Yazar "Topcu, Alparslan" seçeneğine göre listele

Listeleniyor 1 - 8 / 8
  • [ X ]
    Öğe
    Characterization of TiO2 Nanoparticle-Reinforced Polymer Nanocomposite Materials Printed by Stereolithography Method
    (Springer, 2021) Aktitiz, Ismail; Aydin, Kadir; Topcu, Alparslan
    Additive manufacturing (AM) is a novel manufacturing technology group that revolutionizes the design and production processes behind material production. This approach is used in a wide range from simple prototypes to direct parts manufacturing in different industries such as aviation, automotive, energy, biomedical, and bioengineering. Stereolithography (SLA), fused deposition modeling, selective laser sintering, laser metal deposition approaches are the most widespread AM methods. SLA method is one of the most attractive approaches in the AM field as high-dimensional sensitivity is achieved by using liquid photosensitive resin and laser light. However, although it is possible to manufacture complex-shaped three-dimensional (3D) polymer structures with the SLA approach, the mechanical, thermal, and electrical properties are not at the desired levels. To develop more functional 3D polymer materials, various additives are dispersed into polymer structures such as metal nanoparticles, inorganic particles, fibre, carbon nanotube, and nanoclay. Titanium dioxide (TiO2) nanoparticles are a very appealing type of additive among these additives owing to their superior mechanical properties. In this study, the photosensitive resin was mixed with four different TiO2 nanoparticle concentrations (pure, 0.25, 0.5, and 1% reinforced). These slurries were then placed in the SLA device, and 3D polymer structures were fabricated. Scanning electron microscope (SEM), thermogravimetric analysis (TGA), differential scanning calorimeter (DSC), tensile tests, and Charpy impact tests were carried out to characterize mechanical, thermal, and morphological properties of developed polymer materials. It was observed that the particle size was below 1 mu m and some agglomerations occurred. The elasticity modulus of the 0.5% TiO2 nanoparticle reinforced sample was measured as 694 MPa and was found to be approximately 20% higher than the pure polymer sample. In addition, polymer structures exhibited more brittle behavior. It was noted that 5% weight loss was experienced at 337 degrees C in all samples. Besides, the existence of unreacted carbon-carbon bonds was proven by the DSC analysis.
  • [ X ]
    Öğe
    Effects of Short-Term Thermal Aging on the Fracture Behavior of 3D-Printed Polymers
    (Springer, 2021) Daricik, Fatih; Delibas, Hulusi; Canbolat, Gokhan; Topcu, Alparslan
    3D printing technologies offer numerous advantages and have attracted the attention of researchers recently. Yet, the most commonly preferred additive manufacturing system is the extrusion-based process that is called fused deposition modeling (FDM) as it is simple, low cost, and prone to customization. In this paper, the effects of the short-term aging of the additively manufactured PLA and ABS specimens were investigated experimentally. The test specimens were aged by keeping them at ambient temperatures of - 80, - 20, 60, 100 degrees C for 10, 20, and 30 days. Thermally aged specimens and the pristine specimens were forced to fracture with bending load at room temperature. Thus, the permanent effects of thermal aging of the specimens were investigated utilizing the load-deflection curve, plane-strain fracture toughness, and the morphologies of fracture surfaces. It was concluded that the printed PLA materials are more susceptible to the thermal aging than the ABS printed materials. The contraction and expansion of the fused polymer filaments affect directly the bonding strength between the adjacent layers. Therefore, plane-strain fracture characteristics of the FDM polymer materials exposed to thermal aging differ according to the filament orientation and the aging time.
  • [ X ]
    Öğe
    Influence of processing parameters on the porosity, thermal expansion, and oxidation behavior of consolidated Fe22Cr stainless steel powder
    (Elsevier, 2021) Ozturk, Bulent; Topcu, Alparslan; Cora, Omer Necati
    The objective of this study was to determine the effects of powder metallurgy process parameters on the porosity, coefficient of thermal expansion, and oxidation behaviors of porous ferritic Fe22Cr stainless steel compacts. Optimum values of the process were also investigated. The results showed that, porosity and the coefficient of thermal expansion decrease with increasing process parameters; and changing powder shape from spherical to flaky at a certain extent. The minimum and maximum porosity values of the samples were recorded as 7% and 30%, respectively. While those for the samples produced from milled powders were noted as 3%, and 19%, respectively. The coefficient of thermal expansion values were measured at 800 degrees C and found to be in the range of 12-14.5 x 10(-6) K-1 for spherical powders and flaky powders. From oxidation kinetics point of view, both process parameters and powder shape influenced the oxidation behavior. (C) 2020 Elsevier B.V. All rights reserved.
