Cadmium(II)bis(oxalato)cobaltate(II)- pentahydrate

A mixed metal carboxylate, cadmium(II)bis(oxalato)cobaltate(II)pentahydrate, has been synthesized and characterized by elemental analysis, IR spectral, reflectance and X-ray powder diffraction studies. Thermal decomposition studies (TG, DTG and DTA) in air showed that the compound decomposed to CdCoO3 at 370°C through the formation of an anhydrous compound at ~194°C. Finally, CdCoO₂ is generated at 1000°C. DSC study in nitrogen up to 550°C showed the formation of a mixture of CdO and Co₃O₄ as end products. The kinetic parameters have been evaluated for the dehydration and decomposition steps using four non-mechanistic equations, i.e., Freeman and Carroll, Coats and Redfern, Flynn and Wall, MacCallum and Tanner equations. Using seven mechanistic equations, the rate controlling processes of the dehydration and decomposition mechanism are also inferred. The kinetic parameters, DH and DS obtained from DSC are discussed. IR and X-ray powder diffraction studies identified some of the decomposition products. A tentative mechanism for the decomposition in air is proposed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal Investigations of M[La(C2O4)3]⋅xH2O (M=Cr(III) and Co(III))

The complexes M[La(C₂O₄)₃]⋅xH₂O (x=10 for M=Cr(III) and x=7 forM=Co(III)) have been synthesized and their thermal stability was investigated. The complexes were characterized by elemental analysis, IR, reflectance and powder X-ray diffraction (XRD) studies. Thermal investigations using TG, DTG and DTA techniques in air of chromium(III)tris(oxalato)lanthanum(III)decahydrate, Cr[La(C₂O₄)₃]⋅10H₂O showed the complex decomposition pattern in air. The compound released all the ten molecules of water within ∼170°C, followed by decomposition to a mixture of oxides and carbides of chromium and lanthanum, i.e. CrO₂, Cr₂O₃, Cr₃O₄, Cr₃C₂, La₂O₃, La₂C₃, LaCO, LaCrO_x (2<x<3) and C at ∼1000°C through the intermediate formation of several compounds of chromium and lanthanum at ∼374, ∼430 and ∼550°C. Thecobalt(III)tris(oxalato)lanthanum(III)heptahydrate, Co[La(C₂O₄)₃]⋅7H₂O becomes anhydrous around 225°C, followed by decomposition to Co₃O₄, La₂(CO₃)₃ and C at ∼340°C and several other mixture species of cobalt and lanthanum at∼485°C. The end products were identified to be LaCoO₃, Co₃O₄, La₂O₃, La₂C₃, Co₃C, LaCO and C at ∼ 2>1000°C. DSC studies in nitrogen of both the compounds showed several distinct steps of decomposition along with ΔH and ΔSvalues. IR and powder XRD studies have identified some of the intermediate species. The tentative mechanisms for the decomposition in air are proposed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal decomposition of cerium(III) perchlorate

Thermal decomposition of Ce(ClO₄)₃ ? 9H₂O and Ce(ClO₄)₃ to give cerium(IV) dioxide in the temperature range 240–460°C was studied by DSC–TGA, X-ray powder diffraction, IR and mass spectroscopy. The thermolysis of these salts was shown to proceed through the stage of formation of intermediate product supposedly cerium oxoperchlorate. The thermal decomposition of cerium(III) perchlorate hydrate at 460°C leads to formation of nanocrystalline cerium dioxide with particle size of 13 nm.     

