Journal of Thermal Analysis and Calorimetry (v.100, #3)

Preface by Subhash C. Mojumdar (743-744).

Thermal and spectral properties of natural bentonites and their applications as reinforced nanofillers in polymeric materials by S. L’alíková; M. Pajtášová; D. Ondrušová; T. Bazyláková; M. Olšovský; E. Jóna; S. C. Mojumdar (745-749).
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.
Keywords: Bentonite; IR spectroscopy; TG; DSC; DTA; Nanocomposites; Physical–mechanical properties

Effect of zinc(II) doping on thermal and optical properties of potassium hydrogen phthalate (KHP) crystals by S. Parthiban; S. Murali; G. Madhurambal; S. P. Meenakshisundaram; S. C. Mojumdar (751-756).
The influence of doping the transition metal Zn(II) on potassium hydrogen phthalate (KHP) crystals has been studied. A close observation of FT-IR and XRD profiles of doped and undoped samples reveals some minor structural variations. It appears that the crystal undergoes considerable lattice stress as a result of doping the bivalent zinc. Furthermore, the possibility of cation vacancies aroused owing to the substitution of K1+ by Zn2+ could result in a defective crystal system. Energy dispersive spectra reveal the incorporation of Zn(II) in the crystalline matrix of KHP crystals. Differential scanning calorimetry (DSC) and TG-DTA studies reveal the purity of the sample and no decomposition is observed below the melting point. Small quantity additions of Zn(II) enhance the fluorescence intensity of KHP crystals. The doping results in morphological changes and significantly improves the second harmonic generation (SHG) efficiency of the host crystal.
Keywords: Nonlinear optical materials; Zinc doping; DSC; TG; DTA; KHP; SHG; Zn(II)

Optimization of regenerative cycle with open feed water heater using genetic algorithms and neural networks by A. R. Moghadassi; F. Parvizian; B. Abareshi; F. Azari; I. Alhajri (757-761).
This article determines the operating conditions leading to maximum work in a regenerative cycle with an open feed water heater through a procedure that combines the use of artificial neural networks (ANNs) and genetic algorithms (GAs). Water is an active fluid in the thermodynamical cycle; an objective function is obtained by using vapor enthalpy (a nonlinear function of operating conditions). Utilizing classical methods for maximizing the objective function usually leads to suboptimal solutions. Therefore, this article uses ANNs to estimate the steam properties as a function of operating conditions and GAs to optimize the thermodynamical cycle. The operating conditions are chosen with the aim of gaining maximum work in a boiler for a specific heat. To estimate the thermodynamic properties, an ANN was used to provide the necessary data required in the GA calculation.
Keywords: Genetic algorithm; Artificial neural network; Rankin cycle; Maximum work

Thermal, UV and FTIR spectral studies of urea–thiourea zinc chloride single crystal by G. Madhurambal; M. Mariappan; S. C. Mojumdar (763-768).
A single crystal of urea–thiourea was grown by slow evaporation of aqueous solution at room temperature. The bright and transparent crystals obtained were characterised by TG–DTA, UV and FTIR spectral analyses. A fitting decomposition pattern for the title compound was formulated on the TG curve which shows a two stage mass loss between 200 and 750 °C. DTA curve shows exothermic peaks supporting the formulated decomposition pattern in this temperature range. The UV and FTIR spectra show the characteristic absorption, vibration frequencies due to urea–thiourea zinc chloride crystals. Detailed structural analysis of the compound is under progress.
Keywords: Solution growth; Urea–thiourea zinc chloride single crystal; TG–DTA; UV; FTIR

Spectral and thermal characteristics of copper(II) carboxylates with fatty acid chains and their benzothiazole adducts by M. Pajtášová; D. Ondrušová; E. Jóna; S. C. Mojumdar; S. L’alíková; T. Bazyláková; M. Gregor (769-777).
The carboxylato–Cu(II) complexes of type [Cu2(RCOO)4] and their benzothiazole adducts [Cu2(RCOO)4bt2] (bt = benzothiazole, R = CH3(CH2) n−2, n = 12, 14, 16, 18) form the main objectives of this study. The studied carboxylato–Cu(II) complexes are formed from dimeric units to polymeric chains (chromofor CuO5). The structural changes are due to coordination of ligand (benzothiazole). The polymeric chains of carboxylato–Cu(II) complexes degraded to discrete centrosymetric tetracarboxylate-bridged dimmers (chromofor CuO4N). These prepared compounds [Cu2(RCOO)4] and [Cu2(RCOO)4L2] were submitted to measurements relating to spectral (IR, UV–Vis) and thermal properties (TG, DTA, DSC).
Keywords: Carboxylato–Cu(II) complexes; Benzothiazole adducts; TG–DTA–DSC–IR–UV–Vis

Microstructure of Portland cement mortar amended by burnt kaolin sand by L’. Krajči; S. C. Moujmdar; M. Kuliffayová; I. Janotka (779-787).
Two types of raw materials, original kaolin sand OKS I and OKS II were used for experiment. They were transformed (1 h at 650 °C with 10 °C/min temperature increase) to burnt kaolin sand (BKS I and BKS II) with pozzolanic properties. Contents of decisive mineral—metakaolinite—in BKSs are as follows: BKS I (fraction below 0.06 mm) 20%; BKS II (fraction below 0.06 mm) 36% and BKS II (fraction below 0.1 mm) 31% by mass. Mortars with blends of Portland cement (PC) and BKS were prepared announced as: MK I (0.06) with 5 and 10% cement substitution by metakaolinite; MK II (0.06) with 5 and 10% cement substitution by metakaolinite and MK II (0.1) with 5, 10, 15 and 20% cement substitution by metakaolinite. The reference mortar with 100% of PC was made for comparison. All mortars were adjusted on the constant workability 180 ± 5 mm flow. Besides significant increase in compressive strengths—the refinement of pore structure in mortars with BKS connected with decreases in permeability and Ca(OH)2 content were revealed. The above facts confirm pozzolanic reaction of BKS in contact with hydrated PC and indicate perceptiveness of BKS for the use in cement-based systems as a pozzolanic addition.
Keywords: Blended cements; Burnt kaolin sand; Pozzolana; Metakaolinite; Pore structure; Refinement

Synthesis of cobalt nickel ferrite nanoparticles via autocatalytic decomposition of the precursor by L. R. Gonsalves; S. C. Mojumdar; V. M. S. Verenkar (789-792).
The chemistry, structure, and properties of spinel ferrites are largely governed by the method of preparation. The metal carboxylato-hydrazinate precursors are known to yield nanosized oxides at a comparatively lower temperature. In this study, we are reporting the synthesis of one such precursor, cobalt nickel ferrous fumarato-hydrazinate which decomposes autocatalytically to give cobalt nickel ferrite nanoparticles. The XRD study of this decomposed product confirms the formation of single-phase spinel, i.e., Co0.5Ni0.5Fe2O4. The thermal decomposition of the precursor has been studied by isothermal, thermogravimetric (TG), and differential scanning calorimetric (DSC) analysis. The precursor has also been characterized by FTIR, EDX, and chemical analysis, and its chemical composition has been determined as Co0.5Ni0.5Fe2(C4H2O4)3·6N2H4.
Keywords: Nanoparticles; Ferrite; Autocatalytic decomposition; Fumarato-hydrazinate precursor

