Showing papers in "Journal of Thermal Analysis and Calorimetry in 2005"
TL;DR: In this paper, high-resolution thermogravimetric analysis has been used to study the thermal decomposition of montmorillonite modified with octadecyltrimethylammonium bromide.
Abstract: High resolution thermogravimetric analysis has been used to study the thermal decomposition of montmorillonite modified with octadecyltrimethylammonium bromide. Thermal decomposition occurs in 4 steps.The first step of mass loss is observed from ambient to 100°C temperature range and is attributed to dehydration of adsorbed water. The second step of mass loss occurs between 87.9 to 135.5°C temperature range and is also attributed to dehydration of water hydrating metal cations such as Na+. The third mass loss occurs between 179.0 and 384.5°C; it is assigned to the loss of surfactant. The fourth step is ascribed to the loss of OH units due to dehydroxylation of the montmorillonite and takes place between 556.0 and 636.3°C temperature range. These TG steps are related to the arrangement of the surfactant molecules intercalating the montmorillonite. Changes in the basal spacing of the clay with surfactant are followed by X-ray diffraction. Thermal analysis provides an indication of the stability of the organo-clay.
152 citations
TL;DR: In this paper, the optimization of the kaolin calcination is studied, aiming at using the produced metakaolin as supplementary cementitious material, and it is shown that heating at 650°C for 3 h is efficient to convert poor kaolins with low alunite content to highly reactive metakaolins.
Abstract: In this paper the optimization of the kaolin calcination is studied, aiming at using the produced metakaolin as supplementary cementitious material. Representative samples of poor Greek kaolin (Milos island) and a high purity commercial kaolin were tested. Samples were heated at different temperatures during different times. The optimization of calcination conditions was studied by DTA-TG and XRD analysis of the raw and thermal treated kaolin samples, by pozzolanic activity analysis of metakaolins and finally by strength development analysis of cement-metakaolin mixtures. This approach showed that heating at 650°C for 3 h is efficient to convert poor kaolins with low alunite content to highly reactive metakaolins. However in the case of kaolin with a high alunite content, thermal treatment at 850°C for 3 h is required in order to remove undesirable SO3. Evidence was found that poor kaolins can be efficiently used for the production of highly reactive metakaolins.
136 citations
TL;DR: The dependence of the preexponential factor on the temperature has been examined and the errors involved in the activation energy calculated from isothermal and non-isothermal methods without considering such dependence have been estimated as discussed by the authors.
Abstract: The dependence of the preexponential factor on the temperature has been examined and the errors involved in the activation energy calculated from isothermal and non-isothermal methods without considering such dependence have been estimated. It has been shown that the error in the determination of the activation energy calculated ignoring the dependence of Aon Tcan be rather large and it is dependent on x=E/RT, but independent of the experimental method used. It has been also shown that the error introduced by omitting the dependence of the preexponential factor on the temperature is considerably larger than the error due to the Arrhenius integral approach used for carrying out the kinetic analysis of TG data.
129 citations
TL;DR: In this article, the principles of CA-CCA and zero curve calculations are discussed, and the methods for calculating key solidification characteristics of metals from cooling curves are presented, and their importance in the quality control of manufacturing processes are demonstrated.
Abstract: Thermal analysis is widely used to determine solidification characteristics of metals and alloys in various metallurgical processes. Computer-Aided Cooling Curve Analysis (CA-CCA) is the most popular thermal analysis technique because of its ease of use and low cost. This paper discusses the principles of CA-CCA and zero curve calculations. The methods for calculating key solidification characteristics of metals from cooling curves are presented, and their importance in the quality control of manufacturing processes are demonstrated. Examples are presented for cast iron, copper and aluminum alloys.
124 citations
TL;DR: In this paper, the incorporation of a compatibilizing agent into the lignocellulosic material-thermoplastic polymer composites is recommended to improve their compatibility and interfacial adhesion.
Abstract: In the TG analysis of the bio-composites, their thermal stability was found to slightly decrease and the ash content to increase as the lignocellulosic filler loading increased. This is a logical consequence of the lower thermal stability of the lignocellulosic filler compared to that of the matrix polymer. The dispersion and interfacial adhesion between the lignocellulosic filler and thermoplastic polymer were important factors affecting the thermal stability of the composite system. In order to improve their compatibility and interfacial adhesion, the incorporation of a compatibilizing agent into the lignocellulosic material-thermoplastic polymer composites is recommended. In the TMA analysis, the thermal expansion of the composites was found to decrease with increasing filler loading and incorporating compatibilizing agent. Lignocellulosic filler is a suitable material for preventing the thermal expansion of the composite materials caused by atmospheric changes.
