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Characterization of nanostructured bulk cobalt triantimonide doped with tellurium and indium prepared by pulsed plasma in liquid method

Zybała R., Schmidt M., Kaszyca K., Chmielewski M., Kruszewski M. J., Jasiński M., Rajska M., Ciupiński Ł.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2020

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Vol. 68, nr 1

125--134

EN

One of the ways to decrease thermal conductivity is nano structurization. Cobalt triantimonide (CoSb3) samples with added indium or tellurium were prepared by the direct fusion technique from high purity elements. Ingots were pulverized and re-compacted to form electrodes. Then, the pulsed plasma in liquid (PPL) method was applied. All materials were consolidated using rapid spark plasma sintering (SPS). For the analysis, methods such as X-ray diffraction (XRD), scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM) with a laser flash apparatus (LFA) were used. For density measurement, the Archimedes’ method was used. Electrical conductivity was measured using a standard four-wire method. The Seebeck coefficient was calculated to form measured Seebeck voltage in the sample placed in a temperature gradient. The preparation method allowed for obtaining CoSb3 nanomaterial with significantly lower thermal conductivity (10 Wm–1K–1 for pure CoSb3 and 3 Wm–1K–1 for the nanostructured sample in room temperature (RT)). The size of crystallites (from SEM observations) in the powders prepared was about 20 nm, joined into larger agglomerates. The Seebeck coefficient, α, was about –200μVK–1 in the case of both dopants, In and Te, in microsized material and about −400 μK−1 for the nanomaterial at RT. For pure CoSb3 , α was about 150 μVK−1 and it stood at −50 μVK−1 for nanomaterial at RT. In bulk nanomaterial samples, due to a decrease in electrical conductivity and inversion of the Seebeck coefficient, there was no increase in ZT values and the ZT for the nanosized material was below 0.02 in the measured temperature range, while for microsized In-doped sample it reached maximum ZT = 0.7 in (600K).

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A Two-Stage Monte Carlo Approach for Optimization of Bimetallic Nanostructures

Mikhov Rossen, Myasnichenko Vladimir, Kirilov Leoneed, Sdobnyakov Nickolay, Matrenin Pavel, Sokolov Denis, Fidanova Stefka

Annals of Computer Science and Information Systems

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2020

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Vol. 21

285--288

EN

In this paper we propose a two-stage lattice Monte Carlo approach for optimization of bimetallic nanoalloys: simulated annealing on a larger lattice, followed by simulated diffusion. Both algorithms are fairly similar in structure, but their combination was found to give significantly better solutions than simulated annealing alone. We also discuss how to tune the parameters of the algorithms so that they work together optimally.

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Review on hierarchically microstructured monolithic reactors for high yield continuous production of fine chemicals

Mrowiec-Białoń J., Ciemięga A., Maresz K., Szymańska K., Pudło W., Jarzębski A. B.

Chemical and Process Engineering

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2018

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Vol. 39, nr 4

367–-375

EN

Preparation and properties of hierarchically structured porous silica monoliths have been discussed from the viewpoint of their application as continuous microreactors for liquid-phase synthesis of fine chemical in multi kilogram scales. The results of recent topical papers published by two research teams of Institute of Chemical Engineering Polish Academy of Sciences (ICE) and Department of Chemical Engineering and Process Design, Chemical Faculty, Silesian University of Technology (SUT) have been analyzed to specify the governing traits of microreactors. It was concluded that even enhancement factor of 100 in activity, seen in enzyme catalyzed reactions, can be explained by a proportional reduction of its physical constraints, i.e. huge enhancement of external mass transfer and micromixing. It is induced by very chaotic flows of liquid in tens of thousands of waving connected channels of ca. 25–50 mm in diameter, present in the skeleton. The scale of enhancement in the caseof less active catalysts was smaller, but still large enough to consider the most practical applications.

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Investigation of the Ultrafine-Grained Structure Formation Under Different Strain Rates

Kováčová A., Kvačkaj T., Bidulský R., Bidulská J., Kočiško R., Dutkiewicz J., Lityńska-Dobrzyńska L.

