Hybrid molecular dynamic Monte Carlo simulation and experimental production of a multi-component Cu-Fe-Ni-Mo-W alloy

ABSTRACT: High-entropy alloys are a class of materials intensely studied in the last years due to their innovative properties. Their unconventional compositions and chemical structures hold promise for achieving unprecedented combinations of mechanical properties. The Cu-Fe-Ni-Mo-W multicomponent alloy was studied using a combination of simulation and experimental production to test the possibility of formation of a simple solid solution. Therefore, Molecular Dynamics and hybrid Molecular Dynamic/Monte Carlo simulations from 10K up to the melting point of the alloy were analyzed together with the experimental production by arc furnace and powder milling. The Molecular Dynamics simulations starting with a bcc type-structure show the formation of a singlephase bcc solid solution type-structure, whereas using Monte Carlo one, generally produced a two-phase mixture. Moreover, the lowest potential energy was obtained when starting from a fcc type-structure and using Monte Carlo simulation giving rise to the formation of a bcc Fe-Mo-W phase and a Cu-Ni fcc type-structure. Dendritic and interdendritic phases were observed in the sample produced by arc furnace while the milled powder evidence an separation of two phases Cu-Fe-Ni phase and W-Mo type-structures. Samples produced by both methods show the formation of bcc and a fcc type-structures. Therefore, the Monte Carlo simulation seems to be closer with the experimental results, which points to a two-phase mixture formation for the Cu-Fe-Ni-Mo-W multicomponent system.info:eu-repo/semantics/publishedVersio

Microstructure characterization of ODS-RAFM steels

Results of the microstructural characterization of four different RAFM ODS Eurofer 97 batches are presented and discussed. Analyses and observations were performed by nuclear microprobe and scanning and transmission electron microscopy. X-ray elemental distribution maps obtained with proton beam scans showed homogeneous composition within the proton beam spatial resolution and, in particular, pointed to a uniform distribution of ODS (yttria) nanoparticles in the Eurofer 97 matrix. This was confirmed by transmission electron microscopy. Scanning electron microscopy coupled with energy dispersive spectroscopy made evident the presence of chromium carbide precipitation. Precipitates occurred preferentially along grain boundaries (GB) in three of the batches and presented a discrete distribution in the other, as a result of different thermo-mechanical routes. Additional electron backscattered diffraction experiments revealed the crystalline textures in the ferritic polycrystalline structure of the ODS steel samples

Microstructure characterization of ODS-RAFM steels

Results of the microstructural characterization of four different RAFM ODS Eurofer 97 batches are presented and discussed. Analyses and observations were performed by nuclear microprobe and scanning and transmission electron microscopy. X-ray elemental distribution maps obtained with proton beam scans showed homogeneous composition within the proton beam spatial resolution and, in particular, pointed to a uniform distribution of ODS (yttria) nanoparticles in the Eurofer 97 matrix. This was confirmed by transmission electron microscopy. Scanning electron microscopy coupled with energy dispersive spectroscopy made evident the presence of chromium carbide precipitation. Precipitates occurred preferentially along grain boundaries (GB) in three of the batches and presented a discrete distribution in the other, as a result of different thermo-mechanical routes. Additional electron backscattered diffraction experiments revealed the crystalline textures in the ferritic polycrystalline structure of the ODS steel samples

A comparison between the quality of eggs from indigenous chicken breeds and that from commercial layers

There is an increased interest in animal products from more sustainable farming practices, which may include using local breeds. In addition, maintaining biodiversity is important, and naturally, indigenous breeds of chickens are well adapted to the local environmental conditions. In the current study, 286 eggs from 4 Portuguese breeds of chickens (Branca, Amarela, Pedr^es Portuguesa, and Preta Lusit^anica) and from a commercial hybrid laying hen were used. Chemical and physical characteristics of the eggs and the egg components such as weights, Haugh units, yolk color, albumen protein content, yolk fatty acid content, and mineral content in the albumen and yolk were analyzed. The Branca breed produced eggs with a lighter brown shell color and lower Haugh unit values than the remaining native breeds (P,0.05). The commercial hens produced eggs that were found to be more rounded shape than the ideal and with a darker colored shell and yolk than eggs from the 4 local breeds. In addition, the commercial hens also produced heavier eggs but with lower Haugh units than the Amarela, Pedr^es Portuguesa, and Preta Lusit^anica breeds (P , 0.05). The range of saturated fatty acids, monounsaturated fatty acids, and total polyunsaturated fatty acids between eggs from the 4 breeds was small and not significantly different. No differences were found in the percentage of albumen protein between breeds. Albumen and yolk ash content was not different between breeds. The overall analysis indicated that eggs from these native genotypes match the quality of a commercial product in many characteristics. In markets where eggs from local breeds are available, consumers are purchasing a high-quality product while aiding in the expansion of local genetic resources and investing in local farmersinfo:eu-repo/semantics/publishedVersio

Technological Feasibility of Couscous-Algae-Supplemented Formulae: Process Description, Nutritional Properties and In Vitro Digestibility