106 citations
TL;DR: Differential scanning calorimetry and thermogravimetry (TG/DTG) have been used to obtain information on the temperature-controlled combustion characteristics of seventeen coals of different origin from the Thrace basin of Turkey as discussed by the authors.
Abstract: Differential scanning calorimetry (DSC) and thermogravimetry (TG/DTG) has been used to obtain information on the temperature-controlled combustion characteristics of seventeen coals of different origin from Thrace basin of Turkey. Experiments were performed in air atmosphere up to 600°C at a heating rate of 10°C min-1. The DSC/TG curves clearly demonstrate distinct transitional stages in the entire coal samples studied. Reaction intervals, peak and burn-out temperatures of the coal samples are also determined. Two different kinetic methods known as, Arrhenius and Coats-Redfern, were used to analyze the kinetic data and the results are discussed.
104 citations
TL;DR: In this article, the thermal decomposition of the complexes Ni(SCN)2(fp)4·2H2O (I), Ni( SCN) 2(mfp) 4 ·2H 2O (II), Ni[SCN] 2(dmfp)3 (III) (where fp=furo[3,2-c]pyridine, mfp=2-methylfuro [3, 2-c]-polymorphic pyridine and dmfp =2,3-dimethy-lf
Abstract: The thermal decomposition of the complexes Ni(SCN)2(fp)4·2H2O (I), Ni(SCN)2(mfp)4 (II) and Ni(SCN)2(dmfp)3 (III) (where fp=furo[3,2-c]pyridine, mfp=2-methylfuro[3,2-c]pyridine and dmfp=2,3-dimethylfuro[3,2-c]pyridine) have been investigated in dynamic air from room temperature to 1000°C by means of TG, DTG and DTA. The chemical composition of the complexes, solid intermediates and the resultant products of thermolysis have been identified by means of elemental analysis and complexometric titration. The results revealed that NiO was left as residue at the end of the thermal degradation experiments. IR data suggested that fp, mfp and dmfp were coordinated to Ni(II) through the N atom of the respective heterocyclic ring.
102 citations
TL;DR: In this paper, two-point heat flow calibration is proposed based on the relationship between the sensitivity of a thermocouple and calibration coefficient of a DSC sensor made from it.
Abstract: One-point (Mettler) and many-point (Netzsch) heat flow calibration of a DSC is discussed. It is shown that the two types of calibration are the alternative extremes between quick but rough procedure and time-consuming but accurate one. One-point calibration compares a ‘typical’ function k(T) at the melting point of indium with the measured value for particular DSC and multiplies k(T) by a scaling factor. Many-point calibration is based on general mathematical procedure, namely fitting a set of experimental values of sensitivity to a polynomial. The polynomial coefficients are evaluated by the method of least squares. Based on the relationship between the sensitivity of a thermocouple and calibration coefficient of a DSC sensor made from it, two-point heat flow calibration is suggested. This is an optimal calibration procedure, for the relationship contains only two unknown coefficients. An example of how to perform the two-point calibration with Netzsch-Proteus Software is described in the Appendix.
100 citations
TL;DR: In this article, the thermal properties of agro-flour-filled polybutylene succinate (PBS) bio-composites were investigated, and the authors found that the thermal degradation of the bio composites was not affected by agroflour mesh size and the glass transition (Tg) and melting (Tm) temperatures were not significantly changed.
Abstract: In this study, the thermal properties of agro-flour-filled polybutylene succinate (PBS) bio-composites were investigated. PBS is one of the biodegradable polymers made from the condensation reaction of glycols and dicarboxylic acid and is naturally degraded by natural soil burial system. The thermal properties of the bio-composites were analyzed according to the agro-flour content and mesh size. On increasing agro-flour content, the thermal stability, degradation temperature and derivative thermogravimetric curve (DTGmax) temperature of the bio-composites decreased while the ash content increased. The thermal degradation of the bio-composites was not affected by agro-flour mesh size. The glass transition (Tg) and melting (Tm) temperatures of the bio-composites were not significantly changed. The storage modulus (E’) of the bio-composites was higher than that of neat PBS, because the incorporation of agro-flour increased the stiffness of the bio-composites. At higher temperatures, E’ of the bio-composites decreased due to the increasing viscosity and chain mobility of neat PBS. The thermal properties of bio-composites have an important effect on the manufacturing system and application methods.
