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The solid-metal/silicate-melt partition coefficient for W has been determined experimentally for the temperature and oxygen fugacity conditions at which eucritic basalts formed. The partition coefficient for W is 25 ± 5 at 1190°C and an oxygen fugacity of 10⁻¹³∙⁴. The solid-metal/silicate-melt partition coefficient for P, D(P), has been determined experimentally at 1190°C and 1300°C. The dependence of the partition coefficient on oxygen fugacity is consistent with a valence state of 5 for P in the silicate melt. The experimental partition coefficients are given by: (1) log D(P) = -1.21 log fO₂ -15.95 at 1190°C (2) log D(P) = -1.53 log fO₂ -17.73 at 1300°C The partition coefficients may be used to interpret the depletion of W/La and P/La ratios in the Earth, Moon, and eucrites relative to Cl chondrites. The depletion of the W/La ratios in the eucrites may be explained by partitioning of W into 2% to 10% solid metal assuming equilibration and separation of the metal from the silicates at low degrees of partial melting of the silicates. The depletion of P/La ratios requires an additional 5% to 25% sulfur-bearing metallic liquid. The depletion of both P/La and W/La ratios in the Moon can be explained by partitioning of P and W into liquid metal during formation of a small lunar core by metal-silicate separation at low degrees of partial melting of the silicates. The W/La ratios in the Earth and Moon are virtually indistinguishable, while P/La ratios differ by a factor of two. The concentrations of FeO also appear to be different. These observations are difficult to reconcile with the hypothesis of a terrestrial origin of the Moon following formation of the Earth's core, but are consistent with an independent formation of the Earth and Moon. In contrast to the Moon and eucrites, the depletion of P/La and W/La ratios in the Earth cannot be explained by an internally consistent model involving equilibrium between metal and silicate at low pressures.

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Tungsten will be a key material for the plasma-facing components in future fusion devices. Its mechanical performance under neutron irradiation will strongly influence the lifetime of these devices. Pure tungsten has been subjected to a variety of irradiating species - tungsten ions, helium ions and fission neutrons - between 500°C and 900°C and the change in mechanical properties measured by micro-mechanical testing methods. Pure tungsten has been ion-irradiated using self-ions and helium ions at 500°C and 800°C. Nanoindentation has been performed on all specimens, and the 800°C specimens have been tested at temperatures up to 750°C using high-temperature nanoindentation. The irradiation temperature has no effect on the hardening of tungsten. Hardening from self-ion irradiation has not saturated by 4.5 dpa with an increase in hardness of 3.3 GPa. The hardening from helium implantation is only 0.73 GPa, and a comparison with literature shows that this hardening only depends on the concentration of the injected helium. The difference is likely due to the much smaller defect size of helium-vacancy clusters when compared to dislocation loops. High-temperature nanoindentation shows that helium-implanted tungsten softens rapidly, with the hardening from the radiation damage becoming negligible above 450°C. Self-ion implanted tungsten does not soften by 650°C, again likely due to the size difference of the defects. Micro-mechanical tests - namely micro-cantilever bending - have been used to investigate the plastic and fracture characteristics of tungsten before and after irradiation. Plastic behaviour is dominated by size effects due to the 3 μm depth of the implanted layers, which makes nanoindentation a better method for investigating radiation damaged layers. In fracture testing, fracture is rarely seen. Using the yield stress to calculate fracture toughness, the hardening from irradiation damage results in an increase in fracture toughness from 2.2 MPa√m to 6.0 MPa√m. The work of deformation at 1% is also increased after irradiation from 7.2 x 10^-11 Nm to 2.8 x 10^-10 Nm, implying that the implanted damage is not leading to an increase in embrittlement by reducing K^1c. Neutron irradiated tungsten also shows an increase in fracture toughness after irradiation from 6.5 MPa√m to 14.5 MPa√m. However, the BDTT increases by ∼ 100°C in poly-crystal tungsten and ∼ 500°C in single-crystal tungsten. The difference in BDTT does not exist in the unimplanted material. The change after irradiation is likely due to the fine (˜ 3 μm) grain size and 900°C irradiation temperature causing a significant amount of the displacement damage to be absorbed at the grain boundaries. The hardness of neutron irradiated and ion irradiated tungsten is very close: 10.4 GPa and 11.2 GPa respectively, demonstrating the ions are likely well-representing the neutron damage in pure tungsten.

