3,806 research outputs found
Tailoring the exchange bias properties of Ni/NiO nanogranular samples by the structure control
No full textThe exchange bias (EB) effect has been studied in Ni/NiO nanogranular samples obtained by an original method that combines mechanical milling and hydrogen partial reduction of NiO. In this procedure, precursor NiO powder is ball-milled to reduce the grain size to the nanometric scale; then, the milled powder is subjected to high-temperature treatments in H2, inducing the reduction to metallic Ni. Typically, the samples consist of Ni nanocrystallites (size of the order of 10 nm) dispersed in a nanocrystalline NiO matrix, as observed by electron microscopy (HRTEM) [1].
In particular, Ni/NiO samples have been prepared by annealing in H2, at selected temperatures (200 < Tann < 300 °C), NiO powder previously milled for 5, 10, 20 and 30 hours. The structural features of the samples have been investigated by X-ray diffraction and the low-temperature magneto-thermal behavior and EB properties have been analyzed by SQUID magnetometry.
The structure and composition of the Ni/NiO samples can be satisfactorily controlled during the synthesis procedure by varying both Tann and the milling time of the precursor NiO powders [2]. By increasing this last parameter, the mean grain size of the NiO phase reduces down to the final value of 16 nm and the microstrain increases, which is consistent with an enhancement of the structural disorder. The structure of the milled NiO matrix strongly affects the process of nucleation and growth of the Ni nanocrystallites, so that, Tann being equal, the amount and the mean grain size DNi of the Ni phase vary substantially in samples having different milling times. Such features of the Ni phase determine the extent of the Ni/NiO interface and consequently the magnitude of the exchange field Hex: the highest value (~ 940 Oe) has been measured at T = 5 K in a sample containing ~7 wt % Ni and with DNi = 19 nm. However, in Ni/NiO samples with very different structural characteristics and different values of Hex at T = 5 K, the EB effect vanishes at the same temperature (~ 200 K) and the same thermal dependence of Hex is observed. We consider that the evolution of the EB effect with temperature is ultimately determined by the microstructure of the Ni/NiO interface, which cannot be substantially modified by changing the synthesis parameters, milling time and Tann.
[1] L. Del Bianco, F. Boscherini, A.L. Fiorini, M. Tamisari, F. Spizzo, M. Vittori Antisari, E. Piscopiello, Phys. Rev. B 77 (2008) 094408
[2] L. Del Bianco, F. Spizzo, M. Tamisari, J. Magn. Magn. Mater. (2009, in press
Spin-dependent conductivity of nanosized magnetic inhomogeneities
No full textSpin-dependent scattering (SDS) originates at the interface between magnetic (M) and non-magnetic (NM) regions, and gives rise to the giant magnetoresistive effect (GMR), that is observed when M and NM regions are interleaved at the nanoscale level. The GMR intensity, i.e. the change in resistivity observed due to the application of an external magnetic field, is affected by the SDS strength that, in its turn, is inversely proportional to the lateral size of the magnetic regions [1]. Such a lateral scale is the effective size of the magnetic regions [2], Deff, that is the result of the effect of magnetic interactions on the real size of the magnetic regions, D. Similarly, if the magnetic morphology of the system is not uniform, the SDS strength changes with the lateral scale of the magnetization inhomogeneities [3].
The dependence of GMR on the external field is the counterpart of Deff, so direct indications about D are not easily accessed. However, if we resort to the GMR efficiency, gamma, [4], i.e. the change in GMR for a unit change of squared magnetization, the comparison between the values of gamma measured at low and at high applied field as a function of Deff enables one to evidence D with respect to Deff. Indeed, if Deff is larger than D, as soon as the external applied field overcomes the effect of magnetic interactions, the efficiency of the magnetic structure is expected to change, as the large effective magnetic volumes break into smaller parts. As a consequence of that, the lateral scale of the system decreases, and gamma is expected to increase accordingly.
