X-ray diffraction study of isomorphous crystal nonahydrates of aluminum, gallium, and scandium perchlorates

Crystal structures of isomorphous crystal nonahydrates of aluminum, gallium, and scandium perchlorates were determined by the X-ray crystal analysis at room temperature. The estimate of associates present in concentrated solutions was carried out by the method of X-ray diffraction in aqueous solutions of aluminum perchlorate.     

Sound-producing sand in Japan: major element composition and its minerals determined by X-ray diffraction and X-ray fluorescence.

The major element composition, including two kinds of clay minerals and moisture content of sound-producing sand are reported for the first time. Sand from 33 beaches in Japan has been found to make sound. Ten sound-producing beaches were selected to compare with silent beach sand. Both sound-producing sand and silent beach sand are mostly composed of quartz and feldspar. The range of SiO2 content of sound-producing sand is not different from silent sand samples. This indicates that a high quartz content is not necessary to produce sound, although more than 60 weight percent of quartz is necessary. One silent sand recovered its sound after a 3.5 percent HNO3 treatment. Also, a small portion of clay minerals was found. A clean grain surface is a necessary factor for sand to produce sound. Illite was found in all silent sand samples.     

Real-time X-ray scattering study during heating of oriented injection-molded polyethylene

Highly oriented linear polyethylene was prepared by elongational flow injection molding. The changes in crystal orientation were investigated as a function of temperature by real-time wide-angle X-ray diffraction. Additionally, the influence of molecular weight upon the microstructure and the changes in orientation, during heating near the melting point, and after cooling have been examined. A shish-kebab structure is inferred for the high molecular weight samples (M_w≥10⁵) from SAXS observations, while for samples with M_w<10⁵ only an oriented lamellar structure is found. Consequently, a higher thermal stability is shown by the higher molecular weight samples. Furthermore, a recovery of crystal orientation on rapid cooling of the samples from the melt is only observed for samples with M_w≥10⁵. The results are discussed in terms of a preferential recrystallization of chain-folded lamellae, on cooling, onto the shish fibrils which survive at high temperature.     

Structure of iron (II) and cobalt (II) bromide complexes in aqueous solution by X-ray diffraction analysis

Structures of bromo-metal complexes in concentrated aqueous solutions of FeBr₂ and of CoBr₂ were investigated by X-ray diffraction analysis. The complexes possess an octahedral geometry coordinating Br^– along with H₂O ligands. The frequency factors of metal-Br contacts per one atom of metal were 0.325 for the 2.7M (mol-dm^–3) and 0.747 for the 4.5M FeBr₂ solutions, and 0.280 for the 2.8M and 0.595 for the 4.3M CoBr₂ solutions. The frequency factors suggested that the tendency of metal ions to forming monobromo complexes is in the order, Fe>Co>Ni相似文献   

X-ray diffraction study of the structure of carboxymethylcellulose-cationic surfactant complexes.

We have investigated dilute aqueous solutions of an anionic polymer (carboxymethylcellulose) mixed with cationic surfactants of different chain lengths (dodecyl to octadecyl trimethylammonium bromides: DTAB, TTAB, CTAB and OTAB). The structures of the concentrated phases formed above the precipitation threshold were studied by X-ray diffraction. Different body-centred cubic structures with space groups Pm3n were observed in the presence of surfactant with a short aliphatic chain (DTAB), despite the fact that the polymer persistence length is comparable to the repeat distance of the structure (5 nm). For larger surfactant chain lengths (TTAB and CTAB), the structure of the precipitates can be either cubic (Pm3n) or 2D hexagonal depending on the initial surfactant and polymer concentrations. For still larger chain length (OTAB), the structure becomes lamellar. This structural evolution from micellar cubic towards 2D hexagonal and lamellar is attributed to the decrease of the local curvature of the surfactant aggregates, as observed for flexible synthetic polymers and short DNA fragments under similar conditions. Furthermore, the structure of the bulk complexes formed just below the precipitation threshold anticipates the structure seen in the precipitated phases.     

Asymmetry between charge and discharge during high rate cycling in LiFePO4 – In Situ X-ray diffraction study

Asymmetric behavior of structural changes during charge and discharge of C-coated LiFePO₄ has been investigated using synchrotron based in situ XRD. C-coated LiFePO₄ undergoes phase transformation from triphylite to heterosite during charge and vise versa during discharge. However, it is observed that the phase transformation of C-coated Li_1−xFePO₄ during discharge is more difficult to be complete than that during charge. At 2C rate, the phase transformation from heterosite to triphylite was hardly observed during discharge while the complete phase transformation was observed in the previous charge. This indicates that the degree of the phase transformation completeness depends on the direction of the phase transformations.     

In situ high-temperature X-ray diffraction,FT-IR and thermal analysis studies of the reaction between natural hydroxyapatite and aluminum powder

Journal of Thermal Analysis and Calorimetry - The present work focuses on the study of the effects of mechanical activation on the reaction between hydroxyapatite (HAp) and aluminum metal powder...     

