scholarly journals The peculiarities of formation and thermodynamic functions of τ-phase

2018 ◽  
Vol 26 (2) ◽  
pp. 37-44
Author(s):  
N. Yu. Filonenko ◽  
O. M. Galdina
Keyword(s):  
Boron Carbide ◽  
Carbon Content ◽  
Thermodynamic Functions ◽  
Thermodynamic Potential ◽  
Boron Content ◽  
Point Of View ◽  
No Formation ◽  
High Temperature Expansion ◽  
Temperature Dependences ◽  
First Time

It is shown that for alloys with boron content of 0.1–6.5% (wt.) and carbon content of 0.3–4.0% (wt.) without pretreatment no formation of cubic boron carbide takes place under crystallization. The cubic boron carbide can be obtained by pre-annealing at a temperature of 1173 K for an hour and further heating to a temperature of 30 K above the liquidus and cooling of alloys with boron content of 2.5–4.0% (wt.) and carbon content of 0.8–3.0% (wt.). Formation of crystals of cubic boron carbide is possible as a constituent of multiphase inclusions for alloys with boron content of 0.1–0.3% (wt.) and carbon content up to 0.4–0.5% (wt). It should be noted that for alloys with boron content of 4.2–6.0% (wt.) and  carbon content of more than 3.0% (wt.) the pretreatment does not result in formation of cubic boron carbide. The increase in boron content in the alloy to 0.3–0.5% (wt.) and carbon content to 0.5–0.7% (wt.) leads to formation of the eutectic α-Fe+Fe23(CB)6, which is arranged on the boundaries of pearlite grains. The thermodynamic functions of Fe23(CB)6 cubic boron carbide are derived for the first time using the Hillert and Staffonsson model and accounting for the first degree approximation of high-temperature expansion of the thermodynamic potential for binary alloys. We obtain temperature dependences of such thermodynamic functions for Fе23(CB)6 phase as Gibbs energy, entropy, enthalpy and heat  capacity CP , as well as calculate their values at the formation temperature of the phase. The approach used in this paper enables to give the most complete from the thermodynamic point of view description of cubic boron carbide formed from a liquid.

scholarly journals The Physical and Thermodynamic Functions of Borides

2017 ◽  
Vol 18 (1) ◽  
pp. 58-63
Author(s):  
N.Yu. Filonenko
Keyword(s):  
Free Energy ◽  
Physical Properties ◽  
Thermodynamic Functions ◽  
Point Of View ◽  
Energy Potential ◽  
High Temperature Expansion ◽  
Temperature Dependences ◽  
Function Calculation ◽  
First Time ◽  
Good Agreement

In the paper the physical properties and thermodynamic functions of borides Х2В (Х=W, Mo, Mn, Fe, Co, Ni та Cr) are studied with accounting for fluctuation processes. We use the microstructure analysis, the X-ray structural and the durometric analyses to determine the physical properties of alloys. In the paper it is determined the phase composition and physical properties of borides. In this paper for the first time it is determined the thermodynamic functions of borides using the Hillert and Staffansson model with accounting for the first degree approximation of high-temperature expansion for the free energy potential of binary alloys. We obtain the temperature dependences for such thermodynamic functions as Gibbs free energy, entropy, enthalpy and heat capacity Ср along with their values at the formation temperature for Х2В (Х=W, Mo, Mn, Fe, Co, Ni та Cr). The approach under consideration enables to give more thorough from the thermodynamic point of view description of borides formed from the liquid. The outcomes of the thermodynamic function calculation for borides are in good agreement with experimental data and results of other authors.

scholarly journals Structural State and Thermodynamic Stability of Fe-B-C Alloys

2019 ◽  
Vol 20 (4) ◽  
pp. 437-444 ◽  
Author(s):  
N.Yu. Filonenko ◽  
A. N. Galdina ◽  
А.I. Babachenko ◽  
G.A. Kononenko
Keyword(s):  
Phase Composition ◽  
Carbon Content ◽  
Thermodynamic Stability ◽  
Short Range ◽  
Thermodynamic Potential ◽  
Boron Content ◽  
Liquidus Surface ◽  
Temperature Expansion ◽  
High Temperature Expansion ◽  
First Time

