DTA Data Research Articles

Исследование условий максимального использования тепла химических реакций при сульфатизирующем обжиге чернового медного сульфидного концентрата

The paper describes the results of multifactorial experiments of roughing granulated copper sulphide concentrates on the influence of the sulfur content in the concentrate, specified air temperature, the granule size, the air flow on the study of conditions of the maximum use of the chemical reactions heat in the sulphatization roasting process. Mathematical models are received, which are used to determine the roasting optimal area from the point of view of getting into the zone under the terms of allowable temperature to avoid sintering material as well as the terms of preservation of the sulfates image. It is found that not exceeding admissible calcining temperature can be achieved even if the sulfur content is greater than 10 % due to the temperature decrease and the use of larger granules. But at an air temperature of 500 °C the optimum temperature is exceeded at any circumstances. The apparent activation energy calculated from the DTA data amounted to 27.714 kJ/mol and shows that the process is controlled by internal diffusion of gaseous reactants through the bed of formed sulfates.

Preparation and characterization of multilayer mesoporous γ-alumina membrane obtained via sol-gel using new precursors

AbstractIn this paper, a mesoporous γ-alumina membrane coated on a macroporous α-alumina support via sol-gel method has been reported. A crack-free γ-alumina membrane was obtained by adding PVA to the alumina solution and optimum parameters of roughness, temperature and porosity were achieved. The support was dip-coated in different solutions using two new different solvents with different particle size distributions. Using these two solvents led to the uniform distribution of pore size in the final membrane. The alumina sols showed particle size distributions in the range of 20 to 55 nm which was measured by a DLS Zeta Sizer. X-ray diffraction technique, atomic force microscopy and scanning electron microscopy were used to characterize the membrane layer. XRD and DTA data for the γ-alumina membrane showed its thermal stability up to around 600 °C. The thickness of the mesoporous γ-alumina membrane was about 4 μm with 16 nm of surface roughness and 5 nm pore size. The resultant crack-free mesoporous membrane shows that the membrane preparation procedure was optimum. In this work, it has been investigated the performance of γ-alumina membranes for single gas permeation and separation of binary gas mixtures.

Investigation of thermal stability and fingerprint spectra of energetic 1,2,3-triazole using pulsed photoacoustic pyrolysis technique

This paper reports on a comparative study of UV and visible radiation-based pulsed photoacoustic (PA) pyrolysis technique examining thermal stability and acoustic fingerprint spectra of a newly synthesized high-energy molecule named 1-(2,4-dinitrobenzyl)-4-nitro-1H-1,2,3-triazole (S6). The thermal PA spectra of S6 were recorded in temperatures ranging between 30 and 350 °C using second and fourth harmonic wavelengths (i.e., 532 and 266 nm), obtained from Q-switched Nd:YAG laser pulses of duration 7 ns at 10 Hz repetition rate. The PA results are further compared with TG–DTA data to understand the release mechanism of NO2 along with other gaseous by-products. The difference in thermal PA spectra of S6 which follows two different mechanisms, such as vibronic transition V–V and V–T relaxation in NO2 functional group, while electronic π* ← n transition in the entire molecule, is due to selection of visible and UV wavelengths. In addition, the effect of data acquisition time and incident laser energy has been examined in order to understand the behavior of acoustic modes of a PA cavity at the desired vapor temperature. The stability of the compound is also evaluated on the basis of thermal quality factor (Q), of PA cavity.

Syntheses and structural studies on some new dithiophosphinato complexes of nickel(II), cobalt(II) and mixed pyridino complexes thereof

Four different, alkyl(4-methoxyphenyl)dithiophosphinic acid metal complexes, namely, trans-bis-[iso-propyl (4-methoxyphenyl)dithiophosphinato]nickel(II), 1; bis-{[iso-propyl (4-methoxyphenyl)-dithiophosphinato]}cobalt(II), 2; bis-{[sec-butyl (4-methoxyphenyl)-dithiophosphinato]}cobalt(II), 3 and bis-{[iso-amyl (4-methoxyphenyl)-dithiophosphinato]}cobalt(II), 4 were prepared. As 1 and 2 were synthesized for the first time, their structures were also elucidated. Starting with these four-coordinated complexes, novel, mixed (pyridino) dithiophosphinic acid complexes of Ni(II) and Co(II) were also prepared. These complexes were characterized by elemental analysis and NMR (1H-, 13C-, 31P-); MS; FTIR; and Raman spectroscopies. TGA and DTA data were also made use of to support the structures revealed by spectroscopy. The magnetic susceptibilities of the complexes were measured to confirm the hybridization patterns and the geometries. The crystal structures of the cobalt pyridino-DTPA complexes were analyzed. X-ray analyses show that the P–S bonds in the complexes are essentially of the same order; that is, electron delocalization prevails.

