led to the decision to exercise an in-depth analysis of the bonding between the WC particles and the matrix. Chemical analysis of the matrix revealed more WC dissolution as compared to particle form within the clad. It was observed that WC reinforcement particles built a strong chemical bond with the steel matrix. This was shown by electron backscatter diffraction (EBSD) analysis. The hard clad layer composed of WC reinforced steel matrix gave an matching friction coefficient to high-strength steel in cold wear conditions through Pin-on-Disc wear and friction testing. A prototype railway brake disc was created with the established GTAW parameters to find out the difficulties of producing industrial scale components.

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Solution chemistry is a versatile and powerful tool in the synthesis of designed, complex nano-level high-tech materials. Normally, the technique is considered too expensive for large-scale production of complex multi-component ceramic materials. This thesis describes the expansion of the useful area of solution processing to multi-component bulk materials such as ZnO-based high-field varistors and WC–Co cutting tools, by developing novel techniques for solution-based coating of conventionally prepared metal and ceramic powders. The chemistry and microstructure development in the preparation of coatings, and the sintering of the coated powders to compacts, were studied in detail by SEM-EDS, TEM-EDS, XRD, IR-spectroscopy, dilatometry, TGA and DSC chemical analysis. ZnO powder with a ca 20 nm thick, homogeneous oxide coat of Bi–Sb–Ni–Co–Mn–Cr–Al oxide was prepared. After sintering to dense varistor bodies, much improved microstructures with much reduced ZnO-grain sizes were obtained. This shows that the oxides added as liquid sintering aid and grain-growth inhibitor become much more active when added homogeneously as a skin on the ZnO powder. After sintering of cobalt-coated WC, much improved micro-structures were obtained with a much more narrow WC grain-size distribution than that obtained from starting powders mixed by a conventional milling route. Coated powders also obviate the need for the extensive milling of WC and Co powders used in conventional mixing. The novel solution route was also applied to preparation of porous sponges and thin films on metal, glass and Al2O3 of sub 20 nm sized Co- or Ni-particles.

Makrophagen sind professionelle phagozytische Zellen, welche körpereigene gealterte oder toten Zellen und in den Körper eingedrungene Krankheitserreger aufnehmen. Die phagozytierten Partikel werden von lysosomalen Hydrolasen abgebaut und daraus hervorgehende Antigene an Zellen des spezifischen Immunsystems präsentiert. Aufgabe der lysosomalen Phospholipase A1 (PLA1) ist der Abbau von Phospholipiden. Sie spielt damit nicht nur eine elementare Rolle bei dem Abbau von Phospholipidmembranen nach Phago- und Autophagozytose, sondern kann auch an der Generation von Lipidantigenen beteiligt sein. Die vorliegende Arbeit bietet zum ersten Mal Hinweise auf die Sequenz der lysosomalen PLA1. Mittels proteinbiochemischer Reinigung und nachfolgender massenspektrometrischer Sequenzanalyse wurden zwei Proteinkandidaten identifiziert, welche der lysosomalen PLA1-Aktivität zugrunde liegen können. Des Weiteren werden ausführliche Untersuchungen zu den Katalyseeigenschaften des Enzyms an Liposomen präsentiert. Die Lipidzusammensetzung der Membran beeinflusst maßgeblich die Aktivität der lysosomalen PLA1. So haben in die Membran integrierte anionische Phospholipide eine stark enzymaktivierende Wirkung. Eine Erhöhung der Ionenstärke oder des pH-Wertes vermindern die Bindungsfähigkeit der lysosomalen PLA1 an die Membran und damit deren Aktivität. Dies lässt vermuten, dass elektrostatische Wechselwirkungen eine Rolle bei der Membranbindung spielen. Das Enzym besitzt pIs / Macrophages are professional phagocytes which engulf and degrade senescent and dead cells as well as pathogens. Phagocytosed particles are subsequently degraded by lysosomal enzymes. The lysosomal phospholipase A1 (PLA1) degrades phospholipids, the major components of biological membranes and, hence, plays a mandatory role in decomposition of phagocytosed and autophagocytosed membranes. Furthermore the enzyme might play a role in the processing of lipid antigens for immune presentation. Nevertheless, the gene encoding this important enzyme activity is as yet unknown. Here, we used proteinbiochemical methods to isolate the lysosomal PLA1 activity from RAW B cells and identified resulting sequences by tandem mass spectrometry. This analysis revealed for the first time two putative protein candidates responsible for lysosomal PLA1 activity. Using native enzyme fractions and liposome-embedded substrate, we show that PLA1 activity depends on the presence of anionic phospholipids, low pH and low ionic strength. Lysosomal PLA1 only attaches to membranes with anionic but not zwitterionic charges. High ionic strength impairs binding demonstrating that electrostatic attraction is responsible for membrane partitioning. Upon binding the enzyme remains on membranes for numerous catalytic cycles. The enzyme’s pIs at

