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Polycrystalline layered α-titanium phosphate, α-Ti(HPO4)2·H2O, has been obtained under H3PO4(aq) reflux conditions, and its intercalation compound with propylamine, α-Ti(HPO4)2·2C3H7NH2·H2O, was used for trapping luminescent Eu-centers in two-dimensional confined space. All materials were characterized by X-ray powder diffraction, scanning electron microscopy, solid-state nuclear magnetic resonance (SS-NMR, 31P MAS and 13C CPMAS) and thermogravimetric analysis coupled with mass spectrometry. Moreover, the activation energy of thermal decomposition has been calculated as a function of the extent of conversion, applying both a modified Friedman method developed in our laboratory and the advanced nonlinear method proposed by Vyazovkin. [ABSTRACT FROM AUTHOR]

A series of layered alkylammonium–chromium phosphates, formulated as [C n H 2 n +1 NH 3 ]Cr(OH)PO 4 ( n =2–6), has been synthesized under hydrothermal conditions. The interlayer spacing, increasing linearly with the increase of alkyl-chain length from 13.61 Å ( n =2) to 21.20 Å ( n =6), is occupied by a double sheet of packed amine molecules with a tilt angle of ca. 51° respect to the inorganic sheet. The powders are constituted by circular plates (diameter=0.5–3 µm, thickness=~50 nm) with central holes when n =4–6, stacked in axial direction showing worm-like morphologies. The presence of holes, and some corrugated and zig-zag fashions observed on the edge of thin circular plates are the most probable ways for the reduction of the steric tensions between organic and inorganic portions in these hybrid materials. The thermal and thermo-oxidative stability of selected compounds have been studied, including the determination of activation energy data for the decomposition processes. [ABSTRACT FROM AUTHOR]

(CNH)CrO(HPO)·HO has been synthesized hydrothermally using piperazine as organic template. Its crystal structure was solved ab initio using synchrotron powder X-ray diffraction data [monoclinic, a = 16.9649(4) Å, b = 9.8609(2) Å, c = 7.14375(14) Å, and β = 94.896(3)°, space group P2/ a, Z = 4]. 1D structure is composed by isolated infinite anionic chains [CrO(HPO)] (vertex-sharing {CrO} octahedra joined by phosphate moieties). Their 2D plate-like morphology is propitiated by a very strong inter-chain interaction (P-O···H···O-P symmetric hydrogen bonds). KAS isoconversional method was applied to determine the activation energy for both thermal and thermo-oxidative decomposition of (CNH)CrO(HPO)·HO. [ABSTRACT FROM AUTHOR]

Abstract: New polymeric yttrium-succinates, Y2(C4H4O4)3(H2O)4·6H2O and Y2(C4H4O4)3(H2O)2, have been synthesized, and their structures (solved by single crystal XRD) are compared with that of Y2(C4H4O4)3(H2O)2·H2O. Three compounds were obtained as single phases, and their thermal behaviour is described. [Copyright &y& Elsevier]

Morphological and structural characterization of both (NH 4 ) 2 Th(PO 4 ) 2 ·H 2 O ( 1 ) and Th 2 (PO 4 )(P 3 O 10 ) ( 2 ) have been performed by using electron microscopy techniques (SEM, HR-TEM, DF-STEM and SAED), which reveal a morphological transformation from star-shaped particles to irregularly rhombohedral-like aggregates after thermal treatment at 1000 °C. The 1 → 2 thermal conversion is monitored by thermogravimetric analysis and the activation energy has been obtained by using isoconversional methods. A discrete model describing the kinetic process is obtained and so the original data set can be reconstructed and compared with the experimental measures. By using heating rates different from those involved for getting the model, predictions can be also made. The procedure has worked efficiently in recovering the original kinetic parameters in two theoretical simulations. [ABSTRACT FROM AUTHOR]

Abstract The hydrothermal synthesis and the chemical-physical characterization of an ammonium-chromium(III)-iron(III) bis(hydrogenphosphate), Cr 0.34 Fe 0.66 NH 4 (HPO 4) 2 [CrFeNP] is reported. It was obtained in aqueous media by reaction between chromium(III) chloride, iron(III) chloride, urea, and orthophosphoric acid. The crystal structure of CrFeNP was determined from single-crystal X-ray diffraction data. It crystallizes in the triclinic system, space group P -1, and exhibits two types of different infinite tunnels along [0 1 0] and [1 0 0] directions, where the ammonium cations are located. Thermal analysis shows that the solid is stable up to ca. 600 K. The activation energy of the thermal decomposition up to 1273 K was computed by isoconversional methods. In addition, the magnetic behaviour of the material was investigated from magnetic susceptibility and magnetization measurements. CrFeNP undergoes two successive magnetic transitions at temperatures T C = 17.9 K and T t = 3.1 K, which could be related to a ferri- and an antiferromagnetic magnetic phase transitions, respectively. Graphical abstract fx1 Highlights • Hydrothermal synthesis of a new ammonium phosphate. • Thermal decomposition: obtaining the activation energy by isoconversional methods. • Comparison of the experimental and reconstructed α - T curves. • Double magnetic transition phase: para–, ferri– and antiferromagnetic. [ABSTRACT FROM AUTHOR]