Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 1Citation - Scopus: 1Fast Firing Technique for Martian Regolith Simulant: Advancing Isru Capabilities(Academic Press inc Elsevier Science, 2025) Karacasulu, Levent; Tomasini, Alessandro; Vakifahmetoglu, Cekdar; Biesuz, MattiaIn-Situ Resource Utilization (ISRU) approaches hold significant importance in plans for space colonization. This work explores a different ISRU concept applying fast-firing, a robust and well-known industrial process, to Mars regolith simulant (MGS-1). The fast-fired specimens were compared to the ones obtained by conventional sintered under low heating rates. When the holding time at the firing temperature is longer than 15 min, fast-fired specimens exhibited higher density and flexural strength (> 35 MPa) than conventional sintering. For both processes, the bulk density values and the mechanical properties of the regolith compacts were enhanced with increasing dwell time. This was attributed to higher heating rates changing the densification/crystallization kinetics involving the basalt glass in the regolith composition. Specifically, high heating rate promotes sintering over crystallization. On these bases, fast firing can be considered a potential candidate for ISRU on Mars.Article Citation - WoS: 1Citation - Scopus: 1Pressureless Joining of Soda Lime Silicate Glass Using Polysilazane-Derived Silica at Near-Room Temperature(Elsevier Sci Ltd, 2025) Karacasulu, Levent; Biesuz, Mattia; Pastorelli, Virginia; Vakifahmetoglu, Cekdar; Sglavo, Vincenzo M.; Ferraris, Monica; Soraru, Gian D.Perhydropolysilazane (PHPS) pre-ceramic polymer was used to join soda lime silicate glass at temperatures below 200 degrees C under pressureless conditions. The results show that: (i) the junction material is largely converted to silica at 100 degrees C and fully converted to glass at 150 degrees C; (ii) the samples treated at room temperature and 100 degrees C show a perfectly dense and clean bond, whereas porosity develops starting from 150 degrees C as a result of the hydrolysis reactions and solvent evaporation; (iii) a maximum tensile bond strength of about 5-6 MPa is obtained after treatments at 100 degrees C. Remarkably, after treatment at 500 degrees C, the junction remains intact. These preliminary findings provide the first successful attempt regarding the use of PHPS as a joining material to produce inorganic and transparent bonds for glass at relatively low temperatures.Article Citation - WoS: 5Citation - Scopus: 5Ultrafast High-Temperature Sintering of Yttria-Stabilized Zirconia in Reactive N<sub>2</Sub> Atmosphere(Elsevier Sci Ltd, 2025) Karacasulu, Levent; de Beauvoir, Thomas Herisson; De Bona, Emanuele; Cassetta, Michele; Vakifahmetoglu, Cekdar; Sglavo, Vincenzo M.; Biesuz, MattiaSo far, ultrafast high-temperature sintering (UHS) has always been carried out in an inert environment. In the present work, we investigated UHS of 3YSZ in nitrogen and argon atmosphere showing that "the atmosphere matters". Highly densified samples can be obtained in both environments but densification and grain growth are significantly retarded in N-2. Moreover, the phase evolution is strongly atmosphere-dependent with the samples treated in Ar remaining tetragonal and those treated under N-2 progressively reducing their tetragonality, eventually converting into cubic zirconia and rock salt oxynitride. The results can be explained by the incorporation of nitrogen within the ZrO2 lattice. Electrochemical impedance spectroscopy demonstrates that while the ionic bulk conductivity are marginally influenced by the sintering atmosphere, the grain boundaries' capacitive behavior strongly changes. After UHS under 30 A, excellent ionic conductors were obtained without substantial grain boundary-blocking effects.Article Citation - WoS: 5Citation - Scopus: 5Sioc Foam-Aerogel Composites: Optimal Balance of Lightness and Excellent Thermal Insulation(Wiley, 2024) Icin, Oyku; Abebe, Adane Muche; Soraru, Gian Domenico; Vakifahmetoglu, CekdarFoam-aerogel composites are synthesized in polymeric, hybrid, and ceramic states by completing the open cells of the foam with a solution forming a wet gel, carbon dioxide (CO2) supercritically dried, and pyrolyzed. Thermal diffusivity measurements are conducted using the laser flash, and for mechanical performance, cold crushing tests are done to obtain compressive strengths. Samples possess a range of specific surface area (SSA) values up to similar to 650 m2/g contingent upon the material state, that is, polymeric, hybrid, or ceramic. While SSA values can be deliberately altered, almost all samples demonstrated a total porosity of similar to 90 vol%, with superb specific compressive strength reaching around 2 MPa. In addition to adjustable surface characteristics granting hydrophobic and hydrophilic features, the study revealed the potential use of these foam-aerogel composites as thermal insulators with low thermal conductivities of 0.02 W<middle dot>m-1<middle dot>K-1 at RT and 0.05 W<middle dot>m-1<middle dot>K-1 at 500 degrees C. When exposed directly to a butane flame gun with a flame temperature reaching similar to 1200 degrees C, from the backside of a 5 mm-thick foam-aerogel composite, only similar to 200 degrees C is recorded, which is lower than a comparable commercial insulator panel tested under the same conditions.Article Citation - WoS: 8Citation - Scopus: 12Synthesis of Potassium-Sodium Niobate (Knn) From Nbo2(Elsevier, 2021) Piskin, Cerem; Karacasulu, Levent; Bortolotti, Mauro; Vakifahmetoglu, CekdarKxNa1-xNbO3 (0 < x < 1) were synthesized via hydrothermal method using niobium dioxide (NbO2) as the niobium source instead of the most common one, Nb2O5. Potassium-rich KxNa1-xNbO3 (x > 0.5) was obtained from 8 M total hydroxide concentration after 6 h of reaction at 200 degrees C. Rietveld refinement of the XRD data revealed that all samples exhibited the secondary NaNbO3 phase. However, the lowest amount (3.74 vol%) was obtained for 24 h of reaction under 10 M alkaline solution. After 3 h of reaction, dodecahedra shaped hexaniobate phase (KxNa8-xNb6O19.nH(2)O) was observed. Those structures were, subsequently, replaced by similar to 3 mu m cube shaped KNN crystals, obtained under 10 M reaction in 24 h time period.