Thermal stability of ammonium chlorocobaltates(II)

The thermal destruction of ammonium penta-, tetra-, and trichlorocobaltates(II) was studied. Thermogravimetric analysis (TGA) data was used to calculate the thermal destruction activation energy, which was 8.6 kJ/mol for (NH₄)₃CoCl₅, 14.8 kJ/mol for (NH₄)₂CoCl₄, and 117.4 kJ/mol for NH₄CoCl₃. The decomposition enthalpy of 35.9 kJ/mol for (NH₄)₃CoCl₅, 12.1 kJ/mol for (NH₄)₂CoCl₄, and 166.3 kJ/mol for NH₄CoCl₃ was determined from differential scanning calorimetry (DSC) data.     

Zur thermischen Zersetzung vom (NH4)2[FeF5(H2O)] unter quasi-isobaren Bedingungen

On the Thermal Decomposition of (NH₄)₂[FeF₅(H₂O)] on Quasi-Isobaric Conditions The thermal decomposition of (NH₄)₂[FeF₅(H₂O)] was investigated by thermal and X-ray analysis. Quasi-isobaric conditions are realized by using a special crucible which guaranteed a pressure of the gaseous products of 70 kPa. In dependence on the partial pressure α- or β-(NH₄)₂FeF₅ were formed during dehydration. Further intermediate products are NH₄FeF₄, (NH₄)_1?xFeF_4?x, and (NH₄)_yFeF₃ with x = 0.15–0.20 and y = 0.12–0.15. Structural relations between these phases are discussed and comparable considerations to the Al system were made.     

Thermal decomposition of ammonium fluoromanganates(III)

The thermal decomposition of ammonium fluoromanganates (III) has been investigated in air and argon by simultaneous thermogravimetry and differential thermal analysis. Chemical analysis, X-ray powder data, and infrared spectra have been employed to characterise the intermediate and final products. The thermal decomposition can be described by the sequence (NH₄₃MnF₆ → (NH₄)₂MnF₅ → NH₄MnF₄ → MnF₂. Although penta- and tetra-fluoromanganates are well-defined compounds, the intermediate states could not be separated. In addition, a high temperature form of ammonium hexafluoromanganate has been observed.     

Amino-group excites vitality in nitrogen-rich energetic salts of triazolium

Incorporating amino groups is an efficient strategy for the tuning properties of energetic materials. However, there is no unanimous conclusion on the effect of the number of amino groups (−NH₂) on performance. Therefore, in this study, different number of −NH₂ of four energetic salts of triazolium based on oxadiazole and triazole were designed and synthesized. The structure features of energetic salts 4 – 6 were then investigated by single-crystal X-ray diffractions and Hirshfeld surfaces analyses. Afterward, the effects of −NH₂ were evaluated by thermal stability, impact sensitivity and detonation performance. All these energetic salts were insensitive to mechanical stimulation (IS >40 J), but the thermal decomposition temperatures of energetic salt 5 – 7 with −NH₂ are 24 °C to 54 °C higher than energetic salt 4 without −NH₂. Moreover, energetic salt 5 with one −NH₂ has the highest theoretical detonation properties compared to those without −NH₂ ( 4 ) and with two −NH₂ ( 6 , 7 ). These observations revealed that appropriate amount of −NH₂ can lead to desirable increase in the energetic properties, and this work can offer guidance for the design and synthesis of further energetic salts.     

ChemInform Abstract: Synthesis and Crystal Growth of Microcrystals of the Cubic and New Orthorhombic Polymorphs of (NH4)2SnCl6.

Single crystals of (NH₄)₂SnCl₆ are obtained by thermal decomposition of SnCl₄·5NH₃ in the gas phase under a stream of gaseous NH₃ (quartz tube, 298 °C, 6 h).     

