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Cakal G.O.,National Boron Research Institute
Chemical Industry and Chemical Engineering Quarterly | Year: 2012

In this study, zinc borate production in an industrial scale batch reactor was carried out at the optimum process conditions, determined in the previous studies performed at the laboratory and pilot scale reactors. The production was done via the heterogeneous reaction of boric acid and zinc oxide. The samples were characterized by chemical analysis, XRD, TGA, SEM and particle size distribution. The final product which was obtained in the industrial scale reactor was 2ZnO·3B2O3·3H2O. The kinetic data for the zinc borate production reaction fit to a modified logistic model where the lag time was taken into account. As observed, the reaction time was influenced by scaling up. There was a lag time of 120 min for the industrial scale production and thus, the reaction completion time was 70 min longer compared to pilot scale. It should be emphasized that the specific reaction rate, k, as well as the average particle size and the hydration temperature of zinc borate were unaffected by scale up. Source

Akkurt F.,National Boron Research Institute
Journal of Molecular Liquids | Year: 2014

Liquid crystals have become the focus of great interest in recent years particularly with applications in display technology. Guest-host liquid crystal displays (GH-LCDs) are widely utilized because of their many advantages such as color, wide viewing angle and high brightness. The aim of this study is to determine the electro-optical properties of disperse orange 11 dye and fullerene C60 doped GH-LCDs. A 40 mW He-Cd (λ = 441.6 nm) laser was used as a pumping source during the measurements, which were carried out by an impedance analyzer to observe the effect of laser illumination on the samples. Dielectric anisotropy was quantitatively estimated by using capacitive measurements and estimated as positive for all samples. Photoconductivity of the samples was defined under dark and illuminated conditions. Experimental results also indicate that laser pumping has a considerable effect on the photoconductivity. © 2014 Elsevier B.V. Source

Celik A.G.,National Boron Research Institute
Journal of the Balkan Tribological Association | Year: 2015

In the present study, tribological properties of borides formed on AISI D3 steel have been investigated. The boride layer was characterised by optical microscopy, X-ray diffraction technique and the micro-Vickers hardness tester. X-ray diffraction analysis of boride layers on the surface of the steels revealed the existence of FeB, Fe2B, CrB and Cr2B compounds. Depending on the chemical composition of substrates and boriding time, the boride layer thickness on the surface of the steel ranged from 32.15 and 73.68 μm. The boride layer hardness of the steel borided at 1123 and 1223 K for 6 h were found to be 1692 HV0.1 and 1874 HV0.1, whereas Vickers hardness values of the untreated the steels was 584 HV0.1. The wear tests were carried out in a ball-disc arrangement under a dry friction condition at room temperature with applied load of 10 and 20 N with a sliding speed of 0.4 m/s at a sliding distance of 1000 m. It was observed that the wear rate of borided and unborided AISI H10 steel ranged from 3.86 to 61.32 mm3/N m. Source

Kln M.,Middle East Technical University | Cakal G.O.,National Boron Research Institute | Yeil S.,Middle East Technical University | Bayram G.,Middle East Technical University | And 2 more authors.
Journal of Crystal Growth | Year: 2010

Synthesis of zinc borate was conducted in a laboratory and a pilot scale batch reactor to see the influence of process variables on the reaction parameters and the final product, 2ZnO·3B2O 3·3.5H2O. Effects of stirring speed, presence of baffles, amount of seed, particle size and purity of zinc oxide, and mole ratio of H3BO3:ZnO on the zinc borate formation reaction were examined at a constant temperature of 85 °C in a laboratory (4 L) and a pilot scale (85 L) reactor. Products obtained from the reaction in both reactors were characterized by chemical analysis, X-ray diffraction, particle size distribution analysis, thermal gravimetric analysis and scanning electron microscopy. The kinetic data for the zinc borate production reaction was fit by using the logistic model. The results revealed that the specific reaction rate, a model parameter, decreases with increase in particle size of zinc oxide and the presence of baffles, but increases with increase in stirring speed and purity of zinc oxide; however, it is unaffected with the changes in the amount of seed and reactants ratio. The reaction completion time is unaffected by scaling-up. © 2010 Elsevier B.V. Source

Akkurt F.,National Boron Research Institute
Liquid Crystals | Year: 2014

During the recent years, liquid crystals (LCs) have much attention owing to their wide range of possible application and structural properties in electronics and optics. In this study, two different azo structured dyes (Disperse Yellow 3 and 7) and their mixture were separately doped to each of two different nematic LCs (E8 and E63). Their solubilities (except dye mixture), order parameters, textures and phase transition temperatures were determined. Single-walled nanotubes and fullerene C60 in a small amount were separately added to each of these solutions, and the experiments were repeated at the final stage analogously except solubilities. The solubilities of dyes in the LC E63 were lower than those of E8. The highest order parameter value was attained with Yellow 7 dye in E63 nematic host. © 2014 Taylor & Francis. Source

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