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Microwave hydrothermal processing of Undaria pinnatifida for bioactive peptides
No full textInternational audienceMicrowave hydrothermal processing was employed to obtain valuable gelling or bioactive fractions from U. pinnatifida, assessing the processing conditions following a biorefinery concept. It was identified a relevant impact on the antioxidant properties, sulfate, protein and oligosaccharides content, with the highest values above 200°C, although the maximum in fucose was obtained at 160°C. The lowest temperature involved the highest minerals and sulfate content of the solid phases. Rheology indicated that hydrothermal treatment at 160 °C is adequate to extract alginates with structural and viscoelastic properties similar to those commercially available. The incorporation of the hydrothermal residual solids in the proposed alginate matrices favored the development of systems with potential non-food applications applications. Selected extracts, after an intensification stage using ultrasound, featured interesting biological activities for two human cancer cell lines (A2780; HeLa 229) with percentage of cellular inhibition > 83 and 57%, without positive effects on A549 and HCT-116
Development of a multi-scale and coupled cutting model for the drilling of Ti-6Al-4V
No full textInternational audienceThe present paper investigates the thermo-mechanical loading involved in hole drilling of Ti-6Al-4V. Indeed, the heat and strains developed in a very restricted area at the tool vicinity are responsible for various undesired side effects among which: tool damage, residual stresses, poor surface roughness, and metallurgical alterations. The confined nature of the drilling process prevents from any experimental access to some governing physical data such as local strain fields and local energies. Therefore a mixed numerical-experimental approach is herein proposed in order to provide local in-sight to essential tool-related thermal and mechanical sources. It relies on strain and temperature measurements at various locations of the cutting edge that are used to validate a multi-scale numerical model. This latter is then used to assess the energy budget involved in the material removal. The presented results prove the ability of such technique in obtaining valuable information on the in-process generated heat and the way it spreads within the workpiece and beyond. Results also show the spatial heterogeneity of the cutting phenomenon along the cutting edge and highlight the complexity of defining optimal cutting parameters and optimal tool design
Post-Weld Heat Treatment of Additively Manufactured Inconel 718 Welded to Forged Ni-Based Superalloy AD730 by Linear Friction Welding
No full textInternational audienceA new post-weld heat treatment (PWHT) cycle was designed for novel dissimilar linear friction welding (LFW) of selective laser melted (SLM) Inconel 718 (IN718) to AD730 forged nickel-based superalloy. The microstructure and hardness of the joints after the PWHT are investigated and compared with those of as-linear friction welded samples. The precipitation of γ′ + γ″ is determined as the main mechanism to increase the mechanical properties of SLM IN718 alloy. These particles coarsened during heat treatment at 1253 K and double aging. The results show that the thermomechanical history of linear friction welded joints can affect the microstructure of IN718 alloy such as the morphology of δ phase after solution treatment (ST) from the platelike in the weld zone (WZ) to the needlelike in the base material (BM). It was found that in AD730, nanometric size γ′ particles reprecipitated close to the weld line during rapid cooling after welding. The presence of ultrafine γ′ particles and coarsening of the remaining particles in the microstructure of the alloy, during PWHT, can enhance the strength and hardness. The developed PWHT resulted in uniform hardness across the new dissimilar joint
Facile One‐Step Synthesis of Calcium Phosphate/Cellulose Composite: Synthesis, Morphology, Structure and Properties
No full textInternational audienceThis study focusses on reporting a facile one-step synthesis method to fabricate calcium phosphate-microcrystalline cellulose composite with an enhanced surface area. The composite preparation is done using a simple one-step method called co-precipitation method under ambient and 60 °C temperature. The calcium carbonate and orthophosphoric acid are taken, which are the two best known widely available starting materials for the synthesis of calcium phosphate. The sample is collected and taken for the drying process in an oven at 105 °C. The characterizations like XRD, SEM, BET, FTIR, TGA, and DSC of the demonstrated composites are done. From BET analysis, it can be concluded that the surface area of the demonstrated composite enhances substantially after the incorporation of the microcrystalline cellulose
Actionability in a Situation Awareness world: Implications for social media processing system design
No full textInternational audienceThe field of crisis informatics now has a decade-long history of designing tools that leverage social media to support decision-makers situation awareness. Despite this history, there remains few examples of these tools adopted by practitioners. Recent fieldwork with public safety answering points and first responders has led to an awareness of the need for tools that gather actionable information, rather than situational awareness alone. This paper contributes to an ongoing discussion about these concepts by proposing a model that embeds the concept of actionable information into Endsley's model of situation awareness. We also extend the insights of this model to the design implications of future information processing systems
