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1

Nanoparticles of cerium dioxides for gas sensor applications.

Villain S., Leroux C., Musso J., Fremy M.A., Pischedda M.H., Gavarri J.R.

Inżynieria Materiałowa

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2001

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R. XXII, nr 5

935-938

EN

The aim of this work is to elaborate nanostructured cerium dioxides for catalytic and gas sensor applications. Nanosized cerium oxide powders were prepared via three chemical routes: 1) chemical precipitation followed by high-energy mechanical milling; 2) soft chemical preparation, 3) an unusual method of pulverization of liquid solution developed in our laboratory. The obtained powders were characterized using X-Ray diffraction analyses and Transmission Electron Microscopy experiments. Nanoparticles of pure CeO2 oxide having their sizes ranging from 2 to 10 nanometers have been obtained.

2

Effect of cracks on elastic properties of superconductor Bi-2223 - Stainless steel composites

Siwek A., Suliga I., Gavarri J.R., Pischedda M.H., Jasieńska M. H., Paćko M.

Metallurgy and Foundry Engineering

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1999

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T. 25, no. 1

s. 9--14

EN

The mechanical properties of granular composites fabricated from compacted stainless steel and superconducting oxide powders are studied as a function of sintering parameters (temperature, time, steel volume fraction). The evolution of the elastic Young modulus E as a function of the sintering parameters is modeled taking into account the formation of cracks (absence of cohesion) between the steel grains and the superconducting matrix. The cracks are observed by scanning electron microscopy.

PL

W pracy badano wpływ parametrów spiekania (temperatura, czas) na własności mechaniczne kompozytu wykonanego z proszków stali austenitycznej i nadprzewodnika wysokotemperaturowego typu Bi2223. Zmianę wartości modułu Younga, w zależności od udziału objętościowego stali, modelowano biorąc pod uwagę brak spójności pomiędzy ziarnami stali i nadprzewodnikicm. Obserwacje mikrostruktury przeprowadzono mikroskopem skaningowym.

3

Sintering effects in superconductor/ferrite composites.

Kopia-Zastawa A., Suliga I., Fremy M.A., Pischedda M.H., Gavarri J.R., Jasieńska S.

Inżynieria Materiałowa

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1998

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R. XIX, nr 4

876-879

EN

Granular superconductor/ferrite composites have been fabricated using various sintering conditions such as: volume fraction, sintering temperature and sintering time. The superconducting phase is the well known Bi (Pb)-2223 phase with Tc=110K. The ferrite is NiFe2O4. Using magnetic measurements, X-ray diffraction, scanning electron microscopy and susceptibility measurements the composites after sintering have been characterized.

4

Microstructure, transport properties and chemical reactions in ceramics and composities: application to superconductor based composites.

Gavarii J.R., Kopia-Zastawa A., Fremy M.A., Pischedda M.H., Suliga I., Jasieńska S.

Inżynieria Materiałowa

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1998

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R. XIX, nr 4

813-818

EN

In this review, we deal with active two-phase composites made of one superconducting constituent (S) and of an additional phase (F) having a mechanical or electrical role. To interpret the effects of sintering processes, two types of modelling approaches are discussed: firstly, the modelling of the chemical diffusions and, secondly, the chemical reactivity which conditions both electrical and mechanical properties of the resulting F/S composites. The chemical reactions at the interfaces of the F/S composites are firstly described by a simplified Fick law approach: each element can be characterized by one apparent chemical diffusion coefficient D. Then expressing the chemical reaction following the classical form: F + n.S -> P, and considering elemental kinetics laws (d[F]/dt = -k1. [F][S]), we propose to determine two new parameters characteristic of the degradation of the system during the sintering process. Finally, three types of parameters (D, n, k1) are available to describe the chemical evolutions in composites.