Solid-state thermal decomposition of heterobimetallic oxalate coordination compounds, zinc(II)tetraaquatris(oxalato)lanthanate(III)hexahydrate and cadmium(II)heptaaquatris(oxalato)lanthanate(III)tetrahydrate

Two heterobimetallic oxalate coordination compounds, zinc(II)tetraaquatris(oxalato)lanthanate(III)hexahydrate (ZnOLa) and cadmium(II)heptaaquatris(oxalato)lanthanate(III)tetrahydrate (CdOLa) were synthesized and characterized by elemental analysis, IR, electronic spectral and powder X-ray diffraction studies. Both the compounds were found to have monoclinic structure. Thermal decomposition studies by TG, DTG and DTA in air have proved that the aqua ligands are associated with metals in a stronger coordination mode. The temperatures for pyrolysis were adopted from the TG results chosen from the stable range of thermograms. In case of ZnOLa, it decomposes through two steps and the end product at 1000 °C was found to be consisting of mainly, La₂O_3, ZnO and La₂ZnO _x through the intermediate formation of several oxycarbonates of lanthanum at ca. 525 °C. In case of cadmium analogue, three steps decomposition were observed and the final products were confirmed as CdO₂, La₂O₃, LaCO and La₂CdO _x via the formation of several intermediates at 340 and 590 °C. The La₂C₃ and carbon are also found as part of the end product. The kinetic parameters, E ^*, lnk _o, ?H ^# and ?S ^# of all the deaquated and decomposition steps are investigated and discussed from the DSC study in nitrogen.     

An investigation on solid-state pyrolytic decomposition of barium trihemiaquatris(oxalato)lanthanate(III)decahydrate using TG–DTA in air and DSC in nitrogen

A heterobimetallic oxalate coordination compound, barium(II)trihemiaquatris(oxalato)lanthanate(III)decahydrate, has been synthesized and characterized by elemental analysis, IR and electronic spectral studies. Crystalline nature of the compound with orthorhombic symmetry is corroborated from powder X-ray diffraction studies. The solid-state pyrolytic decomposition studies (TG, DTG and DTA) in air showed that the compound decomposed mainly to BaO, La₂O₃ and BaLa₂O₄ along with carbides of both the metal at ca. 1,000 °C through a number of intermediate steps. The DSC studies in nitrogen up to 670 °C found that the compound crumbled through several endothermic and one exothermic processes. The kinetic parameters, E*, lnk _o, ΔH ^# and ΔS ^# of dehydration and decomposition steps in nitrogen are evaluated from DSC peaks and discussed.     

Physico-chemical Studies on Zinc Hexa(formato)ferrate(III) Decahydrate

Thermal analysis of zinc hexa(formato)ferrate(III) decahydrate, Zn₃ [Fe(HCOO)₆]₂ 10H₂O has been investigated up to 800°C in static air atmosphere employing TG, DSC, XRD, IR, ESR and Mössbauer spectroscopic techniques. After dehydration at 160°C, the anhydrous complex decomposes into α-Fe₂ O₃ and zinc carbonate in successive stages. Subsequently the cations remix to yield fine particles of zinc ferrite, ZnFe₂ O₄ , as a result of solid state reaction between α-Fe₂ O₃ and zinc carbonate at a temperature (600°C) much lower than for ceramic method.     

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.     

Thermal decomposition of manganese(II)bis(oxalato)nickelate(II)tetrahydrate

Summary A mixed metal oxalate, manganese(II)bis(oxalato)nickelate(II)tetrahydrate, has been synthesized and characterized by elemental analysis, IR spectral and X-ray powder diffraction (XRD) studies. Thermal decomposition studies (TG, DTG and DTA) in air showed that the compound decomposed mainly to Mn₂O₃, MnO₂ and NiO at ca.1000°C, via. the formation of several intermediates. DSC study in nitrogen upto 500°C showed the endothermic decomposition. The tentative mechanism for the thermal decomposition in air is proposed.     

Thermal decomposition of chromium(III) nitrate(V) nanohydrate

Thermal decomposition of Cr(NO₃)₃·9H₂O in helium and in synthetic air was studied by means of TG, DTA, EGA and XRD analysis. The dehydration occurs together with decomposition of nitrate(V) groups. Eight distinct stages of reaction were found. Intermediate products of decomposition are hydroxy- and oxynitrates containing chromium in hexa- and trivalent states. The process carried out in helium leads to at about 260°C and in air is formed at about 200°C. The final product of decomposition (>450°C) is Cr₂O₃, both in helium and in air. This revised version was published online in July 2006 with corrections to the Cover Date.     

