Interactions of 2,5- and 3,5-dimethylphenols with co-exchanged montmorillonite

The influence of different steric and electronic properties of 2,5- and 3,5-dimethylphenols (2,5 and 3,5-DMP) on the type of interactions with Cobalt-exchanged montmorillonite (Co-MMT) was studied. The results of X-ray diffraction (XRD), IR-spectroscopy and thermal (TG, DTG) analysis show that phenol derivatives are intercalated into the interlayer space of montmorillonite. Thermal decomposition in the temperature interval 20–700 °C of Co-MMT with 3,5-DMP proceeds in four steps while Co-MMT with 2,5-DMP decompose only in three steps. These differences are connected with different acid–base interactions of individual phenol derivatives in the interlayer space of montmorillonite, which is in agreement with the results of IR-spectroscopy.     

Co(II)-exchanged montmorillonite with ethylenediamine,trimethyl- and tetramethyl-ethylenediamine and their thermal decomposition

The influence of different steric properties of ethylenediamine (EDA), trimethylenediamine (TrMeEDA) and tetraethylenediamine (TeMeEDA) on the type of interactions with Co(II)-exchanged montmorillonite and thermal decomposition of these materials were studied. The results of X-ray diffraction (XRD), thermogravimetry (TG), derivative thermogravimetry (DTG) and spectral analysis shows that the studied ethylenediamines are intercalated into the interlayer space of montmorillonite. Thermal decomposition at 20–500 °C of studied samples with EDA proceeds in three steps (the release of chemosorbed amines, coordinated EDA and dehydroxylation) while the sample with TrMeEDA and TeMeEDA in five steps (also release the protonated forms). The effect of different steric properties of individual diamines is evident.     

Thermal behavior of Cu(II)-, Cd(II)-, and Hg(II)-exchanged montmorillonite complexedwith cysteine

The thermal behavior of montmorillonite and organically modified montmorillonite, both treated with heavy metal cations [Cu(II), Cd(II) and Hg(II)], was characterized via thermal analyses (TG, DTG and DTA) combined with evolved species gas mass spectrometry (MS-EGA), and X-ray diffraction at in situ controlled temperature (HTXRD). The reactions involving Cu(II)- and Cd(II)-montmorillonite samples are mostly related to H₂O and OH loss, unlike Hg(II)-montmorillonite, where effects associated to Hg(II) loss are also present. Finally reactions related to dehydration, dehydroxylation and to organic matter decomposition can be observed in montmorillonite samples treated with cysteine.     

Thermoanalytical, spectral and biological study of 4-bromobenzoatozinc(II) complexes containing bioactive organic ligands

New zinc(II) 4-bromobenzoate complex compounds with general formula [Zn(4-BrC₆H₄COO)₂L₂]·xH₂O (where L?=?urea, nicotinamide, phenazone or thiourea, x?=?0?C2) were prepared and characterized by elemental analysis, IR spectroscopy and thermal analysis. The thermal decomposition of hydrated compounds started with dehydration process. During the thermal decomposition, the neutral organic ligand, bis(4-bromophenyl)methanone and carbon dioxide were evolved. The solid intermediates and volatile products of thermal decomposition were proved by IR spectroscopy and mass spectrometry. The final solid product of the thermal decomposition heated up to 800?°C was zinc oxide, which was confirmed by X-ray powder diffractometry. Antimicrobial activity of the prepared compounds was tested against various strains of bacteria, yeasts and filamentous fungi (E. coli, S. aureus, C. albicans, R. oryzae, A. alternata and M. gypseum). It was found that bacterium S. aureus and fungi A. alternata are the most sensitive to the studied compounds.     

Ni-exchanged montmorillonite with methyl-, dimethyl- and trimethylamine and their thermal properties

The influence of different steric properties of methylamine (MA), dimethylamine (DIMA) and trimethylamine (TRMA) on the type of interactions with Ni-exchanged montmorillonite and thermal properties of these materials were studied. The results of diffraction, spectral (IR) and thermal (TG, DTG) analysis show that MA, DIMA and TRMA are intercalated into the interlayer space of montmorillonite. Thermal decomposition in the temperature interval 20–450°C of studied samples with MA and DIMA proceeds in three steps (the release of chemisorbed amines, coordinated amines and alkylammonium cations) while the sample with TRMA decompose only in two steps (the peak corresponds to the release of coordinated TRMA is absent). The effect of different steric properties of individual amines is evident.     

