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- MakaleAçık Erişim2026Scopus SJRQ1Comparative Mechanical and Thermal Performance of Graphene- and Silver Nanoparticle-Reinforced PLA Fabricated by FDM 3D Printing
Karabudak, Filiz
The increasing demand for high-performance and multifunctional polymer materials has driven interest in improving the mechanical properties of polymer components produced through additive manufacturing. This study aims to systematically investigate and comparatively evaluate the effects of low-content nanofiller incorporation on the structural, thermal, and mechanical performance of PLA-based materials produced via fused deposition modeling (FDM), with a focus on identifying filler-dependent behavior under different loading conditions. In this study, polylactic acid (PLA) composites reinforced with 0.5 wt.% graphene (Gr) and 0.5 wt.% silver (Ag) nanoparticles, added separately, were produced using fused deposition modeling (FDM) and comparatively investigated. Each nanofiller was incorporated individually into PLA-based filaments, and standard test specimens were fabricated via 3D printing. Structural, thermal, and mechanical properties were evaluated using tensile, compressive, and three-point bending tests, along with SEM, EDS, XRD, FTIR, DSC, and TGA analyses. The results showed that pure PLA exhibited typical brittle behavior and a single-stage thermal degradation profile. The tensile strength of pure PLA was 41.93 MPa, and the flexural strength was 70.76 MPa. The addition of 0.5 wt.% graphene led to noticeable improvements, particularly in flexural properties, while only a minimal (almost negligible) increase was observed in tensile strength, with tensile strength increasing to 42.24 MPa (+0.74%) and flexural strength increasing to 110.78 MPa (+56.6%). In contrast, 0.5 wt.% Ag exhibited mixed and load-dependent mechanical behavior, with slight improvements in flexural strength but reductions in tensile and compressive properties, where tensile strength decreased to 22.13 MPa (−47.2%) while flexural strength increased to 112.06 MPa (+58.3%). Structural and thermal analyses indicated that both nanofillers did not significantly alter the PLA matrix chemically, while contributing to controlled changes in material properties primarily through physical interactions. The novelty of this work lies in the comparative evaluation of graphene and silver nanoparticle reinforcement at a fixed low loading level within FDM-processed PLA, combined with a comprehensive and correlated analysis of mechanical, structural, and thermal behavior on the same specimen sets, enabling a clearer understanding of filler-dependent performance mechanisms in additively manufactured nanocomposites. Overall, it was concluded that low-rate nanofiller additions, when properly dispersed, may lead to selective improvements in the performance of PLA-based composites depending on filler type and loading mode, and show potential for advanced engineering applications such as lightweight structural components, functional sensors, and additive-manufactured parts requiring tailored mechanical performance and multifunctionality.
- Yüksek Lisans TeziAçık Erişim2022Klinik gram negatif bakterilerde virulans faktör genleri ile biyofilm oluşumlarının belirlenmesi ve rumex gümüş nanopartikülünün antibiyofilm aktivitesinin araştırılması
Gamze Yüksel
Çeşitli örneklerden 188 Gram negatif bakteri izole edilmiş ve antibiyotik duyarlılık testleri yapılmıştır.188 suşta, sınıf 1 integron, virülans ve antibiyotik direnç genlerinin varlığı PCR ile araştırıldı. blaOXA-23 ve blaOXA-51 genleri pozitif olan örnekler, pGEM-T vektörüne klonlandı ve plazmitler, DNA dizi analizine gönderildi. Suşların biyofilm oluşturma kapasiteleri ve Rumex gümüş nanopartikülün antibiyofilm etkisi kantitatif olarak belirlendi. İzolatlarda sırasıyla aer (%29.78), sfa (%28.19), afa (%27.12), cnf (%21.27), pap (%12.76) ve hly (%12.76) virulans faktör genleri bulundu. Sınıf 1 integronlar suşlar arasında yüksek oranda (%88.82) tespit edildi. İzolatların %46.27'sinin biyofilm oluşturma yeteneğine sahip olduğu belirlendi. PMQR genleri, 15 izolatta tespit edildi. 16 suşta blaOXA-23 geni, 19 izolatta ise blaOXA-51 geni tespit edildi. Bu çalışmada Türkiye'den ilk kez hem blaOXA-23 hem de blaOXA-51 genlerini taşıyan klinik K. oxytoca izolatı tanımlandı. Rumex gümüş nanoparçacıklarının (NP'ler), orta ve güçlü biyofilm oluşturma kabiliyetine sahip farklı izolatlara karşı antibiyofilm aktivitesi gösterdiği ortaya çıktı. NP'ler, 2.66 kat A. baumannii'nin, 3.25 kat K. pneumonaie'nin ve 1.25 kat E.coli'nin biyofilm oluşturma kapasitesini azalttığı gözlemlendi. Mikrobiyal biyofilmin araştırılması, tedavi seçenekleri için yeni stratejiler geliştirmede önemli bir rol oynayabilir. Sonuç olarak, ciddi enfeksiyonlara neden olan antibiyotiğe dirençli Gram negatif patojenlerin tedavi seçeneklerinin sınırlı olması halk sağlığı açısından önemli bir sorun olduğundan, bu patojenlerde antibiyotik direnci, virülans faktör genleri ve biyofilm oluşumunun araştırılması önemlidir.
- MakaleYalnız künye2022Scopus SJRQ3The Effect of Surface Morphology of Silver Nanoparticles on the Selectivity of Styrene Epoxidation
Sarlblylk, Oǧuz Yunus
Catalytic materials at the nanoscale level have an enormous impact on sustainable environmental protection, which is important for the future. Therefore, the researchers will intensively carry out the design of catalytic materials with well-ordered surface structures. In more detail, morphology-controlled nanoparticles have special interactions with the reactants that increase catalytic performance and influence the selectivity for catalytic reactions. For those reasons, obtaining specifically surface structure-tuned nanocrystals having different surface arrangements is a significant priority that promises the best model relationship between well-oriented surface structure and catalytic performance. In this study, silver nanocrystals shaped with cubes, truncated octahedrons, and octahedrons were produced. Their catalytic behaviors were examined as an innovation for epoxidation/oxidation reactions of styrene in mild conditions. The morphological and surface characterizations of nanocrystals were determined by analytical and instrumental methods such as high-resolution transmission electron microscopy energy dispersive X-ray (HR-TEM-EDX), X-ray diffraction (XRD), as well as inductively coupled plasma mass spectroscopy optical emission spectrometry (ICP-OES), and gas chromatography-mass spectrometry (GC-MS). According to the results, nanoparticles having different surface-facets fractions can be employed to increase the selectivity of styrene epoxide.
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