In this work, we study different FexAg1-x nanogranular systems, where x is the relative Fe atomic concentration, 0.1 < x < 0.5. Under equilibrium conditions, Fe and Ag are not miscible, so using an out-of-equilibrium technique, in our case dc-magnetron sputtering, we obtain a deep intermixing of the two species. In this way, as a function of x, different samples with a different average magnetic length scale, namely with a different Deff, can be produced [3]. The evolution of the magnetic morphology of the systems was followed with zero-field-cooled and field-cooled magnetization measurements. Magnetization and GMR loops were recorded at two different temperatures, at 300 K and at 4 K. Indeed they represent two conditions were the contribution of interparticle interactions to systems dynamics is expected to be different. In this way, the effect of Deff can be better appreciated. We present the gamma dependence on x, measured both at low and at high applied field, gamma_L and gamma_H, respectively. For low values of x, gamma_L and gamma_H display the same dependence as a function of x, whilst for higher values gamma_L shows a broad maximum whilst gamma_L has a monotonic dependence that eventually approaches saturation. These data are presented and discussed and compared to magnetization loops and diffraction data in order to give an estimation of the Deff of the different samples.
[1] S. Zhang and P. M. Levy, J. Appl. Phys. 73, 5315, 1993.
[2] P. Allia, M. Coisson, F. Spizzo, P. Tiberto, F. Vinai, Phys. Rev. B 73 (2006) 054409
[3] P. Vavassori, E. Angeli, D. Bisero, F. Spizzo, F. Ronconi, J. Magn. Magn. Mater. 262 (2003) 52
[4] M. Tamisari, F. Spizzo, F. Ronconi, M. Sacerdoti, G. Battaglin, submitted to Journal of Applied Physics
Analisi della vulnerabilità dei sistemi di distribuzione idrica rispetto a potenziali fenomeni di contaminazione
No full textDrinking Water Distribution Systems (DWDSs), as well as other complex systems are characterized by an intrinsic vulnerability which can be both quantitative and qualitative: the first one related to the possible lack of water and the second one related to presence of substances concentrations higher than the legal threshold. Assessing the DWDSs’ vulnerability and resilience in an objective way is necessary to understand the potential impacts of random disturbances, deliberate attacks, and natural disasters and to be aware of the system critical points that need to be monitored. The work that is presented, in collaboration with Cafc S.p.a. (the Udine water utililty), aims to be a preliminary study on the vulnerability assessment and reduction of a real DWDS, i.e. the Udine DWDS. A general assessment of the vulnerability of DWDS in Udine was made using indices and metrics derived from the Complex Networks Theory (CNT). By comparing these topological parameters with those of other real and literature networks, it was possible to understand the level of redundancy and robustness, as indicators of resilience of the network under consideration. This analysis, already in use for different types of network and based solely on its topology, is a fundamental step to have an overview of the network and understand the critical areas of improvement. From the interpretation of the results of this first analysis, it was clear that, in terms of operating conditions, a major improvement in the network would be achieved by reducing the failures research time. In order to reach this goal, it was decided to partitioning the network through a procedure based on the CNT. The Water Distribution Network Partitioning (WDNP), which aims to subdivide the network into hydraulically independent subsystems, has provided for the use of optimization procedures using Genetic Algorithms (GAs) operating on a suitably calibrated hydraulic network simulation model. The size and level of detail of this model has certainly been an added value throughout the study, which among the many examples of literature can be considered a rare case of applied engineering. Always considering the operating conditions, it was decided to study the qualitative vulnerability deriving from the Disinfection by-Products (DBPs). These substances, resulting from the reaction of the disinfectant with the natural organic matter (NOM) in the network, are harmful to human health. Therefore, knowing both the concentration of these substances in the DWDS and their variation with the initial concentration of disinfectant, it becomes possible to simultaneously assess and manage any critical issue. To this end, it was decided to build a chemical-hydraulic model, using the EPANET-MSX software, capable of predicting the decay of disinfectant and the formation of DBPs. Being the Udine network disinfected by chlorine dioxide, the expected DBPs are chlorite and chlorate whose concentrations have a legal limit of 0.7 mg/l. There is few literature on the subject, and the attempts to model these substances have significant approximations that reduce the quality of model predictions. Moreover, there are no cases of chemical modelling of these substances for real networks of the size and level of detail of the WDN of Udine. The results of the simulation, compared with the concentration values of the three chemical species measured in the real network have confirmed an excellent predictive ability of the model that was finally used to simulate a contamination scenario in order to assess the possibility of increased concentration of DBPs above the legal limit
Coupling between exchange bias effect and giant magnetoresistance in a Ni/NiO nanogranular sample
No full textWe have studied the magnetotransport properties of a Ni/NiO nanogranular sample, showing exchange bias (EB) effect. The sample was obtained by milling precursor NiO powder for 30 hours to reduce the mean grain size to ~ 20 nm; then, the milled powder was annealed in H2 for 30 minutes at the temperature of 250 °C, to induce the partial reduction to metallic Ni. Typically, samples prepared by this procedure consist of Ni nanocrystallites dispersed in a nanocrystalline NiO matrix [1]. As for this sample, X-ray diffraction analysis reveals that the Ni phase is about 30 volume % and the mean grain size DNi = 14 nm.
