Dynamic Air Atmosphere Research Articles

Thermal behavior of Cd2+ and Co2+ phenyl-vinyl-phosphonates under non-isothermal condition

The thermal behavior of Cd2+ and Co2+ phenyl-vinyl-phosphonates was studied using two different experimental strategies: the coupled TG-EGA (FTIR) technique by decomposition in nitrogen respectively air, and the kinetic analysis of TG data obtained in dynamic air atmosphere at four heating rates. In nitrogen two decomposition steps were observed: the loss of crystallization water, respectively the decomposition of the phenyl-vinyl radical. In air, the same dehydration was observed as the first step, but the second one is a thermooxidation of the organic radical with formation of the pyrophosphoric anion.

Thermal decomposition of cadmium formate in inert and oxidative atmosphere

Thermal decomposition of cadmium formate, Cd(HCOO) 2, was studied in dynamic helium and air atmosphere by means of simultaneous TGA, DTA and MS analysis. It was found that the cadmium formate decomposes at about 210 °C to metallic cadmium and cadmium carbonate which next decomposes with formation of cadmium oxide. In helium cadmium melts, evaporates and the reaction residue consists of CdO and a small amount of elementary carbon formed in result of pyrolysis of formate groups. In air cadmium oxidizes and the final solid product of decomposition is CdO. The gaseous products of cadmium formate decomposition are: carbon dioxide, water, carbon monoxide, formaldehyde, methyl alcohol and methyl formate.

Thermal characterization of new complexes of Zn(II) and Cd(II) with some bipyridine isomers and propionates

Abstract New mixed ligand complexes of the following stoichiometric formulae: M(2-bpy)2(RCOO)2·nH2O, M(4-bpy)(RCOO)2·H2O and M(2,4’-bpy)2(RCOO)2·H2O (where M(II)=Zn, Cd; 2-bpy=2,2’-bipyridine, 4-bpy=4,4′-bipyridine, 2,4′-bpy=2,4′-bipyridine; R=C2H5; n=2 or 4) were prepared in pure solid-state. These complexes were characterized by chemical and elemental analysis, IR and conductivity studies. Thermal behaviour of compounds was studied by means of DTA, DTG, TG techniques under static conditions in air. The final products of pyrolysis of Cd(II) and Zn(II) compounds were metal oxides MO. A coupled TG/MS system was used to analyse of principal volatile products of thermal decomposition or fragmentation of Zn(4-bpy)(RCOO)2·H2O under dynamic air and argon atmosphere. The principal species correspond to: C+, CH+, CH3 +, C2H2 +, HCN+, C2H5 + or CHO+, CH2O+ or NO+, CO2 +, 13C16O2 + and 12C16O18O+ and others; additionally CO+ in argon atmosphere.

Thermal decomposition kinetics of some aromatic azomonoethers

Thermal analysis of 4-[(4-chlorobenzyl)oxy]-4′-chloro-azobenzene dye, exhibiting liquid crystalline properties, was performed in dynamic air atmosphere. The compound behavior was investigated using TG, DTG, DTA and DSC techniques, under non-isothermal linear regime. The evolved gases were analyzed by FTIR spectroscopy. Kinetic parameters of the first decomposition step were obtained by means of multi-heating rates methods, such as isoconversioanl methods, IKP method and Perez-Maqueda et al. criterion.

Thermal behavior study and decomposition kinetics of salbutamol under isothermal and non-isothermal conditions

Abstract The thermal decomposition of salbutamol (β2 — selective adrenoreceptor) was studied using differential scanning calorimetry (DSC) and thermogravimetry/derivative thermogravimetry (TG/DTG). It was observed that the commercial sample showed a different thermal profile than the standard sample caused by the presence of excipients. These compounds increase the thermal stability of the drug. Moreover, higher activation energy was calculated for the pharmaceutical sample, which was estimated by isothermal and non-isothermal methods for the first stage of the thermal decomposition process. For isothermal experiments the average values were E act=130 kJ mol−1 (for standard sample) and E act=252 kJ mol−1 (for pharmaceutical sample) in a dynamic nitrogen atmosphere (50 mL min−1). For non-isothermal method, activation energy was obtained from the plot of log heating rates vs. 1/T in dynamic air atmosphere (50 mL min−1). The calculated values were E act=134 kJ mol−1 (for standard sample) and E act=139 kJ mo...

