- Synthesis of the hydroxide cluster [Al13(μ3-OH) 6(μ-OH)18(H2O)24]15+ from an aqueous solution
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A scalable synthesis of the "flat" tridecameric inorganic cluster [Al13(μ3-OH)6(μ-OH)18(H 2O)24]15+ has been realized by treating an aqueous aluminum nitrate solution with a zinc-metal powder at room temperature. Single crystals and polycrystalline samples are readily obtained in yields exceeding 55% relative to the starting reagent Al(NO3)3. Products have been characterized by X-ray diffraction and solid-state 27Al MAS and MQMAS NMR.
- Wang, Wei,Wentz, Katherine M.,Hayes, Sophia E.,Johnson, Darren W.,Keszler, Douglas A.
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- Metal-organic phase-change materials for thermal energy storage
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The development of materials that reversibly store high densities of thermal energy is critical to the more efficient and sustainable utilization of energy. Herein, we investigate metal-organic compounds as a new class of solid-liquid phase-change materials (PCMs) for thermal energy storage. Specifically, we show that isostructural series of divalent metal amide complexes featuring extended hydrogen bond networks can undergo tunable, high-enthalpy melting transitions over a wide temperature range. Moreover, these coordination compounds provide a powerful platform to explore the specific factors that contribute to the energy density and entropy of metal-organic PCMs. Through a systematic analysis of the structural and thermochemical properties of these compounds, we investigated the influence of coordination bonds, hydrogen-bond networks, neutral organic ligands, and outer-sphere anions on their phase-change thermodynamics. In particular, we identify the importance of high densities of coordination bonds and hydrogen bonds to achieving a high PCM energy density, and we show how metal-dependent changes to the local coordination environment during melting impact the entropy and enthalpy of metal-organic PCMs. These results highlight the potential of manipulating order-disorder phase transitions in metal-organic materials for thermal energy storage.
- McGillicuddy, Ryan D.,Thapa, Surendra,Wenny, Malia B.,Gonzalez, Miguel I.,Mason, Jarad A.
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- Structural, magnetic and M?ssbauer spectral studies of nanocrystalline Ni0.5Zn0.5Fe2O4 ferrite powders
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Nanocrystalline Ni0.5Zn0.5Fe2O4 powders, synthesized by a combustion method are investigated by X-ray diffraction, vibrating sample magnetometry and M?ssbauer spectroscopic techniques. We adopt a strategy to systematically control the particle sizes between 4 and 45 nm simply by changing the elemental stoichiometric coefficient, Φe, of the combustion mixture. Curie temperature of the superparamagnetic particles of size 4 nm is higher than that of the bulk particles. Interestingly, bigger particles (45 nm) show a comparable room temperature saturation magnetization and exceptionally very high Curie temperature of 833 K, when compared to that of the bulk Ni0.5Zn 0.5Fe2O4 material (563 K).
- Verma, Seema,Joy,Kurian, Sajith
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- Sol-gel synthesis of lithium niobate doped by zinc and boron and study of the luminescent properties of ceramics LiNbO3: Zn: B
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A technological scheme was developed for the sol-gel synthesis of lithium niobate doped by zinc and boron with sol-gel method, and the optimal conditions at each stage of the process were determined. The limiting concentrations of doping impurities, at which a single-phase charge can be synthesized, were established. A ceramic composition LiNbO3: Zn: B with a bulk weight of ~2.3 g cm?3 is formed during the thermal treatment of the hydrate residue at 1100 ?? and an exposure for 3 h. Owing to the proposed method the product quality can be increased and the cost of the syntgesis of the LiNbO3: Zn: B ceramics minimized. The study of the luminescence properties of the ceramics based on the charge prepared from the charge mixture synthesized by the sol-gel method revealed that boron in the lithium niobate structure is an activator of luminescence in the high-energy visible spectral range. The obtained results can serve as a basis for the technology of production of both crystalline and ceramic new functional materials.
- Masloboeva, S. M.,Palatnikov, M. N.,Smirnov, M. V.
