Synthetic hackmanites as detection materials for ionizing radiation

Hackmanite (Na8Al6Si6O24(Cl,S)2) exhibits reversible photochromism or tenebrescence (Latin tenebra, shadow), which can be induced by exposure to UV light. In this phenomenon the off-white mineral turns pink or purple, and the original color can be restored with visible light or heat. For this to happen, there must be traps in the material’s crystal structure, and in hackmanite the traps are chloride vacancies which are sites where a chloride ion should reside, but due to sulfur anions being present, the charge balance does not allow a chloride ion to enter the structure at some point near the sulfur ion. The incident UV photon excites a sulfur atom’s electron which gets trapped in the vacancy. This creates an F center (German Farbzentrum, color center) which absorbs visible light in the green-yellow part (520−540 nm) of the spectrum, causing the coloration of the material. The aim of this study was to gain knowledge on how particle radiation and exposure to X-rays induce tenebrescence in hackmanites. The theoretical background reviews different types of radiation, current trends in radiation dosimetry and the use of thermoluminescence and optically stimulated luminescence in the ionizing radiation monitoring. Some theory about color spaces and representation models are discussed shortly. Finally, the X-ray analysis techniques used in the experimental section are reviewed. The experimental section focuses on the synthetically prepared hackmanite to gain knowledge on whether the material could be used as a novel application in the field of radiation detection and dosimetry. The section also contains specific instructions on how to make hackmanites and cast them as flexible tapes via the doctor blading method. Tiivistelmää muokattu työn hyväksymisen jälkeen 19.8.2019

Reversible photochromism of synthetic hackmanites in radiation detection and quantification

