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Powder X-ray Diffraction (powder + x-ray_diffraction)
Terms modified by Powder X-ray Diffraction Selected AbstractsThe Structure of Yttrialite and Its Identification Using Laboratory and Synchrotron-Based Powder X-Ray DiffractionJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2009William J. Heward A highly crystalline sample of the impurity stabilized phase y -Y2Si2O7, generally known as yttrialite, has been formed from the melt of a glass with a nominal composition of 62(SiO2),10(Al2O3),28(Y2O3) mol%. Powder X-ray diffraction patterns were collected using in-house instrumentation and the 11-BM diffractometer at the Advanced Photon Source, Argonne National Laboratory, Argonne, IL. Rietveld refinements were carried out on the patterns using two structural models. On patterns collected using in-house instrumentation the correct structure assignment was difficult to determine; however, the extremely high-quality data afforded by the 11-BM instrument showed conclusively that the sample was found to crystallize in the monoclinic system (SG=P21/m) with lattice parameters a=5.03032(6), b=8.06892(6), c=7.33620(6) Å, and ,=108.673(1). Furthermore, simulations have shown that it is likely that this structure model can be used to describe natural yttrialite or yttrialite that is formed at low temperatures, though the possibility that such materials are paracrystalline is also discussed. [source] Variable-Temperature Powder X-ray Diffraction of Aromatic Carboxylic Acid and Carboxamide CocrystalsCHEMISTRY - AN ASIAN JOURNAL, Issue 4 2007L. Sreenivas Reddy Abstract The effect of temperature on the cocrystallization of benzoic acid (BA), pentafluorobenzoic acid (FBA), benzamide (BAm), and pentafluorobenzamide (FBAm) is examined in the solid state. BA and FBA formed a 1:1 complex 1 at ambient temperature by grinding with a mortar and pestle. Grinding FBA and BAm together resulted in partial conversion into the 1:1 adduct 2 at 28,°C and complete transformation into the product cocrystal at 78,°C. Further heating (80,100,°C) and then cooling to room temperature gave a different powder pattern from that of 2. BAm and FBAm hardly reacted at ambient temperature, but they afforded the 1:1 cocrystal 3 by melt cocrystallization at 110,115,°C. Both BA+FBAm (4) and BA+BAm (5) reacted to give new crystalline phases upon heating, but the structures of these products could not be determined owing to a lack of diffraction-quality single crystals. The stronger COOH and CONH2 hydrogen-bonding groups of FBA and FBAm yielded the equimolar cocrystal 6 at room temperature, and heating of these solids to 90,100,°C gave a new crystalline phase. The X-ray crystal structures of 1, 2, 3, and 6 are sustained by the acid,acid/amide,amide homosynthons or acid,amide heterosynthon, with additional stabilization from phenyl,perfluorophenyl stacking in 1 and 3. The temperature required for complete transformation into the cocrystal was monitored by in,situ variable-temperature powder X-ray diffraction (VT-PXRD), and formation of the cocrystal was confirmed by matching the experimental peak profile with the simulated diffraction pattern. The reactivity of H-bonding groups and the temperature for cocrystallization are in good agreement with the donor and acceptor strengths of the COOH and CONH2 groups. It was necessary to determine the exact temperature range for quantitative cocrystallization in each case because excessive heating caused undesirable phase transitions. [source] Study on the Photochromism of Ni,Al Layered Double Hydroxides Containing Nitrate AnionsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 14 2006Min Wei Abstract The photochromism of nitrate-containing nickel,aluminum layered double hydroxides (NiAl-NO3 -LDHs) has been studied. Powder X-ray diffraction (PXRD), FTIR, UV/Vis, XPS, ESR, EXAFS, and elemental analysis were used to investigate the structure, composition, and photochromic behavior of NiAl-NO3 -LDHs. A possible photochromic mechanism in NiAl-NO3 -LDHs has been proposed.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Phase Relations Between ,-Tricalcium Phosphate and Hydroxyapatite with Manganese(II): Structural and Spectroscopic PropertiesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 7 2006Isaac Mayer Abstract The preparation of Mn-containing ,-tricalcium phosphate (,-TCP) samples was achieved in two ways: a) transformation of precipitated Mn-containing calcium hydroxyapatite (HA) to ,-TCP by heating at 1100 °C, and b) preparation by solid-state reaction of a mixture of CaCO3, (NH4)2HPO4, and Mn(NO3)2 at 1100 °C. Powder X-ray diffraction (XRD) analyses of the samples, obtained by both methods, show well-defined patterns with structural data of the rhombohedral R3c, ,-TCP phase. The calculated lattice constants are smaller than those known for ,-Ca3(PO4)2 because of substitution of Ca2+ by Mn2+. EPR spectroscopy indeed reveals that manganese is divalent in the samples. Apparently, the Ca(5) site in the ,-TCP structure is occupied by Mn2+. The distribution of Mn2+ between the ,-TCP and the HA phase in the case of preparation (b) was studied by EPR spectroscopy, and a pronounced preference for the former lattice was found. Micron- and submicron-sized crystals with visible faces were observed by TEM in the case of ,-TCP prepared by solid-state reaction, and large micron-sized, droplike-shaped crystals, sensitive to beam radiation, were found in the case of samples prepared by heating HA at elevated temperatures. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Incorporation of a (Cyclopentadienyl)molybdenum Oxo Complex in MCM-41 and Its Use as a Catalyst for Olefin EpoxidationEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 24 2004Marta Abrantes Abstract The tricarbonyl complex [(,5 -C5H4 -COOMe)Mo(CO)3Cl] was prepared from the reaction of sodium (methoxycarbonyl)cyclopentadienide, (C5H4 -CO2Me)Na, with (Bu4N)[Mo(CO)5I]. Heating the ester with 3-(triethoxysilyl)propylamine gave the amide derivative {[,5 -C5H4 -CONH-C3H6Si(OEt)3]Mo(CO)3Cl}. The functionalised tricarbonyl complex was immobilised in the ordered mesoporous silica MCM-41 with a loading of 13 wt.-% Mo (1.4 mmol·g,1) by carrying out a grafting reaction in dichloromethane. Powder X-ray diffraction and nitrogen adsorption,desorption analysis indicated that the structural integrity of the support was preserved during the grafting and that the channels remained accessible, despite significant reductions in surface area, pore volume and pore size. The success of the coupling reaction was confirmed by 29Si and 13C (CP) MAS NMR spectroscopy. A supported dioxo complex of the type [(,5 -C5H4R)MoO2Cl] was subsequently prepared by oxidative decarbonylation of the tethered tricarbonyl complex using tert -butyl hydroperoxide (TBHP). The oxidised material is an active catalyst for the liquid phase epoxidation of cyclooctene with TBHP as the oxygen source. Similar catalytic results were obtained using the tethered tricarbonyl complex directly as a pre-catalyst since fast oxidative decarbonylation occurs under the reaction conditions used. For both systems, the desired epoxide was the only product and the initial activities were about 13 mol·molMo,1·h,1. The solid catalysts were recycled several times. Some activity was lost between the first and second runs but thereafter tended to stabilise. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Selective Zinc(II)-Ion Fluorescence Sensing by a Functionalized Mesoporous Material Covalently Grafted with a Fluorescent Chromophore and Consequent Biological ApplicationsADVANCED FUNCTIONAL MATERIALS, Issue 2 2009Krishanu Sarkar Abstract A highly ordered 2D-hexagonal mesoporous silica material is functionalized with 3-aminopropyltriethoxysilane. This organically modified mesoporous material is grafted with a dialdehyde fluorescent chromophore, 4-methyl-2,6-diformyl phenol. Powder X-ray diffraction, transmission electron microscopy, N2 sorption, Fourier transform infrared spectroscopy, and UV-visible absorption and emission have been employed to characterize the material. This material shows excellent selective Zn2+ sensing, which is due to the fluorophore moiety present at its surface. Fluorescence measurements reveal that the emission intensity of the Zn2+ -bound mesoporous material increases significantly upon addition of various concentrations of Zn2+, while the introduction of other biologically relevant (Ca2+, Mg2+, Na+, and K+) and environmentally hazardous transition-metal ions results in either unchanged or weakened intensity. The enhancement of fluorescence is attributed to the strong covalent binding of Zn2+, evident from the large binding constant value (0.87,×,104M,1). Thus, this functionalized mesoporous material grafted with the fluorescent chromophore could monitor or recognize Zn2+ from a mixture of ions that contains Zn2+ even in trace amounts and can be considered as a selective fluorescent probe. We have examined the application of this mesoporous zinc(II) sensor to cultured living cells (A375 human melanoma and human cervical cancer cell, HeLa) by fluorescence microscopy. [source] Structure and composition of CO2/H2 and CO2/H2/C3H8 hydrate in relation to simultaneous CO2 capture and H2 productionAICHE JOURNAL, Issue 6 2009Rajnish Kumar Gas hydrates from a (40/60 mol %) CO2/H2 mixture, and from a (38.2/59.2/2.6 mol %) CO2/H2/C3H8 mixture, were synthesized using ice powder. The gas uptake curves were determined from pressure drop measurements and samples were analyzed using spectroscopic techniques to identify the structure and determine the cage occupancies. Powder X-ray diffraction (PXRD) analysis at ,110°C was used to determine the crystal structure. From the PXRD measurement it was found that the CO2/H2 hydrate is structure I and shows a self-preservation behavior similar to that of CO2 hydrate. The ternary gas mixture was found to form pure structure II hydrate at 3.8 MPa. We have applied attenuated total reflection infrared spectroscopic analysis to measure the CO2 distribution over the large and small cavities. 