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To investigate the magnetic behavior of starch-coated cobalt ferrites, well-established synthetic methods, i.e., coprecipitation, mechanochemical, ultrasonically assisted coprecipitation, microemulsion, and microwave-assisted hydrothermal syntheses were chosen for their preparation. The obtained materials had pure single-phase spinel structures. Scanning and transmission electron microscopy analyses revealed that the morphology of the samples is not uniform, and particle aggregation is a dominant process. Fourier transform infrared spectra and thermogravimetric analysis confirmed the presence of starch in all–coated samples. The unusually higher saturation magnetization of starch-coated samples than their as-prepared analogs, obtained by coprecipitation, ultrasonically assisted coprecipitation, and microwave-assisted hydrothermal methods, might be explained by the Ostwald ripening mechanism induced by the coating process. A decrease in magnetization was noticed for the starch-functionalized nanomaterials synthesized by mechanochemical and microemulsion methods, in comparison to their as-prepared analogs, i.e., the size distribution of such nanoparticles is narrow, and the average diameter of the grains is near critical for the Ostwald ripening process.

Barium titanate (BaTiO3) attracts high scientific and technological attention due to good dielectric and electromechanical properties. Although BaTiO3 is one of the most frequently investigated ferroelectric materials, the need for finding new and/or improved synthesis methods of this material still exists. In this paper, a novel, mild synthesis route for producing tetragonal BaTiO3 from barium nitrate and Ti-oxalate precursor is presented. Morphology of the prepared and subsequently sintered BaTiO3 was determined by SEM. Particle size distribution of the as prepared powder was monitored by the laser diffraction. The phase composition, structure and lattice dynamics were investigated by XRD and Raman spectroscopy. Finally, dielectric parameters were determined in the temperature range from 30 to 180 degrees C, and within a variety of frequencies. Curie temperature was detected at 130 degrees C.

Pt(II) and Pd(II) complexes (1 and 2, respectively) with thiomorpholine-4-carbonitrile (TM-CN), an N-substituted thiomorpholine derivative, were synthesized from tetrachlorido precursors in water. Structural analysis has shown that 1 represents the first monomeric metal complex with this ligand type with an axial M-S bond with respect to the TM-CN ring chair conformation, while in 2 a typical equatorial M-S bond position with respect to the ring chair conformation was observed. A detailed DFT investigation revealed that axial conformers are more stable for molecular forms of both metals, while intermolecular interactions in the crystals stabilize the axial conformer for Pt(II) and the equatorial conformer for Pd(II). The magnitude of this stabilization in the case of 2 is large enough to change the most stable axial conformer in the molecular form to the equatorial conformer in the crystal. Further investigation of the strength of individual intermolecular interactions revealed significant differences of some interactions between the two structures. The likely cause of the difference in the crystal structures of experimentally obtained complexes is the fact that 1 and 2 exhibit different dominant interactions: C-H/M and C-H/S are more dominant in 1 and C-H/Cl interactions are more dominant in 2. In addition, DFT calculations have shown that while the axial position of the Pt-S bond with respect to the ring chair conformation results in a significantly shorter C-H/Pt interaction distance than that in the hypothetical equatorial conformer, there is very little difference in C-H/Pd interaction distances in conformers with axial and equatorial positions of Pd-S bond with respect to the ring chair conformation.

Four silver-based coordination polymers, {[Ag(L)(2)](BF4)}(infinity) (1), {[Ag(H2BTC)(L)]center dot(H3BTC)}(infinity) (2), {[Ag-2(H2BTEC)(L)(2)]..3.33H(2)O}(infinity) (3), and [Ag(H(25)SSA)(L)](infinity) (4), were synthesized using thiomorpholine-4-carbonitrile (L) as the primary ligand and three aromatic polyoxoacids as coligands: trimesic (H3BTC), pyromellitic (H4BTEC), and 5-sulfosalicylic acid (H(35)SSA). Compounds 1 and 3 are two-dimensional, while 2 and 4 are one-dimensional. L acts as a bis-monodentate ligand, while the Ag(I) ion is three-coordinated in 2 and four-coordinated in all of the other compounds. The tetrahedral coordination of Ag(I) in 3 leads to an almost complete absence of intermolecular interactions with the metal center. All compounds show reasonable photocatalytic activity for photocatalytic degradation of mordant blue 9 dye, with reaction rates in the 0.036-0.056 min(-1) range. Changes in the reaction rates can be correlated with the type and coordination of the coligand. Complex 3 exhibits photoluminescence at 77 K, while 4 exhibits photoluminescence at both room temperature and 77 K. Luminescence lifetimes indicate electronic transitions of singlet parentage, where transitions are allowed. A TD-DFT study determined the contributions of individual singlet-singlet electronic excitations to the fluorescence, indicating that metal- intraligand transitions are responsible for luminescence in both complexes.

