Journal of Thermal Analysis and Calorimetry (v.99, #3)
Preface by Isabelle Beurroies; Jean Rouquerol (721-722).
Thermal transitions of polylactide false-twist textured multifilaments determined by DSC and TMA by A. M. Manich; J. Carilla; R. A. L. Miguel; J. M. Lucas; F. G. F. Franco; L. A. Montero; D. Cayuela (723-731).
A partially oriented melt-extruded PLA multifilament was false-twist textured to stabilize its structure. Conventional DSC analysis showed a relaxation peak at the end of glass transition. Simultaneous consideration of the TMA curve enabled us to evaluate both the relaxation and the cold crystallisation produced during the DSC scan. The periodic load applied during TMA experiments also enabled us to examine the evolution of Young’s modulus along the glass transition, relaxation and cold crystallisation phenomena. Increases in Young’s modulus and in enthalpy are related because of crystallisation. Texturing increased crystallinity and decreased cold crystallisation of PLA during the DSC scan.
Keywords: Crystallisation; False-twist texturing; Polylactide; Relaxation; Thermal transitions
Adsorption of organic pollutants over microporous solids investigated by microcalorimetry techniques by B. Dragoi; V. Rakic; E. Dumitriu; A. Auroux (733-740).
This work is focused on the gas and liquid-phase adsorption of pollutants: propanol, 2-butanone, phenol and nicotine onto zeolites (H-BETA, H-ZSM-5, H-MCM-22, and clinoptilolite). Textural properties and origin of zeolites were taken into account as criteria of adsorbents selection. The aldehyde and the ketone were adsorbed in the gas phase using microcalorimetry linked to a volumetric line to evaluate adsorption. Adsorptions in water were carried out for phenol and nicotine and the evolved heats during adsorption were measured by a differential heat flow reaction calorimeter with stirring. Results are discussed in relation with the pore sizes and various interactions which could occur between the adsorbent and the adsorbate.
Keywords: Adsorption; Depollution; Microcalorimetry; Organic pollutants; Zeolites
Effect of amyloid beta peptides Aβ1–28 and Aβ25–40 on model lipid membranes by Maksim Ionov; Barbara Klajnert; Konstantinos Gardikis; Sophia Hatziantoniou; Bartlomiej Palecz; Bakhtiyar Salakhutdinov; Josep Cladera; Maria Zamaraeva; Costas Demetzos; Maria Bryszewska (741-747).
To investigate the molecular interaction of amyloid beta peptides Aβ1–28 or Aβ25–40 with model lipid membranes differential scanning calorimetry (DSC) and DPH and TMA DPH fluorescence anisotropy approaches were used. The main transition temperature (T m) and enthalpy change (ΔH) of model lipid membranes composed of DMPC/DPPG on addition of Aβ25–40 or Aβ25–40 at 10:1 (w/w) phospholipid/peptide ratio either non-aggregated or previously aggregated were examined. The effect of Aβ1–28 and Aβ25–40 on the membrane fluidity of liposomes made of DMPC/DPPG (98:2 w/w) was determined by fluorescence anisotropy of incorporated DPH and TMA DPH. The results of this study provide information that Aβ1–28 preferentially interacts with the hydrophilic part of the model membranes, while Aβ25–40 rather locates itself in the hydrophobic core of the bilayer where it reduces the order of the phospholipids packing.
Keywords: Amyloid beta peptides; DMPC membrane; DPH fluorescence anisotropy; DSC
Thermal behaviour of ammonium nitrate prills coated with limestone and dolomite powder by I. Rudjak; T. Kaljuvee; A. Trikkel; V. Mikli (749-754).
The thermal behaviour of ammonium nitrate (AN) and its prills coated with limestone and dolomite powder was studied on the basis of commercial fertilizer-grade AN and six Estonian limestone and dolomite samples. Coating of AN prills was carried out on a plate granulator and a saturated solution of AN was used as a binding agent. The mass of AN prills and coating material was calculated based on the mole ratio of AN/(CaO + MgO) = 2:1. Thermal behaviour of AN and its coated prills was studied using combined TG-DTA-FTIR equipment. The experiments were carried out under dynamic heating conditions up to 900 °C at the heating rate of 10 °C min−1 and for calculation of kinetic parameters, additionally, at 2, 5 and 20 °C min−1 in a stream of dry air. A model-free kinetic analysis approach based on the differential isoconversional method of Friedman was used to calculate the kinetic parameters. The results of TG-DTA-FTIR analyses and the variation of the value of activation energy E along the reaction progress α indicate the complex character of the decomposition of neat AN as well as of the interactions occurring at thermal treatment of AN prills coated with limestone and dolomite powder.
Keywords: Coated ammonium nitrate; Dolomite; Kinetics; Limestone; TG-DTA; Thermal stability
Thermal behaviour of melamine-modified urea–formaldehyde resins by Kadri Siimer; Tiit Kaljuvee; Tõnis Pehk; Ilmar Lasn (755-762).
Thermal behaviour of industrial UF resins modified by low level of melamine was followed by TG-DTA technique on the labsys TM instrument Setaram together with the 13C NMR analysis of resin structure and testing boards in current production at Estonian particleboard factory Pärnu Plaaditehas AS. DTA curve of UF resin which has been cocondensed during synthesis with even low level of melamine shows the shift of condensation exotherm and water evaporation endotherm to considerable higher temperatures. The effect of melamine monomer introduced to UF resin just before curing was compared. The effect of addition of urea as formaldehyde scavenger was studied.
