Silica Meets Tannic Acid: Designing Green Nanoplatforms for Environment Preservation

Hybrid tannic acid-silica-based porous nanoparticles, TA-SiO2 NPs, have been synthesized under mild conditions in the presence of green and renewable tannic acid biopolymer, a glycoside polymer of gallic acid present in a large part of plants. Tannic acid (TA) was exploited as both a structuring directing agent and green chelating site for heavy metal ions recovery from aqueous solu-tions. Particles morphologies and porosity were easily tuned by varying the TA initial amount. The sample produced with the largest TA amount showed a specific surface area an order of magnitude larger than silica nanoparticles. The adsorption performance was investigated by using TA-5SiO2 NPs as adsorbents for copper (II) ions from an aqueous solution. The effects of the initial Cu2+ ions concentration and the pH values on the adsorption capability were also investigated. The resulting TA-SiO2 NPs exhibited a different adsorption behaviour towards Cu2+, which was demonstrated through different tests. The largest adsorption (i.e., ~50 wt% of the initial Cu2+ amount) was obtained with the more porous nanoplatforms bearing a higher final TA content. The TA-nanoplatforms, stable in pH value around neutral conditions, can be easily produced and their use would well comply with a green strategy to reduce wastewater pollution

On the aerodynamics of a vertical axis wind turbine wake: An experimental and numerical study

THE recent trend in wind energy industry, with the increasing deployment of offshore wind farms, has revived the interest in the concept of a vertical axis wind turbine. The scientific, technological and economical challenges of the next generation of wind turbines indicate that a transformative approach is the key for the reduction of the cost of energy. The adaptation of current designs and practice may not be the best solution to face rotor up-scaling, wind farmlosses, floating support structures and improved reliability.In this context, the vertical axis wind turbine has the potential to respond to someof the new environment’s challenges. The new interest has to face a lack of knowledge and proper models; the tendency to adapt both from the more developed horizontal axis wind turbine research field is often inaccurate.Wind Energ

Geothermal fluid circulation in a caldera setting: The Torre Alfina medium enthalpy system (Italy)

The Torre Alfina medium enthalpy geothermal field is located about 10 km north of the Bolsena caldera (Italy). The reservoir is a buried structural high consisting of fractured Meso-Cenozoic carbonate sequences and sealed by clayey flysch successions and Pliocene marine clays. We performed TOUGH2 numerical simulations, testing different model designs based on contrasting conceptual models. Results indicate that deep circulation is forced by the geometry of the reservoir and by the applied T and P gradients. We interpret the Torre Alfina field as a “blind” system, mostly recharged by lateral advection of heat and fluids from the Bolsena caldera deep high-enthalpy system, through the permeable caldera faults

Electromagnetic SQUID Based NDE: a Comparison Between Experimental Data and Numerical FEM Modeling

Over the existing electromagnetic sensors used in eddy-current Non-Destructive Evaluation (NDE), SQUID (Superconducting QUantum Interference Device) magnetometers are very attractive as multi-mode instruments capable of obtaining very high magnetic field sensitivity (detection of sub-pT signals) even in unshielded environments, high resolution imaging of low frequency eddy current distributions, large bandwidth (up to MHz) and high spatial resolution [1,2,3]. Moreover, a well optimized flux-locked-loop electronics allows SQUID systems to operate with large dynamic range and high linearity. These characteristics are extremely important in order to perform quantitative measurements of magnetic field distributions produced by induced currents in test samples. Of course, the need to operate the SQUID at cryogenic temperatures limits its use in many practical applications. The advent of High Temperature Superconductors (HTS) and the development of HTS SQUIDs has renewed the interest for NDE with these superconducting sensors [4].</p

