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Chemical Vapour Infiltration (CVI) technique has been long used to produce carbon/carbon composites. The Pyrolytic Carbon (Py-C) matrix infiltrated by CVI could have different microstructures, i.e. Rough Laminar (RL), Smooth Laminar (SL) or Isotropic (ISO). These matrix microstructures, characterized by different properties, influence the mechanical behaviour of the obtained composites. Tailoring the process parameters, it is possible to direct the infiltration towards a specific Py-C type. However, the factors, influencing the production of a specific matrix microstructure, are numerous and interconnected, e.g. temperature, pressure, flow rates etc. Due to the complexity of the physical and chemical phenomena involved in CVI process, up to now it has not been possible to obtain a general correlation between CVI process parameters and Py–C microstructure. This study is aimed at investigating the relationship between infiltration temperature and the microstructure of obtained Py-C, for a pilot - sized CVI/CVD reactor. Fixing the other process parameters and varying only the temperature, from 1100°C to 1300°C, the Py-C infiltration was performed on fibrous preforms. Polarized light microscopy, with quantitative measurements of average extinction angle (Ae), and Raman spectroscopy were used to characterize the obtained Py-C microstructures.

One of the options currently taken into account for the realization of the first DEMO reactor is the “water-cooled lanket”. This option implies an irradiation temperature for the blanket material in the range of 280–350 °C. Therefore, in light of the under irradiation behaviour of EUROFER, namely of the DBTT shift toward high temperature due to the low irradiation temperature embrittlement, the target of the hereby reported activities is the development of much tougher alloys, to try to tolerate the embrittlement due to the low irradiation temperature. We report in this paper the work done to optimize the toughness of Eurofer 97, increasing the normalizing temperature and maintaining a small grain size using multiple normalizing treatments. We report also the mechanical behaviour of two 9Cr1WTa type alloys, produced and tested with the same aim to find alloys more resistant to embrittlement at low irradiation temperature. Keywords: EUROFER 97, RAFM steels, Microstructure, Heat treatment, Tensile, Charpy, KLST

Silicon (Si) nanowires (NWs) grown on stainless-steel substrates by Cu-catalysed Chemical Vapour Deposition (CVD) have been prepared to be used as anodes in lithium-ion batteries. The use of NWs can overcome the problems related to the Si volume changes occurring during lithium alloying by reducing stress relaxation and preventing material fragmentation. Moreover, since the SiNWs are grown directly on the substrate, which also acts as a current collector, an excellent electrical contact is generated between the two materials without the necessity to use additional binders or conducting additives. The electrochemical performance of the SiNWs was tested in cells using lithium metal as the anode. A large irreversible capacity was observed during the first cycle and, to a lesser extent, during the second cycle. All the subsequent cycles showed good reversibility even if the coulombic efficiency did not exceed 95%, suggesting the formation of an unstable SEI film and a continuous decomposition of the electrolyte on the silicon surface. The absence of a stable SEI film was assumed responsible for a linear capacity fade observed upon cycling. On the other hand, the electrochemical characterization performed at different values of the charging current showed that SiNWs possess an exceptionally high rate capability.

Carbon nanostructures are achieved by bio-waste Allium cepa, L., (onion vulgaris) peels through pyrolysis at 900 &deg, C. They contain dispersed elements derived by their bio-precursors, like Mg, Ca, S, Na, K, and Cu. Here, we report the self-assembly of new Cu flower-shaped nanostructures organized as nano-roses. Remarkably, the nano-roses show rolled-up petals of Cu0 with a high chemical stability in air, exhibiting an intrinsic pure Cu crystalline phase. This suggests the exceptional potentiality to synthesize Cu0 nanostructures with novel physical/chemical properties. The size, morphology, and chemical composition were obtained by a combination of high-resolution scanning electron microscopy, energy dispersive X-ray spectroscopy, energy dispersive X-ray diffraction, and Raman spectroscopy.

