<p>Proces pečenja u proizvodnji keramičkog crepa u većini slučajeva se izvodi u<br />oksidavionoj atmosferi. Dobijena mikrostruktura koja obezbeđuje najvažnije osobine<br />primene zavisi od mineralo&scaron;kog sastava polaznog materijala i temperature termičkog<br />tretmana.<br />Sa stanovi&scaron;ta proizvodnje glinenog crepa, sirovina sa značajnim sadržajem karbonata kao &scaron;to je kop gline u Kanjiži, predstavlja problem te se ne može koristiti u njenom prirodnom sastavu. U oksidacionom termičkom tretmanu, staklasta faza koja se formira razgradnjom lakotopivih glinenih minerala ne kvasi u dovoljnoj meri zemnoalkalne okside nastale razgradnjom karbonata. Očekivane nove kristalne faze, kao &scaron;to su gelenit i anortit, koje predstavljaju osnovu dobrih tehničkih osobina crepa, ne mogu nastati u potrebnoj količini. Jedno od re&scaron;enja ovog problema je pobolj&scaron;anje interakcije između silikata i CaO/MgO promenom kvaliteta atmosfere pečenja.<br />Cilj je bio da se dobije odgovor na pitanje, da li se mogu promenom tehnolo&scaron;kih<br />parametara pečenja pobolj&scaron;ati karakteristike finalnog proizvoda dobijenog od sirovinske sme&scaron;e sa visokim masenim udelom karbonata.<br />Dati su rezultati pečenja u oksidacionoj i redukcionoj atmosferi u pogledu fizičkomehaničkih karakteristika i nastanka novih kristalnih faza. U radu su primenjene metode 57Fe M&ouml;ssbauer spektroskopije, difrakcija X zraka i dilatometrijska analiza za<br />identifikaciju promena faza tokom pečenja u oksidacionoj i redukcionoj atmosferi<br />(CO/N2 atmosfera) na temperaturama od 700-1060&deg;C. Ove promene reflektuju<br />dehidroksilaciju glinenih minerala, dekompoziciju karbonata, denzifikaciju i formiranje<br />novih kristalnih faza (plagioklasi). U cilju analize industrijskih uzoraka, pored 57Fe<br />M&ouml;ssbauer spektroskopije, primenjene su i sledeće metode: skenirajuća elektronska<br />mikroskopija (SEM) sa EDS analizom, živina porozimetrija, fotoelektronska spektroskopija (XPS) i karakterizacija apsorbcije vode, otpornosti na mraz i nosivosti.<br />Primena redukujuće atmosfere pokazala se kao opravdana, dobijen je glineni crep<br />pobolj&scaron;anih karakteristika u odnosu na standardni proizvod pečen u oksidacionoj<br />atmosferi.</p> / <p>The firing process in clay roofing tile production is normally carried out in oxidizing<br />firing atmosphere. The obtained microstructure which provides the most important<br />properties of the application depends on the mineralogical composition of the starting raw material and the firing temperature.<br />Concerning the production of roofing tiles, clay raw materials with a high content of<br />carbonates such as the Kanjiza clay material, possess an inappropriate composition. The melt phase is formed after the decomposition of clay minerals during the common firing process. This liquid phase, due to its extent wetting characteristics, is not able to wet properly the earth alkali oxides obtained after the decomposition of the carbonates. The expected new crystalline phases, like gehlenite and anorthite, which are needed for the favorable technical properties of the roofing tiles, can not be formed in the required quality and quantity. One solution to this problem is the limebonding improvement by changing the conditions of the firing atmosphere.<br />The main aim of this work is to examine the effects of firing conditions on the<br />properties of clay roofing tiles with high carbonate content. The obtained physical and<br />mechanical properties and the obtained new crystalline phases are described in detail.<br />The experiment used dilatometry, X-ray diffractometry, 57Fe M&ouml;ssbauer<br />spectroscopy to identify the changes during the firing process in oxidizing and<br />reducing atmosphere (CO/N2 atmosphere) at temperatures between 700 and 1060&deg;C.<br />Furthermore, for industrial sample analysis, scanning electronmicroscopy with EDS,<br />XPS, Hg porosimetry, water absorption procedure, frost resistance and bending<br />measurements were applied.<br />The application of reducing atmosphere was proved to be valid. The obtained<br />roofing tiles had improved properties compared to the standard production which uses<br />oxidizing firing atmosphere.</p>

