Published in a leading journal for ceramic materials we have published our work based on demonstrating a simple, viable and effective solution for modification of the 3Y-TZP dental implant surfaces by a combination of micro- and nano-roughnening improving their osseointegration and antibacterial properties. Micro-roughening was achieved by gentle sandblasting, while nano-roughening by a simple, non-invasive, additive approach of a nanostructured alumina coating deposition. The combination of micro- and nano-roughness performed best regarding the adhesion and differentiation of human osteoblasts, while also minimising the attachment of bacteria by either limiting their adhesion or by killing significant proportions of the adhered ones. Since both methods of 3Y-TZP surface functionalisation are already well established in dental laboratories, the presented results bring exciting practical applicability. The work was based on experimental part of diploma thesis of Juliane Moritz from TU Dresden, Germany, which Juliane conducted within the activities of research programme work under the supervision of dr. Andraž Kocjan. In addition, the work was recognised by Deutsche Keramische Gesellschaft since awarding the first author, Juliane Moritz, with prestigious Hans-Walter Hennicke lecture prize for the best lecture given by young ceramists during the annual 2018 DKG conference that was held in Munich in April 2018.
COBISS.SI-ID: 32431143
Tungsten (W) and various composites are being considered as the primary plasma-facing materials for application with harsh operational environment such as fusion reactors. Like all engineering materials, they contain certain levels of impurities, which can have an important impact on mechanical properties. In the present work, oxygen was identified as a major impurity in our starting tungsten powder. At elevated temperatures, the presence of interstitial elements such as oxygen leads to the formation of an oxide-rich tungsten phase at the tungsten grain boundaries. In this study, we determined the capacity of tungsten carbide (WC) nanoparticles to remove the oxide impurities from a tungsten body. Tungsten composites with 0.05, 0.25 and 0.51 wt. % carbon (C) in the form of WC were sintered using a field-assisted sintering technique (FAST or SPS – Spark Plasma Sintering) at 1900 °C for 5 min. The sintered samples were characterized using field-emission scanning and transmission electron microscopy. Thermodynamic and kinetic considerations allowed us to determine the optimum theoretical amount of WC to prevent the in-situ formation of WO2. The properties of metals and alloys depend to a large extent on impurities. The presence of oxygen in tungsten greatly reduces its mechanical properties as well as thermal and electrical conductivity, which severely limits its ability to use. The presented article examines the influence of oxygen on the concentration of tungsten metal and the prevention of the formation of undesirable oxides by the addition of carbon during the concentration itself. The achieved research results enables the preparation of tungsten-based materials by the SPS sintering process, which do not contain undesirable oxide phases in their composition. In this way, many possibilities of preparation and use of tungsten, tungsten alloys and composites are opened, which will enable their use in advanced engineering applications such as future fusion power plants.
COBISS.SI-ID: 32476967
In an interdisciplinary research conducted in a collaboration with researchers from the Department for Materials synthesis JSI and Department of Catalysis and Reaction Engineering of the National Institute of Chemistry we have published our work in the renowned scientific journal Green Chemistry. We demonstrate application of magnetic heating of nanoparticles in AC-field to drive chemical reaction. The authors showed that conversion of furfural to furfuryl alcohol over the catalyst in the same time interval reached 95% when “targeted” heating by AC magnetic field was used, but only 63% when conventional heating was applied. They were the first to show that a well-designed hierarchical composite (UK patent application; COBISS.SI-ID 32193319) can simultaneously serve as a catalyst and heat source to drive a technologically important chemical reaction in a slurry-type reactor. The long-term activities of the P2-0087 program in connection with the research of AlN powder hydrolysis contributed to the success and impact of the achievement. Understanding and controlling hydrolysis reactions enabled us to exploit the hydrolysis for facile synthesis of extremely pure hierarchically ordered boehmite nanoparticles (g-AlOOH), which after calcination was converted to alumina (g-Al2O3) with a high proportion of mesoporosity and a large specific surface area (MA). These MA particles were used as a platform or carrier for magnetic and catalytic nanoparticles in the exposed study. Successful handling of MA particles was key in the abovementioned achievement - in parallel we studied dispersion and rheological behaviour of aqueous suspensions containing high solid loading of MA powder. The aim was to prepare suspensions, containing micron-sized particles of ??Al2O3, able to defy sedimentation and segregation. The addition of divalent cations (Mg2+ in Ca2+) or cellulose nanofibers (CNF) triggered the formation of various interparticle associations for tailoring the sedimentation and the stability of these suspensions (Figure 7). The work was published in the leading scientific journal for ceramic materials Journal of the European Ceramic Society (A˝, IF 4.5, COBISS.SI-ID 28158467). Preparation of such suspensions is an important milestone in preparation of advanced, porous ceramic materials relevant in catalysis and adsorption.