The subject of this thesis is centered on a mineral called hackmanite, also known as photochromic sodalite. It is found naturally in remote, mountainous places in Afghanistan, Pakistan, Greenland, Russia, Canada, and the United States. The natural mineral is costly to extract and – depending on the location – its optical properties and chemical impurities vary arbitrarily. Thus, it is not only more predictable, but also sustainable to synthesize the mineral in a laboratory from traceable reagents that contain known amounts of impurities. The synthesis route used in the experimental section in this work is a solid-state method where the reagents are mixed and heated in an oven at 850 °C and reduced with a hydrogen‒nitrogen gas mixture. The product, hackmanite (Na8Al6Si6O24(Cl,S)2), shows properties including luminescence, persistent luminescence, and reversible photochromism upon exposure to UV, X, gamma, nuclear, or particle radiation. Hackmanite’s photochromism is of particular interest since the coloration from white to pink can be reversed with visible light or heat, and this cycle can be repeated indefinitely. Hackmanite is thus able to react to its surrounding radiation atmosphere, and what makes the property even more interesting is that upon high-energy gamma radiation exposure the material “remembers” the exposure with a change of its color centers. In UV-induced coloration, the mechanism involves an electron transfer from a disulfide anion to a nearby chloride vacancy, which is a defect in the lattice due to the requirement of charge neutrality in the crystal. However, in X-ray- or other highenergy radiation-induced coloration the incident energies are so high that the coloration is caused by core-shell electrons and subsequent holes trapping after thermalization. Due to the nature of the coloration process, hackmanite’s application region spans from the high-energy gamma radiation to UV, however the material can also be used to detect visible light since the bleaching process (electrons returning to disulfide ions from the trap) occurs in the visible wavelength region. This property can be used for taking a photograph, as is shown in this thesis. KEYWORDS: hackmanite, photochromism, radiation detection, dosimetry, photographyTämän väitöskirjan aiheena on hackmaniitti-niminen mineraali, joka tunnetaan myös nimellä fotokrominen sodaliitti. Sitä esiintyy luonnossa syrjäisillä vuoristoseuduilla Afganistanissa, Pakistanissa, Grönlannissa, Venäjällä, Kanadassa ja Yhdysvalloissa. Luonnonmineraalin louhinta on kallista ja kestämätöntä, ja sen optiset ominaisuudet ja kemialliset epäpuhtaudet vaihtelevat satunnaisesti riippuen sijainnista. Näin ollen on ennakoitavampaa ja kestävämpää syntetisoida mineraalia laboratoriossa reagensseista, jotka ovat jäljitettäviä ja sisältävät tunnetut määrät epäpuhtauksia. Tämän työn kokeellisessa osassa synteesit toteutettiin kiinteän olomuodon menetelmällä, jossa lähtöaineiden seos kuumennetaan uunissa 850 °C:ssa ja pelkistetään vetytyppikaasuseoksella. Tuotteella eli hackmaniitilla (Na8Al6Si6O24(Cl,S)2), on ominaisuuksinaan luminesenssi, jälkiloiste ja palautuva fotokromismi altistuessaan UV-, röntgen-, gamma‑, ydin- ja hiukkassäteilylle. Hackmaniitin fotokromismi on erityisen kiinnostava ominaisuus, sillä vaaleanpunaiseksi värjätty hackmaniitti voidaan palauttaa takaisin valkoiseksi näkyvällä valolla tai lämmöllä, ja tätä sykliä voidaan toistaa loputtomasti. Tämän ominaisuuden tekee vielä mielenkiintoisemmaksi se, että gammasäteilyaltistuksen yhteydessä materiaali ”muistaa” korkeaenergisen altistuksensa värikeskuksensa ‒ joka on olennainen rakenne värjäytymismekanismissa ‒ muutoksella. UV-värjäytymisessä mekanismi sisältää elektronin virittymisen disulfidianionista läheiseen kloridivakanssiin, mikä on kiteen varaustasapainovaatimuksen mukaisesti muodostunut hilavirhe. Röntgen- tai muun korkeaenergisen säteilyn aiheuttamassa värjäytymisessä energiat ovat kuitenkin niin suuria, että värjäytymisen aiheuttaa sisäkuorten elektronien ja aukkojen loukkuuntuminen termalisaation jälkeen. Värjääntymisprosessin ansiosta hackmaniitin käyttöalue ulottuu korkeaenergisestä gammasäteilystä UV-säteilyyn, mutta materiaalia voidaan käyttää myös näkyvän valon havaitsemiseen, sillä haalenemisprosessi (elektronien palaaminen loukuista takaisin disulfidi-ioneihin) tapahtuu näkyvällä aallonpituusalueella. Tätä ominaisuutta voidaan käyttää valokuvaamisessa. ASIASANAT: hackmaniitti, fotokromismi, säteilyn havainnointi, dosimetria, valokuvau

Preparation of glass-based composites with green upconversion and persistent luminescence using modified direct doping method

AbstractNew oxyfluorophosphate glass-based composites which exhibit not only green upconversion under 980 nm pumping but also green persistent luminescence (PeL) after being UV charged were successfully prepared using the direct doping method. The composites are composed of a glass-ceramic with Er3+ doped CaF2 crystals and of the persistent luminescent particles with the SrAl2O4:Eu,Dy composition. In the standard direct doping method, the glass melt is quenched few minutes after adding the PeL particles in the melt held at a temperature lower than the melting temperature. It is demonstrated that the direct doping method should be modified when preparing oxyfluoride glasses with PeL particles to limit not only the decomposition of the PeL particles in the glass but also the fluorine evaporation occurring during the glass preparation. Here, the composites were prepared by quenching the melt right after adding the PeL particles. The modified direct doping method allows the preparation of glass-based composites with strong green upconversion and homogeneous green persistent luminescence.</p

UV-Sensing Cellulose Fibers Manufactured by Direct Incorporation of Photochromic Minerals

