Browsing by Author "Topuz, Fatma Coskun"

Now showing 1 - 3 of 3

Drying Kinetics and Quality Properties of Mellaki (Pyrus Communis L.) Pear Slices Dried in a Novel Vacuum-Combined Infrared Oven
(Wiley-hindawi, 2022) Topuz, Fatma Coskun; Bakkalbasi, Emre; Aldemir, Adnan; Javidipour, Issa
In a specially designed infrared oven equipped with a two-way infrared heating and vacuum pump systems, the effects of drying parameters (100-300 W infrared powers and 100-250 mmHg vacuum pressures) on drying kinetics and quality properties of pear slices were comprehensively studied. The samples dried at 300 W had high HMF values (12.73-95.68 mg/kg d.m). The highest sensory scores were observed in pear slices dried at 300 W and 250 mmHg. Six different mathematic models were taken into account to analyze the drying characteristics of pear slices, with the Wang and Singh model (R-2 = 0.9996, chi(2) = 0.0004, and RSME = 0.0062) presenting the best prediction of the drying behavior. The effective moisture diffusivity values were 1.1829-4.6684 x 10(-8). The activation energies for 100 and 250 mmHg vacuum applications were 44.21 and 43.89 kJ/mol, respectively. It was concluded that a vacuum-combined infrared dryer (300 W, 250 mmHg) could be a fast and economic method for drying pear slices. Novelty impact statement A combination of 300 W infrared power and 250 mmHg vacuum pressure was the fastest combination for the drying of pear slices and gave the highest score in sensory evaluation. The Wang & Singh model exhibited the best results in fitting the experimental data. As a result, the vacuum-combined infrared technology was improved the drying efficiency and quality of dried pear.
Nb2CTx Mxene-Pistachio Shell-Filled Chitosan Coatings on Zn Biomaterial for In Vitro Corrosion and Bioactivity Improvement
(MDPI, 2025) Topuz, Mehmet; Topuz, Fatma Coskun
This study aims to enhance the corrosion resistance and bioactivity of zinc surfaces through the development of chitosan-pistachio shell (CPM) coatings reinforced with Nb2CTx MXene. The approach introduces a sustainable pathway by incorporating waste pistachio shells as a natural, eco-friendly additive within a biopolymer matrix. Comprehensive structural and surface characterizations confirmed the homogeneous dispersion of Nb2CTx and the successful fabrication of the hybrid coating. Electrochemical analyses in simulated body fluid demonstrated that the CPM coatings markedly improved the corrosion protection of zinc by shifting the corrosion potential to more noble values, reducing current density and increasing polarization resistance. Impedance results further indicated enhanced charge transfer resistance and stable diffusion-controlled behavior. The coatings also exhibited stronger adhesion, higher hydrophilicity, and improved surface compatibility. After immersion in simulated body fluid, the formation of a dense apatite layer on the CPM surface confirmed the coating's excellent bioactivity. These findings demonstrate that Nb2CTx-reinforced CPM coatings significantly enhance the functional performance of zinc, combining corrosion resistance, biocompatibility, and mechanical stability. Moreover, the use of pistachio shell waste underscores the potential of sustainable biomaterials in developing environmentally friendly coatings for biomedical applications.
Sustainable Walnut Shell-Filled Polylactic Acid-Hydroxyapatite Hybrid Coatings for Enhanced Corrosion Resistance and Bioactivity of Magnesium Biomaterials
(Wiley, 2025) Topuz, Mehmet; Topuz, Fatma Coskun; Dikici, Burak; Seifzadeh, Davod
Due to the high corrosion rate and limited biocompatibility of commonly used magnesium (Mg) and its alloys, current studies have focused on surface modification techniques. In this study, which is aimed at overcoming these obstacles in biomedical applications, hybrid coatings of PLA-HA-Walnut shell (Wshell) were successfully applied to Mg substrates. The presence of micropores on the surfaces of the hybrid coatings was detected using SEM surface morphology, and the elemental composition and structural characterization of the coatings were confirmed through analyses. With a higher Wshell fraction, the corrosion current density decreased significantly compared to uncoated Mg and PLA-coated Mg, increasing the electrochemical corrosion resistance of Mg. The adhesion strength between the coatings and the Mg substrates increased to grade 3B with Wshell-filled hybrid coatings. Moreover, the contact angle of PLA-coated Mg decreased as the Wshell fraction increased, indicating enhanced surface wettability. Wshell hybrid coatings exhibit fibrous morphology and the formation of Ca- and P-rich layers. These results, along with the filling of Wshell, suggest that PLA-HA-Wshell hybrid coatings could be a promising additive material for potential next-generation low-cost and sustainable biomedical coatings to enhance the corrosion resistance and bioactivity of Mg.