Thermal decomposition kinetics of some aromatic azomonoethers

Thermal analysis of three azomonoether dyes, exhibiting liquid-crystalline properties, was performed in dynamic air atmosphere. Thermal stability studies and the evaluation of the kinetic parameters of each physical or chemical transformations are essential for a full characterization, before attempting accurate thin films' depositions of such materials used in non-linear optical applications. New synthesized dyes with general formula: Cl CH 2 -O N=N R where R is a nematogenic group: CN, CF 3 or a highly polarizable group: NO 2 were investigated using TG, DTG, DTA and DSC techniques, under non-isothermal regime. The evolved gases were analyzed by FTIR spectroscopy. The activation energies of the first decomposition step were evaluated for each compound, the obtained results revealing complex mechanisms.

Kinetics of non-isothermal decomposition of three IRGANOX-type antioxidants

In the present work a comparative kinetic study was performed on the thermal behavior of three antioxidants of IRGANOX-type (L101, L109 and L115) in dynamic air atmosphere under non-isothermal conditions.

Kinetics of thermal decomposition of mixed-ligand nikkel(II) and copper(II) complexes of 4-acyl pyrazolone derivative and pyridine

Thermal behaviors of two mixed-ligand complexes, [Ni(PMPP-SAL)(Py)3] and [Cu(PMPP-SAL)Py]·MeOH, (PMPP-SAL=1-phenyl-3-methyl-4-(salicylidene hydrazide)-propenylidene-pyrazolone-5, Py=pyridine), were studied by TG-DTG-DTA in dynamic air atmosphere. The complexes show the loss of pyridine molecule is followed by the decomposition of the PMPP-SAL anion and give respective metal oxides as residues. Meanwhile, the Ozawa-Flynn-Wall model-free analyses and multivariate non-linear regressions were applied to perform single and overall steps optimization. Kinetic parameters were given and the most probable mechanism functions were suggested in this study.

Study of the aluminothermic reduction of niobium pentoxide through thermal analysis experiments and high energy milling processing

Aluminothermic reduction of niobium pentoxide was studied through thermal analysis techniques such as differential thermal analysis (DTA) and thermogravimetry (TG) as well as through high energy milling processing. Reactants mixtures were composed by powders of Nb2O5 and Al. In the case of DTA-TG experiments, different molar ratios Nb2O5:Al were heated in a dynamic atmosphere of synthetic air under controlled conditions. The high energy milling runs were carried out via SPEX vibratory mill under argon atmosphere and with milling power equal to 7:1 (ratio of mass of balls to mass of mixture) with 10 pct excess of Al over the stoichiometric mass of aluminum necessary. In both kinds of experiments, X ray diffraction was used in order to identify the products of reaction. From DTA-TG experiments, it was possible to determine the experimental value of the enthalpy change (-595.9 kJ.mol-1), which is near to the theoretical one. From the milling experiments, it was possible to verify the possibility of the occurance of aluminothermic reducion of niobium pentoxide via this kind of processing.

Thermal behaviour of some industrial and food dyes

Thermal behavior of four food dyes, i.e. tartrazine, crysoine, azorubine and amarant was studied under non-isothermal conditions, in dynamic air atmosphere and at heating rates of 5, 10, 15 and 20°C min–1. The TG data were correlated to the FTIR spectra of each sample, before and after the thermal decomposition. Kinetic study by processing the TG data was performed. The main conclusion of this study is that the non-parametric kinetic method allows a separation of the steps of a complex process and that the values of the activation energy obtained by this method agree satisfactory with that of Flynn–Wall–Ozawa estimation.

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.