Glass formation and structure of glasses in the WO3–ZnO–Nd2O3–Al2O3 system

Glass formation ability in three different sections: WO3–ZnO–Nd2O3; (100-x) (0.8WO3·0.1ZnO·0.1Nd2O3)·xAl2O3, x=5–30mol% and 90(xWO3·yZnO·zNd2O3)·10Al2O3 from WO3–ZnO-Nd2O3–Al2O3 system is investigated by melt quenching technique. Glasses are obtained from the compositions with a high WO3 content (65–75mol%). According to DTA data the glass transition temperature (Tg) is in the range 508–525°C and the glass crystallisation temperature (Tx) is around 600°C. Neodymium tungstates, Al2(WO4)3, ZnWO4 and WO3 are identified in the XRD patterns of quenched samples beyond the glass formation region. The structure of glasses is studied by IR, Raman and DR-UV–Vis spectroscopies. It is established that the amorphous network is built up mainly by WO6 octahedra, connected by W–O–W bridges. This structure does not satisfy the classical concept for the formation of an amorphous network which is built up by MeO4 tetrahedra.

Synthesis, characterisation, spectral, thermal, XRD, molecular modelling and potential antibacterial study of metal complexes containing octadentate azodye ligands

Twelve tetrametallic complexes of Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II) with two new octadentate azodye ligands, 4,4′-bis(2′,4′-dihydroxy-5′carboxyphenylazo) diphenylether (LH6) and 4,4′-bis(2′,4′-dihydroxy-5′-acylphenylazo) diphenylether (L′H4) have been synthesised. The structural elucidation of the complexes was made basing upon analytical, conductance, magnetic susceptibility, IR, electronic spectra, ESR, NMR, ESI-MS, TG, DTG, DTA and X-ray diffraction (powder pattern) data. The cobalt (II) and nickel (II) complexes are found to be octahedral, copper (II) complexes are distorted octahedral and a tetrahedral stereochemistry has been suggested to zinc (II), cadmium (II) and mercury (II) complexes. The thermal analysis data provided the kinetic parameters as order of decomposition reaction, activation energy and frequency factor. The geometry of the ligands and their Co(II), Ni(II), Cu(II) and Zn(II) complexes were optimised and their physicochemical properties were calculated by using molecular modelling procedure. The ESI-MS determination supports the molecular formula and molecular weight of the ligands and the complexes. The Ni(II) complex is found to have a triclinic crystal system. The potential antibacterial study of the two ligands and eight metal complexes was made by cup-plate method against one gram positive and one gram negative bacteria. The results showed increase in the activity of some metal complexes as compare with azodye ligands.

Axial vibration control of melt structure of sodium nitrate in crystal growth process

The melt structure evolution under the action of the low-frequency axial vibration control (AVC) technique was studied in situ by Raman spectroscopy for several complex chemical compound melts: sodium nitrate, margarine acid, paraffin mixture (C17-C20). The measurements were conducted in the temperature range from the melting point up to 60°C above. Comparison of crystallization heats for AVC activated and steady melts with melting heats of AVC-CZ and conventional CZ produced powders allowed to propose the energy diagram of NaNO3 states for activated and non-activated melts and crystals based on DTA, XRD, DSC and Raman experimental data.

The Elemental, Mineralogical, IR, DTA and XRD Analyses Characterized Clays and Clay Minerals of Central and Eastern Uganda

The results on the elemental and mineralogical compositions of clays from Central Uganda differed from those from the volcanic sediments of the Mt. Elgon in Eastern Uganda. Utilisation of the two types of clays should be strict after understanding their structural differences. Whereas elemental, mineralogical, DTA, IR, XRD and pH data on selected clays from Kumi, Nakawa, Seeta, Kajansi, Kawuku, Lwanda, Chodah and Umatengah indicated that they were kaolinites. Similar data on clays from Mutufu, Budadiri, Chelel and Siron indicated that they were largely smectites. The IR data accumulated on Kawuku, Kajansi, Lwada, Seeta, Chodah, Umatengah, Kumi and Nakawa clays revealed they were largely kaolinites yet that on Mutufu, Chelel, Budadiri and Siron clays indicated they were smectite-rich.

