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1

Wyspowy diagram fazowy dla nanokryształów

Tomaszewski Paweł E.

Wiadomości Chemiczne

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2022

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[Z] 76, 3-4

145--155

EN

The new form of the phase diagram is proposed for nanocrystals. This diagram shows the regions of the calcination temperature required to obtain the nanocrystals of given range of crystallite size. This explains why the temperature induced phase transitions are not possible in some crystals. However, the change of crystallite size can induce the phase transition.

2

The Monte Carlo Computer Experiment to Study the Order and Phase Transitions in the Mixed Phase Region Based on the Example of the 3D Ashkin-Teller Model

Wojtkowiak Z., Musiał G.

Computational Methods in Science and Technology

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2021

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Vol. 27, No. 3

129--136

EN

In this paper, we demonstrate a new way of performing Monte Carlo (MC) simulations in a mixed phase region that is difficult to study, where with certain probabilities there are different ordering ways. That results in a large oscillation of the values of the computed thermodynamic quantities, which makes their interpretation very problematic. Our results are presented on the example of the 3D Askin-Teller (AT) model, where within a certain range of parameters with equal probabilities there are two different, but equivalent, ways of ordering two of the three order parameters showing independent behavior. The use of our new approach in an MC computer experiment allowed us to use Binder cumulant as well as Challaand the Lee-Kosterlitz-like cumulants. This made it possible to locate phase transitions precisely enough to be able to use the energy distribution histogram method. According to the most effective strategy in the critical region we use our recently proposed cluster MC algorithm and the Metropolis algorithm beyond it, which are suitable for both the first-order and the continuous phase transitions in the 3D AT model. The new approach was demonstrated by determining smooth curves of magnetization and internal energy, and as a consequence by determining the location and character of the phase transition on the line between the mixed phase region and the paramagnetic phase.

3

Crystalline structures of Rb2UBr6 ionic conductor determined by neutron diffraction

Małetka Krzysztof, Ressouche Eric, Rundlof Hakan, Tellgren Rolland, Szczepaniak Włodzimierz, Zabłocka-Malicka Monika

Nukleonika

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2020

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Vol. 65, No. 1

3--11

EN

The neutron powder diffraction technique has been used for structural studies of Rb2UBr6 solid electrolyte as a function of temperature. The low-, room-, and high-temperature structures have been determined. At the temperature range of 4.2–80 K, the compound crystallizes in a monoclinic unit cell in the P21/c space group. At 80 K and 853 K, the compound crystallizes in a tetragonal unit cell in the P4/mnc space group. At 300 K, the lattice constants are a = b = 7.745(1) and c = 11.064(1) Å. At the temperature range of 853–960 K, a trigonal phase is observed in the P–3ml space group.

4

Properties of Pb1-xBax(Zr1-yTiy)1-zSnzO3 (x = 0.03, y = 0.02, z = 0÷0.08) Ceramics

Brzezińska D.

Archives of Metallurgy and Materials

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2020

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Vol. 65, iss. 2

975--982

EN

This paper presents the results of obtaining and investigations of Pb1-xBax(Zr1-yTiy)1-zSnzO33(PBZTS) ceramics with constant x = 0.03 and y = 0.02, and variable z = 0, 0.04, 0.06 and 0.08 (abbreviations of the samples were following PBZTS0, PBZTS4, PBZTS6, PBZTS8, respectively). The investigated compositions are close to rhombohedral-orthorhombic morphotropic phase boundary. The ceramic samples have been obtained by conventional ceramic technology from simple oxides PbO, ZrO2, TiO2, SnO2 and barium carbonate BaCO3. The ceramic powders, after calcination, have been pressed into discs and sintered using free sintering (FS) method. For samples obtained in such a way, the dielectric properties at various frequencies and electrical conductivity have been investigated. The increase of Sn content orders the microstructure of ceramics, and as a result the improvement of the dielectric properties of ceramic samples can be obtained.