The magnetoresistance (MR) was measured as a function of T and H on a cold-compacted Ni/NiO specimen, using the standard four-probe technique, in a SQUID magnetometer operating in the 5-300 K temperature range at a maximum applied field H = 50 kOe. Magnetization loops, M(H), and MR(H) loops were measured both after zero-field-cooling (ZFC) and after field-cooling (FC) in Hcool = + 20 kOe, from T = 300 K down to selected measuring temperatures T.
At T = 5 K, the sample exhibits EB effect, as revealed by the horizontal shift of the FC M(H) loop (the exchange field Hex ~ 460 Oe); it decreases with increasing T and is almost vanished at T = 250 K.
The low value of the electric resistance R at T = 5 K (~ 0.5 Ohm) and its 20% increase with increasing T up to 300 K indicate the existence of a metallic conduction channel across the sample. We define MR = [R(H)-R(0)]/R(0), where R(0) is the highest resistance value. At T = 5 K, a negative MRmax ~ – 0.40 % is measured at H = 50 kOe, both in the mode with the current flowing perpendicular to H and in the mode with the current parallel to H. This implies that the effect is of the type usually referred to as Giant-MR and is caused by the electronic scattering from the nonaligned magnetic moments of the Ni nanocrystallites. Thus, despite the creation of a percolation metallic network allowing electronic transport, the Ni nanocrystallites, or at least a part of them, act as separated ferromagnetic entities and are not magnetically coupled. In fact, in this last condition, they would form a ferromagnetic network, unsuitable for the observation of Giant-MR.
At T = 5 K, the FC MR(H) loop appears shifted along the H axis, in good agreement with the value of Hex, and the effect exhibits the same thermal dependence as derived from the M(H) loops. Hence, at all T, a strict coupling exists between EB and MR effects in the investigated sample.
Finally, the MR effect is seen to increase with increasing T and, at T = 300 K, MRmax ~ – 0.57%. This anomalous behaviour is explained considering that a structural NiO disordered phase, with glassy magnetic properties, surrounds the Ni nanocrystallites [1]. At very low T, below ~ 50 K, the magnetic moments of this phase are completely frozen and even under the maximum H a poor alignment is attained. However, with increasing T, the magnetic moments become progressively unfrozen and, for applied field H > 20 kOe, they provide a substantial contribution to MR.
