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Magnesium aluminate has the spinel structure along with good mechanical, chemical, and thermal properties. Magnesium aluminate has a wide range of applications including refractory ceramics, optically transparent ceramic windows, and armors. Its low dielectric permeability and low loss tangent enable its applications for integrated electronic devices, as well. In this paper, MgO and Al2O3 powders were mixed in a one-to-one molar ratio and calcined at temperatures ranging from 1500 to 1800oC to produce phase pure spinel. Thereafter, pellets were crushed and treated in a planetary ball mill for 60 min to obtain a fine powder. All powders were examined for phase composition, crystal structure, and morphology. The obtained results showed that by increasing the temperature, samples with higher density were synthesized. Milling for 1 h led to formation of larger particles, but finer powders after milling. XRPD and Raman spectroscopy showed disorder in the crystal structure after milling.

Zinc oxide (ZnO) nanoparticles were obtained by thermal decomposition of one-dimensional zinc–benzenepolycarboxylato complexes as single- -source precursors at 450 °C in an air atmosphere. The mechanism and kinetics of thermal degradation of zinc–benzenepolycarboxylato complexes were analyzed under non-isothermal conditions in an air atmosphere. The results of X-ray powder diffraction and field emission scanning electron microscopy revealed hexagonal wurtzite structure of ZnO with an average crystallite size in the range of 39–47 nm and similar morphology. The band gap and the specific surface area of ZnO nanoparticles were determined using UV–Vis diffuse reflectance spectroscopy and the Brunauer, Emmett and Teller method, respectively. The photoluminescent, photocatalytic and antimicrobial properties of the ZnO nanoparticles were also examined. The best photocatalytic activity in the degradation of C. I. Reactive Orange 16 dye was observed for the ZnO powder where the crystallites form the smallest agglomerates. All ZnO nanoparticles showed excellent inhibitory effect against Gram-positive bacterium Staphylococcus aureus and Gram-negative bacterium Escherichia coli.

Single phase MgAl2O4 was made from a one-to-one molar ratio of MgO and Al2O3 powders mixed using ball-milling. Mixtures of MgO and Al2O3 were subsequently treated in planetary ball mill for 30, 60, 90 and 120 minutes in air. The aim of this study was to examine phase composition, microstructure, and densification behavior of sintered specimens. After sintering in dilatometer at 1500°C, the powder was converted to single phase MgAl2O4. The results show that mechanical activation improved the densification behavior of MgAl2O4 sintered specimens, and it reduced the onset temperature for sintering by approx. 100°C. Based on dilatometer data, powders were subsequently densified at 1450°C by hot pressing. Almost аll specimens exhibited full density, while sample activated for 30 minutes showed the fastest densification rate. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. OI 172057, and Grant no. III 45007]

It is well known that alumina possesses good mechanical and chemical properties. Nanofibers having α - alumina structure was used as reinforcement for metal, polymer and ceramic matrix composites. In this study, three series of nanofibers were prepared. The first series was made from 10 % water solution of the aluminium chloride hydroxide/polyvinyl alcohol with a mass ratio of 5:1. The other two series were made with the addition of 1 wt.% of MgCl2 or 1 wt.% of FeCl3 regarding the aluminium chloride hydroxide content. Nanofibers were prepared using the electrospinning technique and they were characterized by the TGA/DTA, XRD and FESEM methods. It was proven that addition of FeCl3 into the initial spinning solution lowers the temperature for the corundum structure formation while the addition of MgCl2 results if the formation of mixed oxides that eases the sintering process. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. TR34011]