5

Alternative, Direct Synthesis Method of the Ceramic Solid Solutions Based on BaTiO3 Through a High Energy Ball Milling

Bąk W., Dulian P., Garbarz-Glos B., Czekaj D., Lisińska-Czekaj A.

Archives of Metallurgy and Materials

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2020

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Vol. 65, iss. 2

805--810

EN

Polycrystalline samples BaTiO3 and the solid solutions Ba0.9 Sr0.1 TiO3, 0.9 Sr0.1 Ti0.9 Sn0.1 O3, Ba0.9 Sr0.1 Ti0.8 Sn0.2 O3 were obtained by means of a mechanochemical treatment based on the high-energy ball milling technique and next a high temperature solid state reaction method. The influence of synthesis condition on microstructural, dielectric and ferroelectric properties of obtained solid solutions were investigated. The structure and morphology of the investigated samples were characterized by an X-ray diffraction (XRD) and scanning electron microscopy (SEM). The characterization of electrical properties of the ceramics within the temperature range from –130°C to 250°C were performed by means of a dielectric spectroscopy method at the frequency ranging from 0.1 Hz to10 MHz. The diffusion of the paraelectric – ferroelectric phase transition and dielectric relaxation for ceramic samples are described.

6

Heat and Mass Transfer During Phase Transitions in Liquid Mixtures

Pavlenko Anatoliy, Koshlak Hanna

Rocznik Ochrona Środowiska

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2019

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Tom 21, cz. 1

234--249

EN

The work is devoted to the study of the transient processes of heat and mass transfer in the volume of a liquid. The method of calculating the temperature field in a liquid takes into account phase transitions, motion of the bubble wall and heat exchange processes near its surface. The method takes into account the change in the thermophysical characteristics of a liquid when its temperature changes. The results of the research can be used to optimize the various technological processes associated with cavitation, boiling and the formation of gas hydrates. Of particular interest are the processes of spontaneous boiling of superheated liquids under conditions when the liquid is in a non-equilibrium metastable state, since studying the kinetics of metastable state dysfunction can contribute to the creation of new high-intensity technologies for creating gas emulsions, as well as combustion and explosion technologies. The proposed method will allow a numerical analysis of the processes of destruction or the creation of gas hydrates, emulsions, taking into account both thermal and dynamic aspects of the problem.

PL

Praca poświęcona jest badaniu przejściowych procesów przenoszenia ciepła i masy w objętości cieczy. Metoda obliczania pola temperatury w cieczy uwzględnia przemiany fazowe, ruch ściany pęcherzykowej i procesy wymiany ciepła w pobliżu jej powierzchni. Metoda uwzględnia zmianę właściwości termofizycznych płynu w miarę zmian temperatury. Wyniki badań można wykorzystać do optymalizacji różnych procesów technologicznych związanych z kawitacją i tworzeniem się hydratów gazowych. Szczególnie interesujące są procesy samorzutnego wrzenia przegrzanych cieczy w warunkach, w których ciecz jest w stanie nierównowagi metastabilnej, ponieważ badanie kinetyki dysfunkcji stanu metastabilnego może przyczynić się do stworzenia nowych technologii tworzenia emulsji gazowych, jak również technologii spalania i wybuchu. Proponowana metoda pozwoli na analizę numeryczną procesów niszczenia lub tworzenia hydratów gazowych, emulsji, biorąc pod uwagę zarówno termiczne, jak i dynamiczne aspekty problemu.

7

Production of zinc oxide thin films and crystals in different deposition times and investigation of their structural, optical and electronic properties

