Large Polarization and Susceptibilities in Artificial Morphotropic Phase Boundary PbZr1−xTixO3 Superlattices

The ability to produce atomically precise, artificial oxide heterostructures allows for the possibility of producing exotic phases and enhanced susceptibilities not found in parent materials. Typical ferroelectric materials either exhibit large saturation polarization away from a phase boundary or large dielectric susceptibility near a phase boundary. Both large ferroelectric polarization and dielectric permittivity are attained wherein fully epitaxial (PbZr0.8Ti0.2O3)n/(PbZr0.4Ti0.6O3)2n (n = 2, 4, 6, 8, 16 unit cells) superlattices are produced such that the overall film chemistry is at the morphotropic phase boundary, but constitutive layers are not. Long- (n ≥ 6) and short-period (n = 2) superlattices reveal large ferroelectric saturation polarization (Ps = 64 µC cm−2) and small dielectric permittivity (εr ≈ 400 at 10 kHz). Intermediate-period (n = 4) superlattices, however, exhibit both large ferroelectric saturation polarization (Ps = 64 µC cm−2) and dielectric permittivity (εr = 776 at 10 kHz). First-order reversal curve analysis reveals the presence of switching distributions for each parent layer and a third, interfacial layer wherein superlattice periodicity modulates the volume fraction of each switching distribution and thus the overall material response. This reveals that deterministic creation of artificial superlattices is an effective pathway for designing materials with enhanced responses to applied bias

Lead electrorefining process from exhausted lead acid batteries by using acidic and alkaline electrolytes

The recycling of lead acid batteries (LABs) comprises relevant concerns on the suitable methodologies to recover lead. In this investigation, two electrorefining processes, by using acidic and alkaline electrolytes, have been compared to determine the most significant results of both methodologies. Acidic electrolytes used 200 g/L HBF4, 1.2 g/L H3PO4, 10 g/L H3BO3, and 100 g/L PbO, while the alkaline ones employed 120 g/L NaOH, 75 g/L PbO, 50-92 g/L glycerol, and 2 g/L gelatin. All the solutions were studied by varying temperature and current density (CD) to determine remarkable changes on current efficiency (CE), cell voltage (CV), specific energy consumption (SEC), and on the deposit quality. The results highlighted that by using the acidic electrolyte containing dextrin it is possible to obtain a compact deposit even using high CDs. Acidic solution without dextrin addition allows to obtain good quality deposits by working at 40 degrees C and 100 A/m(2) CD. After testing the behavior of different alkaline electrolytes, it is possible to observe that the solution containing the highest glycerol concentration allows to obtain, for intermediate valued of CD, CE higher than 97% with a SEC of about 0.37 kWh/kg. By comparing the results it is evident that the acidic electrolyte is the one that allows to reach higher productivity with lower SEC. In the selected conditions, lead deposits appear pure and compact.[GRAPHICS]

On the Design of Constructively Aligned Educational Unit

Modern pedagogy is moving away from traditional transmissive approaches, and it is extensively embracing constructive theory of learning. A prominent practical embodiment of this paradigm shift is a method called Constructive Alignment (CA). This approach focuses on learners’ actions and starts from a clear communication of the Intended Learning Outcomes (ILOs) of the focal unit. ILOs are made of content, a context, and an Educational Goal Verb (EGV). According to the Bloom Taxonomy, the EGV is the core of an ILO and refers to the action the learners are expected to be able to master after completing the educational unit. The ILO is then aligned to the course activity using the EGV (i.e., EGVs are enacted through Teaching and Learning Activities (TLAs) and verified through Assessment Tasks (ATs)). Despite the ILO definition being extensively investigated and described, the extant literature has poorly explored how to devise suitable TLAs and ATs, lacking comprehensive contributions that identify and describe the different kinds of TLAs and ATs available to course designers. In view of the above gap, the authors searched and reviewed the literature (scientific papers (i.e., top-down, deductive approach)) and practices in higher education (university websites and blogs (i.e., bottom-up, inductive approach)) to identify all the possible sources of TLA and AT descriptions available. The results propose standardized templates that support the course design process, providing extensive descriptions of TLA and AT based on the best practices identified. The proposed templates include the core dimensions that proved to be suitable for designing traditional and remote-learning activities. Finally, the examples provided in the paper show how to use these templates on a few kinds of selected on-campus and digital TLAs and ATs from the educational units identified in the Erasmus+ MAESTRO project, which is based on Industry 4.0 technological enablers and their application in support of manufacturing sustainability

