217 research outputs found
Borges: imágenes de una expansión estética
No full textFil: Minguzzi, Armando V. Universidad de Buenos Aires; Argentina.12 ref
Borges: imágenes de una expansión estética
No full textFil: Minguzzi, Armando V. Universidad de Buenos Aires; Argentina.12 ref
Electroreductive dehalogenation: crossroads for waste detoxification and conversion to valued compounds
No full textThe environmental impact of halogenated organic compounds is bound to their present (and past) use in a wide variety of industrial and civil applications, thanks to the wide spectrum of their physical and chemical properties, which, in turn, are at the basis of the assessed risks connected with their persistency and rapid dissemination in soils, water- and air-streams.
An integrated approach for environmental remediation and protection requests both long-term activities devoted to eradicate the risks, and immediate actions to drastically abate the toxicity of the actual wastes while controlling the treatment costs.
In this complex context, the electrochemical technologies can play a key role in terms not only of detoxification efficiency, but also of energy/cost saving and earning potentialities.
The exploitation of these technologies for the electroreductive (hydro)dehalogenation of organic halides is discussed in terms of the recent advances [1-5] on the preparation of cathode materials, reactor design, and investigation tools/methodologies (e.g. C-ME and FEXRAV [3,6]) purportedly developed to characterize both the reaction pathways and the process performances.
[1] O. Lugaresi, H. Encontre, C. Locatelli, A. Minguzzi, A. Vertova, S. Rondinini, Ch.
Comninellis, Electrochem. Commun. submitted
[2] O. V. Klymenko, O. Buriez, E. Labbè, D.-P. Zhan, S. Rondinini, Z.-Q. Tian, I. Svir,
Ch. Amatore, ChemElectroChem 2014, 1, 227-240
[3] A. Minguzzi, C. Locatelli, O. Lugaresi, A. Vertova, S. Rondinini, Electrochim.
Acta 2013, 114, 637-642
[4] O. Lugaresi, A Minguzzi, C Locatelli, A. Vertova, S. Rondinini, Ch. Amatore,
Electrocatalysis 2013, 4, 353-357
[5] A. Minguzzi, O. Lugaresi, G. Aricci, S. Rondinini, A. Vertova, Electrochem.
Commun. 2012, 22, 25-28
[6] A. Minguzzi, O. Lugaresi, C. Locatelli, S. Rondinini, F. D’Acapito, E. Achilli, P.
Ghigna, Anal. Chem. 2013, 85, 7009−
Il Medioevo
No full textsi analizzano i materiali dmedioevali e post medioevali conservati nel museo di Castelbolognese e provenienti da scavi cittadin
Onde di pietra. Il motivo a pelte subacquee nei mosaici pavimentali altoadriatici (V-XII secc)
No full textViene trattato l'evoluzione e la diffusione in area altoadriatica del motivo a "pelte subacquee" utilizzato nel repertorio decorativo dei mosaici pavimentali, dall'introduzione in area ravennate nel V secolo fino alle ultime testimonianze nei pavimenti delle chiese veneziane di XII secol
La Fontana della Pigna di Rimini- Studio dei materiali e stato conservativo
No full textNel presente lavoro viene analizzata nel dettaglio la Fontana della Pigna, da sempre considerata simbolo della città di Rimini, non solo dal punto di vista storico ed architettonico, ma soprattutto dal punto di vista materico e conservativo.
A tal fine sono stati caratterizzati, mediante studi mineralogici e petrografici, i materiali che la costituiscono e sono state formulate ipotesi relative alla loro provenienza. Sono state inoltre collegate le modifiche apportate alla Fontana della Pigna durante i secoli con le vicende storiche della città di Rimini.
Le analisi minero-petrografiche effettuate hanno reso possibile l’identificazione e la classificazione dei vari litotipi individuati nei vari prospetti della fontana.
Sono state individuate le seguenti tipologie lapidee provenienti da vari bacini estrattivi:
Pietra d’Istria (di due tipologie diverse) e Pietra di Aurisina (di due tipologie diverse) dalla penisola istriana e dalle coste dalmate
Pietra di Verona dal Veronese
Pietra di San Marino dalla Repubblica di San Marino
Marmo di Candoglia dalla Lombardia.
