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The effect of mechanical activation of TiAl powder on the structural and phase transformations in mechanochemical synthesis of the powder mixture of the composition 60.8Fe + 39.2TiAl, intended to produce Fe3Al intermetallics, alloyed with titanium was studied. Using a semi-empirical Miedema’s model, the changes of Gibbs energy for the binary systems Ti-Al, Fe-Ti and Fe-Al were calculated. The results showed that the driving force for the formation of intermetallic phases for all the binary systems is higher as compared to the formation of solid solutions and amorphous phases. A range of compositions was established, in which the formation of amorphous phases in the binary systems Ti-Al and Fe-Al is possible. Carrying out the mechanical activation of TiAl intermetallic powder in a high-energy planetary mill allowed reducing the size of a coherent scattering from 280 to 9 nm with a partial amorphization. The formation of particles with a homogeneous microstructure consisting of intermetallic phase (Fe, Ti)3Al and Lavhes’s phases – Fe2 Ti was established in the process of mechanchemical synthesis of a powder mixture 60.8Fe+39.2 TiAl when using nanostructural TiAl powder. The change in the area of coherent scattering of powders of 60.8Fe+39.2TiAl mixture was evaluated, obtained by the method of mechanochemical synthesis, and it was established that interaction of a nanostructural powder TiAl with Fe begins to occur when the size of the coherent scattering area is <70 nm. The resulting product has an amorphous-nanocrystalline structure with the size of the coherent scattering area of <15 nm. The use of the developed powder in thermal spraying technologies will allow producing coatings based on Fe3Al intermetallics with a nanocrystalline structure, a higher modulus of elasticity and ductility. [ABSTRACT FROM AUTHOR]

The thermodynamics of the alkaline leaching of ilmenite was investigated in this work. Thermodynamic parameters (enthalpy, entropy, Gibbs energy, etc.) are important and necessary for understanding both the course of the chemical reaction as a whole and the possibility of its implementation in the production process. The change in Gibbs energies at different temperatures during the chemical reaction of ilmenite leaching was calculated by the Temkin-Schwartzman method. The calculated values of the Gibbs energies of the reactions for the production of sodium and potassium titanates allowed us to state that the interaction of ilmenite with potassium hydroxide is energetically more advantageous. With the help of X-ray diffraction studies, it was established that ilmenite from the Irshansky deposit is leukoxenized. The identification of the main reflexes of the diffraction patterns confirmed that the interaction of potassium hydroxide and ilmenite yields potassium titanate. [ABSTRACT FROM AUTHOR]

The conformational analysis of the biologically important 2-deoxy-D-ribose molecule adopting the form of pyranose ring in α-and β-anomeric states has been carried out by the quantum-mechanical density functional theory method at the MP2/6-311++G(d,p)//DFT B3LYP/6-31G(d,p) theory level. As many as 74 conformations of its α-and 83 conformations of β-anomeres were detected with relative gas-phase Gibbs free energies under standard conditions within 0)16,8 and 0)14,7 kcal/mole respectively. The thermodynamically equilibrium populations of different forms of the 2-deoxy-D-ribose molecule in gas phase at T=298,15 K have been shown to be: 53 % (α-pyranose) : 23 % (β-pyranose): 22 % (α-furanose) : 2 % (β-furanose). In 6 conformations of 2-deoxy-β-D-ribopyranose the O1NH···HC4N intramolecular HH-contact having the energy of 1,4)1,9 kcal/mole was revealed. [ABSTRACT FROM AUTHOR]

On the MP2/6-311++G(2df,pd)//B3LYP/6-311++G(d,p) level of theory it is established the new physic-chemical mechanism of the transformation of watson-crick base pair Ade∙Thy to the mispairs formed by the rare tautomers (designated by the asterisk) Ade*∙Thy and Ade∙Thy* through the same transition state as ion pair Ade∙Thy* with the Gibbs energy of activation 17.38 kcal/mol which is stabilized by four hydrogen bonds N6H…O4, N6H…N3-, N1+H…N3- and N1+H…O2. Stable pairs Ade*∙Thy and Ade∙Thy* have acceptable relative Gibbs free energy and dissociation (9.94 and 12.43 kcal/mol and 6.06 and 1.61 kcal/mol accordingly) for the explanation of spontaneous point DNA replication errors arising. [ABSTRACT FROM AUTHOR]