A multi-technique approach to study the microstructural properties of tin-based transparent conductive oxides

Transparent conductive oxides (TCOs) are semiconductor-like materials that exhibit high electrical conductivity and high optical transparency combined. They are adopted in various applications ranging from gas sensors, to electrochromic windows, to photovoltaic cells. Indium-based TCOs represent the industry standard. Nevertheless, indium is among the less abundant elements in the earth crust and forecasts based on its current consumption envisage an urgent need to replace it. Tin-based TCOs are a promising alternative, since their opto- electronic characteristics mimic the ones of indium-based materials. This thesis aims to investigate the link between optoelectronic and microstructural properties of tin dioxide and zinc tin oxide (ZTO) with a composition Zn0.05Sn0.30O0.65 and their stability when submitted to thermal treatments. Indeed, lots of practi- cal applications require the TCO to operate in high temperature conditions. To conduct this study, a combination of analytical techniques, such as transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), X- ray diffraction (XRD), electron paramagnetic resonance (EPR) and differential scanning calorimetry (DSC) was employed. Amorphous SnO2 and ZTO were deposited by RF sputtering and annealed up to 1050°C in different atmospheres. The influence of annealing temperature and atmosphere were decoupled and led us to an in-depth comprehension of the mechanisms governing the optoelectronic properties of both materials. When annealed in air, between room temperature and 300°C, ZTO exhibits increased mobility and carrier concentration with respect to the as-deposited state. This increase, investigated with DSC, was ascribed to a structural relaxation that allows point defects to release electrons in conduction band. Between 300°C and 500°C atmospheric oxygen passivates oxygen vacancies, drastically decreasing the carrier concentration and therefore causing a large drop of the conductivity. EPR experiments allowed to ascribe the drop in conductivity to the decrease of carrier concentration, which occurs slightly before the phase change. At 570°C (and 930°C for the case of vacuum annealing) the phase change occurs and the ZTO crystallizes in the rutile form of SnO2. The material becomes completely insulating. When the temperature is increased to 1050°C, evaporation of zinc is observed. In order to improve the electrical conductivity of ZTO at high temperature, a doping strategy was implemented starting from DFT calculations conducted by a partner group, who screened among the entire periodic table, which elements are the best candidates to act as n-dopants for ZTO. Bromine and iodine were retained, since they were found to be the most energetically favorable to become substitutional defects for a tin site. An exploratory doping route is therefore presented and the treated samples analyzed with TEM, EDX and UV-VIS-IR spectroscopy. Finally, the structural properties of an indium-based TCO (zirconium-doped indium oxide) were investigated and used as a benchmark to propose a crystallization model for the tin-based, as well as the indium-based materials. The influence of pa- rameters such as the material thickness, annealing atmosphere and temperature and deposition pressure are discussed for both materials

Lumped model for the assessment of the thermal and mechanical response of LNG tanks exposed to fire

Fires may impact on liquefied natural gas (LNG) process and storage units causing severe damages and potential accident escalation. In the present work, a lumped model able to predict the thermal response of LNG tanks exposed to fire is presented. The model is based on a thermal nodes approach, solving heat and material balances on the equipment exposed to fire, contemplating boiling regime phenomena, heat-up and pressure build up. The model allowed obtaining key indications for the evaluation of the vessel resistance during fire exposure. The model was applied to reproduce the accident scenario occurred at Tivissa (Spain) in 2002 and applied to an industrial case study

Thermal hazard analysis of organic peroxides by adiabatic calorimetry

Organic peroxides are widely used in the chemical industry as initiators or curing agents for polymerization reactions. However, the use of peroxides presents an intrinsic hazard due to the presence of the highly unstable peroxy group which causes peroxides readily decompose. In present study, the thermal hazards of a selected organic peroxide, the benzoyl peroxide (BPO), were experimentally investigated by using adiabatic calorimetry. On the basis of experimental results, the thermal hazard parameters under adiabatic conditions were estimated. Preliminary data with respect to decomposition onset temperatures and decomposition heat were obtained by simultaneous TG-DSC-FTIR analysis. A Phi-Tec II adiabatic calorimeter was used to study the thermal decomposition of the selected peroxide. The experimental data obtained allowed the assessment of thermokinetic parameters. Decomposition products formed during the experimental runs were sampled and characterized by FTIR and gas chromatographic techniques. The results obtained in the present investigation could be useful for the adoption of inherently safer design in the manufacturing, handling, storage, and disposal of organic peroxides

