Sürdürülebilir Kalkınma Amaçları
Yayınlar
- MakaleYalnız künye2026Scopus SJRQ1Upcycling marble waste into construction materials and heavy metal adsorbents via hot-pressed geopolymerization technique
Öksüzer, Nurullah; Uslu, Emin; Gökçe, H. Süleyman
This study presents a sustainable approach to utilizing marble dust waste by producing bifunctional metakaolin-based geopolymers via a synchronized hot-pressing technique. In this study, the environmental footprint was minimized by designing mixtures in which marble waste constituted 50% of the total volume. Three stoichiometric series were investigated by varying the activator modulus (SiO2/Na2O = 3 and 4) and the Si/Al ratio (2 and 3) under two curing temperatures (150 and 300 °C) and three compaction stresses (5, 25, and 50 MPa). Thus, a high-volume industrial byproduct was transformed into a functional component. In this context, it investigated the transformation of industrial products into next-generation materials by using them to produce cementless composite geopolymers for civil engineering and to adsorb heavy metal (Cu2+). As a result of the research, an early compressive strength of 58 MPa was obtained through heat treatment and pressing applied at 300 °C and 50 MPa. This optimum strength was achieved in the SiO2/Na2O = 3, Si/Al = 3 series, whereas excess silica (SiO2/Na2O = 4) and excess aluminum (Si/Al = 2) limited the strength to 16.8 and 35.2 MPa, respectively. Microstructural analyses (SEM/EDS and FT-IR) revealed that marble dust was used as a filler material in the microstructure to produce an N-A-S-H-containing matrix. The produced materials were then ground after their service life and used to purify water containing heavy metals. More than 99.75% of Cu2+ was removed through ion exchange between copper ions used as heavy metals. The residual Cu2+ concentration fell below 0.25 mg/L from an initial concentration of 100 mg/L, and the released Na+-to-adsorbed Cu2+ molar ratio of approximately 1.8–2.3 confirmed an ion-exchange-dominated uptake mechanism. This structural and environmental impact demonstrates that marble waste, which is otherwise discarded as waste, is considered inert, offering an alternative model for the circular economy and environmental applications.
- MakaleAçık Erişim2025Scopus SJRQ2Importance of Melt Cleaning Parameters on Reliability of Tensile Properties in A356 Alloy
Tigli, Ahmet; Uslu, Emin; Çolak, Murat; Dispinar, Derya
This study examines how melt treatment and pouring temperature affect the microstructure and mechanical properties of A356 aluminum alloy. Samples were cast under degassed, non-degassed, and upgassed conditions at 725, 750, and 775 °C. Melt quality was assessed using the reduced pressure test (RPT) and the bifilm index (BI), while microstructural features were analyzed via SEM and EDS. Tensile testing and Weibull statistics were used to evaluate mechanical performance and variability. Results showed that by improper degassing the reproducibility of mechanical properties decreased regardless of hydrogen content of the melt. When bifilm index (BI) was high (> 50 mm), the ductility was lowered and caused greater variability in strength and elongation. SEM confirmed large oxide films in samples, linked to the brittle fracture. The work also highlighted the importance of melt cleaning parameters for the reliability of cast aluminum alloys regardless of the hydrogen content.
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İncele - MakaleAçık Erişim2025Scopus SJRQ1Joule heating of carbon fiber in hybrid composites with glass fibers: Investigation of electro-thermal and vibration characteristics
Uslu, Emin; Yilmaz, Galip; Uyar, Mehmet
This study explores the innovative dual-purpose use of carbon fiber, functioning both as a structural and a heating element, expanding its potential in hybrid composites. A prototype composite was fabricated using the vacuum infusion process, featuring a single carbon fiber layer at the core for dual-purpose and two outer layers of glass fiber. Electrical heating tests revealed a stable relationship between voltage, resistance, power, and temperature, demonstrating efficient heat generation as the voltage increased. Thermal imaging confirmed uniform heat distribution with minor variations. Free vibration tests evaluated the composite's dynamic behavior under various electro-thermal conditions. Results showed that increasing temperature reduced the natural frequencies, particularly in the second vibration mode. Changes in Rayleigh damping coefficients at higher temperatures highlighted the composite's sensitivity to thermal inputs. These findings underline the potential of hybrid composites for advanced applications like turbine blades and aerospace components, where multifunctionality, self-heating, and vibration control are critical.
