Correction to: Multistage thermal decomposition in films of cadmium chloride-doped PVA–PVP polymeric blend

Core/shell composites of CuC₂O₄·2H₂O@AP and ZnC₂O₄·2H₂O@AP were prepared from metal oxalates on suspended AP particles in ethanol. CuO and ZnO nano-metal oxides as the nano-catalysts were made from CuC₂O₄·2H₂O and ZnC₂O₄·2H₂O simultaneously by thermal decomposition of AP. The particle size of CuO nano-particles was very finer, and the ZnO particles showed a considerable growth during formation. The kinetic triplet of activation energy, frequency factor, and model of thermal decomposition of pure AP, CuC₂O₄·2H₂O@AP, and ZnC₂O₄·2H₂O@AP composites were estimated by applying three model-free (FWO, KAS, and Starink) and model-fitting (Starink) methods. Based on the thermal analysis, the CuC₂O₄@AP composite has better catalytic performance and the thermal decomposition temperature of AP decreased to about 126.44 °C.     

The study of thermal decomposition kinetics of zinc oxide formation from zinc oxalate dihydrate

This study is devoted to the thermal decomposition of ZnC₂O₄·2H₂O, which was synthesized by solid-state reaction using C₂H₂O₄·2H₂O and Zn(CH₃COO)₂·2H₂O as raw materials. The initial samples and the final solid thermal decomposition products were characterized by Fourier transform infrared and X-ray diffraction. The particle size of the products was observed by transmission electron microscopy. The thermal decomposition behavior was investigated by thermogravimetry, derivative thermogravimetric and differential thermal analysis. Experimental results show that the thermal decomposition reaction includes two stages: dehydration and decomposition, with nanostructured ZnO as the final solid product. The Ozawa integral method along with Coats–Redfern integral method was used to determine the kinetic model and kinetic parameters of the second thermal decomposition stage of ZnC₂O₄·2H₂O. After calculation and comparison, the decomposition conforms to the nucleation and growth model and the physical interpretation is summarized. The activation energy and the kinetic mechanism function are determined to be 119.7 kJ mol^?1 and G(α) = ?ln(1 – α)^1/2, respectively.     

草酸锌空心纳米结构的一步固相合成及其表征

本文利用醋酸锌和草酸的一步低热固相化学反应制备了草酸锌空心纳米球，并通过在该反应体系中加入表面活性剂聚乙二醇400得到了草酸锌空心纳米链。采用X-射线粉末衍射（XRD）、透射电镜（TEM）、高倍透射电镜(HRTEM)、扫描电镜(SEM)、红外(IR) 以及热重-差热(TG/DTA)分析对所合成的样品进行了表征.     

On the use of electron paramagnetic resonance to implement thermogravimetry data: the thermal decomposition of zinc oxalate dihydrate

The complementary use of thermogravimetric analysis and electron paramagnetic resonance spectroscopy enables the identification on interrelated and successive steps in the vacuum decomposition of ZnC₂O₄ · 2H₂O. After completion of the oxalate dehydration, CO adsorbed species (analogous to those previously reported on MgO) are observed by EPR, starting at a temperature of 250°C. In the temperature range 250–350°C, the CO ad-species disappear while paramagnetic ZnO_1?x and possibly CO^?₄ entities are formed. It is proposed that the latter stems from the reaction of oxygen released by the decomposition of ZnO with CO₂ produced during the oxalate decomposition. Above 300°C, ZnO_1?x and CO^?₄ disappear, leading to the formation of O^3?₃ centers. The latter are gradually decomposed between 350 and 575°C, releasing O₂ observed in EPR as O^?₂ molecular anions and trapped electrons which are again detected as ZnO_1?x. A partially reduced ZnO phase is most probably the end-product of the decomposition.     

Traitement mecanique des materiaux

Within the limits of a comparative study of solid-state transformations induced by different constraints (thermodynamics, mechanics, electromagnetics, etc.), the authors present the phase-modifications brought about by the grinding of someoxalates (K₂C₂O₄. H₂O; CaC₂O₄. H₂O; BaC₂O₄ ·n H₂O withn=0, 1/2, 1 and 2). The water vapour pressure and temperature during the mechanical treatment were selected and fixed. The specificity of the mechanical constraint is discussed. This study mainly shows that (a) the grinding may or may not bring about dehydration, but it may also bring about rehydration; (b) the evolution of a hydrate during treatment, following a well-defined process, shows all the phases known from the most hydrated to the anhydrous form; (c) the mechanical dehydration may be stopped by a change in the grinding temperature and vapour pressure conditions.     

