Textured ferroelectric ceramics with high electromechanical coupling factors over a broad temperature range

The figure-of-merits of ferroelectrics for transducer applications are their electromechanical coupling factor and the operable temperature range. Relaxor-PbTiO3 ferroelectric crystals show a much improved electromechanical coupling factor k33 (88~93%) compared to their ceramic counterparts (65~78%) by taking advantage of the strong anisotropy of crystals. However, only a few relaxor-PbTiO3 systems, for example Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3, can be grown into single crystals, whose operable temperature range is limited by their rhombohedral-tetragonal phase transition temperatures (Trt: 60~120 °C). Here, we develop a templated grain-growth approach to fabricate <001>-textured Pb(In1/2Nb1/2)O3-Pb(Sc1/2Nb1/2)O3-PbTiO3 (PIN-PSN-PT) ceramics that contain a large amount of the refractory component Sc2O3, which has the ability to increase the Trt of the system. The high k33 of 85~89% and the greatly increased Trt of 160~200 °C are simultaneously achieved in the textured PIN-PSN-PT ceramics. The above merits will make textured PIN-PSN-PT ceramics an alternative to single crystals, benefiting the development of numerous advanced piezoelectric devices.

Electrochemical synthesis of nanostructured super-alloys with valuable electrochemical, electrocatalytic and corrosion properties

A study of the electrochemical formation of functional coatings by binary and ternary alloys M1M2, M1M3, M1M2M3 (where M1 is 3d6-8 metal of the iron subgroup: Fe, Co, Ni, and M2 is Mo, W; M3 is Re), from complex aqueous solutions and ionic melts. Such alloys are called "superalloys" due to a wide range of valuable physicochemical (corrosive, electrocatalytic) and functional properties and are designed to operate in extreme temperature and power modes with simultaneous exposure to an aggressive environment. The presence of rhenium in the alloy also simultaneously increases its strength and ductility (the so-called "rhenium effect"). A fundamentally new electrolyte (highly concentrated ammonia-acetate) has been developed for the formation of molybdenum alloys (NiMo, CoMo, FeMo) with a maximum content of a refractory component (about 85 at.%), such as those that exhibit a high electrocatalytic effect in the hydrogen evolution reaction (HER). The deposition of binary CoRe and ternary CoWRe alloys from a citrate electrolyte was carried out. The influence of the composition of solutions and electrolysis parameters on the chemical and phase composition, structure and properties of coatings has been established. The parameters of pulse electrolysis for obtaining multilayer CoMo and CoW coatings from carbamide melts containing cobalt and molybdenum / tungsten oxides have been determined.

Effect of Electrodeposition Parameters on the Composition and Surface Topography of Nanostructured Coatings by Tungsten with Iron and Cobalt

The electrodeposition of binary and ternary coatings Fe-W and Fe-Co-W from mono ligand citrate electrolyte has been investigated. The Fe-Co-W coatings were formed from electrolytes, which composition differs in the ratio of the concentrations of the alloying components and the ligand content. The investigation results indicate a competitive reduction of iron, cobalt and tungsten, the nature of which depends both on the ratio of electrolyte components, and electrolysis parameters. The effect of both current density amplitude and pulse on off time on quality, composition and surface morphology of the galvanic alloys was determined. Coatings deposited on a direct current with a density of more than 6.5 A/dm2, crack and peel off from the substrate due to the inclusion of Fe (III) compounds containing hydroxide anions. The use of non-stationary electrolysis allows us to extend the working range of current density to 8.0 A/dm2 and form electrolytic coatings of sufficient quality with significant current efficiency and the content of the refractory component. The presence of the Co7W6, Fe7W6, α-Fe, and Fe3C phases detected in the Fe-Co-W deposits reflects the competition between the alloying metals reducing from hetero-nuclear complexes. The surface of binary and ternary coatings is characterized by the presence of spherical agglomerates and is more developed in comparison with steel substrate. The parameters Ra and Rq for electrolytic alloy Fe-W are of 0.1, for Fe-Co-W are 0.3, which exceeds the performance of a polished steel substrate (Ra = 0.007 and Rq = 0.010). These properties prospect such alloys as a multifunctional layer are associated with structural features, surface morphology, and phase composition.