1H MAS NMR and Raman were used to follow H2 enclathration in the small cages of structure I, as well as structure II hydrate. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Combustion synthesis and characterization of nano-crystalline LaFeO3 powderPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2009Hui Shen Abstract Nano-crystalline LaFeO3 was synthesized by a sol,gel auto-combustion method from a mixed aqueous solution of lanthanum and iron nitride, using citric acid as the fuel. Powder X-ray diffraction and TG/DTA analysis show that the LaFeO3 crystallites can be directly obtained by the sol,gel combustion process, without any other undesired phase. The results of SEM and TEM reveal that the as-burnt samples and powder calcined at 700 °C are agglomerated with particle size in the range of 25,50 nm and 60,80 nm, respecitvely. The M (T) and M (H) curves measurements show the existence of a weak ferromagnetism and the mainly anti-ferromagnetic ordering of the spins in the calcined sample. Compared with the powder calcined at 600 °C and 700 °C, the as-burnt LaFeO3 exhibits much stronger ferromagnetic behavior, with larger magnetization and smaller coercive field. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Electrical transport properties of aliovalent cation-doped CeO2ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2009Mark C. Pearce Abstract We report the comparative electrical properties of monovalent (Na+), divalent (Ca2+, Sr2+), trivalent (In3+, La3+) and coupled substitution of divalent and trivalent (Ca2+ + Sm3+) cation-doped CeO2. The investigated samples were prepared by solid-state reaction (ceramic) using the corresponding metal oxides and salts in the temperature range 1000,1600 °C in air. Powder X-ray diffraction (PXRD), laser particle size analysis (LPSA), scanning electron microscopy (SEM), and ac impedance spectroscopy measurements were employed for structural, morphology, and electrical characterization. PXRD studies reveal the formation of single-phase cubic fluorite-type structures for all investigated samples except those doped with In3+. The variation of lattice parameters is consistent with ionic radii (IR) of the dopant metal ions, with the exception of Na+ -doped CeO2. Our attempt to substitute In3+ for Ce4+ in CeO2 using both ceramic and wet chemical methods was unsuccessful. Furthermore, diffraction peaks attributed to CeO2 and In2O3 were observed up to sintering conditions of 1600 °C. Among the single-phase compounds investigated, Ce0.85Ca0.05Sm0.1O1.9 exhibits the highest bulk conductivity of 1.3 × 10,3 S/cm at 500 °C with activation energy of 0.64 eV in air. The electrical conductivity data obtained for Ce0.85Ca0.05Sm0.1O1.9 in air and Ar were found to be very similar over the investigated temperature range, indicating the absence of p-electronic conduction in the high oxygen partial pressure (pO2) range which is consistent with literature reported on Sm-doped CeO2. Copyright © 2008 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Growth of big single crystals of a new magnetic superconducting double perovskite Ba2PrRu1,xCuxO6CRYSTAL RESEARCH AND TECHNOLOGY, Issue 2 2006S. M. Rao Abstract Single crystals of Ba2PrRu1,xCuxO6 with x = 0 to 0.2, have been grown from high temperature solutions of a mixture of PbO-PbF2 in the temperature range 1100,1200 °C. Thin crystals with mostly a hexagonal and triangular plate like habit measuring up to 1,2 mm across and 0.1,0.2 mm thick were obtained. The size, quality and morphology of the crystals were improved by varying the solution volume as well as additives like B2O3. Large crystals measuring up to 3 mm across and 0.3 to 0.5 mm thick were obtained with 5,7 wt% solute concentration and 0.51 wt% of B2O3. The ZFC curves exhibit a spin glass like behavior with x = 0 and a superconducting transition at 8 to 11 K depending on x = 0.05 to 0.1. The transition was also influenced by the growth temperature and post growth annealing. Powder x-ray diffraction, EDS and Raman spectroscopic measurements confirm the presence of Cu in the crystals. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Transformation of a zinc inclusion complex to wurtzite ZnS microflowers under solvothermal conditionsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 9 2010Liwei Mi Abstract Wurtzite zinc sulfide (ZnS) microflowers were synthesized successfully by a convenient solvothermal route in ethylene glycol (EG) and ethylenediamine (EN) using thiourea and zinc inclusion complex as starting materials. The inclusion complex {[Zn(bipy)2(H2O)2](4-Cl-3-NH2 -C6H3SO3)2(bipy) (H2O)2}n was achieved by the reaction of zinc oxide (ZnO) and 4-Cl-3-NH2 -C6H3SO3 with the bridging ligand bipy under moderate conditions, in which bipy is 4,4,-bipyridine and 4-Cl-3-NH2C6H3SO3NH is 4-Chloro-3-aminobenzene sulfonic acid. The phase purity of bulk products was confirmed by powder X-ray diffraction and element analysis. The factors that might affect the purity of the ZnS product during the synthesis were discussed in detail. It was found that the products were significantly affected by the mixed solvents and the starting materials. X-ray single crystal diffraction, scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDS), and X-ray diffraction (XRD) were used to characterize the products. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Growth of tetrakis thiourea potassium iodide as new second order optical materialCRYSTAL RESEARCH AND TECHNOLOGY, Issue 4 2008J. Thomas Joseph Prakash Abstract A novel organometallic nonlinear optical (NLO) crystal, namely thiourea complex of tetrakis thiourea potassium iodide (TTPI), has been grown by slow evaporation solution growth technique. The harvested crystal is large in size. To our knowledge there is no report is available for the bulk size single crystal of TTPI. This material has a positive temperature coefficient and has been grown by slow evaporation solution growth technique. The grown crystal have been characterized by employing several techniques such as single crystal and powder X-ray diffraction, FTIR, UV-Vis-NIR spectra, thermo gravimetric analyses respectively. Etching studies have also been carried out in order to know the surface defects on the as grown specimen of TTPI. The relative second harmonic generation efficiency have been tested by using Nd:YAG laser as source. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] PSSS-controlled synthesis of CaCO3 superstructuresCRYSTAL RESEARCH AND TECHNOLOGY, Issue 9 2007Hua Tang Abstract Complex CaCO3 superstructure can be easily synthesized by using poly (sodium 4-styrenesulfonate) (PSSS) as a structure directing agent to direct the controlled precipitation of calcium carbonate from aqueous solution. The products were characterized by scanning electron microscopy (SEM), and powder X-ray diffraction (XRD) analysis. The results revealed that the morphology of the products changed significantly with the increasing of the concentration of PSSS in solution, from rhombohedral particles to plate-packed aggregates to spheres with smooth surface, to sponge-like spheres and finally to complex spherical superstructure consisted of plate-like sub-units. We hypothesize that the observed sequential changes in morphology of CaCO3 particles with added PSSS concentration may be due to the influence of PSSS on nucleation, growth and aggregation of CaCO3 crystals. The formation mechanisms of CaCO3 crystals with different morphologies were discussed. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Studies on the structural, thermal and optical behaviour of solution grown organic NLO material: 8-hydroxyquinolineCRYSTAL RESEARCH AND TECHNOLOGY, Issue 2 2007N. Vijayan Abstract Single crystal of 8-hydroxyquinoline (8HQ) having chemical formula C9H7NO, an organic nonlinear optical (NLO) material has been successfully grown by slow evaporation solution growth technique at room temperature. The crystal system has been confirmed from the powder X-ray diffraction (PXRD) analysis. The crystalline perfection was evaluated by high resolution X-ray diffractometry (HRXRD). From this analysis we found that the quality of the crystal is quite good. However, a very low angle (tilt angle 14 arc sec) boundary was observed which might be due to entrapping of solvent molecules in the crystal during growth. Its optical behavior has been examined by UV-Vis. analysis, which shows the absence of absorbance between the wavelengths ranging from 400 to 1200 nm. From the thermal analysis it was observed that the material exhibits single sharp weight loss starting at 113°C without any degradation. The laser damage threshold was measured at single shot mode and the SHG behavior has been tested using Nd:YAG laser as a source. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Controllable Synthesis of Shuttle-Shaped Ceria and Its Catalytic Properties for CO OxidationEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 26 2009Chunwen Sun Abstract Shuttle-shaped ceria was obtained in a high yield via a surfactant octadecylamine and urea assisted solvothermal process. The crystalline structure and morphology were characterized with powder X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscope (TEM). Preliminary catalytic measurement shows that the shuttle-shaped CeO2 exhibits an enhanced activity for CO oxidation, which may be attributed to its higher porosity and more oxygen vacancies.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Base-Induced Formation of Two Magnesium Metal-Organic Framework Compounds with a Bifunctional Tetratopic LigandEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 23 2008Pascal D. C. Dietzel Abstract Two coordination polymers constructed from magnesium and the tetratopic organic linker 2,5-dihydroxyterephthalic acid are reported, denominated CPO-26-Mg and CPO-27-Mg. The organic component carries two different types of protic functional groups. The degree of deprotonation of the organic component can be regulated by the amount of sodium hydroxide employed in the synthesis, thus determining which of the compounds forms. In CPO-26-Mg, only the carboxylic acid groups of the linker are deprotonated and take part in