Magnetic properties of epsilon iron(III) oxide nanorod arrays functionalized with gold and copper(II) oxide

A sequential chemical vapor deposition (CVD) - radio frequency (RF)-sputtering approach was adopted to fabricate supported nanocomposites based on the scarcely investigated \u3b5-iron(III) oxide polymorph. In particular, \u3b5-Fe2O3 nanorod arrays were obtained by CVD, and their subsequent functionalization with Au and CuO nanoparticles (NPs) was carried out by RF-sputtering under mild operational conditions. Apart from a multi-technique characterization of material structure, morphology and chemical composition, particular efforts were dedicated to the investigation of their magnetic properties. The pertaining experimental data, discussed in relation to the system chemico-physical characteristics, are directly dependent on the actual chemical composition, as well as on the spatial distribution of Au and CuO nanoparticles. The approach adopted herein can be further implemented to control and tailor different morphologies and phase compositions of iron oxide-based nanomaterials, meeting thus the open requests of a variety of technological utilizations

Progetto e realizzazione di un setup per l’analisi del rolling contact: risultati preliminari

Presso il Dipartimento di Ingegneria Meccanica dell’Università di Cagliari (DIMECA) è attiva, da alcuni anni, una linea di ricerca orientata alla valutazione dei principali parametri di contatto (forma e dimensioni dell’area nominale di contatto, area reale di contatto, distribuzione delle pressioni di contatto) in interfacce metalliche, mediante una tecnica sperimentale basata sull’impiego di onde ultrasoniche. L’applicazione di questo metodo ha consentito di ottenere informazioni su contatti a geometria semplice quali, ad esempio, quelli sfera-piano [1-2] su casi più complessi di rilevante impatto ingegneristico come quello relativo all’interazione tra ruota e rotaia ferroviaria [3-4]. Il principale punto di forza dell’indagine ultrasonica risiede nella sua capacità di fornire informazioni sullo stato del contatto a partire da misure del coefficiente di riflessione all’interfaccia, garantendo in tal modo sia la più completa non-invasività (nessun mezzo viene ad interporsi tra i corpi a contatto) e sia la possibilità di investigare “in process”. In particolare quest’ultima peculiarità permette di monitorare le variazioni del parametri di contatto in tempo reale (ad esempio a seguito di variazioni nel carico applicato o nella configurazione geometrica dell’accoppiamento) senza che sia necessario rimuovere i corpi per esaminare gli effetti che tali modifiche hanno generato. Appare importante sottolineare che, a tutt’oggi, la letteratura riporta esempi di impiego de metodo ultrasonico a problemi di contatto quasi esclusivamente nell’analisi di situazioni statiche. Tuttavia, è facilmente intuibile che la possibilità di estendere il campo di applicazione della tecnica a situazioni dinamiche, aumenterebbe in misura considerevole il range di casi di interesse ingegneristico potenzialmente testabili. In considerazione di ciò, il presente studio si pone come obiettivo principale quello di verificare la validità ed affidabilità del metodo ultrasonico per lo studio di situazioni dinamiche, con particolare riferimento a problemi di “rolling contact”

Memory and rejuvenation in a spin glass

The temperature dependence of the magnetisation of a Cu(Mn) spin glass ($T_g$ $\approx$ 57 K) has been investigated using weak probing magnetic fields ($H$ = 0.5 or 0 Oe) and specific thermal protocols. The behaviour of the zero-field cooled, thermoremanent and isothermal remanent magnetisation on (re-)cooling the system from a temperature (40 K) where the system has been aged is investigated. It is observed that the measured magnetisation is formed by two parts: (i) a temperature- and observation time-dependent thermally activated relaxational part governed by the age- and temperature-dependent response function and the (latest) field change made at a lower temperature, superposed on (ii) a weakly temperature-dependent frozen-in part. Interestingly we observe that the spin configuration that is imprinted during an elongated halt in the cooling, if it is accompanied by a field induced magnetisation, also includes a unidirectional excess magnetisation that is recovered on returning to the ageing temperature.Comment: EPL style; 7 pages, 5 figure

Magnetic properties of cobalt ferrite-silica nanocomposites prepared by a sol-gel autocombustion technique

The magnetic properties of cobalt ferrite-silica nanocomposites with different concentrations (15, 30, and 50 wt %) and sizes (7, 16, and 28 nm) of ferrite particles have been studied by static magnetization measurements and Mossbauer spectroscopy. The results indicate a superparamagnetic behavior of the nanoparticles, with weak interactions slightly increasing with the cobalt ferrite content and with the particle size. From high-field Mossbauer spectra at low temperatures, the cationic distribution and the degree of spin canting have been estimated and both parameters are only slightly dependent on the particle size. The magnetic anisotropy constant increases with decreasing particle size, but in contrast to many other systems, the cobalt ferrite nanoparticles are found to have an anisotropy constant that is smaller than the bulk value. This can be explained by the distribution of the cations. The weak dependence of spin canting degree on particle size indicates that the spin canting is not simply a surface phenomenon but also occurs in the interiors of the particles. (c) 2006 American Institute of Physics