TG and DSC studies on Sm(III) and Tb(III) tartrates

The tartrate monohydrates of Sm(III) and Tb(III), Sm₂C₁₂H₁₂O₁₈·H₂O and Tb₂C₁₂H₁₂O₁₈·H₂O, were prepared and characterized on the basis of their elemental analysis and IR spectral studies. The thermal decompositions of these compounds, studied by TG and DSC methods, were found to follow an almost uniform pattern. Decomposition occurs in four steps. The first step involves dehydration, accompanied by partial decomposition to the oxalate, followed by conversion to the carbonate. The ultimate product in each case is the oxide M₂O₃, whereM=Sm or Tb. Reflectance spectra of the terbium compound were recorded at various stages of decomposition. The kinetics of the first decomposition step was studied by the non-isothermal method. TG and DSC data for this step were analysed for the evaluation of various kinetic parameters. Reasonable values ofE, Z, andΔS ⁺ were obtained.α vs. T curves were drawn on the basis of the TG and DSC data. The results suggest that the mechanism involves random nucleation.     

NOx and N2O precursors from co-pyrolysis of biomass and sludge

Heterobimetallic oxalate complex precursor, Ca₃[La(C₂O₄)₃(H₂O)₄]₂·5H₂O (CaOLa) was synthesized in aqueous medium and characterized by elemental analysis, IR, electronic spectral, and powder X-ray diffraction studies. It is found to be fined crystalline in nature with triclinic symmetry. Thermal studies (TG, DTG, and DTA) in air showed that the departure of aqua ligands completed at ca. 240 °C. A mixture of mainly CaO, La₂O₃, and La₂CaO _x along with a trace of carbides of calcium and lanthanum were identified in the end products at 1,000 °C. The nature of decomposition in nitrogen was explored from DSC study and discussed the evaluated kinetic parameters.     

Synthesis and Thermal Decomposition of Cobalt(II) bis (Tartrato) Cobaltate(II) Trihydrate

The paper describes the synthesis and characterization of cobalt(II) bis (tartrato) cobaltate(II) trihydrate Co[Co[C₄O₆H₄)₂]·3H₂O. The complex was characterized on the basis of elemental analysis, infrared, electronic, e.s.r. spectra and X-ray powder diffraction studies. The thermal decomposition of the complex led to a mixture of Co₂O₃and Co₃O₄in air at about 400°C, whereas in nitrogen it was decomposed to a mixture of CoO and C at about 384°C. A tentative reaction mechanism is suggested for the thermal decomposition of the complex in air and nitrogen. This revised version was published online in July 2006 with corrections to the Cover Date.     

An investigation on the solid state pyrolytic decomposition of bimetallic oxalate precursors of Ca,Sr and Ba with cobalt: A mechanistic approach