- MakaleAçık Erişim2025Scopus SJRQ2Evaluation of Fe Content on the Fluidity of A356 Aluminum Alloy by New Fluidity Index
Durmuş, Melek; Dispinar, Derya; Gavgali, Mehmet; Uslu, Emin; Çolak, Murat
Elements that are deliberately added to aluminum alloys or are incorporated into the alloy later depending on the production process affect the final product properties. In addition, liquid metal cleaning is important in minimizing undesirable elements. Considering the production process, one of the most harmful impurities that is likely to pass into the alloy via diffusion for aluminum is the element, Fe. It is known that this is due to the fact that although Fe is highly soluble in liquid aluminum and its alloys, it has very little solubility in solids. Depending on the Fe content, mechanical properties, porosity and fluidity properties are affected in aluminum alloys. In this study, stainless and carbon steel rods were dipped into the melt at 700 °C and 750 °C for 1, 2 and 5 h. Castings were performed before and after degassing. Four-channel fluidity mold with different section thickness was used in the trials. Additionally, microstructure characterization was performed under varying casting conditions. Fluidity Index was proposed which is a single value measured from all fluidity values in different sections. When the results were examined, it was determined that the diffusion material, holding time, casting temperature and liquid metal cleanliness had an effect on the fluidity. Due to the increase in diffusion time, a decrease in fluidity was observed in both carbon steel and stainless steel. It was found that fluidity was significantly reduced when using stainless steel.
AtıfScopus14WoS14OpenAlex15İncele - MakaleAçık Erişim2024Design, Manufacturing, and Comparative Analysis of a Mini Extruder for Polymer Flow Characterization: A Case Study on HDPE and PMMA Polymers
Yilmaz, Galip; Uslu, Emin
Polymer extrusion is one of the most widely used polymer processing methods and the sole option for many standard products. The modern extrusion machine has a very sophisticated design; for example, the extrusion screw has different zones and complex geometry. Determining the proper processing settings is always a challenge for engineers. Additionally, complex rheological properties of the polymers in extrusion sometimes yield challenging and unpredictable problems to troubleshoot. For convenience, a small-scale extrusion machine can be used to troubleshoot and analyze the polymers rather than the large manufacturing machines that are hard to work with. This study has produced a small-scale extrusion machine that is easy to manufacture without deviating from the extrusion process's nature. The extruder, whose production details are given, was tested with two different polymers: HDPE and PMMA. The correct temperature and screw rotation speed were determined with the extruder for the proper process parameters. In addition, the temperature-viscosity relationship of the polymers' flow nature was also determined.
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İncele - MakaleAçık Erişim2024Scopus SJRQ3The effect of cooling plate, mechanical vibration, and grain refinement on the microstructure and hardness of A380 produced by sand mold
Uslu, Emin; Tiğli, Ahmet; Çolak, Murat
The mechanical properties of aluminium alloys can be increased by controlling the grain size and morphology of the alloy. In these studies, mechanical vibration, cooling slope plate (CSP), and grain refiner were applied on sand mould casting using A380 alloys. The hardness, and microstructure of the cast samples are investigated. These processes lead to the refinement of grain structures and a decrease in the tendency for dendritic structure formation. The Effect of the solidification time (modulus) on the microstructure is investigated. It was determined that the solidification time varies depending on the section thickness, which affects the SDAS values. It was observed that the lowest SDAS values were in CSP and the highest values were in grain refiners added casting. The lowest hardness value was recorded at CSP casting. Meanwhile, the grain refiner added vibration casting exhibits the highest hardness.
