Search results for "Powder diffraction"
showing 10 items of 243 documents
Electronic Properties of Mixed-Valence Manganates: The Role of Mn Substitutional Defects
2002
Single-phase perovskites in the solid solution series La0.7+yA0.3-yMn1-xMxO3 (with 0.00 ≤ x ≤ 0.10; A = Sr2+, M = Cu2+, Zn2+, Sc3+, Cr3+, Co3+, and Ga3+; A = Ba2+, M = Cu2+, Zn2+, and Sc3+) have been prepared via the acetic acid solutions freeze-drying method. This soft procedure makes possible strict stoichiometric control, and the synthetic variables allow one to maintain a constant proportion of Mn4+ (ca. 32%) in the 47 compounds prepared. In this way, the concentration of cationic vacancies at A and B sites is practically negligible in all cases. X-ray powder diffraction patterns corresponding to the 47 compounds have been completely indexed with rhombohedral perovskite cells. The cryst…
Crystallized nano-sized alpha-tricalcium phosphate from amorphous calcium phosphate: microstructure, cementation and cell response
2015
New insight on the conversion of amorphous calcium phosphate (ACP) to nano-sized alpha tricalcium phosphate (α-TCP) provides a faster pathway to calcium phosphate bone cements. In this work, synthesized ACP powders were treated with either water or ethanol, dried, crystallized between 700 and 800 °C, and then cooled at different cooling rates. Particle size was measured in a scanning electron microscope, but crystallite size calculated by Rietveld analysis. Phase composition and bonding in the crystallized powder was assessed by x-ray diffraction and Fourier-transform infrared spectroscopy. Results showed that 50 nm sized α-TCP formed after crystallization of lyophilized powders. Water trea…
Does phosphorus affect the industrial Portland cement reactivity?
2018
Abstract The effect of phosphorous on the mineralogy and reactivity of Portland cement has been investigated through an industrial clinkers series. The samples were collected from the same Tunisian cement plant and classified according to the content of P2O5 from 0.5% to 1.1%. All samples were manufactured at the same thermal and cooling conditions as well as possible. The specimens were characterized by X-ray fluorescence spectrometry and optical microscopy techniques and their mineralogy was determined by X-ray powder diffraction coupled to the Rietveld analysis. The cements reactivity prepared from the clinkers was followed by means of isothermalcalorimetry. The compressive strength of t…
Structural characterization of iron oxide/hydroxide nanoparticles in nine different parenteral drugs for the treatment of iron deficiency anaemia by …
2013
Drug products containing iron oxide and hydroxide nanoparticles (INPs) are important for the treatment of iron deficiency anaemia. Pharmaceuticals prepared by the complexation of different kinds of INPs and carbohydrates have different physicochemical and biopharmaceutic characteristics. The increasing number of parenteral non-biological complex drugs (NBCD) containing iron requires physicochemical methods for characterization and enabling of cross comparisons. In this context the structure and the level of crystallinity of the iron phases may be connected to the in vitro and in vivo dissolution rates, which etiologically determine the therapeutic and toxic effects. X-ray powder diffraction…
Microphase separation upon crystallization of small amphiphilic molecules: ‘low’ temperature form II of sodium benzoate (E 211)
2016
A so far unknown low temperature polymorph (form II crystallized at 350 °C) of the common food preservative sodium benzoate (NaBz; E 211) could be crystallized by annealing (7 days) of the poorly crystalline technical material. Its crystal structure was solved by indexing a tiny single crystal by electron diffraction followed by structure solution and refinement applying powder X-ray diffraction (PXRD). The new polymorph shows many structural similarities to form I (crystallized at 420 °C). Both form I and II are the result of a microphase separation: the structures consist of pseudo-hexagonal packings of rod-shaped micelles where the core consists of sodium cations being coordinated by the…
