Authors:J. Madarász, M. Krunks, L. Niinistö, and G. Pokol
Identification and monitoring of gaseous species released during thermal decomposition of the title compound 1, Zn(tu)2Cl2, (tu=thiourea, (NH2)2C=S) have been carried out in flowing air atmosphere up to 800°C by both online coupled TG-EGA-FTIR and simultaneous TG/DTA-EGA-MS.
The first gaseous products of 1, between 200 and 240°C, are carbon disulfide (CS2) and ammonia (NH3). At 240°C, an exothermic oxidation of CS2 vapors occurs resulting in a sudden release of sulphur dioxide (SO2) and carbonyl sulphide (COS). An intense evolution of hydrogen cyanide (HCN) and beginning of the evolution of cyanamide
(H2NCN) and isothiocyanic acid (HNCS) are also observed just above 240°C. Probably because of condensation and/or polymerization
of cyanamide vapors on the windows and mirrors of the FTIR gas cell optics, some strange baseline shape changes are also occurring
above 330°C. Above 500°C the oxidation process of organic residues appears to accelerate which is indicated by the increasing
concentration of CO2, while above 600°C zinc sulfide starts to oxidize resulting in the evolution of SO2. All species identified by FTIR gas cell were also confirmed by mass spectrometry, except for HNCS.
Analytically pure nickel(II)- and cobalt(II)-acetylacetonate were used to prepare several addition compounds with Lewis-bases (2-picoline-N-oxide, 4-picoline-N-oxide, pyridine-N-oxide) in order to investigate their thermal stability in oxidative atmospheres. Comparison of the thermoanalytical TG-DTA data of the chelates with those on the adducts showed similarities in thermal degradation. A fragmentation pattern observed on simultaneous mass spectrometric investigation is discussed. Elimination of ligand or base molecules corresponding quantitatively to the estimated mass loss values from the TG-curves has been demonstrated.
Authors:Imre Miklós Szilágyi, Eero Santala, Mikko Heikkilä, Marianna Kemell, Timur Nikitin, Leonid Khriachtchev, Markku Räsänen, Mikko Ritala, and Markku Leskelä
solutions of PVP and AMT. The annealing process of the PVP/AMT fibers and the product WO 3 nanofibers are characterized by thermal analysis (TG/DTA) and evolved gas analysis with a mass spectrometer (TG/DTA-MS), X-ray diffraction (XRD), scanning electron
Authors:I. Szilágyi, J. Madarász, G. Pokol, F. Hange, G. Szalontai, Katalin Varga-Josepovits, and A. Tóth
This paper discusses the changes in the structure and thermal reduction of nanosize hexagonal ammonium tungsten bronze (HATB),
(NH4)0.33−xWO3−y, which were caused by K+ ion exchange (doping) and studied by XRD, XPS, 1H-MAS NMR, FTIR, SEM and TG/DTA-MS. Comparison of the cell parameters of undoped and doped HATB revealed that both a and c cell parameters decreased after the ion exchange reaction, which showed that smaller K+ ions partly replaced the larger NH4+ ions in the hexagonal channels of HATB. After the reaction, from the hexagonal channels less NH3 evolved, which also supported the incorporation of K+ ions into the hexagonal channels.
Authors:Imre Szilágyi, István Sajó, Péter Király, Gábor Tárkányi, Attila Tóth, András Szabó, Katalin Varga-Josepovits, János Madarász, and György Pokol
This article discusses the formation and structure of ammonium tungsten bronzes, (NH4)xWO3−y. As analytical tools, TG/DTA-MS, XRD, SEM, Raman, XPS, and 1H-MAS NMR were used. The well-known α-hexagonal ammonium tungsten bronze (α-HATB, ICDD 42-0452) was thermally reduced and
around 550 °C a hexagonal ammonium tungsten bronze formed, whose structure was similar to α-HATB, but the hexagonal channels
were almost completely empty; thus, this phase was called reduced hexagonal (h-) WO3. In contrast with earlier considerations, it was found that the oxidation state of W atoms influenced at least as much the
cell parameters of α-HATB and h-WO3, as the packing of the hexagonal channels. Between 600 and 650 °C reduced h-WO3 transformed into another ammonium tungsten bronze, whose structure was disputed in the literature. It was found that the
structure of this phase—called β-HATB, (NH4)0.001WO2.79—was hexagonal.
complexes were further characterized by spectral and chemical analysis. The halide content in the complexes was determined by Volhard’s method [ 11 ].