Le travail de thèse, présenté dans ce mémoire, est consacré à l'étude de nouveaux matériaux d'électrode négative pour batteries Li-ion et plus particulièrement aux phosphures d'éléments de transition (PET). En général, ces matériaux présentent des capacités massiques et volumiques de l'ordre de 600-1200mAh/g, très supérieures à celles des composés carbonés utilisés dans les dispositifs actuellement commercialisés. Les phases des deux systèmes binaires Fe-P et Ni-P ont été étudiées dans ce travail en tant qu'électrodes négatives pour les batteries Li-ion. Les phosphures de fer et de nickel présentent des performances et mécanismes électrochimiques vis-à-vis du lithium intéressants. Diverses méthodes de synthèse ont été employées pour obtenir des matériaux de morphologie, de structure et de stoechiométrie variées. Plusieurs techniques de caractérisation ont été employées pour analyser les mécanismes électrochimiques : diffraction des rayons X, spectroscopie XANES, spectroscopie Mössbauer de 57Fe, RMN 31P et mesures magnétiques. L'étude approfondie de la réactivité de ces phases vis-à-vis du lithium nous a permis d'expliquer leurs fortes capacités massiques par un mécanisme redox impliquant le phosphore. Une étude du rôle de la mise en forme de l'électrode sur les performances a été également menée.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / The structural and thermal decomposition properties of Mg-Fe and Co-Cu-Fe hy- drotalcites (HT) have been studied through thermogravimetric analysis, X ray powder difraction (XRD), Fourier transform infrared spectroscopy and 57Fe MÃssbauer spec- troscopy. In the Mg-Fe system, the destruction of the layered structure took place at about 300 oC. The broad peaks observed in the X ray difractograms suggests that the resultant oxides constitute a solid solution. For samples treated at temperatures higher than 500 oC the formation of the MgO and MgFe2O4 formation of the MgO and MgFe2O4 spinel phases is observed. 57Fe MÃssbauer spectroscopy was employed to monitor the Fe chemical environment for the samples annealed at diferent temperatures (100-900 oC). In situ XRD experiments revealed that the HTs start an interlayer contraction at about 180 oC. This phenomenon is identified as being due to a grafting process for which the interlamellar anions attach to the layers through a covalent bond. The reconstruction of the Mg-Fe HTs was also investigated and its eficiency depends on the thermal anneal- ing temperature and on the Mg/Fe ratio. The structure of the reconstructed samples was found to be exactly the same as the parent structure. The in situ 57Fe MÃssbauer experiments were performed in the 100-500 oC temperature range confirm an increasing structural disorder in this temperature range. The quadrupolar splitting indicates that the maximum disorder occurs at 300 oC. Regarding the Co-Cu-Fe ternary system we have observed that due to the strong Jahn-Teller effect the Cu-Fe layered system is stabilized only in the presence of Co2+. At low Co2+ contents, additional phases are segregated in the solids. X ray patterns diffraction show the presence of Cu(OH)2 and CuO. The decomposition process was investigated by in situ X ray, in situ MÃssbauer and FTIR experiments. By increasing the temperature from 25 oC up to 180 oC we observed that the structural disorder increases. This effect has been likely attributed to the Co2+ to Co3+ oxidation since thermal decomposition was carried out under static air atmosphere. Part of the Co3+ cations could migrate to the interlayer region, thus forming a metastable compound that still has a layered structure. Collapse of the layered structure was ob- served at about 200 oC. By further increasing the temperature the system becomes more crystalline and the formation of Co3O4 is observed in the X ray patterns. In Cu-rich HT, some of the carbonate anions are released at temperatures higher than 550 oC and this phenomenon is attributed to the formation of a carbonate-rich phase. The specific surface area data present its highest values in the temperature range where the collapse of the layered structure takes place. / As propriedades estruturais e de decomposiÃÃo tÃrmica das hidrotalcitas Mg-Fe e Co-Cu-Fe foram estudadas atravÃs de espectroscopia MÃssbauer de 57Fe, anÃlise termo- gravimÃtrica, difraÃÃo de raios X, e espectroscopia de absorÃÃo no infravermelho (FTIR). No sistema Mg-Fe a destruiÃÃo da estrutura lamelar ocorre em torno de 300 oC. O alargamento dos picos de difraÃÃo de raios X observados nos difratogramas sugerem que os Ãxidos resultantes constituem uma soluÃÃo sÃlida. Para as amostras tratadas em temperaturas maiores do que 500 oC a formaÃÃo de fases do tipo MgO e MgFe2O4 à observada. A espectroscopia MÃssbauer de 57Fe foi empregada para monitorar o ambiente quÃmico do Fe na faixa 100-900 oC de temperatura. As medidas in situ de difraÃÃo de raios X revelam que em 180 oC inicia-se uma contraÃÃo interlamelar. Este fenÃmeno à atribuÃdo ao processo de âgrafting" no qual os Ãnions interlamelares ligam-se nas camadas atravÃs de uma ligaÃÃo covalente. A reconstruÃÃo estrutural da hidrotalcita Mg-Fe tambÃm foi investigada. A eficiÃncia da reconstruÃÃo estrutural depende da temperatura de tratamento e da razÃo molar Mg/Fe. A estrutura das amostras reconstruÃdas sÃo as mesmas da amostra inicial. As medidas in situ de espectroscopia MÃssbauer de 57Fe foram realizadas na faixa 100-500 oC confirmaram uma desordem estrutural crescente nesta regiÃo de temperaturas. Os valores do desdobramento quadrupolar indicam que o mÃximo de desordem ocorre em 300 oC. Com relaÃÃo ao sistema ternÃrio Co-Cu-Fe observamos que devido ao efeito Jahn-Teller o sistema Cu-Fe somente à estabilizado na presenÃa de Co2+. Para baixas concentraÃÃes Co2+ fases adicionais segregadas sÃo observadas nos sÃlidos. Os padrÃes de difraÃÃo de raios X indicam a presenÃa de Cu(OH)2 e CuO. O processo de decomposiÃÃo tÃrmica foi investigado atravÃs de difraÃÃo de raios X, espectroscopia MÃssbauer de 57Fe in situ e de espectroscopia de absorÃÃo no infravermelho (FTIR). Aumentando a temperatura de tratamento tÃrmico das amostras de 25 oC a 180 oC observamos um aumento da desordem estrutural. Este efeito tem sido atribuÃdo a oxidaÃÃo Co2+ para Co3+ uma vez que a decomposiÃÃo foi realizada ao ar. Parte dos cÃtions Co3+ migram para a regiÃo interlamelar formando um composto metastÃvel que ainda possui uma estrutura lamelar. O colapso da estrutura lamelar à observado a 300 oC. Com o aumento posterior da temperatura o sistema torna-se mais cristalino e a formaÃÃo de Co3O4 à observada atravÃs do ensaio de raios X. Nas hidrotalcitas com maior teor de Cu, alguns dos Ãnions carbonato sÃo liberados somente acima de 550 oC sendo este fenÃmeno atribuÃdo a formaÃÃo de uma fase rica em carbonato. Os valores de Ãrea superficial especÃfica apresentam um mÃximo na faixa de temperatura onde ocorre o colapso da estrutura lamelar.