Kangarlou Haleh, Esmaili Parisa

Materials Science Poland

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2019

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Vol. 37, No. 1

90--99

EN

An aqueous colloidal solution was prepared at 80 °C and pH = 9 from suitable chemical compounds to produce zinc oxide (ZnO) crystals and thin films. The ZnO crystals were grown in the colloidal solution under special conditions. Their micrographs showed ZnO rods with hexagonal structure. The number of the rods, increased over time. The ZnO thin films were produced on glass substrates in the same colloidal solution using the chemical bath deposition (CBD) method in different deposition times. The produced films were post-annealed for about one hour at 400 °C. Crystalline structure, phase transitions and nanostructure of the films were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). ZnO wurtzite structure was dominant, and by increasing the deposition time, the films became more crystalline. Nanostructure of the films changed from rod to wire and transformed into pyramid-like structures. Also, morphology of the films changed and re-nucleation ocurred. Optical reflectance was measured in the wavelength of 300 nm to 800 nm with a spectrophotometer. Other optical properties and optical band gaps were calculated using Kramers-Kronig relation on reflectivity curves. Second harmonic generation was calculated by Z-scan technique. Nonlinear refraction and real part of susceptibilities were obtained. Both positive and negative nonlinear refractions appeared in the ZnO films. It is important for the use in optoelectronic devices. Electronic properties were assessed by the full potential linearized augmented plane wave (FP-LAPW) method, within density functional theory (DFT). In this approach, the generalized gradient approximation (GGA) was used for the exchange-correlation potential calculation. The band gap structure and density of states were calculated.

8

Określenie spawalności stali i stopów tytanu na podstawie wykresów przemian fazowych

Jastrzębski Ryszard, Jastrzębski Adam, Denisewicz Grzegorz, Adamski Paweł

Dozór Techniczny

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2019

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z. 3

14--21

PL

W artykule w oparciu o schematy praktyczne, wykresy i tabele omówiono problemy z pękaniem stali i stopów tytanu. Na wykresie żelazo-węgiel naniesiono wykresy stopów tytanu, a w tabelach podano współrzędne punktów wykresu przemian fazowych dla stopów tytanu odpowiadajacym stalom konstrukcyjnym, ferrytycznym, austenitycznym i martenzytycznym. Porównano też wykresy chłodzenia stali konstrukcyjnych i stopów tytanu, a także ich wpływ na pękanie na zimno. Dla nowoczesnych stali niskowęglowych (<0,02%C) zaproponowano zastąpienie równoważnika węgla równoważnikiem niklu uzupełnionym o wodór.

9

Diffusive and Displacive Phase Transformations in Nanocomposites under High Pressure Torsion

Straumal B., Kilmametov A., Gornakova A., Mazilkin A., Baretzky B., Korneva A., Zięba P.

Archives of Metallurgy and Materials

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2019

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Vol. 64, iss. 2

457--465

EN

The high-pressure torsion (HPT) of Ti-Fe alloys with different iron content has been studied at 7 GPa, 5 anvil rotations and rotation speed of 1 rpm. The alloys have been annealed before HPT in such a way that they contained different amounts of α/α' and β phases. In turn, the β phase contained different concentration of iron. The 5 anvil rotations correspond to the HPT steady-state and to the dynamic equilibrium between formation and annihilation of microstructure defects. HPT leads to the transformation of initial α/α' and β-phases into mixture of α and high-pressure ω-phase. The α → ω and β → ω phase transformations are martensitic, and certain orientation relationships exist between α and ω as well as β and ω phases. However, the composition of ω-phase is the same in all samples after HPT and does not depend on the composition of β-phase (which is different in different initial samples). Therefore, the martensitic (diffusionless) transformations are combined with a certain HPT-driven mass-transfer. We observed also that the structure and properties of phases (namely, α-Ti and ω-Ti) in the Ti – 2.2 wt. % Fe and Ti – 4 wt. % Fe alloys after HPT are equifinal and do not depend on the structure and properties of initial α'-Ti and β-Ti before HPT.

10

Peculiarities of phase processes in the volume of liquid

Pavlenko A., Koshlak H. V.

Structure and Environment

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2018

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Vol. 10, no. 1

66--74

EN

The work is devoted to the study of the transient processes of heat and mass transfer in the volume of a liquid. The method of calculating the temperature field in a liquid takes into account phase transitions, motion of the bubble wall and heat exchange processes near its surface. The method takes into account the change in the thermophysical characteristics of a liquid when its temperature changes. The results of the research can be used to optimize the various technological processes associated with cavitation, boiling and the formation of gas hydrates.

