Functionalised metal-organic frameworks: a novel approach to stabilising single metal atoms

We have investigated the potential of metal-organic frameworks for immobilising single atoms of transition metals using a model system of Pd supported on NH2-MIL-101(Cr). Our Transmission Electron Microscopy and in-situ Raman spectroscopy results give evidence for the first time that functionalised metal-organic frameworks may support, isolate and stabilise single atoms of palladium. Using Thermal Desorption Spectroscopy we were able to evaluate the proportion of single Pd atoms. Furthermore, in a combined theoretical-experimental approach, we show that the H-H bonds in a H2 molecule elongate by over 15% through the formation of a complex with single atoms of Pd. Such deformation would affect any hydrogenation reaction and thus the single atoms supported on metal-organic frameworks may become promising single atom catalysts in the future

Formation of hollow structures through diffusive phase transition across a membrane

We report on the formation of hollow structures driven by a phase transition that proceeds via diffusion through a membrane. The mechanism is demonstrated for Mg/MgO core/shell nanoparticles: When they undergo successive metal-hydride transitions at sufficiently high temperature, the core material progressively diffuses outward and evaporates, leaving a hollow shell with the original shape and thickness. This phenomenon might become a general approach to the design of materials with controlled porosity

Comunicazione sociale e pedagogia. Itinerari e intersezioni

Questo libro nasce dall’esperienza del corso di Pedagogia della comunicazione, tenutosi negli ultimi anni presso lo IUSVE di Mestre e Verona nell’ambito del corso di laurea triennale in Scienze e tecniche della comunicazione grafica e multimediale. La prima parte del testo, a carattere teorico, si focalizza sui paradigmi e i modelli educativi, mentre la seconda propone delle pratiche operative riguardanti la pedagogia narrativa e in particolare il digital storytelling. Questa impostazione teorico-pratica intende far sperimentare alcune forme di comunicazione sia nella prospettiva della ricerca pedagogica sia per quanto riguarda l’utilizzo operativo degli strumenti, in particolare i video

Metal-hydride transformation Kinetics in Mg nanoparticles

The hydrogen sorption kinetics of magnesium nanoparticles prepared by inert gas condensation and coated by a magnesium oxide layer were investigated by a volumetric apparatus. The metal-hydride transformation was studied by transmission electron microscopy of the nanoparticles both in the as prepared state and after hydrogen cycling

Hydrogen Sorption in Magnesium Nanoparticles: Size- and Surface-Related Phenomena

Mg nanoparticles with metal-oxide core-shell morphology were synthesized by inert-gas condensation and decorated by in-situ deposition of transition metals: Pd, Ni, Ti. The effects of nanoparticle size on the hydrogen sorption kinetics and the specific action of the different catalysts are presented and discussed in connection with structural and functional analysis

Local structure at interfaces between hydride-forming metals: A case study of Mg-Pd nanoparticles by x-ray spectroscopy

The structure at the interface between elements or phases that exhibit different hydrogen (H) binding energies exerts a profound influence on the thermodynamics of H in nanophase materials. In this paper, we study the local structure at the Mg/Pd interface in Mg nanoparticles with partial Pd coating, and we map its evolution in response to annealing and H sorption. This task is accomplished by x-ray photoelectron spectroscopy and x-ray absorption spectroscopy, also including in situ experiments, with the support of crystallographic information from x-ray diffraction. It is shown that the initial Pd surface layer reacts with Mg at relatively low temperatures, leading to irreversible formation of a Mg-rich intermetallic phase Mg(6)Pd. Due to the high Mg-H binding energy, this phase reversibly transforms, upon H absorption, into a nanophase mixture of magnesium hydride and a Pd-rich intermetallic with H in solid solution, MgPdH(delta). These reversible structural changes are discussed with reference to recent calculations that highlight their relevance to the thermodynamics of the metal-hydride transition. The picture drawn here might be relevant to other multiphase materials presently investigated in the field of hydrogen-related science and technology

Effectiveness of an Expert System for Astronaut Assistance on a Sleep Experiment

Principal Investigator-in-a-Box ([PI]) is an expert system designed to train and assist astronauts with the performance of an experiment outside their field of expertise, particularly when contact with the Principal Investigators on the ground is limited or impossible. In the current case, [PI] was designed to assist with the calibration and troubleshooting procedures of the Neurolab Sleep and Respiration Experiment during the pre-sleep period of no ground contact. It displays physiological signals in real time during the pre-sleep instrumentation period, and alerts the astronauts when a poor signal quality is detected. Results of the first study indicated a beneficial effect of [PI] and training in reducing anomaly detection time and the number of undetected anomalies. For the in-flight performance, excluding the saturated signals, the expert system had an 84.2% detection accuracy, and the questionnaires filled out by the astronauts showed positive crew reactions to the expert system