Cette thèse concerne l'étude des propriétés structurales et magnétiques de nanoparticules magnétiques creuses (HMNPs), coquille et coquille/coquille. Les effets de surface sont exaltés de par la présence des surfaces interne et externe. L'étude expérimentale de HMNPs basée sur des mesures magnétiques et de spectrométrie Mössbauer du 57Fe a montré une structure magnétique complexe. Les HMNPs ayant une épaisseur ultrafine présentent une structure magnétique décrite par 2 sous-réseaux spero-magnétiques opposés, en plus de la présence d’un champ d'échange bias significatif. L'effet de la taille et de l'épaisseur des HMNPs a été également étudié. Les spectres Mössbauer obtenus sous champ magnétique montrent que la structure magnétique est fortement corrélée au rapport surface/volume. Ces résultats expérimentaux ont été confirmés par simulation Monte Carlo. Après optimisation du modèle, l’approche numérique montre d’abord que l'anisotropie de surface Ks gouverne le comportement magnétique des HMNPs et ensuite que la valeur critique de Ks nécessaire pour obtenir une configuration radiale (spike) diminue lorsque la taille des HMNPs augmente. L'étude numérique menée pour différentes tailles et épaisseurs de coquille, a permis de suivre leurs effets sur la structure magnétique des HMNPs. Par ailleurs, l'étude expéri-mentale menée sur des HMNPs shell/shell, montre que le désordre des spins et le champ d'échange bias deviennent plus importants lorsque les HMNPs sont recouvertes d’une coquille antiferromagnétique (NiO). De ces résultats, on peut déduire l'effet du désordre des spins sur les phénomènes d'échange bias dans un tel système. / This thesis concerns the study of structural and magnetic properties of hollow magnetic nanoparticles (HMNPs), shell and shell/shell. These HMNPs present enhanced surface effects resulting from the presence of both inner and outer surface layers. The experimental investigation combining magne-tic measurements and 57Fe Mössbauer spectrometry of such HMNPs has revealed a complex spin magnetic structure. Small HMNPs with ultrathin thickness show highly disordered magnetic structure and the corresponding in-field hyperfine structure can be described by means of 2 speromagnetic antiferromagnetically coupled, in addition to the significant exchange bias phenomenon. The in-field Mössbauer study of the effect of size and thickness of HMNPs shows that the spin disorder is strongly correlated to the surface to volume ratio. Those experimental magnetic behaviors were confirmed using Monte Carlo simulation. Indeed, after improving the numeric model, it is concluded that surface anisotropy Ks has a dominant role in the magnetic behavior of HMNPs and the value of critical Ks necessary to obtain radial (spike) configuration decreases as the size of HMNPs increases, keeping the same thickness. The numeric study for different sizes and shell thicknesses allows the effect of these parameters on the spin structure of HMNPs to be followed. Then, the experi-mental study extended to shell/shell HMNPs indicates that the spin disorder is enhanced in HMNPs with antiferromagnetic shell (NiO) in addition to larger exchange bias field. From those results, one can try to deduce the effect of spin disorder on the exchange bias phenomena in such system.

De nouveaux composés fluorés et oxyfluorés d'étain ainsi que des fluorures ternaires d'antimoine ont été synthètises et caractérisés. Des transitions de phases ont été mises en évidence par ATD et macrocalorimétrie. Des structures cristallines ont été déterminées soit a partir de monocristaux, soit a partir d'échantillons polycristallins par la méthode de Rietveld. Une étude par diffraction de neutrons sur un échantillon pulvérulent a montre qu'un ordre cationique existait pour le fluorure mixte Sn2F6. Des techniques spectroscopiques ont permis de préciser la nature des liaisons chimiques et de confirmer l'existence de transitions de phases. Des corrélations ont été établies entre les paramètres Mössbauer et les propriétés structurales.