The mixed metal oxalate precursors, calcium(II)bis(oxalato)cobaltate(II)hydrate (COC), strontium(II)bis(oxalato)cobaltate(II)pentahydrate (SOC) and barium(II)bis(oxalato)cobaltate(II)octahydrate (BOC) have been synthesized and their thermal stability was investigated. The complexes were characterized by elemental analysis, IR spectral and X-ray powder diffraction studies. Thermal decomposition studies (TG, DTG and DTA) in air showed that the compound COC decomposed mainly to CaC₂O₄ and Co₃O₄ at 340 °C, and a mixture of CaCO₃ and Co₃O₄ identified at 510 °C. A mixture of CaCO₃ and Ca₃Co₂O₆ along with the oxides and carbides of both the cobalt and calcium were attributed at 1000 °C as end products. DSC study in nitrogen ascertained the formation of a mixture of CaO and CoO along with a trace of carbon at 550 °C. The mixture species, SrC₂O₄, CoC₂O₄ and Co₃O₄ were generated at 255 °C in case of SOC in air, which ultimately changed to CoSrO₃, SrCO₃ and oxides of strontium and cobalt at 1000 °C. The several mixture species also generated as intermediate at 332 and 532 °C. The DSC study in nitrogen indicated the formation of CoSrO_x (0.5 < x < 1) as end product. In case of BOC in air, a mixture of BaCoO₂, BaO, CoO and carbides are identified as end product at 1000 °C through the generation of several intermediate species at 350 and 530 °C. A mixture of BaO and CoO is identified as end product in DSC study in nitrogen. The kinetic parameters have been evaluated for all the dehydration and decomposition steps of all the three compounds using four non-mechanistic equations. Using seven mechanistic equations, the kind of dominance of kinetic control mechanism of the dehydration and decomposition steps are also inferred. The kinetic parameters, ΔH and ΔS of all the steps are explored from the DSC studies. Some of the decomposition products are identified by IR and X-ray powder diffraction studies.     

Analytical and thermal investigations of new solid Y(III) and La(III) complexes

New compounds with formulae Y(2,4′-bpy)_1.5Cl₃·8H₂O (I), Y(2,4′-bpy)_0.5Br₃·8H₂O (II), La(2,4′-bpy)Cl₃·5H₂O (III) and La(2,4′-bpy)_1.5Br₃·5H₂O (IV) were prepared and characterized by chemical and elemental analysis, IR spectroscopy and powder X-ray diffraction. The thermal properties of compounds in the solid state were studied using TG-DTA techniques under dry air atmosphere. The thermal behavior of investigated compounds was studied in the temperature range 298–1273 K. They are stable up to 323 K. The complexes decompose in several stages, accompanied by endo- and exothermic effects. In all cases, the first step of pyrolysis is partial or total dehydration. When the temperature rises, deamination takes place. The solid final products of decomposition are Y₂O₃ and La₂O₃, respectively. Additionally, for all complexes mass spectrometry was used to analyze principal volatile thermal decomposition and fragmentation products evolved during pyrolysis under dry air atmosphere.

     

Thermal stability and flammability of butadiene–styrene rubber nanocomposites

Heterobimetallic oxalato complex precursors, manganese(II)tetraaquatris(oxalato)lanthanate(III)hexahydrate (MnOLa), cobalt(II)pentaaquatris(oxalato)lanthanate(III)trihydrate (CoOLa), nickel(II)pentaaquatris(oxalato)lanthanate(III)hexahydrate (NiOLa) and copper(II)diaaquatris(oxalato)lanthanate(III)monohydrate (CuOLa) of the type, M₃[La(C₂O₄)₃(H₂O) _m ]₂·nH₂O have been synthesized in aqueous medium. The precursors were characterized by elemental analysis, IR, electronic spectral and powder X-ray diffraction studies. The good crystalline nature with monoclinic structures predominates in MnOLa and NiOLa whereas triclinic structures were found in CoOLa and CuOLa. The solid-state thermal behaviour of the precursors was explored using TG, DTG and DTA in air. The MnOLa generated a mixture species consisting mainly of MnO₂, Mn₃O₄, Mn₅O₈, La₂O₃ and LaMn₇O₁₂ at 1000 °C through the formation of several intermediate species at 380 and 570 °C. The studies revealed that CoOLa led mainly to LaCoO₃ and La₂CoO₄ along with some oxides of both the cobalt and lanthanum at 1000 °C. In case of nickel analogue the mixture species identified at 1000 °C are mainly of La₂NiO₄, La₂O₃, Ni₂O₃ and NiO_2. In case of CuOLa the product at 1000 °C consisted of La₂CuO₄, La₂Cu₂O₅ and oxides of copper and lanthanum. The nature of decomposition of the precursors in nitrogen were seen from DSC study and the kinetic parameters i.e., E ^* , lnk ₀, ΔH ^# , ΔS ^# and order of reaction of all the steps were evaluated and discussed.     