Thermal Behaviour of Ammonium Oxofluorotitanates(IV)

The thermal behaviour of ammonium oxofluorotitanates (NH₄)₃TiOF₅, (NH₄)₂TiOF₄ and NH₄TiOF₃ was investigated by thermoanalytical, X-ray and IR spectroscopic methods. The first decomposition stages under quasi-isobaric conditions are characterized by the formation of (NH₄)₂TiF₆ and ammonium oxofluorotitanate with the less content of ammonium and fluorine than in the initial compound. The decomposition process is accompanied by the Ti(IV) reducing due to ammonia evolved. The new ammonium oxofluorotitanate of high volatility was isolated and characterized. Ammonium-containing non-stoichiometric titanium oxyfluorides are the final products of thermal decomposition of ammonium oxofluorotitanates.This revised version was published online in November 2005 with corrections to the Cover Date.     

Untersuchungen zur thermischen Zersetzung der Ammoniumyttriumhalogenide II. Ammoniumyttriumiodid

Investigation on the Thermal Decomposition of Ammonium Yttrium Halides II. Ammonium Yttrium Iodide (NH₄)₃YI₆ decomposes directly into YI_3,s NH_3,g and HI_,g. In connection with the thermal decomposition of NH₄I the decomposition-pressure-function is given and the enthalpy of formation and the standard entropy of the phases are derived.     

Effect of Impurities on Thermal Decomposition Kinetics of Mineral Fertilizers Based on (NH<Subscript>4</Subscript>)<Subscript>2</Subscript>HPO<Subscript>4</Subscript> in Self-Generated Atmosphere

The effect of impurities on the thermal decomposition kinetics of mineral fertilizers based on (NH₄)₂HPO₄ in self-generated atmosphere was studied by the methods of thermogravimetry and differential thermal analysis. Results are presented of isothermal measurements made in the temperature range 100–110°C. An analysis of the experimental data made it possible to suggest reaction models of the decomposition and to reveal a dependence of the activation energy on the degree of decomposition. A strong deviation of the temperature dependence of rate constants from the Arrhenius law was observed. Conclusions were made on the basis of the study about the influence exerted by impurities on the thermal decomposition of mineral fertilizers based on (NH₄)₂HPO₄ in the self-generated atmosphere and reasons for the deviation from the Arrhenius law.     

Thermal behaviour of NH4ReO4 supported on inorganic gels

Results of TG and DTA studies as well as an analysis of the liberated gas products have led us to recognize differences in the mechanisms of transformations taking place in the systems NH₄ReO₄/Al₂O₃-SiO₂ (25 wt% SiO₂ and NH₄ReO₄/Al₂O₃ containing 1.1, 3.3 and 3.3, 9.9, 17.8 wt% NH₄ReO₄. Thermal decomposition of NH₄ReO₄ on the supports used begins with release of ammonia, which is strongly bound with the surface in the system of 3.3 wt% NH₄ReO₄/Al₂O₃, and undergoes oxidation to nitrogen oxides in the air atmosphere. In the other systems studied, the process of ammonia release starts already at 473 K and ammonia does not get oxidized. Moreover, it has been established that ammonia perrhenate supported on the surface of Al₂O₃-SiO₂ in the amount of 1.1 or 3.3 wt% undergoes partial thermal decomposition to ReO₂ which is further oxidized in the air atmosphere. As follows from the thermal studies as well as the measurements of activity in a reaction of 1-hexene metathesis, the active centres of the reaction of olefin metathesis are formed on the surface of the studied systems after their calcination at 473 K.     

Analysis of (NH4)2SO4/(NH4)H2PO4 mixtures by thermogravimetry and X-ray diffraction

(NH₄)₂SO₄ and (NH₄)H₂PO₄ are the principal components in the powder material used in fire extinguishers. In this paper the mutual influence in their thermal decomposition is investigated by thermogravimetry. Two methods for the quantification of both salts in mixtures (NH₄)₂SO₄/(NH₄)H₂PO₄ are proposed. The first employs thermogravimetry and is based on the measurement of the mass fraction in the 500-550 °C interval, once (NH₄)₂SO₄ has totally decomposed to yield gaseous products. The second uses some selected peaks in the X-ray diffractogram.     

