Compound Formation in the Systems TeO2?SeO2 and TeO2?SeO2?H2O

The solid state reaction between TeO₂ and SeO₂ in inert atmosphere was studied by x-ray diffraction techniques and compound formation was observed. The pale-white reaction product α-TeSeO₄, obtained at 300°C, is not isostructural with the component oxides. The substance is stable at room temperature under exclusion of moisture but decomposes above about 320°C in dry atmosphere. Evidence is given for the formation of 3 TeO₂ · SeO₂ · nH₂O and other hydrated mixed oxides in the system TeO₂? SeO₂? H₂O; d-spacings are reported.     

Synthesis, crystal structure and thermal stability of a novel 3D microporous coordination polymer: Na2[Co(1,4-napdc)2(DMF)2]

A new 3D inorganic–organic hybrid framework microporous material Na₂Co(1,4-napdc)₂(DMF)₂(1,4-napdc =  napthalene-1,4-dicarboxylate), which is constructed by coordination of cobalt ion and sodium ions with napthalene-1,4-dicarboxylate and DMF, is synthesized under solvothermal conditions. Two bidentate-bridging and two chelate-bridged carboxylate link a cobalt (II) and two sodiums (I) to the dimer structure. The square grids constructed with the caged-laddered-shaped secondary building units (SBUs) built by Co–O–Na–O and Co–O–C–O bond and 1,4-napdc links stack over each other to generate infinite 3D networks, which have a microporous channel (11.05 × 11.05 Å²) along the crystallographic c-axis. The thermal stability of the compound was investigated by differential scanning calorimetric and thermogravimetric analysis. The complexes could be anticipated as potential heat-resistant energetic material.     

Investigation of the Reaction of Roasted Serpentine Ore with Some Ammonium Salts

The reaction between roasted serpentine ore and ammonium sulfate was studied at the range of temperature 250–1000°C using different molar ratios to determine the maximum extraction of magnesia and also to characterize the different reaction products. The maximum extraction of MgO from the roasted ore reached 92.4% at 400°C. It was found from XRD that ammonium magnesium sulfate [(NH₄)₂Mg₂(SO₄)₃] was produced as the main product at 400°C, which decomposes to magnesium sulfate at 500–600°C. The last compound decomposes to magnesium oxide at 900–1000°C. Thermal analysis of the reaction mixture confirmed the results obtained by XRD. Extraction of magnesia by ammonium chloride at 300–400°C showed low percentage of extraction (7.8%). Comparison was made between using ammonium chloride instead of sulfate taking into consideration the thermal decomposition products of both ammonium salts. Extraction of magnesia from the roasted ore by aqueous ammonium sulfate or ammonium chloride showed good results.     

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.     

The temperature-composition phase diagram of the HgTe?HgI2 pseudobinary system on the HgTe rich side

The temperature-composition phase diagram of the HgTe? HgI₂ system was determined from 0 to 45 Mol-% HgI₂ between 25 and 670°C using Debye-Scherrer powder X-ray diffraction techniques and differential thermal analysis. Solid solutions of HgTe and HgI₂ with the cubic, zinc blende-type structure exist above 300°C, having a maximum solubility of 11.7 ± 0.8 Mol-% HgI₂ in HgTe at 501 ± 5°C. The known monoclinic compound Hg₃Te₂I₂ is formed by a peritectic reaction upon cooling at 501 ± 5°C, with the peritectic point at approximately 37 ± 4 Mol-% HgI₂.     

Spectrothermal investigation of the decomposition course of lanthanum acetate hydrate

