Effects of different needles and substrates on CuInS2 deposited by electrostatic spray deposition

Copper indium disulphide (CuInS2) thin films were deposited using the electrostatic spray deposition method. The effects of applied voltage and solution flow rate on the aerosol cone shape, film composition, surface morphology and current conversion were investigated. The effect of aluminium substrates and transparent fluorine doped tin oxide (SnO2:F) coated glass substrates on the properties of as-deposited CuInS2 films were analysed. An oxidation process occurs during the deposition onto the metallic substrates which forms an insulating layer between the photoactive film and substrate. The effects of two different spray needles on the properties of the as-deposited films were also studied. The results reveal that the use of a stainless steel needle results in contamination of the film due to the transfer of metal impurities through the spray whilst this is not seen for the glass needle. The films were characterised using a number of different analytical techniques such as X-ray diffraction, scanning electron microscopy, Rutherford back-scattering and secondary ion mass spectroscopy and opto-electronic measurements

Evolutionary spectral model for thunderstorm outflows and application to the analysis of the dynamic response of structures

Thunderstorms are destructive phenomena at the mesoscale with extension of few kilometres and short duration, potentially dangerous for mid-low structures. The nonstationary nature of the wind field generated by thunderstorm outflows makes most of the theory and models developed for extra-tropical cyclones unsuitable and their small extension make them difficult to be detected by one single anemometer. These circumstances prevent the collection of precious data over which research can be carried out and the development of robust models for rapid engineering calculations shared by the scientific community. Therefore, a unified and reliable analytical model for the assessment of the maximum dynamic response to thunderstorms coherent with the techniques commonly adopted in wind engineering is not yet available. In this framework, the thesis introduces an Evolutionary Power Spectral Density (EPSD) model of the wind velocity related of thunderstorm outflows, consistent with full-scale records, and studies its application to calculate the alongwind dynamic response of structures and its maximum from an operative perspective. The EPSD model is derived starting from the analysis of 129 full-scale thunderstorm records, assuming the turbulent fluctuations uniformly modulated and the turbulence intensity constant. The reliability of the assumptions are verified on the basis of the data available. Three analytical models for the modulating function of the slowly-varying mean wind velocity are proposed. The models are based on the functions extracted from the records and include parameters of physical meaning for the thunderstorm outflow. Moreover, the possibility of adopting the classical spectral models of synoptic winds to model the stationary part of the turbulence is verified. Successively, the EPSD model is adopted to calculate the dynamic response of a set of linear elastic point-like SDOF systems with variable fundamental frequency and damping ratio, both accounting and neglecting the effects of the transient dynamics. In this framework a closed-form solution of the Evolutionary Frequency Response Function (EFRF) is derived. The mean value of the maximum response is estimated based on an Equivalent Parameter Technique (EPT) from literature, generalizing the Davenport\u2019s gust factor technique. The effects of the Poisson hypothesis are investigated and mitigated introducing an equivalent expected frequency. The results are validated with the ones obtained in the time domain starting from the real thunderstorm records available. Successively, a sensitivity analysis is carried out to assess the influence on the maximum dynamic response of the parameters that shape the modulating function of the velocity. A closed-form solution for the equivalent parameters and the gust factor is introduced. The comparison with alternative formulations proposed in the literature demonstrates the improved accuracy of the proposed one. Finally, the formulation is extended to the analysis of slender vertical structures, adopting a vertical profile for the mean wind velocity from the literature and the equivalent wind spectrum technique. Two case studies of vertical slender structures are analysed and a comparison with synoptic wind loading conditions is outlined, showing that the proposed model constitutes a valid and handy tool for the evaluation of the wind loading on structures provided by thunderstorm outflows

