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Journal of Thermal Analysis and Calorimetry
Authors: D. Giron, Ch. Goldbronn, M. Mutz, S. Pfeffer, Ph. Piechon, and Ph. Schwab

Abstract  

Manufacturing processes may involve the presence of water in the crystallization of the drug substance or in manufacturing or in the composition of the drug product through excipients. Dehydration steps may occur in drying, milling, mixing and tabletting processes. Furthermore, drug substances and drug products are submitted to different temperatures and relative humidities, due to various climatic conditions giving rise to unexpected hydration or dehydration aging phenomena. Therefore the manufacture and the characterization of hydrates is part of the study of the physical properties of drug substances. Several hydrates and even polymorphic forms thereof can be encountered. Upon dehydration crystal hydrates may retain more or less their original crystal structure, they can lose crystallinity and give anamorphous phase, they can transform to crystalline less hydrated forms or to crystalline anhydrous forms. The proper understanding of the complex polyphasic systemhydrates–polymorphs–amorphous state needs several analytical methods. The use of techniques such as DSC-TG, TG-MS, sorption-desorption isotherms, sub-ambient experiments, X-ray diffraction combined with temperature or moisture changes as well as crystal structure and crystal modelling in addition to solubilities and dissolution experiments make interpretation and quantitation easier as demonstrated with some typical examples.

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Abstract  

The results of theoretical analysis of the electronic and crystal structural properties and bonding in relation to thermal decomposition process in anhydrous calcium oxalate are presented. The methods used in this analysis—topological analysis of electron density (Bader’s Quantum Theory of Atoms in Molecules approach) obtained from DFT calculations performed by Wien2k package (Full Potential Linearized Augmented Plane Wave Method); bond order model (Cioslowski&Mixon), applied to topological properties of the electron density; as well as Brown’s Bond Valence Model (bonds valences and strength’, and bond and crystal strains, calculated from crystal structure and bonds lengths data) are described. The analysis of the obtained results shows that these methods allow us to explain the way of thermal decomposition process of anhydrous calcium oxalate to calcium carbonate as a decomposition product, and to describe the structural transition taking place during such process (from monoclinic anhydrous CaC2O4 to rhombohedral calcite structure). In the light of the results of our similar calculations performed previously for other anhydrous oxalates (zinc, cadmium silver, cobalt, and mercury) the proposed theoretical approach can be considered as promising and reliable tool, which allow analyzing the properties of the structure and bonding and hence predicting the most probable way of thermal decomposition process for given crystal structure.

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Abstract  

Two compounds of antimony trichloride and bismuth trichloride with valine are synthesized by solid phase synthesis at room temperature. Their compositions, determined by element analysis, are Sb(C5H10O2N)3·2H2O and Bi(C5H10O2N)2Cl·0.5H2O. The crystal structure of antimony complex with valine belongs to triclinic system and its lattice parameters are: a=0.9599 nm, b=1.5068 nm, c=1.9851 nm, α=92.270, β=95.050, γ=104.270. The crystal structure of bismuth complex with valine belongs to monoclinic system and its lattice parameters are: a=1.6012 nm, b=1.8941 nm, c=1.839 nm, β=99.73°. The far-infrared spectra and infrared spectra show that the amino group and carboxyl of valine may be coordinated to antimony and bismuth, respectively, in two compounds. The TG-DSC results also reveal that the complexes were formed.

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Abstract  

Systematic trends in the thermodynamic properties of congruently melting M3CeBr6 compounds (molar enthalpies of the solid–solid phase transitions, molar heat capacity) following those found for another M3LnX6 compounds (Ln = lanthanide; X = halide, M = Li, Na, K, Rb, Cs) were evidenced. These data were complemented by electrical conductivity measurements over the wide temperature range. The results obtained clearly show that the M3CeBr6 compounds can be divided into two groups. The first one with K3CeBr6 compound having a single high temperature modification of cubic, elpasolite-type, crystal structure, and the second one with Rb3CeBr6 and Cs3CeBr6 compounds having both low- (monoclinic, Cs3BiCl6-type) and high-temperature (cubic, elpasolite-type) modifications. Transition from low- to high-temperature modification of these compounds is non-reconstructive phase transition. Within the two groups, the thermodynamic and transport properties of M3CeBr6 compounds are well correlated with their crystal structure. These results suggest different order–disorder mechanisms of the alkali metal cations whereas the CeBr6 octahedra, forming anionic sublattice, retain their normal lattice positions.

