Studies on the non-isothermal kinetics of the thermal decomposition of [Cu(NBOCTB)][Cu(NO3)4]· H2O

The thermal decomposition process of the complex [Cu(NBOCTB)][Cu(NO₃)₄] H₂O has been studied by TG and DTG technique, and possible intermediates of the thermal decomposition have also been conjectured from the TG and DTG curves. The results suggest that the decomposition of the complex involves five steps: The non-isothermal kinetics of steps 1, 2 and 3 have been studied by means of the Achar and Coats-Redfern method based on TG and DTG curves. Step 1 is a Coring and Growth mechanism (n= 1), its kinetic equation may be expressed as: d/dt=Ae^–E/RT(1–). Steps 2 and 3 are both two order chemical reaction mechanisms, their kinetic equations can be expressed as: d/dt=Ae^–E/RT(1–)².This project was supported by the National Natural Science Youth Fundation of China.     

Bending modes of the water molecules and the MO stretching modes in the series MF2 · 4H2O (M = Fe,Co, Ni,Zn)

The infrared spectra of the series MF₂·4X₂O (M = Fe, Co, Ni, Zn; X = H, D) are reported in the frequency ranges of the bending vibrations of the water molecules (ν₂) at 296 and ∼100 K and the MO lattice vibrations (ν_MO) at 296 K. Four ν_MO vibrations consisting of two doublets are identified using deuterium substitution. The various ν_ZnO vibrations correlate well with the metal-oxygen distances R(ZnO), and this correlation is further used to calculate R(MO)'s of the remainder of the series and to refine R(ZnO). Four ν₂(H₂O, HDO, D₂O) vibrations, consisting of two sharp overlapping bands flanked by two broad shoulders, are identified. The number of ν₂(H₂O) components, the sequence of ν₂ in the series and the correlation with R(MO) suggest that the ν₂ frequencies are mainly determined by R(MO). Using this assignment the two types of ν₂ bands are assigned to the two types of crystallographically distinct water molecules found in the MF₂·4H₂O structure.     

Study on the thermal decomposition kinetics of cis/trans-[Cu(gly)_2]·H_2O

The thermal decomposition reactions of the complexes cis/trans-[Cu(gly)2]·H2O were studied by TG-DSC methods. The results showed that they have similar decomposition process, which occur in two steps. The first step is the loss of water and the second step is the decomposition of anhydrous complexes. But for cis-[Cu(gly)2]·H2O, the temperature of losing water is higher than that of trans-isomer. Their reaction mechanisms of the two-step decomposition were also proposed.     

Thermal magnetic investigation of the decomposition of NixMn1−xC2O4·2H2O

The systems Ni_xMn_1?xC₂O₄·2H₂O (x = 0.11, 0.34) are characterized by XRD, SEM, TG/DTA, EGA-MS and magnetic measurements. The last confirmed that the studied samples are real solid solutions. The SEM reveals that the morphology depends on both the excess of C₂O₄^2? and the initial ratio Ni/Mn. The thermal magnetic investigations (in situ) show that: (i) the presence of Ni in Ni_xMn_1?xC₂O₄·2H₂O leads to decreasing in the decomposition temperature in regard to that of the manganese oxalate; (ii) upon increasing the Ni content the temperature of decomposition (in air) is growing up; (iii) the presence of Ni stabilizes the manganese with respect to oxidation, in spite of the occurring process of decomposition.     

Role of Bismuth Oxide in Bi-MCo2O4（M=Co,Ni,Cu,Zn） Catalysts for Wet Air Oxidation of Acetic Acid

Two series of cobalt (Ⅲ)-containing spinel catalysts were prepared by the decomposition of the corre-sponding nitrates. The catalysts doped with bismuth oxide exhibit a higher activity in the wet air oxidation ofacetic acid than those without dopant bismuth oxide. The catalysts were investigated by XRD, TEM, ESR,UV-DRS and XPS, and the interaction between Co and Bi was studied as well. It has been found that nano-sized bismuth oxide is paved on the surface of cobalt spinel crystal and the structures of cobalt(Ⅲ)-containingspinel are still maintained. The shift of the binding energy of Bi4/7/2 is related to the catalytic activity of thesecatalysts doped with bismuth oxide.     