Hazards and safety issues associated to the residual solid content in crude edible oil processing

The present work focuses on the hazards connected with edible oil refining during process and maintenance operations. A specific experimental protocol was set up in order to verify the possibility of having fire hazards connected with the unwanted residual solids which might accumulate on the bottom of storage tanks, due to sedimentation, or in process equipment, due to progressive fouling. The analysis of residual solid samples taken from an actual edible oil refinery allowed evaluating the possible formation of flammable mixtures or products during maintenance operations. Specific hazard indexes were defined in order to analyse two case studies which provided indications for the safety enhancement of process and maintenance operations

Efficacy of new class I medical device for actinic keratoses: a randomized controlled prospective study

AbstractBackground: The presence of Actinic Keratoses (AKs) represent the most important warning sign of subclinical ultraviolet radiation. Currently, the regular use of sunscreens is considered es..

New national and regional Annex I Habitat records: from #26 to #36

New Italian data on the distribution of the Annex I Habitats 1510*, 2130*, 2250*, 3180*, 3260, 5230*, 6410, 7140, 7220*, 9320 are reported in this contribution. Specifically, 14 new occurrences in Natura 2000 sites are presented and 20 new cells are added in the EEA 10 km × 10 km reference grid. The new data refer to the Italian administrative regions of Abruzzo, Apulia, Friuli Venezia Giulia, Liguria, Marche, Molise, Sardinia, Sicily, Tuscany and Umbria

Numerical study of pressure build-up in vertical tanks for cryogenic flammables storage

Large-scale installations for cryogenic fluid storages, such as liquefied natural gas (LNG) and ethylene are critical units in the framework of the chemical and petrochemical industries. Modelling the thermal performance of such installations is therefore a critical task to enhance the safety and effectiveness of operations. In the present work, Computational Fluid Dynamics (CFD) is used to investigate the pressurisation behaviour of cryogenic storage tanks by applying the Volume-Of-Fluid method and taking into account vaporization-condensation phenomena. The boundary conditions are estimated from a 1-dimensional model to solve the heat transfer through the tank insulation layers, eventually taking into account accidental damages. The tank CFD model is preliminary validated against small-scale experimental data obtained for cryogenic nitrogen and then extended to the simulation of an industrial cylindrical tank, whose volume is 100m3. The effect of fluid, i.e. ethylene and LNG (modelled as pure methane), filling level and possible insulation damage, on natural convection driving liquid stratification and ultimately tank pressurisation is analysed. Specific performance indexes are proposed to efficiently compare the different scenarios

A three-dimensional visualization tool to support HSE management of chemical facilities

Chemical and process facilities may feature complex procedures to manage health, safety, and environmental (HSE) related documentation in real time. These procedures may sometimes have negative implications on plant management and on inspections/audits. Therefore, the aim of this work is to show the benefits in developing and applying an innovative software framework to support the integrated management of HSE aspects of industrial installations. The tool is a three-dimensional technology designed to monitor and control the activities in industrial facilities by collecting process and environmental data in real time. The software is aimed to collect, monitor, and manage general process variables, status of maintenance and reliability of equipment, and many other aspects related to HSE aspects. A consequence assessment module, based on literature integral models, is also implemented in the software to perform real-time consequences analysis, and to display the evolution of the credible events resulting in case of accident. Either prefixed conditions or real-time input data (e.g. meteorological conditions, information on release features, etc.) may be implemented in the software. Real time three-dimensional consequence assessment may be carried out to support emergency response, training, and also risk based inspection and maintenance activities. The potentialities of the developed tool are tested though the application to an industrial case study