Novel Method for Preparing NH4NiPO4·6H2O: Hydrogen Bonding Coacervate Selective Self-assembly

The single phase NH₄NiPO₄·6H₂O was synthesized by solid‐state reaction at room temperature using NiSO₄·6H₂O and (NH₄)₃PO₄·3H₂O as raw materials. The NH₄NiPO₄·6H₂O and its calcined products were characterized using X‐ray powder diffraction (XRD), thermogravimetry and differential thermal analyses (TG/DTA), Fourier transform IR (FT‐IR), ultraviolet‐visible (UV‐vis) absorption spectroscopy, and scanning electron microscopy (SEM). The results showed that the product dried at 80°C for 3 h was orthorhombic NH₄NiPO₄·6H₂O [space group Pmm2(25)], and surfactant polyethylene glycol (PEG)‐400 can direct growth of crystal NH₄NiPO₄·6H₂O. The thermal process of NH₄NiPO₄·6H₂O experienced three steps, which involve the dehydration of the five crystal water molecules at first, and then deamination, dehydration of the one crystal water, intramolecular dehydration of the protonated phosphate groups together, at last crystallization of Ni₂P₂O₇. The product of thermal decomposition at 150°C for 2 h, orthorhombic NH₄NiPO₄·H₂O, is layered compound with an interlayer distance of 0.8370 nm.     

Thermal behaviour of (NH4)3VO2F4 and Na(NH4)2VO2F4

The thermal behaviour of (NH₄)₃VO₂F₄ and Na(NH₄)₂VO₂F₄ was investigated using TG, DTA and DSC techniques. The occurrence of a first order phase transition with the onset of decomposition in both the compounds is confirmed. The temperature, energetics and hysteresis of the transition are obtained. A possible path for the thermal degradation is given for both the compounds, and the residues are identified.     

Untersuchungen zur thermischen Zersetzung der Ammoniumyttriumhalogenide III. Ammoniumyttriumbromid, (NH4)3YBr6

Investigation on the Thermal Decomposition of Ammonium Yttrium Halides. III. Ammonium Yttrium Bromide, (NH₄)₃YBr₆ The decomposition equilibria of NH₄Br and (NH₄)₃YBr₆ were determined by total pressure measurements. It was shown by high temperature X-ray patterns and DTA that (NH₄)₃YBr₆ and YBr₃ show phase transitions in the measured temperature region. An endothermic transition of YBr₃ starts near 300°C and is very slow. By interpretation of the thermal decomposition of (NH₄)₃YBr₆, the enthalpy of formation, and the standard entropy was derived. In the system NH₄Br/YBr₃ only the described phase (NH₄)₃YBr₆ exists.     

The thermal decomposition of ammonium heptamolybdate

The thermal decomposition of ammonium heptamolybdate has been investigated by TG. The decomposition is discussed, making use of additional information obtained from isothermal studies, X-ray and IR measurements. The formation of two new compounds, namely (NH₄)₂O · 14 MoO₃ and (NH₄)₂O · 22 MoO₃, prior to the formation of MoO₃ is detected, as well as the main intermediate compounds (NH₄)₂O · 2.5 MoO₃ or (NH₄)₂O · 3 MoO₃ (according to the water content of the starting material) and (NH₄)₂O · 4 MoO₃.     

Thermal Behaviour of Some Polyhydrocarboxylic Coordination Compounds with Neodium

New Nd-Co based polynuclear coordination compounds containing as ligand polyhydrocarboxylic acid as tartaric, malic and gluconic acids were prepared, namely: [NdCo(tart)₃]·4H₂O, (NH₄)[NdCo_0.5Cu_0.5(tart)₃]·4H₂O, (NH₄)[NdCo(malic)₃]·4H₂O, (NH₄)[NdCo_0.5Cu_0.5(malic)₃]·4H₂O, [NdCo(gluc)₄]·4H₂O and [Nd₂CoCu(gluc)₇]·5H₂O. A comparison between the thermal behaviour of the studied polynuclear coordination compounds concerning thermal stability and thermal decomposition stoichiometry was inferred. Oxalic and malonic intermediates were identified at about 300°C in the thermal decomposition of tartaric and malic compounds. In all the decomposition processes at about 400°C the presence of oxocarbonate is shown. The residual products are mixed oxides of perovskite type. This revised version was published online in August 2006 with corrections to the Cover Date.     