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.     

Synthesis,characterization, and thermal study of solid-state alkaline earth metal mandelates,except beryllium and radium

Characterization, thermal stability, and thermal decomposition of alkaline earth metal mandelates, M(C₆H₅CH(OH)CO₂)₂, (M = Mg(II), Ca(II), Sr(II), and Ba(II)), were investigated employing simultaneous thermogravimetry and differential thermal analysis or differential scanning calorimetry, (TG–DTA or TG–DSC), infrared spectroscopy (FTIR), complexometry, and TG–DSC coupled to FTIR. All the compounds were obtained in the anhydrous state and the thermal decomposition occurs in three steps. The final residue up to 585 °C (Mg), 720 °C (Ca), and 945 °C (Sr) is the respective oxide MgO, CaO, and SrO. For the barium compound the final residue up to 580 °C is BaCO₃, which is stable until 950 °C and above this temperature the TG curve shows the beginning of the thermal decomposition of the barium carbonate. The results also provide information concerning the thermal behavior and identification of gaseous products evolved during the thermal decomposition of these compounds.     

Synthesis, spectroscopy, electrochemistry and thermal study of uranyl N3O2 Schiff base complexes

The new [UO₂L(CH₃OH)] [where L?=?bis(salicylaldehyde)2,6-diiminopyridine (L¹), bis(5-methoxysalicylaldehyde)2,6-diiminopyridine (L²), bis(5-bromosalicylaldehyde)2,6-diiminopyridine (L³), bis(5-nitrosalicylaldehyde)2,6-diiminopyridine (L⁴)] complexes were synthesized and characterized by IR, UV?Cvis and elemental analysis. Methanol solvent is coordinated to uranyl complexes. The electrochemical properties of the uranyl complexes were investigated by cyclic voltammetry in DMF solvent. Thermogravimetry and differential thermoanalysis of the uranyl complexes were carried out in the range of 20?C700?°C. The UO₂L⁴ complex was decomposed in two and the others were decomposed in three stages. Up to 85?°C, the coordinated solvent was released then the Schiff base ligands were decomposed in one or two steps. Decomposition of synthesized complexes is related to the Schiff base characteristics. The thermal decomposition reaction is first order for the studied complexes.     

Thermal decomposition of the layered double hydroxides of formula Cu6Al2(OH)16CO3 and Zn6Al2(OH)16CO3

Zn-Al hydrotalcites and Cu-Al hydrotalcites were synthesised by coprecipitation method and analysed by X-ray diffraction (XRD) and thermal analysis coupled with mass spectroscopy. These methods provide a measure of the thermal stability of the hydrotalcite. The XRD patterns demonstrate similar patterns to that of the reference patterns but present impurities attributed to Zn(OH)₂ and Cu(OH)₂. The analysis shows that the d003 peak for the Zn-Al hydrotalcite gives a spacing in the interlayer of 7.59 ? and the estimation of the particle size by using the Debye-Scherrer equation and the width of the d003 peak is 590 ?. In the case of the Cu-Al hydrotalcite, the d003 spacing is 7.57 ? and the size of the diffracting particles was determined to be 225 ?. The thermal decomposition steps can be broken down into 4 sections for both of these hydrotalcites. The first step decomposition below 100°C is caused by the dehydration of some water absorbed. The second stage shows two major steps attributed to the dehydroxylation of the hydrotalcite. In the next stage, the gas CO₂ is liberated over a temperature range of 150°C. The last reactions occur over 400°C and involved CO₂ evolution in the decomposition of the compounds produced during the dehydroxylation of the hydrotalcite.     

Thermal decomposition of natural iowaite

The thermal decomposition of natural iowaite of formula Mg₆Fe₂(Cl,(CO₃)_0.5)(OH)₁₆·4H₂O was studied by using a combination of thermogravimetry and evolved gas mass spectrometry. Thermal decomposition occurs over a number of mass loss steps at 60°C attributed to dehydration, 266 and 308°C assigned to dehydroxylation of ferric ions, at 551°C attributed to decarbonation and dehydroxylation, and 644, 703 and 761°C attributed to further dehydroxylation. The mass spectrum of carbon dioxide exhibits a maximum at 523°C. The use of TG coupled to MS shows the complexity of the thermal decomposition of iowaite. This revised version was published online in July 2006 with corrections to the Cover Date.     

