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Nowadays, there is the widespread use of clay minerals as fillers in polymeric materials. One of the most widely used mineral is montmorillonite belonging to the smectite. We have prepared organically modified clays using two different types of accelerators TP and ZDT for sulfur vulcanization. Intercalation of these accelerators into the interlayer of clays was performed using a gas reaction at room temperature. They were examined (characterized) by thermal analysis (DTA, TG), X-ray analysis, and infrared spectroscopy (FTIR). [ABSTRACT FROM AUTHOR]

The thermal decomposition of the complexes Mg(SCN)(2-OHpy)·HO(I), Mg(SCN)(quin)·2HO(II) and Mg(SCN)(quinox)·5HO(III) (2-OHpy-2-hydroxypyridine, quin-quinoline, quinox-quinoxaline) has been investigated in static air atmosphere at 20-1000 °C by means of thermogravimetry (TG), differential thermal analysis (DTA), and infrared (IR) spectroscopy. The composition of the complexes had been identified by means of elemental analysis and complexometric titration. The possible scheme of destruction of the complexes is suggested. The final product of the thermal decomposition was MgS. IR data suggest that heterocyclic ligands were coordinated to Mg(II) through the nitrogen atom of their heterocyclic ring. Thiocyanate group is also coordinated through the nitrogen atom. [ABSTRACT FROM AUTHOR]

Thermal and structural properties of three clays (sepiolite and two kaolinites) from Turkey were studied by thermal analysis (TG-DTA), X-ray diffraction (XRD), X-ray fluorescence (XRF), Fourier transform infrared (FT-IR), and surface area measurement techniques The adsorption of sulfur dioxide (SO) gas by these clays was also investigated. SO adsorption values of K1, K2, and S clay samples were measured at 20 °C and pressures up to 106 kPa. Sepiolite sample (S) primarily consists of pure sepiolite, only dolomite present as accompanying mineral. Both kaolinite samples, K1 and K2, mainly contain kaolinite as the major clay mineral and quartz as impurity. In K2 sample, muscovite phase is also present. Simultaneous TG-DTA curves of all clay samples were obtained at three different heating rates 10, 15, and 20 °C min over the temperature range 30-1200 °C. It was found that the retention value of SO by S clay (2.744 mmol/g) was higher than those of K1 (0.144 mmol/g) and K2 (0.164 mmol/g) samples. [ABSTRACT FROM AUTHOR]

The results of thermal analysis of speciality elastomers CSM with different chlorine and sulphur contents is presented in the article. The thermal curves obtained under the atmosphere of inert gas have been interpreted from the point of view of phase transitions and chemical reactions of the examined polymers during their heating. It has been stated that from among the investigated chlorosulphonated polyethylenes, only CSM24, which has the lowest chlorine content, contains a crystalline phase, clearly influences on its T temperature. Results of the thermal analysis obtained under inert gas atmosphere have been compared with results obtained under termooxidative atmosphere. Irrespective of the research atmosphere, the thermal decomposition of investigated CSM takes place in three stages. The maximum rate of thermal destruction of modified by heating elastomers, d m/d t, decreases with the increase in chlorine content in the sample having been heated. [ABSTRACT FROM AUTHOR]

This study deals with possibility of the applications of inorganic substances specifically natural bentonite in function of reinforced nanofillers in polymeric materials. X-ray diffraction, FTIR spectroscopy and thermal analysis (TG, DSC and DTA) were used to characterize natural bentonite in more detail. At the prepared model, rubber compounds with various amounts of added filler were determinated vulcanization characteristics and physical–mechanical properties. The measured values were compared with the values of commercially used polymeric materials with the original composition. [ABSTRACT FROM AUTHOR]

Thermal properties of Co2FeV3O11 have been reinvestigated. It has been proved that this compound does not exhibit polymorphism. It melts incongruently at the temperature of 770±5°C and the phase with lyonsite type structure is the solid product of this melting. Phase relations in the whole subsolidus area of the CoO–V2O5–Fe2O3 system have been determined. The solidus area projection onto the component concentration triangle plane of this system has been constructed using the DTA and XRD methods. 15 subsidiary subsystems can be distinguished in this system. [ABSTRACT FROM AUTHOR]