Lors du fonctionnement d’une machine de fusion, les interactions plasma-parois conduisent à des processus d’érosion des matériaux et à la production de particules. Ces poussières sont principalement composées de carbone et de tungstène. Pour des raisons de sureté et afin de garantir un fonctionnement optimum du réacteur, il est important de garder en quantité raisonnable les poussières dont la taille varie entre 10 nm et 100 $m. La mise en suspension de ces poussières est une étape préliminaire à leur récupération, et le laser est une technique prometteuse pour cette application. Afin d’optimiser le nettoyage, les mécanismes physiques à l’origine de l’éjection induite par laser de ces poussières ont été identifiés. Les agrégats sont directement ablatés par le laser et les gouttelettes métalliques sont éjectées intactes par une force électrostatique induite par les photoélectrons. Nous avons également caractérisé l’éjection des particules pour choisir un système de récupération adapté. / During tokamak operation, plasma-wall interactions lead to material erosion processand dusts production. These dusts are mainly composed by carbon and tungsten, with sizesranging from 10 nm to 100 $m. For safety reasons and to guarantee an optimum reactorfunctioning, the dusts have to be kept in reasonable quantity. The dusts mobilization is a firststep to collect them, and the laser is a promising technique for this application. To optimizethe cleaning, physical mechanisms responsible for dust ejection induced by laser have beenidentified. Some particles, such as aggregates, are directly ablated by the laser. The metaldroplets are ejected intact by an electrostatic force, induced by the photoelectrons. We alsocharacterized the particles ejection to choose an appropriate collection device.

Tungsten oxide (WO3) is a semiconducting transition metal oxide with interesting electronic, structural, and chemical properties that have been exploited in applications including catalysis, gas sensing, electrochromic displays, and solar energy conversion. Nanocrystalline WO3 can absorb visible light to catalyze heterogeneous photooxidation reactions. Also, the acidity of the WO3 surface makes this oxide a good thermal catalyst in the dehydration of alcohols to various industrially relevant chemicals. This dissertation explores the photocatalytic and thermal catalytic reactivity of nanocrystalline porous WO3 microparticles. Furthermore, investigations into the changes in WO3 reactivity are carried out after modifying the porous WO3 particles with gold nanoparticles (Au NPs). On their own, Au NPs are an important class of materials that have had a large impact in many fields such as catalysis, biomedical imaging, and drug delivery. When combined with WO3, however, their influence as part of a composite Au/WO3 catalyst has not been widely studied. Porous WO3 microparticles were first prepared using mesoporous silica (SiO2) spheres as hard templates and the physical properties of these materials were fully characterized. A facile sonochemical method was used to deposit Au NPs on the WO3 surface. Using methylene blue (MB) as a photocatalytic probe, the reaction products and the catalytic activity of WO3 and Au/WO3 catalysts were compared. Composite Au/WO3 photocatalysts exhibited significantly greater rates of MB degradation compared to pure WO3. Interestingly, the observed mechanism of MB degradation was not vastly different between the two types of catalysts. The gas-phase photocatalytic oxidation of methanol (MeOH) was studied to further understand the role of WO3 and Au NPs in these photocatalysts. Porous WO3 showed greater photooxidation rates compared to bulk WO3 because of its increased active surface area. Pure WO3 and Au NPs on porous SiO2 (SiO2-Au) were both active MeOH photooxidation catalysts and were highly selective to formaldehyde (HCHO) and methyl formate (MF), respectively. Two different mechanisms, namely band gap excitation of WO3 and surface plasmon resonance (SPR) on Au NPs, were responsible for this result. Again, the Au/WO3 composite catalysts showed greater photocatalytic activity than WO3, which increased with Au loading. This high activity led to the complete photooxidation of MeOH to carbon dioxide (CO2) over Au/WO3 catalysts. Finally, the thermal catalytic transformation of MeOH under aerobic conditions was carried out to further characterize the acid and redox active sites of WO3 and Au/WO3 catalysts. Pure WO3 was highly selective for MeOH dehydration to dimethyl ether (DME), whereas Au/WO3 showed increased oxidation selectivity to products such as HCHO, FM, and COx. The Au NPs increased the reducibility of the WO3 species, which made surface oxygen atoms more labile and reactive towards MeOH. Also, the WO3 facilitated the formation of cationic Au (Au δ+) species. This combination of effects created through a strong Au/WO3 interaction increased the activity of WO3 species, but it decreased the activity of the Au NPs.

