Application of 7N In as secondary cathode for the direct current-glow discharge mass spectrometry analysis of solid, fused high-purity quartz

Direct current glow discharge mass spectrometry with an indium-based secondary cathode technique is used to analyze solid, nonconducting, fused high-purity quartz regarding metallic impurities of relevance to the solar industry. Details of the analytical routines are presented. In this work, the secondary cathode design and glow discharge conditions are optimized beyond the commonly applied practices. In addition, relative sensitivity factors (RSFs) for these optimized conditions are established and compared to previously published results. The results indicate that the technique enables stable measurements with detection limits down to the part per billion (ppb) range.publishedVersio

How Slight Solidification Rate Variations within Cast Plate Affect Mechanical Response: A Study on As-Cast A356 Alloy with Cu Additions

The present work investigates a narrow range of secondary dendrite arm spacing (SDAS), in an as-cast A356 alloy with and without copper (Cu) additions. Cu was added to the base A356 alloy melt to reach the target concentration of 0.5 and 1 wt.%. Samples were selected from 3 different positions within the cast plate, offering 30, 35, and 40 μm SDAS variants. Tensile curves revealed a strong influence between the specimen cutting position and strength, with a pronounced effect in the Cu-containing alloys. Hardness measurements did not confirm the tensile response; hence, to understand the phenomenon, microstructural features have been investigated in detail. Eutectic silicon (Si) particle equivalent diameter (ED) size decreased from the top (T) to the bottom (B) position of the cast. Eutectic Si particle surface area (A%) was found to be denser at the B as compared to the T and simultaneously in the Cu-containing alloy as compared to the Cu-free reference alloy. Backscattered electron (BSE) images were employed to investigate the nature of the Cu-rich intermetallic phases. In conclusion, electrical conductivity measurements were performed to confirm the trends observed

Novel technique to study the wet chemical etching response of multi-crystalline silicon wafers

The current work aimed to demonstrate the application of a technique where white light interferometry (WLI) and Laue X-ray crystallography scanner characterisation were combined to study the chemical etching response of diamond cut multi-crystalline Si (mc-Si) wafers. Using this technique, the effect of different texturing additives (isopropyl alcohol, natrium hypochlorite) was evaluated by examining the topography of the mc-Si surfaces before and after etching. The etching responses of monocrystalline Si wafers of (1 0 0), (1 1 0) and (1 1 1) orientations were used as reference for comparison with the multi-crystalline wafers investigated. The texturing results illustrated the influence of different crystal-orientations on the etching rate. It was revealed that for the mc-Si wafers, the etching speed of the different crystal grain-planes is increasing with their crystallographic similarity with the main (hkl) planes (100, 110,111). The comparison of isopropyl alcohol (IPA) and sodium hypochlorite (NaOCl) additives to KOH solutions showed that NaOCl additive is favourable for the polishing of mc-Si wafers, while IPA can be used as polishing only for crystal grains close to the (1 1 1) orientation.publishedVersio

NTNU-SINTEF SolarNet: A solar irradiation monitoring network at high latitudes

This study presents a monitoring network for solar irradiation at high latitudes, called NTNU-SINTEF SolarNet. The network collects, with a time resolution ranging from seconds to hours, solar irradiance data, e.g. global horizontal irradiation, diffuse horizontal irradiation, direct normal irradiation, global tilted irradiation, solar energy generation, which are required in solar irradiation modelling in built environments. The network will be used for specific applications, such as (i) anomalies detection, (ii) influences of ground albedo, and (iii) ageing/degradation of solar modules, that are described in this paper. Some characteristics that make the NTNU-SINTEF SolarNet relevant for solar energy research at high latitudes are identified: short distances among the sensors, the ease of data accessibility, the use of the same sensor typologies, and different solar module technologies. The research holds the potential to boost the solar energy digitalization, impacting on several aspects such as predictive and adaptive control strategies for energy management, design of renewable energy system, multi-scale optimization and efficient exploitation of solar energy.publishedVersio

Depth profiling at a steel-aluminum interface using slow-flow direct current glow discharge mass spectrometry