Dental materials restore morphology and function of lost or destroyed teeth, but cannot completely rebuild the structural relationship with soft periodontal tissues. The induction of bioactivity on classic dental porcelain can be achieved through the addition of bioactive glass. The aim of this study was to investigate the effect of Bioglass® on the thermal properties of dental porcelain in order to correlate the proportions of mixtures with the changes in thermal properties. Differential thermal analysis was performed in order to determine the characteristic temperatures of the mixtures. The increase of bioactive glass concentration in mixtures induces a shift to lower temperatures of the melting point temperature. This observation is attributed to the substitution of silicon ions by aluminium ions and to the formation of Al–O bond, which is weaker than Si–O bond. Mixtures heated at 950°C were examined also by the transmission electron microscopy (TEM) in order to be studied the microstructure of these samples at this critical temperature. The observed microstructural changes, confirm the process of substitution of Si 4+ ions by Al 3+ ions. [ABSTRACT FROM AUTHOR]

Dental materials restore morphology and function of lost or destroyed teeth, but cannot completely rebuild the structural relationship with soft periodontal tissues. The induction of bioactivity on classic dental porcelain can be achieved through the addition of bioactive glass. The aim of this study was to investigate the effect of Bioglass® on the thermal properties of dental porcelain in order to correlate the proportions of mixtures with the changes in thermal properties. Differential thermal analysis was performed in order to determine the characteristic temperatures of the mixtures. The increase of bioactive glass concentration in mixtures induces a shift to lower temperatures of the melting point temperature. This observation is attributed to the substitution of silicon ions by aluminium ions and to the formation of Al–O bond, which is weaker than Si–O bond. Mixtures heated at 950°C were examined also by the transmission electron microscopy (TEM) in order to be studied the microstructure of these samples at this critical temperature. The observed microstructural changes, confirm the process of substitution of Si 4+ ions by Al 3+ ions. [ABSTRACT FROM AUTHOR]

Simultaneous DTA/TG technique has been used to study the influence of various model compounds (aromatics, organic acids, alkanes, ketone, heterocyclic and sterole) on the thermo-oxidative behavior of lignite humic acids. As a measure of stability the shift of the onset temperature of the exothermic degradation peak has been used. Further, the ratio of mass loss recorded in the high and low temperature ranges (thermogravimetric index) was used to evaluate the role of added compounds on the recombination reactions occurring during the thermooxidative degradation of humic acids. It has been demonstrated that most of added compounds play a role during those processes at relatively low concentrations (1% mass/mass) and affect the humic acid stability as well as the value of thermogravimetric index (i.e. the degree of the apparent aromaticity). It has been clearly shown, that the latter parameter reflects more the ‘qualitative’ than the ‘quantitative’ relationship between biodegradable humified parts in the extracted pool of organic matter. [ABSTRACT FROM AUTHOR]

Iron, cobalt, nickel, copper, zinc, cadmium and mercury murexide complexes have been prepared and characterized. The thermal properties of these complexes are studied deeply by DTA technique where their thermal peaks are explained. The multi-stages thermal decomposition mechanism is proposed. The thermodynamic parameters of the decomposition steps are calculated. The entropy change values for all complexes are of the same magnitude and all transition states of the thermal reactions are more ordered than the reactants. The thermal reactions proceed in complicated mechanisms. The fractions appeared in the calculated orders of the thermal reactions confirmed that these reactions proceeded via complex mechanisms. [ABSTRACT FROM AUTHOR]