Os(VIII) doping effects on the properties and crystalline perfection of potassium hydrogen phthalate (KHP) crystals by K. Muthu; G. Bhagavannarayana; C. Chandrasekaran; S. Parthiban; S. P. Meenakshisundaram; S. C. Mojumdar (793-799).
The effect of dopant, Os(VIII) on the growth process, crystalline perfection and properties of potassium hydrogen phthalate (KHP) single crystals grown by a slow evaporation solution growth technique has been investigated. The XRD analysis of black-colored doped specimen reveals slight structural changes as a result of doping. The SEM images exhibit defect centers and crystal voids. The complex formation of KHP with Os(VIII) is evidenced by the considerable shift in λmax of the doped specimen and enhanced fluorescence intensity is observed by doping. Differential scanning calorimetry (DSC) and TG-DTA studies reveal the purity of the sample and no decomposition is observed up to the melting point. The high resolution X-ray diffraction (HRXRD) studies used to evaluate the crystalline perfection reveal some features on the capability of accommodating the dopant in the crystalline matrix. The diffraction curve (DC) patterns indicate that the high valence transition metal predominantly occupies the interstitial positions and the doping depresses the second harmonic generation (SHG) efficiency owing to the deterioration of crystalline perfection disturbing the charge transfer and nonlinearity.
Keywords: HRXRD; Nonlinear optical properties; Osmium; Potassium hydrogen phthalate

Three isomorphous series of new compounds are reported: complexes [M(DBM)2Q2] and [M(DBM)2Iq2] (M = M(II) = Co, Ni, Zn, Cd; DBM is C6H5COCHCOC6H5 ) and inclusion compounds [M(DBM)2Q2]*Q (M = Co, Zn, Cd). All the compounds comprise a trans configured octahedral complex molecule. Inclusion compounds of modified Zn and Cd DBM complexes are reported for the first time and their inclusion ability is attributed to the trans isomeric state induced by the bulky Q or Iq ligand. The TG measurements indicate the following order of thermal stability of the complexes defined by the strength of the metal–ligand bonds: Ni > Co > Cd > Zn. The inclusion compounds do not follow this trend.
Keywords: Metal complexes; Molecular crystals; Clathrates; DBM; Cistrans isomerism; Thermal analysis; Stability

Thermal, UV and FTIR spectral studies in alkali metal cinnamates by G. Madhurambal; B. Ravindran; M. Mariappan; S. C. Mojumdar (811-815).
A single crystal of sodium and potassium cinnamates was grown by slow evaporation of methanol solution at room temperature. The effect of metals sodium and potassium on the electronic structure of cinnamic acid was studied. In this research many analytical methods such as FTIR, UV, second harmonic generation (SHG) and TG–DTA were used: The spectroscopic studies lead to conclusions containing the distribution of the electronic charge in molecule, the delocalisation of π electrons and the reactivity of metal complexes. The SHG efficiency is more pronounced in the presence of sodium and potassium dopant in the growth medium. Incorporation of sodium and potassium increase the thermal stability ensuring the suitability of material for possible non-linear optical (NLO) application up to 180 °C.
Keywords: Solution growth; Sodium and potassium cinnamate; Single crystal; TG–DTA; UV; FTIR

Thermal stability of Li2O–SiO2–TiO2 gels evaluated by the induction period of crystallization by K. Moricová; E. Jóna; A. Plško; S. C. Mojumdar (817-820).
To evaluate the thermal stability of materials, various criteria have been used. Not only the simple parameters, as characteristic temperatures, but also the combined criteria E/RT p , k f (T) and criterion based on the length of induction period of crystallization have been taken into account. Four gels with the composition Li2O–2SiO2nTiO2 (n = 0.00, 0.03, 0.062, and 0.1) were prepared and the validity of the criteria was tested by applying them to these gels. The results indicate that thermal stability of the studied gels decrease with amount of TiO2.
Keywords: DTA; Crystallization; Thermal stability; Induction period and gels

Effect of anthracene doping on potassium hydrogen phthalate crystals by S. Meenakshisundaram; S. Parthiban; U. R. Pisipaty; G. Madhurambal; S. C. Mojumdar (821-826).
The influence of the highly fluorescent dopant, anthracene (over a concentration range from 5 × 10−4 to 1.2 × 10−2 mol dm−3) on the nonlinear optical properties and fluorescence intensity of potassium hydrogen phthalate (KHP) single crystals grown at 30 °C by a slow evaporation solution growth technique (SEST) has been investigated. Powder XRD and FTIR spectral analyses confirm the slight distortion of the structure of crystal because of doping. UV–Visible study shows that the transparency is not affected much by the dopant. The SEM investigation reveals that KHP suffers from crack development. Thermal analysis indicates that there is no decomposition of the crystal up to the melting point. It is interesting to observe that additions of small quantity anthracene to KHP results in the enhancement of fluorescence intensity. The fluorescence intensity dependence on dopant concentration is observed. Interestingly, second harmonic generation (SHG) efficiency of KHP is dramatically improved by doping with small quantities of anthracene.
Keywords: Organic dopants; Non-linear optical; Thermal analysis; XRD; KHP

Growth, spectral and thermal characterization of 8-hydroxyquinoline by M. Rajasekaran; P. Anbusrinivasan; S. C. Mojumdar (827-830).
A novel nonlinear optical organic crystal 8-hydroxyquinoline has been grown by slow evaporation technique at room temperature (RT) using chloroform as the solvent. The solubility of 8-hydroxyquinoline in chloroform has been determined at various temperatures. The grown crystals were found to be transparent in the visible region. The grown crystals were characterized employing several techniques such as UV, FT-IR, 1H NMR spectral analysis and TG–DTA studies. Preliminary measurements indicate that the second-harmonic generation efficiency at a fundamental wavelength of 1064 nm is roughly 4.28 times that of KDP crystal.
Keywords: 8-Hydroxyquinoline; TG–DTA; UV; FT-IR; 1H NMR; SHG

Thermal and optical properties of ZTS single crystals in the presence of 1,10-phenanthroline (Phen) by S. P. Meenakshisundaram; S. Parthiban; R. Kalavathy; G. Madhurambal; G. Bhagavannarayana; S. C. Mojumdar (831-837).
The influence of heteroaromatic N-base (1,10-phenanthroline) (Phen), a new additive as complexing agent on tris(thiourea)zinc(II)sulphate (ZTS) crystals from aqueous solutions at 30 °C is investigated. Crystals were grown using low concentration of the dopant (0.005 M L−1) in the aqueous growth medium and the growth promoting effect (GPE) is much greater because of an increase in the metastable zone width. High dopant concentration decreases GPE. The crystalline perfection of the grown crystals is quite good both in doped and undoped crystals as evaluated by high-resolution X-ray diffractometry (HRXRD). The diffraction curve of a typical Phen doped as-grown ZTS crystal was observed to contain a single peak indicating that the crystal does not contain any epitaxial layer on the surface or internal structural grain boundaries. Not much variation is observed in FT-IR and XRD of pure and doped ZTS. Phen depresses the NLO efficiency of ZTS. It could be ascribed due to the disturbance of charge transfer in the presence of the dopant. The grown crystals were also characterized by UV–Vis, SEM and TG–DTA techniques.
Keywords: Characterization; XRD; 1,10-Phenanthroline; Crystalline perfection; Nonlinear optical properties; Thermal analysis