The studies were performed for the specimens of Fe-B-C alloys with boron content of 0.005–7.0 wt.% and carbon content of 0.4–5.5 wt.%, the rest was iron. As a result of the experiment carried out in this work, the phase composition and phase transformations occurring in the alloys are investigated and the liquidus surface is constructed; it is shown that the point with minimum temperature of 1375 K at the liquidus surface is observed at boron content of 2.9 wt.% and carbon content of 1.3 wt. %. For the first time, considering the contribution of the first degree approximation of high-temperature expansion of thermodynamic potential into the Gibbs energy of Fe-B-C melt, we obtain the surface of thermodynamic stability of Fe-B-C melt, depending on temperature and content of boron and carbon in the alloy. The findings show that in order to obtain the homogeneous Fe-B-C melt, which does not contain micro-inhomogeneous structures in the form of short-range microregions, it is necessary to perform overheating more than to 150 K.

scholarly journals Thermodynamic Functions of Fe3B Borides

2019 ◽  
Vol 20 (2) ◽  
pp. 139-143
Author(s):  
N.Yu. Filonenko ◽  
O.M. Galdina ◽  
A.V. Kochenov
Keyword(s):  
Diffraction Analysis ◽  
Thermodynamic Functions ◽  
Boron Content ◽  
Liquidus Line ◽  
Complete Suppression ◽  
X Ray Diffraction ◽  
Cast State ◽  
X Ray ◽  
Eutectic Colony ◽  
First Time

In this work we study the structural properties of hypoeutectic and hypereutectic Fe-B alloys, depending on the temperature of heating above the liquidus line and the cooling rate. Experiments were carried out for the Fe-B system alloys with boron content of 2.0 - 4.5 % (wt.), the rest is iron. To determine physical properties of the alloys microstructural and X-ray diffraction analysis were used. It is shown that overheating of the molten alloy to 150 K above the liquidus line and aftercooling leads to complete suppression of the formation of primary iron crystals in the hypoeutectic alloys and partially to suppression of Fe2B formation in the hypereutectic alloys of the Fe-B system. For the first time it is shown that heating of Fe-B hypoeutectic alloys to 150 K above the liquidus line and cooling with a rate of 103 K/s lead to formation of Fe3B boride in as-cast state, which was present in the eutectic colony.

scholarly journals Study of Thermodynamic Functions for Iron Monoboride FeB

2015 ◽  
Vol 16 (1) ◽  
pp. 136-139
Author(s):  
N. Yu. Filonenko
Keyword(s):  
Heat Capacity ◽  
High Temperature ◽  
Temperature Dependence ◽  
Binary Alloy ◽  
Thermodynamic Functions ◽  
Thermodynamic Potential ◽  
Thermodynamic Quantities ◽  
Zeroth Order ◽  
Temperature Expansion ◽  
High Temperature Expansion

The thermodynamic quantities for iron monoboride FeB, such as entropy, enthalpy, heat capacity and their temperature dependence, are considered. It is shown, that accounting for contribution to the zeroth-order high-temperature expansion of thermodynamic potential for Fe-B binary alloy enables to describe forming monoboride FeB in more complete way from the viewpoint of thermodynamics.

scholarly journals Liquidus Surface and Spinodal of Fe-B-C Alloys

2020 ◽  
Keyword(s):  
Carbon Content ◽  
Boron Content ◽  
Liquidus Surface ◽  
Thermal Analyses ◽  
Primary Phase ◽  
Binary Section ◽  
Quasi Binary Section ◽  
Point Of Intersection ◽  
First Time ◽  
Primary Crystals