L’analisi autoptica dello stato conservativo eseguito sulla fontana, ha permesso di rilevare morfologie di degrado sia di natura biologica (presenza di vegetazione, patine biologiche dovute ad alghe verdi e ad attacco lichenico) che chimico-fisica (incrostazione, esfoliazione, fratturazione, macchie di ruggine e scagliatura) distinguibili per la diversa cromia con la pietra sottostante.
Tali fenomeni di deterioramento rientrano tra quelli più generali, ampiamente investigati da ricerche condotte su edifici e sculture realizzate con gli stessi litotipi.
Conclusioni
Alla luce dei risultati presentati in questo lavoro si può affermare che la caratterizzazione mineralogico-petrografica della Fontana della Pigna di Rimini si è rivelata molto importante per approfondire la conoscenza della storia materica del monumento. Sono state acquisite, inoltre, indicazioni sullo stato di degrado preliminari ad un corretto intervento di manutenzione.
In particolare lo studio ha definito i materiali impiegati, l’area geologica e geografica di provenienza utile per eventuali sostituzioni o integrazioni, rivedendo, talora, affermazioni errate venute a consolidarsi nel tempo
Study of photoelectrochemical behavior of copper oxides based materials using X-ray absorption spectroscopy
No full textThe use of sunlight to convert water into fuel is very attractive and ambitious since H2 is considered to be the energy carrier of the future thanks to its high mass energy density and its environmental friendliness [1,2]. Copper oxides-based photocathodes are attractive for their absorption in the visible range, low cost, high abundance and easy synthetic protocols as well as high photoactivity [3,4].
Two p-type semiconducting copper based materials has been prepared, characterized and tested as a photocathode for H2 production: CuO and Cu2O. The first one is prepared by thermal treatment of nanocrystalline CuI, which shows high efficiency in light conversion and interesting self-protection properties [5].
Cu2O instead was prepared by electrochemical deposition from a lactate-stabilized Cu++ bath [3]. Viceversa the main drawback of Cu(I) oxide is its lack of stability during photoelectrochemical conditions. For this material the influence of a metallic underlayer (Au, Cu) between the semiconductor itself and the FTO support was studied, together with the presence of a small load of Pt catalyst.
In-situ and in-operando techniques like X-ray absorption near edge structure (XANES), Extended X-Ray Absorption Fine Structure (EXAFS) and Fixed Energy X-ray Absorption Voltammetry (FEXRAV) [6] allow us to better understanding materials behavior. We observe changes in copper oxidation states upon light and/ or applied potential. Moreover, the role of methanol as hole-scavenger during photoelectrochemical experiment has been studied. FEXRAV measurements allow following the material degradation processes and defining the stability windows. With differential light and dark XANES spectra, we investigated the local changes in electronic structure upon spectroelectrochemical conditions. These results will allow us obtaining more stable system for photoelectrochemical hydrogen production.
References
[1] G. Centi, S. Perathoner, ChemSusChem. 3 (2010) 195–208.
[2] F. Malara, A. Minguzzi, M. Marelli, S. Morandi, R. Psaro, V. Dal Santo, A. Naldoni, ACS Catal. 5 (2015) 5292–5300.
[3] A. Paracchino, V. Laporte, K. Sivula, M. Grätzel, E. Thimsen, Nat. Mater. 10 (2011) 456–461.
[4] C. Li, T. Hisatomi, O. Watanabe, M. Nakabayashi, N. Shibata, K. Domen, J.-J. Delaunay, Energy Environ. Sci. 8 (2015) 1493–1500.
[5] T. Baran, S. Wojtyła, C. Lenardi, P. Ghigna, E. Achilli, S. Rondinini, A. Minguzzi, ACS Appl. Mater. Interfaces. (submitted).
[6] A. Minguzzi, O. Lugaresi, C. Locatelli, S. Rondinini, F. D’Acapito, E. Achilli. P. Ghigna. Anal. Chem. (2013), 85, 7009-7013
How many futures on Finsler spacetime?