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- Thermal studies on energetic compounds: Part 30. Kinetics and mechanism of bis(diethylenetriamine)metal nitrate complexes
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The nitrate complexes of copper, nickel and zinc with diethylenetriamine (dien) i.e. [Cu(dien)2](NO3)2, [Ni(dien) 2](NO3)2·2H2O and [Zn(dien)2](NO3)2 have been prepared and characterised. Thermal studies were undertaken using TG-DTG, DSC, ignition delay (tid) and ignition temperature (IT) measurements. Impact sensitivity was measured using drop mass technique. The kinetic parameters for both non-isothermal and isothermal decomposition of the complexes were evaluated by employing Coats-Redfern (C-R) method and Avrami-Erofeev (A-E) equations (n=2 and 3), respectively. The kinetic analysis, using isothermal TG data, was also made on the basis of model free isoconversional method and plausible mechanistic pathways for their decomposition are proposed. Rapid process was assessed by ignition delay measurements. All these complexes were found to be insensitive towards impact of 2 kg mass hammer up to the height limit (110 cm) of the instrument used. The heat of reaction (ΔH) for each stage of decomposition was determined using DSC.
- Singh,Pandey
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- Development of a novel one-pot synthetic method for the preparation of (Mn0.2Ni0.4Zn0.4Fe2O4)x-(BaFe12O19)1-x nanocomposites and the study of their microwave absorption and magnetic properties
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The development of a simple yet novel aqueous solution based 'one-pot' method has been reported for the preparation of nanocomposites composed of soft ferrite (Mn0.2Ni0.4Zn0.4Fe2O4) and hard ferrite (BaFe12O19) phases. A physical mixing method has also been employed to prepare nanocomposites having the same compositions. The effects of synthetic methodologies on the microstructures of the nanocomposites as well as their magnetic and microwave absorption properties have been evaluated. The crystal structures and microstructures of these composites have been investigated using X-ray diffraction, transmission electron microscopy and scanning electron microscopy. In the nanocomposites prepared by both methods, the presence of nanocrystalline Mn0.2Ni0.4Zn0.4Fe2O4 and BaFe12O19 phases were detected. However, nanocomposites prepared by the one-pot method possessed better homogeneous distribution of hard and soft ferrite phases than the nanocomposites prepared by the physical mixing method. Very good spring exchange coupling interaction between the hard and soft ferrite phases was observed for the nanocomposites prepared by the one-pot method and these composites exhibited magnetically single phase behaviour. The spring exchange coupling interaction enhanced the magnetic properties (high saturation magnetization and coercivity) and microwave absorption properties of the nanocomposites prepared by the one-pot method, in comparison with the nanocomposites prepared by the physical mixing method as well as pure Mn0.2Ni0.4Zn0.4Fe2O4 and BaFe12O19 nanoparticles. The minimum reflection loss of the composites was found to be ～-25 dB (i.e. >99% absorption) at 8.2 GHz with an absorber thickness of 3.5 mm. This journal is
- Hazra, Subhenjit,Ghosh, Barun Kumar,Joshi, Hrishikesh Ravindra,Patra, Manoj Kumar,Jani, Raj Kumar,Vadera, Sampat Raj,Ghosh, Narendra Nath
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- Coordination chemistry of Cu(II), Co(II), Zn(II) and Ag(I) complexes of isomeric pyridine 2- and 4-carboxamides and their biological activity evaluation
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Eight complexes of Cu(II), Co(II), Zn(II) and Ag(I) with rarely studied ligands, N,N-diisopropyl/butylpicolinamide (L1/L2), and N,N-diisopropyl/butylisonicotinamide (L3/L4), have been synthesized and characterized spectroscopically, and their molecular and crystal structures have been reported. Diverse coordination modes of these positional isomers have been discovered, discussed and compared with the limited available literature in light of their respective convergent and divergent nature. All the complexes show stable and extended 1D, 2D or 3D coordination/H-bonded networks owing to a large number of weak C–H?O/X and other intermolecular interactions. Further, the ligands as well as the metal complexes have been evaluated for their antimicrobial activity and have turned out to be potent antimicrobial agents.