Archives of Metallurgy and Materials

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2017

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Vol. 62, iss. 2A

851--856

EN

The present paper deals with a study on formation of specific substructural features in OFHC copper processed by equalchannel angular pressing (ECAP) considering different strain rate conditions. Since two mechanical tensile testing equipments were being used, strain rate response could be studied in a wide range (both in static and dynamic regimes). Moreover, the copper before tensile testing was subjected to drawing and ECAP, separately, which allows to study the influence of both structural and substructural features (CG vs. UFG structure). Considering the static regime, it was found that UFG materials have advanced properties, showing higher strength and ductility in comparison to their CG counterparts. However, this is valid only to the critical value of the strain rate. In the dynamic regime, mathematical linearized results imply that ultimate tensile strength in samples processed by ECAP increases twice every 10 s-1 rising, however, they lost approximately the same plastic properties than samples after drawing. Differences in the progress of mechanical properties are related to specific structural and substructural features evolved in the material during ECAP processing. Above mentioned features were studied in detail by methods of transmission and scanning electron microscopy (TEM, SEM).

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Mechanizmy odkształcenia materiałów nanostrukturalnych

Krella A.

Inżynieria Materiałowa

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2011

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Vol. 32, nr 5

844-850

PL

Nanomateriały stanowią obecnie ważną grupę materiałów znajdujących zastosowanie prawie we wszystkich dziedzinach przemysłu. W badaniach nanomateriałów stwierdzono, że zależność Halla-Petcha nie jest spełniona dla całego zakresu 1÷100 nm. W przypadku nanomateriałów o wielkości ziaren poniżej pewnej wartości krytycznej zaobserwowano efekt zmniejszenia twardości wraz ze zmniejszeniem się wielkości ziarna. Z tego względu wiele badań poświęcono poznaniu ich budowy i mechanizmów odkształcania. Badania prowadzone za pomocą transmisyjnego mikroskopu elektronowego wykazały, że nanokrystaliczne materiały są zbudowane z małych krystalitów o zróżnicowanej orientacji krystalograficznej, oddzielonych od siebie szerokokątowymi granicami ziaren, w których są obserwowane pustki (rys. 1). Pustki te były wyraźnie większe w miejscach styku trzech ziaren, tzw. triple junction. Ze względu na istotny wzrost udziału granic ziaren (rys. 2) wraz ze zmniejszaniem się wielkości ziaren oraz mniejszą gęstość atomową w porównaniu z ziarnami, najczęstszym modelem struktury nanomateriałów jest model dwufazowy składający się fazy wewnętrznej ziarna i fazy granicy ziarna (rys. 3). Jednym z wyjaśnień zjawiska zmniejszenia twardości nanomateriałów jest zwiększenie w budowie nanomateriału udziału granic ziaren (rys. 2), których gęstość jest znacznie mniejsza niż gęstość ziaren oraz odmienne mechanizmy odkształcania. Badania doświadczalne, symulacje dynamiki molekularnej oraz modele odkształcenia nanokrystalicznych materiałów wykazały, że odkształcanie nanomateriałów przebiega na skutek poślizgu wzdłuż granic ziaren, dyfuzji po granicy ziaren, dyfuzji w ziarnach, rotacji ziaren, powstania pasm ścinania, generowania dyslokacji przez granice ziaren, mechanicznego bliźniakowania, a także w wyniku ruchu dyslokacji wewnątrz ziaren, z tym, że ten ostatni mechanizm zanika wraz ze zmniejszaniem się wielkości krystalitów.

