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Volume 24 (1997)
- Issue 5 Pages 219-
- Issue 4 Pages 158-
- Issue 3 Pages 111-
- Issue 2 Pages 57-
- Issue 1 Pages 2-
Volume 24, Issue 4
Displaying 1-8 of 8 articles from this issue
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German Moiseev, Jaroslav Šesták, Nina Ilynych, Svetlana ...1997 Volume 24 Issue 4 Pages 158-164
Published: September 30, 1997
Released on J-STAGE: September 07, 2009
JOURNAL FREE ACCESSOn the basis of statistical treatment and empirical dependencies of literature data the standard enthalpies of formation from simple oxides, ΔfH°ox (298), have been estimated for YBa2Cu3O6, YBa2Cu3O6, YBa2Cu3O6.5, YBa2Cu3O7, YBa2Cu3.5O7.5, YBa2Cu4O8, YBa2Cu5O9, YBa4Cu3O8.5, Y2BaCuO5, Y2Cu2O5, YCuO2, Y2BaO4, Y2Ba2O5, Y2Ba4O7 and Y4Ba3O9.View full abstractDownload PDF (783K) -
Marek Danielewski, Robert Filipek1997 Volume 24 Issue 4 Pages 165-170
Published: September 30, 1997
Released on J-STAGE: September 07, 2009
JOURNAL FREE ACCESSGeneralized solutions play an important role in the modern theory of partial differential equations. The mathematical model of interdiffusion in the bounded mixture (i. e. layer) showing constant concentration (e. g. in solid or liquid solutions) and variable diffusivity of the components is presented. Using the idea of generalized solution, we will show an exact expression for the evolution of components distribution. The experimental results for ternary Co-Ni-Fe alloy are presented. We present the practical solution of the interdiffusion in multi layer materials and uphill diffusion (diffusional structures) in ternary diffusional couples of finite thickness. Presented model allows for many conclusions to be derived. The key massage is a great potential of generalized Darken model of interdiffusion in describing the mass transport in solid solutions. We show that modern mathematics now-days allows for the modelling, practical calculation and the better understanding of the real transport problems.View full abstractDownload PDF (745K) -
Ragnhild E. Aune, Du Sichen, Seshadri Seetharaman1997 Volume 24 Issue 4 Pages 171-178
Published: September 30, 1997
Released on J-STAGE: September 07, 2009
JOURNAL FREE ACCESSIn the present work, phase relationships in the Mn- and Co- rich regions of the Mn-Co-C system have been investigated at 1173 and 1273K by using an equilibration technique. Alloys of Mn-Co-C were prepared from ultra pure Mn, Co and C powders by mixing the components in required ratios and melting the mixtures in an induction furnace. The melted samples were placed inside quartz capsules and sealed under vacuum. The samples were then placed in the even temperature zone (±0.15°C) of a vertical furnace and heat treated. The duration of the heat treatment was 14 days at 1173K and 7 days at 1273K. The samples were quenched in water after heat treatment. The phase identification of the heat treated samples were carried out by SEM (Scanning Electron Microscope), and the chemical analyses of the various phases present were obtained by the EDS (Electron Dispersion Spectroscopy)-detector attached to the SEM-unit.