In this paper, the results of copper-lead matte investigations are presented. Investigated copper-lead matte is intermediate product of the lead production in TREPCA-Zvečan. In the first part of the paper characterization of starting material is presented, consisting of: chemical composition analysis (XRQ), scanning electron microscopy (SEM) and diffractometry (XRD). Thermal properties of investigated matte were determined using differential thermal analysis (DTA) at characteristic temperatures. Using results of induced analysis, mechanism of matte oxidation process was determined. In the second part of the paper kinetic parameters describing oxidative roasting of copper-lead matte are presented. For activation energy calculations, non-isothermal methods defined by Kissinger and Ozawa were used [1, 2]. Kinetic equation describing oxidation process was determined using Sharps method of reduced half time of reaction [3]. [ABSTRACT FROM AUTHOR]

We have fabricated glasses in the Bi-2223 H Tc superconductor system with Bi2Sr2Ca2Cu3-xErxO10+ δ nominal composition, where x=0.5 and 1.0, by the glass-ceramic technique. Using an analysis developed for non-isothermal crystallization studies, information on some aspects of crystallization temperature and thermal properties has been obtained. The crystallization studies were made using DTA with several uniform rates. The calculations of crystallization activation energies, Ea, and the Avrami parameters, n, were made based on the non-isothermal kinetic theory of Kissinger and the Ozawa’s equations. The DTA data of the samples showed that the first crystallization temperature, Tx1, increases and the second crystallization temperature, Tx2, decreases by increasing the Er concentration. This suggests that the Er substitution had significant effect on the glassification of the BSCCO material due to change on the surface nucleation and increased ionic activities at high temperature region. The activation energy for crystallization, Ea, of the samples was also showed an increase at high Er concentration case. However, the Avrami parameter, n, decreased from 2.5 to 1.7 for x=0.5 and 1.0 samples, respectively. This suggests that the growth mechanism is diffusion-controlled and three-dimensional parabolic growth takes place near the first crystallization temperature. The oxidization rates and the activation barrier for oxygen out-diffusion process, E, was calculated using the TG data. It was found that the total mass gain in the x=0.5 sample is comparably smaller than that of the x=1.0 sample. This shows that the oxygen absorption of the x=1.0 sample is faster than the x=0.5 sample, leading to increase in the oxidization rate in the x=1.0 material. [ABSTRACT FROM AUTHOR]

A new compound Co3Fe4V6O24 has been obtained by solid state reaction. Temperature of its incongruent melting amounts to 890±5°C. Results of indexing the powder diffraction pattern and unit cell parameters of Co3Fe4V6O24 are also given. This compound is probably isostructural with M3Fe4V6O24 (whereM= Zn, Mg, Mn). IR spectrum of Co3Fe4V6O24 phase is presented. [ABSTRACT FROM AUTHOR]

Reactivity of FeVO4 towards Ni2V2O7 and Ni3V2O8 in the solid state was investigated. On the base of XRD and DTA results, phase diagrams in subsolidus area of the FeVO4-Ni2V2O7 and FeVO4-Ni3V2O8 intersections of the ternary system NiO-V2O5-Fe2O3 have been worked out and the phase diagram of this ternary system in subsolidus area in the whole component concentration range has been verified. [ABSTRACT FROM AUTHOR]

A compound of the formula Fe3Mg2Mo2V3O20 has been obtained as a result of a reaction between FeVO4 and MgMoO4 taken at a molar ratio of 3:2. This compound crystallises in the monoclinic system and its unit cell parameters are the following:a=0.6971 nm,b=0.9055 nm,c=1.2542 nm,g=102.00°,Z=2. [ABSTRACT FROM AUTHOR]

The mutual reactivity in mixtures containing Nasicon (Na3Zr2Si2PO12) or YSZ (ZrO2:Y2O3) solid electrolytes with Li2CO3 or Li2CO3:BaCO3 sensing electrode materials was investigated using simultaneous DTA and TG and ex situ XRD techniques. The uncontrolled chemical reaction is suspected to be responsible for the instability of electrochemical gas sensors constructed from these materials. DTA and TG results obtained for Nasicon-carbonate mixtures indicate the possibility of reaction in the temperature range from about 470 to 650°C, which overlaps the sensor operating temperature range (300-525°C). The results obtained for YSZ-carbonate mixtures indicate that reaction between carbonate and the ZrO2 takes place at higher temperatures and cannot explain the instability drift of investigated sensors. The mechanism of observed reactions in systems studied is also discussed. [ABSTRACT FROM AUTHOR]