Humidity controlled thermal analysis

The low temperature formation of crystalline zinc oxide via thermal decomposition of zinc acetylacetonate monohydrate C₁₀H₁₄O₄Zn·H₂O was studied by humidity controlled thermal analysis. The thermal decomposition was investigated by sample-controlled thermogravimetry (SCTG), thermogravimety combined with evolved gas analysis by mass spectrometry (TG-MS) and simultaneous differential scanning calorimetry and X-ray diffractometry (XRD-DSC). Decomposition of C₁₀H₁₄O₄Zn·H₂O in dry gas by linear heating began with dehydration around 60°C, followed by sublimation and decomposition above 100°C. SCTG was useful because the high-temperature parallel decompositions were inhibited. The decomposition changed with water vapor in the atmosphere. Formation of ZnO was promoted by increasing water vapor and could be synthesized at temperatures below 100°C. XRD-DSC equipped with a humidity generator revealed that C₁₀H₁₄O₄Zn·H₂O decomposed directly to the crystalline ZnO by reacting with water vapor.     

Shape-controlled fabrication of porous ZnO architectures and their photocatalytic properties

In this paper, we report a simple two-step approach to prepare porous octahedron- and rod-shaped ZnO architectures. The morphology of porous ZnO particles can be conveniently tuned by controlling morphologies of the ZnC₂O₄·2H₂O precursor. SEM and TEM characterization results indicate that these porous ZnO architectures are built up by numerous ZnO primary nanoparticles with random attachment. Based on thermogravimetry analysis, we believe that the release of water vapor, CO and CO₂ leads to the formation of high-density pores in shape-controlled particles during the calcination process. Further experimental results indicate that as-prepared porous ZnO particles exhibit good photocatalytic activity due to large surface area.     

Thermal studies on metal complexes of 5-nitroso-pyrimidine derivatives

The following Zn(II) complexes of deprotonated 6-amino-5-nitrosouracil (AH), 6-amino-3-methyl-5-nitrosouracil (BH) and 6-amino-1-methyl-5-nitrosouracil (CH) have been prepared and their thermal behaviour studied by TG and DSC techniques: ZnA₂(H₂O)₂, ZnB₂ · 4 H₂O, ZnC₂ · 4 H₂O and ZnC₂(H₂O)₂ · H₂O. The values of the dehydration enthalpy of the complexes are in the 31.3–76.5 kJ mol^?1 H₂O range and, except in the first complex, the dehydration processes take place in several steps. The pyrolysis of the complexes finishes between 540 and 725° C ZnO remaining as residue.     

Non-isothermal kinetic and thermodynamic study for the dehydration of copper(II) chloride dihydrate and nickel chloride hexahydrate

Non-isothermal dehydration of copper chloride dihydrate and nickel chloride hexahydrate were studied by using TG, DTG, DTA and DSC measurements. The copper chloride salt loses its two water molecules in one step while nickel chloride salt dehydrates in three consecutive steps. The first two steps involve the loss of 4 water molecules in two overlapped steps while the third step involves the dehydration of the dihydrate salt to give the anhydrous NiCl₂. Activation energies (ΔE) and the frequency factor (A) were calculated from DTG and DTA results. We have also calculated the different thermodynamic parameters, e.g. enthalpy change (ΔH), heat capacity (C _p) and the entropy change (ΔS) from DSC measurements for both reactants. The isothermal rehydration of the completely dehydrated salts was studied in air and under saturated vapour pressure of water. Anhydrous nickel chloride was found to rehydrate in three consecutive steps while the copper salt rehydrated in one step.     

Exploration of the thermal decomposition of zinc oxalate by experimental and computational methods

Zinc oxalate dihydrate has been synthesized by precipitation method and characterized by FT-IR, XRD and SEM-EDAX. The kinetics of dehydration and decomposition were studied by non-isothermal DSC technique in the N₂ atmosphere at different heating rates: 4, 6, 8 and 10 K min^?1. The product of thermal decomposition, ZnO has been characterized by UV, TEM, SEM-EDAX and XRD and found that the particles are in nanometer range. The activation energy for thermal dehydration and decomposition was calculated by various isoconversional methods. Furthermore, structure and reactivity of zinc oxalate have also been investigated using B3LYP/631+g (d, p) level of theory with the help of Gaussian 09W software. The theoretical investigation indicates that most probably the compound decomposes to ZnO along with the evolution of CO₂ and CO.

