Quando l'idea acquista spessore: tecnologie additive a confronto

"Le “nuove” tecnologie additive [1] stanno cambiando il mondo del manufacturing sia in termini di progettazione sia di modalità di produzione; tale rinnovamento si traduce, di fatto, nella realizzazione secondo una nuova modalità di oggetti dalle caratteristiche più svariate. Il miglioramento più evidente si è avuto grazie al superamento dei tradizionali vincoli che, per esempio, la produzione con stampi comporta; il principale vantaggio ottenuto è l’enorme fl essibilità che le nuove tecnologie additive garantiscono, fl essibilità da intendersi sia in termini di forme e materiali, sia in relazione alla grande varietà di pezzi differenti che è possibile realizzare contemporaneamente

Functionalized carbon black for elastomer composites with low hysteresis

The prime application of elastomeric composites is tire compounds. The tuning of dynamic rigidity and hysteresis is key to achieve the desired tire performances. Car tires require hysteresis to be high at low temperatures, to promote wet traction, and low at medium-high temperatures, for low energy dissipations. To achieve these properties amorphous precipitated silica is commonly selected as reinforcing filler due to its nano dimensions and the possibility of establishing chemical bonds with the elastomers’ chains. Carbon black (CB), another common filler for tire compounds, does not have functional groups able to promote chemical bonds with the rubber matrix yet it would be highly desirable. A CB with a cradle to gate LCA comparable if not even better than silica’s LCA could be used in replacement of silica in tire compounds. In this work, a pyrrole compound (PyC) containing a thiol group was used to functionalize CB by the so-called “pyrrole methodology” . The thiol group was expected to react with the sulphur-based crosslinking system, thus forming chemical bonds with the rubber chains. The synthesis of the PyC and the functionalization reaction were characterized by high atom efficiency. A poly(styrene-co-butadiene) copolymer from anionic solution polymerization was used as the main rubber for the compound preparation. The crosslinked composite material filled with functionalized CB revealed substantial improvements with respect to the composite with pristine CB, in particular: high rigidity and low hysteresis at high temperature. These findings seem to confirm the formation of the expected rubber-filler chemical bond and are even comparable to those of silica- based rubber composites. The results here reported pave the way to CB-based rubber composites with a low environmental impact

Functionalized carbon black for elastomeric composites with low dissipation of energy

The most important application of elastomeric composites, tire compounds, relies on the following dynamic-mechanical properties: dynamic rigidity and hysteresis. For car tires, hysteresis is tuned as a function of temperature: high at low temperature and low at medium-high temperature, to promote traction on wet roads and low energy dissipation (rolling resistance), respectively. To obtain these properties, amorphous precipitated silica is used as reinforcing filler. The strengths of silica are: nano dimensions and the possibility of incorporating and establishing chemical bonds with the elastomers’ chains. Carbon black (CB), which is also largely used in tire compounds, does not have functional groups able to promote chemical bonds with the rubber matrix. It would be highly desirable to functionalize the surface of carbon black with such functional groups: a CB with a cradle to gate LCA comparable if not even better than silica’s LCA could be used in replacement of silica in tire compounds. In this work, a pyrrole compound (PyC) was used for functionalizing CB by applying the so-called “pyrrole methodology”. The selected PyC contained a thiol group which was expected to react with the sulphur-based crosslinking system, thus forming chemical bonds with the rubber chains. The synthesis of the PyC and the functionalization reaction were characterized by high atom efficiency. A poly(styrene-co-butadiene) copolymer from anionic solution polymerization was used as the main rubber for the compound preparation. The crosslinked composite material filled with functionalized CB revealed substantial improvements with respect to the composite with pristine CB, in particular: high rigidity and low hysteresis at high temperature. These findings seem to confirm the formation of the expected rubber-filler chemical bond and are even comparable to those of silicabased rubber composites. The results here reported pave the way to CB-based rubber composites with a low environmental impact

DCIS and LCIS are confusing and outdated terms. They should be abandoned in favor of ductal intraepithelial neoplasia (DIN) and lobular intraepithelial neoplasia (LIN)

Abstract The terms ductal and lobular intraepithelial neoplasia (DIN and LIN) were introduced by Tavossoli 15 years ago, who proposed they should replace, respectively, ductal and lobular carcinoma in situ (DCIS and LCIS). This proposal has been slowly gaining ground. We argue that DCIS and LCIS should now be definitively abandoned. Bringing together 'in situ' and other entities into the simpler and more logical DIN/LIN framework–as has been done with intraepithelial neoplasias of cervix, vagina, vulva, prostate, and pancreas–would eliminate the artificial and illogical distinctions between 'not cancers' (e.g. flat epithelial atypia, atypical ductal hyperplasia–now classified as low grade DIN) and 'cancers' (e.g. DCIS–now considered medium–high grade DIN). Elimination of the term 'carcinoma' from entities that cannot metastasize will reduce confusion among health professionals and patients, and contribute to reducing the risk of overtreatment, as well as reducing adverse psychological reactions in patients