Textile-based wearable sensors integrated into daily wear offer opportunities for on-demand, real-time self-diagnosis to monitor health conditions with changing environmental surroundings and hazards. One still underrated environmental hazard is accumulated UV irradiation, causing skin burns, accelerated aging, and skin cancers. Here, we have demonstrated a sustainable fiber manufacture process to integrate photochromic hackmanite micro-particles directly into a cellulose body to achieve UV-sensing functionality in daily-life textiles. The hackmanite particles were dispersed into an ionic liquid cellulose dope using ultrasonication and nanofibrillated cellulose as a dispersant, resulting in good spinnability. The obtained fibers possess high mechanical strength with up to 10% photochromic hackmanite loading. To demonstrate its application in wearable UV sensors, the fibers were spun into yarn and then knitted into a piece of jersey fabric. The coloration of hackmanite-incorporated textiles under UV irradiation is readily quantified by image analysis using red–green–blue ratios, which was further utilized for UV dosimetry with a smartphone application showcasing the practical use of the UV sensor. The UV-sensing functionality remained the same after intensive washing and abrasion tests, further demonstrating the feasibility of its application in everyday garments.</p

Detection of X-Ray Doses with Color-Changing Hackmanites: Mechanism and Application

Hackmanites, a variety of sodalite with the general formula Na$_{8}$Al$_{6}$Si$_{6}$O$_{24}$(Cl,S)$_{2}$, are a family of nature-based smart materials having the ability for reversible photochromism upon UV or X-ray exposure. Being nontoxic, cheap, and durable, hackmanite would be an optimal material for the visual detection of the presence of X-rays in simple portable systems. However, its X-ray-induced coloring abilities are so far known only qualitatively. In this work, a combination of experimental and computational methods is used to reveal the mechanism of X-ray-induced color changing in these materials. Finally, their use is demonstrated both in color intensity-based X-ray dosimetry and photochromic X-ray imaging

Detection of X-Ray Doses with Color-Changing Hackmanites: Mechanism and Application

Hackmanites, a variety of sodalite with the general formula Na8Al6Si6O24(Cl,S)(2), are a family of nature-based smart materials having the ability for reversible photochromism upon UV or X-ray exposure. Being nontoxic, cheap, and durable, hackmanite would be an optimal material for the visual detection of the presence of X-rays in simple portable systems. However, its X-ray-induced coloring abilities are so far known only qualitatively. In this work, a combination of experimental and computational methods is used to reveal the mechanism of X-ray-induced color changing in these materials. Finally, their use is demonstrated both in color intensity-based X-ray dosimetry and photochromic X-ray imaging

Rintamamiestalon kuntoarvio ja korjaussuunnitelma

Opinnäytetyön tarkoituksena oli tehdä 1950-luvulla valmistuneeseen rintamamiestaloon kuntoarvio ja korjaussuunnitelma ja parantaa talon lämmöneristävyyttä. Korjaussuunnitelmaa tehtäessä pohdittiin eri tapoja tehdä korjaus mahdollisimman taloudellisesti sekä siten että rakenteet toimisivat oikein. Korjaussuunnitelman perusteel-la rintamamiestaloon tehdään kustannusarvio korjauksista. Kuntoarvio tehtiin kohteeseen avaamalla rakenteita muutamista kohdista ulkoseinässä, ala- ja välipohjassa. Lisäksi kohdetta tarkasteltiin silmämääräisesti. Rakenteiden kosteuksia mitattiin pintakosteusmittarilla. Korjaussuunnitelma tehtiin rakennusmääräysten ja hyvän rakennustavan mukaisesti. Ulkoseinien, alapohjan ja yläpohjan suunnittelussa otettiin huomioon että rakenteiden U-arvo olisi nykymääräyksien mukainen. Opinnäytetyön tuloksena saatiin korjaussuunnitelma, joka auttaa määrittämään kustannusarviota rintamamiestalon peruskorjaukseen. Lisäksi se auttaa parantamaan rintamamiestalon rakennusfysikaalista toimivuutta ja energiatehokkuutta