The goal of this work was the synthesis of a montmorillonite based catalyst for advanced oxidative degradation of organic water pollutants. Montmorillonite (Mt) –rich bentonite was acid-activated (MtA), and impregnated with cobalt (II) solution using the incipient wetness impregnation method. The impregnation was followed by heat treatment. Cobalt(II) ions were added in the quantities corresponding to 0.5 and 1.0 of the cation exchange capacity value. All samples were characterized by using chemical analysis, X-ray powder diffraction (XRPD), Electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy (SEM) coupled with Energy-dispersive X-ray spectroscopy (EDS), Transmission electron microscopy (TEM) and low temperature N2 physisorption. The incorporation of the cobalt in the impregnated samples and the development of porous structure in the acid-activated ones were confirmed. The montmorillonite (Mt) was used as a catalyst support, while the cobalt in its oxide form was responsible for the generation of sulfo-radicals from Oxone®. Two aromatic N-compounds were tested as model pollutants: diazo dye - Acid Orange 10 (AO10) and nicotine. It was found that the synthesized catalysts could be used for the degradation of both pollutants, although more efficiently in AO10 degradation. The acid activation, higher cobalt loading, and temperature were found to be beneficial for the degradation of AO10.

A simple organic-phase synthesis process was used to produce bare NiFe2O4 and ZnFe2O4 and core-shell ZnFe2O4@NiFe2O4 ferrite nanoparticles. X-ray powder diffractograms for all investigated powders show characteristic peaks of a spinel cubic structure without a secondary phase. Transmission electron microscopy (TEM) indicated the presence of nanoparticles that are smaller than 20 nm. The release of divalent ions (Ni2+ and Zn2+) from synthesized nanoparticles that were dispersed in saline solution, phosphate-buffered saline (PBS) and human serum, as determined by the inductively coupled plasma mass spectrometry (ICP-MS) method, was lower than 2 wt %. These results demonstrate the stability of the investigated nanoparticles in biologically relevant media and exclude the toxicity of Ni2+ and Zn2+ due to metal ion release, thereby opening a broad range of (bio)medical applications.

Light-transmitting measurements of white light and a consequentially chosen laser beam of 655 nm propagating through citrate- and oleate-coated CoFe 2 O 4 , FeFe 2 O 4 and MgFe 2 O 4 nanoparticles under the influence of an external magnetic field were presented. New experimental settings were developed for the optical study of ferrites’ behavior in ferrofluid with the applied magnetic field strength within the 30–400 mT range. A magnetic field-induced change of light transmittance occurred and a precipitation of all studied samples was obtained. Optical investigations of ferrofluid suspensions revealed that, contrary to the linear aggregates of colloidal CoFe 2 O 4 and FeFe 2 O 4 , spheroidal aggregates were formed in the case of MgFe 2 O 4 . In all three cases, the surface modification resulted in decreased dipole–dipole interactions between ferrite cores, and thus, less precipitates were noticed. All oleate-coated nanoparticles have demonstrated weaker magnetic responses compared to the citrate-encapsulated samples. The aggregation of nanoparticles potentially increases cytotoxicity. Regarding non-linear clustering of MgFe 2 O 4 suspensions, it can be concluded that its excretion from the organism may likely be easier and faster when used in diagnosis and/or therapy. Therefore, more attention should be paid to the lowly toxic MgFe 2 O 4 regarding its medical application.

