93 research outputs found
Characterization of CdS sputtering deposition on low temperature pulsed electron deposition Cu(In,Ga)Se2 solar cells
No full textThe present paper reports the investigation of sputtered CdS as a buffer layer in Cu(In,Ga)Se-2 (CIGS) solar cells, for a dry-low temperature all in-line production technology method. The CdS film is deposited using radio-frequency magnetron sputtering in argon atmosphere. Compared to the well-known CdS grown by chemical bath deposition, the sputtering technology is feasible for the serial manufacturing process. The morphology and optical transmittance of CdS thin films are studied, as well as the CdS/CIGS interface and the solar cell characteristic. We observe that CdS layer deposited on glass is uniform and continuous with optical transmittance above 90% in the wavelengths range corresponding to the energy gap of the absorber. Current density-voltage (J-V) curve shows an overall efficiency of 6% affected by inhomogeneity at the CIGS/CdS interface. Sputtering deposition is not able to create a homogeneous layer on the absorber irregularities due its growth process. Moreover, Auger depth profile shows oxygen contamination at the interface, due to absorber surface oxidation. Within this work, the main crucial aspects of a new solar cell production technology, as well as related solutions, are reported
A spectroscopic investigation of pyrite nanoparticles for energy conversion and storage
No full textPyrite (FeS2) nanoparticles were produced by one-pot solvothermal synthesis, carried out at
room pressure and mild temperature (≈180 °C). With this approach the sulfide anion is cogenerated
during the synthesis. This method allows one to reduce the environmental impact,
because the solvent, Fe and S are the only reactants involved in the process. A thorough characterization
of the synthesis products was performed by SEM micromorphology, XRD, Diffuse
Reflectance Spectroscopy (DRS) and XAS spectroscopy (both in the XANES and EXAFS regions)
Discoloration of the smalt pigment: experimental studies and ab initio calculations
No full textSmalt is a blue pigment used by many European artists in mural and easel paintings, mainly in the period from the XV to XVIII century. It is a potassium glass where cobalt is added to the glassy matrix to get the blue hue. The pigment deteriorates with age, changing its colour from an intense blue to a grey-yellowish hue, causing severe problems in the conservation of the paintings. In this study a set of specimens of smalt dispersed in linseed oil was prepared and artificially aged to simulate the progressive deterioration of the pigment in a painting on canvas. The artificially aged smalt specimens were compared with some samples of naturally aged smalt taken from a banner painted at the end of XV century by Luca Signorelli, the “Baptism of Jesus”. A multi-technique approach, including SEM-EDX, spectro-colorimetry, X-ray absorption spectroscopy and ab initio calculations, was used to understand the progressive discoloration and to reveal its correlation with changes occurring in the pigment structure
Green synthesis of pyrite nanoparticles for energy conversion and storage: A spectroscopic investigation
No full textPyrite, FeS2, nanoparticles were obtained through a one-pot solvothermal synthesis, without surfactants, carried out at room pressure and mild temperature (≈180°C). A thorough characterization of the products was thus performed, including scanning-electron-microscope micromorphology, X-ray diffraction (XRD), diffuse reflectance spectroscopy, and X-ray absorption spectroscopy (both in the XANES and EXAFS regions).
Monophasic pyrite products are obtained as aggregates having an approximate dimension of few hundreds of nm. The Scherrer analysis of the Bragg reflections suggests that these aggregates are clusters of smaller units, having a mean size of ~25 nm. The XRD measurements point to a small but significant increase of the Fe–S bond distance (+1.7 %) with respect to reference data. The optical behavior of the pyrite nanoparticles is indistinguishable from that of the bulk pyrite.
These results point to the one-pot synthesis as an efficient and “green” way of obtaining pyrite nanoparticles exhibiting the same technological properties as bulk pyrite. Indeed these nanoparticles can be considered as a product viable for numerous technological applications in the solar-energy conversion and storage fields
Numerical Analysis of a Nozzle Guided Vane Filled With Lattice Structures
No full textGas turbines play a critical role in industries such as power generation and aviation. Additive manufacturing has emerged as a game-changing technology for gas turbine components, offering superior design flexibility and performance enhancements. The present work provides an overview of a multistep approach for integrating lattice structures into a specific gas turbine component, the Nozzle Guide Vane (NGV), using additive manufacturing technology. The first step involves a comprehensive assessment of lattice structures’ influence on the mechanical and thermal properties of the exposed part of NGV. Through computational simulations and experiments, an ideal lattice geometry is determined, optimizing structural integrity and heat transfer properties while minimizing volume usage. The second step sets the baseline performances of the current NGV system components, which were investigated and selected for additive manufacturing analysis. The third step focuses on the overall effect of additive manufacturing capabilities in the NGV system. The fourth and final step optimizes the additive manufacturing process for fabricating gas turbine components with lattice structures. Laser Powder Bed Fusion (L-PBF) technology, united with advanced Topological Optimization analyses, and high-temperature alloys were selected to withstand the demanding gas turbine operating conditions. This multistep approach represents a significant step forward in gas turbine technology, capitalizing the advanced mechanical applications as lattice designs and additive manufacturing, aiming in enhanced performance, reduced weight, and improved efficiency. These developments hold the potential to achieve more sustainable and cost-effective energy generation and transportation systems
The chemical environment of iron in mineral fibres. A combined X-ray absorption and Mössbauer spectroscopic study