A thermogravimetric and infrared emission spectroscopic study of alunite

Thermogravimetric and differential thermogravimetric analysis has been used to characterize alunite of formula [K₂(Al³⁺)₆(SO₄)₄(OH)₁₂]. Thermal decomposition occurs in a series of steps (a) dehydration up to 225°C, (b) well defined dehydroxylation at 520°C and desulphation which takes place as a series of steps at 649, 685 and 744°C.The alunite minerals were further characterized by infrared emission spectroscopy (IES). Well defined hydroxyl stretching bands at around 3463 and 3449 cm^?1 are observed. At 550°C all intensity in these bands is lost in harmony with the thermal analysis results. OH stretching bands give calculated hydrogen bond distances of 2.90 and 2.84–7 Å. These hydrogen bond distances increase with increasing temperature. Characteristic (SO₄)^2? stretching modes are observed at 1029.5, 1086 and 1170 cm^?1. These bands shift to lower wavenumbers on thermal treatment. The intensity in these bands is lost by 550°C.     

Thermal decomposition of liebigite

Summary A combination of high resolution thermogravimetric analysis coupled to a gas evolution mass spectrometer has been used to study the thermal decomposition of liebigite. Water is lost in two steps at 44 and 302°C. Two mass loss steps are observed for carbon dioxide evolution at 456 and 686°C. The product of the thermal decomposition was found to be a mixture of CaUO₄ and Ca₃UO₆. The thermal decomposition of liebigite was followed by hot-stage Raman spectroscopy. Two Raman bands are observed in the 50°C spectrum at 3504 and 3318 cm^-1 and shift to higher wavenumbers upon thermal treatment; no intensity remains in the bands above 300°C. Three bands assigned to the υ₁ symmetric stretching modes of the (CO₃)^2- units are observed at 1094, 1087 and 1075 cm^-1 in agreement with three structurally distinct (CO₃)^2- units. At 100°C, two bands are found at 1089 and 1078 cm^-1. Thermogravimetric analysis is undertaken as dynamic experiment with a constant heating rate whereas the hot-stage Raman spectroscopic experiment occurs as a staged experiment. Hot stage Raman spectroscopy supports the changes in molecular structure of liebigite during the proposed stages of thermal decomposition as observed in the TG-MS experiment.     

Thermal decomposition of the oxo-diperoxo-molibdenum (VI)-potassium oxalate

The oxo-diperoxo-molibdenum(VI)-potassium oxalate, K₂[MoO(O₂)₂(C₂O₄)] was synthesized using an adapted version of the method suggested by Dengel. The thermal behavior of the synthesized complex was investigated by simultaneous thermal analysis TG/DTG/DTA, in air or nitrogen atmosphere, to identify and characterize the mass-loss decomposition processes. In addition, for the characterization of the observed decomposition steps, the FT-IR spectra for the initial complex, evolved gaseous compounds and isolated complex at 230 and 430/383 °C in air/nitrogen atmosphere, were recorded. On the 35–500 °C temperature range, the K₂[MoO(O₂)₂(C₂O₄)] complex presented three main decomposition steps, accompanied by mass-loss. The first degradation step is due to the elimination of one oxygen molecule, by the breaking of the peroxo groups, with the formation of an intermediary, like [MoO₃L]. The other two degradation steps can be attributed to the decomposition of the organic ligand, with the final formation of a stable metallic oxide.     