A geochemical and mineralogical study was performed on lignite samples from the Upper Miocene Kovin deposit, hosting three coal seams. The Kovin lignite is characterized by high moisture content, medium to high ash yield, medium to high sulphur content and a relatively low gross and net calorific value. The mineralogical composition, and major and trace element contents were determined by X-ray diffraction, scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) analyses, and inductively coupled plasma optical emission spectrometry (ICP-OES). The most abundant minerals in all lignite samples from the three coal seams are clays (illite/smectite), silicates (quartz, plagioclase), sulphates (gypsum/anhydrite) and carbonate (calcite). The other iron-rich minerals are sulphides, oxides and hydroxides (pyrite, mag-netite, haematite, and limonite). In general, mineral matter in the matrix coal consists of illite/ smectite and quartz, while xylite-rich coals, apart from illite/smectite, have a higher content of sulphates and Fe-oxide/hydroxide minerals. The lignite from the Kovin deposit is enriched in As, Cd, Co, Cr, Cu, Ga, Li, Mn, Mo, Ni, Pb, V, Zn, Gd, Tb, Er and Lu in comparison with the Clarke values for brown coals. The statistical analysis of bulk compositional data shows inorganic affinity for the majority of the major and trace elements and possible association with pyrite, illite/ smectite and calcite.

A geochemical and mineralogical study was performed on lignite samples from the Upper Miocene Kovin deposit, hosting three coal seams. The Kovin lignite is characterized by high moisture content, medium to high ash yield, medium to high sulphur content and a relatively low gross and net calorific value. The mineralogical composition, and major and trace element contents were determined by X-ray diffraction, scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) analyses, and inductively coupled plasma optical emission spectrometry (ICP-OES). The most abundant minerals in all lignite samples from the three coal seams are clays (illite/smectite), silicates (quartz, plagioclase), sulphates (gypsum/anhydrite) and carbonate (calcite). The other iron-rich minerals are sulphides, oxides and hydroxides (pyrite, mag-netite, haematite, and limonite). In general, mineral matter in the matrix coal consists of illite/ smectite and quartz, while xylite-rich coals, apart from illite/smectite, have a higher content of sulphates and Fe-oxide/hydroxide minerals. The lignite from the Kovin deposit is enriched in As, Cd, Co, Cr, Cu, Ga, Li, Mn, Mo, Ni, Pb, V, Zn, Gd, Tb, Er and Lu in comparison with the Clarke values for brown coals. The statistical analysis of bulk compositional data shows inorganic affinity for the majority of the major and trace elements and possible association with pyrite, illite/ smectite and calcite.

The crystal structure of new lanthanum strontium borate glass-ceramics was refined by the Rietveld method. The results showed that La2SrB10O19 has the monoclinic crystal structure, space group C2 (No. 5) with a = 11.1170(6), b = 6.5667(3), c = 9.2363(3) angstrom,beta = 91.481 degrees, V = 674.04(7) angstrom(3), two formula units per unit-cell, and density 3.830 g cm(-3). The main building units of the crystal structure are BO4 tetrahedra and BO3 triangles. Clusters composed of [B5O12] form an infinite double layer running perpendicular to the c-axis. Lanthanum atoms, situated in [B5O12](n) layers, are coordinated with 10 oxygen atom in a form of LaO10 polyhedra, while Sr atoms, located between [B5O12](n) layers, are coordinated with 8 oxygen atoms in a form of SrO8 polyhedra. Microstructural measurements contain both crystallite domain sizes and microstrain calculations obtained by the Warren Averbach and the simplified integral-breadth methods.

Zinc-ferrite, nickel-ferrite and mixed nickel-zinc ferrites were successfully synthesized via the thermal decomposition method from acetylacetonate complexes. To control the particle size and enhance dispersibility in an aqueous medium, starch, a natural and biocompatible compound, was used for the first time for coating such magnetic powders. X-ray powder diffraction (XRPD) was performed to study the structural properties of all samples. The presence of a single-phase spinel structure as well as the cation distribution in both sites of all investigated magnetic powders was confirmed. The values of unit cell parameters obtained from the results of the Rietveld analysis decreased, while the average crystallite size increased with increasing Ni2+ content. The average microstrain parameters unambiguously showed a change in the spinel structure with cation distribution. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR) analyses were also utilized to characterize the synthesized materials, corroborating the XRPD data. The obtained results indicated that functionalization by starch was successfully achieved.

