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Bulbul M.S.,Canakkale Onsekiz Mart University | Kantar C.,Canakkale Onsekiz Mart University | Keskin S.,NanoMagnetics Instruments Ltd.
Water, Air, and Soil Pollution | Year: 2016

Laboratory batch and column experiments were performed to better understand the effects of Ca2+, Mg2+, and HCO3 - on Cr(VI) removal from aqueous systems with pyrite. Batch results show that increasing HCO3 - concentration led to an increase in Cr(VI) removal by pyrite due to pH buffering capacity of HCO3 -. However, while Ca2+ and Mg2+ individually had no effect on Cr(VI) removal at pH 4, the addition of Ca2+ or Mg2+ to systems containing HCO3 - resulted in a significant decrease in Cr(VI) removal at pH 8 relative to the systems containing HCO3 - alone. The XPS data proved that while Ca2+ precipitated as CaCO3(S) onto pyrite surface, Mg2+ sorbed and/or accumulated as Mg(OH)2(S) onto oxidized pyrite surface. The formation of surface precipitates (e.g., CaCO3) inhibited further Cr(VI) reduction by blocking electron transfer between Cr(VI) and pyritic surface sites. While the precipitation of Ca2+ as CaCO3 led to a significant decrease in effluent pH, the decrease in effluent pH was very low in systems containing Mg2+, most probably due to much higher solubility of Mg2+ at pH 8. Zeta potential measurements provided further evidence that while Ca2+ or Mg2+ had no effect on zeta potential of pyrite particles under acidic conditions (e.g., pH < 7), the addition of Ca2+ or Mg2+ to systems containing Cr(VI) reversed the pyrite surface potential from negative to positive under alkaline pH conditions (e.g., pH > 8) relative to system containing only Cr(VI), suggesting the sorption and/or accumulation of surface precipitates on pyrite surface. © 2016 Springer International Publishing. Source

Gurbuz M.,Ondokuz Mayis University | Celik U.,NanoMagnetics Instruments Ltd. | Sakurai H.,Mitsubishi Group | Kuromitsu Y.,Mitsubishi Group | And 2 more authors.
2014 Joint IEEE International Symposium on the Applications of Ferroelectric, International Workshop on Acoustic Transduction Materials and Devices and Workshop on Piezoresponse Force Microscopy, ISAF/IWATMD/PFM 2014 | Year: 2014

In piezoelectric market, infrared detectors, pyroelectric and piezoelectric sensors, microwave devices, actuators, transducers, non-volatile random access memories, and micro electromechanical systems are fabricated using lead zirconate titanate (PZT) based films. These films are deposited by chemical vapor deposition, physical vapor deposition spin coating, screen printing and electrospray deposition (ESD) technique. Among them, ESD is the most preferred method because of its high material efficiency, simplicity of experimental set up, wide choice of precursor and low cost. Therefore, the purpose of this study is to fabricate and characterize the ESD deposited PZT films. In our study, Pb(Zr0.52 Ti0.48)O3(PZT) nano powders (Nanotech Corp. Turkey) and MMC PZT sol (Mitsubishi Corp. Japan) combinations were mixed in various concentrations. Prepared composite PZT slurries were coated with ESD technique. Fabricated PZT thick films were characterized with scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray diffraction method (XRD) to evaluate surface and crystal structure of the films. The results show that, MMC sol and PZT nanopowder combinations provide smooth and homogeneous film surface, dense and non-cracked film microstructure was observed using excess PbO during sintering. © 2014 IEEE. Source

Karamat S.,Middle East Technical University | Sonusen S.,Sabanc University | Dede M.,NanoMagnetics Instruments Ltd. | Uysall Y.,Middle East Technical University | And 2 more authors.
Journal of Materials Research | Year: 2015

Few layer graphene is attractive due to its extraordinary electronic and optical properties, which are strongly influenced by the orientation between the layers called as stacking sequence. It is challenging to synthesize high quality large size single or multi layer graphene crystals on the metal catalyst using chemical vapor deposition technique. The present work is about synthesis of few layer graphene grains on platinum foil using ambient pressure chemical together vapor deposition technique. The main focus is how the different grains coalesced and maintain the stacking sequence. Different characterization techniques are used to analyze the grains when they are in the process of merging to make a bigger grain. Scanning electron microscopy clearly shows different stacking sequences and merging of different nucleation sites of different grains. Interestingly, different stacking sequences are observed during the process of coalescence of grains. Raman spectroscopy gives accurate information about the number of layers and their stacking sequence. We observed Bernal AB and twisted layer stacking in the grains when they were combining together to grow into a bigger size. The full width at half maximum (FWHM) value of 2D Raman peaks appeared in the range of 52–69 cm−1 which shows an increase from the value of single layer graphene (30.18 cm−1) and identifies Bernal stacking in grains. For twisted stacking FWHM values lie in the range of 19–32 cm−1. Copyright © Materials Research Society 2015 This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited. Source

Kantar C.,Canakkale Onsekiz Mart University | Ari C.,Canakkale Onsekiz Mart University | Keskin S.,NanoMagnetics Instruments Ltd. | Dogaroglu Z.G.,Mersin University | And 2 more authors.
Journal of Contaminant Hydrology | Year: 2015

Laboratory batch and column experiments, in conjunction with geochemical calculations and spectroscopic analysis, were performed to better understand reaction mechanisms and kinetics associated with Cr(VI) removal from aqueous systems using pyrite as the reactive material under both static and dynamic flow conditions similar to those observed in in situ permeable reactive barriers (PRBs). The X-ray photoelectron spectroscopy (XPS) and geochemical calculations suggest that the Cr(VI) removal by pyrite occurred due to the reduction of Cr(VI) to Cr(III), coupled with the oxidation of Fe(II) to Fe(III) and S2 2 - to SO4 2 - at the pyrite surface. Zeta potential measurements indicate that although the pyrite surface was negatively charged under a wide pH range in the absence of Cr(VI), it behaved more like a "metal oxide" surface with the surface potential shifting from positive to negative values at pH values > pH 6 in the presence of Cr(VI). Batch experiments show that increasing solution pH led to a significant decrease in Cr(VI) removal. The decrease in Cr(VI) removal at high Cr(VI) concentrations and pH values can be explained through the precipitation of sparingly soluble Cr(OH)3(s), Fe(OH)3(s) and Fe(III)-Cr(III) (oxy) hydroxides onto pyrite surface which may, then, lead to surface passivation for further Cr(VI) reduction. Batch results also suggest that the reaction kinetics follow a first order model with rate constants decreasing with increasing solution pH, indicating proton consumption during Cr(VI) reduction by pyrite. Column experiments indicate that nearly 100% of total Fe in the column effluent was in the form of Fe(II) species with a [SO4 2 -]/[Fe2 +] stoichiometric ratio of 2.04, indicating that the reduction of Cr(VI) by pyrite produced about 2 mol of sulfate per mole of Fe (II) release under excess surface sites relative to Cr(VI) concentration. Column experiments provide further evidence on the accumulation of oxidation products which consequently led to a significant pressure build up in pyrite packed columns over time. © 2015 Elsevier B.V. All rights reserved. Source

NanoMagnetics Instruments Ltd. | Date: 2012-02-23

Easy to use atomic force microscope and associated computer operating software sold as a unit.

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