COBISS.SI-ID: 25023491
In collaboration with the Department of Prosthetics Dentistry (MF-UL), we recently achieved an important milestone with the finalisation of an in vivo clinical study of the aging of 3Y-TZP ceramics in the oral environment. The results were published in consecutive articles "In vivo aging of zirconia dental ceramics - Part I and II" in the leading scientific journal from the field of dental materials Dental Materials (COBISS.SI-ID 4373990 and 44538115). We were the first to report on the results of in vivo aging in such a thorough study, varying the 3Y-TZP chemical composition, surface treatment (intact, polished or sandblasted) and sintering conditions. We provided a more appropriate correlation of in vitro–in vivo data, which will allow a true estimate of the lifespan of 3Y-TZP. We showed that conventional 3Y-TZP was susceptible to in vivo aging, as after two years the in vivo aging kinetics were almost 3 times faster than the generally accepted in vivo–in vitro extrapolation. High translucent 3Y-TZP ceramics were more susceptible to aging than conventional 3Y-TZP. After 4 years of aging, the in vivo extent of transformation was not yet a cause for clinical concern, but was more pronounced in materials prepared by rapid sintering. The results provide a broad insight into the stability of one of the most popular dental ceramics, enabling dental technicians and dentists to more easily predict and plan 3Y-TZP`s life expectancy and consequently more comprehensive patient care planning. The publications are integral parts of the final results related to the ARRS project J2-9222 Towards reliable implementation of monolithic zirconia dental restorations (PI doc. dr. Andraž Kocjan).
COBISS.SI-ID: 43739907
In the scope of doctoral dissertation studies of Hermina Hudelja we have studied naturally self-driven AlN powder hydrolysis and exploited it for a quick, facile and pure synthesis path for the preparation of abundant amounts of hierarchically-assembled, nanocrystalline, mesoporous alumina (MA) powder in the form of micron-sized bundles of agglomerated nanocrystalline 2D lamellas, or nanosheets, forming flower-like structures. A part of Hermina Hudelja's PhD project included a study of dispersion and rheological behaviour of aqueous suspensions containing MA powder. The aim was to prepare suspensions, containing micron-sized particles of ??Al2O3, able to defy sedimentation and segregation. The addition of divalent cations (Mg2+ in Ca2+) or cellulose nanofibers (CNF) triggered the formation of various interparticle associations for tailoring the sedimentation and the stability of these suspensions. The work was published in the leading scientific journal for ceramic materials Journal of the European Ceramic Society. Preparation of such suspensions is an important milestone in preparation of advanced, porous ceramic materials relevant in catalysis and adsorption. Stable suspensions were subsequently freeze-casted. The ceramic foams prepared in this way showed extremely high porosity (70-90%) and low thermal conductivity (20-80 mW / mK) but satisfactory compressive strength. The results pubished in the newly established openaccess sisterly journal of JECS Open Ceramics (COBISS.SI-ID 51386371) represent a second published paper from PhD student Hermina Hudelja. The longterm-based expertise on the hydrolysis of AlN powder led to successful cooperation, which has led to the achievement described under point 3.
COBISS.SI-ID: 28158467