[1] L. Del Bianco, F. Boscherini, A.L. Fiorini, M. Tamisari, F. Spizzo, M. Vittori Antisari, E. Piscopiello, Phys. Rev. B 77 (2008), 09440
MAGNETIC MICROSTRUCTURE OF EXCHANGE BIASED Ni/NiO NANOGRANULAR SAMPLES INVESTIGATED BY MAGNETORESISTANCE MEASUREMENTS
No full textWe present the magnetotransport properties of two Ni/NiO nanogranular samples, produced in form of powder through a two-step procedure based on mechanical milling from coarse-grained NiO and subsequent thermal treatments in hydrogen, inducing the partial reduction to metallic Ni. Typically, samples prepared by this method consist of Ni nanocrystallites dispersed in a NiO matrix [1]. As for the selected samples, X-ray diffraction analysis revealed that the Ni volume fraction was ~ 33 % and ~ 61% and the Ni mean grain size was ~ 13 nm and ~15 nm, respectively (the two samples were labeled Ni30 and Ni60). The magnetoresistance (MR) was measured on cold-compacted pellets, using the standard four-probe technique, in a SQUID magnetometer. The field was applied parallel to the specimen surface and the current was applied in-plane, both parallel and perpendicular to the field. Magnetization loops, M(H), and MR(H) loops were measured in the 5-250 K range after both zero-field-cooling and field-cooling.
In both samples, the Ni content is above the percolation threshold for electrical conductivity, as revealed by the low resistivity (of the order of 10-3 Ohm m in Ni30 and 10-5 Ohm m in Ni60) and by its growth with increasing T. However, Ni30 exhibits just isotropic spin-dependent magnetoresistance (GMR), whereas in Ni60 both GMR and anisotropic magnetoresistance (AMR) contributions are present.
A key feature of these Ni/NiO samples is that they show exchange bias (EB) effect: it originates from the exchange interaction at the interface between the Ni phase and a structurally disordered component of the NiO matrix, which surrounds the Ni nanocrystallites and exhibits spin-glass like properties [1].
We will show that EB and MR phenomena are strictly intertwined so that both the GMR and, in Ni60, the AMR signals, measured in field-cooling, undergo a shift along the field axis as observed in the field-cooled M(H) loops, corresponding to exchange field values, at T = 5 K, of ~ 460 Oe and ~ 130 Oe for Ni30 and Ni60, respectively. This coupling between EB and MR allows gaining a deeper insight into the magnetic microstructure of the samples and its evolution with temperature. In fact, the results can be explained considering that the glassy NiO phase, giving rise to EB, is also present in the boundary region between adjacent Ni nanocrystallites and regulates the electronic transport as well as the transmission of the ferromagnetic exchange interaction to neighboring Ni nanocrystallites. Thus, depending on the Ni content, two different magnetic arrangements of the Ni nanocrystallites stem out (below and above the magnetic percolation threshold), determining the magnetotransport and EB properties.
[1] L. Del Bianco, F. Boscherini, A.L. Fiorini, M. Tamisari, F. Spizzo, M. Vittori Antisari, E. Piscopiello, Phys. Rev. B 77 (2008) 09440
Combined Mössbauer and neutron scattering investigation of ball-milled FeSiB samples
No full textFerromagnetic amorphous alloys are very intriguing systems, combining a long range ferromagnetic (FM) order with the absence of long range crystalline order. In spite of that, the actual atoms disposition may have a remarkable effect on the alloy properties. Indeed, we observed that submitting Fe80Si7B13 ribbons prepared by melt spinning to mechanical milling, a transition at T ~ 50 K from a low temperature frozen collective state, similar to a cluster-glass, to a high temperature ferromagnetic regime (reentrant ferromagnet transition) was observed [1].
To investigate this result, we performed Mössbauer and inelastic neutron scattering measurements. We produced three samples, milled for 10, 20 and 70 hours in a shaker-type milling device under Ar atmosphere (ball to powder weight ratio 4:1); the samples, in form of micrometric powder, were labeled as M10h, M20h and M70h, respectively. Transmission Mössbauer spectra were collected at room temperature using a 57Co in Rh source, and the spectrometer was calibrated using an α-Fe foil. The neutron spectra were recorded at the same temperature and were integrated over all scattering angles, corrected for self-absorption coefficient and finally normalized to the sample mass.