In this work the study is performed for the specimens of Fe-B-C alloys with boron content of 0.005–7.0 wt. % and carbon content of 0.4–6.67 wt. %, the rest is iron. According to the findings of microstructure analysis, XRD and differential thermal analyses, the primary phases and the temperatures of their formation are determined. Depending on boron content (in the range of 1.5–8.80 wt. %) and carbon content (0.5–6.67 wt. %) in the Fe-B-C alloys, the primary phases in the process of crystallization are γ-Fe, boron cementite Fe3(CB) and boride Fe2В. The outcomes of the experiment carried out in this work determine the phase composition and phase transformations occurring in the alloys and the liquidus surface is constructed. The findings show that the liquidus temperature for Fe-B-C system alloys is low compared to binary Fe-B and Fe-C alloys. At the liquidus surface of the Fe-B-C alloys, there is a point at boron content of 2.9 wt. % and carbon content of 1.3 wt. % with the lowest temperature of 1375 K and it is the point of intersection of monovariant eutectics. This fact is in a good agreement with the results of other authors. The microstructure of alloys located at the curves of monovariant eutectics is represented by the γ–Fe+Fe2B and γ–Fe+Fe3(CB) eutectics and the primary crystals of Fe2B iron boride in the shell of Fe3(BC) boron cementite. In this paper it is shown experimentally the existence of a quasi-binary section and the coordinates of the peritectic point are fixed: the boron content is 5.0 wt. %, carbon content is 3.0 wt. % and the temperature is 1515 K. The free energy of the Fe-B-C melt is calculated for the first time by the quasi-chemical method and the surface of thermodynamic stability of the Fe-B-C melt is plotted, depending on temperature and boron and carbon content in the alloy. The results obtained in the paper show that in order to obtain a homogeneous Fe-B-C melt, which does not contain any microheterogeneous structure in the form of short-order microregions, it is necessary to perform the overheating more than to 180 K for the region where the primary phase is iron, and no less than to 200 K for the regions with boron cementite and boride.

scholarly journals Solubility of Boron and Carbon in Ferrite of the Fe-B-C System Alloys

2019 ◽  
Keyword(s):  
Solid Solution ◽  
Carbon Content ◽  
Mass Fraction ◽  
Room Temperature ◽  
Boron Content ◽  
Solubility Limit ◽  
Content Increase ◽  
X Ray ◽  
First Time ◽  
Structure Imperfection

Investigation was carried out for Fe-B-C alloys with carbon content of 0.0001–0.01 % (wt.) and boron content of 0.0001–0.01 % (wt.), the rest is iron. To determine the structural state of alloys we use the microstructure analysis, X-ray microanalysis and X-ray structure analysis. The level of microstraines, dislocation density and the coercive force of ferrite is determined, and it is shown that structure imperfection grows with boron content increase in the alloy. The obtained results enable to suggest that boron atoms in a solid solution of α-iron occupy substitutional-interstitial positions depending on boron content. In the paper it is shown experimentally, that at room temperature solubility limit of boron and carbon in the ferrite is 0.00012 % (wt.) and 0.006 % (wt.). When boron and carbon content increases further, the following phases are formed: Fe2B, Fe3(CB) and Fe23(CB)6. In this paper by means of quasi-chemical method we obtain for the first time temperature dependence of the free energy for α-iron solid solution, as well as solubility limit of carbon and boron. Maximum mass fraction of carbon may be up to 0.016 % (wt.), and maximum boron mass fraction – up to 0.00025 % (wt.). At room temperature the boron solubility limit in ferrite is 0.0001 % (wt.), and carbon one is 0.004 % (wt.). The calculated numerical values of the solubility of boron and carbon in ferrite of the Fe-B-C system alloys are less than that of the experimental results. This can be explained by the fact that boron atoms interact more actively with structure imperfections than carbon atoms. At high temperatures the solubility of carbon and boron in given phase increases.

Thanato-Laboratorien. Theorien von Tod und Sterben und Elias Canettis Buch gegen den Tod

2020 ◽  
Vol 4 (1) ◽  
pp. 67-86
Author(s):  
Elisabeth Heyne
Keyword(s):  
Human Life ◽  
Death And Dying ◽  
Point Of View ◽  
Visual Images ◽  
Elias Canetti ◽  
History Of ◽  
Series Of Experiments ◽  
First Time ◽  
Textual Form ◽  
Or History

AbstractAlthough visual culture of the 21th century increasingly focuses on representation of death and dying, contemporary discourses still lack a language of death adequate to the event shown by pictures and visual images from an outside point of view. Following this observation, this article suggests a re-reading of 20th century author Elias Canetti. His lifelong notes have been edited and published posthumously for the first time in 2014. Thanks to this edition Canetti's short texts and aphorisms can be focused as a textual laboratory in which he tries to model a language of death on experimental practices of natural sciences. The miniature series of experiments address the problem of death, not representable in discourses of cultural studies, system theory or history of knowledge, and in doing so, Canetti creates liminal texts at the margins of western concepts of (human) life, science and established textual form.