Enabling pseudo-ductility in geopolymer based glass-ceramics matrix composites by slurry dilution
No full textInternational audienceCarbon fibre reinforced composites with matrix consisting of porous glass-ceramics obtained by high temperature heat-treatment of geopolymer based material are studied. The matrix is obtained from a slurry. Several composites have been manufactured by in-laboratory stratification of pre-impregnated plies with slurries diluted at various rates. Slurry dilution changes the porosity and leads to pseudo-ductile behaviour of the composite. Dilution implies a drop of non-linearity stress threshold together with a slower decrease of the strength. An optimal dilution rate is evidenced, which exhibits high strength but lower non-linearity stress threshold, and then, a significant failure strain. The optimized prepreg material is compared with a reference composite processed by an industrial prepreg process. The origin of the pseudo-ductility is related to decohesion at the interface between tows and inter-tow matrix. RTM also provides a pseudo-ductile composite but with very low non-linearity stress threshold, in relation to poorly impregnated tows
Influence of abrasive water jet parameters on the surface integrity of Inconel 718
No full textInternational audienceInconel 718 (IN718) is a precipitation hardened nickel-base super-alloy exhibiting high strength and good corrosion resistance at elevated temperatures and on the downside; it is characterized by poor machinability. Abrasive water jet (AWJ) process offers a potential method to machining difficult-to-cut materials such as IN718. The present work investigates the influence of AWJ parameters on surface roughness, topography, depth of cut, and residual stress when milling IN718. Surface characterization was conducted through 3D optical microscopy and SEM techniques. Residual stresses were measured in longitudinal and transverse directions with respect to the machining path using X-ray diffraction (XRD) technique. The obtained results showed that milled surfaces have a homogeneous texture with embedded abrasive particles and high surface roughness. AWJ process introduced high compressive residual stresses with similar order of level in both directions (X and Y). In addition, it was observed that jet pressure is the most influencing parameter on roughness and depth of cut, whilst traverse speed and step-over distance had a significant effect on the residual stress. Based on the experimental analysis, an empirical model to predict the depth of cut was proposed. The validation of the proposed model has shown around 5% error in the predicted and actual pocket depth
Screening for Al2O3 failure in MCrAlY APS coatings using short-term oxidation at high temperature
No full textInternational audienceThe high temperature oxidation behavior of an APS processed γ–β NiCoCrAlY coating was investigated at 1150 °C. Ultrathin freestanding coating specimens ranging from 16 to 240 μm in thickness were tested for short-term oxidation time (< 300 h). Intrinsic chemical failure (InCF) occurred after the full consumption of Al, and resulted in Cr2O3 growth and CrN precipitation at the Al2O3/alloy interface. Mass gain slowed down after InCF, even leading to a mass loss associated with the volatilization of Cr2O3. InCF occurred after [10–20] h and [20–100] h for the ∼ 21 μm and ∼ 31 μm-thick specimens, respectively. Severe metal recession was observed after InCF
Elucidation of the Diels–Alder Reaction Kinetics between Diphenylfulvene and Maleimide by Mechanochemistry and in Solution
No full textInternational audienceThe Diels–Alder reaction kinetics between diphenylfulvene and maleimide using mechanochemistry and in liquid state is described. This reaction was carried out in solid state using a modified vibratory ball-mill with temperature control and in solution with toluene as solvent. The effect of temperature, ball mass, material, additives, and aging reaction were studied. We reported for the first time the kinetics of a mechanochemical reaction depending on the ratio ball mass/mass of the reagent. A new kinetic model has been established that corresponds well to our experimental data and allows an estimation of the global activation energy. In solution, the retro Diels–Alder reaction was observed. The reaction was second order for the formation of endo and exo and first order for the retro Diels–Alder reaction. The grinding method shows many advantages compared to solution: shorter reaction time, total reaction, and better selectivity
Biomass fast pyrolysis: Chemistry and thermodynamics
No full textInternational audienceThe project, PYROKINE, aims at developing new modeling approaches adapted to one of the most promising thermochemical processes, fast pyrolysis, applied to the conversion of contaminated lignocellulosic biomass. The fast pyrolysis converts solid biomass into volatiles and a limited amount of char. The volatiles are then rapidly quenched resulting in a high yield of bio-oil, 70-75wt% of the starting material on a dry basis. The liquified biomass can be further upgraded catalytically or blended to produce new advanced biofuels. In addition to the yield, the product distribution determines their quality, and this is critically dependent on biomass type and its temperature-time history. In the present study, we propose to establish a dynamic model adaptable to the conversion of different biomass types under various pyrolysis regimes according to two research programs