One of the options currently taken into account for the realization of the first DEMO reactor is the “water-cooled blanket”. This option implies a minimum irradiation temperature for the blanket material in the range of 280–350 °C. In addition to the DBTT (Ductile to Brittle Transition Temperature) shift due to the DPA (displacement per atom) damage under irradiation, also the issue of the increased embrittlement due to He production must be taken into account. This issue appears even more detrimental and less manageable because the DBBT shift due to the Helium production does not saturate with the dose, as it results from previous works reported in literature. The experimental results and the difference in behaviour between ODS (Oxide Dispersion Strengthened Steels) RAFM (Reduced Activation Ferritic Martensitic) and other FM (Ferritic Martensitic) alloys (EM10, P91) showed that it is possible to improve the resistance to He embrittlement by both intra-granular precipitation of Y-Ti oxides and by decreasing the grain size at the same time. Nevertheless, anyway, the multiplication of the grain boundaries increases the dilution of He on grain surface, delaying the formation of He bubbles on grain boundaries and, therefore, the susceptibility to the He embrittlement. Several grain size reduction strategies have then been investigated on EUROFER both at the austenitization stage, on the PAGS (Prior Austenite Grain Size), and at the tempering stage, on the tempered martensite. The microstructural observations have been carried out by means of SEM (Scanning Electron Microscopy). Also the effect of grain size reduction on the toughness of the material will be taken into account; The DBTTs resulting from impact tests on KLST specimens will be shown. The outcomes of the microstructural observations, as well as the preliminary mechanical characterization (impact tests) will be discussed in this paper. Keywords: EUROFER 97, RAFM steels, Microstructure, Multiple normalization, Asymmetric rolling, Recrystallization, KLST

Ten Eurofer97 steel variants, produced by non-standard fabrication-processing routes and modified alloying chemistries, were studied by neutron irradiations in the high flux isotope reactor. The irradiations were performed to ITER-TBM relevant conditions of ∼255–350 °C, 2.94–3.24 dpa. We quantified the irradiation-induced degradation of the steels using mechanical property tests. All the steels suffered from irradiation hardening, where a significant increase in Vickers microhardness and yield stress (σYS) occurred, accompanied with severe loss of tensile elongation. The extent of hardening was material dependent. For Tirr = 300±30 °C, most steels showed σYS increase in the range of ∼30% to as high as ∼66%, except for a low temperature tempered steel with σYS increase below 15%. Despite large losses in elongation, most failures were ductile. Significant post-necking ductility was retained with reduction in area (RA) between 65–75%, but

Presently available data on neutron irradiation damage raise doubts on the feasibility of using EUROFER97 steel for a water-cooled starter blanket in a DEMO reactor, since the ductile-to-brittle transition temperature (DBTT) increases significantly for irradiation temperatures below 350°C. The additional DBTT shift caused by H and He transmutation can only be estimated based on very few results with isotopically tailored EUROFER97 steel. Conservative calculations show that the DBTT of EUROFER97 steel could exceed the operating temperature in water-cooled starter blankets within a relatively short time period. This paper presents results from a EUROfusion funded irradiation campaign that was performed in the High Flux Isotope Reactor at Oak Ridge National Laboratory. The paper compares ten newly developed reduced activation ferritic-martensitic (RAFM) steels irradiated to a nominal dose of 2.5 dpa at 300°C. The post-irradiation experiments using Small Specimen Test Technology included hardness, tensile, and fracture mechanics tests combined with fractography and microstructure analysis are presented. Results show that micro-alloying EUROFER97-type steels influenced the mechanical properties but a dominating impact on irradiation damage resistance could not be identified. In contrast, specific thermo-mechanical treatments lead to better DBTT behavior. Discussion about irradiation response to heat treatment conditions is also given. Despite requiring data also at high dpa values, the results indicate that with these modified materials an increased lifetime and potentially also an increased operating temperature window can be achieved compared to EUROFER97.