Influence of Heating Rate on the Burning Profiles of Hazelnut Shell

In this study, hazelnut shell was subjected to thermogravimetric analysis to establish burning profiles in a dynamic dry air atmosphere. The Turkish hazelnut shell with a particle size of −0.250 mm was heated up to 1,173 K by heating rates of 5, 10, 20, 30, 40, and 50 K/min. This study revealed that heating rate during oxidation is an important parameter affecting thermal behavior of hazelnut shell. A strong relation was determined between the heating rate and the intensity of the peaks on the burning profiles.

Thermal reactivity of rapeseed ( Brassica napus L.) under different gas atmospheres

Non-isothermal thermogravimetric method was applied to rapeseed to investigate its thermal reactivity under both individual dynamic atmospheres of nitrogen, steam, carbon dioxide and dry air, and under several mixtures of these gases (nitrogen + steam), (steam + dry air), and (nitrogen + carbon dioxide + steam). In this method, the sample was heated from ambient to 1273 K with a constant heating rate of 20 K/min. The trend of the TGA curves and the derived DTG profiles were interpreted regarding the conversion yields and the reactivity of the samples. Conversion yields of biomass to gaseous products changed in the range of 75–94% on original basis, with respect to the atmosphere under which the experiment was carried out. The maximum rates of the mass losses from the sample were found between 2.6 and 4.3 mg/min. The activation energies were calculated using the method of Coats–Redfern, and varied between 21.3 and 96.0 kJ/mol.

TG/DTA/MS/IR study on decomposition of cadmium malonate hydrates in inert and oxidative atmosphere

Thermal decomposition of cadmium malonate hydrates was studied in dynamic helium and air atmospheres. It was found that content of hydration water in the initial sample strongly influences the way of decomposition reaction. The dehydration of cadmium malonate hydrate takes place in the temperature range 80–170 °C. The anhydrous cadmium malonate decomposes at about 250 °C. It was stated that the primary solid product of cadmium malonate decomposition is metallic cadmium. The gaseous products of cadmium malonate decomposition are CO 2, acetone, isobutylene and propyne and traces of water, acetic acid and oxygen. In helium majority of cadmium evaporates and the residue consists of small amount of elementary carbon formed in result of pyrolysis of malonate. The residue after decomposition of cadmium malonate with low amount of crystallization water molecules contains additionally CdO. The secondary reactions between decomposition products occur: oxidation of cadmium by oxygen in statu nascendi and formation of CdCO 3 in reaction between cadmium oxide and CO 2. In air cadmium instantaneously oxidizes and the final solid product of decomposition is CdO.

Thermal behaviour of TEGMMA copolymers obtained by photopolymerization using iron complexes

Copolymers of methyl methacrylate (MMA) and triethyleneglycol dimethacrylate (TEGDMA) obtained by photoinitiated polymerization using Fe(III) complexes were submitted to thermogravimetry (TGA) under dynamic air atmosphere and N2, and differential scanning calorimetric analysis (DSC). Thermal events were observed only between 90 - 110 ºC. Glass transitions were observed at ca. 100 ºC, followed by an exothermic peak at 170 ºC. The exothermic peak was assigned to a thermal curing process due to the presence of unreacted vinyl groups of the monomers. DSC revealed to be a useful tool to evaluate the curing completeness in this kind of material, using small amounts of sample in relatively short time.

Estudo termogravimétrico do efeito da temperatura e da atmosfera na absorção de dióxido de enxofre por calcário

Thermogravimetry was applied to investigate the effects of temperature and atmosphere on conversion of sulfur dioxide (SO2) absorbed by limestone. Ranges of temperature and particle size were studied, typical of fluidized-bed coal combustion. Isothermal experiments were performed at different temperatures (between 750 and 950 oC) under local atmospheric pressure (~ 697 mmHg) in dynamic atmospheres of air and nitrogen. The maximum conversion was 29% higher in nitrogen atmosphere than in air atmosphere. The optimum conversion temperature was found at 831 oC in air atmosphere and at 894 oC in nitrogen atmosphere.

