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European chemical bulletinVol. 6., No. 11. (2017.)

Tartalom

Materials and environmental chemistry

  • Eszter Bódis ,
    Ádám Fábián ,
    Krisztián Bán ,
    Zoltán Károly ,
    Szilvia Klébert ,
    Anna Mária Keszler ,
    Péter Fazekas ,
    János Szépvölgyi :

    Silicon carbide-based (SiC) ceramics has attracted quite broad attention due to their excellent mechanical, chemical and thermal properties. However, their widespread industrial application is hindered by difficulties in sintering and poor fracture toughness of sintered bodies. In this work, we present an alternative way to produce SiC-based ceramics with improved microstructure and mechanical properties. We incorporated ZrO2 nanofibres into the ceramic matrix to achieve a combined reinforcing effect of partially stabilized zirconia, namely fibre and phase transformation strengthening. For comparison, we also prepared silicon carbide ceramics containing yttria stabilized zirconia (YSZ) particles. SiC-based green bodies containing 5, 10 and 15 wt % ZrO2 nanofibres and particles, respectively, were subjected to spark plasma sintering (SPS) at relatively low (1700 °C) temperatures with high heating and cooling rates. The effects of nanofibres on mechanical properties were studied by determining the Vickers hardness and Young’s modulus of sintered ceramics from instrumented indentation tests. The microstructural patterns were investigated, as well.

    Keywords: SiC, ZrO2 nanofibres, mechanical properties, spark plasma sintering (SPS)

  • Ekemini Ituen ,
    Onyewuchi Akaranta ,
    Abosede James :

    Different solvents were used to extract Griffonia simplicifolia and tested corrosion inhibitors for as X80 steel in 1 M HCl solution. The corrosion tests were conducted by thermo-gravimetric analyses (TGA), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) while the surface morphologies were checked by scanning electron microscopy (SEM). The essence was to investigate the effects of the solvents on the yield, phytochemical profile, corrosion inhibition properties and thermal stability of the extracts. The highest yields of 63.24 g kg-1 and 51.63 g kg-1 were obtained with seeds (SEGS) and leaves (LEGS) extracts respectively in ethanol-water (1:1) system. Acetone extract showed presence of all the tested phytochemicals namely alkaloids, tannins, saponins, glycosides, steroids and terpenoids. The highest inhibition efficiencies of 95.86 % (SEGS) and 82.14 % (LEGS) were obtained with acetone extracts. Acetone extract was also most thermally stable being 66.4 % (SEGS) and 50.05 % (LEGS) efficient at 90 C, followed by ethanol extract while methanol extract was least stable and least efficient. Inhibitors act as mixed type and their addition increased charge transfer resistance and decreased corrosion current density with respect to the free acid solution. Micrographs of the steel surface in some systems show evidence of slight surface protection by the inhibitors. It has been inferred from this study that both acetone and ethanol are better solvents for extraction of Griffonia simplicifolia based corrosion inhibitors.

    Keywords: Griffonia simplicifolia, adsorption, solvent effect, EIS, SEM, corrosion inhibitor

  • Fatma Özge Gökmen ,
    Nursel Pekel Bayramgil :

    The nanocomposite hydrogel of N-[3-(dimethylamino)propyl]methacrylamide (DMAPMAAm) with different SiO2 particles were prepared by free radical polymerization. The nano-SiO2 as reinforcement material was used in original, hydrophilic and perlite forms. The swelling values of nanocomposite hydrogels containing amine-modified nano-SiO2 were found to be higher than those of the original DMAPMAAm hydrogel and the nanocomposite hydrogel containing original SiO2. SEM and mapping studies with SEM proved the presence of nano-SiO2 particles incorporated into the hydrogel structure

    Keywords: Nanocomposite hydrogels, nano-SiO2, biocompatibility, SEM-mapping, N-[3-(dimethylamino)propyl]methacrylamide (DMAPMAAm)

  • Nehad Hamdi ,
    Doaa M. El-Mekkawi ,
    Mohamed M. Selim ,
    S. A. Hassan ,
    Amir Ezzat :

    The anti-bacterial characteristics of different nano-structured metal and metal oxides modified cotton fabrics were investigated. In this study, silver metal, copper, zinc and magnesium oxides have been supported on bleached cotton fabrics. Reduction, wet method, sol gel and precipitation methods were used in the preparation of the antibacterial nanoparticles (NPs). The preparation of the antibacterial-loaded cotton was carried out in-situ and ex-situ by pad dry methods. Formation of the supported nanoparticles was confirmed using x-ray diffraction (XRD), scanning electron microscopy studies (SEM) and energy dispersive x-ray (EDX) analyses. Antibacterial studies on the supported nanoparticles were done on gram positive (Bacillus and S. aureus) and gram negative (E-coli) bacteria by agar diffusion method. The loaded antibacterial nanoparticles are effective against the bacteria under investigation. Under the given experimental conditions, the maximum inactivation performances of each loaded inorganic agent were investigated. The loaded fabrics show the following antibacterial performance order against Bacillus subtilis is Ag=CuO>ZnO>MgO. However, the activity order is CuO>Ag>ZnO=MgO against S.aureus and E. coli. The inactivation performances depend on the type, purity and the amount of antibacterial nanoparticles on the textile surfaces.