Thermal Barrier Coatings phase stability and in service degradation

This thesis work is the result of a collaboration between Ansaldo Energia's Materials Laboratory and the Department of Chemistry and Industrial Chemistry of the University of Genoa. The study developed from the industrial need to better understand the degradation processes of the turbine blade thermal barriers coating already used in Ansaldo Energia gas turbines and to test new materials that could be used in the future. The material mostly used as a protective coating is 7YSZ (ZrO2 with 7 wt% of Y2O3) which has excellent characteristics and has been used inside turbines for land use and on aircraft engines since the 1960s. The need to increase the operating temperature of the machines, with a consequent increase in efficiency, makes it necessary to modify this material, as it tends to degrade when it works at temperatures above 1300\ub0C. With cooling from high temperatures, the 7YSZ tends to modify its crystallographic structure until the formation of the monoclinic phase, extremely harmful because it is a source of mechanical fragility and an increase in thermal conductivity. A new material has been proposed by Ansaldo Energia, consisting of a double layer, with the upper layer formed by 14YSZ (ZrO2 with 14% of Y2O3), while the lower one remains 7YSZ for better compatibility with the metal substrate. The new material is crystallographically stable but its properties must be characterized before being used in gas turbines. Starting from their precursor powders and reacting long exposure time at high temperature of sprayed material. In addition, the TBC modifications due to interactions with CMAS (Calcium-Magresium-Alluminium-Silicates) have been investigated. Several tests have been performed for times up to 10000h and temperatures between 1100 and 1400\ub0C. The samples have been examined mainly to evaluate the effect of the interaction on the formation of the monoclinic and other secondary phases, the modification of the microstructure and the variation of physical properties. Finally, to better study the interaction phenomena between oxides, a multicomponent thermodynamic database (Al-Ca-Si-Mg-Si-Y-Zr-O) has been implemented using the CALPHAD method. The thesis work has been divided into an experimental part, carried out at the Ansaldo Energia laboratories and a thermodynamic modeling part, conducted at the Department of Chemistry and Industrial Chemistry. The thermodynamic database for oxides has been also implemented through the experimental study of the MgO-Y2O3-ZrO2 system at the University of Freiberg in Germany, in the group of Prof.Olga Fabrichnaya. The experimental part focused on the analysis of thermal barrier specimens exposed at high temperature and examined with usual materials characterization techniques. For this purpose, quantitative analysis of the detected phases has been carried out using Xray diffraction with quantification using the Rietveld method. The microstructural analyzes have been done using optical microscope and FEG-SEM (Field Emission Gun-Scanning Electron Microscope) equipped with EDS (Energy- dispersive detector) and EBSD (Electron Back Scattered Diffraction) to evaluate microstructure variations, phase compositions, grain shapes and dispersion of the phases within the sample. Furthermore, thermal conductivity tests have been carried out, using thermography technique, thank to the collaboration with the group of Dr. Paolo Bison and Dr. Giovanni Ferrarini of the ITC-CNR of Padua. At the same time, by means of thermodynamic modeling according to the CALPHAD method, the development of a thermodynamic database has been started. It includes the seven main oxides relevant to the CMAS-TBC interaction and our work was mainly focused on the definition of thermodynamic models for the description of the phases present in the system and the assessment of a series of pseudo-binary and pseudo-ternary subsystems . The results obtained allow the definition of the critical conditions of the tested materials in service, to better understand their evolution and the degradation and to define the range of use

Thunderstorm gust response factor: General tendencies and sensitivity analysis

This paper aims to provide a sensitivity analysis of the thunderstorm gust response factor. The study is based on the extension of the gust response factor technique to the assessment of the maximum dynamic response of structures to thunderstorm outflows, starting from an evolutionary spectral model of the thunderstorm wind speed. The thunderstorm evolutionary spectral model depends on the modulating function of the slowly-varying mean speed, which is a function of two parameters, i.e. the background mean wind speed and the duration of the intense phase of the outflow. Starting from 129 full-scale thunderstorm records, the parameters of three different analytical models of the modulating function are extracted and a statistical analysis is carried out defining their range of variation. The dependence of the gust response factor on the analytical expression of the modulating function is studied as well as its sensitivity to the parameters of the function. Results show that the dependence of the gust response factor on the analytical expression of the modulating function is negligible, while it is very sensitive to the variation of the background wind and duration of the intense phase, especially for flexible and lowly-damped systems

Renewable energy production and demand dataset for the energy system of Colombia

During the last decades, an increasing number of studies have focused their attention on the development of energy system models in order to facilitate sustainable energy planning strategies and understand the technical challenges associated with the integration of renewable energy sources. However, these models usually require detailed and large amount of data as inputs. The data presented in this article provides key inputs and modelling assumptions adopted in the research paper titled “Large scale integration of renewable energy sources (RES) in the future Colombian energy system” [1]. These datasets can be used by researchers and policymakers in order to analyse different pathways oriented to the development of low carbon strategies for Colombia and countries with similar energy systems

Deposition and characterization of copper chalcopyrite based solar cells using electrochemical techniques

Cu(In,Ga)Se2 films were electrodeposited on molybdenum substrates from a single pH buffered bath and annealed in a reducing selenium atmosphere. The opto-electronic properties of the films were characterized using a potentiostatically- controlled three electrode setup and an electrolyte contact. Pulsed illumination was used to determine the carrier type and the speed of photoresponse. Chopped monochromatic illumination was used to measure photocurrent spectra. The electrodeposited copper chalcopyrite films were compared with films prepared by sputtering and spraying techniques

Modelling of thunderstorm outflows by means of the evolutionary power spectral density