Size and purity of gold nanoparticles changes with different types of thiolate ligands by Weijuan Jia; Jessica McLachlan; Jiayan Xu; S. Holger Eichhorn (839-845).
Gold nanoparticles (Au-NPs) were prepared by a surfactant-free single-phase reduction of hydrogen tetrachloroaurate(III) hydrate in the presence of different organic thiol ligands. Sizes, size distributions, and crystallinity of the Au-NPs were determined by high-resolution transmission electron microscopy and powder X-ray diffraction, whereas thermogravimetric analysis provided information on the organic ligand-to-gold ratios as well as amounts of contaminants. A systematic decrease in size with increasing conical bulk of the thiolate ligand is observed but large size distributions and contamination of the generated Au-NPs prohibit detailed mechanistic studies. A first-generation Fréchet dendron thiol produced the smallest and cleanest Au-NPs of the narrowest size distribution.
Keywords: Chemical; Gold; Nanoparticles; Mass spectrometry; Solution synthesis; Transmission electron microscopy (TEM); Thermogravimetric analysis (TG); UV–Vis spectroscopy; X-ray diffraction

The role of thermal analysis in detecting impurity levels during aluminum recycling by Musbah Mahfoud; A. K. Prasada Rao; Daryoush Emadi (847-851).
Recycling of aluminum scrap has gained interest owing to its economic and ecological benefits. Unfortunately, during the collection of scrap from a mixer of junk from various sectors it is difficult to ensure that the recycled alloy has the same chemical composition as that of already existing commercial alloys. Consequently, some of the alloying elements become trace/tramp elements in the recycled alloy. Therefore, in order to obtain high performance recycled alloys, controlling the impurity levels of the aluminum melt is of vital importance. Normally, computer aided cooling curve analysis (CA-CCA) is used to find the relationship between cooling curve parameters, melt treatments, alloy composition, and properties. In the present study, the first differential thermal analysis (DTA) approach has been used to detect and quantify impurity elements in scrap-like liquid aluminum alloys.
Keywords: Aluminum recycling; Thermal analysis; Trace elements; Computer-aided cooling curve analysis; Solidification

TG–DTA, UV and FTIR spectroscopic studies of urea–thiourea mixed crystal by G. Madhurambal; M. Mariappan; S. C. Mojumdar (853-856).
A mixed crystal of urea–thiourea was grown by slow evaporation of aqueous solution at room temperature. The bright and transparent crystals obtained were characterized by thermogravimetric–differential thermal analysis (TG–DTA), UV and FTIR spectroscopic analyses. A fitting decomposition pattern for the title compound was formulated on the TG curve which shows a two stage weight loss between 200 and 750 °C. In this temperature range DTA curve shows exothermic peaks supporting the formulated decomposition pattern. The UV and FTIR spectra show the characteristic absorption, vibration frequencies due to urea–thiourea mixed crystals. Detailed structural analysis of the compound is under progress.
Keywords: Solution growth; Urea–thiourea mixed crystal; TG–DTA; UV; FTIR

Thermal properties of solid complexes with biologically important heterocyclic ligands by L’. Lajdová; E. Jóna; J. Miklovič; P. Segl’a; L’. Kvasnicová; S. Šnircová; R. Janík; S. C. Mojumdar (857-860).
The stoichiometry of thermal decomposition of the complexes Co(NCS)2(fpy)4 (I), Co(NCS)2(Mefpy)4 (II) and Co(NCS)2(bfpy)4 (III) (where fpy = furo[3,2-c]pyridine, Mefpy = methylfuro[3,2-c]pyridine, bfpy = benzo-[2, 3]furo[3,2-c]pyridine) have been investigated in nitrogen atmosphere from room temperature (RT) to 800 °C by means of TG and DTA. The results revealed that release of heterocyclic ligands occurs in one step. Infrared data suggested that fpy, Mefpy and bfpy were coordinated to Co(II) through the nitrogen atom of the respective heterocyclic ring and anionic ligands through nitrogen atom of the NCS groups.
Keywords: Co(II) complexes; Furopyridine derivatives as ligands; Thermal analysis; IR spectra

Influence of alkali metal sodium doping on the properties of potassium hydrogen phthalate (KHP) crystals by G. Ramasamy; S. Parthiban; S. P. Meenakshisundaram; S. C. Mojumdar (861-865).
The effect of doping sodium on the growth process and properties of potassium hydrogen phthalate (KHP) single crystals by slow evaporation solution growth technique has been investigated. Incorporation of sodium into the crystalline matrix even in the presence of low dopant concentration in aqueous growth medium is well confirmed by energy dispersive X-ray spectroscopy and quantified by atomic absorption spectroscopy and inductively coupled plasma emission spectrometer (ICP) techniques. The FT-IR spectral analysis confirms the slight distortion of the structure of the crystals as a result of doping. The TG-DTA studies reveal the purity of the material and no decomposition is observed up to the melting point. Low Na-doping (10 mol%) slightly increases the second harmonic generation efficiency, whereas heavy doping {[KHP]:[Na] = 1:1} results in significant enhancement. It has also been found that the doping results in morphological changes.
Keywords: Potassium hydrogen phthalate (KHP); Nonlinear optical properties; Sodium; TG; DTA; Energy dispersive X-ray spectroscopy (EDS); ICP and FT-IR

Manganese zinc ferrous fumarato–hydrazinate precursor, Mn0.6Zn0.4Fe2(C4H2O4)3·6N2H4 was synthesized for the first time and characterized by chemical analysis, infrared spectral studies, and thermal analysis. Infrared studies show band at 977 cm−1 indicating bidentate bridging nature of the hydrazine in the complex. Thermogravimetric (TG) studies show two steps dehydrazination followed by two steps total decarboxylation. The precursor on touching with burning splinter undergoes self propagating autocatalytic decomposition yielding ultrafine Mn0.6Zn0.4Fe2O4. XRD studies confirms single phase formation as well as nanosize nature of “as prepared” Mn0.6Zn0.4Fe2O4. The saturation magnetization of the “as prepared” Mn0.6Zn0.4Fe2O4 was found to be 31.46 emu gm−1, which is lower than the reported, confirms the ultrafine nature of the oxide.
Keywords: Hydrazine precursor; Ultrafine oxide; Autocatalytic decomposition; DSC; TG; XRD

A new dimensionless group model for determining the viscosity of nanofluids by S. Masoud Hosseini; A. R. Moghadassi; Dale E. Henneke (873-877).
This article presents a model, based on dimensionless groups, to predict the viscosity of nanoparticle suspensions, nanofluids. This empirical model expresses the viscosity of a nanofluid as a function of the following: viscosity of the base liquid, particle volume fraction, particle size, properties of the surfactant layer, and temperature. According to this model, viscosity changes nonlinearly with nanoparticle loading. Compared to other models, the new model is in good agreement with experimentally determined viscosity data for alumina–water nanofluids.
Keywords: Dimensionless group; Nanofluid; Viscosity; Nanoparticle suspension

Regular papers (879-879).

