Powder XRD (powder + xrd)

Distribution by Scientific Domains

Selected Abstracts

Characterization of pure and doped potassium hydrogen tartrate single crystals grown in silica gel

I. Quasim
Abstract Growth of pure-, sodium- and lithium- doped potassium hydrogen tartrate single crystals by gel technique is reported. Growth conditions conducive for the growth of single crystals are worked out. The crystals are characterized by using powder XRD, SEM, FTIR, AES, EDAX, CH analysis and thermoanalytical techniques. The stoichiometric composition for the grown crystals are established as KHC4H4O6.H2O, (K)0.98(Na)0.02.H2O and (K)0.94(Li)0.06HC4H4O6.H2O. Doping of sodium and lithium in the pure potassium hydrogen tartrate single crystals is found to influence the size, perfection, morphology, crystal structure and the thermal stability of crystals. ( 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Mu-35: A Fluorogallophosphate Obtained by In Situ Generation of the Template

Louwanda Lakiss
Abstract A two-dimensional microporous fluorogallophosphate, named Mu-35, closely related to ULM-8, was hydrothermally synthesized by in situ generation of the structure-directing agent. The precursor of the structure-directing agent is ethylformamide, which is generated in situ by decomposition, and goes on to form ethylamine molecules that act as templates in the medium used for the synthesis. The fluorogallophosphate Mu-35 (Mu is Mulhouse), Ga3(PO4)2(HPO4)F3(C2H8N)2(C2H7N)0.5 (Z = 8), crystallizes in the orthorhombic space group Pbcn with the following unit cell parameters: a = 22.117(1), b = 17.3740(8), c = 10.1550(4) . The structure of fluorogallophosphate Mu-35 was determined from single-crystal XRD data. It exhibits anionic layers composed of an unusual arrangement of three-, five-, and eight-membered rings (MR) [Ga2PO2F, Ga3P2O4F, and Ga3P3O8, respectively], and intercalated by protonated and nonprotonated ethylamine molecules. Mu-35 was also characterized by powder XRD, SEM, elemental and thermal analyses, and solid-state NMR spectroscopy (1H, 13C, 19F, and 31P MAS and 1H- 31P HETCOR experiments). ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

Hybrid Inorganic-Organic Materials Carrying Tertiary Amine and Thiourea Residues Tethered on Mesoporous Silica Nanoparticles: Synthesis, Characterization, and Co-Operative Catalysis

Alessandra Puglisi
Abstract Mesoporous silica nanoparticles carrying different loadings of tertiary amine and thiourea residues (residues ratios 53/47, 68/32, and 22/78, respectively) were synthesized by the co-condensation method and fully characterized by CP MAS NMR, powder XRD, SEM, BET, BJH and FT-IR techniques. These materials were tested as bifunctional catalysts in the conjugate addition of acetylacetone to 2-nitrostyrene, a reaction that under solvent-free conditions occurred in quantitative yield. By carrying out several experiments with the bifunctional catalysts featuring different molar ratios of active sites, and with different combinations of monofunctional supported and non-supported catalyst, the co-operativity of the tertiary amine and thiourea residues in catalyzing the reaction was demonstrated. The use of the bifunctional catalyst was extended to the addition of acetylacetone to an activated imine. Catalyst recycling for a total of three reaction cycles was demonstrated without significant erosion of activity. [source]

A mechanistic model for the water-gas shift reaction over noble metal substituted ceria

AICHE JOURNAL, Issue 5 2010
Parag A. Deshpande
Abstract The water-gas shift (WGS) reaction was carried out in the presence of Pd and Pt substituted nanocrystalline ceria catalysts synthesized by solution combustion technique. The catalysts were characterized by powder XRD and XPS. The noble metals were found to be present in ionic form substituted for the cerium atoms. The catalysts showed high activity for the WGS reaction with high conversions below 250C. The products of reaction were only carbon dioxide and hydrogen, and no hydrocarbons were observed even in trace quantities. The reactions were carried out with different amounts of noble metal ion substitution and 2% Pt substituted ceria was found to be the best catalyst. The various possible mechanisms for the reaction were proposed and tested for their consistency with experimental data. The dual site mechanism best described the kinetics of the reaction and the corresponding rate parameters were obtained. 2009 American Institute of Chemical Engineers AIChE J, 2010 [source]