PL

Artykuł dotyczy analizy nieustalonych zjawisk wymiany ciepła i masy w dużej objętości cieczy. Metoda określenia pola temperatur w cieczy uwzględnia przemiany fazowe, ruch pęcherzy i procesy wymiany ciepła przy ścianie. Metoda ta bierze pod uwagę zmianę właściwości termofizycznych cieczy, gdy zmienia się jej temperatura. Wyniki badań mogą być wykorzystane do optymalizacji różnych procesów technologicznych związanych z kawitacją, wrzeniem i tworzeniem hydratów gazowych.

11

Existence and uniqueness of a problem in thermo-elasto-plasticity with phase transitions in TRIP steels under mixed boundary conditions

Boettcher S.

Journal of Applied Analysis

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2018

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Vol. 24, nr 1

87--98

EN

In this paper a complex model describing thermo-elasto-plasticity, phase transitions (PT) and transformation-induced plasticity (TRIP) is studied. The main objective is the analysis of the corresponding initial and boundary value problem (IBVP) considering linearized thermo-elastic dissipation and a viscosity-like regularization.

12

DSC analysis of tvarogs depending on the fat content

Brożek O. M., Bohdziewicz K.

Aparatura Badawcza i Dydaktyczna

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2018

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T. 23, nr 2

83--90

EN

Differential Scanning Calorimetry (DSC) allows qualitative and quantitative determination of changes heats flow in a sample by physicochemical changes such as melting or oxidation as a function of time and temperature, during heating or cooling of the sample. The aim of the study was to determine the use of DSC in the evaluation of tvarogs. To the analysis were used 9 tvarogs with differed fat content (skimmed, half-fat and full-fat). The basic chemical composition of tvarogs was determined (FoodScanTMLab), and tvarogs were freeze-dried (Alpha LD plus), then their chemical composition was calculated on the grounds of dry matter concentration. A Differential Scanning Calorimeter (TA Instruments DSC Q10) with the closed cooling system (RCS) was used to determine the heat transfer rate. Two tests were conducted. The first one in ranges of temperature from -30 to 60°C and the second in ranges from -40 to 80°C. The graphical representations to illustrate the dependence of heat transfer in function of temperature of the analyzed tvarogs were obtained. The full-fat tvarogs were characterized by significant differences, as opposed to the skim and half-fat tvarogs. In the half-fat and full-fat tvarogs were occurred the peaks of phase change in the temperature range of 3.68 to 18.33°C. The most peaks was observed in full-fat tvarogs, where exothermic reactions were observed more often than in the other tvarogs. The protein content in the tvarogs was not influenced to the results of DSC analysis in the range of used temperature. Differential Scanning Calorimetry can be used to determine and compare the thermal properties of tvarogs with different fat content.

PL

Skaningowa kalorymetria różnicowa (DSC) pozwala na jakościowe oraz ilościowe określenie zmian przepływu ciepła w badanej próbce, które zachodzą w wyniku przemian fizykochemicznych np. topnienia czy utleniania, w funkcji czasu i temperatury, podczas ogrzewania lub chłodzenia tej próbki. Badania miały na celu określenie możliwości wykorzystania DSC w ocenie twarogu. Do analiz wybrano 9 twarogów, które różniły się między sobą zawartością tłuszczu (chude, półtłuste i tłuste). Dokonano oznaczenia podstawowego składu chemicznego (FoodScanTMLab), twarogi zliofilizowano (Alpha LD plus), a następnie na podstawie koncentracji suchej masy wyliczono ich skład chemiczny. Do określenia zależności przepływu ciepła od zmieniającej się temperatury próbki użyto skaningowego kalorymetru różnicowego (TA Instruments DSC Q10) z zamkniętym układem chłodzącym (RCS). Przeprowadzono dwie próby. Pierwszą w zakresie stosowanych temperatur od -30 do 60°C, a drugą od -40 do 80°C. Otrzymano wykresy zależności przepływu ciepła od temperatury analizowanych twarogów. Twarogi tłuste charakteryzowały się znacznymi różnicami uzyskanych wyników, w przeciwieństwie do twarogów chudych i półtłustych. W twarogach półtłustych i tłustych odnotowano piki przemian fazowych, które występowały w zakresie temperatur od 3,68 do 18,33°C. Najwięcej pików zaobserwowano w twarogach tłustych, gdzie wystąpiło także więcej reakcji egzotermicznych niż w pozostałych twarogach. Zawartość białka w badanych twarogach nie wpłynęła na wyniki analizy DSC w badanym zakresie temperatur. Metodę skaningowej kalorymetrii różnicowej można wykorzystać do porównania twarogów, ze względu na różną zawartość tłuszczu.