O desgaste é um dos fatores que causam a maior parte das falhas e redução na vida útil de ferramentas, além de resultar em produtos com condições superficiais inadequadas. A crescente demanda da indústria por menores custos, maior produtividade e melhor qualidade estão entre as justificativas para que se busquem maneiras de incrementar o desempenho dessas ferramentas. Neste contexto, o trabalho tem como objetivo avaliar e caracterizar superfícies projetadas para resistência ao desgaste utilizando o processo de aspersão térmica oxicombustível de alta velocidade (HVOF). Fez-se um estudo comparativo de caracterização e comportamento tribológico de um aço ferramenta com deposição por aspersão térmica de dois diferentes revestimentos. O estudo abrange o aço ABNT H13, utilizando o tratamento superficial de aspersão térmica HVOF com revestimentos de Cr3C2-25(NiCr) e WC-10Co-4Cr. A avaliação da superfície e do comportamento tribológico envolveu perfis de microdureza, análise de fases por difração de raios X, metalografias, obtenção da composição química, caracterização da rugosidade, ensaio de abrasão e adesão, pino-disco e ensaio do anel. O objetivo de conseguir aumentar a resistência ao desgaste utilizando um aço ferramenta com deposição via processo de HVOF, bem como o de caracterizar este processo foi alcançado. A utilização do aço ABNT H13 com deposição via aspersão térmica HVOF e revestimentos à base de carboneto de cromo e tungstênio demonstrou-se recomendável para proteção de substratos, fornecendo alta dureza e boa resistência ao desgaste. O revestimento de WC-10Co-4Cr obteve o melhor desempenho geral, apresentando uma microdureza 192% maior frente ao aço sem revestimento, uma redução de 315% do coeficiente de atrito, além de uma adesão maior ao substrato quando comparado com o revestimento Cr3C2-25(NiCr). / Wear is one of the factors that cause most of the failures and reduction of lifespan for tools, it also results in products with no quality in the surface conditions. The increasing demand of the industry for lower costs, higher productivity and better quality are among the justifications for finding ways to increase the performance of these tools. In this context, the objective of this work is to evaluate and characterize surfaces designed for wear resistance using the high velocity oxyfuel (HVOF) thermal spray process. A comparative study of characterization and tribological behavior of a tool steel with thermal spray deposition was performed for two different coatings. The study covers the ABNT H13 steel, using the surface treatment of HVOF thermal spray with coatings of Cr3C2-25(NiCr) and WC-10Co-4Cr. The surface and the tribological behavior evaluation involved microhardness profiles, phase analysis by x-ray diffraction, metallography, chemical composition, roughness characterization, abrasion and adhesion test, pin-on-disk and ring test. The objective of increasing the wear resistance using a tool steel with deposition through HVOF process, as well as to characterize this process was achieved. The use of ABNT H13 steel with chrome and tungsten carbide coatings deposited by thermal spray HVOF has proved to be recommended for substrates protection, providing high hardness and good wear resistance. The WC-10Co-4Crcoating had the best overall performance, presenting a microhardness 192% higher than the steel with no coating, a reduction of 315% of the coefficient of friction, and a higher adhesion to the substrate compared to the Cr3C2-25(NiCr) coating.

<p>Solution chemistry is a versatile and powerful tool in the synthesis of designed, complex nano-level high-tech materials. Normally, the technique is considered too expensive for large-scale production of complex multi-component ceramic materials. This thesis describes the expansion of the useful area of solution processing to multi-component bulk materials such as ZnO-based high-field varistors and WC–Co cutting tools, by developing novel techniques for solution-based coating of conventionally prepared metal and ceramic powders. The chemistry and microstructure development in the preparation of coatings, and the sintering of the coated powders to compacts, were studied in detail by SEM-EDS, TEM-EDS, XRD, IR-spectroscopy, dilatometry, TGA and DSC chemical analysis. </p><p>ZnO powder with a ca 20 nm thick, homogeneous oxide coat of Bi–Sb–Ni–Co–Mn–Cr–Al oxide was prepared. After sintering to dense varistor bodies, much improved microstructures with much reduced ZnO-grain sizes were obtained. This shows that the oxides added as liquid sintering aid and grain-growth inhibitor become much more active when added homogeneously as a skin on the ZnO powder.</p><p>After sintering of cobalt-coated WC, much improved micro-structures were obtained with a much more narrow WC grain-size distribution than that obtained from starting powders mixed by a conventional milling route. Coated powders also obviate the need for the extensive milling of WC and Co powders used in conventional mixing.</p><p>The novel solution route was also applied to preparation of porous sponges and thin films on metal, glass and Al₂O₃ of sub 20 nm sized Co- or Ni-particles. </p>

