Furthering the understanding of silicate-substitution in α-tricalcium phosphate : an X-ray diffraction, X-ray fluorescence and solid-state nuclear magnetic resonance study

High-purity (SupT) and reagent-grade (ST), stoichiometric and silicate-containing α-tricalcium phosphate (α-TCP: ST0/SupT0 and Si-TCP x = 0.10: ST10/SupT10) were prepared by solid-state reaction based on the substitution mechanism Ca3(PO4)(2-x)(SiO4)x. Samples were determined to be phase pure by X-ray diffraction (XRD), and Rietveld analysis performed on the XRD data confirmed inclusion of Si in the α-TCP structure as determined by increases in unit cell parameters; particularly marked increases in the b-axis and β-angle were observed. X-ray fluorescence (XRF) confirmed the presence of expected levels of Si in Si-TCP compositions as well as significant levels of impurities (Mg, Al and Fe) present in all ST samples; SupT samples showed both expected levels of Si and a high degree of purity. Phosphorus (31P) magic-angle-spinning solid-state nuclear magnetic resonance (MAS NMR) measurements revealed that the high-purity reagents used in the synthesis of SupT0 can resolve the 12 expected peaks in the 31P spectrum of α-TCP compared to the low-purity ST0 that showed significant spectral line broadening; line broadening was also observed with the inclusion of Si which is indicative of induced structural disorder. Silicon (29Si) MAS NMR was also performed on both Si-TCP samples which revealed Q0 species of Si with additional Si Q1/Q2 species that may indicate a potential charge-balancing mechanism involving the inclusion of disilicate groups; additional Q4 Si species were also observed, but only for ST10. Heating and cooling rates were briefly investigated by 31P MAS NMR which showed no significant line broadening other than that associated with the emergence of β-TCP which was only realised with the reagent-grade sample ST0. This study provides an insight into the structural effects of Si-substitution in α-TCP and could provide a basis for understanding how substitution affects the physicochemical properties of the material

Synthesis And Crystal Structure Of 2,4-dihydro-4-[(5-hydroxy-3-methyl-1-phenyl-1h-pyrazol-4-yl)imino]-5-met Hyl-2-phenyl-3h-pyrazol-3-one And Its Copper(ii) Complex

2-Diazo-3-methyl-1-phenyl-5-pyrazolone (2) and 2,4-dihydro-4-[(5-hydroxy-3-methyl-1-phenyl-1H-pyrazol-4-yl)imino]-5-met hyl-2-phenyl-3H-pyrazol-3-one (3) were obtained in a one-pot reaction from 3-methyl-1-phenylpyrazol-5-one (1), mesyl azide, and K2CO3 in MeOH or CH2Cl2 solution. NMR, IR and ESI mass spectra as well as the crystal structure are reported for red colored 3. The crystal structure determined at 150 K reveals that the corresponding bonds in the two phenylpyrazol-5-one moieties in each of the two independent "U" shaped molecules have essentially the same lengths, with an extensive delocalization in the central O-C-C-N-C-C-O fragment of the molecule. In particular, the hydrogen atom, formally a part of a hydroxyl group, is found near-midway [O1-HY and O11-HY = 1.24(4) and 1.19(4) Å, in molecule 1, and O21-HX and O31-HY = 1.203(4) and 1.19(4) Å, in molecule 2] between the two oxygen atoms (formally in a carbonyl and a hydroxy group), with near linear O-H-O bond angles of 173.8(4)° and 172.7(4)° in the two independent molecules. All C-O bond lengths are in the narrow range of 1.271(3)-1.288(3) Å. Further, since this compound shows different coordinating groups, its binding ability towards copper(II) ions was investigated. A dark red complex 4, obtained by reaction of 3 with copper(II) ions at stoichiometric ratio, was characterized as a neutral 1:1 species, [3:CuCl2], involving tautomeric forms, by ESI-MS, ESI-MS/MS, IR, UV/Vis and EPR spectra. Interestingly, copper coordination to ligand 3 occurs solely by oxygen atoms, in spite of the presence of nitrogen donor centers. 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The Effects of Sb Substitution on Structural Properties in YBa2Cu3O7 Superconductors

In this study, the effects of partial Sb 3+ ion substitutions for the Y sites and the Cu sites on the superconducting properties of YBa 2Cu 3O y (Y123) ceramic superconductors were investigated. The samples were prepared by the conventional solid-state reaction method and the properties of the samples were investigated by means of X-ray diffraction, AC magnetic susceptibility measurements, scanning electron microscope, and energy dispersive X-ray analysis. The critical temperatures were determined to be in the range of 80-92 K for both Systems I and II. It was found that Sb-addition leads to the formation of the non-superconducting YBa 2SbO 6 phase, which has a negative effect on the critical temperature, since the highest critical temperature was measured for pure Y123. However, the increasing substitution level has a negligible effect on the X-ray diffraction analysis peak intensities of the superconducting phases. In addition, SEM images showed that Sb substitution decreases the grain size and modifies the microstructure development, which makes the samples denser