It has been shown by the methods of X-ray powder diffraction (XRD), differential thermal analysis (DTA) and infrared spectroscopy (IR) that solid solutions of a formula Cr1-xAlxVMoO7, wherexe (0-0.65), are formed in the system CrVMoO7 -AlVMoO7. The obtained research results have proven that the ions Al3+ are incorporated into the crystal lattice of CrVMoO7 instead of Cr3+, which causes a contraction of the lattice and a shift of IR absorption bands towards higher values of wavenumbers. The phases Cr1-xAlxVMoO7 melt incongruently in the temperature range from 710°C (forx=0.65) to ~820°C in the case of x close to zero [ABSTRACT FROM AUTHOR]

Thermal reactivity of eleven nitramines has been examined by means of non-isothermal differential thermal analysis, and the data were analyzed according to the Kissinger method. The reactivity was expressed as theEaR-1 slopes of the Kissinger relationship. Electronic charges,qN, at nitrogen atoms of the nitramine molecules were calculated by means of ab initio DFT B3LYP/6-31G** method. The relationships were confirmed between the slopesEaR-1 and the q values for the nitro groups that are primarily split off. Conclusions are made in relation to the mechanism of initiation of polynitro compounds in general. [ABSTRACT FROM AUTHOR]

DTA method was used to follow the hydration process of cement admixtures containing fluidized bed combustion by-product, formed on joined combustion and desulphurisation in some installations with fluidized bed. Based on endothermic peaks attributed to the dehydration of phases formed on hydration, the conditions leading to the formation of so-called 'delayed' ettringite were found. This calcium alumino-sulphate hydrate is responsible for lower durability of fluidized bed ash containing material. DTA method is also beneficial in the studies of fluidized bed combustion by-product itself, giving information about the un-burnt carbon content and pozzolanic properties. [ABSTRACT FROM AUTHOR]

A new compound Co3Fe4V6O24 has been obtained by solid state reaction. Temperature of its incongruent melting amounts to 890±5°C. Results of indexing the powder diffraction pattern and unit cell parameters of Co3Fe4V6O24 are also given. This compound is probably isostructural with M3Fe4V6O24 (whereM= Zn, Mg, Mn). IR spectrum of Co3Fe4V6O24 phase is presented. [ABSTRACT FROM AUTHOR]

This paper reports an investigation of thermal and spectral properties of the complexes Cu2(3,5-Cl2sal)4·H2O (I), Cu(3,5-Br2sal)2·2H2O (II), Cu(3,5-I2sal)2·2H2O (III) and Cu(5-Isal)2·2H2O (IV), (where sal=salicylate). TG, DTG, DTA, IR, EPR and electronic spectra have been applied to investigate thermal and spectral properties of these complexes. The chemical composition of the complexes has been identified by means of elemental analysis and complexometric titration. Schemes of destruction of these complexes are suggested. Heating of these compounds first resulted in a release of water molecules. The thermal stability of these complexes can be ordered in the sequence: IV=I

The thermal stability of gelatine-polyacrylonitrile graft copolymers fibres obtained under various conditions of deformation has been studied. The thermal properties of examined fibres depend on the synthetic component of the fibre forming material – polyacrylonitrile which appears in the form of grafted PAN chains and PAN homopolymer. It was stated that the highest thermal stability have those fibres which formation process included two stages of drawing with the use of deformation close to the maximal values, with the value of the total draw ratio amounting to 691%. It should be supposed that with such a drawing process, already in its first stage, are created advantageous conditions for the formation of paracrystalline regions to a larger extent and their orientation along the fibre axis. [ABSTRACT FROM AUTHOR]