     

Thermal dehydration of CeP<Subscript>3</Subscript>O<Subscript>9</Subscript>·3H<Subscript>2</Subscript>O by controlled rate thermal analysis

The aim of this work is to highlight the importance of controlling the residual water vapour pressure above the sample as well as the rate of the thermal decomposition during the thermal dehydration of cerium cyclotriphosphate trihydrate CeP₃O₉·3H₂O. For this reason, the dehydration of the titled compound was followed by both techniques: the constant rate thermal analysis at P _H2O = 5 hPa and the conventional TG-DTA in air.     

Thermal decomposition kinetics and reversible hydration study of the Li2Zn(HPO4)2·H2O

The dilithium zinc hydrogen phosphate monohydrate (Li₂Zn(HPO₄)₂·H₂O) was synthesized at the ambient temperature by using zinc acetyl acetonate monohydrate, phosphoric acid and lithium hydroxide monohydrate. The thermal stability of the Li₂Zn(HPO₄)₂·H₂O was studied by non-isothermal kinetic method (Ozawa and Kissinger) from the differential scanning calorimetric (DSC) data. The studied hydrate undergoes two endothermic thermal transformations, which the first transformation is due to the release of water molecule of crystallization and the second one is due to the release of water of constituent from HPO₄^2? anions and transforms to P₂O₇^4?. The activation energies (E_a) calculated for the dehydration step and decomposition step of the Li₂Zn(HPO₄)₂·H₂O from different methods were found to be consistent. The dehydration and rehydration processes of the synthesized compound were investigated and found that the water of crystallization can be removed and rehydrated without the disrupting the structure of the material, provided it is not heated beyond 200 °C. The dehydration and rehydration processes of the synthesized Li₂Zn(HPO₄)₂·H₂O exhibits similar property to the zeolite.     

Thermal decomposition of cadmium succinate dihydrate

Thermal decomposition of cadmium succinate dihydrate, CdC₄H₄O₄·2H₂O, was studied in dynamic helium and air atmospheres by means of simultaneous TG, DTA and MS analysis. It was found that dehydration of CdC₄H₄O₄·2H₂O takes place in the temperature range 80–165°C and at low heating rates formation of monohydrate was stated. The anhydrous cadmium succinate decomposes at about 350°C to metallic cadmium. The gaseous products of cadmium succinate decomposition are CO₂ and H₂O. Formation of small amounts of 3-phenylpropanal and 1,7-octadiene during decomposition in helium was revealed. In helium cadmium evaporates at the temperature of decomposition and the residue consists of small amount of elementary carbon formed in result of pyrolysis of succinate groups. In air cadmium oxidizes and the final solid product of decomposition is CdO.     

Study of a lacunary solid phase II—Morphological and kinetic characteristics of its formation

The morphological changes which take place during the formation of the lacunary phase αH₂C₂O₄·BaC₂O₄ by isothermal dehydration of the oxalate H₂C₂O₄·BaC₂O₄·2H₂O, are characteristic for dihydrations of hydrates which, with water vapor, form a divariant system.They show that the transformation affects the entire bulk of the solid from the very first moments of the reaction. The dihydrate crystal undergo a very regular fragmentation and the pseudomorph appears as a stacking of microcrystals whose shape and dimensions are unique and independent of the size and habit of the initial crystals.The kinetic characteristics of the reaction show that the microcrystal dimensions do not depend on dehydration rate, they enable the precise role of crystalline faces in gas evacuation to be evaluated.The origin of fragmentation, the microcrystal habit produced, the anisotropy of transformation of the crystalline faces and the process of water elimination are explained by means of structural considerations.     