The aim of this work is to assess damage to the City of Belgrade caused by the unfavorable weather condition of hail due to the absence of anti-hail defense of the city, and to argumentatively point out the necessity of introducing new technical-technological systems for preventing the effects of adverse weather conditions. The results are based on the direct correlation-analyses of two real unfavorable weather events and the estimated financial damage caused by these events. The overall calculation also takes into account financial investments (new financial model) necessary to establish two essentially different systems for anti-hail protection. The damage caused by the hail on the territory of the City of Belgrade and the financial investment in anti-hail protection to reduce it are empirically established for the first time. It is shown how the damage could be transformed to profit, as the financial investment in anti-hail protection is lower than the damage that hail can cause.

The design of mixed-ligand complexes are of increasing interest from fundamental as well as technological and curative aspects. Having that in mind, we studied zinc complex containing 2,2'-dipyridylamine (dipya) and dianion of isophthalic acid (ipht), [Zn(dipya)(ipht)](n), as promising precursor for synthesis of nanostructured metal oxide. In that sense, the mechanism and degradation kinetics of [Zn(dipya)(ipht)](n), was analyzed under non-isothermal conditions in nitrogen and in air atmospheres. Peak deconvolution of the [Zn(dipya)(ipht)](n), decomposition profile, in the form of a derivative thermogram (DTG), in nitrogen atmosphere, revealed the presence of three decomposition steps, while in air five single steps were isolated. In both cases ZnO is formed as residue at 530 degrees C: pure (in air) or in amorphous matrix (nitrogen). In air we obtained well crystalized ZnO nanospheres (-25 nm), by thermal treatment in temperature range 370-530 degrees C showing that this complex could be considered as good precursor for production of nanosized ZnO.

This study was undertaken to determine the impact of the organic complex concentration on the adsorption of herbicide (acetochlor) at the surface of the organic modified montmorillonite. In this work, natural montmorillonite from Bogovina (Boljevac municipality, Serbia) was used for organic modification. Cation-exchange capacity of this montmorillonite was determined using a methylene blue method (86mmol/100g of clay). Montmorillonite has been modified first with NaCl and then with hexadecyltrimethylammonium bromide (HDTMA-bromide) organic complex. Saturation of cation exchange capacity (CEC) was 50%, 100%, and 150%. Changes in the properties of the inorganic and organic montmorillonite have been examined using the X-ray diffraction, Fourier transform infrared spectroscopy, and batch equilibrium method. Montmorillonite modified with HDTMA-bromide demonstrated higher uptake of the herbicide, compared to the inorganic montmorillonite. Comparing the values Freundlich coefficients in batch equilibrium method, it can be seen that the adsorption of acetochlor decreased in the series: 0.5 CEC HM gt 1 CEC HM gt 1.5 CEC HM gt NaM.

This study was undertaken to determine the impact of the organic complex concentration on the adsorption of herbicide (acetochlor) at the surface of the organic modified montmorillonite. In this work, natural montmorillonite from Bogovina (Boljevac municipality, Serbia) was used for organic modification. Cation-exchange capacity of this montmorillonite was determined using a methylene blue method (86mmol/100g of clay). Montmorillonite has been modified first with NaCl and then with hexadecyltrimethylammonium bromide (HDTMA-bromide) organic complex. Saturation of cation exchange capacity (CEC) was 50%, 100%, and 150%. Changes in the properties of the inorganic and organic montmorillonite have been examined using the X-ray diffraction, Fourier transform infrared spectroscopy, and batch equilibrium method. Montmorillonite modified with HDTMA-bromide demonstrated higher uptake of the herbicide, compared to the inorganic montmorillonite. Comparing the values Freundlich coefficients in batch equilibrium method, it can be seen that the adsorption of acetochlor decreased in the series: 0.5 CEC HM > 1 CEC HM > 1.5 CEC HM > NaM.

Herein, the synthesis, structural and crystal field analysis and optical spectroscopy of Mn4+ doped metal titanates ATiO(3) (A = Ca, Mg) are presented. Materials of desired phase were prepared by molten salt assisted sol-gel method in the powder form. Crystallographic data of samples were obtained by refinement of X-ray diffraction measurements. From experimental excitation and emission spectra and structural data, crystal field parameters and energy levels of Mn4+ in CaTiO3 and MgTiO3 were calculated by the exchange charge model of crystal-field theory. It is found that crystalline field strength is lower (Dq = 1831 cm(-1)) in the rhombohedral Ilmenite MgTiO3 structure due to the relatively longer average Mn4+-O2- bond distance (2.059 angstrom), and higher (Dq = 2017 cm(-1)) in orthorhombic CaTiO3 which possess shorter average Mn4+-O2- bond distance (1.956 angstrom). Spectral positions of the Mn(4+2)Eg - GT (4)A(2g) transition maxima is 709 nm in MgTiO3 and 717 nm in CaTiO3 respectively in good agreement with calculated values. (C) 2017 Elsevier B.V. All rights reserved.