Mössbauer investigation as a function of milling time features the progressive precipitation of a minor fraction of bcc Fe nanocrystallites, also displayed by X-Ray diffraction measurements. The Mössbauer analysis indicates that, during this process, the averaged hyperfine field relative to the amorphous component does not change upon milling compared to the as-cast ribbon, suggesting that the value of the magnetic moment per Fe atom remains constant. In parallel, the comparison between the dynamic structure factor S(E) as a function of energy for the as-cast FeSiB ribbon and for the milled samples reveals a depletion of the energy region around 10 meV with increasing the milling time, corresponding to the suppression of vibrational modes proper of the amorphous FeSiB alloy. This behavior is consistent with the formation of bcc Fe nanocrystallites. The inelastic area of the S(E) spectra decreases upon milling over 10 hours; the elastic area decreases as well passing from 10 to 20 hours milling, in an amount larger than 3%.
This reduction of the elastic scattering intensity may be accounted for considering that the milling process, prolonged for 20 hours, brings about a decrease in the magnetic cross section of the FeSiB powders, with respect to the as-cast ribbon. Measurements of the saturation magnetization of the samples by SQUID magnetometer fully support this description.
As the Mössbauer analysis suggest that the magnetic moment per Fe atom remains constant, to discuss these results we resort to the peculiar magnetic properties of the ball milled ribbons. Indeed, the magnetic properties of the ball milled samples were explained in terms of the existence of a magnetic phase showing spin-glass like properties (speromagnetism), dispersed into the ferromagnetic FeSiB matrix and coexisting with the bcc Fe nanocrystallites. Hence, although ferromagnetism predominates at T = 300 K, we propose that antiferromagnetic interactions and imperfect magnetic moments alignment persist in the regions showing spin-glass like behavior at low temperature, which causes the decrease in the magnetic cross section.
[1] L. Del Bianco, F. Spizzo, M. Tamisari, E. Bonetti, F. Ronconi, D. Fiorani, J. Phys.: Condens. Matter 22 (2010) 296010
Concentration dependence of interclusters interaction role in sputtered Fe-Ag nanogranular samples
No full textAn ideal nanogranular sample is an ensemble of independent nanosized magnetic (M) particles dispersed in a non magnetic (NM) matrix. The magnetic particles can be seen as large magnetic moments; in case their dynamics is affected just by thermal energy contributions, the whole system is referred to as a superparamagnet (SP) [1]. Real systems, due to growth conditions, often differ from this picture and interparticle magnetic interactions, e.g. dipolar or exchange ones, are one of the main sources of deviation from the ideal SP behaviour.
If M and NM metallic species are used, the samples display a spin-dependent electronic resistivity that remarkably decreases if an external magnetic field, H, is applied, i.e. they show the so called giant magnetoresistance (GMR) [1]. GMR is ascribable to the magnetic ordering effect induced by H, so the higher the degree of disorder at zero field the larger the GMR effect. Interactions induce correlations among the magnetic moments, in particular when H is small, viz. an higher degree of order. As a consequence, the overall resistivity change is reduced. It’s therefore important to study interactions effects when H ≈ 0.
In this work, we have studied dc-cosputtered nanogranular FexAg100-x thin films with a volume Fe concentration, x, varying from 10 up to 30 as measured by Rutherford Backscattering Spectrometry. At room temperature, for x < 20 a SP behaviour is observed. A recently devel-oped model [2], based on the simultaneous investigation of magnetic and GMR data, has pointed out that magnetic interactions affect samples dynamics for all concentrations. The correlation length, λ, is always larger than particles average distance and increases with tem-perature and x [2]. These systems are therefore suitable to study interparticle interactions and their effect on low-field magnetic configuration. The investigation was performed with sus-ceptibility measurements in field-cooled (FC) and zero-field-cooled (ZFC) configuration, re-laxation and Mössbauer measurements; X-Ray diffraction data were collected, as well.