Synthesis,characterization and thermal behaviour of Fe4(OH)11NO3·2H2O

A new iron basic salt, Fe₄(OH)₁₁NO₃·2H₂O, has been prepared by partially hydrolyzing a solution of Fe(NO₃)₃·9H₂O with urea. The X-ray powder diffraction pattern has been indexed within a monoclinic cella=9.99(3) ?,b=9.48(2) ?,c=3.074(3) ? andβ=90.57(1)°. Thermal decomposition reactions in still air and nitrogen flow have been studied by DTA and TG analysis, and the intermediate and final products have been characterized by X-ray diffraction and IR spectroscopy. When this material is thermally decomposed in an X-ray high temperature diffraction chamber, pure iron is formed at 900 °C together with Fe(III) and Fe(II) oxides.

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Zusammenfassung Mittels Hydrolyse einer L?sung von Fe(NO)₃)₃·9H₂O mit Karbamid wurde das neue basische Eisensalz Fe₄(OH)₁₁NO₃·2H₂O dargestellt. Aus einem R?ntgenpulververfahren resultierena=9,55(3) ?,b=9,48(2) ?,c=3,074(3) ? undβ=90,57(1)° für eine monozyklische Zelle. Mittels DTA- und TG-Untersuchungen wurden die thermischen Zersetzungsreaktionen an Luft und im Stickstoffflu? untersucht und die Zwischen- und Endprodukte mit r?ntgendiffraktionsverfahren und IR-Spectroskopie charakterisiert. Bei einer thermischen Zersetzung dieses Stoffes in einer Hochtemperatur-r?ntgendiffraktionskammer wird bei 900 °C elementares Eisen zusammen mit Fe(II)- und Fe(III)-oxiden gebildet.

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Резюме Частичным гидролизо м раствора соли Fe(NO₃)₃ · 9H₂O с мочевиной получен а новая основная соль Fe₄(OH)₁₁NO₃ · 2Н₂О, для которой методо м порошкового рентген оструктурного анализа была установ лена моноклинная стр уктура с параметрами ячейкиа=9,55(3) А,b=9,48(2) ?,c=3,074(3) ? иβ=90,57(1)°. Термиче ское разложение соли изучено методом ДТА и ТГ в динамическо й атмосфере воздуха и азота, а образующиеся промеж уточные и конечные продукты ре акции были охарактер изованы рентгенофазовым ана лизом и ИК спектроскопией. ˉПри термическом разложе нии соли в высокотемпературно й рентгено-диффракци онной камере при 900° образует ся чистое железо вмес те с оксидами двух- и трехвалентного желе за.

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The authors are greateful to Dr. R. M. Rojas for his helpful suggestions.     

Synthesis,Characterisation and Thermal Decomposition of Double Sulphates of Al and Cr(III) with Diisopropylammonium Ion

On evaporation at room temperature of an aqueous mixture of M(III) sulphate and diisopropylammonium sulphate in a molar ratio 1:3, double sulphates of Aland Cr as crystalline products were obtained. The stoichiometry of the obtained compounds was determined by means of elemental and TG analysis. The above compounds were characterized by their IR spectra and X-ray powder diffraction patterns, as well. It was found that they have a general empirical formula M(CH₃CHCH₃)₂NH₂(SO₄)₂·6H₂O and that they are isostructural. TG, DTG and DTA curves were done in static air atmosphere from room temperature up to 1000°C. The dehydration of the compounds takes place in one step and it points out that the six water molecules are bound in the same way. This assumption is confirmed by their IR spectra, where single sharp HOH deformation band at 1694 cm^-1 appears in both compounds. The thermal decomposition of the anhydrous compounds starts at about 260°C and is very complex. This process takes place in many steps which are not well resolved. The diisopropylammonium sulphateis prepared from the diisopropylamine by neutralization up to pH 3–4 with diluted sulphuric acid and permanent cooling in an ice-water bath. This revised version was published online in August 2006 with corrections to the Cover Date.     