On the basis of the present results and the phase diagram information for the three binary systems available in literature, the major part of the Mn-Co-C phase diagram at 1173 and 1273K has been constructed. The results indicate that β-Mn, γ-Mn and α-Co solid solutions exist over appreciable ranges of composition, and cubic (Mn, Co)23C6, hexagonal (Mn, Co)15C4, monoclinic (Mn, Co)5C2 as well as hexagonal (ortrigonal) (Mn, Co)7C3 occur essentially as line compounds. The various two- and three phase regions existing in this system at the temperatures in question are mapped and the isothermal sections are presented.View full abstractDownload PDF (1362K) -
Vicenç Torra, Antoni Isalgue, Henri Tachoire1997 Volume 24 Issue 4 Pages 179-187
Published: September 30, 1997
Released on J-STAGE: September 07, 2009
JOURNAL FREE ACCESSReliability is a critical word in industrial applications of Shape Memory Alloys (SMA) usually called smart materials. Applications of these materials require a rigorous stability of the transformation temperatures and a small hysteresis. The applications of the SMA to the continuous actuators involve a time guarantee about the constructed devices related to the suitable composition and heat treatment. From a mechanical model for a single martensite plate, the shape of the hysteresis cycle (single crsytal of Cu-Zn-Al alloys) is obtained by generalizing the representation to N plates. The observed time effects on the hysteresis loops related to diffusion processes were also taken into account. They allow to explain the martensite recoverable creep and the micromemory effects. Using high resolution on resistance measurements, the room temperature effects on the parent phase acting over the transformation temperature Ms is evaluated. The effect produced by two atomic order parameters (i. e. B2 and L21) related to the yearly room temperature evolution (for instance, summer to winter) induces predictive evolution of transformation temperature and the mean uncertainty reduces drastically (δMs≈±0.05).View full abstractDownload PDF (1063K) -
Hans Jürgen Seifert, Fritz Aldinger1997 Volume 24 Issue 4 Pages 188-193
Published: September 30, 1997
Released on J-STAGE: September 07, 2009
JOURNAL FREE ACCESSAssembling of thermodynamic databases requires the development of consistent analytical descriptions of the functions of states for all phases of the treated system. To provide high-quality data sets the Gibbs energy functions are assessed by computer supported optimisation of phase diagrams using all experimental data available in the literature as well as own experiments. The unary, binary and ternary system descriptions are combined in order to extrapolate to higher-component systems. The CALPHAD method (CALculation of PHAse Diagrams) and the phase modelling is described with special emphasis on ceramic solution phases. The method is illustrated by the thermodynamic assessment of the B-C-N-Si-O system. The results are compared with experimental data.View full abstractDownload PDF (835K) -
Rubin R. Aliev, Vasily A. Davydov, Toshinori Kusumi, Tomohiko Yamaguch ...1997 Volume 24 Issue 4 Pages 194-198
Published: September 30, 1997
Released on J-STAGE: September 07, 2009
JOURNAL FREE ACCESSExperimental study and computer simulations of interaction of vortices in the Belousov-Zhabotinsky reaction show that a small difference in the frequency of vortex rotation causes a marked drift of a vortex with lower frequency. The trajectory of the drift is a logarithmic spiral. Analytical estimations are in a good agreement with the experimental results.View full abstractDownload PDF (1480K) -
Vladimir S. Iorish, Gleb V. Belov1997 Volume 24 Issue 4 Pages 199-205
Published: September 30, 1997
Released on J-STAGE: September 07, 2009
JOURNAL FREE ACCESSQuality of numerical data in thermodynamic databases is known critically influence upon the results of modeling of various processes. That is why the analysis of data quality and searching for erroneous values are very actual.
This paper outlines automated procedure which allows to find the most considerable mistakes in thermodynamic properties of individual substances adopted in a database. HSC-database is analyzed as an example. Comparison procedure of this database and IVTANTHERMO database is supposed to reveal large discrepancies as a sign of erroneous values in one of two databases. Detail examination of the case allows to find the errors.
The most remarkable discrepancies are analyzed to show their influences upon the result of thermodynamic modeling.
General approach to prevent erroneous values usage is discussed. The data quality in databases could be improved by automated control of input values using a set of conditions. These conditions may be added and corrected taking into account theoretical and experimental data.
The importance of international cooperation in improvement of thermodynamic databases quality is emphasized. The time has come for special program development to agree and combine all databases on thermodynamic properties of individual substances. The ultimate goal of the program may be a joint international database, which could be maintained and developed on “real time” regime.View full abstractDownload PDF (819K) -
Oana-Arina Antoce, Vasile Antoce, Katsutada Takahashi1997 Volume 24 Issue 4 Pages 206-213
Published: September 30, 1997
Released on J-STAGE: September 07, 2009
JOURNAL FREE ACCESSUsing a multiplex isothermal calorimeter with 24 sample units the heat evolved during incubation of yeast cultures on glucose-peptone broth was detected under the form of growth thermograms, based on which the values of the growth rate constant μ were calculated. The effect of the initial pH of the yeast cultures was investigated for single strains of four yeast species. Judging from the calculated values of μ, the yeasts studied presented stable growth for pH values ranging approximately from 4 to 8. From growth experiments performed at various temperatures, the effect of the incubation temperature could be observed in the growth thermograms recorded. Using Arrhenius-type plots of the growth rate versus temperature the apparent activation energy of growth was calculated for the four yeasts studied. Furthermore, when ethanol was added in various concentrations to the yeast cultures, changes occurred in the growth thermograms which could be analyzed for the determination of the 50% inhibitory concentration (Kμ) and the minimum inhibitory concentration (MICμ) of ethanol. The variation of parameters Kμ and MICμ with the initial pH and the incubation temperature is also reported for a strain of Saccharomyces cerevisiae.View full abstractDownload PDF (1042K)
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