Authors:Agus Pramono, Klodian Dhoska, Irida Markja, and Lembit Kommel
The pressing of equal channel angular pressing - parallel channel process has an effect on microstructure and mechanical properties of the composite materials. Finite element has been used for conducting pressure effect through parallel channel for knowing distribution effect pressing. The materials AA1070 and AA6061 powder matrix composite with Al2O3 nano fiber were used as reinforcement. Mechanical properties and scanning electron microscope were observed in room temperature pressure and in case where the temperatures were higher than recrystallization value. Both results were compared to determine the effectiveness of pressure on each process. The characterization of aluminum composites on the aspects and phenomena of the distribution of pressing effect on hot and cold conditions treasured by finite elements will be explained in this paper.
Authors:Gabriel de Araujo, Dalva de Faria, Márcio Zaim, Flávio de Souza Carvalho, Fabio de Andrade, and Jivaldo Matos
Tibolone polymorphic forms I (monoclinic) and II (triclinic) have been prepared by recrystallization from acetone and toluene,
respectively, and characterized by different techniques sensitive to changes in solid state, such as polarized light microscopy,
X-ray powder diffractometry, thermal analysis (TG/DTG/DSC), and vibrational spectroscopy (FTIR and Raman microscopy). The
nonisothermal decomposition kinetics of the obtained polymorphs were studied using thermogravimetry. The activation energies
were calculated through the Ozawa’s method for the first step of decomposition, the triclinic form showed a lower Ea (91 kJ mol−1) than the monoclinic one (95 kJ mol−1). Furthermore, Raman microscopy and DSC at low heating rates were used to identify and follow the thermal decomposition of
the triclinic form, showing the existence of three thermal events before the first mass loss.
Authors:J. Van den Brande, Ilse Weuts, G. Verreck, J. Peeters, M. Brewster, and G. Van den Mooter
Thermal analysis was performed on the anti-HIV agent loviride in order to test its suitability to be processed using hot-melt
extrusion. Temperature characteristic parameters of crystallization were determined to quantify the stability of amorphous
loviride. The present study has shown that cooling and heating loviride at different rates influenced its thermal stability.
At high cooling rates melted loviride did not crystallize during cooling, and formed a glass that recrystallized during reheating.
Very low cooling rates resulted in significant decomposition of the drug. The glass transition temperature was found to increase
as a function of increasing heating rates and the activation energy for the transition from the glassy to the super-cooled
liquid state was relatively high, indicating good stability of the glass.
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.
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,
. 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.
Authors:Felicitász Velledits, János Csizmeg, and Anna Oravecz-Scheffer
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.
Authors:Daniel Plano, Elena Lizarraga, Juan Antonio Palop, and Carmen Sanmartín
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
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.
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.
The heterogeneous isotopic exchange reactions in strontium polymolybdates of Sr2+ and MoO42- ions in the strontium nitrate and sodium molybdate solutions have been studied using 90Sr and 99Mo as tracers. Electrometric methods have been used to study the compositions of strontium molybdates obtained by adding strontium chloride to a progressively acidified solution of sodium molybdate. It has been found that the exchange fraction increases with increasing chain length of strontium polymolybdate. The exchange equilibrium constant (Kex) has been calculated between 298 and 348 K as well as DG°, DH° and DS°. The results indicate that Sr2+ cations have a much higher affinity for exchangers than MoO42- anions. By fitting the data to the Dubinin-Radushkevich (D-R) isotherm it has been shown that the exchange capacity (Xm) for both ions is affected by the ion adsorption process at low temperatures and by the ion exchange process at high temperatures. At high concentrations, the recrystallization process contributes to on the cation exchange but is ineffective on the anion exchange mechanism.