A Nabatean port on the Red Sea: note on the pottery finds from al-Qusayr (al-Wajh, Saudi Arabia)

2020 ◽  
Author(s):  
Caroline Durand
Keyword(s):  
Saudi Arabia ◽  
19Th Century ◽  
Red Sea ◽  
Point Of View ◽  
The Other ◽  
Trade Routes ◽  
Other Hand ◽  
Roman Egypt ◽  
Pottery Sherds ◽  
First Time

Al-Qusayr is located 40 km south of modern al-Wajh, roughly 7 km from the eastern Red Sea shore. This site is known since the mid-19th century, when the explorer R. Burton described it for the first time, in particular the remains of a monumental building so-called al-Qasr. In March 2016, a new survey of the site was undertaken by the al-‘Ula–al-Wajh Survey Project. This survey focused not only on al-Qasr but also on the surrounding site corresponding to the ancient settlement. A surface collection of pottery sherds revealed a striking combination of Mediterranean and Egyptian imports on one hand, and of Nabataean productions on the other hand. This material is particularly homogeneous on the chronological point of view, suggesting a rather limited occupation period for the site. Attesting contacts between Mediterranean merchants, Roman Egypt and the Nabataean kingdom, these new data allow a complete reassessment of the importance of this locality in the Red Sea trade routes during antiquity.

Ground state molecular parameters of phosphine, PH3, from the simultaneous analysis of the high-resolution infrared, microwave and submillimeterwave spectra

1985 ◽  
Vol 50 (11) ◽  
pp. 2480-2492 ◽  
Author(s):  
Soňa Přádná ◽  
Dušan Papoušek ◽  
Jyrki Kauppinen ◽  
Sergei P. Belov ◽  
Andrei F. Krupnov ◽  
...  
Keyword(s):  
Fourier Transform ◽  
High Resolution ◽  
Ground State ◽  
Unitary Transformation ◽  
Point Of View ◽  
Acoustic Detection ◽  
Molecular Parameters ◽  
Microwave Spectrometer ◽  
Fourier Transform Spectra ◽  
First Time

Fourier transform spectra of the ν2 band of PH3 have been remeasured with 0.0045 cm-1 resolution. Ground state combination differences from these data have been fitted simultaneously with the microwave and submillimeterwave data to determine the ground state spectroscopical parameters of PH3 including the parameters of the Δk = ± 3n interactions. The correlation between the latter parameters has been discussed from the point of view of the existence of two equivalent effective rotational operators which are related by a unitary transformation. The ΔJ = 0, +1, ΔK = 0 (A1 ↔ A2, E ↔ E) rotational transitions in the ν2 and ν4 states have been measured for the first time by using a microwave spectrometer and a radiofrequency spectrometer with acoustic detection.

Nω-Hydroxy-L-arginine and Its Homologues. Chemical and Biological Properties. A Review

2004 ◽  
Vol 69 (3) ◽  
pp. 499-510 ◽  
Author(s):  
Petra Beranová ◽  
Karel Chalupský ◽  
Gustav Entlicher
Keyword(s):  
Inhibitory Activity ◽  
Biological Activities ◽  
Biological Effects ◽  
Biological Properties ◽  
No Synthase ◽  
Point Of View ◽  
No Donor ◽  
Good Substrate ◽  
No Formation ◽  
Vasorelaxant Activity

Nω-Hydroxy-L-arginine (NOHA) is a stable intermediate in NO formation from L-arginine catalyzed by NO synthase (NOS). Apparently, NOHA can be released and serve as a stable reserve NO donor (as a substrate of NOS) or transported and exert its own biological effects. It shows endothelium-dependent as well as endothelium-independent vasorelaxant activity. The latter case indicates that NOHA can be metabolized by pathways independent of NOS. These possibilities are discussed in detail. Of the available NOHA homologues homo-NOHA is a good substrate of NOS while nor-NOHA seems to be a very poor substrate of this enzyme. On the contrary, nor-NOHA exerts arginase inhibitory activity 20 times higher than NOHA whereas homo-NOHA is inactive. Detailed investigation of biological activities of NOHA and its homologues seems to be promising from the pharmacological point of view. A review with 43 references.

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