EN

Nanomaterials are nowadays very important group of materials which are used in most branches of industry. The investigations of the strength of nanomaterials showed that the Hall-Petch law is not valid in the same form for the whole range from 1 to 100 nm. When the grain size falls below the critical size the effect of decrease of strength (softening) is observed. Therefore, many studies were performed to learn their structure and deformation mechanisms. Investigation performed by means of high resolution transmission electron microscopy (HRTEM) showed that nanocrystalline materials consist of small crystallites of different crystallographic orientations separated by the grain boundaries of large angle type, which consists of pores (Fig. 1). These pores have bigger size at triple junctions. Due to low atomic density of grain boundary and an increase of grain boundary fraction with decrease of grain size (Fig. 2), the most frequent model of nanomaterials structure is two-phase model which consists of the grain interior phase and the grain boundary phase (Fig. 3). One of the explanation of the softening effect of the nanostructured materials is the increase of fraction of grain boundary (Fig. 2), whose density and strength is lower than those of grains. Another explanation says that the softening effect is due to deformation mechanisms that are different from those present in their coarse-grained counterparts. Experimental investigations, molecular dynamic simulation and many models showed that deformation of nanocrystalline materials develops via grain boundary sliding, grain boundary diffusion, shear-band formation, mechanical twinning, dislocation climb, rotation at triple junctions, grain-boundary dislocation creation and annihilation and also via dislocation motion inside grain.

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Effect of milling time and addition of alumina powder on the structural properties and fracture surface of nanocrystalline Al

Razavi Tousi S. S., Yazdani Rad R., Salahi E., Razavi M.

Materials Science Poland

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2009

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Vol. 27, No. 3

875--884

EN

The effects of milling time and the addition of alumina reinforcement on the structural evolution of Al matrix were investigated. By analysing the cross section of powder, cold welding mechanism for both monolithic and composite powders was studied. Results show that presence of the alumina powder has a marked effect on variation of apparent density, preferred orientation, impurity content and thus lattice parameter of Al by milling time. The reduction of the grain size to the nanometeric scale changes the fracture mechanism of Al particles completely, from dimpled into intergranular, though alumina addition does not seem to have notable influence on the fracture mechanism.

7

Nanostrukturalne materiały termoelektryczne

Wojciechowski K.

Elektronika : konstrukcje, technologie, zastosowania

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2009

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Vol. 50, nr 9

68-71

PL

W artykule dokonano zwięzłego przeglądu najważniejszych koncepcji dotyczących nowej grupy nanostrukturalnych materiałów termoelektrycznych. Dzięki kwantowym efektom rozmiarowym możliwe jest zwiększenie ponad dwukrotnie efektywności konwersji energii w stosunku do dotąd stosowanych klasycznych materiałów litych. Nowe materiały nanostrukturalne mogą znaleźć szerokie zastosowanie w m.in. w elektronice do konstrukcji miniaturowych elementów chłodzących oraz mikrogeneratorów termoelektrycznych.

EN

A brief overview of key concepts of a new group of nanostructured thermoelectric materials is given. Owing to quantum size effects it is possible to increase the efficiency of energy conversion, in relation to previously used c1assical bulk materials, more than twice. New nanostructured materials may find wide application, especially in electronics, in manutacture of miniature thermoelectric coolers and microgenerators.

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Nanoproszki i warstwy z materiałów termoelektrycznych-otrzymywanie i charakterystyka

Wojciechowski K., Gajerski R., Grzonka J., Mania R., Mars K., Morgiel J., Zybała R.

Elektronika : konstrukcje, technologie, zastosowania

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2009

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Vol. 50, nr 9

65-67

PL

Przedstawiono wybrane wyniki prac dotyczące dwóch metod otrzymywania nanostrukturalnych materiałów termoelektrycznych z grupy skutterudytów oraz warstw tellurku antymonu. Nanoproszki CoSb₃ otrzymywane były metodą rozkładu termicznego aerozoli a następnie redukcji w atmosferze wodoru. Warstwy tellurku antymonu wytwarzano techniką impulsowego rozpylania magnetronowego. Otrzymane materiały poddane były szczegółowym badaniom mikrostruktury i składu fazowego oraz właściwości termoelektrycznych.

EN

The paper presents selected results of two methods of preparation of nanostructured thermoelectric materials from group of skutterudites and antimony telluride layers. Nanopowders ot CoSb₃ were obtained using thermal decomposition and reduction of aerosol s in the atmosphere of hydrogen. Antimony telluride layers were produced by pulse magnetron sputtering. The materials were subject of detailed examination of the microstructure, phase composition and thermoelectric properties.