Corundum (α-alumina) is a suiTab. material for usage in various industry fields owing to its chemical stability, electrical and mechanical features. It is known that properties of ceramics could be modified by addition of different oxides, as well as by changing the consolidation parameters. In this respect, alumina was doped with 1 wt.% of Cr2O3, Mn2O3 and NiO, followed by 1 hour of mechanical activation in a high-energy planetary ball mill. A sensitive dilatometer was used for sintering of powder mixtures up to 1400 oC and recording the obtained dilatation. The final density varied between cca. 1.9 and 3.3 g/cm3. Microstructural changes were detected by SEM measurements. Changes in electrical permittivity and loss tangent were associated with the preparation conditions (types of additives, duration of mechanical activation). For a given mixture, the sintering increases the relative permittivity and decreases losses, exhibiting the optimal values of 8.32 and 0.027, respectively, for the sample activated 60 minutes and sintered, with the addition of MnO2. Mechanical measurements indicate significant differences in strength with the addition of different transition metal oxides. Samples with Mn and Ni, activated and sintered, with strength of 121 and 86 MPa, respectively, have a significantly higher tensile strength than the other tested samples, due to their more compact microstructures. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. OI 172057, Grant no. III 45007 and Grant no. III 45019]

A terephthalate-bridged heteronuclear Cu(II)–Mn(II) complex [Cu2Mn(dipya)2(tpht)3]n, I, where dipya is 2,2′-dipyridylamine and tpht is the anion of 1,4-benzenedicarboxylic (terephthalic, H2tpht) acid was synthesized under hydrothermal conditions. The obtained complex I was characterized by a single-crystal X-ray diffraction, FTIR spectroscopy, TG/DSC analysis and magnetic measurements. The Cu(II) and Mn(II) metal centers adopt distorted octahedral geometry and they are linked by bridging tpht ligands. Two crystallographically different tpht anions are coordinated as tridentate and hexadentate ligands forming two-dimensional layers. The layers are interconnected by hydrogen bonds and additionally stabilized by non-covalent C–H···π interactions. The measurements of magnetic susceptibility proved that I is an almost perfect paramagnet. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. III45007]

Two series of poly(e-caprolactone) nanocomposites with different organo-modified clays (1 to 8 wt%) were prepared by the solution casting method. Organoclays with polar (Cloisite®C30B) and nonpolar (Cloisite®C15A) organic modifier and with different miscibility with poly(e-caprolactone) matrix, were chosen. Exfoliated and/or intercalated nanocomposite’s structures were obtained by using high dilution and an ultrasonic treatment for the composite preparation. The effect of the surface modification and clay content on the morphology, mechanical and thermal properties of the nanocomposites was studied. Scanning electron microscopy excluded the formation of microcomposite. The wide-angle X-ray diffraction analysis revealed that the tendency toward exfoliated structure is higher for the Cloisite®C30B, which had better miscibility with poly(e-caprolactone) matrix. Differences in spherulites’ sizes and morphology between two series of the nanocomposites were observed by the optical microscopy performed on as-casted films. Enthalpies of fusion and degrees of crystallinity were higher for nanocomposites than for neat poly(e-caprolactone) and increase with the clay loading in both series, as a consequence of the clay nucleating effect. Decreased thermal stability of nanocomposites was ascribed to thermal instability of organic modifiers of the clays. The Halpin-Tsai model was used to compare the theoretically predicted values of the Young’s modulus with experimentally obtained ones in tensile tests.[Projekat Ministarstva nauke Republike Srbije, br. 172062]

Pt-based nanocatalysts supported on Vulcan XC-72R carbon, were prepared by water-in-oil microemulsion method, with addition of various amounts of HCl in the water phase. Polyethileneglycoldodecylether (BRIJ 30) was used as a surfactant, which influenced the Pt surface structure, along with HCl. Catalysts prepared with addition of 0, 15, 25 and 35 % of HCl during the synthesis, were electrochemically characterised in 0,5 M H2SO4 using cyclic voltammetry and CO oxidation. Formic acid electrooxidation was examined on all investigated catalysts, in terms of their electrocatalytic activity and stability. Platinum loading on carbon support was examined by Thermogravimetric analysis. Catalysts showed different features in hydrogen region, and slight differences in formic acid oxidation mechanisms.