X-ray diffraction study of the structure of Al-Co melts

The structure of Al-Co melts with 0 at.%, 10 at.%, 18 at.%, 23.5 at.%, 26 at.%, 80.7 at.%, and 100 at.% Co has been studied by X-ray diffraction. Inverse Monte Carlo simulation using the experimental curves of the structural factor was employed to reconstruct the models of melts, analyzed by the Voronoi-Delaunay technique. The dependence of parameters that define short-and longer range ordering of atoms is nonmonotonous in the range 85–74 at.% Al and is extremal in the vicinity of a melt with 76.5 at.% Al. In the stated range of concentrations, the cobalt atoms basically lie at distances of ≈4.2 Å in the pentagonal rings of icosahedral type polytetrahedral clusters. Therefore one can speak about correlation in the character of atomic ordering in melts and corresponding periodic and quasiperiodic phases.     

Chemistry of iron complexes—III. X-ray diffraction,ESR and other spectral studies of new iron(II) and iron(III) complexes with tri-p-tolylarsine oxide

Reactions of iron(II) and iron(III) salts with tri-p-tolylarsine oxide(L) in suitable organic solvents yield complexes of formulas: (i) [FeL₂Cl₂(OH₂)₂] [FeCl₄].2H₂O, [FeL₂Br₂] [FeBr₄].2H₂O; (ii) [Fe(NCS)₃L₂].H₂O; (iii) [FeL(O₂ClO₂)₂(OH₂)] (ClO₄).0.25C₆H₆; (iv) [FeL₃I] [FeI₃].H₂O and (v) [Fe(CO)₃LI]I. Characterization has been done through elemental analyses, IR, far IR, ESR, and reflectance spectra, molar conductance, magnetic moments, t.g.a. and X-ray diffraction (powder) data. The species [FeL₂Cl₂(OH₂)₂]⁺, [FeL₂Br₂]⁺, [Fe(NCS)₃L₂], [FeL(O₂ClO₂)₂OH₂]⁺, [FeL₃I]⁺ and [Fe(CO)₃LI]⁺ have been assigned trans-octahedral, trans-square planar, trans-trigonal bipyramid, trans-octahedral, tetrahedral and cis-trigonal bipyramid structures respectively.     

X-ray spectroscopic and diffraction study of the structure of the active species in the Ni(II)-catalyzed polymerization of isocyanides.

The structure of the active complex in the Ni-catalyzed polymerization of isocyanides to give polyisocyanides is investigated. It is shown by X-ray absorption spectroscopy (XAS), including EXAFS (extended X-ray absorption fine structure) and XANES (X-ray absorption near edge structure), and single-crystal X-ray diffraction, to contain a carbene-like ligand. This is the first structural characterization of a crucial intermediate in the so-called merry-go-round mechanism for Ni-catalyzed isocyanide polymerization.     

Structure of organoclays--an X-ray diffraction and thermogravimetric analysis study

X-ray diffraction has been used to study the changes in the surface properties of a montmorillonitic clay through the changes in the basal spacings of montmorillonite (SWy-2) and surfactant-intercalated organoclays. Variation in the d-spacing was found to be a step function of the surfactant concentration. High-resolution thermogravimetric analysis (HRTG) shows that the thermal decomposition of SWy-2-MMTs modified with the surfactant octadecyltrimethylammonium bromide takes place in four steps. A mass-loss step is observed at room temperature and is attributed to dehydration of adsorption water. A second mass-loss step is observed over the temperature range 87.9 to 135.5 degrees C and is also attributed to dehydration of water hydrating metal cations such as Na+. The third mass loss occurs from 178.9 to 384.5 degrees C and is assigned to a loss of surfactant. The fourth mass-loss step is ascribed to the loss of OH units through dehydroxylation over the temperature range 556.0 to 636.4 degrees C. A model is proposed in which, up to 0.4 CEC, a surfactant monolayer is formed between the montmorillonitic clay layers; up to 0.8 CEC, a lateral-bilayer arrangement is formed; and above 1.5 CEC, a pseudotrimolecular layer is formed, with excess surfactant adsorbed on the clay surface.     

X-ray diffraction study of polycrystals and films of lead (II) hexafluoroacetyl acetonate and pivaloyltrifluoroacetyl acetonate

Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturmoi Khimii, Vol. 35, No. 3, pp. 136–140, May–June, 1994.     

Synchrotron-radiated X-ray and neutron diffraction study of native cellulose

Precise determination of d-spacings and compositional ratio of cellulose I_α and I_β in various native cellulose samples was successfully carried out by synchrotron-radiated X-ray diffraction and time-of-flight (TOF) neutron diffraction from quasi-powder specimens. X-ray diffraction peaks were separated by the deconvolution method using six types of profile function: Gaussian, Lorentzian, intermediate Lorentzian, modified Lorentzian, pseudo-Voigt, and Pearson VII. In terms of R-factors, the pseudo-Voigt function gave the best fit with the observation, and was used for determination of d-spacings. The numerical results for Valonia cellulose were: dI_α (1 0 0) = 0.613 nm; dI_β (1 1 0) = 0.603 nm; dI_β (1 1 0) = 0.535 nm; dI_α (0 1 0) = 0.529 nm; I_α content = 0.65. The differences determined between dI_α (1 0 0) and dI_β (1 1 0) and between dI_β (1 1 0) and dI_α (0 1 0) were similar to those previously reported. Comparison between unresolved peaks for the two types of cellulose samples revealed a small but definite difference between dI_α (1 1 0) and dI_β (2 0 0). The TOF neutron diffractometry using deuterated samples confirmed this difference. This revised version was published online in August 2006 with corrections to the Cover Date.