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    Design of dual-conductive polyacrylonitrile-based composite nanofiber: Synergistic effect of copper nanoparticles decorated-boron nitride and polyaniline
    (Wiley, 2024) Orhun, Zumer; Dogan, Deniz; Erdem, Uemit; Yildirim, Gurcan; Pehlivanli, Zuhtu Onur; Metin, Aysegul Uelkue
    Conductive composite nanofibers are promising materials, especially wearable strain sensors, due to their lightweight, breathability, flexibility, and skin affinity. Here, we propose a dual-conductive network by the sequential decoration of amin-modified boron nitride nanosheets (BN), copper nanoparticles (Cu), and polyaniline (PANI) into the elastic thermoplastic polyacrylonitrile (PAN) nanofiber. The Cu nanoparticles/BN-enwrapped PANI nanocomposite was synthesized using successive environmentally friendly reduction and chemical oxidation polymerization. First, Cu (II) ions were immobilized on modified BN and reduced with L-ascorbic acid (BN@Cu), followed by a chemical oxidation polymerization of aniline using ammonium persulfate as an initiator (BN@Cu/PANI). The XRD (X-ray diffraction), FTIR (Fourier Transform Infrared Spectroscopy), SEM (Scanning Electron Microscopy), and TEM/EDXS (Transmission Electron Microscopy/Energy Dispersive X-ray Spectroscopy) analysis confirmed the coexistence of the BN@Cu/PANI phase and composition. The DC electrical conductivity of BN@Cu/PANI nanocomposite (0.567 S/cm) was quietly higher than PANI (0.167 S/cm) and BN@Cu (0.077 S/cm). The thermal conductivity of BN@Cu and BN@Cu/PANI was 0.626 and 0.444 W/mK, respectively. The BN@Cu/PANI loaded-PAN composite nanofibers were successfully produced by electrospinning. SEM studies confirmed that the composite nanofibers have uniform fiber structure and suitable BN@Cu/PANI dispersion/distribution within the PAN. BN@Cu/PANI-reinforced PAN nanofibers showed a 2-fold decrease in the specific heat capacity and a 50-fold increase in electrical conductivity of the nanofibers at 10 wt%BN@Cu/PANI loading. This work offers dual-conductive polymer-based composites, which can be used in thermal management applications in microelectronics devices.HighlightsThe dual-conductive nanocomposite, BN@Cu/PANI, was prepared a simple, low-cost method.BN@Cu/PANI, core/shell nanocomposite, was easily produced this way for the first time.BN@Cu nanoparticles increased the polymerization rate of PANI.The thermal and electrical conductivity of BN@Cu/PANI was 0.444 W/mK and 0.567 S/cm.Electrical conductivity of BN@Cu/PANI-PAN increased 50-fold increase at 10 wt%BN@Cu/PANI. The dual conductive nanocomposite (BN@Cu/PANI) was prepared using environmentally friendly reduction and chemical oxidation polymerization methods, respectively (a). The BN@Cu/PANI is used as filler in polyacrylonitrile (PAN) nanofibers prepared by electrospinning for potential applications such as soft electronics, hydrogen production, photocatalytic, and biosensors due to the lightweight and dual conductivity of composite nanofibers (b).image
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    The effect of different fiber reinforcement on the thermal and mechanical properties of autoclaved aerated concrete
    (Elsevier Sci Ltd, 2016) Pehlivanli, Zuhtu Onur; Uzun, Ibrahim; Yucel, Zeynep Pinar; Demir, Ilhami
    In this study, the changes in thermal conductivity value, compression and flexural strength of autoclaved aerated concrete were investigated experimentally by adding polypropylene, carbon, basalt and glass fibers into the G3/05 and G4/06 class autoclaved aerated concrete used as wall elements in buildings and the commercial production of which is made. Fibers were substituted with the aggregate in autoclaved aerated concrete in equal amounts volumetrically. The produced samples were subjected to autoclaved cure as in non-fibrous autoclaved aerated concrete. As a result of the experimental study; it has been seen the thermal conductivity of fiber substituted autoclaved aerated concrete changes linearly with thermal conductivity of the substituted fibers and basalt fiber reinforced autoclaved aerated concrete gives the highest thermal conductivity. But, it has been seen that the best compression and flexural strength was given by the carbon fiber reinforced samples. (c) 2016 Elsevier Ltd. All rights reserved.
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    Effect of polypropylene fiber length on mechanical and thermal properties of autoclaved aerated concrete
    (Elsevier Sci Ltd, 2022) Pehlivanli, Zuhtu Onur; Uzun, Ibrahim
    In this experimental study, the effect of polypropylene fiber (PF) length on the thermal conductivity, pressure and flexural strength values of autoclaved aerated concrete (AAC) was investigated. The investigation used samples from G2/04, G3/05, and G4/06 classes AAC manufacturing in three different density and compressive strength groups. PF of three different lengths, 3, 6, and 12 mm, were chosen as reinforcement material, and AAC samples were made by adding 1.0% in the same volumetric ratios into the matrix material, taking into consideration their specific gravity. After the samples were kept in curing at 60 degrees C for 4 h, they were cured in an autoclave at 180 degrees C at 11 bar pressure for 7 h. After the autoclave process was completed, the flexural and compressive strength, thermal conductivity values of the samples were tested and the internal structure images were examined with a scanning electron microscope (SEM). It was observed that the flexural and compressive strengths of the samples increased with PF reinforcement in all density groups, while the thermal resistances decreased and the fiber length (for 3, 6 and 12 mm) had a positive effect on the compressive and flexural strengths of all examined AAC classes. It was obtained by 70.4% increase in the compressive and flexural strengths of G2/04 class of AAC samples with 12 mm length PF addition. As the PF length increases, the thermal conductivity values of all samples also increase and the highest thermal conductivity increase was observed in the G5/06 class samples with a value of 20.2%. In general, it was observed that the compressive strength, bending strength and thermal conductivity values of all samples increased depending on the increase in PF length. It has been observed that thermal conductivity values are worsen at more higher rates while the strength values of AAC at all fiber lengths is improves with PF additive.