No full textAlthough asbestos represents today one of the most harmful contaminant on Earth, in 72% of the countries worldwide only amphiboles are banned while controlled use of chrysotile is allowed. Uncertainty on the potential toxicity of chrysotile is due to the fact that the mechanisms by which mineral fibres induces cyto- and geno-toxic damage are still unclear. We have recently started a long term project aimed at the systematic investigation of the crystal-chemistry, bio-interaction and toxicity of the mineral fibres. This work presents a systematic structural investigation of iron in asbestos and erionite (considered the most relevant mineral fibres of social and/or economic-industrial importance) using synchrotron X-ray absorption and Mössbauer spectroscopy. In all investigated mineral fibres, iron in the bulk structure is found in octahedral sites and can be made available at the surface via fibre dissolution. We postulate that the amount of hydroxyl radicals released by the fibers depends, among other factors, upon their dissolution rate; in relation to this, a ranking of ability of asbestos fibres to generate hydroxyl radicals, resulting from available surface iron, is advanced: amosite> crocidolite≈chrysotile > anthophyllite > tremolite. Erionite, with a fairly high toxicity potential, contains only octahedrally coordinated Fe3+. Although it needs further experimental evidence, such available surface iron may be present as oxide nanoparticles coating and can be a direct cause of generation of hydroxyl radicals when such coating dissolves
A dual-readout cryogenic detector for double-beta decay: the CUPID-0 experiment
No full textA convincing observation of neutrino-less double beta decay (0DBD) relies on the possibility of operating high-energy resolution detectors in background-free conditions. Scintillating cryogenic calorimeters are one of the most promising tools to fulfill the requirements for a next-generation experiment. Several steps have been taken to demonstrate the maturity of this technique, starting from the successful experience of CUPID-0. The CUPID-0 experiment demonstrated the complete rejection of the dominant alpha background measuring the lowest counting rate in the region of interest for this technique. Furthermore, the most stringent limit on the Se-82 0DBD was established running 26 ZnSe crystals. In this contribution we present the final results of CUPID-0 including a detailed model of the background, the measurement of the 2DBD half-life and the evidence that this nuclear transition is single state dominated
CALDER: Cryogenic light detectors for background-free searches
No full textCALDER is a R&D project for the development of cryogenic light detectors with an active surface of 5x5cm2 and an energy resolution of 20 eV RMS for visible and UV photons. These devices can enhance the sensitivity of next generation large mass bolometric detectors for rare event searches, providing an active background rejection method based on particle discrimination. A CALDER detector is composed by a large area Si absorber substrate with superconducting kinetic inductance detectors (KIDs) deposited on it. The substrate converts the incoming light into athermal phonons, that are then sensed by the KIDs. KID technology combine fabrication simplicity with natural attitude to frequency-domain multiplexing, making it an ideal candidate for a large scale bolometric experiments. We will give an overview of the CALDER project and show the performances obtained with prototype detectors both in terms of energy resolution and efficiency
Phonon-Mediated KIDs as Light Detectors for Rare Event Search: The CALDER Project
No full textBackground suppression plays a crucial role in particle physics experiments searching for rare events, such as neutrinoless double beta decay and dark matter interactions. Bolometers, that are among the most competitive devices in this field, would largely benefit from the development of ultrasensitive light detectors, as the combined readout of the bolometric and light signals enables the particle identification. The CALDER collaboration is developing superconducting light detectors that will match the requirements of next generation experiments: noise lower than 20 eV, large active area (>20 cm ), wide temperature range of operation, high radiopurity, and ease in fabricating hundreds of channels. For this purpose, we are exploiting the excellent energy resolution and the natural multiplexed readout provided by kinetic inductance detectors (KIDs). KIDs have already demonstrated their potentiality as direct detectors of photons for different astrophysical applications. The aim of our project is to apply this technology in particle physics, using indirect detection. These devices can be operated in a phonon-mediated approach, in which KIDs are coupled to a large insulating substrates in order to increase the active surface from a few mm to 25 cm . We have already demonstrated the feasibility of a phonon-mediated KIDs-based light detectors, using aluminium sensors. These device reached a baseline sensitivity of around 80 eV with an overall efficiency of about 20%. Currently, we are testing new materials (e.g., Ti-Al and nonstoichiometric TiN) to enhance the sensitivity and reach the goal of our project. We present our results and the physical interpretation of the device behavior. Finally, we also discuss the impact of this project on the most advanced bolometric experiments searching for neutrinoless double beta decay and dark matter. © 2002-2011 IEEE
CALDER: The second-generation light detectors
No full textThe main aim of the cryogenic wide-area light detectors with excellent resolution project is the development of cryogenic light detectors with large active area (∼50 mm × 50 mm) and noise energy resolution smaller than 20-eV RMS. Such detectors will be used to discriminate the background in next generation large-mass bolometric experiments, such as cryogenic underground observatory for rare events. In this paper, we present the fabrication process of the phonon-mediated kinetic inductance detectors (KIDs). In the first part of the project, Al KIDs have been developed. Thin film Al (40 nm) were evaporated on high quality, high resistivity (>10 kΩ·cm) Si(1 0 0) wafers using a high vacuum electron beam evaporator. Detectors were patterned by direct-write Electron Beam Lithography (EBL) using positive tone resist AR-P 669.06. To improve the energy resolution of our detector, superconductors with higher kinetic inductance, such as the substoichiometric titanium nitride (TiNx), were developed. TiNxis deposited with reactive dc magnetron sputtering. Thus, the fabrication process is subtractive and consists of EBL patterning through negative tone resist AR-N 7700 and SF6etch using a Deep Reactive Ion Etching-Inductively Coupled Plasma. Critical temperature of TiNxsamples was measured using the 4-point probe geometry
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