Direct current glow discharge mass spectrometry (dc-GDMS), which relies on sector field mass analyzers, is not commonly used for depth profiling applications because of its slow data acquisition. Nevertheless, dc-GDMS has good reproducibility and low limits of detection, which are analytical features that are encouraging for investigating the potential of dc-GDMS for depth profiling applications. In this work, the diffusion of traces of chromium and nickel was profiled at the interface of a steel-aluminum bilayer using a new sensitive dc-GDMS instrument. The depth profile of the non-treated sample was compared with that of a heat-treated specimen at 400°C for 30 min. Scanning electron micrographs, energy dispersive X-ray spectroscopy (EDS), and electron probe microanalysis (EPMA) were used to study the diffusion process. The results of the study show that both chromium and nickel are enriched at the steel-aluminum interface, with higher concentrations of both elements for the heat-treated specimen. Two peaks for both chromium and nickel were clearly present at the interface, with a high concentration of chromium in the aluminum layer. This observation is likely a consequence of elemental diffusion from the interface towards the aluminum layer. The presence of the third layer, steel beneath the aluminum layer, might also have contributed to this observation.acceptedVersio

Low-Temperature Plasma-Enhanced Atomic Layer Deposition of SiO2 Using Carbon Dioxide

In this work, we report the successful growth of high-quality SiO2 films by low-temperature plasma-enhanced atomic layer deposition using an oxidant which is compatible with moisture/oxygen sensitive materials. The SiO2 films were grown at 90 degrees C using CO2 and Bis(tertiary-butylamino)silane as process precursors. Growth, chemical composition, density, optical properties, and residual stress of SiO2 films were investigated. SiO2 films having a saturated growth-per-cycle of similar to 1.15 angstrom/cycle showed a density of similar to 2.1g/cm(3), a refractive index of similar to 1.46 at a wavelength of 632nm, and a low tensile residual stress of similar to 30MPa. Furthermore, the films showed low impurity levels with bulk concentrations of similar to 2.4 and similar to 0.17at. % for hydrogen and nitrogen, respectively, whereas the carbon content was found to be below the measurement limit of time-of-flight elastic recoil detection analysis. These results demonstrate that CO2 is a promising oxidizing precursor for moisture/oxygen sensitive materials related plasma-enhanced atomic layer deposition processes.Peer reviewe

Beta-Blocker Use in Older Hospitalized Patients Affected by Heart Failure and Chronic Obstructive Pulmonary Disease: An Italian Survey From the REPOSI Register

Beta (β)-blockers (BB) are useful in reducing morbidity and mortality in patients with heart failure (HF) and concomitant chronic obstructive pulmonary disease (COPD). Nevertheless, the use of BBs could induce bronchoconstriction due to β2-blockade. For this reason, both the ESC and GOLD guidelines strongly suggest the use of selective β1-BB in patients with HF and COPD. However, low adherence to guidelines was observed in multiple clinical settings. The aim of the study was to investigate the BBs use in older patients affected by HF and COPD, recorded in the REPOSI register. Of 942 patients affected by HF, 47.1% were treated with BBs. The use of BBs was significantly lower in patients with HF and COPD than in patients affected by HF alone, both at admission and at discharge (admission, 36.9% vs. 51.3%; discharge, 38.0% vs. 51.7%). In addition, no further BB users were found at discharge. The probability to being treated with a BB was significantly lower in patients with HF also affected by COPD (adj. OR, 95% CI: 0.50, 0.37-0.67), while the diagnosis of COPD was not associated with the choice of selective β1-BB (adj. OR, 95% CI: 1.33, 0.76-2.34). Despite clear recommendations by clinical guidelines, a significant underuse of BBs was also observed after hospital discharge. In COPD affected patients, physicians unreasonably reject BBs use, rather than choosing a β1-BB. The expected improvement of the BB prescriptions after hospitalization was not observed. A multidisciplinary approach among hospital physicians, general practitioners, and pharmacologists should be carried out for better drug management and adherence to guideline recommendations