84 citations
TL;DR: In this paper, the effect of pH on the thermal denaturation of BSA containing fatty acids was studied by use of differential scanning calorimetry (DSC), which gave various types of DSC curves depending on the protein concentration and on the pH.
Abstract: The effect of pH on the thermal denaturation of BSA containing fatty acids was studied by use of differential scanning calorimetry (DSC). Thermal scanning of BSA aqueous solutions gave various types of DSC curves depending on the protein concentration and on the pH. The broad bimodal endothermic transition was suggested to be connected with loose protein structure in contradistinction to single peak for compact molecule structure. The propensity toward precipitation at pH conditions ranging from 3.8 to 5 was observed. A scan-rate independent and partly reversible behavior of the thermal heating of BSA was found. Deconvolution of DSC traces in non-two-state model with assumption of two- or three-component transition allowed to study the effect of pH on different parts of BSA molecule.
82 citations
TL;DR: In this paper, isoconversional methods based on non-Arrhenius temperature functions are presented and corresponding formulas for isothermal, integral, differential and incremental isoconvolutional methods are derived.
Abstract: Solid-state reactions ordinarily demonstrate a tangled interplay of various chemical and physical processes. The single-step kinetics approximation resides in substituting a generally complex set of kinetic equations by the sole single-step kinetics equation. It enables to describe the kinetic hypersurface in a simple way irrespective of the complexity of the overall process. The kinetic hypersurface is the dependence of conversion on temperature and time. The functions describing the temperature and conversion components of the hypersurface should be separable. For a complex process, the adjustable parameters in the temperature function have no mechanistic significance so that there is no reason to be confined to the Arrhenius relationship. Two groups of isoconversional methods based on non-Arrhenius temperature functions are presented and the corresponding formulas for isothermal, integral, differential and incremental isoconversional methods are derived. As an example of the method using the explicit expression of the conversion function, the first-order kinetics is treated. Comparing with the methods based on the Arrhenius relationship, the greatest advantage of the methods presented here is that the problems with calculating the temperature integral are eliminated since the corresponding integrals can be expressed in a closed form.
TL;DR: In this paper, Pectin-based cerium (IV) and thorium-IV phosphates have been synthesized as new phases of hybrid fibrous ion exchangers, and both materials were characterized using X-ray diffraction, infrared (IR) spectra, thermogravimetric analysis (TG), differntial thermograimetry (DTG), differentntial thermal analysis (DTA), and scanning electron microscopy (SEM), as well as the determination of their ion exchange capacity, elution and pH titration.
Abstract: Pectin based cerium (IV) and thorium (IV) phosphates have been synthesized as new phases of hybrid fibrous ion exchangers. Both materials were characterized using X-ray diffraction, infrared (IR) spectra, thermogravimetric analysis (TG), differntial thermogravimetry (DTG), differntial thermal analysis (DTA) and scanning electron microscopy (SEM), as well as the determination of their ion exchange capacity, elution and pH titration. The X-ray study reveals the amorphous nature of the materials, while SEM studies confirm the fibrous nature of the materials. The thermal studies of these materials indicate that both of them are highly stable on heating as they retain about 97% of their ion-exchange capacity (i.e.c.) on heating up to 100°C and about 81% on heating up to 200°C.
TL;DR: In this article, the thermal behavior of Aughinish red mud was investigated using thermal gravimetric analysis (TG) and differential thermal analysis (DTA) for identification of oxide and mineral phases in the red mud sample, XRD method, scanning electron microscopy (SEM), EDAX were used.
Abstract: Red mud is insoluble, fine-grained waste residue which is generated as a by product during the production of alumina from the Bayer process. In this article, the thermal behavior of Aughinish red mud was investigated using thermal gravimetric analysis (TG) and differential thermal analysis (DTA). For identification of oxide and mineral phases in the red mud sample, XRD method, scanning electron microscopy (SEM), EDAX were used. Iron (30.4%), aluminium (23.6%) and titanium (17.85%) oxides are major oxides in the sample. Two endothermic peaks were shown on DTA curve. The total mass loss in the red mud was found to be 10.1%, which was associated with moisture and water molecules in gibbsite and boehmite phases.