Among the options currently taken into account for the realization of the first DEMO reactor there are the “helium-cooled” and the “dual coolant” breeding blanket. Therefore the high temperature (650 °C) behavior of the proposed innovative martensitic alloys should be improved, namely the frame of the hereby reported activities is the development of martensitic alloys more resistant to creep, suitable to tolerate such a high operating temperature. In order to improve the high temperature mechanical properties, concerning the alloy design strategies, two alternative routes are proposed; the effect of Nitrogen and Tungsten increase are taken into account as well as the addition of carbo-nitride forming elements, like Vanadium, combined with the “ausforming” thermo-mechanical treatments. Two alloys have been designed and a special thermo-mechanical treatment on Eurofer 97-2 is proposed. The “ausforming” treatment, consisting in a sort of hot-working at a lower temperature with respect to the austenitization one after the austenitization stage, is aimed at the achievement of a beneficial dislocation “pinning” at high temperature due to carbide precipitation. Generally the improvement of tensile properties is associated to the hardening of the steel due to dislocation network and precipitation effects. This hardening is accompanied by a DBTT increase to markedly higher values with respect to Standard Eurofer. The proposed materials should be, in any case, at least room temperature ductile in order to undergo safe manufacturing and assembling processes. Therefore the issue of the DBTT increase has been taken into account by tuning the tempering temperature adequately. The two variations from chemical composition of Eurofer 97 have been casted and the thermo-mechanical treatments have been selected by means of SEM and hardness measurements to tune grain size and precipitation of carbides. The outcomes of the preliminary mechanical characterization (tensile, creep and impact tests) will be discussed in this paper. Keywords: EUROFER 97, RAFM steels, Thermo-mechanical treatment, Ausforming, Tensile, Creep, Charpy

We show that using the same reaction procedure, by hindering or allowing the formation of a reaction intermediate, the Ag+dodecanethiolate polymeric complex, it is possible to selectively obtain Ag dodecanethiolate nanoparticles or Ag dodecanethiolate nanoclusters in the size range 4-2 nm. Moreover, the Ag dodecanethiolate nanoclusters display a lamellar superstructure templated from the precursor Ag+dodecanethiolate polymeric complex. A plausible formation mechanism is illustrated where, starting from the precursor and scaffold lamellar Ag+ thiolate polymeric complex, first the nanocluster Agn 0 core is formed by reduction of isoplanar Ag+ ions, followed by Ag+ thiolate units that build protection, the nanocluster shell, around the core. The nanoclusters are characterized by elemental analyses, XRD, ATR-FTIR, XPS, XAS, MALDI, ESI, UV-Vis and fluorescence measurements. The luminescent Ag15(dodecanethiolate)11·2H2O nanocluster is achieved in good yield after 4 hours of reaction whereas after 2 hours, the luminescent Ag35(dodecanethiolate)16 is isolated. Both Ag nanoclusters present emission bands in the range 330-450 nm, the shifting depending on the excitation wavelength. This phenomenon is attributed to a possible dipolar state causing distribution in energies due to variability of dipole-dipole interactions. Moreover, both nanoclusters further present a NIR emission at about 700 nm independent from the excitation wavelength. Thanks to their optical and structural properties, the synthesized nanoclusters, perfect molecular/nanoparticle hybrids, have great potentiality for new applications in nanotechnologies. © 2018 The Royal Society of Chemistry.

Eurofer97 steel has been recognised in Europe as the reference steel for nuclear application under high radiation density. Following to this a detailed knowledge of microstructure evolution is required for such steel after thermo-mechanical processing. In this paper the effect of thermo-mechanical parameters on the mechanical behavior of Eurofer97 was investigated by hot rolling and heat treatment on pilot scale. Results show a strong effect was found of reheating temperature before rolling on the material hardness, due to an increase of hardenability following the austenite grain growth. A minor effect was found of the hot reduction and the tempering temperature in the total investigated deformation range. A loss of impact energy was found coupled with the hardness increase. © 2018 Andrea Di Schino et al., published by De Gruyter.

Ultrathin stable transparent conductive nickel films were deposited on quartz substrates by radio frequency sputtering at room temperature. Such films showed visible transmittance up to 80% and conductivity up to 1.8 × 104 S/cm, further increased to 2,3 × 105 S/cm by incorporation of a micrometric silver grid. Atomic force microscopy and scanning electron microscopy revealed quite compact, smooth and low surface roughness films. Excellent film stability, ease, fast and low cost process fabrication make these films highly competitive compared to indium tin oxide alternative transparent conductors. Films were characterized regarding their morphological, optical and electrical properties. © 2015 Elsevier B.V.