Thermogravimetry, differential thermal, X-ray diffraction and infrared spectroscopy analyses showed La(CH₃COO)₃·1.5H₂O to decompose completely at 700°C yielding La₂O₃. The results revealed that the compound dehydrates in two steps at 130 and 180°C, and recrystallizes at 210°C. Water thus produced hydrolyzes surface acetates (at 310°C), releasing acetic acid into the gas phase. At 334°C, the anhydrous acetate releases gas phase CH₃COCH₃ to give La₂(CO₃)₃ residue, which decomposes to La₂O₂(CO₃) via the intermediate La₂O(CO₃)₂. On further heating up to 700°C, La₂O₃ is formed. IR spectroscopy of the gaseous products indicated a chemical reactivity at gas/solid interfaces formed throughout the decomposition course. As a result, CH₃COCH₃ was involved in a surface-mediated, bimolecular reaction, releasing CH₄ and C₄H₈ (isobutene) into the gas phase. Non-isothermal kinetic parameters, the rate constantk, frequency factorA, and activation energy ΔE, were calculated on the basis of temperature shifts experienced in the thermal processes encountered, at various heating rates (2–20 deg·min^?1).     

Thermal dehydration and decomposition of M[M(C2O4)2]·xH2O (x=3 forM=Sr(II) andx=6 forM=Hg(II))

Strontium(II) bis (oxalato) strontium(II) trihydrate, Sr[Sr(C₂O₄)₂]·3H₂O and mercury(II) bis (oxalato) mercurate(II) hexahydrate, Hg[Hg(C₂O₄)₂]·6H₂O have been synthesized and characterized by elemental analysis, reflectance and IR spectral studies. Thermal decomposition studies (TG, DTG and DTA) in air showed SrCO₃ was formed at ca. 500°C through the formation of transient intermediate of a mixture of SrCO₃ and SrC₂O₄ around 455°C. Sharp phase transition from γ-SrCO₃ to β-SrCO₃ indicated by a distinct endothermic peak at 900°C in DTA. Mercury(II) bis (oxalato) mercurate(II) hexahydrate showed an inclined slope followed by surprisingly steep slope in TG at 178°C and finally 98.66% of weight loss at 300°C. The activation energies (E ^*) of the dehydration and decomposition steps have been calculated by Freeman and Carroll and Flynn and Wall's method and compared with the values found by DSC in nitrogen. A tentative reaction mechanism for the thermal decomposition of Sr[Sr(C₂O₄)₂]·3H₂O has been proposed.     

Solvothermal Synthesis and Crystal Structure of a Novel Inorganic—Organic Hybrid Material,Fe2O（OH）（C5H4NCOO）SO4

IntroductionThereisatremendousactivityforthepastyearsintheareaofinorganic organichybridmaterialsinviewoftheirdi versifiedstructuresandinterestingproperties.1,2 Theeffortshavebeenmadeinsynthesizingandcharacterizingtheclassofmaterials.3Thecontrolofinorganicstructurebyanorganiccomponentrevealsaninteractivestructuralrelationinthema terials .4 Assemblyofaninorganic organichybridmaterialcanbeachievedbyselectingorganiccomponents (multidentateligands)andinorganiccomponents (transitionmetalions ,metalo…     

The synthesis and thermal property of sodium cyclo-octaphosphate

Sodium cyclo-octaphosphate heptahydrate, (NaPO₃)₈ · 7H₂O, has been made by heating lead cyclo-tetraphosphate at 340°C, dissolving the thermal product in a 3% aqueous solution of tetrasodium ethylene-diaminetetraacetate, and then crystallizing it by addition of sodium chloride and acetone to the solution. When the cyclo-octaphosphate was heated up to 400°C, it decomposed to produce phosphates with both shorter and longer chain lengths. A main product at 300° to 350°C was sodium cyclo-triphosphate, and the thermal product melted at about 630°C.     

Beiträge zur Chemie des Bauxitaufschlusses. Untersuchungen im System Na2O?CaO?Al2O3?TiO2?H2O im Temperaturbereich 100–275°C

On the Chemistry of Bauxite Extraction. II. Studies in the System Na₂O? CaO? Al₂O₃? TiO₂? H₂O between 100 and 275°C The formation of crystalline compounds in the system Na₂O? CaO? Al₂O₃? TiO₂? H₂O was studied between 100 and 275°C. With caustic alkali concentrations up to 300 g Na₂O/l the calcium aluminate 3 CaO · Al₂O₃ · 6 H₂O is formed. With rising temperatures two different calcium titanates, among them perovskite, CaTiO₃, are identified. Above 200°C perovskite is formed at all concentrations investigated.     