Tuotannon layoutin suunnittelu

Opinnäytetyön tavoitteena oli liikennemerkkejä valmistavan Normiopaste Oy:n jo olemassa olevien tuotantotilojen uudelleen suunnittelu. Yrityksessä halutaan kehittyä ja saada nykyisistä tuotantotiloista mahdollisimman tuottavat ja kasvua tukevat. Tuotannon keskittäminen Tampereelle sekä uusien koneiden paikoitus loi tarpeen layoutin uudelleen suunnitteluun. Työn alussa käsitellään erilaisia tuotannon layout-tyyppejä sekä lean-ajattelusta tunnettuja käsitteitä, kuten seitsemää hukkaa ja 5S-menetelmää. Kirjallisuuden avulla avataan erilaisia layout-malleja ja käydään läpi layout-suunnittelun periaatteet ja tavoitteet. Ennen uusien koneiden hankkimista selvitettiin nykyisten tuotantotilojen kehittämiskohdat sekä huonosti hyödynnetyt tilat. Ensimmäiseksi luotiin piirustus nykyisistä tuotantotiloista Siemens NX -mallinnusohjelmalla. Layoutista tehtiin piirustus, johon hahmoteltiin työkoneet, työtasot, kiinteät ratkaisut ja kuormalavahyllyt. Tämän piirustuksen avulla voitiin luoda uusi layout ja varmistaa uusien koneiden tarvitsema tila teoriassa. Opinnäytetyön tuloksena Normiopasteelle luotiin uudempi layout. Sen avulla yritys voi tehdä konehankintoja kasvattaakseen tuotantomääriä sekä parantaakseen tuottavuutta.The purpose of the thesis was to redesign the already existing production facilities of Normiopaste, which manufactures traffic signs. The company wants to develop and make the current facilities as productive as possible to support growth. The production centralization to Tampere developed the need for a design new layout. The start of the thesis represents different types of production layouts and concepts known from lean methodology such as seven wastes and the 5S method. With the help of literature different layout models are explained. Principles and objectives on the layout planning are reviewed. Before acquiring new equipment, the develop areas of the current production facilities and poorly utilized spaces were examined. Then a layout model of the current production facilities was created using the Siemens NX modelling program. From the layout, a model was created in which the equipment, worktops, fixed solutions, and the pallet shelves were outlined. As a result of the thesis an improved layout was created for Normiopaste, which can be carry out machine acquisitions to increase production volumes. During the following years it will be important to collect data to see results of the thesis development

UV-Sensing Cellulose Fibers Manufactured by Direct Incorporation of Photochromic Minerals

Funding Information: This project is funded by the Academy of Finland Project WTF-Click-Nano. We would like to thank Simone Haslinger (Reima Oy) for providing knowledge of the textile market and fruitful discussions, Kaniz Moriam (Aalto University) for her support in fiber spinning, and Sami Rantasalo for technical support in the lab. We acknowledge the provision of facilities and technical support by Aalto University at the OtaNano–Nanomicroscopy Center (Aalto-NMC). Publisher Copyright: © 2021 The Authors. Published by American Chemical Society.Textile-based wearable sensors integrated into daily wear offer opportunities for on-demand, real-time self-diagnosis to monitor health conditions with changing environmental surroundings and hazards. One still underrated environmental hazard is accumulated UV irradiation, causing skin burns, accelerated aging, and skin cancers. Here, we have demonstrated a sustainable fiber manufacture process to integrate photochromic hackmanite micro-particles directly into a cellulose body to achieve UV-sensing functionality in daily-life textiles. The hackmanite particles were dispersed into an ionic liquid cellulose dope using ultrasonication and nanofibrillated cellulose as a dispersant, resulting in good spinnability. The obtained fibers possess high mechanical strength with up to 10% photochromic hackmanite loading. To demonstrate its application in wearable UV sensors, the fibers were spun into yarn and then knitted into a piece of jersey fabric. The coloration of hackmanite-incorporated textiles under UV irradiation is readily quantified by image analysis using red-green-blue ratios, which was further utilized for UV dosimetry with a smartphone application showcasing the practical use of the UV sensor. The UV-sensing functionality remained the same after intensive washing and abrasion tests, further demonstrating the feasibility of its application in everyday garments.Peer reviewe