Keywords: Curing; 13C NMR; Particleboards; TG-DTA analysis; Urea–formaldehyde modified resins
CO2 and SO2 uptake by oil shale ashes by Andres Trikkel; Merli Keelmann; Tiit Kaljuvee; Rein Kuusik (763-769).
In the present research, CO2 and SO2 binding ability of different oil shale ashes and the effect of pre-treatment (grinding, preceding calcination) of these ashes on their binding properties and kinetics was studied using thermogravimetric, SEM, X-ray, and energy dispersive X-ray analysis methods. It was shown that at 700 °C, 0.03–0.28 mmol of CO2 or 0.16–0.47 mmol of SO2 was bound by 100 mg of ash in 30 min. Pre-treatment conditions influenced remarkably binding parameters. Grinding decreased CO2 binding capacities, but enhanced SO2 binding in the case of fluidized bed ashes. Grinding of pulverized firing ashes increased binding parameters with both gases. Calcination at higher temperatures decreased binding parameters of both types of ashes with both gases studied. Clarification of this phenomenon was given. Kinetic analysis of the binding process was carried out, mechanism of the reactions and respective kinetic constants were determined. It was shown that the binding process with both gases was controlled by diffusion. Activation energies in the temperature interval of 500–700 °C for CO2 binding with circulating fluidized bed combustion ashes were in the range of 48–82 kJ mol−1, for SO2 binding 43–107 kJ mol−1. The effect of pre-treatment on the kinetic parameters was estimated.
Keywords: CFBC ashes; CO2 capture; Kinetics; Oil shale; SO2 capture
Calorimetric approach to metabolic carbon conversion efficiency in soils by N. Barros; J. Salgado; J. A. Rodríguez-Añón; J. Proupín; M. Villanueva; L. D. Hansen (771-777).
Soil carbon is the largest reservoir of organic carbon on the planet and CO2 production by soil thus has potentially large effects on atmospheric CO2. Carbon sequestration in soil is determined by the metabolic efficiency (substrate carbon conversion efficiency) of soil micro-organisms. That could be measured by calorespirometric methodology (parallel measurement of metabolic heat rate and CO2 production rate) and by theoretical thermodynamic models. Carbon conversion efficiency of the glucose degradation reaction in soil is calculated from both the calorespirometric ratio of heat rate to CO2 rate and from energy and mass balance models combined with calorimetric heat rates. Results obtained, 0.77 and 0.75, are in good agreement.
Keywords: Metabolic efficiency; Calorespirometry; Soils; Energy balance
Effect of different clay concentrations on crude oil combustion kinetics by thermogravimetry by M. V. Kok; A. S. Gundogar (779-783).
The objective of this research was to investigate the effect of different clay composition and concentrations on the thermal behaviour and kinetics of heavy crude oil in limestone matrix by thermogravimetry (TG/DTG). In TG/DTG experiments, three distinct reaction regions were identified in all of the crude oil + limestone mixture known as low temperature oxidation (LTO), fuel deposition (FD) and high temperature oxidation (HTO) respectively. Addition of clay to porous matrix significantly affected the reaction regions. Significant reduction of activation energy due to addition of clay to crude oil indicates the catalytic effect of clay on crude oil combustion.
Keywords: Clay; Crude oil; Thermogravimetry; Kinetics; Activation energy
A calorimetric study of the temperature effect on Calcium Phosphate precipitation by Anastasios I. Mitsionis; Tiverios C. Vaimakis (785-789).
The precipitation of calcium phosphate was studied using a heat flow twin calorimeter (C80, Setaram, France). The process was carried out using two identical membrane vessels. In the lower parts of both vessels 2 mL of a supersaturated solution (solution A) containing Ca(H2PO4)·2H2O (0.054 M) and CaCl2·H2O (0.125 M) with a molar ratio Ca/P = 1.67 were added. Then 0.05 mL of an ammonium solution (25% w/w) (solution B) and 0.05 mL of distilled water were transferred in the upper parts of sample and reference vessels, respectively. After temperature had been maintained at 303, 313, 323 and 333 K the membranes of both sample and reference vessels were broken simultaneously. The precipitation process also repeated with the same conditions for periods of 15, 60 and 120 min in a bath. The first two calorimetric curves (303, 313 K) show a single exothermic step during the process as a sharp peak in the initial stage. On the contrary at the experimental temperature of 323 K except of the sharp peak in the initial stage, a steadily exothermic tendency appears after 100 min time. In higher temperature (333 K) the sharp peak appears in the initial stage followed by a broad exothermic step between 75 and 320 min time. The XRD analyses show that the solids in the initial experimental stages are mainly consisted of dicalcium phosphate dihydrate (DCPD) for the lower temperature and a biphasic or triphasic system consisted of hydroxyapatite (HA), dicalcium phosphate anhydrous (DCPA) and octacalcium phosphate (OCP) for the rest temperatures. The XRD analyses show also that during the solution aging the initial products are transformed into the more stable thermal forms of HA and octacalcium phosphate (OCP).
Keywords: Calcium phosphate; Calorimeter; Hydroxyapatite
Modelling of the thermal effects involved in the determination of heat of mixing, using an ITC operating in continuous mode by M. Rodríguez de Rivera; F. Socorro; J. S. Matos (791-797).
A simplified RC model which simulates the operation mode of an isothermal titration calorimeter (ITC), when it is used in a continuous mode to determine heat of mixing, is proposed. The model takes into account several thermal effects that are evident in the mixing process and it must be identified and quantified to determine reliable values of heat of mixing. The main effects considered in the development of the model were those caused by: (i) the difference between the temperatures of the injected liquid and the mixture, (ii) the increase in heat capacity of the mixture and the thermal conductance of the couplings between the mixture and its surroundings and (iii) the changes in the power dissipated by stirring after injection. A good agreement between model and experimental results is observed.