When x < 18, FC and ZFC data display the typical lambda shape but, for temperatures lower than the blocking temperature, FC signal displays an unexpected maximum at about 40 K. This effect is less and less pronounced as x increases and it vanishes starting from x = 18. The comparison between ZFC/FC curves and magnetic relaxation data confirms that interparticle interactions have a remarkable influence on low-field dynamics and this finding is supported by low-temperature Mössbauer measurements. However, the kind of interactions seems to change with x. Indeed, for low Fe concentration the samples possibly behave like a cluster-glass system, where frustrated interactions produce the FC maximum. Whilst approaching x ≈ 18, the interactions turn to dipolar and for higher concentrations the samples approach a re-entrant ferromagnetic behaviour. Eventually, X-Ray diffraction data suggest that the whole transition is related to the effects induced on samples structure/morphology by the change in iron concentration.
[1] A. E. Berkowitz et al, Phys. Rev. Lett. 68 (1992) 3745
[2] P. Allia, M. Coisson, F. Spizzo, P. Tiberto, and F. Vinai, Phys. Rev. B 73 (2006) 05440
Provenance of obsidians from the neolithic archaeological site of San Martino Spadafora (Messina - Italy) by Mössbauer spectroscopy
No full textIn the San Martino of Spadafora area (Messina-Italy), during the proceedings of the third line of the pipeline Eni-Snam, a Neolithic site was found, related to two diverse phases of occupation: Ancient Neolithic Age (of stentinelliana culture) and Late Neolithic (of Diana culture). Almost all lithic artifacts discovered in that site are made of obsidian (Neolithic black gold), a volcanic rock of dark color very rich of SiO2, used during the neolithic age to realize tools and objects. Due to the vicinity to the Aeolian Islands, the obsidians may came directly from Lipari; however, the chemical analysis point out slight differences in composition with respect to the Lipari outcrops. Therefore, a compositional comparison was performed, to see if the discovered obsidians have an extra territorial origin or if the differences are ascribable to lavic flows covered by successive eruptions. This allows to check whether San Martino site is part of a complex exchange network that encouraged the arrival of raw material from afar. The structural and compositional characteristics that made interesting to exchange high value obsidians, not only for their use but also for their symbolic and aesthetic value, may be highlighted, as well.
We investigated the composition and provenance of different obsidian samples, S1 – S12, obtained from obsidian artifacts resulting from industry lithic chipped excavations. They were analyzed by transmission Mössbauer spectroscopy measurements performed at room temperature with a 57Co in Rh source; the spectrometer was calibrated using an α-Fe foil.
The typical shape of the spectrum consists of an asymmetrical doublet. The presence of sextet subspectra, possibly ascribable to the presence of magnetite and/or hematite contributions [1,2], was not observed. The experimental spectra were simulated using three different quadrupole doublets (QD) as in obsidians the presence of two Fe2+ sites and one Fe3+ site is found [1,2,3]. Symmetrical quadrupole doublets were used, as a preferential texture is not expected [4]. The possible presence of QD distributions was considered, as well, but that did not improve the fitting quality, so each of the Fe ions chemical/structural environment seems to be rather uniformly reproduced within the sample. In this contribution, the results of the analysis performed on the obsidian samples will be presented and compared with the results obtained from obsidians coming from Aeolian islands and from other obsidian sites of the Mediterranean area. In particular, the Mössbauer data collected on S1- S12 display a negligible spread, indicating a common source for what concerns the artifacts from San Martino site.
[1] A. Bustamante, M. Delgado, M. R. Lattini, A. V. Bellido, Hyperfine Interactions 175 (2007) 43.
[2] M. Duttine, R. B. Scorzelli, G. Popeau, A. Bustamante, A. V. Bellido, M. R. Lattini, N. Guillaume Gentil, Hyperfine Interactions 175 (2007) 85.
[3] R. B. Scorzelli et al., C. R. Acad. Sci. Paris 332 (2001) 769.