Fluidity of Aluminium Foundry Alloys

The fluidity of an alloy plays a key role for the foundry and transport industries as it affects the quality and soundness of the cast products. Particularly, fluidity influences the reject rates, hence casting costs and the production of thinwalled, hence light components. Fluidity is a complex technological property and depends on many parameters. However, many aspects of this subject are still not fully understood. The motivation of the research presented in this doctoral thesis was, therefore, to fill this gap in knowledge. The study has aimed at understanding the influence of various parameters on the fluidity of aluminium foundry alloys and, in particular, Al-Si foundry alloys. A literature review of previously reported results on fluidity was carried out. It was found that a lack of a highly reproducible test method as well as some contradictory results existed in the literature. Therefore, a new fluidity test method was developed. To study the accuracy and reproducibility of this test was one of the goals of this work. The new test method allowed a constant melt superheat, which is considered as one of the major factors affecting fluidity measurements, and a constant pouring velocity. It was found that the reproducibility of the new method was higher than previous methods. The effect of casting temperature, and hence melt superheat, was assessed through a series of tests. A linear relationship between casting temperature and fluidity length was observed. The effect of grain refiner on the fluidity of an A356 alloy was systematically investigated. The fluidity lengths without grain refiner and with three additions of Al-5wt%Ti-1wt%B master alloy were measured. The results showed that grain refinement reduced the grain size throughout the spiral somewhat, particularly at the tip, but there were no statistically significant effects on fluidity. The effect of dissolved hydrogen was also investigated in this study. The hydrogen content was drastically increased by plunging pieces of wood beneath the surface of the molten metal. The fluidity of this melt was measured and compared to a melt with low hydrogen content. It was concluded that the difference in fluidity between the melts with different hydrogen levels was not significant. The effect of minor alloying elements (Sr, Ti, Fe and Mg) on the fluidity of Al-7wt%Si alloys was investigated. The Design Of Experiment (DOE) technique and the Taguchi approach were used to design the experiments. The Analysis Of Variance (ANOVA) was performed to analyse the results. It was concluded that the addition of minor alloying elements to a major alloy system, e.g. Al-7wt%Si, does not significantly affect its fluidity and the melt superheat had a far greater impact on fluidity than the minor alloying elements. The effect of mould coating on fluidity was studied on a commercial strip mould which consisted of a H13 die with five channels of different cross sectional areas. The coating was sprayed to achieve a thickness of 0.2mm. Fluidity measurements were performed on the uncoated and coated mould. It was concluded that mould coating significantly increases fluidity. In addition, fluidity measurements on the uncoated and coated mould were undertaken at two different melt superheats and it was found that coating the mould plays a more significant role at low melt superheats. The effect of oxide content on fluidity was also investigated. Three alloys, namely a standard A356 alloy, the same alloy with 20% (A356+20%) and 50% (A356+50%) re-melted turning chips, were used and their fluidities compared. Qualitative analysis on the type of oxides present in the three alloys was carried out with a PoDFA test apparatus and the oxide level was quantified with optical microscopy analysis. The results showed that the addition of turning chips significantly increased the oxide content. Among the investigated alloys, A356 without turning chip additions showed the lowest oxide content and the highest fluidity. No significant differences in either oxide content or fluidity were found between the A356+20% and A356+50% melts. Two fluidity test methods, a commercially available one and an experimentally developed test, were used for measuring the fluidity of Al-Mg-Si alloys. Although the two methods were different, they gave consistent results. Numerical simulations of fluidity tests were carried out on an A356 alloy and the results showed that numerical simulation software can be a useful tool for predicting fluidity in aluminium foundry alloys. These are the major findings achieved by this thesis work which contribute to improve our understanding of the effect of several key variables on fluidity. It is believed that these results will solve some of the problems currently encountered in foundries and improve their processes

Methodology to analyse small silicon samples by glow discharge mass spectroscopy using thin wafer mask

Glow discharge mass spectrometry (GDMS) is widely used for trace element analysis of bulk solid samples. Thegeometry of the GD source limits the minimum size of the sample, which for the instrument used in this work(ThermoElementGD) is 20mm in diameter. From time to time, there is the need to analyse smaller samples withthis technique, and we present here a methodology to analyse samples of 9–20mm diameter through the use ofthin masks.Thin masks have been previously used mostly as secondary cathode for the analysis of non-conducting materials,with hole size smaller than the area of the glow discharge. The use of masks in this work includes the followingcustomization: The choice of highly-pure Si as mask material, to decrease the chance of interferences with the Si samples. The use of a hole in the mask of the same size as the discharge area. This implies that the mask material is notsputtered, thus decreasing chances for contamination from the mask itsel

Investigation of pinholes in Czochralski silicon ingots in relation to structure loss

acceptedVersio