WC-Co cutting tools are widely used in the machining industry. The application of diamond coatings on the surfaces of the tools would prolong the cutting lifetime and improves the manufacturing efficiency. However, direct chemical vapor deposition (CVD) of diamond coatings on WC-Co suffer from severe premature adhesion failure due to interfacial graphitization induced by the binder phase Co. In this research, a combination of hydrochloric acid (HCl) and hydrogen (H2) plasma pretreatments and a novel double interlayer of carbide forming element (CFE)/Al were developed to enhance diamond nucleation and adhesion. The results showed that both the pretreatments and interlayers were effective in forming continuous and adhesive nanocrystalline diamond coatings. The method is a promising replacement of the hazardous Murakami's regent currently used in WC-Co pretreatment with a more environmental friendly approach.<p> Apart from coatings, diamond can be fabricated into other forms of nanostructures, such as nanotips. In this work, it was demonstrated that oriented diamond nanotip arrays can be fabricated by ion beam etching of as-grown CVD diamond. The orientation of diamond nanotips can be controlled by adjusting the direction of incident ion beam. This method overcomes the limits of other techniques in producing nanotip arrays on large areas with controlled orientation. Oriented diamond nano-tip arrays have been used to produce anisotropic frictional surface, which is successfully used in ultra-precision positioning systems.<p> Diamond-like carbon (DLC) has many properties comparable to diamond. In this thesis, the preparation of á-C:H thin films by end-Hall (EH) ion source and the effects of ion energy and nitrogen doping on the microstructure and mechanical properties of the as-deposited thin films were investigated. The results have demonstrated that smooth and uniform á-C:H and á-C:H:N films with large area and reasonably high hardness and Youngs modulus can be synthesized by EH ion source with a low ion energy. The EH ion beam deposition of carbon-based thin films have potential applications such as protective coatings on high capacity magnetic memory disk, for which coating uniformity and smoothness cannot be achieved by the traditional sputtering methods.

WC-Co cutting tools are widely used in the machining industry. The application of diamond coatings on the surfaces of the tools would prolong the cutting lifetime and improves the manufacturing efficiency. However, direct chemical vapor deposition (CVD) of diamond coatings on WC-Co suffer from severe premature adhesion failure due to interfacial graphitization induced by the binder phase Co. In this research, a combination of hydrochloric acid (HCl) and hydrogen (H2) plasma pretreatments and a novel double interlayer of carbide forming element (CFE)/Al were developed to enhance diamond nucleation and adhesion. The results showed that both the pretreatments and interlayers were effective in forming continuous and adhesive nanocrystalline diamond coatings. The method is a promising replacement of the hazardous Murakami's regent currently used in WC-Co pretreatment with a more environmental friendly approach.<p> Apart from coatings, diamond can be fabricated into other forms of nanostructures, such as nanotips. In this work, it was demonstrated that oriented diamond nanotip arrays can be fabricated by ion beam etching of as-grown CVD diamond. The orientation of diamond nanotips can be controlled by adjusting the direction of incident ion beam. This method overcomes the limits of other techniques in producing nanotip arrays on large areas with controlled orientation. Oriented diamond nano-tip arrays have been used to produce anisotropic frictional surface, which is successfully used in ultra-precision positioning systems.<p> Diamond-like carbon (DLC) has many properties comparable to diamond. In this thesis, the preparation of á-C:H thin films by end-Hall (EH) ion source and the effects of ion energy and nitrogen doping on the microstructure and mechanical properties of the as-deposited thin films were investigated. The results have demonstrated that smooth and uniform á-C:H and á-C:H:N films with large area and reasonably high hardness and Youngs modulus can be synthesized by EH ion source with a low ion energy. The EH ion beam deposition of carbon-based thin films have potential applications such as protective coatings on high capacity magnetic memory disk, for which coating uniformity and smoothness cannot be achieved by the traditional sputtering methods.

