21 research outputs found
Synthèse de matériaux de type metal-organic frameworks pour l'énergétique
No full textThis thesis is dedicated to the study of the energetic behaviors and performances of Lyophobic Heterogeneous Systems (LHSs) in intrusion–extrusion experiments. In this work, LHSs involve Metal-Organic Frameworks (MOFs) as porous materials and water or aqueous electrolyte solutions as non-wetting liquids. Upon the application of an external pressure to a LHS, the applied mechanical energy is converted into interfacial energy. When the external pressure is released, the LHS can either completely restore or (partially or completely) dissipate the stored mechanical energy, thereby behaving as a spring, shock-absorber, or bumper, respectively.This work aims at defining the effects of various parameters, such as the nature of the non-wetting liquid, the material’s topology and the linker substitution, on the energetic behaviors and performances of LHSs in order to design perfect systems for practical applications. As an example, the presence of an electron donating or withdrawing group on the linker in SOD-type MOFs is shown to enable tuning the energetic behavior of the LHS when using aqueous electrolyte solutions.Moreover, the energetic performances of two hydrophobic MOF materials, MAF-6 and ZIF-71 of RHO topology are also studied. The “MAF-6‒water” and “MAF-6‒ or ZIF-71‒LiCl 20 M” systems display mainly bumper behavior, as the supplied mechanical energy is principally absorbed by the materials when undergoing an irreversible phase transformation. Different scenarios, experimentally supported, explain these results. Finally, the optimization of the syntheses of promising MOF materials, their full characterization and the study of their energetic performances are described.Cette thèse est dédiée à l'étude des performances énergétiques de systèmes hétérogènes lyophobes (SHLs) par des expériences d'intrusion-extrusion. Dans ce travail, les SHLs sont constitués de matériaux de type Metal-Organic Framework (MOF) en tant que solide poreux et d'eau ou de solution aqueuse d’électrolyte comme liquide non mouillant. Lors de l'application d'une pression externe au SHL, l'énergie mécanique appliquée est convertie en énergie interfaciale. Lorsque la pression est relâchée, le SHL peut soit restaurer complètement, soit dissiper (partiellement ou complètement) l'énergie mécanique stockée, se comportant ainsi comme un ressort, un amortisseur ou un pare-chocs.Ce travail vise à définir les effets de divers paramètres tels que la nature du liquide non mouillant, la topologie du matériau ou la substitution du ligand afin de concevoir des SHLs optimaux. Par exemple, la présence d'un groupe donneur ou attracteur d’électrons sur le ligand de MOFs de type SOD permet d’ajuster le comportement énergétique avec l'utilisation de solutions aqueuses d'électrolytes.De plus, les performances énergétiques de deux matériaux MOF hydrophobes, MAF-6 et ZIF-71, de topologie RHO sont également étudiées. Les systèmes «MAF-6‒eau» et «MAF-6‒ ou ZIF-71‒LiCl 20 M» affichent principalement un comportement pare-chocs, car l'énergie mécanique fournie est principalement absorbée par les matériaux lors d’une transformation de phase irréversible. Différents scénari, soutenus expérimentalement, expliquent ces résultats.Enfin, l'optimisation de synthèses de MOFs prometteurs, leurs caractérisations complètes et l'étude de leurs performances énergétiques sont décrites
Phase Transformations of Metal–Organic Frameworks MAF-6 and ZIF-71 during Intrusion–Extrusion Experiments
No full textInternational audienceIn this work, the energetic behaviors of two zeolitic imidazolate framework (ZIF) materials, ZIF-71 and the highly porous MAF-6, of RHO topology are studied in high-pressure intrusion−extrusion experiments using LiCl 20 M aqueous solution and/or water as nonwetting liquids. During the intrusion−extrusion experiments, both MAF-6 and ZIF-71 structures undergo phase transformations under the combined effects of high pressure and the nonwetting liquid. For the “MAF-6−H2O” system, the volume variation step observed on the intrusion curve of the first intrusion−extrusion cycle partially corresponds to the intrusion of water molecules inside the MAF-6 pores associated with a partial and irreversible phase transformation of MAF-6 into a nonporous and unidentified phase X. When the pressure is released, that is, when the experiment is stopped at the end of the volume variation step and the system returns to atmospheric pressure, the intruded water molecules are