Thermal stability of CR/CSM rubber blends filled with nano- and micro-silica particles by Gordana Marković; Suzana Samaržija-Jovanović; Vojislav Jovanović; Milena Marinović-Cincović (881-888).
The properties of filled polymers depend on the properties of the matrix and the filler, the concentration of the components and their interactions. In this research we investigated the rheological and mechanical properties and thermal stability of polychloroprene/chlorosulfonated polyethylene (CR/CSM) rubber blends filled with nano- and micro-silica particles. The density of the nano-silica filled CR/CSM rubber blends was lower than that of the micro-silica filled samples but the tensile strength and elongation at break were much higher. The nano-silica filled CR/CSM rubber blend has higher V r0/V rf values than micro-silica composites and show better polymer–filler interaction according to Kraus equation. The nano-silica filled CR/CSM rubber blends were transparent at all filler concentration, and have higher glass transition values than micro-silica filled compounds. The higher values of the glass transition temperatures for the nano- than the micro-filled cross-linked systems are indicated by DMA analysis. The nano-filled cross-linked systems have a larger number of SiO–C links than micro-filled cross-linked systems and hence increased stability.
Keywords: Nano- and micro-silica filler; Polychloroprene/chlorosulfonated polyethylene (CR/CSM) rubber blends; Thermal stability

Toluene and naphthalene sorption by iron oxide/clay composites by Marilda M. G. R. Vianna; Jo Dweck; Frank H. Quina; Flavio M. S. Carvalho; Claudio A. O. Nascimento (889-896).
Commercial bentonite (BFN) and organoclay (WS35), as well as iron oxide/clay composite (Mag_BFN) and iron/oxide organoclay composite (Mag_S35) were prepared for toluene and naphthalene sorption. Mag_BFN and Mag_S35 were obtained, respectively, by the precipitation of iron oxide hydrates onto sodium BFN and S35 clay particles. The materials were characterized by powder X-ray diffraction (XRD), X-ray Fluorescence (XRF), and TG and DTA. From XRF results and TG data on calcined mass basis, a quantitative method was developed to estimate the iron compound contents of the composites, as well as the organic matter content present in WS35 and Mag_S35.
Keywords: Clay; Organoclay; Iron oxide/clay composites; Characterization; Thermal analysis

High-temperature differential scanning calorimetry was used to investigate the thermodynamic parameters of the γ–β and β–α transitions in calcium pyrophosphate (Ca2P2O7). The measured enthalpy of transition compared well with previous results when higher heating rates (≥20 K min−1) were used. Recommendations for optimal use of HTDSC in high-temperature phase transition measurements are presented.
Keywords: Thermal analysis; Calcium pyrophosphate; Enthalpy of transformation; HTDSC

Assessment of evolution of loss on ignition matter during heating of iron ores by Vladimir Strezov; Artur Ziolkowski; Tim J. Evans; Peter F. Nelson (901-907).
Ironmaking involves reduction of iron ores to metallic iron using coke, coal or gas as reductants. Although different iron ore reduction processes exist, prior to each reduction type, commonly, the hydroxyl and clay materials present in the iron ores undergo decomposition as a first stage. The mass loss during decomposition of these materials is termed as Loss on Ignition (LOI). The aim of this work is to apply a computer aided thermoanalytical technique to evaluate five different iron ore types during decomposition of the LOI matter and determine associated decomposition temperature ranges and heats of reactions. Fourier Transform Infrared (FTIR) spectroscopy and thermogravimetric analysis (TG) were also incorporated to support the analysis interpretation. Three distinctive temperature ranges of decomposition of iron ore LOI matter were detected. The first region was associated with dehydration of the hygroscopic moisture at a temperature range between 100 and 150 °C. The second region occurred at a temperature range between 260 and 425 °C during which strongly bonded water was released and the OH groups associated with primarily iron oxyhydroxides were fractured. The third range, which occurred at a temperature range of 530 and 605 °C, was related to decomposition of the aluminosilicate clay materials.
Keywords: Goethite; Hematite; LOI; Iron; Specific heat

Dependence of kinetic parameters (activation energy and pre-exponential factor) and procedural factors (sample mass and heating rate) independent of the reversibility and the type of reactions in non-isothermal thermogravimetry have been established. Tris(ethylenediamine)nickel(II) oxalate dihydrate has been selected as a model complex and experiments were carried out at different heating rates and sample masses to study the dependence quantitatively. The kinetic parameters calculated using mechanistic and non-mechanistic equations show a systematic decrease with increase in either sample mass or heating rate for the dehydration and deamination reactions. For the decomposition reaction, the kinetic parameters are not influenced by the procedural factors. Mathematical correlations of high reliability are established between kinetic parameters and heating rate/sample mass using both mechanistic and non-mechanistic equations for dehydration and deamination reactions. The quantification follows an exponential decay of second order relation with respect to heating rate and a sigmoidal relation with regard to sample mass for both the dehydration and deamination reactions. No quantitative correlation is possible for the final decomposition stage. Thus, it is found that independent of the type of reaction (deamination or dehydration) the kinetic parameters have a particular dependence on the procedural variables. The equations for exponential decay and sigmoidal dependence can be represented as $$ y = y_{0} + A_{1} { ext{e}}^{{ - x/t_{1} }} + A_{2} { ext{e}}^{{ - x/t_{2} }} $$ and $$ y = {frac{{A_{1} - A_{2} }}{{1 + { ext{e}}^{{(x - x_{0} )/{ ext{d}}x}} }}} + A_{2} $$ respectively, where y represents kinetic parameters (E or A) and x represents the procedural variables (φ or m). Mechanism of the dehydration reaction is found to be random nucleation with the formation of one nucleus on each particle and the deamination is a phase boundary reaction. It is observed that the mechanism of these reversible reactions is not affected by the variation in sample mass and heating rate.
Keywords: Exponential decay; Kinetic parameters; Thermal decomposition; Tris(ethylenediamine)nickel(II) oxalate dihydrate

Thermal behavior of titania grafted with phosphonic acids under non-isothermal conditions by Gheorghe Ilia; Madalina Drehe; Titus Vlase; Gabriela Vlase; Lavinia Macarie; Nicolae Doca (917-923).
Metal or metal oxide nanoparticles possess unique features compared to equivalent larger-scale materials. In this paper we present the synthesis of grafted titania with phosphonic acids, their characterization and an extended non-isothermal kinetic study. The obtained results show that there in no significant difference between acids and esters in grafting reaction. The phosphorus content wary between 0.9 and 1.80% and is comparable with literature data. IR and AFM studies confirmed the formation of grafted titania. Extended non-isothermal kinetic study using different methods confirmed the complexity of thermooxidative degradation processes in non-isothermal conditions.
Keywords: Titania; Grafted; Phosphonic; Non-isothermal kinetic

Thermal treatment of zeolitic tuff by E. Yörükoğulları; G. Yılmaz; S. Dikmen (925-928).
In this study, the zeolitic tuffs having clinoptilolite obtained from Bigadic region of western of Anatolia, Turkey were investigated as regards to whether it is possible to be transformed into amorphous phase from them. At first, the zeolite tuffs rich in clinoptilolite were characterized using XRD, DTA, TG, DSC, and FTIR standard methods. All the samples were heated at 110 °C for 2 h and then were expanded within 5 min between the temperatures 1200 and 1400 °C. In addition, porosity and density were determined. The resistance values of all the samples were measured in acidic and basic media. These samples were also analyzed. As a result of this study, zeolitic tuffs in clinoptilolite were transformed into amorphous phase, and especially in chemical industry were found convenient.
Keywords: Zeolitic tuff; Clinoptilolite; Thermal treatment; DTA; TG; FTIR