TL;DR: In this article, aroylhydrazone Schiff's bases derived from isoniazide (hydrazide of isonicotinic acid) with p-hydroxybenzaldehyde; 2,4-dihydroxy benzaldehyde or 2,hydroxy-1-naphthaldehyde are prepared and characterized.
Abstract: Summary Cobalt(II), nickel(II) and copper(II) complexes of some aroylhydrazone Schiff’s bases derived from isoniazide (hydrazide of isonicotinic acid) with p-hydroxybenzaldehyde; 2,4-dihydroxybenzaldehyde or 2-hydroxy-1-naphthaldehyde are prepared and characterized. The study reveals that the ligands coordinate in the keto form. That transformed to the enol through the loss of HCl upon heating the solid complexes. The copper(II) complexes are thermochromic in the solid-state while the cobalt(II) complex, 3 of 2,4-dihydroxybenzaldehyde moiety is solvatochromic in hot DMF. The chromisms obtained were discussed in terms of change in the ligand field strength and/or coordination geometry.
TL;DR: In this article, thermally carbonized mesoporous silicon microparticles were produced and loaded with two active pharmaceutical ingredients, ibuprofen and antipyrine, by combining the results measured with TG and DSC, reliable estimations for the degrees of the drug loads were obtained.
Abstract: Thermally carbonised mesoporous silicon microparticles were produced and loaded with two active pharmaceutical ingredients, ibuprofen and antipyrine. By combining the results measured with TG and DSC, reliable estimations for the degrees of the drug loads were obtained. To distinguish the drug adsorbed on the surfaces of the microparticles from that absorbed into the pores, the principle of thermoporometry on the DSC measurements was employed. According to the principle, the drug held in the capillaries of porous material has a depressed melting temperature because of the higher pressure of the drug in cavities with a curved interface. On the other hand, the drug located on the external surface of the microparticles exhibits the normal melting of bulk drug. The loading degrees obtained with the thermoanalytical methods (31 and 26 massp for ibuprofen and antipyrine, respectively) were comparable with the results obtained with helium pycnometry (the corresponding values were 33 and 28 massp). Nitrogen sorption studies were not reliable for quantitative determinations due to the inability of nitrogen to penetrate in all pores, which might be blocked by the drug on the surface of the microparticles.
TL;DR: In this paper, the influence of calcium carbonate nanoparticles with different shapes (spherical and elongated) on the thermal properties and crystallization behavior of isotactic polypropylene was investigated CaCO3 nanoparticles were covered by an appropriate coating agent to improve the interfacial adhesion between the filler and the polyolefin matrix.
Abstract: The influence of calcium carbonate nanoparticles with different shapes (spherical and elongated) on the thermal properties and crystallization behavior of isotactic polypropylene was investigated CaCO3 nanoparticles were covered by an appropriate coating agent to improve the interfacial adhesion between the filler and the polyolefin matrix The nanocomposites were prepared by melt mixing and subsequent compression molding A remarkable effect of CaCO3 on the thermal properties of iPP was observed Moreover, the analysis of crystallization kinetics showed that CaCO3 nanopowder coated with PP-MA are efficient nucleating agents for iPP, and the overall crystallization rate results higher than plain iPP
TL;DR: In this paper, polyvinylalcohol (PVA) and kraft lignin (KL) solutions were separately prepared and then mixed in appropriate ratios, to yield the films after solvent (DMSO) evaporation.
Abstract: Lignin and poly(vinylalcohol) (PVA) solutions were separately prepared and then mixed in appropriate ratios, to yield the films after solvent (DMSO) evaporation. Two lignin samples were used: kraft lignin (KL) and acetone soluble fraction of kraft lignin (AKL). Different carbonyl and hydroxyl contents were detected by 1 HNMR and by FTIR for KL and AKL. PVA films containing up to 25p of lignin were prepared and irradiated with UV light for different time intervals. These films were analyzed using FTIR, TG and DSC. Due to the lignin incorporation in PVA films an increase in the thermal stability was observed. From DSC experiments, PVA/KL seems to provide a more homogeneous material compared to PVA/AKL, especially at 95/5 composition. PVA/KL films seem to have greater resistance to photochemical attack, as evaluated by crystallinity changes after irradiation of the film.
TL;DR: In this article, the authors performed a thermal-FTIR spectroscopy analysis of cooking pottery from the Iron Age at Tel Hadar on the eastern shore of the Sea of Galilee.