The title compound, (Hdipya)(H3pyr), where Hdipya is protonated 2,2’-dipyridilamine and H3pyr is monoanion of pyromellytic acid (H4pyr), was obtained from the reaction mixture containing Zn(II) ions, dipya, Na4pyr (the molar ratio 2 : 2 : 1) and HNO3. The products (micro- and single-crystalline) were characterized by X-ray structure determination, FT-IR spectroscopy and TG/DSC analysis. The most striking structural feature of (Hdipya)(H3pyr) are short inter- and extremely short intramolecular hydrogen bonds. These bonds mutually connect cations and anions making thin layers parallel to the crystallographic (223) plane. Also, quite unusual, linear proton-bound polymeric {H(H2pyr)-}n anions were identified in the structure. The results of crystal structure determination are compared with FT-IR and TG/DSC data. The low position of nas(COO) vibration at 1660 cm-1 is in accordance with strong hydrogen bonding. This value can be used as a measure of C=O bond order, which is calculated to be 1.81. [Projekat Ministarstva nauke Republike Srbije, br. 45007]

Four novel polymeric iron(III) complexes with 2,2’-bipyridine (bipy) and different aromatic polycarboxylato ligands as anions of phthalic (pht), isophthalic (ipht), terephthalic (tpht) and pyromellitic (pyr) acid were synthesized by ligand exchange reaction. The complexes were characterized by elemental and TG/DSC analysis, FTIR and diffuse reflectance UV-VIS-NIR spectroscopy and magnetic susceptibility measurements. Based on analytical and spectral data the formulae of the complexes are {[Fe4(bipy)2 (H2O)2(OH)6(pht)3]•2H2O}n (1), {[Fe4(bipy)2(Hipht)2(ipht)2(OH)6]•4H2O}n (2), {[Fe4(bipy)2(Htpht)2(OH)6(tpht)2]•4H2O}n (3) and {[Fe4(bipy)(H2O)8(OH)4 (pyr)2]•H2O}n (4). All complexes are red brown and low-spin with a distorted octahedral geometry and FeO6 or FeN2O4 chromophore. Polycarboxylato ligands have a bridging role in all cases, whereas monodentate COO groups are present in 2 and 3, bridging and chelate COO groups are established in 1 and 4. The thermal behaviour of 1-4 was investigated in detail and the molar dehydration enthalpies were calculated. According to the all those results, the structural formulae of the complexes 1-4 were proposed. [Projekat Ministarstva nauke Republike Srbije, br. III45007]

In this study, the synthesis, structure and physical properties of two series of thermoplastic polyurethanes based on hydroxypropyl terminated poly(dimethylsiloxane) (HP-PDMS) or hydroxyethoxy propyl terminated poly(dimethylsiloxane) (EO-PDMS) as a soft segment, and 4,4’-methylenediphenyl diisocyanate and 1,4-butanediol as a hard segment were investigated. Each series is composed of samples prepared with a different soft segment. The polyurethanes were synthesized by two-step polyaddition in solution. The effects of the type and content of PDMS segments on the structure, thermal and surface properties of copolymers were studied by 1H NMR, 13C NMR and two-dimensional NMR (HMBC and ROESY) spectroscopy, GPC, DSC, TGA, WAXS, SEM, water contact angle and water absorption measurements. Thermal properties investigated by DSC indicated that the presence of soft PDMS segments lowers the glass transition and melting temperatures of the hard phase as well as the degree of crystallinity. SEM analysis of copolymers with a lower soft segment content confirmed the presence of spherulite superstructures, which arise from the crystallization of the hard segments. When compared with polyurethanes prepared from HP-PDMS, copolymers synthesized from EO-PDMS with the same content of the soft segments have higher degree of crystallinity, better thermal stability and less hydrophobic surface. Our results show that the synthesized polyurethanes have good thermal and surface properties, which could be further modified by changing the type or content of the soft segments.