13

Phase transitions of ferruginous minerals in the course of thermal processing of feldspar-quartz raw materials from the Sobótka region (Lower Silesia)

Lewicka E.

Gospodarka Surowcami Mineralnymi

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2017

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T. 33, z. 1

93--110

EN

This paper presents the results of analyses of feldspar-quartz raw materials from deposits of leucogranites located in the Sobótka region. This is a successive stage of research carried out by the author on reasons for colour variation of ceramic materials obtained from them. This step encompassed the firing of sample pairs of analogous chemical composition in different conditions: in a standard cycle lasting more than 2 hours (at a maximum temperature of 1200°C), and a fast one – lasting around 50 minutes (at a max. temperature of 1260°C). The obtained ceramic bodies were analysed using the XRD method, scanning microscopy SEM-EDS and 57Fe Mössbauer spectroscopy at room temperature. The XRD investigations revealed the presence of quartz in both samples, while remnants of sodium feldspar were observed in the one fired in the fast cycle. The scanning microscopy confirmed that the principal component of the examined bodies is the aluminosilicate melt, resulting from the thermal decomposition of mainly feldspars and quartz. Single quartz grains and other minerals of high melting temperatures, i.e. zirconium, were also observed in the course of microscopic examinations. Products of other mineral phases’ transformations at high temperature, such as: titanomagnetite (spinel Fe-Ti), magnetite, biotite, xenotime, sphalerite as well as probably chlorites and garnets, were also relatively frequent. Mössbauer studies demonstrated the presence of three basic components constituting 30% (each) of the spectra, i.e. Fe2O3 (presumably hematite), Fe3+ ions (dispersed in aluminosilicate glassy phase), and nanocrystalline or amorphous oxide phase of iron (Fe-O). Some relatively small amounts (5 and 10%) of mixed valence iron cations (Fe2+/3+) that are not expected to influence the colour difference between samples after firing were also found. A paramagnetic doublet referring to them can be attributed to a titanomagnetite spinel or products of its thermal decomposition. The above-mentioned observations and examinations lead to the finding that the main reason for colour variation in the examined bodies as well as their different microstructure and advancement of phase transitions in the course of firing are different conditions of thermal treatment. These probably also influenced the forms in which iron and other colouring elements occur in the samples studied.