The material development cycle is becoming too slow if compared with other technologies sectors like IT and electronics. The materials scientists’ community needs to bring materials science back to the core of human development. ICME (Integrated Computational Materials Engineer) is a new discipline that uses advanced computational tools to simulate material microstructures, processes and their links with the final properties. There is the need for a new way to design tailor-made materials with a faster and cheaper development cycle while creating products that meet “real-world” functionalities rather than vague set of specifications. Using the ICME approach, cutting edge computational thermodynamics models were employed in order to assist the microstructure characterization and refinement during the TIG welding of a functionally graded composite material with outstanding wear and corrosion resistance. The DICTRA diffusion model accurately predicted the carbon diffusion during sintering, Thermo-Calc and TC-PRISMA models described the thermodynamic and kinetics of harmful carbide precipitation, while COMSOL Multhiphysic furnished the temperature distribution profile at every timestep during TIG welding of the material. Bainite transformation and the influence of chromium and molybdenum was studied and modelled with MAP_STEEL software. The simulations were then compared with experimental observations and a very good agreement between computational works and experiments was found for both thermodynamic and kinetics predictions. The use of this new system proved to be a robust assistance to the classic development method and the material microstructures and processes were carefully adjusted in order to increase corrosion resistance and weldability. This new approach to material development can radically change the way we think and we make materials. The results suggest that the use of computational tools is a reality that can dramatically increase the efficiency of the material development.

O desgaste é um dos fatores que causam a maior parte das falhas e redução na vida útil de ferramentas, além de resultar em produtos com condições superficiais inadequadas. A crescente demanda da indústria por menores custos, maior produtividade e melhor qualidade estão entre as justificativas para que se busquem maneiras de incrementar o desempenho dessas ferramentas. Neste contexto, o trabalho tem como objetivo avaliar e caracterizar superfícies projetadas para resistência ao desgaste utilizando o processo de aspersão térmica oxicombustível de alta velocidade (HVOF). Fez-se um estudo comparativo de caracterização e comportamento tribológico de um aço ferramenta com deposição por aspersão térmica de dois diferentes revestimentos. O estudo abrange o aço ABNT H13, utilizando o tratamento superficial de aspersão térmica HVOF com revestimentos de Cr3C2-25(NiCr) e WC-10Co-4Cr. A avaliação da superfície e do comportamento tribológico envolveu perfis de microdureza, análise de fases por difração de raios X, metalografias, obtenção da composição química, caracterização da rugosidade, ensaio de abrasão e adesão, pino-disco e ensaio do anel. O objetivo de conseguir aumentar a resistência ao desgaste utilizando um aço ferramenta com deposição via processo de HVOF, bem como o de caracterizar este processo foi alcançado. A utilização do aço ABNT H13 com deposição via aspersão térmica HVOF e revestimentos à base de carboneto de cromo e tungstênio demonstrou-se recomendável para proteção de substratos, fornecendo alta dureza e boa resistência ao desgaste. O revestimento de WC-10Co-4Cr obteve o melhor desempenho geral, apresentando uma microdureza 192% maior frente ao aço sem revestimento, uma redução de 315% do coeficiente de atrito, além de uma adesão maior ao substrato quando comparado com o revestimento Cr3C2-25(NiCr). / Wear is one of the factors that cause most of the failures and reduction of lifespan for tools, it also results in products with no quality in the surface conditions. The increasing demand of the industry for lower costs, higher productivity and better quality are among the justifications for finding ways to increase the performance of these tools. In this context, the objective of this work is to evaluate and characterize surfaces designed for wear resistance using the high velocity oxyfuel (HVOF) thermal spray process. A comparative study of characterization and tribological behavior of a tool steel with thermal spray deposition was performed for two different coatings. The study covers the ABNT H13 steel, using the surface treatment of HVOF thermal spray with coatings of Cr3C2-25(NiCr) and WC-10Co-4Cr. The surface and the tribological behavior evaluation involved microhardness profiles, phase analysis by x-ray diffraction, metallography, chemical composition, roughness characterization, abrasion and adhesion test, pin-on-disk and ring test. The objective of increasing the wear resistance using a tool steel with deposition through HVOF process, as well as to characterize this process was achieved. The use of ABNT H13 steel with chrome and tungsten carbide coatings deposited by thermal spray HVOF has proved to be recommended for substrates protection, providing high hardness and good wear resistance. The WC-10Co-4Crcoating had the best overall performance, presenting a microhardness 192% higher than the steel with no coating, a reduction of 315% of the coefficient of friction, and a higher adhesion to the substrate compared to the Cr3C2-25(NiCr) coating.