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Journal of Thermal Analysis and Calorimetry
Authors: Lucinéia de Carvalho, Milena Segato, Ronaldo Nunes, Csaba Novak, and Éder Cavalheiro

Abstract  

The thermal decomposition behavior of acesulfame-K (ACK), aspartame (ASP), sodium cyclamate (SCL), saccharine (SAC), and sodium saccharine (SSA) were investigated. After re-crystallization of the commercial samples the compounds were characterized by using elemental analysis, IR spectroscopy and thermoanalytical techniques (TG/DTG, DTA, and DSC). Evidences of hydrate water loss were observed for SSA and ASP. Melting was detected for SSA and SAC. Each compound decomposed in a characteristics way. The decomposition of APS and SAC took place completely, while ACK, SCL and SSA resulted in K2SO4, Na2SO4, and Na2SO4, as residues respectively. The Flynn-Wall-Ozawa method for kinetic calculations was applied for the volatilization of saccharine resulting in E a = 80 ± 1 kJ mol−1 and log A = 7.36 ± 0.07 min−1.

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Summary  

The differences on the thermal behaviour (DTG-DTA) of antigorite sample measured before and after sonication have been studied. Sonication treatment produces negligible changes in the structure of the material but substantial textural modifications. These modifications produce changes in the thermal behaviour of antigorite sample. Thus, it has been observed a decrease in the dehydroxylation temperature as measured by DTG and DTA effects. For sonication treatments longer than 20 h, two new effects of dehydroxylation are observed, the intensity of these two new effects increases with the sonication time showing a modification in the release of structural OH. It has been also observed that the formation of forsterite takes place simultaneously with the dehydroxylation of the antigorite. The high temperature exothermic effect is due to the recrystallization of forsterite and not to the formation of forsterite as traditionally assumed. Modifications in the thermal dehydroxylation of antigorite observed in this study are related to the pronounced decrease in particle size obtained by sonication.

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Abstract  

Methods for kinetic description of induction periods, based on the single-step kinetics approximation and various expressions of the temperature functions, are presented. The formulas for evaluation of both isothermal and non-isothermal lengths of induction periods are derived. Use of the formulas is demonstrated on the thermooxidative degradation of polyolefines. The kinetic parameters obtained from isothermal and non-isothermal experiments are compared and possible reasons of inconsistencies are analyzed. Applications of the determination of induction periods for thermooxidation of various systems are reviewed. The theory outlined in this paper can be applied not only for thermooxidation in condensed phase, but also for other processes exhibiting the induction period, such as the curing of rubber compounds, recrystallization of nickel sulfide and crystallization of silicate and metal glasses.

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Abstract  

Equal channel angular pressing (ECAP) was carried out on solution annealed samples of Al–Mg–Si–Zr and Al–Mg–Si–Zr–Sc alloys to achieve a substantial grain refinement of the materials. Post ECAP aging was then investigated on the ultrafine grained alloys by DSC and TEM analyses. DSC scans were carried out with heating rates ranging from 5 to 30°C min–1. Peak identification was performed by the support of literature information and TEM analyses. Precipitation kinetics revealed to be similar for both alloys but the Sc-free alloy showed a recrystallization peak at temperatures ranging from 310 to 340°C, depending on the strain accumulated during ECAP. On the contrary, the Sc-containing alloy showed a greater grain stability. Analyses of peak positions and of activation energies as a function of ECAP passes experienced by the samples revealed large modifications of precipitation kinetics in the ultrafine-grained alloys with respect to the coarse-grained materials.

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The Little Plain Basin is one of the largest units in the Pannonian Basin System. Its continuation in Slovakia is called the Danube Basin. The Little Plain Basin is one of the most underexplored areas in Hungary. Based on archival geologic and geophysical data the lithostratigraphic composition of the area is controversial. The significance of the area is increased by the known Neogene and the supposed basement (Paleozoic and Mesozoic) hydrocarbon systems in Hungary and in Slovakia.

The purpose of this study is to identify the exact age, facies, geologic formations and possible source rocks of the Triassic section penetrated by the Gyõrszemere-2 well in the Little Plain Basin.

Based on new facies and paleontological results it can be stated that two Triassic sequences are identified in the well, separated by fault breccia. A carbonate sequence was deposited between the Induan and Early Anisian and above that a homogeneous recrystallized dolomite appears, the age of which is unknown.

The following formations were encountered, from base upward:

Arács Marl Fm. (3,249.5–3,030 m), silty marl with ooids, bivalves, gastropods and ostracode shells. Occasionally layers of angular quartz grains in large quantities appear. Postcladella kahlori and Spirobis phlyctaena indicates Induan (Early Triassic) age.

Köveskál Dolomite Fm. (3,030–2,790 m), rich in ooids and also containing anhydrite. The Glomospira and Glomospirella dominance indicates an age interval between Olenekian and earliest Anisian age.

Fault breccia (2,790–2,690 m) separating the Köveskál and overlying dolomites.

Upper dolomite (2,690–2,200 m): homogeneous, saccharoidal, and totally recrystallized. The age is unknown.

