Espedito Vassallo

The effect of permeation direction on gas permeability has never been systematically investigated for barrier-coated biodegradable packaging films. In this work, oxygen and carbon dioxide transport through SiOx-coated PBS, PLA and PLA/PBAT films was characterized using a high-vacuum gas permeation apparatus. Permeability was measured and diffusivity was derived from time-lag data using separate but equivalent specimens cut from the same coated film sheet and mounted in opposite orientations under otherwise identical experimental conditions. The corresponding apparent solubility coefficients were calculated by means solution-diffusion model.,A reproducible directional asymmetry was observed for all investigated materials and for both gases. The effect primarily involved permeability and apparent solubility, whereas diffusivity remained nearly unaffected by membrane orientation, suggesting the possible involvement of interfacial or adsorption-related phenomena.,These results provide the first systematic experimental evidence that gas permeability in SiOx-coated biodegradable packaging films depends on the direction of permeation. Beyond their fundamental significance, the findings indicate that specimen orientation may represent a relevant experimental variable in the characterization of asymmetric barrier-coated packaging materials.

Boron coatings were deposited by RF magnetron sputtering in an Ar atmosphere at a constant power of 80 W, varying the working pressure in the 0.6–5 Pa range. Plasma diagnostics were performed by means of a Langmuir probe to determine the electron temperature and electron density under different operating conditions. Within the investigated pressure range, the deposition rate remained nearly constant, whereas a significant decrease in coating mass density was observed with increasing pressure. The coatings display a columnar structure at all investigated pressures, with no significant differences in bulk morphology. Pressure primarily affects the surface features, leading to an increase in the density, lateral dimensions, and height of surface agglomerates with increasing pressure. Compositional analysis by EDX revealed a substantial oxygen incorporation in the films, with the lowest oxygen content (~11 at.%) measured for the coating deposited at 0.6 Pa. XPS depth profiling confirmed the presence of oxygen and evidenced the formation of boron oxide species, while the boron concentration exceeded 80 at.% in all samples. These results highlight the strong sensitivity of boron film density and oxygen uptake to sputtering pressure.

The study introduces ice sliding on coatings with roughness in the nanometer range. The hydrophilicity of the coatings allows the formation of a quasi-liquid water layer with a thickness higher than roughness, which allows ice sliding.

This work investigates the role of surface topography in the sputtering process of tungsten (W) exposed to helium plasma using the GyM linear device. Surfaces with varying roughness, from sub-nanometer to approximately 1 µm, and different textures, including random-like and regular configurations, were studied. The samples were exposed to helium plasma of GyM at energies ranging from 30 to 350 eV, with a fluence of ≈ 4.3 × 10 24 He⁺m⁻² and temperatures well below the bulk W fuzz formation threshold of ≈700 ^∘C. The interpretation of the experimental results was supported by simulations with the 3D Monte Carlo ERO2.0 code. Analysis with atomic force and scanning electron microscopy revealed that surface topography remained largely unchanged, while a nanoscale undulating surface structure formed on all samples at the highest incident energies. The effective sputtering yield ( Y eff ) of tungsten, derived from mass and thickness loss data, was consistently lower than predictions from simulations by up to an order of magnitude, likely due to the dynamic retention of helium on the tungsten surface. On the other hand, both experimental results and modelling agree that surface topography’s influence on sputtering can be entirely captured by the average surface inclination angle ( δ m ), which unequivocally characterises each specimen, unlike the average roughness ( R a ). Moreover, Y eff values from both mass loss data and ERO2.0 simulations as a function of δ m align well with a decreasing sigmoid fit function. A reduction of more than 50% was observed when comparing the flat surface to that with the highest R a , attributed by ERO2.0 to the increasing fraction of sputtered tungsten atoms being deposited on neighbouring surfaces. These findings underscore the importance of accurately calibrating simulation tools against linear plasma device experiments for predicting the lifetime of plasma-facing components in fusion reactors such as ITER and DEMO, emphasising the potential of structured tungsten surfaces to reduce erosion and impurity concentration in the plasma core.