Raman spectra,Pippard relations and critical exponents for NH4Cl

The Pippard relations have been extended to correlate the vibrational frequency shifts with the relevant thermodynamic quantities in the vicinity of the λ-point in NH₄Cl. It has been shown that they describe the NH₄Cl system adequately below its λ-transition temperature. (T_λ = 242.8 K). This has been examined using our temperature-dependent frequency data for the ν₅ (174 cm^?1) Raman mode of NH₄Cl at zero pressure by means of the equations developed. The slope of the λ-transition line. (dP/dT)_λ that has been calculated from these equations, is in good agreement with those obtained by previous workers. We have deduced the critical exponents a′ and c′ for the thermal expansion and the isothermal compressibility of NH₄Cl from our temperature and pressure-dependent frequency data for the ν₅ mode. We have identified our exponent value for the thermal expasion with the specific heat exponent, a′, (Pippard relation) to demonstrate the scaling law a′+2b+c′=2, using our value of the critical exponent b for the order parameter from our previous work on NH₄Cl.     

Thermal decomposition of ammonium fluoroferrates (NH4)xFeF2x (2≤x≤3)

Different ammonium fluoroferrates (NH₄)_xFeF_2x (2≤x≤3) have been investigated. The thermal decomposition of the compounds obtained can be interpreted by their identical crystal structures (cryolite type). The decomposition products of all ammonium fluoroferrates formed in initial stage are isostructural of NH₄FeF₄. The decomposition is accompanied by the partial reduction of Fe(III) to Fe(II) by ammonium isolated. The end product of the thermal decomposition is FeF₂ and FeF₃ mixture.     

An Unprecedented‐Type Intramolecular Redox Reaction of Solid Tetraamminecopper(2+) Bis(permanganate) ([Cu(NH3)4](MnO4)2) – A Low‐Temperature Synthesis of Copper Dimanganese Tetraoxide‐Type (CuMn2O4) Nanocrystalline Catalyst Precursors

Tetraamminecopper(2+) bis(permanganate) ([Cu(NH₃)₄](MnO₄)₂; 1 ) was prepared, and its properties were studied in both aqueous solution and the solid phase. The presence of H‐bond interactions between the ammonia ligand of the complex cation and an O‐atom of the permanganate ion was detected by IR and Raman methods. The solid‐phase thermal deammoniation of 1 led to an unusual intramolecular redox reaction between the Mn O⋅⋅⋅H N linkage with formation of NH₄NO₃ and CuMn₂O₄‐type mixed oxides instead of stepwise deammoniation, even below 100°. The thermal deammoniation of 1 in aqueous solution led, instead of to hydrated copper(2+) bis(permanganate), to the formation of NH₄MnO₄ ( 2 ). Since the temperature of the thermal deammoniation of 1 is lower than the decomposition temperature of the permanganate ion, the regulated solid‐phase decomposition of 1 allowed preparation of CuMn₂O₄‐type oxides with mixing of copper and manganese at the atomic level.     

Thermal decomposition of some dihalotetramminecobalt(III) nitrates

The thermal decomposition of some dihalotetramminecobalt(III) nitrates [tetrammire =(NH₃)₄, (NH₃)₂(en), (NH₃)(dien), (en)₂, (pn)₂, (trien), etc.] with different degrees of chelation was studied by various thermoanalytical techniques. A partial oxidation—reduction was observed for these complexes above 200°C which was indicated by a rapid TG mass-loss and a large exothermic DTA peak. A relative order thermal stability is reported.     

Thermal decomposition study of selected isopolymolybdates

The thermal decomposition of ammonium trimolybdate (NH₄)₂Mo₃O₁₀·H₂O, anilinium trimolybdate (C₆NH₈)₂Mo₃O₁₀·4H₂O and anilinium pentamolybdate (C₆NH₈)₂Mo₅O₁₆ in air and nitrogen has been investigated. The decomposition of molybdates was studied in situ by powder X-ray diffraction. Moreover, results of TG, as well as scanning microscopy studies, are presented. It was found that during thermal treatment in air phases of MoO_x type are obtained, while thermal treatment in nitrogen leads to obtaining a mixture of Mo_yC_z and Mo_pN_q. It is worth noting that even though chemical decomposition and formation of new compounds took place, in some cases needle-like or plate-like shapes of crystallites were preserved during thermal treatment.