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: 2Citation - Scopus: 1Pressureless Synthesis and Consolidation of the Entropy-Stabilized (hf<sub>0.25</Sub>zr<sub>0.25< Composite by Ultra-Fast High-Temperature Sintering (uhs)(Elsevier Sci Ltd, 2025) Feltrin, Ana C.; De Bona, Emanuele; Karacasulu, Levent; Biesuz, Mattia; Sglavo, Vincenzo M.; Akhtar, FaridEntropy-stabilized Ultra High-Temperature Ceramics (UHTC) offer a groundbreaking solution to the challenges of extreme environments, showcasing enhanced mechanical properties, thermal stability, and resistance to oxidation at high temperatures. The consolidation of UHTC by ultra-fast high-temperature sintering (UHS) significantly reduces processing times and temperature and can produce dense high-performance ceramics with superior mechanical properties. This study reports the pressureless synthesis and consolidation of the entropy-stabilized (Hf0.25Zr0.25Ti0.25V0.25)B-2-B4C composite through UHS within 1 minute, starting from transition metal diboride powders. B4C acts as an effective sintering aid, promoting the densification of the system and the formation of a nearly single-phase hexagonal diboride with a diboride-eutectic phase. Furthermore, a secondary minor hexagonal phase rich in V and Zr is formed close to the eutectic regions. Sintering currents of 40 A were necessary to reach densities higher than 90 % under pressureless conditions, achieving nano hardness higher than 27.3 GPa, comparable with high-entropy diborides produced by Spark Plasma Sintering. The study highlights the entropy-stabilized phase formation, diffusion, densification, and grain growth mechanisms involved during UHS. The work contributes to the understanding of entropy-stabilized ceramics produced by UHS as a faster and less energy-consuming process than conventional sintering methods.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: 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.Article Citation - WoS: 103Citation - Scopus: 110Cold Sintering of Ceramics and Glasses: a Review(Elsevier Ltd., 2020) Ahmetoğlu, Çekdar Vakıf; Karacasulu, LeventTraditionally ceramic artifacts are processed at high temperatures (> 1000 degrees C) by classical sintering techniques such as solid state, liquid phase and pressure-assisted sintering. Recently, inspired from the geology, novel sintering approaches that allow the densification of ceramic components at relatively low temperatures <= 400 degrees C have been proposed. While initial efforts for such low temperature densification concept were developed in the mid-70s, the topic has become increasingly prominent in the last decade. Currently, these low temperature methods can be classified into four main groups: (i) hydrothermal reaction sintering (HRS), (ii) hydrothermal hot pressing (HHP), (iii) pressure-assisted densification techniques: room-temperature densification (RTD), cold sintering (CS), warm press (WP), and finally no-pressure assisted method called (iv) reactive hydrothermal liquid phase densification (rHLPD). Above named techniques are commonly assisted by an aqueous solution used as either reactant or transient liquid phase to assist densification. Starting from the background in traditional sintering processes, this review aims to explore in depth the existing literature about low temperature densification approaches along with their advantages & disadvantages, and probable application areas.Article Citation - WoS: 14Citation - Scopus: 17Electrical Characteristics of Low Temperature Densified Barium Titanate(Elsevier, 2020) Karacasulu, Levent; Tokkan, Melike; Bortolotti, Mauro; Ischia, Gloria; Adem, Umut; Ahmetoğlu, Çekdar VakıfA low temperature densification technique, i.e. reactive hydrothermal liquid-phase densification (rHLPD) was followed to obtain highly dense BaTiO3 components at temperatures <= 240 degrees C. The formed ceramics were characterized concerning not only the structural features but also the electrical properties. The increase of both reaction time and temperature resulted in enhanced densification of BaTiO3 components reaching about 90% of theoretical density. The presence of the tetragonal BaTiO3 was demonstrated by both XRD and TEM analysis. Despite the low reaction temperatures, the samples showed promising dielectric, ferroelectric and piezoelectric functionality without additional annealing. A broad dielectric peak was observed around 135 degrees C at the Curie temperature; saturated hysteresis loops and corresponding butterfly-shaped strain-electric field loops were obtained. BaTiO3 sample subjected to hydrothermal reaction at 240 degrees C for 72 h yielded a piezoelectric coefficient of 84 pC/N.