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EN
A thermodynamic lattice theory has been developed for determination of the melting curves and eutectic points of binary alloys. Analytical expressions for the melting curves of binary alloys composed of constituent elements with the same structure have been derived from expressions for the ratio of root mean square fluctuation in atomic positions on the equilibrium lattice positions and the nearest neighbor distance. This melting curve provides information on Lindemann’s melting temperatures of binary alloys with respect to any proportion of constituent elements, as well as on their eutectic points. The theory has been applied to fcc and bcc structure. Numerical results for some binary alloys provide a good correspondence between the calculated and experimental phase diagrams, where the calculated results for Cu1−x Nix agree well with the measured ones, and those for the other alloys are found to be in a reasonable agreement with experiment.
EN
The Co1–xFex alloys where x ranges from 0.01 to 0.06 were measured at room temperature using transmission Mössbauer spectroscopy (TMS). The analysis of the obtained data allowed the determination of the short-range order (SRO), the binding energy Eb between two iron atoms in the studied materials using the extended Hrynkiewicz-Królas idea and the enthalpy of solution HCo-Fe of Fe in Co. The results showed that the Fe atoms dissolved in a Co matrix interact repulsively and the estimated value of HCo-Fe = –0.166(33) eV/atom. Finally, values of the enthalpy of solution were used to predict the enthalpy of mixing for the Co-Fe system. These findings were compared with corresponding data given in the literature, which were derived from calorimetric experiments and from the cellular atomic model of alloys described by Miedema.
EN
In this work we used the first ab initio calculations to study the stability of the binary alloys BN, BP and BAs and their behavior in the different phases of zinc-blende, Nacl and CsCl. The full potential linearized augmented plane wave method was employed within density functional theory. Our results show the difference in the calculated structural properties and the band structure is obtained for the zinc-blende structure. We have investigated the lattice parameters and band gap energies. We also give the valence charge density at a high pressure and the analysis of the density of states.
EN
The room temperature Mössbauer spectra of ⁵⁷Fe were measured for Fe_{1-x}Au_x with the gold concentration ranging from 1 at.% till 4.8 at.%. They were analysed in terms of hyperfine parameters of their components related to unlike surroundings of the iron probes, determined by different numbers of gold atoms existing in the neighbourhood of iron atoms. Basing on the intensities of the spectrum components we determined binding energy E_b between two gold atoms in the studied materials. The latter was done for properly annealed samples using the extended Hrynkiewicz-Królas idea. It was found that the binding energy is positive or Au atoms interact repulsively. The extrapolated value of E_b for x =0 was used for computation of an enthalpy of solution of Au in Fe. Finally the obtained value of the enthalpy was used to predict the mixing enthalpy for the Fe-Au solid solutions. The results were compared with both the corresponding values resulting from the cellular atomic model of alloys by Miedema and those derived from experimental calorimetric data given in the literature.
EN
The solution of the inverse problem involving the designation of the boundary condition in the problem of the binary alloy solidification for known temperature measurements at a selected point of the cast is presented. In the discussed model, the temperature distribution is described by means of the Stefan problem with varying in time temperature corresponding to the beginning of solidification and depending on the concentration of the alloy component. Whereas to describe the concentration, the Scheil model was used.
PL
W pracy przedstawiono rozwiązanie zagadnienia odwrotnego polegającego na określeniu warunku brzegowego w zagadnieniu krzepnięcia stopu dwuskładnikowego, gdy znane są pomiary temperatury w wybranym punkcie odlewu. W rozważanym modelu rozkład temperatury opisany został zagadnieniem Stefana ze zmienną w czasie temperaturą odpowiadającą początkowi procesu krzepnięcia, zależną od stężenia składnika stopowego. Do opisu stężenia wykorzystano model Scheila.
EN
In the paper mathematical and numerical model of binary alloy solidification process is proposed. The metal alloy is viewed as mixture of basic component and solute. The approach basing on moving, sharp phase interface between liquid and solid region isintroduced. Constitutional undercooling phenomenon is taken into consideration.
