Authors:D. Janke, J. Madarász, S. Lukács, and G. Pokol
Differential scanning calorimetric (DSC) measurements have been carried out on Bi-Sn based amalgam precursors to be used in
compact fluorescent lamps (CFLs) to study the changes in melting and solidifying behaviour caused by In dopant. The phase
and elemental compositions of the samples have been characterized by using X-ray diffraction (XRD) and scanning electron microscopy-energy
dispersive X-ray analysis (SEM-EDX), respectively. One of the endothermic peaks of the liquid amalgam formation shifted from
121°C to 112 and 105°C, with increasing content of 2.5 and 4.8 mass% In of samples, respectively.
Authors:M. Kök, G. Pokol, C. Keskin, J. Madarász, and S. Bagci
In this study the combustion characteristics of crude oils (Karakuę and Beykan) in the presence of a limestone matrix were
determined using the thermogravimetry (TG/DTG). Experiments were performed at a heating rate of 10C min-1, whereas the air flow rate was kept constant at 10 L h-1 in the temperature range of 20-900C. In combustion with air, three distinct reaction regions were identified in all crude
oil/limestone mixtures studied known as low temperature oxidation (LTO), fuel deposition (FD) and high temperature oxidation
(HTO). The individual activation energies for each reaction region may be attributed to different reaction mechanisms, but
they do not give any indication of the contribution of each region to the overall reactivity of the crude oils. Depending
on the characteristics, the mean activation energy of samples varied between 50.3 and 55.8 kJ mol-1.
Authors:S. Békássy, T. Cseri, G. Kenessey, G. Pokol, K. Tomor, and G. Liptay
Montmorillonite-supported iron(III) nitrate and copper(II) nitrate reagents, and other supported metal nitrates prepared in
the same way, were investigated by thermal and X-ray powder diffraction methods. The metal nitrates are present on the support
in the form of crystalline hydrate and not as acetone solvate as supposed earlier. Thermal decomposition of metal nitrates
that are active in model reactions proceeds in a different way from that of the practically inactive nitrates. In the former
case, water release and nitrate decomposition itself are simultaneous process. These and other results contributed to determination
of suitable reaction conditions for the montmorillonite-supported reagents.
Authors:H. Simon, Z. Vincze, K. Marthi, G. Lévai, G. Pokol, E. Fogassy, and D. Kozma
A non-isothermal experimental study using thermogravimetry (TG) and differential scanning calorimetry (DSC) was conducted
for investigation the oxidation reactivity of natural phosphate and its demineralised products. The analyses were carried
out in oxygen atmosphere and at different heating rate (5, 10, 20, 30, 50, 60C min-1) up to 1000C. The results indicated that the material washed with HCl from the original phosphate, mainly apatite and carbonates
of calcium and magnesium, as well as with HCl/HF, silicates minreals, had an inhibition effect during oxidation reactions
of organic material. The increase of the heating rate shifted the reactions to higher temperatures. In addition, kinetic parameters
were determined by assuming a single first-order kinetic model, using the Coats-Redfern method. The influences of demineralization
process of natural phosphate and the heating rate were examined and discussed.
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:J. Zsakó, G. Pokol, Cs. Novák, Cs. Várhelyi, A. Dobó, and G. Liptay
A number of 30 [Co(en)3 ]Y3 , [Co(en)2 X2 ]Y and [Co(en)2 X(amine)]Y2 type complexes (X =Cl, Br; Y =Cl, Br, I, NCO, NCS, NO3 , ClO4 , etc.; amine =aromatic and alkylamines) were obtained from trans-[Co(en)2 Cl2 ]Cl by double decomposition and by substitution reactions, respectively. The structure of the complexes was proved by means
of far and middle FTIR spectra. The thermal decomposition was studied by TG, DTA and DSC measurements. Mass spectra were also
recorded. In the case of [Co(en)3 ]Y3 complexes the nitrate, perchlorate and dimesoperiodates decompose suddenly, frequently explosion like. The halides and thiocyanates
seem to substitute an ethylenediamine ligand, yielding a rather unstable intermediate. The pyrolysis of [Co(en)2 X2 ]Y type derivatives yields no relatively stable intermediates, but the decomposition temperatures may be correlated with
the nature of Y and with the cis or trans configuration of the compound. With the [Co(en)2 X(amine)]Y2 type complexes one observes the formation of [Co(en)2 XY]Y as intermediate product. From the TG curves kinetic parameters were derived for some dehydration and deamination processes,
by using the nomogram method. The validity of a non-linear kinetic compensation law was observed.
Authors:Cs. Várhelyi Jr., G. Pokol, Á. Gömöry, A. Gănescu, P. Sohár, G. Liptay, and Cs. Várhelyi
chelates of the type [Ni(II)(Diox.H)2], ((Diox.H)2:
various α-dioximes) have been studied by means of FTIR, NMR, MS data
and various thermoanalytical methods (TG, DTA, DTG, DSC). In some cases kinetic
parameters of the thermal decomposition of the complexes were also calculated
using Zsak’s ‘nomogram method’. The mechanism of
the decomposition processes was characterised on the basis of mass spectra.
Authors:J. Bajdik, K. Pintye-Hódi, Cs. Novák, P. Szabó-Révész, G. Regdon, I. Erős, and G. Pokol
Dimenhydrinate is a heat-sensitive antihistamine with a low melting point. The heat-sensitive feature is of importance if
direct compression is used. Direct measurement of the heat originating in the texture of tablets during compression is very
difficult. Thermoanalytical methods were used as indirect methods to describe the changes in material properties at high temperature:
differential scanning calorimetry, thermomicroscopy and thermogravimetric analysis. Film coating method is widely used in
pharmaceutical technology. A fluidized bed apparatus was applied to coat the crystals. The coating film forming agent was
hydroxy-propyl-methylcellulose (HPMC), which is a gastric-soluble polymer. Thermoanalytical measurements reveal that dimenhydrinate
crystals are sensitive to heat. Film coating method does not alter the shape of the DSC curve of dimenhydrinate, but increases
the melting point. The presence of a macromolecular film reduces the thermal conductivity, because it separates the particles.