Investigation of structure and dynamics in the sodium metallocenes CpNa and CpNaTHF via solid-state NMR, X-ray diffraction and computational modelling

Cory M. Widdifield
Abstract Solid-state 23Na NMR spectra of two organometallic complexes, cyclopentadienylsodium (CpNa) and the tetrahydrofuran (THF) solvate of CpNa (CpNaTHF), are presented. Analytical simulations of experimental spectra and calculated 23Na electric-field gradient (EFG) tensors confirm that both complexes are present in microcrystalline samples of CpNa recrystallized from THF. For the solvate, 23Na NMR experiments at 9.4 T and 11.7 T elucidate sodium chemical shielding (CS) tensor parameters, and establish that the EFG and CS tensor frames are non-coincident. Single-crystal X-ray diffraction (XRD) experiments are used to determine the crystal structure of CpNaTHF: Cmca (a = 9.3242(15) , b = 20.611(3) , c = 9.8236(14) , , = , = , = 90 , V = 1887.9(5)3, Z = 8). For CpNa, 23Na NMR data acquired at multiple field strengths establish sodium CS tensor parameters more precisely than in previous reports. Variable-temperature (VT) powder XRD (pXRD) experiments determine the temperature dependence of the CpNa unit cell parameters. The combination of 23Na quadrupolar NMR parameters, pXRD data and calculations of 23Na EFG tensors is used to examine various models of dynamic motion in the solid state. It is proposed that the sodium atom in CpNa undergoes an anisotropic, temperature-dependent, low frequency motion within the ab crystallographic plane, in contrast with previous models. Copyright 2007 John Wiley & Sons, Ltd. [source]

Characterisation of indomethacin and nifedipine using variable-temperature solid-state NMR

David C. Apperley
Abstract We have characterised the stable polymorphic forms of two drug molecules, indomethacin (1) and nifedipine (2) by 13C CPMAS NMR and the resonances have been assigned. The signal for the CCl carbon of indomethacin has been studied as a function of applied magnetic field, and the observed bandshapes have been simulated. Variable-temperature 1H relaxation measurements of static samples have revealed a T1, minimum for indomethacin at 17.8 C. The associated activation energy is 38 kJ mol,1. The relevant motion is probably an internal rotation and it is suggested that this involves the COCH3 group. Since the two drug compounds are potential candidates for formulation in the amorphous state, we have examined quench-cooled melts in detail by variable-temperature 13C and 1H NMR. There is a change in slope for and at the glass transition temperature (Tg) for indomethacin, but this occurs a few degrees below Tg for nifedipine, which is perhaps relevant to the lower real-time stability of the amorphous form for the latter compound. Comparison of relaxation time data for the crystalline and amorphous forms of each compound reveals a greater difference for nifedipine than for indomethacin, which again probably relates to real-time stabilities. Recrystallisation of the two drugs has been followed by proton bandshape measurements at higher temperatures. It is shown that, under the conditions of the experiments, recrystallisation of nifedipine can be detected already at 70 C, whereas this does not occur until 110 C for indomethacin. The effect of crushing the amorphous samples has been studied by 13C NMR; nifedipine recrystallises but indomethacin does not. The results were supported by DSC, powder XRD, FTIR and solution-state NMR measurements. Copyright 2005 John Wiley & Sons, Ltd. [source]

Real-time XRD Investigations During the Formation of Cu(IngGa)Se2 Thin Films

Frank Hergert
Abstract Knowledge of the solid-state reactions providing the synthesis of the absorber material Cu(IngGa)Se2 well below its melting point is an essential prerequisite for the further optimization of the technologically relevant production processes. Therefore, powder XRD has been applied as nondestructive tool to follow chemical solide-state reactions in-situ. Subsequent Rietveld refinement provides the quantitative phase evolution time. [source]

