This paper presents a theoretical model for describing the thermodynamic properties of doped ferroelectric crystals based on a modified Weiss mean-field approach. Accounting for quadrupole and ...octupole terms in the expression for the effective field within the Weiss model makes it possible to move from the Langevin equation to the Landau–Ginzburg equation. Furthermore, the coefficients of the Landau–Ginzburg equation can be expressed in terms of the physical parameters of the crystal lattice. For these parameters, analytical expressions are proposed that describe their change when adding dopants in ceramic matrix composites. Perovskite barium titanate ceramics with a variety of inclusions is considered as an application example of the developed method. The obtained agreement between the analytical and experimental results for barium titanate ceramics with lanthanum/magnesium/zirconium dopants gives us hope of the applicability of the present theory to the calculation of other doped ferroelectrics as well.
Diltiazem is a drug used as a calcium channel blocker in the treatment of cardiovascular disorders. Because of the poor aqueous solubility of the drug, its hydrochloride salt has been marketed. Due ...to the short elimination half-life of diltiazem, extended-release formulations were developed. In the present work, the crystal engineering approach has been employed to obtain diltiazem forms with lower water solubility by treating with carboxylic acids. Three molecular salts of diltiazem with aspirin, niacin and l -malic acid were synthesized and characterized by single crystal and powder XRD, DTA, solid state CP-MAS, NMR and UV/vis techniques. The single crystal structure determination allowed us to study the supramolecular structures and proton transfer interactions from the carboxylic acids to diltiazem in the solid state, while the NMR studies showed the interactions in solution. In the crystal, the N , N -(dimethyl)ethylamine fragment of the drug molecule interacts with the carboxylic groups of the acids to form heterosynthons. The maximum 40-fold decrease of the aqueous solubility is achieved for diltiazem acetylsalicylate hydrate in comparison with the solubility of diltiazem hydrochloride.
Mechanical, damping and specific properties of new structural high-damping steel have been studied in the present research. Studied high-damping steel was specially produced by the JSC Severstal in ...order to obtain metallic material with specified level of damping and mechanical properties. Experiments show that the damping properties of industrial high-damping steel are comparable with damping properties of high-purity damping alloys, produced using laboratory equipment. Mechanical properties of the industrial high-damping steel were found to be comparable with the level of properties of well-known structural steels, widely used in the modern industry. Analysis of the combination of mechanical and specific properties of the new steel indicates that this material can be used for the construction of rigid structures requiring high damping. Specific features of practical application of high-damping steels are also discussed.
Results are provided for an experimental study of the effect of deoxidation on the composition of nonmetallic inclusions in pipe steels melted in a vacuum induction furnace with a periclase lining. ...Thermodynamic calculations are made for oxygen activity within melts with lanthanum, cerium, aluminum, and yttrium for the metal of four melts. Conditions are evaluated for magnesium spinel inclusion formation in relation to deoxidant used and the extent of deoxidation. The effect is demonstrated of reduced aluminum concentration during metal ladle treatment on nonmetallic inclusion composition and the possibility of modifying them in the course of an industrial pipe steel melt.
Formation of the microstructure and properties of pipe steel grade K60 (X70) are studied using physical modeling of thermomechanical processing in a DUO 300 laboratory mill and industrial experiment. ...Steel microstructure is investigated and temperature ranges for formation of various phases and structural components (ferrite, bainite, martensite, M/A-component) with accelerated cooling are determined. It is found that formation of martensitic regions and M/A-component as secondary structural constituents in a ferrite matrix instead of cementite-containing secondary structures facilitates an increase in steel strength and improvement of the σ
y
/σ
f
ratio without a significant reduction in cold resistance. The chemical composition of steel grade K60 (X70) is developed on the basis of laboratory and industrial experiments, as well as a new industrial process for producing rolled product for pipes for the Sila Sibiri gas pipeline sections crossing active tectonic disturbance zones. Sheet and pipes have a low σ
y
/σ
f
ratio, high values of relative and uniform elongation, impact strength and proportion of ductile component in a fracture after DWTT testing at – 20°C.
Adsorption by graphene sponge (GS) manufactured by annealing nickel-carbon powder mixture in inert atmosphere has been studied. By determining the specific surface area (SSA) for the GS sample, it ...has been found that Brunauer, Emmett, Teller method (BET) of approximation of experimental isotherms gives wrong results in the pressure range of 0.025–0.12 because adsorption in this pressure region is affected by walls of ampoule. Real SSA value has been found by subtracting pore effect method (SPE) or by BET approximation in a low range of relative pressure of 0.0004–0.002.
•Submitted laser bench for coatings, deposited on the inner surfaces of tubes by PLD.•Sprayed multilayered Ti/TiN coatings on the inner surfaces of tubes of small diameter.•We study this of coatings ...by method RBS and X-ray fluorescence spectroscopy (TXRF).•Shown a significant mixing of the layers thickness of 90μm.
The multilayer Ti/TiN/Ti coatings (consisting of nano-scale layers) on the inner surface of stainless steel tubes of small diameter were studied. The coatings were deposited by using the pulsed laser deposition (PLD) technique (in the reactive and non-reactive deposition modes). The coatings were analyzed using the X-ray fluorescence analysis with total external reflection (TXRF) and the Rutherford backscattering spectroscopy (RBS). It was found that the deposition of multilayer Ti/TiN/Ti coatings leads to the essential mixing of coating layers due to sputtering of coatings with fast atoms and ions from the laser plume and the evaporation of the coating under the laser radiation reflected from the target surface.
Effects of various factors such as the grain size, the morphology of nonmetallic inclusions, and joint microalloying with boron and titanium on the high-temperature ductility of pipe steels are ...studied. Physical modeling of the conditions of cooling of the skin of a continuous-cast preform in the zone of secondary cooling in a Gleeble facility is performed. Technical recommendations are given for raising the hot ductility of steels under industrial conditions.
A cheap, comparatively simple and effective method is proposed for the large quantity production of the sheets of graphenic carbon materials (GCM) by annealing the mixture of nickel powder with a ...suitable carbon amount at the temperatures close to 1000 ºC. The number of graphene layers in the sheets of GCM may be varied by altering the amount of carbon in the mixture and parameters of annealing and drying of the obtained products. Samples of GCM were prepared in the form of heat-dried GCM paper and in the form of graphene sponge with freeze-drying. The appearance of GCM on the surface of Ni particles was identified using a scanning electron microscope (SEM) at a low accelerating voltage of 5 kV. The thickness and properties of the layers were investigated by electron microscopy and X-ray diffraction. The fabrication processes were carried out at the concentrations of added carbon from 0 to 1 at%. The results obtained are fully consistent with the well-known solid phase reactions of carbon dissolution in Ni at 1000 °C and graphene or graphite precipitation on the surface with cooling down to the room temperatures.
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