Alessia Cemmi

Comparison of high surface Pt/C catalysts by cyclic voltammetry

A detailed procedure for comparing high surface Pt/C catalysts was pointed out. Platinum dispersed carbon was prepared from carbonaceous material and chloroplatinic acid solution using sodium formiate. The real platinum metal surface area was evaluated by cyclic voltammetry on a thin porous coated disk electrode. The performance of catalysts prepared in our laboratory were similar to those of a well-known commercial one. The results show that electrochemical active surface (EAS) measurement is strongly influenced by the gas diffusion electrode (GDE) preparative method. It is only by means of a well-defined preparative procedure and data analysis that it is possible to use this technique to compare different carbon supported platinum catalysts.

Interaction between reinforce carbon black and polymeric matrix for industrial applications

Abstract In this work the interaction between the carbon black reinforcement agent and a polymeric rubber matrix is investigated. Chemical activity of carbon black powder samples was enhanced using γ radiation in the dose range 168–1000 kGy and the radiation induced free radical concentration was investigated by EPR measurements. Activated powder samples were mixed with rubber and the bound rubber values of obtained compounds was measured by TG analysis. A comparison between EPR and bound rubber data shows that the greatest filler–polymer chemical interaction corresponds to the highest radiation induced free radical concentration.

Broadband infrared luminescence in γ-ray irradiated bismuth borosilicate glasses

The influence of γ-ray irradiation on the optical properties of Bi(2)O(3)-B(2)O(3)-SiO(2) glass has been investigated. Broadband infrared (IR) emission at 1310 nm with a FWHM over 200 nm is observed in the γ-ray irradiated glass. The IR luminescence depends on the γ-ray irradiation dose and the concentration of Bi(2)O(3). The thermal stability of the γ-ray irradiated IR luminescence center is studied, and the origin of the IR luminescence center has been suggested.

Colour centres induced by γ irradiation in scintillating glassy matrices for middle and low energy physics experiments

Abstract The effect of 60 Co irradiation (1–250 Gy) on the optical properties of selected phosphate and silicate-based scintillating glasses was investigated by transmission measurements performed at room temperature in the UV–Visible part of the spectra. Samples doped with rare-earth ions (Ce 3+ , Tb 3+ as emission centres, and Gd 3+ as an additional constituent in certain compositions) have been studied. The results are discussed taking into account the possible influence of different glass compositions on radiation induced colour centres.

Enhanced and shortened Mn 2+ emissions by Cu + co-doping in borosilicate glasses for W-LEDs

A novel pair of transition metal ions Cu+, Mn2+ is co-doped in borosilicate glasses. Both copper and manganese ions exist in lower valence states (Cu+, Mn2+) in the as-prepared glasses. Around 5-time enhanced Mn2+ emission under the UV excitation is observed, which, as demonstrated by excitation spectra and emission decay curves, is due to an energy transfer from Cu+ ions resulting in greatly increased absorption of Mn2+ ions in the UV region, and relaxation on doubly-forbidden transition of Mn2+ leading to the much shortened Mn2+ emission lifetime from millisecond to microsecond level. Besides, a composite white emission is generated by combining the blue-green part from Cu+ ions with the green-red part from Mn2+ ions and it can be effectively tuned from cold to warm by adjusting host glass composition and altering excitation wavelength. Relevant mechanisms are discussed.

In-phantom dose mapping in neutron capture therapy by means of solid state detectors

Abstract A method has been developed, based on thermoluminescent dosimeters and alanine, aimed at measuring the absorbed dose in tissue-equivalent phantoms exposed to an epithermal neutron beam suitable for neutron capture therapy (NCT), separating the contributions due to the various secondary radiations generated by neutrons. Exposures have been made at the TAPIRO nuclear reactor (ENEA, Italy), in the epithermal column properly designed and set up for experiments on boron NCT.