Synthesis, spectral and thermal studies of new copper (II) complexes with 1,2-di(imino-2-aminomethylpyridil)ethane by Angela Kriza; Mariana Loredana Dianu; Cristian Andronescu; Adina Elena Rogozea; Adina Magdalena Musuc (929-935).
New copper (II) complexes of Schiff bases with 1,2-di(imino-2-aminomethylpyridil)ethane with the general composition CuLX m (H2O) x , [L = Schiff base, X = Cl, Br, NO3 , ClO4 , CH3COO, m = 2; X = SO4 2−, m = 1] were prepared by template synthesis. The complexes were characterized by elemental analysis, conductivity measurements, magnetic moments, IR, UV–VIS and EPR spectra. The thermal behavior of complexes was studied using thermogravimetry (TG), differential thermal analysis (DTA) and differential scanning calorimetry (DSC). Infrared spectra of all complexes are in good agreement with the coordination of a neutral tetradentate N4 ligand to the cooper (II) through azomethinic and pyridinic nitrogen. Magnetic, EPR and electronic spectral studies show a monomeric distorted octahedral geometry for all Cu(II) complexes. Conductance measurements suggest the non-electrolytic nature of the compounds, except for copper (II) nitrate and perchlorate complexes which are 1:2 electrolytes. Heats of decomposition, ΔH, associated with the exothermal effects were also determined.
Keywords: 2-aminomethylpyridine; Cu(II) complexes; Glyoxal; Template synthesis; Thermal analysis

Modulated DSC studies of Pb1−X Ca X TiO3 ferroelectric ceramics by Praniti Dave; M. Roy; Shiv Kumar Barbar; Sumit Jangid (937-940).
The polycrystalline ceramic samples of general formula Pb1−X Ca X TiO3 with X = 0.00, 0.1, 0.2 and 0.3 have been synthesized by standard high temperature solid state reaction method using high purity oxide and carbonates. The formation of the single phase compounds have been checked by X-ray diffraction technique. The Modulated Differential Scanning Calorimetry has been used to investigate the effect of substitution on the phase transition temperature and the corresponding change on the enthalpy and other thermal parameters of the substituted compound/solid solutions. It was observed that the phase transition temperature (T c ) decreases linearly with the increase of substitution concentration. The linear decrease in T c with increase of substitution concentration may be useful for the eventual functionality of the materials for different ferroelectric devices. The results are discussed in detail.
Keywords: Curie temperature; Ferroelectrics; Modulated DSC; Oxide ceramics; Phase transition; X-ray diffraction

Thermodynamic effects of linear dissipative small deformations by Afshin Anssari-Benam; Giuseppe Viola; Theodosios Korakianitis (941-947).
This paper presents a phenomenological model of dissipative losses manifested as heat transfer effects in small linear deformations of solid continua. The impetus is the need for a unified theory characterizing heat transfer effects (called “stretching calorimetry” in the literature) on the mechanics of deformations from a macroscopic point of view, overcoming the fragmentary description of these thermodynamic effects in the available literature. The model is based on derivation of mathematical expressions that quantify the contribution of the heat transfer effects and of the mechanical work in small linear deformations. The formulation has been developed by considering the Gibbs’ free energy and the entropy functions of the body under deformation and applying the energy balance to the continuum. The model has been compared to available experimental data of measurements of such heat effects in linear deformations (“stretching calorimetry”) of a broad range of materials. Results are presented by illustrating force-elongation values under the Hooke’s law, the proposed model, and the experimental data. The calculated model results show excellent agreement with the reported experimental data, for all the different classes of materials considered.
Keywords: Linear deformation; Deformation heating effect; Internal energy; Stretching calorimetry; Force-elongation

Thermal behavior of nitroguanidine (NQ) has been investigated by TG/DSC-MS-FTIR simultaneous analysis performed under both isothermal and nonisothermal conditions. The isothermal test at 230 °C indicated that the release of gas products can be divided into several stages. The processing of the non-isothermal data, namely 5, 10, 15, and 20 K/min, was performed by using Netzsch Thermokinetics. The dependence of the activation energy evaluated by Friedman’s isoconversional method on the conversion degree shows that the investigated process is complex one, and can be divided into three parts. The mechanism of the process and the corresponding kinetic parameters were determined by Multivariate Non-linear Regression Program. The kinetic results was used to simulate the thermal decomposition of NQ under isothermal condition at 210 °C. The simulated curve is in agreement with the tested curve. The obtained results were also used for prediction of the thermal lifetime of NQ corresponding to a certain temperature.
Keywords: Explosives; Nitroguanidine; Thermal decomposition; Multivariate non-linear regression

Trimellitate complexes of divalent transition metals with hydrazinium cation by S. Vairam; T. Premkumar; S. Govindarajan (955-960).
New dihydrazinium divalent transition metal trimellitate hydrates of empirical formula (N2H5)2M(Html)2·nH2O, where n = 1 for M = Co or Ni, and n = 2 for M = Mn, Zn, or Cd (H3tml = trimellitic acid), and monohydrazinium cadmium trimellitate, [(N2H5)Cd(Html)1.5·2H2O] have been prepared and characterized by physico-chemical methods. Electronic spectroscopic, and magnetic moment data suggest that Co and Ni complexes adopt an octahedral geometry. The IR spectra confirm the presence of monodentate carboxylate anion (Δν = νasy(COO) − νsym(COO) > 190 cm−1) and coordinated N2H5 + ion (νN–N 1015 − 990 cm−1) in all the complexes. All the complexes undergo endothermic decomposition eliminating CO2 in the temperature region 200–250 °C, followed by exothermic decomposition (in the range of 500–570 °C) of organic moiety to give the respective metal carbonate as the end products except nickel and cobalt complexes, which leave respective metal oxides. X-ray powder diffraction patterns reveal that Ni and Co complexes are isomorphous as are those of, Zn(II) and Cd(II) of the type, (N2H5)2M(Html)2·2H2O.
Keywords: Chemical synthesis; Inorganic compounds; Thermogravimetric analysis (TGA); X-ray diffraction

Thermoanalytical studies of natural potassium, sodium and ammonium alunites by János Kristóf; Ray L. Frost; Sara J. Palmer; Erzsébet Horváth; Emma Jakab (961-966).
Dynamic and controlled rate thermal analysis (CRTA) has been used to characterise alunites of formula [M(Al)3(SO4)2(OH)6] where M+ is the cations K+, Na+ or NH4 +. Thermal decomposition occurs in a series of steps: (a) dehydration, (b) well-defined dehydroxylation and (c) desulphation. CRTA offers a better resolution and a more detailed interpretation of water formation processes via approaching equilibrium conditions of decomposition through the elimination of the slow transfer of heat to the sample as a controlling parameter on the process of decomposition. Constant-rate decomposition processes of water formation reveal the subtle nature of dehydration and dehydroxylation.
Keywords: Alunite thermal analysis; Controlled rate thermal analysis; Dehydration; Dehydroxylation