TG/DTA–MS studies were carried out using a Rigaku TG-8120
Authors:E. L. Charsley, S. B. Warrington, P. Emmott, T. T. Griffiths, and J. Queay
Simultaneous TG-DTA-MS and TG-DSC have been used to investigate the complex reaction which takes place in the region of 300°C when the chlorinated rubber Alloprene is added to pyrotechnic compositions containing equal parts by weight of titanium and sodium nitrate. The results have been compared with those obtained for the titanium-strontium nitrate-Alloprene system.
Authors:Margit Bán, Petra Bombicz, and J. Madarász
A new co-crystal of theophylline and phthalic acid with 1:1 molar ratio has been prepared. It crystallises in the monoclinic
crystal system, space group P21/c, a=11.5258(9), b=10.1405(6), c=13.9066(12) Å, β=106.827(4)°. The structure of the co-crystal has been revealed by single crystal X-ray diffraction. An infinite
helical polymeric chain is formed by intermolecular hydrogen bonds of the two neutral constituents. The hydroxyl group and
carbonyl oxygen atom in one of the carboxyl groups of phthalic acid form hydrogen bonds to O6 and to N(7)H atoms of theophylline,
respectively, while the other carboxyl OH group of phthalic acid is in hydrogen bond to N9 atom of theophylline by very strong
intermolecular interactions proven by 1883 cm−1 centred peak in FTIR spectrum.
Thermal degradation of this new supramolecular compound is a two-step process in air. At first phthalic acid (47.4%) released
up to 230°C, meanwhile it loses water and transforms into phthalic anhydride. In EGA-MS spectra, the characteristic fragments
of water (m/z=17, 18) appear from about 180°C, while absorption bands of phthalic anhydride are shown in EGA-FTIR spectrum at about 210°C.
In the second step theophylline begins to sublime, melts at 276°C, and then evaporates up to 315°C with minute residues.
1,2,4-triazole-3-one (TO) and guanidine nitrate (GN) have the potential to be used as alternative gas-generating agents. To
obtain a better understanding of thermal decomposition properties of TO/GN mixtures, sealed cell differential scanning calorimetry,
thermogravimetry–differential thermal analysis–infrared spectroscopy (TG–DTA–IR), and thermogravimetry–differential thermal
analysis–mass spectrometry (TG–DTA–MS) were carried out. The endothermic peak and onset temperatures of TO/GN mixtures were
lower than those of individual TO and GN. TG–DTA–IR and TG–DTA–MS showed that the mass of TO/GN mixtures decreased with heat
generation and N2 evolved as the major gas during thermal decomposition. The interaction between TO and nitric acid from the dissociation of
GN is proposed for the thermal decomposition of TO/GN mixtures.
Authors:Göktürk Avsar, Hüseyin Altinel, Mustafa Yilmaz, and Bilgehan Guzel
Trifluoromethoxy functionalized copper(II) Schiff base complexes N,N′-bis(5-trifluoromethoxysalicylaldehyde)cyclohexanediiminatodiaquacopper(II) and N,N′-bis(5-trifluoromethoxysalicylaldehyde)phenylenediiminatocopper(II) were synthesized and characterized. Thermal decompositions
of the synthesized complexes were studied by thermogravimetry in order to evaluate their thermal stability and thermal decomposition
pathways. Three similar decomposition steps occurred for the two copper complexes. Mass losses and evolved gasses were characterized
by TG/DTA-MS. Kinetic parameters were calculated and the results showed that the values obtained are comparable.