AtıfScopus10WoS10OpenAlex10İncele - MakaleYayıncıda açık erişim2023Scopus SJRQ3Solidification analysis for variable thickness aluminum castings: simulation and chill design insights
Yilmaz, Galip; Colak, Murat; Uslu, Emin
Manufacturing high-quality casting parts with complex geometries requires high engineering skill and precision. One essential quality concern is isolated hot spots within the castings, often in thick sections. Each hot spot must be consistently fed or mitigated through directional solidification techniques. The impact of various mold sands and the geometry of chill parts on solidification direction was investigated using specialized casting and general-purpose simulation programs. A parametric optimization method was employed to analyze directional solidification to adjust the geometry of the chill parts. The results indicate that employing diverse mold sands to enhance cooling in the thick sections was a viable strategy for achieving directional solidification in parts where the feeding pathway is obstructed due to changes in cross-section. Furthermore, the study revealed that intricate details in the chill part’s geometry are not critical; however, a minimum volume (or weight) was necessary for adequate directional solidification. Lastly, an easily applicable mathematical model has been developed to determine the required volume of chill parts to ensure successful directional solidification.
AtıfScopus1WoS1OpenAlex1İncele - MakaleAçık Erişim2023Scopus SJRQ1A new approach for high-quality production of UHMWPE by applying powder vibration densification before sintering
Yilmaz, Galip; Uslu, Emin
Due to its extreme viscosity, UHMWPE powder requires elevated pressure and temperature settings to ensure a fully solid structure. But a gentle process is vital for reliability in certain applications, such as prosthetic liners. A unique type of large gap, not mentioned in the literature, has been observed to resist closing more than regular gaps due to the number of particles forming a shield against pressure. As a solution, a mechanical vibration treatment of the particles before heating was used to eliminate these particular large gaps. Optimum vibration parameters were found, and the samples' final solid density and mechanical properties increased. The particles' dimensions and coefficient of friction were measured, and their vibration-dependent characteristics were discussed. A custom-made microscope apparatus was used to observe the vibration-induced densification of the particles and the gaps resisting closing.
AtıfScopus14WoS14İncele - MakaleAçık Erişim2022Tek ve çift katmanlı yapay damar konfigürasyonlarının Holzapfel-Gasser-Ogden hiperelastik modeli ile mekanik uyumluluk analizi
Yilmaz, Galip; Uslu, Emin
Yaygınlaşan kalp-damar hastalıkları, yapay damarların önemini artırmıştır. Üretim şartları gereği farklı tasarımlar içeren bu damarların, doğal bir mekanik davranış göstermesi gerekmektedir. Üretim öncesi ihtiyaç duyulan analizlerin yapılması için karmaşık ve hiperelastik bir özellik gösteren damar mekaniğini modelleyen birçok çalışma bulunmaktadır. Bunlar arasından yaygın kullanımı olan Holzapfel-Gasser-Ogden (HGO) hiperelastik modeli bu çalışmada kullanılmıştır. Bu çalışma kapsamında bir simülasyon ortamı HGO modeliyle hazırlanmış ve literatürdeki verilerle doğruluğu teyit edilmiştir. İlk numune iki katmanlı tipik bir yapıda oluşturulmuştur. Sonraki numunelerde üretimde karşılaşılan farklı yöntemlere dayanan katman konfigürasyonları denenmiştir. İkinci numune için dış katmanın normalden çok ince bir yapıda tasarlandığı durum incelenmiştir. Az bir uyumsuzluk olmasına rağmen kalınlığı azalan dış katmanın damarın mekanik özellikleri üzerinde güçlü bir etkisinin olmadığı gözlemlenmiştir. Üçüncü tip numunede ise dış katmanın geometrik ve malzeme özellikleri bakımından iç katman olarak tasarlandığı bir durum denenmiştir. Mekanik özelliklerinin karmaşık ve uyumsuz olduğu gözlemlenmiştir. Son numune olarak, tek katmanlı bir yapı tasarlanmıştır. Bir miktar uyumsuzluk gösterse de bu numune sadelik açısından avantajlı bulunmuştur. Ayrıca ikinci ve üçüncü numunelerin malzeme parametreleri değişimiyle uyum analizi yapılmıştır. Üçüncü numunenin aksine ikinci numune için dış katman içindeki liflerin malzeme özelliklerinin ayarlanmasıyla kolayca referans numunesinin özelliklerinin yakalanabileceği gösterilmiştir.