The aim of this work was to develop functional couscous in a traditional Tunisian manner (hand rolling), enriched in algae biomass (6% w/w). Four Chlorella vulgaris (C. vulgaris) biomasses and one mixture of C. vulgaris and two macroalgae biomasses (Ulva rigida and Fucus vesiculosus) were used. The C. vulgaris strain was subjected to random mutagenesis and different culture conditions (Allmicroalgae), resulting in different pigmentations and biochemical compositions. Couscous samples were characterized in terms of nutritional properties, oscillatory rheology properties and digestibility. All biomasses provided a significant supplementation of nutrients and excellent acceptance. The enrichment resulted in lower firmness, higher viscoelastic functions (G0 and G”) and a significant improvement in the cooking quality. Major differences between couscous samples with different microalgae were observed in protein and mineral contents, fully meeting Regulation (EC) No. 1924/2006 requirements for health claims made on foodstuffs. The amount of digested proteins was also higher in algae-containing samples. The fatty acid profile of the enriched couscous varied in a biomass-specific way, with a marked increase in linolenic acid (18:3 !3) and a decrease in the !6/!3 ratio. Sensory analysis revealed that microalgae-containing products could compete with conventional goods with an added advantage, that is, having an ameliorated nutritional value using algae as a “trendy” and sustainable ingredientinfo:eu-repo/semantics/publishedVersio

New WC-Cu thermal barriers for fusion applications: high temperature mechanical behaviour

ABSTRACT: The combination of tungsten carbide and copper as a thermal barrier could effectively reduce the thermal mismatch between tungsten and copper alloy, which are proposed as base armour and heat sink, respectively, in the divertor of future fusion reactors. Furthermore, since the optimum operating temperature windows for these divertor materials do not overlap, a compatible thermal barrier interlayer between them is required to guarantee a smooth thermal transition, which in addition may mitigate radiation damage. The aim of this work is to study the thermo-mechanical properties of WC-Cu cermets fabricated by hot pressing. Focus is placed on the temperature effect and composition dependence, as the volume fraction of copper varies from 25 to 50 and 75 vol%. To explore this behaviour, fracture experiments are performed within a temperature range from room temperature to 800 degrees C under vacuum. In addition, elastic modulus and thermal expansion coefficient are estimated from these tests. Results reveal a strong dependence of the performance on temperature and on the volume fraction of copper and, surprisingly, a slight percent of Cu (25 vol%) can effectively reduce the large difference in thermal expansion between tungsten and copper alloy, which is a critical point for in service applications. The thermal performance of these materials, together with their mechanical properties could indeed reduce the heat transfer from the PFM to the underlying element while supporting the high thermal stresses of the joint. Thus, the presence of these cermets could allow the reactor to operate above the ductile to brittle transition temperature of tungsten, without compromising the underlying materials.info:eu-repo/semantics/publishedVersio

Magnetotelluric Imaging of the Lithosphere Across the Variscan Orogen (Iberian Autochthonous Domain, NW Iberia)

A new magnetotelluric (MT) survey comprising 17 MT soundings throughout a 30 km long N30°W transect in the Iberian autochthons domain of NW Iberia (Central Iberian Zone) is presented. The 2-D inversion model shows the resistivity structure of the continental crust up to 10 km depth, heretofore unavailable for this region of the Variscan Orogen. The MT model reveals a wavy structure separating a conductive upper layer underlain by a resistive layer, thus picturing the two main tectonic blocks of a large-scale D2 extensional shear zone (i.e., Pinhel shear zone). The upper layer represents a lower grade metamorphic domain that includes graphite-rich rocks. The lower layer consists of high-grade metamorphic rocks that experienced partial melting and are associated with granites (more resistive) emplaced during crustal thinning. The wavy structure is the result of superimposed crustal shortening responsible for the development of large-scale D3 folds (e.g., Marofa synform), later deflected and refolded by a D4 strike-slip shear zone (i.e., Juzbado-Penalva do Castelo shear zone). The later contribution to the final structure of the crust is marked by the intrusion of postkinematic granitic rocks and the propagation of steeply dipping brittle fault zones. Our study demonstrates that MT imaging is a powerful tool to understand complex crustal structures of ancient orogens in order to design future prospecting surveys for mineral deposits of economic interest

Thermal Field Theory and Generalized Light Front Coordinates

The dependence of thermal field theory on the surface of quantization and on the velocity of the heat bath is investigated by working in general coordinates that are arbitrary linear combinations of the Minkowski coordinates. In the general coordinates the metric tensor $g_{\bar{\mu\nu}}$ is non-diagonal. The Kubo, Martin, Schwinger condition requires periodicity in thermal correlation functions when the temporal variable changes by an amount $-i\big/(T\sqrt{g_{\bar{00}}})$. Light front quantization fails since $g_{\bar{00}}=0$, however various related quantizations are possible.Comment: 10 page

An extended immersive learning environment for solid mechanics theory and demonstration(s)

This paper presents a collaborative virtual learning environment, which includes technologies such as 3D virtual representations, learning and content management systems, remote experiments, and collaborative learning spaces, among others. It intends to facilitate the construction, management and sharing of knowledge among teachers and students, in a global perspective. The environment proposes the use of 3D social representations for accessing learning materials in a dynamic and interactive form, which is regarded to be closer to the physical reality experienced by teachers and students in a learning context. A first implementation of the proposed extended immersive learning environment, in the area of solid mechanics, is also described, including the access to theoretical contents and a remote experiment to determine the elastic modulus of a given object.info:eu-repo/semantics/publishedVersio