the construction of the three-dimensional framework. The structure is non-porous, and its topology is based on the PtS net. In CPO-27-Mg, both the carboxylic acid and the hydroxy groups are deprotonated and involved in the construction of a microporous three-dimensional framework which is based on a honeycomb motif containing large solvent-filled channels. The metal atoms are arranged in chiral chains along the intersection of the honeycomb and contain one water molecule in their coordination sphere, which allows for the creation of coordinatively unsaturated metal sites upon dehydration. CPO-27-Mg is a potentially useful lightweight adsorbent with a pore volume of 60,% of the total volume of the structure and an apparent Langmuir surface area of up to 1030 m2,g,1. Its thermal stability was investigated by thermogravimetry and variable-temperature powder X-ray diffraction, which shows framework degradation to commence at 160 °C in air, at 235 °C under nitrogen, and at 430 °C in a dynamic vacuum. Thermogravimetric dehydration and re-hydration experiments at miscellaneous temperatures indicate that it is possible to obtain open metal sites in CPO-27-Mg, but the water is more tightly bound in this material than in the previously reported isostructural nickel compound.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Order-Disorder Phase Transition in Type-I Clathrate Cs8Sn44,2,EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 26 2007Andreas Kaltzoglou Abstract The clathrate compound ,-Cs8Sn44,2 has been synthesized from its elements under inert gas conditions and has been characterized by single-crystal and powder X-ray diffraction. At room temperature, it crystallizes with cubic symmetry [a = 24.256(3) Å, space group Iad, Z = 8] and adopts a 2,×,2,×,2 superstructure of the type-I clathrate and a high ordering of the vacancies (,) in the Sn framework. Single crystals of ,-Cs8Sn44,2 reversibly transform at 90 °C to the high-temperature , form with primitive symmetry [a = 12.135(1) Å, space group Pmn, Z = 1] and a lower ordering of the defects. Differential thermal analysis corroborates the reversible character of the phase transition, which occurs with an enthalpy change of approximately 0.38 J,g,1. An atom-migration mechanism describing the order-disorder transition involving spiro-connected six-membered rings only (scsr mechanism) is proposed. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Pyridine Carboxylate Complexes of MoII as Active Catalysts in Homogeneous and Heterogeneous PolymerizationEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 18 2007Maria Vasconcellos-Dias Abstract New lamellar materials intercalated with molybdenum(II) complexes with potential catalytic properties were prepared by a stepwise procedure. The lamellar material was first calcined at 823 K for four hours to eliminate all the carbonate ions; the layered structure was reconstructed after treatment with a solution of either pycH (pyridine-2-carboxylic acid) or pydcH2 (pyridine-2,6-dicarboxylic acid) in a KOH solution of dmf at 343 K. Impregnation with a solution of the organometallic precursor [Mo(CO)3I2(NCCH3)2] led to substitution of the nitrile groups by two pyridine ligands. All the materials were characterized by powder X-ray diffraction, FTIR, and 13C CP MAS and 27Al MAS solid-state NMR spectroscopy. Similar MoII complexes were also prepared by using pycH or pydcH2 and characterized by elemental analysis as well as FTIR and 1H and 13C solution NMR spectroscopy. These new materials and the complexes of pyc or pydc ligands containing 4.54 wt.-% and 6.33 wt.-% of Mo respectively, catalyze the ring-opening-metathesis polymerization of norbornene and the polymerization of styrene at 333 K, their performance increasing upon the addition of methylalumoxane (MAO) as cocatalyst.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Comparative Sol,Hydro(Solvo)thermal Synthesis of TiO2 NanocrystalsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2006Xianfeng Yang Abstract Three small inorganic compounds [acetic acid (CH3COOH), nitric acid (HNO3), and hydrochloric acid (HCl)] andfive small organic compounds [n -butyl alcohol (CH3CH2CH2CH2OH), 1,2-propanediol (CH2OHCHOHCH3), propane-1,3-dicarboxylic acid (HOOCCH2COOH), butane-1,4-dicarboxylic acid (HOOCCH2CH2COOH), and ethylenediamine (H2NCH2CH2NH2)] with different donors (Cl,, NO3,, OH, COO,, and NH2) are used respectively and comparatively in different reaction media for tailoring the sol,hydrothermal synthesis of TiO2 nanocrystals at a specific reaction temperature and/or for different reaction times. Both anatase and rutile with a variety of nanostructures such as nanocubes, nanorods, nanoneedles, and their self-assembled nanospheres are selectively grown. Well-defined and crystalline anatase nanocrystals with a narrow size distribution are prepared in the presence of n -butyl alcohol. With the use of HCl, nanoneedles and their assembled nanospheres of phase-pure rutile are obtained under much less drastic conditions, even at 100 °C and for only two hours. The effects