Radiation hardness test of un-doped CsI crystals and Silicon Photomultipliers for the Mu2e calorimeter

The Mu2e calorimeter is composed by 1400 un-doped CsI crystals coupled to large area UV extended Silicon Photomultipliers arranged in two annular disks. This calorimeter has to provide precise information on energy, timing and position. It should also be fast enough to handle the high rate background and it must operate and survive in a high radiation environment. Simulation studies estimated that, in the hottest regions, each crystal will absorb a dose of 300 Gy and will be exposed to a neutron fluency of 6 x 10^{11} n/cm^2 in 3 years of running. Test of un-doped CsI crystals irradiated up to 900 Gy and to a neutron fluency up to 9 x 10^{11} n/cm^2 have been performed at CALLIOPE and FNG ENEA facilities in Italy. We present our study on the variation of light yield (LY) and longitudinal response uniformity (LRU) of these crystals after irradiation. The ionization dose does not modify LRU while a 20% reduction in LY is observed at 900 Gy. Similarly, the neutron flux causes an acceptable LY deterioration (<15%). A neutron irradiation test on different types of SIPMs (two different array models from Hamamatsu and one from FBK) have also been carried out by measuring the variation of the leakage current and the charge response to an ultraviolet led. We concluded that, in the experiment, we will need to cool down the SIPMs to 0 C reduce the leakage current to an acceptable level.

Irradiation study of UV Silicon Photomultipliers for the Mu2e Calorimeter

The Mu2e calorimeter is composed of 1400 un-doped CsI crystals, coupled to large area UV extended Silicon Photomultipliers (SiPMs), arranged in two annular disks. This calorimeter has to provide precise information on energy, timing and position resolutions. It should also be fast enough to handle the high rate background and it must operate and survive in the high radiation environment. Simulation studies estimated that, in the highest irradiated regions, each photo-sensor will absorb a dose of 20 krad and will be exposed to a neutron fluency of 5.5×1011n1 MeV/cm2 in three years of running, with a safety factor of 3 included. At the end of 2015, we have concluded an irradiation campaign at the Frascati Neutron Generator (FNG, Frascati, Italy) measuring the response of two different 16 array models from Hamamatsu, which differ for the protection windows and a SiPM from FBK. In 2016, we have carried out two additional irradiation campaigns with neutrons and photons at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR, Dresden, Germany) and at the Calliope gamma irradiation facility at ENEA-Casaccia, respectively. A negligible increment of the leakage current and no gain change have been observed with the dose irradiation. On the other hand, at the end of the neutron irradiation, the gain does not show large changes whilst the leakage current increases by around a factor of 2000. In these conditions, the too high leakage current makes problematic to bias the SiPMs, thus requiring to cool them down to a running temperature of ~0oC.

Radiation activities and application of ionizing radiation on cultural heritage at ENEA Calliope gamma facility (Casaccia R.C., Rome, Italy)

Abstract Since the 1980s, research and qualification activities are being carried out at the 60Co gamma Calliope plant, a pool-type irradiation facility located at the Research Centre ENEA-Casaccia (Rome, Italy). The Calliope facility is deeply involved in radiation processing research and on the evaluation and characterization of the effects induced by gamma radiation on materials for different applications (crystals, glasses, optical fibres, polymers and biological systems) and on devices to be used in hostile radiation environment such as nuclear plants, aerospace and high energy physics experiments. All the activities are carried out in the framework of international projects and collaboration with industries and research institutions. In the present work, particular attention will be paid to the cultural heritage activities performed at the Calliope facility, focused on two different aspects: (a) conservation and preservation by bio-deteriogen eradication in archived materials, and (b) consolidation and protection by degraded wooden and stone porous artefacts consolidation.

PEFC electrodes based on carbon black supporting electrocrystallised nanostructured Pt particles

This work is focused on the study of electro-crystallisation of Pt nanostructured particles used as catalyst on carbon black support for polymer electrolyte fuel cells electrodes. Electrochemical single and multiple pulse galvanostatic depositions have been applied defining the best operational parameters leading to a highly nanostructured electro-catalysts morphology. Electrochemical measurements such as cyclic voltammetries have been carried out in order to determine the electrochemical active surface together with morphological analysis by means of scanning electron microscopy. The influence of electro-deposition parameters on the Pt loading have been studied and optimised. The investigated materials have been then characterised by means of polarisation curves. The electrodeposited catalyst cathodes present performances and maximum specific power density values similar or better than those of standard E-TEK electrode, prepared by conventional powder-type technique. These results strongly encourage the implementation of cathodes obtained by electro-deposition in a real-world device.