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Powder X-ray Diffractometry (powder + x-ray_diffractometry)
Selected AbstractsLow-Temperature Synthesis of Fully Crystallized Spherical BaTiO3 Particles by the Gel,Sol MethodJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2004Un-Yeon Hwang The synthesis of spherical BaTiO3 particles was attempted by a new technique, the "gel,sol method," at 45°C. The (Ba,Ti) gel used as a starting material was prepared by aging mixtures of titanyl acylate with a barium acetate aqueous solution ([glacial acetic acid (AcOH)]/[titanium isopropoxide (TIP)] = 4, [barium acetate]/[TIP] = 1) at 45°C for 48 h. Potassium hydroxide (KOH) was used as a catalyst for the formation of BaTiO3. Powder X-ray diffractometry (XRD) results and Fourier-transform infrared (FT-IR) measurements for the (Ba,Ti) gel showed that the gel was amorphous, but the spatial arrangement of barium and titanium in the (Ba,Ti) gel is similar to that in crystalline BaTiO3 particles. Fully crystallized spherical BaTiO3 powder with a particle size of 40,250 nm formed at the very low reaction temperature of 45°C. Scanning electron microscopy images showed that the final particles formed via aggregation of the fine particles that seem to be the primary particles of bulk (Ba,Ti) gel. From the XRD, FT-IR, and Raman spectroscopy analysis, it was found that the crystal structure of the as-prepared particles continuously transformed from cubic to tetragonal as the calcination temperature increased, and high crystalline tetragonal BaTiO3 phase was obtained at 1000°C after 1 h of heat treatment. [source] Deconvolution of instrumental aberrations for synchrotron powder X-ray diffractometryJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 2 2003T. Ida A method to remove the effects of instrumental aberrations from the whole powder diffraction pattern measured with a high-resolution synchrotron powder diffractometer is presented. Two types of asymmetry in the peak profiles caused by (i) the axial-divergence aberration of the diffractometer (diffractometer aberration) and (ii) the aberration of the monochromator and focusing optics on the beamline (beamline aberration) are both taken into account. The method is based on the whole-pattern deconvolution by Fourier technique combined with the abscissa-scale transformation appropriate for each instrumental aberration. The experimental powder diffraction data of LaB6 (NIST SRM660) measured on beamline BL-4B2 at the Photon Factory in Tsukuba have been analysed by the method. The formula of the scale transformation for the diffractometer aberration has a priori been derived from the instrumental function with geometric parameters of the optics. The strongly deformed experimental peak profiles at low diffraction angles have been transformed to sharp peak profiles with less asymmetry by the deconvolution of the diffractometer aberration. The peak profiles obtained by the deconvolution of the diffractometer aberration were modelled by an asymmetric model profile function synthesized by the convolution of the extended pseudo-Voigt function and an asymmetric component function with an empirical asymmetry parameter, which were linearly dependent on the diffraction angle. Fairly symmetric peak profiles have been obtained by further deconvolution of the empirically determined asymmetric component of the beamline aberration. [source] Inclusion and release of fenbufen in mesoporous silicaJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 8 2010Daniel Carriazo Abstract This work reports the immobilization of Fenbufen, a nonsteroidal anti-inflamatory drug, into two different hexagonal mesoporous silicas (MCM-41) which exhibit some differences in terms of morphology and pore size, and their behavior as systems for sustained release at pH 7.5. The drug/mesoporous silica systems have been characterized by powder X-ray diffractometry (PXRD), Fourier transform infrared spectroscopy (FT-IR), N2 adsorption,desorption, and transmission electron microscopy (TEM). The results show that the drug is mainly incorporated inside the pores, and its loading is dependent on both the pore size and the impregnation temperature. The Fenbufen/mesoporous-silica systems give a well-sustained release profile, releasing 100% of the initially loaded drug at the end of the in vitro assays. © 2010 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99:3372,3380, 2010 [source] Piroxicam/2-hydroxypropyl-,-cyclodextrin inclusion complex prepared by a new fluid-bed coating techniqueJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 2 2009Xingwang Zhang Abstract This work was aimed at investigating the feasibility of fluid-bed coating as a new method to prepare cyclodextrin inclusion complex. The inclusion complex of the model drug piroxicam (PIX) and 2-hydroxypropyl-,-cyclodextrin (HPCD) in aqueous ethanol solution was sprayed and deposited onto the surface of the pellet substrate upon removal of the solvent. The coating process was fluent with high coating efficiency. Scanning electron microscopy revealed a coarse pellet surface, and a loosely packed coating structure. Significantly enhanced dissolution, over 90% at 5 min, was observed at stoichiometric PIX/HPCD molar ratio (1/1) and at a ratio with excessive HPCD (1/2). Differential scanning calorimetry and powder X-ray diffractometry confirmed absence of crystallinity of PIX at PIX/HPCD molar ratio of 1/1 and 1/2. Fourier transform-infrared spectrometry and Raman spectrometry revealed interaction between PIX and HPCD adding evidence on inclusion of PIX moieties into HPCD cavities. Solid-state 13C NMR spectrometry indicated possible inclusion of PIX through the pyridine ring. It is concluded that fluid-bed coating has potential to be used as a new technique to prepare cyclodextrin inclusion complex. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:665,675, 2009 [source] Enhanced solubility and dissolution rate of lamotrigine by inclusion complexation and solid dispersion techniqueJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 9 2008Vikram R. Shinde ABSTRACT The solid-state properties and dissolution behaviour of lamotrigine in its inclusion complex with ,-cyclodextrin (,CD) and solid dispersions with polyvinylpyrrolidone K30 (PVP K30) and polyethyl-eneglycol 6000 were investigated. The phase solubility profile of lamotrigine with ,CD was classified as AL -type, indicating formation of a 1:1 stoichiometry inclusion complex, with a stability constant of 369.96 ± 2.26 M,1. Solvent evaporation and kneading methods were used to prepare solid dispersions and inclusion complexes, respectively. The interaction of lamotrigine with these hydrophilic carriers was evaluated by powder X-ray diffractometry, Fourier transform infrared spectroscopy and differential scanning calorimetry. These studies revealed that the drug was no longer present in crystalline state but was converted to an amorphous form. Among the binary systems tested, PVP K30 (1:5) showed greatest enhancement of the solubility and dissolution of lamotrigine. [source] Thermal Expansion of ,-Yttrium DisilicateJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2004Koichiro Fukuda Crystals of ,-Y2Si2O7 (space group P121/c1) were examined using high-temperature powder X-ray diffractometry to determine their unit-cell dimensions from 296 to 1473 K. The lattice deformation induced by thermal expansion was investigated using matrix algebra analysis to determine the directions and magnitudes of the principal distortions (,i, i= 1,2, and 3). The directions of ,1 and ,3 were defined by the acute angle ,1c, which linearly decreased from 5(2)° to ,5.5(3)° with increased temperature from 504 to 1473 K. The ,2 -axis invariably coincided with the crystallographic b -axis. The magnitudes of ,1 and ,2 steadily increased to, respectively, 1.0061(1) and 1.0068(1) during heating to 1473 K, while ,3 remained almost constant for the entire temperature range. The mean principal distortion, ,m (= (,1+,2+,3)/3), steadily increased to 1.0044(1) with increased temperature to 1473 K. The coefficient of mean linear thermal expansion (,) was derived from the mean principal strain (,m - 1) as ,= (,m - 1)/,T. The temperature dependence was determined to be ,= 2.03 times 103+ 1.36(T - 296) (10 -9 K -1). Provided that the rule-of-mixtures holds for the Y2Si2O7/Y2SiO5 composites as protective coating on SiC substrates, the volume fractions of 0.72-0.77 (70,75 mass%) would be necessary for the Y2Si2O7 component to match the ,-values of both materials. [source] Polymorphism of 4-bromobenzophenoneACTA CRYSTALLOGRAPHICA SECTION B, Issue 2 2007Mikhail A. Strzhemechny A combination of single-crystal and powder X-ray diffractometry was used to study the structure of two polymorphs of 4-bromobenzophenone over the temperature range from 100 to 300,K. One of the polymorphs of the title compound was known previously and its structure has been determined at room temperature [Ebbinghaus et al. (1997). Z. Kristallogr.212, 339,340]. Two crystal growth methods were employed, one of which (a modification of the Bridgman,Stockbarger technique) resulted in single crystals of a previously unknown structure. The basic physical properties of the stable polymorph are: growth method, from 2-propanol solutions or gradient sublimation; space group, monoclinic P21/c; melting point, Tm = 355.2,K; X-ray density (at 100,K), Dx = 1.646,g,cm,3. The same properties of the metastable polymorph (triclinic ) are: growth method, modified Bridgman,Stockbarger method; X-ray density (at 100,K), Dx = 1.645,g,cm,3; Tm = 354,K. Thermograms suggest that the melting of the metastable form is accompanied by at least a partial crystallization presumably into the monoclinic form; the transformation is therefore monotropic. Analysis of short distances in both polymorphs shows that numerous weak hydrogen bonds of the C,H,, type ensure additional stabilization within the respective planes normal to the longest dimension of the molecules. The strong temperature dependence of the lattice constants and of the weak bond distances in the monoclinic form suggest that the weak bond interactions might be responsible for both the large thermal expansion within plane bc and the considerable thermal expansion anisotropy. [source] | ||||||||||