- MakaleYalnız künye2021Scopus SJRQ2Determination of mechanical properties of polymer matrix composites reinforced with electrospinning N66, PAN, PVA and PVC nanofibers: A comparative study
Uslu, Emin; Gavgali, Mehmet; Erdal, Mehmet Okan; Yazman, Şakir; Gemi, Lokman
Fiber-reinforced polymer matrix composites are widely used in many structural applications thanks to their exceptional properties. In recent years, the use of electrospinning nanofibers with unique properties as reinforcement agents has attracted a great deal of attention in improving the performance of these composites. Although there are many promising studies on this subject in the literature, there are still many issues that need to be investigated. In this study, an experimental research reporting on the production and mechanical properties of two-phase polymer matrix composites reinforced with various types of thermoplastic nanofibers is presented. Nanofiber mats were produced from N66, PAN, PVA, and PVC polymers by electrospinning technique. Composites were obtained by embedding these nanofibers into epoxy resin by using vacuum infusion process. Mechanical properties of the composites were determined by performing tensile tests and the results were compared. The morphologies of nanofibers and the fracture surfaces of the composites were examined with SEM. Finally, statistical evaluations were carried out using mechanical data. According to tensile test results, the best ultimate tensile strength of 38.04 ± 3.7 MPa, elongation of 2.46 ± 0.4 % and toughness of 532 ± 137 kJ/m3 were obtained from N66 nanofiber composite, while PVA nanofiber composite was the most favorable in terms of Young's modulus (2.40 GPa). It was observed that the polymer type significantly affected the performance of the composite. In addition to the best mechanical properties, N66 composite was found to be more stable and reproducible than other specimens. Due to the good impregnation of nanofibers, it was conclusively determined that the use of vacuum infusion process is suitable for the production of these materials.
AtıfScopus79WoS73OpenAlex81İncele - MakaleYalnız künye2019Scopus SJRQ1A novel perspective for Lactobacillus reuteri: Nanoencapsulation to obtain functional fish fillets
Ceylan, Z.; Uslu, Emin; İspirli, Hümeyra; Meral, Raciye; Gavgalı, Mehmet; 'Yilmaz, Mustafa Tahsin; Dertli, Enes
Enrichment of food products with beneficial Lactic Acid Bacteria (LAB) is an important methodology used to develop functional food products. Lactobacillus reuteri E81 was successfully nanoencapsulated into poly (vinyl alcohol)-based nanofibers for its application to the surface of fish fillets. The Scanning Electron Microscopy analysis confirmed the nanoencapsulation of L. reuteri E81 in electrospun nanofibers (LRNF) that had an average diameter of 381.83 ± 130.69 nm. LAB growth in rainbow trout fillets and fatty fish (mackerel) and were found to be 2.92 and in the range of 3.27 and 2.66 log CFU/g, respectively. Importantly, the antioxidative characteristics of fish fillets significantly increased following their coating with LRNF. The results revealed a significant increase in the inhibition of free radicals in the samples treated with nanoencapsulated L. reuteri as compared to control group fish fillet samples. DPPH activity significantly increased to 40.24%, 44.96%, 44.97 in mackerel samples treated with nanoencapsulated L. reuteri (MLR) and increased to 19.76%, 20.87%, 21.46% in rainbow samples treated with nanoencapsulated L. reuteri (RLR). MLR samples exhibited the highest ABTS radical-scavenging activity (1631 μmol TEAC/g). FRAP value of MLR samples was found to be 1.70 times higher than the control group samples.
AtıfScopus50WoS37OpenAlex45İncele