TG–MS–FTIR (evolved gas analysis) of kaolinite–urea intercalation complex

The products evolved during the thermal decomposition of kaolinite–urea intercalation complex were studied by using TG–FTIR–MS technique. The main gases and volatile products released during the thermal decomposition of kaolinite–urea intercalation complex are ammonia (NH₃), water (H₂O), cyanic acid (HNCO), carbon dioxide (CO₂), nitric acid (HNO₃), and biuret ((H₂NCO)₂NH). The results showed that the evolved products obtained were mainly divided into two processes: (1) the main evolved products CO₂, H₂O, NH₃, HNCO are mainly released at the temperature between 200 and 450 °C with a maximum at 355 °C; (2) up to 600 °C, the main evolved products are H₂O and CO₂ with a maximum at 575 °C. It is concluded that the thermal decomposition of the kaolinite–urea intercalation complex includes two stages: (a) thermal decomposition of urea in the intercalation complex takes place in four steps up to 450 °C; (b) the dehydroxylation of kaolinite and thermal decomposition of residual urea occurs between 500 and 600 °C with a maximum at 575 °C. The mass spectrometric analysis results are in good agreement with the infrared spectroscopic analysis of the evolved gases. These results give the evidence on the thermal decomposition products and make all explanation have the sufficient evidence. Therefore, TG–MS–IR is a powerful tool for the investigation of gas evolution from the thermal decomposition of materials and its intercalation complexes.     

Kinetic parameters of unsaturated polyester resin modified with poly(ε -caprolactone)

The mineral sabugalite (HAl)_0.5[(UO₂)₂(PO₄)]₂⋅8H₂O, has been studied using a combination of energy dispersive X-ray analysis, X-ray diffraction, dynamic and controlled rate thermal analysis techniques. X-ray diffraction shows that the starting material in the thermal decomposition is sabugalite and the product of the thermal treatment is a mixture of aluminium and uranyl phosphates. Four mass loss steps are observed for the dehydration of sabugalite at 48°C (temperature range 39 to 59°C), 84°C (temperature range 59 to 109°C), 127°C (temperature range 109 to 165°C) and around 270°C (temperature range 175 to 525°C) with mass losses of 2.8, 6.5, 2.3 and 4.4%, respectively, making a total mass loss of water of 16.0%. In the CRTA experiment mass loss stages were found at 60, 97, 140 and 270°C which correspond to four dehydration steps involving the loss of 2, 6, 6 and 2 moles of water. These mass losses result in the formation of four phases namely meta(I)sabugalite, meta(II)sabugalite, meta(III)sabugalite and finally uranyl phosphate and alumina phosphates. The use of a combination of dynamic and controlled rate thermal analysis techniques enabled a definitive study of the thermal decomposition of sabugalite. While the temperature ranges and the mass losses vary due to the different experimental conditions, the results of the CRTA analysis should be considered as standard data due to the quasi-equilibrium nature of the thermal decomposition process. The online version of the original article can be found at     

Studies regarding the formation from metal nitrates and diol of NiM 2 III O4 spinels, inside a silica matrix

The present study deals with preparation and characterization of spinel mixed oxide systems NiM ₂ ^III O₄, where M^III?=?Fe^III, Cr^III. In order to obtain 50% NiFe₂O₄/50% SiO₂ and 50% NiCr₂O₄/50% SiO₂ nanocomposite, we have used a versatile route based on the thermal decomposition inside the SiO₂ matrix, of some particular precursors, coordination compounds of the involved M^II and M^III cations with dicarboxylate ligands. The ligands form in the redox reaction between metal nitrates mixture and 1,3-propanediol at the heating around 140?°C of the gels (tetraethylorthosilicate?Cmetal nitrates?C1,3-propanediol?Cwater). The as-obtained precursors, embedded in silica gels, have been characterized by FT-IR spectrometry and thermal analysis. Both precursors thermally decompose up to 350?°C leading to the formation of the corresponding metal oxides inside the silica matrix. X-ray diffraction of the annealed powders have evidenced the formation of NiFe₂O₄ starting with 600?°C, and NiCr₂O₄ starting with 400?°C. This behavior can be explained by the fact that, by thermal decomposition of the Fe(III) carboxylate at 300?°C, the spinelic phase ??-Fe₂O₃ is formed, which interacts with the NiO, forming the ferrite nuclei. By thermal decomposition of chromium carboxylate, a nonstoichiometric chromium oxide (Cr₂O_3+x ) is formed. In the range 380?C400?°C, Cr₂O_3+x turns into Cr₂O₃ which immediately interacts with NiO leading to the formation of nickel chromites nuclei inside the pores of silica matrix. Both spinels have been obtained as nanocrystalites homogenously dispersed as resulted from XRD and TEM data.     