Exploring the magnetic properties and magnetic coupling in SrFe12O19/Co1-xZnxFe2O4 nanocomposites

Abstract Among hard/soft nanocomposites (NCs), ferrite-based materials are potentially promising for developing exchange-coupled systems, thus leading to enhanced magnetic properties. In this regard, we investigate the role of the synthesis approach in the development of SrFe12O19/CoFe2O4 (SFO/CFO) NCs, with special focus on tuning the magnetic features of the softer phase (CFO) by introducing Zn2+ in the spinel structure. X-ray powder diffraction (XRPD), transmission electron microscopy (TEM) and squid magnetometry were employed to clarify the relationship between morphology, size, and magnetic properties of the NCs, pointing out the feasibility of this method in obtaining successfully exchange-coupled systems. This work shows how optimizing the intrinsic magnetic properties of the CFO may be used to tune the extrinsic ones of the NCs. Despite the promising results in magnetic coupling, our study clearly confirms/strengthens that an enhancement of remanent magnetization is the most important factor for improving the magnetic performance

Is empathy an emotion?

The main aim of my thesis is to ascertain whether empathy has the required qualities of an emotion. Disagreement is rife regarding the process leading to the arousal of an emotion, which creates uncertainty as to what exactly an emotion is, and how it appears. This is the first issue I tackle in my work, as I concentrate on examining some of the significant cognitive and feeling theories of emotions. My study of these theories outlines their downsides, and I instead propose to retain a hybrid definition that combines the advantages of both families of theories to provide a balanced approach that recognises the importance of both physical changes and cognitions. The focus of my work then moves specifically onto empathy, with the intention of precisely defining this term too, its functioning, as well as the meaning of the expression ‘feeling empathy for someone’. The existing literature on empathy fails to provide a clear understanding of empathy’s classification as an emotion or a skill. My work is original in that I avoid assertions and clearly establish that empathy constitutes an emotion based on the definition of emotion I advance in the first part of my work

Exploring Sex/Gender Perspectives in Nanotechnology and Nanomaterials Research

This article aims to draw attention to the integration of sex/gender dimensions within the scientific community investigating nanomaterials and nanotechnology. Despite the significant impact of these fields on society, there remains a gap in understanding how the gender dimension can intersect with research practices and outcomes. The presence of gender-specific terminology, involving references to gender, sex, masculinity, femininity, and other related concepts can allow us to shed light on the current state of a sex/gender dimension integration in nanotechnology research. By analyzing the presence of gender-related terms in the proceedings of the IEEE Nano-Community, this paper contributes to the ongoing discussions on the importance of integrating a sex/ gender dimension in research and education in the field and highlights the need to make the nanotechnology and nanomaterials research landscape more inclusive and insightful in the future

Individuazione del presupposto del tributo di soggiorno, principi di sistema e principi fondamentali di coordinamento.

Il contributo analizza le politiche di tassazione turistica e strumenti di tutela ambientale, con particolare riguardo ai tributi ecologici in ambito comunitari

Novel mixed precursor approach to prepare multiferroic nanocomposites with enhanced interfacial coupling

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Synthesis of BaTiO3-CoFe2O4 nanocomposites using a one-pot technique

Abstract Low-cost and scalable sol–gel chemistry was employed to obtain ferroelectric-ferrimagnetic BaTiO3-CoFe2O4 nanocomposites. In a novel one-pot synthesis method, both the constituent phases of nanocomposites are formed during the same time and symbiotically participate to each other's growth. X-ray powder diffraction evidences the phase purity of the systems, with average crystallite sizes in the order of 20 nm for the BaTiO3 phase. The optimization of the synthesis conditions, precursors, and chemical agents for nanoscale BaTiO3 and BaTiO3-CoFe2O4 nanocomposites is presented, together with the magnetic and/or dielectric properties of the obtained materials. BaTiO3-CoFe2O4 nanocomposites with up to 20% CoFe2O4 volume fractions were found to display ferrimagnetic properties at room temperature akin to those of CoFe2O4, while preserving a dielectric behavior reminiscent of BaTiO3. Preliminary results describing the spin coating of BaTiO3 and BaTiO3-CoFe2O4 nanocomposites as thin films are also reported