New materials and related fabrication processes for hot structures on RLV'S

The next generation of Reusable Launch Vehicles (RLV's) will implement the substitution of traditional blunt bodies with new aerodynamic configurations characterized by slender profiles with sharp leading edges. The main advantage of this redesign of hypersonic space vehicle is represented by enhanced maneuverability and improved cross range capability and consequently increased mission safety, In addition the reduction of wave drag in the ascent phase will reduce the costs of the payload deployment. The real possibility to adopt sharp profiles is strictly related to the selection and availability of materials with suitable performance. In fact at hypersonic speeds, sharp edges of slender configurations reach values of the surface temperatures much higher than any temperature allowable by traditional thermal protection system (TPS) and more the geometrical radius of curvature decreases, more the heat flux at leading edge increases. Recent research and developments of a new class of materials named Ultra High Temperature Ceramics (UHTC) seems to offer the right chance to fabricate hot structures for RLV's applications which can withstand temperatures above 2000°C. This paper deals with a new process technology based on the employment of zirconium diborides ceramic matrix composites that appropriately modified and reinforced can be considered, as our previous numerical investigation showed, very promising candidate materials for the fabrication of hot structures of slender bodies such as nose cap, wing leading edges, etc. The materials developed in the frame of a consistent scientific collaboration coordinated by CIRA, and involving Centre Sviluppo Materiali SpA (CSM) and University of Rome "La Sapienza", have been thermally and mechanically characterized in order to assess their applicability to a specific space mission requirements. Copyright © 2003 by the International Astronautical Federation. All rights reserved

Numerical/Experimental Correlation of a Plasma Wind Tunnel Test on a UHTC-Made Nose Cap of a Reentry Vehicle

The nose cap demonstrator named Nose-2 has been tested for the second time in the plasma wind tunnel (PWT) facility which is part of the sharp hot structure (SHS) technology project, focused on the assessment of the applicability of ultrahigh temperature ceramics (UHTC) to the fabrication of high performance vehicles and SHS for reusable launch vehicles. In this paper the FEM based thermal analyses, carried out for the rebuilding of this PWT test, are presented. Experimental data measured in the PWT have been compared with numerical ones in order to validate the FEM model and to help in interpreting the experimental test itself. The knowledge on the physical phenomenon under investigation has been greatly improved, thanks to the synergy between numerical and experimental activities. In particular, a qualitative study of the modeling of the tip-dome interface has been performed in order to estimate the thermal contact resistance that heat flux encounters in passing through the demonstrator. The correlation between numerical and experimental temperature curves has been found to be satisfactory for both internal and surface temperature distribution, and the FEM model was found reliable in reproducing the thermal behavior of the nose cap

“Thermo-Structural Behaviour of an UHTC Made Nose Cap of a Re-entry Vehicle

In the frame of the technology project sharp hot structures (SHS), focused on the assessment of the applicability of ultra-high temperature ceramics (UHTCs) to the fabrication of high performance and SHS for reusable launch vehicles, the nose cap demonstrator named Nose_2 has been tested in the plasma wind tunnel (PWT) facility. In this paper, the FEM based thermo-structural analyses, carried out for the rebuilding of this PWT test are presented. Comparisons with experimental data measured in the PWT have been introduced to validate the FEM model and to help in interpreting the experimental test itself. Synergies between numerical and experimental activities have been finalized to the improvement of knowledge on the physical phenomenon under investigation. The effects on the thermal response due to the assumption of the catalytic condition of the wall, due to the uncertainties related to heat flux and pressure measurements on the probe (which influence the heat flux computation) and due to uncertainties in the determination of some UHTC thermal properties, have been investigated. The experimental temperatures curves falls very close to the numerical envelope (taking in account several sources of error) for all the test duration and the NCW model was found more reliable in reproducing thermal behaviour of the nose cap

Synthesis structure and stability of amino functionalized PEGylated silica nanoparticles

Amino functionalized PEGylated silica nanoparticles were prepared by one pot-procedure, based on ammonia catalysed hydrolysis and polycondensation of Tetraethoxysilane (TEOS) and 3-Aminopropyltriethoxysylane (APTS), in alcohol medium (ethanol) (Sather method), containing PEG 5000 monomethyl ether. Particles size was studied using Transmission Electron Spectroscopy (TEM). PEGylation and amino functionalization was investigated through FT-IR and Thermogravimetric analysis (TG). The structure of nanoparticles consists of nanosilica (a few nanometers in size) dispersed into a PEG matrix, produced by entanglement of PEG chains. The stability of the water colloidal suspension depends on the PEG/silica mass ratio, that changes with PEG concentration in the reaction batch. By properly selecting the PEG concentration, nanoparticles smaller than 150 nm were obtained, stable towards aggregation in water media up to 6 months. The observed need of an optimal PEG/silica mass ratio for long-term stability can be explained on the basis of particles structure and assuming that both steric and electrostatic effect concur to stabilisation. (C) 2010 Elsevier BM. All rights reserved