Studies of structures and properties of polymeric systems containing bis-(hydroxy-arylidene)alkanones as NLO-active chromophores
2002
Abstract NLO-properties of polymer systems containing bis-(hydroxy-arylidene)alkanone chromophores were studied experimentally and analyzed using ab initio quantum chemical calculations. A monoclinic crystal structure (space group P2111) of the polyester containing fragments of such chromophores in the backbone was simulated and a reasonable agreement between the experimental and simulated X-ray powder diffraction patterns was achieved. Ab initio quantum-mechanical estimations of the SHG-observable macroscopic second-order non-linearity tensor coefficients, obtained for the polymer crystal structure at the HF SCF level, led to the major dXZZ-coefficient of 1.9 pm/V. Films of ionic complexes…
Spark Plasma Sintering (SPS)-Assisted Synthesis and Thermoelectric Characterization of Magnéli Phase V6O11
2018
The Magneli phase V6O11 was synthesized in gram amounts from a powder mixture of V6O11/V7O13 and vanadium metal, using the spark plasma sintering (SPS) technique. Its structure was determined with synchrotron X-ray powder diffraction data from a phase-pure sample synthesized by conventional solid-state synthesis. A special feature of Magneli-type oxides is a combination of crystallographic shear and intrinsic disorder that leads to relatively low lattice thermal conductivities. SPS prepared V6O11 has a relatively low thermal conductivity of κ = 2.72 ± 0.06 W (m K)-1 while being a n-type conductor with an electrical conductivity of σ = 0.039 ± 0.005 (μΩ m)-1, a Seebeck coefficient of α = -(3…
Ionic conductivity in monophasic Ag2xNa2(1 − x)ZnSiO4 materials with 0 ≤ x ≤ 1
1996
Abstract Solid solution samples Ag 2 x Na 2(1 − x ) ZnSiO 4 with 0 ≤ x ≤ 1 have been prepared by heat treating powder mixtures of Na 2 ZnSiO 4 and Ag 2 ZnSiO 4 at 300 °C and characterised by X-ray powder diffraction. The ionic conductivity of the solid solution has been determined as a function of composition and temperature by means of impedance measurements. The ionic conductivity of the mixed-mobile ion compositions (0 ≤ x ≤ 1) shows no substantial deviation from the mutually similar conductivities of the end compositions Na 2 ZnSiO 4 and Ag 2 ZnSiO 4 , and neither activation energy nor conductivity pre-factor varies significantly with composition. The results indicate that the mixed-alk…
Crystal structures of R2Pd2Pb (R = Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, and Lu) compounds
2004
Abstract The crystal structures of the R2Pd2Pb (R=Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, and Lu) compounds were determined using X-ray powder diffraction. The investigated compounds crystallize with Mo2FeB2 structure type (space group P4/mbm, Pearson code tP10). The importance of stabilization by polar intermetallic R–Pd bonding is underscored by a bonding analysis derived from electronic band structure calculations.
Crystal structures and thermal behavior of bis[dibenzyldimethylammonium]CuBr4, bis[dibenzyldimethylammonium]CuCl4 and bis[dimethyldi(2-phenylethyl)am…
2006
Abstract Bis[dibenzyldimethylammonium]CuBr4, bis[dibenzyldimethylammonium]CuCl4 and bis[dimethyldi(2-phenylethyl)ammonium]CuBr4 were crystallized from acetonitrile and/or dilute HX solutions. Five different kinds of single crystals were obtained. In the case of bis[dibenzyldimethylammonium]CuX4 (X=Br or Cl), the acetonitrile molecules cocrystallized into the crystal structure when acetonitrile solution was used. As a result, the isomorphic structures of Bis[dibenzyldimethylammonium]CuX4·0.5 CH3CN (X=Br or Cl) in monoclinic space group P21/n were obtained. When a dilute HX solution was used, the bis[dibenzyldimethylammonium]CuX4 (X=Br or Cl) crystallized without solvent molecules. The formed…