No full textSome recent results by the author on the geometry and dynamics of Finsler spacetimes are reviewed. It is shown that in Finslerian generalizations of general relativity the number of predicted lightlike cones is two, one past and one future, as in general relativity. This result is non-trivial as it can fail, for instance, in spacetime dimension two. It is also shown that suitable versions of the reverse Cauchy-Schwarz and reverse triangle inequalities hold on Finsler spacetimes. Finally, a long standing problem of Finslerian gravity concerns the development of dynamical equations which imply a conservation law. We make some progress following a recent proposal by the author according to which physical Finsler spacetimes have ane sphere indicatrices of hyperbolic type
THE COMBINED USE OF THE CAVITY-MICROELECTRODE AND THE SCANNING ELECTROCHEMICAL MICROSCOPE
No full textIn this communication we introduce the use of the cavity-microelectrode (C-ME) as a versatile SECM tip. The C-ME consists of a recessed disk tip that can host a known amount of a desired finely dispersed material [1-3].
Adopting a C-ME as SECM tip opens the access to an almost infinite variety of tip materials, for which the corresponding micro-wires needed to prepare the tips are not available.
The first part of the work is therefore devoted to verify the effectiveness of a filled C-ME as an SECM tip, e.g. by evaluating the approach curves.
The combined C-ME_SECM is then adopted for screening materials as catalysts for energetic applications.
[1] Cachet-Vivier, C.; Vivier, V.; Cha, C. S.; Nedelec, J.-Y.; Yu, L. T. Electrochim. Acta 2001, 47, 181.
[2] Locatelli, C.; Minguzzi, A.; Cava, P.; Vertova, A.; Rondinini S. Anal. Chem. 2011, 83, 2819
[3] Minguzzi, A.; Locatelli, C.; Cappelletti, G.; Bianchi, C. L.; Vertova, A.; Ardizzone, S.; Rondinini, S. J. Mater. Chem 2012, 22, 889
Electrodeposited iridium oxide as studied by tip/substrate steady state voltammetry
No full textElectrodeposited iridium oxide as studied by tip/substrate steady state voltammetry
Alessandro Minguzzi, Cristina Locatelli, Alberto Vertova, Sandra Rondinini
Dipartimento di Chimica Fisica ed Elettrochimica, Università degli Studi di Milano, via Golgi 19, 20133, Milan, Italy
[email protected]
Iridium oxide is well known for its wide field of applications that range from electrocatalysis to electroanalysis, from electrochromism to neural stimulation.
In this work, the properties of electrodeposited iridium oxide films (EIROFs) have been studied by scanning electrochemical microscopy (SECM) in the feedback mode by means of the so-called tip/substrate (T/S) voltammetry under steady state conditions.
This SECM mode was intensively used in the past for the study of conducting polymers, as in reference [1].
The main purpose is the study of the reversible solid state-redox transitions that occur over iridium oxide in the potential range around 0.4 -1.4 V (RHE) and that are at the basis of all its applications. The transitions are observed and studied by combining (i) the use of suitable reversible redox couples and (ii) the effect of selecting different solution pHs for “shifting” the potential of the redox transitions themselves. In fact, the latter are pH dependent as evident from the common equation:
IrOx(OH)y + H+(solution) + e(oxide) = IrOx-(OH)y+ (1)
Moreover, being EIROFs highly hydrated films, protons are free to move in the whole electrode mass. In particular conditions, the transition includes a conversion semiconductor/conductor (like in the Ir(III)/Ir(IV) transition), that has a remarkable effect on the feedback current. The possible individuation of electrogenerated iridium species of different valencies via their reaction with one form of the redox couple, by analogy with a recent publication [2] on oxidized Pt, is also discussed.
[1] Lee, C.; Bard, A.J. Anal. Chem. 1990, 62, 1906
[2] Rodriguez Lopez, J.; Minguzzi, A.; Bard, A.J. J. Phys. Chem. C. 2010, 114, 18645
Acknowledgements: The financial contributions of PRIN 2008 – “Pt-free electrocatalysts for direct alcohol fuel cells.” 2008N7CYL5 and PUR-Università degli Studi di Milano (2009 – 2010) funds are gratefully acknowledged
- …
