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).

Electron Beam (EB) welding has been used to realize seams on 2 mm-thick plates of directionally solidified (DS) IN792 superalloy. The first part of this work evidenced the importance of pre-heating the workpiece to avoid the formation of long cracks in the seam. The comparison of different pre-heating temperatures (PHT) and pass speeds (v) allowed the identification of optimal process parameters, namely PHT = 300 °C and v = 2.5 m/min. The microstructural features of the melted zone (MZ); the heat affected zone (HAZ), and base material (BM) were investigated by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS), electron back-scattered diffraction (EBSD), X-ray diffraction (XRD), and micro-hardness tests. In the as-welded condition; the structure of directionally oriented grains was completely lost in MZ. The γ’ phase in MZ consisted of small (20–40 nm) round shaped particles and its total amount depended on both PHT and welding pass speed, whereas in HAZ, it was the same BM. Even if the amount of γ’ phase in MZ was lower than that of the as-received material, the nanometric size of the particles induced an increase in hardness. EDS examinations did not show relevant composition changes in the γ’ and γ phases. Post-welding heat treatments (PWHT) at 700 and 750 °C for two hours were performed on the best samples. After PWHTs, the amount of the ordered phase increased, and the effect was more pronounced at 750 °C, while the size of γ’ particles in MZ remained almost the same. The hardness profiles measured across the joints showed an upward shift, but peak-valley height was a little lower, indicating more homogeneous features in the different zones.

AISI 316L steel, subjected to a low temperature carburizing treatment (kolstering), has been examined by Mechanical Spectroscopy (MS) and nanoindentation to determine the Youngs modulus of the surface hardened layer (S phase). MS results showed that the average value of elastic modulus of S phase is 202 GPa, a little higher than that of the untreated material.Nanoindentation tests, carried out with loads of 5, 15 and 30 mN, evidence a modulus profile vs depth: E is ~ 400 GPa at a distance from the surface of ~ 110 nm, then decreases to reach the value of the steel substrate (190 GPa) at 33 μm.These results, together with X-ray Photoelectron Spectroscopy (XPS) and Auger Electron Spectroscopy (AES) measurements of carbon concentration profile, can be explained by considering the presence of a very thin surface layer, different from S phase and consisting of a mixed structure of Diamond-like carbon (DLC) and tetrahedral carbon (taC).Furthermore, the same experiments have been carried out also after heat treatments at 450 °C to correlate the modulus change to the decomposition of the metastable S phase leading to the formation of (Cr,Mo)C and Cr₂₃C₆carbides in a Cr-depleted austenitic matrix.

The knowledge of the ways in which post-synthesis treatments may influence the properties of carbon quantum dots (CDs) is of paramount importance for their employment in biosensors. It enables the definition of the mechanism of sensing, which is essential for the application of the suited design strategy of the device. In the present work, we studied the ways in which post-synthesis thermal treatments influence the optical and electrochemical properties of Nitrogen-doped CDs (N-CDs). Blue-emitting, N-CDs for application in biosensors were synthesized through the hydrothermal route, starting from citric acid and urea as bio-synthesizable and low-cost precursors. The CDs samples were thermally post-treated and then characterized through a combination of spectroscopic, structural, and electrochemical techniques. We observed that the post-synthesis thermal treatments show an oxidative effect on CDs graphitic N-atoms. They cause their partially oxidation with the formation of mixed valence state systems, [CDs]⁰⁺, which could be further oxidized into the graphitic N-oxide forms. We also observed that thermal treatments cause the decomposition of the CDs external ammonium ions into ammonia and protons, which protonate their pyridinic N-atoms. Photoluminescence (PL) emission is quenched.