MCrAlY coatings are usually adopted to improve the environmental resistance of Ni-based superalloy components of turbine engines against high-temperature oxidation and hot corrosion. In this work, CoNiCrAlYRe coatings were produced by atmospheric plasma spraying. The coatings exhibited relatively low oxygen content and porosity. X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy analyses revealed that the high-temperature exposure at 1383ﾠK (1110ﾠﾰC) promoted the growth of an oxide scale on the top surface being composed of a continuous and dense Al2O3 inner layer followed by an outer mixed layer (Cr2O3 and spinels). The oxide scale was mainly composed of Al2O3, while the formation of mixed oxides occurred at lesser extent. After high-temperature exposure, the formation of internal oxides in some areas reduced the inter-lamellar cohesion, so that a decrease in microhardness was found.

Nanocomposites formed by hard and soft magnetic phases are very promising for magnetic energy storage and biomedical applications. Highly challenging is the development of simple synthesis methods able to tune the phase composition and a thorough structural, morphologic and magnetic characterization in order to understand and optimize the interactions between hard and soft magnetic phases. Mainly depending on Fe:Pt atomic ratio, multi-phase or single phase FePt nanocomposites have been prepared by thermal treatment of core–shell FePt(Ag)@Fe 3 O 4 nanoparticles at 750 °C for 1 h under flow of a Ar + 5% H 2 gas mixture (H 2 is necessary to reduce Fe 2+ and Fe 3+ ions of Fe 3 O 4 to Fe 0 atoms and the thermal treatment to form the crystalline soft and hard magnetic FePt phases). Performing Rietveld refinement of the XRD data as well as HR-TEM and electron diffraction analyses, the different phases have been singled out. Besides single phase hard L1 0 FePt and soft magnetic L1 2 Fe 3 Pt nanoparticles, two phase soft α-FePt and γ-FePt and hard and soft magnetic L1 0 FePt and L1 2 FePt 3 nanocomposites have been formed and the structure and morphology correlated to their magnetic behavior. Moreover, for possible applications, it is important to form stable nanoparticle layers; as-prepared FePt(Ag)@Fe3O 4 nanoparticles have been chemically attached on a Si substrate, thermally annealed and the morphology, structure and magnetic properties of the layered nanoparticle sample investigated.

Highly conductive and transparent NiOx films can be very useful as buffer layers for the optimization of the p-type contacts of optoelectronic devices. Thin NiOx films were fabricated by reactive radio frequency (RF) sputtering at room temperature starting from a Ni target. A systematic study of the influence of oxygen partial pressure, RF power and sputtering gas pressure on the films' properties was carried out. The structural, microstructural, optical and electrical properties were affected differently by the sputtering parameters. Resistivity decreased by increasing the oxygen partial pressure and the sputtering total pressure and by decreasing the RF power, while transmittance increased by decreasing the oxygen partial pressure and by increasing the RF power and sputtering pressure. Minimum resistivity of 1.6 × 10-2 Ωcm and a visible transmittance of 40% were achieved for a film grown in a pure oxygen atmosphere, while a higher transmittance of 54% and a resistivity of ρ = 1.1×10-1 Ωcm were obtained for a film grown at 30% oxygen partial pressure. The trends of transmittance and resistivity as a function of the oxygen pressure during the sputtering process can be explained in terms of the amount of Ni3+ defects deduced by x-ray photoelectron spectroscopy (XPS) measurements. The full interpretation of the other results is less straightforward and highlights the relevance of the samples' structural properties. © 2016 IOP Publishing Ltd.

Atmospheric plasma spraying of WC-Co particles with standard gas mixtures (Ar-H2) typically results in largely decarburized coatings with relatively low wear resistance. To fabricate cermet coatings with enhanced tribological properties, nanostructured WC-Co coatings were plasma sprayed using two different process gas mixtures. Phase composition and microstructure were investigated by X-ray diffraction and scanning electron microscopy, respectively. Microhardness increased by increasing the amount of retained WC grains in coating microstructure. Friction and wear properties, measured under dry sliding conditions, strongly depended on the degree of decarburization. They were comparable to those of conventional coatings produced using identical conditions. © 2012 The American Ceramic Society.