Keywords: Calorimetric model; Calorimetric simulation; Excess molar enthalpies; Isothermal titration calorimeter
Development of a calorimetric sensor for medical application by F. Socorro; M. Rodríguez de Rivera (799-802).
A calorimetric sensor has been developed to measure the calorific dissipation through a determined area of the human body surface. An experimental laboratory prototype with a capturing surface of 36 cm2 has been built, and a functioning model suggesting an operational method that allows to determine the calorific power going through the sensor has been proposed.
Keywords: Calorimetric sensor; Calorimetric model; Medical calorimetry
A thermal study approach to roman age wall painting mortars by A. Duran; L. A. Perez-Maqueda; J. Poyato; J. L. Perez-Rodriguez (803-809).
Roman ancient mortars have been widely studied, in connection with both diagnosis and application required for restoring. Thermoanalytical experiments performed on mortars from Pompeii and Herculaneum provided a very good understanding of the technology employed. The mortars from Pompeii were obtained by the proper mixing of lime and marble grains while mortars of Herculaneum by lime and silicates compounds. The position of the endothermic peak of calcite decomposition showed important variations in the different samples studied, which was assigned to the different crystallinity and particle sizes. Experiments under CO2 flow confirmed the presence of magnesium calcium carbonates.
Keywords: Historic mortars; Lime; Marble; TG–DTG–DTA; Carbonates decomposition; CO2 flow
TGMS analysis of archaeological bone from burials of the late Roman period by T. Devièse; M. P. Colombini; M. Regert; B. H. Stuart; J. P. Guerbois (811-813).
The use of thermogravimetric analysis–mass spectrometry (TGMS) to study the state of preservation of archaeological bones has been investigated. As part of a collaborative multi-analytical study, bones exhumed from graves of the late Roman period in France and Italy were examined. A decrease in organic matter for the archaeological bones compared to that for new bone was confirmed, demonstrating that diagenesis of aged bones can be detected using TGMS. Different amounts of collagen were determined for bones from different graves and could, for the majority of specimens, be correlated with the visually observed preservation states.
Keywords: Archaeology; Bone; Collagen; TGMS
Thermal, spectral and antimicrobial study on some Cu(II) complexes with ligands bearing biguanide moieties by Rodica Olar; Mihaela Badea; Dana Marinescu; Emilia Elena Iorgulescu; Eliza Frunza; Veronica Lazar; Carmen Chifiriuc (815-821).
New complexes of type [Cu(HTBG)2]Cl2 (1), [Cu(TBG)2]·3H2O (2) and [CuL]·nH2O (3) L:L1, n = 2 and (4) L:L2, n = 1 (HTBG: 2-tolylbiguanide, L1 and L2: ligands resulted from 2-tolylbiguanide, ammonia/hydrazine and formaldehyde one pot condensation) were synthesised and characterised. The features of complexes have been assigned from microanalytical, IR and UV–Vis data. Redox behaviour was established by cyclic voltammetry. The in vitro qualitative and quantitative antimicrobial activity assays showed that the complexes exhibited variable antimicrobial activity against Gram-negative and Gram-positive strains isolated from the hospital environment. The thermal analyses have evidenced the thermal intervals of stability and also the thermodynamic effects that accompany them. After water elimination, complexes have a similar thermal behaviour. Processes as water elimination, melting, chloride anion removal as well as oxidative degradation of the organic ligands were observed. The final product of decomposition was copper (II) oxide.
Keywords: Antimicrobial activity; Copper (II) complex; One pot condensation; Thermal behaviour; o-Tolylbiguanide
Thermal stability of new vanadyl complexes with flavonoid derivatives as potential insulin-mimetic agents by Mihaela Badea; Rodica Olar; Dana Marinescu; Valentina Uivarosi; Victoria Aldea; Teodor Octavian Nicolescu (823-827).
A series of new complexes of the type VO(OH)L·nH2O ((1) L: fisetin, n = 3; (2) L: quercetin, n = 2; (3) L: morin, n = 4) were synthesised and characterised by analytical as well as IR and electronic data. The modification evidenced in IR spectra was correlated with the presence of flavonoid as bidentate in all complexes. The electronic reflectance spectra showed the d–d transition characteristic for the square-pyramidal stereochemistry of vanadium (IV) ion. The thermal analysis (TG, DTA) in synthetic air flow elucidated the composition and also the number and nature of the water molecules. The TG curves show three well-separated thermal events. The first corresponds to the water loss at lower temperatures, which is followed by flavonoid derivative decomposition and pyrolysis at higher temperatures. The final product is vanadium (V) oxide.
Keywords: Flavonoid derivative; Vanadyl(IV) complex; Thermal stability
Thermal study of some new quinolone ruthenium(III) complexes with potential cytostatic activity by Mihaela Badea; Rodica Olar; Dana Marinescu; Valentina Uivarosi; Teodor Octavian Nicolescu; Daniela Iacob (829-834).