of the reaction media, synthesis temperatures, and aging times on the structures and shapes of the products are investigated in detail by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Structural Studies of ,-Cyclodextrin and Permethylated ,-Cyclodextrin Inclusion Compounds of Cyclopentadienyl Metal Carbonyl ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 8 2006Susana S. Braga Abstract [CpM(CO)nCl] complexes with M = Fe (n = 2) and Mo (n = 3) have been immobilised in plain ,-cyclodextrin (,-CD) and permethylated ,-CD (TRIMEB) by methods tailored according to the stabilities and solubilities of the individual components. Four adducts were obtained with a 1:1 host/guest stoichiometry. The compounds were studied by powder X-ray diffraction (XRD), thermogravimetric analysis (TGA), 13C{1H} CP/MAS NMR and FTIR spectroscopy. A comparison of the experimental powder XRD data for the TRIMEB/[CpMo(CO)3Cl] inclusion compound with reference patterns revealed that the crystal packing is very similar to that reported previously for a TRIMEB/ethyl laurate inclusion compound. The unit-cell parameters refined to a = 14.731, b = 22.476, c = 27.714 Å (volume = 9176.3 Å3), and the space group was confirmed as P212121. A hypothetical structural model of the inclusion compound was subsequently obtained by global optimisation using simulated annealing. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Luminescent Polyoxotungstoeuropate Anion-Pillared Layered Double HydroxidesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 4 2006Filipa L. Sousa Abstract Novel luminescent polyoxometalate anion-pillared layered double hydroxides (LDHs) were prepared by aqueous ion exchange of a Zn,Al LDH precursor in nitrate form with the europium-containing polyoxotungstate anions [EuW10O36]9,, [Eu(BW11O39)(H2O)3]6, and [Eu(PW11O39)2]11,. The host,guest interaction has a strong influence on the nature of the final intercalated species, as evidenced by elemental analysis, powder X-ray diffraction (XRD), infra-red (IR) and Raman spectroscopy, solid state magic-angle spinning (MAS) 11B and 31P NMR spectroscopy, and photoluminescence spectroscopy. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Restoration of Conductivity with TTF-TCNQ Charge-Transfer SaltsADVANCED FUNCTIONAL MATERIALS, Issue 11 2010Susan A. Odom Abstract The formation of the conductive TTF-TCNQ (tetrathiafulvalene,tetracyanoquinodimethane) charge-transfer salt via rupture of microencapsulated solutions of its individual components is reported. Solutions of TTF and TCNQ in various solvents are separately incorporated into poly(urea-formaldehyde) core,shell microcapsules. Rupture of a mixture of TTF-containing microcapsules and TCNQ-containing microcapsules results in the formation of the crystalline salt, as verified by FTIR spectroscopy and powder X-ray diffraction. Preliminary measurements demonstrate the partial restoration of conductivity of severed gold electrodes in the presence of TTF-TCNQ derived in situ. This is the first microcapsule system for the restoration of conductivity in mechanically damaged electronic devices in which the repairing agent is not conductive until its release. [source] Synthesis and Lithium Storage Properties of Co3O4 Nanosheet-Assembled Multishelled Hollow SpheresADVANCED FUNCTIONAL MATERIALS, Issue 10 2010Xi Wang Abstract Single-, double-, and triple-shelled hollow spheres assembled by Co3O4 nanosheets are successfully synthesized through a novel method. The possible formation mechanism of these novel structures was investigated using powder X-ray diffraction, scanning and transmission electron microscopies, Fourier transform IR, X-ray photoelectron spectroscopy, and thermogravimetric analysis. Both poly(vinylpyrrolidone) (PVP) soft templates and the formation of cobalt glycolate play key roles in the formation of these novel multishelled hollow structures. When tested as the anode material in lithium-ion batteries (LIBs), these multishelled microspheres exhibit excellent cycling performance, good rate capacity, and enhanced lithium storage capacity. This superior cyclic stability and capacity result from the synergetic effect of small diffusion lengths in the nanosheet building blocks and sufficient void space to buffer the volume expansion. This facile strategy may be extended to synthesize other transition metal oxide materials with hollow multishelled micro-/nanostrucutures, which may find application in sensors and catalysts due to their unique structural features. [source] Topotactic Conversion Route to Mesoporous Quasi-Single-Crystalline Co3O4 Nanobelts with Optimizable Electrochemical PerformanceADVANCED FUNCTIONAL MATERIALS, Issue 4 2010Li Tian Abstract The growth of mesoporous quasi-single-crystalline Co3O4 nanobelts by topotactic chemical transformation from , -Co(OH)2 nanobelts is realized. During the topotactic transformation process, the primary , -Co(OH)2 nanobelt frameworks can be preserved. The phases, crystal structures, morphologies, and growth behavior of both the precursory and resultant products are characterized