    Keywords: inorganic antibacterial, antibacterial textile, metal and metal oxide nanoparticle

  • Sayeda Elewa Eid ,
    Abdel Gawad Mohamed Rabie ,
    Seif El-Din Ebraheem ,
    Asmaa Sobhy :

    Dyed poly(vinyl alcohol) (PVA) films prepared by a simple technique of casting aqueous PVA solution incorporating a mixture of two dyes namely chlorophenol red (CPR) and Quinaldine Red (QR) on a horizontal glass plate are useful as high dose dosimeter in the dose range 2-30 kGy range. The colour of these films change from deep red to yellow when exposed to gamma radiation. Chloral hydrate was added with different concentrations. The response of the prepared films can be modified either by change of chloral hydrate concentration or ratio of the two dyes. As a result, these films can be used as a dosimeter in two dose ranges. The dosimetric parameters, e.g.; dose response, effect of relative humidity on response as well as pre- and post-irradiation stability of these films have been investigated.

    Keywords: Poly(vinyl alcohol), chlorophenol Red, Quinaldine Red, dosimetry

  • Eszter Bódis ,
    Ádám Fábián ,
    Krisztián Bán ,
    Zoltán Károly ,
    Szilvia Klébert ,
    Anna Mária Keszler ,
    Péter Fazekas ,
    János Szépvölgyi :

    Silicon carbide-based (SiC) ceramics has attracted quite broad attention due to their excellent mechanical, chemical and thermal properties. However, their widespread industrial application is hindered by difficulties in sintering and poor fracture toughness of sintered bodies. In this work, we present an alternative way to produce SiC-based ceramics with improved microstructure and mechanical properties. We incorporated ZrO2 nanofibres into the ceramic matrix to achieve a combined reinforcing effect of partially stabilized zirconia, namely fibre and phase transformation strengthening. For comparison, we also prepared silicon carbide ceramics containing yttria stabilized zirconia (YSZ) particles. SiC-based green bodies containing 5, 10 and 15 wt % ZrO2 nanofibres and particles, respectively, were subjected to spark plasma sintering (SPS) at relatively low (1700 °C) temperatures with high heating and cooling rates. The effects of nanofibres on mechanical properties were studied by determining the Vickers hardness and Young’s modulus of sintered ceramics from instrumented indentation tests. The microstructural patterns were investigated, as well.

    Keywords: SiC, ZrO2 nanofibres, mechanical properties, spark plasma sintering (SPS)

  • Nagwan M. Afify ,
    Abdel Aziz S. Sheta ,
    Sayed M. Arafat ,
    Afify A. Afify ,
    Mohammed S. Abd-Elwahed ,
    Adel S. El-Beltagy :

    Earth Observation (EO-1) data provides a highest spectral resolution to get spectral information of Earth's Surface targets within 242 spectral bands at 30 m spatial resolution. In this context, the main objective of this paper is to produce a land cover map using hyperspectral data acquired by EO-1 Hyperion instrument over one test site. Atmospheric correction on the hyperspectral data was performed using ENVI’s Fast Line-of-sight Atmospheric Analysis of Spectral Hyper-cubes (FLAASH) module. Support Vector Machine (SVM) classification was implemented on the dominant elements to produce a land cover map for test site. SVM is carried out in this research to deal with the multi-class issue of Hyperion data. Classification using the kernel functions in classification made the classifier robust against the outliers. The Land Cover Classification System (LCCS) was used to know the land cover classes. The result showed high accuracy for land cover map with machine learning classifier like SVM using hyperspectral remote sensing data. The overall classification accuracy obtained was 97.85.

    Keywords: Hyperion Data, Land cover, Support Vector Machine, Remote Sensing and GIS

  • Ghada Khdery ,
    Sayed Arafat ,
    Mohamed Aboelghar ,
    Mohamed Tantawy ,
    Maged Abou-El-Enain ,
    Usama Kamal :

    Remote sensing enables for cost-effective, timely efficient and multi-temporal monitoring of natural vegetation. Spectral reflectance pattern either in forms of row reflectance values or form of spectral vegetation indices (SVIs) could be used as estimators of plant biophysical and biochemical parameters through statistical models. The main objective of the current study is to correlate plant chlorophyll concentration with different (SVIs) and to identify the most sufficient index to discriminate among the twenty common natural vegetation species in Sinai Peninsula. Calculated values of five hyperspectral vegetation indices (normalized difference vegetation index (NDVI); Chlorophyll Index; Chlorophyll a,b; Simple ratio index (SRI); Modified chlorophyll absorption ratio index (MCARI) for the twenty observed vegetation species were used as spectral factors in the modeling process. The result showed that the relatively high chlorophyll content was found in broad leaves plants when needle-leaved plant species showed relatively low ones. Laboratory chlorophyll estimation indicated that Asclepias sinaica had the highest chlorophyll content (79 mg cm-2) when the same plant specious showed the highest chlorophyll index value. It was found that plants of family Zygophyllaceae have low chlorophyll content. Among observed SVIs, NDVI was the most correlated index with chlorophyll. At the same time, it was the optimal index to differentiate the different species.

    Keywords: Hyperspectral; Spectral indices; Chlorophyll content