USE OF SURFACING MATERIALS MODIFIED WITH REFRACTORY COMPONENTS FOR REDUCTION OF ROLLERS IN BLANK CONTINUOUS CASTING MACHINES

At metallurgical enterprises the worn out rollers of BCCM are reduced by means of a surfacing technology. In most cases the rollers of BCCM are made of heat-resistant steel of 20H13 and 25H1M1F grades and others and their reduction is carried out by surfacing with the use of powder wire, for instance PP-Np-25H5FMS. Life increase of the reduced rollers of BCCM twice as many and more is an urgent problem requiring the use of more wear-resistant materials. The paper reports the results of X-ray structural, phase, structural, tribological, thermocyclic investigations directed to the analysis of the possibility in use of ASM 4603-SA filler modified with 3% of refractory components of tungsten carbide (TC) and 0.2% hexagonal boron nitride (BN) for roller reduction of blank continuous casting machines. It is defined that ASM 4603-SA powder wire application with the refractory component addition is promising for roller surfacing reduction in BCCM. As a result of mentioned material electro arc surfacing on the roller surface of BCCM there is formed a wear-resistant layer with hardness up to 57 HRC resistant to a crack formation and burn back grid as a result of cyclic hightemperature impacts characterized with the decreased friction coefficient in comparison with the layer surfaced with the basic material.

Diffusion Rates of Components in Metal-Silicides Depending on Atomic Number of Refractory Metal Component

Interdiffusion studies conducted in group IVB, VB and VIB metal-silicon systems are discussed in detail to show a pattern in the change of diffusion coefficients with the change in atomic number of the refractory metal (M) component. MSi2and M5Si3phases are considered for these discussions. It is shown that integrated diffusion coefficients increase with the increase in atomic number of the refractory component when the data are plotted with respect to the melting point normalized annealing temperature. This indicates the increase in overall defect concentration facilitating the diffusion of components. This is found to be true in both the phases. Additionally, the estimated ratios of tracer diffusion coefficients indicate the change in concentration of antisite defects in certain manner with the change in atomic number of the refractory components.

Development of emulgel technology with saw palmetto extracts and of japanese sophora tincture for androgenetic alopecia treatment

Androgenic alopecia is a hair disease caused by an excessive influence of androgens on hair follicles, whose treatment requires long-term use of systemic and / or local action drugs. In Ukrainian pharmaceutical market for the androgenic alopecia treatment synthetic drug minoxidil is presented, which in the local long-term application causes many side effects. Therefore, the drugs development of plant origin is important. Taking into account of the androgenic alopecia pathogenesis, it was developed the emulgel composition and technology, which has Saw Palmetto extract and Sophora Japonica tincture as active ingredients. Their main biological active substances applying topically provide anti-androgenic, venotonic and follicles protective action. The qualities of dermatological remedies in large measure are influenced by their technological process. Therefore, the purpose of this investigation was the development of a rational emulgel technology with Saw Palmetto extract and Sophora Japonica tincture for the androgenic alopecia prevention and treatment. Samples of emulgel were manufactured with applying of different technological methods, namely: the method of emulsification, temperature, rate and duration of stirring. Prepared samples were controlled by uniformity, dispersion degree (with microscope Delta Optical Genetic Pro, Poland), pH (with pH-meter 150 MI, Russia) and structure viscosity (with rotational viscometer Brookfield VR-3000, Myr VISKOTECH, Spain). The optimal temperature for the emulgel preparation is 60 °C, since the melting temperature of cetyl alcohol (the most refractory component of the formulation) is 52 °C. When choosing the emulsifying method it was found that sequential addition of hydrophilic and oil phases to emulgators provided the highest dispersion and optimally rheological properties of the emulgel. The best homogenization speed, providing a high degree of dispersion and structural viscosity in the range 3 200–3 400 mPas, is 2 000 rev/min. The intensive size reduction of the dispersed phase was observed for 30 min stirring. As a result of investigation, it was established that the best method of emulsification was the sequential adding of oil and aqueous phase to the mixture of emulsifiers at the temperature – 60 °C, the speed – 2 000 rev/min for 30 min.