Carbon supported Pt and Pt-Rh-Sn catalysts were synthesized by microwave-polyol method in ethylene glycol solution and investigated for the ethanol electro-oxidation reaction. The catalysts were characterized in terms of structure, morphology and composition by employing XRD, STM and EDX techniques. STM analysis indicated rather uniform particles and particle size of below 2 nm for both catalysts. XRD analysis of the Pt/C catalyst revealed two phases, one with the main characteristic peaks of face centered cubic crystal structure (fcc) of platinum and another related to graphite like structure of carbon support Vulcan XC-72R. However, in XRD pattern of the Pt-Rh-Sn/C catalyst diffraction peaks for Pt, Rh or Sn cannot be resolved, indicating an extremely low crystallinity. The small particle sizes and homogeneous size distributions of both catalysts should be attributed to the advantages of microwave assisted modified polyol process in ethylene glycol solution. Pt-Rh- Sn/C catalyst is highly active for the ethanol oxidation with the onset potential shifted for more than 150 mV to negative values and with currents nearly 5 times higher in comparison to Pt/C catalyst. The stability tests of the catalysts, as studied by the chronoamperometric experiments, reveal that the Pt-Rh-Sn/C catalyst is evidently less poisoned then Pt/C catalyst. The increased activity of Pt-Rh-Sn/C in comparison to Pt/C catalyst is most probably promoted by bifunctional mechanism and the electronic effect of alloyed metals.

The crystal structure of the complex [Ni2(btc)(dipya)2(H2O)6]⋅6H2O·DMSO (btc = tetra-anion of 1,2,4,5-benzenetetracarboxylic acid, dipya = 2,2’-dipyridylamine) was refined in the triclinic system, space group P1, using low temperature (170 K) X-ray diffraction data. The compound consists of binuclear complex entities and lattice solvent molecules making pseudo-layers parallel to the 101 plane and channels parallel to the b-axis. The observed structural features were compared with the previously reported results and formula [Ni2(btc)(dipya)2(H2O)6]⋅4H2O based on room temperature X-ray diffraction data. A possible arrangement of the disordered lattice solvent molecules located in the structural channels is described and discussed. It is concluded that the layout of these molecules is non-centrosymmetric, although the remaining and main part of the structure is centrosymmetric. .

X-Ray crystal structure analysis of the complex [Cu(tpth)(phen)(H2O)]n, where tpht is the dianion of terephthalic acid and phen is 1,10-phenanthroline showed that two crystallographically different, but chemically identical tpht ions with monodentately coordinated COO groups exist; both tpht ions act as bridging ligands forming zigzag chains. The Cu(II) ions are in a deformed trigonal bipyramidal environment consisting of two N atoms from phen, two O atoms from different tpht ligands and one O atom from coordinated H2O molecule. The crystal data are as follows: C20H14CuN2O5, Mr = 425.87 triclinic system, space group P 1, a = 9.007(5), b = 10.557(5), c = 11.554(5) Å, α= 114.343(5), β = 92.942(5), γ = 114.516(5) º, V = 877.3(7) Å3, Z = 2 F(000) = 434, ρx = 1.612 g cm-3, μ = 1.281 mm-1, R1 = 0.0280 for 4363 reflections with I > 2σ(I), wR2 = 0.0785 for 5104 independent reflections and 254 refined parameters. Some of data were compared with isostructural Co(II) and Zn(II) complexes having the same ligands.

Nowadays, exopolysaccharides (EPS) produced from bacterial cells are manufactured for their use in different industries in the world, mainly in the food, pharmaceutical, and wastewater industries. The characteristics of EPS, such as being biodegradable, safe, high adsorption capacity, and reusable, make them significant and potential applications in the purification of contaminated water of heavy metals. In this study, the possible application in biosorption Ni2+ ions from contaminated water was assessed using this exopolysaccharide as a biosorbent. The new exopolysaccharide from the bacterial strain K. oxytoca J7 was extracted, isolated, and characterized using SEM, FTIR, XRD, TGA/DTG, and MALDI-TOF MS analysis. Likewise, the cytotoxic activity was performed for EPS from K. oxytoca J7 strain. The aim of this study was to investigate the possible application of non-toxic exopolysaccharide in the purification of contaminated water by removing Ni2+ ions. The results obtained from the biosorption study showed that the Langmuir model is well suited to describe the adsorption process of Ni2+ ions by EPS from K. oxytoca J7, with a maximum adsorption capacity of 269.97 mg g–1. The importance of this study is the possible use of natural nontoxic exopolysaccharide extracted from the pathogen microorganism, K. oxytoca J7, for the removal of Ni2+ ions from the contaminated water. [ABSTRACT FROM AUTHOR]