Evidence of a pressure-induced metallization process in monoclinic VO2_2

Raman and combined trasmission and reflectivity mid infrared measurements have been carried out on monoclinic VO$_2$ at room temperature over the 0-19 GPa and 0-14 GPa pressure ranges, respectively. The pressure dependence obtained for both lattice dynamics and optical gap shows a remarkable stability of the system up to P*$\sim$10 GPa. Evidence of subtle modifications of V ion arrangements within the monoclinic lattice together with the onset of a metallization process via band gap filling are observed for P$>$P*. Differently from ambient pressure, where the VO$_2$ metal phase is found only in conjunction with the rutile structure above 340 K, a new room temperature metallic phase coupled to a monoclinic structure appears accessible in the high pressure regime, thus opening to new important queries on the physics of VO$_2$.Comment: 5 pages, 3 figure

Electrodynamics near the Metal-to-Insulator Transition in V3O5

The electrodynamics near the metal-to-insulator transitions (MIT) induced, in V3O5 single crystals, by both temperature (T) and pressure (P) has been studied by infrared spectroscopy. The T- and P-dependence of the optical conductivity may be explained within a polaronic scenario. The insulating phase at ambient T and P corresponds to strongly localized small polarons. Meanwhile the T-induced metallic phase at ambient pressure is related to a liquid of polarons showing incoherent dc transport, in the P-induced metallic phase at room T strongly localized polarons coexist with partially delocalized ones. The electronic spectral weight is almost recovered, in both the T and P induced metallization processes, on an energy scale of 1 eV, thus supporting the key-role of electron-lattice interaction in the V3O5 metal-to-insulator transition.Comment: 7 pages, 5 figure

Mutagenicity evaluation with Ames test of hydro-alcoholic solution of terpenes

Mutagenic properties of terpenes (both synthesis and plant derived) have been tested, up to now, as a single molecule. A terpenes containing hydro-alcoholic solution deriving from frankincense and myrrh resins and hyssop essential oil was assayed for mutagenicity by means of Ames test. Extraction tech- nique conducted with electromagnetic fields at room temperature enabled to obtain a solution of free active molecules that did not undergo thermal degradation and characterized by biocidal activity. In order to verify lack of mutagenic hazard in coming into contact with human, the solution was appropriately diluted and tested with Salmonella typhimurium TA98, TA1535 and YG1024 strains, both in absence and in presence of metabolic system S9. For none of the tested conditions a 2-fold increase of induced revertants, as regards to spontaneous, was registered. The ratio between induced and spontaneous His+ revertants (Mutagenic Index) was around 1.00 in all the determinations and no statistically significant differences have been identified comparing the sample and the negative control. A similar result has been obtained for the dose-response curve. In conclusion, we verified that tested terpenes solution lacks of mutagenicity on Salmonella typhimurium with and without metabolic activator so this plant extract can be safely used as biocide

Transmittance and reflectance measurements at terahertz frequencies on a superconducting BaFe_{1.84}Co_{0.16}As_2 ultrathin film: an analysis of the optical gaps in the Co-doped BaFe_2As_2 pnictide

Here we report an optical investigation in the terahertz region of a 40 nm ultrathin BaFe$_{1.84}$Co$_{0.16}$As$_2$ superconducting film with superconducting transition temperature T$_c$ = 17.5 K. A detailed analysis of the combined reflectance and transmittance measurements showed that the optical properties of the superconducting system can be described in terms of a two-band, two-gap model. The zero temperature value of the large gap $\Delta_B$, which seems to follow a BCS-like behavior, results to be $\Delta_B$(0) = 17 cm$^{-1}$. For the small gap, for which $\Delta_A$(0) = 8 cm$^{-1}$, the temperature dependence cannot be clearly established. These gap values and those reported in the literature for the BaFe$_{2-x}$Co$_{x}$As$_2$ system by using infrared spectroscopy, when put together as a function of T$_c$, show a tendency to cluster along two main curves, providing a unified perspective of the measured optical gaps. Below a temperature around 20 K, the gap-sizes as a function of T$_c$ seem to have a BCS-like linear behavior, but with different slopes. Above this temperature, both gaps show different supra-linear behaviors