Thermal Degradation of Bisphenol A Type Novolac Epoxy Resin Cured with 4,4′-Diaminodiphenyl Sulfone

The curing reaction of bisphenol A type novolac epoxy resin (bis-ANER) with 4,4′-diaminodiphenyl sulfone (DDS) was investigated with Fourier-transform infrared (FTIR) spectroscopy. It was found that the obvious structure changes involve the disappearance of epoxide groups and increase of hydroxyls. Thermal degradation of the bis-ANER/DDS network was studied with thermogravimetry in both dynamic air and nitrogen atmospheres. The degradation takes place in two steps in air but in only one step in nitrogen. FTIR measurement was carried out to identify the changes in the structure during the degradation at different steps. In addition, the thermal degradation reaction mechanism of bis-ANER/DDS with the Coats-Redfern method showed that the kinetic model function of the thermal degradation obeys the Avrami-Erofeev model equation, that is, g(α) = [−ln(1 − α)]2/3.

New complexes of Mn(II), Co(II), Ni(II) AND Cu(II) with 2,2’- OR 2,4’-bipyridine and formates (Synthesis, thermal and other properties)

New mixed-ligand complexes with empirical formulae: Mn(2-bpy)1.5L2·2H2O, M(2-bpy)2L2·3H2O (M(II)=Co, Cu), Ni(2-bpy)3L2·4H2O and M(2,4’-bpy)2L2·2H2O (where 2-bpy=2,2’-bipyridine, 2,4’-bpy=2,4’-bipyridine; L=HCOO– ) have been obtained in pure solid-state. The complexes were characterized by chemical and elemental analysis, IR and VIS spectroscopy, conductivity (in methanol and dimethylsulfoxide). The way of metal-ligand coordination discussed. The formate and 2,4’-bpy act as monodentate ligands and 2-bpy as chelate ligand. The new complexes with ligand isomerism were identified. During heating the complexes lose water molecules in one or two steps. Thermal decomposition after dehydration is multistage and yields corresponding metal oxides as final products. A coupled TG-MS system was used to analysis principal volatile thermal decomposition (or fragmentation) products of Ni(2,4’-bpy)2(HCOO)2·2H2O under dynamic air or argon atmosphere.

Thermal degradation and their kinetics of biodegradable poly(butylene succinate- co-butylene terephthate)s under nitrogen and air atmospheres

In this study, thermal degradation and their related kinetics have been investigated mainly by means of thermal gravimetrical analyzer (TGA) under the dynamic nitrogen and air atmospheres for the chemically prepared biodegradable aliphatic–aromatic copolyesters of poly(butylene succinate- co-butylene terephthalate) (PBST). To further shed new lights on the comonomer molar composition and experimental condition dependences of thermal degradation kinetics, the as-known Friedman model was at first applied to quantitatively evaluate the kinetic parameters in terms of activation energy ( E), degradation reaction order ( n) and the frequency factor ( Z). The results clearly demonstrated that thermal stabilities of these PBST copolyesters were substantially enhanced with the incorporation of more rigid butylene terephthalate comonomer, and tended to be much better in nitrogen than in air. Furthermore, the Friedman, Freeman–Carroll and Chang models were concurrently employed to quantitatively evaluate the thermal degradation kinetic parameters of the PBST copolyesters in nitrogen at different heating rates of 1, 2 and 5 K/min. It was found that the thermal degradation kinetic parameters for the PBST copolyesters were strongly dependent on the heating rate and calculating models. In addition, life-time parameters of the biodegradable PBST copolyesters were first calculated to predict the maximum usable temperatures, and this would be useful for practical application of these new bio-based green plastics.

Synthesis, characterization and thermal studies on solid compounds of 2-chlorobenzylidenepyruvate of heavier trivalent lanthanides and yttrium(III)

Solid-state compounds of general formula LnL3⋅nH2O, where Ln represents heavier lanthanides and yttrium and L is 2-chlorobenzylidenepyruvate, have been synthesized. Chemical analysis, simultaneous thermogravimetry-differential analysis (TG-DTA), differential scanning calorimetry (DSC), X-ray powder diffractometry, elemental analysis and infrared spectroscopy have been employed to characterize and to study the thermal behaviour of these compounds in dynamic air atmosphere.