Thermal Decomposition and Dehydration Kinetics of Tetra(piperidinium) Octamolybdate Tetrahydrate in Air

Thermal decomposition of tetra(piperidinium) octamolybdate tetrahydrate, [C₅H₁₀NH₂]₄[Mo₈O₂₆]·4H₂O, was investigated in air by means of TG‐DTG/DTA, DSC, TG‐IR and SEM. TG‐DTG/DTA curves showed that the decomposition proceeded through three well‐defined steps with DTA peaks closely corresponding to mass loss obtained. Kinetics analysis of its dehydration step was performed under non‐isothermal conditions. The dehydration activation energy was calculated through Friedman and Flynn‐Wall‐Ozawa (FWO) methods, and the best‐fit dehydration kinetic model function was estimated through the multiple linear regression method. The activation energy for the dehydration step of [C₅H₁₀NH₂]₄[Mo₈O₂₆]·4H₂O was 139.7 kJ/mol. The solid particles became smaller accompanied by the thermal decomposition of the title compound.     

Thermoanalytical and microscopic investigations of the thermal dehydration of α-nickel (II) sulphate hexahydrate

Thermoanalytical (TA) and hot-stage microscopic techniques were employed to investigate the complicated behaviour of the non-isothermal dehydration of single crystals of α-NiSO₄·6H₂O. Non-isothermal dehydration to the tetrahydrate proceeds in two stages: (1) surface nucleation and growth of nuclei, followed by advancement of reaction fronts inward; (2) random nucleation and growth near the reaction front as well as in the bulk. Corresponding TA curves were interpreted to represent diffusional removal of evolved water vapour through the surface layer created in stage (1). The dehydration process of the tetrahydrate to the monohydrate is explained on the basis of textural structures produced in the previous step. Crack formation in the surface layer and rapid escape of the water vapour were observed in this step.     

Thermal decomposition of the biguanide complexes of the 3d-transition metals

The thermal decomposition (TG, DTG and DTA) of the complexes of biguanide with the following metals was studied: V, Cr, Mn, Co, Ni, Cu and Zn. Structural water, when present, is first eliminated at ～100–150°C; this is followed by a main decomposition state at ～300–350°C. Pyrolytic residues are analysed and characterised by their x-ray powder diffraction patterns and are found to be the oxides V₂O₅, Cr₂O₃, Mn₃O₄, Co₃O₄, NiO, CuO and ZnO, respectively. The decomposition curves of the free ligand (biguanide) and biguanide sulphate are also given. The decomposition characteristics are discussed.     

Study of the products of the dehydration reaction of CuSO4 · 5H2O in X-shaped and elliptic nuclei

The products of the dehydration of CuSO₄ · 5H₂O under different conditions have been studied by the methods of local X-ray diffraction analysis and EPR. It is shown that the dehydration in vacuo when X-shaped nuclei are formed proceeds through the formation of an intermediate product having a monohydrate composition and a crystalline lattice close to the initial lattice of the pentahydrate. Then the amorphization and crystallization of CuSO₄ · H₂O follows. When dehydration occurs in water vapour through ellipsoidal nuclei the structure of the trihydrate formed is oriented relative to the initial structure of CuSO₄ · 5H₂O.     

Thermochemistry of the Decomposition of Some Cobalt Compounds

Differential scanning calorimetry (DSC) was used to determine the molar enthalpies of dehydration and decomposition of CoC₂O₄·2H₂O, Co(HCOO)₂·2H₂O and [Co(NH₃)₆]₂(C₂O₄)₃·4H₂O. The first stage of dissociation of each compound is a single-step dehydration both in air and argon atmospheres. The next stages are decomposition processes influenced by experimental parameters. The enthalpies of dehydration and decomposition vary from compound to compound in each atmosphere. The obtained data have been related to the macromechanisms proposed for the thermal decomposition and the parallel-consecutive decomposition-oxidation processes. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal decomposition of basic copper sulphate monohydrate

The thermal decomposition of copper sulphate hydroxide hydrate, (CuO·CuSO₄). 2Cu(OH)₂·H₂O, to copper oxysulphate and CuO was investigated by X-ray phase analysis, IR spectroscopy, complex thermal analysis and electron microscopy. The effect of water vapour and time of treatment on the formation of decomposition products with a large surface area is studied. The strong decrease in specific surface area of the precipitate (from 80 m²/g to 20 m²/g) thermally treated at a temperature above 250°C is associated with the elimination of water having a coordination bond with the Cu²⁺ ion. During this process, the interplanar distances of the crystal lattice of copper sulphate hydroxide hydrate decrease. The time of decomposition of this compound essentially affects the decrease of the specific surface area. When the decomposition proceeds in an atmosphere containing water vapour sintering processes are predominating and the phase obtained has a considerably smaller specific surface area than in cases of decomposition under dry air.