In this work, the effectiveness of nanocomposite surface treatments as protective systems for artistic stones was evaluated. Pyrolitic silica and titania nanoparticles were dispersed in a commercial silicon-based polymer and applied on marble and travertine samples. Artificial aging processes, both in climatic chamber and in solar box, were carried out to simulate real degradation processes in terms of photo-thermal effects and physical-chemical damage. The performances of the nanocomposites used as consolidant were evaluated comparatively by means of diverse diagnostic techniques, namely: scanning electron microscopy (SEM), laser induced fluorescence (LIF), ultrasonic technique, colorimetry, total immersion water absorption and contact angle. The results show that some properties of conservation materials can be improved by the presences of nanoparticles because they induce substantial changes of surface morphology of the coating layer and counter the physical damage observed during artificial weathering. © 2014 AIP Publishing LLC.

Properties of consolidant and protective materials modified with nanoparticles were analysed in this study following their application onto marble samples. For this purpose, different solutions of an acrylic resin with dispersed SiO2 and TiO2 nanoparticles were prepared. The relative durability of Paraloid B72, an acrylic resin used as consolidant and modified by nanoparticles, was evaluated comparatively by means of diverse diagnostic techniques, namely, scanning electron microscopy, laser-induced fluorescence, ultrasonic sound, colorimetry, total immersion water absorption and contact angle. The results demonstrate that nanoparticles enhance the effectiveness of consolidant and protective material because they induce substantial changes of surface morphology of the coating layer.

The contribution of ENEA together with Rina-CSM to the Eurofusion programme “WPMAT-Advanced Seels” deals with the development of innovative RAFM steels able to withstand the critical temperatures typical of the different operational environments foreseen for the blanket of the first DEMO reactor. The optimization of the chemical composition and the Thermo Mechanical Treatment for these materials should be done according to the blanket operating temperatures that are related to two possible working conditions: the WCLL-BB (Water Cooled Lead Lithium Breeding Blanket) or the H(D)CLL-BB (Helium (Dual) Cooled Lead Lithium Breeding Blanket). On the one hand the “water-cooling” option implies a minimum irradiation temperature for the blanket material in the range of 280–350 °C. On the other hand, the “helium-cooled” and the “dual-coolant” solutions imply an operating temperature for the blanket material in the range of 650 °C. Therefore in the first case the target is the improvement of the toughness of the martensitic alloys; whilst concerning the second scenario the target is the development of more creep resistant martensitic steels, suitable to tolerate such a high operating temperature. In both the cases the Tungsten content plays a key role, both in terms of solid solution hardening and influence on the DBTT. Two alloys aimed at fulfilling the specifications for the two DEMO operating conditions, both with increased Tungsten content respect to Eurofer, have been produced and characterized. The mechanical properties of these two alloys are hereby reported and discussed.

Small-angle neutron scattering (SANS) and neutron diffraction have been utilized for micro-structural characterization of Eurofer97/2 heats submitted to thermo-mechanical treatments, with the aim to investigate macroscopic material volumes and to complete the local information provided by scanning electron microscopy. The measurements were carried out at MLZ in Garching, utilizing for SANS also a polarized neutron beam. The investigated samples had been submitted to austenitization and tempering at different temperatures, as well as to double austenitization and to “ausforming”, that is austenitization followed by hot rolling. For most of the examined treatments, nearly identical SANS cross-sections were measured, close to the one of Eurofer97/1. In the ausformed sample the nuclear SANS cross-section is also nearly identical to the other samples but the magnetic one is one order of magnitude higher. Furthermore, over a wide experimental interval its nuclear-magnetic interference, measured by polarized SANS, is of opposite sign with respect to the non-ausformed samples. Neutron diffraction measurements provided strong evidence that the origin of such effects is due to the presence of the non-magnetic austenite phase in the ausformed sample, with an estimated volume fraction of 0.17 ± 0.02; within the experimental resolution, it disappears after subsequent tempering.