1. Deuterium retention in tungsten, tungsten carbide and tungsten-ditungsten carbide compositesPetra Jenuš, Anže Abram, Saša Novak, Mitja Kelemen, Matic Pečovnik, Thomas Schwarz-Selinger, Sabina Markelj, 2023, izvirni znanstveni članek Povzetek: The selection of the most suitable material for the EU DEMO divertor is still underway. Current research focuses on the development of tungsten-based materials for plasma-facing applications. In addition to other requirements, the candidate material must also exhibit low intrinsic hydrogen isotope retention. To verify the suitability of the tungsten carbide-containing materials, we examined the effect of carbon in the form of carbide or free carbon on deuterium (D) retention. The samples were consolidated by Field Assisted Sintering (FAST) and examined in terms of phase composition and microstructure before the d-retention studies. The Nuclear Reaction Analysis (NRA) technique was used to determine the depth distribution of D after the exposure to D plasma (fluence of 1.3 × 1024 D/m2 and 1.3 × 1025 D/m2 and an exposure temperature of 370 K and 523 K, respectively). Thermal Desorption Spectroscopy (TDS) was used to measure the D desorption spectra. The surfaces of samples exposed to D plasma were also examined in terms of microstructure by scanning electron microscopy. The study has shown that apart from the d-fluence and exposure temperature, the materials’ composition plays a vital role in d-retention, accompanied by blisters and pillar formation. The lowest d-retention was observed for tungsten and the highest in the W-W2C composite. The blisters and pillars were formed in these two materials but not in the WC, which also contains free carbon. At higher D fluence, approximately 15 to 20-times more blisters and pillars were formed in the W-W2C composite than in the tungsten prepared by the same method. The results suggest that the number of defects causing higher d-retention is the highest in W-W2C. On the other hand, the absence of surface irregularities in the WC-C sample after D retention studies indicates that the cause for higher D retention does not lie in the carbides, but, presumably, the microstructural and crystal lattice defects govern the D retention in tungsten-tungsten carbide systems.
Ključne besede: tungsten, (di)tungsten carbide, deuterium, nuclear reaction analysis, thermal desorption spectroscopy
Objavljeno v DiRROS: 03.09.2025; Ogledov: 781; Prenosov: 370
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2. Titanium dioxide in our everyday life : is it safe?Matej Skočaj, Metka Filipič, Jana Nunić, Saša Novak, 2011, pregledni znanstveni članek Povzetek: Background. Titanium dioxide (TiO2) is considered as an inert and safe material and has been used in many applications for decades. However, with the development of nanotechnologies TiO2 nanoparticles, with numerous novel and useful properties, are increasingly manufactured and used. Therefore increased human and environmental exposure can be expected, which has put TiO2 nanoparticles under toxicological scrutiny. Mechanistic toxicological studies show that TiO2 nanoparticles predominantly cause adverse effects via induction of oxidative stress resulting in cell damage, genotoxicity, inflammation, immune response etc. The extent and type of damage strongly depends on physical and chemical characteristics of TiO2 nanoparticles, which govern their bioavailability and reactivity. Based on the experimental evidence from animal inhalation studies TiO2 nanoparticles are classified as "possible carcinogenic to humans" by the International Agency for Research on Cancer and as occupational carcinogen by the National Institute for Occupational Safety and Health. The studies on dermal exposure to TiO2 nanoparticles, which is in humans substantial through the use of sunscreens, generally indicate negligible transdermal penetration; however data are needed on long-term exposure and potential adverse effects of photo-oxidation products. Although TiO2 is permitted as an additive (E171) in food and pharmaceutical products we do not have reliable data on its absorption, distribution, excretion and toxicity on oral exposure. TiO2 may also enter environment, and while it exerts low acute toxicity to aquatic organisms, upon long-term exposure it induces a range of sub-lethal effects.
Conclusions. Until relevant toxicological and human exposure data that would enable reliable risk assessment are obtained, TiO2 nanoparticles should be used with great care.
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4. Insights into microstructural evolution of tungsten-tungsten carbide plasma facing composite materials prepared by field assisted sintering techniqueAljaž Iveković, Matej Kocen, Petra Jenuš, Anže Abram, Črtomir Donik, Saša Novak, 2023, izvirni znanstveni članek Ključne besede: tungsten, tungsten carbide, interface, microstructure, fusion energy
Objavljeno v DiRROS: 07.02.2024; Ogledov: 1587; Prenosov: 1448
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