The low TOC values of the supposed source rock interval (marl between 3,249.5 and 3,030 m) indicate poor hydrocarbon potential.

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Abstract  

A new method is presented to analyze the irreversible melting kinetics of polymer crystals with a temperature modulated differential scanning calorimetry (TMDSC). The method is based on an expression of the apparent heat capacity,
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$\Delta \tilde C{e}^{---{i\alpha }} = mc_p + i(1/{\omega }F'_{T}$$ \end{document}
, with the true heat capacity, mcp, and the response of the kinetics,
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$F'_{\text{T}}$$ \end{document}
. The present paper experimentally examines the irreversible melting of nylon 6 crystals on heating. The real and imaginary parts of the apparent heat capacity showed a strong dependence on frequency and heating rate during the melting process. The dependence and the Cole-Cole plot could be fitted by the frequency response function of Debye's type with a characteristic time depending on heating rate. The characteristic time represents the time required for the melting of small crystallites which form the aggregates of polymer crystals. The heating rate dependence of the characteristic time differentiates the superheating dependence of the melting rate. Taking account of the relatively insensitive nature of crystallization to temperature modulation, it is argued that the ‘reversing’ heat flow extrapolated to ω → 0 is related to the endothermic heat flow of melting and the corresponding ‘non-reversing’ heat flow represents the exothermic heat flow of re-crystallization and re-organization. The extrapolated ‘reversing’ and ‘non-reversing’ heat flow indicates the melting and re-crystallization and/or re-organization of nylon 6 crystals at much lower temperature than the melting peak seen in the total heat flow.
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four types of thermal behavior for the series A and B: • Behavior I Compounds that do not alter the thermal behavior after an initial fusion–recrystallization cycle ( Fig. 1 ). Under these conditions there is no evidence of polymorphic behavior. The

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Journal of Thermal Analysis and Calorimetry
Authors: M. D. Baró, N. Clavaguera, S. Bordas, M. T. Clavaguera-Mora, and J. Casas-Vázquez

The kinetics of bulk crystallization of Se61.5Ge15 4Sb23.1 glasses was investigated from their thermal behaviour. In the thermal characterization of a glass the recrystallization temperature is highly dependent on both the rate of heating and the thermal history of the glass. Vitreous samples were prepared by quenching. From ratedependent curves it was found that the recrystallization process obeys first-order kinetics with an apparent activation enthalpy of 48±5 kcal/mole. Further analysis allows determination of both the activation enthalpy,H=90±4 kcal/mole, and the kinetic exponent of the Avrami equation,n=1.9±0.3.

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Central European Geology
Authors: Szabolcs Nagy, Sándor Józsa, Arnold Gucsik, Szaniszló Bérczi, Kiyotaka Ninagawa, Hirotsugu Nishido, Miklós Veres, Ákos Kereszturi, and Henrik Hargitai

Abstract

We studied optical microscopic and micro-Raman spectroscopic signatures of shocked olivine from the ALH 77005 Martian meteorite sample. The purpose of this study is to document pressure and temperature-related effects in olivine over the entire sample, which can aid in understanding structural changes due to shock metamorphism and the post-shock thermal annealing processes of lherzolitic Martian meteorites. According to the optical microscope observations, three areas may be discernible in olivine of the ALH 77005 in the vicinity of the melt pocket. The first area is the thermally undisturbed part of a grain, which contains a high density of shock-induced planar microdeformations such as Planar Deformation Features (PDFs) and Planar Fractures (PFs). Compared to the first area, the second area shows less shock-induced microstructures, while the third area is a strongly recrystallized region, but not formed from a melt.

A common Raman spectral feature of these olivines is a regular doublet peak centered at 823 and 852 cm−1; additionally, two new peaks at 535 and 755 cm−1 appear in the weakly annealed transition zones.

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This paper is devoted to the description of spessartine-almandine garnet (Sps: 39.8-60.2%; Alm: 29.1-56.76%; Grs <7%, Prp <3.6%, Adr <5%) from aplitic dyke rocks of the Mórágy granitoid near Erdõsmecske and Aranyos valley. The aplitic dyke rocks contain K-feldspar, plagioclase, quartz, (myrmekite), ±garnet, ±biotite, chlorite or secondary muscovite, ±ore minerals, ±calcite, ±apatite and ±epidote. Two different zoning types in garnet were detected by electron microprobe. Zoning type I means either Mn enrichment at the expense of Fe towards the rim or towards the core or plateau garnet profiles. Zoning type II displays Ca enrichment at the rim of garnet. A high proportion of Sps component in garnet and the character of zoning type I are considered as typical magmatic features.  The pressure-temperature estimation for aplite formation arises from experimental investigations of Green (1977) in agreement with the hypothetical approach of liquidus relationships by Abott and Clarke (1979) giving a minimum temperature estimation of c. 675 °C-700 °C at pressure of 1-3 kbar. Following the magmatic crystallization, solid state deformation is evidenced by dynamic recrystallization of quartz and feldspars at temperatures of about 450-500 °C in the upper greenschist to lower amphibolite facies. Grossular-rich rim of garnet indicates pressure increase during ductile deformation.

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