Magnetic structure of ZnFe2O4 normal spinel is re- examined. Antiferromagnetic structure non-collinear model is established within C(a)2 space group having four different crystallographic/magnetic sites for 32 Fe3+ spins within magnetic unit cell.

The design and synthesis of various mixed ligand complexes with amazing architecture and topology are promoted due to their potential applications as functional materials in fields such as gas storage, chemical separation, catalysis and luminescence [1]. The structural diversity and properties of these materials strongly depend on the organic Odonor ligand. For example, dianion of isophthalic (ipht) acid is widely used as ligand due to its ability to coordinate up to four metal centres with different coordination modes. The addition of Ndonor ligands significantly contributes to their structural versatility increasing their thermal stability [2]. There are only three ipht complexes containing dipya (2,2’-dipyridylamine) as N-donor ligand recently published: [Cu(dipya)(ipht)]·H2O [2, 3], [Mn(dipya)(ipht)]n [4] and [Zn(dipya)(ipht)]n [5]. The highest thermal stability was observed for [Zn(dipya)(ipht)]n. In addition, [Zn(dipya)(ipht)]n exhibits also a great antibacterial activity [4]. The decomposition of [Zn(dipya)(ipht)]n was studied in detail using simultaneous TG/DSC analysis in conjunction with TG/MS measurements and XRPD analysis in nitrogen atmosphere under non-isothermal conditions at four heating rates: 15, 20, 25 and 30 ºC min−1 . The first two decomposition steps are highly overlapped and for that reason the peak deconvolution using FraserSuzuki function was employed. The deconvolution was performed at each heating rate and the three single step processes were isolated. The application of isoconversional method confirmed that deconvoluted steps are individual processes while the determination of conversion functions was done according to the Màlek algorithm [6]. The third degradation step ends around 970 ºC, depending on the heating rate, yielding ZnO.

In this study, a novel electrochemical sensor for quantification of ascorbic acid with amperometric detection in physiological conditions was constructed. For this purpose, cobalt and nickel ferrites were synthesized using microwave and ultrasound assistance, characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and X-ray powder diffraction (XRPD), and used for modification of glassy carbon paste electrode (GCPE). It was shown that introducing these nanoparticles to the structure of GCPE led to increasing analytical performance. Co ferrite modified GCPE (CoFeGCPE) showed better characteristics toward ascorbic acid sensing. The limit of detection (LOD) obtained by sensor was calculated to be 0.0270 mg/L, with linear range from 0.1758 to 2.6010 mg/L. This sensor was successfully applied for practical analysis, and the obtained results demonstrated that the proposed procedure could be a promising replacement for the conventional electrode materials and time-consuming and expensive separation methods. (C) 2016 Elsevier Inc. All rights reserved.

This paper describes determination of trace level of copper ions on a new type of modified glassy carbon paste electrode based on addition of different amount of Co-ferrites in glassy carbon paste (CoFeMGCPE). Co-ferrite nanoparticles with different amount of cobalt were synthesized and characterized using scanning electron microscopy (SEM) and X-ray powder diffraction (XRPD). A significant increase in current was achieved by introducing modifier in composition of the electrode in comparison with the bare glassy carbon paste electrode. Electrochemical parameters such as percentage of modifier, accumulation time and potential, pH and the optimized amount of cobalt in the ferrites were determined. The best voltammetric response was observed for Co0.5Fe0.5Fe2O4 when percentage of modifier was 3%. In acetate buffer solution, pH 4.5, thus prepared electrode displays selective detection toward copper ions, detection limit of 96 nM and it was successfully applied for the determination of copper ions in natural water samples, with satisfactory recovery.