Structure of glass near eutectics of phase diagrams on the example of the barium-borate system according to the DTA data

For the quantitative estimation of the crystallization ability of glass according to the thermal analysis data, the coefficient of the tendency to crystallization has been introduced Kcr, where the drawbacks of the well-known Hruby’s coefficient were eliminated. The opportunities of Kcr were demonstrated on the example of the glasses of system BaO-B2O3 in the composition range of 16–37 mol % BaO and the concentration dependence of Kcr has been plotted individually for powders and monoliths. It has been shown that the crystallization ability of the glass powders weakly depends on their composition, while for the monolithic glasses with a flame-polished surface it is exceptionally sensitive to the proximity of special points in phase diagrams, namely, stoichiometries and eutectics.

Renewable energy in focus: In5Se5Br, a solid material with promising thermoelectric properties for industrial applications

We obtained via solid state synthesis needle-shaped crystals of In5Se5Br crystallizing in the space group Pmn21 and containing indium simultaneously in three different oxidation states: In+, formal In2+ and In3+. Bulk sample of In5Se5Br shows n-type conductivity and linear increase of Seebeck voltage with the temperature difference increase. Seebeck voltage of approx. 720mV is recorded at a temperature difference of 80K, corresponding to a Seebeck coefficient −8900μV/K. A voltage increase up to 250mV is recorded within 10min upon application of a 27K temperature difference between the contacts. On-off switching of the heating source unveils repeatable results. Linear I–U behavior with a resistivity of 2.32×1011Ω is observable for individual needles of In5Se5Br. In bulk In5Se5Br the resistivity oscillates between 2.6MΩ and 23MΩ. DTA and HT-powder XRD data show incongruent melting to InBr, InSe and In2Se3 at 805K. The ternary compound expands 1.02% along [010] showing a coefficient of thermal expansion αb=2.3(4)×10−5K−1. Lower expansions of 0.6% and 0.16% along a and c axes corresponding to mean coefficients of thermal expansion of αa¯=1.3(1)×10−5K−1, αc¯=4.4(5)×10−6K−1 are observed. Thin layer growing of In5Se5Br on glass substrate with targeted doping/substitutions can improve the sample conductivity, increase the Seebeck coefficient and lower the thermal conductivity making In5Se5Br a good alternative material for industrial thermoelectric applications.

Synthesis, structure and magnetic properties of homotrinuclear Ni(II) complexes with asymmetric Schiff-base ligands

By using 1,3-propanediamine, 2-hydroxyacetophenone and salicylaldehyde an asymmetric ONNO type Schiff base, N(hydroxyphenylidene)-N′(2-hydroxyacetophenylidene)-1,3-propanediamine (H2metsalpn), has been prepared and isolated. This Schiff base has been reduced yielding N(2-hydroxybenzyl)-N′[1-(2-hydroxyphenyl)ethyl]-1,3-diaminopropane (H2metsalpnH) These two ligands were used in preparing three trinuclear Ni(II) complexes with catena-[Ni3] structural motif, where DMF and carboxylato (formato, acetato, benzoato) ligands occur. These complexes were characterized by EA, IR, TG, DTA and MS data. The X-ray diffraction confirms that the Ni(II) central atoms are in a distorted octahedral coordination environment: the terminal centers possess {NiN2O4} octahedral coordination sphere whereas the very central atom possesses {NiO6} chromophore. The coordinated DMF groups are liberated between 140–240°C. The SQUID magnetometry confirms presence of weak exchange coupling of the antiferromagnetic nature, J/hc=−2 to −7cm−1, with a moderate single-ion anisotropy reflected by the zero-field splitting D/hc=+4 to +7cm−1.

On the thermal properties of Ag2Te and Ag2Se in the region of the phase transition

A setup is developed for measuring the thermal properties of Ag2Te and Ag2Se near the main phase transition and in the region of it in high vacuum. The samples are of stoichiometric composition with an excess of Ag, Te, and Se. Differential thermal analysis is performed and the temperature differences across and along the samples are measured by the pulsed light method. Using data on the thermal diffusivity a(T), the temperature dependence of the thermal conductivity K = apc is determined, where p is the density and c is the specific heat. The measurement technique used allows us to establish that the main phase transitions are accompanied by intense heat release. New phase transitions before and after the main structural phase transition with heat absorption are found. According to the DTA data, in the Ag2Te sample with an excess of Ag (0.25 at.%, cn = 1.2 × 1019 cm−3) the phase transition at 365 K is also accompanied by heat absorption. Thus, it is established that all of the phase transitions in Ag2Te and Ag2Se are first-order.

