Study of the phase transition in polycrystalline (Ba_{0.90}Pb_{0.10})(Ti_{0.90}Sn_{0.10})O_3

Polycrystalline sample of (Ba_{0.90}Pb_{0.10})(Ti_{0.90}Sn_{0.10})O_3 was obtained by means of a conventional ceramic technology. The dielectric measurements were performed depending on temperature and frequency of electric measuring field. The character of the phase transitions of (Ba_{0.90}Pb_{0.10})(Ti_{0.90}Sn_{0.10})O_3 ceramics strongly depends on the presence of Pb in the sample. The obtained results pointed out the diffused character of phase transition. The temperature dependence of the dielectric properties showed that the phase transition from the paraelectric phase to ferroelectric one takes place at the same temperature (T_{m}=367 K). It does not depend on the frequency of the measuring electric field. A change of the value of the parameter \gamma takes place in the paraelectric phase.Comment: 5 pages, 6 figure

Mathematical modeling of phenomena of dynamic recrystallization during hot plastic deformation in high-carbon bainitic steel

Based on the research results, coefficients were determined in constitutive equations, describing the kinetics of dynamic recrystallization in high-carbon bainitic steel during hot deformation. The developed mathematical model takes into account the dependence of changing kinetics in the size evolution of the initial austenite grains, the value of strain, strain rate, temperature and time. Physical simulations were carried out on rectangular specimens measuring 10 × 15 × 20 mm. Compression tests with a plane state of deformation were carried out using a Gleeble 3800

Investigation of dielectric properties of LixNa₁₋xNbO₃ ceramics for x = 1 and x=4

The a.c. electrical response of LixNa₁₋xNbO₃ (LNN) solid solution in low frequency range (100 Hz–20 kHz) has been analysed as a function of temperature (300 K–750 K). A complex picture of the dependence of the studied properties on the chemical composition has been obtained. The data indicate the presence of relaxation and transport processes as well as their thermally activated character.Досліджено електричний відгук в змінному полі твердих розчинів LixNa₁₋xNbO₃ (LNN) як функцію температури (300 K–750 K) в низькочастотній області (100 Hz–20 kHz). Отримано комплексну картину залежності досліджених величин від хімічного складу. Отримані дані свідчать про наявність релаксаційних і транспортних процесів та про тепловий характер їх активації

Study of Physical Properties of Ba(Ti 1−2x Fe x Nb x )O 3 Ceramics

Ba(T

On Effective Potential in Tortoise Coordinate

In this paper, we study the field dynamics in Tortoise coordinate where the equation of motion of a scalar can be written as Schrodinger-like form. We obtain a general form for effective potential by finding the Schrodinger equation for scalar and spinor fields and study its global behavior in some black hole backgrounds in three dimension such as BTZ black holes, new type black holes and black holes with no horizon. Especially, we study the asymptotic behavior of potential at infinity, horizons and origin and find that its asymptotic in BTZ and new type solution is completely different from that of vanishing horizon solution. In fact, potential for vanishing horizon goes to a fixed quantity at infinity, while in BTZ and new type black hole we have an infinite barrier.Comment: 18 pages, 9 figure

Temperature changes of Seebeck coefficient of SbSJ modified

The temperature dependency of Seebeck coefficient has been measured for a needle-shaped crystal of SbSJ:0.1%Cl. The measurements have been made in the temperature range from 190 K to 370 K. The obtained results made it possible to determine the type and the mechanisms of electric conduction.В роботі наведено результати вимірювань коефіцієнта Зеебека для кристалу SbSJ:0.1%Cl голкоподібної форми в діапазоні температур від 190 K до 370 K. Отримані результати дають можливість визначити тип і механізм електричної провідності в цьому кристалі

Prospects for progress in the manufacturing technologies and applications of ultra-strength nanobainitic steel products

Opisano i zilustrowano wynikami badań, morfologiczne cechy struktury i charakterystyki mechaniczne grupy gatunkowej stali nanobainitycznych, do której należą nanostrukturalne stale dwufazowe bainityczno-austenityczne i trójfazowe bainityczno-austenityczno-martenzytyczne. Przedstawiono wyniki badań wpływu procesów zachodzących w badanych stalach w trakcie wytwarzania, takich jak segregacja międzydendrytyczna pierwiastków stopowych powstająca w wyniku krzepnięcia, odwęglenie w wyniku wysokotemperaturowych obróbek cieplnych, skłonność do pękania w trakcie chłodzenia z zakresu trwałości austenitu - na strukturę i właściwości półwyrobów i wyrobów. Zaproponowano metody zmniejszenia niepożądanych skutków wymienionych procesów. Na podstawie dostępnych źródeł informacji przedstawiono aktualny stan komercjalizacji gatunków stali nanobainitycznych w świecie oraz działania Instytutu Metalurgii Żelaza mające na celu wdrożenie wyników zrealizowanych projektów dotyczących tej nowej klasy stali konstrukcyjnych, na tle konkurencji z obecnie stosowanymi gatunkami ultrawytrzymałymi, głównie ze stalami stopowymi ulepszanymi cieplnie.Morphological features of microstructure and mechanical characteristics of nanobainitic steel grades, comprising dual phase bainite-austenite and triple phase bainite-austenite-martensite nanostructured steels, were described and exemplified by research outputs. Results of investigation of the influence of processes occurring in the investigated steels during manufacturing - such as interdendritic segregation of alloying elements arising as the effect of solidification, decarburisation caused by high temperature heat treatments, propensity to cracking due to cooling from the austenite temperature range - on microstructure and properties of the semi-products and products were presented. Methods for reducing the adverse infl uence of the mentioned processes were proposed. Based on available information the current status of commercialisation of nanobainitic steels in the world and activities of Instytut Metalurgii Żelaza aimed at application of the results of the accomplished projects concerning this new structural steels were presented, taking into account the competition with the ultra-strength steel grades currently used, mainly with the quenched and tempered grades