PL

Opracowanie przedstawia wyniki badań kopaliny skaleniowo-kwarcowej pochodzącej ze złóż leukogranitów z rejonu Sobótki. Jest to kolejny etap prowadzonych przez autorkę badań nad wpływem składu chemicznego i mineralnego tych utworów na barwę uzyskanych z nich tworzyw ceramicznych. Obejmował on wypalanie par próbek o analogicznym składzie chemicznym w odmiennych warunkach: w cyklu standardowym, trwającym ponad 2 godziny (w maksymalnej temperaturze 1200°C), oraz szybkim, około 50-minutowym (w maks. 1260°C). Uzyskane tworzywa zostały poddane analizie rentgenowskiej, a także badaniom metodą mikroskopii skaningowej SEM-EDS i spektroskopii mössbauerowskiej w temperaturze pokojowej. Analiza rentgenowska ujawniła obecność kwarcu w obu próbkach, a w przypadku pastylki wypalonej w krótkim cyklu – również reliktów skalenia sodowego. Badania skaningowe potwierdziły, że podstawowym składnikiem badanych tworzyw jest stop glinokrzemianowy, który powstał w wyniku termicznego rozkładu głównie skaleni i częściowo kwarcu. W toku obserwacji stwierdzono obecność pojedynczych ziaren kwarcu oraz innych minerałów cechujących się wysoką temperaturą topienia, takich jak cyrkon. Stosunkowo często obserwowano także produkty przeobrażenia pod wpływem wysokiej temperatury innych faz mineralnych, takich jak: tytanomagnetyt (spinel Fe-Ti), biotyt, ksenotym, sfaleryt oraz przypuszczalnie chloryty i granaty. Badania mössbauerowskie wykazały obecność w tworzywie trzech równorzędnych składowych o względnych zawartościach rzędu 30% każda: Fe2O3 (przypuszczalnie hematyt), kationów Fe3+ (rozproszonych w stopie glinokrzemianowym) oraz słabo krystalicznej względnie amorficznej fazy tlenkowej żelaza (Fe-O). Stwierdzono również występowanie podrzędnej ilości kationów żelaza o mieszanej walencyjności (Fe2+/3+), których względny udział w obu próbkach jest niewielki (10 i 5%) i – jak się przypuszcza – nie może przesądzać o zróżnicowaniu ich zabarwienia. Odpowiadający im dublet paramagnetyczny ma przypuszczalnie związek z obecnością tytanomagnetytu lub produktów jego rozkładu termicznego. Powyższe obserwacje i uzyskane wyniki badań skłaniają do stwierdzenia, że główną przyczyną zróżnicowania barwy próbek są odmienne warunki ich obróbki termicznej, w wyniku czego uzyskano tworzywa różniące się stopniem spieczenia oraz zaawansowania przemian fazowych , co zapewne rzutowało na formę związania żelaza i innych pierwiastków barwiących.

14

Temperature-dependent Shock Initiation of CL-20-based High Explosives

Pi Z., Chen L., Wu J.

Central European Journal of Energetic Materials

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2017

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Vol. 14, no. 2

361--374

EN

To investigate the effects of temperature on the shock initiation characteristics of hexanitrohexaazaisowurtzitane (CL-20), shock initiation experiments on heated C-1 explosive (94% epsilon phase CL-20, and 6% binder, by weight) were performed at temperatures of 20 °C, 48 °C, 75 °C, 95 °C, 125 °C, 142 °C, and 175 °C. An explosive driven flyer device was used to initiate the C-1 charges and manganin pressure gauges were embedded in the C-1 specimen to record the pressure changes with time. Our results show that C-1 becomes more sensitive as the temperature is increased from 20 °C to 95 °C. The ε to γ phase transition in CL-20 occurs at 125 °C; C-1 with CL-20 in the γ phase at 142 °C is less shock sensitive than C-1 with CL-20 in the ε phase at 95 °C or 75 °C. Compared with C-1 at 142 °C, C-1 at 175 °C shows a dramatic increase in shock sensitivity. An ignition and growth reactive flow model was used to simulate the shock initiation of C-1 at various temperatures, and the parameters were obtained by fitting the experimental data. With this parameter set, the shock initiation characteristics of C-1 for temperatures between 20 °C and 175 °C can be derived.

15

Budowa i funkcje układów białkowo-lipidowych

Litwińczuk-Mammadova A., Cieślik-Boczula K., Rospenk M.

