Reactivity of phosphate raw materials and conditions of its evaluation

Physicochemical aspects of the decomposition of the main types of phosphate raw materials by an aqueous solution of citric acid were studied.     

Thermodynamic properties of 1-butyl-3-methylpyridinium tetrafluoroborate

Pressure, density, temperature (p, ρ, T) data of 1-butyl-3-methylpyridinium tetrafluoroborate [C4mpyr][BF₄] at T = (283.15 to 393.15) K and pressures up to p = 100 MPa are reported with an estimated experimental relative combined standard uncertainty of Δρ/ρ = ±(0.01 to 0.08)% in density. The measurements were carried out with a newly constructed Anton-Paar DMA HPM vibration-tube densimeter. The system was calibrated using double-distilled water, methanol, toluene and aqueous NaCl solutions. An empirical equation of state for fitting of the (p, ρ, T) data of [C4mpyr][BF₄] has been developed as a function of pressure and temperature to calculate the thermal properties of the ionic liquid (IL), such as isothermal compressibility, isobaric thermal expansibility, differences in isobaric and isochoric heat capacities, thermal pressure coefficient and internal pressure. Internal pressure and the temperature coefficient of internal pressure data were used to make conclusions on the molecular characteristics of the IL.     

Electronic structure and lattice stability in the dihydrides of titanium, zirconium, and hafnium

A self-consistent linear MT-orbital method in the atomic sphere approximation (LMTO-ASA) is used to calculate the electronic structure of the dihydrides of the group IV metals in their cubic and tetragonal phases. The effect of tetragonal deformation and hydrogen vacancies on the electronic characteristics is studied. Satisfactory agreement is obtained with experimental data of photoelectron spectra. The nature of the instability in the high-temperature cubic phase is discussed. Fiz. Tverd. Tela (St. Petersburg) 41, 1922–1930 (November 1999)     

Effect of Ti on the galvanomagnetic properties of single-crystal Sb2−x TixTe3

A study is reported of the lattice parameters, Hall effect, Shubnikov-de Haas effect, and thermopower of single-crystal Sb_2−x Ti_xTe₃ as functions of titanium content within the range 0<x<0.04. An increase in titanium content is shown to decrease the initial hole concentration in a sample without a noticeable change of the energy spectrum. Fiz. Tverd. Tela (St. Petersburg) 40, 441–444 (March 1998)     

Vacancies and their complexes in FCC metals

The formation energies of vacancies and their complexes in copper and nickel at zero and finite temperatures are calculated by the embedded-atom method in the quasi-harmonic approximation. The role of temperature effects in the formation of various atomic configurations of intrinsic point defects is studied.     

Calculation procedure for adhesive joints of composite-made components

The stress-strain state of the zone of adhesive bonding between docking module and pressure balloon made of composite materials by the winding is calculated through a corrected procedure. It is shown that the available analytical procedures may be employed to calculate the strength of the considered adhesive joints, provided that the bonded components are sufficiently rigid and have a virtually constant thickness distribution.     

Structure and properties of a hard alloy deposited on a copper substrate by means of a pulsed plasma spray technology

A pulsed plasma spray generator based on a new principle is developed for depositing ceramicmetal, ceramic, and metal coatings on solid substrates. Calculations of the plasma-generator parameters are presented. A hard alloy (W-Co) was deposited on a copper substrate to demonstrate the use of the plasma generator. A Rutherford backscattering (RBS) technique, x-ray diffraction microanalysis of phase composition, diffraction transmission electron microscopy (TEM), and hardness and adhesion measurements were used to examine the hard-alloy coating. It is shown that the coating consists of W-Co crystals with hexagonal and cubic lattices and contains ∼25-nm cobalt α-and β-phase crystallites, with W₃Co₃C particles revealed at the crystallite edges.     

Transformation technologies in forming composite structures

A design model of axisymmetric transformation of a helically wound shell preform into a given shape is considered. Types of design problems are determined, and examples of their solution are given. Examples of fabrication techniques for structural prototypes by using the transformation method are included.