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Abstract  

There is no statistically significant difference in the response of the enantiomers and the racemate of -alanine to -radiation (60Co) and accelerated electrons (10 MeV). The response was measured by the yield of ammonia, one of the separated final products of solid alanine radiolysis and the concentration of free radical CH3·CH·COO, the intermediate product of radiolysis. Some of the properties of the racemate may affect the precision of measurements. TheDL-alanine shows different crystal structure, morphology of crystals, specific density and bulk density than the enantiomers. The response ofL andDL alanines built into composites may be different because of different reactivity of the enantiomer and the racemate with components during the processing and irradiation.

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Abstract  

The Na4UO2(O2)3·8H2O complex was prepared from aqueous systems and its crystallographic and chemical structural conformation characterized. IR spectroscopy and X-ray diffraction were used for analyzing the solid crystal extracted with ethanol to determine the anionic compositon. Composition of the solid phase did not depend on the molar ratio of the reactants or on the pH of the medium, but only upon the absolute concentrations of uranium and alkali. It was observed that the temperature significantly influenced the crystal structure of the product and that a limit to the UO2 concentration existed for inducing the production of a mixture of soluble and insoluble species.

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Abstract  

The57Fe Mössbauer spectra were measured in mixed crystals with different types of chemical bonding and crystal structure, i.e., (Fe,Al)(acac)3, (Fe,Co)(acac)3, K3[(Fe,Al)(ox)3]3H2O, and NH4(Fe,Al)(SO4)212H2O. The broadening of Mössbauer linewidth with increasing Fe3+–Fe3+ distance became less enhanced in the order: (Fe,Al)(acac)3>(Fe,Co)(acac)3, or K3[(Fe,Al)(ox)3]3H2O>(Fe,Al)(acac)3>NH4(Fe,Al)(SO4)212H2O. Furthermore, it was found that the broadening of the linewidth was larger in neat tris (-diketonato) iron(III) complexes than in (Fe,Al)(acac)3. Based on these results, the determining factors of the paramagnetic relaxation time other than Fe3+–Fe3+ distance and temperature were examined in terms of the Mössbauer linewidth as an indicator.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: V. Radchenko, A. Seleznev, V. Shushakov, R. Droznik, M. Ryabinin, L. Lebedeva, and V. Vasilyev

Abstract  

Americium and curium alloys with palladium and platinum containing up to 20% of actinide were prepared by the coupled reduction technique. The alloys obtained were investigated by X-ray, differential thermal analysis and metallography. Phase diagram sections for Pd–Am, Pd–Cm, Pt–Am and Pt–Cm systems have been constructed. Intermetallics Pt5An (An=243Am,244Cm,249Bk,249Cf), Ir2 249Bk and Rh3 239Bk were obtained as thin layers on the surfaces of metallic substrates. X-ray investigation has shown that Pt5An compounds have hexagonal structures of the Cu5Ca-type, Ir2Bk- cubic lattice of the Cu2Mg-type and Rh3Bk intermetallic has fcc lattice of the Cu3Au-type. The influence of intensive -decay of transplutonium nuclides on the crystal structure of the intermetallics prepared has been investigated.

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Abstract  

The initial retentions (at ∼20°C) of (n, γ) activated rare earth bromates were studied using a252Cf fission neutron source with respect to80Br,80mBr and82Br. They lay over the ranges 19–23, 21–23 and 28–32%, respectively. On heating, retention progressively increases and closes on ∼100% for Sm-bromate while for other systems the optimum values reach <85%. Thus, cation effect becomes more pronounced during thermal annealing. The isothermal data show that the weight-loss is due to dehydration. The cation effect on retention is discussed in the light of various parameters like lanthanide contraction, crystal structure, lattice energy, crystal water, properties of anion and mode of thermal decomposition.

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Abstract  

The structure changes and the degree of reduction of U3O8 after mechanoactivation in agate and stainless steel vessels in different media are studied. Clearly expressed reduction of U(IV, VI) oxide, accompanied by oxygen release as a result of mechanochemical activation is observed. The highest degree of reduction is reached when mechanoactivation is performed in suspension with nonpolar organic solvents. The presence of acetaldehyde as a reducing agent did not cause valuable increase of the reduction process. Quantitative evaluation of the mechanochemically induced changes in the crystal structure of U3O8 is done. Decrease of the crystallite sizes of both the U3O8 and the reduced form, provoked by the mechanochemical treatment is observed for all the samples. No other uranium-contained compounds, formed during the mechanoactivation in the different media and mixtures were found.

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