Wiadomości Chemiczne

|

2016

|

[Z] 70, 11-12

723--746

EN

Biomembranes play many structural and functional roles in both prokaryotic and eukaryotic cells [10]. They define compartments, the communication between the inside and outside of the cell. The main components of biomembranes are lipids and proteins, which form protein-lipid bilayer systems [10]. A structure and physicochemical properties of protein-lipid membranes, which determines biological activities of biomembranes, are strongly dependent on interactions between lipid and protein components and external agents such as a temperature, pH, and a membrane hydration [4]. A lipid bilayer matrix serves as a perfect environment for membrane proteins (Fig. 1), and it assures activities of these proteins. Because biomembranes are composed of many different groups of lipids and proteins and have a complex structure, it is difficult to study in details their physicochemical properties using physicochemical methods. For these reason, lipid membranes of liposomes are used in many scientific laboratories for studding processes associated with a lipid phase transition, a membrane hydration, or protein-membrane interactions. The structure of liposomes (Fig. 5), and an influence of pH and an ionic strength on a lipid bilayer structure are discussed in the presented work. The role of membrane proteins in determination of biological activities of biomembranes is highlighted. A high variety of a structure and an enzymatic activity of membrane proteins is responsible for a high diversity of biological functions of cell membranes [2]. α-Lactalbumin (α-LA) is a peripheral membrane protein (Figs 8 and 9), its biological function is strongly related to its conformational structure and interaction with lipid membranes [49]. The complex of α-LA in a molten globule conformational state with oleic acid, termed as a HAMLET complex, are disused in a context of its anti-tumor activity.

16

The determinants of the dynamics of business processes

Lewicki A., Czyżewska M.

Organizacja i Zarządzanie : kwartalnik naukowy

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2016

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nr 3

75--84

EN

The article presents the properties of the market system consisting of economic entities subjected to processes determined by the natural behavior of the nonlinear dissipative system. The rules of chaos govern this system, but they are associated with the system’s goal to reach an equilibrium. It is done using the mechanism of emergence, phase transition, and nomicity rules. This is often accomplished at the cost of unpredictable and undefined fluctuations that even in the case of a single object may affect the balance, or even cause a crisis of the entire system. However, we can prevent this by fulfilling certain conditions and by assuming the appropriate model of bottom-up management.

PL

W artykule przedstawiono własności systemu rynkowego, złożonego z podmiotów gospodarczych, podlegających procesom determinowanym przez naturalne zachowania dyssypatywnego układu nieliniowego. W układzie tym rządzą prawa chaosu, ale są one związane z dążeniem przez układ do osiągnięcia stanu równowagi. Odbywa się to z wykorzystaniem mechanizmu emergencji, przejść fazowych i praw nomiczności. Jest to realizowane bardzo często jednak również kosztem nieprzewidywalnych i nieokreślonych fluktuacji, które nawet w przypadku pojedynczego obiektu mogą wpływać na zachwianie równowagi, a nawet kryzys całego systemu. Możemy jednak temu zapobiegać, spełniając pewne uwarunkowania i przyjmując właściwy model zarządzania oddolnego.

17

Effect of Semiconductor Element Substitution on the Electric Properties of Barium Titanate Ceramics

Garbarz-Glos B., Lisińska-Czekaj A., Czekaj D., Bąk W.

Archives of Metallurgy and Materials

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2016

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Vol. 61, iss. 2A

887--890

EN

The investigated ceramics were prepared by a solid-state reaction from simple oxides and carbonates with the use of a mixed oxide method (MOM). The morphology of BaTi0.96Si0.04O3 (BTSi04) ceramics was characterised by means of a scanning electron microscopy (SEM). It was found that Si+4 ion substitution supported the grain growth process in BT-based ceramics. The EDS results confirmed the high purity and expected quantitative composition of the synthesized material. The dielectric properties of the ceramics were also determined within the temperature range (ΔT=130-500K). It was found that the substitution of Si+4 ions had a significant influence on temperature behavior of the real (ε’) and imaginary (ε”) parts of electric permittivity as well as the temperature dependence of a.c. conductivity. Temperature regions of PTCR effect (positive temperature coefficient of resistivity) were determined for BTSi04 ceramics in the vicinity of structural phase transitions typical for barium titanate. No distinct maximum indicating a low-temperature structural transition to a rhombohedral phase in BTSi04 was found. The activation energy of conductivity was determined from the Arrhenius plots. It was found that substitution of Si ions in amount of 4wt.% caused almost 50% decrease in an activation energy value.