This study proposes a model of time-modulating function for the evolutionary power spectral density (EPSD) of thunderstorm outflows, based on the slowly-varying wind speed and standard deviation records extracted from a database of 137 10-minutes thunderstorm time-histories. The analyses have been carried out under the hypothesis that the residual turbulent fluctuations can be considered an uniformly modulated process. Three different models have been proposed and provided with parameters characteristic of both the thunderstorm event and the background wind. Said models have been adopted to fit the ensemble value and its variation with the standard deviation of the dimensionless functions of both the slow-varying mean velocity and standard deviation records. Successively the relations between parameters have been provided and the procedure for the derivation of the EPSD have been outlined. The aim is to adopt this model for the derivation of the dynamic response of structures to thunderstorms outflows

Genetic diversity and linkage disequilibrium using SNP (KASP) and AFLP markers in a worldwide durum wheat (Triticum turgidum L. Var durum) collection

The aim of this work was to analyze the genetic diversity and linkage disequilibrium in a collection of 168 durum wheat accessions (Triticum turgidum L. var. durum) of different origins. Our collection was mainly composed of released and unreleased Argentinian germplasm, with additional genotypes from Italy, Chile, France, CIMMYT, Cyprus, USA and WANA region. To this end, the entire collection was characterized with 85 Single Nucleotide Polymorphism (SNP) markers obtained by Kompetitive Allele Specific PCR (KASP), giving a heterozygosity (He) mean value of 0.183 and a coefficient of genetic differentiation (Gst) value of 0.139. A subset of 119 accessions was characterized with six Amplified Fragment Length Polymorphism (AFLP) primer combinations. A total of 181 polymorphic markers (125 AFLP and 56 SNP) amplified across this subset revealed He measures of 0.352 and 0.182, respectively. Of these, 134 were selected to estimate the genome-wide linkage disequilibrium obtaining low significant values (r2 = 0.11) in the subset, indicating its suitability for future genome-wide association studies (GWAS). The structure analysis conducted in the entire collection with SNP detected two subpopulations. However, the structure analysis conducted with AFLP markers in the subset of 119 accessions proved to have greater degree of resolution and detect six subpopulations. The information provided by both marker types was complementary and showed a strong association between old Argentinian and Italian germplasm and a contribution of CIMMYT germplasm to modern Argentinian, Chilean and Cypriot accessions. The influence of Mediterranean germplasm, mainly from Italy, on part of the modern Argentinian cultivars or breeding lines was also clearly evidenced. Although our analysis yields conclusive results and useful information for association mapping studies, further analyses are needed to refine the number of subpopulations present in the germplasm collection analyzed.Fil: Roncallo, Pablo Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; ArgentinaFil: Beaufort, Valeria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; ArgentinaFil: Larsen, Adelina Olga. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires Sur. Estación Experimental Agropecuaria Barrow; ArgentinaFil: Dreisigacker, Susanne. Centro Internacional de Mejoramiento de Maiz y Trigo; MéxicoFil: Echenique, Carmen Viviana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; Argentin

Use of combinatorial analysis for the study of new material for solar cells applications

This paper presents a combinatorial method for the deposition and characterization of new metallic precursors for photovoltaic materials. Onedimensional thin film alloy “libraries” were electrodeposited on Mo-coated glass. The library elements were deposited in two consecutive baths and then heated in a reducing atmosphere to promote interdiffusion of the elements. At the end of this process, the libraries possessed a composition gradient along their lengths, with single elements at their two opposite ends and one or more alloys and/or a solid state solution in between. This continuous range of compositions can therefore be considered a collection of specific precursors that can be interrogated by examining their corresponding locations, with the crystallographic structure along the library changing in accordance with the phase diagram for the metals. The libraries were then sulphurised or selenised by heating in a sulphur-rich or selenium rich atmosphere; this converted the metallic precursors in a continuous range of materials, candidates for potential solar cells absorbers. The libraries were analysed by X-ray diffraction and energy dispersive X-ray spectrometry. The X-ray diffraction results show phase changes across the libraries, which can be correlated with the original precursor concentration at that particular p

A new species of \u3cem\u3eTarsoporosus\u3c/em\u3e Francke, 1978 (Scorpiones: Scorpionidae: Diplocentrinae) from northeastern Colombia

A new species of Tarsoporosus Francke, 1978 is described herein from two localities in La Guajira Peninsula, northeastern Colombia. This new taxon inhabits arid environments, and is morphologically close to Tarsoporosus flavus González-Sponga, 1984, from northwestern Venezuela. With this addition, the total number of described species in Tarsoporosus is raised to five, with at least two occurring in Colombia