Volkan Eskizeybek

Removal of chromium (VI) using activated carbon-supported-functionalized carbon nanotubes

AbstractThen powdered activated carbon (AC) supported by carbonaceous nano-adsorbents were examined to remove hexavalent chromium [Cr(VI)] from aqueous solution The adsorption behaviour of micro-level concentration of Cr(VI) on those nano-adsorbents was investigated as a function of the experimental conditions such as the contact time, the pH, the dosage of adsorbent, and the initial concentration of Cr(VI). The structural characterization of the adsorbents was accomplished by Fourier transform infrared spectroscopy and scanning electron microscopy. Adsorption isotherms including Freundlich and Langmuir have been applied to study the equilibrium of the adsorption behaviour and identify the adsorption capacity of the activated carbon-functionalizedxa0 multiwalled carbon nanotubes (AC/f-MWCNTs) and activated carbon-functionalizedxa0carbon nanospheres (AC/f-CNSs). Langmuir isotherm model showed that the adsorption process was monolayer type under working with an adsorption capacity of 113.29 and 105.48xa0mg/g, respectively, for AC/f-MWCNTs and (AC/f-CNSs).

Electrospun TiO2/ZnO/PAN hybrid nanofiber membranes with efficient photocatalytic activity

Electrospun polyacrylonitrile (PAN) nanofibers were decorated with TiO2, ZnO and TiO2/ZnO nanoparticles for the first time to prepare flexible multifunctional nanofibrous membranes. First, the arc-discharge process was utilized to prepare TiO2, ZnO and TiO2/ZnO nanoparticles and then the hybrid electrospun nanofibers were spun from PAN/nanoparticle colloids. X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were utilized to characterize the resulting nanoparticles and nanofiber loaded nanoparticles. The microscopic investigations revealed that the specifically TiO2 nanoparticles tend to agglomerate within the PAN nanofiber resulting increased surface roughness; however, ZnO nanorods with 1D morphology are aligned as parallel to the fiber axis. Photocatalytic activity of the hybrid nanofibers was performed by pursuing the degradation of malachite green (MG) dye under UV light irradiation. The fabricated TiO2/ZnO/PAN hybrid nanofibers showed excellent photocatalytic efficiency with at least two times higher reaction rates compared to the bare PAN nanofibers. The results suggest that the photocatalytically active TiO2/ZnO/PAN hybrid nanofibers can be considered as filtering materials for a variety of applications in the fields of wastewater systems without the need of post processing stages for separating catalysts from the liquid medium.

Preparation and mechanical properties of carbon nanotube grafted glass fabric/epoxy multi-scale composites

In the present paper, carbon nanotubes (CNTs) were chemically grafted onto surfaces of the amino silane treated glass fabric by a novel chemical route for the first time to create 3D network on the glass fibers. The chemical bonding process was confirmed by Fourier transform infrared spectroscopy and scanning electron microscopy. The glass fabric/CNT/epoxy multi-scale composite laminates were fabricated with the CNT grafted fabrics using vacuum assisted resin infusion molding. Tensile tests were conducted on fabricated multi-scale composites, indicating the grafting CNTs on glass fabric resulted a decrease (11%) in ultimate tensile strength while toughness of the multi-scale composite laminates were increased up to 57%. Flexural tests revealed that the multi-scale composite laminates prepared with CNT grafted glass fabric represent recovering after first load fall. The interfacial reinforcing mechanisms were discussed based on fracture morphologies of the multi-scale composites.

Low-velocity impact behavior of carbon fiber/epoxy multiscale hybrid nanocomposites reinforced with multiwalled carbon nanotubes and boron nitride nanoplates

In this article, the mechanical properties and dynamic response of hybrid filler-modified epoxy/carbon fiber multiscale composites were investigated. The hybrid fillers composed of multiwalled carbon nanotubes and boron nitride nanoplates were dispersed in epoxy resin and used as matrix material. The multiscale hybrid laminated composites were stacked symmetrically consisting of 10 plies of woven carbon fibers and fabricated by vacuum infusion technique. The mechanical properties of the hybrid composites were investigated by tensile tests. Impact response and energy absorption capacity were investigated by using weight drop test method and the tests were performed according to ASTM-D-7136 standard with impact energies of 5, 10, and 15u2009J. The impact force and displacement versus interaction time were measured. The impulsive force, energy absorption capability, and damage formation were also investigated. It is observed that when the resin is modified by nanoparticles, both strength and the % strain at fracture increase considerably. However, it is shown in the subject manuscript that the enhancement of mechanical has not fully transferred to dynamic response and energy absorption capacities of nanocomposites.

Entrapment and venting of bubbles during vacuum bag prepreg processing

During composites manufacturing with partially pre-impregnated fibers (i.e. “prepregs”) in Out-of-Autoclave processes, non-impregnated fabric cross-sections serve as air pathways to evacuate entrapped bubbles of air, moisture, or volatiles. The bubbles trapped within a laminate during processing lead to decreased structural performance. In this work, the motion of resin and bubbles during the processing of a characteristic prepreg is directly visualized in situ. This is performed utilizing a previously developed flow visualization technique under known pressure and temperature conditions. This study investigates the processing conditions under which a bubble succeeds or fails to meet and coalesce with available air pathways in order to escape the laminate. A key finding of this study is that tunable process parameters, such as pressure and temperature, are less important for successful bubble removal as compared to the initial state of resin impregnation in the prepreg. Prepregs with initially high states of resin impregnation will often fail to draw bubbles into air pathways through the center of fiber tow cross sections, whereas prepregs with initially low states of resin impregnation have clear pathways for bubbles to meet local resin flow fronts, coalesce, and escape. The relevant literature on the motion of bubbles in confined spaces is discussed. It is observed that small Capillary number theory (i.e. Cau2009<u20090.01) under predicts the relative velocity of bubbles, and the faster than expected bubble transport is likely due to effects given by the bubble aspect ratio via the fibrous micro-channel geometry.

Karbon Elyaf Dolgulu Pa6 Polimer Kompozitlerinin Aşınma Özellikleri Üzerine Uygulanan Yük ve Kayma Hızının Etkisi

Bu calismada, karbon elyaf (KE) dolgulu poliamit 6 (PA6) polimer kompozitlerinin surtunme ve asinma davranislari uzerine kayma hizi ve yukun etkileri incelenmistir. PA6 polimeri ve PA6 kompozitlerinin surtunme ve asinma testleri 1040 celik diske karsi kuru ortamda pim-disk sistemi ile gerceklestirilmistir. Tribolojik testler oda sicakliginda, farkli yuk (10-40N) ve kayma hizi (0.4-1.2m/s) sartlarinda yapilmistir. Deneysel calismalar sonucunda, tum polimer numuneler icin yukun ve kayma hizinin artmasiyla surtunme katsayisi artmistir. PA6 kompozitleri icin asinma orani 10 -10 mm 3 /Nm civarinda elde edilmistir. PA6 polimer kompozitlerinin asinma oranini etkileyen en onemli parametrenin uygulanan kayma hizi oldugu belirlenmistir.