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.     

Short-range order in some polymer melts from X-ray diffraction

Wide-angle X-ray diffraction measurements were performed on polymer melts of isotactic and syndiotactic polypropylene (IPP and SPP), poly(ethylenepropylene) (PEP), polystyrene (PS), polyisobutylene (PIB), and polyethylene (PE), to study the dependence of the short-range structure of polymer liquids on chain architecture. Total structure functions, which comprise intra- and intermolecular contributions, were derived from the scattering data. The trivial Fourier components of the intramolecular structure (C(SINGLE BOND)>C ≃ 1.54 Å and C(SINGLE BOND)C(SINGLE BOND)C ≃ 2.55 Å) were subtracted from the total structure functions. The remaining functions contain only those intramolecular contributions dependent on the chain's conformational degrees of freedom, plus the intramolecular contributions. The structural differences between the polymers in momentum space are discerned only when the trivial components are subtracted. This subtraction also reduces the effects of truncation errors on Fourier transformation to real space. The short-range structure of PIB appears very different compared to all the others, which correlates with anomalies in a number of physical properties for this polymer. © 1996 John Wiley & Sons, Inc.     

The thermodynamic properties of Al-Si system melts

The thermochemical properties of Al-Si system melts were determined by an improved isoperibolic calorimetry method. The data obtained correlated with the reliable partial and integral enthalpies of mixing reported in the literature. The method developed was used to model the thermodynamic properties of melts with the use of the liquidus coordinates of the phase diagram of the Al-Si system. The modeled and experimental results were in close agreement with each other.     

X-ray diffraction study of human serum

Blood serum from people suffering from cancer and healthy subjects was subjected to a comparative study by X-ray diffraction. The diffraction patterns were referred to that of pure water. The patterns obtained for blood serum of healthy subjects were similar to that of pure water, while those of cancer patients (two kinds of cancer changes) were different. The former similarity is accounted for by the dominant interaction of water molecules in healthy blood serum with non-polar side chains of amino acids, stabilising the serum structure. In samples from cancer patients the structure of water in blood serum is destroyed because of enhanced interactions of water with polar molecules of conformationally changed proteins. This observation suggests X-ray examination of blood serum from cancer patients and healthy subjects, indicating X-ray diffraction as a diagnostic tool for the occurrence of cancer. The results of this work have shown that the presence of protein affected by cancer has a destructive effect on the structure of water in human serum. The results reported confirm the earlier finding relating cancer changes to optical circular birefringence effects.     

X-ray diffraction study of ammonium octamolybdate

Ammonium isopolymolybdate (NH₄)₄[Mo₈O₂₆]·4H₂O was prepared for the first time and studied by X-ray diffraction analysis.     

X-ray diffraction study of zirconia pillared clays

X-ray powder diffraction (XRPD) and X-ray radial electronic distribution density (RED) of initial and zirconia-pillared interlayered clays (Zr-PILC) were studied. After pillaring, the basal (001) spacing was found to increase from 11 Å in the initial clay kept under air to 17.7 Å in Zr-PILC. The structure of zirconium nanopillars was characterized. The interatomic distances with corresponding coordination numbers obtained from the RED curves were close to those in zirconium tetramers.This revised version was published online in December 2005 with corrections to the Cover Date.     

X-ray diffraction study of acid anilinium dodecatungstenphosphate

Acid anilinium dodecatungstenphosphate of composition (C₆H₅NH₃)₂H[PW₁₂O₄₀] 2H₂O is synthesized and characterized by X-ray diffraction analysis, IR spectroscopy, and thermogravimetry. The crystals are monoclinic: space group P2₁/m, a = 9.940(2) , b = 15.412(3) , c = 16.201(3) , = 100.42(3)°, Z = 2, _calcd = 4.221 g/cm³. The structure contains heteropolyanions [PW₁₂O₄₀]^3–, cations [C₆H₅NH₃]⁺ and H⁺, and molecules of water of crystallization. The heteropolyanions and anilinium cations in crystal are linked by the electrostatic interaction and hydrogen bonds.__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 4, 2005, pp. 273–279.Original Russian Text Copyright © 2005 by Kaziev, Dutov, Quinones, Koroteev, Belskii, Stash, Kuznetsova.     