This paper investigates how negative substrate bias voltage and sputtering pressure influence tungsten coatings deposited via radiofrequency magnetron sputtering. Increasing the absolute value of negative bias voltage (up to −150 V) of the substrate results in higher mass density, higher surface roughness, better crystallinity, improved adhesion, and lower electrical resistivity. Raising the sputtering pressure (from 1 to 5 Pa) causes a reduction in bulk density, a decrease in crystallinity, increased electrical resistivity, lower conductivity, and weaker adhesion. These findings highlight the importance of carefully optimizing negative substrate bias voltage and sputtering pressure to tailor the microstructural, mechanical, and electrical properties of tungsten coatings to specific applications.

A capacitively coupled radio-frequency argon plasma, used for tungsten sputtering deposition, is characterized using Langmuir probe measurements. Druyvesteyn’s method is used to evaluate plasma parameters through the integral of the Electron Energy Distribution Function (EEDF). In the pressure range analyzed (0.6–10 Pa), the obtained distributions are not Maxwellian, which suggests some depletion of electrons with higher energies. The obtained plasma parameters are compared with those derived from the graphical method. The electron temperature obtained via the graphical method is always lower than the effective temperatures derived from EEDFs, and vice versa, the electron density is overestimated by the graphical method. Optical Emission Spectroscopy is used to monitor the atoms sputtered in the plasma process. The behavior of excited species correlates with the plasma parameters.

Biodegradable polymers (poly(butylene succinate (PBS)), poly(butylene adipate terephthalate (PBAT)) and poly(lactic acid)/poly(butylene adipate terephthalate (PLA/PBAT)) blend) were treated in radiofrequency (13.56 MHz) low-pressure (10 Pa) oxygen with argon post-crosslinking plasma to enhance wettability and adhesion properties. Surface morphology and roughness modification caused by plasma exposure were observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Surface chemical modifications of plasma-treated samples were evaluated by Fourier Transform infrared spectroscopy (FTIR). Due to the limited durability of plasma activation, the hydrophobic recovery was evaluated by water contact angle (WCA) measurements. The ageing effect was measured over 15 days in order to assess this kind of treatment as a potential industrial scalable method to increase biodegradable polymers hydrophilic properties for food packaging applications. The effects of polymer activation on its weight loss were also determined. Differential scanning calorimetry (DSC) analysis was used to study the effect of plasma treatment on the thermal properties of the polymers, while the crystallinity was investigated by X-ray diffraction (XRD).

The Divertor Tokamak Test (DTT) facility, whose construction has started in Frascati (Italy), will be equipped with an ECRH (electron cyclotron resonance heating) system including 32 gyrotrons as microwave power sources. The procurement of the first batch of sources with 16 MW total power, based on 170 GHz/≥ 1 MW/100 s vacuum tubes, is in progress and will be available for the first DTT plasma. The system is organized into four clusters of 8 gyrotrons each. The power is transmitted from the Gyrotron Hall to the Torus Hall Building (THB) by a quasioptical transmission line (TL), mainly composed of large mirrors shared by eight beams coming from eight different gyrotrons and designed for up to 1.5 MW power per single beam, similar to the TL installed at the stellarator W7-X. One of novelties introduced in the DTT system is that the mirrors of the TLs are embodied in a vacuum enclosure, using large metal seals, mainly to avoid air absorption and risk of arcs. The main reason is to reduce the risk of air breakdown, maintaining a pressure of 10−5 mbar far away from the Paschen minimum. The TL estimated volume is between ∼70 and ∼85 m3. The direct connection of the TL to the tokamak vacuum vessel has been evaluated, and different solutions have been proposed in order to prevent a possible impact on DTT operations. The microwave power is injected into the tokamak using independent single-beam front-steering launchers, real-time controlled and located in the equatorial and upper ports of four DTT sectors. In-vessel piezoelectric walking drives are the most promising candidates for the launcher mirror movement considering their compactness and capability to operate in an environment with strong magnetic field under ultra-high vacuum. The DTT ECRH system design, presented here, is based mainly on existing and assessed solutions, although the challenging adaptations to the DTT case are considered.

Tungsten coatings were deposited on silicon substrates by radio frequency (rf) magnetron sputtering from a metallic target in Ar atmosphere. The process parameters during the sputtering process were evaluated by a Langmuir probe, particularly, the electron density and electron temperature were measured by changing the rf power and gas pressure. The morphological and structural properties of the coatings were studied as a function of the pressure. Significant correlations were found between process parameters and characteristics properties of W coatings. The influence of deposition parameters on electrical properties was investigated. The electrical resistivity of the coatings was increased from 1.3 × 10−6 to 3 × 10−5 Ω m as the pressure increased as well.