by powder X-ray diffraction (XRD), electron microscopy,scanning electron (SEM) and transmission electron (TEM) microscopy, and selected area electron diffraction (SAED). Detailed investigation of the formation mechanism of the porous Co3O4 nanobelts indicates topotactic nucleation and oriented growth of textured spinel Co3O4 nanowalls (nanoparticles) inside the nanobelts. Co3O4 nanocrystals prefer [0001] epitaxial growth direction of hexagonal , -Co(OH)2 nanobelts due to the structural matching of [0001] , -Co(OH)2//[111] Co3O4. The surface-areas and pore sizes of the spinel Co3O4 products can be tuned through heat treatment of , -Co(OH)2 precursors at different temperatures. The galvanostatic cycling measurement of the Co3O4 products indicates that their charge,discharge performance can be optimized. In the voltage range of 0.0,3.0,V versus Li+/Li at 40,mA g,1, reversible capacities of a sample consisting of mesoporous quasi-single-crystalline Co3O4 nanobelts can reach up to 1400,mA h g,1, much larger than the theoretical capacity of bulk Co3O4 (892,mA h g,1). [source] Enhanced Optical Properties and Opaline Self-Assembly of PPV Encapsulated in Mesoporous Silica SpheresADVANCED FUNCTIONAL MATERIALS, Issue 23 2009Timothy L. Kelly Abstract A new poly(p -phenylenevinylene) (PPV) composite material has been developed by the incorporation of insoluble PPV polymer chains in the pores of monodisperse mesoporous silica spheres through an ion-exchange and in situ polymerization method. The polymer distribution within the resultant colloidal particles is characterized by electron microscopy, energy dispersive X-ray microanalysis, powder X-ray diffraction, and nitrogen adsorption. It was found that the polymer was selectively incorporated into the mesopores of the silica host and was well distributed throughout the body of the particles. This confinement of the polymer influences the optical properties of the composite; these were examined by UV,vis and fluorescence spectroscopy and time-correlated single-photon counting. The results show a material that exhibits an extremely high fluorescence quantum yield (approaching 85%), and an improved resistance to oxidative photobleaching compared to PPV. These enhanced optical properties are further complemented by the overall processability of the colloidal material. In marked contrast to the insolubility of PPV, the material can be processed as a stable colloidal dispersion, and the individual composite spheres can be self-assembled into opaline films using the vertical deposition method. The bandgap of the opal can be engineered to overlap with the emission band of the polymer, which has significant ramifications for lasing. [source] Evaluation of RuxWySez Catalyst as a Cathode Electrode in a Polymer Electrolyte Membrane Fuel CellFUEL CELLS, Issue 1 2010K. Suárez-Alcántara Abstract The oxygen reduction reaction (ORR) on RuxWySez is of great importance in the development of a novel cathode electrode in a polymer electrolyte membrane fuel cell (PEMFC) technology. The RuxWySez electrocatalyst was synthesised in an organic solvent for 3,h. The powder was characterised by transmission electron microscopy (TEM), and powder X-ray diffraction (XRD). The electrocatalyst consisted of agglomerates of nanometric size (,50,150,nm) particles. In the electrochemical studies, rotating disc electrode (RDE) and rotating ring-disc electrode (RRDE) techniques were used to determine the oxygen reduction kinetics in 0.5,M H2SO4. The kinetic studies include the determination of Tafel slope (112,mV,dec,1), exchange current density at 25,°C (1.48,×,10,4,mA,cm,2) and the apparent activation energy of the oxygen reaction (52.1,,,0.4,kJ,mol,1). Analysis of the data shows a multi-electron charge transfer process to water formation, with 2% H2O2 production. A single PEMFC with the RuxWySez cathode catalysts generated a power density of 180,mW,cm,2. Performance achieved with a loading of 1.4,mg,cm,2 of a 40,wt% RuxWySez and 60,wt% carbon Vulcan (i.e. 0.56,mg,cm,2 of pure RuxWySez). Single PEMFC working was obtained with hydrogen and oxygen at 80,°C with 30,psi. [source] Synthesis, Structure and Electrical Properties of Mo-doped CeO2,Materials for SOFCsFUEL CELLS, Issue 5 2009Q. Li Abstract In this paper, we report the synthesis, structure and electrical conductivity of Mo-doped compounds with a nominal chemical formula of Ce1,xMoxO2+, (x,=,0.05, 0.07, 0.1) (CMO). The formation of fluorite-like structure with a small amount of Ce8Mo12O49 impurity (JCPDS Card No. 31-0330) was confirmed using a powder X-ray diffraction (PXRD). The fluoride-type structure was retained under wet H2 and CH4 atmospheres at 700 and 800,°C, while diffraction peaks due to metal Mo were observed in dry H2 under the same condition. AC impedance measurements showed that the total conductivity increases with increasing Mo content in CMO, and among the investigated samples, Ce0.9Mo0.1O2+, exhibited the highest electrical conductivity with a value of 2.8,×,10,4 and 5.08,×,10,2 S cm,1 at 550,°C in air and wet H2, respectively. The electrical