Studies of the Henry reaction catalyzed by Cu–O and Zn–O complexes with dimethoxysilane-bridged derivatives

Dimethyldimethoxysilane, methylphenyldimethoxysilane, and diphenyldimethoxysilane have been synthesized by a one-step, simple method and used as catalysts in the Henry reaction with Cu(OAc)₂·H₂O and Zn(OAc)₂·2H₂O, affording 60–96% conversion under the optimum catalytic conditions.     

Synthesis, Characterization and Crystal Structure of the First Tri-nuclear MFe2（M = Cu and Ni） Complexes Based on Nitroprusside

IntroductionSince 184 8,whenPlayfairpublishedthefirstpaperrelatedtonitroprussides ,1thetransitionmetalpenta cyanonitrosylmetallatehydrateshavebeenwidelystudiedbecauseoftheirimportantrolesinmolecularsieves ,cationexchangers,electronscavengersandradionuclidesor bents .2 4 Thenitroprussides ,regardlessofthecationicmetal,arecurrentlyemployedasreversibleinhibitorsofagroupofenzymesknownassuperoxidedismutases .5Recently ,using [Fe(CN ) 5(NO) ]2 - asabuildingblock ,somenitroprusside bridgedpolymeri…     

Magnetic properties of isostructural M(H2O)4[Au(CN)4]2-based coordination polymers (M = Mn, Co, Ni, Cu, Zn) by SQUID and μSR studies

A series of isomorphous M(H(2)O)(4)[Au(CN)(4)](2)·4H(2)O (M = Mn, Co, Ni, Zn; Cu is similar) coordination polymers was synthesized from the reaction of M(II) with KAu(CN)(4); they consist of octahedrally coordinated metal centres with four equatorial water molecules and trans-axial N-cyano ligands from [Au(CN)(4)](-) moieties, generating a linear 1-D chain of M(H(2)O)(4)[Au(CN)(4)]-units. An additional interstitial [Au(CN)(4)](-) unit forms AuN and hydrogen bonds with adjacent chains. The Cu(II) system readily loses water to yield Cu[Au(CN)(4)](2)(H(2)O)(4), which was not structurally characterized. The magnetic properties of these polymers were investigated by a combination of SQUID magnetometry and zero-field muon spin relaxation (ZF-μSR). Only weak antiferromagnetic interactions along the chains are mediated by the [Au(CN)(4)]-units, but the ZF-μSR data indicates that interchain interactions yield a phase transition to a magnetically ordered state for Cu[Au(CN)(4)](2)(H(2)O)(4) below 0.6 K, while for M(H(2)O)(4)[Au(CN)(4)](2)·4H(2)O (M = Co), depopulation of zero-field split Kramer's doublets to an effective "S = 1/2" ground state yields a transition to a spin-frozen magnetic state below 0.26 K. On the other hand, only a simple slowing-down of spins above 0.02 K is observed for the more weakly zero-field split M(H(2)O)(4)[Au(CN)(4)](2)·4H(2)O (M = Mn, Ni) complexes.     

Determination of kinetic triplet of the synthesized Ni3(PO4)2·8H2O by non-isothermal and isothermal kinetic methods

The nickel phosphate octahydrate (Ni₃(PO₄)₂·8H₂O) was synthesized by a simple procedure and characterized by FTIR, TG/DTG/DTA, AAS, and XRD techniques. The morphologies of the title compound and its decomposition product were studied by the SEM method. The dehydration process of the synthesized hydrate occurred in one step over the temperature range of 120–250 °C, and the thermal decomposition product at 800 °C was found to be Ni₃(PO₄)₂. The kinetic parameters (E and A) of this step were calculated using the Ozawa–Flynn–Wall and Kissinger–Akahira–Sunose methods. The iterative methods of both equations were carried out to determine the exact values of E, which confirm the single-step mechanism of the dehydration process. The non-isothermal kinetic method was used to determine the mechanism function of the dehydration, which indicates the contracting disk mechanism of R₁ model as the most probable mechanism function and agrees well with the isothermal data. Besides, the isokinetic temperature value (T _i) was calculated from the spectroscopic data. The thermodynamic functions of the activated complex (ΔS ^≠, ΔH ^≠, and ΔG ^≠) of the dehydration process were calculated using the activated complex theory of Eyring. The kinetic parameters and thermodynamic functions of the activated complex for the dehydration process of Ni₃(PO₄)₂·8H₂O are reported for the first time.     

