Thermodynamic properties of two zinc borates: 3ZnO·3B2O3·3.5H2O and 6ZnO·5B2O3·3H2O

Two pure zinc borates with microporous structure 3ZnO·3B₂O₃·3.5H₂O and 6ZnO·5B₂O₃·3H₂O have been synthesized and characterized by XRD, FT-IR, TG techniques and chemical analysis. The molar enthalpies of solution of 3ZnO·3B₂O₃·3.5H₂O(s) and 6ZnO·5B₂O₃·3H₂O(s) in 1 mol · dm⁻³ HCl(aq) were measured by microcalorimeter at T = 298.15 K, respectively. The molar enthalpies of solution of ZnO(s) in the mixture solvent of 2.00 cm³ of 1 mol · dm⁻³ HCl(aq) in which 5.30 mg of H₃BO₃ were added were also measured. With the incorporation of the previously determined enthalpy of solution of H₃BO₃(s) in 1 mol · dm⁻³ HCl(aq), together with the use of the standard molar enthalpies of formation for ZnO(s), H₃BO₃(s), and H₂O(l), the standard molar enthalpies of formation of −(6115.3 ± 5.0) kJ · mol⁻¹ for 3ZnO·3B₂O₃·3.5H₂O and −(9606.6 ± 8.5) kJ · mol⁻¹ for 6ZnO·5B₂O₃·3H₂O at T = 298.15 K were obtained on the basis of the appropriate thermochemical cycles.     

Synthesis and thermochemical characteristics of Na2O · Al2O3 · 2.5H2O

A pure phase of monosodium aluminate hydrate Na₂O · Al₂O₃ · 2.5H₂O (MAH) is synthesized and characterized by means of XRD, IR, SEM, TGA, and DSC. The heat capacity of the compound is measured in the temperature range of ?100 to 100°C, and the thermal contributions to enthalpy and entropy are calculated. The standard entropy, enthalpy, and Gibbs energy of formation of MAH at 298 K are estimated.     

209Bi NQR in Mixed Oxides 2Bi2O3· B2O3, 3Bi2O3· 5B2O3, and Bi2O3· 3B2O3

It was earlier found from nuclear quadrupole resonance (NQR) measurements and computer modeling that -Bi₂O₃, Bi₃O₄Br and mixed oxides Bi₂O₃· 2Al₂O₃, Bi₂O₃· 2Ga₂O₃, Bi₂O₃· 3GeO₂, and 2Bi₂O₃· 3GeO₂exhibit local ordered magnetic fields from 30 to 200 G. It thus follows that these compounds are not diamagnets in a conventional sence of the word. With the aim of revealing previously unknown magnetic properties in bismuth(III) oxide-based Main Group element compounds, the mixed bismuth–boron oxides 2Bi₂O₃· B₂O₃, 3Bi₂O₃· 5B₂O₃, and Bi₂O₃· 3B₂O₃were prepared and studied using ²⁰⁹Bi NQR. The quadrupole interactions of the ²⁰⁹Bi nuclei and their electronic environment were studied, the crystallochemical features of the compounds were discussed, and the conformity of the ²⁰⁹Bi results to the X-ray structure data was verified. The preliminary tests in the field of a permanent magnet showed that the resonance intensities increase in external magnetic fields, indicating that a magnetism of unknown nature develops in the titled compounds. It was found reasonable to continue studies of the magnetic properties of these compounds using single-crystal ²⁰⁹Bi NQR in external magnetic fields.     

Magnetic and optical investigation of 40SiO2·30Na2O·1Al2O3·(29 − x)B2O3·xFe2O3 glass matrix

Samples of 40SiO₂·30Na₂O·1Al₂O₃·(29 − x)B₂O₃·xFe₂O₃ (mol%), with 0.0 ≤ x ≤ 17.5, were prepared by the fusion method and investigated by electron paramagnetic resonance (EPR), optical absorption (OA) and Mössbauer spectroscopy (MS). The EPR spectra of the as-synthesized samples exhibit two well-defined EPR signals around g = 4.27 and g = 2.01 and a visible EPR shoulder around g = 6.4, assigned to isolated Fe³⁺ ion complexes (g = 4.27 and g = 6.4) and Fe³⁺-based clusters (g = 2.01). Analyses of both EPR line intensity and line width support the model picture of Fe³⁺-based clusters built in from two sources of isolated ions, namely Fe²⁺ and Fe³⁺; the ferrous ion being used to build in iron-based clusters at lower x-content (below about x = 2.5%) whereas the ferric ion is used to build in iron-based clusters at higher x-content (above about x = 2.5%). The presence of Fe²⁺ ions incorporated within the glass template is supported by OA data with a strong band around 1100 nm due to the spin-allowed ⁵E_g–⁵T_2g transition in an octahedral coordination with oxygen. Additionally, Mössbauer data (isomer shift and quadrupole splitting) confirm incorporation of both Fe²⁺ and Fe³⁺ ions within the template, more likely in tetrahedral-like environments. We hypothesize that ferrous ions are incorporated within the glass template as FeO₄ complex resulting from replacing silicon in non-bridging oxygen (SiO₃O⁻) sites whereas ferric ions are incorporated as FeO₄ complex resulting from replacing silicon in bridging-like oxygen silicate groups (SiO₄).     

