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1

Mechanism and Synthesis of Yttrium Iron (Y-Fe) Alloy by Low Temperature Process Using Calcium as Reductant

Ilayaraja Marimuthu, Berchmans L. John, Sankaranarayan Sankara Raman

Archives of Metallurgy and Materials

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2019

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Vol. 64, iss. 4

1593--1596

EN

In this paper, study the preparation of Y-Fe alloy by reduction-diffusion process, which is novel technique for producing an alloy from its ores directly at different temperatures. From this work, investigates the particles size and morphology structure of alloy by X-Ray Diffraction (XRD), Energy dispersive-X-ray analyzer (EDAX) and Scanning Electron Microscope (SEM) respectively. Here study the thermodynamics of property of system such as Gibbs free energy and reaction kinetics of system respectively. The Vibrating Sample magnetometer (VSM) is used to study the magnetic properties of alloy such as cocerviety, saturation magnetization and retentivity.

2

Effect of Hydrostatic Pressure on Thermodynamic Properties of NiTi Shape Memory Alloy

Tatar C., Yildirim Z., Kaygili O.

Archives of Metallurgy and Materials

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2017

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Vol. 62, iss. 2A

799--806

EN

The effect of hydrostatic pressure and different heating/cooling rates on physical properties and microstructure of NiTi shape memory alloy has been investigated. The transformation temperatures and physical properties of the alloy have changed with applied pressure. It has been clearly seen from Differential Scanning Calorimetry (DSC) that with the increase of applied pressure, while As and Af, and Mf transformation temperatures decrease, Ms value increase. Moreover, based on the increase of the pressure amount applied on the sample, there was an average increase of 48% for Gibbs free energy and 18% for elastic strain energy. Entropy of the alloys decreases depending on the increase in the amount of applied pressure for all heating rates. Depending on the amount of applied pressure on the sample, an interior strain of 0.177% at most was observed. With the increase of applied pressure on the sample, it was determined that activation energy increased. Additionally, the Scanning Electron Microscopy (SEM) images of the samples show that the grain sizes of the unpressured sample and the samples on which pressure is applied are between 40 and 120 μm, which was determined by Image Analysis Method.

3

Calculation of the Fe-Fe3C phase equilibrium diagram

Adrian H., Marynowski P., Jędrzejczyk D.

Computer Methods in Materials Science

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2015

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Vol. 15, No.1

179--184

EN

In heat treatment processes of steel the very important role plays the Fe-Fe3C phase equilibrium diagram. It enables the selection of the temperature of austenitisation in respect to carbon content in steel as well as to predict the microstructure composition of annealed steel. For numerical calculation of the phase equilibrium diagrams the CALPHAD method is applied, based on the knowledge of Gibbs energy of phases existing in alloy as functions of temperature and chemical composition of alloy, G=f(T,C). The existing phases in Fe-Fe3C system are: liquid, austenite, ferrite and cementite. The functions of Gibbs free energy, G(T,C), for these phases were published elsewhere. The basic rule for the phase equilibrium diagrams calculations is to calculate the minimum free energy, G, conditions in system for actual parameters: temperature, T, pressure, p, and chemical composition of alloy. In presented paper the algorithm for Fe-Fe3C phase diagram calculation and developed computer program, PD_Fe_Fe3C are presented. Results of calculations using this program were compared with date obtained using commercial program, Thermo-Calc and both results were identical. Developed computer program is open and can take into account the alloy elements applied in steel in order to improve their physical properties. The data base for the effect of alloying elements on the free energy of system was prepared, enabling to calculate the effect of common alloying elements, such as Mn, Cr, Si or Ni, on critical temperatures, A1, A3, Acm. The program may be used for calculation the driving force for phase transformations which occur during heat treatment of steel process as well as in modeling the image of microstructure formed during heat treatment using such numerical methods as cellular automata, CA, or phase field method, PFM.

PL

W obróbce cieplnej stopów żelaza ważnym narzędziem pomocniczym jest wykres równowagi fazowej Fe-Fe3C. Umożliwia dobór parametrów obróbki cieplnej stali węglowych. jak również pozwala określić skład strukturalny stali po obróbce cieplnej. Obliczanie wykresów równowagi fazowej metoda CALPHAD jest oparte na znajomości energii swobodnej Gibbsa jako funkcji temperatury i składu chemicznego, G=f(T,C) faz istniejących w układzie: austenit, ferryt, cementyt, ciecz. Obliczanie wykresu równowagi fazowej polega na obliczam, minimum energii swobodnej układu metodami numerycznym: W prezentowanej pracy przedstawiono program komputerowy PD_FeF3C do obliczania wykresu Ke-Fc3C. Program umożliwia również obliczanie wpływu pierwiastków stopowych na temperatury krytyczne wykresu wstali niskostopowej. Pozwala również obliczać siłę pędną przemian fazowych zachodzących podczas obróbki cieplnej stali, co może być przydatne przy obliczaniu obrazu mikrostruktury metodami np. automatów komórkowych czy pola fazowego.