expelled from the porosity of the remaining MAF-6 material, and the “MAF-6−H2O” system, therefore, displays a mixture of shock-absorber and bumper behaviors. In the case of both “MAF-6−” and “ZIF-71−LiCl 20 M aqueous solution” systems, the volume variation step is shifted to a higher pressure range, indicating that the intrusion of the nonwetting liquid molecules occurs at a higher pressure because of the presence of electrolytes. For the “MAF-6−LiCl 20 M aqueous solution” system, a mixture of MAF-6 and phase X is obtained at the end of the volume variation step, which probably indicates energetic behavior similar to the one observed for the “MAF-6−H2O” system (i.e., a mixture of shock-absorber and bumper behaviors). In the case of the “ZIF-71−LiCl 20Maqueous solution” system, the volume variation step observed on the intrusion curve of the first intrusion−extrusion cycle corresponds to a phase transformation. At the end of this step, the ZIF-71 structure is completely transformed into ZIF-72 (lcs). The “ZIF-71−LiCl 20 M aqueous solution” system, thus, displays bumper behavior, as the supplied mechanical energy is absorbed during the irreversible phase transformation phenomenon
Energetic Performances of ZIF-8 Derivatives: Impact of the Substitution (Me, Cl, or Br) on Imidazolate Linker
No full textInternational audienceThe energetic performances of three isomorphic ZIF materials, i.e., ZIF-8_CH3 (Basolite Z1200), ZIF-8_Cl, and ZIF-8_Br, of SOD topology are studied with high-pressure intrusion−extrusion experiments using water and aqueous electrolyte solutions (KCl 4 M and LiCl 20 M) as nonwetting liquids. This work represents an important progress in the field of energetic applications, as the “ZIF-8_Cl−LiCl 20 M” system exhibits a spring behavior with a stored energy of 77 J g−1. To the best of our knowledge, this is the highest value for the stored energy obtained using intrusion−extrusion experiments. Experimental results reveal that the intrusion pressure increases with the addition of electrolytes. The systems evolve from a bumper to a shock-absorber or spring behavior with the decrease in the strength of the interactions between the cation of the salt and the imidazolate linker. This explains the bumper or rather the shock-absorber behavior observed for the “ZIF-8_Br−KCl 4 M” and “ZIF-8_CH3−LiCl 20 M” systems compared to the spring behavior observed with the other systems reported in this work
Phase Transformations of Metal–Organic Frameworks MAF‑6 and ZIF-71 during Intrusion–Extrusion Experiments
No full textIn
this work, the energetic behaviors of two zeolitic imidazolate
framework (ZIF) materials, ZIF-71 and the highly porous MAF-6, of
RHO topology are studied in high-pressure intrusion–extrusion
experiments using LiCl 20 M aqueous solution and/or water as nonwetting
liquids. During the intrusion–extrusion experiments, both MAF-6
and ZIF-71 structures undergo phase transformations under the combined
effects of high pressure and the nonwetting liquid. For the “MAF-6–H2O” system, the volume variation step observed on the
intrusion curve of the first intrusion–extrusion cycle partially
corresponds to the intrusion of water molecules inside the MAF-6 pores
associated with a partial and irreversible phase transformation of
MAF-6 into a nonporous and unidentified phase X. When the pressure
is released, that is, when the experiment is stopped at the end of
the volume variation step and the system returns to atmospheric pressure,
the intruded water molecules are expelled from the porosity of the
remaining MAF-6 material, and the “MAF-6–H2O” system, therefore, displays a mixture of shock-absorber
and bumper behaviors. In the case of both “MAF-6–”
and “ZIF-71–LiCl 20 M aqueous solution” systems,
the volume variation step is shifted to a higher pressure range, indicating
that the intrusion of the nonwetting liquid molecules occurs at a
higher pressure because of the presence of electrolytes. For the “MAF-6–LiCl
20 M aqueous solution” system, a mixture of MAF-6 and phase
X is obtained at the end of the volume variation step, which probably
indicates energetic behavior similar to the one observed for the “MAF-6–H2O” system (i.e., a mixture of shock-absorber and bumper
behaviors). In the case of the “ZIF-71–LiCl 20 M aqueous
solution” system, the volume variation step observed on the
intrusion curve of the first intrusion–extrusion cycle corresponds
to a phase transformation. At the end of this step, the ZIF-71 structure
is completely transformed into ZIF-72 (lcs). The “ZIF-71–LiCl
20 M aqueous solution” system, thus, displays bumper behavior,