7
Content available remote Phase transitions in binary alloys: nanoparticles and nanowires
63%
EN
The phase diagram of nanosystems is known to be a function of their size and shape. The variation with temperature depends on the surface tensions involved in the phase transitions. When looking at the nucleation process in nanoparticles, it turns out that it is necessary to take into account the fact that the reservoir of matter is limited. In a nanosystem, the total amount of one of the chemical components may be too small for the synthesis of the critical nucleus. This gives rise to three possibilities: phase separation, prohibition of decomposition, formation of metastable phases. A new effects arise for phase transformations in binary and multicomponent nanosize systems with change of composition – finite depletion effect. It is shown theoretically that the usual concept of phase diagram has to be re-formulated when dealing with multicomponent nanosystems. The liquidus and solidus lines are shifted due to size effects. Moreover, it turns out that it is required to differentiate the solidus and liquidus curves and equilibrium curves after the first order phase transition. In this work, we study how the phase transitions of binary nanoalloys are treated in the case of nanoparticles and nanowires.
PL
Wykres fazowy nanoukładów zależy od wielkości i kształtu cząstek. Temperaturowe zmiany zależą od napięć powierzchniowych faz wystepujących podczas przejść fazowych. Rozpatrując proces zarodkowania w układach z nanocząstkami musimy uwzględnić fakt, że zasób materii w otoczeniu jest ograniczony. W nanoukładzie, całkowita ilość jednego ze składników może być zbyt mała dla syntezy krytycznego zarodka. To prowadzi do trzech mozliwości: separacji faz, uniemożliwienia rozpadu lub formowania faz metastabilnych. Pojawiają się nowe efekty związane ze zmianą składu podczas transformacji fazowych w podwójnych lub wieloskładnikowych układach w skali nano – efekt krańcowego wyczerpania. Teoretycznie wykazano, że powszechna koncepcja układu fazowego powinna być sformułowana na nowo przy rozpatrywaniu wieloskładnikowych nanosystemów. Linie likwidusu i solidusu ulegają przesunięciu związanemu z efektem wymiarowym. Poza tym, należy rozrózniać linie likwidusu i solidusu i krzywe równowagowe po transformacji fazowej pierwszego rzedu. W tej pracy, pokazano jak należy rozpatrywać transormacje fazowe podwójnych nanostopów w przypadku nanocząstek i nanodrutów.
EN
The paper presents the possibility of application of the developed computer script which allows the assessment of non-equilibrium solidification of binary alloys in the ThermoCalc program. The script makes use of databases and calculation procedures of the POLY-3 module. A solidification model including diffusion in the solid state, developed by Wołczyński, is used to describe the non-equilibrium solidification. The model takes into account the influence of the degree of solute segregation on the solidification process by applying the so-called back-diffusion parameter. The core of the script is the iteration procedure with implemented model equation. The possibility of application of the presented calculation method is illustrated on the example of the Cr-30% Ni alloy. Computer simulations carried out with use of the developed script allow to determine the influence of the back-diffusion parameter on the course of solidification curves, solidus temperature, phase composition of the alloy and the fraction of each phase after the solidification completion, the profile of solute concentration in liquid during solidification process, the average solute concentration in solid phase at the eutectic temperature and many other quantities which are usually calculated in the ThermoCalc program.
PL
W pracy przedstawiono teoretyczne podstawy oraz weryfikację eksperymentalną nowatorskiej metody określania stężenia i ruchliwości dominujących defektów punktowych w tlenkach i siarczkach metali przejściowych. Istota proponowanej metody sprowadza się do badania struktury defektów i własności transportowych tlenków i siarczków metali na drodze pośredniej, tj. badając wpływ różnowartościowych domieszek na kinetykę powstawania tych związków. Wykazano, że analiza wyników utleniania odpowiednio dobranych stopów dwuskładnikowych pozwala na wyznaczenie entalpii i entropii powstawania i migracji defektów. W oparciu o te dane istnieje możliwość obliczenia stężenie defektów oraz ich ruchliwość w czystych, tzn. niedomieszkowanych materiałach tlenkowych, co przedstawiono na przykładzie niestechiometrycznego tlenku niklu, Ni1-yO.
EN
The theoretical basis and experimental verification of novel method, enabling the calculation of point defect concentration and their mobility in transition metal oxides and sulphides have been presented. The idea of proposed method consists in determination of the defect structure and transport properties of metal oxides and sulphides in indirect way, i.e. in studying the influence of aliovalent metallic additions on the oxidation kinetics of a given metal. It has been shown that from the results of oxidation kinetics of binary alloys, the enthalpy and entropy of defect formation and their migration can be calculated. These data, in turn, can be used for the calculation of defect concentration and defect mobility in pure, undoped oxides. Such a possibility has been illustrated on the example of nonstoichiometric nickel oxide, Ni1-yO.