An X-ray diffraction study of alkylammonium humate complexes

By exchange of cations of different humates (synthetic, brown coal and compost humates) with an equivalent amount of long-chain organic cations, derivatives with the following alkylammonium ions were prepared: n-decyl, n-dodecyl, n-tetradecyl, n-hexadecyl and n-octadecyl ammonium ions. X-ray diffraction of the humic acids and the alkylammonium humates revealed a behaviour similar to that of smectite-type clay minerals. The results seem to support the layer structure of humic substances. The layers of synthetic, brown coal and compost humate are about 0.60, 0.45 and 0.84 nm thick, and the bilayers of alkylammonium cations are bound to the carboxyl and phenolic hydroxyl groups. The chain tilt is 41–45 .     

X-ray diffraction study of Raney nickel catalyst structure

X-ray diffraction studies have revealed that the modification of Raney nickel catalysts by iron leads to formation of Ni–Fe solid solution, whereas modification by chromium and titanium produces Cr₂O₃ and TiO₂. The higher dispersity of chromium — and especially of titanium-promoted catalysts is ascribed to the interaction of nickel with oxide components.

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, Ni–Fe, Cr₂O₃ TiO₂-, . , , .

     

X-ray diffraction study of bulk poly N-substituted maleimides

Summary A series of 7 aliphatic and 6 aromatic poly N-substituted maleimides (PNMI) was synthetized by free radical polymerization. The series was characterized by means of intrinsic viscosity, number average molecular weight and glass transition temperature measurements. The X-ray diffractograms of all samples show two rather broad maxima indicative of non-crystalline structures. The location of the innermost peak strongly depends on the length of the substituted groups and can be associated to intermolecular vectors. The observed linear increase of the spacing associated to the inner maximum with the number of methylene groups of the substituted aliphatic chain favours the idea of predominantly extended lateral conformations. The outer peak due is to intramolecular average distances along the backbone chain and slightly depends on the shape of the substituted groups. This repeat distance fits well with the assumption of a 4/1 helix for the chain conformation. In the aryl series a third maximum appearing as a shoulder on the outer peak suggests the presence of chain sequences coiled in 3/1 helices. The chain bundle dimensions calculated from the broadening of the innermost maximum are of the order of two intermolecular vectors suggesting, hence, the absence of a well defined short range order. A model for the packing of PNMI molecules with lengthy substituted groups is proposed.

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Zusammenfassung Eine Serie von 7 aliphatischen und 6 aromatischen Poly-N-substituierten Maleimiden (PNMI) wurden mit radikalischer Polymerisation synthetisiert. Die Proben wurden mit Hilfe von Messungen der intrinsic-Viskosität, des Molekulargewichts-Zahlenmittels und der Glas-Temperatur charakterisiert. Röntgendiagramme der Proben zeigen zwei ziemlich breite Maxima, entsprechend der nichtkristallinen Struktur. Die Lage des inneren Piks hängt streng von der Länge der substituierten Gruppen ab und kann mit diesbezüglichen zwischenmolekularen Abständen verknüpft werden: Das beobachtete lineare Anwachsen des mit dem inneren Maximum verknüpften Abstandes entspricht nämlich der Anzahl der Methylengruppen in der substituierten aliphatischen Kette und weist darauf hin, daß sich die laterale Konformation vergrößert. Der äußere Pik entspricht mittleren intramolekularen Abständen längs der Kette und hängt nur wenig von den substituierten Gruppen ab. Die Distanz paßt zur Annahme einer 4/1-Helix-Konformation. In der Arylserie erscheint ein 3. Maximum, das auf das Auftreten von 3/1 Helices hinweist. Die berechneten Dimensionen von Kettenbündeln aus der Verbreiterung des inneren Maximums sind von der Größenordnung des doppelten inter-molekularen Abstands und zeigen somit an, daß keine wohldefinierte Nahordnung besteht. Ein Modell für die Packung der PNMI-Moleküle mit substituierten Seitengruppen wird vorgeschlagen.

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Dedicated to Prof. Dr.R. Hosemann on the occasion of his 60th birthday.