Structure of (C3H5NH3)2H2P2O7·H2O

The bis(cyclopropylammonium)dihydrogenodiphosphate monohydrate is a new diphosphate associated with the organic molecule C₃H₅NH₂. We report the chemical preparation and the crystal structure of this organic cation diphosphate. (C₃H₅NH₃)₂H₂P₂O₇.H₂O is orthorhombic (S.G. : P2₁2₁2₁), with Z = 4 and the following unit-cell parameters : a = 4.828(1) Å, b = 11.011(1) Å, c = 25.645(2) Å. The P₂O₇ groups and H₂O water molecules form a succession of bidimensional layers perpendicular to the c axis. The organic cations ensure the three-dimensional cohesion by NH-O hydrogen bonds.     

Al2O3·3H2O阻燃环氧树脂机理探讨

采用氧指数测定法与热重法研究了Al2O3·3H2O对环氧树脂固化物的阻燃效果与机理.结果表明,Al2O3·3H2O在热分解方面与树脂固化物有阻燃匹配性,并能以零级反应快速失去2个结晶水分子,失水后形成的活性氧化铝促进了树脂固化物热解时转化成难燃物的能力,具有较高的阻燃效果.     

Thermal dehydration and decomposition of FeCl3·xH2O

Thermal dehydration and decomposition characteristics of Fe(III) chloride hydrate have been studied by both isothermal and non-isothermal methods. After the initial melting at 35–40°C both dehydration and decomposition of the salt proceed simultaneously at temperature above 100°C. At 250–300°C a stable hydrated Fe(OH)₂Cl is formed representing the first plateau region in the TG curve. Around 400°C, a second plateau is observed corresponding to the formation of mostly Fe₂O₃ which however retains some OH groups and Cl^– ions. However, these temperature ranges vary with the TA equipments used. Chemical analysis of the products of decomposition at temperatures above 140°C also gives evidence for the formation of FeOCl which on hydrolysis in water gives FeCl₃ in solution. The FT-IR spectra suggest the presence of structural OH groups even for samples calcined at 300–400°C. The XRD patterns of the products of decomposition in the temperature range 160–400°C indicate the presence of -FeOOH, some unidentified basic chlorides and -Fe₂O₃.The authors wish to thank the Director, R. R. L. Bhubaneswar for his kind permission to publish this paper. One of the authors (SKM) is grateful to the Council of Scientific and Industrial Research (CSIR), New Delhi for the award of a fellowship.     

Hydrothermal synthesis and thermodynamic properties of 2ZnO · 3B2O3 · 3H2O

The important zinc borate of 2ZnO · 3B₂O₃ · 3H₂O has been synthesized and characterized by means of chemical analysis, XRD, FT-IR, and DTA–TG techniques. The molar enthalpies of solution of H₃BO₃(s) in HCl · 54.561H₂O, of ZnO(s) in the mixture of HCl · 54.561H₂O and calculated amount of H₃BO₃, and of 2ZnO · 3B₂O₃ · 3H₂O(s) in HCl · 54.604H₂O were measured, respectively. With the use of the standard molar enthalpies of formation for ZnO(s), H₃BO₃(s), and H₂O(l), the standard molar enthalpy of formation of ?(5561.7 ± 4.9) kJ · mol^?1 for 2ZnO · 3B₂O₃ · 3H₂O(s) was obtained. Thermodynamic properties of this compound were also calculated by a group contribution method.     

Synthesis and Thermodynamic Properties of MgO·B_2O_3·4H_2O

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Refining the Phase Diagram of the System 3Al2O3·2SiO2-ZrO2

The quasi-binary section mullite-zirconium dioxide in the ternary system Al₂O₃-SiO₂-ZrO₂, described by an eutectic phase diagram with T _{e u t} = 1750°C, was studied experimentally.     

Molecular geometries of H2S···ICF3 and H2O···ICF3 characterised by broadband rotational spectroscopy

