Browsing by Author "Basturk, SB"

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    Fabrication and characterization of composites of a perovskite and polymers with high dielectric permittivity
    Basturk, SB; Dancer, CEJ; McNally, T
    Composites of strontium titanate (SrTiO3) at loadings up to 50 vol.% with polar poly(butylene terephthalate) (PBT) and non-polar linear low density polyethylene (LLDPE) were prepared to investigate their dielectric responses in the wireless frequency range. The SrTiO3 particles were uniformly dispersed in the polymers at low loadings, but were more bead-like and agglomerated at higher SrTiO3 loadings. The SrTiO3 has a strong nucleating effect on both polymers, increasing the crystallization temperature and reducing the crystallinity of both polymers. Dielectric properties of composites were measured between 2.45-5 GHz. Dielectric permittivity (epsilon') of composites at 2.45 GHz increased with increasing SrTiO3 content. epsilon' increased by a factor of 5 for PBT, from 3.7 for unfilled PBT to 16.5 and by a factor of similar to 8.5 for unfilled LLDPE, from 2.3 to 19.7 for maximum SrTiO3 loading. The composites had similar dissipation factor values as the unfilled polymers. The Lichtenecker model was in good agreement with the experimental data.
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    Dielectric performance of composites of BaTiO3 and polymers for capacitor applications under microwave frequency
    Basturk, SB; Dancer, CEJ; McNally, T
    Composites of nano-sized barium titanate (BaTiO3) with volume fractions up to 0.5 and poly(butylene terephthalate) (PBT) or linear low-density polyethylene (LLDPE) were made via extrusion. Scanning electron microscopy demonstrated that BaTiO3 is well dispersed in the polymer matrices. The crystalline content (DSC) and thermal stability (TGA) of both polymers decreased with increasing BaTiO3 loading. Dielectric properties of the composites were measured using a vector network analyzer. Both dielectric permittivity and tangent loss increased with increasing BaTiO3 content. At 2.45 GHz, the dielectric permittivity for 48 vol% BaTiO3-filled LLDPE and 43 vol% BaTiO3-filled PBT was 25 and 21.2, respectively. There was a good fit between the Lichtenecker model and experimental data obtained up to a certain value, with the permittivity variations being dependent on volume fraction. The improved dielectric performance achieved on inclusion of BaTiO3 confirms both composite systems as potential candidates for microwave frequency capacitor applications.
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    Ceramic fibers
    Yalamaç, E; Sutcu, M; Basturk, SB
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    Mechanical and thermo-mechanical properties of nanoclay/epoxy composites: synergistic effects of silanization and surfactant application
    Basturk, SB; Erbas, SC
    In the present work, montmorillonite based bentonite nanoclay was modified with surfactant application and silanization, sequentially. The chemically modified clay/epoxy nanocomposites were prepared with three different filler concentrations (0.5%, 1% and 2% wt) and produced with conventional casting technique. The XRD and FTIR techniques were used to reveal the effects of modification process. Based on FTIR, the modified clay particles exhibited alterations that confirmed the modification effect and the XRD results pointed out that the characteristic peak of neat nanoclay transformed into a hump, which was probably the indication of amorphous phase presence/increase. The tensile performance of modified clay based samples did not satisfy the expectations and showed slightly lower properties. However the flexural modulus of modified clay/epoxy specimens showed 11.1% improvement while their strength values decreased with the introduction of more powder. Similarly, same nanocomposite group exhibited an enhancement in terms of glass transition temperature-T-g (3.6 degrees C-4.9 degrees C) and storage modulus (approaximately 23.2%) as compared to neat epoxy. Nevertheless it was also observed that the neat clay based samples mostly achieved better quasistatic and viscoelastic performence than chemically modified structures. This situation can be mainly attributed to the penetration capacity decrease of epoxy due to the excessive/various modifiers existence within the clay galleries.
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    Effect of methyl orange as the modifier on the mechanical, thermal, and thermo-mechanical properties of clay/epoxy composites
    Basturk, SB
    In this study, bentonite clay/epoxy composites were simply and successfully produced via conventional casting method for 0.5, 1, and 2 wt% filler content. Previously modified clay (surfactant and silane agent applied) was treated with methyl orange (MO) and its effects on composites were investigated in terms of crystallographic, thermal, thermo-mechanical, morphologic, and topographic aspects as well as quasi-static characteristics. According to XRD graphs, MO presence led to the increase of interlayer distance and resulted in partial intercalation for modified clay (MC) based mixture, while an opposite case was seen in neat clay (NC) blend. The 2 wt% MO/MC loaded composite achieved the highest tensile modulus, flexural stiffness, and hardness values among all samples-increase of 14%, 40%, and 3%, respectively. Same composite system exhibited improved results for both glass transition temperature (similar to 7%up arrow) and storage modulus (similar to 35%up arrow), in spite of insufficient thermal characteristics. Irregular particles/tactoids were present in the fracture images, which probably promoted the stress concentration and caused the reduction of strength parameter for all composites. Furthermore, independent of clay type (MC or NC) whole structures showed similar surface roughness values but different topographic textures in terms of surface profiles.