The main purpose of this study is to review the current state of the problem of the impact of gaseous environment on the kinetics of solid-state decompositions. Three different theoretical approaches to the interpretation of the decomposition kinetics have been considered. As it follows from the literature published over the past 80 years, the Arrhenius and Knudsen–Langmuir approaches based on the assumption of two different reaction mechanisms (congruent and incongruent) could not solve the problem. At the same time, successes in the application of the thermochemical approach that is based on the assumption of a unitary congruent dissociative vaporization mechanism with condensation of oversaturated vapor remain unnoticed by the TA community. Taking into account this situation, the author has outlined the key points of the thermochemical kinetics in a compact but rigorous and complete form once more. The revised kinetic equations for the different modes of decomposition, several important interrelations between the kinetic parameters, and, finally, the results in the interpretation or reappraisal of the main effects related to the impact of gaseous environment on the kinetics have been considered. In the framework of the thermochemical approach, the problem being discussed may be considered nowadays practically resolved.
Keywords: Decomposition equations; Decomposition modes; Diffusion restriction; Impact of gaseous environment; Thermochemical kinetics; Topley–Smith effect; Zawadzki–Bretsznajder effect

Nonisothermal calorimetric study of the precipitation processes in a Cu–1Co–0.5Ti alloy by E. Donoso; A. Zúñiga; M. J. Diánez; J. M. Criado (975-980).
The precipitation processes in a Cu–1.0 at.%Co–0.5 at.%Ti (Cu–1.5 at.%Co2Ti) alloy were studied using differential scanning calorimetry (DSC), transmission electron microscopy (TEM), and microhardeness measurements. The analysis of the calorimetric curves from room temperature to 900 K shows the presence of two exothermic reactions attributed to the formation of CoTi and Co2Ti particles in the copper matrix. On the basis of enthalpy calculations, it was found that the decomposition begins with the precipitation of CoTi, followed by the formation of Co2Ti particles. The activation energies calculated using the modified Kissinger method were lower than the ones corresponding to diffusion of cobalt and titanium in copper. Kinetic parameters were obtained by a convolution method based on the Johnson–Mehl–Avrami (JMA) formalism. The values obtained for the parameter n were indicative of a particle nucleation process from preexistent nuclei. Microhardness measurements and TEM micrographs confirmed the formation of the mentioned phases.
Keywords: Copper alloys; DSC; Kinetics; Precipitation; Cu–Co–Ti alloys

Synthesis and thermal stability of hydrotalcites containing manganese by Laure-Marie Grand; Sara J. Palmer; Ray L. Frost (981-985).
The hydrotalcite based upon manganese known as charmarite Mn4Al2(OH)12CO3·3H2O has been synthesised with different Mn/Al ratios from 4:1 to 2:1. Impurities of manganese oxide, rhodochrosite and bayerite at low concentrations were also produced during the synthesis. The thermal stability of charmarite was investigated using thermogravimetry. The manganese hydrotalcite decomposed in stages with mass loss steps at 211, 305 and 793 °C. The product of the thermal decomposition was amorphous material mixed with manganese oxide. A comparison is made with the thermal decomposition of the Mg/Al hydrotalcite. It is concluded that the synthetic charmarite is slightly less stable than hydrotalcite.
Keywords: Charmarite; Rhodochrosite; Hydrotalcite; Hydrocalumite; Synthesis; Thermal stability

Human serum albumin (HSA) adsorbed onto silica nanoparticles modified by 3-aminopropyltriethoxysilane (APTES) and polyethyleneimine (PEI) was investigated by differential scanning calorimetry, IR spectroscopy, and photon correlation spectroscopy. The structural alterations of the protein molecules induced from adsorption process were estimated on the basis of temperatures of denaturation transition (T d) of the protein in free (native) and adsorbed form. It was found that adsorption of the protein onto the APTES-modified silica nanoparticles results in an increase in the temperature of denaturation transition from 42 to 47.4 °C. HSA adsorbed onto the PEI-modified silica nanoparticles unfolds extensively.
Keywords: DSC; Human serum albumin; Modified silica nanoparticles temperature of denaturation transition; Structural alterations

Reactions of manganese oxides with K2S2O7 by Monika Mazur; Zygmunt Gontarz (993-998).
The course of reactions of potassium disulphate(VI) with manganese oxides: MnO, Mn2O3 and MnO2 was studied in solid phase. In the reactions all the manganese oxides were reduced to Mn2+ which then became a component of one of the reaction products namely K2Mn2(SO4)3. A classification scheme of the reaction path has been proposed.
Keywords: Sodium disulphate(VI); Manganese oxides; Thermal decomposition

The crystallization and melting behavior of PP/CaCO3 nanocomposites during thermo-oxidative degradation process were studied using differential scanning calorimetry and X-ray diffraction. The results indicated that addition of nano-CaCO3 and compatibilizer significantly reduced the thermo-oxidative stability of PP. Before degradation, thermal aging resulted in an increase in the melting temperature and crystallinity of PP due to the annealing crystallization. Thermo-oxidative degradation decreased the melting temperature and increased melting range, and caused an increase in crystallinity of PP due to the chemi-crystallization. The investigation also indicated that the influence of degradation on the small crystals were much more significant than that on the large ones.
Keywords: Crystallization; Nanocomposites; Polypropylene; Thermo-oxidative stability

Organic–inorganic hybrid composites of epoxy and phenyltrisilanol polyhedral oligomeric silsesquioxane (Ph7Si7O9(OH)3, POSS-triol) were prepared via in situ polymerization of epoxy monomers. The nanocomposites of epoxy with POSS-triol can be prepared in the presence of metal complex latent catalyst, aluminum triacetylacetonate ([Al]) for the reaction between POSS-triol and diglycidyl ether of bisphenol A (DGEBA). The dispersion morphology of organic–inorganic hybrid was characterized by scanning electronic microscopy (SEM). The thermostability of composites was evaluated by thermal gravimetric (TG) analysis. The flammability was evaluated by cone calorimeter test. The presence of [Al] latent catalyst leads to a decrease in combustion rate with respect to epoxy and epoxy/POSS composites as well as reduction in smoke, CO and CO2 production rate. The effect of [Al] is to reduce the size of spherical POSS particles from 3–5 μm in epoxy/POSS to 0.5 μm in epoxy/POSS[Al]. Furthermore, POSS with smaller size may form compact and continue char layer on the surface of composites more efficiently.
Keywords: Polyhedral oligomeric silsesquioxane; Flame retardancy; Latent catalyst; Cone calorimeter

Thermal studies of DBSA-doped polyaniline/PVC blends by isothermal microcalorimetry by Asma Binat Afzal; Muhammad Javed Akhtar; Lars-Gunnar Svensson (1017-1025).
A series of blends of dodecylbenzenesulfonic acid (DBSA)-doped polyaniline (PANDR) and PVC were synthesized by solution blending technique and investigated by heatflow microcalorimetry (HFC) for thermal and oxidative stability and for PVC–PANDR compatibility. FTIR results provided evidence for strong dipole–dipole interactions between PANDR and PVC. The energy of the oxidation is independent of the composition. The interaction energy and thermal stability increased with the increase of PANDR content in the blend. The activation energies calculated by using Arrhenius relationship can be employed for accelerated ageing of the synthesized blends. It has been observed that the average degradation of PANDR component is higher than that of PVC.
Keywords: Blends; Microcalorimetry; HFC; Polyaniline