Abstract: The Iron Age ceramic technology used in the manufacturing of cooking pots was studied by thermo-FTIR spectroscopy analysis. The pottery was excavated at Tel Hadar on the eastern shore of the Sea of Galilee. The results demonstrate that the cooking pots were manufactured using noncalcareous or slightly calcareous raw material proceeds from soil. The firing was at about 750-850°C and the cementation to ceramic was obtained by low temperature sintering of the clay. The use of soil raw material composed of smectitic (montmorillonitic) clay enabled the low temperature sintering. The clay from soil is relatively poorly crystallized and rich in natural iron oxide, both of which induce earlier sintering. Most of the cooking pots were tempered with broken pieces of large calcite crystals that were added to the clayey raw material from an additional source. Alternative tempering with limestone particles composed of polycrystalline calcite is inappropriate as it brings about earlier and intense decarbonation during the firing, which causes defects in the pots.
TL;DR: In this paper, a series of calcium silicate hydrate (C-S-H)-polymer nanocomposite materials were synthesized by incorporating polyvinyl alcohol (PVA) into the inorganic layers of C-s-H during precipitation of quasicrystalline C-S -H from aqueous solution.
Abstract: A series of calcium silicate hydrate (C-S-H)-polymer nanocomposite (C-S-HPN) materials were prepared by incorporating poly(vinyl alcohol) (PVA) into the inorganic layers of C-S-H during precipitation of quasicrystalline C-S-H from aqueous solution. The as synthesized C-S-HPN materials were characterized by Fourier-transform infrared photoacoustic (FTIRPAS) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy/energy dispersed spectroscopy (SEM/EDS), thermogravimetric analysis (TG), differential thermogravimetry (DTG) and differential scanning calorimetry (DSC). The XRD peaks of C-S-HPN materials suggest the intermediate organizations presenting both intercalation of PVA and exfoliation of C-S-H. The SEM micrographs of C-S-H, PVA and C-S-HPN materials with different PVA contents exhibit the significant differences in their morphologies. Effects of the material compositions on the thermal stability of a series of C-S-HPN materials along with PVA and C-S-H were studied by TG, DTG and DSC. Three significant decomposition temperature ranges were observed in the TG curves of all C-S-HPN materials.
TL;DR: The main contribution of the single-step kinetics approximation is that it enables a mathematical description of the kinetics of solid-state reactions without a deeper insight into their mechanism.
Abstract: Mechanism of the processes in condensed phase are very often unknown or too complicated to be characterised by a simple kinetic model. They tend to occur in multiple steps that have different rates. To describe their kinetics, the single-step kinetics approximation is often applied which resides in substituting a generally complex set of kinetic equations by the sole single-step kinetics equation. The main contribution of the single-step kinetics approximation is that it enables a mathematical description of the kinetics of solid-state reactions without a deeper insight into their mechanism. The single-step kinetics approximation is based on the assumption that the temperature and conversion functions are separable. In the paper, some consequences originating from ignoring the function separability are discussed.
TL;DR: In this paper, a model-free isoconversional method (Flynn-Wall-Ozawa and Kissinger methods) was used to evaluate the activation energy of the combustion process.
Abstract: Non-isothermal thermogravimetric data were used to evaluate the Arrhenius parameters (activation energy and the pre-exponential factor) of the combustion of two carbonaceous materials, selected as diesel soot surrogates. The paper reports on the application of model-free isoconversional methods (Flynn-Wall-Ozawa and Kissinger methods) for evaluating the activation energy of the combustion process. On the other hand, by means of the compensation relation between E and lnA, which was established by the model-dependent Coats-Redfern method, the value of the pre-exponential factor was estimated from the known value of the model-independent activation energy.
TL;DR: In this article, the effect of adding tailored substances to lower the crystallization temperature (T c ) of methyl hexadecanoate (PalMe) was studied, and it was shown that the additive can reduce the temperature by 10°C depending on the molecular mass, molecular structure and concentration of the additive.
Abstract: Solid methyl esters of saturated fatty acids can cause technological problems when modified vegetable oils are used at low temperatures. In this work the effect of adding tailored substances to lower the crystallization temperature ( T c ) of methyl hexadecanoate (PalMe) was studied. These substances were esters of carboxylic acids with linear or branched alkyl chains of up to 16 carbon atoms with alcohols having cyclic or branched alkyl chains or an alkoxy group. Results of DSC measurements have shown that the crystallization temperature of PalMe could be decreased by 10°C depending on the molecular mass, molecular structure and concentration of the additive. The best results were obtained using hexadecanoic acid derivatives.