TIME RESOLVED OPTICAL MEASUREMENTS ON DIFFERENT CARBON NANOTUBES ARCHITECTURES

Multi Wall Carbon Nanotubes (MWCNT) and Single Wall Carbon Nanotubes (SWCNT) can be grown in several architectures. A crucial aim is the theoretical and experimental study of the fundamental dynamics of photo-excited charge carriers into these ensembles. In fact the understanding of the charge transfer dynamics and of the exciton interaction is of great importance to improve the efficiency of the Carbon Nanotubes (CNT) based applications, as sensor, bio-medical, energy storage and photovoltaic technologies. In this thesis, performing time resolved optical measurements with several experimental techniques, we analyze the fundamental dynamics in different CNT architectures. Charge transfer mechanisms from semiconductor to metallic are evidenced in unaligned SWCNT, whereas this process is not present in the vertically aligned. The excitonic behavior, revealed in all ensembles, are an interesting novelty in aligned MWCNT. The study of this behavior allows to addressed a long debated question about the graphite-like or SWCNT-like behavior of MWCNT, unveiling that the MWCNT electronic structure under 3 eV presents structured peaks like the Van Hove Singularities in SWCNT. Non-linear excitonic effects are analyzed and, controlling the light polarization direction with respect to the CNT long-axis, we are able to select and unveil, in MWCNT architectures, different optical responses, evidencing linear and non-linear effects. In particular exciton-exciton annihilation and Multiple Exciton Generation (MEG) non-linear processes are discussed. The initial studies on a possible presence of MEG in MWCNT can pave the way to disentangle the complex processes occurring in the photo-excited MWCNT in the violet light region. The possibility to control the effects as a multiple generation of excitons represent crucial challenges in order to improve the photovoltaic performances of MWCNT based devices. This thesis represents the initial step of a wide project whose ultimate goal is to improve the efficiency of photovoltaic devices based on SWCNT or MWCNT. In order to address this aim, heterogeneous systems are considered, in which different CNT architectures are combined with nanoparticles or organic groups. Starting from the basic systems and adding in subsequent stages the different components up to the complete devices, for each step the optical response will be studied

Chemical functionalization of graphene surface as filler for rubber compounds

Over the last few years, the surface modification of fillers for high-level technological applications such as polymer composites for tyre industry, conductive inks and coatings has seen a considerable increase in interest since it can increase mechanical, electrical, and thermal properties of the final material. Nano-sized carbon allotropes such as graphene and carbon nanotubes are a suitable class of compounds for these purposes: high thermal and electrical conductivity along with considerable mechanical reinforcement are the main improvements that these fillers bring to the composite and their elevated surface area allows to reduce the filler volume ratio compared to more common alternatives. An efficient and reliable method to modify the surface of these nano-fillers is the so-called pyrrole methodology, a mild procedure that involves bio-sourced reagents to introduce functional groups on the graphitic planes and that has been recently employed in the fabrication of elastomeric composites with improved mechanical properties. In order to understand the mechanism beneath the interaction between the pyrrole and the substrate and thus the behavior of the functionalized filler, a more in-depth analysis is requested. A theoretical work based on molecular dynamics simulations and a DFT study were performed in order to investigate the interaction energy, the geometry of interaction and the mobility of N-substituted pyrrole molecules adsorbed on the graphene planes. This theoretical study at atomistic level can help design a new class of high-performance fillers by better understanding the interaction mechanism given the important role of supramolecular interactions

A Molecular Dynamics Study of Noncovalent Interactions between Rubber and Fullerenes

The percolation and networking of filler particles is an important issue in the field of rubber reinforcement, and much effort is given to clarify the true nature of the reinforcement mechanism and the viscoelastic behavior. The concentration of nanofillers also in the presence of large amounts of carbon black is a parameter that can influence the macroscopic rubber behavior. In this paper, noncovalent interactions between C60 fullerenes with poly-1,4-cis-isoprene (PI) either as such or modified are studied through atomistic simulations based on molecular mechanics (MM) and molecular dynamics (MD) methods. At first, the conformational properties of a single chain and of 12 PI chains in a periodic simulation box are studied. Afterwards, the conformational properties of a single PI chain polymer terminated with a -COOH group, and then a bulk system formed by chains of unmodified and some PI modified chains are considered. Then, the systems formed by adding fullerenes to these two different bulk systems are studied. Relatively small interaction energy between rubber and fullerenes being well dispersed in the sample is found. The simulations showed a preferential tendency of fullerenes to display self-aggregation, in the presence of even a small fraction of modified polymer chains

Hardware-Software Co-Design of BIKE with HLS-Generated Accelerators

In order to mitigate the security threat of quantum computers, NIST is undertaking a process to standardize post-quantum cryptosystems, aiming to assess their security and speed up their adoption in production scenarios. Several hardware and software implementations have been proposed for each candidate, while only a few target heterogeneous platforms featuring CPUs and FPGAs. This work presents a HW/SW co-design of BIKE for embedded platforms featuring both CPUs and small FPGAs and employs high-level synthesis (HLS) to timely deliver the hardware accelerators. In contrast to state-of-the-art solutions targeting performance-optimized HLS accelerators, the proposed solution targets the small FPGAs implemented in the heterogeneous platforms for embedded systems. Compared to the software- only execution of BIKE, the experimental results collected on the systems-on-chip of the entire Xilinx Zynq-7000 family highlight a performance speedup ranging from 1.37x, on Z-7010, to 2.78x, on Z-7020