The title terpolymer (8-HQ5-SAMF-II) is synthesized by the condensation of 8-hydroxyquinoline 5-sulfonic acid (8-HQ5-SA) and melamine (M) with formaldehyde (F) in the presence of acid catalyst and using 2:1:3 M proportions of the reacting monomers. The synthesized terpolymer resin is then characterized by different physicochemical techniques viz. number average molecular mass determination, intrinsic viscosity determination, and spectral studies like UV–Visible, IR, 1H NMR, and 13C NMR spectra. The morphology of synthesized terpolymer was studied by scanning electron microscopy (SEM). The thermogravimetry of the terpolymer resin prepared in this study has been carried out by non-isothermal thermogravimetry technique in which sample is subjected to condition of continuous increase in temperature at linear rate. Thermal study of the resin was carried out to determine their mode of decomposition and relative thermal stabilities. Thermal decomposition curves were studied carefully with minute details. The Freeman-Carroll and Sharp-Wentworth methods have been used in the present investigation to calculate thermal activation energy and different kinetic parameter of the terpolymer resins. Thermal activation energy E a calculated with the two above-mentioned methods are in close agreement. The advantage of Freeman-Carroll method is to calculate both the order of reaction n and energy of activation in one single stage by keeping heating rate constant. By using data of thermogravimetry, various thermodynamic parameters like frequency factor Z, entropy change ΔS, free energy change ΔF, and apparent entropy S* have been determined using Freeman-Carroll method.
Keywords: Decomposition; Polycondensation; Resins; Synthesis; Thermogravimetric analysis

Influence of surface modification on thermal stability and flammability of cross-linked rubbers by Przemysław Rybiński; Grażyna Janowska; Agnieszka Kucharska-Jastrząbek (1037-1044).
The paper discusses the test results of thermal stability and flammability of cross-linked diene rubbers containing silica prepared “in situ” from alkoxysilane precursors. The effect of the surface modification of unfilled vulcanizates by means of aqueous solutions of halogens, boron and organo-phosphoric compounds on their flammability was also assessed. The thermal analysis has been performed in air with the use of derivatography. The flammability of vulcanizates has been determined by the method of oxygen index and in air. It has been found that the modification of the vulcanizates with tetraethoxysilane that makes it possible to form silica “in situ” considerably reduces the flammability of cross-linked rubbers. The surface modification of the vulcanizates with halide and organo-phosphoric compounds allows one to radically decrease their flammability. The boric flame-retardant agents are the most effective modifiers. The most beneficial results were obtained with the use of boric acid.
Keywords: Elastomers; Flammability; Surface modification; Thermal properties

A comparative study of the non-isothermal degradation of natural rubber from Mangabeira (Hancornia speciosa Gomes) and Seringueira (Hevea brasiliensis) by Eliton S. Medeiros; Patrini D. Galiani; Rogerio M. B. Moreno; Luiz H. C. Mattoso; José A. Malmonge (1045-1050).
Due to the increasing search for alternative sources of natural rubber (NR) whose properties are similar to Hevea brasiliesis, several sources have been studied in the past few years. Among them, Mangabeira (Hancornia speciosa Gomes), which is native to Amazon rainforest and other regions of Brazil, has a potential as another viable rubber source. As a continuation of a series of comparative studies between Hancornia and Hevea (clone RRIM 600) these two species by our research team, their thermal behavior was analyzed by thermogravimetry (TG) using Flynn–Wall–Ozawa’s approach in order to obtain kinetic parameters (reaction order, pre-exponential factor and activation energy) of the decomposition process. Results indicated that the thermal behavior of NR from Hancornia was comparable to Hevea with some differences observed as follows: reaction order for Hancornia was higher than for Hevea at the beginning of degradation and very close for temperatures over 350 °C; activation energy and pre-exponential factor had the same trend, i.e., increased with increasing degree of conversion remaining almost constant between 20 and 70% and then increasing for higher degrees, although Hevea was slightly more thermally stable than Hancornia. These major influences in the degradation process in the early stage are attributed to differences in non-rubber constituents present in these two species.
Keywords: Natural rubber; Thermal behavior; Hevea brasiliensis and Hancornia speciosa Gomes; Mangabeira

Thermal analysis of the combustion of charcoals from Eucalyptus dunnii obtained at different pyrolysis temperatures by Andrés Cuña Suárez; Nestor Tancredi; Paulo César C. Pinheiro; María Irene Yoshida (1051-1054).
DSC and TG/DTA were used to study charcoals obtained from eucalyptus wood at different pyrolysis temperatures, as well as the exchanged energy, and the transformations involved during the pyrolysis process. Charcoals DSC curves showed two exothermic peaks, at ~610 and ~750 K. The first peak was squashed for those charcoals obtained at higher final pyrolysis temperatures, and it disappeared in the charcoals obtained at 873 and 923 K. The second peak intensity increased and its location changed at the higher temperatures. Charcoal characterization showed a rise of heat values with the pyrolysis temperature.
Keywords: Biomass; Charcoal; Combustion; DSC; TG/DTA

Kinetics of thermal degradation of poly(aryl ether)s containing phthalazinone and life estimation by W. He; F. Deng; G.-X. Liao; W. Lin; Y.-Y. Jiang; X.-G. Jian (1055-1062).
New special engineering thermoplastics, poly(phthalazinone ether sulfone) (PPES) and poly(phthalazinone ether sulfone ketone) (PPESK), containing phthalazinone are synthesized through step-polymerization. The kinetics of thermal degradation of PPES and PPESK (1/1) in nitrogen is investigated at several heating rates by thermogravimetry (TG). It is concluded that, based on using Satava’s theory, the thermal degradation mechanism of PPESK (1/1) is nucleation and growth, the order of reaction of the degradation process is one (n = 1). In contrast, the thermal degradation mechanism of PPES is a phase boundary controlled reaction and the order of the reaction is two (n = 2). The kinetic parameters, including reaction energy and frequency factor of thermal degradation reaction for PPES and PPESK (1/1) are analyzed using isoconversional Friedman, Kissinger–Akahira–Sunose (K–A–S) and Ozawa method. In addition, the study focus on the influence of heating rate and ratio of ketone/sulfone on thermal stability and the life estimation are described.
Keywords: Poly(aryl ether); Thermal degradation; Kinetics; Life estimation

A series of PET/acid-treated multi-walled carbon nanotubes (MWCNTs) nanocomposites of varying nanoparticles’ concentration were prepared, using the in situ polymerization technique. TEM micrographs verified that the dispersion of the MWCNTs into the PET matrix was homogeneous, while some relatively small aggregates co-existed at higher filler contents. Intrinsic viscosity of the prepared nanocomposites was increased at low MWCNTs contents (up to 0.25 wt%), while at higher contents a gradual reduction was observed. The surface carboxylic groups of acid-treated MWCNTs probably reacted with the hydroxyl end groups of PET, acting as chain extenders at smaller concentrations, while at higher concentrations, on the other hand, led to the formation of branched and cross-linked macromolecules, with reduced apparent molecular weights. From the thermogravimetric curves, it was concluded that the prepared samples exhibited good thermostability, since no remarkable mass loss occurred up to 320 °C (<0.5%). The activation energy (E) of degradation of the studied materials was estimated using the Ozawa, Flynn, and Wall (OFW), Friedman and Kissinger’s methods. Pure PET had an E = 223.5 kJ/mol, while in the PET/MWCNTs nanocomposites containing up to 1 wt% the E gradually increased, indicating that MWCNTs had a stabilizing effect upon the decomposition of the matrix. Only the sample containing 2 wt% of MWCNTs exhibited a lower E due to the existence of the aforementioned cross-linked macromolecules. The form of the conversion function for all the studied samples obtained by fitting was the mechanism of nth-order auto-catalysis.
Keywords: Poly(ethylene terephthalate); Multi-walled carbon nanotubes; Nanocomposites; Thermal degradation kinetics; Activation energy