TL;DR: In this paper, the kinetics of the high-temperature oxidation of the powder amorphous carbon and bulk single-wall carbon nanotubes are studied using differential scanning calorimetry using the continuous heating regime up to 1273 K.
Abstract: In this work the kinetics of the high-temperature oxidation of the powder amorphous carbon and bulk single-wall carbon nanotubes is studied. The thermal degradation of the sample is measured by differential scanning calorimetry using the continuous heating regime up to 1273 K. Also, the oxidation resistance of the samples is evaluated by the mass loss in a thermogravimetric analyzer. Both flowing and static oxygen and dry-air atmospheres are used. The specific role of the external diffusivity of the reagent gas is analyzed. The kinetics of the chemical reaction is specified using the Kissinger, Coats and Redfern methods.
TL;DR: In this article, the use of rice husk as filler for increasing the value of recycled tire rubber was proposed, where the degradation process of major constituents of scrap tires or their composites was observed at temperatures between 150 and 550°C.
Abstract: The disposal of used automotive tires has caused many environmental and economical problems to most countries. We propose the use of rice husk as filler for increasing the value of recycled tire rubber. Thermal degradation of both components and their sintering mixtures is presented in this paper. Thermal decomposition of rice husk occurs in various steps in the temperature range between 150 and 550°C. This complex process is the result of the overlapping of thermal decomposition of the three major constituents common in all lignocellulosic materials, i.e., hemicellulose, lignin and cellulose. Hemicellulose is degraded at temperatures between 150 and 350°C, cellulose from 275 to 380°C and lignin from 250 to 550°C. The degradation process of major constituents of scrap tires or their composites is observed at temperatures between 150 and 550°C. For composites, the addition of rice husk (maximum 25%) produces an increase in the mass loss rate. This effect is higher as the amount of rice husk increases. However, the degradation initial temperature of elastomeric matrix is not affected with addition of rice husk. Apparent kinetic parameters were also studied by the isoconversional Friedman method. We observed that the addition of rice husk produces a decrease in apparent activation energy for low conversions (up to 0.6). For higher conversions this decrease was not so clearly observed.
TL;DR: In this paper, the authors used thermal analysis coupled with mass spectrometry to study three Australian jarosites which are predominantly K, Na and Pb, and found that the first mass loss step for Na-jarosite is attributed to deprotonation.
Abstract: Jarosites are a group of minerals formed in evaporite deposits and form a component of efflorescence. As such the minerals can function as cation and heavy metal collectors. Thermogravimetry coupled to mass spectrometry has been used to study three Australian jarosites which are predominantly K, Na and Pb jarosites. Mass loss steps of K-jarosite occur over the 130 to 330 and 500 to 622°C temperature range and are attributed to dehydroxylation and desulphation. In contrast the behaviour of the thermal decomposition of Na-jarosite shows three mass loss steps at 215 to 230, 316 to 352 and 555 to 595°C. The first mass loss step for Na-jarosite is attributed to deprotonation. For Pb-jarosite two mass loss steps associated with dehydroxylation are observed at 390 and 418°C and a third mass loss step at 531°C is attributed to the loss of SO3. Thermal analysis is an excellent technique for the study of jarosites. The analysis depends heavily on the actual composition of the jarosite.
TL;DR: In this article, the pozzolanic reactivity of thermally treated zeolites was studied on the basis of the Chapelle test combined with X-ray diffraction (XRD) and Fourier Transform (FTIR) spectroscopy, as well as thermogravimetric analysis (TG/DTG) and differential thermal analysis (DTA).
Abstract: The pozzolanic reactivity of thermally treated zeolites was studied on the basis of the Chapelle test combined with X-ray diffraction (XRD) and Fourier Transform (FTIR) spectroscopy, as well as thermogravimetric analysis (TG/DTG) and differential thermal analysis (DTA). The raw zeolite samples are from the Pentalofos area, Thrace, NE Greece. Their main mineral constituent is 'heulandite type-II', an intermediate type of the heulandite-clinoptilolite isomorphous series. Calcination of the samples was carried out up to 400, 500, 600, 700 and 1000°C for 15 h. The changes were recorded using the above methods. The deformation of the zeolite crystal lattice starts at about 400°C and proceeds as the temperature of thermal treatment rises. The thermal treatment of zeolite at 400°C improves its pozzolanic reactivity and accelerates the reaction with Ca(OH)2.