Thermal and spectroscopic study of the lanthanide 2-aminoterephthalate compounds in the solid state

Lanthanides 2-aminoterephthalate compounds were synthetized and characterized on the basis of TG–DTA data in order to study their thermal behavior, as well as to establish hydration grade and stoichiometry, while TG/FTIR system identified the gaseous products evolved during the thermal decomposition of these compounds in each step of the TG curve, in which water and carbon dioxide were the main products with a small amount of carbon monoxide and ammonia. Through the FT-IR spectroscopic data of the compounds in the solid state, information concerning the coordination mode of the carboxylate groups to the metal was provided, and by analysis of fluorescence, with excitation at 405 nm, the respective electronic transitions supported by the data reported in the literature were identified. In addition, the excitation was made for the ligand salt and acid with the aim of understanding the contribution of the ligand in the emission of the compounds. In summary, the ligand influenced on the fluorescence of lanthanide ions, being more intense for the compounds of La, Ce, Pr, and Nd, making this material interesting for optical and photonic applications.

Influence of the lead difluoride on ion mobility and thermal behavior of glasses in the TeO2–PbO·P2O5–PbF2 system according to NMR and DTA data

New glasses doped with the Er3+, Nd3+, and Eu3+ ions were synthesized in the oxyfluoride system (100−х−у)TeO2–хPbO·P2O5–уPbF2:zMF3 (x=42.5–30mol%, y=5–30mol%, z=0.5–3.0mol%, M=Er; z=0.5mol%, M=Eu, Nd) and studied by the 19F and 207Pb NMR, 31P MAS NMR, XRD and DTA. It was found that an increase in the PbF2 content causes a decrease in the temperatures of glass transition Tg and crystallization Tc. The glass doping with erbium fluoride in an amount up to 3.0mol% at the constant PbF2 content has no effect virtually on values of the characteristic temperatures. According to the 19F NMR data, a possibility of local motion activation in the fluoride sublattice is determined by the lead fluoride content in the glass composition. There is no diffusion mobility in the fluoride sublattice of the considered glasses in the entire studied temperature range up to 570K. The temperature range of 450–570K is transitive, in which there are observed various reorientations of the fluorine-containing groups. According to the 31P NMR spectrum data at the magic angle (31P MAS NMR), there is a symmetric environment of PO4 structures in the glass.

Phase diagram of a tetrapropylammonium bromide-water system according to DTA data

The phase diagram of a tetrapropylammonium bromide-water binary system is studied by means of differential thermal analysis. Three tetrapropylammonium bromide hydrates are identified that include one stable compound of 1: 4 composition (bromide: water; mp, −32.6°C) and two metastable hydrates of 1: 6 (mp, −70.4°C) and 1: 24 compositions (mp, −57.0°C).

Development of Melt-processed (Nd,Eu,Gd)Ba2Cu3Oy Superconductors in Air

(Nd0.1Eu0.1Gd0.8)Ba2Cu3Oy “NEG-123”superconductors were synthesized as a function of BaO2 content with the aim of reducing NEG/Ba substitution and preparing batch production in air. The DTA data were used to schedule the heat treatment profile of the melt growth process. The magnetization measurements indicated that superconducting transition temperature increased with increasing the BaO2 concentration and a Tc (onset) reached around 95K for the sample with 24 mol% BaO2, which is similar to the NEG samples processed in reduced oxygen pressure. Moreover, the superconducting transition temperature decreased when BaO2 content exceeded 28 mol%. The irreversibility field was increased with increasing the BaO2 concentration and reached >5 T for the sample with 24 mol% BaO2 and decreased thereafter. The experimental results suggest that the present approach will contribute to large scale batch production of melt-processed NEG-123 materials in air.

Synthesis, spectroscopic characterization, electrochemistry and biological evaluation of some binuclear transition metal complexes of bicompartmental ONO donor ligands containing benzo[b]thiophene moiety

A series of new binucleating Cu(II), Co(II), Ni(II) and Zn(II) complexes of bicompartmental ligands with ONO donor were synthesized. The ligands were obtained by the condensation of 3-chloro-6-substituted benzo[b]thiophene-2-carbohydrazides and 4,6-diacetylresorcinol. The synthesized ligands and their complexes were characterized by elemental analysis and various spectroscopic techniques. Elemental analysis, IR, 1H NMR, ESI-mass, UV–Visible, TG–DTA, magnetic measurements, molar conductance and powder-XRD data has been used to elucidate their structures. The bonding sites are the oxygen atom of amide carbonyl, azomethine nitrogen and phenolic oxygen for ligands 1 and 2. The binuclear nature of the complexes was confirmed by ESR spectral data. TG–DTA studies for some complexes showed the presence of coordinated water molecules and the final product is the metal oxide. All the complexes were investigated for their electrochemical activity, only the Cu(II) complexes showed the redox property. Cu(II) complexes were square planar, whereas Co(II), Ni(II) and Zn(II) complexes were octahedral. Powder-XRD pattern have been studied in order to test the degree of crystallinity of the complexes and unit cell calculations were made. In order to evaluate the effect of antimicrobial activity of metal ions upon chelation, both the ligands and their metal complexes were screened for their antibacterial and antifungal activities by minimum inhibitory concentration (MIC) method. The results showed that the metal complexes were found to be more active than free ligands. The DNA cleaving capacities of all the complexes were analyzed by agarose gel electrophoresis method against supercoiled plasmid DNA. Among the compounds tested for antioxidant capacity, ligand 1 displayed excellent activity than its metal complexes.

