Quality assessment of surface and groundwater in Solaklı Basin (Trabzon, Turkey)

The paper reports a study of the surface and ground water in Solakl? Basin, Trabzon, from an assessment of 33 sampling points. Many of the parameters analysed are only marginally acceptable as potable water, even though the samples were collected during the wet season. The highest concentrations of contaminants were found downstream of the centres of population. The results indicate regular monitoring is required and some measures should be taken to protect the limited resources.     

Application of nanostructured titanium dioxide pigments in paper coating: a comparison between prepared and commercially available ones

Nano-TiO₂ pigments in pure crystallographic anatase and rutile phases have been successfully prepared by hydrothermal at 120°C and hydrolysis methods, respectively. The laboratory-prepared pigments were characterized parallel to two commercial pigments of the same crystal structure. All pigments were applied in paper coating mixtures, and their influence on coated paper properties was systematically investigated. X-ray diffraction investigation showed that the laboratory-prepared pigments using the hydrothermal method at 120°C were pure anatase, whereas hydrolysis method produced pure rutile phase pigment. The application of the prepared nanopigments and the corresponding commercial TiO₂ phases in paper coating revealed that clay/rutile nano-TiO₂ pigments in paper coating mixture decreased coated paper roughness more than blending clay with anatase nano-TiO₂ pigments. Commercial nano-TiO₂ pigments increased porosity of coated paper at both the 30% and 50% addition of nano-TiO₂ pigments to clay, while laboratory-prepared nano-TiO₂ pigments highly decreased it at 30% addition of nano-TiO₂ to clay, compared to clay only. Blending of clay/nano-TiO₂ pigments improved both brightness and opacity of the coated paper where commercial pigments are more effective. Burst, tensile strength, stretching, and TEA were improved in the case of all pigments. The 50% addition of the prepared and commercial nanopigments in conjunction with clay improved the mechanical coated paper properties more than 30% addition (except the cases of stretching and TEA of the commercial pigments). The coated paper samples were offset printed. It was found that blending of clay/nano-TiO₂ pigments improved print density. Commercial nano-TiO₂ pigments improved print gloss more than the laboratory-prepared ones. This result was found consistent with the results of coated paper roughness.     

Evaluation of surface/interface quality,microstructure and mechanical properties of hybrid additive-subtractive aluminium parts

A disadvantage of selective laser melting (SLM) processes for the manufacture of large parts is their slow build time per unit volume. A hybrid route is to generate core simple shapes traditionally, for example by machining, followed by adding final features by SLM. Here the mechanical integrity of such hybrid parts is studied, choosing the building of AlSi10Mg by SLM on a machined AA6082 base, in the shape of a tensile test piece, as a simple example. These materials are chosen for their relevance to lightweight parts. As-built parts fail at the SLM/machined interface but standard heat treatments transfer failures to the machined material. Optimised SLM processing conditions and microstructures of the SLM and interfacial regions are reported.     

Synthesis,Thermal Properties and Electrical Conductivity of Na-Sialate Geopolymer

This work aims to study the thermal behavior of basic-geopolymers derived from metakaolin (clay). The geopolymers were characterized by different techniques: thermal analysis (DTA, TGA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and impedance spectroscopy. Some physicochemical properties of the products were also determined: the phases obtained after geopolymer heat treatment and their electrical properties. The results obtained after drying and heat treatment showed that the products kept their initial shapes, but revealed variable colors depending on the temperatures at which they were treated. The products obtained are amorphous between 300 up to 600 °C with peaks relating to the presence of nanocrystallites of muscovites and zeolite, thus at 900 °C it is quite amorphous but only contains nanocrystallites of muscovites. From the temperature of 950 °C, we notice that the geopolymer has been transformed into a crystalline compound predominated by the Nepheline (NaAlSiO₄) with the presence of a crystalline phase by minor peaks of Muscovite, this crystalline character has been increased at 1100 °C to obtain a whole phase crystalline of a Nepheline. The treatment of this geopolymer for one hour at 1200 °C shows an amorphous phase again corresponding to corundum (α-Al₂O₃). This indicates that the dissolution of the grains by the liquid phase induces the conversion of the material structure from sialate [–Si–O–Al–O] to sialate siloxo [–Si–O–Al–O–Si–O–] and the formation of a new crystalline phase (α-Al₂O₃). This development of sialate to sialate-siloxo was confirmed by IR spectroscopy. As mentioned above, from 300 to 900 °C, Na-sialate geopolymer exhibits the same disorder structure of nepheline. The crystal structure of nepheline is characterized by layers of six-membered tetrahedral rings of exclusively oval conformation. The rings are built by Regularly alternating tetrahedral AlO₄ and SiO₄. Stacking the layer’s parallel to the c axis gives a three-dimensional network containing channels occupied by Na cations. This topology favors easy movement of Na⁺ ions throughout the structure. For this reason, ionic migration in nepheline is widely reported. The refinement of Na-Sialate geopolymer at room temperature gives bulk high ionic conductivity of about 5 × 10^?5 S cm^?1 and this is due to the probable joint contribution of H⁺ and Na⁺ ions. Above 200 °C, Na⁺ seems to remain the only charge carrier with a low activation energy of about Ea?=?0.26 eV. At higher temperatures, the characteristic frequencies become so close that it is impossible to distinguish the contributions. A total resistance comprising both grain and grain boundaries contribution is then determined.