  • [ X ]
    Öğe
    Morphological, mechanical, magnetic, and thermal properties of 3D printed functional polymeric structures modified with Fe2O3 nanoparticles
    (Wiley, 2021) Aktitiz, Ismail; Delibas, Hulusi; Topcu, Alparslan; Aydin, Kadir
    The Fe2O3 nanoparticle structures, which have many application areas such as electronics, marine, and aviation, have been studying extensively due to the compliance between organic polymer and inorganic Fe2O3 nanoparticles. Nanocomposite structures are successfully produced in the desired complexity with the additive manufacturing method. In the current study, Fe2O3 nanoparticles were doped into the photocurable resin at different concentrations (pristine, 0.25%, 0.5%, and 1% in wt), and the prepared 3D polymer nanocomposite mixtures were printed via stereolithography method. To investigate the morphological, mechanical, magnetic, and thermal properties of the printed nanocomposite structures, scanning electron microscopy, hardness, vibrating sample magnetometer, thermogravimetric analysis, and differential scanning calorimeter analysis were performed, respectively. It was revealed that the Fe2O3 nanoparticles improved the thermal stability of the structures. Moreover, an increase in magnetic properties has been observed up to 459%.
  • [ X ]
    Öğe
    Oxidation, electrical and mechanical properties of Crofer®22 solid oxide fuel cell metallic interconnects manufactured through powder metallurgy
    (Pergamon-Elsevier Science Ltd, 2018) Ozturk, Bulent; Topcu, Alparslan; Ozturk, Sultan; Cora, Omer Necati
    This study aimed to investigate oxidation, electrical and mechanical properties of solid oxide fuel cell interconnects. To this goal, two different Crofer (R) 22 interconnects samples were produced via different manufacturing routes (machining from bulk material, and powder metallurgy approach). The samples were characterized by scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), X-ray diffractions. Four-probe area specific resistance (ASR), bonding strength, leakage tests were also performed. The results indicated that interconnect sample manufactured through powder metallurgy approach can be a reliable alternative to the one manufactured from commercially available Crofer (R) 22 alloy in bulk form. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
  • [ X ]
    Öğe
    Production of different metal oxide nanoparticle embedded polymer matrix composite structures by the additive manufacturing technology and investigation of their properties
    (Wiley, 2022) Aktitiz, Ismail; Aydin, Kadir; Daricik, Fatih; Topcu, Alparslan
    Metal oxide nano additives are widely used as a second phase modifier as they improve the properties of the matrix materials. Nano additives also supply various advantages for polymers which can be employed in additive manufacturing methods. Among the additive manufacturing methods, stereolithography is one of the most remarkable to produce nano-modified polymers because of the easy nano modification of the photocurable resins. In the present study, we mixed the metal oxide particles; Fe2O3, ZnO, NiO, Al2O3, TiO2, and MgO with the photocurable epoxy and used the mixtures to print the specimens. We investigated the structural morphology, thermal and mechanical properties of the printed specimens with an optical microscope, scanning electron microscope, Fourier transform infrared spectroscopy, differential scanning calorimeter, differential thermogravimetric analysis, and microhardness, respectively. Findings proved the dilute agglomeration of the nano additives. Besides, nano additives can improve the thermal stability of the photo-cured polymer. The microhardness of the Fe2O3 added polymers reached 27.63 HV levels while it was measured as 16.16 HV for the pristine samples (similar to 70% raise was experienced). The maximum degradation temperatures of the polymer nanocomposite structures were measured in the range of 396-420 degrees C.
  • [ X ]
    Öğe
    Stereolitografi (SLA) Tekniği ile Basılan 3 Boyutlu Polimer Yapılarda İkincil Kürleme Süresinin Mekanik Özelliklere Etkisi
    (2020) Aktitiz, İsmail; Aydın, Kadir; Topcu, Alparslan
    Sıvı fotoduyarlı reçine ve lazer ışığı kullanılarak yüksek boyutsal hassasiyetin elde edildiği Stereolitografi (SLA) yöntemi, eklemeli imalat yöntemleri arasında en dikkat çeken tekniklerden birisi olmuştur. Bu çalışmada, SLA cihazı kullanılarak 3B polimer parçalar basılmış, ikincil kürleme süresinin polimer yapıların mekanik (çekme testi, çentik darbe testi) ve termal (diferansiyel taramalı kalorimetre (DSC) analizi) özelliklerine etkisini incelemek için farklı sürelerde (30, 60, 180 ve 300 dk) UV ikincil kürleme işlemi uygulanmıştır. İşlem uygulanmış polimerlerin elastisite modülü değerinde yaklaşık %49’luk bir artış gerçekleşmiş ve 63,71 MPa mertebelerine ulaşılmıştır. DSC analiz sonuçları 180 dakika ve üzeri ikincil kürleme proseslerinin karbon-karbon çift bağlarının oluşması için yeterli olduğunu göstermektedir.
  • [ X ]
    Öğe
    Theoretical Analysis on the Thermal and Electrical Properties of Fiber Reinforced Laminates Modified with CNTs
    (2020) Darıcık, Fatih; Topcu, Alparslan
    In the present study, the effect of the multi-walled carbon nanotubes (MWCNTs) fillers weight fraction on the mechanical, electrical, and thermal properties of the epoxy was calculated analytically. The results were then compared and it was found out that the MWCNTS has a significant effect on the electrical conductivity of the epoxy. The MWCNT modified epoxy composites were considered as the matrix material to design quasi-isotropic carbon fibre/epoxy composite. The change of the weight fraction of the MWCNTs on the mechanical, electrical, and thermal properties of the carbon fibre/epoxy laminates was also calculated. Finally, the hygrothermal load and the bending load response of the laminated composites were researched. MWCNTs fix the mismatch between the hygrothermal properties of the epoxy matrix and the carbon fiber.