as the supplied mechanical energy is absorbed during the irreversible
phase transformation phenomenon
Back-extraction of major actinides from organic phase through precipitation
No full textInternational audienc
Synthesis, Structural Investigation, and Energetic Performance Study of ZIF-25
No full textInternational audienceThe synthesis of ZIF-25 was successfully optimized by using acetic acid as a modulator agent, yielding a highly crystalline material. The product exhibits significant porosity, thermal stability up to 300 °C, and hydrophobicity, making it ideal for use in lyophobic heterogeneous systems (LHSs). Notably, the crystal structure of ZIF-25 was refined for the first time using the Rietveld method and fully reported in space group Pm-3m. Energetic performance evaluation in intrusion−extrusion experi- ments shows that the “ZIF-25−water” system dissipates mechanical energy with adsorbed and released energies of ∼15−19 and ∼10 J g−1, respectively. These features make it an LHS with shock- absorber characteristics. The study highlights that the energetic behavior of ZIFs is topology-dependent, with RHO-type ZIFs such as ZIF-25 and ZIF-71 showing shock-absorber properties, while SOD-type ZIFs (like ZIF-8) exhibit spring-like behavior. Post-experiment characterizations, performed by X-ray diffraction, nitrogen adsorption at 77 K, and scanning electron microscopy, indicate moderate and pressure-dependent degradation when the material is subjected to pressurized water intrusion
Memory and politics: a study of social psychology from the testimony of student militants
No full textEsta pesquisa teve como alvo o exame psicossocial da participação política a partir do depoimento de militantes estudantis. Trata-se de uma investigação orientada metodologicamente por Ecléa Bosi, José Moura Gonçalves Filho e Maria Isaura Pereira de Queirós, envolvendo a realização de entrevistas semidirigidas analisadas qualitativamente. Foram realizadas e interpretadas duas entrevistas com militantes que atuaram no final dos anos 80 e início dos anos 90 no Instituto de Psicologia da USP. Entre os assuntos abordados pela pesquisa, destacam-se: as motivações dos depoentes para a política; a importância dos agentes políticos e acontecimentos sociais para o convite à militância; a relação entre a condição social dos militantes e a forma pela qual assumem a política; a relação entre o convite à política e o surgimento do interesse pelo estudo; as características dos episódios de maior efervescência e entusiasmo políticos lembrados pelos depoentes; as disputas aguerridas entre os grupos estudantis; a severa hierarquia entre os militantes e a distância estabelecida entre militantes e não-militantes; a burocratização das entidades e partidos políticos; e por último as convergências e divergências entre psicologia e política. São temas que esta pesquisa procurou enfrentar a partir dos depoimentos. Confrontando as lembranças e discussões dos depoentes com as do próprio pesquisador; confrontando-as também com autores dedicados ao tema, esta pesquisa procura contribuir para o estudo psicossocial da militância estudantil.In this research, a psycho-social exam about militant students political participation is made, using their testimonies in semi-guided interviews analysed qualitatively. This investigation was methodologically oriented by Ecléa Bosi, José Moura Gonçalves Filho and Maria Isaura Pereira de Queirós. Two student militants who were engaged in politics during the 80s and the beginning of the 90s in the University of São Paulo Psychology Institute were interviewed. Among the discussed issues, some stand out: what motivated towards politics; the importance of political agents and social events as an invitation to politics; the relation between the invitation to politics and the emerging of their interest to study; the characteristics of the most enthusiastic and exciting political episodes remembered by them; the strong disputes between students groups; the strict hierarchy between the student militants and the distance established between activist and non-activist; the bureaucracy of institutions and political parties; and last but not least the convergences and divergences between psychology and politics. These are themes this research attempted to face from the declarations. Confronting the memories and discussion of the interviewed people with those of the researcher himself as well as with author who study the theme, this work attempts to enrich the psycho-social study of student political militancy