- Lumb, Isha,Sran, Balkaran Singh,Sood, Henna,Arora, Daljit Singh,Hundal, Geeta
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- Local investigation of hyperfine interactions in pure and Co-doped ZnO
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In the present work bulk samples of pure as well as Co-doped ZnO with different concentrations were prepared by sol-gel method from highly pure metallic Zn (99.9999%) and Co (99.9999%). The samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray microanalysis (EDS) and perturbed gamma-gamma angular correlation (PAC) spectroscopy. Carrier-free 111In nuclei were introduced during preparation of the samples and used as probe nuclei at Zn sites for PAC measurements. PAC results show that both pure and Zn1 - x Cox O (x ≤ 0.15) samples have the same electric quadrupole frequency when Co-doped samples are annealed in air, argon or nitrogen atmosphere at 1173 K. SEM and EDS results showed that Co-doped samples are homogeneous without any secondary Co phases. These observations indicate that Co ions are substituted for Zn ions and have a similar electronic structure of Zn ions. A weak local magnetism was observed at temperatures below about 300 K for Co concentration of 10% when sample was annealed in Nitrogen.
- Mercurio,Carbonari,Cordeiro,Saxena,D'Agostino
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- Is it possible the substitution of Cr cations from spinel-type oxides with bulky rare-earth cations by sol-gel auto-combustion method?
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Rare-earth La3+ cations, with large ionic radii, substituted ZnCr2-xLaxO4 nanoparticles with x ranging from 0.0 to 0.50 were synthesized by sol-gel auto-combustion technique. Effect of La substitution on structural and magnetic properties of ZnCr2O4 spinel oxide is reported. The phase composition of the obtained powders was investigated by Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy. Magnetic measurements were made using a SQUID magnetometer. FT-IR and X-ray diffraction revealed the transition of spinel structure to perovskite structure because of the exchange of Zn2+ and La3+ cations among constituent A-sites. The particle size were estimated from the SEM micrographs and were found to increase with the La ions substitution from 48 to 80 nm. It was revealed from the magnetic measurements that magnetization follow a decreasing trend with substitution of Cr3+ ions by paramagnetic La3+ ions. Also, the magnetization showed a drastic decrease with increase of temperature from 2 K to 300 K because of enhanced domain pinning effect, due to the La3+ substitution.
- Borhan,Samoila,Gherca,Iordan,Palamaru
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- Thermal decomposition of zinc-iron citrate precursor
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A citrate precursor technique has been used to synthesize ultrafine particles of zinc ferrite (ZnFe2O4). The precursor, Zn3Fe6(C6H5O7)8 . (12+n)H2O, was studied using thermoanalytical techniques. It was found that decomposition in air was suitable for obtaining ZnFe2O4. The thermal decomposition involved seven steps, with the citrate precursor first losing the adsorbed and coordinated water molecules. In subsequent steps, the citrate groups lost water molecules to form metal aconitates, which further decomposed in the temperature range 260-320°C to give hydrozincite and FeO.OH. These intermediates decomposed further with the formation of ZnO and Fe2O3, along with the evolution of CO2 and H2O. A further step involved the formation of ZnFe2O4 in the temperature range 460-560°C at the expense of the ZnO and Fe2O3 phases. The citrate precursor and decomposed products were analysed by IR and X-ray diffraction techniques.
- Gajbhiye, N. S.,Bhattacharya, U.,Darshane, V. S.
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- Kinetics and mechanism of Copper(II), Zinc(II), and Cadmium(II) Incorporation into 5,10,15,20-Tetraphenylporphine and N-Methyl-5,10,15,20-tetraphenylporphine in N,N-Dimethylformamide
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The kinetics of reactions of 5,10,15,20-tetraphenylporphine (H2(tpp)) and N-methyl-5,10,15,20-tetraphenylporphine (H(metpp)) with CuII, ZnII, and CdII ions was studied spectrophotometrically in N,N-dimethylformamide.The rate of incorporation of metal ions (M2+: Cu2+, Zn2+, Cd2+) into H(metpp) is first order with respect to both H(metpp) and metal ion: d+>/dt = k2+> with k(25 deg C)=11.5 +/- 0.5 mol-1 dm3 s-1 for Zn2+ and (5.8 +/- 0.8)x102 mol-1 dm3 s-1 for Cd2+.The rate of incorporation of copper and zinc into H2(tpp) is first order in H2(tpp) and the conditional first-order rate constants are expressed as follows: k0(M)=K2+>(1+K2+>)-1(k1+k22+>) where for Cu2+ and Zn2+ K/mol-1 dm3, k1/s-1, and k2/mol-1 dm3 s-1 at 25 deg C are (1.6 +/- 0.2)x104 and (7.2 +/- 1.5)x102, (1.2 +/- 0.1)x10-4 and (3.5 +/- 0.7)x10-5, and (5.2 +/- 0.2)x10-2 and (8.6 +/- 0.2)x10-4, respectively.Metal ion incorporation into H2(tpp) proceeds through the formation of intermediates prior the rate-limiting step.For the H(metpp) system, the methyl group on the pyrrole in H(metpp) prevents the formation of such an intermediate.On the other hand, the rate of cadmium incorporation into H2(tpp) is first order with respect to Cd2+ and H2(tpp) and its second order rate constant k is (6.5 +/- 1.0)x10-3 mol-1 dm3 s-1.The large cadmium(II) ion can not fit into the porphyrin nucleus and its reaction proceeds through a pathway involving a mononuclear activated complex.