A series of new complexes with mixed ligands of the type RuL m (DMSO) n Cl3·xH2O ((1) L: oxolinic acid (oxo), m = 1, n = 0, x = 4; (2) L: pipemidic acid (pip), m = 2, n = 1, x = 2; (3) L: enoxacin (enx), m = 2, n = 1, x = 0; (4) L: levofloxacin (levofx), m = 2, n = 2, x = 8; DMSO: dimethylsulfoxide) were synthesized and characterized by chemical analysis, IR and electronic data. Except oxolinic acid that behaves as bidentate, the other ligands (quinolone derivatives and DMSO) act as unidentate. Electronic spectra are in accordance with an octahedral stereochemistry. The thermal analysis (TG, DTA) in synthetic air flow elucidated the composition and also the number and nature of both water and DMSO molecules. The TG curves show 3–5 well-separated thermal steps. The first corresponds to the water and/or DMSO loss at lower temperatures followed either by quinolone thermal decomposition or pyrolisys at higher temperatures. The final product is ruthenium(IV) oxide.
Keywords: DMSO; Quinolone; Ruthenium complex; Thermal behavior
On the lifetime prediction of old documents by N. Melniciuc-Puica; G. Lisa; I. Rusu (835-842).
The paper deals with the study of thermal degradation of some new and old paper supports. The experimental data allows the prediction of the dependence between the half time and the temperature at which the paper support must to be kept.
Keywords: Isoconversional method; Paper supports; Thermal degradation
Calorimetric study of the acidic character of V2O5–TiO2/SO4 2− catalysts used in methanol oxidation to dimethoxymethane by H. Zhao; S. Bennici; J. Shen; A. Auroux (843-847).
The surface acidic properties of sulfated vanadia–titania catalysts prepared by various methods were investigated by adsorption microcalorimetry, using ammonia as probe molecule. The acidic characteristics of the samples were shown to be strongly affected by the preparation method, calcination temperature, and sulfur content. The samples prepared by sol–gel and mechanical grinding exhibited higher acidity than co-precipitated samples. Moreover, increasing the calcination temperature of co-precipitated samples resulted in a decrease in surface area from 402 to 57 m2 g−1 and sulfur content from around 4 to 0.2 mass%, but up to a certain point generated a stronger acidity. The optimal calcination temperature appeared to be around 673 K.
Keywords: Acidity; Calorimetry; Dimethoxymethane; Methanol selective oxidation; V2O5–TiO2/SO4 2−
Study of acidic commercial WO x /ZrO2 catalysts by adsorption microcalorimetry and thermal analysis techniques by R. Kourieh; S. Bennici; A. Auroux (849-853).
In this work we report about the characterization of the acidic and redox properties of four different commercial tungstated zirconia catalysts with W loadings of about 12–13 mass%. The samples have been characterized in terms of their micro-structural and surface properties by BET, X-ray diffraction, temperature programmed reduction, elemental chemical analysis and adsorption microcalorimetry of NH3. Improved acidity has been detected upon addition of WO3 to zirconia and differences between the samples were pointed out thanks to the results obtained by the complementary physico-chemical techniques used in this study.
Keywords: Tungsten oxide; Zirconia supported catalysts; Surface acidity; Adsorption microcalorimetry
The effect of mechanochemical treatments of sepiolite with CsCl on the calcination products by Isaak Lapides; Shmuel Yariv (855-860).
Calcination of sepiolite and of two sepiolite/CsCl mixtures, unground and air-ground was investigated by thermo-XRD-analysis. At 200 °C sepiolite, neat, mixed or air-ground with CsCl lost interparticle and zeolitic water. The framework of sepiolite persisted during the dehydration but became defected, mainly in the air-ground mixture, less in the unground mixture and little in the neat clay. At 500 °C, with the loss of bound water, the neat clay was folded and transformed into sepiolite anhydride. In sepiolite/CsCl mixtures the dehydrated variety persisted but the degree of crystal-imperfection increased in the air-ground mixture more than in the unground mixture. At 700 °C the neat clay remained crystallized, but the CsCl mixtures became amorphous. Some crystalline dehydrated sepiolite or sepiolite anhydride persisted in the unground and air-ground CsCl mixtures, respectively. At 850 °C, the neat clay crystallized into protoenstatite with some enstatite and clinoenstatite. The amorphous fraction of sepiolite in the unground sepiolite/CsCl mixtures crystallized into pollucite and forsterite and the crystalline fraction was transformed into enstatite, protoenstatite, and clinoenstatite. In the air-ground mixture, the amorphous phase was transformed into pollucite with some forsterite and the crystalline fraction into enstatite.
Keywords: Cesium chloride; Clinoenstatite; Enstatite; Forsterite; Mechanochemistry of sepiolite; Pollucite; Protoenstatite; Thermo-XRD-analysis
Thermal properties of Australian sedimentary opals and Czech moldavites by P. S. Thomas; J. Šesták; K. Heide; E. Fueglein; P. Šimon (861-867).
The thermal properties are presented for a precious opal sourced from Coober Pedy, South Australia and a moldavite from Bohemia, Czech Republic whose origins differ significantly as opal is derived from the slow isothermal diagenesis of silica, while the tektites are specimens of vitreous silica formed from the terrestrial impact of asteroids. The differences between the two glassy silicates are presented through measurement of the TG–DSC, TMA and high-vacuum-hot-extraction DEGAS analysis.
Keywords: Amorphous Silica; DEGAS; Moldavite; Opal; TG–DSC; TMA
A study of storage conditions and treatments for forensic bone specimens using thermogravimetric analysis by S. Raja; P. S. Thomas; B. H. Stuart (869-872).
Bone provides an important source of forensic evidence. The storage conditions of bone have been recognised as a factor in maintaining the integrity of such evidence. Thermogravimetric analysis (TG) has been employed to examine the effects of storage environments and preparation methods on the structural properties of pig bones. A comparison of oven and freeze drying has been made to study the effect of storage conditions. A comparison has also been made of ground bone specimens with cut specimens. Freeze-dried hand ground specimens provided the most consistent results and, thus, this is the recommended method of preparation of bone specimens for TG analysis.