[4] U. Gonser, Mössbauer Spectroscopy, Springer-Verlag (1975
Tailoring the exchange bias of Ni/NiO nanogranular samples by the structure control
No full textThe exchange bias (EB) effect has been studied in Ni/NiO nanogranular samples obtained by annealing in H2, at selected temperatures (200≤Tann≤300 °C), NiO powder previously milled for 5, 10, 20 and 30 h. Both the as-milled NiO powders and the Ni/NiO samples have been analyzed by X-ray diffraction and the exchange bias properties have been investigated in the 5–200 K temperature range. The structure and the composition of the Ni/NiO samples can be satisfactorily controlled during the synthesis procedure by varying both Tann and the milling time of the precursor NiO powders. In particular, by increasing this last parameter, the mean grain size of the NiO phase reduces down to the final value of 16 nm and the microstrain increases, which is consistent with an enhancement of the structural disorder. The structure of the milled NiO matrix strongly affects the process of nucleation and growth of the Ni nanocrystallites induced by the H2 treatments, so that, Tann being equal, the amount and the mean grain size DNi of the Ni phase vary substantially in samples having different milling times. Such features of the Ni phase determine the extent of the Ni/NiO interface and consequently the magnitude of the exchange field Hex: the highest value (not, vert, similar940 Oe) has been measured at T=5 K in a sample containing not, vert, similar7 wt% Ni and with DNi=19 nm. However, in Ni/NiO samples with very different structural characteristics and different values of Hex at T=5 K, the EB effect vanishes at the same temperature (not, vert, similar200 K) and the same thermal dependence of Hex is observed. We consider that the evolution of the EB effect with temperature is ultimately determined by the microstructure of the Ni/NiO interface, which cannot be substantially modified by changing the synthesis parameters, milling time and Tann
ESPERIENZE DI DIDATTICA DELLA FISICA IN DIVERSI LIVELLI DEL SISTEMA EDUCATIVO
No full textLa crescente partecipazione delle persone a eventi di divulgazione scientifica, i progetti sostenuti dal MIUR (http://www.progetto laureescientifiche.eu; http://hubmiur.pubblica.istruzione.it/web/ricerca/dif fusione) per promuovere l’insegnamento delle materie STEM (Science, Technology, Engineering, Mathematics) nei diversi livelli del sistema educativo e l’introduzione di argomenti di fisica moderna e contemporanea nelle programmazioni di alcuni Licei (http://www.indire.it/ lucabas/lkmw_file /licei2010///indicazioni_nuovo_impaginato/_Liceo%20scientifico%20opzione %20Scienze%20Applicate .pdf) hanno contribuito, in molti casi, a rafforzare il legame tra scuola, Università e centri di ricerca. Questo legame si è concretizzato nell’istituzione di attività dedicate in cui è stato necessario impiegare metodologie comunicative e didattiche sempre più efficaci. L’articolo presenta lo spettro delle attività realizzate negli ultimi tre anni, a partire dall’anno accademico 2015/2016, dall’Università di Ferrara e dall’Istituto Nazionale di Fisica Nucleare per la comunicazione e la didattica della fisica. Verranno analizzati alcuni casi studio che si differenziano per contenuti, destinatari, contesti e strategie didattiche. In particolare verranno prese in esame le attività dedicate all’insegnamento della fisica moderna e contemporanea condotte con gli allievi delle scuole secondarie di II grado (http://www.fe. infn.it/ orientamento_fisica/courses/laboratori-di-fisica-moderna/), i laboratori scientifici hands-on realizzati con gli allievi delle scuole primarie e un’esperienza di didattica museale inserita in una mostra di storia della fisica dedicata al binomio arte-scienza (www.fe.infn.it/fisicaeme tafisica). Il primo è un caso di out-of-school learning in cui gli allievi delle scuole secondarie di II grado lavorano in gruppo a fianco dei ricercatori, per realizzare un esperimento di fisica moderna, e una volta tornati in classe devono relazionare ai pari quanto svolto e appreso durante l’attività laboratoriale. Nel secondo caso, gli allievi delle scuole primarie sono chiamati a condurre esperimenti guidati per acquisire familiarità con il metodo scientifico, investigando alcuni fenomeni fisici presenti nel quotidiano. Nell’ultimo caso, alcune scoperte della fisica moderna vengono introdotte dalla corrispondenza tra opere d’arte e strumenti scientifici e collegate alla storia di Ferrara
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