1,720,980 research outputs found
Il condominio fotovoltaico: un'opportunità economicamente sostenibile del fotovoltaico per le amministrazioni locali nell'ambito degli obiettivi previsti dal Protocollo di Kyoto
No full textORGANIC SEMICONDUCTING CRYSTALS AS ROOM TEMPERATURE RADIATION DETECTORSAstroparticle, Particle, Space Physics and Detectors for Physics Applications
No full textWe report on the use of organic semiconducting single crystals (OSSCs) as direct ionizing radiation detectors that directly convert the X-ray photons into an electrical signal, thanks to their stability, good transport properties and large interaction volume. X-ray detectors, based on low-cost solution-grown OSSCs are here shown to operate at room temperature, providing a stable linear response with increasing dose rate in atmosphere and in radiation-hard environment. The intrinsic conversion of ionizing radiation within the crystals allowed one to fabricate all-organic optically transparent devices, indicating OSSCs as very promising candidates for a novel generation of low-cost, room temperature radiation detector
Novel Green Poly (Lactic Acid) – Silica Aerogel Composites for Thermal Insulation
No full textThe development of biodegradable polymers is showcased as one of the most effectiveinnovations in the polymer industry for addressing environmental issues,[1] and poly (lactic acid)(PLA) is one of the most promising environmentally friendly biodegradablepolymers, due to itseasy availability and favorable processability.[2] In fact, PLA is a thermoplastic bio-basedpolymer, produced from lactic acid via fermentation of agricultural products such as corn,cornstarch, or sugarcane.[2,3] It shows a relatively low thermal conductivity of 0.193 Wm−1K−1at ambient temperature. It also has a relatively light weight (density of 1.24 g/ml), a glass transitiontemperature of around 55–60°C and a low production cost. However, being derived from lacticacid, it is easily biodegradable, especially at high temperatures and high moisture levels, whichlimits its practical applications, confined until now mainly in the fields of filaments for 3D printingand disposable tableware and cutlery, even though applications in biomedicine (as a scaffoldmaterial for tissue engineering, in cosmetics or biomedical implants) are extensively studied andare growingly commercialized.[2,4]Silica aerogel is the most common type of aerogel.[5,6] Due to its unique properties, such as highspecific surface area (surface-to-volume ratio) (of 901m2/g), ultra-low density (0.365g/cm3) andhigh porosity (up to 99%+), it has received significant attention over the last few decades. One ofits main properties is a very low thermal conductivity, down to 0.013 Wm−1K−1 at roomtemperature and atmospheric pressure, with a further decrease to 0.010 Wm−1K−1 under vacuumat 300 K.[7] Being essentially a highly porous glass, it is also fully recyclable. In practicalapplications, it is usually treated to become hydrophobic in order to avoid the entrance of waterin its nanometric pores, which would rapidly decrease its thermal insulation properties.We present here preliminary studies over novel green composites prepared using PLA as thematrix and hydrophobized silica aerogel (SA) as the filler. In order to increase the resistance ofPLA towards atmospherical agents (i.e., rain and humidity) and temperatures, we explored thepossibility to crosslink the PLA chains using carbodiimidic compounds (CDI), which cause acontrollable crosslinking of the polymer chains, providing better mechanical properties andthermal stability, as also demonstrated by other researchers.[7] We hence prepared a ternarysolution (PLA + liquid solvent + SA), exploring different types of solvents (for example THF,Dioxane or DCM), different PLA/SA ratios and different amounts of CDI, from which all-solidsamples of appropriate sizes were produced. The samples have been characterized via FT-IR inorder to identify possible interactions between the hydrophobized silica functional groups and thePLA chains and to measure their thermal conductivities. The so-obtained results are presented and discussed
Polarized Infrared Studies on Charge Transport in 4-Hydroxycyanobenzene Single Crystals
No full text4-Hydroxycyanobenzene (4HCB) semiconducting single crystals have been probed by polarized IR radiation under various
conditions. Linearly polarized IR spectroscopy was found to be sufficient to identify the main crystal axes, provided that
crystallographic and electrical analyses have been carried out at least once on the crystal. Moreover, a 2D anisotropic hydrogen
bonding degree, which results to be higher along the axis a (one of the two planar axes), has been found. Static electrical polarization
induces a rather large and anisotropic rotation of the 3D electric dipole vector of the crystal (pB), which increases its component along
the axis a and decreases the one along b (the other planar axis). When the crystal is probed under actual charge transport conditions
in a field effect transistor (FET) structure, the IR radiation is more effectively screened along axis a (which presents the highest
carrier mobility) than along axis b
Solution-grown, macroscopic organic single crystals exhibiting three-dimensional anisotropic charge transport properties
No full textSolid State Organic X-Ray Detectors Based on Rubrene Single Crystals
No full textIn this work we report the results on the investigation of rubrene single crystals as solid state direct ionizing radiation detectors. With the aim to understand how electrical properties,
and in particular a large charge carrier mobility, affect the radiation detection process in organic semiconducting single crystals, we compare the detection performance of rubrene-based devices with those of 1,5-dinitronaphthalene (DNN)-based ones. DNN has been recently proven to be a stable and reliable X-ray direct
detector, operating at very low voltages, in air and at room temperature, with a carrier mobility values about two orders of magnitude lower than rubrene. We demonstrate here that the large charge carrier mobility of rubrene crystals does not result in a better X-rays detection performance. In fact, rubrene devices are shown to be less performing than DNN as detectors, with lower sensitivity to X-rays, poorer stability and reproducibility, and longer rise and decay times of the signal
Radiation Detectors: Ionizing Radiation Detectors Based on Solution‐Grown Organic Single Crystals (Adv. Funct. Mater. 14/2016)
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