18

Analysis of the Phase Transitions in BNT-BT Lead-Free Ceramics Around Morphotropic Phase Boundary by Mechanical and Dielectric Spectroscopies

Silva Jr P. S., Diaz J. C. C. A., Florêncio O., Venet M., M’Peko J. C.

Archives of Metallurgy and Materials

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2016

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Vol. 61, iss. 1

17--20

EN

In this work, the syntheses and characterization by mechanical and dielectric spectroscopies of (1-x) Bi0.5Na0.5TiO3-xBaTiO3 (BNT-100xBT), with x = 0.05, 0.06 and 0.07, lead-free piezoelectric ceramics is reported. Ceramic samples of BNT-BT have been prepared by mixed-oxide method and then conventionally sintered. X-ray diffraction patterns of sintered samples, indicated for BNT-7BT the presence of tetragonal (P4mm) complex perovskite structure, whereas for BNT-5BT and BNT-6BT the samples exhibit a mixture of tetragonal (P4mm) and rhombohedral (R3c) crystalline phases, which reveal the presence of a morphotropic phase boundary (MPB) in the BNT-BT system. Measurements of internal friction, Q-1, and the storage modulus, E’, as a function of temperature at various frequencies were carried out in a Dynamic Mechanical Analyzer (DMA), in the temperature range from 0ºC to 600ºC. Dielectric profiles are recorded in the frequency range from 1kHz to 100kHz and the temperature range from room temperature to 475ºC. Mechanical loss spectra obtained for investigated compositions of BNT-BT samples showed different frequency-independent anomalies. Two main anomalies for BNT-5BT and BNT-6BT, observed around 100ºC and 430ºC were associated with the ferroelectric-antiferroelectric and antiferroelectricparaelectric phase transitions, respectively. The results obtained from mechanical loss measurements were supported by dielectric relaxation spectra. For BNT-7BT, outside the MPB, four different frequency-independent processes were observed.

19

Zaawansowana analiza termiczna poli(3-hydroksymaślanu)

Czerniecka-Kubicka A., Zarzyka I., Pyda M.

Przemysł Chemiczny

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2015

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T. 94, nr 11

1919-1923

PL

Przedstawiono zaawansowaną analizę termiczną poli(3-hydroksymaślanu) (PHB) przeprowadzoną na podstawie molekularnej interpretacji zmian ciepła właściwego oraz ilościowy opis przejść fazowych zachodzących w PHB podczas zmian temperatury lub czasu. Taka analiza pozwoliła na rozdzielenie pozornego ciepła właściwego, otrzymywanego za pomocą pomiarów różnicowej kalorymetrii skaningowej, na termodynamiczne ciepło właściwe i ciepło przejść fazowych. Jest to szczególnie ważne przy charakterystyce przejść fazowych, takich jak np. krystalizacja, tzw. „zimna krystalizacja”, topnienie lub przejście szkliste. Zaawansowana analiza umożliwiła dokładniejsze wyznaczenie stopnia krystaliczności w funkcji temperatury oraz parametrów przejść fazowych PHB.

EN

The heat capacity of semicryst. poly(3-hydroxybutyrate) was detd. by differential scanning calorimetry at 233–463 K. Three phase transitions (crystn., glass transition and melting) of the polymer were obsd.

20

Positron annihilation in liquid crystals

Dryzek E., Juszyńska-Gałązka E.

Nukleonika

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2015

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Vol. 60, No. 4, part 1

703--708

EN

Positron annihilation studies of liquid crystals are reviewed with particular reference to thermotropic liquid crystals with rod-like molecules. The studies of compounds exhibiting smectic A or smectic E phases indicate that local arrangement of dipole molecules play an important role because high electron density at the end group of molecules can influence substantially formation and annihilation of positronium. The obtained ortho-positronium lifetimes in these phases can be explained by antiparallel pairing of molecules in case of the smectic A phase or a structure with a nanosegregation of alkyl chains and others parts of molecules into sublayers and liquid-like state of alkyl chains in case of the smectic E phase.