conductivity was found to be nearly the same, especially at high temperatures, in air, O2 and N2. Chemical compatibility of Ce0.9Mo0.1O2+, with 10,mol-% Y2O3 stabilised ZrO2 (YSZ) and Ce0.9Gd0.1O1.95 (CGO) oxide ion electrolytes in wet H2 was evaluated at 800,1,000,°C, using PXRD and EDX analyses. PXRD showed that CMO was found to react with YSZ electrolyte at 1,000,°C. The area specific polarisation resistance (ASPR) of Ce0.9Mo0.1O2+, on YSZ was found to be 8.58,ohm,cm2 at 800,°C in wet H2. [source] Silicon-Doped LiFePO4 Single Crystals: Growth, Conductivity Behavior, and DiffusivityADVANCED FUNCTIONAL MATERIALS, Issue 11 2009Ruhul Amin Abstract Single crystals of silicon doped LiFePO4 with a silicon content of 1% are grown successfully by the floating zone technique and characterized by single-crystal and powder X-ray diffraction, secondary ion mass spectroscopy, and chemical analysis. Electron paramagnetic resonance demonstrates the presence of only Fe2+; no traces of Fe3+ are found. Impedance spectroscopy as well as step-function polarization/depolarization (DC) measurements are carried out using the cells Ti/LiFe(Si)PO4/Ti and LiAl/LiI/LiFe(Si)PO4/LiI/LiAl. The electronic and ionic conductivities as well as the Li-diffusivity of the sample in the major crystallographic directions ([h00], [0k0], and [00l]) are determined. Within experimental error the transport properties along the b- and c-axes are found to be the same but differ significantly from the a-axis, which exhibits lower values. Compared to undoped LiFePO4, Si-doping leads to an increase of the ionic conductivity while the electronic conductivity decreases, which is in agreement with a donor effect. The activation energies of conductivities and diffusivities are interpreted in terms of defect chemistry and relevant Brouwer diagrams are given. [source] One-Dimensional Microwires Formed by the Co-Assembly of Complementary Aromatic Donors and AcceptorsADVANCED FUNCTIONAL MATERIALS, Issue 11 2009Jie-Yu Wang Abstract A truxene derivative (Tr3) with a C3 symmetric conjugated plane is synthesized; this derivative is a perfect match, in both size and structure, with its oxidized counterpart, the truxenone derivative (TrO3), a new electron acceptor that was recently reported. The complementary pair, Tr3 and TrO3, sets a good platform for the investigation of aromatic donor,acceptor interactions. Detailed 1H NMR experiments, photoluminescence spectroscopy, as well as differential scanning calorimetry are performed to investigate the interaction between Tr3 and TrO3, from solution to mesophase. One-dimensional microbelts readily formed from a 1:1 mixture of Tr3 and TrO3. Scanning electron microscopy, powder X-ray diffraction, as well as fluorescence microscopy are performed to elucidate their co-assembly structure in the solid state. Moreover, modulation of the co-assembly structure is easily realized by changing the concentration or mixing ratio. The present system opens the possibility of forming 1D heterostructures via electron donor,acceptor interaction, and its potential application as P,N junction and photowaveguide materials in optoelectronic devices. [source] Synthesis, Mechanism, and Gas-Sensing Application of Surfactant Tailored Tungsten Oxide NanostructuresADVANCED FUNCTIONAL MATERIALS, Issue 11 2009Suman Pokhrel Abstract Widely applicable nonaqueous solution routes have been employed for the syntheses of crystalline nanostructured tungsten oxide particles from a tungsten hexachloride precursor. Here, a systematic study on the crystallization and assembly behavior of tungsten oxide products made by using the bioligand deferoxamine mesylate (DFOM) (product I), the two chelating ligands hexadecyltrimethylammoniumbromide (CTAB) (II) and poly(alkylene oxide) block copolymer (Pluronic P123) (III) is presented. The mechanistic pathways for the material synthesis are also discussed in detail. The tungsten oxide nanomaterials and reaction solutions are characterized by Fourier transform IR, 1H, and 13C NMR spectroscopies, powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, and selected-area electron diffraction. The indexing of the line pattern suggests WO3 is in its monoclinic structure with a,=,0.7297,nm, b,=,0.7539,nm, c,=,0.7688,nm, and ,-i;,=,90.91,°. The nanoparticles formed have various architectures, such as chromosomal shapes (product I) and slates (II), which are quite different from the mesoporous one (III) that has internal pores or mesopores ranging from 5 to 15,nm. The nanoparticles obtained from all the synthetic procedures are in the range of 40,60,nm. The investigation of the gas-sensing properties of these materials indicate that all the sensors have good baseline stability and the sensors fabricated from material III present very different response kinetics and different CO detection properties. The possibility of adjusting the morphology and by that tuning the gas-sensing properties makes the preparation strategies used interesting candidates for fabricating gas-sensing materials. [source] | |||||||||||||||||||||||||||||||||||||