Thermodynamics of liquid Fe-Si and Fe-Ge alloys

The enthalpies of mixing of liquid binary Fe-Ge (1765±5 K) and Fe-Si (1750±5 K) alloys were determined using a high-temperature isoperibolic calorimeter. The thermodynamic properties of Fe-Ge melts were also studied by electromotive force method in the temperature range of 1250-1580 K. The comparison of our measurement results with literature data has been performed. The extreme negative values of integral enthalpy of mixing and alternating-sign deviations from Raoult's low for germanium can be explained by the influence of binary clusters formation. This revised version was published online in July 2006 with corrections to the Cover Date.     

Calorimetric study of liquid gadolinium-based alloys

The enthalpies of mixing of liquid Gd-Si (1770±5 K) and Al-Gd (1760±5 K) alloys have been measured by high-temperature isoperibolic calorimetry. The calorimetric study of the gadolinium-based liquid alloys demonstrates the great negative enthalpies of mixing, which is associated with the contribution of GdSi and GdAl₂ intermetallides into the liquid-state thermodynamics. The comparison of obtained results with literature data has been performed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Complex Analysis of Phosphate-based Material Oxidation

The thermal stability of sample Mo(PO₃)₃ that is the initial material for novel catalysts for carbonmonoxide oxidation has been studied. It has been concluded that molybdenum(III) methaphosphate is stable up to 435°C. Processes of partial oxidation and layering of specimens are determined. Novel material based on partial oxidized Mo(PO₃)₃ gives significant rise of the carbon oxidation rate. The molybdenum(III) metaphosphate is of a definite interest in view of its application in practice as initial material for new catalysts row formation with different content of Mo(PO₃)₃ and MoOPO₄ layers. This revised version was published online in August 2006 with corrections to the Cover Date.     

Formation of Pyrogenic Silica: Spectroscopic and Quantum Chemical Insight

This article describes the genesis of amorphous silica under high-heat conditions from SiO₂ molecules through protoparticles, primary particles, and aggregates to agglomerates using vibrational spectra and quantum chemical simulations data. The impact of small molecules (water, HCl, CO₂) is also discussed. The article also explains the nature of the pyrogenic silica amorphism.     

Thermodynamics of formation of aluminum-iron-germanium amorphous alloys

Thermodynamic properties of ternary liquid Al-Fe-Ge alloys were studied by electromotive force method at 1050-1250 K and by high-temperature isobasic calorimetry at 1740 ± 5 K. The heat capacity change at ternary alloy formation (Δ_mixC_p) was estimated using the temperature dependence of integral enthalpy of mixing. Thermodynamics of the formation of Al-Fe-Ge amorphous alloys was evaluated by extrapolation of thermodynamic functions of mixing to the temperature of amorphization. The process of glass forming is preferable by both enthalpy and entropy for compositions of (0.1<x_Fe<0.6, x_Ge<0.5). The area with most negative integral Gibbs free energy and enthalpy of amorphous alloy formation corresponds well to the area of amorphization estimated by a glass-forming tendency (GFT) criterion.     

Peculiarities of the electrophysical characteristics of platinum silicide-silicon contacts under impulsive overloads

The extremal operating states of the active elements of integrated circuits and discrete devices as well as the different actions on semiconductor devices with a Schottky barrier based on metal silicide-silicon contacts lead to a change in their physical parameters. In this work the effect of impulsive overloads on a formed platinum silicide-silicon contact is studied. It is shown, with the help of analytical expressions for the currents in the superbarrier region and in the region of resonant tunneling charge transfer, that under impulsive action a change occurs in both the transitional layer and in the region of space charge; the change is associated with the increase in the concentration of deep levels in the region of space charge that participate in the resonance tunneling. Estimates of the Joule heating by the current flowing in the structures employed do not exceed 100°C, indicating that defect formation under the impulsive actions is nonthermal.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 70–73, September, 1988.     

The catalytic efficiency of Fe-containing nanocomposites based on highly dispersed silica in the reaction of CO2 hydrogenation

Research on Chemical Intermediates - Oxide Ni(80)Fe(20)/SiO2, Co(93)Fe(7)/SiO2, and Ni(19)Co(77)Fe(4)/SiO2 nanocomposites (NCs) were prepared using highly dispersed silica. It was modified by...     

Crystal and molecular structure of β-cyclodextrin inclusion complex with succinic acid

The crystal complex of β-cyclodextrin with succinic acid, intermediate product of hydrolysis reaction of succinic anhydride in the presence of β-cyclodextrin, was isolated and studied by X-ray analysis (monoclinic, space group P2₁, a = 15.1977(7) Å, b = 10.1763(5) Å, c = 20.6943(6) Å, β = 109.239(4)°, V = 3021.8(2) Å³, Z = 2, R ₁ = 0.0359, wR ₂ = 0.0947). It was proved that β-cyclodextrin and succinic acid form an inclusion complex, which exists in crystal state as a heptahydrate. The molecule of succinic acid is fully included in the β-cyclodextrin cavity with its carboxyl groups accessible for water molecules. Water molecules located at borders of cavity rims and in interstices between molecules of β-cyclodextrin participate in formation of intermolecular hydrogen bonds. The overall structure does not contain disordered fragments. The crystal conformation of succinic acid corresponds to one of possible conformers of the molecule in vacuo and is almost not disturbed by intermolecular interactions in crystal. Based on the analysis of structural features of the crystal conformation of succinic acid and character of its location in the β-cyclodextrin cavity, it was suggested that hydrolysis of succinic anhydride via ring opening and formation of succinic acid is mediated by cyclodextrin microenvironment and it likely occurs near the narrow rim of the macrocycle cavity.     

Crystallization and Thermodynamic Properties of Titanium Stannides

Thermodynamic properties of pure titanium stannides obtained by crucible-less growth techniques under vacuum are determined by differential scanning calorimetry and Knudsen effusion. The enthalpy, specific heat capacity, entropy and Gibbs energy temperature dependence were simulated using Maier and Kelly equations. Standard enthalpies of evaporation, formation and atomization of titanium stannides were determined and compared with earlier-known data. This revised version was published online in August 2006 with corrections to the Cover Date.