Seostettujen litiumioniakkumateriaalien karakterisointi

Litiumioniakkujen kysyntä on kasvanut vuosia ja kasvu jatkunee hybridi- sekä sähköautojen yleistyessä. Litiumioniakut koostuvat katodista, anodista, niiden välisestä separaattorista ja elektrolyytistä. Anodimateriaaliksi on vakiintunut erilaiset hiiliyhdisteet, kuten grafiitti. Litiumioniakkujen kapasiteettia rajoittavana tekijänä on pitkään ollut katodimateriaalit. Katodimateriaalien toimivuutta rajoittaa litiumionien irrotukseen liittyvä epästabiilius. Perinteisesti käytetyn litiumkobolttioksidi tilalle on etsitty uusia, halvempia ja parempia materiaaleja. Kobolttioksidiin on pitkään sekoitettu nikkeli- ja mangaanioksidia erilaisissa suhteissa, mutta litiumioniakkumateriaaleihin kohdistuvien vaatimusten, kuten käyttöikä ja -jännite, kasvaessa perinteiset metallioksidiseokset eivät riitä. Seostamalla (engl. doping) muita metallioksideja pienissä pitoisuuksissa (alle 5 mol-% metallioksidien kokonaispitoisuudesta) saadaan valmistettua katodimateriaaleja, joiden ominaisuudet ovat puhtaita materiaaleja paremmat. Uudet seostetut katodimateriaalien myötä tutkimus siirtynee esimerkiksi elektrolyytin stabiilisuuteen, kun katodimateriaalin käyttöjännite ylittää elektrolyytin stabiilisuusalueen. Myös elektrodimateriaalien pinnoituksella voidaan estää elektrolyytin reaktioita. Seostetuttuja materiaaleja koskevia julkaisuja on viimevuosina ollut paljon. Materiaalien karakterisointimenetelmät kuitenkin vaihtelevat. Työssä käydään lävitse tutkielman aikana kirjallisuudesta löydettyjä menetelmiä, ja arvioidaan niiden käytön yleisyyttä lähdekirjallisuuden pohjalta. Menetelmien tuloksia kuvaillaan. Tutkielman perusteella yleisimmin käytettyjä menetelmiä ovat akun toimintaan liittyvät sähköiset analyysit, mikroskooppiset menetelmät sekä röntgensädediffraktio. Lisäksi tutkielmassa esitellään lähdekirjallisuuden seostusmenetelmiä ja niiden vaikutuksia litiumioniakkujen toimintaan

Utilization of waste sodium sulfate from battery chemical production in neutral electrolytic pickling

Abstract Several industrial activities produce metal sulfates, which are controlled by strict limitations for wastewater concentrations of sulfate. One emerging area where these activities occur is the production of lithium-ion battery chemicals in which sodium sulfates are formed because of cathode precursor co-precipitation. Several solutions for sulfate removal exist, but one option is to reuse the sulfate side stream in other processes to increase circular economy and atom efficiency. In this paper, the reuse of sodium sulfate solution in a steel industry pickling solution is considered. Neutral electrolytic pickling experiments were carried out to compare the pickling behavior of the electrolyte dissolved from pure sodium sulfate and the electrolyte diluted from a side stream solution. Effect of impure electrolyte was evaluated using field emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectrometry (EDS). Concentrations of the metal ions were determined by inductively coupled plasma-optical emission spectrometry (ICP-OES). The results indicated a slight increase in current efficiency with the side stream electrolyte solution, while overall the pickling behavior remained similar. This suggests that a side stream sodium sulfate solution could be used as a pickling electrolyte, reducing the need for pure reagents

Oxide scale formation of EN 1.4622 and EN 1.4828 stainless steels during annealing and descaling behavior in neutral electrolytic pickling

Abstract Oxide scale formation during short-term annealing and electrolytic pickling behavior of ferritic EN 1.4622 and austenitic EN 1.4828 stainless steels are investigated. The annealing is performed at temperatures between 1000 and 1100 °C for ferritic and 1100 and 1200 °C for austenitic steel grade under humid atmospheres in simulated industrial process. Neutral electrolytic pickling, also referred to as neutral electrochemical pickling or the Ruthner Neolyte Process, is performed in Na₂SO₄ electrolyte, and pickling efficiency is evaluated visually and by image analysis of pickled surfaces. The results show that annealing conditions have a more impactful effect on the structure and the composition of the resulting oxide in the austenitic grade within the studied condition range. The thicknesses of the ferritic scales are mainly less than 0.4 μm, while almost all austenitic scales are thicker than it. In addition, the amount of silicon oxide formation inside the steel matrix of the austenitic and ferritic grades is highly different. Longer exposure times and higher temperatures promote scale growth during annealing, resulting in inefficient electrolytic pickling for the ferritic grade. For the austenitic grade, almost all steel surfaces are still covered with oxide scale after electrolytic pickling

Effect of simulated annealing conditions on scale formation and neutral electrolytic pickling

Abstract Scale formation of AISI 304 stainless steel during annealing at temperatures between 1100 and 1200 °C under a water vapor‐containing atmosphere is studied. Characterization of the oxide scale is performed with field‐emission scanning electron microscopy–energy dispersive spectroscopy (FESEM–EDS) and glow discharge optical emission spectroscopy (GDOES) and removal of oxide scale is done via neutral electrolyte pickling. The pickling conditions are kept constant and the effect of the annealing conditions and scale properties on the pickling result are examined. The effectiveness of pickling is evaluated using analysis FESEM images taken on polished sections of pickled surfaces. Research shows that the thickness, morphology, and composition of the oxide scale are dependent on annealing temperature and time. The thicknesses of the scale formed under the established conditions vary from 0.2 to over 30 μm, and morphologies between the chromium rich oxide layer and layered scale structure formed by breakaway oxidation. The pickling response of oxide scales remains good at all annealing temperatures with the shortest exposure time

eHealth competence building for future doctors and nurses:attitudes and capabilities

Abstract Background: Digitalisation is rapidly changing health care processes and the health care sector, thus increasing the need to improve the digital competence of future health care professionals. Purpose: The aim of this study was to describe the attitudes of medical and nursing students towards digital health based on self-evaluation as well as to compare the differences in perceptions between the two student groups. Methods: A cross-sectional study was conducted as an online survey using the Webropol in April 2021 at the University of Oulu and Oulu University of Applied Sciences in Finland. The survey questionnaire consisted of seven background questions and 16 statements on a five-point Likert scale (fully disagree to fully agree) to survey student attitudes towards eHealth, and their digital capabilities. Results: A total of 250 medical and nursing students were invited to participate in the study and 170 of them took the survey (response rate 68 %). Of those answered, 38 % (n = 64) were nursing and 32 % (n = 106) medical students. Students generally had a positive attitude towards eHealth and health care digitalisation. The differences in perceptions and preparedness between medical and nursing students were surprisingly small in the two student groups. There was a statistically significant difference between the two groups in three out of 16 statements: these were related to changes in the roles of health care professionals and patients as well as the students’ knowledge of information contained in the national patient portal. Conclusions: The results of this study provide a good starting point for further harmonisation of the curriculum for both health professional groups regarding the teaching of eHealth and telemedicine