MF2 vibrations and librations of water molecules in the series MF2·4H2O (M = Fe,Co, Ni or Zn)

The infrared absorption spectra of the series MF₂·4H₂O (M = Fe, Co, Ni or Zn) and of the respective deuterates were recorded at 296 and ∼ 100 K in the 1200-400 cm⁻¹ wavenumber region. Using the known ZnF₂·4H₂O structure as a model, the number of i.r. active librations and MF₂ vibrations was predicted with the aid of a group theoretical treatment. The librations were distinguished from the MF₂ and MO vibrations and assigned, using isotopic ratios and correlations between the unit cell volumes, the uncoupled OH and OD stretch vibrations of HDO and the twisting libration. The six librations are assigned to two types of water molecules with low symmetry and with different hydrogen bond strengths, and are compatible with an orthorhombic Pca2₁ structure. The v₁ and v₃ intramolecular MF₂ vibrations are assigned, using ZnF₂·4H₂O crystal data and matrix-isolated v₁ and v₃ (v_1.3) values as guide. Shifts of v_1.3 and v₁/v₃ relative to the matrix-isolated values suggest smaller MF bond lengths. The shifts in the values of v_1.3 and v₁/v₃ upon deuteration and lowering of the temperature indicate smaller MF bond lengths and FMF angles.     

Comparative investigation of several types of γ-Fe2O3 ferro-powders by the methods of thermal analysis

Commercial -Fe₂O₃ ferro-powders obtained by the sulphate technology, have been compared by means of thermal analysis. Depending on the technology, each type of -F₂O₃ was found to be characterized by certain thermal transformation sequence. Thermal analysis and data systematisation allowed to find criteria for the qualification of - Fe₂O₃ particles. LKN ferropowders were found to have more disbalanced surface properties and chemical composition than PERK and GX ferro-powders.

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Zusammenfassung Mittels Thermoanalyse wurden kommerzielle, mit der Sulfattechnologie erhaltene -Fe₂O₃ Ferropulver untereinander verglichen. In Abhängigkeit von der Technologie kann jeder -Fe₂O₃-Typ durch gewisse thermische Umwandlungsfolge charakterisiert werden. Thermoanalyse und Datensystematisierung ermöglichten es, Kriterien zur Qualifizierung von -Fe₂O₃ Partikeln zu finden. Man fand, daß LKN Ferropulver mehr unausgewogene Oberflächeneigenschaften und chemische Zusammensetzungen besitzt als PERK- und GX-Ferropulver.

     

Effect of the thermal treatment conditions on the formation of zinc ferrite nanocomposite, ZnFe2O4, by sol–gel method

Zinc ferrite nanocomposite was synthesized via thermal decomposition of zinc acetate and iron nitrate at three different temperatures (350, 450, and 550 °C). The influence of the thermal decomposition of precursors on the formation zinc ferrites was studied by differential thermal gravimetry and thermogravimetry (TG). The TG curve shows two steps for the thermal decomposition with mass loss of 17.3 % at 78 °C and 63.3 % at 315 °C. The prepared zinc ferrites nanocomposite was characterized by X-ray diffraction and scanning electron microscopy. The X-ray diffractograms of ZnFe₂O₄ shows that a crystalline phase, spinel system is formed. SEM micrograph of the zinc ferrite nanocomposite indicates the formation of uniformly spherical 48-nm nanograins. The properties of the zinc ferrite phase were strongly dependent on their calcinations temperature and molar ratio of precursors.     

Catalytic activity of nanocrystalline ZnM2O4 (M = Fe,Co) prepared via simple and facile synthesis of thermal decomposition of mixed metal complexes of Schiff bases generated from α-ketobutyric acid and diaminoguanidine

Metal complexes ([ML₂], where M = Fe, Co, or Zn; HL = 2-[(6-ethyl-5-oxo-4,5-dihydro-2H-[1,2,4]triazin-3-ylidene)-hydrazono]-butyric acid, C₉H₁₃N₅O₃) of a Schiff base derived from α-ketobutyric acid (α-KBA) and diaminoguanidine (Damgu) were synthesized and characterized using elemental, spectral, and thermal studies. The metal complexes exhibited similar decomposition behavior, with a highly exothermic final decomposition step resulting in the formation of metal oxides. Isomorphism among the complexes was revealed using a powder X-ray diffraction (PXRD) technique. Solid solution precursors ([Zn_1/3M_2/3(L)₂], where M = Fe, Co) were synthesized and characterized using various physico-chemical techniques. A thermal decomposition technique was used to prepare spinel-type zinc cobaltite (ZnCo₂O₄) and zinc ferrite (ZnFe₂O₄) nanocrystalline particles with the synthesized single source precursors. Structural studies using PXRD ascertained the predominant crystal phase to be spinel. Transmission electron microscopy (TEM) and high-resolution TEM (HRTEM) showed a mean nanoparticle size of 18 ± 2 nm. Magnetic measurements revealed a weak magnetic behavior in the synthesized spinels. In the aqueous phase, the spinels exhibited catalytic activity, reducing 4-nitrophenol (4-NP) in the presence of NaBH₄ at room temperature. Additionally, the study demonstrated that the catalyst can be recovered and reused for five cycles with a more than 85% conversion efficiency.     