Analytical applications of the reaction of thorium with benzenephosphonic acid

Benzenephosphonic acid quantitatively precipitates thorium as Th(C₆H₅PO₃)₂·3H₂O at pH values as low as 0.5. The compound may be dried at 140° to 180° C and weighed, as a gravimetric means of determining thorium. On ignition, Th (C₂H₅PO₃)₂ 3 H₂O undergoes decomposition at 240° to 300° C to form Th(C₆H₅PO₃)₂·2H₂O, at 450° to 650° C to form Th(HPO₄)₂·2H₂O and finally at 800° to 1000° C to form Th(HPO₄)₂. The latter compound is stable to 1200° C.Potentiometrically (pK₁' = 0.91, pK₂' = 6.41) and spectrophotometrically (pK₁' = 0.96, pK₂' = 6.51) determined pK' values are reported. Absorption spectra of C₆H₅PO₃H₂, C₆H₅PO₃H^- and C₆H₅PO₃^-2 are reported. The solubility of Th (C₆H₅PO₃)₂·3H₂O was studied as a function of pH and the average value of the solubility product (K_sp = 4s³) was found to be 3.24·10^-31.     

High-temperature thermal analysis study of the reaction between magnesium oxide and silica

The reaction between SiO₂ and MgO at temperatures up to 1500°C was studied using thermal analysis, with X-ray diffraction being used to identify reaction products. The reaction is slow and results in the formation of Mg₂SiO₄ and MgSiO₃, with minor amounts of SiO₂·nH₂O and residual amounts of unreacted SiO₂ and MgO. Complete reaction of the starting materials to form Mg₂SiO₄ can only be achieved by maintaining the mixture at 1500°C for extended periods of time (>1 h).     

Synthesis and thermal behavior of gem-dinitro valerylated polystyrene

Commercial polystyrene has been chemically modified with 4,4-dinitro valeryl chloride by use of Friedel–Crafts acylation reaction in the presence of anhydrous aluminum chloride in a mixture of 1,2-dichloroethane and nitrobenzene. The modified polystyrene containing –COCH₂CH₂C(NO₂)₂CH₃ fragments in side phenyl rings, named gem-dinitro valerylated polystyrene (GDN-PS), was characterized by an Ubbelohde’s viscometer, FTIR, and ¹H NMR spectroscopy. Simultaneous thermogravimetry–differential thermal analysis and differential scanning calorimetry (DSC) have been used to study thermal behavior of the polymer. The results of TG analysis revealed that the main thermal degradation for the GDN-PS occurs during two temperature ranges of 200–300 and 300–430 °C. The DTA curve of GDN-PS is showing a visible exothermic peak at 253.8 °C corresponding to the decomposition of gem-dinitro valeryl groups. The decomposition kinetic of the gem-dinitro groups for GDN-PS with degree of substitution (DS) 11 % was studied by non-isothermal DSC under various heating rates. Kinetic parameters such as activation energy and frequency factor for thermal decomposition of GDN-PS with DS 11 % were evaluated via the ASTM E698 and two isoconversional methods.     

Solid lithium electrolytes based on Fe3+-modified lithium orthogermanate

Solid lithium electrolytes in the Li_4-3x Fe _x GeO₄ system were synthesized. Their phase composition, thermal behavior, and electrical conductivity were studied in the temperature interval 300–750°C. Introduction of Fe³⁺ ions into lithium orthogermanate leads to the formation of a γ-Li₃PO₄-type structure and to a sharp increase in the conductivity, with a maximum reached at x = 0.075–0.15: about 10^?1 S cm^?1 at 300°C and more than 1 S cm^?1 at 700°C. The main current carriers are interstitial Li⁺ cations weakly bound with the rigid framework. Owing to high conductivity, the electrolytes studied are of interest for use in high-temperature electrochemical devices.     