Keywords: Bone; Forensic; Thermogravimetric analysis
Use of thermal analysis in the study of soil Pb immobilization by Irena Wacławska; Magdalena Szumera (873-877).
Immobilization of lead contamination in soils by precipitation of non-assimilable for plants Pb-phosphate was considered. Glassy fertilizer of controlled release rate of the nutrients for plants as a source of phosphate anions was applied. Thermal analysis methods (TG/DTG/DTA) were used for the identification of components of Pb-precipitate, which being in statu nascendi have nonstoichiometric composition and disordered crystallographic structure difficult to identify by XRD method. Application of TA methods permits to demonstrate the negative role of Pb complexing citric acid solution simulating the natural soil conditions, which inhibits the Pb-phosphate of pyromorphite type formation.
Keywords: Soil environment protection; Pb immobilization; Thermal analysis (TG/DTG/DTA); Thermal decomposition
Influence of B2O3 on the structure and crystallization of soil active glasses by Magdalena Szumera; Irena Wacławska; Zbigniew Olejniczak (879-886).
Glasses of the SiO2–P2O5–K2O–MgO–CaO–B2O3 system acting as nutrients carriers in the soil environment were synthesised by the melt-quenching technique. Thermal properties were studied using DTA/DSC methods and the influence of B2O3 and P2O5 content on thermal stability and crystallization process of these glasses was examined. The structure of the glass network was characterized by FTIR, 31P, and 11B MAS NMR. The chemical activity of the glasses in the 2 mass% citric acid solution was measured by the ICP-AES method. The analysis indicated that the formation of P–O–B units with chemically stable tetrahedral borate groups decreases the glass solubility in conditions simulating the soil environment.
Keywords: Crystallization; Dissolution; Glass structure; Silicate–borophosphate glasses
Solid–liquid phase diagrams of binary mixtures by Luigi Campanella; Valentina Micieli; Mauro Tomassetti; Stefano Vecchio (887-892).
This study reports the investigation of three binary mixtures represented by acetylsalicylic acid (ASA) with its most important degradation product, salicylic acid (SA), and two of the most commonly used excipients (polyethylene glycol 4000 (PEG-4000) and d-mannitol (MA)). The liquidus and solidus equilibrium temperatures determined by DSC for pure components and solid binary mixtures at a fixed composition (mass fraction of ASA, w) were used to construct the corresponding solid–liquid phase diagrams. On the basis of the DSC results, the binary mixtures ASA/SA and ASA/PEG exhibit eutectic behavior (T eu = 155.0 ± 0.5 °C, w eu = 0.55 ± 0.02 and T eu = 53.3 ± 0.5 °C, w eu = 0.32 ± 0.01 ), respectively), while the binary mixture ASA/MA revealed the presence of a monotectic with a mean melting temperature of 162.2 °C in the range 0.2 < w 1 < 0.8. The composition of the two eutectics formed was confirmed by the related Tamman triangles. Finally, the liquidus curves of ASA/SA and ASA/PEG mixtures were also successfully predicted providing suitable polynomial (second-order) fitting equations.
Keywords: Acetylsalicylic acid; DSC; d-mannitol; Eutectic composition; PEG-4000; Phase diagrams; Salicylic acid; Second-order fitting equation
Thermal study of some new Ni(II) and Cu(II) complexes with ligands derived from N,N-dimethylbiguanide as potential antimicrobials by Rodica Olar; Mihaela Badea; Dana Marinescu (893-898).
The reaction between [M(DMBG)2]·nH2O ((1) M:Ni, n = 0; (4) M:Cu, n = 1), ammonia/hydrazine and formaldehyde in methanol resulted in new complexes of type [ML]·nH2O ((2) M:Ni, L:L1, n = 0; (3) M:Ni, L:L2, n = 0, (5) M:Cu, L:L1, n = 0 and (6) M:Cu, L:L2, n = 3; HDMBG: N,N-dimethylbiguanide, L1 = ligand resulted from ammonia system and L2 = ligand resulted from hydrazine system). The features of complexes have been assigned from microanalytical, IR and UV–Vis data. The thermal transformations of compounds are complex processes according to TG and DTG curves including melting, phase transition, dehydration, oxidative condensation of –C=N– units as well as thermolysis processes. The final products of decomposition are the most stable metal oxides.
Keywords: Complex; N; N-dimethylbiguanide; One pot condensation; Thermal behaviour
Alternative biofuels by A. Arteconi; G. Di Nicola; M. Moglie; G. Santori; R. Stryjek (899-903).
This study presents the experimental results for the dimethyl ether (DME) + propane system obtained using the Burnett method. The apparatus was calibrated using helium. PVTx measurements were taken for four isotherms (344, 354, 364, and 375 K), performing 16 Burnett expansions in pressures ranging from about 3,000 to 70 kPa. The second and third virial coefficients were derived from experimental results. The experimental uncertainty in the second and third virial coefficients was estimated to be within ±5 cm3/mol and ±1,000 cm6/mol2, respectively.
Keywords: Biofuels; Burnett; DME; Propane; Thermophysical properties
Martensitic transformation in Mn–Ni–Sn Heusler alloys by R. Coll; L. Escoda; J. Saurina; J. L. Sánchez-Llamazares; B. Hernando; J. J. Suñol (905-909).