Catalytic effect investigation of α-Fe2O3 and α-Fe2O3-CMS nanocomposites on the thermal behavior of NC/DEGDN mixture: DSC measurements and kinetic modeling

In this work, the thermal behavior and kinetics of energetic systems containing α-Fe₂O₃ and iron oxide–carbon mesospheres (α-Fe₂O₃-CMS) with nitrocellulose (NC)/diethylene glycol dinitrate (DEGDN)-based composites have been investigated using differential scanning calorimetry DSC and four isoconversional kinetic methods, respectively. The obtained results indicate that NC/DEGDN show only one decomposition peak, corresponding to the decomposition of the nitrate esters. Furthermore, the introduction of α-Fe₂O₃ and α-Fe₂O₃-CMS have lowered the peak temperature by 3.1 °C and 4.7 °C, respectively. Besides, the activation energy of the thermal decomposition of NC/DEGDN was decreased by 11.9 kJ/mol and 27.97 kJ/mol, after the introduction of α-Fe₂O₃ NPs and α-Fe₂O₃ NPs supported on CMS. These results confirm the good catalytic effect of the added catalysts on the thermal decomposition of the NC/DEGDN mixtures. However, the best catalytic effect was provided by the α-Fe₂O₃-CMS. Furthermore, the three considered systems were found to decompose according to different integral models g(α).     

Microstructure and electrical properties of IrO2 prepared by thermal decomposition of IrCl3·x H2O: Role played by the conditions of thermal treatment

Some features of the thermal decomposition of IrCl₃·3 H₂O in an oxygen atmosphere are presented. The formation of IrO₂ phases has been followed by X-ray diffractometry, and the onset of definite reflections has been documented for samples pyrolyzed at 350° C, although moderate weight losses are observed by thermogravimetry at this temperature. The effect of the thermal history of iridium oxide coatings on their structure has been studied by means of electrical resistance measurements. An explanation of the results has been attempted in terms of impurity segregation to the oxide grain boundaries.     

The thermal dehydration and decomposition of Ba[Cu(C2O4)2(H2O)]·5H2O

The thermal behaviour of Ba[Cu(C₂O₄)₂(H₂O)]·5H₂O in N₂ and in O₂ has been examined using thermogravimetry (TG) and differential scanning calorimetry (DSC). The dehydration starts at relatively low temperatures (about 80°C), but continues until the onset of the decomposition (about 280°C). The decomposition takes place in two major stages (onsets 280 and 390°C). The mass of the intermediate after the first stage corresponded to the formation of barium oxalate and copper metal and, after the second stage, to the formation of barium carbonate and copper metal. The enthalpy for the dehydration was found to be 311±30 kJ mol^–1 (or 52±5 kJ (mol of H₂O)^–1). The overall enthalpy change for the decomposition of Ba[Cu(C₂O₄)₂] in N₂ was estimated from the combined area of the peaks of the DSC curve as –347 kJ mol^–1. The kinetics of the thermal dehydration and decomposition were studied using isothermal TG. The dehydration was strongly deceleratory and the -time curves could be described by the three dimensional diffusion (D3) model. The values of the activation energy and the pre-exponential factor for the dehydration were 125±4 kJ mol^–1 and (1.38±0.08)×10¹⁵ min^–1, respectively. The decomposition was complex, consisting of at least two concurrent processes. The decomposition was analysed in terms of two overlapping deceleratory processes. One process was fast and could be described by the contracting-geometry model withn=5. The other process was slow and could also be described by the contracting-geometry model, but withn=2.The values ofE _a andA were 206±23 kJ mol^–1 and (2.2±0.5)×10¹⁹ min^–1, respectively, for the fast process, and 259±37 kJ mol^–1 and (6.3±1.8)×10²³ min^–1, respectively, for the slow process.Dedicated to Prof. Menachem Steinberg on the occasion of his 65th birthday