In situ infrared and EXAFS studies of an Ag cluster in zeolite X

The in situ measurements of infrared spectra and the Ag K-edge EXAFS spectra of the fully Ag⁺ exchanged zeolite X (Ag₈₆–X) were carried out from room temperature to 300 °C under vacuum. By evacuation at room temperature the O–H stretch vibration (ν(O–H)) mode around 3 μm disappears and the coordination number of oxygen around Ag, N_Ag–O, decreases due to removal of water molecules. The T–O asymmetric stretch (ν_as(T–O)) mode associated with zeolite framework oxygen appears around 10 μm. These infrared spectra are fitted by summing up Gaussian peaks. The positions of the main two peaks are 1000 and 1100 cm⁻¹ at room temperature. At 100 °C, a third infrared peak appears at around 955 cm⁻¹, the total N_Ag–O becomes small and the coordination number of Ag around Ag, N_Ag–Ag, is 0.5. These results suggest that Ag atoms change sites in the zeolite and play an important role as a precursor of the Ag clusters. At 300 °C, the peaks around 1000 and 1100 cm⁻¹ shift to 1050 and 1140 cm⁻¹, respectively, and N_Ag–Ag becomes 2.9, which indicates that the Ag clusters attached to the zeolite framework are stabilized at high temperature. When the zeolite with Ag clusters is exposed to atmosphere, it is found that: (1) the ν(O–H) mode around 3 μm appears again, (2) there are two main peaks (1000 and 1100 cm⁻¹) and a small peak around 856 cm⁻¹ and (3) the local structure of the Ag clusters formed at 300 °C never reverses.     

A new layered Ca–succinate coordination polymer

A new layered Ca–succinate coordination polymer, poly[μ₃‐succinato‐calcium(II)], [Ca(C₄H₅O₄)]_n, was synthesized by reaction of CaCl₂·2H₂O and succinic acid in an aqueous medium under hydrothermal microwave conditions. The structure contains infinite layers of edge‐sharing calcium pentagonal–bipyramidal polyhedra forming six‐membered rings connected through succinate ligands. Such an assembly of inorganic building units is unique for calcium metal–organic framework‐type structures. Adjacent layers are packed into a final pseudo‐three‐dimensional structure through weak C—H...O hydrogen bonds.     

New synthesis method for M(II) chromites/silica nanocomposites by thermal decomposition of some precursors formed inside the silica gels

In this article, we present a new method for the obtaining of ZnCr₂O₄ and MgCr₂O₄ embedded in silica matrix. This method consists in the formation of Cr(III), Zn(II) and Cr(III), Mg(II) hydroxycarboxylate/carboxylate compounds, during the redox reaction between the nitrate ion and diol (1,3-propanediol), uniformly dispersed in the pores of hybrid gels. The thermal decomposition of these precursors leads to a mixture of corresponding metal oxides. The gels were synthesized starting from mixtures of Cr(NO₃)₃·9H₂O, Zn(NO₃)₂·6H₂O and Cr(NO₃)₃·9H₂O, Mg(NO₃)₂·6H₂O with tetraethyl orthosilicate and 1,3-propanediol for final compositions 50% ZnCr₂O₄/50% SiO₂ and 50% MgCr₂O₄/50% SiO₂. The obtained gels have been thermally treated at 140?°C, when the redox reaction nitrates-diol took place with formation of the precursors within the xerogels pores. The thermal decomposition of all precursors took place up to 300?°C, with formation of oxides mixtures (Cr₂O_3?+?x and ZnO) and (Cr₂O_3?+?x and MgO), respectively. At 400?°C, Cr₂O_3?+?x turn to Cr₂O₃ which reacts with ZnO forming ZnCr₂O₄/SiO₂. Starting with 400?°C, Cr₂O₃ reacts with MgO to an intermediary phase MgCrO₄, which decomposes with the formation of MgCr₂O₄/SiO₂. The formation of the precursors inside the silica matrix and the evolution of the crystalline phases were studied by thermal analysis, FT-IR spectrometry, XRD, and TEM.     