Three magnetic shape memory alloys: Mn50Ni50−x Sn x (x = 5, 7.5, and 10) were produced as bulk polycrystalline ingots by arc melting. The structural austenite–martensite transformation was checked by calorimetry. The transformation temperatures decrease as increasing the Sn content. The same trend is found in the entropy and enthalpy changes related to the transformation. The control of the valence electron by atom e/a determines the transformation temperatures range in this kind of alloys and it is possible to develop alloys that can be candidates in applications as sensors and actuators. Furthermore, X-ray diffraction was performed to check the crystalline structure at room temperature.
Keywords: Magnetic shape memory; DSC; Martensitic transformation
Effect of the soil uses on their thermal stability by J. Salgado; J. Proupín; M. Villanueva; J. A. Rodríguez-Añón; N. Barros (911-916).
Differential scanning calorimetry was applied to assess on seasonally soil organic matter changes. Soils were collected in two sites located in Viveiro (Galicia, Spain). One of them has been used as arable land and the other one was under pinewood. Soil samples were seasonally collected during a year. The heat of combustion and the ignition temperature of the soil organic matter were calculated by analyzing the thermograms obtained by differential scanning calorimetry. The shape and the maximum and end temperatures of the two exothermic peaks observed in the thermograms, yielded information about the relations between the labile and recalcitrant pools, and hence information about carbon stabilization degree in both soils.
Keywords: DSC; Heat of combustion; Recalcitrance; Soil organic matter; Soil quality
Thermal degradation and isoconversional kinetic analysis of light-cured dimethacrylate copolymers by Dimitris S. Achilias; Maria M. Karabela; Irini D. Sideridou (917-923).
Thermal degradation kinetics of copolymers based on bis-phenol A ethoxylated dimethacrylate (Bis-EMA) with triethylene glycol dimethacrylate (TEGDMA), and urethane dimethacrylate (UDMA) with TEGDMA in wt/wt ratios 30/70, 50/50, or 70/30 were investigated using thermogravimetric analysis as a means to provide specific information regarding the internal structures of these resins. Thermogravimetric scans were taken at four different heating rates to perform an isoconversional analysis to determine the change of the effective activation energy as a function of conversion. A two-step degradation mechanism was found to occur in almost all copolymer compositions attributed to the existence of inhomogeneities in the macromolecular structure and the formation of weak links inside the polymeric network.
Keywords: Activation energy; Dimethacrylate copolymers; Thermal degradation; Thermogravimetric analysis
Vitrification and devitrification during the non-isothermal cure of a thermoset by I. Fraga; J. M. Hutchinson; S. Montserrat (925-929).
The processes of vitrification and devitrification that occur in an epoxy resin when it cures non-isothermally with a hardener are studied in terms of their frequency dependence and as a function of the heating rate. A novel modulated DSC technique, TOPEM, has been used which permits the evaluation of the frequency dependence for a single sample in a scan at constant underlying heating rate, thus avoiding errors arising from the composition of the sample. The effects of both frequency and heating rate on vitrification and devitrification are investigated. Some advantages of this technique are observed and discussed.
Keywords: Devitrification; Non-isothermal cure; Thermoset; TMDSC; TOPEM; Vitrification
Lanthanide complexes of 3-methoxy-salicylaldehyde by Christos Papadopoulos; Nikolaos Kantiranis; Stefano Vecchio; Maria Lalia-Kantouri (931-938).
The reaction of a lanthanide(III) nitrate (Ln = Pr, Nd, Gd, Dy, Er) with 3-methoxy-salicylaldehyde(3-OCH3-saloH), afforded neutral complexes of the general formula [Ln(3-OCH3-salo)3], which were characterized by means of elemental analysis, FT-IR spectra, TG-DTA curves, and magnetic measurements. The released products, due to the thermal decomposition were analyzed by on-line coupling MS spectrometer to the thermobalance in argon, allowed to prove the proposed decomposition stages. In order to confirm the stability scale provided on the basis of the onset decomposition temperature, a kinetic analysis of the three decomposition stages was made using the Kissinger equation, while the complex nature of the decomposition kinetics was revealed by the isoconvertional Ozawa–Flynn–Wall method.
Keywords: Lanthanide(III) complexes; 3-Methoxy-salicylaldehyde; Coupled TG-MS; Decomposition kinetics; TG/DTG–DTA; PXRD
Modernization and validation of an isoperibol rotating bomb calorimeter for the measurement of energies of combustion of sulphur compounds by Mohammed Ellaite; Didier Dalmazzone (939-945).
A rotating bomb calorimeter belonging to the Laboratory of Chemistry and Process Engineering (UCP) at ENSTA ParisTech since the 1960s was modernized and re-set in order of service for the measurement of heats of combustion of sulphur-containing compounds. The parts of the calorimeter that were replaced concerned essentially the thermal regulation, firing system and data acquisition, while most of the mechanical organs were found to work perfectly. The apparatus was tested extensively and calibrated using standard benzoic acid. The standard energy of combustion of thianthrene was measured to validate the operating protocol for sulphur compounds.
Keywords: Energy of combustion; Enthalpy of formation; Rotating bomb calorimetry; Sulphur compounds
Theoretical analysis of electronic and structural properties of anhydrous calcium oxalate by A. Koleżyński; A. Małecki (947-955).