10
Content available remote Substitute thermal capacity of binary alloys : review of hypotheses
63%
EN
In the paper the problems connected with the mathematical modeling of alloys solidification (macro scale) are presented. The similar lecture was delivered by the authors during the IV Conference on Mathematical Modelling in Physics and Technique, Kleszczów, 28-30 June 2012. In particular the one domain method (fixed domain approach) in which the parameter called 'a substitute thermal capacity' appears will be discussed. The one domain method bases on the Fourier equation describing the thermal processes in the whole conventionally homogeneous casting domain. The substitute thermal capacity (STC) can be defined in the different ways. The first group of definitions results from the differentiation of the function determining the local volumetric solid state fraction in the neighborhood of the point considered, while the second one is based on the direct assumption of the STC form, at the same time this function should fulfill the condition resulting from the change of alloy physical enthalpy during the phase change. The details of these approaches will be presented in the Sections 2 and 3.
EN
A numerical model of binary alloy crystallization, based on the cellular automaton technique, is presented. The model allows to follow the crystallization front movement and to generate the images of evolution of the dendritic structures during the solidification of a binary alloy. The mathematic description of the model takes into account the proceeding thermal, diffusive, and surface phenomena. There are presented the results of numerical simulations concerning the multi-dendritic growth of solid phase along with the accompanying changes in the alloying element concentration field during the solidification of Al + 5% wt. Mg alloy. The model structure of the solidified casting was achieved and compared with the actual structure of a die casting. The dendrite interaction was studied with respect to its influence on the generation and growth of the primary and secondary dendrite arms and on the evolution of solute segregation both in the liquid and in the solid state during the crystallization of the examined alloy. The morphology of a single, free-growing dendritic crystal was also modelled. The performed investigations and analyses allowed to state e.g. that the developed numerical model correctly describes the actual evolution of the dendritic structure under the non-equilibrium conditions and provides for obtaining the qualitatively correct results of simulation of the crystallization process.
12
Content available remote Manufacturing Cu-Pb alloys and studying efficiency in resisting oxidation
63%
EN
Binary alloys of copper and lead were produced by casting these elements in specially designed moulds with dimensions appropriate to the tests to be carried out on them. The effectiveness of these alloys in resisting oxidation was then studied in an atmosphere of a mixture of sodium chloride vapour and sodium sulphate at specific concentrations and heating the mixture to 180°C. Recently, corrosion has become a major problem in the overall performance of many engineering devices due to automotive exhaust gases produced by the internal combustion engine, which leads to corrosion of materials that make up some components of engineering industries. Copper also has good corrosion performance due to the formation of a copper oxide layer, which has made it the most important material in industrial applications. Through this research, we have achieved the desired goal as the alloys produced have shown their efficiency in resisting saline and acidic conditions and at high levels. The best sample is Cu95Pb5 and Cu90Pb10 with little difference between them in terms of efficiency. The aim of this work is to produce alloys and study their efficiency in resisting oxidation at high temperatures.
PL
Binarne stopy miedzi i ołowiu zostały wytworzone metodą odlewania w specjalnie zaprojektowanych formach o wymiarach dostosowanych do badań. Odporność stopów na utlenianie została zbadana w atmosferze mieszaniny oparów chlorku sodu i siarczanu sodu w określonych stężeniach i po podgrzaniu mieszaniny do 180°C. Korozja jest poważnym problemem, zaburza funkcjonowanie wielu urządzeń inżynieryjnych. Jej źródłem są m.in. spaliny wytwarzane przez silniki spalinowe. Miedź ma dobre właściwości antykorozyjne ze względu na warstwę tlenku miedzi, tworzącą się na jej powierzchni w wyniku utleniania. Z tego względu jest głównym materiałem stosowanym w przemyśle. Badane stopy miedzi i ołowiu wykazały wysoką odporność na działanie soli i kwasów w dużych stężeniach. Najlepsze wyniki uzyskano dla stopów Cu95Pb5 i Cu90Pb10 (różnica między nimi była niewielka). Celem pracy było zbadanie odporności wytworzonych stopów na utlenianie w wysokich temperaturach.