- Funahashi, Shigenobu,Yamaguchi, Yushi,Tanaka, Motoharu
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- High quality Al-doped ZnO thin films deposited using targets prepared by chemical coprecipitation
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In order to grow high-quality aluminum-doped zinc oxide films (AZO), the chemical coprecipitation method was adopted to synthesize ultra-fine AZO powder, in which Al2O3O was more easily and more uniformly doped in ZnO compared to the
- Cai,Jiang,Zhu,Wang
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- Catalyst for the synthesis of dimethyl carbonate from urea and methanol, preparation and use thereof
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A catalyst for the preparation of dimethyl carbonate from urea and methanol having a composition on weight base of: active component of from 20 to 50 wt %, and carrier of from 80 to 50 wt %, and prepared by equal-volume spraying and impregnating method is disclosed. The method for the synthesis of dimethyl carbonate can be carried out in a catalytic rectification reactor, said method comprising: (1) dissolving urea in methanol to form a methanol solution of urea; and (2) feeding the methanol solution of urea and methanol counter-currently into the reaction zone, wherein the reaction is carried out at conditions including reaction temperature of from 120°C to 250°C, reaction pressure of from 0.1 MPa to 5 MPa, kettle bottom temperature of from 70°C to 210°C, stripping section temperature of from 70°C to 250°C, rectifying section temperature of from 70°C to 280°C, and reflux ratio of from 1: 1 to 20 : 1. The preparation of the catalyst according to the present invention is simple and has good repeatability, and the catalyst could further enhance the yield of DMC as well as conversion of urea in the catalytic rectification reactor.
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- Catalyst for oxidizing methylbenzenes and method for producing aromatic aldehyde
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The present invention has for its object to provide a novel catalyst by use of which methylbenzenes can be oxidized in gaseous phase in the presence of molecular oxygen to give the corresponding aromatic aldehydes in high yields, a process for producing an aromatic aldehyde from the corresponding methylbenzene in a high yield by use of said catalyst, and a process for producing cyclohexanedimethanol which comprises hydrogenating phthalaldehyde among the aromatic aldehydes which can be obtained as above. The present invention is directed to a catalyst for oxidation of methylbenzene which is used for the production of the corresponding aromatic aldehyde by the gas-phase oxidation of a methylbenzene in the presence of molecular oxygen, and has a composition of the following general formula (1): WaXbYcOx??(1) ?wherein W represents a tungsten atom; X represents at least one kind of element selected from the group consisting of P, Sb, Bi and Si; Y represents at least one element selected from the group consisting of Fe, Co, Ni, Mn, Re, Cr, V, Nb, Ti, Zr, Zn, Cd, Y, La, Ce, B, Al, Tl, Sn, Mg, Ca, Sr, Ba, Li, Na, K, Rb and Cs; O represents an oxygen atom; a, b, c and x represent the numbers of atoms of W, X, Y and O, respectively; provided, however, the proportions of a, b and c are such that when a=12, b=0.5 to 10 and c=0 to 15; X represents a numerical value which is determined by the oxidized states of the elements other than oxygen.
