Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection

Permanent URI for this collectionhttps://hdl.handle.net/11147/7148

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Author: search.filters.author.Toprak, SeyraLanguage: search.filters.language.en

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  • Article
    Effect of TiO2 and ZrO2 Additions on Sintering and Mechanical Properties of Dental Porcelain Material
    (Springer, 2025) Aouadja, Faycal; Toprak, Seyra; Demir, Mustafa M.; Boudchicha, Mohamed Redda
    This study investigates the influence of varying TiO2 (0-15 wt.%) and ZrO2 (15-0 wt.%) additions on the microstructure, densification, and mechanical properties of dental porcelain composites fabricated from local Algerian raw materials. The samples were produced by cold compaction and sintered at temperatures ranging from 1100 degrees C to 1250 degrees C. Advanced characterization techniques-X-ray diffraction, Fourier-transform infrared spectroscopy, and scanning electron microscopy-were employed to analyze phase evolution and microstructural morphology. The results indicated that increasing TiO2 content while decreasing ZrO2 enhanced both densification and mechanical strength. The optimal composition-15 wt.% TiO2 sintered at 1200 degrees C-achieved the highest bending strength (177 MPa) and Martens hardness (2931 MPa). TiO2 functioned as a fluxing agent, promoting grain cohesion, whereas excessive ZrO2 content led to the formation of structural defects. These findings highlight the potential of optimized formulations to meet the requirements for high-performance, biocompatible dental ceramics and support the development of sustainable porcelain using abundant natural resources.
  • Article
    Citation - Scopus: 4
    One-step hydrothermal synthesis of spinel manganese oxide ion-sieve from commercial Γ-Mno2 and its uptake performance for lithium
    (Elsevier Ltd, 2024) Toprak, Seyra; Demir, Mustafa Muammer
    The selective extraction of lithium from aqueous systems necessitates efficient sorbent materials. Spinel-type lithium manganese oxide ion sieves (LMOs) have been bee recognized for their high performance in this application. However, the elevated market cost of the spinel form (λ-MnO2) raises economic concerns, posing challenges to the feasibility of the extraction process. In this study, the one-step hydrothermal synthesis of Li1.33Mn1.67O4 was carried out at 200 °C for 7 days using commercial γ-MnO2 powder and aqueous LiOH solution as reactants. The synthesized powder exhibited characteristic XRD reflections consistent with spinel Li1.33Mn1.67O4. Lithium ion-sieve (H1.33Mn1.67O4) was obtained by leaching the LMO product with dilute hydrochloric acid solution. The sorption capacity of γ-MnO2 is increased from 8.4 to 23.1 mg/g (C0=200 mg/L), this capacity is very close to the one of the commercial λ-MnO2. The synthesized spinel HMO sorbent achieved a maximum Langmuir adsorption capacity of 52.1 mg/g. The extraction efficiency reached 94% at the sorbent dose of 20 g/L. The distribution coefficients of metal ions were in the order Li+ > Ca2+ > K+ > Na+, emphasizing selective Li+ extraction from brines with high Na+ content. These findings highlight the successful development of a spinel-type lithium manganese oxide ion sieve from γ-MnO2 polymorph, which is nearly an order of magnitude cheaper than the selective λ-MnO2. The study addresses critical issue of economic feasibility in lithium extraction processes, providing a potential solution for the selective recovery of bulk lithium. © 2024 Elsevier Ltd