EN
A novel heterogeneous catalyst, Fe/Mn supported on NaY zeolite, was effectively applied for treating pulp mill effluents. The results of the wastewater quality analysis showed that aromatic structures were present in raw pulp mill effluents, which indicated the difficulty for biodegradation treatments. Two different catalysts were prepared by impregnation (Fe-Mn/NaYim) and sol-gel (Fe-Mn/NaYsg) methods, respectively. The Fe-Mn/NaYsg catalyst demonstrated higher COD removal efficiency and was more stable than the Fe-Mn/NaYim catalyst. The synergistic effects were found between Fe and Mn for COD removal. The highest COD removal efficiency (75.2%) was yielded with the Fe-Mn/NaYsg catalyst (Fe/Mn molar ratio of 2) with 4 mmol/dm3 of H2O2 and 1.2 g/dm3 of catalyst addition. A constant COD removal over time was obtained; the COD removal efficiency amounted to 45% after the Fe-Mn/NaYsg catalyst repeatedly degrading pulp mill effluents for five times. The distribution and transformation of the polarity and molecular weight (MW) of dissolved organic carbon (DOC) in the heterogeneous Fenton process were also studied. Experiments showed that the hydrophobic fraction comprised the largest fraction of DOC (60%) in raw wastewater and high MW molecules were transformed into low MW molecules after the heterogeneous Fenton process. This study broadened the application of the Fenton technology.
EN
One of the trends in the studies on Pb-free solders is to correlate surface tension obtained both experimentaly and by modelling and wettability by means of Young-Dupre relation. In the previous studies surface tension has been measured with the maximum bubble pressure method for pure liquid components: Sn, Bi, In, Ag, Pb; for binary liquid alloys: Pb-Sn, Ag-Sn (the most promising candidate to replace Pb-Sn eutectic or near-eutectic alloys), Ag-In, In-Sn, Bi-Sn and for the eutectic Ag-Sn alloy with Zn, In, Bi or Cu additions (ternary systems). Surface tension measurements were performed in wide range of temperature, and the range of concentration depending upon the investigated system. For binary alloys measurements were performed in the entire concentration range, and only for small ternary additions to the eutectic (Sn-3,5 weight % Ag) alloys to confirm the change of the surface tension in relation to the binary eutectic. Recently, studies of the Ag-Sn-In and Ag-Sn-Bi ternary systems have been completed, and the influence of the Bi and In additions on the surface tension of (Sn-Ag)eut+(Bi, In) alloys has been discussed regarding the wetting tests.
PL
Jednym z kierunków badań nad bezołowiowymi materiałami do lutowania jest określanie korelacji pomiędzy napięciem powierzchniowym z pomiarów eksperymentalnych i z modelowania opartego o własności termodynamiczne rozpatrywanych stopów a zwilżalnością z wykorzystaniem zależności Younga-Dupre. W naszym Instytucie zostały przerowadzone pomiary napięcia powierzchniowego dla ciekłych metali: Sn, Bi, In, Ag, oraz Pb; dla ciekłych dwuskładnikowych stopów: Pb-Sn, Ag-Sn (najpoważniejszy kandydat do zastąpienia stopów Pb-Sn eutektycznych lub około-eutektycznych), Ag-In, In-Sn oraz Bi-Sn a także stopów (Ag-Sn)eut z dodatkami takich metali jak Zn, In, Bi oraz Cu. Pomiary napięcia powierzchniowego prowadzono w szerokim zakresie temperatury, a zakresy stężeń zależały od charakteru badanego układu. Dla stopów dwuskładnikowych badania prowadzono w całym zakresie stężeń, a w przypadku układów trójskładnikowych pomiary ograniczono do stopów zawierających niewielkie ilości cytowanych wcześniej dodatków metali do eutektyki dwuskładnikowej Ag-Sn. Celem tych badań było potwierdzenie zmian napięcia powierzchniowego w stosunku do eutektyki podwójnej Sn-Ag i skorelowanie go z temperaturą topnienia otrzymaną z odrębnych informacji pochodzących z wykresów fazowych. Dotychczas zostały zakończone badania dla dwóch trójskładnikowych stopów: Ag-Sn-In oraz Ag-Sn-Bi, w których przeanalizowano zmiany napięcia powierzchniowego związane z dodatkami indu lub bizmutu do dwuskładnikowej eutektyki Ag-Sn, a prezentowanymi w literaturze wynikami badań nad zwilżalnością.
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