The results of theoretical analysis of the electronic and crystal structural properties and bonding in relation to thermal decomposition process in anhydrous calcium oxalate are presented. The methods used in this analysis—topological analysis of electron density (Bader’s Quantum Theory of Atoms in Molecules approach) obtained from DFT calculations performed by Wien2k package (Full Potential Linearized Augmented Plane Wave Method); bond order model (Cioslowski&Mixon), applied to topological properties of the electron density; as well as Brown’s Bond Valence Model (bonds valences and strength’, and bond and crystal strains, calculated from crystal structure and bonds lengths data) are described. The analysis of the obtained results shows that these methods allow us to explain the way of thermal decomposition process of anhydrous calcium oxalate to calcium carbonate as a decomposition product, and to describe the structural transition taking place during such process (from monoclinic anhydrous CaC2O4 to rhombohedral calcite structure). In the light of the results of our similar calculations performed previously for other anhydrous oxalates (zinc, cadmium silver, cobalt, and mercury) the proposed theoretical approach can be considered as promising and reliable tool, which allow analyzing the properties of the structure and bonding and hence predicting the most probable way of thermal decomposition process for given crystal structure.
Keywords: Bond order; Bond strength; Bond valence; Electron density topology; FP-LAPW DFT calculations; Thermal decomposition of oxalates
Thermal stability of metastable nano-composites in planar flow cast Ti–Zr–Ni alloys by Emília Illeková; Helene Lefaix; Frederic Prima; Dušan Janičkovič; Peter Švec (957-963).
The influence of the solidification rate, the thermal stability, and devitrification process of the rapidly solidified Ti45Zr38Ni17 alloy have been examined on ribbons prepared by the planar flow casting method. Differential scanning calorimetry in the continuous heating mode, X-ray diffraction, and electron microscopy techniques were applied. Comparison of the so-obtained microstructures revealed the competition between icosahedral quasi-crystalline and β-Ti(Zr) phases, both dispersed in an amorphous matrix. It has been found that the decomposition process of rapidly quenched ribbons consists of the sequence of several independent exothermic and endothermic reactions involving the additional precipitation of quasi-crystalline nanoparticles and both irreversible and reversible changes between the unstable high-temperature β and stable low-temperature α phases. The formation of the intermetallics as well as the transformation of quasi-crystals into Laves phase has been observed at higher temperatures in all ribbons.
Keywords: Amorphous phase; Kinetics; Quasi-crystals; Rapid solidification; Thermal stability; Ti–Zr–Ni alloy
Characterization of gold supported on Al2O3–CuO–Mn2O3 catalysts obtained by thermal decomposition of aerosols by Barbara Małecka; Maria Rajska (965-971).
Gold (~1%) has been supported on the mixed oxides Al2O3–CuO–Mn2O3 with molar compositions 1:1:1, 1:0.7:0.3, 1:0.3:0.7, prepared by spray pyrolysis method. The supports and catalysts have been characterized by TG, DTA, N2 physisorption, XRD, SEM, and TEM methods and tested for CO oxidation (25–300 °C). The catalysts revealed high specific surface area and amorphous form for compositions 1:0.7:0.3 and 1:0.3:0.7. Gold deposited on the supports lowered the T 50 values by 50–80 °C. The highest CO conversion was obtained for 1:1:1 composition.
Keywords: TG; DTA; Spray pyrolysis; Gold catalysts; Transition metal oxides; Oxidation of CO
Thermooxidative stabilization of a MDI by Titus Vlase; Constantin Bolcu; Gabriela Vlase; Alin Mogoş; Nicolae Doca (973-979).
Samples of flexible PU foam were prepared from a polyol (Elastoflex W 5516/115) and an isocyanate prepolymer (Iso 145/8), both commercial Elastogram products. For the thermooxidative stabilization, two phenolic compounds were used, separately or in mixture. These compounds were: 2,6-di-t-butyl-4-methyl-phenol (non-reactive) (AO-1), 3,5-di-t-butyl-4-hydroxy-benzyl alcohol (reactive, AO-2), used in total mass% of 0.3/1.5. The TG/DTG/DTA curves were drawn up in dynamic air, with a heating rate of 10 °C min−1, until 500 °C. For the unstabilized sample a single thermodegradative TG step, with a maximum rate at 268–270 °C was observed, whereas for the stabilized samples, supplementary steps at higher temperature were observed. The changes in the TG/DTG/DTA parameters are not in a single relationship with the mass% of the stabilizator, due to the following: AO-1 is easily migrated out from PV, especially, at higher concentrations. AO-2 had positive effect at all studied concentrations. But the most remarkable effect is the synergetic effect of a 1:1 mixture of AO-1 and AO-2.
Keywords: Thermal stability; Thermal analysis; Stabilized polyol polyisocyanate
Agricultural valorisation of de-inking paper sludge as organic amendment in different soils by Sandra Barriga; Ana Méndez; Joaquín Cámara; Francisca Guerrero; Gabriel Gascó (981-986).
The objective of this study is to study the influence of de-inking paper sludge (DPS) and sewage sludge (SL) mixtures addition at different rates (2, 4 and 8%) in two soils. Incubation experiments were performed during 60 days and the influence of treatments in physical soil properties was determined by soil porosity and stability of aggregates. Differential thermal analysis (DTA) of amended soils after incubation was performed. Experimental results show that amendment increased biological soil activity, soil porosity and stability of aggregates. DTA analysis shows that the first exothermic peak generally increases with the dosage of DPS:SL due to the addition of immature organic matter. Moreover, the second peak enlarges probably due to the humification process during incubation.
Keywords: De-inking paper sludge; Agricultural valorisation; Thermal analysis
Thermal behaviour of cephalexin in different mixtures by Adriana Fuliaş; Titus Vlase; Gabriela Vlase; Nicolae Doca (987-992).