Elevated concentrations of arsenic in groundwater, which is used as a source for drinking water, is a worldwide problem. Use of TiO2 and iron doped TiO2 synthesized by a microwave-assisted hydrothermal method for As(III) and As(V) removal were examined. Synthesized sorbents were characterized with XRD and nitrogen physisorption. Synthesized sorbents have predominantly anatase structure, and no peaks for iron could be observed. Doping of iron increases the surface area of synthesized sorbents. Sorption experiments show that increase of iron in sorbents increases the sorption capacity for As(III) and As(V). Increase of pH from 3 to 11 has no influence on As(III) sorption but decreases the sorption of As(V). Batch isotherm studies were performed to determine the binding capacities of As(III) and As(V). As(III) followed the Freundlich isotherm model, while for As(V) a better fit was with the Langmuir isotherm. The results of competition of SO42- and PO43- anions on adsorption of As(III) indicated that both anions reduced substantially the efficiency of adsorption on both adsorbents while for As(V) only the presence of PO43- anion interfered with adsorption. Testing 10Fe/TiO2 sorbent with arsenic contaminated natural water showed that this material could be used for removal of arsenic to the level recommended by WHO without pretreatment.

This paper describes the preparation of a new sensor based on Zn-ferrite modified glassy carbon paste electrode and its electrochemical application for the determination of trace Cd(II) ions in waste waters using differential pulse anodic stripping voltammetry (DPASV). Different Zn/Ni ferrite nanoparticles were synthesized and characterized using scanning electron microscopy (SEM) and X-ray powder diffraction (XRPD). The prepared ferrite nanoparticles were used for the preparation of Zn-ferrite-modified glassy carbon paste electrode (ZnMGCPE) for determination of Cd(II) at nanomolar levels in waste water at pH 5. The different parameters such as conditions of preparation, Zn2+/Ni2+/Fe2+ ratio and electrochemical parameters, percentage of modifier, accumulation time, pH and accumulation potential were investigated. Besides, interference measurements were also evaluated under optimized parameters. The best voltammetric response was observed for ZnFe2O4 modifier, when the percentage of modifier was 3%, accumulation time 9 min, pH of supporting electrolyte 5 and accumulation potential -1.05 V. Thus prepared electrode displays excellent response to Cd(II) with a detection limit of 0.38 ppb, and selective detection toward Cd(II) was achieved.

Fe-doped TiO2 photocatalysts with different contents of Fe (0.5, 1.6, 3.4 and 6.4 %) were synthesized by a microwave-hydrothermal method and characterized by X-ray diffraction analysis, N-2 physisorption at 77 K and UV-Vis spectrometry. The characterization showed that the Fe ions were highly dispersed in the TiO2 lattice. It was found that all the synthesized catalysts had a mesoporous structure and that Fe-doping increased the BET surface area. The UV-Vis study showed that the absorption spectra were shifted to longer wavelengths (red shift) with increasing dopant concentration. The photocatalytic activity of the samples was evaluated by the decolorization of the textile dye Reactive Blue 52 (RB) in aqueous solutions under sun-like radiation in the presence of H2O2 (a heterogeneous photo-Fenton process). The photocatalyst with 3.4 % Fe was found to be the most efficient in the presence of H2O2. The effect of the initial pH of the dye solution was assessed and dissolution of iron ions was studied as a function of pH value. It was concluded that decolorization was more favorable in acidic pH, and that at pH values gt 4, the release of Fe ions into the solution was negligible. Photocatalytic degradation of 4-chlorophenol (4-CP) was investigated under the optimal conditions and it was shown that the catalyst was capable of degrading colorless pollutants.

Fuel cell application of tungsten carbide is revisited starting with four different tungsten carbide precursors used for high temperature synthesis. It was shown that the final products greatly depend on the nature of the precursor. Using tungsten peroxide/2-propanol derived precursor almost pure WC was obtained which was subjected to further electrochemical investigation. It was shown that it is necessary to decorate WC with Pt nanoparticles in order to obtain satisfactory fuel cell performance, but catalytic activity of Pt/WC anode catalyst is not expected to overcome the activity of Pt/C. It is argued that new synthetic routes for the preparation of WC should be directed towards obtaining highly dispersed WC, that is, WC with high external surface area available for Pt deposition, rather than high specific surface area WC with large contribution of micropores having no importance when it comes to the use of WC as a catalyst support. The true benefit of the use of WC as catalyst support is found in increased CO tolerance/CO oxidation activity of WC-supported Pt catalysts. Qualitative mechanistic view on increased CO oxidation activity of Pt/WC is offered. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