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    The Effect of Reinforcement Volume Ratio on Porosity and Thermal Conductivity in Al-Mgo Composites
    (Univ Fed Sao Carlos, Dept Engenharia Materials, 2012) Çalın, Recep; Pul, Muharrem; Pehlivanli, Zuhtu Onur
    In this study, the effects of reinforcement volume ratios (RVR) on composite structure and thermal conductivity were examined in Al-MgO reinforced metal matrix composites (MMCs) of 5%, 10% and 15% RVR produced by melt stirring. In the production of composites, EN AW 1050A aluminum alloy was used as the matrix material and MgO powders with particle size of -105 mu m were used as the reinforcement material. For every composite specimen was produced at 500 rev/min stirring speed, at 750 degrees C liquid matrix temperature and 4 minutes stirring time. Composite samples were cooled under normal atmosphere. Then, microstructures of the samples were determined and evaluated by using Scanning Electron Microscope (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) analysis. In general, it was observed that the reinforcement exhibited a homogeneous distribution. Furthermore, it was determined that the increase in the RVR increased porosity. From the Scanning Electron Microscope images, a thermal Ansys model was generated to determine effective thermal conductivity. Effective thermal conductivity of Al-MgO composites increased with the decrease in reinforcement volume ratio.
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    Manufacturing and characterization of polypropylene/boric acid composite
    (Springer, 2021) Pehlivanli, Zuhtu Onur
    This experimental study is conducted to investigate the effects of boric acid additive into polypropylene in terms of microstructure formation and thermal properties. Boric acid granules are added into pure polypropylene at three mass rates of 0.5, 1.5, and 2.5% which are notated as PP/BA-0.5, PP/BA-1.5, and PP/BA-2.5, respectively. The pure polypropylene material (pure PP) and boric acid reinforced polypropylene composite materials (PP/BA) are manufactured in an injection molding machine. The microstructure of composite materials is examined with an SEM (scanning electron microscope) device. Thermal analyses are conducted by using a TGA (thermogravimetric analyzer) device. In addition, thermal conductivities of composite materials are measured between 10 and 50 degrees C temperatures. SEM images show that boric acid at 0.5% additive rate forms a homogeneous composite by uniformly spreading the polymer chains, while boric acid at high additive rates of 1.5% and 2.5% becomes agglomerated within the polymer. TGA analyses show that the initial evaluation degradation temperature (T-i) tends to decrease with the addition of boric acid. Thermal conductivity for all examined materials almost linearly increases with temperature at a slope of about 0.0004 [(W m(-1) K-1)/K]. Thermal conductivity is reversely proportional to the boric acid additive rate. The thermal conductivity for 2.5% boric acid added polypropylene is about 5% less than pure polypropylene.
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    Mechanical and microstructural features of autoclaved aerated concrete reinforced with autoclaved polypropylene, carbon, basalt and glass fiber
    (Elsevier Sci Ltd, 2015) Pehlivanli, Zuhtu Onur; Uzun, Ibrahim; Demir, Ilhami
    Autoclaved aerated concrete (MC) is a construction material obtained by being pore-forming of the mixture prepared with finely crushed siliceous aggregate lime, water and limestone with the addition of aluminum powder and being cured with steam cure (autoclave). MC is a widely used material today in the constructions as a material that is very light compared to concrete or conventional stone material and that has high insulation properties and fire-resistant light construction material. In this study, the effect of fiber type and size in the production of MC on compressive, flexural strength and thermal conductivity values has been investigated. In the study, G2/04 class having 400 kg/m(3) density of MC production used for wall element and commercially produced was taken as a reference. Fiber types were substituted for an equal amount of aggregate and MC samples were produced. The mechanical properties and thermal conductivity values as well as microstructural features of the sample produced were examined. The samples produced were waited at the temperature of 60 degrees C in 4 h-cure, then they were subjected to the cure at the temperature of 180 degrees C, at the pressure of 11 bar and in an autoclave for 6.5 h. As well as the mechanical properties of the samples produced and thermal conductivity values, their microstructural features were also examined. In the study, it was seen that fiber was supplemented instead of quartzite increased flexural and compressive strength of MC and carbon fiber reinforced MC gave the best flexural and compressive strength compared to fiber types. (C) 2015 Published by Elsevier Ltd.
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    The Effect of Sintering Temperature and Time on Microstructure, Hardness and Wear Behaviors of Al 99.9/GNP Composites
    (Int Inst Science Sintering (I I S S), 2023) Pul, Muharrem; Erdem, Umit; Pehlivanli, Zuhtu Onur
    In this study, it was aimed to investigate the microstructure, hardness and wear behavior of graphene nanoplate (GNP) reinforced composites with Al 99.9 matrix produced by powder metallurgy. Different temperatures and times were applied in the sintering process. The hardness values of the composites increased as the sintering temperature and time increased. The hardness values decreased with the increase of GNP reinforcement ratio. The wear losses decreased depending on the increase in sintering temperature and time. With the increase in the GNP reinforcement ratio, reductions in wear losses were recorded. It has been concluded that the GNP reinforcement element in the composite structure reduces the friction coefficient and wear losses by having some lubricating effect. It was observed that the neck and bonding formation between Al 99.9 matrix grains improved with increasing sintering temperature and time. It was concluded that with the development of intergranular bonds, the porosity in the composite structure decreased and the mechanical properties increased.