Synthetic, spectral as well as in vitro antimicrobial studies on some bismuth(III) bis(N,N -dialkyldithiocarbamato) alkylenedithiophosphates

H. P. S. Chauhan
Abstract Mixed sulfur donor ligand complexes of the type bismuth(III) bis(N,N -dialkyldithiocarbamato) alkylenedithiophosphate, [R2NCS2]2BiS2POGO [where R = CH3 and C2H5; G = -CH2 -C(C2H5)2 -CH2 -, -CH2 -C(CH3)2 -CH2 -, -CH(CH3)-CH(CH3)- and -C(CH3)2 -C(CH3)2 -] were synthesized in 1:1 molar ratio of bismuth(III) bis(N,N -dialkyldithiocarbamate) chloride and ammonium alkylenedithiophosphate in refluxing benzene and characterized by melting point, molecular weight determinations, elemental analysis (C, H, N, Bi and S) and spectral [UV, IR,NMR (1H,13C and 31P) and powder X ray diffraction] studies; all these studies were in good agreement with the synthesized complexes. These newly synthesized derivatives are yellow and brown colored solids and are soluble in common organic solvents like benzene, chloroform, dichloromethane and DMF. Based on the physicochemical and spectral studies, a tentative structure of these newly synthesized complexes was assigned and the average particle size of the synthesized complexes determined by powder XRD, showing that nano range polycrystalline particles were formed with a monoclinic crystal system. These complexes were also screened for their antimicrobial activities using the well diffusion method. The free ligands as well as their mixed metal complexes were tested in vitro against four bacterial strains: two Gram-positive, Staphylococcus aureus (ATCC 9144) (G+) and Bacillus subtilis (ATCC 6051), (G+) and two Gram-negative, Escherichia coli (ATCC 9637) (G,) and Pseudomonas aeruginosa (ATCC 25619) (G,) to assess their antimicrobial properties. The results were indeed positive and exhibited good antibacterial effects. Chloroamphenicol used as a standard for comparison and synthesized complexes showed good antibacterial effects over chloroamphenicol. On the basis of these studies, the synthesized complexes help to understand the different structural and biological properties of main group elements with sulfur donor ligands. Copyright 2010 John Wiley & Sons, Ltd. [source]

ChemInform Abstract: Topotactic Redox Chemistry of NaFeAs in Water and Air and Superconducting Behavior with Stoichiometry Change.

CHEMINFORM, Issue 37 2010
Iliya Todorov
Abstract The redox chemistry and transformations of NaFeAs in water and air are characterized by single crystal and powder XRD, magnetization measurements, TEM, and Moessbauer spectroscopy. [source]

ChemInform Abstract: Optical Properties of the Complex Perovskite Ceramic Oxide Ba2YZrO6-d.

CHEMINFORM, Issue 32 2010
V. R. Kumar
Abstract Nanocrystalline Ba2YZrO6-d is prepared by auto-ignition combustion of an aqueous HNO3 solution of Ba(NO3)2, Y2O3, ZrOCl2, citric acid, and NH4OH, and characterized by powder XRD, TEM, and UV/VIS spectroscopy. [source]

ChemInform Abstract: Structure and Physical Properties of the Layered Pnictide-Oxides: (SrF)2Ti2Pn2O (Pn: As, Sb) and (SmO)2Ti2Sb2O.

CHEMINFORM, Issue 32 2010
R. H. Liu
Abstract The title compounds are prepared by solid state reactions using SrPn (Pn: As, Sb), SrF2, Sm2O3, TiO2, and Ti as starting materials (1000,1150 C, 50 h) and characterized by powder XRD, resistivity, susceptibility, Hall coefficient, thermoelectric power, and heat capacity measurements. [source]