The evolution of the magnetic state, crystal structure and microstructure parameters of nanocrystalline zinc-ferrite, tuned by thermal annealing of similar to 4 nm nanoparticles, was systematically studied by complementary characterization methods. Structural analysis of neutron and synchrotron x-ray radiation data revealed a mixed cation distribution in the nanoparticle samples, with the degree of inversion systematically decreasing from 0.25 in an as-prepared nanocrystalline sample to a non-inverted spinel structure with a normal cation distribution in the bulk counterpart. The results of DC magnetization and Mossbauer spectroscopy experiments indicated a superparamagnetic relaxation in similar to 4 nm nanoparticles, albeit with different freezing temperatures T-f of 27.5 K and 46 K, respectively. The quadrupole splitting parameter decreases with the annealing temperature due to cation redistribution between the tetrahedral and octahedral sites of the spinel structure and the associated defects. DC magnetization measurements indicated the existence of significant interparticle interactions among nanoparticles (superspins). Additional confirmation for the presence of interparticle interactions was found from the fit of the Tf(H) dependence to the AT line, from which a value of the anisotropy constant of K-eff = 5.6 x 10(5) erg cm(-3) was deduced. Further evidence for strong interparticle interactions was found from AC susceptibility measurements, where the frequency dependence of the freezing temperature T-f(f) was satisfactory described by both Vogel-Fulcher and dynamic scaling theory, both applicable for interacting systems. The parameters obtained from these fits suggest collective freezing of magnetic moments at T-f.

Pure and Pt-doped ZnO nanophase particles were synthesized by ultrasonic spray pyrolysis. The particles were obtained through the decomposition of zinc nitrate and with a newly developed Pt(IV) complex with 1,3 -propylenediamine-NN'-diacetate tetradentate class ligand (pdda). The complex was characterized by elemental analysis, electronic absorption and infrared spectroscopy. The form of the determined complex structure {trans-[Pt(pdda)Br-2]center dot H2O} implies that Pt(IV) ion has a distorted octahedral coordination due to intramolecular N-H center dot center dot center dot Br interaction. The results of structural refinement (cell parameters, bond lengths, and ion occupancy) of ultrasonically derived pure and Pt-doped ZnO particles suggest either the formation of Zn-i interstitials or platinum ion incorporation into the ZnO lattice in octahedral interstitial positions, respectively. A well-crystallized hexagonal wurtzite structure of ZnO was pronounced in all investigated samples [JCPDS card 36-1415, Joint Committee on Powder Diffraction Standards, defined by International Centre for Diffraction Data (www.icdd.com)]. Phase determination also indicated the presence of a nitrate hydroxide hydrate phase (JCPDS card 24-1460), as a result of incomplete precursor decomposition and a spinel Zn2PtO4 phase (below 1.0 wt%) located in the boundary region for a Pt-doped ZnO sample. Based on x-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy analyses, it was shown that the different particle growing morphologies, which were either spheroidally or pyramidally shaped, were influenced by the precursor chemistry, processing parameters and the presence of platinum ions. The composite internal particle structure revealed by transmission electron microscopy and selected area electron diffraction analyses, implied that the secondary particles represent an assembly of primary particles sized under 60 nm aroused during the processes of nucleation, grow

An equimolar mixtures of starting ZnO and Cr2O3 powders were mechanically activated by grinding using a planetary ball mill for various periods of time (40-320min). Formation of nanocrystalline ZnCr2O4 as normal spine] structure at room temperature is detected in all samples-after ball-milling. A detailed XRD structural analysis (the relative phase abundances of different phases, lattice parameter changes, site occupancy, the average primary crystallite sizes, crystal lattice microstrains) is realized by the pattern decomposition technique, performed in accordance with the procedure based on Rietveld software KOALARIET-XFIT. Due to the importance of cation distribution on the chemical and physical properties of spinels, a study of site occupation factors of ZnCr2O4 spinels has been undertaken. The calculation based on the atomistic methods for the description of the perfect and defect spinel ZnCr2O4 crystal lattice is applied and the presence of the individual structural defects is determined.