TL;DR: In this article, the results of the chemical and thermal characterization by TG and DSC of the seed derivatives of Cnidoscolus quercifolius, hereinafter called faveleira, aiming at the application of these materials as an alternative of food source for animals and for the human population at this region.
Abstract: Taking into account the problems of desertification and agricultural practices able to provide income to the population at the semi-arid region of North-East Brazil, this work presents the results of the chemical and thermal characterization by TG and DSC of the seed derivatives of Cnidoscolus quercifolius , hereinafter called faveleira, aiming at the application of these materials as an alternative of food source for animals and for the human population at this region. The faveleira seed derivatives present thermodynamic properties similar to the ones of other foods utilized for human use, as well as an acceptable calorific value. According to TG and DSC results, was verified that the faveleira derivatives presents good thermal and oxidative stabilities.
TL;DR: In this article, an advanced kinetic study on the thermal behavior of pyrotechnic ignition mixtures has been carried out by differential scanning calorimetry using different B/KNO3 mixtures (50:50, 30:70, 20:80) as a model reaction.
Abstract: An advanced kinetic study on the thermal behaviour of pyrotechnic ignition mixtures has been carried out by differential scanning calorimetry using different B/KNO3 mixtures (50:50, 30:70, 20:80) as a model reaction. The experimental conditions applied (isochoric conditions/closed crucibles and isobaric conditions/open crucibles) as well as the composition of the mixtures noticeably influences the relative thermal stabilities of the energetic materials. The kinetic study focused on the prediction of the thermal stability of the different mixtures both in extended temperature ranges and under temperature conditions at which ordinary investigation would be very difficult. Using advanced numerical tools [1], thermal ageing and influence of the complex thermal environment on the heat accumulation conditions were computed. This can be done for any surrounding temperature profile such as isothermal, non-isothermal, stepwise, modulated, shock, adiabatic conditions and additionally for temperature profiles reflecting real atmospheric temperature changes (yearly temperature profiles of different climates with daily minimal and maximal fluctuations). Applications of accurate decomposition kinetics enabled the determination of the time to maximum rate under adiabatic conditions (TMRad) with a precision given by the confidence interval of the predictions. This analysis can then be applied for the examination of the effects of the surrounding temperature for safe storage or transportation conditions (e.g. determination of the safe transport or storage temperatures).
TL;DR: In this paper, a kinetic study of epoxy resin based on a diglycidyl ether of bisphenol A (DGEBA), with poly(oxypropylene) diamine (Jeffamine D230) as a curing agent, was performed by means of differential scanning calorimetry (DSC).
Abstract: A kinetic study of cure kinetics of epoxy resin based on a diglycidyl ether of bisphenol A (DGEBA), with poly(oxypropylene) diamine (Jeffamine D230) as a curing agent, was performed by means of differential scanning calorimetry (DSC). Isothermal and dynamic DSC characterizations of stoichiometric and sub-stoichiometric mixtures were performed. The kinetics of cure was described successfully by empirical models in wide temperature range. System with sub-stoichiometric content of amine showed evidence of two separate reactions, second of which was presumed to be etherification reaction. Catalytic influence of hydroxyl groups formed by epoxy-amine addition was determined.
TL;DR: The thermal decomposition of gallium nitrate hydrate (Ga(NO3)3·xH2O) to gallium oxide has been studied by TG/DTG and DSC measurements performed at different heating rates.
Abstract: The thermal decomposition of gallium nitrate hydrate (Ga(NO3)3·xH2O) to gallium oxide has been studied by TG/DTG and DSC measurements performed at different heating rates. It is concluded that 8 water molecules are present in the hydrate compound. The anhydrous gallium nitrate does not form at any temperature as the reaction consists of coupled dehydration/decomposition processes that occur with a mechanism dependent on heating rate. TG measurements performed with isothermal steps (between 31 and 115°C) indicate that Ga(OH)2NO3 forms in the first stage of the reaction. Such a compound undergoes further decomposition to Ga(OH)3 and Ga(NO3)O, compounds that then decompose respectively to Ga(OH)O and finally to Ga2O3 and directly to Ga2O3. Diffuse reflectance Fourier transform IR spectroscopy (DRIFTIR) has been of help in assessing that the reaction consists of parallel dehydration/decomposition processes.