Enthalpic interactions of anti-tumor drug matrine in aqueous sodium chloride solutions by Xiang Jun Sun; Xiang Yu Xu; Min Liu; Lin Wei Li; De Zhi Sun (1073-1077).
The enthalpies of dilution of matrine (MAT) in pure water and aqueous sodium chloride solutions were determined by isothermal titration microcalorimetry at 298.15 K, and the corresponding homogeneous enthalpic interaction coefficients were calculated according to the modified McMillan–Mayer model. The values of enthalpic pair-wise interaction coefficients, h 2, are all positive and become more positive with increasing concentration of sodium chloride.
Keywords: Aqueous sodium chloride solution; Enthalpic pair-wise interaction coefficients; Enthalpy of dilution; Matrine

Thermodynamic study on the interaction of cyanide ion and jack bean urease at different temperatures by G. Rezaei Behbehani; A. A. Saboury; M. Mohebbian; J. Abedini; S. Tahmasebi Sarvestani (1079-1083).
A method based on Isothermal Titration Calorimety (ITC) is described for the thermodynamic assay of jack bean urease. Inhibitory activity of cyanide ion was examined against jack bean urease (JBU), at 27 and 37 oC in 30 mM Tris buffer of pH = 7. The binding parameters of the CN + JBU complexation have been calculated. It was found that in the low and high concentrations of the cyanide ions, the JBU structure was destabilized, resulting in a decrease in its biological activity.
Keywords: Jack bean urease; Cyanide ion; Isothermal titration calorimetry; Binding parameters; Solvation model

Because of the health problems associated with trans fatty acids (TFAs) in hydrogenated oil, the objective of this research was to accelerate crystallization of the trans-free unhydrogenated palm oil (UPO) as a hydrogenated palm oil (HPO) substitute. Crystallization thermograms of UPO blended with icing sugar (1:1.5 mass ratio) from different initial heating temperatures were measured by differential scanning calorimetry (DSC), to study its effects on crystallization rate. DSC thermograms of UPO and HPO cooled from two melt states (the complete melting state 80 °C and the incomplete state 40 °C) were also compared. Crystallization rates from temperatures above the melting point (m.p.) were faster than those below the top limit of the m.p. The reason may be that a higher initial heating temperature induced a completely melted state and thus a larger driving force toward the solid phase. Raising the processing temperature to 80 °C, UPO may have a crystallization rate the same as, if not faster than, HPO. This study provides a new way to accelerate the crystallization of the trans-free UPO, making HPO a realistic substitute in the food industry.
Keywords: Unhydrogenated palm oil; Trans fatty acid; Initial heating temperature; Crystallization rate; Differential scanning calorimetry

The heat capacities of Ln(Me2dtc)3(C12H8N2) (Ln = La, Pr, Nd, Sm, Me2dtc = dimethyldithiocarbamate) have been measured by the adiabatic method within the temperature range 78–404 K. The temperature dependencies of the heat capacities, C p,m [La(Me2dtc)3(C12H8N2)] = 542.097 + 229.576 X − 27.169 X 2 + 14.596 X 3 − 7.135 X 4 (J K−1 mol−1), C p,m [Pr(Me2dtc)3(C12H8N2)] = 500.252 + 314.114 X − 17.596 X 2 − 0.131 X 3 + 16.627 X 4 (J K−1 mol−1), C p,m [Nd(Me2dtc)3(C12H8N2)] = 543.586 + 213.876 X − 68.040 X 2 + 1.173 X 3 + 2.563 X 4 (J K−1 mol−1) and C p,m [Sm(Me2dtc)3(C12H8N2)] = 528.650 + 216.408 X − 16.492 X 2 + 12.076 X 3 + 4.912 X 4 (J K−1 mol−1), were derived by the least-squares method from the experimental data. The heat capacities of Ce(Me2dtc)3(C12H8N2) and Pm(Me2dtc)3(C12H8N2) at 298.15 K were evaluated to be 617.99 and 610.09 J K−1 mol−1, respectively. Furthermore, the thermodynamic functions (entropy, enthalpy and Gibbs free energy) have been calculated using the obtained experimental heat capacity data.
Keywords: Ln(Me2dtc)3(C12H8N2); Adiabatic calorimetry; Heat capacity

Study of the polythermal diagram water–sodium sulphate–piperidine by E. Labarthe; A. J. Bougrine; H. Delalu (1099-1105).
Two isothermal sections of the isobaric ternary system H2O–Na2SO4–C5H10NH were determined by isoplethic thermal analysis at 293 and 323 K. The compositions of the aqueous and organic invariant liquids, respectively L1 and L2, as well as that of the critical point, were characterized for each isotherm. The temperature of the invariant reaction was obtained by controlled flow thermal analysis and the temperature of the demixing ending, by interpolation of the monovariant lines. All these informations allowed us to establish the isobaric polythermal diagram of the H2O–Na2SO4–C5H10NH system, for the temperature range 293–323 K, as well as a qualitative representation of the monovariant curves. This system is then characterized by a wide miscibility gap, three crystallization domains, and four-three-phase invariant domains. The relevant exploitation of this diagram so permits us to deduce the demixing temperature leading to the optimal transfer of the organic compounds in the light phase and also the composition of the organic phase recovered after this first step of extraction.
Keywords: Ternary system; Miscibility gap; Piperidine; Sodium sulphate; Water

Thermal behaviour and spectroscopic investigation of some methyl 2-pyridyl ketone complexes by Mariana Tătucu; Petre Rotaru; Ileana Rău; Cezar Spînu; Angela Kriza (1107-1114).
Pyridine derivative complexes are widely employed as biological active materials especially as antibacterial agents. Five transition metal(II) mpk complexes (mpk = methyl 2-pyridyl ketone) were synthesized and investigated using elemental analysis, spectroscopic techniques (IR and UV–Vis–NIR) and conductometric measurements. The general formulae established from experimental data were found to be [M(mpk)2(NO3)2xH2O (x = 0 for M = Cd(II), Zn(II), x = 2 for M = Cu(II)) and [M(mpk)2(H2O)2](NO3)2 (M = Co(II), Ni(II)). These compositions were further confirmed by thermal analysis and their thermal stability in dynamic air atmosphere investigated.
Keywords: Methyl 2-pyridyl ketone; Transition metal(II) complexes; Thermal analysis

A novel complex [Ni(H2O)4(TO)2](NO3)2·2H2O (TO = 1,2,4-triazole-5-one) was synthesized and structurally characterized by X-ray crystal diffraction analysis. The decomposition reaction kinetic of the complex was studied using TG-DTG. A multiple heating rate method was utilized to determine the apparent activation energy (E a) and pre-exponential constant (A) of the former two decomposition stages, and the values are 109.2 kJ mol−1, 1013.80 s−1; 108.0 kJ mol−1, 1023.23 s−1, respectively. The critical temperature of thermal explosion, the entropy of activation (ΔS ), enthalpy of activation (ΔH ) and the free energy of activation (ΔG ) of the initial two decomposition stages of the complex were also calculated. The standard enthalpy of formation of the new complex was determined as being −1464.55 ± 1.70 kJ mol−1 by a rotating-bomb calorimeter.
Keywords: 1,2,4-Triazole-5-one; Nickel complex; Thermal analytical kinetic; Standard enthalpy of formation