     

Microwave Dehydration of Borax: Characterization,Dehydration Kinetics,and Modelling

Glass Physics and Chemistry - In the present study, borax (Na2B4O7·10H2O) was dehydrated using microwave radiation and the dehydration rate curves were calculated. The kinetic parameters and...     

Investigation of the effect of ytterbium doping on photoluminescence and photocatalytic activity of Li4Ti5O12

This work reports the combined effect of the morphology and crystallization to investigate the role of Yb³⁺ as an additive in Li₄Ti₅O₁₂ crystals on its photocatalytic and photoluminescence (PL) properties. With the pure phase, the synthesized samples have a spherical morphology and spherical structure with good crystallinity and uniform particle size distribution. Li₄Ti₅O₁₂ doped with ytterbium (Yb³⁺), were obtained by a new optimized hydrothermal approach. The crystal properties and surface morphology of the synthesized compounds were examined by X-ray diffraction method and field emission scanning electron microscopy. Bond structures and surface areas were investigated by Fourier transform infrared spectroscopy and Brunauer-Emmett-Teller analyses. Finally, the excitation and emission spectra were obtained by a PL spectrophotometer. The PL results show that room-temperature PL of Yb³⁺ doped Li₄Ti₅O₁₂ phosphor has an emission peak at 710 nm which can be attributed to Li₄Ti₅O12 crystal defect emission. Moreover, it has been found that Yb doping resulted in enhancement of photocatalytic activity, evaluated by monitoring the degradation of methylene blue solution. Note that, 0.01% Yb doped lithium titania phosphor exhibited excellent photocatalytic activity.     

Anticonvulsant activity of furanocoumarins and the essential oil obtained from the fruits of Heracleum crenatifolium

The anticonvulsant activity of furanocoumarins, coumarin mixture and the essential oil obtained from the fruits of Heracleum crenatifolium was examined against maximal electroshock (MES)-induced seizures in mice. Bergapten showed significant anticonvulsant activity. The furanocoumarins isolated from the fruits of the plant were identified using thin-layer chromatography, melting points and spectroscopic methods (IR, MS, ¹H NMR) as isobergapten (1), pimpinellin (2), bergapten (3), isopimpinellin (4), sphondin (5) and byak-angelicol (6). The essential oil content of the fruits were found as 5.5%. Twenty-two compounds representing 99.3% of the essential oil obtained from the fruits of H. crenatifolium were determined and the major components were identified as octanol and octyl acetate (3.1% and 88.4% respectively) by GC and GC–MS.     

Effects of ZnO and MoS<Subscript>2</Subscript> Solid Lubricants on Mechanical and Tribological Properties of M50-Steel-Based Composites at High Temperatures: Experimental and Simulation Study

Prospective beneficial effects of mixtures of temperature-adaptive solid lubricants (ZnO–MoS₂) on mechanical and tribological properties of M50 alloy steel were investigated at temperatures from 25 to 800 °C. ZnO and MoS₂ were mixed with M50 (designated as M) to create composites MZ (M50 steel plus ZnO), MM (M50 steel plus MoS₂), and MZM (M50 steel plus both additives). Sliding friction and wear experiments were performed at different temperatures using a pin-on-disk at a sliding speed of 0.2 m s^?1 and a load of 12 N. Silicon nitride and M50 steel were used as the pin materials. In order to understand the friction and wear behavior of composites, analyses of their surfaces were done using XRD, EPMA, FESEM, EDS line/mapping, and XPS tests. A dynamic simulation model based on the finite element method was built to simulate the different stresses on the contact pairs. Results elucidated that MZM attained the least friction (0.17), compared to M (0.40), MZ (0.26), or MM (0.29) at 800 °C. The increase in surface roughness of MZM due to sliding was reduced by 37.3% compared to that of MZ (11.9%) or MM (22.7%). The good lubricating behaviors were referred to the synergetic effects of ZnO, MoS₂, and formed lubricating components on worn surfaces.     

Investigation of water gas-shift activity of Pt–MOx–CeO2/Al2O3 (M = K,Ni, Co) using modular artificial neural networks

The water gas shift activity of promoted Pt–CeO₂/Al₂O₃ catalysts were investigated in this work. The catalysts were prepared by incipient to wetness impregnation and tested using a microflow reaction system. It was found that K has beneficial effects under product-containing feed compositions while Co and Ni promoters worsen catalyst performance. The reaction temperature and feed H₂O/CO ratio positively affect the catalytic activity, whereas CO₂ and H₂ addition to the feed decreases CO conversion, as expected. The experimental results were also modeled using modular neural networks, at which the catalyst preparation and operational (reaction) variables were used together in the same network because they are interacting but processed differently because they are dissimilar in their form (i.e. categorical versus continuous) and their effects on catalytic activity. It was concluded that the effects of catalyst preparation and operational variables and their relative importance could be comprehended more accurately by using this approach, which may be also employed in other similar systems.