4

Zastosowanie metod kwantowych w badaniu ścieżek reakcji w CVD

Tkacz-Śmiech K., Jonas S.

Inżynieria Materiałowa

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2011

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Vol. 32, nr 4

776-780

PL

Praca podejmuje problem termodynamicznych aspektów reakcji chemicznych, jakie decydują o przebiegu procesów CVD. Opisano sposób wyznaczania parametrów termochemicznych z zastosowaniem metod kwantowych. Przedstawiono teoretyczne podstawy metody obliczeń z uwzględnieniem kluczowego znaczenia funkcji sumy statystycznej. Wskazano przyczynki do energii cząsteczki, które należy uwzględnić w obliczeniach ciepła i energii swobodnej reakcji. Przykładowe obliczenia wykonano z zastosowaniem programu Gaussian03W dla wybranych reakcji o istotnym znaczeniu dla procesów CVD. Pokazano również, że metody kwantowe stanowią efektywne narzędzie w przewidywaniu ścieżek reakcji.

EN

This article concerns thermodynamic aspects of chemical reactions which determine CVD processes. A way of calculation of thermochemical parameters with application of quantum methods is presented. Theoretical basis of computational model are described and key role of partition function is discussed. The contributions to the molecular total energy which are to be included into reaction heat and free energy calculations are indicated. Exemplary results of calculations performed with use of Gaussian03W program for some typical CVD reactions are presented. It is also shown that quantum methods provide effective tool in predicting reaction pathway.

5

The study of interactions between FAD - flavin adenine dinucleotide and histidine

Sabara D.

Zeszyty Naukowe. Chemia Spożywcza i Biotechnologia / Politechnika Łódzka

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2008

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Z. 72

63-71

EN

In view of the fact that one of the amino acids, histidine, performs an important role in the interactions with flavin adenine dinucleotide (FAD) in the catalytic center of glucose oxidase (GOD), we performed an investigation if interactions between FAD and histidine. The theoretical approach indicates the stacked conformation of FAD, in which the isoalloxazine and adenine ring couple with each other, and an extended - unstacked conformation. Formation of the complex was studied using fluorescence method and computer modeling in order to define the geometrical parameters of the hydrogen bond formation by means of the semi-empirical method (AM1, PM3). The possible distances, angles and stretch vibrations were supported by fluorescence lifetime decay and the Gibbs free energy of the complex.

PL

W pracy opisano badania oddziaływań pomiędzy dinukleotydem flawinoadeninowym a histydyną. Jeden z aminokwasów - histydyna odgrywa ważną rolę w oddziaływaniu z dinukleotydem flawinoadeninowym znajdującym się w centrum aktywnym oksydazy glukozowej (GOD). Teoria potwierdza istnienie dwóch konformacji dinukleotydu flawinoadeninowego; zamkniętej, w której pierścienie adeninowy i izoaloksazynowy reagują ze sobą oraz otwartej - liniowej. Tworzenie kompleksu pomiędzy FAD a histydyną zbadano metodami fluorescencyjnymi oraz przy użyciu optymalizacji komputerowej w celu zdefiniowania parametrów wiązania wodorowego (AM1, PM3). Określenie możliwych interakcji i konfiguracji molekuł zostało wsparte fluorescencyjnymi pomiarami czasów życia oraz wyliczeniem energii Gibbsa powstałego kompleksu.

6

An Implementation of the Steepest Descent Method to Evaluation of Equilibrium Composition of Reactive Mixtures Containing Components in Condensed Phases

Papliński A.

Central European Journal of Energetic Materials

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2007

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Vol. 4, nr 1-2

135-150

EN

Thermodynamic evaluation of equilibrium state of the reacting mixture is considered. The principle of minimization of the Gibbs free energy is adopted for determining of the final chemical composition and thermodynamic state of the mixture. The steepest descent method is employed to evaluate the distribution of individual species concentrations of considered chemical system. A particular attention is paid to the cases in which substances in solid or liquid phase are present in the reactive medium. A method of reduction of the number of equations in the primary set of equations is described. Accuracy of calculations performed with the presented method is discussed.