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- Kinetics and Mechanism for the Formation and Dissociation Reactions of 21-(4-Nitrobenzyl)-5,10,15,20-tetrakis(4-sulfonatophenyl)-23H- porphyrinatozinc(II) and -cadmium(II)
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The incorporation reaction of zinc(II) and cadmium(II) into 21-(4-nitrobenzyl)-5,10,15,20-tetrakis(4-sulfonatophen- yl)-23H-porphyrin (NO2Bz(Htpps)4-; HP4-) and the dissociation reaction of the metalloporphyrins ([MP]3-) have been studied spectrophotometrically at I = 0.1 mol dm-3 (NaNO3). The formation rate of the metalloporphyrins is expressed by the following equation: d[MP3-]/dt = kMf[M2+][HP4-]+kMOH f[MOH+][HP4-]-kMP d[MP3-][H+]. The rate constants and the activation parameters of the reaction were found to be kZnf = (4.86±0.06)× 102 mol-1 dm3 s-1 (25 °C), ΔH? = 62.1±1.6 kJ mol-1, and ΔS? = 14.8±5.3 J mol-1 K-1; kZnOHf = (6.39±0.14)×103 mol-1 dm3 s-1 (25 °C), ΔH?=22.8±0.9 kJ mol-1,and ΔS? = -90.2±3.1 J mol-1 K-1; kZnPd = 122.3±2.3 mol-1 dm3 s-1 (25 °C), ΔH? = 19.8±2.2 kJ mol-1, and ΔS? = -139±18 J mol-1 K-1 for zinc(II) and kCdf = (1.17±0.02)×105mol-1 dm3 s-1 (25 °C), ΔH? =42.5±1.3 kJ mol-1, and ΔS? = -5.3±4.2 J mol-1 K-1; kCdPd = (2.51±0.04)×107 mol-1 dm 3 S-1 (25 °C), ΔH? = 14.6±0.5 kJ mol-1, and ΔS? = -54.3±1.7 J mol-1 K-1 for cadmium(II). Nitrobenzyl group lowers the basicity of porphyrin. The effect of the lowered basicity appeared strongly in the following order for the formation rate and equilibrium constants of the metalloporphyrins: Cd2+ 2+ +. A hydrogen-bond formation between [ZnOH]+ and the pyrrole proton in NO2Bz(Htpps)4- is proposed for the reaction based on the larger rate constant than the water-exchange rate constant enhanced by the hydroxide ion bound to zinc(II), the small activation enthalpy, the negative activation entropy, and the dependence of porphyrin basicity.
- Tabata, Masaaki,Ishimi, Hiroaki
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p. 1353 - 1359
(2007/10/03)
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- Process for producing diol compounds
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A diol compound, for example, hexanediol, is produced with a high efficiency by esterifying a carboxylic acid mixture, collected from a reaction product mixture of a liquid phase oxidation of cyclohexane, with an esterifying agent and hydrogenate-decomposing the resultant esterification product mixture with hydrogen. The hydrogenate-decomposition is carried out by using a specific catalyst free from chromium and including a member selected from (A) copper and zinc-containing catalytic materials which are prepared by mixing an aqueous solution of water-soluble copper and zinc salts with an aqueous alkali metal or ammonium carbonate or alkali metal or ammonium hydrogen carbonate solution, reducing the resultant precipitate comprising a basic copper and zinc carbonate mixture with hydrogen and partially oxidizing the resultant reduction product with an oxygen-containing gas, and (B) copper and zinc-containing catalytic materials which are prepared by conducting the same mixing procedure as that for the catalytic material (A) except that the mixing is carried out at a temperature of 60° to 95° C. at a pH of 6.5 to 9.0, and by calcining the resultant precipitate at a temperature of 300° C. to 450° C.
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- Vicinal di(hetro) alkylene organometalates and processes for the production of amines therewith
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This invention relates to vicinal di(hetero)alkylene organometalate compounds comprising one or more metal oxides in association with an alkanolamine, an alkyleneamine, an alkylene glycol or mixtures thereof. This invention also relates to an alkyleneamines producers composition rich in triethylenetetramine (TETA), tetraethylenepentamine (TEPA) and pentaethylenehexamine (PEHA), and to processes for the preparation thereof using the vicinal di(hetero)alkylene organometalates.
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