Institute for Energetics and Interphases

• Multiple DTG peaks correspond to hemicellulose, cellulose, young char, less reactive char, lignin and annealed char. • Torrefaction (hemicellulose removal) increases thermal annealing tendency. • Heat treatment in N 2 and CO 2 yields similar char reactivity; γ and δ peaks are sharper and earlier in CO 2 . • Particle size and morphology changes are similar in CO 2 and N 2 atmospheres. Pyrolysed biomass char particles may have different morphologies, as various types of biomass are prone to shrinking/swelling, spheroidisation and thermal annealing during pyrolysis in flow reactors. These features have important implications on burning mode, conversion rate and combustion efficiency. However, addressing these effects is difficult due to the inherent complexity of biomass structure. In fact, both thermal annealing and changes in particle morphology during heat treatment have often been neglected and underestimated. In this work, experiments were carried out to measure the effects of biomass lignocellulosic compositions on char reactivity and morphology. Torrefaction converts raw biomass into a solid fuel with reduced moisture and increased calorific value, mainly by degrading hemicellulose. Natural biomasses with different lignocellulosic compositions and pre-torrefied samples are compared. The experimental campaign included experiments in a drop tube reactor and a heated strip reactor, with fast heating rates of 10 3 °C/s, maximum temperatures up to 1800 °C, and residence times ranging from 0.2 s to 2 s. Combustion reactivity, particle shape and size are analysed to discuss the role of holocellulose/lignin in the propensity of biomass to undergo thermal annealing and plastic deformation. Hemicellulose appears to play a significant role, limiting the effects of heat treatment in terms of thermal annealing and the tendency to particle shrinkage and spheroidisation. This is attributed to its capacity to link with other structural parts of the biomass, such as lignin, making the biomass structure more rigid and to the formation of a plastic melt, which hinders free rearrangement of the biomass structural units.

In the global fight against climate change, the bio-based supply chain represents an interesting solution as it offers the potential to produce high-value-added products and bioenergy through the utilization of waste and by-products. In this work, a new route is proposed for the conversion of bio-based glycerol to H2/CO2 and high value-added liquid and solid products. The innovative process used pure or crude glycerol or ethanol-glycerol mixture along with water and sodium metaborate as reagents at 300 °C under discontinuous conditions. The gas stream consists mainly of hydrogen, followed by biogenic CO2 (31–54 %), CO (4–13 %) and CH4 in traces. The presence of water in the tested crude glycerol improved the hydrogen selectivity to 55 %. Characterization of the liquid reaction products revealed the synthesis of products such as 1,2-propanediol, propanoic acid, acetic acid, cyclopentenones and cyclic diglycerol. In the solid phase, an aliphatic hydrocarbon resin with oxygenated carbon along the saturated chain and an aromatic cluster were also characterized by NMR, FTIR and TG analyses. Based on these findings, the global reaction route to the general reaction products was proposed.

Several studies have shown that combining TiO2 and Cu2O enhances the photocatalytic activity of the material by generating a heterojunction capable of extending the light absorption in the visible and reducing the electron-hole recombination rate. Ball milling has been chosen as an alternative methodology for photocatalyst preparation, among the several techniques documented in the literature review. The results of a previously reported investigation enabled the identification of the most effective photocatalyst that can be prepared for hydrogen generation by combining Cu2O and TiO2 (i.e., 1%wt Cu2O in TiO2 photocatalyst prepared by ball-milling method at 200 rpm and 1 min milling time). To optimize photocatalytic hydrogen generation in the presence of the greatest photocatalyst, the effects of (i) sacrificial species and their concentration, (ii) temperature, and (iii) pH of the system are taken into account, resulting in a light-to-chemical energy efficiency of 8% under the best-tested conditions. Last but not least, the possibility of using the present photocatalytic system under direct solar light irradiation is evaluated: the results indicate that nearly 60% of the hydrogen production recorded under sunlight can be attributed to the visible component of the solar spectrum, while the remaining 40% can be attributed to the UV component.

The main purpose of this work was to prepare and optimize glues consisting primarily of natural components. The fundamental component was the laricio pine resin to which different additives were added, varying their nature and quantity. The additives used were: charcoal, activated carbon and carbon nanotubes (MWCNTs). The optimization of the systems continued to identify and select suitable solvents, in order to improve dispersion and solubilization of the phases and to obtain glues in the fluid phase at room temperature. The best results were obtained with ethyl alcohol which, moreover, represents a solvent with a limited environmental impact. The evaluation of the adhesive capacity of the glues was carried out by cutting, tensile and flexural tests on prepared wooden specimens. Furthermore, the specimens and the same glue were subjected to thermal cycles and observed by Scanning Electron Microscope (SEM). The carbon nanotubes, used in very low percentages (1%, in a system consisting mainly of natural origin products) in the presence of an adequate solvent, such as ethyl alcohol, make it possible to obtain a glue that is easy to apply, with an excellent adhesive capacity.

In this paper, a novel 3D printed Rotational Joint (RJ) embedding an integrated elastic element is presented. The RJ, produced as a single piece by means of an FDM printer, comprises a traditional pin hinge coupled with a pair of spiral torsion springs, providing the desired compliance for the application at hand. Benefits of the proposed design include monolithic manufacturing and possibility to be successfully employed in robotic articulated devices requiring joint elasticity for their functioning. On the other hand, the sub-optimal RJ behavior, mainly caused by the unavoidable friction between 3D printed mating surfaces, must be accurately taken into account for design purposes. In this context, preliminary reliability tests have been performed showing promising results in terms of lifetime and negligible fatigue effects. Then, a mathematical model of the system is derived, which comprises the spring elasticity along with any frictional effects that may be due to either the pin hinge itself or the tendon transmission (frequently employed in underactuated robotic devices). The model parameters have been empirically evaluated by comparing simulated and experimental data. In addition, the last part of the paper describes how the proposed RJ can be effectively employed for the design of modular, underactuated fingers, providing three degrees of freedom and a single tendon transmission. To this end the model of the joint module proposed in this work will be the starting point for the geometry dimensioning of a finger with a desired free closure motion.

Polar or pyroelectric materials have a non-centrosymmetric structure and possess an electrical dipole moment even in the absence of an external electric field. This chapter focuses on the synthesis methods developed for the preparation on nanowires (NWs) and nanotubes (NTs) either free-standing or grown on a substrate. It also describes the crystal structure, domain organization and the ferroelectric properties of these nanostructures, including local scale measurement by means of atomic force microscopy techniques. Considering the very small size of NWs and NTs, the crystal structure is commonly investigated by powder X-ray diffraction methods, which provide the average structure of a large number of nanoobjects with a more or less wide size and aspect ratio distributions. Rich information on crystal structure, lattice arrangement, growth direction, domain patterns, and the existence of defects in individual NWs can be obtained by means of high-resolution transmission electron microscopy and scanning transmission electron microscopy.