Software-Defined Networking (SDN) is an emerging trend in networking that offers a number of advantages such as smoother network management over traditional networks. By decoupling the control and data planes from network elements, a huge amount of new opportunities arise, especially in network virtualization. In cloud datacenters, where virtualization plays a fundamental role, SDN presents itself as the perfect candidate to ease infrastructure management and to ensure correct operation. Even if the original SDN ideology advocates openness of source and interfaces, multiple networking vendors offer their own proprietary solutions. In this work, an open-source SDN solution, named Tungsten Fabric, will be deployed in a virtualized datacenter and a number of SDN-related use-cases will be examined. The main goal of this work is to determine whether Tungsten Fabric can deliver the same set of use-cases as a proprietary solution from Juniper, named Contrail Cloud. Finally, this work will give some guidelines on whether open-source SDN is the right candidate for Ericsson.

A presente Tese de Doutorado analisa as modificações induzidas por prensagem isostática a quente (HIP) após a sinterização na resistência à fadiga de compósitos de metal duro com partículas de carboneto de tamanho médio na faixa de 0,6 a 2,0 ?m. A correlação entre a redução de porosidade no processo de prensagem isostática a quente e o aumento de resistência à ruptura transversal é bem conhecida. No entanto, existem questões em relação à eficácia deste processo no aumento da resistência à fadiga, devido à existência de outras imperfeições na microestrutura do material. Um aumento maior na resistência transversal é reportado na literatura para temperaturas de HIP acima do ponto eutético da liga. Os experimentos foram realizados em dois níveis diferentes de pressão de HIP, simulando condições de processo que existem em fornos de média e alta pressão (5,4 MPa e 150 MPa). Também são analisadas duas condições de temperatura de sinterização, 1.350ºC e 1.430ºC. A análise das diferentes condições de processamento mostra que a microestrutura mais homogênea, praticamente sem presença de lagos de cobalto, foi obtida a 1.430°C de temperatura de sinterização e de HIP. Esta condição de processamento resultou em melhores valores de resistência mecânica (estática e dinâmica). As diferenças de microestrutura e propriedades mecânicas obtidas nas duas condições de pressão de HIP (5,4 MPa e 150 MPa) são pouco significativas, tendo maior impacto a correlação entre a microestrutura e propriedades mecânicas em função dos diferentes ciclos de temperatura e tempo de sinterização. A análise das superfícies de fratura do material em fadiga indica uma importante influência de defeitos microestruturais, como regiões alinhadas da fase ? entre grãos de carboneto de tungstênio na iniciação e na propagação da trinca de fratura. / The present Thesis evaluates modifications induced by hot isostatic pressing (HIP) after sintering on fatigue strength of WC-11Co (in weight %) composites with sintered tungsten carbide grains of 0.6 to 2 ?m. The correlation between decreasing porosity due to hot isostatic pressing process and subsequent increase on transversal rupture strength is well known. Nevertheless, there are questions related to the efficiency of HIP process to increase fatigue strength, mainly due to the existence of microstructure defects besides porosity. An increase on transversal rupture strength is reported in the literature for HIP temperatures above the eutectic point of the composite. Experiments were carried out at two different levels of HIP pressure (5.4 and 150 MPa) covering conditions existing on medium and high pressure furnaces. Two temperatures were also evaluated (1,350 and 1,430°C). The analysis of different processing conditions shows that a more uniform microstructure, without the presence of cobalt lakes, was obtained at a sintering and HIP temperature of 1,430°C. This processing condition also resulted in better statical and dynamical mechanical properties. Microstructure and mechanical properties obtained at two different HIP pressure conditions (5.4 and 150 MPa) were rather similar. Major changes in microstructure and mechanical properties were found as a function of different cycles of temperature and sintering time. Fatigue fracture surfaces were evaluated revealing major influence of microstructural defects such as regions of aligned ? phase where crack initiation and fracture propagation are favored.