Search results for " material"

Acetic acid leaching of neodymium magnets and iron separation by simple oxidative precipitation

2022

Neodymium-iron-boron (NdFeB) has become the most prominent permanent magnet alloy, with a wide variety of applications and an ever-increasing demand. Their recycling is important for securing the supply of critical raw materials used in their manufacturing. The use of organic acids such as acetic acid has been of recent interest for the recycling of waste NdFeB magnets. Despite achieving good leaching efficiencies, the published literature has not properly investigated the effects of key factors influencing the acetic acid leaching process and their respective interactions, which has lead to conflicting findings as to what conditions are optimal. The present work goes to show that no such o…

Exotic Spin-Orbital Physics in Hybrid Oxides

2016

We compare the effective spin-orbital super\-exchange triggered by magnetic $3d$ impurities with $d^3$ and $d^2$ configurations and either no orbital degree of freedom (orbital dilution) or hole replacing a doublon (charge dilution) in a $4d^4$ Mott insulator with $S=1$ spins. Impurities causing orbital dilution act either as spin defects decoupled from the surrounding ions, or generate orbital polarons along $d^3$-$d^4$ hybrid bonds. The exchange on these bonds determines which orbital is occupied by a doublon on the host site. In case of charge dilution by $3d^2$ impurities additional $\propto T_i^+T_j^+$ terms arise which enhance orbital fluctuations. We show that such terms may radicall…

Design Scheme of New Tetragonal Heusler Compounds for Spin-Transfer Torque Applications and its Experimental Realization

2012

Band Jahn-Teller type structural instabilities of cubic Mn(2)YZ Heusler compounds causing tetragonal distortions can be predicted by ab initio band-structure calculations. This allows for identification of new Heusler materials with tunable magnetic and structural properties that can satisfy the demands for spintronic applications, such as in spin-transfer torque-based devices.

Spin caloric transport from density-functional theory

2019

Spin caloric transport refers to the coupling of heat with spin transport. Its applications primarily concern the generation of spin currents and control of magnetisation by temperature gradients for information technology, known by the synonym spin caloritronics. Within the framework of ab initio theory, new tools are being developed to provide an additional understanding of these phenomena in realistic materials, accounting for the complexity of the electronic structure without adjustable parameters. Here, we review this progress, summarising the principles of the density-functional-based approaches in the field and presenting a number of application highlights. Our discussion includes th…

Ultrafast Coherent THz Lattice Dynamics Coupled to Spins in the van der Waals Antiferromagnet FePS3

2022

Coherent THz optical lattice and hybridized phonon–magnon modes are triggered by femtosecond laser pulses in the antiferromagnetic van der Waals semiconductor FePS3. The laser-driven lattice and spin dynamics are investigated in a bulk crystal as well as in a 380 nm-thick exfoliated flake as a function of the excitation photon energy, sample temperature and applied magnetic field. The pump-probe magneto-optical measurements reveal that the amplitude of a coherent phonon mode oscillating at 3.2 THz decreases as the sample is heated up to the Néel temperature. This signal eventually vanishes as the phase transition to the paramagnetic phase occurs, thus revealing its connection to the long-ra…

Natural stabilization for bio-polymeric systems

2014

The role of fouling mechanisms in a submerged membrane bioreactor during the start-up

2006

A specific operative protocol set up during the restoration of San Michele Arcangelo’s marble statue

2009

Questo lavoro descrive le diverse fasi dell’intervento di conservazione di una statua di marmo del XVI secolo, raffigurante San Michele Arcangelo, custodita presso la Galleria Regionale di Palazzo Abatellis di Palermo. Inizialmente è stata effettuata un’indagine di archivio per inquadrare l’opera dal punto di vista storico artistico ed iconografico. Quindi sono stati effettuati: un rilievo grafico e digitale 3D, una mappatura di tutte le forme di degrado rilevate e dei segni di interventi precedenti, le analisi dei materiali costitutivi e dello stato di conservazione, mediante tecniche non distruttive o microdistruttive. Infine è stato progettato ed eseguito l’intervento di conservazione, a…

Flexural Behavior of Steel Fibrous Reinforced Concrete Deep Beams

2012

Experimental research was carried out regarding the flexural behavior of deep beams cast with plain and fibrous concrete with hooked steel fibers, and subjected to monotonic vertical loads. Four deep fiber-reinforced concrete beams were cast. Two of them were made of plain concrete with main and web steel reinforcements (RC), and two were made of hooked steel fiber-reinforced concrete (SFRC) with main steel reinforcements. The experimental results show the brittle behavior of reinforced deep RC members characterized by crushing of concrete struts and fracture of web steel bars. SFRC deep beams exhibit higher strength and, above all, ductility with respect to RC members due to the bridging a…

Building the space: vaults’ geometry and stereotomy. Materials and architectural technologies in the Mediterranean area

2018

Costruire una volta ha sempre nei secoli rappresentato un’arte pratica che si nutriva del contributo di chi operava in cantiere: indispensabile risultava la tecnica, il sapiente taglio della pietra e l’opportuna collocazione della stessa nel gioco statico dell’organismo murario. Un sapere tecnico, questo, che combinava l’estetica con la organizzazione strutturale della fabbrica costruenda; l’esperienza pratica aveva dettato a muratori e scalpellini i precetti in merito ai differenti compiti organizzativi e alle relative gerarchie degli esecutori dell’opera edilizia, all’attrezzature e alle macchine da cantiere, agli utensili e alle lavorazioni da usare, incentivando una spiccata attitudine …