Ein anionischer Oxohydroxo‐Komplex mit Bismut(III): Na6[Bi2O2(OH)6](OH)2 · 4H2O

An Anionic Oxohydroxo Complex with Bismuth(III): Na₆[Bi₂O₂(OH)₆](OH)₂ · 4H₂O Colourless, plate‐like, air sensitive crystals of Na₆[Bi₂O₂(OH)₆](OH)₂ · 4H₂O are obtained by reaction of Bi₂O₃ or Bi(NO₃)₃ · 5H₂O in conc. NaOH (58 wt %) at 200 °C followed by slow cooling to room temperature. The crystal structure (triclinic, P 1¯, a = 684.0(2), b = 759.8(2), c = 822.7(2) pm, α = 92.45(3)°, ß = 90.40(3)°, γ = 115.60(2)°, Z = 1, R1, wR2 (all data), 0, 042, 0, 076) contains dimeric, anionic complexes [Bi₂O₂(OH)₆]^4— with bismuth in an ψ¹‐octahedral coordination of two oxo‐ and three hydroxo‐ligands. The thermal decomposition was investigated by DSC/TG or DTA/TG and high temperature X‐ray powder diffraction measurements. In the final of three steps the decomposition product is Na₃BiO₃.     

Heteroleptic tri-<Emphasis Type="Italic">tert</Emphasis>-butoxysilanethiolate complexes of manganese(II)

The thermal behavior of Mn(II) silanethiolate series [Mn(SR)₂L(MeOH)_n], where R=SSi(OBut)₃, L=heterocyclic nitrogen base and n=0, 1 or 2 has been comparatively investigated using differential scanning calorimetry (DSC), thermogravimetry (TG) and TG-infrared spectoscopy (IR) techniques. The TG curves indicate the differences in the thermal decomposition due to presence of distinct N-donor ligands and labile MeOH molecules coordinated to the central atom. The first step on the TG curves (60–110°C) corresponds to the elimination of alcohol from respective complexes. The main step (150–350°C) can be assigned to the decomposition of the complexes yielding Mn₃O₄ and silica as the main final products, identified by X-ray diffraction patterns.     

Isolation,spectroscopic and thermal properties of hydrazinium tris(oxydiacetato)lanthanate(III) hemi(pentahydrate)

Oil-bath reaction of respective metal nitrate with an aqueous mixture of oxydiacetic acid (H₂oda) and hydrazine hydrate led to the formation of crystalline compounds with formula (N₂H₅)₃[Ln(oda)₃]·2.5H₂O (where Ln = La, Ce, Pr, Nd and Sm), which are stable for a week and undergo efflorescence. The resulting complexes were characterized by infrared spectral, thermal (air and nitrogen atmosphere), UV–visible and PXRD studies. From the thermal studies, both in air and nitrogen atmosphere, these compounds show endothermic dehydration below 100 °C to give anhydrous compounds. Next, the anhydrous compounds (in air) undergo endothermic decomposition between 190 and 225 °C to form Ln(Hoda)₃ intermediate, which further show exothermic decomposition to yield respective metal oxide as the end residue. But, in nitrogen atmosphere, the same anhydrous compounds exhibit endo-followed by exothermic decompositions to give respective metal as end product. This is observed as a continuous single step of decomposition in TG. The structure of (N₂H₅)₃[Nd(oda)₃]·2.5H₂O has been determined by single-crystal X-ray analysis. The neodymium atom is coordinated by nine oxygen atoms from three tridentate (O, O, O) oxydiacetate ions with tricapped trigonal prismatic geometry. In addition, both the parent acid and its compounds display strong fluorescent emission due to the ligand, which renders them as fluorescent materials at room temperature.