Activation energy in the thermal decomposition of MgH2 powders by coupled TG–MS measurements

The catalytic effect of SnO2 doping on the hydrogen thermal desorption of MgH2 was investigated by coupled thermogravimetric–mass spectrometric (TG–MS) analyses, among a set of samples prepared with different SnO2/MgH2 molar ratios. A small release of water and carbon dioxide was detected at temperatures preceding to the reductive thermal decomposition of MgH2 yielding molecular hydrogen. While TG and DTA data collected at different heating rate provided an apparent activation energy for the entire thermal process, appropriate ion-current signals from the MS-data were used to obtain the activation energies of the single chemical reactions yielding the formation of H2O, CO2, and H2. The most common equations derived from model-free isoconversion methods (Kissinger–Akahira–Sunose; Flynn–Wall–Ozawa; Starink) were used by processing temperatures referred to the different kinds of signals (TG-, DTG-, DTA-, TIC-, molecular-ion IC-curves) for isoconversion points corresponding to the maximum rate of transformation. Temperature and activation energy values were used to compare the kinetic behavior of MgH2 powder with the best performance of a doped sample, prepared by high energy grinding of SnO2/MgH2 mixture. Doped-MgH2 samples prepared with SnO2 mass ratio of 0.2 showed the best kinetic thermal decomposition behavior, with respect to the pristine MgH2 powder: a decreasing of the main thermal decomposition event of ca. 51–57 °C associated to a coherent decreasing of ca. 20 % (ca. 30 kJ mol−1) of its activation energy value.

Interfacial Reaction Thermodynamics between Sn-Cu-Ag Solder and Ni Substrate

Interfacial reaction during wetting and spreading of Sn-Ag-Cu solder on Ni substrate is a key factor in order to improve the mechanical properties of the joints and the weld quality. Therefore, it’s important to focus on the thermodynamic and kinetic analysis of this interface reaction. In this paper, the sessile drop method was used to study the spreading contour evolution. The Kissinger method was used to calculate thermo-kinetic parameters of reactions between Sn-Ag-Cu solder and Ni substrate based on DTA data. The results show that Cu reduces activation energy and reaction rate of Sn-Ag-Cu/Ni system. (Cu, Ni)6Sn5 phase mainly constitute the interface reaction layer of Sn-Ag-Cu/Ni. As the temperature increases, partial (Cu, Ni)6Sn5 phase is substituted by Ni3Sn4 phase.

Pd(II) complexes bearing chromone based Schiff bases: Synthesis, characterisation and biological activity studies

Pd(II) complexes of 3-formyl chromone Schiff bases such as 3-((2-hydroxyphenylimino) methyl)-4H-chromen-4-one (HL1), 2-((4-oxo-4H-chromen-3-yl)methylneamino)benzoic acid (HL2), 3-((3-hydroxypyridin-2-ylimino)methyl)-4H-chromen-4-one (HL3), 3-((2-mercaptophenylimino) methyl)-4H-chromen-4-one (HL4) and 3-((pyridine-2-ylimino)methyl)-4H-chromen-4-one (L5) have been synthesised and characterised by elemental analysis, molar conductivity, IR, electronic, magnetic, TG–DTA, powder XRD and fluorescence spectral data. From the analytical, electronic and magnetic data square-planar geometry has been proposed for all the Pd(II) complexes. Powder XRD studies indicate the crystalline state of the Pd(II) complexes. The antimicrobial activity of Pd(II) complexes was performed against two Gram(−ve), two Gram(+ve) and fungal microorganisms and the results indicate that, complexes show better microbial inhibition activity than the ligands. Pd(II) complex of HL1 displayed comparable antioxidant activity with reference to the standard drug (BHT). Agarose gel electrophoresis assay demonstrates the ability of complexes to cleave the pUC19 plasmid DNA. The cytotoxicity was tested by the MTT assay. The results indicate that the complexes exert cytotoxic effects against tested cell lines but their cytotoxicity is less than that of cisplatin.