The rotational spectra of three isotopologues of H(2)S···ICF(3) and four isotopologues of H(2)O···ICF(3) are measured from 7-18 GHz by chirped-pulse Fourier transform microwave spectroscopy. The rotational constant, B(0), centrifugal distortion constants, D(J) and D(JK), and nuclear quadrupole coupling constant of (127)I, χ(aa)(I), are precisely determined for H(2)S···ICF(3) and H(2)O···ICF(3) by fitting observed transitions to the Hamiltonians appropriate to symmetric tops. The measured rotational constants allow determination of the molecular geometries. The C(2) axis of H(2)O/H(2)S intersects the C(3) axis of the CF(3)I sub-unit at the oxygen atom. The lengths of halogen bonds identified between iodine and sulphur, r(S···I), and iodine and oxygen, r(O···I), are determined to be 3.5589(2) ? and 3.0517(18) ? respectively. The angle, φ, between the local C(2) axis of the H(2)S/H(2)O sub-unit and the C(3) axis of CF(3)I is found to be 93.7(2)° in H(2)S···ICF(3) and 34.4(20)° in H(2)O···ICF(3). The observed symmetric top spectra imply nearly free internal rotation of the C(2) axis of the hydrogen sulphide/water unit about the C(3) axis of CF(3)I in each of these complexes. Additional transitions of H(2)(16)O···ICF(3), D(2)(16)O···ICF(3) and H(2)(18)O···ICF(3) can be assigned only using asymmetric top Hamiltonians, suggesting that the effective rigid-rotor fits employed do not completely represent the internal dynamics of H(2)O···ICF(3).     

The double-layered hydro­xide 3CaO·Al2O3·0.5CaBr2·0.5CaCl2·10H2O

The title compound, calcium oxide–dialuminium trioxide–calcium dibromide–calcium dichloride hydrate (3/1/0.5/0.5/10), also formulated as Ca₂Al(OH)₆Br_0.478Cl_0.522·2H₂O (dicalcium aluminium hydro­xide hemibromide hemichloride dihydrate), is a double-layered hydro­xide which belongs to the solid solution Ca₂Al(OH)₆Br_xCl_1−x·2H₂O, where x can vary from 0 to 1. Chloride and bromide anions of the negatively charged interlayer [Br_0.5Cl_0.5·2H₂O]⁻ share statistically the same crystallographic site. Al³⁺ and Ca²⁺ cations are coordinated by six and seven O atoms, respectively. All water mol­ecules are bonded to Ca²⁺ cations and assume the seventh coordination position. Anions in the interlayer are surrounded by ten H atoms. Br⁻ and Cl⁻ are therefore connected to the main layer by ten hydrogen bonds, six of 2.74 (2) Å and four of 2.52 (5) Å, where the donors are hydroxyl groups and water mol­ecules, respectively. Like the chloride equivalent, the title compound is a 6R polytype with trigonal space group Rc and lattice parameters a = 5.7537 (4) Å and c = 48.108 (4) Å.     

Preparation and Characterization of Cu3V2O7(OH)2·2H2O Hollow Spheres from NazV6O16·3HzO Nanobelts

Monoclinic Cu3V2O7(OH)2·2H2O(copper polyvanadate) hollow spheres were prepared with Na2V6O16·3H2O nanobelts as V-precursor by hydrothermal method.The purity and structure of the products were characterized by X-ray powder diffraction(XRD),Fourier transform infrared(FTIR) spectroscopy,Raman spectroscopy,thermogravimetric analysis(TGA) and X-ray photoelecton spectroscopy(XPS).The morphology and size were observed by scanning electron microscopy(SEM).We found that the Kagomé staircase-structural copper polyvanadate hollow spheres with an average diameter of 7 μm could be easily synthesized via the reaction of Na2V6O16·3H2O nanobelts with sufficient copper sulfate.The dielectric property of the copper polyvanadate demonstrates that dielectric loss hardly changes when the frequency of applied electric field is higher than 100 kHz.The formation process of the hollow spheres is discussed in detail by the observation of a series of products prepared for different reaction time.     

Synthesis and characterization of substitutional solid solutions aLn2O3 · (1 − a)Bi2O3 · 4TiO2

The solubility of 10 lanthanide elements and of scandium is solid Bi₂Ti₄O₁₁ has been determined using Raman spectroscopy and X-ray diffraction. The data obtained were used to construct a diagram of solubility as a function of the ionic radii of bismuth and the lanthanide elements. The thermal stability of the solid solutions as a function of temperature and duration of thermal treatment has been qualitatively established.     

Synthesis and study of lithium triuranate Li2U3O10 · 6H2O

Li₂U₃O₁₀ · 6H₂O crystal hydrate was synthesized by the reaction between synthetic schoepite UO₃ · 2.25H₂O and aqueous lithium nitrate solution under hydrothermal conditions at 200°C. The composition and structure of the obtained compound were established, and its dehydration and thermal decomposition were studied, by chemical analysis, X-ray diffraction, IR spectroscopy, and scanning calorimetry.     

RhCl3·3H2O catalyzed tritiation of acid amides with HTO

It was established by chemical degradation that RhCl₃·3H₂O catalyzed tritiation with HTO occurred with virtually 100% regioselectivity at the ortho-positions of benzamide as well as various anilides and benzoic acid. While tritiation has not been found in the alkyl C–H bond in anilide molecules, in the present experiments tritium was incorporated into the active methylene group of -phenylacetamide. This finding suggests that the present tritiation occurs more readily at polar C^-–H⁺ bonds than at nonpolar ones in accordance with previous results.