Preparation of thin plate-like calcium phosphate particles with slit-shaped micropores and their molecular sieve effect

The formation of plate-like calcium phosphate particles with slit-shaped micropores produced from the forced hydrolysis reaction of 10?mM Ca(OH)₂, 3.2?mM triphosphate(tripolyphosphate, tpp; $ {{\text{P}}_3}{\text{O}}_{{10}}^{{5 - }} $ ) and 20?mM HCl mixed solution at 100?°C for 2?h were investigated. The molecular sieve effect of produced particles was also explored by using five kinds of adsorptives with various molecular diameters. The large thin plate-like particles as prepared exhibited a large and sharp peak at 2θ?=?6.929° with small diffraction patterns of β-Ca₂P₂O₇. This characteristic peaks at 2θ?=?6.929° suggested that the particles possess a layer structure with ordered basal plane and the large thin plate-like particles are made up of thin sheets. However, the large peak at 2θ?=?6.929° shifted to higher 2θ value after evacuated the particles at 50～200?°C, and these characteristic peak was diminished after treated over 300?°C. The interlayer distances of basal plane were estimated to be 1.280 to 0.980?nm. TG and FTIR measurements disclosed that large amounts of water molecules exist in the particles. It was also revealed that tpp molecules are not completely hydrolyzed to phosphate (orthophosphate, op; $ {\text{PO}}_4^{{3 - }} $ ) ions but still remain tpp and diphosphate (pyrophosphate, pp: $ {{\text{P}}_2}{\text{O}}_7^{{4 - }} $ ) ones, and are adsorbed in slit-shaped micropores. The N₂ adsorption isotherms for the particles were of Type II and they did not change significantly by changing the evacuation temperature from 25?°C to 300?°C. On the contrary, the amount of adsorbed H₂O molecules on the particles after evacuated at 25 and 50?°C steeply increased at ca. 0.3?<?p/p ⁰ ?<?0.6 to provide a step-like adsorption isotherm, but it disappeared after evacuated over 75?°C. From the molecular adsorption experiments employing adsorptives with different molecular diameters, it was indicated that the slit-shaped micropores possess a width less than 0.353?nm being exhibits a high selective adsorption of H₂O molecules into slit-shaped ultramicropores that are accessible to H₂O molecules but not to N₂ and other adsorptive ones. It was indicated that ultramicropores can be formed by the narrowing effect of residual tpp and pp ions unhydrolyzed in the slit-shaped micropores. The residual tpp and pp ions may serve for the adsorption of H₂O molecules by their strong hydrogen bonding nature.     

Thermal runaway reaction evaluation of two by-products mixed with cumene hydroperoxide in the oxidation tower

Oxygen (O₂) or air is widely used to produce cumene hydroperoxide (CHP) in the cumene oxidation tower. The aim of this study was applied to analyze thermal hazard of two by-products including alpha-methylstyrene (AMS) and acetophenone (AP) in a CHP oxidation tower. Differential scanning calorimetry (DSC) and thermogravimetry (TG) were operated to evaluate thermal runaway reaction of CHP mixed with AMS and AP. Exothermic onset temperature (T ₀), maximum temperature (T _max), activation energy (E _a), etc., that were employed to prevent and protect thermal runaway reaction and explosion in the manufacturing process and storage area. In view of proactive loss prevention, the inherently safer handling procedure and storage situation should be maintained in the chemical industries. The T ₀ of 30 mass% CHP was determined to be 105 °C by DSC. Therefore, the T ₀ of 30 mass% CHP mixed with AMS was determined to be 60–70 °C by DSC. The exothermic reaction of CHP/AP and CHP/AMS by DSC under N₂ reaction gas is thermal decomposition of oxygen–oxygen bond (–O–O–) because of the anaerobic reaction.     

Thermal reactivities of potassium and cadmium hydrogenhexavanadates

The thermal reactivities of KHV₆O₁₆·3H₂O and Cd(HV₆O₁₆)₂·12H₂O were investigated. By means of IR spectroscopy and X-ray phase analysis it was found that, after dehydration, both compounds decompose to vanadium pentoxide and the corresponding metavanadate. Potassium metavanadate and vanadium pentoxide react together to form bronzes of different compositions. In contrast, vanadium pentoxide and cadmium metavanadate are the predominant components of the reaction products obtained within the temperature range from 300° to 800°C.