The thermoanalytical curves (TA), i.e. TG, DTG and DTA for pure cephalexin and its mixtures with talc, magnesium stearate, starch and microcrystalline cellulose, respectively, were drawn up in air and nitrogen at a heating rate of 10 °C min−1. The thermal degradation was discussed on the basis of EGA data obtained for a heating rate of 20 °C min−1. Until 250 °C, the TA curves are similar for all mixtures, up this some peculiarities depending on the additive appears. These certify that between the pure cephalosporin and the excipients do not exists any interaction until 250 °C. A kinetic analysis was performed using the TG/DTG data in air for the first step of cephalexin decomposition at four heating rates: 5, 7, 10 and 12 °C min−1. The data processing strategy was based on a differential method (Friedman), an integral method (Flynn–Wall–Ozawa) and a nonparametric kinetic method (NPK). This last one allowed an intrinsic separation of the temperature, respective conversion dependence on the reaction rate and less speculative discussions on the kinetic model. All there methods had furnished very near values of the activation energy, this being an argument for a single thermooxidative degradation at the beginning (192–200 °C).
Keywords: Cephalexin; Thermal stability; Kinetic parameters; NPK method
Removal of malachite green by adsorbents from paper industry waste materials by Ana Méndez; Sandra Barriga; Antonio Saa; Gabriel Gascó (993-998).
The objective of this work is to study the removal of malachite green (MG) from water by adsorbents obtained from pyrolysis of two paper industry waste materials: one de-inking paper sludge (HP) and one organic sludge from virgin pulp mill (RT). Both adsorbents showed elevated MG removal. Maximum adsorption Q 0 obtained by Langmuir equation was higher for the adsorbent from HP (HP-3, 982 mg/g) than RT (RT-3, 435 mg/g). However, K L (Langmuir) and 1/n (Freundlich) indicated that affinity and intensity of adsorption is higher for the adsorbents from RT. Thermal analysis (TG, DTG and DTA) of adsorbents before and after MG removal was performed in N2 atmosphere.
Keywords: De-inking; Sludge; Malachite green; Thermal analysis
Study by DTA/TG of the formation of calcium aluminate obtained from an aluminium hazardous waste by A. López-Delgado; F. A. López; L. Gonzalo-Delgado; S. López-Andrés; F. J. Alguacil (999-1004).
A Spanish hazardous waste from tertiary aluminium industry was used as a raw material for the synthesis of calcium aluminate. An amorphous precursor was obtained by a hydrothermal method at different values of pH. The transformation of the precursor in a crystalline aluminate was followed by TG/DTA up to 1300 °C. At temperatures between 719 and 744 °C, the precursors evolve towards the formation of C12A7 which becomes CA at circa 1016 °C. Mass spectrometry coupled to thermal analyser allowed the identification of the decomposition products.
Keywords: Aluminium waste; Calcium aluminate; TG/DTA
Soot oxidation kinetics from TG experiments by Maria Kalogirou; Zissis Samaras (1005-1010).
Thermogravimetric analysis (TG) has been used extensively for soot oxidation studies. Its known experimental and computational difficulties, however, have led to extended criticism concerning the reliability of the extracted kinetics and their potential for reliable reaction modelling. This study explores if TG kinetics could lead to successful simulation results notwithstanding the related disputes. For this, TG and mini-scale soot oxidation experiments with oxygen (O2) were conducted. The TG kinetics reliability was controlled through comparison with the corresponding mini-scale results and by the satisfactory simulation of the mini-scale experiments.
Keywords: Kinetics; Modelling; Oxidation; Soot; TG
Thermal characterization of usnic acid/collagen-based films by Paula Santos Nunes; Marília Santos Bezerra; L. P. Costa; Juliana Cordeiro Cardoso; R. L. C. Albuquerque Jr.; M. O. Rodrigues; Gabriela Borin Barin; Francilene Amaral da Silva; A. A. S. Araújo (1011-1014).
The purpose of this study was to evaluate the physical–chemical properties of collagen (CL) and usnic acid/collagen-based (UAC) films, using differential thermal analysis (DTA), thermogravimetry (TG/DTG), infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). Both films were prepared by casting process using polyethylene glycol 1500 (PEG 1500) as plasticizer. In the spectrum of UAC, similar bands of the usnic acid are observed, indicating that the polymerization (film formation) did not affect the stability of the drug. Distinctly, DTA curve of UAC did not show an endothermic peak at 201 °C, indicative that the drug was incorporated into the polymeric system. These results were corroborated by the scanning electron microscopy (SEM). The TG/DTG curves of UAC presented a different thermal decomposition profile compared to the individual compounds and CL. These findings suggest the occurrence of molecular dispersion or solubilization of the drug in the collagen film.
Keywords: Casting; Biodegradable films; Usnic acid; Collagen; Thermal characterization
Calorimetric study of nitro group/solvent interactions by Silvia Porcedda; D. Falconieri; B. Marongiu; Alessandra Piras (1015-1023).
A flow microcalorimeter, model 2277-LKB, has been used to determine excess enthalpies, H E, at 298.15 K, for liquid mixtures containing 1-nitrobutane or 1-nitropentane or 1-nitrohexane + benzene or + tetrachloromethane. The experimental results, taken from literature, concerning thermodynamic properties of nitroalkanes + benzene or + tetrachloromethane mixtures have been interpreted in terms of the DISQUAC group contribution model. Two sets of structure-dependent interaction parameters for the nitro group/benzene and for the nitro group/tetrachloromethane contacts have been obtained. The model provides a fairly consistent description of the excess functions, G E and H E and of activity coefficients at infinite dilution, γ i ∞ .
Keywords: Benzene; DISQUAC model; Experimental excess enthalpies; Nitroalkanes; Tetrachloromethane