A study of the thermal decomposition of Se2O2F8 and Te2O2F8, using molecular beam techniques

The thermal decomposition of the vapor phases of the oxygen bridged dimers Se₂O₂F₈ and Te₂O₂F₈ has been studied by mass spectrometry, electric deflection and flight time analysis on a molecular beam generated directly from the decomposition products. Se₂O₂F₈ begins to decompose at ?250°C; the principal products are SeF₄ and O₂, with SeOF₂ as a minor product. Decomposition is complete by ?500°C. There is some decomposition to monomeric SeOF₄ between 200 and 350°C. Te₂O₂F₈ did not begin to decompose until a temperature of 400°C was reached. Again, the principal products observed were TeF₄, O₂, and TeOF₂ with no evidence for decomposition to the monomeric TeOF₄.     

Research on pyrolysis of PCB waste with TG-FTIR and Py-GC/MS

The purpose of this study is to determine the pyrolysis characteristics and gas product properties of printed circuit board (PCB) waste. For this purpose, a combination of Thermogravimetry-Fourier Transform Infrared Spectrum (TG-FTIR) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) techniques is employed. In the TG-FTIR experiment, a heating rate of 10?°C min^?1 and a terminal pyrolysis temperature of 600?°C are applied. The thermal decomposition temperature, weight losses, and the temperature trend of evolving gaseous products of PCB waste are investigated. Py-GC/MS is used for the qualitative and semi-quantitative analysis of the higher-molecular-weight volatile decomposition products. Associated with the analysis results of TG-FTIR and Py-GC/MS for the volatile products, PCB waste degradation could be subdivided into three stages. The main products in the first stage (<293?°C) are H₂O, CH₄, HBr, CO₂ and CH₃COCH₃. High-molecular-weight organic species, including bromophenols, bisphenol A, p-isopropenyl phenol, phenol, etc., mainly evolve in the second stage. In the last stage, at temperature above 400?°C, carbonization and char formation occur. This fundamental study provides a basic insight of PCB waste pyrolysis.     

Thermal analysis of beaverite in comparisonwith plumbojarosite

The thermal decomposition of beaverite and plumbojarosite was studied using a combination of thermogravimetric analysis coupled to a mass spectrometer. The mineral beaverite Pb(Fe,Cu)₃(SO₄)₂(OH)₆ decomposes in three stages attributed to dehydroxylation, loss of sulphate and loss of oxygen, which take place at 376 and 420, 539 and 844°C. In comparison three thermal decomposition steps are observed for plumbojarosite PbFe₆(SO₄)₄(OH)₁₂ at 376, 420 and 502°C attributed to dehydroxylation; loss of sulphate occurs at 599°C; and loss of oxygen and formation of lead occurs at 844 and 953°C. The temperatures of the thermal decomposition of the natural plumbojarosite were found to be less than that for the synthetic jarosite. A comparison of the thermal decomposition of plumbojarosite with argentojarosite is made. The understanding of the chemistry of the thermal decomposition of minerals such as beaverite, argentojarosite and plumbojarosite and related minerals is of vital importance in the study known as ‘archeochemistry’.     

Synthesis of nanosized zinc and magnesium chromites starting from PVA–metal nitrate solutions

In this article, we present a detailed study regarding the preparation of nanosized zinc and magnesium chromites starting from a 4% poly(vinyl)alcohol (PVA) aqueous solution and metal nitrates. The controlled thermal treatment of these solutions has permitted the isolation of an intermediary solid product, used as precursor of the preferred mixed oxides: zinc and magnesium chromites. The as-obtained precursors were characterized by FT-IR spectrometry and thermal analysis. FT-IR spectrometry has evidenced the disappearance of the NO₃ ^? anions at 140?°C, due to the redox interaction with PVA. The thermal decompositions of the synthesized precursors were different, as resulted from both thermal analysis and FT-IR spectrometry. Thus, while ZnCrPVA precursor decomposes up to 400?°C with formation of zinc chromite, the precursor MgCrPVA decomposes up to 500?°C, with formation of MgCrO₄ as intermediary amorphous phase. By thermal decomposition of MgCrO₄ at 500?°C, weakly crystallized MgCr₂O₄ powder is obtained. The obtained chromite powders consist of fine nanoparticles with diameters ranging from 10 to 30?nm at 500?°C; on raising the annealing temperature to 1000?°C, chromite particles become octahedral, with diameter up to 500?nm, but with no sign of sintering.